What does “safe” mean?  How much risk is too much? Is your answer different for risks that you choose to assume on your own (such as skiing fast downhill) as opposed to risks that someone might encounter at work?  Think about your own lives.  Do you live in a risk-free world? A safe world? Do you choose to do things that are “risky” out of choice? Did the coronavirus pandemic clarify or change your thinking about risk?

One expert suggests, “A thing is safe if its risks are judged to be acceptable.”  He goes on to note, “[T]his definition contrasts sharply with simplistic dictionary definitions that have ‘safe’ meaning something like ‘free from risk.’ Nothing can be absolutely free of risk…Notice that this definition emphasizes the relativity and judgmental nature of the concept of safety.  It also implies that two very different activities are required for determining how safe things are: measuring risk, an objective but probabilistic pursuit; and judging the acceptability of that risk (judging safety), a matter of personal and social value judgment.”  William W. Lowrance, Of Acceptable Risk: Science and the Determination of Safety, p. 8. Lowrance goes on to point out that measuring risk “is an empirical, scientific activity,” while judging safety “is a normative, political activity.”

As you can see from the decisions in Hardy, Lochner and Martinez-Cuevas, different people (and different judges) reach different conclusions regarding this second question. That very fact has huge consequences for any governmental attempt to regulate risks. There can also be arguments regarding the empirical data – and these arguments also may reflect normative political views. 

There is also a question of what level of risk individuals may choose to accept – and the extent to which there should be regulatory intervention to prevent the assumption of risks at work. If something is safe if its risks are acceptable, who should make the assessment of what is acceptable? the employer? the worker? the worker's union? OSHA? the courts? Congress?

When a worker was killed by a killer whale at SeaWorld in Florida, OSHA pursued a general duty case against the employer. We will be returning to this case later, but think about what Judge (now Justice) Kavanaugh had to say about the risk in this case:

Many sports events and entertainment shows can be extremely dangerous for the participants. Football. Ice hockey. Downhill skiing. Air shows. The circus. Horse racing. Tiger taming. Standing in the batter’s box against a 95 mile per hour fastball. Bull riding at the rodeo. Skydiving into the stadium before a football game. Daredevil motorcycle jumps. Stock car racing. Cheerleading vaults. Boxing. The balance beam. The ironman triathlon. Animal trainer shows. Movie stunts. The list goes on.

But the participants in those activities want to take part, sometimes even to make a career of it, despite and occasionally because of the known risk of serious injury. To be fearless, courageous, tough—to perform a sport or activity at the highest levels of human capacity, even in the face of known physical risk—is among the greatest forms of personal achievement for many who take part in these activities. American spectators enjoy watching these amazing feats of competition and daring, and they pay a lot to do so. Americans like to witness the thrill of victory, to cheer the linebacker who hammers the running back at the goal line, to yell with admiration as Derek Jeter flies into the stands down the left-field line to make a catch, to applaud the gymnast who nails the back flip off the balance beam, to hold their collective breath as Jack Hanna plays with pythons, to root on the marathoner who is near collapse at the finish line, to scream “Foreman” when the announcer says “Down goes Frazier.” And American spectators also commiserate during the “agony of defeat,” as immortalized in the Wide World of Sports video of a ski jumper flying horribly off course.

The broad question implicated by this case is this: When should we as a society paternalistically decide that the participants in these sports and entertainment activities must be protected from themselves—that the risk of significant physical injury is simply too great even for eager and willing participants? And most importantly for this case, who decides that the risk to participants is too high?

Perez v. SeaWorld of Florida, 748 F.3d 1202, 1217 (D.C. Cir. 2014)

The questions of safety, what is safe enough, and when workers should have latitude to choose to perform risky work – or the right to insist on greater workplace safety than the employer is offering – are all issues that we will return to throughout the course.

In occupational safety and health, there are two types of risk that may affect workers.

Safety hazards are immediate and can usually be seen. They include, for example, whether the ladders used are stable, whether people working on a roof have some sort of effective fall protection, whether there are guards on machines that perform cutting functions, whether there is a lockdown-tagout procedure to ensure that equipment is shut off while someone works on it, whether cranes and derricks are stable. The effect of the hazard is immediate injury. These hazards are simpler to regulate since the existence of the hazard is easy to identify and the risk is clear (though no hazard is easy to regulate, as we will discuss).

Health hazards are those that affect an employee’s health through exposure to chemical, biological, or physical agents in the environment; these include dusts, gases, toxic substances, noise, heat (and so on). The health effects generally occur over time and can range from respiratory disorders to cancer to effects on human reproduction (and so on). They also include the effects of infectious agents such as Covid-19. The OSHAct has a separate subsection that specifically addresses regulation of these risks, 29 USCA § 655(b)(5), which is discussed at length in the cases below.

Identifying the risk and the health effects requires that researchers (often epidemiologists and public health experts) notice and then study the effects of an exposure through the performance of risk assessments. There are three elements of risk assessment: hazard identification, dose-response assessment, exposure assessment. These provide the basis for the fourth element: risk characterization, or the estimated incidence of the adverse effect in a given population.  In each step, scientists address key questions, with the goal of formulating a complete understanding of the seriousness and scope of a hazard. 

Once a risk is characterized, we move from risk assessment to questions of risk management. In an administrative framework such as OSHA (or the EPA), this involves the development of regulatory options, including evaluations of the public health, economic, social, and political consequences of these options; this ultimately culminates in agency decisions and actions (or inaction).

This is an interesting process in the arena of environmental and occupational regulation.  There is often a collision between scientific ideas about proof, that may rely on probabilities, and legal ideas about proof, that seek higher levels of certainty. As the excerpt above from Of Acceptable Risk suggests, the scientific analysis, on its own, does not necessarily tell us what the right regulatory answer would be. The decision to regulate, and the level of the regulation, is inevitably based on competing factors: how safe or unsafe are the alternatives?  are the proposals technologically feasible?  economically feasible?  and so on.  These questions are often easier to answer when dealing with safety hazards than with health hazards (but not always). 

There are special challenges at each step along the way from risk assessment through development of a regulatory strategy to deal with that risk to enforcement of the regulation.  A well-identified health hazard may not become a risk that is subject to regulation; a regulated hazard may not always be a hazard for which the regulation is enforced effectively.

The standard setting process itself can be convoluted and difficult, as these agencies try to navigate the scientific, economic, political and bureaucratic issues. The basic process for development of standards was described in Chapter 1.

Justice STEVENS announced the judgment of the Court and delivered an opinion, in which THE CHIEF JUSTICE and Mr. Justice STEWART joined and in Parts I, II, III-A, III-B, III-C and III-E of which Mr. Justice POWELL joined.

The Occupational Safety and Health Act of 1970 (Act), 84 Stat. 1590, 29 U.S.C. §  651 et seq., was enacted for the purpose of ensuring safe and healthful working conditions for every working man and woman in the Nation. This litigation concerns a standard promulgated by the Secretary of Labor to regulate occupational exposure to benzene, a substance which has been shown to cause cancer at high exposure levels.   The principal question is whether such a showing is a sufficient basis for a standard that places the most stringent limitation on exposure to benzene that is technologically and economically possible.

The Act delegates broad authority to the Secretary to promulgate different kinds of standards.   The basic definition of an "occupational safety and health standard" is found in §  3(8), which provides:

"The term 'occupational safety and health standard' means a standard which requires conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment and places of employment."   84 Stat. 1591, 29 U.S.C. §  652(8).

Where toxic materials or harmful physical agents are concerned, a standard must also comply with § 6(b)(5), which provides:

"The Secretary, in promulgating standards dealing with toxic materials or harmful physical agents under this subsection, shall set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life.   Development of standards under this subsection shall be based upon research, demonstrations, experiments, and such other information as may be appropriate.   In addition to the attainment of the highest degree of health and safety protection for the employee, other considerations shall be the latest available scientific data in the field, the feasibility of the standards, and experience gained under this and other health and safety laws."   84 Stat. 1594, 29 U.S.C. §  655(b)(5).

Wherever the toxic material to be regulated is a carcinogen, the Secretary has taken the position that no safe exposure level can be determined and that §  6(b)(5) requires him to set an exposure limit at the lowest technologically feasible level that will not impair the viability of the industries regulated.   In this case, after having determined that there is a causal connection between benzene and leukemia (a cancer of the white blood cells), the Secretary set an exposure limit on airborne concentrations of benzene of one part benzene per million parts of air (1 ppm), regulated dermal and eye contact with solutions containing benzene, and imposed complex monitoring and medical testing requirements on employers whose workplaces contain 0.5 ppm or more of benzene.  29 CFR § §  1910.1028(c), (e) (1979).

On pre-enforcement review pursuant to 29 U.S.C. §  655(f), the United States Court of Appeals for the Fifth Circuit held the regulation invalid.  American Petroleum Institute v. OSHA, 581 F.2d 493 (1978).   The court concluded that the Occupational Safety and Health Administration (OSHA) had exceeded its standard-setting authority because it had not shown that the new benzene exposure limit was "reasonably necessary or appropriate to provide safe or healthful employment" as required by §  3(8), and because §  6(b)(5)  does "not give OSHA the unbridled discretion to adopt standards designed to create absolutely risk-free workplaces regardless of costs." Reaching the two provisions together, the Fifth Circuit held that the Secretary was under a duty to determine whether the benefits expected from the new standard bore a reasonable relationship to the costs that it imposed.  The court noted that OSHA had made an estimate of the costs of compliance, but that the record lacked substantial evidence of any discernible benefits.  

We agree with the Fifth Circuit's holding that §  3(8) requires the Secretary to find, as a threshold matter, that the  toxic substance in question poses a significant health risk in the workplace and that a new, lower standard is therefore "reasonably necessary or appropriate to provide safe or healthful employment and places of employment."   Unless and until such a finding is made, it is not necessary to address the further question whether the Court of Appeals correctly held that there must be a reasonable correlation between costs and benefits, or whether, as the federal parties argue, the Secretary is then required by §  6(b)(5) to promulgate a standard that goes as far as technologically and economically possible to eliminate the risk.

Because these are unusually important cases of first impression, we have reviewed the record with special care.   In this opinion, we (1) describe the benzene standard, (2) analyze the Agency's rationale for imposing a 1 ppm exposure limit, (3) discuss the controlling legal issues, and (4) comment briefly on the dermal contact limitation.

I

Benzene is a familiar and important commodity.   It is a colorless, aromatic liquid that evaporates rapidly under ordinary atmospheric conditions. Approximately 11 billion pounds of benzene were produced in the United States in 1976.   Ninety-four percent of that total was produced by the petroleum and petrochemical industries, with the remainder produced by the steel industry as a byproduct of coking operations.   Benzene is used in manufacturing a variety of products including motor fuels (which may contain as much as 2% benzene), solvents, detergents, pesticides, and other organic chemicals. 

The entire population of the United States is exposed to small quantities of benzene, ranging from a few parts per billion to 0.5 ppm, in the ambient air. Over one million workers are subject to additional low-level exposures as a consequence of their employment.   The majority of these employees work in gasoline service stations, benzene  production (petroleum refineries and coking operations), chemical processing, benzene transportation, rubber manufacturing, and laboratory operations.

Benzene is a toxic substance.   Although it could conceivably cause harm to a person who swallowed or touched it, the principal risk of harm comes from inhalation of benzene vapors.   When these vapors are inhaled, the benzene diffuses through the lungs and is quickly absorbed into the blood. Exposure to high concentrations produces an almost immediate effect on the central nervous system.   Inhalation of concentrations of 20,000 ppm can be fatal within minutes;  exposures in the range of 250 to 500 ppm can cause vertigo, nausea, and other symptoms of mild poisoning.  Persistent exposures at levels above 25-40 ppm may lead to blood deficiencies and diseases of the blood-forming organs, including aplastic anemia, which is generally fatal.

Industrial health experts have long been aware that exposure to benzene may lead to various types of nonmalignant diseases.   By 1948 the evidence connecting high levels of benzene to serious blood disorders had become so strong that the Commonwealth of Massachusetts imposed a 35 ppm limitation on workplaces within its jurisdiction.   In 1969 the American National Standards Institute (ANSI) adopted a national consensus standard of 10 ppm averaged over an 8-hour period with a ceiling concentration of 25 ppm for 10-minute periods or a maximum peak concentration of 50 ppm.  In 1971, after the Occupational Safety and Health Act was passed, the Secretary adopted this consensus standard as the federal standard, pursuant to 29 U.S.C. §  655(a).

As early as 1928, some health experts theorized that there might also be a connection between benzene in the workplace and leukemia. In the late 1960's and early 1970's a number of epidemiological studies were published indicating that workers exposed to high concentrations of benzene were subject to significantly increased risk of leukemia. In a 1974 report recommending a permanent standard for benzene, the National Institute for Occupational Safety and Health  NIOSH), OSHA's research arm, noted that these studies raised the "distinct possibility" that benzene caused leukemia.   But, in light of the fact that all known cases had occurred at very high exposure levels, NIOSH declined to recommend a change in the 10 ppm standard, which it considered sufficient to protect against nonmalignant diseases.   NIOSH suggested that further studies were necessary to determine conclusively whether there was a link between benzene and leukemia and, if so, what exposure levels were dangerous.

Between 1974 and 1976 additional studies were published which tended to confirm the view that benzene can cause leukemia, at least when exposure levels are high. In an  August 1976 revision of its earlier recommendation, NIOSH stated that these studies provided " conclusive" proof of a causal connection between benzene and leukemia.     Although it acknowledged that none of the intervening studies had provided the dose-response data it had found lacking two years earlier, id., at 9, NIOSH nevertheless recommended that the exposure limit be set low as possible.   As a result of this recommendation, OSHA contracted with a consulting firm to do a study on the costs to industry of complying with the 10 ppm standard then in effect or, alternatively, with whatever standard would be the lowest feasible.  

In October 1976, NIOSH sent another memorandum to OSHA, seeking acceleration of the rulemaking process and "strongly" recommending the issuance of an emergency temporary standard pursuant to §  6(c) of the Act, 29 U.S.C. §  655(c),[1] for benzene and two other chemicals believed to  be carcinogens.   NIOSH recommended that a 1 ppm exposure limit be imposed for benzene.   Apparently because of the NIOSH recommendation, OSHA asked its consultant to determine the cost of complying with a 1 ppm standard instead of with the "minimum feasible" standard.   It also issued voluntary guidelines for benzene, recommending that exposure levels be limited to 1 ppm on an 8-hour time-weighted average basis wherever possible

In the spring of 1976, NIOSH had selected two Pliofilm plants in St. Marys and Akron, Ohio, for an epidemiological study of the link between leukemia and benzene exposure.   In April 1977, NIOSH forwarded an interim report to OSHA indicating at least a fivefold increase in the expected incidence of leukemia for workers who had been exposed to benzene at the two plants from 1940 to 1949.  The report submitted to OSHA erroneously suggested that exposures in the two plants had generally been between zero and 15 ppm during the period in question. As a result of this new evidence and the continued prodding of NIOSH, OSHA did issue an emergency standard effective May 21, 1977, reducing the benzene exposure limit from 10 ppm to 1 ppm, the ceiling for exposures of up to 10 minutes from 25 ppm to 5 ppm, and eliminating the authority for peak concentrations of 50 ppm.   In its explanation accompanying the emergency standard, OSHA stated that benzene had been shown to cause leukemia at exposures below 25 ppm and that, in light of its consultant's report, it was feasible to reduce the exposure limit to 1 ppm.

On May 19, 1977, the Court of Appeals for the Fifth Circuit entered a temporary restraining order preventing the emergency standard from taking effect.   Thereafter, OSHA abandoned its efforts to make the emergency standard effective and instead issued a proposal for a permanent standard patterned almost entirely after the aborted emergency standard.

In its published statement giving notice of the proposed permanent standard, OSHA did not ask for comments as to whether or not benzene presented a significant health risk at exposures of 10 ppm or less.   Rather, it asked for comments as to whether 1 ppm was the minimum feasible exposure limit.   As OSHA's Deputy Director of Health Standards, Grover Wrenn, testified at the hearing, this formulation  of the issue to be considered by the Agency was consistent with OSHA's general policy with respect to carcinogens. Whenever a carcinogen is involved, OSHA will presume that no safe level of exposure exists in the absence of clear proof establishing such a level and will accordingly set the exposure limit at the lowest level feasible. The proposed 1 ppm exposure limit in this case thus was established not on the basis of a proven hazard at 10 ppm, but rather on the basis of "OSHA's best judgment at the time of the proposal of the feasibility of compliance with the proposed standard by the [a]ffected industries."   Given OSHA's cancer policy, it was in fact irrelevant whether there was any evidence at all of a leukemia risk at 10 ppm.   The important point was that there was no evidence that there was not some risk, however small, at that level.   The fact that OSHA did not ask for comments on whether there was a safe level of exposure for benzene was indicative of its further view that a demonstration of such absolute safety simply could not be made.

Public hearings were held on the proposed standard, commencing on July 19, 1977.   The final standard was issued on February 10, 1978.  29 CFR §  1910.1028 (1979). In its final form, the benzene standard is designed to protect workers from whatever hazards are associated with low-level benzene  exposures by requiring employers to monitor workplaces to determine the level of exposure, to provide medical examinations when the level rises above 0.5 ppm, and to institute whatever engineering or other controls are necessary to keep exposures at or below 1 ppm.

In the standard as originally proposed by OSHA, the employer's duty to monitor, keep records, and provide medical examinations arose whenever any benzene was present in a workplace covered by the rule. Because benzene is omnipresent in small quantities, NIOSH and the President's Council on Wage and Price Stability recommended the use of an "action level" to trigger monitoring and medical examination requirements.  OSHA accepted this recommendation, providing under the final standard that, if initial monitoring discloses benzene concentrations below 0.5 ppm averaged over an 8-hour work day, no further action is required unless there is a change in the company's practices. If exposures are above the action  level, but below the 1 ppm exposure limit, employers are required to monitor exposure levels on a quarterly basis and to provide semiannual medical examinations for their exposed employees.   Neither the concept of an action level, nor the specific level selected by OSHA, is challenged in this proceeding.

Whenever initial monitoring indicates that employees are subject to airborne concentrations of benzene above 1 ppm averaged over an 8-hour workday, with a ceiling of 5 ppm for any 15-minute period, employers are required to modify their plants or institute work practice controls to reduce exposures within permissible limits.   Consistent with OSHA's general policy, the regulation does not allow respirators to be used if engineering modifications are technologically feasible. Employers in this category are also required to perform monthly monitoring so long as their workplaces remain above 1 ppm, provide semiannual medical examinations to exposed workers, post signs in and restrict access to "regulated areas" where the permissible exposure limit is exceeded, and conduct employee training programs where necessary. * * *

The permanent standard is expressly inapplicable to the storage, transportation, distribution, sale, or use of gasoline or other fuels subsequent to discharge from bulk terminals. This exception is particularly significant in light of the fact that over 795,000 gas station employees, who are exposed to an average of 102,700 gallons of gasoline (containing up to 2% benzene) annually, are thus excluded from the protection of the standard.

As presently formulated, the benzene standard is an expensive way of providing some additional protection for a relatively small number of employees. According to OSHA's figures, the standard will require capital investments in engineering controls of approximately $266 million, first-year operating costs (for monitoring, medical testing, employee training, and respirators) of $187 million to $205 million and  recurring annual costs of approximately $34 million. The figures outlined in OSHA's explanation of the costs of compliance to various industries indicate that only 35,000 employees would gain any benefit from the regulation in terms of a reduction in their exposure to benzene.  Over two-thirds of these workers (24,450) are employed in the rubber-manufacturing industry. Compliance costs in that industry are estimated to be rather low, with no capital costs and initial operating expenses estimated at only $34 million ($1,390 per employee);  recurring annual costs would also be rather low, totalling less than $1 million.   By contrast, the segment of the petroleum refining industry that produces benzene would be required to incur $24 million in capital costs and $600,000 in first-year operating expenses to provide additional protection for 300 workers ($82,000 per employee), while the petrochemical industry would be required to incur $20.9 million in capital costs and $1 million in initial operating expenses for the benefit of 552 employees ($39,675 per employee).

Although OSHA did not quantify the benefits to each category of worker in terms of decreased exposure to benzene, it appears from the economic impact study done at OSHA's direction that those benefits may be relatively small.   Thus, although the current exposure limit is 10 ppm, the actual exposures outlined in that study are often considerably lower.   For example, for the period 1970-1975 the petrochemical industry reported that, out of a total of 496 employees exposed to benzene, only 53 were exposed to levels between 1 and 5 ppm and only 7 (all at the same plant) were exposed to between 5 and 10 ppm.

II

The critical issue at this point in the litigation is whether the Court of Appeals was correct in refusing to enforce the 1 ppm exposure limit on the ground that it was not supported by appropriate findings.

Any discussion of the 1 ppm exposure limit must, of course, begin with the Agency's rationale for imposing that limit.  The written explanation of the standard fills 184 pages of the printed appendix. Much of it is devoted to a discussion of the voluminous evidence of the adverse effects of exposure to benzene at levels of concentration well above 10 ppm. This discussion demonstrates that there is ample justification for regulating occupational exposure to benzene and that the prior limit of 10 ppm, with a ceiling of 25 ppm (or a peak of 50 ppm) was reasonable.   It does not, however, provide direct support for the Agency's conclusion that the limit should be reduced from 10 ppm to 1 ppm.

The evidence in the administrative record of adverse effects of benzene exposure at 10 ppm is sketchy at best.   OSHA noted that there was "no dispute" that certain nonmalignant blood disorders, evidenced by a reduction in the level of red or white cells or platelets in the blood, could result from exposures of 25-40 ppm.   It then stated that several studies had indicated that relatively slight changes in normal blood values could result from exposures below 25 ppm and perhaps below 10 ppm.   OSHA did not attempt to make any estimate based on these studies of how significant the risk of nonmalignant disease would be at exposures of 10 ppm or less.  Rather, it stated that because of the lack of data concerning the linkage between low-level exposures and blood abnormalities, it was impossible to construct a dose-response  curve at this time.  OSHA did conclude, however, that the studies demonstrated that the current 10 ppm exposure limit was inadequate to ensure that no single worker would suffer a nonmalignant blood disorder as a result of benzene exposure.   Noting that it is "customary" to set a permissible exposure limit by applying a safety factor of 10-100 to the lowest level at which adverse effects had been observed, the Agency stated that the evidence supported the conclusion that the limit should be set at a point "substantially less than 10 ppm" even if benzene's leukemic effects were not considered.   OSHA did not state, however, that the nonmalignant effects of benzene exposure justified a reduction in the permissible exposure limit to 1 ppm.

OSHA also noted some studies indicating an increase in chromosomal aberrations in workers chronically exposed to  concentrations of benzene "probably less than 25 ppm."  However, the Agency took no definitive position as to what these aberrations meant in terms of demonstrable health effects and stated that no quantitative dose-response relationship had yet been established.   Under these circumstances, chromosomal effects were categorized by OSHA as an "adverse biological event of serious concern which may pose or reflect a potential health risk and as such, must be considered in the larger purview of adverse health effects associated with benzene."

With respect to leukemia, evidence of an increased risk (i. e., a risk greater than that borne by the general population) due to benzene exposures at or below 10 ppm was even sketchier.  * * *   In the end OSHA's rationale for lowering the permissible exposure limit to 1 ppm was based, not on any finding that leukemia has ever been caused by exposure to 10 ppm of benzene and that it will not be caused by exposure to 1 ppm, but rather on a series of assumptions indicating that some leukemias might result from exposure to 10 ppm and that the number of cases might be reduced by reducing the exposure level to 1 ppm.   In reaching that result, the Agency first unequivocally concluded that benzene is a human carcinogen. Second, it concluded that industry had failed to prove that there is a safe threshold level of exposure to benzene below which no excess leukemia cases would occur.   In reaching this conclusion OSHA rejected industry contentions that certain epidemiological studies indicating no excess risk of leukemia among workers exposed at levels below 10 ppm were sufficient to establish that the threshold level of safe exposure was at or above  10 ppm.  It also rejected an industry witness' testimony that a dose-response curve could be constructed on the basis of the reported epidemiological studies and that this curve indicated that reducing the permissible exposure limit from 10 to 1 ppm would prevent at most one leukemia and one other cancer death every six years.

Third, the Agency applied its standard policy with respect to carcinogens,  concluding  that, in the absence of definitive proof of a safe level, it must be assumed that any level above zero presents some increased risk of cancer.   As the federal parties point out in their brief, there are a number of scientists and public health specialists who subscribe to this view, theorizing that a susceptible person may contract cancer from the absorption of even one molecule of a carcinogen like benzene. 

Fourth, the Agency reiterated its view of the Act, stating that it was required by §  6(b)(5) to set the standard either at the level that has been demonstrated to be safe or at the lowest level feasible, whichever is higher. If no safe level is established, as in this case, the Secretary's interpretation of the statute automatically leads to the selection of an exposure limit that is the lowest feasible.  Because of benzene's importance to the economy, no one has ever suggested that it would be feasible to eliminate its use entirely, or to try to limit exposures to the small amounts that are omnipresent.   Rather, the Agency selected 1 ppm as a workable exposure level, see n. 14, supra, and then determined that compliance with that level was technologically feasible and that "the economic impact of  . . . [compliance] will not be such as to threaten the financial welfare of the affected firms or the general economy.”   It therefore held that 1 ppm was the minimum feasible exposure level within the meaning of §  6(b)(5) of the Act.

Finally, although the Agency did not refer in its discussion of the pertinent legal authority to any duty to identify the anticipated benefits of the new standard, it did conclude that some benefits were likely to result from reducing the exposure limit from 10 ppm to 1 ppm.   This conclusion was based, again, not on evidence, but rather on the assumption that the risk of leukemia will decrease as exposure levels decrease.   Although the Agency had found it impossible to construct a dose-response curve that would predict with any accuracy the number of leukemias that could be expected to result from exposures at 10 ppm, at 1 ppm, or at any intermediate level, it nevertheless "determined that the benefits of the proposed standard are likely to be appreciable.  In light of the Agency's disavowal of any ability to determine the numbers of employees likely to be adversely affected by exposures of 10 ppm, the Court of Appeals held this finding to be unsupported by the record.

It is noteworthy that at no point in its lengthy explanation did the Agency quote or even cite §  3(8) of the Act.   It made no finding that any of the provisions of the new standard were "reasonably necessary or appropriate to provide safe or healthful employment and places of employment."   Nor did it allude to the possibility that any such finding might have been appropriate.             

III

Our resolution of the issues in these cases turns, to a large extent, on the meaning of and the relationship between §  3(8), which defines a health and safety standard as a standard that is "reasonably necessary and appropriate to provide safe or healthful employment," and §  6(b)(5), which directs the Secretary in promulgating a health and safety standard for toxic materials to "set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity  . . . ."

In the Government's view, § 3(8)'s definition of the term "standard" has no legal significance or at best merely requires that a standard not be totally irrational.   It takes the position that §  6(b)(5) is controlling and that it requires OSHA to promulgate a standard that either gives an absolute assurance of safety for each and every worker or reduces exposures to the lowest level feasible.   The Government interprets "feasible" as meaning technologically achievable at a cost that would not impair the viability of the industries subject to the regulation.   The respondent industry representatives, on the other hand, argue that the Court of Appeals was correct in holding that the "reasonably necessary and appropriate" language of §  3(8), along with the feasibility requirement of §  6(b)(5), requires the Agency to quantify both the costs and the benefits of a proposed rule and to conclude that they are roughly commensurate.

In our view, it is not necessary to decide whether either the Government or industry is entirely correct.   For we think it is clear that §  3(8) does apply to all permanent standards promulgated under the Act and that it requires the Secretary, before issuing any standard, to determine that it is reasonably necessary and appropriate to remedy a significant risk of material health impairment.   Only after the Secretary has made the threshold determination that such a risk exists with respect to a toxic substance, would it be necessary to decide whether §  6(b)(5) requires him to select the most protective standard he can consistent with economic and technological feasibility, or whether, as respondents argue, the benefits of the regulation must be commensurate with the costs of its implementation. Because the Secretary did not make the required threshold finding in these cases, we have no occasion to determine whether costs must be weighed against benefits in an appropriate case.

A

Under the Government's view, §  3(8), if it has any substantive content at all, merely requires OSHA to issue standards that are reasonably calculated to produce a safer or more healthy work environment.  Apart from this minimal requirement of rationality, the Government argues that §  3(8) imposes no limits on the Agency's power, and thus would not prevent it from requiring employers to do whatever would be "reasonably necessary" to eliminate all risks of any harm from their workplaces.  With respect to toxic substances and harmful physical agents, the Government takes an even more extreme position.   Relying on §  6(b)(5)'s direction to set a standard "which most adequately assures  . . . that no employee will suffer material impairment of health or functional capacity," the Government contends that the Secretary is required to impose standards that either guarantee workplaces that are free from any risk of material health impairment, however small, or that come as close as possible to doing so without ruining entire industries.

If the purpose of the statute were to eliminate completely and with absolute certainty any risk of serious harm, we would agree that it would be proper for the Secretary to interpret § §  3(8) and 6(b)(5) in this fashion.  But we think it is clear that the statute was not designed to require employers to provide absolutely risk-free workplaces whenever it is technologically feasible to do so, so long as the cost is not great enough to destroy an entire industry.   Rather, both the language and structure of the Act, as well as its legislative history, indicate that it was intended to require the elimination, as far as feasible, of significant risks of harm.        

B

By empowering the Secretary to promulgate standards that are "reasonably necessary or appropriate to provide safe or healthful employment and places of employment," the Act implies that, before promulgating any standard, the Secretary must make a finding that the workplaces in question are not safe.   But "safe" is not the equivalent of "risk-free."   There are many activities that we engage in every day--such as driving a car or even breathing city air--that entail some risk of accident or material health impairment; nevertheless, few people would consider these activities "unsafe."   Similarly, a workplace can hardly be considered "unsafe" unless it threatens the workers with a significant risk of harm.

Therefore, before he can promulgate any permanent health or safety standard, the Secretary is required to make a threshold finding that a place of employment is unsafe--in the sense that significant risks are present and can be eliminated or lessened by a change in practices.   This requirement applies to permanent standards promulgated pursuant to §  6(b)(5), as well as to other types of permanent standards.   For there is no reason why §  3(8)'s definition of a standard should not be deemed incorporated by reference into §  6(b)(5).   The standards promulgated pursuant to §  6(b)(5) are just one species of the genus of standards governed by the basic requirement.   That section repeatedly uses the term "standard" without suggesting any exception from, or qualification of, the general definition;  on the contrary, its directs the Secretary to select "the standard"--that is to say, one of various possible alternatives that satisfy the basic definition in §  3(8)--that is most protective.  Moreover, requiring the  Secretary to make a threshold finding of significant risk is consistent with the scope of the regulatory power granted to him by §  6(b)(5), which empowers the Secretary to promulgate standards, not for chemicals and physical agents generally, but for "toxic materials" and "harmful physical agents."[2]

This interpretation of § §  3(8) and 6(b)(5) is supported by the other provisions of the Act.   Thus, for example, §  6(g) provides in part that "[i]n determining the priority for establishing standards under this section, the Secretary shall give due regard to the urgency of the need for mandatory safety and health standards for particular industries, trades,   crafts, occupations, businesses, workplaces or work environments."

The Government has expressly acknowledged that this section requires the Secretary to undertake some cost-benefit analysis before he promulgates any standard, requiring the elimination of the most serious hazards first. If such an analysis must precede the promulgation of any standard, it seems manifest that Congress intended, at a bare minimum, that the Secretary find a significant risk of harm and therefore a probability of significant benefits before establishing a new standard. * * *

In the absence of a clear mandate in the Act, it is unreasonable to assume that Congress intended to give the Secretary the unprecedented power over American industry that would result from the Government's view of § §  3(8) and 6(b)(5), coupled with OSHA's cancer policy.   Expert testimony that a substance is probably a human carcinogen--either because it has caused cancer in animals or because individuals have contracted cancer following extremely high exposures--would justify the conclusion that the substance poses some risk of serious harm no matter how minute the exposure and no matter how many experts testified that they regarded the risk as insignificant.   That conclusion would in turn justify pervasive regulation limited only by the constraint of feasibility.   In light of the fact that there are literally thousands of substances used in the workplace that have been identified as carcinogens or suspect carcinogens, the Government's theory would give OSHA power to impose enormous costs that might produce little, if any, discernible benefit. [3] 

* * * The legislative history also supports the conclusion that Congress was concerned, not with absolute safety, but with the elimination of significant harm.   The examples of industrial hazards referred to in the Committee hearings and debates all involved situations in which the risk was unquestionably significant.   For example, the Senate Committee on Labor and Public Welfare noted that byssinosis, a disabling lung disease caused by breathing cotton dust, affected as many as 30% of the workers in carding or spinning rooms in some American cotton mills and that as many as 100,000 active or retired workers were then suffering from the disease.   It also noted that statistics indicated that 20,000 out of 50,000 workers who had performed insulation work were likely to die of asbestosis, lung cancer, or mesothelyioma as a result of breathing asbestos fibers.   * * *

Moreover, Congress specifically amended §  6(b)(5) to make it perfectly clear that it does not require the Secretary to promulgate standards that would assure an absolutely risk-free workplace.   Section 6(b)(5) of the initial Committee bill provided that

"[t]he Secretary, in promulgating standards under this subsection, shall set the standard which most adequately and feasibly assures, on the basis of the best available evidence, that no employee will suffer any impairment of health or functional capacity, or diminished life expectancy even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life."  (Emphasis supplied.)   S. 2193, 91st Cong., 2d Sess., p. 39 (1970), Leg.Hist. 242.

On the floor of the Senate, Senator Dominick questioned the wisdom of this provision, stating:

"How in the world are we ever going to live up to that?   What are we going to do about a place in Florida where mosquitoes are getting at the employee-- perish the thought that there may be mosquitoes in Florida?   But there are black flies in Minnesota and Wisconsin.   Are we going to say that if employees get bitten by those for the rest of their lives they will not have been done any harm at all?   Probably they will not be, but do we know?"  116 Cong.Rec. 36522 (1970), Leg.Hist. 345.

He then offered an amendment deleting the entire subsection.  After discussions with the sponsors of the Committee bill, Senator Dominick revised his amendment.   Instead of deleting the first sentence of §  6(b)(5) entirely, his new amendment limited the application of that subsection to toxic materials and harmful physical agents and changed " any" impairment of health to "material" impairment.* * *

D

Given the conclusion that the Act empowers the Secretary to promulgate health and safety standards only where a significant risk of harm exists, the critical issue becomes how to define and allocate the burden of proving the significance of the risk in a case such as this, where scientific knowledge is imperfect and the precise quantification of risks is therefore impossible.   The Agency's position is that there is substantial evidence in the record to support its conclusion that there is no absolutely safe level for a carcinogen and that, therefore, the burden is properly on industry to prove, apparently beyond a shadow of a doubt, that there is a safe level for benzene exposure.   The Agency argues that, because of the uncertainties in this area, any other approach would render it helpless, forcing it to wait for the leukemia deaths that it believes are likely to occur  before taking any regulatory action.

We disagree.   As we read the statute, the burden was on the Agency to show, on the basis of substantial evidence, that it is at least more likely than not that long-term exposure to 10 ppm of benzene presents a significant risk of material health impairment.   Ordinarily, it is the proponent of a rule or order who has the burden of proof in administrative proceedings.   See 5 U.S.C. §  556(d).   In some cases involving toxic substances, Congress has shifted the burden of proving that a particular substance is safe onto the party opposing the proposed rule. The fact that Congress did not follow this course in enacting the Occupational Safety and Health Act indicates that it intended the Agency to bear the normal burden of establishing the need for a proposed standard.

In this case OSHA did not even attempt to carry its burden of proof.   The closest it came to making a finding that benzene presented a significant risk of harm in the workplace was its statement that the benefits to be derived from lowering the permissible exposure level from 10 to 1 ppm were "likely" to be "appreciable."   The Court of Appeals held that this finding was not supported by substantial evidence.   Of greater importance, even if it were supported by substantial evidence, such a finding would not be sufficient to satisfy the Agency's obligations under the Act. * * *

Contrary to the Government's contentions, imposing a burden on the Agency of demonstrating a significant risk of harm will not strip it of its ability to regulate carcinogens, nor will it require the Agency to wait for deaths to occur before taking any action.   First, the requirement that a "significant" risk be identified is not a mathematical straitjacket.   It is the Agency's responsibility to determine, in the first instance, what it considers to be a "significant" risk.   Some risks are plainly acceptable and others are plainly unacceptable.   If, for example, the odds are one in a billion that a person will die from cancer by taking a drink of chlorinated water, the risk clearly could not be considered significant.   On the other hand, if the odds are one in a thousand that regular inhalation of gasoline vapors that are 2% benzene will be fatal, a reasonable person might well consider the risk significant and take appropriate steps to decrease or eliminate it.   Although the Agency has no duty to calculate the exact probability of harm, it does have an obligation to find that a significant risk is present before it can characterize a place of employment as "unsafe."[4]

Second, OSHA is not required to support its finding that a significant risk exists with anything approaching scientific certainty. Although the Agency's findings must be supported by substantial evidence, 29 U.S.C. §  655(f), §  6(b)(5) specifically allows the Secretary to regulate on the basis of the "best available evidence." * * * Thus, so long as they are supported by a body of reputable scientific thought, the Agency is free to use conservative assumptions in interpreting the data with respect to carcinogens, risking error on the side of overprotection rather than underprotection.

Finally, the record in this case and OSHA's own rulings on other carcinogens indicate that there are a number of ways in which the Agency can make a rational judgment about the  relative significance of the risks associated with exposure to a particular carcinogen.[5]

It should also be noted that, in setting a permissible exposure level in reliance on less-than-perfect methods, OSHA would have the benefit of a backstop in the form of monitoring and medical testing.   Thus, if OSHA properly determined that the permissible exposure limit should be set at 5 ppm, it could still require monitoring and medical testing for employees exposed to lower levels.  By doing so, it could keep a constant check on the validity of the assumptions made in developing the permissible exposure limit, giving it a sound evidentiary basis for decreasing. * * *

[Section on dermal contact omitted]

The judgment of the Court of Appeals remanding the petition for review to the Secretary for further proceedings is affirmed.

Mr. Chief Justice Burger, concurring (opinion omitted)

Mr. Justice POWELL, concurring in part and concurring in the judgment.

* *  *  Although I regard the question as close, I do not disagree with the plurality's view that OSHA has failed, on this record, to carry its burden of proof on the threshold issues summarized above.   But even if one assumes that OSHA properly met this burden, I conclude that the statute also requires the agency to determine that the economic effects of its standard bear a reasonable relationship to the expected benefits.   An occupational health standard is neither "reasonably necessary" nor "feasible," as required by statute, if it calls for expenditures wholly disproportionate to the expected health and safety benefits.

OSHA contends that §  6(b)(5) not only permits but actually requires it to promulgate standards that reduce health risks without regard to economic effects, unless those effects would cause widespread dislocation throughout an entire industry. Under the threshold test adopted by the plurality today, this authority will exist only with respect to " significant" risks.   But the plurality does not reject OSHA's claim that it must reduce such risks without considering economic consequences less serious than massive dislocation.   In my view, that claim is untenable.

Although one might wish that Congress had spoken with greater clarity, the legislative history and purposes of the statute do not support OSHA's interpretation of the Act. It is simply unreasonable to believe that Congress intended OSHA to pursue the desirable goal of risk-free workplaces to the extent that the economic viability of particular industries--or significant segments thereof--is threatened.   As the plurality observes, OSHA itself has not chosen to carry out such a self-defeating policy in all instances.  If it did, OSHA regulations would impair the ability of American industries to compete effectively with foreign businesses and to provide employment for American workers.

I therefore would not lightly assume that Congress intended OSHA to require reduction of health risks found to be significant whenever it also finds that the affected industry can bear the costs.  Perhaps more significantly, however, OSHA's interpretation of §  6(b)(5) would force it to regulate in a manner inconsistent with the important health and safety purposes of the legislation we construe today.   Thousands of toxic substances present risks that fairly could be characterized as "significant." Even if OSHA succeeded in selecting the gravest risks for earliest regulation, a standard-setting process that ignored economic considerations would result in a serious misallocation of resources and a lower effective level of safety than could be achieved under standards set with reference to the comparative benefits available at a lower cost. I would not attribute such an irrational intention to Congress.

In these cases, OSHA did find that the "substantial costs" of the benzene regulations are justified.   But the record before us contains neither adequate documentation of this conclusion, nor any evidence that OSHA weighed the relevant considerations.   The agency simply announced its finding of cost-justification without explaining the method by which it determines that the benefits justify the costs and their economic effects. * * *

Mr. Justice REHNQUIST, concurring in the judgment.

* * *  In considering [the] alternative interpretations, my colleagues manifest a good deal of uncertainty, and ultimately divide over whether the Secretary produced sufficient evidence that the proposed standard for benzene will result in any appreciable benefits at all. * * *   I would also suggest that the widely varying positions advanced in the briefs of the parties and in the opinions of Mr. Justice STEVENS, THE CHIEF JUSTICE, Mr. Justice POWELL, and Mr. Justice MARSHALL demonstrate, perhaps better than any other fact, that Congress, the governmental body best suited and most obligated to make the choice confronting us in this litigation, has improperly delegated that choice to the Secretary of Labor and, derivatively, to this Court. * * * Read literally, the relevant portion of §  6(b)(5) is completely precatory, admonishing the Secretary to adopt the most protective standard if he can, but excusing him from that duty if he cannot. In the case of a hazardous substance for which a "safe" level is either unknown or impractical, the language of §  6(b)(5) gives the Secretary absolutely no indication where on the continuum of relative safety he should draw his line. Especially in light of the importance of the interests at stake, I have no doubt that the provision at issue, standing alone, would violate the doctrine against uncanalized delegations of legislative power.   * * *

Mr. Justice MARSHALL, with whom Mr. Justice BRENNAN, Mr. Justice WHITE, and Mr. Justice BLACKMUN join, dissenting.

In cases of statutory construction, this Court's authority is limited.   If the statutory language and legislative intent are plain, the judicial inquiry is at an end.   Under our jurisprudence, it is presumed that ill-considered or unwise legislation will be corrected through the democratic process;  a court is not permitted to distort a statute's meaning in order to make it conform with the Justices' own views of sound social policy.  

Today's decision flagrantly disregards these restrictions on judicial authority.   The plurality ignores the plain meaning of the Occupational Safety and Health Act of 1970 in order to bring the authority of the Secretary of Labor in line with the plurality's own views of proper regulatory policy.   The unfortunate consequence is that the Federal Government's efforts to protect American workers from cancer and other crippling diseases may be substantially impaired.

The first sentence of §  6(b)(5) of the Act provides:

"The Secretary, in promulgating standards dealing with toxic materials or harmful physical agents under this subsection, shall set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life."  29 U.S.C. §  655(b)(5).

In this case the Secretary of Labor found, on the basis of substantial evidence, that (1) exposure to benzene creates a risk of cancer, chromosomal damage, and a variety of nonmalignant but potentially fatal blood disorders, even at the level of 1 ppm;  (2) no safe level of exposure has been shown;  (3) benefits in the form of saved lives would be derived from the permanent standard;  (4) the number of lives that would be saved could turn out to be either substantial or relatively small;  (5) under the present state of scientific knowledge, it is impossible to calculate even in a rough way the number of lives that would be saved, at least without making assumptions that would appear absurd to much of the medical community;  and (6) the standard would not materially harm the financial condition of the covered industries. The Court does not set aside any of these findings.   Thus, it could not be plainer that the Secretary's decision was fully in accord with his statutory mandate "most adequately [to] assur[e]  . . .  that no employee will suffer material impairment of health or functional capacity  . . . ."

The plurality's conclusion to the contrary is based on its interpretation of  29 U.S.C. §  652(8), which defines an occupational safety and health standard as one "which requires conditions  . . .  reasonably necessary or appropriate to provide safe or healthful employment.  . . ."   According to the plurality, a standard is not "reasonably necessary or appropriate"  unless the Secretary is able to show that it is "at least more likely than not," ante, at 2869, that the risk he seeks to regulate is a "significant" one. . Nothing in the statute's language or legislative history, however, indicates that the "reasonably necessary or appropriate" language should be given this meaning.   Indeed, both demonstrate that the plurality's standard bears no connection with the acts or intentions of Congress and is based only on the plurality's solicitude for the welfare of regulated industries.   And the plurality uses this standard to evaluate not the agency's decision in this case, but a strawman of its own creation.

Unlike the plurality, I do not purport to know whether the actions taken by Congress and its delegates to ensure occupational safety represent sound or unsound regulatory policy.   The critical problem in cases like the ones at bar is scientific uncertainty.   While science has determined that exposure to benzene at levels above 1 ppm creates a definite risk of health impairment, the magnitude of the risk cannot be quantified at the present time.   The risk at issue has hardly been shown to be insignificant;  indeed, future research may reveal that the risk is in fact considerable.   But the existing evidence may frequently be inadequate to enable the Secretary to make the threshold finding of "significance" that the Court requires today.   If so, the consequence of the plurality's approach would be to subject American workers to a continuing risk of cancer and other fatal diseases, and to render the Federal Government powerless to take protective action on their behalf.   Such an approach would place the burden of medical uncertainty squarely on the shoulders of the American worker, the intended beneficiary of the Occupational Safety and Health Act.   It is fortunate indeed that at least a majority of the Justices reject the view that the Secretary is prevented from taking regulatory action when the magnitude of a health risk cannot be quantified on the basis of current techniques.  

Because today's holding has no basis in the Act, and because the Court has no authority to impose its own regulatory policies on the Nation, I dissent.

I

Congress enacted the Occupational Safety and Health Act as a response to what was characterized as "the grim history of our failure to heed the occupational health  needs of our workers." The failure of voluntary action and legislation at the state level had resulted in a "bleak" and "worsening" situation in which 14,500 persons had died annually as a result of conditions in the workplace.   In the four years preceding the Act's passage, more Americans were killed in the workplace than in the contemporaneous Vietnam War.   The Act was designed as "a safety bill of rights for close to 60 million workers."  Its stated purpose is "to assure so far as possible every working man and woman in the Nation safe and healthful working conditions and to preserve our human resources."  29 U.S.C. §  651(b).  

The Act is enforced primarily through two provisions.   First, a "general duty" is imposed upon employers to furnish employment and places of employment "free from recognized hazards that are causing or are likely to cause death or serious physical harm  . . . ."  29 U.S.C. §  654(a)(1).   Second, the Secretary of Labor is authorized to set "occupational safety  and health standards," defined as standards requiring "conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment and places of employment."  29 U.S.C. §  652(8).

The legislative history of the Act reveals Congress' particular concern for health hazards of "unprecedented complexity" that had resulted from chemicals whose toxic effects "are only now being discovered.. . .Recent scientific knowledge points to hitherto unsuspected cause-and-effect relationships between occupational exposures and many of the so-called chronic diseases--cancer, respiratory ailments, allergies, heart disease, and others.”  Members of Congress made repeated references to the dangers posed by carcinogens and to the defects in our knowledge of their operation and effect. One of the primary purposes of the Act was to ensure regulation of these "insidious 'silent' killers."

This special concern led to the enactment of the first sentence of 29 U.S.C. §  655(b)(5), which, as noted above, provides:

"The Secretary, in promulgating standards dealing with toxic materials or harmful physical agents under this subsection, shall set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life."

This directive is designed to implement three legislative purposes. First, Congress recognized that there may be substances that become dangerous only upon repeated or frequent exposure. The Secretary was therefore required to provide protection even from substances that would cause material impairment only upon exposure occurring throughout an employee's working life.   Second, the requirement that the Secretary act on the basis of "the best available evidence" was intended to ensure that the standard-setting process would not be destroyed by the uncertainty of scientific views.  Recognizing that existing knowledge may be inadequate, Congress did not require the Secretary to wait until definitive information could be obtained.   Thus "it is not intended that the Secretary be paralyzed by debate surrounding diverse medical opinions."   Third, Congress' special concern for the "silent killers" was felt to justify an especially strong directive to the Secretary in the standard-setting process. 

The authority conferred by §  655(b)(5), however, is not absolute.   The subsection itself contains two primary limitations.   The requirement of "material" impairment was designed to prohibit the Secretary from regulating substances that create a trivial hazard to affected employees. Moreover, all standards promulgated under the subsection must be "feasible." During the floor debates Congress expressed concern that a prior version of the bill, not clearly embodying the feasibility requirement, would require the Secretary to close down whole industries in order to eliminate risks of impairment.   This standard was criticized as unrealistic. The feasibility requirement was imposed as an affirmative limit on the standard-setting power.

The remainder of §  655(b)(5), applicable to all safety and health standards, requires the Secretary to base his standards "upon research, demonstrations, experiments, and such other information as may be appropriate."   In setting standards, the Secretary is directed to consider "the attainment of the highest degree of health and safety protection for the employee" and also "the latest available scientific data in the field, the feasibility of the standards, and experience gained under this and other health and safety laws."

The Act makes provision for judicial review of occupational safety and health standards promulgated pursuant to §  655(b)(5).   The reviewing court must uphold the Secretary's  determinations if they are supported by " substantial evidence in the record considered as a whole."  29 U.S.C. §  655 (f).   It is to that evidence that I now turn.

II

The plurality's discussion of the record in this case is both extraordinarily arrogant and extraordinarily unfair.   It is arrogant because the plurality presumes to make its own factual findings with respect to a variety of disputed issues relating to carcinogen regulation.  It should not be necessary to remind the Members of this Court that they were not appointed to undertake independent review of adequately supported scientific findings made by a technically expert agency. And the plurality's discussion is unfair because its characterization of the Secretary's report bears practically no resemblance to what the Secretary actually did in this case.   Contrary to the plurality's suggestion, the Secretary did not rely blindly on some Draconian carcinogen "policy."   If he had, it would have been sufficient for him to have observed that  benzene is a carcinogen, a proposition that respondents do not dispute.   Instead, the Secretary gathered over 50 volumes of exhibits and testimony and offered a detailed and evenhanded discussion of the relationship between exposure to benzene at all recorded exposure levels and chromosomal damage, aplastic anemia, and leukemia.   In that discussion he evaluated, and took seriously, respondents' evidence of a safe exposure level.  

The hearings on the proposed standard were extensive, encompassing 17 days from July 19 through August 10, 1977.   The 95 witnesses included epidemiologists, toxicologists, physicians, political economists, industry representatives, and members of the affected work force.   Witnesses were subjected to exhaustive questioning by representatives from a variety of interested groups and organizations.

Three basic positions were presented at the hearings.   The first position was that the proposed 1 ppm standard was necessary because exposure to benzene would cause material impairment of the health of workers no matter how low the exposure level.   Some direct evidence indicated that exposure to benzene had caused chromosomal damage, blood disorders, and leukemia at or below the 10 ppm level itself.   More important, it was suggested that the recorded effects of benzene at higher levels required an inference that leukemia and other disorders would result at levels of 1 ppm and lower, especially after the prolonged exposure typical in industrial settings.   Therefore, the standard should be set at the lowest feasible level, which was 1 ppm.

The second position was at a 1 ppm exposure level would itself pose an unwarranted threat to employee health and safety and that the available evidence necessitated a significantly lower level.   An exposure limit below 1 ppm, it was argued, would be feasible.   There were suggestions that benzene was gradually being replaced in many of the affected  industries and that most companies were already operating at or below the 1 ppm level.

The third position was that the 1971 standard should be retained.   Proponents of this position suggested that evidence linking low levels of benzene exposure to leukemia was uncertain, that the current exposure limit was sufficiently safe, and that the benefits of the proposed standard would be insufficient to justify the standard's costs.   In addition, there was testimony that the expenses required by the proposed standard would be prohibitive.

The regulations announcing the permanent standard for benzene are accompanied by an extensive statement of reasons summarizing and evaluating the results of the hearings.   The Secretary found that the evidence showed that exposure to benzene causes chromosomal damage, a variety of nonmalignant blood disorders, and leukemia. He concluded that low concentrations imposed a hazard that was sufficiently grave to call for regulatory action under the Act.

Evidence of deleterious effects.   The Secretary referred to studies which conclusively demonstrated that benzene could damage chromosomes in blood-forming cells.  Id., at 5932.   There was testimony suggesting a causal relationship between chromosomal damage and leukemia, although it could not be determined whether and to what extent such damage would impair health.  Id., at 5933. Some studies had suggested chromosomal damage at exposure levels of 10-25 ppm and lower. No quantitative dose-response curve, showing the relationship between exposure levels and incidence of chromosomal damage could yet be established.  The evidence of chromosomal damage was, in the Secretary's view, a cause for "serious concern." 

The most common effect of benzene exposure was a decrease in the levels of blood platelets and red and white blood cells.   If sufficiently severe, the result could be pancytopenia or aplastic anemia, noncancerous but potentially fatal diseases.   There was testimony that some of the nonmalignant blood disorders caused by benzene exposure could progress to, or represented, a preleukemic stage which might eventually evolve into a frank leukemia. 

Considerable evidence showed an association between benzene and nonmalignant blood disorders at low exposure levels.   Such an association had been established in one study in which the levels frequently ranged from zero to 25 ppm with some concentrations above 100 ppm, ibid.;   in another they ranged from 5 to 30 ppm, id., at 5923.   Because of the absence of adequate data, a dose-response curve showing the relationship between benzene exposure and blood disorders could not be constructed.   There was considerable testimony, however, that such disorders had resulted from exposure to benzene at or near the current level of 10 ppm and lower. The Secretary concluded that the current standard did not provide adequate protection.   He observed that a "safety factor" of 10 to 100 was generally used to discount the level at which a causal connection had been found in existing studies. Under this approach, he concluded that, quite apart from any leukemia risk, the permissible exposure limit should be set at a level considerably lower than 10 ppm.

Finally, there was substantial evidence that exposure to benzene caused leukemia.   The Secretary concluded that the evidence established that benzene was a carcinogen.   A causal relationship between benzene and leukemia was first reported in France in 1897, and since that time similar results had been found in a number of countries, including Italy, Turkey, Japan, Switzerland, the Soviet Union, and the United  States.   The latest study, undertaken by the National Institute for Occupational Safety and Health (NIOSH) in the 1970's, reported a fivefold excess over the normal incidence of leukemia among workers exposed to benzene at industrial plants in Ohio.  There was testimony that this study seriously understated the risk.

The Secretary reviewed certain studies suggesting that low exposure levels of 10 ppm and more did not cause any excess incidence of leukemia.   Those studies, he suggested, suffered from severe methodological defects, as their authors frankly acknowledged. Finally, the Secretary discussed a study suggesting a statistically significant excess in leukemia at levels of 2 to 9 ppm.  He found that, despite certain deficiencies in the study, it should be considered as consistent with other studies demonstrating an excess leukemia risk among employees exposed to benzene.

Areas of uncertainty.   The Secretary examined three areas  of uncertainty that had particular relevance to his decision.   First, he pointed to evidence that the latency period for benzene-induced leukemia could range from 2 to over 20 years.  Since lower exposure levels lead to an increase in the latency period, it would be extremely difficult to obtain evidence showing the dose-response relationship between leukemia and exposure to low levels of benzene.   Because there has been no adequate monitoring in the past, it would be practically impossible to determine what the exposure levels were at a time sufficiently distant so that the latency period would have elapsed.   The problem was compounded by the difficulty of conducting a suitable study.   Because exposure levels approaching 10 ppm had been required only recently, direct evidence showing the relationship between leukemia and exposure levels between 1 and 10 ppm would be unavailable in the foreseeable future.

Second, the Secretary observed that individuals had differences in their susceptibility to leukemia.  Among those exposed to benzene was a group of unknown but possibly substantial size having various "predisposing factors" whose members were especially vulnerable to the disease.  The permanent standard was designed to minimize the effects of exposure for these susceptible individuals as well as for the relatively insensitive, id., at 5946, and also to facilitate early diagnosis and treatment. 

The Secretary discussed the contention that a safe level of exposure to benzene had been demonstrated.   From the testimony of numerous scientists, he concluded that it had not.  He also found that although no dose-response curve could be plotted, the extent of the risk  would decline with the exposure level.  Exposure at a level of 1 ppm would therefore be less dangerous than exposure at one of 10 ppm.   The Secretary found that the existing evidence justified the conclusion that he should not "wait for answers" while employees continued to be exposed to benzene at hazardous levels.

Finally, the Secretary responded to the argument that the permissible exposure level should be zero or lower than 1 ppm.  Even though many industries had already achieved the 1 ppm level, he found that a lower level would not be feasible. 

Costs and benefits.   The Secretary offered a detailed discussion of the role that economic considerations should play in his determination.   He observed that standards must be "feasible," both economically and technologically.   In his view the permanent standard for benzene was feasible under both tests.  The economic impact would fall primarily on the more stable industries, such as petroleum refining and petrochemical production.  Id., at 5934.   These industries would be able readily to absorb the costs or to pass them on to consumers.   None of the 20 affected industries, involving 157,000 facilities and 629,000 exposed employees, id., at 5935, would be unable to bear the required expenditures, id., at 5934.   He concluded that the compliance costs were "well within the financial capability of the covered industries." Id., at 5941.   An extensive survey of the national economic impact of the standard, undertaken by a private contractor, found first-year operating costs of between $187 and $205 million, recurring annual costs of $34 million, and investment in engineering controls of about $266 million.[6]  Since respondents have not attacked   the Secretary's basic conclusions as to cost, the Secretary's extensive discussion need not be summarized here.

Finally, the Secretary discussed the benefits to be derived from the permanent standard.   During the hearings, it had been argued that the Secretary should estimate the health benefits of the proposed regulation.   To do this he would be required to construct a dose-response curve showing, at least in a rough way, the number of lives that would be saved at each possible exposure level. Without some estimate of benefits, it was argued, the Secretary's decisionmaking would be defective.   During the hearings an industry witness attempted to construct such a dose-response curve.   Restricting himself to carcinogenic effects, he estimated that the proposed standard would save two lives every six years and suggested that this relatively minor benefit would not justify the regulation's costs.

The Secretary rejected the hypothesis that the standard would save only two lives in six years.   This estimate, he concluded, was impossible to reconcile with the evidence in the record.  He determined that, because of numerous uncertainties in the existing data, it was impossible to construct a dose-response curve by extrapolating from those data to lower exposure levels. More generally, the Secretary observed  that it had not been established that there was a safe level of exposure for benzene.   Since there was considerable testimony that the risk would decline with the exposure level, the new standard would save lives.   The number of lives saved "may be appreciable," but there was no way to make a more precise determination. The question was " on the frontiers of scientific knowledge." 

The Secretary concluded that, in light of the scientific uncertainty, he was not required to calculate benefits more precisely.  Id., at 5941.   In any event he gave "careful consideration" to the question of whether the admittedly substantial costs were justified in light of the hazards of benzene exposure. He concluded that those costs were "necessary" in order to promote the purposes of the Act.

III

A

This is not a case in which the Secretary found, or respondents established, that no benefits would be derived from a permanent standard, or that the likelihood of benefits was insignificant.   Nor was it shown that a quantitative estimate of benefits could be made on the basis of "the best available evidence."   Instead, the Secretary concluded that benefits will result, that those benefits "may" be appreciable, but that the dose-response relationship of low levels of benzene  exposure and leukemia, nonmalignant blood disorders, and chromosomal damage was impossible to determine.   The question presented is whether, in these circumstances, the Act permits the Secretary to take regulatory action, or whether he must allow continued exposure until more definitive information becomes available.

As noted above, the Secretary's determinations must be upheld if supported by  "substantial evidence in the record considered as a whole."  29 U.S.C. §  655(f).   * * * Careful performance of this task is especially important when Congress has imposed the comparatively more rigorous "substantial evidence" requirement.   As we have emphasized, however, judicial review under the substantial evidence test is ultimately deferential.   The agency's decision is entitled to the traditional presumption of validity, and the court is not authorized to substitute its judgment for that of the Secretary.   If the Secretary has considered the decisional factors and acted in conformance with the statute, his ultimate decision must be given a large measure of respect. 

The plurality is insensitive to three factors which, in my view, make judicial review of occupational safety and health standards under the substantial evidence test particularly difficult.   First, the issues often reach a high level of technical complexity.   In such circumstances the courts are required to immerse themselves in matters to which they are unaccustomed  by training or experience.   Second, the factual issues with which the Secretary must deal are frequently not subject to any definitive resolution.   Often "the factual finger points, it does not conclude."  Society of Plastics Industry, Inc. v. OSHA, 509 F.2d 1301, 1308 (CA2) (Clark, J.), cert. denied, 421 U.S. 992, 95 S.Ct. 1998, 44 L.Ed.2d 482 (1975).   Causal connections and theoretical extrapolations may be uncertain.   Third, when the question involves determination of the acceptable level of risk, the ultimate decision must necessarily be based on considerations of policy as well as empirically verifiable facts.   Factual determinations can at most define the risk in some statistical way;  the judgment whether that risk is tolerable cannot be based solely on a resolution of the facts.

The decision to take action in conditions of uncertainty bears little resemblance to the sort of empirically verifiable factual conclusions to which the substantial evidence test is normally applied.   Such decisions were not intended to be unreviewable;  they too must be scrutinized to ensure that the Secretary has acted reasonably and within the boundaries set by Congress.   But a reviewing court must be mindful of the limited nature of its role. * * *  Under this standard of review, the decision to reduce the permissible exposure level to 1 ppm was well within the Secretary's authority.   The Court of Appeals upheld the Secretary's conclusions that benzene causes leukemia, blood disorders, and chromosomal damage even at low levels, that an exposure level of 10 ppm is more dangerous than one of 1 ppm, and that benefits will result from the proposed standard.   It did not set aside his finding that the number of lives that would be saved was not subject to quantification.  Nor did it question his conclusion that the reduction was "feasible."

In these circumstances, the Secretary's decision was reasonable and in full conformance with the statutory language requiring that he "set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life."  29 U.S.C. §  655(b)(5).   On this record, the Secretary could conclude that regular exposure above the 1 ppm level would pose a definite risk resulting in material impairment to some indeterminate but possibly substantial number of employees. Studies revealed hundreds of deaths attributable to benzene exposure.   Expert after expert testified that no safe level of exposure had been shown and that the extent of the risk declined with the exposure level.   There was some direct evidence of incidence of leukemia, nonmalignant blood disorders, and chromosomal damage at exposure levels of 10 ppm and below.   Moreover, numerous experts testified that existing evidence required an inference that an exposure level above 1 ppm was hazardous.   We have stated that "well-reasoned expert testimony--based on what is known and uncontradicted by empirical evidence--may in and of itself be 'substantial evidence' when first-hand evidence on the question  . . .  is unavailable."  FPC v. Florida Power & Light Co., 404 U.S. 453, 464-465, 92 S.Ct. 637, 644, 30 L.Ed.2d 600 (1972).   Nothing in the Act purports to prevent the Secretary from acting when definitive information as to the quantity of a standard's benefits is unavailable.[7] Where, as here, the deficiency in  knowledge relates to the extent of the benefits rather than their existence, I see no reason to hold that the Secretary has exceeded his statutory authority.

B

The plurality avoids this conclusion through reasoning that may charitably be described as obscure.   According to the plurality, the definition of occupational safety and health standards as those "reasonably necessary or appropriate to provide safe or healthful  . . .  working conditions" requires the Secretary to show that it is "more likely than not" that the risk he seeks to regulate is a "significant" one.  The plurality does not show how this requirement can be plausibly derived from the "reasonably necessary or appropriate" clause.   Indeed, the plurality's reasoning is refuted by the Act's language, structure, and legislative history, and it is foreclosed by every applicable guide to statutory construction.   In short, the plurality's standard is a fabrication bearing no connection with the acts or intentions of Congress.

At the outset, it is important to observe that "reasonably necessary or appropriate" clauses are routinely inserted in regulatory legislation, and in the past such clauses have uniformly been interpreted as general provisos that regulatory actions must bear a reasonable relation to those statutory purposes set forth in the statute's substantive provisions.   The Court has never--until today--interpreted a "reasonably necessary or appropriate" clause as having a substantive content that supersedes a specific congressional directive embodied in a provision that is focused more particularly on an agency's authority.   This principle, of course, reflects the common understanding that the determination of whether regulations are "reasonably necessary" may be made only by reference to the legislative judgment reflected in the statute;  it must not be based on a court's own, inevitably subjective view of what steps should be taken to promote perceived statutory goals.

The plurality suggests that under the "reasonably necessary" clause, a workplace is not "unsafe" unless the Secretary is able to convince a reviewing court that a "significant" risk is at issue.  That approach is particularly embarrassing in this case, for it is contradicted by the plain language of the Act.   The plurality's interpretation renders utterly superfluous the first sentence of §  655(b)(5), which, as noted above, requires the Secretary to set the standard "which most adequately assures  . . .  that no employee will suffer material impairment of health." Indeed, the plurality's interpretation reads that sentence out of the Act.   By so doing, the plurality makes the test for standards regulating toxic substances and harmful physical agents substantially identical to the test for standards generally--plainly the opposite of what Congress intended.   And it is an odd canon of construction that would insert in a vague and general definitional clause a threshold requirement that overcomes the specific language placed in a standard-setting provision.   The most elementary principles of statutory construction demonstrate that precisely the opposite interpretation is appropriate. In short, Congress could have provided that the Secretary may not take regulatory action until the existing  scientific evidence proves the risk as issue to be "significant," but it chose not to do so.

The plurality's interpretation of the "reasonably necessary or appropriate" clause is also conclusively refuted by the legislative history.   * * *  The plurality ignores applicable canons of construction, apparently because it finds their existence inconvenient.   But as we stated quite recently, the inquiry into statutory purposes should be "informed by an awareness that the regulation is entitled to deference unless it can be said not to be a reasoned and supportable interpretation of the Act."  Whirlpool Corp. v. Marshall, 445 U.S. 1, 11, 100 S.Ct. 883, 890, 63 L.Ed.2d 154 (1980).   Can it honestly be said that the Secretary's interpretation of the Act is "unreasoned" or "unsupportable"?   And as we stated in the same case, "safety legislation is to be liberally construed to effectuate the congressional purpose. The plurality's disregard of these principles gives credence to the frequently voiced criticism that they are honored only when the Court finds itself in substantive agreement with the agency action at issue.

In short, today's decision represents a usurpation of decisionmaking authority that has been exercised by and properly belongs with Congress and its authorized representatives.   The plurality's construction has no support in the statute's language, structure, or legislative history.   The threshold finding that the plurality requires is the plurality's own invention.   It bears no relationship to the acts or intentions of Congress, and it can be understood only as reflecting the personal views of the plurality as to the proper allocation of resources for safety in the American workplace. * * *  In these circumstances it seems clear that the Secretary found a risk that is  "significant" in the sense that the word is normally used.   There was some direct evidence of chromosomal damage, nonmalignant blood disorders, and leukemia at exposures at or near 10 ppm and below.   In addition, expert after expert testified that the recorded effects of benzene exposure at higher levels justified an inference that an exposure level above 1 ppm was dangerous.   The plurality's extraordinarily searching scrutiny of this factual record reveals no basis for a conclusion that quantification is, on the basis of "the best available evidence," possible at the present time.   If the Secretary decided to wait until definitive information was available, American workers would be subjected for the indefinite future to a possibly substantial risk of benzene-induced leukemia and other illnesses.   It is unsurprising, at least to me, that he concluded that the statute authorized him to take regulatory action now.

Under these circumstances, the plurality's requirement of identification of a  "significant" risk will have one of two consequences.   If the plurality means to require the Secretary realistically to "quantify" the risk in order to satisfy a court that it is "significant," the record shows that the plurality means to require him to do the impossible.   But the regulatory inaction has very significant costs of its own.   The adoption of such a test would subject American workers to a continuing risk of cancer and other serious diseases;  it would disable the Secretary from regulating a wide variety of carcinogens for which quantification simply cannot be undertaken at the present time. * * *

D

Since the plurality's construction of the "reasonably necessary or appropriate" clause is unsupportable, I turn to a brief discussion of the other arguments that respondents offer in support of the judgment below.

First, respondents characterize the Act as a pragmatic statute designed to balance the benefits of a safety and health regulation against its costs. Respondents observe that the statute speaks in terms of relative protection by providing that safety must be assured "so far as possible," 29 U.S.C. §  651(b), and by stating that the "no material impairment" requirement is to be imposed only "to the extent feasible." Respondents contend that the term feasible should be read to require consideration of the economic burden of a standard, not merely its technological achievability.   I do not understand the Secretary to disagree.   But respondents present no argument that the expenditure required by the benzene standard is not feasible in that respect.   The Secretary concluded on the basis of substantial evidence that the costs of the standard would be readily absorbed by the 20 affected industries.   One need not define the feasibility requirement with precision in order to conclude that the benzene standard is "feasible" in the sense that it will not materially harm the financial condition of the regulated industries.

Respondents suggest that the feasibility requirement should be understood not merely to refer to a standard's expense, but also to mandate a finding that the benefits of an occupational safety and health standard bear a reasonable relation  to its costs.   I believe that the statute's language, structure, and legislative history foreclose respondents' position.   In its ordinary meaning an activity is "feasible" if it is capable of achievement, not if its benefits outweigh its costs.   See Webster's Third New International Dictionary 831 (1976).   Moreover, respondents' interpretation would render §  655(b)(5) internally inconsistent by reading into the term "feasible" a requirement irreconcilable with the express language authorizing the Secretary to set standards assuring that "no employee will suffer material impairment  . . . ."   Respondents' position would render that language merely hortatory.   As noted above, no cost-benefit analysis is referred to at any point in the statute or its legislative history, an omission which cannot be deemed inadvertent in light of the explicit cost-benefit requirements inserted into other regulatory legislation. Finally, the legislative history of the feasibility requirement demonstrates that Congress' sole concern was that standards be economically and technologically achievable.   The legislative intent was to prevent the Secretary from materially harming the financial condition of regulated industries in order to eliminate risks of impairment.   Congress did not intend to preclude the Secretary from taking regulatory action where, as here, no such threat to industry is posed.

In order to decide these cases, however, it is not necessary to resolve the question whether the term "feasible" may contemplate some balancing of the costs and benefits of regulatory action. Taking into account the uncertainties in existing knowledge, the Secretary made an express finding that the hazards of benzene exposure were sufficient to justify the regulation's costs.  Any requirement to balance costs and benefits cannot be read to invalidate this wholly rational conclusion.   A contrary result, forcing the Secretary to wait for quantitative data that may not be available in the foreseeable future, would run directly counter to the protective purposes of the Act. * * *   In recent years there has been increasing recognition that the products of technological development may have harmful effects whose incidence and severity cannot be predicted with certainty.   The responsibility to regulate such products has fallen to administrative agencies.   Their task is not an enviable one.   Frequently no clear causal link can be established between the regulated substance and the harm to be averted.   Risks of harm are often uncertain, but inaction has considerable costs of its own.   The agency must decide whether to take regulatory action against possibly substantial risks or to wait until more definitive information becomes available--a judgment  which by its very nature cannot be based solely on determinations of fact.

Those delegations, in turn, have been made on the understanding that judicial review would be available to ensure that the agency's determinations are supported by substantial evidence and that its actions do not exceed the limits set by Congress.   * * *  Because the approach taken by the plurality is so plainly irreconcilable with the Court's proper institutional role, I am certain that it will not stand the test of time.   In all likelihood, today's decision will come to be regarded as an extreme reaction to a regulatory scheme that, as the Members of the plurality perceived it, imposed an unduly harsh burden on regulated industries.   But as the Constitution "does not enact Mr. Herbert Spencer's Social Statics," Lochner v. New York, 198 U.S. 45, 75, 25 S.Ct. 539, 546, 49 L.Ed. 937 (1905) (Holmes, J., dissenting), so the responsibility to scrutinize federal administrative action does not authorize this Court to strike its own balance between the  costs and benefits of occupational safety standards.   I am confident that the approach taken by the plurality today, like that in  Lochner itself, will eventually be abandoned, and that the representative branches of government will once again be allowed to determine the level of safety and health protection to be accorded to the American worker.

[1] Section 655(c) provides:

"(1) The Secretary shall provide, without regard to the requirements of chapter 5 of title 5, for an emergency temporary standard to take immediate effect upon publication in the Federal Register if he determines (A) that employees are exposed to grave danger from exposure to substances or agents determined to be toxic or physically harmful or from new hazards, and (B) that such emergency standard is necessary to protect employees from such danger.

"(2) Such standard shall be effective until superseded by a standard promulgated in accordance with the procedures prescribed in paragraph (3) of this subsection.

[2] * * * Mr. Justice MARSHALL states that our view of §  3(8) would make the first sentence in §  6(b)(5) superfluous.   We disagree.   The first sentence of §  6(b)(5) requires the Secretary to select a highly protective standard once he has determined that a standard should be promulgated.   The threshold finding that there is a need for such a standard in the sense that there is a significant risk in the workplace is not unlike the threshold finding that a chemical is toxic or a physical agent is harmful.   Once the Secretary has made the requisite threshold finding, §  6(b)(5) directs him to choose the most protective standard that still meets the definition of a standard under §  3(8), consistent with feasibility.

[3] OSHA's proposed generic cancer policy, 42 Fed.Reg. 54148 (1977), indicates that this possibility is not merely hypothetical.   Under its proposal, whenever there is a certain quantum of proof--either from animal experiments, or, less frequently, from epidemiological studies--that a substance causes cancer at any exposure level, an emergency temporary standard would be promulgated immediately, requiring employers to provide monitoring and medical examinations and to reduce exposures to the lowest feasible level.   A proposed rule would then be issued along the same lines, with objecting employers effectively foreclosed from presenting evidence that there is little or no risk associated with current exposure levels.   Id., at 54154-54155;  29 CFR, Part 1990 (1977).

The scope of the proposed regulation is indicated by the fact that NIOSH has published a list of 2,415 potential occupational carcinogens, NIOSH, Suspected Carcinogens:  A Subfile of the Registry of Toxic Effects of Chemical Substances (HEW Pub. No. 77-149, 2d ed. 1976).   OSHA has tentatively concluded that 269 of these substances have been proved to be carcinogens and therefore should be subject to full regulation.   See OSHA Press Release, USDL 78-625 (July 14, 1978).

[4]  In his dissenting opinion, Mr. Justice MARSHALL states:  "[W]hen the question involves determination of the acceptable level of risk, the ultimate decision must necessarily be based on considerations of policy as well as empirically verifiable facts.   Factual determinations can at most define the risk in some statistical way;  the judgment whether that risk is tolerable cannot be based solely on a resolution of the facts."   We agree.   Thus, while the Agency must support its finding that a certain level of risk exists by substantial evidence, we recognize that its determination that a particular level of risk is "significant" will be based largely on policy considerations.   At this point we have no need to reach the issue of what level of scrutiny a reviewing court should apply to the latter type of determination.

[5]  For example, in the coke-oven emissions standard, OSHA had calculated that 21,000 exposed coke-oven workers had an annual excess mortality of over 200 and that the proposed standard might well eliminate the risk entirely.     In hearings on the coke-oven emissions standard the Council on Wage and Price Stability estimated that 8 to 35 lives would be saved each year, out of an estimated population of 14,000 workers, as a result of the proposed standard. Although noting that the range of benefits would vary depending on the assumptions used, OSHA did not make a finding as to whether its own staff estimate or CWPS's was correct, on the ground that it was not required to quantify the expected benefits of the standard or to weigh those benefits against the projected costs.  In other proceedings, the Agency has had a good deal of data from animal experiments on which it could base a conclusion on the significance of the risk.   For example, the record on the vinyl chloride standard indicated that a significant number of animals had developed tumors of the liver, lung, and skin when they were exposed to 50 ppm of vinyl chloride over a period of 11 months.   One hundred out of 200 animals died during that period.  39 Fed.Reg. 35890, 35891 (1974).   Similarly, in a 1974 standard regulating 14 carcinogens, OSHA found that one of the substances had caused lung cancer in mice or rats at 1 ppm and even 0.1 ppm, while another had caused tumors in 80% of the animals subjected to high doses. In this case the Agency did not have the benefit of animal studies, because scientists have been unable as yet to induce leukemia in experimental animals as a result of benzene exposure.   It did, however, have a fair amount of epidemiological evidence, including both positive and negative studies.   Although the Agency stated that this evidence was insufficient to construct a precise correlation between exposure levels and cancer risks, it would at least be helpful in determining whether it is more likely than not that there is a significant risk at 10 ppm. * * *

[6] The plurality's estimate of the amount of expenditure per employee, see ante, at 2858, is highly misleading.   Most of the costs of the benzene standard would be incurred only once and would thus protect an unascertainable number of employees in the future;  that number will be much higher than the number of employees currently employed.

[7] This is not to say that the Secretary is prohibited from examining relative costs and benefits in the process of setting priorities among hazardous substances, or that systematic consideration of costs and benefits is not to be attempted in the standard-setting process.   Efforts to quantify costs and benefits, like statements of reasons generally, may help to promote informed consideration of decisional factors and facilitate judicial review.   See Dunlop v. Bachowski, 421 U.S. 560, 571-574, 95 S.Ct. 1851, 1859-61, 44 L.Ed.2d 377 (1975).   The Secretary indicates that he has attempted to quantify costs and benefits in the past.   See 43 Fed.Reg. 54354, 54427-54431 (1978) (lead);  id., at 27350, 27378-27379 (cotton dust). It is not necessary in the present litigation to say whether the Secretary must show a reasonable relation between costs and benefits.   Discounting for the scientific uncertainty, the Secretary expressly--and reasonably-- found such a relation here.

After the Benzene Case was decided, the scientific evidence of the link between benzene and leukemia grew.  In 1987, OSHA issued a new standard, setting the permissible exposure limit (PEL) at 1.0 ppm. The new scientific studies concluded that there was significant increase in mortality from leukemia for workers exposed to benzene at below the 10 ppm level.  The rulemaking also followed the filing of a Writ of Mandamus against the agency, demanding that OSHA issue a reduced benzene standard in light of this scientific evidence.  You can find the current standard at 29 CFR 1910.1028.  The justification for the adoption of the more protective standard can be found in the Federal Register at 52 FR 34460-01, Friday, September 11, 1987. 

The following is an excerpt from the 1987 justification for the revised standard. It provides some insight into OSHA’s reading of the benzene decision.  This excerpt is from the Executive Summary of the rulemaking: 

The 1987 final benzene standard lowers the 8-hour time-weighted average (TWA) for occupational exposures to benzene from 10 parts per million (ppm) to 1 ppm and the short-term exposure limit (STEL) from 25 ppm to 5 ppm. Various important industrial hygiene provisions including monitoring, engineering controls, respiratory protection, medical surveillance and hazard communication are incorporated.  The standard will result in a substantial reduction in the workers' risk of developing leukemia and other diseases of the blood and blood-forming organs. According to OSHA's best estimates, a working lifetime of exposure to benzene at 10 ppm would cause an excess leukemia risk of 95 leukemia deaths per 1000 exposed workers. Other reasonable estimates of risk range from 8 to 160 deaths per 1000 workers. These are clearly significant risks, greatly exceeding the excess risks of occupationally related accident deaths in high and average risk industries which are 30 and 3 per 1000 workers, respectively.

The new standard will create a minimum reduction in excess risk of 90 percent, a very substantial reduction based on comparing exposures at 10 ppm to 1 ppm. On the basis of the current distribution of exposures, OSHA estimates that the new standard will prevent a minimum of 326 deaths from leukemia and diseases of the blood and blood-forming organs over a working lifetime of 45 years.

In reality, the reduction in risk will be much greater. The standard incorporates an action level of 0.5 ppm. below which many industrial hygiene and medical surveillance provisions are not required. Many employers having workplaces in which such reductions are feasible will reduce employee exposures to below 0.5 ppm in order to have a high degree of confidence that they are protecting their employees, to avoid the costs of the industrial hygiene and medical surveillance provisions, and to have an adequate margin for exposure variability when there is an inspection.

Employers with exposures above the action level are required to implement a variety of industrial hygiene provisions which will increase employee protection. The monitoring provisions increase the probability that overexposures will be detected and reduced. The medical surveillance provisions will aid in the early detection of employees with abnormal blood counts.

The combination of these provisions, when carried out, assures OSHA that workers will be substantially better protected than the numbers estimated by the risk assessments indicate. Indeed, OSHA believes employers who fully comply with the standard's provisions as intended will provide substantial protection to their benzene-exposure workers.

OSHA wishes to commend industry, labor and public interest groups whose combined efforts have already led to substantial lowering of benzene exposures. These groups have also assisted OSHA in analyzing the data and coming to better decisions through the rulemaking process. OSHA sincerely hopes that the remaining, relatively narrow differences of opinion regarding practical issues of workers protection will not prevent the rapid implementation of the standard.

OSHA also believes that the standard, in addition to being protective, is cost-effective. A carefully developed series of practical exclusions for industry sectors where technology assures that exposures will be under the action level, concentrates industrial hygiene resources in areas of need. Similarly, a series of provisions reflective of industrial hygiene experience permits employers the choice of compliance strategies in maintenance and repair activities, when exposures are intermittent or are for a short term, where respirators are sometimes the control of choice. However, engineering and work practice controls are given preference in production activities and more continual exposures where they are generally the most effective control strategy.

OSHA is confident that the standard is technically feasible and that engineering controls, where required, can generally achieve the 1 ppm 8-hour TWA and 5 ppm STEL, consistently, with a high degree of confidence in most production operations in the covered industries. This conclusion is based on an extensive contractor survey, evidence submitted to the record and detailed analyses. Types of controls available include leak detection and repair, vapor recovery, automated sampling, dual seal valves, enclosures and many others. Exposures are already quite low as benzene and mixtures containing substantial amounts of benzene are handled in closed systems. Where one control may not be successful, others are available.

OSHA has concluded that the 1 ppm TWA is the lowest feasible level for industry in general. The action level will strongly encourage those employers who can do so to achieve exposures below 0.5 ppm

The standards will cost approximately $24 million in annualized costs (annual costs plus annualized costs of capital). This is clearly economically feasible, representing less than 0.2 percent of the annual revenues in the various industry sectors. 

* * In 1980, the Supreme Court in Industrial Union Dept., AFL-CIO v. American Petroleum Institute (IUD v. API). 448 U.S. 607 (1980), held that before OSHA issued a new health standard it must attempt to quantify risk, if possible, and determine whether the risk is significant. It must also determine that the new standard would achieve a substantial reduction in significant risk. OSHA had not performed a quantitative risk assessment on benzene prior to issuing the 1978 standard. In addition, the Supreme Court's analysis indicated that it desires a more careful economic analysis. * * *  Since the issuance of the 1978 standard and 1980 Supreme Court decision, there have been a number of major scientific developments. The two major epidemiologic studies available at the time have been upgraded and extended. (Infante/Rinsky and Ott/Bond). Several additional major epidemiologic studies have been completed (Wong, Decoufle et al.). These continue to demonstrate that benzene exposure causes increased risk of leukemia and other blood disorders. Several recent studies have demonstrated that benzene causes multiple-site specific cancers in animals. Other studies, which took substantially longer and proved to be more complex than predicted, have definitively demonstrated that benzene is absorbed through the skin. In addition, a number of risk assessments have been performed.

A series of studies (Infante 1977, Rinsky 1981, Rinsky 1986), analyzing the mortality of workers exposed to benzene at two rubber hydrochloride manufacturing locations, demonstrated excess risk of leukemia. The most recent demonstrated a Standardized Mortality Ratio (SMR) of 337 leukemia and 409 for multiple myeloma (An SMR of 100 is the normal value if an excess is not observed. An SMR of 200 represents a 100% excess risk over normal). The Rinsky 1986 study has excellent follow-up, 98.6% of the employees were traced to determine whether they were dead or alive and if dead, the cause of death. The study also carefully analyzed extensive past exposure data and was able to assign doses to individuals exposed 10 to 40 years in the past.
The Rinsky 1986 study also demonstrates a dose-response relationship. Workers who had lower exposure to benzene had a smaller excess risk (SMR=105). Medium exposure workers experienced medium excess risks (SMR=322 & 1186) and high exposure workers, very high excess risk (SMR=6637). The dose-response relationship increases the confidence in the results, provides a stronger basis for risk assessment and provides measured as opposed to extrapolated evidence that lowering exposure substantially reduces risk.

The Ott 1978 study and the Bond 1986 follow-up study demonstrate myelogenous leukemia risks about 4 times greater for benzene-exposed workers than for the general population. Because these studies were of small numbers of employees, the confidence intervals of the relative risks are large. However, the workers were exposed to low levels of benzene with average exposure being about 5 ppm of benzene. * * * The Chemical Manufacturers Association sponsored a study, Wong, 1983, of workers in chemical plants. The mortalities of the benzene-exposed workers at the plant were compared to the mortalities or workers at the plants who were not exposed to benzene and to the general population. A statistically demonstrable dose response relationship between benzene exposure and leukemia was observed.

OSHA believes these studies clearly demonstrate an association between benzene exposure and increased risk of leukemia. The Agency does not believe this conclusion is now seriously challenged. * * *

OSHA has followed a consistent approach for determining the significance of risk since 1982 when it first put into practice the directions of the Supreme Court in IUD v. API, the benzene decision. The approach has been used for the arsenic and ETO final standards which have been upheld by 2 Courts of Appeal. The approach was also used in the asbestos final standard and in the ethylene dibromide and formaldehyde proposals.* * *  OSHA concludes as it preliminarily concluded in the proposal that significant risk exists at the 10 ppm level. Based on the best supported estimates of 95 excess deaths per 1000, the risk from exposure to benzene at 10 ppm is clearly greater than that in the riskiest occupations and greater than the risk of one in 1000 which the Supreme Court found a reasonable person might find significant. Even the lowest estimate of risk, 8 per 1000 at 10 ppm, is greater than both the risks of average occupations and the one in 1000 risk example given by the Supreme Court. Therefore, based on any of these estimates, OSHA would determine that the risk is significant. No major party challenged OSHA's decision to reduce exposures from 10 ppm.

OSHA also concludes that the new benzene standard will result in a substantial reduction in significant risk. All the risk assessments indicate that the reduction in risk will be at least 90 percent, a clearly substantial reduction. * * *  In addition, the standard at a minimum, will save 326 lives over a working lifetime, a substantial number.
OSHA believes that the actual reduction in risk will be substantially greater than the 90 percent predicted by its preferred risk assessment. The action level, industrial hygiene and medical provisions further reduce risk. OSHA also finally concludes after reviewing all the evidence and comments and as it preliminarily concluded in its proposal, that the final standard is carrying out Congressional intent within the limits of feasibility and does not attempt to reduce insignificant risks * *  * The standard places a preference on engineering and work practice controls for production activities or where exposures to benzene over 1 ppm are more frequent than intermittent. However, the employer may choose a compliance strategy including use of respirators in maintenance and repair activities, when exposures are intermittent in nature and limited in duration, during the time before engineering controls can be installed or where they are not feasible, and when benzene will be present in the area less than 30 days a year. This approach was supported almost without exception in the record and reflects industrial hygiene expertise as the best approach to protecting employees. 

Justice BRENNAN delivered the opinion of the Court.

Congress enacted the Occupational Safety and Health Act of 1970 (Act) "to assure so far as possible every working man and woman in the Nation safe and healthful working conditions...."  §  2(b), 84 Stat. 1590, 29 U.S.C. §  651(b).   The Act authorizes the Secretary of Labor to establish, after notice and opportunity to comment, mandatory nationwide standards governing health and safety in the workplace.  29 U.S.C. § §  655(a), (b).   In 1978, the Secretary, acting through the Occupational Safety and Health Administration (OSHA), promulgated a standard limiting occupational exposure to cotton dust, an airborne particle byproduct of the preparation and manufacture of cotton products, exposure to which induces a "constellation of respiratory effects" known as "byssinosis.  This disease was one of the expressly recognized health hazards that led to passage of the Act.

Petitioners in these consolidated cases, representing the interests of the cotton industry, challenged the validity of the "Cotton Dust Standard" in the Court of Appeals for the District of Columbia Circuit pursuant to §  6(f) of the Act.  They contend in this Court, as they did below, that the Act requires OSHA to demonstrate that its Standard reflects a reasonable relationship between the costs and benefits associated with the Standard.   Respondents, the Secretary of Labor and two labor organizations, counter that Congress balanced the costs and benefits in the Act itself, and that the Act should therefore be construed not to require OSHA to do so.   They interpret the Act as mandating that OSHA enact the most protective standard possible to eliminate a significant risk of material health impairment, subject to the constraints of economic and technological feasibility.   The Court of Appeals held that the Act did not require OSHA to compare costs and benefits.  We granted certiorari to resolve this important question, which was presented but not decided in last Term's Industrial Union Dept. v. American Petroleum Institute, 448 U.S. 607, 100 S.Ct. 2844, 65 L.Ed.2d 1010 (1980), and to decide other issues related to the Cotton Dust Standard.

I

Byssinosis, known in its more severe manifestations as "brown lung" disease, is a serious and potentially disabling respiratory disease primarily caused by the inhalation of cotton dust.^[1]  Byssinosis is a "continuum ... disease," that has been categorized into four grades.^[2]  In its least serious form, byssinosis produces both subjective symptoms, such as chest tightness, shortness of breath, coughing, and wheezing, and objective indications of loss of pulmonary functions.  In its most serious form, byssinosis is a chronic and irreversible obstructive pulmonary disease, clinically similar to chronic bronchitis or emphysema, and can be severely disabling.  Ibid.  At worst, as is true of other respiratory diseases including bronchitis, emphysema, and asthma, byssinosis can create an additional strain on cardiovascular functions and can contribute to death from heart failure. One authority has described the increasing seriousness of byssinosis as follows:

"In the first few years of exposure [to cotton dust], symptoms occur on Monday, or other days after absence from the work environment;  later, symptoms occur on other days of the week;  and eventually, symptoms are continuous, even in the absence of dust exposure."   A. Bouhuys, Byssinosis in the United States, Exhibit 6-16, App. 15. ^[3]

While there is some uncertainty over the manner in which the disease progresses from its least serious to its disabling grades, it is likely that prolonged exposure contributes to the progression.   It also appears that a worker may suddenly contract a severe grade without experiencing milder grades of the disease

Estimates indicate that at least 35,000 employed and retired cotton mill workers, or 1 in 12 such workers, suffer from the most disabling form of byssinosis.  The Senate Report accompanying the Act cited estimates that 100,000 active and retired workers suffer from some grade of the disease.  One study found that over 25% of a sample of active cotton-preparation and yarn-manufacturing workers suffer at least some form of the disease at a dust exposure level common prior to adoption of the current Standard.  Other studies confirm these general findings on the prevalence of byssinosis.

Not until the early 1960's was byssinosis recognized in the United States as a distinct occupational hazard associated with cotton mills.^[4] In 1966, the American Conference of Governmental Industrial Hygienists (ACGIH), a private organization, recommended that exposure to total cotton dust be limited to a "threshold limit value" of 1,000 micrograms per cubic meter of air (1000 ug/m 3) averaged over an 8-hour workday.  The United States Government first regulated exposure to cotton dust in 1968, when the Secretary of Labor, pursuant to the Walsh-Healey Act, 41 U.S.C. §  35(e), promulgated airborne contaminant threshold limit values, applicable to public contractors, that included the 1,000 ug/m 3 limit for total cotton dust.  34 Fed.Reg. 7953 (1969). Following passage of the Act in 1970, the 1,000 ug/m 3 standard was adopted as an "established Federal standard" under §  6(a) of the Act, 84 Stat. 1593, 29 U.S.C. §  655(a), a provision designed to guarantee immediate protection of workers for the period between enactment of the statute and promulgation of permanent standards.

In 1974, ACGIH, adopting a new measurement unit of respirable rather than total dust, lowered its previous exposure limit recommendation to 200 ug/m 3 measured by a vertical elutriator, a device that measures cotton dust particles 15 microns or less in diameter.  That same year, the Director of the National Institute for Occupational Safety and Health (NIOSH),  pursuant to the Act, 29 U.S.C. § §  669(a)(3), 671(d)(2), submitted to the Secretary of Labor a recommendation for a cotton dust standard with a permissible exposure limit (PEL) that "should be set at the lowest level feasible, but in no case at an environmental concentration as high as 0.2 mg lint-free cotton dust/cu m," or 200 ug/m 3 of lint-free respirable dust.^[5] Ex. 1, Ct. of App.J.A. 11;  41 Fed.Reg. 56500, col. 1 (1976).   Several months later, OSHA published an Advance Notice of Proposed Rulemaking, 39 Fed.Reg. 44769 (1974), requesting comments from interested parties on the NIOSH recommendation and other related matters.   Soon thereafter, the Textile Worker's Union of America, joined by the North Carolina Public Interest Research Group, petitioned the Secretary, urging a more stringent PEL of 100 ug/m 3.

On December 28, 1976, OSHA published a proposal to replace the existing federal standard on cotton dust with a new permanent standard, pursuant to §  6(b)(5) of the Act, 29 U.S.C. §  655(b)(5).  The proposed standard contained a PEL of 200 ug/m 3 of vertical elutriated lint-free respirable cotton dust for all segments of the cotton industry.  It also suggested an implementation strategy for achieving the PEL that relied on respirators for the short term and engineering controls for the long term. OSHA invited interested parties to submit written comments within a 90-day period.

Following the comment period, OSHA conducted three hearings in Washington, D. C., Greenville, Miss., and Lubbock, Tex., that lasted over 14 days.   Public participation was widespread, involving representatives from industry and the work force, scientists, economists, industrial hygienists, and many others.  By the time the informal rulemaking procedure had terminated, OSHA had received 263 comments and 109 notices of intent to appear at the hearings.   The voluminous record, composed of a transcript of written and oral testimony, exhibits, and post-hearing comments and briefs, totaled some 105,000 pages.  OSHA issued its final Cotton Dust Standard--the one challenged in the instant case--on June 23, 1978.   Along with an accompanying statement of findings and reasons, the Standard occupied 69 pages of the Federal Register.

The Cotton Dust Standard promulgated by OSHA establishes mandatory PEL's over an 8-hour period of 200 ug/m 3 for yarn manufacturing, 750 ug/m 3 for slashing and weaving operations, and 500 ug/m 3 for all other processes in the cotton industry. These levels represent a relaxation of the proposed PEL of 200 ug/m 3 for all segments of the cotton industry.

OSHA chose an implementation strategy for the Standard that depended primarily on a mix of engineering controls, such as installation of ventilation systems, and work practice controls, such as special floor-sweeping procedures.  Full compliance with the PEL's is required within four years, except to the extent that employers can establish that the engineering and work practice controls are infeasible.  §  1910.1043(e)(1).   During this compliance period, and at certain other  times, the Standard requires employers to provide respirators to employees.  §  1910.1043(f).   Other requirements include monitoring of cotton dust exposure, medical surveillance of all employees, annual medical examinations, employee education and training programs, and the posting of warning signs.   A specific provision also under challenge in the instant case requires employers to transfer employees unable to wear respirators to another position, if available, having a dust level at or below the Standard's PEL's, with "no loss of earnings or other employment rights or benefits as a result of the transfer."  §  1910.1043(f)(2)(v).

On the basis of the evidence in the record as a whole, the Secretary determined that exposure to cotton dust represents a "significant health hazard to employees"  and that "the prevalence of byssinosis should be significantly reduced" by the adoption of the Standard's PEL's.   In assessing the health risks from cotton dust and the risk reduction obtained from lowered exposure, OSHA relied particularly on data showing a strong linear relationship between the prevalence of byssinosis and the concentration of lint-free respirable cotton dust.  Even at the 200 ug/m 3 PEL, OSHA found that the prevalence of at least Grade 1/2 byssinosis would be 13% of all employees in the yarn manufacturing sector. 

In promulgating the Cotton Dust Standard, OSHA interpreted the Act to require adoption of the most stringent standard to protect against material health impairment, bounded only by technological and economic feasibility.  OSHA therefore rejected the industry's alternative proposal for a PEl of 500 ug/m 3 in yarn manufacturing, a proposal which would produce a 25% prevalence of at least Grade 1/2 byssinosis.   The agency expressly found the Standard to be both technologically and economically feasible based on the evidence in the record as a whole.   Although recognizing that permitted levels of exposure to cotton dust would still cause some byssinosis, OSHA nevertheless rejected the union proposal for a 100 ug/m 3 PEL because it was not within the "technological capabilities of the industry."  Similarly, OSHA set PEL's for some segments of the cotton industry at 500 ug/m 3 in part because of limitations of technological feasibility. Finally, the Secretary found that "engineering dust controls in weaving may not be feasible even with massive expenditures by the industry," and for that and other reasons adopted a less stringent PEL of 750 ug/m 3 for weaving and slashing.

The Court of Appeals upheld the Standard in all major respects. * * *   Rejecting the industry position that OSHA must demonstrate that the benefits of the Standard are proportionate to its costs, the court instead agreed with OSHA's interpretation that the Standard must protect employees against material health impairment subject only to the limits of technological and economic feasibility.   The court held that "Congress itself struck the balance between costs and benefits in the mandate to the agency" under §  6(b)(5) of the Act, 29 U.S.C. §  655(b)(5), and that OSHA is powerless to circumvent that judgment by adopting less than the most protective feasible standard.  Finally, the court held that the agency's determination of technological and economic feasibility was supported by substantial evidence in the record as a whole. 

We affirm in part, and vacate in part.

II

The principal question presented in these cases is whether the Occupational Safety and Health Act requires the Secretary, in promulgating a standard pursuant to §  6(b)(5) of the Act, 29 U.S.C. §  655(b)(5), to determine that the costs of the standard bear a reasonable relationship to its benefits.   Relying on § §  6(b)(5) and 3(8) of the Act, 29 U.S.C. § §  655(b)(5) and 652(8), petitioners urge not only that OSHA must show that a standard addresses a significant risk of material health impairment, see Industrial Union Dept. v. American Petroleum Institute, 448 U.S., at 639, 100 S.Ct., at 2863 (plurality opinion), but also that OSHA must demonstrate that the reduction in risk of material health impairment is significant in light of the costs of attaining that reduction.  Respondents on the other hand contend that the Act requires OSHA to promulgate standards that eliminate or reduce such risks "to the extent such protection is technologically and economically feasible."   To resolve this debate, we must  turn to the language, structure, and legislative history of the Act.

A

The starting point of our analysis is the language of the statute itself.  Section 6(b)(5) of the Act, 29 U.S.C. §  655(b)(5) (emphasis added), provides:

"The Secretary, in promulgating standards dealing with toxic materials or harmful physical agents under this subsection, shall set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life." ^[6]

Although their interpretations differ, all parties agree that the phrase "to the extent feasible" contains the critical language in §  6(b)(5) for purposes of these cases.

The plain meaning of the word "feasible" supports respondents' interpretation of the statute.   According to Webster's Third New International Dictionary of the English Language 831 (1976), "feasible" means "capable of being done, executed, or effected."   Thus, §  6(b)(5) directs the Secretary to issue the standard that "most adequately assures ... that no employee will suffer material impairment of health," limited only by the extent to which this is "capable of being done."   In effect then, as the Court of Appeals held, Congress itself defined the basic relationship between costs and benefits, by placing the "benefit" of worker health above all other considerations save those making attainment of this "benefit" unachievable. Any standard based on a balancing of costs and benefits by the Secretary that strikes a different balance than that struck by Congress would be inconsistent with the command set forth in §  6(b)(5).   Thus, cost-benefit analysis by OSHA is not required by the statute because feasibility analysis is. See Industrial Union Dept. v.  American Petroleum Institute, 448 U.S., at 718-719, 100 S.Ct., at 2902-2903 (MARSHALL, J., dissenting).

 When Congress has intended that an agency engage in cost-benefit analysis, it has clearly indicated such intent on the face of the statute. * * *   Congress uses specific language when intending that an agency engage in cost-benefit analysis.   Certainly in light of its ordinary meaning, the word "feasible" cannot be construed to articulate such congressional intent.   We therefore reject the argument that Congress required cost-benefit analysis in §  6(b)(5).

B

Even though the plain language of §  6(b)(5) supports this construction, we must still decide whether §  3(8), the general definition of an occupational safety and health standard, either alone or in tandem with §  6(b)(5), incorporates a cost-benefit requirement for standards dealing with toxic materials or harmful physical agents.   Section 3(8) of the Act, 29 U.S.C. §  652(8) (emphasis added), provides:

"The term 'occupational safety and health standard' means a standard which requires conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment and places of employment."

Taken alone, the phrase "reasonably necessary or appropriate" might be construed to contemplate some balancing of the costs and benefits of a standard.   Petitioners urge that, so construed, §  3(8) engrafts a cost-benefit analysis requirement on the issuance of §  6(b)(5) standards, even if §  6(b)(5) itself does not authorize such analysis.   We need not decide whether §  3(8), standing alone, would contemplate some form of cost-benefit analysis.   For even if it does, Congress specifically chose in §  6(b)(5) to impose separate and additional requirements for issuance of a subcategory of occupational safety and health standards dealing with toxic materials and harmful physical agents:  it required that those standards be issued to prevent material impairment of health to the extent feasible.   Congress could reasonably have concluded that health standards should be subject to different criteria than safety standards because of the special problems presented in regulating them.  

Agreement with petitioners' argument that §  3(8) imposes an additional and overriding requirement of cost-benefit analysis on the issuance of §  6(b)(5) standards would eviscerate the "to the extent feasible" requirement.   Standards would inevitably be set at the level indicated by cost-benefit analysis, and not at the level specified by §  6(b)(5).   For example, if cost-benefit analysis indicated a protective standard of 1,000 ug/m 3 PEL, while feasibility analysis indicated a 500 ug/m 3 PEL, the agency would be forced by the cost-benefit requirement to choose the less stringent point. We cannot believe that Congress intended the general terms of §  3(8) to countermand the specific feasibility requirement of §  6(b)(5). Adoption of petitioners' interpretation would effectively write §  6(b)(5) out of the Act.  We decline to render Congress' decision to include a feasibility requirement nugatory, thereby offending the well-settled rule that all parts of a statute, if possible, are to be given effect.  Congress did not contemplate any further balancing by the agency for toxic material and harmful physical agents standards, and we should not " 'impute to Congress a purpose to paralyze with one hand what it sought to promote with the other.' " 

C

The legislative history of the Act, while concededly not crystal clear, provides general support for respondents' interpretation of the Act.   The congressional Reports and debates certainly confirm that Congress meant "feasible" and nothing else in using that term.   Congress was concerned that the Act might be thought to require achievement of absolute safety, an impossible standard, and therefore insisted that health and safety goals be capable of economic and technological accomplishment.   Perhaps most telling is the absence of any indication whatsoever that Congress intended OSHA to conduct its own cost-benefit analysis before promulgating a toxic material or harmful physical agent standard.   The legislative history demonstrates conclusively that Congress was fully aware that the Act would impose real and substantial costs of compliance on industry, and believed that such costs were part of the cost of doing business. * * *  Not only does the legislative history confirm that Congress meant "feasible" rather than "cost-benefit" when it used the former term, but it also shows that Congress understood that the Act would create substantial costs for employers, yet intended to impose such costs when necessary to create a safe and healthful working environment.^[7]  Congress viewed the costs of health and safety as a cost of doing business. Senator Yarborough, a cosponsor of the Williams bill, stated:  "We know the costs would be put into consumer goods but that is the price we should pay for the 80 million workers in America.   * * *

Nowhere is there any indication that Congress contemplated a different balancing by OSHA of the benefits of worker health and safety against the costs of achieving them.  Indeed Congress thought that the financial costs of health and safety problems in the workplace were as large as or larger than the financial costs of eliminating these problems.   In its statement of findings and declaration of purpose encompassed in the Act itself, Congress announced that "personal injuries and illnesses arising out of work situations impose a substantial burden upon, and are a hindrance to, interstate commerce in terms of lost production, wage loss, medical expenses, and disability compensation payments."  29 U.S.C. §  651(a).

"[T]he economic impact of industrial deaths and disability is staggering. Over $1.5 billion is wasted in lost wages, and the annual loss to the Gross National Product is estimated to be over $8 billion.   Vast resources that could be available for productive use are siphoned off to pay workmen's compensation benefits and medical expenses."   Senator Eagleton summarized:  "Whether we, as individuals, are motivated by simple humanity or by simple economics, we can no longer permit profits to be dependent upon an unsafe or unhealthy worksite

III

Section 6(f) of the Act provides that "[t]he determinations of the Secretary shall be conclusive if supported by substantial evidence in the record considered as a whole."  29 U.S.C. §  655(f).   Petitioners contend that the Secretary's determination that the Cotton Dust Standard is "economically feasible" is not supported by substantial evidence in the record considered as a whole.   In particular, they claim (1) that OSHA underestimated the financial costs necessary to meet the Standard's requirements;  and (2) that OSHA incorrectly found that the Standard would not threaten the economic viability of the cotton industry.

In statutes with provisions virtually identical to §  6(f) of the Act, we have defined substantial evidence as "such relevant evidence as a reasonable mind might accept as adequate to support a conclusion."  Universal Camera Corp. v. NLRB,  340 U.S. 474, 477, 71 S.Ct. 456, 459, 95 L.Ed. 456 (1951). * * * [O]ur inquiry is not to determine whether we, in the first instance, would find OSHA's findings supported by substantial evidence.   Instead we turn to OSHA's findings and the record upon which they were based to decide whether the Court of Appeals "misapprehended or grossly misapplied" the substantial evidence test.

A

OSHA derived its cost estimate for industry compliance with the Cotton Dust Standard after reviewing two financial analyses, one prepared by the Research Triangle Institute (RTI), an OSHA-contracted group, the other by industry representatives (Hocutt- Thomas). The agency carefully  explored the assumptions and methodologies underlying the conclusions of each of these studies.   From this exercise the agency was able to build upon conclusions from each which it found reliable and explain its process for choosing its cost estimate.  * * *

B

After estimating the cost of compliance with the Cotton Dust Standard, OSHA analyzed whether it was "economically feasible" for the cotton industry to bear this cost. OSHA concluded that it was, finding that "although some marginal employers may shut down rather than comply, the industry as a whole will not be threatened by the capital requirements of the regulation.  (compliance with the standard is well within the financial capability of the covered industries).”   In reaching this conclusion on the Standard's economic impact, OSHA made specific findings with respect to employment, energy consumption, capital financing availability, and profitability. * * *  The Court of Appeals found that the agency "explained the economic impact it projected for the textile industry," and that OSHA has "substantial support in the record for its ... findings of economic feasibility for the textile industry."  199 U.S.App.D.C., at 80, 617 F.2d, at 662.   On the basis of the whole record, we cannot conclude that the Court of Appeals "misapprehended or grossly misapplied" the substantial evidence test.

IV

The final Cotton Dust Standard places heavy reliance on the use of respirators to protect employees from exposure to cotton dust, particularly during the 4-year interim period necessary to install and implement feasible engineering controls.^[8]  One part of the respirator provision requires the employer to give employees unable to wear a respirator ^[9] the opportunity to transfer to another position, if available, where the dust level meets the Standard's PEL.  29 CFR §  1910.1043(f)(2)(v) (1980).   When such a transfer occurs, the employer must guarantee that the employee suffers no loss of earnings or other employment rights or benefits.^[10] Petitioners do not object to the transfer provision, but challenge OSHA's authority under the Act to require employers to guarantee employees' wage and employment benefits following the transfer.   The Court of Appeals held that OSHA has such authority.  We hold that, whether or not OSHA has this underlying authority, the agency has failed to make the necessary determination or statement of reasons that its wage guarantee requirement is related to the achievement of a safe and healthful work environment.

Respondents urge several statutory bases for the authority exercised here.  They cite §  2(b) of the Act, 29 U.S.C. §  651(b), which declares that the purpose of the Act is "to assure so far as possible every working man and woman in the Nation safe and healthful working conditions";  §  2(b)(5), which suggests achievement of the purpose "by developing innovative methods, techniques, and approaches for dealing with occupational safety and health problems";  §  6(b)(5), which requires the agency to "set the standard which most adequately assures ... that no employee will suffer material impairment of health or functional capacity ...";  and §  3(8), which provides that a standard must require "conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment. Whatever methods these provisions authorize OSHA to apply, it is clear that such methods must be justified on the basis of their relation to safety or health.

Section 6(f) of the Act, 29 U.S.C. §  655(f), requires that "determinations of the Secretary" must be supported by substantial evidence.   Section 6(e), 29 U.S.C. §  655(e), requires the Secretary to include "a statement of the reasons for such action, which shall be published in the Federal Register."  In his "Summary and Explanation of the Standard," the Secretary stated:  "Each section includes an analysis of the record evidence and the policy considerations underlying the decisions adopted pertaining to specific provisions of the standard.  But OSHA never explained the wage guarantee provision as an approach designed to contribute to increased health protection.   Instead the agency stated that the "goal of this provision is to minimize any adverse economic impact on the employee by virtue of the inability to wear a respirator."  Perhaps in recognition of this fact, respondents in their briefs argue:

"Experience under the Act has shown that employees are reluctant to disclose symptoms of disease and tend to minimize work-related health problems for fear of being discharged or transferred to a lower paying job....  It may reasonably be expected, therefore, that many employees incapable of using respirators would continue to breathe unhealthful air rather than request a transfer, thus destroying the utility of the respirator program."   Brief for Federal Respondent 67.

Whether these arguments have merit, and they very well may,^[11] the post hoc rationalizations of the agency or the parties to this litigation cannot serve as a sufficient predicate for agency action.   For Congress gave OSHA the responsibility to protect worker health and safety, and to explain its reasons for its actions.   Because the Act in no way authorizes OSHA to repair general unfairness to employees that is unrelated to achievement of health and safety goals, we conclude that OSHA acted beyond statutory authority when it issued the wage guarantee regulation.

V

When Congress passed the Occupational Safety and Health Act in 1970, it chose to place pre-eminent value on assuring employees a safe and healthful working environment, limited only by the feasibility of achieving such an environment. We must measure the validity of the Secretary's actions against the requirements of that Act.   For "[t]he judicial function does not extend to substantive revision of regulatory policy.   That function lies elsewhere--in Congressional and Executive oversight or amendatory legislation."  Industrial Union Dept. v. American Petroleum Institute, supra, 448 U.S., at 663, 100 S.Ct., at 2875 (BURGER, C. J., concurring).

Accordingly, the judgment of the Court of Appeals is affirmed in all respects except to the extent of its approval of the Secretary's application of the wage guarantee provision of the Cotton Dust Standard at 29 CFR §  1910.1043(f)(2)(v) (1980).   To that extent, the judgment of the Court of Appeals is vacated and the case remanded with directions to remand to the Secretary for further proceedings consistent with this opinion.

 It is so ordered.

 Justice POWELL took no part in the decision of these cases.

 Justice STEWART filed a dissenting opinion in which he indicated, “Because I believe that OSHA failed to justify its estimate of the cost of the Cotton Dust Standard on the basis of substantial evidence, I would reverse the judgment before us without reaching the question whether the Act requires that a standard, beyond being economically feasible, must meet the demands of a cost-benefit examination.”

Justice REHNQUIST, with whom Chief Justice Burger joins, dissenting.

 A year ago I stated my belief that Congress in enacting §  6(b)(5) of the Occupational Safety and Health Act of 1970 unconstitutionally delegated to the Executive Branch the authority to make the "hard policy choices" properly the task of the legislature.  Industrial Union Dept. v. American Petroleum Institute, 448 U.S. 607, 671, 100 S.Ct. 2844, 2878, 65 L.Ed.2d 1010 (1980) (concurring in judgment).   Because I continue to believe that the Act exceeds Congress' power to delegate legislative authority to nonelected officials, I dissent.

FOOTNOTES

[1] Cotton dust is defined as "dust present in the air during the handling or processing of cotton, which may contain a mixture of many substances including ground up plant matter, fiber, bacteria, fungi, soil, pesticides, non-cotton plant matter and other contaminants which may have accumulated with the cotton during the growing, harvesting and subsequent processing or storage periods.   Any dust present during the handling and processing of cotton through the weaving or knitting of fabrics, and dust present in other operations or manufacturing processes using new or waste cotton fibers or cotton fiber by-products from textile mills are considered cotton dust."  29 CFR §  1910.1043(b) (1980) (Cotton Dust Standard).

[2] Known generally as the Schilling classification grades, they include:

"[Grade] 1/2 :  slight acute effect of dust on ventilatory capacity;  no evidence of chronic ventilatory impairment.

"[Grade] 1:  definite acute effect of dust on ventilatory capacity;  no evidence of chronic ventilatory impairment.

"[Grade] 2:  evidence of slight to moderate irreversible impairment of ventilatory capacity.

"[Grade] 3:  evidence of moderate to severe irreversible impairment of ventilatory capacity.

[3]  Descriptions of the disease by individual mill workers, presented in hearings on the Cotton Dust Standard before an Administrative Law Judge, are more vivid:

"When they started speeding the looms up the dust got finer and more and more people started leaving the mill with breathing problems.   My mother had to leave the mill in the early fifties.   Before she left, her breathing got so short she just couldn't hold out to work.   My stepfather left the mill on account of breaching [sic ] problems.   He had coughing spells til he couldn't breath [sic ], like a child's whooping cough.   Both my sisters who work in the mill have breathing problems.   My husband had to give up his job when he was only fifty-four years old because of the breathing problems."   Ct. of App.J.A. 3791.

"I suppose I had a breathing problem since 1973.   I just kept on getting sick and began losing time at the mill.   Every time that I go into the mill I get deathly sick, choking and vomiting losing my breath.   It would blow down all that lint and cotton and I have clothes right here where I have wore and they had been washed several times and I would like for you all to see them.   That will not come out in washing.

"I am only fifty-seven years old and I am retired and I can't even get to go to church because of my breathing.   I get short of breath just walking around the house or dressing [or] sometimes just watching T.V.   I cough all the time."  Id., at 3793.

  * * *

"... I had to quit because I couldn't lay down and rest without oxygen in the night and my doctor told me I would have to get out of there....  I couln't [sic ] even breathe, I had to get out of the door so I could breathe and he told me not to go back in [the mill] under any circumstances."  Id., at 3804.

Byssinosis is not a newly discovered disease, having been described as early as in the 1820's in England, App. 404-405, and observed in Belgium in a study of 2,000 cotton workers in 1845, Exhibit 6-16, App. 15.

[4] Indeed the Senate Report on the Act expressly observed:

"Studies of particular industries provide specific emphasis regarding the magnitude of the problem.   For example, despite repeated warnings over the years from other countries that their cotton workers suffered from lung disease, it is only within the past decade that we have recognized byssinosis as a distinct occupational disease among workers in American cotton mills."   S.Rep.No.91-1282, p. 3 (1970), U.S.Code Cong. & Admin.News 1970, p. 5179, Leg.Hist. 143.

[5] NIOSH presented its recommendation in a lengthy and detailed document entitled "Criteria for a Recommended Standard:  Occupational Exposure to Cotton Dust."   Ex. 1, Ct. of App.J.A. 11-169.   The report examined the effects of cotton dust exposure and suggested implementation of work practices, engineering controls, medical surveillance, and monitoring to decrease exposure to the recommended level.

[6] Section 6(b)(5) of the Act, 29 U.S.C. §  655(b)(5), also provides:

"Development of standards under this subsection shall be based upon research, demonstrations, experiments, and such other information as may be appropriate.   In addition to the attainment of the highest degree of health and safety protection for the employee, other considerations shall be the latest available scientific data in the field, the feasibility of the standards, and experience gained under this and other health and safety laws.   Whenever practicable, the standard promulgated shall be expressed in terms of objective criteria, and of the performance desired."

[7] Because the costs of compliance would weigh particularly heavily on small businesses, Congress provided in §  28 of the Act an amendment to the Small Business Act, 15 U.S.C. §  636, making small businesses eligible for economic assistance through the Small Business Administration to comply with standards promulgated by the Secretary.  84 Stat. 1618, Leg.Hist. 1257.

[8] The final Standard, 29 CFR §  1910.1043(f)(1) (1980), provides:

"Where the use of respirators is required under this section, the employer shall provide, at no cost to the employee, and assure the use of respirators which comply with the requirements of this paragraph (f). Respirators shall be used in the following circumstances:

"(i) During the time periods necessary to install or implement feasible engineering controls and work practice controls;

"(ii) During maintenance and repair activities in which engineering and work practice controls are not feasible;

"(iii) In work situations where feasible engineering and work practice controls are not yet sufficient to reduce exposure to or below the permissible exposure limit;  and

"(iv) In operations specified under paragraph (g)(1);

"(v) Whenever an employee requests a respirator."

[9] An employee may be unable to wear a respirator because of facial irritation, severe discomfort, or impaired breathing. 

[10] The regulation, 29 CFR §  1910.1043(f)(2)(v) (1980) (emphasis added), provides: "Whenever a physician determines that an employee is unable to wear any form of respirator, including a power air purifying respirator, the employee shall be given the opportunity to transfer to another position which is available or which later becomes available having a dust level at or below the PEL.   The employer shall assure that an employee who is transferred due to an inability to wear a respirator suffers no loss of earnings or other employment rights or benefits as a result of the transfer."

[11] There is evidence in the record that might support such a determination.   Dr. Merchant testified that a medical surveillance program alone would not be sufficient for identifying and relocating employees suffering from byssinosis.   App. 440-441.   He observed:

"There is reluctance very often among the employee himself to leave his job.   I think clearly some guarantees as to wages and opportunities must be an integral part of any recommendation to relocate somebody and it has been the experience in coal mining where miners are allowed, under the Coal Mine Health and Safety Act of 1968, to be transferred, a very low proportion of these men actually exercise their transfer rights."  Id., at 441.

However, the courts will not be expected to scrutinize the record to uncover and formulate a rationale explaining an action, when the agency in the first instance has failed to articulate such rationale.  

AFL-CIO v. OSHA, 965 F.2d 962 (11^th Cir. 1992)

Fay, Circuit Judge:

In 1989, the Occupational Safety and Health Administration ("OSHA") issued its Air Contaminants Standard, a set of permissible exposure limits for 428 toxic substances. Air Contaminants Standard, 54 Fed.Reg. 2332 (1989) (codified at 29 C.F.R. §  1910.1000).   In these consolidated appeals, petitioners representing various affected industries and the American Federation of Labor and Congress of Industrial Organizations ("AFL-CIO" or "the union") challenge both the procedure used by OSHA to generate this multi-substance standard and OSHA's findings on numerous specific substances included in the new standard.   For the reasons that follow, we vacate the Air Contaminants Standard and remand to the agency.

The Occupational Safety and Health Act of 1970 ("OSH Act" or "the Act"), 29 U.S.C. § §  651-71, was adopted "to assure so far as possible every working man and woman in the Nation safe and healthful working conditions."  To this end, the Act authorizes the Secretary to issue occupational health and safety standards with which each employer must comply.   Section 6(a) of the Act provided that in its first two years, OSHA should promulgate "start-up" standards, on an expedited basis and without public hearing or comment, based on "national consensus" or "established Federal standard[s]" that improve employee safety or health.  Pursuant to that authority, OSHA in 1971 promulgated approximately 425 permissible exposure limits ("PELs") for air contaminants, 29 C.F.R. §  1910.1000 (1971), derived principally from federal standards applicable to government contractors under the Walsh-Healey Act. ^[1]

* * *  Most new standards or revised existing standards must be promulgated under the requirements of section 6(b) of the OSH Act.  This section sets forth both procedural requirements and substantive criteria which the standards must meet.  …  As of 1988, OSHA had issued only twenty-four substance-specific and three "generic" health standards under section 6(b).^[2]

On June 7, 1988, OSHA published a Notice of Proposed Rulemaking for its Air Contaminants Standard.   In this single rulemaking, OSHA proposed to issue new or revised PELs for over 400 substances.   OSHA limited the scope of this rulemaking to those substances for which the ACGIH recommended limits that were either new or more protective than the existing PELs.

OSHA then issued its revised Air Contaminants Standard for 428 toxic substances on January 19, 1989.  This standard, which differs from the proposal in several respects, lowered the PELs for 212 substances, set new PELs for 164 previously unregulated substances, and left unchanged PELs for 52 substances for which lower limits had originally been proposed.  The standard established an approximately four-year period for employers to come into compliance with the new standard using engineering and work practice controls.  Until that time, employers may use respirators or any other reasonable methods to comply with the standards. 

Various industry groups, the AFL-CIO, and specific individual companies filed challenges to the final standard in numerous United States Courts of Appeals. * * *

Section 6(f) provides in relevant part that "the determinations of the Secretary shall be conclusive if supported by substantial evidence in the record considered as a whole."  * * *  The substantial evidence test applies to review of policy decisions as well as factual determinations, even though policy decisions are " 'not so susceptible to verification or refutation by the record.' * * *  In challenging the procedure by which OSHA promulgated the Air Contaminants Standard, a group of industry petitioners complain that OSHA's use of generic findings, the lumping together of so many substances in one rulemaking, and the short time provided for comment by interested parties, combine to create a record inadequate to support this massive new set of PELs.   The union also challenges the rulemaking procedure utilized by OSHA for the Air Contaminants Standard.   Not surprisingly, however, the union claims that this procedure resulted in standards that are systematically underprotective of employee health.   The union further challenges OSHA's decision to limit the scope of the rulemaking to substances for which the ACGIH recommendation was more protective than the current PEL, and thereby to ignore both other air contaminant substances in need of regulation and standards for exposure monitoring and medical surveillance.   * * *

Unlike most of the OSHA standards previously reviewed by the courts, the Air Contaminants Standard regulates not a single toxic substance, but 428 different substances.   The agency explained its decision to issue such an omnibus standard in its Notice of Proposed Rulemaking:

OSHA has issued only 24 substance-specific health regulations since its creation.   It has not been able to review the many thousands of currently unregulated chemicals in the workplace nor to keep up with reviewing the several thousand new chemicals introduced since its creation.   It has not been able to fully review the literature to determine if lower limits are needed for many of the approximately 400 substances it now regulates. Using past approaches and practices, OSHA could continue to regulate a small number of the high priority substances and those of greatest public interest. However, it would take decades to review currently used chemicals and OSHA would never be able to keep up with the many chemicals which will be newly introduced in the future.

For this reason, "OSHA determined that it was necessary to modify this approach through the use of generic rulemaking, which would simultaneously cover many substances." 

"Generic" means something "common to or characteristic of a whole group or class;  typifying or subsuming;  not specific or individual."   Webster's Third New International Dictionary 945 (1966).   Previous "generic" rulemakings by OSHA have all dealt with requirements that, once promulgated, could be applied to numerous different situations.   For example, OSHA's Hazard Communication Standard, 29 C.F.R. §  1910.1200, mandates that employers inform employees of potentially hazardous materials.   The regulation includes a basic list of substances which employers must treat as hazardous, but requires that the employers themselves also evaluate substances produced in their workplaces to determine if they are potentially hazardous based on available scientific evidence.  Similarly, OSHA has issued standards regulating employee access to medical and toxic substance exposure records, 29 C.F.R. §  1910.20, and setting forth uniform criteria for application in future regulation of exposure to carcinogens, 29 C.F.R. Part 1990.

By contrast, the new Air Contaminants Standard is an amalgamation of 428 unrelated substance exposure limits.   There is little common to this group of diverse substances except the fact that OSHA considers them toxic and in need of regulation.   In fact, this rulemaking is the antithesis of a "generic" rulemaking;  it is a set of 428 specific and individual substance exposure limits.   Therefore, OSHA's characterization of this as a "generic" rulemaking is somewhat misleading.

Nonetheless, we find nothing in the OSH Act that would prevent OSHA from addressing multiple substances in a single rulemaking.   * * *   However, we believe the PEL for each substance must be able to stand independently, i.e., that each PEL must be supported by substantial evidence in the record considered as a whole and accompanied by adequate explanation.   OSHA may not, by using such multi-substance rulemaking, ignore the requirements of the OSH Act.   Both the industry petitioners and the union argue that such disregard was what in essence occurred.   Regretfully, we agree.

Section 3(8) of the OSH Act defines "occupational health and safety standard" as "a standard which requires conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment and places of employment."  29 U.S.C. §  652(8) (emphasis added).   The Supreme Court has interpreted this provision to require that, before the promulgation of any permanent health standard, OSHA make a threshold finding that a significant risk of material health impairment exists at the current levels of exposure to the toxic substance in question "and that a new, lower standard is therefore 'reasonably necessary or appropriate to provide safe or healthful employment and places of employment.' "  Benzene, 448 U.S. at 615, 100 S.Ct. at 2850. OSHA is not entitled to regulate any risk, only those which present a "significant" risk of "material" health impairment.  OSHA must therefore determine:  (1) what health impairments are "material," and (2) what constitutes a "significant" risk of such impairment. Moreover, OSHA ultimately bears the burden of proving by substantial evidence that such a risk exists and that the proposed standard is necessary.  The agency "has no duty to calculate the exact probability of harm," or "to support its finding that a significant risk exists with anything approaching scientific certainty."  However, OSHA must provide at least an estimate of the actual risk associated with a particular toxic substance and explain in an understandable way why that risk is significant.  In past rulemakings, OSHA has satisfied this requirement by estimating either the number of workers likely to suffer the effects of exposure or the percentage of risk to any particular worker.^[3]

Once OSHA finds that a significant risk of material health impairment exists at current exposure levels for a given toxic substance, any standard promulgated to address that risk must comply with the requirements of section 6(b)(5) of the OSH Act [that]…mandates that the standard adopted "prevent material impairment of health to the extent feasible." 

Material Impairment

In this rulemaking, OSHA grouped the 428 substances into eighteen categories by the primary health effects of those substances, for example, neuropathic effects, sensory irritation, and cancer.  Industry petitioners charge that for several categories of substances OSHA failed to adequately justify its determination that the health effects caused by exposure to these substances are "material impairments."   We disagree.

Petitioners cite the category of "sensory irritation" as a particularly egregious example.   At the beginning of the discussion for each category, the agency summarized the types of health effects within that category, and discussed why those effects constituted "material impairments." The "Description of Health Effects" for the "sensory irritation" category includes the following discussion:

The symptoms of sensory irritation include stinging, itching, and burning of the eyes, tearing (or lacrimation), a burning sensation in the nasal passages, rhinitis (nasal inflammation), cough, sputum production, chest pain, wheezing, and dyspnea (breathing difficulty)....

These effects may cause severe discomfort and can be seriously disabling, as is the case with dyspnea or wheezing.   The tearing and eye irritation associated with exposure to sensory irritants are often severe and can be as disabling as the weeping caused by exposure to tear gas.   In addition to these primary effects, workers distracted by material irritant effects are more likely than nonexposed workers to have accidents and thus to endanger both themselves and others.  (These adverse health effects also clearly have substantial productivity impacts.)

....

OSHA concludes that exposure limits are needed for those substances for which PELs are being established in this rulemaking to protect against sensory irritant effects that result in objective signs of irritation, such as coughing, wheezing, conjunctivitis, and tearing.   Such levels of mucous membrane irritation may require medical treatment, adversely affect the well-being of employees, and place the affected individuals at risk from increased absorption of the substance and decreased resistance to infection.   Exposing workers repeatedly to irritants at levels that cause subjective irritant effects may cause workers to become inured to the irritant warning properties of these substances and thus increase the risk of overexposure.

* * * We interpret this explanation as indicating that OSHA finds that although minor irritation may not be a material impairment, there is a level at which such irritation becomes so severe that employee health and job performance are seriously threatened, even though those effects may be transitory.   We find this explanation adequate.   OSHA is not required to state with scientific certainty or precision the exact point at which each type of sensory or physical irritation becomes a material impairment.   Moreover, section 6(b)(5) of the Act charges OSHA with addressing all forms of "material impairment of health or functional capacity," and not exclusively "death or serious physical harm" or "grave danger" from exposure to toxic substances. See 29 U.S.C. § §  654(a)(1), 655(c).   Overall, we find that OSHA's determinations of what constitute "material impairments" are adequately explained and supported in the record.

Significant Risk

However, the agency's determination of the extent of the risk posed by individual substances is more problematic.  "No one could reasonably expect OSHA to adopt some precise estimate of fatalities likely from a given exposure level, and indeed the Supreme Court has said that the agency has 'no duty to calculate the exact probability of harm.' "  International Union, UAW v. Pendergrass, 878 F.2d 389, 392 (D.C.Cir.1989) (quoting Benzene, 448 U.S. at 655, 100 S.Ct. at 2870-71).   Nevertheless, OSHA has a responsibility to quantify or explain, at least to some reasonable degree, the risk posed by each toxic substance regulated.   Otherwise, OSHA has not demonstrated, and this court cannot evaluate, how serious the risk is for any particular substance, or whether any workers will in fact benefit from the new standard for any particular substance.   If each of these 428 toxic substances had been addressed in separate rulemakings, OSHA would clearly have been required to estimate in some fashion the risk of harm for each substance.   OSHA is not entitled to take short-cuts with statutory requirements simply because it chose to combine multiple substances in a single rulemaking.

However, OSHA's discussions of individual substances generally contain no quantification or explanation of the risk from that individual substance. The discussions of individual substances contain summaries of various studies of that substance and the health effects found at various levels of exposure to that substance.   However, OSHA made no attempt to estimate the risk of contracting those health effects.   Instead, OSHA merely provided a conclusory statement that the new PEL will reduce the "significant" risk of material health effects shown to be caused by that substance without any explanation of how the agency determined that the risk was significant.   However, OSHA did make a generic finding that the Air Contaminants Standard as a whole would prevent 55,000 occupational illnesses and 683 deaths annually. 

Moreover, a determination that the new standard is "reasonably necessary or appropriate," 29 U.S.C. §  652(8), and that it is the standard that "most adequately assures ... that no employee will suffer material impairment of health or functional capacity," id. §  655(b)(5), necessarily requires some assessment of the level at which significant risk of harm is eliminated or substantially reduced.   Yet, with rare exceptions, the individual substance discussions in the Air Contaminants Standard are virtually devoid of reasons for setting those individual standards.   In most cases, OSHA cited a few studies and then established a PEL without explaining why the studies mandated the particular PEL chosen.   For example, the PEL for bismuth telluride appears to be based on a single study that showed almost no effects of any kind in animals at several times that concentration.  Similarly, the PEL for ferrovanadium dust was based on pulmonary changes at exposure levels many hundreds of times higher than OSHA's new standard. * * *   For some substances, OSHA merely repeated a boilerplate finding that the new limit would protect workers from significant risk of some material health impairment.   For example, OSHA did not cite any studies whatsoever for its aluminum welding fume standard, or its vegetable oil mist standard.

 "While our deference to the agency is at a peak for its choices among scientific predictions, we must still look for some articulation of reasons for those choices."  Pendergrass, 878 F.2d at 392 (emphasis added). * * *   Mere conclusory statements, such as those made throughout the Air Contaminants Standard, are simply inadequate to support a finding of significant risk of material health impairment.

On the other hand, OSHA established PELs for carbon tetrachloride and vinyl bromide, both carcinogens, at levels where OSHA itself acknowledged that the risk of material health impairment remained significant.  For carbon tetrachloride, OSHA stated that at the new level, "residual risk continues to be significant ... 3.7 excess deaths per 1,000 workers exposed over their working lifetimes."  For vinyl bromide, OSHA stated that the new PEL "will not eliminate this significant risk, because ... residual risk [at the new level] is 40 excess deaths per 1,000 exposed workers ... [and thus] is clearly significant."  The only explanation given by OSHA in the final rule for setting its standard where a significant risk of material health impairment remains was that the time and resource constraints of attempting to promulgate an air contaminants standard of this magnitude prevented detailed analysis of these substances. OSHA did not claim in the final rule that the PELs for these two substances were necessary because of feasibility concern.

The agency's response to this criticism is unpersuasive.   OSHA first contends that quantitative risk analysis using mathematical models like the ones developed for carcinogens was impossible for this rulemaking because no such models exist for noncarcinogens.

* * * Yet, in several previous rulemakings, OSHA apparently succeeded in determining how many workers were exposed to a particular substance or how much risk would be alleviated by a new standard, even though those particular substances were not carcinogens. It is therefore unclear whether the lack of a method to quantitatively assess the risk for noncarcinogens is a cause or a result of the agency's approach.   In this rulemaking, OSHA concluded that current exposure to 428 substances posed a "significant" risk of material health impairment, and that its new standards were required for most of these substances to eliminate or substantially reduce that risk.   It is not unreasonable to require that the agency explain how it arrived at that determination, and, indeed, this is precisely what Congress required.

The agency further claims that no quantification was required because OSHA's final standards " 'fall[ ] within a zone of reasonableness.'”  However, without any quantification or any explanation, this court cannot determine what that "zone of reasonableness" is or if these standards fall within it.

OSHA also responds by noting that it incorporated "uncertainty" or "safety" factors into many PELs.   However, OSHA did not use a uniform safety factor, but instead claims to have made a case-by-case assessment of the appropriate safety factor. * * * [T]he method by which the "appropriate" safety factor was determined for each of those substances is not explained in the final rule.* * * From OSHA's description, safety factors are used to lower the standard below levels at which the available evidence shows no significant risk of material health impairment because of the possibility that the evidence is incorrect or incomplete;  i.e., OSHA essentially makes an assumption that the existing evidence does not adequately show the extent of the risk.   That may be a correct assumption, but beyond a general statement that the use of safety factors is common in the scientific community, OSHA did not indicate how the existing evidence for individual substances was inadequate to show the extent of the risk from those substances.   Such a rationale is very reminiscent of the "benefits are likely to be appreciable" rationale rejected in Benzene as insufficient to satisfy the agency's obligations under the OSH Act* * *  The lesson of Benzene is clearly that OSHA may use assumptions, but only to the extent that those assumptions have some basis in reputable scientific evidence.   If the agency is concerned that the standard should be more stringent than even a conservative interpretation of the existing evidence supports, monitoring and medical testing may be done to accumulate the additional evidence needed to support that more protective limit.  Benzene does not provide support for setting standards below the level substantiated by the evidence. * * *

More generally, OSHA defends its failure to make more specific findings for each individual substance, as well as its decision to set the standards for several substances at levels where significant risks of material health impairment remain, by citing its authority to set priorities, and the discretion permitted the agency in making policy decisions.   * * * [T]he agency stated that

[i]n response to both the court challenges and the need to face difficult issues, OSHA has engaged in detailed and extensive analyses.   These have resulted in lengthier preamble discussions and in-depth analyses for all issues....

Now that OSHA has reviewed these issues in depth several times, has experience "gained under this * * * law" (sec. 6(b)(5)) on these issues, and has had its analysis upheld in the Courts, somewhat less detailed chemical-by-chemical analyses should be appropriate.   The accumulated judicial guidance and agency experience reduces the need for as extensive a discussion of some of the issues.

This implies that OSHA need no longer perform detailed analysis and explanation when promulgating PELs because the agency's analysis for other substances has been upheld in prior rulemakings.   Besides displaying more than a touch of hubris, this passage reveals a fundamental misperception of the OSH Act and the caselaw interpreting that act.

While OSHA has probably established that most or all of the substances involved do pose a significant risk at some level, it has failed to establish that existing exposure levels in the workplace present a significant risk of material health impairment or that the new standards eliminate or substantially lessen the risk.

Feasibility

The Supreme Court has defined "feasibility" as " 'capable of being done, executed, or effected,' " ATMI, 452 U.S. at 508-09, 101 S.Ct. at 2490-91 (quoting Webster's Third New International Dictionary 831 (1976)), both technologically and economically. Again, the burden is on OSHA to show by substantial evidence that the standard is feasible, although OSHA need not prove feasibility with scientific certainty.  Despite OSHA's repeated claims that it made feasibility determinations on an industry-by-industry basis, it is clear that the agency again proceeded "generically."

Technological Feasibility

To show that a standard is technologically feasible, OSHA must demonstrate  "that modern technology has at least conceived some industrial strategies or devices which are likely to be capable of meeting the PEL and which the industries are generally capable of adopting."  United Steelworkers, 647 F.2d at 1266.   Further, "the undisputed principle that feasibility is to be tested industry-by-industry demands that OSHA examine the technological feasibility of each industry individually."  Courts have remanded OSHA determinations where the agency has not sufficiently analyzed the abilities of different industries to meet proposed standards.

 In this rulemaking, OSHA first identified the primary air contaminant control methods:  Engineering controls are methods such as ventilation, isolation, and substitution. Complementing the engineering controls are work practices and administrative reforms (e.g., housekeeping, material handling or transfer procedures, leak detection programs, training, and personal hygiene).  Finally, personal protective equipment such as respirators and gloves may become necessary when these other controls are not fully effective. 

OSHA then organized its discussion of technological feasibility by industry sector using the Standard Industrial Classification (SIC) groupings. The SIC codes classify by type of activity for purposes of promoting uniformity and comparability in the presentation of data.   As the codes go from two and three digits to four digits, the groupings become progressively more specific. * * *   For most of the SIC codes discussed, OSHA provided only a general description of how generic engineering controls might be used in a given sector.   Then, relying on this generic analysis, OSHA concluded that existing engineering controls are available to reduce exposure levels to the new levels.  In reviewing the comments and hearing testimony on the technological feasibility of achieving the PELs and other limits, OSHA has found that for the overwhelming majority of situations where air contaminants are encountered by workers, compliance can be achieved by applying known engineering control methods and work practice improvements.

However, OSHA made no attempt to show the ability of technology to meet specific exposure standards in specific industries. Except for an occasional specific conclusion as to whether a particular process control could meet a particular PEL, OSHA merely presented general conclusions as to the availability of these controls in a particular industry.  

OSHA correctly notes that all it need demonstrate is "a general presumption of feasibility for an industry."  However, as this quote indicates, "a general presumption of feasibility" refers to a specific industry-by-industry determination that a "typical firm will be able to develop and install engineering and work practice controls that can meet the PEL in most of its operations."  OSHA can prove this "by pointing to technology that is either already in use or has been conceived and is reasonably capable of experimental refinement and distribution within the standard's deadlines."  Only when OSHA has provided such proof for a given industry does there arise "a presumption that industry can meet the PEL without relying on respirators, a presumption which firms will have to overcome to obtain relief in any secondary inquiry into feasibility." United Steelworkers, 647 F.2d at 1266, 1272.

For example, in United Steelworkers, the court analyzed whether the agency had provided enough information about the relative abilities of different industries to meet the standard.   The court upheld OSHA's rationale with regard to lead smelting industries because OSHA made industry-specific findings and identified specific technologies capable of meeting the proposed limit in industry specific process operations.  Id. at 1278-89.   As to numerous other industries, however, the court remanded because OSHA's findings lacked a detailed industry- or operation-specific analysis.   * * *  [I]t is clear that the concept of "a general presumption of feasibility" does not grant OSHA a license to make overbroad generalities as to feasibility or to group large categories of industries together without some explanation of why findings for the group adequately represent the different industries in that group.   We find that OSHA has not established the technological feasibility of the 428 PELs in its revised Air Contaminants Standard.

Economic Feasibility

Nor has OSHA adequately demonstrated that the standard is economically feasible.   OSHA must "provide a reasonable assessment of the likely range of costs of its standard, and the likely effects of those costs on the industry," id. at 1266, so as to "demonstrate a reasonable likelihood that these costs will not threaten the existence or competitive structure of an industry, even if it does portend disaster for some marginal firms," id. at 1272.^[4] The determination of economic feasibility is governed by the same principles as technological feasibility.   It must be supported by substantial evidence and OSHA must demonstrate its applicability to the affected industries.  

In this rulemaking, although OSHA ostensibly recognized its responsibility "to demonstrate economic feasibility for an industry,"  the agency nevertheless determined feasibility for each industry "sector " (i.e., two-digit SIC code), without explaining why such a broad grouping was appropriate.  OSHA's economic feasibility determinations therefore suffer from the same faults as its technological feasibility findings.   Indeed, it would seem particularly important not to aggregate disparate industries when making a showing of economic feasibility. OSHA admits that its economic feasibility conclusions only "have a high degree of validity on a sector basis," id., as opposed to a subsector or more industry-specific basis. * * *

However, reliance on such tools as average estimates of cost can be extremely misleading in assessing the impact of particular standards on individual industries.   Analyzing the economic impact for an entire sector could conceal particular industries laboring under special disabilities and likely to fail as a result of enforcement.   Moreover, for some substances, OSHA failed even to analyze all the affected industry sectors.   We find that OSHA has not met its burden of establishing that its 428 new PELs are either economically or technologically feasible.

* * *  [W]e find nothing in the OSH Act that prohibits OSHA from combining multiple substances in one rulemaking, as long as the statutory requirements are met for each substance.   Neither do we find a requirement that OSHA include all possible substances in one rulemaking.   OSHA has never claimed that this Air Contaminants Standard constituted the total universe of substances needing regulation, and it seems reasonable that some limit needed to be set as to what substances could be considered in this rulemaking.   The list of ACGIH recommendations is a rational choice as the source for that limitation.   The ACGIH recommendations are clearly well known to industry and the safety and health community.^[5]  Therefore, we find that the agency's choice to so limit this rulemaking is a valid exercise of OSHA's authority to set priorities for rulemaking.   The Act is sufficiently flexible to allow OSHA "to initially determine whether or not there will be a standard ... [and] to process higher priority standards more quickly."  National Congress of Hispanic Am. Citizens v. Usery, 554 F.2d 1196, 1199 (D.C.Cir.1977).

* *  * However, the dearth of explanation in the rulemaking record for these 428 PELs makes it difficult to determine how the agency arrived at its conclusions.   We do note that not all final PELs conformed to the ACGIH recommendation, though approximately ninety percent were identical.   On remand, OSHA will be required to carefully review the evidence supporting each of the 428 PELs, and this concern should be addressed at that time. * *  *

It is clear that the analytical approach used by OSHA in promulgating its revised Air Contaminants Standard is so flawed that it cannot stand.   OSHA not only mislabeled this a "generic" rulemaking, but it inappropriately treated it as such.   The result of this approach is a set of 428 inadequately supported standards.   OSHA has lumped together substances and affected industries and provided such inadequate explanation that it is virtually impossible for a reviewing court to determine if sufficient evidence supports the agency's conclusions.   The individual substances discussed in this opinion are merely examples of what is endemic in the Air Contaminants Standard as a whole.

OSHA does have the authority to set priorities for establishing standards under the OSH Act.   That priority-setting authority permits OSHA to combine rulemaking for multiple substances in one rulemaking, to limit the scope of this rulemaking in a rational manner, and to defer issuance of regulations for monitoring and medical surveillance until a later rulemaking.   It does not, however, give OSHA blanket authority to pick and choose what statutory requirements it will follow.   The OSH Act mandates that OSHA promulgate the standards that "most adequately" assure that workers will not be exposed to significant risks of material health impairment "to the extent feasible" for the affected industries.   Further, section 6(e) and caselaw require OSHA to adequately explain its determinations.   Section 6(b) of the Act does not provide an exception to these requirements for administrative convenience.   The only exceptions to the strict statutory criteria are the start-up provisions of section 6(a), the applicability of which has long since passed, and the emergency provisions of section 6(c), neither of which are implicated in this case.

Therefore, although we find that the record adequately explains and supports OSHA's determination that the health effects of exposure to these 428 substances are material impairments, we hold that OSHA has not sufficiently explained or supported its threshold determination that exposure to these substances at previous levels posed a significant risk of these material health impairments or that the new standard eliminates or reduces that risk to the extent feasible.   OSHA's overall approach to this rulemaking is so flawed that we must vacate the whole revised Air Contaminants Standard.

We have no doubt that the agency acted with the best of intentions.   It may well be, as OSHA claims, that this was the only practical way of accomplishing a much needed revision of the existing standards and of making major strides towards improving worker health and safety.   Given OSHA's history of slow progress in issuing standards, we can easily believe OSHA's claim that going through detailed analysis for each of the 428 different substances regulated was not possible given the time constraints set by the agency for this rulemaking.   Unfortunately, OSHA's approach to this rulemaking is not consistent with the requirements of the OSH Act.   Before OSHA uses such an approach, it must get authorization from Congress by way of amendment to the OSH Act.^[6] Legislative decisions on the federal level are to be made in the chambers of Congress.   It is not for this court to undertake the substantial rewriting of the Act necessary to uphold OSHA's approach to this rulemaking.

Therefore, for the reasons stated above, we vacate the revised Air Contaminants Standard, and remand to the agency.

[1] The Walsh-Healey standards, in turn, had been adopted from the 1968 recommendations of the American Conference of Governmental Industrial Hygienists ("ACGIH").   The ACGIH is a private organization consisting of professional personnel who work in governmental agencies and educational institutions engaged in occupational safety and health programs.   ACGIH updates its recommendations (called "Threshold Limit Values" or "TLVs") annually.   Air Contaminants Proposed Rule, 53 Fed.Reg. 20960, 20966 (1988).

[2] The three "generic" rulemakings were:  Cancer Policy, 29 C.F.R. Part 1990;  Access to Employee Exposure and Medical Records Regulation, 29 C.F.R. §  1910.20;  Hazard Communication Standard, 29 C.F.R. §  1910.1200.

[3] The Court in Benzene gave an example, stating that "if the odds are one in a thousand that regular inhalation of gasoline vapors that are 2% benzene will be fatal, a reasonable person might well consider the risk significant and take appropriate steps to decrease or eliminate it." Benzene, 448 U.S. at 655, 100 S.Ct. at 2871.   OSHA has apparently incorporated that example "as a policy norm, at least in the sense of believing that it must regulate if it finds a risk at the 1/1000 level."

[4] However, the Supreme Court has determined that the requirement of economic feasibility does not mean that OSHA must perform a cost-benefit analysis, because Congress has "place[d] the 'benefit' of workers health above all other considerations save those making attainment of this 'benefit' unachievable."  ATMI, 452 U.S. at 509, 101 S.Ct. at 2490.

[5] They were the basis for the Walsh-Healey Act standards and, by extension, the original OSHA start-up standards under section 6(a).  

[6] For a discussion of the need for a massive reworking of the OSH Act, see Sidney A. Shapiro & Thomas O. McGarity, Reorienting OSHA: Regulating Alternatives and Legislative Reform, 6 Yale J. on Reg. 1 (1989).

Some hazards can pose immediate danger of death if not addressed.  The three cases above explored the ability of OSHA to issue standards for health hazards – that is, for toxic materials or harmful physical agents governed by § 6(b)(5) of the OSH Act.  But it is also important to note that the problem of promulgating standards is not confined to health standards.

A good example of the challenges in safety standards can be found in the history of the “lockout- tagout” rule.  Failure to engage in appropriate procedures for lockout and tagout can result in death, and there are numerous examples of fatalities that have followed these failures.

In a challenge to the Control of Hazardous Energy Sources (Lockout/Tagout) regulation [54 Fed.Reg. 36,644 (1989)], the D.C. Circuit explained:

The regulation deals not with the effects of such subtle phenomena as electrical energy fields but with those of ordinary industrial equipment that may suddenly move and cut or crush or otherwise injure a worker. “Lockout” and “tagout” are two procedures designed to reduce these injuries. Lockout is the placement of a lock on an “energy isolating device”, such as a circuit breaker, so that equipment cannot start up until the lock is removed. See 29 CFR § 1910.147(b) (1990). Tagout is the similar placement of a plastic tag to alert employees that the tagged equipment “may not be operated” until the tag is removed. See id. Although OSHA had previously issued specific standards governing especially dangerous equipment, the present rule extends lockout/tagout to virtually all equipment in almost all industries. See 29 CFR § 1910.147(a)(1)(ii) (1990). It generally requires employers to use lockout procedures during servicing and maintenance, unless the employer can show that tagout will provide the same level of safety. See id. § 1910.147(c)(2)(ii).

Representatives of labor and industry both challenged the initial regulation.  The court gave deference to OSHA’s position that §6(b)(5) did not apply to safety standards, and then proceeded to grapple with the problem this then created:

The removal of § 6(b)(5) as a direct constraint on OSHA regulations outside the area of toxics (the term we use hereafter as shorthand for “toxic materials or harmful physical agents”) gives point to the NAM's [the National Association of Manufacturer’s] claim of an excessive delegation of legislative power. The only evident source of constraints remaining is § 3(8). It defines an “occupational safety and health standard” as a standard which requires conditions, or the adoption or use of one or more practices, means, methods, operations, or processes, reasonably necessary or appropriate to provide safe or healthful employment and places of employment.29 U.S.C. § 652(8) (1988)… Though the language is exceedingly vague, the Benzene plurality found it the source of a threshold requirement of “significant risk”, without which OSHA was not to act under § 6(b) at all. It justified this narrowing construction with the argument (among others) that otherwise “the statute would make such a ‘sweeping delegation of legislative power’ that it might be unconstitutional under the Court's reasoning in A.L.A. Schechter Poultry Corp. v. United States, 295 U.S. 495, 539 [55 S.Ct. 837, 847, 79 L.Ed. 1570 (1935) ] and Panama Refining Co. v. Ryan, 293 U.S. 388 [55 S.Ct. 241, 79 L.Ed. 446].” 448 U.S. at 646, 100 S.Ct. at 2866.

Id. at 1316.

This initial decision resulted in a remand to OSHA.  After further review the agency re-issued the rule, and it was again challenged, this time by the National Association of Manufacturers. These cases turned on the constitutional question of nondelegation. In ultimately concluding that OSHA could issue the standard, the court concluded that OSHA would have to provide the same level of justification as it requires for health standards. Int'l Union, United Auto., Aerospace & Agr. Implement Workers of Am., UAW v. Occupational Safety & Health Admin., U.S. Dep't of Labor, 37 F.3d 665 (D.C. Cir. 1994)

In the 1994 decision, OSHA indicated to the court that:

The agency must find that (1) “the standard will substantially reduce a significant risk of material harm” [citing the Benzene case] (2) & (3) compliance will be economically and technologically feasible [citing the Cotton Dust case] and (4) the standard “employs the most cost-effective protective measures.” In addition, it must (5) for any standard differing from an existing national consensus standard, publish its reasons why its standard would better effectuate the purposes of the Act; and (6) support its choice of standard with evidence in the rulemaking record and explain any inconsistency with prior agency practice. …"

The court continued:

Were the six itemized criteria the full statement of OSHA's interpretation of its statutory mandate, we might have to vacate the rule, because the agency might still have too much freedom to “roam between the rigor of § 6(b)(5) standards and the laxity of unidentified alternatives.” But OSHA has gone on to infer from various sections-§ 2(b), 29 U.S.C. § 651(b) (stating congressional purpose “to assure so far as possible ... safe ... working conditions”); § 6(a), 29 U.S.C. § 655(a) (in first two years of Act's application, agency was to choose among existing standards the one “which assures the greatest protection”); § 6(b)(8), 29 U.S.C. § 655(b)(8) (setting out terms for justifying deviation from national consensus standard); and § (5)(a)(1), 29 U.S.C. § 654(a)(1) (requiring each employer to provide each employee a place “free from recognized hazards that are causing death or serious physical harm”)-that the Act's “overriding purpose” is “to provide a high degree of employee protection.” 58 Fed.Reg. at 16,614/3-15/1. Thus the agency reads the Act to require it, once it has identified a “significant” safety risk, to enact a safety standard that provides “a high degree of worker protection”. Id. at 16,615/1. It is not permitted to “do nothing at all”, as we had earlier suggested. Id. (quoting International Union I, 938 F.2d at 1317). Rather, OSHA reads the Act to permit it to deviate only modestly from the stringency required by § 6(b)(5) for health standards. Accordingly, as construed by OSHA, the Act guides its choice of safety standards enough to satisfy the demands of the nondelegation doctrine.

Int'l Union, United Auto., Aerospace & Agr. Implement Workers of Am., UAW v. Occupational Safety & Health Admin., U.S. Dep't of Labor, 37 F.3d 665, 669 (D.C. Cir. 1994).

In essence, this makes the issuance of safety standards almost as difficult as the issuance of health standards – although the development of scientific proof may be somewhat easier. The last safety rule to have been issued was the Cranes and Derricks Standard: a final rule was issued in 2010, although it has been amended through formal rule-making since then. It replaced a 40-year-old standard and is designed to prevent the leading causes of fatalities among crane and derrick operators. 

The issue of constitutionality and the nondelegation doctrine has again arisen, specifically with regard to safety standards. As you have seen, questions of constitutionality are not new (note Justice Rehnquist's dissent in the Benzene Case). See Chapter 6.

1. In the aftermath of the decision in AFL v. OSHA, on June 30, 1993, OSHA retracted the air contaminant standard and reinstated the preexisting PELs. See 58 Fed. Reg. 35338-01.  Since then, the old PELs have remained in effect except for a few substances that have been determined to be carcinogenic, including 1,3-Butadiene, Methylene Chloride, Hexavalent Chromium.  See 29 C.F.R. 1910.1000.
2. Be prepared to argue either side of the OSHA position in AFL-CIO v. OSHA. What are OSHA’s strongest arguments?  Why does the court reject them?
3. Despite the gloomy picture that emerges, there are nevertheless many standards ‘on the books’ that are currently enforced. Take a look again at Part 1910 of 29 CFR, either on the OSHA website (https://www.osha.gov/laws-regs/regulations/standardnumber/1910) or in Westlaw or Lexis. These standards cover general industry; look also at Part 1926, which covers construction. Think about which of these standards are “health” standards and which ones are “safety” standards.
4. Section 6 of the OSHAct sets out the procedure for the promulgation of permanent standards. What are the critical components of a health standard? Note that this is a question regarding the substance of the standard itself, not about the proof that OSHA needs to provide to have a standard upheld.  It might help you to look at one of the health standards that is currently in force.  For example, you can find the cotton dust standard at 29 C.F.R. 1910.1043 or the lead standard at 29 C.F.R. 1910.1025.
5. As part of your exploration of standard setting, take a look at the standard governing silica exposure, issued in 2016. See 29 CFR 1910.1053 (general industry) and 29 CFR 1926.1153 (construction). According to the OSHA website:

Respirable crystalline silica – very small particles at least 100 times smaller than ordinary sand you might find on beaches and playgrounds – is created when cutting, sawing, grinding, drilling, and crushing stone, rock, concrete, brick, block, and mortar. Activities such as abrasive blasting with sand; sawing brick or concrete; sanding or drilling into concrete walls; grinding mortar; manufacturing brick, concrete blocks, stone countertops, or ceramic products; and cutting or crushing stone result in worker exposures to respirable crystalline silica dust. Industrial sand used in certain operations, such as foundry work and hydraulic fracturing (fracking), is also a source of respirable crystalline silica exposure. About 2.3 million people in the U.S. are exposed to silica at work.

Workers who inhale these very small crystalline silica particles are at increased risk of developing serious silica-related diseases, including: Silicosis, an incurable lung disease that can lead to disability and death; Lung cancer; Chronic obstructive pulmonary disease (COPD); and Kidney disease.

In order to understand the complexity of this rule-making process, please look at the Federal Register filing of the final general industry rule: Occupational Exposure to Respirable Crystalline Silica, 81 FR 16286-012016, WL 1159095 (March 25, 2016).

What topics does this filing cover? Why is it so long?

Look at the final rule. What do you think are the key elements of this rule?

Look at the OSHA website and its discussion of the rule: https://www.osha.gov/silica-crystalline. What do you find notable here?

6.  The Mine Safety and Health Act regulates hazards in the mining industries. On November 12, 2020, the Office of the Inspector General of the Department of Labor issued a report saying that MSHA needed to improve efforts to protect coal miners from respirable crystalline silica. See   https://www.oig.dol.gov/public/reports/oa/2021/05-21-001-06-001.pdf. On April 18, 2024, MSHA finally issued a new rule, Lowering Miners’ Exposure to Respirable Crystalline Silica and Improving Respiratory Protection (30 C.F.R. Part 60), designed to reduce miner exposures to respirable crystalline silica and improve respiratory protection for all airborne hazards. Among other things, the rule requires medical surveillance for all miners. The final rule took effect on June 17, 2024. Coal mine operators have 12 months to come into compliance with the final rule’s requirements while metal non-metal mine operators have 24 months to come into compliance (including medical surveillance). This rule took years to be issued -- MSHA's rulemaking process is just as complex as that of OSHA. What do you think of the time periods given to the companies to comply with it? 

7. Hidden within the cotton dust case, in addition to the important discussion of cost-benefit analysis, is another issue: OSHA had established a wage guarantee for workers who transferred jobs as a result of their inability to wear a respirator. The court held, “whether or not OSHA has this underlying authority, the agency has failed to make the necessary determination or statement of reasons that its wage guarantee requirement is related to the achievement of a safe and healthful work environment.”  Can you make the case for the wage guarantee?

8. The on-going problem of regulating ergonomics (see Chapter 4.1 for an in depth exploration of the ergonomics isssue):

In November 2000, in the waning days of the Clinton Administration, OSHA issued a final rule to govern ergonomic hazards.  The standard required employers to reduce the incidence of musculoskeletal disorders (MSDs) – including conditions such as carpal tunnel syndrome and back pain – that result from lifting, assembly, and other cumulative or repetitive stresses.  These types of injuries are very common in large industries – from meatpacking to hospitals – and are the largest source of cost in workers’ compensation programs.  The final standard provided for Work Restriction Protection, giving injured workers specific projections to allow for work limitations in a current job or transfer, or temporary transfer to another job (with wage retention).  It also provided for some wage retention for workers who were unable to work (outside of workers’ compensation).  OSHA estimated that 1.8 million workers have MSDs related to ergonomic factors each year and the standard would prevent 460,000 of these injuries, resulting in cost reduction for employers of $9 billion a year.  OSHA estimated cost of the standard at $4.5 billion.  But one industry group argued that it would in fact cost as much as $99 billion a year.

The rulemaking process before the standard was issued was long and laborious.  Industry organized against any regulatory intervention, challenging the science as well as the all other aspects of the rulemaking.  When the rule was issued, it involved a massive amount of evidence, all set out in the Federal Register at  65 FR 68262-01 et seq. (2000).  The proposed standard itself appears on pages 68846 to 68870 – after almost 600 pages of discussion and justification.  The new federal Administration took office in January, and Congress invoked the CRA for the first time (ever) in March 2001 to overturn the  standard.

OSHA subsequently issued ergonomics guidelines, which constituted advice rather than mandatory regulations, for nursing homes, poultry processing, and retail groceries.  Policy later proposed by the Office of Management and Budget would require that these kinds of guidelines be issued for notice and public comment.  This will inevitably restrict the ability of OSHA to issue guidelines like this. Some states with state plans have moved ahead to regulate ergonomic hazards.

9.  Remember that, in absence of a federal standard, states are free to regulate a hazard. Looking at what states are doing with regard to a known hazard can be quite instructive. Later in the course, we will look at the various state approaches to workplace exposure to the coronavirus, as well as at how some states have addressed ergonomic risks. Another hazard that is well known and has seen various approaches by states is heat. People who work outside - in construction, farming and other jobs - can be exposed to severe heat during the summer months. As of this writing (December 2024), six states, all with approved state plans, have enacted legislation to protect workers who are exposed to heat (California, Colorado, Maryland, Minnesota, Oregon, and Washington) and others are considering protective regulation. In contrast, other states are attempting to prevent protections for workers through state legislation - in Texas, for example, state legislation bans municipalities from enacting ordinances to protect workers from heat. Without federal rules, the level of protection against known hazards that is offered to workers can vary tremendously based on where they live. 

10.  In 2024, the Supreme Court issued three remarkable administrative law cases that will change the way courts review the actions of federal agencies. To what extent will these affect review of OSHA standards and enforcement actions?  

• As noted earlier in these materials, Loper Bright Enterprises v. Raimondo, 144 S.Ct. 2244 (2024), the Supreme Court overruled  Chevron, U.S.A., Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837 (1984), which had allowed courts to give deference to the expertise of agencies when reviewing regulations. This will create considerably more uncertainty in the judicial review process - and will likely also lead agencies to spend even more time in the development of any regulation. As you will see from these readings, OSHA's standards have been subject to scrutiny by the courts in the past, and the statutory language  already sets a higher bar than is generally required. What do you think the effect of Loper will be on judicial review of OSHA standards? 
• In Corner Post Inc. v. Board of Governors of the Federal Reserve System, the Supreme Court ruled that the general statute of limitations governing cases brought under the Administrative Procedure Act does not begin to run until the plaintiff is injured by the agency action. Previously, the six year statute of limitations was assumed to run from the time of the issuance of the rule. Will this affect challenges to OSHA standards? Note that the OSHAct explicitly sets 60 day time limits for injured parties to challenge standards ((29 USC 655(f)) or appeal enforcement rulings ((29 U.S.C. §660 (a)).
• In a civil suit involving fraud that was heard in administrative process by the Securities and Exchange Commission, the court ruled that there is a right to a jury trial. Securities and Exchange Commission v. Jarkesy, 144 S.Ct. 2117 (U.S., 2024). The court explicitly distinguished the preexisting precedent set out in Atlas Roofing Co. v. Occupational Safety and Health Review Commission, 430 U.S. 442 (1977): “Because the public rights exception as construed in Atlas Roofing does not extend to these civil penalty suits for fraud, that case does not control.” But the court also noted: "[W]e need not reach the suggestion made by Jarkesy... [that prior cases] effectively overruled Atlas Roofing to the extent that case construed the public rights exception to allow the adjudication of civil penalty suits in administrative tribunals." Where does that leave us? Do you anticipate that the Supreme Court will extend Jarkesy to these kinds of administrative actions? 

We will return later to the possible effect of Jarkesy on individual whistleblower claims that are adjudicated before administrative law judges within the Department of Labor.