VANCE, Circuit Judge:

The Occupational Safety and Health Administration (OSHA) promulgated regulatory standards for the cotton gin industry under the Occupational Safety and Health Act (the Act). 29 U.S.C. § 651 et seq. Five industry associations petitioned for pre-enforcement review in this court, with four other industry organizations intervening, on the basis that the regulations are too stringent; four gin employee organizations petitioned for review on the ground that the standards do not adequately protect workers against the hazards of cotton dust. The Supreme Court recently ruled that the Act requires OSHA to provide substantial evidence that a significant risk of harm arises from a workplace or employment. Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. ___, 100 S.Ct. 2844, 65 L.Ed.2d 1010 (1980) (plurality opinion). This circuit, affirmed on other grounds by the Supreme Court, had held that the Act also compels OSHA to adduce substantial evidence that the costs imposed by a regulation bear a reasonable relation to the benefits derived. American Petroleum Institute v. OSHA, 581 F.2d 493, 503 (5th Cir. 1978). In protecting workers' safety and health Congress also limited OSHA's regulatory power through statutory requirements that we must enforce.

I. BACKGROUND

Background information about the ginning industry and occupational diseases is essential for analysis of the justification, reasonable necessity, and feasibility of OSHA's regulations.

A. The Ginning Industry

The ginning process consists of a series of mechanical operations that separate the lint from the seed so that the lint may be processed by textile mills and the seeds may be used by cottonseed oil mills. Additionally, ginning removes foreign matter that has become entangled in the raw cotton during harvesting. Most of the cotton crop is ginned in the fall and early winter, immediately after it is picked, on the farm or in the locality where it is grown.

The ginning system is automated to a large extent with the cotton moving through pneumatic pipes. Cotton is delivered to the gin in storage trailers and removed by a pneumatic device. The cotton passes through machinery that separates the lint from the seed. The seed are conveyed to a storage house and the cotton lint is pneumatically conveyed through lint cleaners into the baling press where it is hydraulically pressed into bales.

Although the size of the operation and the capabilities of the individuals influence the composition of the workforce, the job functions in a typical cotton gin crew include a gin stand operator, lint cleaner operator, press man, sucker pipe operator and yard man. The average gin worker spends half of his time outside the gin shed away from cotton dust concentrations, and the typical gin is at least partially open — sided with substantial outside air circulation.

Gin employment is characterized by its seasonal nature, migrant work force, and high employee turnover. Estimates of a typical ginning season vary from four-six weeks, four-eight weeks, and five-twelve weeks. The average employee works only about seven weeks per year, averaging sixty workhours per week. Because a major source of gin workers is local transient labor, there is a rapid turnover among nonsupervisory employees. In the west, the labor force is supplemented by a large number of migrant workers, leading to a very high turnover rate. Additionally, gins often hire workers to meet their immediate needs; consequently, workers frequently move onto other jobs when a gin's operation is interrupted or finished. The general level of cotton dust exposure is significantly lower for gin workers than for textile workers and most other cotton manufacturing workers because of the seasonal nature of ginning, the transitory character of the labor force, and the gin workers' exposure to outside air.

B. Respiratory Disease

Byssinosis, commonly called brown lung disease, is a respiratory impairment linked to inhalation of cotton dust. Acute byssinosis, in its three stages, is characterized by occasional chest tightness on Monday or the first day of the work week (grade 1/2), chest tightness or breathlessness on every Monday (grade 1), and those symptoms on midweek days as well (grade 2). Chronic byssinosis, with symptoms similar to bronchitis and emphysema, involves chest tightness or breathlessness on Mondays and other work days and permanent incapacity from short-windedness or reduced breathing ability (grade 3). Grades 1/2 through 2 are nondisabling and reversible while grade 3 is generally disabling and irreversible. The acute grades of byssinosis presently can be diagnosed only by subjective questions, while chronic byssinosis can also be detected by two pulmonary function tests.

Numerous studies involving the textile industry have linked the occurrence of acute and chronic byssinosis to long term exposure to cotton dust, although they have not fully explained the etiology. The least acute stage does not develop until after several years of a worker's exposure, and the majority of textile and other cotton industry workers never evidence byssinosis. Six studies involving foreign ginning and one surveying the American ginning industry have yielded conflicting results about whether byssinosis and chronic respiratory disease result from the exposure level in gins to cotton dust.

C. The Challenged Ginning Regulations

The Assistant Secretary of Labor for the Occupational Safety and Health Administration in 1978 promulgated regulations of cotton dust exposure by gin employees through informal rulemaking procedures. 29 C.F.R. § 1910.1046 (1979). These cotton gin regulations essentially involve five requirements. Beginning with the most controversial directive, (1) employers must provide medical surveillance of exposed employees. Before ginning employment begins each year, medical technicians must take a medical history, administer a seven page questionnaire about subjective symptoms, give the pulmonary function tests for objective symptoms, and grade any byssinosis symptoms. After at least fourteen days of ginning employment, they must repeat the pulmonary function tests when the employee has been off work for at least twenty-four hours and then after he has worked for at least four hours in the gin that same day. The midseason test results must be compared with each other and with the pre-employment results, and all pulmonary measurements must be compared with the employee's results from prior years and with standard values for the general population. A physician must then prepare a report detailing the results of the examinations, his diagnosis of any byssinosis symptoms, and recommendations for health measures. The medical surveillance requirement does not apply for employees who have already been tested at another gin during that same season. (2) Gin operators must establish and implement a work practice plan to minimize employee exposure to cotton dust by assuring that all surfaces are kept as free as practicable from dust accumulation, providing for regular inspection and maintenance of all equipment and ventilation systems, requiring mechanical handling of cotton and waste products unless infeasible, and prohibiting maintenance or cleaning with compressed air equipment unless alternative methods are not feasible. (3) Employers must provide disposable respirator masks for all employees desiring them and powered air purifying respirators to any employees suffering from respiratory impairment or performing specified tasks, and must assure the use of respirators by employees identified in medical surveillance as susceptible to cotton dust and by employees performing maintenance activities or using compressed air cleaning equipment. (4) Gin operators must post warning signs about the respiratory dangers associated with cotton dust. (5) They must provide training programs before ginning begins concerning those dangers and the protective measures discussed above.

OSHA did not impose on the ginning industry a requirement for a maximum limit on airborne concentration of cotton dust (a permissible exposure limit, or PEL) or for dust emission controls on gin machinery. The basic reasons for not requiring a PEL and emission devices were that gin employees are only exposed to cotton dust for a short season, that the proper maximum level is not known for such seasonal exposure, and that the emission controls are infeasible because they would increase the construction cost of the average gin by sixty-five percent and would increase the farmer's ginning costs by fifty percent.

D. The Petition for Review

Five ginning industry organizations filed petitions for pre-enforcement review in this circuit of the cotton gin regulations, note 1 supra, and four other ginning associations intervened, note 2 supra. See 29 U.S.C. § 655(f). In this consolidated petition, they contend that the OSHA ginning regulations are not required by a material impairment of workers' health, are not feasible in their medical examination requirements, and are not reasonably necessary in their remaining requirements. This court granted their motion for a stay of the regulations pending appeal. Four gin employee organizations submitted petitions for review, note 3 supra, on the ground that the standards are not as high as necessitated by a material impairment of workers' health, because they do not include a maximum exposure limit to cotton dust. Several cotton industry organizations and cotton workers' unions also petitioned for review of the OSHA general regulations for the textile, cotton warehouse, and cottonseed industries, and the District of Columbia Circuit sustained those regulations except their application to the cotton seed oil industry.

II. STANDARD OF REVIEW

A. The Substantial Evidence Standard

The Act unqualifiedly 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). This review standard applies to both factual determinations and policy determinations by OSHA, although its application to the latter is more difficult. AFL-CIO v. Marshall, 617 F.2d 636, 648 n. 43 (D.C. Cir. 1979); Associated Industries of New York State, Inc. v. United States Department of Labor, 487 F.2d 342, 348 (2nd Cir. 1973); see American Petroleum Institute v. OSHA, 581 F.2d 493, 497 (5th Cir. 1978), aff'd on other grounds sub nom. Industrial Union Department, AFL-CIO v. American Petroleum Institute, 446 U.S. ___, 100 S.Ct. 2844, 65 L.Ed.2d 1010 (1980). For factual determinations, "the substantial evidence standard provided in the statute clearly is applicable." 581 F.2d at 497. Accord, Florida Peach Growers Association v. United States Department of Labor, 489 F.2d 120, 127 (5th Cir. 1974). "When available evidence of equivalent quality is conflicting, a finding in accordance with one view or the other should be considered to be supported by substantial evidence." American Petroleum Institute v. OSHA, 581 F.2d at 507.

For policy determinations, the administrative decision "must be scrutinized" even though it is "not so susceptible to verification or refutation by the record" as are factual findings. Id. at 497. Accord, Industrial Union Department, AFL-CIO v. Hodgson, 499 F.2d 467, 475 (D.C. Cir. 1974) ("exacting scrutiny"). This scrutiny of informal rulemaking involves a two-fold examination:

[The courts] have required the Secretary's action to be [1] consistent with the statutory language and purpose. Synthetic Organic Chemical Manufacturers Association v. Brennan, . . . 503 F.2d [1155,] 1159 (3rd Cir. 1977). As this court stated in assessing an emergency temporary standard in Florida Peach Growers, "it seems clear that even with the required substantial evidence test, our review basically must determine whether the Secretary carried out his essentially legislative task in a manner [2] reasonable under the state of the record before him." 489 F.2d at 129. This includes, of course, a review of whether the Secretary exercised his decisionmaking power within the limits imposed by Congress.

American Petroleum Institute v. OSHA, 581 F.2d at 497. Accord, Taylor Diving Salvage Co. v. United States Department of Labor, 599 F.2d 622, 624 (5th Cir. 1979); see Citizens to Preserve Overton Park v. Volpe, 401 U.S. 402, 415-16, 91 S.Ct. 814, 823, 28 L.Ed.2d 136 (1971).

The reasonableness requirement, as applied to OSHA policy determinations, stems from the mandate of the Administrative Procedure Act, 5 U.S.C. § 551 et seq., for a reviewing court to hold unlawful and to set aside agency action, findings, and conclusions, whether adopted through formal or informal rulemaking, that are "arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law." Id. § 706(2)(A). This involves appellate scrutiny to determine (a) whether enough facts are available and have been investigated to render rational the making of a policy judgment; (b) whether the factual premises underlying that policy judgment are "supported by substantial evidence," although there may be other conflicting evidence, in the record considered as a whole; and (c) whether the policy judgment is reasonably related to those substantially supported factual premises so that "`the Secretary carried out his essentially legislative task in a manner reasonable under the state of the record.'" American Petroleum Institute v. OSHA, 581 F.2d at 497 (quoting Florida Peach Growers Association, Inc. v. United States Department of Labor, 489 F.2d at 129). The agency record should contain the data required under the substantial evidence standard for appellate review of the reasonableness of OSHA's policymaking as well as of OSHA's obedience to other statutory limitations.

B. The Statutory Mandate and Limitations

The consistency requirement, which is that OSHA's action must accord with the Act's language and purpose, refers inter alia to several explicit statutory limitations on OSHA rulemaking. The Act authorizes only those OSHA regulations that are elicited by a significant risk of unsafe or unhealthful employment or workplaces, and that are reasonably necessary or appropriate to reduce that risk. For toxic materials or harmful physical agents, 29 U.S.C. § 655(b)(5) authorizes only those regulations that also are justified by a significant risk of material impairment of the health or functional capacity of employees and are feasible from both technological and economic standpoints. The substantial evidence standard applies to appellate review of OSHA's determination regarding each of these limitations. This requires substantive review of the evidence in the agency record and not merely procedural review of the agency's genuine consideration of diverse informed opinions.

C. Summary

The petitioning and intervening ginners in this case question whether the cotton gin regulations are necessitated by a significant risk of material health impairment, whether the ginning regulations are reasonably necessary or appropriate, and whether the medical surveillance requirement is feasible. The petitioning gin employee organizations assert that a permitted exposure limit (PEL) for cotton gin dust would most adequately protect workers and is reasonably necessary or appropriate.

The purpose of the Occupational Safety and Health Act to protect workers is most laudable. The only question that we decide is whether OSHA's regulations for cotton gins comply with the statutory requirements that Congress has prescribed. We conclude that they do not because OSHA has not found as a "threshold matter" that cotton dust poses a "significant health risk" in cotton gins, Part III infra, and that a standard is "reasonably necessary or appropriate to provide safe or healthful employment and places of employment." See Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. ___, 100 S.Ct. 2844, at 2850 (1980) (plurality opinion); Part IV infra.

III. SIGNIFICANT RISK OF MATERIAL HEALTH IMPAIRMENT

Section 3(8) of the Act requires that all OSHA standards must be "reasonably necessary or appropriate to provide safe or healthful employment and places of employment." 29 U.S.C. § 652(8). In Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. ___, 100 S.Ct. 2844 (1980) (plurality opinion), the Supreme Court construed this provision to require the Secretary of Labor to make a threshold finding "that the workplaces in question are not safe." ___ U.S. at ___, 100 S.Ct. at 2864. However, the Court explained:

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.

Id.

Section 6(b)(5) of the Act also provides that "standards dealing with toxic materials or harmful physical agents" shall assure "that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure . . . ." 29 U.S.C. § 655(b)(5). This "empowers the Secretary to promulgate standards, not for chemicals and physical agents generally, but for ` toxic chemicals' and ` harmful physical agents.'" Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. at ___, 100 S.Ct. at 2864 (plurality opinion). The threshold finding of toxicity or harm under section 6(b)(5) is consistent with the threshold finding of significant risk of unsafety or unhealthfulness under section 3(8). Similarly, section 6(b)(5) requires that the toxic substances or harmful physical agent threaten a "material impairment of health or functional capacity." Not just any impairment, but a material impairment, is required as the legislative history emphasizes. Because section 3(8) applies to regulations of toxins and harmful agents as well as to all other OSHA regulations, Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. at ___, 100 S.Ct. at 2864 (plurality opinion), the combined test applicable to toxins and harmful agents is that "the burden [is] on the Agency [OSHA] to show, on the basis of substantial evidence, that it is at least more likely than not that long-term exposure to [toxic material or harmful physical agents] presents a significant risk of material health impairment." Id. at ___, 100 S.Ct. at 2869.

OSHA's finding of a health hazard from cotton ginning is based on the correlation between the occurrence of byssinosis from exposure to cotton dust in other facets of the textile industry and by several studies involving the ginning industry. The studies of ginning employees relied on by OSHA include several studies of ginning operations in foreign countries as well as a study of American gins by Palmer. Despite the fact that the Palmer study found no evidence of byssinosis or other chronic respiratory disease among American gin workers, OSHA inferred a correlation between the foreign studies and the one conducted by Palmer. In view of the significantly different ginning conditions and season in America with reduced worker exposure to cotton dust as well as the lack of evidence of byssinosis by Palmer, these studies do not constitute substantial evidence for OSHA's finding of a significant risk of a material health impairment.

A. The American Ginning Study

Palmer utilized X-ray readings, respiratory symptom questionnaire, and spirometric tests in examining the incidence of byssinosis and other chronic respiratory disease among gin workers and a control group in the Rio Grande Valley and New Mexico. Results from the interviewer administered questionnaire showed that chronic respiratory disease was more prevalent in the control group, thirty-nine percent, than in the gin workers, thirty percent. Furthermore, the amount of chronic respiratory disease diagnosed by spirometric test was identical for the gin workers and the control group. Spirometer results, however, showed that forty-four percent of gin workers, called reactors, suffer a decline in their forced expiratory volume in one second, FEV[1], after several hours on the job of which twenty-seven percent manifested a moderate decline and seventeen percent a severe decline. Nonetheless, only acute, not chronic respiratory effects were shown by the pulmonary function results. Moreover, smokers had the least number of reactors and the most moderate and severe reactors on the pulmonary function tests. The significance of pulmonary function results is their indication that gin workers do not suffer any long term impairment, despite the evidence that gin workers do experience a daily nonchronic decline in pulmonary function during the ginning season.

The Palmer study found no evidence of byssinosis or other chronic respiratory disease among American gin workers. Much of the spirometer data as well as all of the questionnaire data supports the industry petitioners' stance in denying symptoms of byssinosis or other chronic respiratory disease. Some of the spirometer data supports OSHA's position in showing that gin workers suffer a temporary decline in FEV[1] and FVC measures during exposure to cotton dust — but not that they experience a permanent decline in those measures relative to the general nonginning population. This study does not provide substantial evidence of a significant risk of material health impairment.

B. The Foreign Ginning Studies

In concluding that exposure to cotton dust was a health hazard for gin workers, OSHA relied on several foreign studies of ginning employees in Egypt, Uganda, Greece and Sudan. Studies of gin workers in Egypt and Sudan showed a correlation between gin workers and byssinosis. The two El Batawi studies found that thirty-eight percent and thirty-three percent of Egyptian gin workers had various grades of byssinosis and that workers in dusty areas had lower pulmonary function than nonginners as well as a substantial drop in pulmonary function during the workday. The Khogali studies discovered that about twenty percent of Sudanese gin workers have various grades of byssinosis. Although OSHA "views these foreign studies as support" for the promulgation of standards, the agency recognizes the "uncertainty in relying too heavily upon" these studies, explaining that the ginning season in Egypt and Sudan is substantially longer than in the United States, the worker population is more stable and the primitive foreign gins often increase worker exposure to cotton dust because many manual processes are present in the gin. The Gilson study in Uganda and the Kondakis investigation in Greece did not adduce the occurrence of byssinosis in gin workers, although a decline in FEV[1] was found.

C. The Cotton Manufacturing Industry Studies

OSHA argues that numerous studies involving the cotton yarn manufacturing, weaving, fabric manufacturing, and related cotton industries provide substantial evidence that byssinosis and other chronic respiratory disease is linked to cotton exposure. We agree. The agency arguably has adduced substantial evidence of acute respiratory effects on American gin workers from cotton dust exposure; it assumes from cotton industry studies that these acute effects develop into byssinosis and other chronic respiratory disease. OSHA has not provided substantial evidence that byssinosis and other chronic disease arise from the exposure level to cotton dust in the ginning industry with its significantly different conditions and its significantly different exposure level. As discussed in Part I(A) supra, ginning is a seasonal industry involving annual exposure for only about ten weeks, unlike the year-round industries in cotton manufacturing. Workers are highly transitory and migrant, engaging in ginning for about seven weeks annually, unlike cotton industry workers. Gins are generally open-sided with much air circulation; workers spend about half their time outdoors, unlike the strictly indoor processes in cotton manufacturing. These different conditions in the ginning industry yield significantly reduced exposure to cotton dust. OSHA has not adduced substantial evidence that this exposure level produces the same significant risk of byssinosis and other chronic respiratory disease. The Supreme Court decision in Industrial Union Department is on point. There, OSHA failed to provide substantial evidence that a 1-10 part per million exposure to benzene presents a "significant risk of harm"; instead OSHA relied on a series of assumptions that lowering the exposure limit would reduce the occurrence of leukemia. ___ U.S. at ___, 100 S.Ct. at 2873 (plurality opinion).

In the present case, OSHA has not produced substantial evidence that a ten week or less annual exposure for half the workday to cotton dust entails a significant risk, accepting that a year-round exposure does significantly threaten a material health impairment. Instead of findings based on substantial evidence, OSHA has made findings based on assumptions without an adequate evidentiary basis. OSHA has relied on the assumptions, from byssinosis resulting from the high exposure level in textile mills and other cotton manufacturing processes, that byssinosis must result from the substantially lower exposure level in cotton gins. As in Industrial Union Department, "[t]hese assumptions are not a proper substitute for the findings of a significant risk of harm required by the Act." Id. at ___, 100 S.Ct. at 2874. We reverse OSHA's determination and remand for consistent proceedings.

IV. REASONABLY NECESSARY OR APPROPRIATE STANDARD

A. The Statutory Requirement

Section 3(8) of the Act defines an occupational safety and health standard authorized by the Act as a standard whose requirements are "reasonably necessary or appropriate to provide safe or healthful employment and places of employment." 19 U.S.C. § 652(8). The reasonably necessary or appropriate clause does not merely require that OSHA standards must be rational, because Congress added the limitation that standards must be "necessary or appropriate" to the reasonableness limitation. Instead the reasonably necessary requirement imposes a substantive limitation upon the regulatory authority of OSHA, as this circuit stated in American Petroleum Institute v. OSHA, 581 F.2d 493 (5th Cir. 1978), aff'd on other grounds sub nom. Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. ___, 100 S.Ct. 2844 (1980):

The Act imposes on OSHA the obligation to enact only standards that are reasonably necessary or appropriate to provide safe or healthful workplaces. If a standard does not fit in this definition, it is not one that OSHA is authorized to enact.

581 F.2d at 502. The Supreme Court implicitly recognized this substantive restriction when it held that the reasonably necessary clause requires a significant risk of material harm before OSHA can promulgate regulations under Section 6(b)(5), 29 U.S.C. § 655(B)(5). Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. ___, 100 S.Ct. 2844 (1980) (plurality opinion). Because of this and other statutory limitations, the Act "does not give OSHA the unbridled discretion to adopt standards designed to create absolutely risk-free workplaces regardless of cost." American Petroleum Institute v. OSHA, 581 F.2d at 502. Accord, Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. at ___, 100 S.Ct. at 2864; Taylor Diving Salvage Co. v. United States Department of Labor, 599 F.2d 622, 625 (5th Cir. 1979). The reasonably necessary or appropriate limitation requires that OSHA regulations must be reasonably essential or at least reasonably efficacious in reducing a significant risk of material harm.

This circuit in American Petroleum Institute held that the reasonably necessary limitation requires OSHA, before promulgating regulations, (1) to estimate the expected costs of its regulation, (2) to estimate the expected benefits of that regulation, and (3) to determine whether those benefits are reasonably related to those costs.

Before it regulates, the agency must show that a hazard exists and that its regulation will reduce the risk from the hazard, for "no [occupational safety and health] standard would be expected to impose added costs or inconvenience . . . unless there is reasonable assurance that the frequency or severity of injuries or illnesses will be reduced." [ Aqua Slide `N' Dive Corp. v. CPSC,] 569 F.2d at 839. More importantly for today's case, Aqua Slide also requires the agency to assess the expected benefits in light of the burdens to be imposed by the standard. Although the agency does not have to conduct an elaborate cost — benefit analysis, 569 F.2d at 840, it does have to determine whether the benefits expected from the standard bear a reasonable relationship to the costs imposed by the standard. 569 F.2d at 842.

The only way to tell whether the relationship between the benefits and costs of the benzene standard is reasonable is to estimate the extent of the expected benefits and costs. See 569 F.2d at 843.

581 F.2d 493, 502-03. Accord, Florida Peach Growers Association, Inc. v. United States Department of Labor, 489 F.2d 120, 130 (5th Cir. 1974). Although the Supreme Court plurality in Industrial Union Department did not reach the issue, Justice Powell in his concurring opinion also recognized that the reasonably necessary limitation, as well as the feasibility limitation, requires OSHA to estimate and compare the costs and benefits of a proposed regulation:

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. . . . In my view that claim is untenable.

. . . . 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.

Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. at ___, 100 S.Ct. at 2877-78 (concurring opinion). Justice Powell explained that this comparison is required because the "cost of complying with a standard may be `bearable' and still not reasonably related to the benefits expected." Id. at ___, n. 4, 100 S.Ct. at 2850 n. 4. This mandate for estimation of costs and benefits and of a reasonable relationship between those costs and benefits is not a requirement for formal cost — benefit analysis. American Petroleum Institute v. OSHA, 581 F.2d at 503; see Aqua Slide `N' Dive Corp. v. CPSC, 569 F.2d 831, 840 (5th Cir. 1978).

The substantial evidence standard of review applies to OSHA's comparison of costs and benefits. As this court ruled in American Petroleum Institute,

Until OSHA can provide substantial evidence that the benefits to be achieved . . . bear reasonable relationship to the costs imposed . . . it cannot show that the standard is reasonably necessary to provide safe or healthful workplaces.

581 F.2d at 504. OSHA's estimate of the anticipated cost and expected benefit of proposed regulations are factual findings that must be supported by substantial evidence in the record. Id. at 503; see, e. g., Aqua Slide `N' Dive Corp. v. CPSC, 569 F.2d at 844. The agency's determination that the cost bears a reasonable relationship to the benefit, although a policy determination to a large degree, also is subject to the substantial evidence standard. E. g., Florida Peach Growers Association, Inc. v. United States Department of Labor, 489 F.2d at 129; see Aqua Slide `N' Dive Corp. v. CPSC, 569 F.2d at 841; id. at 845 (Wisdom, J., concurring). For such a policy determination to be supported by substantial evidence, sufficient facts must be available to render a policy judgment rational; the factual premises underlying that judgment must be supported by substantial evidence; and the judgment must be rationally related to those factual premises so that the regulatory manner is reasonable. Part II(A) supra. As with other determinations, OSHA must make specific findings of these elements of reasonable necessity, see Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. at ___ n. 45, 100 S.Ct. at 2863 n. 45 and must include its evidence in the record.

B. OSHA's Noncompliance

OSHA conclusorily asserted that "significant worker protection will result" from the cotton ginning regulations and that "it is not possible to estimate anticipated declines in the incidence of byssinosis." An assumption without supporting evidence or even a finding upon substantial evidence that regulatory benefits are "likely to be appreciable" is simply not sufficient to meet the reasonably necessary requirement of the Act. Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. at ___, 100 S.Ct. at 2870; see id., at ___, 100 S.Ct. at 2878 (Powell, J., concurring); American Petroleum Institute v. OSHA, 581 F.2d at 503; see Aqua Slide `N' Dive Corp. v. CPSC, 569 F.2d at 845 (Wisdom, J., concurring). As in American Petroleum Institute, OSHA's refusal here to estimate the expected benefits of its ginning regulations and to show their reasonable relationship to the concomitant costs on the basis of substantial evidence requires the conclusion that the agency has not shown these regulations to be reasonably necessary on the basis of substantial evidence.

OSHA's response that it is impossible to estimate any benefits from its regulations is as inadequate here as it was in American Petroleum Institute:

We are not persuaded by OSHA's argument that this standard should be upheld since the lack of knowledge concerning the effects of exposure to benzene at low levels makes an estimate of benefits expected from reducing the permissible exposure level impossible. The statute requires all conditions imposed by a standard to be reasonably necessary to provide safe or healthful employment, and it requires decisions to be based on "the best available evidence," "research, demonstrations, experiments, and such other information as may be appropriate," "the latest scientific data in the field," and "experience gained under this and other health and safety laws." By requiring the consideration of such kinds of information, Congress provided that OSHA regulate on the basis of knowledge rather than on the unknown . . . Until OSHA can provide substantial evidence that the benefits to be achieved by reducing the permissible exposure limit from 10 ppm to 1 ppm bear a reasonable relationship to the costs imposed by the reduction, it cannot show that the standard is reasonably necessary to provide safe or healthful workplaces.

581 F.2d at 504 (footnote omitted). OSHA was able to estimate the anticipated costs of the cotton ginning regulations, thus, it should be capable of estimating the expected benefits upon substantial evidence. Because of the reasonably necessary limitation, OSHA is not authorized to promulgate regulations until it has substantial evidence that they will ameliorate a significant risk to workers' health or safety and that they are reasonably necessary and appropriate by virtue of the regulatory benefits being reasonably related to the consequent costs.

Although OSHA has neither provided substantial evidence that there is a significant health risk to gin workers from cotton dust nor shown by substantial evidence that the standards promulgated for the cotton ginning industry are reasonably necessary, for the guidance of OSHA we note that there is also a feasibility requirement that must be proven if the other tests are met. Section 6(b)(5) of the Act provides that OSHA standards shall prevent "to the extent feasible," material health impairments from toxic materials or harmful physical agents. 29 U.S.C. § 655(b)(5). Whereas the reasonably necessary limitation ensures that an OSHA regulation will effectively ameliorate a significant health or safety risk without unreasonable cost, the feasibility limitation requires that the regulation must be attainable and that its achievement must be at a practical cost. The feasibility limitation includes both technological and economic feasibility. AFL-CIO v. Marshall, 617 F.2d 636, 655 (D.C. Cir. 1979); American Iron Steel Institute v. OSHA, 577 F.2d 832 (3d Cir. 1978), cert. dismissed, ___ U.S. ___, 100 S.Ct. 2844 (1980). OSHA has the burden of proving the feasibility of its section 6(b)(5) regulations in pre-enforcement review, RMI Co. v. Secretary of Labor, 594 F.2d 566, 573 (6th Cir. 1979) just as it carries the burden of proving feasibility in citation cases. Champlin Petroleum Co. v. OSHRC, 593 F.2d 637, 640 (5th Cir. 1979).

CONCLUSION

OSHA has not adduced substantial evidence that its cotton ginning regulations are "reasonably necessary and appropriate to remedy a significant risk of material health impairment." Industrial Union Department, AFL-CIO v. American Petroleum Institute, ___ U.S. at ___, 100 S.Ct. at 2863 (1980) (plurality opinion). Because the Occupational Safety Health Act requires OSHA to meet these requirements, we vacate the regulations on these grounds and remand the case to OSHA for further consideration of any significant risk of material health impairment that may be remedied by a reasonably necessary and appropriate standard.

VACATED and REMANDED.

BENEFITS

OSHA policy and conclusions on benefit assessment are described in the preamble to the cotton dust regulation for other sectors. In the absence of current, directly relevant epidemiological studies, it is not possible to estimate anticipated declines in the incidence of byssinosis that would result from implementation of the provisions of the final regulation of cotton dust in gins. OSHA is confident that significant worker protection will result from mandated changes in work practices and from medical surveillance and respirator programs. Pending the result of further NIOSH study, more costly controls do not appear to be warranted. The estimated costs of the final regulation of cotton dust in gins are modest when compared to those estimated for the proposed regulation, and OSHA feels that the anticipated benefits in terms of improved worker health will fully justify such costs.

Based upon the foregoing and the record as a whole, OSHA finds that compliance with the standard is well within the financial capability of the ginning industry. Moreover, although the benefits of the standard cannot rationally be quantified in dollars, OSHA has given careful consideration to the question of whether these costs are justified in light of the hazards of exposure to cotton dust. OSHA concludes that these costs are minimal and necessary in order to effectuate the statutory purpose of the Act and to adequately protect employees from the hazards of exposure to cotton dust.