International Union, United Automobile, Aerospace & Agricultural Implement Workers of America, Uaw v. Occupational Safety & Health Administration, U.S. Department of Labor, the Dow Chemical Company, American Petroleum Institute, National Confections Association, Chocolate Manufacturers Association, Intervenors. National Association of Manufacturers v. Occupational Safety & Health Administration, U.S. Department of Labor, Elizabeth Dole, Secretary of Labor, Motor Vehicle Manufacturers Association of the United States, Intervenor. International Union, United Automobile, Aerospace & Agricultural Implement Workers of America, Uaw, Oil, Chemical & Atomic Workers International Union v. Occupational Safety & Health Administration, U.S. Department of Labor

Representatives of labor and industry challenge a regulation of the Occupational Safety and Health Administration,1 "Control of Hazardous Energy Sources (Lockout/Tagout)". 54 Fed.Reg. 36,644 (1989). 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.2 "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 Sec. 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,3 the present rule extends lockout/tagout to virtually all equipment in almost all industries. See 29 CFR Sec. 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. Sec. 1910.147(c)(2)(ii).

The first issue we address is the claim of petitioner UAW that Sec. 6(b)(5) of the Occupational Safety and Health Act, 29 U.S.C. Sec. 655(b)(5) (1988), provides the statutory criteria for the lockout rule. Its claim is that the hazard involved is a "harmful physical agent[ ]" as that term is used in the first sentence of Sec. 6(b)(5), and that, even if the first sentence of Sec. 6(b)(5) is not applicable, the remaining sentences are. OSHA resists both theories, and we find its interpretation reasonable.

The exclusion of Sec. 6(b)(5) from the picture takes us to the claim of the National Association of Manufacturers that Congress has given so little guidance for rules issued under Sec. 6(b) but not covered by Sec. 6(b)(5) that as to such rules the Act invalidly delegates legislative authority. Although we reject that claim, we find that the interpretation offered by the Secretary is, in light of nondelegation principles, so broad as to be unreasonable. We note, however, the existence of at least one interpretation that is reasonable and consistent with the nondelegation doctrine.

Thus, after addressing some objections to the rule that appear likely to survive any reasonable interpretation the Secretary may adopt, we remand the case to the Secretary for further consideration.

* Section 6(b)(5) of the Act4 limits the Secretary's discretion when he is promulgating standards that deal with "toxic materials or harmful physical agents". He must adopt "the standard which most adequately assures, to the extent feasible, ... that no employee will suffer material impairment of health or functional capacity." Id. The Supreme Court has interpreted this language to require that the proposed standard be both technologically and economically "feasible", American Textile Mfrs. Inst., Inc. v. Donovan, 452 U.S. 490, 101 S.Ct. 2478, 69 L.Ed.2d 185 (1981) ("Cotton Dust "), a criterion the Court appeared to regard as satisfied so long as the costs of a standard would not "threaten[ ] the competitive stability of an industry", id. at 530 n. 55, 101 S.Ct. at 2501 n. 55. OSHA and the courts have since embellished that concept. See, e.g., National Cottonseed Products Ass'n v. Brock, 825 F.2d 482, 487-88 (D.C.Cir.1987). The union argues that Sec. 6(b)(5) applies to this case. We agree with OSHA that it does not.

OSHA interprets Sec. 6(b)(5) as applicable only to "health" standards. It views these as coextensive with standards governing latent hazards, such as carcinogens, "which are frequently undetectable to the casual observer because they are subtle or develop slowly or after latency periods", Brief of OSHA at 24, and contrasts them with "safety" standards, such as the lockout regulation, which address hazards that cause immediately visible physical harm.5 We accord considerable weight to an agency's construction of a statutory scheme it is entrusted to administer, rejecting it only if unreasonable. See Chevron U.S.A., Inc. v. NRDC, 467 U.S. 837, 843, 104 S.Ct. 2778, 2781, 81 L.Ed.2d 694 (1984).

The union plays a dictionary game to support its view, noting definitions of "physical" as "of or pertaining to matter or energy", and of "agent" as "an active force or substance producing an effect". The lockout rule of course relates to both "matter" and "energy" and controls their "effects". But it is hard to imagine a workplace hazard within Congress's reach that involves neither matter nor energy, and that produces no "effect". Indeed, the union's notion of physical agents would engulf Sec. 6(b)(5)'s companion term, "toxic materials". More important, the union's reading would obliterate a distinction that Congress drew between "health" and "safety" risks. It referred in the Act's preamble to efforts aimed at

exploring ways to discover latent diseases, establishing causal connections between diseases and work in environmental conditions, and conducting other research relating to health problems, in recognition of the fact that occupational health standards present problems often different from those involved in occupational safety....

29 U.S.C. Sec. 651(b)(6) (1988) (emphasis added).

Other sections of the Act confirm the more limited reading for "harmful physical agents". Section 8(c)(3), 29 U.S.C. Sec. 657(c)(3) (1988), for instance, uses the phrase "toxic materials or harmful physical agents" in association with words that make sense primarily (if not exclusively) for the sort of gradually accumulating hazards depicted by OSHA. It speaks of records of workers' "exposures" to "harmful physical agents", and of notice to workers when their exposure is "in concentrations or at levels" exceeding those of a standard. Similarly, Sec. 20(a)(3), 29 U.S.C. Sec. 669(a)(3) (1988), directs the Secretary of Health and Human Services to develop criteria for safe "exposure levels" for "toxic materials and harmful physical agents and substances". And Sec. 20(a)(5), 29 U.S.C. Sec. 669(a)(5) (1988), authorizes regulations for reporting workers' "exposure" to hazardous "substances or physical agents" and for medical exams and tests to develop information on the subject. OSHA's idea of harmful physical agents fits all these terms well, while many hazards covered by the union's reading do not fit them at all.

The union extracts an argument from Sec. 6(c)(1), which grants the Secretary authority to promulgate emergency standards when he finds that "employees are exposed to grave danger from exposure to substances or agents determined to be toxic or physically harmful or from new hazards". See 29 U.S.C. Sec. 655(c)(1)(A) (1988) (emphasis added). It says that this section "plainly encompasses the kind of harm at issue here", and since it uses the "physically harmful" phrase, the use of similar language in Sec. 6(b)(5) should be construed broadly. See Brief for Union at 31. Neither element of the linkage is sound. First, we think it more likely that Sec. 6(c)(1) applies only to new hazards or to materials whose hazardous character is newly discovered. Such revelations seem improbable about saw blades, drill presses or pipes filled with steam. Second, even if Sec. 6(c)(1) did apply to obvious safety hazards, the language in Sec. 6(b)(5) is not identical, and Congress could well have believed that a distinction between health and safety hazards that was useful for permanent regulations was unnecessary for temporary emergency standards.

The legislative history also supports OSHA. In an early version of the bill Sec. 6(b)(5) did apply to all occupational safety and health standards.6 An amendment added the language restricting its application to "standards dealing with toxic materials or harmful physical agents". Leg.Hist. at 502. This amendment was a pointless exercise if the term "harmful physical agent" embraces all health and safety risks.

Legislative discussion reflects the same distinction. For example, Senator Williams noted specifically that, as to "toxic materials and harmful physical agents", workers "are often unaware of the nature of such exposure or its extent." Leg.Hist. at 415. Throughout the debate, the terms "toxic materials" and "harmful physical agents" were used together, the former to refer to carcinogens, poisons and the like and the latter to cover hazards such as extreme noise and vibration. See, e.g., S.Rep. No. 1282, 91st Cong., 2d Sess. 2-3 (1970), U.S.Code Cong. & Admin.News 1970, pp. 5177, 5179, reprinted in Leg.Hist. at 142-43 (discussing 1967 Surgeon General study that found that 65% of employees in industrial plants "were potentially exposed to harmful physical agents, such as severe noise or vibration, or to toxic materials") (emphasis added); Leg.Hist. at 412 (remarks of Sen. Williams) (same); id. at 446 (remarks of Sen. Harris) (speaking of workers' exposure to "harmful physical effects such as severe noise and toxic materials") (emphasis added); id. at 516 (remarks of Sen. Hart) (similar); id. at 845 (H.R.Rep. No. 91-1291) (similar).

There is no warrant for the union view that obviously dangerous industrial machines fall within the statutory definition of "harmful physical agents". The Secretary's decision that the lockout regulation does not constitute regulation of a "harmful physical agent" is reasonable.

The union next argues that even if the first sentence of Sec. 6(b)(5) does not apply to the lockout regulation, the rest--with an allusion to "feasibility" at least as a relevant factor--does. A footnote in Industrial Union Dept., AFL-CIO v. American Petroleum Institute, 448 U.S. 607, 100 S.Ct. 2844, 65 L.Ed.2d 1010 (1980) ("Benzene "), left the matter open, noting that "the term 'subsection' used in the second sentence" might refer "to the entire subsection 6(b) (which sets out procedures for the adoption of all types of health and safety standards), [or] simply to the toxic materials subsection, Sec. 6(b)(5). " Id. at 612 n. 1, 100 S.Ct. at 2849 n. 1 (emphasis added). As this footnote suggests, there is a grammatical argument that Congress's use of the term "subsection" in the second sentence of Sec. 6(b)(5), as opposed to "subsubsection", argues for reading the latter portion of Sec. 6(b)(5) as universally applicable. But in Moore v. District of Columbia, 907 F.2d 165, 171-72 (D.C.Cir.1990) (en banc ), we declined to place serious weight on Congress's use of "subsection" instead of "subsubsection", viewing it as unlikely to have been a focus of drafting attention. At most, its use creates ambiguity. OSHA's view that Congress intended all of Sec. 6(b)(5) to apply only to latent-hazards standards must prevail if reasonable, see Chevron, 467 U.S. at 844, 104 S.Ct. at 2782, and we agree with OSHA and with National Grain & Feed Ass'n v. OSHA, 866 F.2d 717, 732-33 (5th Cir.1989), that it is reasonable to conclude that the two sentences do not reach beyond toxic materials and "harmful physical agents".

OSHA's view, that the two sentences simply amplify the first sentence's limits on the Secretary's authority over those hazards, fits with Congress's decision to introduce the paragraph with a sentence referring only to the latent-hazard subset. It is also consistent with the Supreme Court's unitary treatment of Sec. 6(b)(5). The Benzene plurality, for example, in justifying its conclusion that Sec. 3(8)'s definition imposed substantive constraints, reasoned that otherwise "there would be no statutory criteria at all to guide the Secretary in promulgating either national consensus standards or permanent standards other than those dealing with toxic materials and harmful physical agents." 448 U.S. at 640 n. 45, 100 S.Ct. at 2863 n. 45 (emphasis added); see also id. at 642, 100 S.Ct. at 2864 ("The standards promulgated pursuant to Sec. 6(b)(5) are just one species of the genus of standards governed by the basic requirement [of Section 3(8) ]."); Cotton Dust, 452 U.S. at 513-14 n. 32, 101 S.Ct. at 2492-93 n. 32 (quoting Benzene footnote 45); id. at 512, 101 S.Ct. at 2492 (saying that because health standards presented special problems Congress chose in Sec. 6(b)(5) to impose separate requirements for "a subcategory of occupational safety and health standards dealing with toxic materials and harmful physical agents").

The substance of the two sentences' requirements also supports OSHA. Standards are to be based upon "research, demonstrations, experiments, and such other information as may be appropriate"; the Secretary may consider a number of factors including "the latest available scientific data in the field" and "experience gained under this and other health and safety laws." 29 U.S.C. Sec. 655(b)(5) (1988). Concern for "scientific data" and "experiments" makes complete sense for regulation of carcinogens but sounds out of place when the hazard is a bacon-slicing machine, a spinning saw blade or a moving conveyor. For them, actual injury rates seem far more likely to be controlling.

If the second and third sentences of Sec. 6(b)(5) provided a clear criterion for rules not covered by the first sentence, one might argue that the advantage of allowing them to perform that service should overcome the arguments from language and context. But in fact they merely list conflicting factors, including "the highest degree of health and safety protection", "feasibility", "experience" and "such other information as may be appropriate". Thus they do not provide much of a benchmark. Again, the Secretary's interpretation is a reasonable one.

The union's final theory is that Sec. 6(b)(5) must state the substantive test for all permanent standards, since Sec. 3(8) (our other candidate for limiting the Secretary's discretion) merely sets a definition. In fact, however, the Supreme Court has read Sec. 3(8) as a source of substantive criteria. See Benzene. We address its meaning in detail below.

We uphold the Secretary's conclusion that Sec. 6(b)(5) does not govern occupational safety standards that regulate hazards causing immediately noticeable physical harm.7

The removal of Sec. 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 claim of an excessive delegation of legislative power. The only evident source of constraints remaining is Sec. 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. Sec. 652(8) (1988) (emphasis added). 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 Sec. 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.

The Benzene construction was, of course, a manifestation of the Court's current general practice of applying the nondelegation doctrine mainly in the form of "giving narrow constructions to statutory delegations that might otherwise be thought to be unconstitutional." Mistretta v. United States, 488 U.S. 361, 373 n. 7, 109 S.Ct. 647, 655 n. 7, 102 L.Ed.2d 714 (1989); see also National Cable Television Ass'n v. United States, 415 U.S. 336, 342, 94 S.Ct. 1146, 1149, 39 L.Ed.2d 370 (1974); FPC v. New England Power Co., 415 U.S. 345, 94 S.Ct. 1151, 39 L.Ed.2d 383 (1974); Kent v. Dulles, 357 U.S. 116, 129, 78 S.Ct. 1113, 1119, 2 L.Ed.2d 1204 (1958) (in face of First Amendment objection to Secretary of State's exercise of discretion, Court adopts narrow construction, observing that where citizen seeks to engage in constitutionally protected activity, the Court will "not readily infer that Congress gave ... unbridled discretion to grant or withhold" permission); Zemel v. Rusk, 381 U.S. 1, 17-18, 85 S.Ct. 1271, 1281, 14 L.Ed.2d 179 (1965) (rejecting delegation claim on basis of Kent 's conclusion that the statute should be read as incorporating prior administrative practice); Synar v. United States, 626 F.Supp. 1374, 1384 (D.D.C.1986) (three-judge panel) (noting evolution of nondelegation rule largely into one of construction), aff'd sub nom. Bowsher v. Synar, 478 U.S. 714, 106 S.Ct. 3181, 92 L.Ed.2d 583 (1986). See generally Cass R. Sunstein, "Law and Administration After Chevron", 90 Colum.L.Rev. 2072, 2111-14 (1990) (arguing that maxims of statutory interpretation based on constitutional norms should trump agency authority under Chevron, in part to assure legislative consideration of troublesome constitutional issues). In effect we require a clear statement by Congress that it intended to test the constitutional waters.

We thus turn to possible constructions.

* One can imagine broader constructions than the one proposed by OSHA, but not easily. It essentially identifies two boundaries. First, in its preamble section entitled "Basis for Agency Action", OSHA found the Benzene decision's "significant risk" requirement satisfied, see 54 Fed.Reg. at 36,65 2/3, evidently regarding it as binding even outside the realm of toxics. Second, it made findings of economic and technological feasibility, see id. at 36,656/2 ("OSHA views this type of lockout to be both technologically and economically feasible"); id. at 36,662/2; id. at 36,667/3; id. at 36,668/2, implicitly acknowledging feasibility as a limit on the stringency of its rules. Cf. Cotton Dust, 452 U.S. at 513 n. 31, 101 S.Ct. at 2492 n. 31 ("any standard that was not economically or technologically feasible would a fortiori not be 'reasonably necessary or appropriate' under the Act") (emphasis omitted). But on the agency's reading, feasibility works only as a ceiling, and not, as for toxics, as a floor; this was evidently the basis for the agency's rejection of union claims that more stringent rules than those adopted were feasible. The upshot is an asserted power, once significant risk is found, to require precautions that take the industry to the verge of economic ruin (so long as the increment reduces a significant risk, compare Building & Construction Trades Dep't v. Brock, 838 F.2d 1258, 1270-71 (D.C.Cir.1988)), or to do nothing at all. All positions in between are evidently equally valid.

The claimed power to roam between the rigor of Sec. 6(b)(5) standards and the laxity of unidentified alternatives would, we believe, raise a serious nondelegation issue. As was true of the standard upset in Schechter, the scope of the regulatory program is immense, encompassing all American enterprise. "When the scope increases to immense proportions (as in Schechter ) the standards must be correspondingly more precise." Synar, 626 F.Supp. at 1386; cf. Schechter, 295 U.S. at 553, 55 S.Ct. at 853 (characterizing challenged regulation as "as wide as the field of industrial regulation" and amounting to "delegation run[ ] riot") (Cardozo, J., concurring). Cases upholding delegations governing a single industry are thus inapposite. See, e.g., Fahey v. Mallonee, 332 U.S. 245, 249-50, 67 S.Ct. 1552, 1553-54, 91 L.Ed. 2030 (1947); Federal Power Commission v. Hope Natural Gas Co., 320 U.S. 591, 64 S.Ct. 281, 88 L.Ed. 333 (1944); American Power and Light Co. v. SEC, 329 U.S. 90, 67 S.Ct. 133, 91 L.Ed. 103 (1946); United States v. Rock Royal Co-Op, 307 U.S. 533, 59 S.Ct. 993, 83 L.Ed. 1446 (1939); Sunshine Coal Co. v. Adkins, 310 U.S. 381, 60 S.Ct. 907, 84 L.Ed. 1263 (1940); cf. Arizona v. California, 373 U.S. 546, 83 S.Ct. 1468, 10 L.Ed.2d 542 (1963) (delegation to Secretary of Interior to apportion Colorado river water, within a stated range, among seven states).

Nor is the delegation claimed by OSHA defensible under any of the special theories that have been invoked for many others that have survived, such as delegations to the President of "war" powers, see, e.g.,Yakus v. United States, 321 U.S. 414, 419-423, 64 S.Ct. 660, 665-67, 88 L.Ed. 834 (1944); Lichter v. United States, 334 U.S. 742, 778-83, 68 S.Ct. 1294, 1313-16, 92 L.Ed. 1694 (1948); Woods v. Miller Co., 333 U.S. 138, 68 S.Ct. 421, 92 L.Ed. 596 (1948), or over foreign policy issues, see, e.g., Knauff v. Shaughnessy, 338 U.S. 537, 542-43, 70 S.Ct. 309, 312-13, 94 L.Ed. 317 (1950); United States v. Curtiss-Wright Corp., 299 U.S. 304, 319-20, 57 S.Ct. 216, 220-21, 81 L.Ed. 255 (1936), or delegations to entities with attributes of sovereignty themselves, such as Indian tribes, United States v. Mazurie, 419 U.S. 544, 556-57, 95 S.Ct. 710, 717-18, 42 L.Ed.2d 706 (1975), or territorial governments, District of Columbia v. Thompson Co., 346 U.S. 100, 106-10, 73 S.Ct. 1007, 1010-13, 97 L.Ed. 1480 (1953).

It is true that price and wage controls blanketing the entire economy have been sustained under quite vague legislative directions. See Amalgamated Meat Cutters v. Connally, 337 F.Supp. 737, 745-63 (D.D.C.1971) (three-judge court). But in view of the inevitable tensions in such controls between such purposes as price stabilization on the one hand and the need for adjustments on ground of changes in cost and other market conditions on the other, compare Stephen G. Breyer & Richard B. Stewart, Administrative Law and Regulatory Policy 86-90 (1985), an insistence on greater clarity from Congress would deny it any power to impose price controls at all. Not so here. Congress can readily articulate some principle by which the beneficent health and safety effects of workplace regulation are to be traded off against the adverse welfare effects. "Policy direction is all that was ever required, and policy direction is what is lacking in much contemporary legislation." John Hart Ely, Democracy and Distrust 133 (1980). OSHA's reading of the Act finds no such direction.

We note that OSHA's claimed discretion is procedurally confined. The agency sets "standards", which would normally apply across an industry, or to a category of machines, or to some other reasonably broad category. Thus, even under its view OSHA would normally not be free to single out the Jones Company for standards embodying strict feasibility while letting the Smith Company off on ones reflecting some different principle. But even the use of general standards leaves opportunities for dangerous favoritism. The cost of compliance with a standard will vary among firms in an industry, s