The Clean Air Act authorizes the Administrator of the Environmental Protection Agency to promulgate "emission standards" for hazardous air pollutants "at the level which in his judgment provides an ample margin of safety to protect the public health." § 112(b)(1)(B), 84 Stat. 1685, 42 U.S.C. § 1857c-7(b)(1)(B). The emission of an air pollutant in violation of an applicable emission standard is prohibited by § 112(c)(1)(B) of the Act, 42 U.S.C. § 1857c-7(c)(1)(B). The knowing violation of the latter section, in turn, subjects the violator to fine and imprisonment under the provisions of § 113(c)(1)(C) of the Act, 42 U.S.C. § 1857c-8(c)(1)(C) (1970 ed., Supp. V). The final piece in this statutory puzzle is § 307(b) of the Act, 84 Stat. 1708, 42 U.S.C. § 1857h-5(b) (1970 ed., Supp. V), which provides in pertinent part:

"(1) A petition for review of action of the Administrator in promulgating . . . any emission standard under ection 112 . . . may be filed only in the United States Court of Appeals for the District of Columbia. . . . Any such petition shall be filed within 30 days from the date of such promulgation, or approval, or after such date if such petition is based solely on grounds arising after such 30th day.

"(2) Action of the Administrator with respect to which review could have been obtained under paragraph (1) shall not be subject to judicial review in civil or criminal proceedings for enforcement."

It is within this legislative matrix that the present criminal prosecution arose.

Petitioner was indicted in the United States District Court for the Eastern District of Michigan for violation of § 112(c)(1)(B). The indictment alleged that petitioner, while engaged in the demolition of a building in Detroit, failed to comply with 40 CFR § 61.22(d)(2)(i) (1975). That regulation, described in its caption as a "National Emission Standard for Asbestos," specifies procedures to be followed in connection with building demolitions, but does not by its terms limit emissions of asbestos which occur during the course of a demolition. The District Court granted petitioner's motion to dismiss the indictment on the ground that no violation of § 112(c)(1)(B), necessary to establish criminal liability under § 113(c)(1)(C), had been alleged, because the cited regulation was not an "emission standard" within the meaning of § 112(c). The United States Court of Appeals for the Sixth Circuit reversed, 545 F.2d 1 (1976), holding that Congress had in § 307(b) precluded petitioner from questioning in a criminal proceeding whether a regulation ostensibly promulgated under § 112(b)(1)(B) was in fact an emission standard. We granted certiorari, 430 U.S. 953, 97 S.Ct. 1596, 51 L.Ed.2d 802 (1977), and we now reverse.

* We do not intend to make light of a difficult question of statutory interpretation when we say that the basic question in this case may be phrased: "When is an emission standard not an emission standard?" Petitioner contends, and the District Court agreed, that while the preclusion and exclusivity provisions of § 307(b) of the Act prevented his obtaining "judicial review" of an emission standard in this criminal proceeding, he was nonetheless entitled to claim that the administrative regulation cited in the indictment was actually not an emission standard at all. The Court of Appeals took the contrary view. It held that a regulation designated by the Administrator as an "emission standard," however different in content it might be from what Congress had contemplated when it authorized the promulgation of emission standards, was sufficient to support a criminal charge based upon § 112(c), unless it had been set aside in an appropriate proceeding commenced in the United States Court of Appeals for the District of Columbia Circuit pursuant to § 307(b).

The Court of Appeals in its opinion relied heavily on Yakus v. United States, 321 U.S. 414, 64 S.Ct. 660, 88 L.Ed. 834 (1944), in which this Court held that Congress in the context of criminal proceedings could require that the validity of regulatory action be challenged in a particular court at a particular time, or not at all. That case, however, does not decide this one. Because § 307(b) expressly applies only to "emission standards," we must still inquire as to the validity of the Government's underlying assumption that the Administrator's mere designation of a regulation as an "emission standard" is sufficient to foreclose any further inquiry in a criminal prosecution under § 113(c)(1)(C) of the Act. For the reasons hereafter stated, we hold that one such as respondent who is charged with a criminal violation under the Act may defend on the ground that the "emission standard" which he is charged with having violated was not an "emission standard" within the contemplation of Congress when it employed that term, even though the "emission standard" in question has not been previously reviewed under the provisions of § 307(b) of the Act.

In resolving this question, we think the statutory provisions of the Clean Air Act are far less favorable to the Government's position than were the provisions of the Emergency Price Control Act considered in Yakus. The broad language of that statute gave clear evidence of congressional intent that any actions taken by the Price Administrator under the purported authority of the designated sections of the Act should be challenged only in the Emergency Court of Appeals. Nothing has been called to our attention which would lead us to disagree with the Government's description of the judicial review provisions of that Act:

"Review of price control regulations was centralized in the Emergency Court of Appeals under a statute giving that court 'exclusive' jurisdiction of all non-constitutional challenges to price control regulations. The Court had no difficulty construing the statute as precluding any attack on a regulation in a criminal case (321 U.S., at 430-431, 64 S.Ct. 660), even though the statute did not explicitly mention criminal cases." Brief for United States 18.

This relatively simple statutory scheme contrasts with the Clean Air Act's far more complex interrelationship between the imposition of criminal sanctions and judicial review of the Administrator's actions. The statutory basis for imposition of criminal liability under Subchapter I of the Act, under which this indictment was brought, is § 113(c)(1), 84 Stat. 1687, as amended, 42 U.S.C. § 1857c-8(c)(1) (1970 ed. and Supp. V):

"(c)(1) Any person who knowingly—

"(A) violates any requirement of an applicable implementation plan (i) during any period of Federally assumed enforcement, or (ii) more than 30 days after having been notified by the Administrator under subsection (a)(1) that such person is violating such requirement, or

"(B) violates or fails or refuses to comply with any order issued by the Administrator under subsection (a), or

"(C) violates section 111(e), section 112(c), or section 119(g)

"shall be punished by a fine of not more than $25,000 per day of violation, or by imprisonment for not more than one year, or by both. If the conviction is for a violation committed after the first conviction of such person under this paragraph, punishment shall be by a fine of not more than $50,000 per day of violation, or by imprisonment for not more than two years, or by both."

Each of the three separate subsections in the quoted language creates criminal offenses. The first of them, subsection (A), deals with violations of applicable implementation plans after receipt of notice of such violation. Under § 307(b)(1), judicial review of the Administrator's action in approving or promulgating an implementation plan is not restricted to the Court of Appeals for the District of Columbia Circuit, but may be had "in the United States Court of Appeals for the appropriate circuit." But § 307(b)(2) does provide that the validity of such plans may not be reviewed in the criminal proceeding itself.

Subsection (C), which we discuss before turning to subsection (B), provides criminal penalties for violations of three separate sections of the Act: § 111(e), 84 Stat. 1684, 42 U.S.C. § 1857c-6(e), which prohibits operation of new stationary sources in violation of "standards of performance" promulgated by the Administrator; § 112(c), which is the offense charged in this case; and § 119(g), 88 Stat. 254, 42 U.S.C. § 1857c-10(g) (1970 ed., Supp. V),1 which requires compliance with an assortment of administrative requirements, set out in more detail below. The Administrator's actions in promulgating "standards of performance" under § 111, or "emission standards" under § 112 are, by the provisions of § 307(b)(1), made reviewable exclusively in the Court of Appeals for the District of Columbia Circuit. However, his actions under subs ctions (A), (B), and (C) of § 119(c)(2), compliance with which is required by § 119(g)(2), are reviewable "in the United States Court of Appeals for the appropriate circuit." Those subsections define the Administrator's authority to issue compliance date extensions to particular stationary sources with regard to various air pollution requirements. The preclusive provisions of § 307(b)(2) prohibit challenges to all of these administrative actions in both civil and criminal enforcement proceedings. But these restrictive review provisions do not apply to other violations of § 119(g); with regard to those offenses, the invalidity of administrative action may be raised as a defense to the extent allowable in the absence of such restrictions.

Finally, subsection (B) of § 113(c)(1) subjects to criminal penalties "any person who knowingly . . . violates or fails or refuses to comply with any order issued by the Administrator under subsection (a)." Subsection (a), in turn, empowers the Administrator to issue orders requiring compliance, not only with those regulations for which criminal penalties are provided under subsections (A) and (C), but also with the recordkeeping and inspection requirements of § 114, 42 U.S.C. § 1857c-9 (1970 ed., Supp. V), for which only civil penalties are ordinarily available under § 113(b)(4). The restrictive review provisions of § 307(b)(1), again do not apply to orders issued under § 113(a) or to the underlying requirements of § 114. Those administrative actions would likely be reviewable under the Administrative Procedure Act, 5 U.S.C. § 701 et seq., and any infirmity in them could be raised as a defense in enforcement proceedings to the same extent as it could be in the absence of a provision such as § 307(b)(2).

The conclusion we draw from this excursion into the complexities of the criminal sanctions provided by the Act are several. First, Congress has not chosen to prescribe either civil or criminal sanctions for violations of every rule, regulation, or order issued by the Administrator. Second, Congress, as might be expected, has imposed civil liability for a wider range of violations of the orders of the Administrator than those for which it has imposed criminal liability. Third, even where Congress has imposed criminal liability for the violation of an order of the Administrator, it has not uniformly precluded judicial challenge to the order as a defense in the criminal proceeding. Fourth, although Congress has applied the preclusion provisions of § 307(b)(2) to implementation plans approved by the Administrator, and it has in § 113(c)(1)(A) provided criminal penalties for violations of those plans, it has nonetheless required, under normal circumstances, that a violation continue for a period of 30 days after receipt of notice of the violation from the Administrator before the criminal sanction may be imposed.

These conclusions in no way detract from the fact that Congress has precluded judicial review of an "emission standard" in the court in which the criminal proceeding for the violation of the standard is brought. Indeed, the conclusions heighten the importance of determining what it was that Congress meant by an "emission standard," since a violation of that standard is subject to the most stringent criminal liability imposed by § 113(c)(1) of the Act: Not only is the Administrator's promulgation of the standard not subject to judicial review in the criminal proceeding, but no prior notice of violation from the Administrator is required as a condition for criminal liability.2 Since Congress chose to attach these stringent sanctions to the violation of an emission standard, in contrast to the violation of various other kinds of orders that might be issued by the Administrator, it is crucial to determine whether the Administrator's mere designation of a regulation as an "emission standard" is conclusive as to its character.

The stringency of the penalty imposed by Congress lends substance to petitioner's contention that Congress envisioned a particular type of regulation when it spoke of an "emission standard." The fact that Congress dealt more leniently, either in terms of liability, of notice, or of available defenses, with other infractions of the Administrator's orders suggests that it attached a peculiar importance to compliance with "emission standards." Unlike the situation in Yakus, Congress in the Clean Air Act singled out violators of this generic form of regulation, imposed criminal penalties upon them which would not be imposed upon violators of other orders of the Administrator, and precluded them from asserting defenses which might be asserted by violators of other orders of the Administrator. All of this leads us to conclude that Congress intended, within broad limits, that "emission standards" be regulations of a certain type, and that it did not empower the Administrator, after the manner of Humpty Dumpty in Through the Looking-Glass, to make a regulation an "emission standard" by his mere designation.

The statutory scheme supports the conclusion that § 307(b)(2), in precluding judicial review of the validity of emission standards, does not relieve the Government of the duty of proving, in a prosecution under § 113(c)(1)(C), that the regulation allegedly violated is an emission standard. Here, the District Court properly undertook to resolve that issue. In so doing, the court did not undermine the twin congressional purposes of insuring that the substantive provisions of the standard would be uniformly applied and interpreted and that the circumstances of its adoption would be quickly reviewed by a single court intimately familiar with administrative procedures. The District Court did not presume to judge the wisdom of the regulation or to consider the adequacy of the procedures which led to its promulgation, but merely concluded that it was not an emission standard.3

In sum, a survey of the totality of the statutory scheme does not compel agreement with the Government's contention that Congress intended that the Administrator's designation of a regulation as an emission standard should be conclusive in a criminal prosecution. At the very least, it may be said that the issue is § bject to some doubt. Under these circumstances, we adhere to the familiar rule that, "where there is ambiguity in a criminal statute, doubts are resolved in favor of the defendant." United States v. Bass, 404 U.S. 336, 348, 92 S.Ct. 515, 523, 30 L.Ed.2d 488 (1971). Cf. Rewis v. United States, 401 U.S. 808, 812, 91 S.Ct. 1056, 1059, 28 L.Ed.2d 493 (1971).

We conclude, therefore, that a federal court in which a criminal prosecution under § 113(c)(1)(C) of the Clean Air Act is brought may determine whether or not the regulation which the defendant is alleged to have violated is an "emission standard" within the meaning of the Act. We are aware of the possible dangers that flow from this interpretation; district courts will be importuned, under the guise of making a determination as to whether a regulation is an "emission standard," to engage in judicial review in a manner that is precluded by § 307(b)(2) of the Act. This they may not do. The narrow inquiry to be addressed by the court in a criminal prosecution is not whether the Administrator has complied with appropriate procedures in promulgating the regulation in question, or whether the particular regulation is arbitrary, capricious, or supported by the administrative record. Nor is the court to pursue any of the other familiar inquiries which arise in the course of an administrative review proceeding. The question is only whether the regulation which the defendant is alleged to have violated is on its face an "emission standard" within the broad limits of the congressional meaning of that term.

It remains to be seen whether the District Court reached the correct conclusion with regard to the regulation here in question. In the Act, Congress has given a substantial indication of the intended meaning of the term "emission standard." Section 112 on its face distinguishes between emission standards and the techniques to be utilized in achieving those standards. Under § 112(c)(1)(B)(ii), the Administrator is empowered temporarily to exempt certain facilities from the burden of compliance with an emission standard, "if he finds that such period is necessary for the installation of controls." In specified circumstances, the President, under § 112(c)(2), has the same power, "if he finds that the technology to implement such standards is not available." Section 112(b)(2) authorizes the Administrator to issue information on "pollution control techniques."

Most clearly supportive of petitioner's position that a standard was intended to be a quantitative limit on emissions is this provision of § 112(b)(1)(B): "The Administrator shall establish any such standard at the level which in his judgment provides an ample margin of safety to protect the public health from such hazardous air pollutant." (Emphasis added.) All these provisions lend force to the conclusion that a standard is an quantitative "level" to be attained by use of "techniques," "controls," and "technology." This conclusion is fortified by recent amendments to the Act, by which Congress authorized the Administrator to promulgate a "design, equipment, work practice, or operational standard" when "it is not feasible to prescribe or enforce an emission standard." Clean Air Act Amendments of 1977, Pub.L. 95-95, § 110, 91 Stat. 703.4

This distinction, now endorsed by Congress, between "work practice standards" and "emission standards" first appears in the Administrator's own account of the development of this regulation. Although the Administrator has contended that a "work practice standard" is just another type of emission standard, the history of this regulation demonstrates that he chose to regulate work practices only when it became clear he could not regulate emissions. The regulation as originally proposed would have prohibited all visible emissions of asbestos during the course of demolitions. 36 Fed.Reg. 23242 (1971). In adopting the final form of the regulation, the Administrator concluded "that the no visible emission requirement would prohibit repair or demolition in many situations, since it would be impracticable, if not impossible, to do such work without creating visible emissions." 38 Fed.Reg. 8821 (1973). Therefore the Administrator chose to "specif[y] certain work practices" instead. Ibid.

The Government concedes that, prior to the 1977 Amendments, the statute was ambiguous with regard to whether a work-practice standard was properly classified as an emission standard, but argues that this Court should defer to the Administrator's construction of the Act.5 Brief for United States 32, and n. 22. While such deference is entirely appropriate under ordinary circumstances, in this case the 1977 Amendments to the Clean Air Act tend to undercut the administrative construction. The Senate Report reiterated its "strong preference for numerical emission limitations," but endorsed the addition of § 112(e) to the Act to allow the use of work-practice standards "in a very few limited cases." S.Rep.No.95-127, p. 44 (1977). Although the Committee agreed that the Amendments would authorize the regulation involved here, it refrained from endorsing the Administrator's view that the regulation had previously been authorized as an emission standard under § 112(c). The clear distinction drawn in § 112(e) between work-practice standards and emission standards practically forecloses any such inference. Cf. Red Lion Broadcasting Co. v. FCC, 395 U.S. 367, 380-381, 89 S.Ct. 1794, 1801-1802, 23 L.Ed.2d 371 (1969).

For all of the foregoing reasons, we conclude that the work-practice standard involved here was not an emission standard. The District Court's order dismissing the indictment was therefore proper, and the judgment of the Court of Appeals is

Reversed.

Mr. Justice POWELL, concurring.

If the constitutional validity of § 307(b) of the Clean Air Act had been raised by petitioner, I think it would have merited serious consideration. This section limits judicial review to the filing of a petition in the United States Court of Appeals for the District of Columbia Circuit within 30 days from the date of the promulgation by the Administrator of an emission standard. No notice is afforded a party who may be subject to criminal prosecution other than publication of the Administrator's action in the Federal Register.1 The Act in this respect is similar to the preclusion provisions of the Emergency Price Control Act before the Court in Yakus v. United States, 321 U.S. 414, 64 S.Ct. 660, 88 L.Ed. 834 (1944), and petitioner may have thought the decision in that case effectively foreclosed a due process challenge in the present case.

Although I express no considered judgment, I think Yakus is at least arguably distinguishable. The statute there came before the Court during World War II, and it can be viewed as a valid exercise of the war powers of Congress under Art. I, § 8, of the Constitution. Although the opinion of Mr. Chief Justice Stone is not free from ambiguity, there is language emphasizing that the price controls imposed by the Congress were a "war emergency measure." Indeed, the Government argued that the statute should be upheld under the war powers authority of Congress. Brief for United States in Yakus v. United States, O.T. 1943, No. 374, p. 35. As important as environmental concerns are to the country, they are not comparable—in terms of an emergency justifying the shortcutting of normal due process rights—to the need for national mobilization in wartime of economic as well as military activity.

The 30-day limitation on judicial review imposed by the Clean Air Act would afford precariously little time for many affected persons even if some adequate method of notice were afforded. It also is totally unrealistic to assume that more than a fraction of the persons and entities affected by a regulation—especially small contractors scattered across the country—would have knowledge of its promulgation or familiarity with or access to the Federal Register. Indeed, following Yakus, and apparently concerned by Mr. Justice Rutledge's eloquent dissent. Congress amended the most onerous features of the Emergency Price Control Act.2

I join the Court's opinion with the understanding that it implies no view as to the constitutional validity of the preclusion provisions of § 307(b) in the context of a criminal prosecution.

Mr. Justice STEWART, with whom Mr. Justice BRENNAN and Mr. Justice BLACKMUN join, dissenting.

Section 307(b)(1) of the Clean Air Act provides that a "petition for review of action of the Administrator in promulgating . . . any emission standard under section 112" may be filed only in the United States Court of Appeals for the District of Columbia Circuit within 30 days of promulgation. Section 307(b)(2) of the Act provides that an "[a]ction of the Administrator with respect to which review could have been obtained under paragraph (1) shall not be subject to judicial review in civil or criminal proceedings for enforcement." Despite these unambiguous provisions, the Court holds in this case that such an action of the Administrator shall be subject to judicial review in a criminal proceeding for enforcement of the Act, at least sometimes. Because this tampering with the plain statutory language threatens to destroy the effectiveness of the unified and expedited judicial review procedure established by Congress in the Clean Air Act, I respectfully dissent.

The inquiry that the Court today allows a trial court to make whether the asbestos regulation at issue is an emission standard of the type envisioned by Congress—is nothing more than an inquiry into whether the Administrator has acted beyond his statutory authority. But such an inquiry is a normal part of judicial review of agency action. 5 U.S.C. § 706(2)(C); see Citizens to Preserve Overton Park v. Volpe, 401 U.S. 402, 415, 91 S.Ct. 814, 823, 28 L.Ed.2d 136. And it is precisely such "judicial review" of an "[a]ction of the Administrator" that Congress has, in § 307(b)(2), expressly forbidden a trial court to u dertake. There is not the slightest indication in the Act or in its legislative history that Congress, in providing for review of the Administrator's actions only in the Court of Appeals for the District of Columbia Circuit, meant nonetheless to allow some kinds of review to be available in other courts. To the contrary, Congress clearly ordained that "any review of such actions" be controlled by the provisions of § 307. S.Rep.No.91-1196, p. 41 (1970) (emphasis supplied).

The Court's interpretation of § 307(b)(2) also conspicuously frustrates the intent of Congress to establish a speedy and unified system of judicial review under the Act. The Court concludes that violation of the regulation involved in this case is not proscribed by §§ 112(c)(1)(B) and 113(c)(1)(C) because the regulation is not an emission standard. This interpretation of the Act would make judicial review of this regulation in the Court of Appeals for the District of Columbia Circuit impossible, since that court has statutory jurisdiction under § 307(b)(1) to review "emission standard[s]" but is not given jurisdiction to review the actions of the Administrator generally. It follows that judicial review of this action of the Administrator could be had only in other courts, either in enforcement proceedings as in this case or under the general provisions of the Administrative Procedure Act, 5 U.S.C. § 701 et seq., despite the clearly expressed congressional intent to centralize all judicial review of the Administrator's regulations. The Court's interpretation thus not only invites precisely the sort of inconsistent judicial determinations by various courts that Congress sought to prevent, but flies in the face of the congressional purpose "to maintain the integrity of the time sequences provided throughout the Act." S.Rep.No.91-1196, p. 41.

Finally, the Court provides no real guidance as to which aspects of an emission standard are so critical that they fall outside the scope of the exclusive judicial review procedure provided by Congress. For example, § 112 requires that an emission standard relate to a "hazardous air pollutant," and that it be set so as to provide "an ample margin of safety to protect the public health." Such express congressional mandates would seem at least as important in determining whether a regulation is a statutorily authorized emission standard as the supposed requirement that the regulation be numerical in form. Are issues such as these, therefore, now to be subject to review in trial court enforcement proceedings? The Court today has allowed the camel's nose into the tent, and I fear that the rest of the camel is almost certain to follow.

Since I believe that the Administrator's action in promulgating this regulation could have been reviewed in the Court of Appeals for the District of Columbia Circuit under § 307(b)(1), and that such review could have included the petitioner's claim that the Administrator's action was beyond his authority under the Act, I would hold that the petitioner was barred by the express language of § 307(b)(2) from raising that issue in the present case.*

Mr. Justice STEVENS, dissenting.

The reason Congress attached "the most stringent criminal liability," ante, at 283, to the violation of an emission standard for a "hazardous air pollutant" is that substances within that narrow category pose an especially grave threat to human health. That is also a reason why the Court should avoid a construction of the statute that would deny the Administrator the authority to regulate these poisonous substances effectively.

The reason the Administrator did not frame the emission standard for asbestos in numerical terms is that asbestos emissions cannot be measured numerically. For that reason, if Congress simultaneously commanded him (a) to regulate asbestos emissions by establishing and enforcing emission standards and (b) never to use any kind of standard except one framed in numerical terms, it commanded an impossible task.

Nothing in the language of the 1970 statute, or in its history, compels so crippling an interpretation of the Administrator's authority. On the contrary, I am persuaded (1) that the Administrator's regulation of asbestos emissions was entirely legitimate; (2) that if this conclusion were doubtful, we would nevertheless be required to respect his reasonable interpretation of the governing statute; (3) that the 1977 Amendments, fairly read, merely clarified his pre-existing authority; and (4) that the Court's reading of the statute in its current form leads to the anomalous conclusion that work-practice rules, even though properly promulgated, are entirely unenforceable. Accordingly, although I agree with the conclusions reached in Parts I, II, and III of the Court's opinion, I cannot accept Part IV's disposition of the most important issue in this case.1

* The regulation which petitioner is accused of violating requires that asbestos insulation and fireproofing in large buildings be watered down before the building is demolished.2 The effect of the regulation is to curtail the quantity of asbestos which is emitted into the open air during demolition. Because neither the rule nor its limiting effect is expressed in numerical terms, the Court holds that the asbestos regulation cannot be a "standard" within the meaning of § 112(b)(1) of the Clean Air Act.3 This conclusion is not compelled by the use of the word "standard"4 or by Congress' expectation that standards would normally be expressed in numerical terms; for the statute contains no express requirement that standards always be framed in such language. The question is simply whether § 112(b), which directs the Administrator to adopt regulations establishing emission standards for hazardous air pollutants, granted him the authority to promulgate the asbestos standard challenged in this case.

Section 112 is concerned with a few extraordinarily toxic pollutants. Only three substances, including asbestos, have been classified as "hazardous air pollutants" within the meaning of § 112.5 These pollutants are subject to special federal regulation. In § 112, Congress ordered the Administrator to identify and to regulate them without waiting for the States to develop implementation plans of their own. Thus, the procedure under § 112 contrasts markedly with the more leisurely and decentralized process of setting and enforcing the general ambient air standards.6 Congress was gravely concerned about the poisonous character of asbestos emissions when it drafted § 112.7 In fact, with regard to the hazardous air pollutants covered by this section, Congress expressed its willingness to accept the prospect of plant closings: "The standards must be set to provide an ample margin of safety to protect the public health. This could mean, effectively, that a plant would be required to close because of the absence of control techniques. It could include emission standards which allowed for no measurable emissions."8

In accord with Congress' expectation, the Administrator promptly listed asbestos as a hazardous air pollutant,9 and published a proposed emission standard. As first proposed, the standard would have prohibited any visible emission of asbestos in connection with various activities, including the repair or demolition of commercial and apartment buildings.10

If that total prohibition had been adopted, it unquestionably would have conformed to the statutory mandate. It was not adopted, however, because industry convinced the Administrator that his proposal would prevent the demolition of any large building.11 At public hearings it was demonstrated that demolition inevitably causes some emission of particulate asbestos and, further, that these emissions cannot be measured. Accordingly, instead of the severe numerical standard of zero emissions—which might have put an entire industry out of business the Administrator adopted a standard which would reduce the emission of asbestos without totally prohibiting it. Not a word in the Administrator's long and detailed explanation of the standard indicates that anyone questioned his statutory authority to promulgate this type of emission standard.12

The promulgated standard is entirely consistent with congressional intent. Congress had indicated a preference for numerical emission standards.13 Congress had also expressed a willingness to accept the serious economic hardships that a total prohibition of asbestos emissions would have caused. But there is no evidence that Congress intended to require the Administrator to make a choice between the extremes of closing down an entire industry and imposing no regulation on the emission of a hazardous pollutant; Congress expressed no overriding interest in using a numerical standard when industry is able to demonstrate that a less drastic control technique is available,14 and that it provides an ample margin of safety to the public health.15

Admittedly, Congress did not foresee the Administrator's dilemma with precision. But there is nothing unique about that circumstance. See, e. g., Mourning v. Family Publications Serv., Inc., 411 U.S. 356, 372-373, 93 S.Ct. 1652, 1662-1663, 36 L.Ed.2d 318. Indeed, there would be no need for interstitial administrative lawmaking if Congress could foresee every ramification of laws as complex as this.16 I am persuaded that the Administrator's solution was faithful to his statutory authority and that he would have misused his power if he had either failed to regulate asbestos emissions at all or unnecessarily demolished an entire industry.

The precise question presented to this Court is not whether, as an initial matter, we would regard the asbestos regulation as an "emission standard" within the meaning of § 112. Rather, the issue is whether the Administrator's answer to the question of statutory construction is "sufficiently reasonable that it should have been accepted by the reviewing courts." Train v. Natural Resources Defense Council, 421 U.S. 60, 75, 95 S.Ct. 1470, 1480, 43 L.Ed.2d 731.

The Administrator, who has primary responsibility for carrying out the purposes f the Clean Air Act, interpreted the term "emission standard" to include the rule before us. Contrary to the Court's implication, ante, at 287, the Administrator did not promulgate this rule "instead" of an emission standard. He unambiguously concluded that the rule was a proper emission standard.17

Because the statute is the Administrator's special province, we should not lightly set aside his judgment. "When faced with a problem of statutory construction, this Court shows great deference to the interpretation given the statute by the officers or agency charged with its administration. 'To sustain the Commission's application of this statutory term, we need not find that its construction is the only reasonable one, or even that it is the result we would have reached had the question arisen in the first instance in judicial proceedings.' " Udall v. Tallman, 380 U.S. 1, 16, 85 S.Ct. 792, 801, 13 L.Ed.2d 616.18

The Administrator began the process of promulgating this rule within weeks of § 112's enactment. 36 Fed.Reg. 23242 (1971). The wise teaching of Mr. Justice Cardozo, who spoke for the Court in Norwegian Nitrogen Co. v. United States, 288 U.S. 294, 53 S.Ct. 350, 77 L.Ed. 796, is therefore directly pertinent. He observed that an administrative "practice has peculiar weight when it involves a contemporaneous construction of a statute by the men charged with the responsibility of setting its machinery in motion; of making the parts work efficiently and smoothly while they are yet untried and new." Id., at 315, 53 S.Ct., at 358.

The Court holds that these well-established doctrines apply only in "ordinary circumstances." Ante, at 288. I do not understand why these rules of cons ruction should be less applicable in the unusual than in the ordinary case. Indeed, it seems to me that the extraordinary importance of regulating a hazardous air pollutant in a way that is both fair and effective provides an additional reason for respecting the Administrator's reliance on well-established doctrine, rather than a reason for reaching out to undermine his authority.19

In the Court's view, however, the enactment of amendments to the Clean Air Act in 1977 was an extraordinary circumstance that justifies a departure from settled principles. The Court takes the novel position that the Administrator's construction of the 1970 Amendments may be ignored because the legislative history of the 1977 Amendments did not produce an explicit endorsement of his construction. In my judgment this holding places an unwise limit on the deference which should be accorded to administrators' interpretations of the statutes they enforce. It also misreads the history of the 1977 Amendments.

The Court's conclusion ultimately rests on the 1977 Amendments. Even accepting the dubious premise that we can rely on the 95th Congress to tell us what the 93d had in mind, the 1977 Amendments do not support the Court's interpretation of the statute.

The history of the Amendments is instructive. In late 1974, several wrecking companies successfully challenged indictments brought against them in the Northern District of Illinois for violating the wetting requirements.20 Six weeks after the first court ruling, the Administrator proposed an amendment that would expressly confirm his authority to establish design, equipment, or work-practice standards when numerical emission limitations were not feasible.21 A major bill to amend the Clean Air Act was proposed in the 94th Congress, but the House and Senate were unable to agree. In 1977, the Senate again proposed a major revision. It included the Administrator's requested authorization. S.Rep. No. 95-127, p. 163. The Senate Report does not indicate whether the Senators considered the Illinois decisions correct or incorrect. Id., at 44. However, as introduced in the Senate, the bill clearly provided that a design, equipment, or operational standard was a species of "hazardous emission standard."22

When the bill emerged from conference, it no longer expressly stated that a work-practice rule was an emission standard. This change therefore lends support to the Court's view. But it is most unlikely that the Conference Committee intended to express indirect disapproval of the Administrator's reading of the 1970 Amendments. The Conference Report explained that the change in language was merely intended to "clarify" an aspect of the Senate version which was unrelated to the question whether a work-practice rule is, or had been a species of emission standard.23

There is only one relevant lesson that may be learned from this history: As soon as someone challenged the Administrator's power to promulgate work-practice rules of this sort, Congress made it unambiguously clear that the Administrator had that power. As the Court notes, Congress preferred numerical standards; it accepted work-practice rules only as a last resort. But the same may be said of the Administrator, who instituted a wetting requirement only after becoming convinced that no other standard was practicable.

It is true, as the Court says, that the Senate Report "refrained from endorsing the Administrator's view that the regulation had previously been authorized as an emission standard under § 112(c)." Ante, at 289. It is equally true that the Senate Report refrained from criticizing the Administrator's view. In short, what Congress said in 1977 sheds no light on its understanding of the original meaning of the 1970 Amendments. But what Congress did when it expressly authorized work-practice rules persuasively indicates that, if Congress in 1970 had focused on the latent ambiguity in the term "emission standard," it would have expressly granted the authority that the Administrator regarded as implicit in the statute as written.24

A reading of the entire statute, as amended in 1977, confirms my opinion that the asbestos regulation is, and since its promulgation has been, an emission standard. If this is not true, as the Court holds today, it is unenforceable, and will continue to be unenforceable even if promulgated anew pursuant to the authority expressly set forth in the 1977 Amendments.

The Clean Air Act treats the Administrator's power to promulgate emission standards separately from his power to enforce them. While it is § 112(b) that gives the Administrator authority to promulgate an "emission standard," it is § 112(c) that prohibits the violation of an "emission standard." Presumably the Court's holding that a work-practice rule is not an "emission standard" applies to both of these sections. Under that holding a work-practice rule may neither be enforced nor promulgated as an emission standard. This holding will not affect the Administrator's power to promulgate work-practice rules, because the 1977 Amendments explicitly recognize that power. But Congress has not amended § 112(c), which continues to permit enforcement only of "emission standards." Accordingly, the Court's holding today has effectively made the asbestos regulation, and any other work-practice rule as well, unenforceable.

Ironically, therefore, the 1977 Amendments, which were intended to lift the cloud over the Administrator's authority, have actually made his exercise of that authority ineffectual. This is the kind of consequence a court risks when it substitutes its reading of a complex statute for that of the Administrator charged with the responsibility of enforcing it. Moreover, it is a consequence which would be entirely avoided by recognizing that the Administrator acted well within his statutory authority when he promulgated the asbestos regulation as an "emission standard" for hazardous air pollutants.

I would affirm the judgment of the Court of Appeals for the Sixth Circuit.