Chapter 7. Regulation of Hazardous Emissions

Theodore L. Garrett and Sonya D. Winner

Editors' Summary: In this second of a three-part series on the Clean Air Act and the 1990 amendments, the authors analyze the background of several key Clean Air Act sections, including the prevention of significant deterioration (PSD) program, new and modified source review, the national emission standard for hazardous air pollutants (NESHAP) program, acid deposition control provisions, and mobile source controls. The authors explore the evolution of the PSD program from its origins in Sierra Club v. Ruckelshaus, 2 ELR 20656, to its current focus on requiring preconstruction review of major sources and modifications to ensure that deterioration is prevented and appropriate control technology is used. The authors next analyze how the Clean Air Act utilizes the review and permitting of new and modified sources as basic planning and control features for regulating such sources and their impact on attainment and maintenance of the national air quality standards. The authors next explore the regulation of hazardous emissions, from the pre-1990 NESHAP program to the ramifications of the 1990 amendments. Finally, the authors analyze the new acid deposition control provisions added by the 1990 amendments, including the new allowance program, and how the amendments impact Title II of the Clean Air Act, which governs emissions from mobile sources.

Theodore L. Garrett is a partner in the law firm of Covington and Burling in Washington, D.C. Mr. Garrett has coordinated the firm's environmental practice and has been extensively involved in litigation and administrative proceedings. A former U.S. Supreme Court law clerk to Chief Justice Burger, Mr. Garrett has served as a featured speaker at numerous environmental law and litigation programs, and has written widely in the environmental area. He is a coauthor of the ALI-ABA book A Practical Guide to Environmental Law and the ABA book Environmental Litigation. Mr. Garrett is vice-chairman of the Solid and Hazardous Waste Committee of the ABA Section of Natural Resources, Energy, and Environmental Law; a member of the Steering Committee of the Environment, Energy, and Natural Resources Section of the District of Columbia Bar; a member of the Editorial Board of the Environmental Law Reporter, and a member of the Advisory Committee on Hazardous Waste of the Center for Public Resources.

Sonya D. Winner is a partner in the law firm of Covington and Burling, where she practices in the areas of environmental law, international trade, and antitrust. She is a graduate of Michigan State University (B.A. 1979) and Harvard Law School (J.D., magna cum laude, 1982). After graduation, she served as a law clerk to Judge Louis F. Oberdorfer of the U.S. District Court for the District of Columbia. She is a member of the adjunct faculty at the American University Washington College of Law, where she has taught courses in international commercial arbitration and legal ethics.

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In addition to creating programs to attain and maintain the national ambient air quality standards (NAAQS), the Clean Air Act of 1970 created a separate program for the control of "hazardous air pollutants." Sometimes referred to as "air toxics," these pollutants were defined as those "which may reasonably be anticipated to result in an increase in mortality or an increase in serious irreversible, or incapacitating reversible, illness."¹ Section 112 of the pre-1990 version of the Act directed the U.S. Environmental Protection Agency (EPA) to promulgate a list of such pollutants and to establish standards for their control.² Such national emission standards for hazardous air pollutants (NESHAPs) were to be established at a level adequate to protect the public health with an ample margin of safety.³

I. The Pre-1990 NESHAP Program

The authors of the 1990 amendments generally regarded the preexisting NESHAP program as a failure.⁴ Between 1970 and 1990, only eight substances or categories of substances were listed for regulation as hazardous air pollutants.⁵ NESHAP regulations were promulgated only for certain sources of seven of those pollutants, and many of the regulations that were promulgated have been the subject of near-continuous litigation.⁶

There were several factors that contributed to the dearth of action under § 112. One was a perception among many observers that emissions of hazardous air pollutants were not a significant or broad-based problem requiring extensive regulation under the Clean Air Act. Emissions from most sources were thought to affect primarily employees and others closely exposed in the workplace. Such exposures were already regulated by the Occupational Safety and Health Administration (OSHA). However, the issuance of the first Toxic Release Inventory in 1989, based on data gathered pursuant to the Emergency Planning and Community Right-to-Know Act of 1986,⁷ for the first time publicized the actual extent of hazardous air emissions nationwide and led to increased public pressure for regulation of such emissions.⁸

Another fundamental cause of EPA's slowness in acting under § 112 was a dispute over the level of control actually required by the statute. The requirement to provide control adequate to protect the public health with an "ample margin of safety" was interpreted by some environmental groups as requiring the total elimination of emissions of carcinogens. Such materials were deemed to have a "zero threshold" of risk, since EPA had not identified a threshold level of exposure beneath which there was no risk of an adverse health effect. Yet standards requiring zero exposure to such emissions would have caused many major U.S. industries to go out of business.⁹

In NRDC v. EPA,¹⁰ the court confirmed that EPA was not required to adopt a zero exposure standard in promulgating NESHAP regulations. However, the court also held that EPA could not consider economic costs or technological feasibility in identifying the level of control necessary "to protect the public health." Instead, EPA was required to perform its analysis in two stages. First, the Agency was to determine, based on health considerations alone, the minimum level of control necessary to protect public health. Second, EPA was to identify whatever additional level of control was appropriate to create the statutory "ample margin of safety." In this second level of analysis, EPA could consider health effects, economic factors, technological feasibility, scientific uncertainty, and other relevant factors.¹¹

This Vinyl Chloride decision resolved some outstanding issues but left others open. Two important areas of controversy that remained were (1) how effects on public health should be measured and (2) what level of protection to public health is minimally necessary.

The issue of how public health effects were to be measured arose from EPA's customary practice of adopting highly conservative models of exposure and health effects that often bear little relationship to reality. For example, in evaluating the impact of emissions on the "maximally exposed individual," EPA models typically assume that such an individual is at a fixed location adjacent to the source and is exposed to emissions at the same level 24 hours per day for 70 years.¹² While this assumption ensures conservatism in EPA's analysis, some have argued that it leads to overestimates of the minimum level of control required to guard against real-world health impacts.

The second issue, identifying the level of public health protection that should be minimally required, was aired by EPA in its first post-Vinyl Chloride rulemaking under § 112. In a Notice of Proposed Rulemaking concerning standards for benzene emissions,¹³ EPA proposed four alternative standards for making its threshold determination of the [22 ELR 10246] minimum level of public health protection that would be required. EPA suggested that control would be deemed minimally adequate if it limited health effects to (1) a risk to the maximally exposed individual of no more than 1 x 10<-4>, (2) a risk to that same individual of no more than 1 x 10<-6>, or (3) a total combined incidence of no more than one fatal cancer per year. Alternatively, EPA suggested as a fourth option that all relevant measures of public health effects would be considered, with a rebuttable presumption that the maximum individual risk should be no greater than 1 x 10<-4>. Under all of these approaches, public health risks and impacts would be measured according to EPA's existing conservative models.

In promulgating the benzene regulations (and the revised regulations on radionuclides that were promulgated a few months later), EPA adopted a modified version of the fourth approach.¹⁴ However, that decision did not end the debate, which was carried forward during consideration of the 1990 amendments.

II. The 1990 Amendments

The resurrection of the NESHAP program was one of the primary goals of the 1990 amendments, which completely rewrote § 112 and established a new regime for the regulation of hazardous air emissions. The principal elements of the amendments were (1) the inclusion in the statute of a long list of hazardous substances to be regulated; (2) creation of a strict timetable for the promulgation of regulations governing emissions of those substances; (3) a new technology-based methodology for regulating hazardous emissions, with the principal focus on maximum control of total source emissions rather than on strict pollutant-by-pollutant emission standards; and (4) a revised strategy for regulating "residual risk." Congress also sought to bolster regulatory programs for prevention and control of accidental releases of hazardous emissions.

A. Listing of Regulated Substances and Source Categories

The 1990 amendments dramatically reduced EPA's discretion to determine which substances are to be listed for regulation as hazardous pollutants: the statute now lists 189 substances and categories of substances as "hazardous air pollutants" that must be regulated.¹⁵ EPA is directed to review the list periodically and to add additional substances that present a threat of "adverse human health effects" or "adverse environmental effects.¹⁶ No pollutants for which an NAAQS has been established under § 108 of the Act may be listed under § 112, although "precursors" to such pollutants may be listed.¹⁷

Section 112(b)(3)(A) provides that any person may petition EPA to add or delete a substance from the list.¹⁸ Such a petition must include a showing "that there is adequate data on the health or environmental effects of the pollutant or other evidence adequate to support the petition."¹⁹ EPA must act on the petition within 18 months, publishing a written explanation for its decision. The Agency is directed to add (or to delete) substances from the list upon a showing by the petitioner (or upon its own determination) that "emissions, ambient concentrations, bioaccumulation, or deposition of the substance" are (or are not) reasonably anticipated to cause adverse health or environmental effects.²⁰

Section 112(c) directs EPA to publish within 12 months of enactment of the 1990 amendments a list of all categories and subcategories of major and area sources of the substances listed under § 112(b).²¹ A "major source" is defined as

any stationary source or group of stationary sources located within a contiguous area and under common control that emits or has the potential to emit considering controls, in the aggregate, 10 tons per year or more of any hazardous air pollutant or 25 tons per year or more of any combination of hazardous air pollutants.²²

Thus, under § 112, "major" sources include sources with much lower levels of emissions than the "major" sources regulated under most other provisions of the Act. Also, under § 112, a source may be a major source based on aggregate emissions of several pollutants even if its emissions of each individual pollutant are relatively small.²³

Section 112(c)(3) requires EPA to list area sources of hazardous air emissions within five years of enactment. An [22 ELR 10247] "area source" is "any stationary source of hazardous air pollutants that is not a major source."²⁴ EPA is directed to ensure that its listing of categories of area sources includes at least 90 percent of the area source emissions of the 30 most serious area source pollutants in urban areas.²⁵ Section 112(c)(6) lists seven specific pollutants for which a full set of source categories (including area sources) must be listed within five years. This listing must, again, include sources accounting for at least 90 percent of emissions.²⁶

EPA may omit or delete from its list of source categories any category in which no source creates a lifetime risk of cancer that is greater than one in one million to the most exposed individual in the population.²⁷ For hazardous pollutants that have been listed because they pose risks of health impacts other than cancer or adverse environmental effects, EPA may omit source categories in which no source has emissions that exceed a level "which is adequate to protect public health with an ample margin of safety" or that cause adverse environmental effects.²⁸ These provisions, in essence, permit EPA to decline to regulate sources only if they would not have required regulation under the most conservative of the standards considered by the Agency before the amendments were enacted. Moreover, even if no adverse health effects are shown, regulation is still required if there are adverse environmental effects.²⁹

A decision by EPA to add additional hazardous air pollutants or source categories to the list of items to be regulated is not subject to judicial review.³⁰ Anyone wishing to challenge such a decision must wait until regulations pertaining to that pollutant or source category are promulgated.

B. MACT Standards

Once EPA has identified and listed major and area source categories of hazardous emissions, the Agency is required to promulgate regulations establishing "emission standards" for each source category.³¹ Such standards need not be uniform for all sources within the category; EPA may "distinguish among classes, types, and sizes of sources." However, all such standards must be based on one basic regulatory requirement: the application of maximum achievable control technology (MACT).

The statute requires emission standards to reflect the maximum degree of reduction in emissions that EPA determines to be achievable, taking into account "the cost of achieving such emission reduction, and any non-air quality health and environmental impacts and energy requirements…."³² Emission standards will be considered achievable if they can be achieved through such measures as, inter alia, changes in processes or materials; the use of closed systems; measures to collect, capture, or treat pollutants; changes in design, equipment, work practice, or operational requirements; or any combination of the above.

For a new source, MACT may not be less stringent than the level of control that is actually achieved in practice by the best controlled similar source.³³ For existing sources, MACT may be no less stringent than the average level of control achieved by the "best performing" 12 percent of existing sources in the category (excluding thosethat have been required within the past 30 months preceding promulgation to comply with the lowest achievable emission rate or LAER).³⁴ If a source category includes fewer than 30 sources, MACT must at least equal "the average emission limitation achieved by the best performing 5 sources."³⁵

The limits based on best performing sources establish only the floor for MACT; in many (perhaps most) cases EPA will establish MACT requirements for individual source categories that are significantly more stringent. It is likely that EPA will, in at least some cases, use a methodology closely resembling a "top-down" approach, under which the most stringent controls that are technically possible will be presumptively required unless they are shown to be economically infeasible.

Section 112(d)(4) states that if a "health threshold" has been established for a particular substance, emission standards governing sources of that substance may take that threshold level into account "with an ample margin of safety." Under this provision, MACT requirements may be relaxed somewhat for substances that are known to cause no adverse health effects at very low levels. However, since EPA's current policy is to treat carcinogens as having no health threshold above zero, this provision is unlikely to [22 ELR 10248] provide a basis for any relaxation of MACT requirements for sources that emit such substances.

Once EPA has promulgated MACT standards for a source category, those standards will apply to all major sources that have operations falling within that category. Since the "source categories" for which EPA is to promulgate MACT standards will be defined based on particular types of operations rather than on complete facilities, some facilities may face separate MACT requirements for different operations.³⁶ Moreover, since the classification of a source as "major" will be based on the total combined emissions of the set of individual sources that together constitute the "major source," some facilities may be required to adopt MACT controls for point sources that, standing alone, would not be major sources.³⁷

MACT requirements may be promulgated for area sources as well as major sources. For area sources, however, § 112(d)(5) authorizes EPA instead to promulgate standards "which provide for the use of generally available control technologies or management practices…."³⁸

In most cases, the new MACT regulations will establish the most stringent requirements applicable to a source. However, if more stringent requirements exist for a source under either federal or state law, § 112(d)(7) provides that MACT regulations will not preempt those requirements.³⁹ If EPA finds that it is not feasible to establish an emission standard for the control of particular hazardous emissions,⁴⁰ it may instead promulgate a design, equipment, work practice, or operational standard to control emissions of that source indirectly. Such standards must include appropriate operation and mainteance requirements.⁴¹ If the standards applicable to a source have been promulgated under this section, EPA may approve an alternative means of emission limitation for the source if the source can demonstrate that it will achieve a reduction in emissions that is at least equivalent to that established under EPA's standards.⁴²

Although the basic regulatory methodology adopted in the 1990 amendments differs fundamentally from that underlying EPA's existing NESHAP regulations, the statute expressly provides that those existing regulations are to remain in force and that the pre-amendment version of the Act is to remain the basis for judicial review in pending actions concerning those regulations.⁴³ If any existing regulations are remanded by the courts for revisions, EPA is given discretion to apply the requirements of either the new or the old statute in promulgating such revisions. However, EPA is directed to review and, if appropriate, revise those regulations within 10 years of enactment of the amendments.⁴⁴

C. Time Limits

To avoid the lengthy delays experienced under the old NESHAP regime, Congress has established a strict timetable for the promulgation of new regulations under § 112. EPA is directed to promulgate standards for at least 40 categories within two years of enactment of the 1990 amendments.⁴⁵ Regulations governing at least 25 percent of listed categories are to be promulgated within four years, and standards for an additional 25 percent must be promulgated within seven years. Regulations for the remaining categories are to be promulgated within 10 years of enactment.⁴⁶ EPA is to establish priorities for promulgating standards based on the adverse effects of the substances to be regulated, the quantity and location of emissions, and the efficiency of [22 ELR 10249] grouping categories on the basis of emissions or processes and technologies.⁴⁷

Regulations promulgated under § 112(d) are to be effective upon promulgation.⁴⁸ The Agency may give existing sources time in which to comply, but it must set a date for compliance that is no later than three years from the date of promulgation.⁴⁹ New sources must ordinarily demonstrate compliance with any applicable standards before construction begins. However, a new source that commences construction after a new standard is proposed but before it is promulgated will receive a three-year extension in complying with the final version if it complies with the proposed version.⁵⁰

D. Residual Risk

Congress recognized that the change from a health-based standard for the regulation of hazardous air pollutants to a technology-based standard might in some cases leave a "residual risk" from such pollutants that would require additional regulation. Section 112(f) requires EPA to study residual risks and to report to Congress on the subject within six years with a recommendation for further legislation. If Congress does not act on that recommendation, EPA is directed to revert to the pre-1990 health-based standard and to promulgate, within eight years after promulgation of MACT regulations for each source category, additional regulations to "provide an ample margin of safety to protect public health," or, if necessary, a more stringent standard to protect the environment, taking into consideration costs, energy, safety, and other relevant factors.⁵¹

Residual risk regulations must be promulgated for any substance that has been classified as a known, probable, or possible human carcinogen and for which the lifetime excess cancer risk to the most exposed individual has not been reduced by MACT regulations to less than one in one million.⁵² Although the statute does not require such regulations necessarily to reduce risk to the "one in one million" level, it expressly disavows any implicit approval (or disapproval) of EPA's existing interpretation of the "ample margin of safety" standard.⁵³ Instead, the 1990 amendments require new studies of residual risk issues, including both scientific and policy aspects of the problem.⁵⁴

Residual risk standards promulgated under § 112(f) will be effective upon promulgation and must be complied with beginning 90 days thereafter.⁵⁵ EPA may grant two-year waivers of the compliance date to individual sources if necessary "for the installation of controls," provided that steps are taken in the interim period "to assure that the health of persons will be protected from imminent endangerment."⁵⁶

E. Modifications, Offsets, and Voluntary Reductions

Section 112 establishes special definitions and requirements for modifications of existing sources of hazardous emissions. Under other provisions of the Act, a "modification" of a source that results in increased emissions is usually subject to the same requirements as construction of a new source.⁵⁷ However, under § 112, a "modification" is required to meet only MACT requirements for existing sources.⁵⁸ Moreover, a change will be considered a "modification" only if it (1) results in a greater than de minimis increase in actual emissions⁵⁹ and (2) is not offset by an [22 ELR 10250] equal or greater decrease in emissions of a more hazardous pollutant.⁶⁰ This provision encourages facilities to change their operations to reduce the hazard level of their emissions.

In addition, to reward sources that undertake early reductions in hazardous emissions, EPA (or a state acting under an approved Title V permit program) may authorize an existing source that voluntarily reduces emissions by 90 percent (95 percent in the case of particulate pollutants) below 1987 levels to comply based on that reduction for six years in lieu of meeting the MACT standard.⁶¹ (No such extension is available for the residual risk standard promulgated under § 112(f).) To qualify for this exemption, a source must either (1) complete the reduction before the standard that would otherwise apply under § 112(d) is first proposed or (2) make an enforceable commitment to achieve the reduction before proposal and complete the reduction before January 1, 1994. EPA or the state must authorize the extension if the required reduction is demonstrated, although a state may require a higher level of reduction as a prerequisite to the extension.⁶²

Extensions are also available for sources that, within five years before promulgation of a standard, have met the best available control technology (BACT) standards of § 169 or the LAER standards of § 171. Such sources need not comply with MACT until five years after the installation of BACT or LAER.⁶³

F. Permits

The requirements created under § 112 are to be incorporated in operating permits issued pursuant to Title V of the Act. If EPA fails to promulgate standards for a source category by the deadline established in § 112(e), permits for sources in that category must state requirements that are "equivalent to the limitation that would apply to such source if an emission standard had been promulgated in a timely manner…."⁶⁴ If EPA thereafter promulgates its own standard, that standard must be incorporated in the permit, either upon issuance if promulgation occurs before the permit is finally issued or, if the permit has already been issued, upon its renewal.⁶⁵

G. Accidental Releases

The 1990 amendments also added new requirements concerning accident prevention, detection, and response. EPA is directed to promulgate "reasonable regulations and appropriate guidance to provide, to the greatest extent practicable, for the prevention and detection of accidental releases" of hazardous pollutants from stationary sources, as well as appropriate response actions by sources.⁶⁶ In promulgating its regulations and guidance, EPA is directed to consult with the Secretaries of Transportation and Labor and to ensure that its regulations are consistent with other applicable law.

Section 112(r)(3) directs EPA to promulgate "an initial list of 100 substances that, in the case of an accidental release, are known to cause or may reasonably be anticipated to cause death, injury, or serious adverse effects to human health or the environment."⁶⁷ The list must include 16 pollutants listed in the statute,⁶⁸ and it is to be based initially on the list of extremely hazardous substances published under the Emergency Planning and Community Right-to-Know Act of 1986.⁶⁹ Pollutants are to be included on the list on the basis of the severity of health effects associated with accidental releases of the pollutant, the likelihood of an accidental release, and the potential magnitude of human exposure in the event of a release. EPA is then to determine "threshold quantities" of the listed substances and to require sources that have the substances present in quantities greater than the threshold quantity to prepare and implement a risk management plan to detect and prevent or minimize accidental releases of the substances.⁷⁰ Such plans are to be made available to all responsible state and federal agencies and to the public.⁷¹ EPA is also authorized to promulgate general regulations addressing accident prevention, detection, and correction.

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If EPA finds that an actual or threatened release of hazardous emissions creates imminent and substantial endangerment to human health or welfare or to the environment, § 112(r)(9) authorizes the Agency to take appropriate action, including issuing administrative orders and seeking injunctive relief in federal district court. Emergency response authority is also provided under § 303, and EPA is directed to act under that section whenever the authority it provides is "adequate."

Section 112(r)(6) creates a Chemical Safety and Hazard Investigation Board (CSHIB), which is to investigate accidental releases and to study programs and methods to prevent and address such releases. TheCSHIB is authorized to establish regulations for reporting accidental releases and may make recommendations to EPA and other agencies concerning revisions in their own regulations governing risk management, hazard assessments, and related subjects. The CSHIB is granted substantial information-gathering tools, including rights of inspection and subpoena authority.⁷²

The CSHIB is to investigate accidental releases in a manner analogous to the investigations of transportation accidents performed by the National Transportation Safety Board (NTSB). Where an accidental release involves issues of concern to other agencies, such as the NTSB or OSHA, the CSHIB is to coordinate its activities with those agencies. None of the CSHIB's conclusions, findings, or recommendations concerning an accidental release may be used in any action for damages relating to the release.⁷³

Finally, § 304 of the 1990 amendments directs the Secretary of Labor to promulgate new regulations under the Occupational Safety and Health Act⁷⁴ to prevent accidental releases of chemicals that could pose a threat to employees.⁷⁵ The Secretary is to promulgate a chemical process safety standard designed to protect employees from hazards associated with accidental releases of highly hazardous chemicals in the workplace. Such "highly hazardous chemicals" may include the list of hazardous substances promulgated by EPA under § 112(r) of the Clean Air Act, with any additions that the Secretary finds appropriate. The chemical process safety standard must include, inter alia, requirements governing workplace hazard assessment, safety information, safety procedures, training, and procedures for investigation of incidents.

H. Solid Waste Incinerators

The 1990 amendments added a new section to Title I of the Act, § 129, governing emissions from solid waste incineration units. Section 129(a)(1) requires EPA to establish performance standards and other requirements for solid waste incineration units.⁷⁶ Such standards are to be established for both new and existing units on a strict statutory timetable.⁷⁷

The standards promulgated under this section must establish numerical emission limitations for certain substances and categories of substances listed in the statute.⁷⁸ These limitations must comply with the same MACT standards established under § 112(d) for hazardous emissions in general.⁷⁹ In addition to providing for removal or destruction of pollutants, the regulations established under this section are to include siting requirements for new units that will minimize potential risks to human health and the environment.⁸⁰

Once EPA has promulgated its standards, each state must, within one year, promulgate and submit for EPA review a plan to implement and enforce the standards.⁸¹ Such plans must provide for full compliance with the standards by all existing sources in the state within three years of approval of the plan by EPA or five years of promulgation of the standards, whichever is earlier.⁸² EPA is directed to review the proposed state plans and approve or disapprove them within 180 days of submission.⁸³ If a state fails to submit [22 ELR 10252] an approvable plan within two years, EPA must promulgate a federal plan for that state.⁸⁴

An implementation plan promulgated under this section must contain, in addition to procedures for general implementation and enforcement, special requirements for monitoring emissions from each regulated unit.⁸⁵ The statute also imposes special requirements governing operator training and permits.⁸⁶

Solid waste incineration units are exempt from regulation under § 112(d). However, EPA must promulgate residual risk standards under § 112(f) if such standards would otherwise be required under that section.⁸⁷ A solid waste incineration unit is also exempted from regulation as a "utility" under Title IV of the Act, provided that more than 80 percent of its annual average fuel consumption is from a fuel other than a fossil fuel.⁸⁸

I. Protection of Lakes and Coastal Waters

The 1990 amendments significantly broadened the scope of § 112 by requiring regulation of hazardous emissions to protect, not only public health and safety, but also the environment. In addition, § 112(m) requires EPA to pay particular attention to hazardous emissions that lead or contribute to pollution of the Great Lakes and coastal waters.⁸⁹

Under § 112(m), EPA is required to monitor and assess the impact of "atmospheric deposition of hazardous air pollutants" on the Great Lakes, Lake Champlain, the Chesapeake Bay, and coastal waters. Beginning in 1993 and every two years thereafter, EPA is to report on the results of its assessment to Congress.⁹⁰ The Agency must include in each report a determination of whether the regulations promulgated under § 112 "are adequate to prevent serious adverse effects to public health and serious or widespread environmental effects" associated with atmospheric deposition to these bodies of water, including effects resulting from bioaccumulation.⁹¹ By 1995, EPA must promulgate additional emission standards and control measures if necessary to correct any deficiency.

III. Practical Effects of the 1990 Amendments

Of all the substantive provisions of the 1990 amendments, the title dealing with emissions of hazardous substances is the most far reaching, both in terms of the number of sources that will be affected and in the extremely stringent character of the new controls. Before the 1990 amendments, federal regulation of hazardous emissions was of little or no concern to most industries. That situation will soon change dramatically.

Within the next 10 years, virtually all medium- and large-sized sources of hazardous pollutants will be required to control emissions (often for the first time) and to adopt control measures that in many cases will push the bounds of economic feasibility. To meet the new standards, facilities will have to focus not only on readily identifiable point sources, but also on "fugitive emissions" — the tiny sources and leaks that, standing alone, are of little significance but that taken together can account for an appreciable portion of a facility's total emissions.

To prepare for this new regulatory regime, several important steps should be taken by any facility that is a source of hazardous emissions. First, the facility should review the extent and nature of its emissions and consider whether to make a "voluntary reduction" under § 112(i)(5). If such a reduction can be achieved through control measures that are less stringent than those likely to be required under MACT, it may make sense to take advantage of the automatic extension in the MACT compliance date for facilities making such reductions. Small-or medium-sized facilities should also consider whether their emissions can be controlled sufficiently to avoid exceeding the threshold level for a major source. If so, those facilities should be able to delay MACT regulation even longer and perhaps avoid it altogether.⁹²

If a facility cannot avoid being classified as a major source, it should monitor closely — and consider active participation in — EPA's upcoming rulemakings under § 112. The first of these is the listing of source categories and subcategories. For some sources, this listing may be the most important regulatory action of all, since it is the definition of each source category and subcategory that will determine the population of sources within it, including the "best performing" 12 percent of sources that will establish the floor for MACT. A facility that ends up in the "wrong" category because of a technical flaw in the way the category is defined could pay a heavy price.

Once source categories are established, it will be important to participate actively in the process through which EPA establishes MACT requirements for each category. Although the statute establishes a floor for MACT, EPA is likely to consider more stringent requirements. Regulated sources will need to be prepared to provide their own input to the Agency on these points.

Finally, although it has been pushed several years into the future, the residual risk problem remains. It was the impossibility of creating acceptable risk levels without imposing unacceptable economic hardships that led to the failure of the original NESHAP program. Technology may provide new and improved control measures in the future, but it seems likely that this dilemma will recur when the time comes to promulgate residual risk regulations under § 112(f). Thus, although Congress carefully designed § 112(f) to mandate further regulatory action whether or not Congress itself acts on EPA's residual risk findings, it seems likely that this issue will again prove relatively impervious to effective administrative resolution.

1. Clean Air Act (CAA) § 112(a)(1), 42 U.S.C. § 7412(a)(1), ELR STAT. CAA 28 (1982).

2. CAA § 112(b), 42 U.S.C. § 7412(b), ELR STAT. CAA 28 (1982).

3. CAA § 112(b)(1)(B), 42 U.S.C. § 7412(b)(1)(B), ELR STAT. CAA 28 (1982). The 1977 amendments established a preference for the control of hazardous air pollutants through emission standards, but permitted EPA instead to promulgate design, equipment, work practice, or operational standards if it found emission standards to be "not feasible." CAA § 112(e), 42 U.S.C. § 7412(e), ELR STAT. CAA 28-29 (1982).

4. See, e.g., H.R. REP. NO. 490, 101st Cong., 2d Sess., pt. 1, at 322-23 (1990); S. REP. NO. 228, 101st Cong., 1st Sess. 3, 128 (1989).

5. These eight were asbestos, beryllium, mercury, vinyl chloride, radionuclides, inorganic arsenic, benzene, and coke oven emissions. Of these, only benzene is among the 50 toxic substances emitted in greatest volume. See H.R. REP. NO. 490, supra note 4, at 322.

6. No federal standards have been promulgated for coke ove emissions. Nor are all sources of the seven other pollutants comprehensively regulated. See S. REP. NO. 228 supranote 4, at 131. In contrast, some states have implemented air toxics programs that regulate hundreds of pollutants.

7. Pub. L. No. 99-499, 100 Stat. 1613, 42 U.S.C. §§ 11001-11050, ELR STAT. EPCRA 001-012.

8. See S. REP. NO. 228, supra note 4, at 128.

9. Id.

10. 824 F.21 1146, 1152-54 (D.C. Cir. 1987) (en banc). The case is usually referred to as Vinyl Chloride because it arose from a challenge to EPA's NESHAP regulations for vinyl chloride.

11. Id. at 1163-66.

12. See, e.g., 54 Fed. Reg. 51654, 51656 (1989).

13. 53 Fed. Reg. 28496 (1988).

14. 54 Fed. Reg. 38044 (1989) (benzene); 54 Fed. Reg. 51654 (1989) (radionuclides). Both sets of regulations are the subject of pending appeals in the D.C. Circuit, and EPA is already reconsidering major elements of the radionuclide regulations.

15. CAA § 112(b)(1), 42 U.S.C. § 7412(b)(1) ELR STAT. CAA 29-30.

16. CAA § 112(b)(2), 42 U.S.C. § 7412(b)(2), ELR STAT. CAA 30-31. Substances may be listed if they are known (or reasonably anticipated) to be "carcinogenic, mutagenic, teratogenic, [or] neurotoxic," or if they "cause reproductive dysfunction, or … are acutely or chronically toxic…." "Adverse environmental effects" may be through "ambient concentrations, bioaccumulation, deposition, or otherwise." Id. These effects include significant and widespread adverse effects on "wildlife, aquatic life, or other natural resources, including adverse impacts on populations of endangered or threatened species or significant degredation of environmental quality over broad areas." CAA §§ 112(a)(7), 112(b)(2), 42 U.S.C. §§ 7412(a)(7), 7412(b)(2), ELR STAT. CAA 29, 30-31. EPA is specifically prohibited from listing elemental lead under this section. CAA § 112(b)(7), 42 U.S.C. § 7412(b)(7), ELR STAT. CAA 31.

17. Thus, for example, individual volatile organic compounds (VOCs) that are precursors to ozone pollution may be listed.

18. 42 U.S.C. § 7412(b)(3)(A), ELR STAT. CAA 31. For general categories of pollutants on the statutory list (e.g., "chromium compounds"), a petition may also be presented to remove "certain unique substances" from the category for purposes of the listing. EPA must act on any petitions filed within 12 months of enactment concerning such "unique substances" before promulgating any emission standards applicable to them. CAA § 112(b)(3)(D), 42 U.S.C. § 7412(b)(3)(D), ELR STAT. CAA 31. No such unique substances may be excluded from the categories of coke oven emissions, mineral fibers, or polycyclic organic matter.

19. CAA § 112(b)(3)(A), 42 U.S.C. § 7412(b)(3)(A), ELR STAT. CAA 31.

20. CAA § 112(b)(3)(B)-(D), 42 U.S.C. § 7412(b)(3)(B)-(D), ELR STAT. CAA 31.

21. 42 U.S.C. § 7412(c), ELR STAT. CAA 31. EPA is directed to review and revise the list, as appropriate, at least once every eight years. Id. Regulations governing sources on the list must also be reviewed at least every eight years. CAA § 112(d)(6), 42 U.S.C. § 7412(d)(6), ELR STAT. CAA 32.

22. CAA § 112(a)(1), 42 U.S.C. § 7412(a)(1), ELR STAT. CAA 29. EPA may establish a lesser threshold quantity for particular emissions on the basis of potency, persistence, potential for bioaccumulation, or other factors. For radionuclides, EPA may develop a definition of "major source" based on criteria other than volume. Id.

23. Section 112(c)(7) requires "research facilities" engaged in research and development activities to be listed as a separate category "as necessary to assure the equitable treatment of such facilities." 42 U.S.C. § 7412(c)(7), ELR STAT. CAA 31.

24. CAA § 112(a)(2), 42 U.S.C. § 7412(a)(2), ELR STAT. CAA 29. Typical examples of such "area sources" are neighborhood dry cleaners and gasoline filling stations. The term excludes mobile sources regulated under Title II of the Act. Id.

25. CAA § 112(c)(3), 42 U.S.C. § 7412(c)(3), ELR STAT. CAA 31. EPA is directed to monitor hazardous emissions from area sources in urban areas and to propose a national urban air toxics strategy within five years. That strategy is to be designed to reduce cancer risks associated with such emissions by 75 percent. CAA § 112(k), 42 U.S.C. § 7412(k), ELR STAT. CAA 36-37.

26. 42 U.S.C. § 7412(c)(6), ELR STAT. CAA 31. Emissions of these substances by electric utility steam generating units are excluded from this requirement. Id.

27. CAA § 112(c)(9)(B)(i), 42 U.S.C. § 7412(c)(9)(B)(i), ELR STAT. CAA 32.

28. CAA § 112(c)(9)(B)(ii), 42 U.S.C. § 7412(c)(9)(B)(ii), ELR STAT. CAA 32.

29. This is a major change from the pre-1990 version of the Act, which required regulation of hazardous emissions solely on the basis of effects on human health.

30. CAA § 112(e)(4), 42 U.S.C. § 7412(e)(4), ELR STAT. CAA 33.

31. CAA §§ 112(c)(2), 112(d), 42 U.S.C. §§ 7412(c)(2), 7412(d), ELR STAT. CAA 31, 32. The conference report suggests that EPA should include in the first group of sources to be regulated the "priority elements of the hazardous organic NESHAP which is under development." H.R. CONF. REP. NO. 952, 101st Cong., 2d Sess. 338 (1990); see also 136 CONG. REC. S16903 (Oct. 27, 1990) (statement of Sen. Mitchell).

32. CAA § 112(d)(2), 42 U.S.C. § 7412(d)(2), ELR STAT. CAA 32.

33. CAA § 112(d)(3), 42 U.S.C. § 7412(d)(3), ELR STAT. CAA 32. This is nearly identical to the lowest achievable emission rate (LAER) standard that already applies to certain major sources in nonattainment areas. See CAA § 171(3), 42 U.S.C. § 7501(3), ELR STAT. CAA 74. As with LAER, MACT will require only controls that have been shown to be viable in practice; controls that have been used only on an experimental or "research" basis will not be required. See 136 CONG. REC. S17238 (Oct. 26, 1990) (statements of Sens. Dole and Durenberger).

34. CAA § 112(d)(3)(A), 42 U.S.C. § 7412(d)(3)(A), ELR STAT. CAA 32. A source that has recently complied with LAER may be included in the 12 percent of best performing sources if LAER is subsequently (but before promulgation of the MACT standard) made more stringent. Thus, the best performing 12 percent may in some cases be a "moving target." See 136 CONG. REC. S16929 (Oct. 27, 1990) (statement by Sen. Durenberger).

35. CAA § 112(d)(3)(B), 42 U.S.C. § 7412(d)(3)(B), ELR STAT. CAA 32. The statute is silent on whether sources that recently complied with LAER should be included in this situation.

36. Thus, for example, instead of one set of MACT requirements for "steel mills," there could be different requirements for coke ovens, for solvent storage and handling, and so on for each category of operation at a steel mill that involves hazardous emissions. See 136 CONG. REC. S16927 (Oct. 27, 1990) (statement by Sen. Durenberger).

37. See id. at S16927. The extent to which this will occur will depend, inter alia, on how EPA elects to define the relevant source categories and subcategories and the extent to which smaller sources within a plant fall within discrete source categories. Even if such sources are not regulated under the MACT standards applicable to major sources, they may still be subject to regulation as area sources.

38. 42 U.S.C. § 7412(d)(5), ELR STAT. CAA 32. The statute also provides alternative bases for regulation of coke oven batteries and radionuclides. CAA § 112(d)(8), (9), 42 U.S.C. § 7412(d)(8), (9), ELR STAT. CAA 32-33. CAA § 112(d)(9) provides that standards for radionuclide emissions from facilities regulated by the Nuclear Regulatory Commission (NRC) are not required if EPA determines that NRC's regulatory program for such facilities "provides an ample margin of safety to protect the public health." EPA may not apply its preexisting regulations under the old version of the Act to medical facilities for two years after enactment unless it has made a negative determination under this section. See CAA § 112(q)(4), 42 U.S.C. § 7412(q)(4), ELR STAT. CAA 40. Section 112(d)(9) confirms, however, that states remain free to promulgate emission standards that are more stringent than EPA's. This is consistent with the Act's general policy against federal preemption of more stringent state requirements. See CAA § 116, 42 U.S.C. § 7416, ELR STAT. CAA 53.

39. 42 U.S.C. § 7412(d)(7), ELR STAT. CAA 32.

40. "Emission standards" are direct quantitative restrictions on the emissions emitted from the source. See Adamo Wrecking Co. v. United States, 433 U.S. 275, 8 ELR 20171 (1978). An emission standard is considered not "feasible" if the substance at issue "cannot be emitted through a conveyance designed and constructed to emit or capture" it, or if there are technological or economic bars to the application of necessary measurement methodology. CAA § 112(h)(2), 42 U.S.C. § 7412(h)(2), ELR STAT. CAA 34.

41. CAA § 112(h)(1), 42 U.S.C. § 7412(h)(1), ELR STAT. CAA 34.

42. CAA § 112(h)(3), 42 U.S.C. § 7412(h)(3), ELR STAT. CAA 34.

43. CAA § 112(q), 42 U.S.C. § 7412(q), ELR STAT. CAA 40.

44. Id. Such revisions are not to include standards for radionuclide emissions from elemental phosphorus plants, grate calcination elemental phosphorous plants, or phosphogypsum stacks. The statute provides that the version of § 112 in effect before the 1990 amendments is to continue to govern radionuclide emissions from those sources. CAA § 112(q)(2), 42 U.S.C. § 7412(q)(2), ELR STAT. CAA 40. EPA is also given discretion to apply the old version of the Act to radionuclide emissions from non-Department of Energy federal facilities that are not licensed by the NRC, coal-fixed utility and industrial boilers, uranium mines, and uranium tailings piles. CAA § 112(q)(3), 42 U.S.C. § 7412(q)(3), ELR STAT. CAA 40. The conference report urges EPA to give a low priority to reviewing the existing beryllium standard unless new data show that delaying that review would pose significant risks to public health and the environment. H.R. CONF. REP. NO. 952, supra note 31, at 339.

45. CAA § 112(e)(1)(A), 42 U.S.C. § 7412(e)(1)(A), ELR STAT. CAA 33. In addition, regulations governing coke oven batteries must be promulgated by December 31, 1992. Regulations for publicly owned treatment works must be promulgated within five years of enactment. CAA § 112(e)(1)(B), 112(e)(5), 42 U.S.C. §§ 7412(e)(1)(B), 7412(e)(5), ELR STAT. CAA 33. Regulations governing emissions by electric utility steam generating units may be promulgated only if EPA finds such regulations "appropriate and necessary" following a study of the public health hazards associated with them. CAA § 112(n)(1), 42 U.S.C. § 7412(n)(1), ELR STAT. CAA 39.

46. CAA § 112(e)(1), 42 U.S.C. § 7412(e)(1), ELR STAT. CAA 33. Regulations governing the area sources listed pursuant to § 112(c)(3) must also be promulgated within 10 years of enactment. 42 U.S.C. § 7412(c)(3), ELR STAT. CAA 31.

47. CAA § 112(e)(2), 42 U.S.C. § 7412(e)(2), ELR STAT. CAA 33; see H.R. CONF. REP. No. 952, supra note 31, at 338-39. EPA is to issue a schedule for promulgation of regulations under this section within 24 months of enactment. CAA § 112(e)(3), 42 U.S.C. § 7412(e)(3), ELR STAT. CAA 33.

48. CAA § 112(d)(10), 42 U.S.C. § 7412(d)(10), ELR STAT. CAA 33.

49. CAA § 112(i)(3), 42 U.S.C. § 7412(i)(3), ELR STAT. CAA 34-35. Individual sources may obtain extensions of up to one year if necessary "for the installation of controls." Id. Mining waste operations may obtain an additional extension of up to three years. Moreover, no source that has, before the date of promulgation of a standard, installed best achievable control technology (BACT) or LAER technology for the relevant pollutant may be required to comply with the standard until five years after installation of that technology. CAA § 112(i)(6), 42 U.S.C. § 7412(i)(6), ELR STAT. CAA 35.

50. CAA § 112(i)(1), (2), 42 U.S.C. § 7412(i)(1), (2), ELR STAT. CAA 34. In addition, if the source commences construction after the MACT standard under § 112(d) is proposed, but before proposal of the residual risk standard under § 112(f), it will not be required to comply with the residual risk standard until 10 years after the date of commencement of construction. CAA § 112(i)(7), 42 U.S.C. § 7412(i)(7), ELR STAT. CAA 35.

51. CAA § 112(f)(2), 42 U.S.C. § 7412(f)(2), ELR STAT. CAA 33. For source categories for which MACT regulations are promulgated within two years of enactment of the 1990 amendments, EPA has nine years in which to promulgate residual risk standards. Residual risk standards are not required for area sources. CAA § 112(f)(5), 42 U.S.C. § 7412(f)(5), ELR STAT. CAA 34.

52. CAA § 112(f)(2)(A), 42 U.S.C. § 7412(f)(2)(A), ELR STAT. CAA 33. The statute does not define "most exposed individual," and it is not clear whether Congress meant to refer here to the theoretical most exposed individual (which is how EPA has traditionally used the term) or to the actual most exposed individual (which was how the term was expressly defined in other provisions of the House and Senate bills that were ultimately deleted in conference). As discussed above, this distinction can have a significant impact on the level of control that is required, and Congress's failure to clarify the ambiguity is likely to lead to significant controversy when EPA promulgates its residual risk regulations.

53. CAA § 112(f)(2)(B), 42 U.S.C. § 7412(f)(2)(B), ELR STAT. CAA 33. See generally 136 CONG. REC. E3710-12 (Nov. 2, 1990) (extended remarks of Rep. Rowland).

54. Section 303 of the 1990 amendments establishes the Risk Assessment and Management Commission, which is directed to "make a full investigation of the policy implications and appropriate uses of risk assessment and risk management in regulatory programs under various Federal laws to prevent cancer and other chronic human health effects which may result from exposure to hazardous substances." 42 U.S.C. § 7412 note, ELR STAT. CAA 44.

55. CAA § 112(f)(3), (4)(A), 42 U.S.C. § 7412(f)(3), (4)(A), ELR STAT. CAA 34.

56. CAA § 112(f)(4)(B), 42 U.S.C. § 7412(f)(4)(B), ELR STAT. CAA 34. Coke oven batteries that achieve a stringent level of control may obtain an extension in the compliance date for residual risk standards to 2020. CAA § 112(i)(8), 42 U.S.C. § 7412(i)(8), ELR STAT. CAA 35.

57. Thus, for example, a modification of an existing source in a non-attainment area is subject to the same LAER requirements applicable to new sources.

58. CAA § 112(g)(2), 42 U.S.C. § 7412(g)(2), ELR STAT. CAA 34. This requirement is to be incorporated into the source's permit application under Title V of the Act. The source must demonstrate compliance with MACT regardless of whether EPA has yet promulgated MACT regulations for its category. Construction of a new source (or "reconstruction" of an existing source) requires compliance with the MACT requirement for new sources.

59. CAA § 112(a)(5), 42 U.S.C. § 7412(a)(5), ELR STAT. CAA 29. This is a significant departure from EPA's practice under other sections, which has been to treat a change as a modification if it creates an increase in potential emissions over past actual emissions. See Letter from David Roe, Director, Air and Pollution Division, EPA, to Timothy Method, Ass't Commissioner, Office of Air Management, Indiana Dep't of Environmental Management (Jan. 30, 1990), reprinted in 136 CONG. REC. S16905, S16907 (Oct. 27, 1990).

60. CAA § 112(g)(1), 42 U.S.C. § 7412(g)(1), ELR STAT. CAA 34. EPA is directed to promulgate guidance for the determination of whether the emissions for which the offset is claimed are more hazardous than the emissions that are increased by the change. A source claiming an offset under this section must submit documentation to EPA showing that the offset is appropriate.

61. CAA § 112(i)(5), 42 U.S.C. § 7412(i)(5), ELR STAT. CAA 35. EPA may allow a source to use 1985 or 1986 as its baseline year if the source submitted verifiable data for one of those years to EPA, before enactment of the 1990 amendments, in response to an information request under § 114.

62. The 90-percent reduction requirement may also be adjusted to take into account emissions of "pollutants for which high risks of adverse public health effects may be associated with exposure to small quantities, including, but not limited to, chlorinated dioxins and furans…." CAA § 112(i)(5)(E), 42 U.S.C. § 7412(i)(5)(E), ELR STAT. CAA 35.

63. CAA § 112(i)(6), 42 U.S.C. § 7412(i)(6), ELR STAT. CAA 35. In addition, the President may exempt a source from compliance for up to two years for national security reasons upon a determination that technology to implement the standards is not available. The exemption is renewable for additional two-year periods. CAA § 112(i)(4), 42 U.S.C. § 7412(i)(4), ELR STAT. CAA 35.

64. CAA § 112(j)(5), 42 U.S.C. § 7412(j)(5), ELR STAT. CAA 36. An existing source must be required to comply with these "equivalent" requirements within three years of the date on which they are first included in its permit. If the source proposes to comply with the regulation through reductions as authorized under § 112(i)(5), the reduction must be achieved by the date on which the relevant standard should have been promulgated under § 112(d). Id.

65. CAA § 112(j)(6), 42 U.S.C. § 7412(j)(6), ELR STAT. CAA 36. In the first case, the source is to be given the usual time to comply with the new standard. In the second, the source must be given a "reasonable time to comply," which may be no longer than eight years after promulgation or eight years after the source is required to comply with "equivalent" requirements in its permit — whichever is earlier. Id.

66. CAA § 112(r)(7)(B)(i), 42 U.S.C. § 7412(r)(7)(B)(i), ELR STAT. CAA 43. EPA may not, however, seek to regulate accidental releases of radionuclides from facilities licensed by the NRC. CAA § 112(r)(7)(D), 42 U.S.C. § 7412(r)(7)(D), ELR STAT. CAA 43.

67. 42 U.S.C. § 7412(r)(3), ELR STAT. CAA 41.

68. Id.

69. No pollutants for which an NAAQS has been established may be included on the list.

70. CAA § 112(r)(5), 112(r)(7)(B)(ii), 42 U.S.C. §§ 7412(r)(5), 7412(r)(7)(B)(ii), ELR STAT. CAA 41, 43. After the effective date of EPA's regulations, it will be unlawful to operate any stationary source subject to the regulation without complying with it. CAA § 112(r)(7)(E), 42 U.S.C. § 7412(r)(7)(E), ELR STAT. CAA 44. However, no source will be required to obtain a permit under Title V solely because it is subject to these regulations. CAA § 112(r)(7)(F), 42 U.S.C. § 7412(r)(7)(F), ELR STAT. CAA 44.

71. CAA § 112(r)(7)(B)(iii), 42 U.S.C. § 7412(r)(7)(B)(iii), ELR STAT. CAA 43.

72. CAA § 112(r)(6)(L), (M), 42 U.S.C. § 7412(r)(6)(L), (M), ELR STAT. CAA 42.

73. CAA § 112(r)(6)(G), 42 U.S.C. § 7412(r)(6)(G), ELR STAT. CAA 41-42.

74. 29 U.S.C. §§ 651-678 (1988).

75. This requirement will not be codified in § 112 of the Act but is a separate requirement established in the 1990 amendments.

76. 42 U.S.C. § 7429(a)(1), ELR STAT. CAA 60. A solid waste incineration unit is defined as "a distinct operating unit of any facility which combusts any solid waste material from commercial or industrial establishments or the general public…." CAA § 129(g)(1), 42 U.S.C. § 7429(g)(1), ELR STAT. CAA 61. The term excludes incinerators and other units required to have a permit under § 3005 of the Resource Conservation and Recovery Act (RCRA), as well as any materials recovery facilities that combust waste for the primary purpose of recovering metals, certain types of small power production facilities and cogeneration facilities, and air curtain incinerators. Id.

77. CAA § 129(a)(1), 42 U.S.C. § 7429(a)(a), ELR STAT. CAA 60. Standards for municipal waste units with capacities greater than 250 tons per day must be promulgated within 12 months of enactment of the 1990 amendments. Standards for smaller municipal waste units and units combusting hospital waste, medical waste, and infectious waste must be promulgated within 24 months of enactment. Standards applicable to commercial or industrial waste incinerators must be proposed within 36 months of enactment and promulgated within 12 months thereafter. Id.

EPA has entered into a consent decree requiring the promulgation of new source performance standards for municipal waste incinerators by December 31, 1990. This requirement is left untouched by the 1990 amendments. CAA § 129(a)(1)(B), 42 U.S.C. § 7429(a)(1)(B), ELR STAT. CAA 60; see H.R. CONF. REP. NO. 952, supra note 31, at 342.

78. CAA § 129(a)(4), 42 U.S.C. § 7429(a)(4), ELR STAT. CAA 60. The substances that must be regulated are particulate matter, sulfur dioxide, hydrogen chloride, oxides of nitrogen, carbon monoxide, lead, cadmium, mercury, and dioxins and dibenzofurans. EPA may establish emission limits for other substances as well. EPA is barred from regulating ash from municipal waste incineration units under RCRA § 3001 for two years following enactment of the 1990 amendments. Clean Air Act Amendments of 1990, Pub. L. No. 101-549, § 306, 104 Stat. 2399, 2584.

79. CAA § 129(a)(2), 42 U.S.C. § 7429(a)(2), ELR STAT. CAA 60. The definition of MACT in this section is essentially identical to that provided in § 112.

80. CAA § 129(a)(3), 42 U.S.C. § 7429(a)(3), ELR STAT. CAA 60.

81. CAA § 129(b)(2), 42 U.S.C. § 7429(b)(2), ELR STAT. CAA 60. Section 129(h)(1) preserves the right of any state or political sub-division thereof to impose more stringent requirements than those imposed under EPA's standards. 42 U.S.C. § 7429(h)(1), ELR STAT. CAA 62.

82. CAA §§ 129(b)(2), 129(f)(2), 42 U.S.C. §§ 7429(b)(2), 7429(f)(2), ELR STAT. CAA 60-61. Standards for new sources are effective six months after promulgation. CAA § 129(f)(1), 42 U.S.C. § 7429(f)(1), ELR STAT. CAA 61.

83. CAA § 129(b)(2), 42 U.S.C. § 7429(b)(2), ELR STAT. CAA 60-61. It is interesting to compare this 180-day approval requirement with the implicit assumption in the date-of-compliance provision that EPA review may in fact take substantially longer.

84. CAA § 129(b)(3), 42 U.S.C. § 7429(b)(3), ELR STAT. CAA 61.

85. CAA § 129(c), 42 U.S.C. § 7429(c), ELR STAT. CAA 61.

86. CAA §§ 129(d), 129(e), 42 U.S.C. §§ 7429(d), 7429(e), ELR STAT. CAA 61.

87. CAA § 129(h)(3), 42 U.S.C. § 7429(h)(3), ELR STAT. CAA 62.

88. CAA § 129(h)(4), 42 U.S.C. § 7429(h)(4), ELR STAT. CAA 62.

89. 42 U.S.C. § 7412(m), ELR STAT. CAA 38-39.

90. CAA § 112(m)(5), 42 U.S.C. § 7412(m)(5), ELR STAT. CAA 38.

91. CAA § 112(m)(6), 42 U.S.C. § 7412(m)(6), ELR STAT. CAA 38.

92. EPA may also impose MACT requirements on smaller "area" sources but has the option of imposing less stringent requirements on such sources instead. Moreover, EPA is not required to promulgate regulations governing area sources before 2000 and will probably not act significantly in advance of that deadline.