Specific Provisions

The CAA has specific provisions for the National Ambient Air Quality Standards, attainment and nonattainment, ozone, prevention of significant deterioration, air toxics, state implementation plans, permits, and mobile sources. These provisions are summarized next.

National Ambient Air Quality Standards

National Ambient Air Quality Standards (NAAQS) are health-based standards used to measure and protect the air around us.1 Section 108 directs the EPA to identify criteria pollutants which may reasonably endanger public health and welfare. The list of criteria pollutants includes:

• Carbon monoxide

• Particulate matter

The act directs the EPA to establish two levels of NAAQS for the criteria pollutants. First, the EPA developed primary air quality standards to protect human health and provide a margin of safety to protect sensitive members of the population, e.g., pregnant woman, children, and the elderly. The EPA can also establish stricter secondary standards to avoid adverse impacts on the environment and protect public welfare by preventing harm to agricultural crops and livestock.

Attainment and Nonattainment

The attainment of ambient standards is a central purpose of the CAA. Areas are in attainment if they meet the NAAQS. Pollution sources in attainment areas are subject to the prevention of significant deterioration (PSD) requirements discussed next.

An area is designated in nonattainment if it exceeds the NAAQS for a given pollutant more than once a year. This determination is made for each criteria pollutant. Consequently, an area can be in nonattainment for one pollutant, while at the same time be in attainment and subject to PSD provisions for another.

Though similar to the classification scheme in the 1977 amendments, the 1990 amendments divide nonattainment areas into categories depending on the severity of each area's problem. It also allows boundaries to be adjusted to accommodate areas that have come into attainment. Amended section 107(d) requires states to designate regions as:

"Nonattainment"—any area that does not meet (or contributes to ambient air quality in a nearby area that does not meet) national primary or secondary ambient air quality standards for the pollutant;

"Attainment"—any area that does meet the standard for the pollutant, or

1. See U.S. Code, Vol. 42, secs. 7408-9; Federal Register 36, 1971, 8186;

Code of Federal Regulations. 1991, Title 40, part 50.

"Unclassifiable "—any area that cannot be classified attainment or nonattainment on the basis of available information.

Any state not meeting implementation deadlines is subject to a moratorium on the construction of new major stationary sources of pollution or on any major modifications of existing major sources in nonattainment areas. A major source is one with emissions or potential to emit 100 tons or more per year of a pollutant subject to regulation under the act.2 A major modification is any physical change in the operation of a major stationary source that would result in a significant net increase in a pollutant subject to regulation under the act.3

Section 173 requires states to adopt permit programs for the construction or modification of major stationary sources in nonattainment areas. It also imposes a more demanding technology requirement, the lowest achievable emission rate (LAER) on those sources. Finally, permits for modified sources in nonattainment areas can be issued only if emissions from existing sources in the area decrease enough to offset the increase in emissions from the new or modified source and continue reasonable further progress.


Ozone, commonly known as smog, is the most serious and common nonattainment problem. The 1990 amendments contain requirements for ozone nonattainment areas (CAA §181, 42 USC 7511). Section 181 divides ozone nonat-tainment areas into five categories depending on their degree of nonattainment:

Each category is assigned a design value, which is a measure of its ambient air quality expressed in parts per million. Attainment deadlines vary among areas and are measured from November 15, 1990, the enactment date of the 1990 amendments. The attainment deadline for each category follows:

• Marginal areas—three years

• Moderate areas—six years

• Serious areas—nine years

• Severe areas—fifteen years

• Extreme areas—twenty years

On the basis of its category and design value, each area is responsible for its own category requirements as well as

2. See Code of Federal Regulations, 1984, Title 40, sec. 52.24(f)(4)(i)(a).

3. See Clean Air Act, sec. 110(a)(2)(I); U.S. Code, Vol. 42, sec. 7410 (a) (2) (I); Code of Federal Regulations, Title 40, sec. 52.24(f)(5)(i).

the requirements for categories of lesser nonattainment. Thus, moderate areas are responsible for their own requirements as well as those applicable to marginal areas. For example, a state with a marginal ozone area must submit:

1. An inventory of all actual emissions to the EPA by November 1992

2. Revisions to its state implementation plans (SIP) designed to meet the three-year deadline for attainment, including the implementation of reasonably available control technology (RACT)

3. Permit programs for new and modified sources

4. An increase in the offset requirement for new sources and modifications, from 1 to 1 to 1.1 to 1

5. The retention of the vehicle inspection and maintenance program previously required for the area

A moderate area must submit requirements (1) through (5) listed for marginal areas, as well as all requirements assigned to moderate areas which include:

1. A revision of its SIP to provide for reasonable further progress through a 15% reduction in emissions within six years for volatile organic compounds (VOCs)

2. Any other annual reductions of VOCs and NO necessary to reach attainment by the deadline

3. The implementation of RACT for each category of VOC source covered by existing control techniques guidance.

Prevention of Significant Deterioration

Areas in attainment for NAAQS are subject to provisions for PSD (CAA §§160-169[B], 42 USC §§7470-7479[B]). PSD provisions seek to protect areas that already enjoy cleaner air than that required by the ambient standards, and to keep that air from deteriorating in quality.4 PSD provisions also require new major facilities to apply for a preconstruction permit and to use the best available control technology (BACT) for each pollutant regulated under this section.5

The BACT is determined on a case-by-case basis and reflects the most effective controls currently in use. The Act defines the BACT as the maximum degree of reduction which considers energy, environmental, economic, and other impacts.

PSD regulations divide the country into three classes on the basis of air quality:

Class I (large national parks and wilderness areas) Class II (very clean areas allowing some industrial growth) Class III (Class II areas established for industrial development)

4. See Code of Federal Regulations, Title, 40 sec. 52.51 for PSD requirements and PSD provisions in SIPs.

5. See Federal Register 53 at 40656.

For each class, the act establishes maximum allowable increases over baseline concentrations (increments) of pollutants (SO2, NO, and PM-10). Baseline concentrations are established based on the ambient concentrations measured at permit application. Allowable increases cannot create concentrations greater than those sanctioned by the NAAQS.

Section 165 of the act controls PSD permits (CAA §165, 42 USC §7475. This section requires new and modified sources to undergo a preconstruction review. The review includes a hearing with public comment to assess a project's potential impact and to consider alternatives to the proposed project. After completing air quality monitoring, the owner or operator must also demonstrate that the expected emissions from the operation or construction of the project will not exceed the limit on the increment of clean air in that area.

Air Toxics

The issue of air toxics is treated separately from attainment and nonattainment of ambient air quality and the prevention of significant deterioration (CAA §112, 42 USC §7412.6 The 1970 act authorized the EPA to set health-based national emission standards for hazardous air pollutants (NESHAPS). However, the EPA acted on only a limited number. The 1990 amendments, under section 112, mandates the establishment of technology-based standards for 189 hazardous substances. Section 112 also calls for the use of maximum achievable control technology (MACT) to regulate the emission of these substances.

The 1990 amendments create a two-step approach to controlling air toxics. First, new sources must use MACT to achieve a reduction level equal to levels reached by the least-polluting existing sources within given categories. All categories of sources are supposed to be promulgated by November 2000: 25% of all standards are to be promulgated by November 1994, and 50% of all standards are to be completed by November 1997. The second step establishes residual risk standards which are more stringent than MACT. Residual risk standards should be used to protect the public health with an ample margin of safety.

The EPA has already issued some MACT standards. One example is the hazardous organic NESHAP (HON) rule, which sets standards for reducing the emissions of 149 toxic chemicals from synthetic-organic chemical manufacturing (SOCMI) processes.7 The rule applies to processes that develop chemicals considered primary products, which are distinct from other by-products created in these processes. The HON applies to any plant that is con-

6. See also Code of Federal Regulations, Title 40, part 61.

7. National Emission Standards for Hazardous Air Pollutants for Source Categories; Organic Hazardous Air Pollutants from the Synthetic Organic Chemical Manufacturing Industry and Seven Other Processes, Federal Register 57, (31 December 1992):62608.

sidered a major source and is a model for future MACT standards developed at the federal level.

The EPA has also developed a final rule on the toxics early reductions program for hazardous air pollutants (57 FR 61970 et seq.)8 This program encourages industrial facilities to pursue early reductions before the final MACT standards are established. Facilities that qualify for the program can defer their compliance with MACT standards for six years if they agree to and can demonstrate reductions of their emissions by 90 and 95% before the MACT standards take effect (CAA § 112[d], 42 USC §7412[d], 40 CFR §63.70 et seq.). Because industries under this program can choose how to reduce their toxics emissions, in theory they have the flexibility to make the most economically viable choices for themselves.

The EPA has published an initial list of categories of major sources and area sources of air toxics (57 FR [16 July 1992] 31576). An area source is defined as a stationary source that is not a major source (CAA §112[a][2], 42 USC §7412[a] [2]). The regulation of area sources is meant to include small diverse sources, such as dry cleaners and service stations, which substantially contribute to the emission of hazardous pollutants. Instead of being subject to MACT, areas sources are subject to less stringent standards called generally available control technology (GACT).

State Implementation Plans

The act requires each state to submit a plan for implementation and enforcement of the national standards within its jurisdiction (CAA §110, 42 USC §7410, 40 CFR §§51.01 et seq., 52.01 et seq., 52.2370 et seq.). SIPs are based on emission inventories and computer models that predict whether violations of the NAAQS will occur. States can decide to meet the NAAQS as long as the regulatory requirements they choose enable them to attain the national standards. Once an SIP is approved, it becomes an element of state and federal law and is enforceable under either. In attainment areas, SIP planning must also account for PSD issues.

In nonattainment areas, SIPs provide for attainment of NAAQS and include:

1. Provisions for RACT

2. Reasonable progress in attaining the required reductions

3. A current emissions inventory

4. Permits for new and modified major stationary sources

5. Emission offset requirements

8. This program is implemented through the Title V operating permits program. The EPA has developed a guidance document outlining pro cedures for facilities to follow in applying for this program, Enabling

Document for Regulations Governing Compliance Extensions for Early Reductions of Hazardous Air Pollutants (EPA-450/3-91-013 [December 1992]).

6. A contingency plan if unable to meet NAAQS by the specified date

SIPs must also contain procedures for the review and permitting of new or modified stationary sources and their impact on the attainment and maintenance of NAAQS. SIPs regulate these sources on the basis of their general provisions. SIPs also contain provisions that apply to individual sources. To obtain a variance or be exempted from SIP provisions, however, involves a lengthy process which includes revising the SIP and review by the state authorities and the EPA.

Some SIPs contain provisions for alternative compliance, which streamline review and allow for in-state revisions of the requirements for individual facilities. In some contexts, the use of "bubbles" provides another means for facilities to make changes within their plant without triggering an SIP revision.9 Put simply, bubbling is the consolidation of multiple emission sources. Bubbling creates one source (for regulatory purposes), which allows certain limited changes in emissions from the sources within the bubble.

If a state fails to gain approval of its SIP, the EPA can promulgate a plan for that state. This plan is called a federal implementation plan (FIP). An implementation plan includes the following requirements:10

1. Enforceable emission limits

2. Necessary monitoring

3. Program for enforcement including a permit program

4. Interstate and international requirements

5. Adequate personal funding and authority

6. Self-monitoring requirements

7. Emergency authority

8. Revision authority

9. Nonattainment plan

10. PSD plans

11. Air quality modelling

12. Federal requirements

13. Consultation and participation


Generally, the federal government delegates the responsibility for issuing permits to the states through the SIPs. Prior to implementing the new operating permit program under the 1990 amendments, new source review was the means for issuing permits to new or modified industrial facilities. Permit requirements vary, depending on whether the project is in a PSD or nonattainment area.11 Apart from PSD

9. The EPA first developed a bubble policy in 1979 but revised it to include not only existing sources but also emissions trading and new sources. Federal Register 51, (1986):43814.

10. For SIP minimum criteria, see Federal Register 56, (26 August 1991):42216.

11. See discussions of Prevention of Significant Deterioration and Nonattainment supra.

and nonattainment concerns, permitting is a two-step process which requires initial authorization to construct a project and then authorization to operate a source.

The permit program under the 1990 amendments brings together the requirements for individual facilities and places them in one document. It also provides a financial basis for the program through permit fees. New permits contain emissions standards, monitoring, record-keeping, and reporting requirements. Major sources, sources subject to air toxics regulation, and all sources subject to new source performance standards are required to obtain a permit.

Mobile Sources

The 1970 act regulated emissions from automobiles. It called for a 90% reduction of emissions below the then-current levels. Subsequently, the 1977 amendments adjusted the NO emissions to allow for a 75% reduction. These standards are applied on a national basis because automobiles move from state to state.

The 1990 amendments go further in reducing emissions from mobile sources (CAA §§202-250, 42 USC §§7521-7590). They establish more stringent tailpipe standards and establish clean fuel requirements.

To implement the new emission standards, the 1990 amendments establish a tier system which phases in standards for NO between 1994 and 1995, and for non-methane hydrocarbons and carbon monoxide between 1994 and 1998. A second tier, if the EPA finds it necessary, will provide for even stricter standards. These standards will be developed between 2003 and 2006. The EPA must also develop controls for emissions resulting from fuel evaporation.

The clean fuel program promotes the use of some fuels like methanol, ethanol, reformulated gasoline, and other fuels such as electricity and natural gas. Reformulated gas, for areas with high ozone levels, has lower levels of oxygen, aromatic hydrocarbons, and benzene. For carbon monoxide nonattainment areas, the oxygenated fuel program will require a minimum oxygen content in fuels.

The 1990 amendments also target fleets of cars and trucks. Fleets of ten or more which can be centrally fueled are subject to the clean fuel requirements. Lesser standards apply to heavy-duty trucks. These standards apply to all cars and trucks in serious, severe, and extreme ozone nonattainment areas.

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