Air Emissions: Definitions

New Source Performance Standards (NSPSs). Nationally uniform emission standards for new stationary sources falling within particular industrial categories. NSPSs are based on the pollution control technology available to that category of industrial source but they allow the affected industries the flexibility of devising a cost-effective means of reducing emissions.

State Implementation Plans (SIPs). Under the Clean Air Act, each state must develop a SIPs to identify sources of air pollution and to determine what reductions are required to meet National Ambient Air Quality Standards (NAAQS). The emission reductions implemented by the states are oriented toward the specific type of emission sources or industrial facilities located within or impacting on the nonattainment areas. The SIPs also typically include a permitting program for the review of air emission impacts due to facility expansions prior to the initiation of construction. Most of these programs were in place prior to the 1990 Clean Air Act Amendments.

National Ambient Air Quality Standards (NAAQS). Pursuant to Title I of the CAA, EPA has established national ambient air quality standards (NAAQSs) to limit levels of "criteria pollutants," including carbon monoxide, lead, nitrogen dioxide, particulate matter, volatile organic compounds (VOCs), ozone, and sulfur dioxide. Geographic areas that meet NAAQSs for a given pollutant are classified as attainment areas; those that do not meet NAAQSs are classified as non-attainment areas.

National Emission Standards for Hazardous Air Pollutants (NESHAP). Under the Clean Air Act, as amended in 1990, EPA is required to regulate sources of listed hazardous air pollutants (HAPs) that are known or suspected to cause cancer or other serious health effects. On July 16, 1992, EPA published a list of industry groups (known as source categories) that emit one or more of these air toxics; several industrial surface coating categories were on this list. For listed categories of "major" sources (those that emit or have the potential to emit 10 tons/year or more of a listed pollutant or 25 tons/year or more of a combination of pollutants), the Clean Air Act directs EPA to develop National Emission Standards for Hazardous Air Pollutants (NESHAPs) that require the application of stringent air pollution reduction measures known as maximum achievable control technology (MACT). The law requires that MACT must not be less stringent than:

emission control that is achieved in practice by the best controlled similar source, for new sources; and
the average emission limitation achieved by the best performing 12 percent of the existing sources.

The Clean Air Act requires that EPA promulgate most of the industrial surface coating MACT standards by the year 2000. As noted above, the categories listed for regulation are major sources. During the development of these regulations, EPA will evaluate whether non-major or "area" sources of the same type should also be regulated in accordance with the law.

Control Technique Guidelines (CTGs). Section 183(e) of the Clean Air Act requires EPA to regulate volatile organic compound (VOC) emissions from consumer and commercial products. VOC emissions contribute significantly to the formation of ground-level ozone (smog) which is associated with a wide variety of human health effects, agricultural crop loss, and damage to forests and ecosystems.

Regulations developed under section 183(e) must be based on "best available controls" (BAC). In the statute, BAC is defined as "The degree of emission reduction that the Administrator determines, on the basis of technological and economic feasibility, health, environmental, and energy impacts, is achievable through the application of the most effective equipment, measures, processes, methods, systems, or techniques, including chemical reformulation, product or feedstock substitution, repackaging, and directions for use, consumption, storage and disposal."

EPA also has discretion to issue a control techniques guideline (CTG) in lieu of a regulation if EPA determines that a CTG would be substantially as effective as a regulation in reducing VOC emissions which contribute to ozone levels in ozone nonattainment areas. Although not specifically defined in the Clean Air Act, a CTG is an EPA guidance document which triggers a responsibility under section 182(b)(2) for States to submit reasonably available control technology (RACT) rules for stationary sources of VOC as part of their State Implementation Plans (SIP's).

Hazardous Air Pollutants (HAPs). Under Title I, EPA establishes and enforces National Emission Standards for Hazardous Air Pollutants (NESHAPs), nationally uniform standards oriented towards controlling particular hazardous air pollutants (HAPs). Title I, section 112(c) of the CAA further directed EPA to develop a list of sources that emit any of 189 HAPs, and to develop regulations for these categories of sources. To date EPA has listed 174 categories and developed a schedule for the establishment of emission standards. The emission standards will be developed for both new and existing sources based on "maximum achievable control technology" (MACT). The MACT is defined as the control technology achieving the maximum degree of reduction in the emission of the HAPs, taking into account cost and other factors. Title I, section 112(r) directed EPA to develop a list of hazardous chemicals and regulations to control and prevent accidental releases of these chemicals. Owners and operators of facilities at which such substances are present in more than a threshold quantity will have to prepare risk management plans for each substance used at the facility. EPA may also require annual audits and safety inspections to prevent leaks and other episodic releases.

Clean Air Act Title I. Title I requires states to develop specific implementation plans (State Implementation Plans or SIPs) to address areas which do not currently attain the National Ambient Air Quality Standards (NAAQS).