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Overview by Section of CAA

Introduction to CAA and Section 112 (Air Toxics)

The 1990 amendments to the Clean Air Act (CAA) mandated significant new air quality programs and substantially enhanced some existing ones.Among the major new programs are the acid rain provisions (Title IV),the operating permits program (Title V), and provisions to phaseout ozone-depleting substances (Title VI). Existing programs that have seen major changes due to the amendments include attainment provisions for National Ambient Air Quality Standards (NAAQS) and the National Emissions Standards for Hazardous Air Pollutants (NESHAP)program, both under Title I of the CAA. (Note that, while the new NESHAP provisions were found in Title III of the 1990 amendments,these provisions amended Title I of the CAA. Therefore, the appropriate citation for the NESHAP program is Title I of the CAA).

Title I of the CAA includes the provisions for attaining the NAAQS for criteria pollutants, and provisions for controlling emissions of hazardous air pollutants (HAP). The criteria pollutants are carbon monoxide, sulfur dioxide, oxides of nitrogen, lead, particulates, and ozone. Some of the primary standards and programs addressing the criteria pollutants include: New Source Review (NSR), State Implementation Plans (SIPs), and New Source Performance Standards (NSPS).

The provisions in Title I that address the control of HAP emissions,or air toxics, are found in Section 112.Section 112 of the CAA includes provisions for the promulgation of NESHAP, or maximum achievable control technology (MACT) standards, as well as several related programs to enhance and support the NESHAP program. The activities and responsibilities required under Section 112 directly affect not only the EPA, but State and local regulatory agencies as well. The complexity and number of these requirements necessitate a high degree of coordination and cooperation between the regulators to ensure that these programs are carried out effectively. At the federal level the majority of Section 112 is the responsibility of the Office of Air Quality, Planning and Standards (OAQPS) within EPA's Office of Air and Radiation (OAR) located in Durham, NC.

Overview of Section 112 and its Subsections

There are 19 subsections to Section 112 of the CAA. Each of these is briefly introduced here and program contacts or hypertext links are added for further information. The lower-case letters preceding the subsection titles correspond with the location in the CAA; for example,"Definitions" are found in Section 112(a) of the CAA.

(a) Definitions: Defines eleven terms found in Section 112: "major source", "area source", "stationary source","new source", "modification", "hazardous air pollutant", "adverseenvironmental effect", "electric utility steam generating unit", "owneror operator", "existing source" and "carcinogenic effect".

(b) List of Pollutants: Contains the list of 189 HAPs that are addressed by Section 112, and provisions for the EPAto add or delete pollutants. See Pollutants and Sources for the list of HAPs.

(c) List of Source Categories: Requires that the EPA publish and regularly update (at least every 8 years)a listing of all categories and subcategories of major and area sources that emit HAPs. The list of source categories itself is not contained inthe CAA; it was initially published in the Federal Register onJuly 16, 1992 (56 FR 31576). See Pollutants and Sourcesfor the current list of source categories.

(d) Emission Standards: States that the EPA must promulgate regulations establishing emission standards (NESHAP) for each category or subcategory of major sources and area sources of HAPs [listed pursuant to Section 112(c)]. The standards must require the maximum degree of emission reduction that the EPA determines to be achievable by each particular source category. Different criteria for maximum achievable control technology (MACT) apply for new and existing sources. Less stringent standards, known as generally available control technology (GACT) standards, are allowed at the Administrator's discretion for area sources. The status of all 112(d) standards can be accessed from the tables linked from the EPA Rules and Implementation Page.

(e) Schedule for Standards and Review: Specifies the schedule requirements for promulgation of MACT standards. The schedule is divided into four groups: 2-year, 4-year, 7-year, and 10-year standards. The 2-year group must include at least 40 source categories (1992 promulgation); the 4-year group must include source categories to bring the total to 25 percent of the list (1994 promulgation); the 7-year group must include an additional 25 percent (1997 promulgation); and the 10-year group must include the remaining 50 percent 2000promulgation). All of the 2-year and 4 year standards have been promulgated on schedule.

(f) Standards to Protect Health and the Environment: Requires the EPA to assess the risk to public health remaining after the implementation of NESHAP. If the "residual risk" for a source category does not protect public health with "an ample margin of safety," the EPA must promulgate health-based standards for that source category to further reduce HAP emissions. The EPA is required to set more stringent standards if necessary to prevent adverse environmental effects (considering energy, costs and other relevant factors). The EPA must set residual risk standards within 9 years after promulgation of each NESHAP in the 2-year group (see subsection (e) for "group" explanation) and within 8 years for all other groups.

(g) Modifications, Construction and Reconstruction: Requires owners or operators of newly constructed, reconstructed, and modified major sources of HAPs to apply MACT if emission increases are above certain levels. For purposes of Section 112(g) sources must submit a pre-construction permit application proposing source-specific MACT. Rulemaking-to-date implements these requirements for construction and reconstruction only.

(h) Work Practice Standards and Other Requirements: Allows the EPA, in cases where it is not feasible to prescribe or enforce an emission standard [under Section 112(d) or (f)], to promulgate a design, equipment, work practice, or operational standard. Also allows an owner or operator to use an alternative means of emission reduction if it can be proven that an equal reduction in emissions of any HAP will be achieved.

(i) Schedule for Compliance: Includes the following four major provisions:

  • New sources (i.e., sources that commence construction or reconstruction after proposal of the standard) must comply with the standard immediately upon start-up (except as provided under thefollowing bullet),

  • Sources constructed or reconstructed after MACT proposal but before promulgation may comply with the proposed standards if thepromulgated standards are more stringent. Compliance with the promulgated standards is required for such sources within 3 years of promulgation,

  • MACT standards must include compliance dates for existing sources no later than 3 years after promulgation. The EPA (or State with an approved Title V program) may grant individual sources a 1-year extension if necessary for the installation of controls, and

  • The Early Reductions Program allows a qualifying facility to defer compliance with MACT standards for 6 years if it reduces HAPemissions by 90 percent (95 percent for hazardous particulate emissions) before the applicable MACT is proposed.

(j) Equivalent Emission Limitation by Permit: Ensures control of HAP emissions even if the EPA should miss a scheduled NESHAP promulgation date. If the EPA misses a scheduled promulgation date by 18 months, major sources in that category must submit to their respective State (or local) agencies a permit application proposing source-specific MACT. Conditions of the MACT determination must be incorporated into the Title V operating permit. Section 112(j) is commonly referred to as the "MACT hammer."

(k) Urban Air Toxics Strategy: Includes programs to substantially reduce HAP risks in urban areas. The EPA is required to conduct a program of research and to develop a national strategy for reducing risk from air toxics in urban areas.The strategy must identify at least 30 HAPs that present the greatest risk to public health from area sources in urban areas. The strategy must achieve substantial reductions in public health risks, including a 75 percent reduction in cancer incidence from stationary sources. The EPA must assure that sources accounting for 90 percent or more of the aggregate emissions of each of the 30 identified HAPs are subject to standards. This must include technology-based control (MACT or GACT) of area sources.

(l) State Programs: Describes how States (and local agencies) that wish to implement NESHAP programs can apply to the EPA for delegation of implementation and enforcement authority. Section 112(l) also allows States to demonstrate equivalency with NESHAP, thus allowing States to implement their rules (that have been approved by EPA) instead of the NESHAP.

(m) Atmospheric Deposition to Great Lakes and Coastal Waters: Requires an EPA program to identify and assess the extent of atmospheric deposition of HAPs and other pollutants to the Great Lakes, the Chesapeake Bay, Lake Champlain, and coastal waters. Requires the EPA to establish a network for monitoring deposition of air pollution to these waters. Affected States may choose to participate.

(n) Other provisions: Requires that the EPA perform studies concerning HAP emissions and control technologies from electric utility steam-generating units, coke oven production, and publicly-owned treatment works. This includes a study of mercury, associated emissions, health and environmental effects, and control technologies for mercury. Additionally, the EPA must assess the public health hazards associated with emissions of hydrogen sulfide from oil and gas extraction, and emissions of hydrofluoric acid in areas that do not have comprehensive health and safety regulations addressing hydrofluoric acid.

(o) National Academy of Sciences Study:Requires the EPA and the National Academy of Sciences to conduct are view of the EPA's risk assessment methodology and to report to Congress concerning the findings of the study. The study must address both cancer and non-cancer risks.

(p) Mickey Leland Urban Air Toxics Research Center: Requires the EPA to establish a National Urban Air Toxics Research Center in a facility with research capabilities in epidemiology, oncology, toxicology, pulmonary medicine, pathology, andbiostatistics.

(q) Savings Provision: States that any standard under Section 112 in effect or promulgated but not yet in effect before the 1990 Amendments are enacted will remain in effect unless modified under the CAA. Within 10 years of enactment of the amendments, all such standards must be reviewed and revised, if needed, to comply with Section 112(d).

(r) Prevention of Accidental Releases:Contains requirements regarding prevention of accidental releases of certain regulated HAPs and other extremely hazardous substances. Directs the EPA to promulgate a list of at least 100 substances "which, in cases 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." All facilities with these chemicals on site in excess of the threshold quantities are subject to these regulations, which include development and submittal to EPA of risk management plans (RMP). RMP include hazard assessments, prevention plans and mitigation-of-release plans. A Chemical Safety and Hazard Investigation Board is required to investigate accidental releases and report to the public and Congress on a periodic basis concerning probable causes and prevention measures for accidental releases. The Board must also establish requirements for reporting accidental releases. The 112(r) provisions are handled by the Chemical Emergency Preparedness and Prevention Office (CEPPO) and all information can be found on their web site at https://www.epa.gov/osweroe1/content/rmp/.

(s) Periodic Reports: Requires the EPA to report to Congress every 3 years regarding measures taken to implement Section 112. The EPA must maintain a database of HAPs and sources of HAPs. Reports to Congress must include the status of standard-setting and compliance, the urban air toxics program, and recommendations regarding accidental releases. The first such report was issued in August, 1994 (Report to Congress on Implementation of Section 112 of the Clean Air Act Amendments; EPA/453/R-93-024).

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