	Introduction

The authorities and responsibilities of the Environmental Protection Agency (EPA) derive primarily from a dozen major environmental statutes. This report provides a concise summary of one of those statutes, the Clean Air Act. In addition, the report describes the statute largely without discussing its implementation. Overview

The Clean Air Act, codified as 42 U.S.C. It requires the Environmental Protection Agency to establish minimum national standards for air quality, and assigns primary responsibility to the states to assure compliance with the standards. The act establishes federal standards for mobile sources of air pollution and their fuels and for sources of 187 hazardous air pollutants, and it establishes a cap-and-trade program for the emissions that cause acid rain. The federal role was strengthened in subsequent amendments, notably the Clean Air Act Amendments of 1970, 1977, and 1990. Changes to the act in 1990 included provisions to (1) classify most nonattainment areas according to the extent to which they exceed the standard, tailoring deadlines, planning, and controls to each area's status; (2) tighten auto and other mobile source emission standards; (3) require reformulated and alternative fuels in the most polluted areas; (4) revise the air toxics section, establishing a new program of technology-based standards and addressing the problem of sudden, catastrophic releases of air toxics; (5) establish an acid rain control program, with a marketable allowance scheme to provide flexibility in implementation; (6) require a state-run permit program for the operation of major sources of air pollutants; (7) implement the Montreal Protocol to phase out most ozone-depleting chemicals; and (8) update the enforcement provisions so that they parallel those in other pollution control acts, including authority for EPA to assess administrative penalties. The remainder of this report describes major programs required by the act, with an emphasis on the changes established by the 1990 amendments. Prevention of Significant Deterioration / Regional Haze

Sections 160-169 of the act establish requirements for the prevention of significant deterioration of air quality (PSD).
This report summarizes the Clean Air Act and its major regulatory requirements. It excerpts, with minor modifications, the Clean Air Act chapter of CRS Report RL30798, Environmental Laws: Summaries of Major Statutes Administered by the Environmental Protection Agency, which summarizes a dozen environmental statutes that form the basis for the programs of the Environmental Protection Agency.
The principal statute addressing air quality concerns, the Clean Air Act was first enacted in 1955, with major revisions in 1970, 1977, and 1990. The act requires EPA to set health-based standards for ambient air quality, sets deadlines for the achievement of those standards by state and local governments, and requires EPA to set national emission standards for large or ubiquitous sources of air pollution, including motor vehicles, power plants, and other industrial sources. In addition, the act mandates emission controls for sources of 187 hazardous air pollutants, establishes a cap-and-trade program to limit acid rain, requires the prevention of significant deterioration of air quality in areas with clean air, requires a program to restore visibility impaired by regional haze in national parks and wilderness areas, and implements the Montreal Protocol to phase out most ozone-depleting chemicals.
This report describes the act's major provisions and provides tables listing all major amendments, with the year of enactment and Public Law number, and cross-referencing sections of the act with the major U.S. Code sections of the codified statute.