Clean Air Act: A Summary of the Act and Its Major Requirements [Updated February 25, 2020] [open pdf - 1MB]
From the Summary: "This report summarizes the Clean Air Act and its major regulatory requirements. The principal statute addressing air quality concerns, the Clean Air Act was first enacted in 1955, with major revisions in 1970, 1977, and 1990. [...] 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."
CRS Report for Congress, RL30853
Congressional Research Service: https://crsreports.congress.gov/