History of PM Standards
- 1971- EPA issued the first National Ambient Air Quality Standards for Total
Suspended Particles (TSP).
- 1987- EPA revised the standards and replaced TSP with PM10 (targeting particles
smaller than 10 micrometers).
- 1997- EPA revised the standards and included PM2.5 (targeting particles
smaller than 2.5 micrometers).
- 1997- Several industry and other organizations, some state governments
challenged EPA’s standards in the U.S. Court of Appeals for the D.C.
Circuit.
- 2001- The U.S. Supreme Court upheld EPA’s authority under the Clean
Air Act to set standards, clarified that EPA cannot consider cost in setting
standards. Remanded several issues to the appellate court.
- 2002- The DC Circuit Court rejected all remaining legal challenges to EPA’s
1997 standards for PM2.5.
- 2004- EPA designated 39 areas as not meeting the standards for PM2.5.