The U.S. Environmental Protection Agency (EPA), under the direction of a court-ordered timetable, will propose a new air quality standard for particulate matter (PM) in November. A final decision will be reached by June 1997. A standard for PM was originally established in the early 1970s as part of the Clean Air Act, National Ambient Air Quality Standards. In the 1980s, the standard was tightened and the emphasis was shifted to fine particles (at that time, less than ten micrometers in size). About three years ago, some advocates pointed to additional health studies that suggested the standard needed to be furthered restricted. In addition, emphasis was shifted to even finer particles, specifically PM-2.5.
展开▼
