Last September, the EPA announced it had revised its rules for particulate matter (PM) standards. The new standards revised PM2.5 exposure levels for 24-hour measurements down from 65 µg/m3 to 35 µg/m3. The annual levels were left at 15 µg/m3. The 24-hour standard for PM10 was left at 150 µg/m3 and the agency revoked the annual requirement.

The agency reviewed thousands of peer-reviewed studies, held three public meetings and received over 120,000 written comments. While the EPA acknowledged receiving additional studies during the comment period, they declined to use the information as a basis for this decision. According to the EPA, the studies will be considered during the next PM review.

Some experts maintained that the studies supported even tighter standards. A spokesman for the Edison Electric Institute, Dan Riedinger, said that power plant operators were not happy with the final ruling, as they thought the agency had not allowed sufficient time to study results of the last reduction in the standards.

The EPA estimated that the new standards will result in $9- to $75-billion savings in health costs. Particulate emissions have been linked to health problems from aggravated asthma to premature death in people suffering from heart and lung disease.

Visit http://epa.gov/pm/actions.html to read the revised rules or http://epa.gov/pm/pdfs/20060921_graphsmaps.pdf to review EPA maps and charts.