EPA issued its long-awaited final rule revising the particulate matter air quality standards. The rule lowers the primary annual fine particulate matter (PM2.5) standard from 15 micrograms per cubic meter of air (µg/m3) down to 12 µg/m3. Fine particles are 2.5 micrometers in diameter and smaller, and coarse particles are larger than 2.5 micrometers but smaller than 10 micrometers.

The Clean Air Act requires the agency to review and consider revising air quality standards every five years. EPA reviewed the particulate matter standards most recently in ’06.

Fine particles are emitted from sources such as vehicles, smokestacks and fires. The final rule also will require near-roadway monitoring in each urban area with a population of 1 million or more.

EPA estimates the new standard will cost industries as much as $350 million a year, but will generate annual health benefits of $4 billion to $9 billion. The agency expects that fewer than 10 counties, out of the more than 3,000 US counties, will need to consider any local actions to reduce fine particulate pollution in order to meet the new standard by ’20. The rest can rely on air quality improvements from current federal rules to meet the new standard.

Although the agency reduced the standard for fine particulates, it did not change the other particulate matter standards. It retained the existing daily standard of 35 µg/m3 for fine particles and the existing daily standard of 150 µg/m3 for coarse particulate matter. Agricultural interests earlier had voiced their opposition to more stringent “farm dust” standards.

EPA issued a proposed rule on June 14 that would have set a separate secondary daily standard visibility but the agency did not finalize that provision, stating that public comments made clear that the existing standards are sufficient for visibility protection.