Abstract
After the U.S. EPA issued the revised primary PM2.5 standard in 2006, the D.C. Circuit remanded the annual standard to the EPA because the EPA failed to adequately explain why the standard provided the requisite protection to exposures of fine particles, including protection for at-risk populations. The EPA then prepared the PM ISA reviewing the new scientific information, and developed the Quantitative Risk Assessment and Policy Assessment. Based on these documents, the EPA issued the Proposed Rule to revise the PM2.5 standard. After considering the advice of the CASAC and public comments to the Proposed Rule, the EPA decided in the Final Rule to revise the annual PM2.5 standard by lowering it from 15.0 to 12.0 µg/m3, and to retain the 24-hour PM2.5 standard at the level of 35 µg/m3. This paper reviews the revision process of the new primary PM2.5 annual standard.
