Proposed Action: Review of the National Ambient Air Quality Standards for Particulate Matter

On April 14, 2020, after carefully reviewing the most recent available scientific evidence and technical information, and consulting with the Agency’s independent scientific advisors, the EPA is proposing to retain, without revision, the existing primary and secondary National Ambient Air Quality Standards (NAAQS) for particulate matter.

For this proposal the Administrator considered the latest scientific evidence and analyses as well as the advice of the Clean Air Scientific Advisory Committee. This proposal supports the Agency’s intent to finalize this NAAQS review by December 2020.

Currently, the EPA has primary and secondary standards for PM2.5 (annual average standards with levels of 12.0 µg/m3 and 15.0 µg/m3, respectively; 24-hour standards with 98th percentile forms and levels of 35 µg/m3) and PM10 (24-hour standards with one-expected exceedance forms and levels of 150 µg/m3).

  • For the primary PM2.5 standards, the Administrator concludes that there are important uncertainties in the evidence for health effects below the current standards and in the potential public health impacts of reducing ambient PM2.5 concentrations below the current standards. As a result, he concludes that the available evidence and information does not call into question the adequacy of the current primary PM2.5 standards.
  • For the primary PM10 standard, the Administrator observes that, while the available health effects evidence has expanded, recent studies are subject to the same types of uncertainties that were judged important in the last review. He concludes that the newly available evidence does not call into question the adequacy of the current primary PM10 standard.
  • For the secondary standards, the Administrator observes that quantitative analyses show results similar to those in the last review and that the expanded evidence for non-ecological welfare effects is consistent with the last review. Therefore, he concludes that the newly available evidence and updated analyses do not call into question the adequacy of the current secondary PM standards. Ecological effects associated with PM are being addressed in the separate review of the secondary NAAQS for oxides of nitrogen, oxides of sulfur and PM.

Links to the pre-publication version of the proposed action and a summary fact sheet are available at:  https://www.epa.gov/pm-pollution/national-ambient-air-quality-standards-naaqs-pm

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