US EPA

The 2019 Integrated Science Assessment for Particulate Matter (PM ISA) provides the scientific foundation for review of the primary and secondary National Ambient Air Quality Standards (NAAQS) for particulate matter (PM). The PM ISA contains an evaluation and synthesis of policy-relevant scientific evidence communicating critical science judgments about the relationships between PM and health effects, including those in at-risk populations, which can comprise communities with environmental justice concerns, and welfare effects, specifically the nonecological welfare effects of visibility impairment, climate forcing, and materials damage.

In June 2021, the EPA announced it would reconsider the December 2020 decision to retain the PM NAAQS because available scientific evidence and technical information indicated that the current standards may not be adequate to protect public health and welfare, as required by the Clean Air Act (CAA). As part of the reconsideration process, the EPA indicated that it would develop a supplement to the PM ISA to thoroughly evaluate the most up-to-date science that became available after the literature cutoff date of the PM ISA that could either further inform the adequacy of the current PM NAAQS or address key scientific topics that have evolved since the 2020 PM NAAQS review was completed.

The draft Supplement to the 2019 PM ISA was reviewed at a public meeting by the chartered Clean Air Scientific Advisory Committee (CASAC) and the CASAC PM Panel. Ultimately, the PM ISA, along with the final Supplement to the 2019 PM ISA, provide the scientific basis for EPA's decision regarding whether the current primary and secondary NAAQS for PM are adequate to protect public health and welfare with an adequate margin of safety.

The Clean Air Act requires EPA to periodically review the science for six major air pollutants, including particulate matter (PM). EPA's Center for Public Health and Environmental Assessment (CPHEA) develops Integrated Science Assessments (ISAs) that summarize the science related to the health and welfare effects of these pollutants. ISAs provide a comprehensive review of the policy-relevant scientific literature published since the last National Ambient Air Quality Standards (NAAQS) review and are a critical part of the scientific basis for updating the NAAQS.

The final Supplement to the 2019 Integrated Science Assessment for Particulate Matter builds on the PM ISA and represents EPA’s targeted evaluation of the latest scientific literature on the potential health and welfare effects associated with PM. The final Supplement and PM ISA collectively forms the scientific basis of the reconsideration of the 2020 PM NAAQS.

This is the final report.

U.S. EPA. Supplement to the 2019 Integrated Science Assessment for Particulate Matter (Final Report, 2022). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-22/028, 2022.