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The Clean Air Scientific Advisory Committee (“CASAC”) sent a February 4th letter to the United States Environmental Protection Agency (“EPA”) addressing the following subject:
CASAC Review of the EPA’s Policy Assessment for the Reconsideration of the 21 National Ambient Air Quality Standards for Particulate Matter (External Review Draft 22 – October 2021) (“Draft Letter”)
The focus of the Draft Letter is the Clean Air Act National Ambient Air Quality Standard (“NAAQS”) for PM2.5 (which is often denominated as soot).
Particulates designated PM2.5 consist of sulfates, nitrates, elemental carbon, organic carbon, compounds and metals. They are formed by chemical reactions, condensation, coagulation, and nucleation processes of gases.
Because of their small size, these particulates can remain in the air for significant periods of time. Further, the suspension can facilitate the transport of these substances over long distance.
EPA announced in June 2021 that it would reconsider the Trump Administration’s prior decision to retain the particulate matter NAAQS. The agency last strengthened the NAAQS for particulate matter in 2012.
The reconsideration is based on EPA’s view that available scientific evidence and technical information indicate that the current NAAQS may not be adequate to protect public health and welfare.
The CASAC is tasked by EPA to formulate advice addressing the NAAQS.
The CASAC Draft Letter states in part regarding the NAAQS for PM2.5 that it reached consensus that:
. . . the indicator, form, and averaging time should be retained, without revision.
However, the CASAC members are stated to agree that:
. . . the current level of the annual standard is not sufficiently protective of public health and should be lowered. In concurring with the EPA’s recommendation to lower the annual standard, the CASAC agrees with the EPA’s assessment that there are large populations at risk of PM2.5 health effects, and that the Draft ISA Supplement provides new evidence of disparities in risk across various population subgroups. The evidence base for adverse health effects below the current annual standard has been strengthened and that, while uncertainties remain in the epidemiologic evidence, recent studies that employ alternative analysis approaches have helped to reduce those uncertainties (e.g., by addressing the potential for residual confounding). The CASAC concurs with the EPA’s assessment that meaningful risk reductions will result from lowering the annual PM2.5 standard.
A copy of the Draft Letter can be downloaded here.
