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US EPA to reexamine NAAQS for particulate matter

11 June 2021

The US Environmental Protection Agency (EPA) announced that it will reconsider the decision to retain the particulate matter (PM) National Ambient Air Quality Standards (NAAQS). In December 2020, under the previous US regime, the agency decided to retain the existing NAAQS for PM. Now, the EPA is reconsidering its earlier decision, because “available scientific evidence and technical information indicate that the current standards may not be adequate to protect public health and welfare, as required by the Clean Air Act”. The PM standards were last strengthened in 2012.

The EPA’s 2020 Policy Assessment suggested revising the annual average standard for PM2.5 to below the current level of 12 μg/m3, while retaining the 24-hour standard of 35 μg/m3, but in the final rule the agency decided not to increase the stringency of the standards. The EPA said it received numerous petitions for reconsideration as well as lawsuits challenging the December 2020 final action.

The EPA said it will now develop a supplement to the 2019 Final Integrated Science Assessment (ISA) that will take into account the most up-to-date science, including new studies in the emerging area of Covid-related research. This supplement will be reviewed at a public meeting by the EPA Clean Air Scientific Advisory Committee (CASAC), supported by a particulate matter review panel of experts on the health and welfare impacts of PM.

The EPA expects to issue a proposed rulemaking in Summer 2022 and a final rule in Spring 2023, following public review and comment.

The WHO air quality guideline for ambient PM2.5 is 10 μg/m3—a value adopted as an ambient air quality standard in Australia, Canada, Iran, Switzerland, UK, and some other countries. The European Union, on the other hand, has a rather relaxed annual PM2.5 standard of 25 μg/m3.

Source: US EPA