EPA Proposes Retention of National Ambient Air Quality Standards for Particulate Matter

On April 14, the U.S. Environmental Protection Agency (EPA) issued a proposal to retain the current national ambient air quality standards (NAAQS) for particulate matter (PM).  The proposal to retain the current standards without revision applies to the primary standards meant to protect against fine particle exposures (i.e., the annual and 24-hour PM2.5 standards), the primary standard meant to protect against coarse particle exposures (i.e. the 24-hour PM10 standard), and the secondary PM2.5 and PM10 standards.

In December 2012, EPA revised the primary and secondary standards for PM to provide requisite protection of public health and welfare. The primary NAAQS are typically more stringent, as they must be set at a level “requisite to protect public health” with an “adequate margin of safety.” EPA sets both annual (long-term exposure) and 24-hour (short-term exposure) primary NAAQS for particulate matter, calibrated in micrograms per cubic meter (µg/c3). For PM2.5, the current annual and 24-hour primary standards are 12 µg/c3 and 35 µg/c3, respectively. The annual secondary standard for PM2.5 is 15 µg/c3. For PM10, the current primary and secondary 24-hour standards are the same at 150 µg/c3. EPA revoked the annual standard for PM10 in 2012.

Under the Clean Air Act, EPA is required to set both primary (health-based) and secondary (welfare-based) NAAQS for air pollutants, including particulate matter, emitted by numerous or diverse mobile or stationary sources. This standard must be reviewed every five years, and EPA cannot consider implementation costs when setting NAAQS. NAAQS are standards for outdoor ambient air that are intended to protect public health and welfare from pollution. “NAAQS do not directly limit emissions of a pollutant; rather, they set in motion a long process in which states and EPA identify areas that do not meet the standards, and states prepare implementation plans to demonstrate how emissions will be lowered sufficiently to reach attainment.”

ACA will submit comments to EPA in support of the NAAQS proposal.

Contact ACA’s Rhett Cash for more information.

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