Developments in NAAQS

EM – June 2024: This month, EM considers recent developments in a series of revisions to the U.S. National Ambient Air Quality Standards (NAAQS).
by Eric Hiser and Sean Alteri
The NAAQS serve as a critical framework for safeguarding public health and the environment. These standards, established under the U.S. Clean Air Act, address six principal pollutants—commonly known as “criteria pollutants”—that pose risks to human health and ecosystems. By setting limits on these pollutants, NAAQS aim to reduce adverse health effects such as respiratory diseases, cardiovascular issues, and premature mortality. Moreover, NAAQS are designed to protect sensitive populations, including children, the elderly, and individuals with respiratory conditions. Additionally, achieving the NAAQS contribute to cleaner air, improved visibility, and enhanced overall welfare.

The U.S. Environmental Protection Agency (EPA) is the federal agency established to set and revise NAAQS. EPA conducts scientific assessments, reviews relevant research, and collaborates with experts to establish the NAAQS. NAAQS are categorized into two types: (1) Primary Standards designed to safeguard public health by ensuring an “adequate margin of safety” for vulnerable populations; and (2) Secondary Standards aimed at protecting public welfare, including visibility, ecosystems, and materials (e.g., buildings, crops). EPA's responsibility extends to periodic reviews of NAAQS, considering scientific advancements and potential adjustments to maintain their effectiveness. To carry out this important charge, the Clean Air Act directs the EPA Administrator to establish an independent scientific review committee, the Clean Air Act Science Advisory Committee (CASAC). The committee “is composed of seven members including at least one member of the National Academy of Sciences, one physician, and one person representing State air pollution control agencies.”

Importantly, CASAC is obligated to “…advise the Administrator on the relative contribution to air pollution concentrations of natural as well as anthropogenic activity, and (iv) advise the Administrator of any adverse public health, welfare, social, economic, or energy effects which may result from various strategies for attainment and maintenance of such national ambient air quality standards.” The critical role of a representative of state air pollution control agencies is emphasized in Section 110 of the Clean Air Act.

Under Section 110 of the Clean Air Act, state air pollution control agencies develop enforceable State Implementation Plans (SIPs) to achieve NAAQS compliance. These plans outline strategies, regulations, and emission reduction measures tailored to local conditions. In some states, such as California, local or regional air pollution control districts work alongside state agencies to address regional air quality challenges. Tribal governments can also administer Clean Air Act programs if the programs meet specific criteria. EPA approves eligible tribal governments to implement air quality programs within their territories.

To carry out its Clean Air Act responsibilities, EPA provides guidance, reviews state and tribal plans, and ensures compliance with statutory duties. It is important to note that preconstruction permits for major sources of air pollution are generally issued by state or local air agencies.

When EPA revises NAAQS, legal actions may follow. Stakeholders—including industry, environmental groups, and states—often challenge NAAQS revisions in court, questioning their scientific basis or stringency. Additionally, petitions are filed over SIPs, emission limits, or enforcement actions related to NAAQS compliance. Ultimately, the Clean Air Act allows for extensive public participation during NAAQS reviews and rulemakings, ensuring transparency and accountability.

In summary, NAAQS serve as a vital tool for cleaner air, protection of human health, and environmental stewardship. The Clean Air Act forces federal, state, local, and tribal air quality agencies to collaborate in achieving these goals.

Continue reading the full June 2024 issue of EM.


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