National Ambient Air Quality Standards

As we have discussed previously, the federal Clean Air Act (CAA) addresses what is often termed “interstate transport.” That is the phenomenon in which emissions from factories, power plants, motor vehicles and many other emission sources are transported by prevailing winds across state lines, sometimes over great distances. The CAA looks to states, first and foremost, to include control measures in implementation plans to reduce emissions that travel into other states. The statutory objective is to prohibit “significant contributions” by upwind states to violations of national ambient air quality standards (NAAQS) in downwind states. Although states have primary responsibility, EPA sometimes has invoked its CAA authority to establish federally enforceable requirements to address significant contributions when it concludes upwind states have not taken sufficient steps. In 2016, EPA adopted its most recent set of regulatory interstate transport controls in a rulemaking action called the “Cross-State Air Pollution Rule Update”—or the “CSAPR Update” for short. On September 13, the US Court of Appeals for the DC Circuit issued a decision in closely-watched litigation involving challenges to the CSAPR Update. (The case is Wisconsin v. EPA, No. 16-1406.) While upholding this EPA regulation in most respects, the court ruled in favor of a challenge that concerns the timing of upwind-state emission controls.
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State environmental regulators are beginning to develop plans designed to meet more stringent air quality standards under the Clean Air Act (CAA), including standards to protect against unhealthful levels of ground-level ozone. In doing so, many states are looking more closely at a factor that contributes to their air quality problems but that they lack any authority to address: the phenomenon of air pollution carried by prevailing winds into their jurisdictions from emission sources located not only outside their own state borders but outside the US itself. The issue of international contributions to air quality concerns has gained currency in part due to the many challenges states face in meeting the stringent nationwide air quality standards for ground-level ozone that the US Environmental Protection Agency (EPA) adopted in 2015.
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In October 2015, EPA reduced the level of the National Ambient Air Quality Standards (“NAAQS”) for ozone from 75 parts per billion (“ppb”) to 70 ppb. What is happening concerning implementation of those NAAQS?

Although litigation over EPA’s decision to lower the ozone NAAQS remains in abeyance as the Trump Administration continues to consider whether the Agency should reconsider the rule or some part of it, the 2015 standard itself has not been stayed. Thus, the Clean Air Act requires that implementation of the standard proceed. One key step in implementation is promulgation by EPA of a list of areas where the standard is violated, including areas that contribute to standard violations in nearby areas. EPA’s identification of these “nonattainment” areas is a trigger for many of the Act’s control requirements.
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Litigation concerning the ozone air quality standards that EPA adopted in 2015 has been placed in abeyance, as the Trump administration decides whether to reconsider the standards. The standards remain in effect, however, and statutory implementation deadlines are approaching. What are those deadlines and what options exist for staying the standards until after any reconsideration proceedings are completed?
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