The U.S. Environmental Protection Agency (EPA) announced its rescission of guidance related to section 179B of the Clean Air Act. Under section 179B of the Clean Air Act, 42 U.S.C. § 7509a, titled “international border areas,” a state can avoid reclassification of a nonattainment area to the next higher classification of nonattainment if it can demonstrate to the EPA that the area would have attained the ozone National Ambient Air Quality Standards by the applicable attainment date "but for" the effect of emissions emanating from outside the United States.
For example, pollution originating from Canada and Mexico can contribute significantly to local air quality in border states. Under section 179B, states are authorized to submit demonstrations to the EPA showing that international emissions are a substantial factor affecting air quality in the state. If approved, they may avoid a “bump up” in nonattainment status.
The EPA's guidance provided a framework for how states should structure these demonstrations, including the types of data and modeling required. However, the guidance was not perfect due to the technical complexity of proving international contribution to local air quality. Demonstration requirements requiring heavy air quality modeling do create burdens, especially for states already dealing with limited resources and difficult environmental conditions.
This change could have several implications. By rescinding the guidance, the EPA appears to indicate that it will give states more flexibility in how they approach the impacts of international emissions. Instead of following a specific demonstration rubric, states may now have more deference in how they gather and present their evidence. Further, allowing states to make their case for regulatory relief as they see fit, rather than relying on a one-size-fits-all process, states might be able to better advocate for themselves in this context. In areas concerned about the economic consequences of nonattainment designations—such as restrictions on new industrial development or federal funding—this could ease pressure and help support local economies.
At the same time, there are concerns that loosening the requirements for 179B demonstrations could make it more difficult to accurately assess the sources of air pollution and ensure accountability. Managing international emissions is a tricky part of assessing domestic air quality, and there is limited additional guidance on this issue.
However, there has been some interest in how this may be played out in the context of the Exceptional Events Rule, which allows for air quality data to be excluded from the record where a state successfully demonstrates that the pollution is caused by unusual events that are outside of the control of the state.
However, international emissions considered under Clean Air Act section 179B cannot be treated as “Exceptional Events” for determining attainment status. The processes and legal frameworks governing these two concepts are distinct and operate independently. The criteria and procedures for exceptional events are distinct from those under section 179B and are governed by separate statutory and regulatory provisions. There is no indication from the EPA or existing law that the Exceptional Events Rule and 179B emissions can be combined into one demonstration or somehow interchanged with one another.
Ultimately, the EPA's decision reflects a broader effort to deregulate and give more authority to state governments in managing various environmental programs. How this policy shift plays out in practice will be closely watched by state, industry, and environmental groups in the years to come.
