The Clean Air Act and Climate Change

The Clean Air Act (CAA) is the most appropriate legal mechanism to reduce greenhouse gas (GHG) emissions in the United States currently. While it may not be a perfect mechanism, there are many important elements in place that make it a useful method of addressing climate change at the national level. There have been many efforts already completed that enable the CAA to be the legal mechanism used to reduce GHGs. Utilizing existing structures can help reduce the time spent starting from scratch when developing a more customized piece of policy.

Attainment of GHG reductions can not come from local measures alone. Federal level policies are required to unify the patchwork approach to GHG emissions that have been taken to date. Under the CAA, the Environmental Protection Agency (EPA) is mandated to create National Ambient Air Quality Standards (NAAQS) for any air pollutant that endangers public health and welfare (Crystal, et al. 2019, 7). In the lawsuit Massachusetts v EPA, the court concluded that GHGs are air pollutants that endanger public health and welfare (Crystal, et al. 2019, 8). Many of the efforts required by EPA prior to setting a NAAQS for GHGs have already been met. The use of the CAA’s NAAQS process would cover diverse sources of GHGs for a more comprehensive approach instead of the piecemeal approach that has been occurring. This would give organizations more definitive timelines and standards to incentivize actions and efforts that utilize free market approaches to help reduce costs of compliance as well.

One issue with utilizing the CAA to reduce GHG emissions is that the NAAQS and state implementation plan (SIP) structure do not fit well with global pollutants (Salzman and Thompson 2019, 167). It may require different approaches to setting the measures and controls for each state since ambient levels of pollutants can be impacted by other countries well outside of the sphere of United States policies, let alone state actions. Determining how to set a GHG NAAQS would also provide some challenges to the current process. Allocation issues are always challenging for property rights and emissions trading systems so determining how to allocate pollution levels appropriate for the national and state levels so there can be specific SIPs would be challenging without developing a new proxy method.

The CAA has provided a long-standing policy framework for addressing air pollutants over the past five decades. While global level pollutants, like GHGs, may not fit in as easily as other pollutants, the CAA still is the most appropriate legal mechanism to reducing GHG emissions in the US. The weaknesses of using the CAA for GHG reductions can be overcome with creative approaches to the valuation and allocation issues. Without the EPA attempting to regulate GHG pollutants under the CAA, the United States will be in a continued period of limbo where no action is being taken. If courts find that NAAQS is not appropriate for reducing GHG emissions, then new solutions can be built under the new guidance, and progress can be made in this important issue (Crystal, et al. 2019, 40). The EPA acting on developing NAAQS for GHG reductions is the most appropriate next step for federal-level policy approaches to climate change and should be undertaken with urgency.

Update 2022-07-01:

With the latest SCOTUS decision to limit the EPA’s ability to manage GHGs, I think it is even more important to utilize NAAQS to regulate GHGs. No action will be supported until all current opportunities to utilize existing mechanisms have been tried. While the SCOTUS decision has been a set-back, it also has highlighted what can and can not be done under the Clean Air Act. Attempting to regulate GHGs via the Clean Air Act’s NAAQS provision is the only remaining element to try. It is important to exhaust those options before trying to undertake major new legislation. While it ultimately may not be successful, the decisions will provide even more direction and insight for the drafting of new stronger legislation.

Author: Logan Callen


Crystal, Howard M., Kassie Siegel, Maya Golden-Krasner, and Clare Lakewood. 2019. “Returning to Clean Air Act Fundamentals: A Renewed Call to Regulate Greenhouse Gases Under the National Ambient Air Quality Standards (NAAQS) Program.” Georgetown Environmental Law Review 31 (2): 233-284. Accessed June 27, 2022.

Salzman, James, and Barton H. Jr. Thompson. 2019. Environmental Law and Policy. 5th ed. St. Paul, MN: Foundation Press.

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