Challenging Unreasonable NAAQS

Arizona v. U.S. Environmental Protection Agency and Wisconsin v. U.S. Environmental Protection Agency


Arizona v. U.S. Environmental Protection Agency


Wisconsin has joined Arizona and several other States challenging EPA's proposed revision to the National Ambient Air Quality Standard (NAAQS) for ozone. Under the Clean Air Act (CAA), the EPA  is responsible for setting NAAQS for certain air pollutants and reviews and revises the NAAQS every five years.  Each state has primary responsibility for ensuring that NAAQS are achieved and maintained. States are required to develop and propose state implementation plans (SIPs) for the implementation, maintenance, and enforcement of new standards, and If a State fails to provide an adequate SIP, the EPA may propose its own federal implementation plan (FIP). Areas classified by EPA as "nonattainment areas" face significant regulations, such as mandatory emission censuses and burdensome permitting requirements.


The States have challenged EPA’s latest amendment to the NAAQS for ozone, decreasing the allowable atmospheric concentration from 75 parts per billion (ppb) to 70 ppb, alleging that this violates the CAA. Specificaly, EPA has failed to adequately address the critical issue of "background ozone," which is ozone that is naturally present in the atmosphere, and which cannot be controlled by the States.


Status: Currently awaiting decision by the D.C. Circuit.


Wisconsin v. U.S. Environmental Protection Agency


Wisconsin, joined by four other States, has challenged EPA's second Cross-State Air Pollution Rule (CSAPR II), a federal implementation plan (FIP) under the Clean Air Act that requires certain "upwind" States to reduce their ozone emissions in order to contribute less to downwind areas.  Briefing in this case began in August, 2017.


Status: In briefing before the D.C. Circuit


Litigation Closed: