Court Upholds 2015 Ozone NAAQS

The U.S. Court of Appeals for the D.C. Circuit on August 23, 2019, issued a ruling upholding EPA’s primary National Ambient Air Quality Standard (NAAQS) for ozone. 

EPA in 2015 lowered the primary and secondary NAAQS for ozone from 75 to 70 parts per billion (ppb). 80 Fed. Reg. 65292; October 26, 2015. In Murray Energy Corp. v. EPA, Case No. 15-1385, some states and industry sought to repeal the 2015 ozone NAAQS on the grounds that they were arbitrary and capricious because EPA failed to provide a reasoned explanation for lowering the standard to 70 ppb.  Environmental groups challenged the rule as being too lenient, further arguing that it would occasionally permit ozone levels to exceed 70 ppb; they also challenged a grandfathering provision of the rule. 

The court denied both industry’s and environmental groups’ challenges to the primary ozone standard. The 70 ppb limit thus remains in place. 

The court did, however, side with environmentalists’ challenges to the secondary ozone standard. The court ruled that EPA failed to justify its decision to use a three-year average benchmark without lowering the secondary ozone standard to account for single-year spikes in ozone exposures, and that it arbitrarily declined to set a level to protect against adverse welfare effects associated with visible leaf injury. The court thus remanded the secondary ozone standard to EPA for reconsideration. 

Environmental groups also prevailed on their challenge of a grandfathering provision in the 2015 rule. In the rule, EPA allowed sources that had completed applications for preconstruction permits before the 2015 rule was adopted to demonstrate compliance with the previous NAAQS rather than the new, more stringent primary and secondary standards. The court found that EPA impermissibly did so and vacated the grandfathering provisions of the rule.