The new standard strengthens limits on ground level ozone to 70 parts per billion (“PPB”), down from 75 PPB adopted in 2008. The EPA’s action arises from the mandate of the Clean Air Act (“CAA”), from which the EPA derives its regulatory powers, 42 U.S.C. § 7409(a)(1), and which requires that pollution levels be set so as to protect public health with an “adequate margin of safety. 42 U.S.C. § 7409(b).

One question for the upcoming challenges is whether the preclusion of cost considerations will be challenged based on the Supreme Court's decision last term in Michigan v. EPA, No. 14-46 (Jun. 29, 2015), in which the Court held that it was unreasonable for EPA not to consider costs in determining whether to regulate power plant emissions of hazardous air pollutants, despite statutory language directing EPA to focus there on health considerations, as well. EPA is required to review the NAAQS every five years based on advice received from the Clean Air Scientific Advisory Committee. 42 U.S.C. § 7409(d)(1), (d)(2). The last EPA review was in 2008, which resulted in the 75 ppb primary and secondary standards.

The Agency will take public comment for 90 days after publication of the proposed rule in the Federal Register. _________________________[1]www.epa.gov/groundlevelozone/pdfs/20141125proposal.pdf [Proposed Rule][2] 42 U.S.C. § 7409(b).[3]www.epa.gov/groundlevelozone/pdfs/20141125fs-overview.pdf.[4]online.wsj.com/articles/epa-to-propose-limit-to-ozone-air-pollution-wednesday-sources-say-1416966904.[5]www.tceq.state.tx.us/news/releases/11-26opposeozone.[6]www.nytimes.com/2014/11/27/us/epa-ozone-limits-divide-industry-and-environmentalists.html; www.washingtonpost.com/national/health-science/epa-to-propose-tougher-rules-on-smog-causing-ozone-setting-up-clash-with-gop/2014/11/26/0a4670ce-756a-11e4-bd1b-03009bd3e984_story.html.[7]www.epa.gov/groundlevelozone/pdfs/20141126-20112013datatable.pdf.[8]Proposed Rule, at 517-518.

In determining not to alter the existing standards, EPA reasoned that doubts about the accuracy of the underlying science prevented the agency from identifying with sufficient certainty a standard that would be, as the Clean Air Act requires, "requisite to protect the public welfare." 42 U.S.C. § 7409(b)(2). The Center for Biological Diversity filed a petition for judicial review on the issue of whether EPA's decision to defer adopting a new standard at this time, pending further scientific study, violated the CAA.

The D.C. Circuit upheld the primary standard for ozone but remanded the identical numeric secondary standard for further explanation or reconsideration. The secondary NAAQS "specify a level of air quality the attainment and maintenance of which… is requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of such air pollutant in the ambient air."42 U.S.C. § 7409(b)(2).EPA set the 2008 secondary ozone NAAQS at .075 ppm 8 hour average to protect against harmful effects on vegetation and indirect effects on other ecosystem components. The D.C. Circuit found that EPA's explanation for setting the secondary standard identical to the primary standard was insufficient.

In February 2012, various environmental groups and several states filed suit against EPA to enforce its non-discretionary duty under the Clean Air Act (CAA) to complete a review of PM NAAQS every five years. 42 U.S.C. §7409(d)(1). The U.S. District Court for the District of Columbia ordered EPA to propose new PM 2.5 standards because the agency had violated its five-year deadline.