On May 9, EPA Administrator Pruitt released a memorandum to Assistant Administrators titled “Back to Basics Process for Reviewing National Ambient Air Quality Standards” (NAAQS). Key provisions include:

1. Meeting statutory deadlines. The Administrator has ordered completion of the pending review of the ozone NAAQS by October 2020 and of the pending PM NAAQS review by December 2020. The memorandum directs the agency to ensure that the Clean Air Scientific Advisory Committee (CASAC) will convene panels with the necessary expertise in a manner consistent with the 2017 directive on federal advisory committees. This is part of a larger effort to ensure that EPA completes its NAAQS reviews within the statutory 5-year period, a requirement that the agency seldom has met, often spawning litigation in the past.

2. Addressing all CAA NAAQS review provisions. This provision focuses on implementation of the Clean Air Act’s (CAA) requirements for CASAC advice in two areas that have historically been given short shrift: (1) adverse public health, welfare, social, economic, or energy effects which may result from various strategies for attainment and maintenance of a standard (presumably including the adverse health effects of unemployment resulting from a standard); and (2) consideration of background pollution, attainability and technological feasibility. Questions on these issues will now be presented explicitly to CASAC in its official charge documents. The memorandum notes that the Supreme Court has held that EPA cannot consider implementation costs in establishing NAAQS, but states that the Court also recognized that CASAC’s “advice concerning certain aspects of ‘adverse public health … effects’ from various attainment strategies is unquestionably pertinent” to the NAAQS rulemaking record and relevant to the standard-setting process. The Memorandum indicates that EPA will consider implementation costs in the policy judgment it makes with respect to the standard’s margin of safety, and also in developing implementation rules. It also directs CASAC to provide advice on certain agency actions where the Committee historically has been silent, including review of the Regulatory Impact Analysis for a proposed standard and any resulting implementation rules.

3. Streamlining and standardizing the process. This section requires a number of changes to the NAAQS review process to speed it up and make the various documents involved more useful.

4. Clearly differentiating between science and policy considerations. This provision requires the agency to establish a clear distinction between the purely scientific findings of a NAAQS Integrated Science Assessment (ISA) and the wider range of policy concerns that the Administrator must consider in making judgments about requisite standards and margins of safety. It also directs EPA to request CASAC to distinguish clearly between its scientific and policy advice.

5. Issuing timely implementation of regulations and guidance. When a NAAQS is revised, EPA is directed to issue concurrent implementation regulations and guidance as necessary, and also to issue technical information to assist states in developing approvable plans and demonstrating how any new NAAQS is to be attained and maintained. The rules and guidance should provide information relevant to the submission and consideration of state implementation plans and preconstruction permit applications, and may address potential tools for regulatory relief to address background concentrations and sources of pollution outside of the control of the state.

These new principles will be applied to the pending reviews of the ozone and PM NAAQS, which are to be completed before the 2020 elections, and likely will spawn litigation over both of EPA’s final decisions in reviewing these standards.

EPA’s Clean Air Scientific Advisory Committee (CASAC) has now completed its review of the agency’s draft Policy Assessment (PA) for the SO2 NAAQS, and supports the EPA staff recommendation that the current scientific literature does not support revision of the current primary (health based) SO2 NAAQS.

In a draft letter recently released, CASAC notes that “key uncertainties” have emerged since the prior SO2 review, particularly with regard to “at-risk” subgroups such as children who are: obese; of African-American ethnicity; severely asthmatic; and/or live in high density areas near sources of exposure. The Committee believes that while many uncertainties remain in quantifying the sizes of the risks for these groups, they should nonetheless be considered in ensuring that the standard provides an adequate margin of safety. CASAC also recommends that efforts should be made to gather the data necessary to ensure that protection of these groups can be considered with less uncertainty in future reviews of the standard.

According to the draft letter, the Committee believes it possible that the current 75 ppb level may not provide an adequate margin of safety in these groups. However, because there is considerable uncertainty in quantifying the sizes of these higher risk subpopulations and the effect of SO2 on them, the Committee did not recommend reconsideration of the level at this time. CASAC strongly recommends that future assessments better quantify the numbers of individuals expected to be affected at the current (or proposed alternative) standard in these groups so that a more informed judgment about the margin of safety in high risk subgroups can be made. In particular, the Committee suggests that EPA express the size of the at-risk population both in percentage form (which is currently done) and also with numerical estimates, providing the number of people expected to be at risk, given the margin of safety.

The Committee recommended a few changes in the draft PA and stated that with those changes it need not review another draft. We expect that CASAC will finalize its draft letter soon and that EPA will then move to finalize the PA and propose to retain the current standard. We doubt that the current Administration will seize on the “margin of safety” points in the CASAC letter to propose a revised standard (as some prior administrations might have done). However, those issues are likely to be a primary focus of the next review of the SO2 standard.

Apart from SO2, this letter is significant because it is the first official CASAC action under the newly appointed Chair, Anthony Cox, and the other new members appointed by this Administration. It therefore appears that the reported “backlog” of NAAQS reviews caused by CASAC appointment delays will now begin to break.