The U.S. Environmental Protection Agency has kicked off the next review of the National Ambient Air Quality Standards for ozone in a memo that also details a new "Back-to-Basics" approach to conducting reviews of critical air pollution standards.
Signed by EPA Administrator Scott Pruitt on May 9, the memo is in line with an April directive from President Donald Trump that set new guidelines for the air quality standards, or NAAQS, reviews. Pruitt's memo explained that the EPA is evaluating "whether to reconsider, modify, or maintain" the 2015 ozone standard, which was tightened from 75 parts per billion to 70 ppb under the Obama administration.
In the meantime, Pruitt has directed staff to begin the next statutorily required review of the ozone standard for 2020, which under the Clean Air Act must be conducted every five years. As part of that review, the EPA will open a docket calling for scientific and policy-relevant information and requesting nominations for the Clean Air Scientific Advisory Committee, or CASAC, ozone review panel. The CASAC committee informs the administrator's decisions on NAAQS and offers advice on any needed changes. But ultimately, the decision to revise or maintain standards is up to the administrator.
The EPA will also continue with its review of the NAAQS for particulate matter for finalization in December 2020. Both of the reviews will be conducted using a streamlined, "Back-to-Basics" process, Pruitt's memo explained.
Pruitt said his principles for future NAAQS reviews include ensuring statutory deadlines are met, addressing all Clean Air Act provisions, streamlining and standardizing the process for development and review of key policy-relevant information, differentiating science and policy judgments in the NAAQS review process, and issuing timely implementation regulations and guidance.
The memo noted that the Clean Air Act does not require the administrator to establish a primary NAAQS limit at a "zero-risk" or background concentration levels, but rather at a level that sufficiently reduces risk to protect public health with an adequate margin of safety.
The memo also outlined a new standardized set of questions that EPA will pose to the CASAC board when reviewing a NAAQS, and said those questions will "frame the entirety" of future NAAQS review processes. The questions will seek recommendations on new or revised standards, new scientific evidence that has developed since the last review, and more information on natural sources of a NAAQS pollutant, among other things.
In the past, Pruitt explained, the EPA has inconsistently sought advice from the CASAC on the relative contribution of natural and anthropogenic activity on the pollutants regulated under NAAQS.
"It should come as no surprise that many state environmental agencies have sought this advice, citing the absolute need for a valid source of information about background concentrations," Pruitt wrote. States also want this information for developing their state implementation plans and for understanding "inter-pollutant tradeoffs." The EPA will also develop more efficient ways to conduct a thorough scientific assessment of the relevant air quality criteria for each review, the memo concluded.