EPA Administrator Andrew Wheeler is proposing to leave the agency's existing soot standards in place for years to come — delivering a win for industry over the conclusions of agency career staff.

Under the plan, EPA would keep the existing limits on fine particulate matter set in 2012.

Those particles, technically known as PM2.5, are associated with a variety of respiratory and cardiovascular ailments; in a study released last week, Harvard University researchers tentatively linked long-term exposure to even slightly higher levels of fine particles to sharply increased odds of death from COVID-19.

Under the Clean Air Act, particulate matter is one of a half-dozen pollutants for which EPA must periodically review its National Ambient Air Quality Standards in light of the latest research into their health and environmental effects.

Business groups like the American Petroleum Institute and U.S. Chamber of Commerce, however, oppose any change to the status quo for the soot standard.

In a draft report last year, EPA air staffers had found that the existing limits may be allowing thousands of premature deaths each year. They tentatively concluded that the evidence warranted a significant tightening of the annual average exposure threshold, currently set at 12 micrograms per cubic meter of air (E&E News PM, Sept. 5, 2019).

An EPA advisory panel mostly made up of Wheeler appointees later rejected those staff findings on the grounds that the underlying research was unconvincing. The panel, known as the Clean Air Scientific Advisory Committee, recommended that both the annual standard and the 24-hour limit of 35 micrograms per cubic meter of air be left in place (Greenwire, Dec. 4, 2019).

The review, set for completion by this December, has been dogged by turmoil and questions about its scientific validity.

In an unprecedented step, for example, Wheeler in late 2018 fired a group of mostly academic experts charged with providing added know-how to the committee, usually known by its acronym CASAC (Greenwire, Oct. 12, 2018).

Those experts then unofficially regrouped under the auspices of the Union of Concerned Scientists to produce a report calling both for stricter annual and 24-hour PM2.5 limits (Greenwire, Dec. 4, 2019).

Wheeler, meanwhile, appointed an alternative group of consultants to aid in the review. As E&E News previously reported, the bulk of those consultants have ties either to CASAC members or to groups with a stake in the rule's outcome (Greenwire, Feb. 8).

PM2.5, often dubbed soot, refers to particles that are no more than 2.5 microns in diameter, or one-thirtieth the width of a human hair. Assuming that EPA meets its self-imposed December deadline for completing the review, the standards will remain in place for at least five years unless a federal court rules otherwise. Whatever the review's ultimate outcome, a legal challenge is likely.