Rejecting the recommendations of its own staff and an outside panel of air pollution experts, the U.S. Environmental Protection Agency has proposed to maintain rather than strengthen Obama-era air quality standards for harmful fine particulate matter pollution.

Fine particulate matter, or PM 2.5, is regulated under the National Ambient Air Quality Standards, or NAAQS, which under the Clean Air Act are supposed to be reviewed every five years.

PM 2.5 is primarily produced by vehicle tailpipes emissions and industrial smokestacks, and scientific studies have linked the pollutant, measuring less than the width of a human hair, to acute respiratory problems and premature death.

Based on a lengthy scientific review, the EPA in 2012 strengthened the primary standard for PM 2.5 to 12 micrograms per cubic meter, down from the previous standard of 15 micrograms per cubic meter. In doing so, it also retained the previous secondary standard of 35 micrograms per cubic meter. Calculated on an annual basis, the primary standard is designed to protect human health with an adequate margin of safety, while the secondary standard, measured over a 24-hour period, is aimed at visibility.

The EPA on April 14 released a proposal to maintain those standards in the face of mounting evidence that elevated levels of PM 2.5 exposure are associated with increased coronavirus death rates. Last fall, EPA career staff also estimated that up to 50,000 annual PM 2.5-linked deaths are occurring annually under the current standards.

But EPA Administrator Andrew Wheeler said he made the call to retain the standards after balancing the recommendations of the agency's career staff and scientists against those of the EPA's seven-member Clean Air Scientific Advisory Committee, or CASAC. "This decision was made after I considered the latest scientific evidence and analysis, as well as the Clean Air Scientific Advisory Committee," Wheeler said April 14 on a conference call with reporters.

Wheeler noted most of the CASAC's members identified a number of uncertainties in the latest science on PM 2.5 during what former committee members alleged to be the most dysfunctional NAAQS review in the agency's history. According to the administrator, those uncertainties included the lack of evidence in experimental studies linking PM 2.5 exposure to premature death, potential for confounding PM 2.5 with other sources of air pollution, and "lack of intervention" in accountability studies showing public health improvements due to PM 2.5 reductions.

'Rigged'

Clean air advocates including Gretchen Goldman, research director for the Center for Science and Democracy at the Union of Concerned Scientists, asserted that the NAAQS review process for PM 2.5 was "rigged" from the start.

"At every step, EPA's political leadership have elbowed scientists out of the process of setting clean air rules," Goldman said in a statement. "This decision comes as no surprise, but it's appalling nonetheless."

Wheeler's move in October 2018 to disband two key outside panels of PM 2.5 and ozone experts, which have for years been tasked with aiding the CASAC in its NAAQS reviews, generated national headlines.

The EPA chief has claimed the decision was in line with an earlier "back-to-basics" memo issued by his predecessor, Scott Pruitt, which outlined a plan to have the EPA meet its statutory requirement of completing its NAAQS reviews for those pollutants within five years.

"What we're trying to do is get all of the NAAQS reviews back on to a five-year review period, which is why we did the 'back-to-basics' memo in 2018," Wheeler said. "That meant disbanding the CASAC subcommittee on PM 2.5, but we don't believe that in any way negatively impacted the review process."

Nevertheless, the move to essentially fire dozens of outside experts prompted many of those same experts, along with former CASAC Chair Chris Frey, to form their own independent panel. In October 2019, the panel recommended that the EPA lower the primary standard for PM 2.5 to between 8 to 10 micrograms per cubic meter and the secondary standard to between 25 to 30 micrograms per cubic meter.

"Based on a thorough review of the science, and not just a thorough review but an honest review, it's clear that the current standard is not adequate to protect public health and EPA staff essentially reached that same conclusion," Frey, an environmental engineering professor at North Carolina State University, said in an April 14 interview. "So the administrator is disregarding external scientific experts and largely disregarding his own staff."

Frey added that the panel's independent review of the latest science on PM 2.5 found the current standard of 12 micrograms per cubic meter to be "harmful to public health."

Addressing EPA staff's estimate that tens of thousands of people could be dying prematurely under the current standards, Wheeler noted that the Trump administration has moved more than two dozen air quality regions from nonattainment into attainment when accounting for all six different air pollutants regulated under the NAAQs.

"We've gotten more than 30 communities to nonattainment to attainment over the last three years and we intend to continue that path forward," he said. "Getting these areas to attainment will help save lives."

The proposed rule will be subject to a 60-day public comment period after it is published in the Federal Register. Wheeler has stressed that he aims to complete NAAQS reviews for both PM 2.5 and ground-level ozone by the end of the year.