In a move expected to be revisited by the incoming Biden administration, the U.S. Environmental Protection Agency on Dec. 7 released a final rule that retains its current standards for harmful airborne soot pollution.
Unveiled six weeks before President Donald Trump is scheduled to leave office, the final rule does not strengthen the existing standards despite the latest science indicating tens of thousands of premature deaths could be avoided annually by tightening those standards. The rule also comes amid a growing nationwide focus on environmental justice issues, with recent studies showing a link between exposure to air pollution, which disproportionately impacts communities of color, and increased coronavirus death rates.
But EPA Administrator Andrew Wheeler said the final rule reflects scientific uncertainty over whether tightening the standards is warranted. He also cited sharply reduced levels of PM 2.5 concentrations in the U.S. since the year 2000.
The EPA is required by the Clean Air Act to set National Ambient Air Quality Standards, or NAAQS, for soot pollution, technically known as fine particulate matter, or PM 2.5. Measuring less in width than the diameter of a human hair, PM 2.5 is mainly produced by vehicle tailpipe emissions and industrial facilities such as fossil fuel-fired power plants.
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 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's latest five-year NAAQS review for PM 2.5 became embroiled in controversy after Wheeler in October 2018 abruptly fired a pair of auxiliary panels traditionally tasked with aiding the agency's seven-member Clean Air Scientific Advisory Committee, or CASAC, in making recommendations to the EPA administrator.
Wheeler claimed the dismissals were necessary to meet the EPA's statutory timelines for NAAQS reviews. But public health and environmental groups argued the decision left the CASAC without the experience and expertise needed to review thousands of pages of scientific studies on the health effects of PM 2.5 exposure.
Wheeler eventually appointed a group of outside advisers to assist the CASAC, a move that was criticized by former EPA career staff.
"They hired consultants that they got to pick, and they could have private, closed-door conversations with them," Chris Zarba, former director of the EPA's Science Advisory Board, said in an interview. "Normally the review process is all done out in the open, and how they came up with their findings is extremely questionable."
In September 2019, EPA career staff released a draft policy assessment estimating that approximately 50,000 premature deaths linked to PM 2.5 are occurring annually under the current standards. It also said that moving to a 9-microgram threshold could save between 9,050 and 34,600 lives a year.
Members of the disbanded PM 2.5 review self-organized a meeting a month later to conduct their own review of the latest science at a hotel just outside of Washington, D.C. There, they 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.
The CASAC failed to reach a consensus in its final report to the EPA administrator. But a majority on the panel sided with the view shared by industry trade groups like the American Petroleum Institute that the current standards should be retained amid scientific uncertainty and a "seriously flawed assessment" of the evidence.
Echoing claims of scientific uncertainty, Wheeler in April proposed to retain both PM 2.5 standards.
'Delay the inevitable'
The final rule released Dec. 7 largely affirms the conclusions in the EPA's proposal released earlier this year.
During a press event, Wheeler noted that average annual PM 2.5 concentrations in the U.S. fell by 43% between 2000 and 2019.
"The U.S. now has some of the lowest fine particulate matter levels in the world," Wheeler said. "Five times below the global average, six times below the average in China, and lower than the PM levels in France, Germany, and the U.K."
On a press call with reporters, Wheeler added that the most recent studies submitted to the EPA for consideration in its latest NAAQS review will be addressed in the next five-year review, which "starts tomorrow."
John Bachmann, a former associate director for science policy in the EPA's Office of Air and Radiation, suggested the new review process would be the best way to address the harmful impacts of the current PM 2.5 standards rather than trying to revise the EPA's latest decision.
Bachmann is a member of the Environmental Protection Network, a bipartisan group of former EPA career staff and political appointees. Over the summer, EPN recommended beginning the next NAAQS review "with a restored science-based process," explaining that doing so "is likely to be a more successful approach than initiating reconsideration of recent EPA actions."
Former CASAC Chairman Chris Frey said assembling a new committee could take between six and nine months to correct for membership changes made under a now-vacated Trump administration policy banning EPA grant recipients from serving on advisory panels.
"I think the goal here has just been to delay the inevitable," Frey, an environmental engineering professor at North Carolina State University, said in an interview. "It's inevitable that in some future review, the PM standard will be more stringent because that's what the science shows and that's what the law requires."
"The unfortunate thing with that is until an appropriately-set standard is implemented, literally tens of thousands of people will die prematurely under the current standard," Frey said.
The final rule is scheduled to become effective immediately upon publication in the Federal Register.