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US EPA’s science advisers split on tightening air pollution limit

Under a new process, a majority of the Clean Air Scientific Advisory Committee says the agency should not toughen particulate matter standard

by Cheryl Hogue
November 10, 2019 | A version of this story appeared in Volume 97, Issue 44

Photo shows a toddler boy using a nebulizer at a hospital.
Credit: Shutterstock
An increased number of emergency room visits for asthma attacks are associated with higher levels of particulate matter pollution, epidemiology data show.

As impeachment investigations hold the US public’s attention, the Trump administration continues to push forward its deregulatory agenda, notably on pollution control.

Part of that deregulation effort has involved modifying how the US Environmental Protection Agency gets science advice—a change that some say diminishes the role of such advice.

Now, the committee of scientists that peer-reviews the agency’s reasoning for tighter air pollution limits must do its job with less expertise than it has drawn on in past decades. Plus, EPA administrator Andrew Wheeler has overturned a longstanding practice with the advisers—he’s given the committee only one chance to scrutinize key documents, even though the scientists asked for a second look after the EPA revises them.

Restricting particulates

EPA staff and an independent review panel roughly agreed on reducing the limit for airborne fine particulate matter to protect public health, while a majority of the agency’s official clean air advisory committee recommended no change. The EPA must finalize a new regulation or justify not changing it by the end of 2020.

12 µg/m3
Current US limit, set in 2012

9–11 µg/m3
New limit proposed by EPA staff in September 2019

8–10 µg/m3
New limit proposed by an independent review panel in October 2019

12 µg/m3
Recommendation by a majority of the EPA’s Clean Air Scientific Advisory Committee in October 2019

The first regulation affected by these moves is a limit for fine particulate matter, a type of pollution consisting of dust, dirt, soot, and droplets of liquids that are 2.5 µm or less in diameter. Exposure to fine particulates is linked to asthma attacks, heart attacks, and decreased lung function, as well as premature death in people with heart or lung disease.

The current national limit for fine particulates is an annual average of 12 µg/m3 of air, set in 2012. As required by the Clean Air Act, the EPA is reviewing the standard as well as the scientific evidence that has accrued since 2012 to decide whether to reduce the limit. If the agency opts to do so, the chemical industry and other sectors would likely have to control emissions of nitrogen oxides and sulfur oxides more tightly than they currently do.

The agency’s process for reviewing air-quality standards is scientific and deeply complex. It draws from mounds of data. It relies heavily on epidemiology studies that have repeatedly linked exposure to fine particulate matter with cardiovascular and respiratory problems that result in emergency room visits, hospitalizations, and deaths.

Under a schedule set by former EPA administrator Scott Pruitt, who resigned amid scandal last year, the agency must determine in the coming months whether the 12 µg/m3 limit protects public health. Wheeler is sticking to that schedule, meaning the agency must complete a new regulation or issue its reasons for not changing the current standard by the end of 2020.

EPA staff is meeting the deadlines, releasing a draft assessment in September that suggested ratcheting down the standard. A level between 9 and 11 μg/m3 could reduce health problems associated with fine particulate air pollution broadly across the US, the draft document says.

The agency’s Clean Air Scientific Advisory Committee (CASAC), a panel of experts from outside the agency, is reviewing and critiquing the assessment. For decades, the EPA has followed the advice of CASAC when determining what level to set air-quality standards.

But CASAC is now bereft of the deep scientific insight it has had in the past. Last year, Wheeler summarily dismissed a review panel that provided CASAC with expertise specific to particulate matter. He also eliminated a similar panel on ground-level ozone. CASAC historically turned to these panels for input as it dug into the details of pollutant-specific health data.

CASAC is currently chaired by Louis Anthony “Tony” Cox Jr., a business analytics consultant who is skeptical about the evidence associating fine particulates with health problems and deaths. The committee also includes four scientist-regulators from Alabama, Georgia, Texas, and Utah and an academic who is a pulmonologist. For the first time, no committee members have a background in epidemiology, the discipline that the EPA’s draft report most relies on.

CASAC has recognized its scientific proficiency is limited. In April, the committee recommended Wheeler reappoint the previous review panel of particulate matter experts or a group with similar expertise.

Wheeler didn’t. Instead, in September, he tapped what the EPA called a “pool of subject matter experts”: 12 scientists with whom CASAC can consult.

But the arrangement between CASAC and the pool of experts is markedly different than the relationship it had with the former review panels. CASAC members may consult with the pool only through CASAC’s chair and only in writing. In the past, the panels did a deep dive into the EPA’s analysis of the science on a pollutant and then reported to CASAC. Members of CASAC also consulted with panelists in oral deliberations, usually face to face.

As CASAC has taken up the issue of whether to tighten the fine particulate matter standard, 20 scientists who were dismissed from the particulate matter review panel took the unprecedented step of forming what they call the Independent Particulate Matter Review Panel. Their aim: to review the EPA’s draft document just as they would have done in the past. Members of the panel are researchers from academia, scientists for regulatory agencies, and consultants.

Since the EPA released the draft fine particulate assessment in September, CASAC and the independent panel have pored over the document, each hewing to CASAC’s review procedures. The EPA foots the bill for the CASAC members to meet. The Union of Concerned Scientists (UCS) reimbursed the independent panel members’ travel costs for an in-person gathering open to the public. Panel members did not accept honoraria or other compensation for their review work, the UCS says.

The independent panel crafted a 183-page report that it released Oct. 22. The panel concluded that the current 12 μg/m3 standard for fine particulates does not protect public health. Retaining it would require disregarding epidemiological evidence, a move that is not scientifically justified, the panel wrote. It recommended the agency revise the fine particulate matter standard to between 8 and 10 μg/m3.

The independent panel provided its report to CASAC, which met Oct. 24 and 25 to draft its own recommendations. CASAC can consider the panel’s work, as it can any relevant scientific comment from the public. But at that public meeting, most committee members did not mention it.

By the end of the CASAC meeting, committee members failed to reach consensus about the adequacy of the current fine particulate standard. And as the meeting drew to a close, their discussions came close to breaking down.

“The review process is so dysfunctional that we need to stop,” said CASAC member Mark Frampton, a pulmonologist and emeritus professor of medicine at the University of Rochester Medical Center. He said the process is weakened because the pool of consultants that CASAC can draw on can’t participate in the committee’s discussions as the review panel used to, and the pool contains fewer epidemiology experts than the review panel did. He agreed to finish the discussions “under protest.” CASAC member James Boylan, an environmental engineer with the Georgia Environmental Protection Division of the Georgia Department of Natural Resources, said he shared Frampton’s frustrations.

But Cox, the committee chair, said that by staying within their own scientific expertise, CASAC members “can deliver something useful” to the EPA.

Cox concluded that the EPA had not convincingly laid out the extent to which health risks would be reduced by tightening the fine particulate matter standard, so there was no justification to change it. Concurring with his view were CASAC members Sabine Lange, a toxicologist at the Texas Commission on Environmental Quality; Corey Masuca, an environmental health scientist from Alabama’s Jefferson County Department of Health; and Steven Packham, a toxicologist at the Utah Department of Environmental Quality. Though most specialists who study particulate matter conclude its risk is directly proportional to exposure, Packham said he believes there is a threshold for exposure to this pollutant below which “the human organism” experiences no effects.

Frampton and Boylan disagreed with the CASAC majority. Citing evidence that has come to light since the EPA issued its 2012 standard, they supported a tighter standard. After CASAC issues an official version of its report to the EPA, which will likely happen in December, the agency will produce a final version of its assessment. Wheeler will take it and CASAC’s divided advice into account as he decides next year whether to tighten or retain the 12 µg/m3 standard to protect public health.

“It is unusual for the CASAC to fail to reach consensus on its final advice regarding whether to retain, revise, or set” an air-quality standard, Christopher Frey, an environmental engineering professor at North Carolina State University, tells C&EN. “It is unusual for CASAC to offer advice that is less protective than supported by the scientific evidence,” he says. Frey chaired CASAC from 2012 to 2015 and the independent review panel this year.

The “EPA set them up to fail,” Gretchen Goldman, research director of the UCS’s Center for Science and Democracy, says of CASAC. The changes affecting the committee’s expertise weaken the role of science advice at the agency, she says.

The outcome, Frey adds, could be dire.

“Real people will die if EPA doesn’t make this standard more stringent,” he says.


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