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Tightening ozone-pollution limit splits US EPA science advisers

Majority backs agency draft plan to keep 70 ppb standard

by Cheryl Hogue
December 6, 2019

Photo shows vehcile traffic on interstate 10 in Houston
Credit: Shutterstock
Gasoline-powered vehicles emit chemicals that can form ground-level ozone in the presence of sunlight.

A panel of science advisers is recommending that the current US air pollution limit for ground-level ozone stay the same rather be tightened.

This might trigger a sigh of relief from operators of chemical plants that release volatile organic compounds and other substances that can form ozone in the presence of sunlight—such facilities are less likely to see tougher emission-control requirements. But the American Lung Association says the current limit puts children with asthma at risk from exposure to ozone pollution, which can trigger lung problems.

The Dec. 6 recommendation from the Environmental Protection Agency’s seven-member Clean Air Scientific Advisory Committee (CASAC) to maintain the current standard of 70 ppb doesn’t represent a consensus, though.

A majority of committee members endorsed an EPA draft decision to retain the current ozone standard, which was set in 2015. Those six members are a business analytics consultant, who is the committee’s chair, along with scientists from regulatory agencies of four Republican-controlled states and an academic toxicologist. They believe that the scientific evidence on ozone health effects that has accumulated since 2015 isn’t compelling enough to change the standard.

The lone dissenter was Mark Frampton, a pulmonologist and emeritus professor of medicine at the University of Rochester Medical Center. He agreed with the other committee members that the scientific evidence hasn’t substantially changed since the previous review. However, he said, that means the committee’s recommendation should stay the same as it was previously: to lower the standard to between 60 and 70 ppb. At the time of the last ozone-standard review, CASAC had an entirely different membership and consulted with a large group of ozone-pollution experts.

CASAC chair Louis Anthony “Tony” Cox Jr. said more study of the health effects of lowering the standard from 70 ppb to 60 ppb “is warranted.”

In a related action, CASAC’s membership also split on its recommendation that the EPA retain its current clean air standard for fine particulate matter of 12 µg/m3 of air, set in 2012. Fine particulate matter consists of dust, dirt, soot, and droplets of liquids that are 2.5 µm or less in diameter. Exposure to this pollution is linked to premature death in people with heart or lung disease, asthma attacks, heart attacks, and decreased lung function.

On Dec. 3, a majority of CASAC members formalized the committee’s October decision against a plan from EPA staff scientists to cut down on particulate-matter pollution. The agency staff proposed tightening the particulate-matter limit to between 9 and 11 µg/m3. CASAC instead is recommending the agency retain the current particulate-matter standard.

Frampton, the only physician on the panel, also disagreed with this decision. He said scientific evidence produced since 2012 suggests the standard should be tighter, a sentiment echoed by a number of health and environmental advocacy groups.

EPA Administrator Andrew Wheeler, who is pushing forward President Donald J. Trump’s deregulatory agenda, wants the agency to complete review of the ozone and fine particulate-matter standards by 2020. The agency will then formally announce whether it will ratchet down those health-protective limits or let them stand and explain why.

A number of scientists who are former CASAC members say the tight time schedule and the fact that Wheeler has rejected the advisers’ request to review revised versions of EPA documents “is harmful to the quality, credibility, and integrity of EPA’s scientific review process” and to CASAC.


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