Bloomberg Law
June 24, 2022, 9:30 AM

Clean Air Panel Takes ‘Unprecedented’ Pause for Science Review

Jennifer Hijazi
Jennifer Hijazi

An independent panel of EPA advisers central to clean air rulemaking is freezing scheduled policy reviews to take a deep dive into ozone pollution science, signaling concerns that the status quo ozone standards aren’t as protective as some research suggests.

The Clean Air Scientific Advisory Committee, or CASAC, in May took a rare step back from reviewing policy plans for ozone standards laid out by the Environmental Protection Agency, and told Administrator Michael Regan on June 15 they’ll be scrutinizing ozone research on public health impacts with a closer eye before making any recommendations to the agency regarding new levels.

At a June 8 public meeting announcing the decision, committee chair Lianne Sheppard said the panel had waded into “uncharted territory” and would need to “take into account the most current science” in order to “do a responsible job.”

The move marked a departure from normal procedure of the advisory panel, which is designed to provide independent analysis to EPA decisions.

“Having a CASAC chair, in essence, suspend the review process to go back and look at something from the EPA staff because they have continuing questions is kind of unprecedented,” according to Paul Miller, the executive director of the Northeast States for Coordinated Air Use Management.

Emission limits for harmful ground-level ozone are part of a suite of rules for six “criteria air pollutants” under National Ambient Air Quality Standards, which are supposed to be reviewed and set every five years for states to craft compliance plans.

The current ozone standard of 70 parts per billion hasn’t been adjusted since 2015, despite clean air advocates insisting limits on ozone need to be bolstered.

The CASAC panel expressed their concerns about the underlying science during an initial briefing of the EPA’s draft policy plans for ozone, which recommended the standards remain unchanged.

Concern With Standards

Members of the panel worried that a limited suite of research had been considered fully, de-emphasizing potentially critical work on cardiovascular, mortality, and natural environment effects of ozone.

Robust analysis of underlying science is a critical part of the panel’s job, according to an EPA statement to Bloomberg Law. “The EPA supports/understands CASAC’s decision to discuss science topics of interest for ozone and we look forward to engaging with the CASAC Ozone Panel further on this activity,” the agency said.

The heart of the panel’s concern comes from skepticism that status quo standards adequately protect public health, American Lung Association senior vice president of advocacy Paul Billings told Bloomberg Law. “I don’t think they would be doing this if they thought that the EPA policy assessment conclusions were correct.”

A decision to lower the 70 parts per billion threshold from 2015 could affect a number of clean air rules, including traveling ozone standards and State Implementation Plans, but Billings said it’s still possible to meet current 2023 deadlines for new ozone limits.

“They’re going have to devote some resources and may have to work differently than EPA staff had planned, but to our mind there’s plenty of time for this work to get done,” Billings said.

Conflicting Research

Part of the issue is the kind of research the EPA prioritized when crafting its science-based rules.

Epidemiological and controlled studies are the key studies used in the rulemaking process. Epidemiological studies draw connections from aggregated real-world data, and controlled experiments gather information from directly exposing people to ozone in lab settings.

Both are integral in rulemaking, but can conflict with each other in the case of ozone impacts—an issue that has contributed to keeping standards static for almost a decade.

The underlying science helps categorize health effects in terms of “causality,” or how likely it is that a pollutant is the cause of certain harms like death or heart disease. Some panel members wondered why, given new research, certain health categories have been downgraded for ozone’s causality.

“One approach is telling you that we can’t see much difference once we get below the level that the standards already set out, and one of them suggests that we might be able to save lives if we got the air even cleaner,” according to Daniel Cohan, Rice University associate engineering professor.

Controlled studies also use relatively healthy young people for experiments, leaving out swaths of critical communities affected by ozone pollution such as the elderly and chronically ill people in pollution-burdened communities, according to Billings.

‘Unattainable Standards’

Adequate ozone standards are especially crucial as climate change makes summers hotter and dryer each year. Precursor chemicals use heat to bake and turn into ground-level ozone, and worsening wildfire seasons also spread pollutants across the US.

Cohan worries that worsening climate stressors are chipping away at the efficacy of air quality rules including ozone standards. Some areas such as Houston are still not even in compliance with the 2015 limits, Cohan said, which raises concerns about the feasibility of tougher standards.

“Are you really improving health if you’re setting unattainable standards and levels that can’t be attained,” Cohan said.

The committee will be briefed by EPA staff on the science used in the policy draft, though a date hasn’t been set. Subsequent meetings, also unset, will allow the panel to deliberate on the research.

To contact the reporter on this story: Jennifer Hijazi in Washington at

To contact the editors responsible for this story: Zachary Sherwood at; Renee Schoof at

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