U.S. Environmental Protection Agency officials have released a draft policy assessment for fine particulate matter, estimating that current federal air quality safeguards for the harmful soot-forming pollutant are set at a level that could allow tens of thousands of deaths annually.
The draft assessment, delivered as part of the Trump administration's expedited review of the National Ambient Air Quality Standards, or NAAQS, could force the EPA to back off a streamlined approach outlined by former Administrator Scott Pruitt or risk putting a final soot pollution rule into legal jeopardy.
Emissions from fossil fuel-fired power plants, industrial facilities and vehicles are the largest sources of fine particulate matter that measure 2.5 micrometers or less, also known as PM 2.5. The tiny soot-like particles can make their way from ambient air through the lungs and into the heart and brain, causing respiratory health problems and premature death. A growing body of scientific research suggests that PM 2.5 is a nonthreshold pollutant, meaning it causes health effects at virtually all levels of human exposure.
Based on a lengthy scientific review, the EPA in 2012 strengthened the annual standard for PM 2.5 to 12 micrograms per cubic meter, down from the previous standard of 15 micrograms per cubic meter. The decision, which withstood a legal challenge from a coalition of electric utilities, was supported by the agency's Integrated Science Assessment, a 1,000-page research document covering the most recent scientific findings on PM 2.5 at the time.
With the NAAQS for PM 2.5 up for review again, the EPA's Clean Air Scientific Advisory Committee, or CASAC — which is required to advise the administrator under the Clean Air Act — in March completed its review of the agency's latest draft Integrated Science Assessment. However, the seven-member committee also told EPA Administrator Andrew Wheeler that it lacked the expertise necessary to thoroughly review the latest science on PM 2.5 after he abruptly dismissed dozens of outside experts tasked with aiding CASAC in its NAAQS reviews. At the same time, the committee also asked the EPA to develop a second draft of the Integrated Science Assessment for the CASAC to review.
Wheeler rejected that request in a July 25 response, informing the committee he had asked his staff to "maintain their focus on meeting our statutory deadlines" that require NAAQS reviews to be completed every five years. But Wheeler also agreed to provide "a pool of subject matter expert consultants" by Aug. 31 who will "make themselves available as requested."
'Rigorous scientific analysis'
However, career staff in the EPA's Office of Air Quality Planning and Standards has now released a policy assessment raising questions about whether the current PM 2.5 standard of 12 micrograms per cubic meter is sufficiently protective of human health. The Sept. 5 document included a risk and exposure assessment that simulated 47 study areas at a level just meeting the current standard. When that was done, the assessment tallied about 50,000 PM 2.5-related deaths, including almost 20,000 heart disease deaths, in a single year.
"When the current standard is not adequate, then that becomes more complicated because it's kind of open as to what the alternative standards might be," said Chris Frey, an environmental engineering professor at North Carolina State University who served as CASAC chair from 2012 to 2015. "And that implies that there should be some rigorous scientific analysis of possible alternatives."
In its draft policy assessment, EPA staff said tightening the standard to 10 micrograms per cubic meter could be supported depending on certain scientific considerations.
"These are complex assessments, and without rigorous external review it's easy to make mistakes or go down the wrong path," Frey added in an interview before the policy assessment was released.
An August ruling by the U.S. Court of Appeals for the District of Columbia Circuit underscored how much weight federal judges place on the CASAC's advice in legal challenges to the NAAQS. In that decision, a three-judge panel remanded the secondary 2015 ozone NAAQS back to the EPA for further consideration after concluding the agency had failed to adequately explain why it did not follow the committee's advice by using a three-year average instead of a one-year average for anticipated exposure levels.
"I think [the decision] reaffirmed that the science is really important and CASAC's role in helping the EPA, and in particular the court, understand what that science means is really important," said Seth Johnson, an Earthjustice attorney who argued the case on behalf of environmental petitioners.
Johnson also sent a letter to the EPA on Aug. 21 raising concerns about the legal status of the pool of scientific consultants selected to help the CASAC in what he described as the EPA's "novel, untested approach" to obtaining the committee's advice.
The EPA could propose a decision on any necessary revision of the NAAQS for PM 2.5 in early 2020, according to the agency's review timeline.