The EPA recently announced it would not be making any changes to the National Ambient Air Quality Standards (NAAQS) for particulate matter (PM).

The EPA is required to set NAAQS by the Clean Air Act (CAA). These standards determine “acceptable” levels for pollutants “that are common in outdoor air, considered harmful to public health and the environment, and that come from numerous and diverse sources,” according to the EPA website.

The CAA defines two types of NAAQS: primary and secondary standards. Primary standards are designed to protect public health, and secondary standards “are designed to protect the public welfare from adverse effects, including those related to effects on soils, water, crops, vegetation, manmade materials, animals, wildlife, visibility, and climate; damage to property; transportation hazards; economic values, and personal comfort and well-being.”

The NAAQS monitors six “criteria pollutants”:

• Carbon monoxide (CO)
• Lead (Pb)
• PM, which includes a standard for PM that is 10 micrometers or smaller (PM-10) and PM that is 2.5 micrometers or smaller (PM-2.5 or fine PM)
• Ozone (O3)
• Nitrogen dioxide(NO2)
• Sulfur dioxide (SO2)

PM-10 causes all sorts of health problems, such as aggravated asthma, decreased lung function, nonfatal heart attacks, and increased respiratory symptoms. PM is the main cause of reduced visibility (haze) in the United States, according to the EPA.

“On April 14, 2020, after carefully reviewing the most recent available scientific evidence and technical information, and consulting with the Agency’s independent scientific advisors, the EPA is proposing to retain, without revision, the existing primary (health-based) and secondary (welfare-based) National Ambient Air Quality Standards (NAAQS) for particulate matter,” stated the Agency.

The Agency took this position after “a five-year review process, in which scientific evidence showed unequivocally that these standards are not adequate to protect public health,” said H. Christopher Frey, a professor of Environmental Engineering at North Carolina State University who has served on the EPA’s Clean Air Scientific Advisory Committee (CASAC) and on 10 specialized panels focused on individual pollutants.

The panel was disbanded by EPA Administrator Andrew Wheeler in October 2018, according to Frey. The current CASAC committee no longer has any epidemiologists on the committee, which is “a key discipline for assessing PM-2.5 health effects,” Frey wrote.

The disbanded panel decided to reconvene on its own in October 2019. “We found that current fine particle standards are not protective of public health,” Frey wrote. “We advised the EPA that the annual standard should be reduced from its current level of 12 micrograms per cubic meter to a range of between 10 and 8 micrograms per cubic meter.”

Wheeler is quoted as saying he questioned the reliability of scientific research suggesting that tighter limits are needed to save lives, as reported in sciencemag.org.

“There’s still a lot of uncertainty” about the research, Wheeler said. “The latest scientific evidence and analysis” and conclusions drawn by an EPA advisory panel that favored not making any changes to the PM standards were the basis for the decision, Wheeler said.

CAA regulations require standards that provide an “adequate margin of safety.” Frey asserts that this means the standards should afford margins of safety for all age and health groups, including “sensitive populations, such as older adults, people with preexisting cardiovascular or respiratory diseases and children with asthma.”

“The EPA proposal acknowledges that these groups exist but does not specify how it will protect them from PM-2.5 in the air,” Frey wrote. “Wheeler is also silent regarding the role of racial and ethnic differences in exposure and risk, even though a federal court called EPA to task in 2009 for not specifically addressing at-risk groups.”

There have been multiple lawsuits attempting to call the EPA to task for air pollution regulations, including greenhouse gas emissions standards, limits for interstate air pollution, and limits upon carbon emissions. “Unless EPA modifies its position on particle air quality to address the law and the science, I expect that this regulation too will end up in court,” Frey concluded.