US EPA projects 99% compliance with final rule tightening soot standards

The US Environmental Protection Agency finalized tighter national air quality standards for soot pollution Feb. 7 in a rule that drew praise from public health organizations and criticism from industry groups.

Approximately 99% of all US counties will meet the more stringent standards by the rule's 2032 attainment date through compliance with other existing regulations, according to the EPA's projections. Those rules include a new interstate smog plan that requires older fossil fuel-fired power plants to install modern pollution controls and tougher tailpipe rules for light- and heavy-duty vehicles through model year 2026.

"The science is clear. Soot pollution is one of the most dangerous forms of air pollution, and it's linked to a range of serious and potentially deadly illnesses," EPA Administrator Michael Regan said ahead of the rule's release. "We have a holistic strategy to simultaneously tackle pollution, protect clean air and ensure we are investing in the growth of our economy."

Fine particulate matter, also known as PM 2.5, has a width smaller than the diameter of a human hair. Primarily produced by vehicles, power plants and other industrial facilities, it can make its way into the bloodstream when inhaled and eventually reach the brain.

Tightening primary standard

The EPA's final rule, issued as part of a regular review of the National Ambient Air Quality Standards for PM 2.5, will tighten the agency's annual primary standard to 9 micrograms per cubic meter. Primary standards are designed to protect human health with an adequate margin of safety.

The rule represents the first update to the NAAQS for PM 2.5 since 2012, when the EPA set the current primary annual standard at 12 micrograms per cubic meter. It was developed in consultation with the EPA's Clean Air Scientific Advisory Committee, a seven-member group of air pollution experts.

"The stronger air quality standard announced today is grounded in the best available science and will undoubtedly save lives," Regan said.

The EPA estimated that the tighter primary standard of 9 micrograms per cubic meter will produce up to $46 billion in net public health benefits by 2032, including 4,500 avoided premature deaths annually with the standards in full effect.

"We're glad to see the Biden administration answered the call to reduce harmful soot pollution," Sierra Club Executive Director Ben Jealous said in a statement.

However, the US Chamber of Commerce argued the EPA should have left its prior PM 2.5 standards in place and focused on nonindustrial sources of fine particulate matter such as wildfires and road dust. Wildfires, for example, now account for more than 40% of all PM 2.5 emissions in the US.

The EPA's projections show all but 52 US counties in compliance with the tighter standard by 2032, with 23 of the nonattainment counties in California. But the chamber contended the rule will push 569 counties out of compliance.

"Tightening the NAAQS PM 2.5 standard will grind permits to a halt for a large portion of our country," Marty Durbin, the chamber's senior vice president for policy, said in a statement.

Human health and prosperity

Regan countered those arguments on a Feb. 6 press call, noting that the nation's gross domestic product has increased 52% since 2000, while PM 2.5 concentrations have fallen 42% over that span. The EPA's first PM 2.5 standards were established in 1997, and the agency began designating attainment areas in 2004.

"We do not have to sacrifice people to have a prosperous and booming economy," Regan told reporters.

In addition to existing regulations, the EPA's regulatory impact analysis accounted for tax incentives in the Inflation Reduction Act and funding in a 2021 bipartisan infrastructure law. Other EPA rules, such as new greenhouse gas emission regulations for oil and gas facilities finalized in December 2023 and a forthcoming climate rule for power plants, were not modeled at the time of the analysis but are expected to drive further PM 2.5 reductions, an EPA spokesperson said.

The EPA will also provide new monitoring tools to help air agencies "evaluate and exclude data associated with exceptional events" related to wildfire smoke, according to a fact sheet.

The Feb. 7 rule will become effective 60 days after its publication in the Federal Register. The EPA will then make initial attainment designations within about two years. States with nonattainment areas must submit cleanup plans within 18 months after the EPA finalizes its designations, but "the earliest" states will likely need to comply with the tighter standards is 2032, the EPA said.