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US EPA proposes tighter limits on fine particulate matter air pollution

Plan would improve public health and could drive up costs for industry

by Cheryl Hogue
January 6, 2023


View across a valley with mountains in the background showing air pollution haze above a city.
Credit: Shutterstock
Phoenix experiences high levels of fine particulate pollution.

The US Environmental Protection Agency has proposed strengthening the US health-based limit for fine particulate air pollution, a change it says would reap billions of dollars annually in public health benefits.

If adopted, a tighter limit on fine particulate matter—particles known as PM2.5 that are 2.5 microns in diameter or smaller—could eventually lead to tougher emission control requirements and greater costs for industry, including chemical manufacturers.

The proposal, unveiled Jan. 6, would ratchet back the health-based standard for PM2.5 to between 9 and 10 µg/m3 of air. The current annual average limit of 12 µg/m3 was established in 2012 under former president Barack Obama.

An extensive review of the latest available evidence and technical information indicate that the 2012 standard is “no longer sufficient to protect public health,” EPA administrator Michael Regan told reporters at a briefing.

Scientific evidence has built up over the last quarter century linking long- and short-term exposure to these tiny particles to heart attacks, lung problems, asthma attacks, and premature death. Direct sources of fine particles include soot from vehicle exhaust, fires, and combustion of oil and coal in industrial facilities. But most PM2.5 forms when gases—primarily sulfur dioxide and nitrogen oxides—emitted from industry, power plants, and gasoline or diesel engines undergo complex chemical reactions in the atmosphere, according to the EPA.

The proposal estimates that the annual costs of a 10 µg/m3 limit would, by 2032, range between $95 million and $260 million, with benefits of $8.5 billion to $20 billion. A 9 µg/m3 standard has estimated annual costs by 2032 of $390 million and benefits of $21 billion to $43 billion. In addition to saving health care costs, a 9 µg/m3 standard would prevent up to 4,200 premature deaths and 270,000 lost workdays per year, the EPA estimates.

Regan pointed out that communities of color and low-income neighborhoods are “at a higher risk for exposure with disproportionately devastating effects” from PM2.5 pollution. Many of these areas are located near industrial facilities, including chemical plants, or roads with heavy traffic.

“The science is clear—PM pollution causes serious health problems, and the biggest impacts are hitting Black, Latinx, and low-income people, many of whom are already overburdened with exposure to multiple pollutants,” Anita Desikan, of the Center for Science and Democracy at the Union of Concerned Scientists, says in a statement. “EPA needs to act quickly, follow the science, and finalize the strongest possible rule."

The American Chemistry Council (ACC), the largest trade association of US chemical manufacturers, has opposed tighter PM2.5 standards in the past. “We are carefully reviewing the EPA’s proposal,” the group says in an emailed statement.

Controversy has swirled around the PM2.5 standard in recent years. In 2017, then-president Donald J. Trump’s EPA administrator changed the rules for membership in the agency’s Clean Air Scientific Advisory Committee (CASAC) and two other influential panels of outside experts, eliminating many academics as science advisors. They were replaced mainly with industry scientists. Next, the then-head of EPA scrapped particulate matter and ozone pollution scientist panels that had reported to CASAC.

In 2019, EPA staff suggested tightening the PM2.5 standard to between 9 and 11 µg/m3. But a majority of Trump’s newly constituted CASAC endorsed keeping the 12 µg/m3 limit.

The following year, the EPA proposed keeping the 12 µg/m3 standard, a move that the ACC endorsed. A day later, a federal court invalidated the Trump administration’s rules for advisory panel membership.

Hours after his inauguration, President Joe Biden ordered the EPA to reexamine the Trump administration’s conclusions on PM2.5, among other decisions.

A newly constituted CASAC last year recommended that the EPA tighten the limit to between 8 and 10 µg/m3.


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