WASHINGTON — The U.S. Environmental Protection Agency said Friday it is tightening national air quality standards for fine particulate pollution for the first time since 2012, a move that could lead to stricter limits on tailpipe and stack emissions.

Sources of fine particulate matter, or soot, range from power plants to cars and trucks. It can cause lung and heart damage, and has been found to disproportionately affect low-income communities, according to the EPA. Particulate matter emissions are separate issues from greenhouse gas emissions.

Vehicles generate particulate pollution in a number of ways – petrol engines, especially diesel engines, produce particulates during combustion; gases from internal combustion engines then combine to form particulates in the atmosphere. Electrification of vehicles will help a lot, although even EVs shed particulates from brake pads and tires.

“Fine particulate matter is deadly and costly,” EPA Administrator Michael Reagan told reporters, adding that the decision was “based on sound science and a rigorous evaluation of the data we have.”

The proposal would lower the allowable concentration of particulate matter, or PM 2.5, which averages less than 2.5 micrometers per year, to 9 to 10 micrograms per cubic meter (µg/m3) from the current 12 µg/m3 by 2012. Levels were modified as low as 8 µg/m3 and as high as 11 µg/m3.

The administration of former President Donald Trump retained the 2012 standards despite a growing body of research showing those levels pose a risk to public health.

The EPA estimates that a PM2.5 standard of 9 μg/m3 per year could prevent as many as 4,200 premature deaths per year and generate a net health benefit of $43 billion in 2032.

Public health and environmental groups said they had hoped for a stricter proposal and hoped to present one during the EPA’s comment period.

“The science is clear that we need standards at the most protective end of the spectrum recommended by the EPA’s own scientific advisors,” said Laura Kate Bender, national assistant vice president for the American Lung Association.

Most members of the EPA’s Clean Air Scientific Advisory Committee (CASAC) recommend an annual average concentration range as low as 8-10 µg/m3.

The EPA has also chosen to retain the current primary 24-hour PM 2.5 standard of 35 µg/m3, although CASAC recommends lowering that figure to 25 µg/m3.

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