The federal EPA announced this week that it will consider strengthening standards for the harmful pollutant known as fine particulate matter, or soot emitted by vehicles, power plants, and factories. The move could have implications for Philadelphia where some neighborhoods fall close to current limits.

The Trump administration declined last year to revisit the rule for an annual average standard for the pollutant PM2.5 that now stands at 12 micrograms per cubic meter and which was set during the Obama administration.

Although EPA Administrator Michael S. Regan did not specify how much the standard might change, the World Health Organization recommends no more than 10 micrograms per cubic meter. Some scientists and environmental groups say the standard should be even lower.

In Philadelphia, the citywide average is about 7.7. However, air monitors set up in a recent test of neighborhoods found PM2.5 levels near City Hall of 10.1, the highest of 50 sites gauged throughout the city, most likely because of traffic congestion.

» READ MORE: Philly’s air pollution soars in summer. This neighborhood has the worst of it.

PM2.5 gets its name from the fact that the particulate matter is smaller than 2.5 micrometers. An average human hair has a diameter of about 50 micrometers.

The Biden administration sees revising the rule as part of the president’s focus on environmental equity. People of color are more likely than whites to live in areas with overall higher concentrations of PM2.5.

“The most vulnerable among us are most at risk from exposure to particulate matter, and that’s why it’s so important we take a hard look at these standards that haven’t been updated in nine years,” Regan said in the Thursday announcement on the potential change to the National Ambient Air Quality Standards.

The EPA said there are strong data showing that both long- and short-term exposure to fine particles can lead to heart attacks, asthma attacks, and premature death. The agency said children, those with heart or lung conditions, and people of color are most at risk of health effects from PM2.5.

Fine particulate matter comes from chemical reactions from sulfur dioxide and nitrogen oxides, which are mostly emitted by vehicles, power plants, and other industry. Because the particulates are so small, they are easily inhaled and can bypass the body’s protective systems.

Long-term exposure to fine particulates may cause as many as 45,000 premature deaths annually at the current allowable limit, according to EPA scientists. Lowering the limit to between 9 and 11 micrograms per cubic meter could save thousands of lives, staff scientists said.

The EPA will also consider how COVID-19 illness and death might relate to PM2.5 and plans to study the latest research with the goal of proposing a final rule by 2023.

Environmental groups praised the Biden administration’s revisiting PM2.5.

“The EPA’s welcome move could help millions of people breathe easier,” said Vijay Limaye, a scientist with the Natural Resources Defense Council. “The science clearly calls for more protective soot standards. These protections are critical for all of us, especially children, older people, communities of color, and low-income communities who are disproportionately burdened by higher levels of pollution in the air.”

Earlier this month, a study by the University of North Carolina and Harvard published in Environmental Research Letters found that ozone and fine particulate matter from vehicle emissions in 2016, the most recent year for which data was available, led to an estimated 7,100 deaths in the Northeast and Mid-Atlantic regions of the U.S.

The researchers looked at tailpipe emissions generated in 12 U.S. states and Washington, D.C., and found that New York, Pennsylvania, and New Jersey were hardest-hit. The researchers estimated damages at $21 billion, $13 billion, and $12 billion, respectively.

They found light-duty trucks, including SUVs, were responsible for the largest number of premature deaths at 2,463 followed by light-duty passenger vehicles (1,881) and heavy-duty trucks (1,465).

In Pennsylvania, emissions from buses in the Philadelphia metro area was linked with the most health damages caused by each ton of pollution emitted, according to the study.