(CNN) — Everyone benefits when there is less air pollution, but it pays off more for older communities with high poverty rates and those where larger populations of Black people live, regardless of income, a new study finds.

The study, published Friday in the New England Journal of Medicine, looked at the connection between deaths and a type of air pollution called PM2.5.

The US Environmental Protection Agency said in January that it is trying to determine how it can best create regulations to strengthen the standards for PM2.5 pollution.

The researchers on the new study said that with that in mind, they wanted to provide policy-makers with additional evidence on how marginalized communities, which already tend to have poorer health outcomes, are disproportionately affected by air pollution.

Other studies have shown this connection for individual groups such as people of color or those with low income, but these researchers wanted to look at the effects on communities based simultaneously on socioeconomic status and race.

Fine particulate matter, or particle pollution, is the mix of solid and liquid droplets floating in the air. It can come in the form of dirt, dust, soot or smoke. Coal- and natural gas-fired power plants create it, as do cars, agriculture, unpaved roads, construction sites and wildfires.

PM2.5 has particles that are 2.5 microns or less in diameter. It's so tiny — 1/20th the width of a human hair — that it can travel past your body's usual defenses when you breathe it in.

Instead of being carried out of your body when you exhale, it can get stuck in your lungs or go into your bloodstream. In the short term, the pollution can irritate the eyes, nose, throat and lungs and cause coughing, sneezing or shortness of breath. Long-term, this dirty air can also cause lasting damage and lead to health conditions like obesity, cancer, stroke, heart problems, asthma, depression, anxiety and even premature death.

In 2019 alone, long-term exposure to particle pollution contributed to 4 million deaths worldwide.

For the new study, researchers analyzed Medicare data from 73 million people who were 65 or older from 2000 through 2016. They estimated the associations between annual PM2.5 exposure and mortality in communities defined by racial identity (Black vs. White) and income level (Medicaid-eligible vs. ineligible).

Everyone would benefit from cleaner air, they found, but higher- and lower-income Black people and low-income White people may benefit more from lower PM2.5 levels than higher-income White people.

The EPA is trying to determine how much stricter US air pollution safety standards should be. It's considering lowering the standards from 12 micrograms per cubic meter to between 9 and 10 micrograms per cubic meter.

This study suggests that if the EPA were to go even further and lower the standard to 8 micrograms, the US would have a 4 percent reduction in overall mortality rate, study co-author Dr. Francesca Dominici, a professor of biostatistics, population and data science at the Harvard T.H. Chan School of Public Health, said.

These stricter standards would have even more advantage for Black people. The mortality rate would be 7 percent lower among Black people who have what the researchers defined as a "higher" income, meaning anyone who was not eligible for Medicaid, and a 6 percent rate reduction among Black people with a lower income. Medicaid eligibility requires earnings below the federal poverty level, which was $13,590 for a single adult and $27,750 for a family of four in 2022.

"So you've doubled the mortality rate rate reduction by putting more stringent standards for marginalized communities," Dominici said. "To me, that was surprising, how much more benefit you're going to get."

The study can't specifically get at the reasons for this difference, but Dominici has a few ideas.

"It's potentially due to the social structure forces that lead to discrimination and social exclusion," she said, rather than to biological differences.

Other studies have shown that, regardless of income or region, decades of segregation mean Black people tend to live in areas where there is greater exposure to air pollution.

This study is looking at an older population, Dominici said, meaning its participants were born when segregated neighborhoods were common.

"I think that it could be the combined effect of living through these times of being denied an equal opportunity to be healthy," she said.

In general, Black Americans have less access to health care and higher rates of health problems, and they breathe a higher level of pollution.

"There is enormous evidence of environmental inequities in the United States, and so with more stringent pollution standards, there will be more equity," Dominici said. "We are at a crucial time when the EPA is thinking about more stringent standards, so it will be important to think about the context involved and to really think through these decisions with regard to environmental justice, race and social class."

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