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Blacks, Latinos and poor people are significantly more likely to be exposed to particulate matter emissions than the population as a whole, U.S. EPA researchers conclude in a new study that adds to the evidence linking race and income level to pollution hazards.

The study, published online in the American Journal of Public Health late last week, finds that “non-whites and those living in poverty face a disproportionate burden from [particulate-matter]-emitting facilities.”

Blacks are especially likely to live in high-emissions areas, the study finds, with a burden — as measured by nearness to power plants and other stationary pollution sources — for the fine particulates known as PM2.5 about 50 percent higher than that of the overall population.

For nonwhites as a whole, the burden is about one-quarter higher; for poor people, it is more than one-third above the level for the general population.

“These patterns were relatively unaffected by sensitivity analyses and disparities held not only nationally but within most states and counties as well,” according to the authors, who work in EPA’s National Center for Environmental Assessment.

For those groups, the potential health effects of pollution exposure should be considered in conjunction with the “well-documented disparities” in access to care and higher rates of some diseases in nonwhite populations, they write.

“Along with other inequitable social and physical determinants of health, these interlocking mechanisms must all be addressed to establish environmental and public health justice,” the paper says.

For the study, the five-member research team meshed data from the U.S. Census Bureau and EPA’s 2011 National Emissions Inventory, which shows pollutant emissions by facility.

The researchers acknowledge some limitations. Because, for example, natural events and other factors may affect ambient air concentrations of particulate matter, the burden level “should not be interpreted as a direct measure of PM exposure,” they write.

Particulate matter, often dubbed “soot,” is an umbrella term for a range of particles that can be made up of hundreds of different chemicals, according to EPA. It’s one of a half-dozen criteria pollutants that the agency is required to regulate under the Clean Air Act.

Air quality standards for those pollutants are supposed to be reviewed every five years in light of the latest research into their impact on public health and the environment.

Among other health effects, exposure to particulate matter is linked to premature death in people with heart or lung disease. PM2.5, so called because it comprises fine particles that are no bigger than 2.5 micrometers in diameter, or one-thirtieth the width of a human hair, is considered especially dangerous because it can penetrate deeply into the lungs.

As evidence that disproportionately high exposure for nonwhites and the poor is not necessarily accidental, the study points to EPA’s finding last year of a “direct link” between racial discrimination and the permitting of a small Michigan power plant in the 1990s.

The research authors also note prior findings of racial and economic disparities in the odds of pollution exposure. A 1986 sample, they write, found that blacks were 1.54 times more likely than whites to live within a mile of a facility listed in the Toxics Release Inventory, while a study published last year concluded that mean residential concentrations of ambient nitrogen dioxide in 2010 “were about 7 percent higher for those in poverty than for those above the poverty line.”

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