Air pollution has decreased across the US, but new research finds health burdens remain unequal among racial groups

 Health benefits that have resulted from reductions in fine particulate air pollution aren't distributed equally among populations in the U.S., a new Yale-led study finds. Racial and ethnic minorities -- and Black people in particular -- still experience disproportionately high rates of cardiovascular disease-related deaths caused by exposure to fine particulate matter, according to the research.

The findings were published Aug. 31 in Nature Human Behavior.

Fine particulate matter, also known as PM2.5, consists of particles or droplets smaller than 2.5 micrometers in diameter, or 30 times smaller than the width of a human hair. While some PM2.5 in the environment comes from natural sources, such as wildfires, the majority of particulate matter pollution in the U.S. is the result of human activities, including emissions from vehicles, power plants, and factories.

The small size makes PM2.5 harmful for human health, said Kai Chen, assistant professor of epidemiology at Yale School of Public Health and senior author of the study.

"When you inhale such small particles, they can get into your lungs and some smaller particles can even get into the blood stream and circulate around the body," said Chen. "That can impact your heart, which leads to a lot of the cardiovascular disease we see today."

Environmental efforts including the 1963 Clean Air Act and the Environmental Protection Agency's (EPA) National Ambient Air Quality Standards for PM2.5, established in 1997, have helped bring down PM2.5 levels throughout the United States. This, in turn, has yielded benefits to human health. But it has remained unclear whether these health benefits are distributed equitably across racial and ethnic groups.

"We know that some minorities, especially Black and Hispanic people, are exposed to higher levels of PM2.5 than white people," said Chen. "In our study, we wanted to go further and assess vulnerability to PM2.5 across different groups and see how that relates to mortality."

For the study, the researchers collected data on cardiovascular disease deaths and monthly PM2.5 concentrations across 3,103 counties in the contiguous U.S. between 2001 and 2016. They then evaluated whether there was a link between increases in PM2.5 levels and changes in cardiovascular disease-related deaths.

Source: ScienceDaily