Cardiovascular deaths from air pollution declining in the U.S., but racial disparities persist

Clean air laws have led to a significant reduction in long-term exposure to fine particulate air pollution across much of the United States over the past two decades, yet tens of thousands of Americans still die each year from cardiovascular disease linked to polluted air.

A new study led by researchers at the Yale School of Public Health (YSPH) shows that air pollution-related cardiovascular deaths are increasingly concentrated among traditionally underserved communities and driven by specific chemical components rather than overall pollution levels.

The authors say their work offers insights for more precise and equitable air pollution control strategies that target not only how much pollution is in the air, but what it’s made of and who is most affected.

The research, published in the journal Science Advances, finds that cardiovascular deaths attributable to fine particulate matter, known as PM2.5, fell nearly 45 percent between 2001 and 2020. But the decline has been uneven across regions and racial and ethnic groups, and progress has stalled in recent years, the authors say. Crucially, the study shows that a handful of PM2.5 components account for most of the current health burden.

“Air quality regulations have worked, but they’ve worked unevenly,” said Dr. Kai Chen, PhD, associate professor of environmental health sciences at YSPH and the study’s senior author. “Our study shows that even at relatively low levels of overall PM2.5, specific components continue to drive cardiovascular mortality.”

PM2.5 is a complex mixture of fine particles produced by sources such as power plants, vehicles, agriculture, wildfires, and dust. While air quality standards focus on total PM2.5 concentrations, the Yale team analyzed six major components—sulfate, ammonium, black carbon, organic matter, nitrate, and soil dust—to determine which ones were most strongly associated with cardiovascular deaths across more than 3,100 U.S. counties.

Using two decades of nationwide mortality and pollution data, the researchers estimated that PM2.5 contributed to about 42,000 cardiovascular deaths in 2001, declining to roughly 23,500 deaths by 2020. Much of that improvement was driven by reductions in sulfate and ammonium, particles closely linked to coal-fired power plants and agricultural emissions.

“Sulfate and ammonium accounted for nearly three-quarters of the decline in PM2.5-attributable cardiovascular deaths over the study period,” said Dr. Ying Hu, PhD, the study’s lead author and a postdoctoral researcher in environmental health sciences at YSPH. “But as those components declined, others, such as black carbon, became increasingly important contributors.”

By 2020, black carbon, a component of soot produced by traffic, diesel engines, and burning, had emerged as the largest contributor to PM2.5-related cardiovascular mortality nationwide, according to the study.

The study also identified persistent and widening racial and ethnic disparities. Although PM2.5-related cardiovascular death rates declined for all groups, non-Hispanic Black and Hispanic populations experienced slower improvements than non-Hispanic white populations. Differences in population growth also contributed to this trend. Non-Hispanic Black and Hispanic populations grew faster than the non-Hispanic White population, which further widened disparities in PM2.5-related deaths.

The researchers also examined how the contribution of individual PM2.5 components to cardiovascular deaths differed across racial and ethnic groups. Compared with non-Hispanic whites, non-Hispanic Blacks were disproportionately affected by black carbon and sulfate, while Hispanic populations faced higher burdens from black carbon, dust, and organic aerosols, which are compounds released into the air by wildfires, fossil fuel consumption, soil disturbance, and other activities.

“These disparities reflect decades of structural and environmental inequities,” Dr. Chen said. “Communities of color are more likely to live near highways, industrial facilities, and other pollution sources, resulting in disproportionately higher exposure to air pollution. What’s more, they also experience systemic disparities in health care access and endure higher baseline cardiovascular risk factors, contributing to the higher burden of PM2.5-related cardiovascular deaths.”

The researchers hope their findings lead to more targeted air pollution control policies that focus on the impact of individual chemical components rather than overall pollution levels, especially as gains in U.S. air quality have slowed in recent years.

“If we want to keep reducing cardiovascular deaths and close racial and regional gaps, we need targeted strategies,” Dr. Chen said. “That means addressing PM2.5 components such as sulfate and black carbon from fossil fuel combustion and ammonium from agricultural emissions—not just lowering the average PM2.5 concentration.”