Transportation-related pollution is more prevalent in neighborhoods of people of color, according to a new UW study.

From 2000 to 2010, researchers at the University of Washington looked at exposure to nitrogen dioxide (NO2)-- a pollutant that can come from vehicle exhaust, power plants and off-road equipment--in neighborhoods across the United States. The researchers found that people of color were, on average, consistently exposed to more air pollution than their white non-Hispanic counterparts during the decade.

The researchers conclude that if people of color had breathed the lower NO2 levels experienced by whites in 2010, it would have prevented an estimated 5,000 premature deaths from heart disease. NO2 is linked to asthma symptoms, increased susceptibility to respiratory problems and heart disease.

“The finding that shocks us is that when it comes to how much NO2 a person breathes, it’s still race that matters,” said senior author Julian Marshall, UW professor of civil and environmental engineering. “At any income level — low to medium to high — there’s a persistent gap by race, which is completely indefensible. It says a lot about how segregated neighborhoods still are and how things are segregated.”

The UW study did not explore the underlying reasons for that gap, but its findings are consistent with previous research. The study claims that both racial minorities and low-income households are disproportionately likely to live near a major road where transportation-related pollution is typically highest.

The UW team concluded that the narrowing of the racial gap in NO2 exposures was driven more by improving air quality than by demographic changes over the 10-year period.

“That suggests that air pollution is coming down faster than cities are becoming less segregated,” Marshall said.