U of M's Julian Marshall surprised by public health implications of race-air pollution study

The more yellow an area, the higher the nitrogen dioxide levels. Orange depicts particularly high concentrations.

The more yellow an area, the higher the nitrogen dioxide levels. Orange depicts particularly high concentrations.

Because people of color tend to live near highways or power plants, they're exposed to a lot more nitrogen dioxide than whites, a new study finds. As a result, there are about 7,000 heart disease deaths in America each year that wouldn't happen if nonwhites were exposed to the same NO2 levels as whites.

That dramatic finding surprised University of Minnesota environmental engineering professor Julian Marshall, who coauthored "National Patterns in Environmental Injustice and Inequality: Outdoor NO2 Air Pollution in the United States" along with Lara Clark and Dylan Millet.

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"It's a huge health impact, and that's surprising, shocking," Marshall tells us. "If we had found there are big differences by income, then, you know, there's all kinds of things that high-income people can buy their way out of... that's how the free market works. But that's not what we found."

"There are disparities [in NO2 exposure] by income, but the disparities by race are larger even after you account for income," Marshall continued. "I can't really put together an ethical justification for that the way I can for income."

Another surprise, Marshall says, is that some cities with relatively clean air, such as Minneapolis, still have large gaps between NO2 exposure levels for whites and nonwhites.

"In our model, the concentration in the Twin Cities, like in most cities, are higher downtown and along major roadways," Marshall says. "Concentrations are higher where traffic is."

In Minnesota, people of color are exposed to about 45 percent more NO2 than whites, according to the study (9.9 parts per billion versus 6.8, respectively). The racial gap is smaller in the Twin Cities, where nonwhites are exposed to 18 percent more N02 than whites, but overall air pollution levels are higher, with people of color being exposed to 11.7 NO2 particles per billion, while whites are exposed to 9.9.

To see an interactive map of NO2 concentration levels throughout the country, click here. The Twin Cities NO2 map at the top of this post is a screengrab from it.

-- Follow Aaron Rupar on Twitter at @atrupar. Got a tip? Drop him a line at [email protected]