People classified by the census as non-white are exposed to 38 percent more nitrogen dioxide air pollution than people who are classified as white, the study found.

The average nitrogen dioxide concentration for non-white people in Wisconsin is 11.1 parts per billion, compared to 7.0 parts per billion for white people.

Among urban areas, Madison falls lower on the list of communities studied. Non-white Madisonians are exposed to 8.7 parts per billion of nitrogen dioxide, compared to 8.5 parts per billion for the city's white residents.

People who breathe nitrogen dioxide are subject to ailments including asthma, heart and lung disease and other respiratory illnesses.

The study's researchers estimated that if non-whites breathed the lower nitrogen dioxide levels whites experience, it would prevent 7,000 deaths from heart disease in those communities each year.

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