U of M study: Race matters most in determining who breathes bad air

The Twin Cities earn yet another racial disparities distinction


By Isaac Peterson
Contributing Writer

In April, researchers at the University of Minnesota released a study showing that people of color in the U.S. typically breathe air that is 38 percent more polluted compared to their White counterparts. The study concluded that race and income are major contributing factors in how much polluted air is breathed, but that race matters more than income.

Using satellite observations, data from the Environmental Protection Agency (EPA), and maps of land uses, the research team was able to compare the geographic data with Census figures to determine socioeconomic disparities in air pollution exposure. The study was national in scope and provided information on air pollution on a nationwide basis, broken down to show comparisons between urban and rural areas as well by city, county, and state.

Disparities by race-income: The more red and the higher the numbers, the greater the pollution disparities between lower-income people of color and higher income Whites. (graphic from U of M study)

The pollutant the study tracked was nitrogen dioxide (NO2), one of the main pollutants targeted by the EPA, which considers it one of the most significant threats to air quality. NO2 has been linked to asthma and heart disease. Sources of NO2 include vehicle exhaust and power plants.

Although overall levels of pollution are down nationwide in recent years, throughout the United States, findings indicate that people of color are still exposed to 38 percent more NO2 than their White counterparts.

Minnesota ranked number 15 nationwide in airborne pollution disparities.

As mentioned above, the disparity gap in pollution exposure showed that although income is a factor, race appears to be a more important factor. For instance, when broken down by race and income, the study found that when compared to low-income Whites, high-income Hispanics experience higher exposure to airborne NO2.

The causes of the disparities were not examined by the research team. Lara Clark, one of the study’s three authors, told us, “Other people have looked at this problem and underlying causes, and there are a lot of contributing factors. Some might argue that it’s economics — property values are lower where pollution is higher.”

While reiterating that the exposure disparities are “not just an economic problem,” Clark went on to speculate on other likely contributing factors: “conditions like discrimination in housing and segregation”; which voices are heard in the community; decision-making processes about where highways will run, resulting in higher traffic in lower-income communities; and closer proximity to industrial sites. All these likely play important roles in the results they found.

Clark also provided the MSR with the following technical information:

“Minneapolis-St. Paul has the 16thhighest disparities in NO2 concentrations between low-income nonwhites and high-income Whites among 448 urban areas (or, higher disparities than 96 percent of the cities). In Minneapolis-St. Paul, NO2 concentrations are 3.7 parts per billion, or 33 percent higher for low-income nonwhites compared to high-income Whites.

“Minneapolis-St. Paul has the 40thhighest disparities in NO2 concentrations between nonwhites and Whites [irrespective of income] among 448 urban areas (or, higher disparities than 91 percent of the cities). In Minneapolis-St. Paul, NO2 concentrations are 1.8 parts per billion, or 17 percent higher for nonwhites than Whites.

“For comparison, Minneapolis-St. Paul has the 189thhighest NO2 concentration (population-weighted mean) among 448 urban areas [or, more polluted than 58 percent of the cities]. The population-weighted mean NO2 concentration in Minneapolis-St. Paul (10.2 parts per billion) is lower than the overall national urban mean (14.2).”

The lead author of the study, Julian Marshall, has remarked that other research results “…estimate that if nonwhites breathed the lower NO2 levels experienced by Whites, it would prevent 7,000 deaths from heart disease alone among nonwhites each year.”

The study, titled “National patterns in environmental injustice and inequality: Outdoor NO2 air pollution in the United States” appeared in the April 15 issue of the journal PLOS ONE.


Isaac Peterson welcomes reader responses to ipeterson@spokesman-recorder.com.

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