Air pollution has dropped significantly in D.C., and around the country, over the past two decades — District-wide average pollution levels have been cut in half. But the benefits of cleaner air are not evenly distributed; neighborhoods with the most Black residents are the most impacted by dirty air. According to newly published research, in some neighborhoods in Southeast D.C., there are more than four times as many pollution-related premature deaths compared to wealthy neighborhoods in Northwest D.C.

D.C. has disparities in both health and air pollution, and those two disparities overlap: the people most vulnerable to air pollution are concentrated in the most polluted neighborhoods.

Kelly Crawford, one of the authors of the research paper, calls it a “double whammy.”

“We have communities that are already overburdened by lack of access to medical care, lack of access to food, lack of access to green space. Then on top of that, we place additional burdens in the form of urban air quality burdens in those same communities,” says Crawford, who leads the air quality division at the District Department of Energy and Environment.

The research, published in the journal GeoHealth, examines health risks from air pollution across the city, overlaying data about fine particulate matter in the air (known as PM 2.5) with data about residents’ underlying health that puts them at higher risk.

“Somebody who has really great access to health care will likely have better health outcomes than somebody who has poorer access to quality health care, even exposed to the same level of pollution,” explains Susan Anenberg, an associate professor of public health at George Washington University, another author of the research.

The health disparities in D.C. “stem from decades of race-based policies,” says Anenberg.

Likewise, the disparities in exposure to air pollution can be traced to racist housing policies that have concentrated Black residents near pollution sources.

Crawford says most of the air pollution generated within the District comes from driving, and the most congested corridors, including most of the District’s freeways, pass through Wards 5, 7 and 8. Those same wards, which have the highest percentage of Black residents in the city, also have the most industrial facilities. Crawford says that while the federal Clean Air Act, passed in 1970, has been successful curbing air pollution overall, “communities of color end up being left behind.”

Neighborhoods with high rates of premature deaths related to air pollution include Fort Dupont, Marshall Heights, Lincoln Heights, and Hillcrest in Ward 7, Washington Highlands in Ward 8, and Woodridge, Fort Lincoln, Trinidad and Michigan Park in Ward 5. Neighborhoods with the lowest rates include Woodley Park, The Palisades, and Tenleytown in Ward 3.

The underlying health disparities vary much more by neighborhood than do the disparities in pollution levels. For example, life expectancy varies greatly by neighborhood: a baby born in Woodley Park, in NW D.C., can be expected to live 21 years longer than a baby born six miles away in Congress Heights, in SE, according to DC Health data. That’s equivalent to the difference between being born in Switzerland versus being born in Haiti.

Baseline disease rates are 5 times higher in SE than in NW for lung cancer, stroke, and chronic obstructive pulmonary disease, and 9 times higher for heart disease, while emergency room visits for asthma are 30 times higher in SE zip codes, according to the study.

Air pollution varied between neighborhoods by up to 2 micrograms per cubic meter, according to the study. This difference is minor compared with how much cleaner air in the city has gotten in the past two decades: average annual PM 2.5 concentrations in D.C. have dropped from 17 μg/m3 to 8.7 μg/m3. Even the most polluted neighborhood today has far cleaner air than the least polluted neighborhood did in the year 2000.

Data on air quality is limited; in fact, there are only three federal air quality monitoring stations in the District, located at McMillan Reservoir in NW, Hains Point in SW, and River Terrace in NE.

“This monitoring network was set up to track regional air pollution,” says Anenberg. “We’re not able to measure from that sparsely located monitoring network what people in different communities are experiencing in terms of pollution levels.”

To get around that limitation, the authors used satellite data from NASA to to map air pollution concentrations across the city, filling in the gaps between the three on-the-ground sensors. Still, the satellite data isn’t detailed enough to show differences in air quality at the street or block level — something that could be addressed in future research with further innovation, such as using mobile sensors, and driving street by street.

Crawford says research like this is a first step toward addressing the inequitable impact of air pollution. Too often, she says, air quality regulations ignore, and thus perpetuate, the disparities in health risks.

“We have to take a deep dive into the regulations to see where racism was structured into those policies,” Crawford says.