A study published in Nature Communications found that racially segregated communities are exposed not only to greater amounts of air pollution but levels of airborne toxic metals 10 times higher than more well-integrated areas.

Lead researcher and environmental scientist Jack Kodros said in a Washington Post article that highly segregated communities are breathing a particularly concentrated and more toxic form of air pollution that contains carcinogenic metal components.

For the study, researchers analyzed and differentiated between components in fine-particle air pollution and the toxic airborne metals within it. The components were then separated into two categories: airborne metals—lead, copper, nickel, zinc—caused by human activities, such as manufacturing and refining, and those occurring naturally, like iron and vanadium.

Researchers then used the “dissimilarity index,” a commonly used method of measuring segregation, to determine the integration of observed communities. They found that areas that were highly segregated had mass proportions of human-caused pollution that were three to 12 times higher, on average, than well-integrated areas and the concentration of toxins produced by human activities were five to 20 times higher in highly segregated areas compared with well-integrated ones.

“Industries such as fossil fuel, coal and other industries create toxic footprints in Black communities that exacerbate long-term health issues for Black communities,” said Abre’ Conner, the NAACP’s director of environmental and climate justice.

Average concentrations of lead, known to cause brain and kidney damage and potentially harm unborn children, were five times higher in highly segregated counties compared with well-integrated ones.

“We must continue to center Black communities and communities of color in any solutions and investments regarding environmental injustices,” Conner said.