A half-century ago, the Rev. Dr. Martin Luther King Jr. was killed in Memphis on the balcony of the Lorraine Motel. To get to the site, which is now the National Civil Rights Museum, you can cross through neighborhoods that are as much as 97 percent black or as much as 93 percent white.

Dr. King preached that segregation was harmful not only to black Americans but also to the nation as a whole. He died before the modern environmental movement, but a growing body of research around pollution and health shows that his belief about segregation hurting everyone extends to the environment as well. Many American cities that are more racially divided have higher levels of pollution than less segregated cities. As a result, both whites and minorities who live in less integrated communities are exposed to higher levels of pollution than those who live in more integrated areas.

“The price that America must pay for the continued oppression of the Negro is the price of its own destruction,” Dr. King wrote in a 1962 address, “An Analysis of the Ethical Demands of Integration.” In it, he set out the political, ethical and spiritual reasons he believed that segregation was harmful for all. Some historians say his thoughts are applicable to understanding environmental issues today.

Researchers have known since at least the 1980s that black and Hispanic communities have higher levels of pollution and its associated harmful health effects than white communities, even when controlling for income. Studies show that racial discrimination leads governments and companies to place polluting facilities, like landfills, power plants and truck routes, in black and Hispanic communities. Race is not the only factor in environmental inequality — poorer people experience more pollution than wealthier people. But for blacks, race trumps income. Middle-class blacks experience higher levels of pollution than low-income whites.