Congress held its first hearing Wednesday on the Flint, Michigan water crisis, and the outrage over the city’s lead-polluted water was palpable. “This is failing at every level,” Rep. Jason Chaffetz, chairman of the U.S. House Committee on Oversight and Government Reform, told the packed room. Critics have called the Flint crisis –and the government’s failure to act promptly –an example of environmental racism, noting the city is mostly black and poor.

In fact, a new study published in Environmental Research Letters lends credence to the idea of “environmental racism,” showing that the biggest polluters in the U.S.– factories, warehouse and other facilities using toxic substances — are overwhelmingly located in poor, non-white neighborhoods. Another study, also published in January in the same journal, shows that hazardous waste treatment, storage, and disposal plants also tend to be built in similar low-income, non-white areas.

Taken together, the studies strongly suggest that low-income communities of color have been the biggest victims of industrial pollution for decades.

Researchers Mary Collins of the State University of New York College of Environmental Science and Forestry and Ian Munoz and Joseph JaJa from the University of Maryland looked at public data from the Environmental Protection Agency (EPA). They profiled 15,758 industrial sites responsible across many industries for more than 1 billion chemical releases. Of those, 809 sites, about a 5% of the total, were responsible for 90% of the pollution. The paper refers to these 809 sites as “toxic outliers.”

Poor, Minority Communities Most Likely To Be Polluted

By using additional data from the U.S. Census, the researchers determined that the polluters were virtually all located near minority or poor communities; of course, residents in these areas often have the least resources and clout to fight problems. The researchers theorized that these areas are “sacrifice zones,” in which the big polluters “can exist without the focus they might receive in other locations.”

The second study — by researchers Paul Mohai of the University of Michigan and Robin Saha from the University of Montana — came to similar conclusions. The researchers examined hazardous waste sites and the neighborhoods in which they were located and found “strong evidence” that the polluting facilities were situated in areas that either were already non-white and low-income. or that were already seeing white flight.

“What was surprising in our finding was the demographic changes started a decade or two before the siting,” Mohai told Fortune. “It doesn’t appear the facilities caused the demographic change. The demographic change in effect caused the siting of the facilities.”

Ironically, the concentrated nature of the problem could make it easier for governments, regulators, and industries to address, according to Collins. Rather than trying to spread resources across all polluting sites, they could focus on the relatively few that cause most of the problem. That might also reduce the regulatory burden for most companies.