During the years that community health researcher Jill Johnston lived and worked in San Antonio, Texas was experiencing an explosion of fracking. She and the community partners she worked with on environmental health issues had a strong hunch that most of the fracking wastewater wells were being located near communities of color. So, they decided to dig a little deeper and quantify the pattern.

The results of that effort were published this month in the American Journal of Public Health. It turns out that Johnston and her colleagues were right — the study found that fracking wastewater disposal wells in southern Texas are disproportionately permitted in areas with higher proportions of people of color and people living in poverty. It’s a pattern that many researchers and advocates describe as “environmental injustice.” Environmental justice, according to the U.S. Environmental Protection Agency, is the “fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies.”

“Those who are profiting off all the oil and gas extraction in the Eagle Ford Shale (in south Texas) are very different communities from the people who bear the externalities of fracking,” Johnston, now an assistant professor of preventive medicine at the University of Southern California Keck School of Medicine, told me. “Who’s getting the benefits and who’s getting left with the waste and the potential negative consequences?”

Johnston and her colleagues examined the pattern of fracking wastewater wells in Texas, with a focus on the Eagle Ford Shale area, a top-producing oil and gas region that covers 26 counties and where more than 1,000 new disposal wells have been permitted since 2007. According to the study, about 100,000 oil and gas wells had been drilled in the U.S. as of 2012, and each needs about 11 million to 19 million liters of water for drilling. Mixed into that water is sand and a combination of chemicals, some of which have been tied to serious health problems and disease. (To read personal health stories from the people living in the Eagle Ford Shale, read this investigative series from the Center for Public Integrity.) At each extraction well, about 5.2 million liters of fracking fluid comes back up as wastewater that’s eventually injected into a disposal well, where it has the potential to seep into drinking water supplies. In fact, the study noted that higher concentrations of chloride and bromide have been detected in groundwater that’s in closer proximity to disposal wells.

“We don’t really know yet what the consequences of these new disposal wells will be, but some of the concern is that communities in south Texas almost entirely rely on groundwater for drinking water,” Johnston said.

To analyze the disposal well pattern, Johnston and her colleagues — who were asked to conduct the study by local community groups — examined disposal well permit data between 2007 and 2014 as well as the racial composition of people living with 5 kilometers and farther from a disposal well. In that time period, they identified 1,152 disposal well permits in the study region as well as 23,435 oil and gas well permits. Overall, the proportion of people of color living near a disposal well was 1.3 times higher than the proportion of whites living near a disposal well. In census blocks with 40 percent or fewer people of color, 10 percent of people lived within 5 kilometers of a disposal well; in areas with between 40 and 60 percent people of color, 12.4 percent lived near a disposal well; and in areas with 60 to 80 percent people of color, 15.5 percent lived near a disposal well.

When it came to oil and gas extraction wells, slightly more white residents lived within 5 kilometers of an extraction well than people of color, though the study also noted that whites own more than 85 percent of the land in the Eagle Ford region. The study also found that 16 percent of the area’s domestic water wells were within 5 kilometers of a disposal well and 1.3 percent were within 1 kilometer. Study authors Johnston, Emily Werder and Daniel Sebastian write:

Permitted disposal wells can be actively used for decades, receiving millions of gallons of toxic wastes, whereas the active life of an extraction well is typically a few years. The Energy Policy Act of 2005 specifically excludes the underground injection of oil and gas fluids from the Safe Water Drinking Act, which authorizes the Environmental Protection Agency to regulate chemicals in drinking water to protect public health. Current regulations allow the oil and gas industry to inject and indefinitely store hazardous materials underground and near drinking water supplies.

“Unfortunately, we weren’t surprised,” Johnston said of the study results. “This pattern of waste being disproportionately located near people of color is a national trend and something we’ve seen for the past several decades.”

Johnston noted that most people in the area rely on private drinking wells rather than regulated community drinking water systems, which fall under EPA standards. But even when it comes to regulated water systems, she said EPA standards don’t necessarily account for all the chemicals found in fracking wastewater. In addition to the potential for drinking water contamination, disposal wells also come with air quality risks associated with daily truck traffic and growing evidence that such injection wells are linked to an increase in seismic activity.

She said that the communities of color and poverty that tend to live closer to wastewater disposal wells may also have fewer resources with which to deal with any negative health impacts. Such communities may also face less access to information about where disposal wells are being located. Johnston said regulations only require that disposal well operators alert adjacent property owners.

“I hope (the study) can help raise awareness around wastewater disposal as a potential public health risk of fracking,” Johnston said. “And help us consider the environmental justice impacts of both whether fracking is occurring and where the waste is going.”

To read a full copy of the study, visit AJPH.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for nearly 15 years.