A new health study in Eastern Kentucky has found that residents in a county where surface mining is prevalent have a higher instance of illness than residents in two control counties.

West Virginia University professor Michael Hendryx analyzed information from 952 adults in Eastern Kentucky. Some of the subjects were from Floyd County, where about two-thirds of the coal mined comes from surface mines. The rest were in Rowan and Elliott counties, where there’s no coal mining but comparable socioeconomic factors. The surveys were done by a Christian group called Restoring Eden, which advocates for environmental stewardship.

Hendryx controlled for factors like age, obesity and cigarette smoking. Even so, he found that people who lived in Floyd County were at significantly elevated risk for a variety of health problems, like hypertension, COPD and asthma, as well as general poor health.

Previous studies have shown higher instances of air pollution in coal counties, as well as higher rates of cancer and birth defects. A lot of the air issues in these counties have been linked to silica dust, which can come from blasting away rocky overburden at mountaintop removal sites.

This study only looked at health data, and can only conclude that the Floyd County residents surveyed were more likely to suffer from poor health than those surveyed from Rowan and Elliott counties. Hendryx says it’s nearly impossible to link one environmental problem with a specific health effect, but he thinks enough evidence exists to suggest policymakers should act.

“The environmental contribution is not the only thing going on,” he said. “These communities have populations that are in poor health for a number of reasons. But I think there is an environmental contribution. I can’t prove it, but just based on everything I’ve seen, I believe that there is.”

He says based on the precautionary principle, there’s enough evidence that links coal mining and health problems that it’s prudent and ethical to address the problem.

Hendryx has conducted numerous studies on coal mining’s effect on health, and the coal industry pointed to this body of work to discredit the most recent study. Another criticism involved the inclusion of Rowan County as a control county; though it’s in Eastern Kentucky, the county is home to Morehead State University and close to Lexington. House Speaker Greg Stumbo argued that the higher education levels and per capita income in Rowan County mean that it’s not a reasonable comparison. Hendryx acknowledged the potential problem, but says it was important to choose a nearby county where there’s no coal mining, and he thinks the comparison is a fair one.