A scientific study into the public health risks of mountaintop-removal coal mining has been halted by the Interior Department. Officials in West Virginia asked the Obama administration to look into the health effects of mountaintop mining last year. Mountaintop mining has occurred on at least 500 Appalachian mountains.

Mountaintop mining is a technique used to extract coal that dates back to the 1960s. Mining companies dump the rubble created by the process into the surrounding valleys and streams. In many cases, this dumping leads to extensive pollution with heavy metals, such as selenium and manganese. Both of these substances can be toxic in high concentrations.

Mountaintop mining has been linked to the development of lung cancer, heart disease, and other medical problems. A 2010 study found that counties near mountaintop mining had higher rates of lung cancer and kidney disease, as well as higher mortality rates. A 2011 study found a higher rate of birth defects in central West Virginia.

The researchers for the study, which begun under President Obama, said that they had been ordered to stop working while Interior Department conducts an agency-wide budgetary review. Heather Swift, with the Interior Department, said a review of grants and cooperative agreements that cost more than $100,000 is being done to ensure tax dollars are used effectively. Swift said that the Trump administration “is dedicated to responsibly using taxpayer dollars and that includes the billions of dollars in grants that are doled out every year by the Department of the Interior.”

The National Academies of Sciences, Engineering, and Medicine was conducting the study. A panel of 12 experts was assembled to study the health risks for people living near Appalachian surface coal mines. The study was expected to take two years to complete and cost about $1 million. Spokesman William Kearney said, “The National Academies believes this is an important study and we stand ready to resume it as soon as the Department of the Interior review is completed.”

Luke Popovich, a spokesman for the National Mining Association, said, “The National Institute of Environmental and Health Sciences concluded in July that after examining available studies, it didn’t see evidence justifying a health hazard, noting that no conclusive evidence connected mountaintop mining with health effects and that studies often failed to account for extraneous health and lifestyle effects.” Earlier this year, the National Institute of Environmental and Health Sciences published a review that acknowledged that it can be difficult to control for variables like poverty in these types of studies.

The Interior Department decision received sharp condemnation from environmental groups. Democrats also criticized the decision. Representative Raúl M. Grijalva of Arizona, the ranking Democrat on the House Committee on Natural Resources, said of the decision, “Stopping this study is a ploy to stop science in its tracks and keep the public in the dark about health risks as a favor to the mining industry, pure and simple.”