The United States should declare a moratorium on hydraulic fracturing, also called fracking, for natural gas in populated areas until the health effects are better understood, doctors said at a conference on the drilling process, Bloomberg reported.

Gas producers should set up a foundation to finance studies on fracking and independent research is also needed, said Jerome Paulson, a pediatrician at George Washington University School of Medicine.

Fracking injects water, sand and chemicals into deep shale formations to free trapped natural gas. A boom in production with the method helped increase gas supplies, cutting prices 32 percent last year. The industry, though, hasn’t disclosed what chemicals are used, raising concerns about tainted drinking water supplies and a call for peer-reviewed studies on the effects. The U.S. Environmental Protection Agency is weighing nationwide regulation.

The gas industry has used hydraulic fracturing for 65 years in 30 states with a “demonstrable history of safe operations,” an industry advocate told Bloomberg in an email.

U.S. natural gas production rose to a record 2.5 trillion cubic feet in October, a 15 percent increase from October 2008.