An investigation by the Associated Press has found pharmaceutical residue—including antibiotics, mood stabilizers, anticonvulsants and sex hormones—in the drinking water supply of at least 41 million Americans.

Water treatment plants clean water taken from reservoirs, rivers and lakes—previous wastewater that contains the residue of pills taken by Americans across the country. However, the treatment plants often do not remove all of the residue.

Should you stop drinking tap water? Not just yet. The AP reports that the concentrations of the drugs are minuscule, far below the levels necessary for a medical dose. While the U.S. Environmental Protection Agency acknowledges that this is a “growing concern,” more research needs to be conducted to determine the long-term effects of ingesting trace amounts of pharmaceuticals in drinking water.