Doctors prescribe hydrocodone for pain. They recommend ranitidine for acid reflux, a diuretic called hydrochlorothiazide for congestive heart failure.

But you don’t need a prescription to get these drugs in tiny doses. They're found already in our nation's water supply—and, according to an upcoming national study, the largest done so far, in higher amounts than drug companies anticipated.

We know how the drugs get there: Our bodies release them when we urinate or flush old drugs down the toilet. And it’s well known by now that pharmaceuticals are affecting fish, frogs and lobsters­—small amounts of estrogen cause male fish to develop eggs, for instance. But the impact on human health is unclear. Although research on pharmaceuticals in the water supply began almost a decade ago, no one seems to know which compounds need to be removed or how to remove them from the water safely. And no one seems to know which government agency should step forward and take action.

“All of these drugs out there on the market are going to be discharged into the environment and we don’t know what the effects are, because there’s no requirement to do an assessment on the front end,” said Nick Schroeck, executive director of the Great Lakes Environmental Law Center in Detroit.

“We’re not trying to scare anyone, but we need to know what these chemical compounds will do to the environment and what are the long-term effects for humans. No one seems to know.”