For more than a decade, studies have shown that pharmaceutical drugs and their by-products are finding their way into the water supply, affecting the drinking water of millions of Americans.

A 2002 U.S. Geological Survey study found that 80 percent of the streams tested had measurable amounts of drugs, steroids and reproductive hormones. Recent studies of Philadelphia-area supplies showed 56 pharmaceuticals or their by-products in treated drinking water; 63 such compounds were discovered in city watersheds.

This is mostly a legacy of being rich enough to afford good health care. The sources for our local water have concentrations of these compounds, but the good news is that water-treatment facilities have good ways to filter out most of them.

It's not clear yet how trace pharmas in water affect the human body. The amounts are extremely tiny - but they are powerful, they're there long-term, and who wants them? It's not cause for panic or paranoia - it's cause for more study.

What science does know is that trace pharmas in water have a profound effect on plant and animal populations around the world. No doubt about that one.

How do the drugs get there? One way we can't do much about: They move through the human body and out again into the water supply.

What we can change is the heedless way we dispose of the drugs. We throw them in the trash - or, worse, flush them right into the water supply.

So what should we do with untaken drugs?

Follow the advice of the Office of National Drug Control Policy:

(a) Trash with care - mix them with coffee grounds or cat litter (to discourage garbage drug thieves), seal them in a plastic bag, and then put them in the trash. Dumps and landfills often have linings that can prevent properly sealed drugs from leaching into groundwater.

(b) Use drug take-back programs, run by some hospitals and pharmacies (check with your local) and a few drug companies.

In the Pennsylvania legislature, House Bill 2073, now in committee (but it's been there since November - giddyup!), is a good start. It requires drug retailers to have take-back programs, and to inform consumers of disposal options for unused drugs.

A lot else could happen:

Towns have special days and ways for picking up trees, electronic components, batteries, etc. Why not do the same for unused drugs? Models exist in Oregon, Wisconsin and California.

Drug companies should continue trying to design drugs so that their post-metabolic remains are not water-soluble.

Everyone is entitled to water he or she can trust - and by and large, we have it. You are what you drink - but you shouldn't be what other folks throw away.