What about drugs? People have been flushing their unused prescriptions for years - antibiotics, painkillers, birth control.

See
http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=recs&obj=food-drink-risks.htm
for the CDC's take on treating drinking water (aimed at travelers, but applies to any questionable water).

I figure I could make myself sick worrying about all the crap in water, so I'll just add the water to my Jack Daniels.