Scientists testing the beds of streams around Portland found the residue of the region's medicine cabinets and coffee shops. The list of compounds includes many known by such names as Prozac, Tagamet, Benadryl, and Micatin, as well as the caffeine that makes the Northwest edgy.

http://news.yahoo.com/s/ap/20070507/ap_on_sc/rivers_drugs_1

How did people think that wasn't going to happen? The right way to purify water is "too expensive," and most of what our technology produces is not easily broken down. This is why environmentalists say humans have a bigger effect than is easily seen: just because a forest is outside the city walls doesn't mean our effects have not changed it thoroughly.