The dangers of discarded drugs getting into drinking water supplies have been under study for more than a decade and although it appears humans are not directly threatened, the same cannot be said for fish and other creatures living in waters tainted by pharmaceuticals. The link below provides a very good explanation of the problem facing fish on drugs. Thanks to my friend Mike Campagna for alerting me to this video.
http://www.youtube.com/watch?v=OYbRlJLBzn4&feature=youtu.be