Estrogen is one thing that is found. Results in an increase in man-boobs? Whos to say... Prozac is another (found in water supply in England).

And then... There is the controversy over flouride in the water.
One side is: prevents tooth decay
Another side is: sedates a population (worked quite well in army populations to that effect). Look at the civil unrest with govt. etc in populations with flouride in the water... Whos to say.

I've heard that if people drank tap water (that is perfectly drinkable) and donated the money they spent on bottled water to the appropriate charity... Then we would have enough money to sponser clean drinking water for all.

Interesting thought...