Pesticides, steroids, residual contaminants from environmental deposition, and many other sources. Drinking water when you're not thirsty is controversial and may actually overwork your kidneys if done too often; however, with the large amount of caffeine, soda, and alcohol (all diuretics) consumed by the general population, that's rarely an issue.
Obviously, I can't speak for any large body of humans without some kind of rigorous scientific evidence, but passive observation of coworkers, friends, and family leads me to believe that most people don't drink nearly enough water. It could be different where you live though.
Obviously, I can't speak for any large body of humans without some kind of rigorous scientific evidence, but passive observation of coworkers, friends, and family leads me to believe that most people don't drink nearly enough water. It could be different where you live though.