Every few months, along with the water bill, I receive a little brochure from the water company that assures me that the level of coliform and fecal bacteria in the water that flows through the taps has been tested at well below required levels. Ditto for the amounts of lead and other heavy metals and nitrates. One important missing category, however, is the residues of pharmaceuticals which have been dumped or excreted into the water sources.
This article gives an indication of the effects of these pharmaceuticals making it into the water supply:
Pharmaceuticals have since been found in treated sewage effluents, surface waters, soil, and tap water, though at very low levels (parts per trillion, ppt). These levels are unable to induce acute effects in humans, i.e., they're far below the recommended prescription dose, but have been found to affect aquatic ecosystems. To date, most attention has been focused on hormone disruption in fish due to pharmaceutical estrogens present in the environment, and the rise of bacterial pathogens resistant to conventional antibiotic treatment due, in part, to their exposure to sub-lethal levels of antibiotics in their environment. Antibiotics and estrogens are only two of many pharmaceuticals suspected of persisting in the environment either due to their inability to naturally biodegrade or continued prevalence as a result of continuous release. Other studies have shown antidepressants to trigger premature spawning in shellfish while drugs designed to treat heart ailments block the ability of fish to repair damaged fins.
Recent monitoring studies fail to address one question: Are the levels of pharmaceuticals in the environment significant? At first glance, one would say 'no' since levels found in the environment are six to seven orders of magnitude lower than therapeutic doses in spite of the fact up to 90 percent of an oral drug can be excreted in human waste. Low and consistent exposures wouldn't likely produce acute, notable effects but rather subtle impacts such as behavioral or reproductive effects that could very well go unnoticed. The good news is any threat to human health is probably not imminent but rather long-term.
So it's not merely the direct route from adulteration of food products such as melamine in pet food and now, Chinese infant formula and milk, or the long-term effect of Bisphenol A used in polycarbonate plastics that is associated with an increase in heart disease and diabetes, apart from phytoestrogenic effects.
Wonder chemicals and drugs are the double-edged sword of modern life. There is probably little we can do to reduce our exposure to these, no matter how hard we might try to avoid it by going 'green', switching to bottled water (bisphenol exposure, anyone?) or switching to organic/hormone free food only.