Tiny amounts of pharmaceuticals -- including antibiotics, hormones, mood stabilizers, and other drugs -- are in our drinking water supplies, according to a media report.

In an investigation by the Associated Press, drinking water supplies in 24 major metropolitan areas were found to include drugs.

According to the investigation, the drugs get into the drinking water supply through several routes: some people flush unneeded medication down toilets; other medicine gets into the water supply after people take medication, absorb some, and pass the rest out in urine or feces. Some pharmaceuticals remain even after wastewater treatments and cleansing by water treatment plants, the investigation showed.

Although levels are low -- reportedly measured in parts per billion or trillion -- and utility companies contend the water is safe, experts from private organizations and the government say they can't say for sure whether the levels of drugs in drinking water are low enough to discount harmful health effects.

WebMD asked experts to give their take on the potential risks of drugs in the water supply.