An investigation by the Associated Press published in March 2008 reported that trace amounts of prescription medications were present in drinking water supplies across the United States. These drug residues enter the water system because many medications are not fully absorbed by the body and are excreted, eventually reaching sewage systems. Although wastewater is treated before being released back into the water supply, standard treatment processes do not completely remove all pharmaceutical compounds.
The Associated Press investigation found detectable levels of medications in the water systems of 24 metropolitan areas. The substances identified included antibiotics, sex hormones, pain medications, antidepressants, and cholesterol-lowering drugs, all present in very small concentrations. In total, pharmaceutical residues were found in 28 of 35 metropolitan areas evaluated. Of the remaining areas, six had not tested for pharmaceutical contamination, and one was still awaiting test results at the time of publication.
