Some 41 million Americans are drinking water contaminated with traces of pharmaceuticals, an investigation has revealed.
Drugs found in the water supply include traces of medicines used to treat anxiety and epilepsy in southern California; high cholesterol, asthma and heart problems in Philadelphia; and angina in New Jersey. In San Francisco, researchers found traces of a sex hormone.
According to the investigation, conducted over five months by the Associated Press, drugs were found in the drinking water in 24 major metropolitan areas. It also found that 28 of the 35 watersheds tested showed traces of drugs.
AP reviewed hundreds of scientific reports, analysed federal drinking water databases, visited environmental study sites and treatment plants and interviewed more than 230 officials, academics and scientists.
The federal government does not require any testing for drugs in drinking water, and sets no limits on the permissible levels of drugs.
But while there are no federal regulations governing the levels of pharmaceuticals in the US water supply, the federal government's Environmental Protection Agency said it was aware of the problem.
"We recognise it is a growing concern and we're taking it very seriously," Benjamin Grumbles of the EPA told AP.
The drugs are passed through the bodies of people taking medications, or they are directly disposed of into the water supply.
The use of pharmaceuticals has soared in the US, with a 12% rise over the last five years in pharmaceutical prescriptions, to 3.7bn. The number of non-pharmaceutical prescriptions issued during the same period remained unchanged, at 3.3bn.
Although the concentrations found in the water supply are minimal, their presence raises concerns about the effects of long-term exposure to unregulated and unintended combinations of drugs.
The study shows that water sampled in Philadelphia included traces of 63 drugs, while the water in Washington DC included six pharmaceuticals. In New Orleans, researchers found a pain reliever, a sex hormone and an anti-cholesterol drug.