Shampoo, Cosmetics May Form Cancer-Causing Substance in Water Supplies

Your shampoo may seem harmless, but it could be contributing to the formation of a mysterious, cancer-causing substance, a new study says.

New research reveals that common household products such as shampoo can interact with disinfectants at U.S. wastewater treatment plants to form a little-studied class of cancer-causing substances. These substances, called nitrosamines, can end up in drinking water, experts say.

(Related: "Cocaine, Spices, Hormones Found in Drinking Water.")

Several nitrosamines, including the chemical NDMA, a focus of the new Yale study, are classified by the U.S. Environmental Protection Agency (EPA) as probable human carcinogens.

Nitrosamines form in small amounts when exposed to chloramine, the disinfectant of choice at the nation's wastewater treatment plants. The chemical—a combination of chlorine and ammonia—has been used increasingly in drinking water disinfection since the EPA set limits for better-known toxic substances that can arise from the use of chlorine, the traditional disinfectant.

Though inconclusive, the study suggests "it's entirely possible that we're producing more problems—and maybe even worse problems—with chloramines," said David Reckhow, an environmental engineer at the University of Massachusetts in Amherst who was not involved in the new study.

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