Cancer incidence associations with drinking water arsenic levels and disinfection methods in Maine, USA.

Maine is a largely rural state where nearly half of the population uses drinking water from private wells. Arsenic (As) is present in some Maine groundwater, has been linked to cancer, and a lack of testing and treatment may expose people with private wells to elevated As levels. Disinfection byproducts (DBPs) include known and suspected carcinogens that form when chlorine or chloramines are added to water.