EPA works with states, tribes, operators of public water systems, and certified laboratories to ensure safe drinking water. Climate change may affect drinking water quality as a result of an increase in the frequency and intensity of storms and warmer air temperatures.

More frequent storms and floods may cause overflows from sewage systems and treatment plants into freshwater sources for drinking water. This may lead to an increase in the prevalence of water-borne parasites, such as Cryptosporidium and Giardia. These parasites can cause gastrointestinal distress and in severe cases, death.