Arsenic in drinking water is a serious health risk — it is colorless, odorless, and tasteless. High arsenic levels are common in well water across the western US and New England.
Arsenic is a naturally occurring element found in rocks and soil. As groundwater flows through arsenic-bearing geology, it dissolves arsenic into the water supply. This is particularly common in the western United States, New England, Michigan, Wisconsin, and Minnesota — but elevated arsenic has been found in wells across all 50 states.
The EPA maximum contaminant level (MCL) for arsenic in drinking water is 10 parts per billion (ppb). Long-term exposure above this level is associated with increased risk of bladder, lung, and skin cancers, as well as cardiovascular and neurological effects. A laboratory water test is the only way to know if your water contains arsenic.