Arsenic in Drinking Water: Testing and Treatment
How arsenic enters well water and what removes it.
A natural contaminant
Arsenic occurs naturally in rock formations across the US, particularly in the Southwest, New England, and Upper Midwest. It dissolves into groundwater and is the most common contaminant in private wells that exceeds health standards. The EPA MCL is 10 ppb. Long-term exposure above this level increases risk of skin, bladder, and lung cancer.
Who is at risk
Private well owners are most at risk because wells are unregulated. Municipal systems are required to test and treat for arsenic. States with the highest arsenic rates include Nevada, Arizona, Maine, New Hampshire, and Michigan.
Treatment
Reverse osmosis (point-of-use) removes 95%+ of arsenic. Specialty adsorptive media (iron-based) designed specifically for arsenic is effective for whole-house treatment. Standard carbon filters do NOT remove arsenic. Testing is essential because arsenic is odorless, colorless, and tasteless.