How are people exposed to arsenic?

  • Naturally occurring arsenic in groundwater used for drinking is a major source of inorganic arsenic exposure. Groundwater contamination occurs when, under certain conditions, naturally occurring arsenic deposits in bedrock dissolve and seep into groundwater.
  • The main exposure to arsenic is via ingestion of drinking and cooking water, because arsenic is poorly absorbed through the skin.  However, treating all the water in the home is the most effective way to reduce arsenic exposure. 
  • During gestation, the developing fetus is exposed to arsenic via passage across the placenta from mother's blood to the baby's blood. In contrast, breast milk is safe, and does not contain inorganic arsenic.
  • The information provided here is focused on groundwater from private wells since it can be a common route of exposure for people; however, some exposure can also come from low levels of arsenic in certain foods. More information on exposure from food and other sources besides groundwater is available at