Arsenic in Drinking Water

What is arsenic and where does it come from?

Arsenic occurs naturally in the earth's crust. Most arsenic in drinking water comes from natural rock formations. As water flows through these formations, it can dissolve arsenic and carry it into underground aquifers, streams, or rivers that may become drinking water supplies. Arsenic also can come from human activities, such as mining or smelting ores that contain arsenic. In the past, it was used in commercial wood preservatives and agricultural chemicals.

Drinking water standard for arsenic

For many years, the drinking water standard for arsenic was 50 parts per billion (ppb). The U.S. Environmental Protection Agency (EPA) tightened the standard from 50 ppb to 10 ppb in January 2001 for federally regulated (Group A) community and nontransient noncommunity (NTNC) water systems. EPA changed the arsenic standard to reduce people's long-term exposure to arsenic in drinking water, which has been linked to chronic health issues.

Washington State adopted the revised arsenic standard January 14, 2004.



External Links to more Arsenic information

DOH Arsenic Contacts:

For drinking water and statewide source monitoring questions, call the regional office nearest you:

Southwest Regional Office, Tumwater: 360-236-3030

Northwest Regional Office, Kent: 253-395-6750

Eastern Regional Office, Spokane: 509-329-2100