Arsenic is a naturally occurring element in the earth’s crust that is widely distributed in the environment. Arsenic is often found in groundwater, mostly due to natural sources. It is also used in the commercial production of pesticides, herbicides, wood preservatives, ammunition, semiconductors, lasers and solar cells. Other sources of arsenic in water include mining, smelting, wastewater, urban runoff and atmospheric deposition.

The federal Maximum Contaminant Level (MCL) of 10 micrograms per liter (µg/L), or 10 parts per billion (ppb), for arsenic was implemented in January 2006. California adjusted its arsenic MCL from 50 ppb to 10 ppb in November 2008.

Golden State Water routinely monitors and tests for more than 230 contaminants, including arsenic, to ensure the water we deliver to customers meets all state and federal drinking water standards. Golden State Water makes water quality information available via annual Consumer Confidence Reports (CCR).

As your water provider, we continually invest in water infrastructure, treatment and testing and take great pride in providing you with high-quality, reliable water.

Frequently Asked Questions

Q:  Has arsenic been detected in my drinking water?
A: All water served is below the MCL for arsenic. In 2017, arsenic was detected at levels below the current MCL in treated drinking water in 12 of our 38 water systems. Some of Golden State Water’s groundwater sources contain arsenic levels above the MCL, and water from those wells is treated using an oxidation/filtration process that utilizes adsorption onto iron hydroxides to remove arsenic to levels below the MCL. Click here to see the most recent results for arsenic levels detected in our treated drinking water.

The water served to customers in each of Golden State Water’s water systems meets all state and federal drinking water standards for arsenic.

Q:   How is arsenic removed from contaminated source waters?
A:  Arsenic can be removed using a number of advanced drinking water treatment technologies, including ion exchange, coagulation/filtration processes, membrane filtration and chemical adsorption using iron oxides. Golden State Water uses an oxidation/filtration process that utilizes adsorption onto iron hydroxides to treat its drinking water sources with arsenic levels above the MCL.

Resources for Additional Information

State Water Resources Control Board