The Power of Information

National Drinking Water Database

Selenium (total) in California

Selenium is a naturally occurring element that contaminates water due to mining or petrolum refining, fly-ash from coal-burning power plants, and irrigation of arid farmland soils high in selenium. [read more]

The Most Polluted Communities in California

443 water utilities reported detecting Selenium (total) in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies

Ranked by highest average Selenium (total) level

RankSystem Population Served Positive test results of total reported tests Average Level
1Resthaven Mobile Home Park
Paso Robles, CA
753 of 356.67 ppb
(35 to 71 ppb)
2Ken Mar Gardens
Arroyo Grande, CA
844 of 541.8 ppb
(0 to 71 ppb)
3Oceano Comm Services Dist.
Oceano, CA
6,700206 of 25834.42 ppb
(0 to 150 ppb)
4Wheeler Farms Headquarters
Bakersfield, CA
252 of 233.5 ppb
(24 to 43 ppb)
5Green River Mutual Water Co.
Paso Robles, CA
3502 of 232.5 ppb
(32 to 33 ppb)
6Austin Acres Mutual Water Company
Cazadero, CA
781 of 231.5 ppb
(0 to 63 ppb)
7Golden State Water Company - Simi
San Dimas, CA
29,2003 of 431.38 ppb
(0 to 54 ppb)
8Hidden Views Mhp Ws
King City, CA
751 of 131 ppb
(31 ppb)
9Golden State Water Company - Edna
Rancho Cordova, CA
1,940135 of 13529.67 ppb
(2.17 to 74 ppb)
10Lakeside Wd
Lakeside, CA
25,0003 of 529.43 ppb
(0 to 134 ppb)

Health Based Limits for Selenium (total)

Maximum Contaminant Limit (MCL)The enforceable standard which defines the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to health-based limits (Maximum Contaminant Level Goals, or MCLGs) as feasible using the best available analytical and treatment technologies and taking cost into consideration. Source: U.S. Environmental Protection Agency.50 ppb
Maximum Contaminant Limit Goal (MCLG)A non-enforceable health goal that is set at a level at which no known or anticipated adverse effect on the health of persons occurs and which allows an adequate margin of safety. Source: U.S. Environmental Protection Agency.50 ppb
Lifetime health-based limit, non-cancer riskConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for a lifetime of exposure. The Lifetime health-based limit (or Health Advisory, HA) is based on exposure for a a 70-kg adult consuming 2 liters of water per day. Source: U.S. Environmental Protection Agency.50 ppb
EPA Human Health Water Quality CriteriaWater quality criteria set by the US EPA provide guidance for states and tribes authorized to establish water quality standards under the Clean Water Act (CWA) to protect human health. These are non-enforceable standards based upon exposure by both drinking water and the contribution of water contamination to other consumed foods. Source: U.S. Environmental Protection Agency.170 ppb
Drinking Water Equivalent LevelA lifetime exposure concentration protective of adverse, noncarcinogenic health effects, that assumes all of the exposure to a contaminant is from drinking water. Source: U.S. Environmental Protection Agency.200 ppb

Violation Summary for Selenium (total) in California

Data from the U.S. Environmental Protection Agency includes the following violations of federal standards in California since 2004

Violation TypeNumber of Violations
Failure to monitor regularly9
Failure to monitor: Check/Repeat/Confirmation sampling1