The Power of Information

National Drinking Water Database

Diquat in California

Diquat is a non-selective herbicide and dessicant used extensively for control of crop and aquatic weeds; it may cause cataracts. [read more]

The Most Polluted Communities in California

8 water utilities reported detecting Diquat in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies

Ranked by highest average Diquat level

RankSystem Population Served Positive test results of total reported tests Average Level
1Upper Lake County Water District
Upper Lake, CA
1,1001 of 20.65 ppb
(0 to 1.3 ppb)
2Travel Shores Trailer Park
Fort Bragg, CA
801 of 20.65 ppb
(0 to 1.3 ppb)
3Windflower Point Mutual Water Company
Clearlake, CA
151 of 20.37 ppb
(0 to 0.73 ppb)
4River Estates Mutual Water Company
Ukiah, CA
2501 of 20.34 ppb
(0 to 0.67 ppb)
5City of Lodi
Lodi, CA
53,9032 of 300.31 ppb
(0 to 6.2 ppb)
6Lower Lake County Water District
Lower Lake, CA
2,0251 of 110.05 ppb
(0 to 0.59 ppb)
7Calif Correctnl Inst Tehachapi
Tehachapi, CA
5,6001 of 20.04 ppb
(0 to 0.08 ppb)
8City of Daly City
Daly City, CA
92,3111 of 70.02 ppb
(0 to 0.13 ppb)

Health Based Limits for Diquat

California Public Health GoalsDefined by the State of California Office of Environmental Health Hazard Assessment (OEHHA) as the level of contaminant that is allowed in drinking water. For acutely toxic substances, levels are set at which scientific evidence indicates that no known or anticipated adverse effects on health will occur, plus an adequate margin-of safety. PHGs for carcinogens or other substances which can cause chronic disease shall be based solely on health effects without regard to cost impacts and shall be set at levels which OEHHA has determined do not pose any significant risk to health.15 ppb
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.20 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.20 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.20 ppb

Violation Summary for Diquat 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 regularly2