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National Drinking Water Database

National Drinking Water Database - Chemical Contaminants


Status: Regulated - EPA has established a maximum legal limit in tapwater for this contaminant.

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

Found above
health guidelines
Found above
legal limit
Water utilities
People Served

Health Concerns for Diquat:

Diquat Exposure by State

Water utilities in 12 states have reported detecting Diquat in treated tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies.

StateWater Suppliers with Diquat contamination

The Most Polluted Communities

37 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
1Wisemans Mobile Court
Colfax, OR
1001 of 22.25 ppb
(0 to 4.5 ppb)
2Brewton Water Works
Brewton, AL
9,9451 of 40.87 ppb
(0 to 3.48 ppb)
3Oakridge Apartments
Mt Charleston, NV
1261 of 10.77 ppb
(0.77 ppb)
4Albany Water Works
Albany, KY
16,3351 of 130.77 ppb
(0 to 10 ppb)
5Upper Lake County Water District
Upper Lake, CA
1,1001 of 20.65 ppb
(0 to 1.3 ppb)
6Travel Shores Trailer Park
Fort Bragg, CA
801 of 20.65 ppb
(0 to 1.3 ppb)
7Village of Racine
Racine, OH
9201 of 60.58 ppb
(0 to 3.5 ppb)
8Santa Cruz Water Company
Phoenix, AZ
17,0051 of 30.57 ppb
(0 to 1.7 ppb)
9North Fairfield, Vlg. of
North Fairfield, OH
5731 of 50.54 ppb
(0 to 2.7 ppb)
10Lake Region Mobile Home Village
Haines City, FL
5651 of 10.44 ppb
(0.44 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

Testing Summary for Diquat

Are tests routinely required for Diquat by federal law?Yes
Water suppliers reporting tests for Diquat (2004-2009):10,443 of 47,576
Average testing rate for water supplier reporting tests (2004-2009):0.4 per year

Violation Summary for Diquat

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

Maximum Contaminant Level Exceedance Violations0
Monitoring Violations896
Reporting Violations0

Occupational hazards

Type of concern: Reference:
Allowed workplace exposures restricted to very low doses RTECS®- TLV/BEI,2007
Allowed workplace exposures restricted to low doses RTECS®- TLV/BEI,2007


Type of concern: Reference:
One or more in vitro tests non-mammalian cells show positive mutation results RTECS®- Environment International 1984

Irritation (skin, eyes, or lungs)

Type of concern: Reference:
One or more animal studies show skin irritation at high doses RTECS®- Contact Dermatitis 1987

Government, industry, academic studies and classifications

government/industry list/academic study appears on list as classification(s)
RTECS®- TLV/BEI,2007DIPYRIDO(1,2-A:2',1'-C)PYRAZINEDIIUM, 6,7-DIHYDRO-• occupationally related - ACGIH TLV (human TWA)
RTECS®- Contact Dermatitis 1987DIPYRIDO(1,2-A:2',1'-C)PYRAZINEDIIUM, 6,7-DIHYDRO-• skin - Primary skin irritant ( human )
RTECS®- Environment International 1984DIPYRIDO(1,2-A:2',1'-C)PYRAZINEDIIUM, 6,7-DIHYDRO-• mutagenic - Positive mutation assay: Mutation in Micro-organism (other micro-organisms )


government/industry list/academic study reference
RTECS®- Contact Dermatitis 1987RTECS®- Contact Dermatitis. Environmental and Occupational Dermatitis. (Munksgaard International Pub., c/o Publications Expediting Inc., 200 Meacham Ave., Elmont, NY 11003) V.1- 17,212,1987
RTECS®- Environment International 1984RTECS®- Environment International. (Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, NY 10523) V.1- 10,285,1984

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