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EWG's Tap Water Database — 2021 UPDATE

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N-Nitrosodimethylamine (NDMA)

Status: No national drinking water standard exists

 

N-Nitrosodimethylamine is one of the DNA-damaging, cancer-causing contaminants called N-nitrosamines that can form during water treatment with the use of certain disinfectants, such as chloramine. Read More.

Pollution of water sources with effluent from municipal wastewater treatment plants and runoff from animal feeding operations contributes to nitrosamine formation. Fifteen different nitrosamines are listed as carcinogens in the U.S. Department of Health and Human Services National Toxicology Program Report on Carcinogens. The federal government has not set a legal limit for nitrosamines in drinking water and water utilities typically do not test for these contaminants. California has set a public health goal for one of the most common nitrosamines, N-nitrosodimethylamine or NDMA, at 0.003 parts per billion in drinking water, a concentration that corresponds to an estimated one-in-one-million cancer risk.

Click here to read more about disinfection byproducts.

2017-2019:

FOUND
FOUND ABOVE HEALTH GUIDELINES

1

states detected

74

utilities detected

6.6 million

people served

1

states over health guideline

7

utilities over health guideline

562,000

people served over health guideline

Health concerns for n-nitrosodimethylamine

Cancer

State and national drinking water standards and health guidelines

EWG Health Guideline 3 ppt

The EWG Health Guideline of 3 ppt for n-nitrosodimethylamine was defined by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer.

ppt = parts per trillion

States reporting n-nitrosodimethylamine in drinking water

UTILITIES REPORTING ABOVE HEALTH GUIDELINES UTILITIES WITH CONTAMINATION
State UtilitiesPeople Served UtilitiesPeople Served
California7561,792746,621,787
MORE
LESS

Filtering technologies that reduce n-nitrosodimethylamine

Reverse Osmosis

Utilities with the highest amounts of n-nitrosodimethylamine, 2017-2019

ALL UTILITIES
LARGE UTILITIES
UtilityLocationTestsAverage levelPeople served
San Gabriel Valley Water Company- El Monte*El Monte, CA561 of 1,35020.2 ppt226,904
San Gabriel Valley Water Company-MontebelloEl Monte, CA561 of 1,35020.2 ppt8,858
California Water Service Company - East Los AngelesSan Jose, CA36 of 474.20 ppt150,446
California Water Service Company - Palos VerdeSan Jose, CA39 of 463.42 ppt69,883
California Water Service - LivermoreLivermore, CA7 of 163.16 ppt56,700
Valencia Water Company*Valencia, CA4 of 43.00 ppt117,251
California Water Service Company - Hermosa / Redondo BeachSan Jose, CA40 of 482.75 ppt95,605
California Domestic Water Company*Whittier, CA156 of 6852.13 ppt1,200
Dublin San Ramon Services DistrictDublin, CA14 of 302.06 ppt75,924
Zone 7 Water Agency*Livermore, CA14 of 302.06 ppt40
City of LivermoreLivermore, CA14 of 302.06 ppt27,000
Coast Springs - Cal. Water Service (puc)San Jose, CA4 of 61.70 ppt210
June Lake Public Utility District VillageJune Lake, CA1 of 21.35 ppt240
Three Valleys Municipal Water District*Claremont, CA2 of 101.18 ppt0
California Water Service Company - DominguezSan Jose, CA2 of 130.723 ppt142,111
Solano Verde Mutual Water CompanyCamarillo, CA3 of 110.591 ppt100
Ventura County Waterworks District No. 17 - Bell CanyonMoorpark, CA3 of 110.591 ppt2,049
California Water Service Company - WestlakeSan Jose, CA3 of 110.591 ppt19,451
Thousand Oaks Water DepartmentThousand Oaks, CA3 of 110.591 ppt50,000
Cal American Water CompanyNewbury Park, CA3 of 110.591 ppt61,206
Oak Park Water ServiceVentura, CA3 of 110.591 ppt12,200
Calleguas Municipal Water District*Thousand Oaks, CA3 of 110.591 ppt0
Lake Sherwood Community Services DistrictMoorpark, CA3 of 110.591 ppt1,527
Cal American Water Company - Las Posas EstatesNewbury Park, CA3 of 110.591 ppt1,800
Suburban Water Systems - San Jose HillsCovina, CA33 of 1750.545 ppt162,031
Vallecitos Water DistrictSan Marcos, CA2 of 120.358 ppt94,871
City of CarlsbadCarlsbad, CA2 of 120.358 ppt84,838
Rainbow Municipal WDFallbrook, CA2 of 120.358 ppt19,611
Rincon Del Diablo MWD(ID-1)Escondido, CA2 of 120.358 ppt24,545
Ramona Municipal WDRamona, CA2 of 120.358 ppt40,000
Valley Center MWD*Valley Center, CA2 of 120.358 ppt25,450
San Diego County Water Authority*Escondido, CA2 of 120.358 ppt0
Monterey Park Water DepartmentMonterey Park, CA7 of 2700.188 ppt62,183
Glendale Water DepartmentGlendale, CA4 of 2120.162 ppt195,799
Golden State Water Company - Cordova*Rancho Cordova, CA9 of 1650.150 ppt47,810
Suburban Water Systems - WhittierCovina, CA1 of 240.125 ppt59,169
Whittier Water Department*Whittier, CA1 of 180.111 ppt49,954
Woodland-davis Clean Water AgencyDavis, CA1 of 630.105 ppt0
Santa Clara Valley Water District*San Jose, CA2 of 870.0560 ppt0
Pomona Water DepartmentPomona, CA2 of 1180.0390 ppt151,713
Central Basin Municipal Water District*Commerce, CA1 of 790.0250 ppt0
Carmichael Water DistrictCarmichael, CA1 of 910.0240 ppt40,000
La Puente Valley County Water District*La Puente, CA1 of 3130.0220 ppt9,852

* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report N-Nitrosodimethylamine (NDMA), but it likely has the contaminant in its water supply.

UtilityLocationTestsAverage levelPeople served
San Gabriel Valley Water Company- El Monte*El Monte, CA561 of 1,35020.2 ppt226,904
California Water Service Company - East Los AngelesSan Jose, CA36 of 474.20 ppt150,446
California Water Service Company - Palos VerdeSan Jose, CA39 of 463.42 ppt69,883
California Water Service - LivermoreLivermore, CA7 of 163.16 ppt56,700
Valencia Water Company*Valencia, CA4 of 43.00 ppt117,251
California Water Service Company - Hermosa / Redondo BeachSan Jose, CA40 of 482.75 ppt95,605
Dublin San Ramon Services DistrictDublin, CA14 of 302.06 ppt75,924
City of LivermoreLivermore, CA14 of 302.06 ppt27,000
California Water Service Company - DominguezSan Jose, CA2 of 130.723 ppt142,111
Oak Park Water ServiceVentura, CA3 of 110.591 ppt12,200
Cal American Water CompanyNewbury Park, CA3 of 110.591 ppt61,206
Thousand Oaks Water DepartmentThousand Oaks, CA3 of 110.591 ppt50,000
California Water Service Company - WestlakeSan Jose, CA3 of 110.591 ppt19,451
Suburban Water Systems - San Jose HillsCovina, CA33 of 1750.545 ppt162,031
Vallecitos Water DistrictSan Marcos, CA2 of 120.358 ppt94,871
City of CarlsbadCarlsbad, CA2 of 120.358 ppt84,838
Rainbow Municipal WDFallbrook, CA2 of 120.358 ppt19,611
Rincon Del Diablo MWD(ID-1)Escondido, CA2 of 120.358 ppt24,545
Ramona Municipal WDRamona, CA2 of 120.358 ppt40,000
Valley Center MWD*Valley Center, CA2 of 120.358 ppt25,450
Monterey Park Water DepartmentMonterey Park, CA7 of 2700.188 ppt62,183
Glendale Water DepartmentGlendale, CA4 of 2120.162 ppt195,799
Golden State Water Company - Cordova*Rancho Cordova, CA9 of 1650.150 ppt47,810
Suburban Water Systems - WhittierCovina, CA1 of 240.125 ppt59,169
Whittier Water Department*Whittier, CA1 of 180.111 ppt49,954
Pomona Water DepartmentPomona, CA2 of 1180.0390 ppt151,713
Carmichael Water DistrictCarmichael, CA1 of 910.0240 ppt40,000

* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report N-Nitrosodimethylamine (NDMA), but it likely has the contaminant in its water supply.