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EWG's Tap Water Database — 2019 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.

2015-2017:

FOUND
FOUND ABOVE HEALTH GUIDELINES

2

states detected

66

utilities detected

6.0 million

people served

1

states over health guideline

10

utilities over health guideline

667,000

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
California10666,931614,088,419
Virginia0021,289,422
District Of Columbia003648,882
MORE
LESS

Filtering technologies that reduce n-nitrosodimethylamine

reverse osmosis icon

Reverse Osmosis

Utilities with the highest amounts of n-nitrosodimethylamine, 2015-2017

ALL UTILITIES
LARGE UTILITIES
UtilityLocationTestsAverage levelPeople served
San Gabriel Valley Water Company- El Monte*El Monte, CA305 of 70620.2 ppt226,904
San Gabriel Valley Water Company-MontebelloEl Monte, CA305 of 70620.2 ppt8,858
California Water Service Company - Palos VerdeSan Jose, CA21 of 223.64 ppt69,883
California Water Service - LivermoreLivermore, CA7 of 143.61 ppt56,700
Valencia Water Company*Valencia, CA2 of 23.50 ppt117,251
California Water Service Company - East Los AngelesSan Jose, CA16 of 223.17 ppt150,446
California Water Service Company - Hermosa / Redondo BeachSan Jose, CA21 of 242.60 ppt95,605
Three Valleys Municipal Water District*Claremont, CA2 of 52.36 ppt0
California Domestic Water Company*Whittier, CA70 of 3182.12 ppt1,200
Coast Springs - Cal. Water Service (puc)San Jose, CA2 of 31.67 ppt210
Zone 7 Water Agency*Livermore, CA6 of 121.55 ppt40
City of LivermoreLivermore, CA6 of 121.55 ppt27,000
Dublin San Ramon Services DistrictDublin, CA6 of 121.55 ppt75,924
June Lake Public Utility District VillageJune Lake, CA1 of 21.35 ppt240
Calleguas Municipal Water District*Thousand Oaks, CA3 of 61.08 ppt0
Ventura County Waterworks District No. 17 - Bell CanyonMoorpark, CA3 of 61.08 ppt2,049
California Water Service Company - WestlakeSan Jose, CA3 of 61.08 ppt19,451
Thousand Oaks Water DepartmentThousand Oaks, CA3 of 61.08 ppt50,000
Cal American Water CompanyNewbury Park, CA3 of 61.08 ppt61,206
Solano Verde Mutual Water CompanyCamarillo, CA3 of 61.08 ppt100
Lake Sherwood Community Services DistrictMoorpark, CA3 of 61.08 ppt1,527
Cal American Water Company - Las Posas EstatesNewbury Park, CA3 of 61.08 ppt1,800
Oak Park Water ServiceVentura, CA3 of 61.08 ppt12,200
California Water Service Company - DominguezSan Jose, CA2 of 100.940 ppt142,111
Washington Aqueduct Division*Washington, DC4 of 260.912 ppt0
D.C. Water and Sewer Authority*Washington, DC4 of 260.912 ppt632,323
Arlington County*Arlington, VA4 of 260.912 ppt215,000
Suburban Water Systems - San Jose HillsCovina, CA14 of 850.415 ppt162,031
Woodland-davis Clean Water AgencyDavis, CA1 of 210.314 ppt0
Golden State Water Company - Cordova*Rancho Cordova, CA4 of 740.182 ppt47,810
Glendale Water DepartmentGlendale, CA2 of 1150.0810 ppt195,799
Santa Clara Valley Water District*San Jose, CA1 of 350.0570 ppt0
Monterey Park Water DepartmentMonterey Park, CA2 of 1300.0310 ppt62,183

* 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, CA305 of 70620.2 ppt226,904
California Water Service Company - Palos VerdeSan Jose, CA21 of 223.64 ppt69,883
California Water Service - LivermoreLivermore, CA7 of 143.61 ppt56,700
Valencia Water Company*Valencia, CA2 of 23.50 ppt117,251
California Water Service Company - East Los AngelesSan Jose, CA16 of 223.17 ppt150,446
California Water Service Company - Hermosa / Redondo BeachSan Jose, CA21 of 242.60 ppt95,605
Dublin San Ramon Services DistrictDublin, CA6 of 121.55 ppt75,924
City of LivermoreLivermore, CA6 of 121.55 ppt27,000
Thousand Oaks Water DepartmentThousand Oaks, CA3 of 61.08 ppt50,000
California Water Service Company - WestlakeSan Jose, CA3 of 61.08 ppt19,451
Oak Park Water ServiceVentura, CA3 of 61.08 ppt12,200
Cal American Water CompanyNewbury Park, CA3 of 61.08 ppt61,206
California Water Service Company - DominguezSan Jose, CA2 of 100.940 ppt142,111
D.C. Water and Sewer Authority*Washington, DC4 of 260.912 ppt632,323
Arlington County*Arlington, VA4 of 260.912 ppt215,000
Suburban Water Systems - San Jose HillsCovina, CA14 of 850.415 ppt162,031
Golden State Water Company - Cordova*Rancho Cordova, CA4 of 740.182 ppt47,810
Glendale Water DepartmentGlendale, CA2 of 1150.0810 ppt195,799
Monterey Park Water DepartmentMonterey Park, CA2 of 1300.0310 ppt62,183

* 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.