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EWG's Tap Water Database — 2021 UPDATE

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N-Nitrosodimethylamine (NDMA)

Zone 7 Water Agency

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.

 

30

Samples

0

Samples exceeding legal limit (MCL)

8

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20143.80 ppt106ND - 9.00 ppt
20151.73 ppt42ND - 4.00 ppt
20161.80 ppt42ND - 3.60 ppt
20171.13 ppt42ND - 2.30 ppt
20181.30 ppt42ND - 2.70 ppt
2019ND40ND

ppt = parts per trillion

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

All test results

Date Lab ID Result
2014-08-139590-008-09452.00 ppt
2014-08-139590-008-09457.00 ppt
2014-08-139590-001-0735ND
2014-08-139590-001-07358.00 ppt
2014-09-189590-008-1110ND
2014-09-189590-008-11107.00 ppt
2014-09-189590-001-11355.00 ppt
2014-09-189590-001-1135ND
2014-10-159590-008-1035ND
2014-10-159590-008-10359.00 ppt
2015-08-129590-001-0835ND
2015-08-129590-008-10102.90 ppt
2015-08-129590-001-08354.00 ppt
2015-08-129590-008-1010ND
2016-08-039590-008-1020ND
2016-08-039590-001-1230ND
2016-08-039590-001-12303.60 ppt
2016-08-039590-008-10203.60 ppt
2017-08-169590-008-09552.30 ppt
2017-08-169590-008-0955ND
2017-08-169590-001-0825ND
2017-08-169590-001-08252.20 ppt
2018-08-079590-008-09502.50 ppt
2018-08-079590-008-0950ND
2018-08-079590-001-0940ND
2018-08-079590-001-09402.70 ppt
2019-08-079590-008-1240ND
2019-08-079590-008-1240ND
2019-08-079590-001-1345ND
2019-08-079590-001-1345ND