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EWG's Tap Water Database — 2021 UPDATE

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Chloroform

Nob Hill Water Association

Chloroform, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Chloroform and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Read More.

In addition to tap water disinfection, chloroform pollution in the environment also comes from industrial discharges from pulp and paper mills, and from urban wastewater effluent. Human studies show that chloroform damages the kidneys, liver and central nervous system. In animals, chloroform causes infertility, birth defects and cancer.

Click here to read more about disinfection byproducts.

 

18

Samples

0

Samples exceeding legal limit (MCL)

11

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20141.80 ppb21ND - 3.60 ppb
20150.550 ppb62ND - 2.40 ppb
20163.60 ppb32ND - 10.00 ppb
20175.60 ppb220.800 ppb - 10.4 ppb
20183.39 ppb32ND - 9.43 ppb
20195.71 ppb221.28 ppb - 10.1 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.4 ppb

The EWG Health Guideline of 0.4 ppb for chloroform was proposed in 2018 by the California Office of Environmental Health Hazard Assessment as a one-in-a-million lifetime risk of cancer. Values greater than one-in-a-million cancer risk level can result in increased cancer cases above one in a million people.

ppb = parts per billion

All test results

Date Lab ID Result
2014-07-15737843.60 ppb
2014-07-1573785ND
2015-06-2375105ND
2015-06-2375103ND
2015-07-1475167ND
2015-07-29752372.40 ppb
2015-07-29752380.900 ppb
2015-09-0175402ND
2016-07-12ND
2016-07-1310.00 ppb
2016-07-130.800 ppb
2017-07-100.800 ppb
2017-07-1010.4 ppb
2018-06-06ND
2018-08-139.43 ppb
2018-08-130.740 ppb
2019-07-0210.1 ppb
2019-07-021.28 ppb