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EWG's Tap Water Database — 2021 UPDATE

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Chloroform

Castle Rock

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.

MORE ABOUT THIS CONTAMINANT

 

113

Samples

0

Samples exceeding legal limit (MCL)

111

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2014N/A00N/A
2015ND10ND
20160.843 ppb24240.540 ppb - 1.34 ppb
20171.05 ppb2423ND - 2.41 ppb
20181.39 ppb32320.500 ppb - 5.30 ppb
20191.33 ppb32320.700 ppb - 5.30 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 Result
2015-03-24ND
2016-05-031.34 ppb
2016-05-030.860 ppb
2016-05-031.01 ppb
2016-05-031.23 ppb
2016-05-030.870 ppb
2016-05-031.21 ppb
2016-05-030.960 ppb
2016-05-030.790 ppb
2016-08-150.740 ppb
2016-08-150.620 ppb
2016-08-150.660 ppb
2016-08-150.680 ppb
2016-08-150.860 ppb
2016-08-150.780 ppb
2016-08-150.780 ppb
2016-08-150.540 ppb
2016-11-141.17 ppb
2016-11-140.630 ppb
2016-11-140.800 ppb
2016-11-140.750 ppb
2016-11-140.730 ppb
2016-11-140.750 ppb
2016-11-140.730 ppb
2016-11-140.740 ppb
2017-05-150.580 ppb
2017-05-150.740 ppb
2017-05-151.74 ppb
2017-05-15ND
2017-05-150.700 ppb
2017-05-150.770 ppb
2017-05-150.620 ppb
2017-05-160.890 ppb
2017-08-151.13 ppb
2017-08-151.04 ppb
2017-08-150.590 ppb
2017-08-150.740 ppb
2017-08-150.940 ppb
2017-08-150.990 ppb
2017-08-150.730 ppb
2017-08-230.950 ppb
2017-11-131.38 ppb
2017-11-131.27 ppb
2017-11-132.41 ppb
2017-11-131.09 ppb
2017-11-131.15 ppb
2017-11-132.40 ppb
2017-11-131.05 ppb
2017-11-131.41 ppb
2018-02-210.500 ppb
2018-02-210.600 ppb
2018-02-211.10 ppb
2018-02-210.900 ppb
2018-02-211.000 ppb
2018-02-210.800 ppb
2018-02-210.800 ppb
2018-02-210.800 ppb
2018-05-141.10 ppb
2018-05-141.20 ppb
2018-05-141.30 ppb
2018-05-142.70 ppb
2018-05-142.80 ppb
2018-05-141.10 ppb
2018-05-141.000 ppb
2018-05-142.30 ppb
2018-08-071.20 ppb
2018-08-075.30 ppb
2018-08-073.10 ppb
2018-08-071.30 ppb
2018-08-071.30 ppb
2018-08-071.80 ppb
2018-08-071.50 ppb
2018-08-071.40 ppb
2018-11-270.800 ppb
2018-11-271.000 ppb
2018-11-270.800 ppb
2018-11-270.900 ppb
2018-11-271.10 ppb
2018-11-271.000 ppb
2018-11-271.000 ppb
2018-11-271.000 ppb
2019-02-190.700 ppb
2019-02-191.40 ppb
2019-02-190.800 ppb
2019-02-191.20 ppb
2019-02-191.10 ppb
2019-02-191.30 ppb
2019-02-191.50 ppb
2019-02-190.900 ppb
2019-05-070.700 ppb
2019-05-071.30 ppb
2019-05-075.30 ppb
2019-05-071.000 ppb
2019-05-081.000 ppb
2019-05-081.20 ppb
2019-05-081.000 ppb
2019-05-081.30 ppb
2019-08-072.20 ppb
2019-08-070.700 ppb
2019-08-072.40 ppb
2019-08-072.00 ppb
2019-08-071.10 ppb
2019-08-070.700 ppb
2019-08-072.20 ppb
2019-08-071.60 ppb
2019-11-120.700 ppb
2019-11-120.800 ppb
2019-11-121.60 ppb
2019-11-121.10 ppb
2019-11-121.20 ppb
2019-11-120.700 ppb
2019-11-120.800 ppb
2019-11-121.20 ppb