Chloroform

Washington Corrections Center

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

Samples

Samples exceeding legal limit (MCL)

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2014	0.510 ppb	2	2	0.440 ppb - 0.580 ppb
2015	0.635 ppb	2	2	0.530 ppb - 0.740 ppb
2016	0.532 ppb	6	3	ND - 1.30 ppb
2017	0.650 ppb	2	2	0.600 ppb - 0.700 ppb
2018	0.670 ppb	2	2	0.610 ppb - 0.730 ppb
2019	0.857 ppb	3	2	ND - 1.31 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
2014-08-13	12546	0.580 ppb
2014-08-22	12683	0.440 ppb
2015-08-12	18018	0.530 ppb
2015-08-12	18019	0.740 ppb
2016-08-19		1.000 ppb
2016-08-19		ND
2016-08-19		0.890 ppb
2016-09-06		1.30 ppb
2016-09-06		ND
2016-12-05		ND
2017-08-10		0.700 ppb
2017-08-10		0.600 ppb
2018-08-08		0.730 ppb
2018-08-08		0.610 ppb
2019-08-14		1.26 ppb
2019-08-14		1.31 ppb
2019-08-14		ND