Chloroform

UC - Davis

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	ND	7	0	ND
2015	ND	2	0	ND
2016	N/A	0	0	N/A
2017	0.433 ppb	6	1	ND - 2.60 ppb
2018	N/A	0	0	N/A
2019	N/A	0	0	N/A

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
2014-03-25	5810-026-1050	ND
2014-05-20	5810-026-0650	ND
2014-09-04	5810-001-0742	ND
2014-09-04	5810-002-0929	ND
2014-09-04	5810-004-0953	ND
2014-09-04	5810-015-1305	ND
2014-09-04	5810-026-0850	ND
2015-02-19	5810-014-1030	ND
2015-03-24	5810-026-0900	ND
2017-09-27	5810-001-1040	ND
2017-09-27	5810-002-1225	ND
2017-09-27	5810-004-1020	ND
2017-09-27	5810-014-1205	ND
2017-09-27	5810-015-0940	2.60 ppb
2017-09-27	5810-026-1005	ND