Chloroform

Cal American Water Company

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

193

Samples

Samples exceeding legal limit (MCL)

151

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2013	N/A	0	0	N/A
2014	3.08 ppb	32	24	ND - 7.60 ppb
2015	4.06 ppb	32	32	1.80 ppb - 5.50 ppb
2016	1.01 ppb	33	17	ND - 3.80 ppb
2017	1.77 ppb	32	30	ND - 3.10 ppb
2018	1.32 ppb	32	24	ND - 3.30 ppb
2019	1.21 ppb	32	24	ND - 4.50 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
2014-02-13	1225-006-1052	ND
2014-02-13	1225-007-1135	ND
2014-02-13	1225-008-1155	ND
2014-02-13	1225-009-1345	ND
2014-02-13	1225-010-1300	ND
2014-02-13	1225-011-1320	ND
2014-02-13	1225-012-0920	ND
2014-02-13	1225-013-1005	ND
2014-05-07	1225-006-1330	2.50 ppb
2014-05-07	1225-007-1415	3.40 ppb
2014-05-07	1225-008-0945	3.20 ppb
2014-05-07	1225-009-1510	3.30 ppb
2014-05-07	1225-010-1030	3.10 ppb
2014-05-07	1225-011-1105	3.10 ppb
2014-05-07	1225-012-1225	2.50 ppb
2014-05-07	1225-013-1150	2.60 ppb
2014-08-12	1225-006-1135	7.60 ppb
2014-08-12	1225-007-1410	4.70 ppb
2014-08-12	1225-008-1350	5.00 ppb
2014-08-12	1225-009-1425	5.60 ppb
2014-08-12	1225-010-1315	4.70 ppb
2014-08-12	1225-011-1210	4.90 ppb
2014-08-12	1225-012-1000	5.40 ppb
2014-08-12	1225-013-1055	6.70 ppb
2014-11-11	1225-006-1500	3.60 ppb
2014-11-11	1225-007-1400	4.90 ppb
2014-11-11	1225-008-1320	3.60 ppb
2014-11-11	1225-009-1430	3.70 ppb
2014-11-11	1225-010-1250	3.50 ppb
2014-11-11	1225-011-1230	3.90 ppb
2014-11-11	1225-012-1545	3.40 ppb
2014-11-11	1225-013-1520	3.60 ppb
2015-02-10	1225-006-1450	3.50 ppb
2015-02-10	1225-007-0933	2.30 ppb
2015-02-10	1225-008-1015	1.80 ppb
2015-02-10	1225-009-1515	3.00 ppb
2015-02-10	1225-010-1047	1.90 ppb
2015-02-10	1225-011-1120	1.90 ppb
2015-02-10	1225-012-1425	1.80 ppb
2015-02-10	1225-013-1350	2.90 ppb
2015-05-12	1225-006-1355	5.10 ppb
2015-05-12	1225-007-1150	5.30 ppb
2015-05-12	1225-008-1120	4.10 ppb
2015-05-12	1225-009-1420	5.00 ppb
2015-05-12	1225-010-1042	4.10 ppb
2015-05-12	1225-011-1000	4.20 ppb
2015-05-12	1225-012-1332	5.30 ppb
2015-05-12	1225-013-1300	5.20 ppb
2015-08-10	1225-006-1350	4.70 ppb
2015-08-10	1225-007-1325	5.20 ppb
2015-08-10	1225-008-1050	3.90 ppb
2015-08-10	1225-009-1410	4.20 ppb
2015-08-10	1225-010-1120	3.90 ppb
2015-08-10	1225-011-1200	3.80 ppb
2015-08-10	1225-012-0945	5.30 ppb
2015-08-10	1225-013-1015	5.00 ppb
2015-11-10	1225-006-1100	5.50 ppb
2015-11-10	1225-007-1200	4.50 ppb
2015-11-10	1225-008-1140	4.60 ppb
2015-11-10	1225-009-0930	4.10 ppb
2015-11-10	1225-010-1055	4.70 ppb
2015-11-10	1225-011-0950	4.60 ppb
2015-11-10	1225-012-1300	4.50 ppb
2015-11-10	1225-013-1200	3.90 ppb
2016-02-09	1225-006-1000	1.30 ppb
2016-02-09	1225-007-1150	3.80 ppb
2016-02-09	1225-008-0950	2.40 ppb
2016-02-09	1225-009-1210	2.50 ppb
2016-02-09	1225-010-1035	2.50 ppb
2016-02-09	1225-011-1120	2.40 ppb
2016-02-09	1225-012-1040	1.20 ppb
2016-02-09	1225-013-1305	2.70 ppb
2016-02-24	1225-007-1045	1.70 ppb
2016-05-10	1225-006-0930	ND
2016-05-10	1225-007-1030	ND
2016-05-10	1225-008-0950	ND
2016-05-10	1225-009-1155	ND
2016-05-10	1225-010-1030	ND
2016-05-10	1225-011-1055	ND
2016-05-10	1225-012-1130	ND
2016-05-10	1225-013-1100	ND
2016-08-09	1225-006-1130	ND
2016-08-09	1225-007-1100	ND
2016-08-09	1225-008-1045	ND
2016-08-09	1225-009-1000	ND
2016-08-09	1225-010-1120	ND
2016-08-09	1225-011-0950	ND
2016-08-09	1225-012-1300	ND
2016-08-09	1225-013-1208	ND
2016-11-09	1225-006-1200	1.50 ppb
2016-11-09	1225-007-1445	1.60 ppb
2016-11-09	1225-008-1355	1.60 ppb
2016-11-09	1225-009-1315	1.70 ppb
2016-11-09	1225-010-1340	1.60 ppb
2016-11-09	1225-012-1045	1.40 ppb
2016-11-09	1225-013-1130	1.50 ppb
2016-11-11	1225-011-1010	1.80 ppb
2017-02-08	1225-006-1000	3.10 ppb
2017-02-08	1225-007-1300	2.10 ppb
2017-02-08	1225-008-1040	2.30 ppb
2017-02-08	1225-009-1050	2.30 ppb
2017-02-08	1225-010-1100	2.40 ppb
2017-02-08	1225-011-1200	2.70 ppb
2017-02-08	1225-012-1100	3.00 ppb
2017-02-08	1225-013-1315	2.60 ppb
2017-05-09	1225-006-1110	1.50 ppb
2017-05-09	1225-007-1330	1.30 ppb
2017-05-09	1225-008-1300	1.50 ppb
2017-05-09	1225-009-1200	1.30 ppb
2017-05-09	1225-010-1150	1.30 ppb
2017-05-09	1225-011-1115	1.40 ppb
2017-05-09	1225-012-1030	1.50 ppb
2017-05-09	1225-013-1030	1.20 ppb
2017-08-08	1225-006-1100	1.30 ppb
2017-08-08	1225-007-1130	ND
2017-08-08	1225-008-1300	1.10 ppb
2017-08-08	1225-009-1030	1.10 ppb
2017-08-08	1225-010-1145	1.10 ppb
2017-08-08	1225-011-1100	1.30 ppb
2017-08-08	1225-012-1200	1.10 ppb
2017-08-08	1225-013-1000	ND
2017-11-09	1225-006-1245	1.70 ppb
2017-11-09	1225-007-1435	2.70 ppb
2017-11-09	1225-008-1409	2.60 ppb
2017-11-09	1225-009-1300	1.80 ppb
2017-11-09	1225-010-1352	2.80 ppb
2017-11-09	1225-011-1337	2.80 ppb
2017-11-09	1225-012-1317	1.90 ppb
2017-11-09	1225-013-1315	1.70 ppb
2018-02-06	1225-006-1000	2.50 ppb
2018-02-06	1225-007-1100	1.50 ppb
2018-02-06	1225-008-1130	2.30 ppb
2018-02-06	1225-009-1030	2.70 ppb
2018-02-06	1225-010-1100	2.40 ppb
2018-02-06	1225-011-1200	2.50 ppb
2018-02-06	1225-012-1200	2.20 ppb
2018-02-06	1225-013-1015	1.90 ppb
2018-05-08	1225-006-0900	3.30 ppb
2018-05-08	1225-007-1100	1.40 ppb
2018-05-08	1225-008-1100	1.70 ppb
2018-05-08	1225-009-0930	ND
2018-05-08	1225-010-1040	2.00 ppb
2018-05-08	1225-011-1012	1.90 ppb
2018-05-08	1225-012-1130	1.10 ppb
2018-05-08	1225-013-0950	ND
2018-08-08	1225-006-1030	1.60 ppb
2018-08-08	1225-007-1130	ND
2018-08-08	1225-008-1110	1.50 ppb
2018-08-08	1225-009-1100	1.30 ppb
2018-08-08	1225-010-1135	1.40 ppb
2018-08-08	1225-011-1155	1.40 ppb
2018-08-08	1225-012-1300	1.10 ppb
2018-08-08	1225-013-1040	1.40 ppb
2018-11-14	1225-006-1355	ND
2018-11-14	1225-007-1455	1.10 ppb
2018-11-14	1225-008-1520	1.000 ppb
2018-11-14	1225-009-1425	1.000 ppb
2018-11-14	1225-010-1540	ND
2018-11-14	1225-011-1555	ND
2018-11-14	1225-012-1250	ND
2018-11-14	1225-013-1320	ND
2019-02-12	1225-006-1400	1.80 ppb
2019-02-12	1225-007-1500	4.50 ppb
2019-02-12	1225-008-1420	1.50 ppb
2019-02-12	1225-009-1430	1.20 ppb
2019-02-12	1225-010-1500	1.50 ppb
2019-02-12	1225-011-1440	1.50 ppb
2019-02-12	1225-012-1600	1.20 ppb
2019-02-12	1225-013-1600	1.30 ppb
2019-05-14	1225-006-1230	ND
2019-05-14	1225-007-1330	ND
2019-05-14	1225-008-1600	1.000 ppb
2019-05-14	1225-009-1300	1.10 ppb
2019-05-14	1225-010-1630	ND
2019-05-14	1225-011-1530	1.30 ppb
2019-05-14	1225-012-1430	ND
2019-05-14	1225-013-1400	ND
2019-08-14	1225-006-1200	ND
2019-08-14	1225-007-1300	ND
2019-08-14	1225-008-1350	2.30 ppb
2019-08-14	1225-009-1230	1.10 ppb
2019-08-14	1225-010-1330	2.60 ppb
2019-08-14	1225-011-1300	2.40 ppb
2019-08-14	1225-012-1400	1.60 ppb
2019-08-14	1225-013-1230	2.50 ppb
2019-11-13	1225-006-1615	1.000 ppb
2019-11-13	1225-007-1749	1.10 ppb
2019-11-13	1225-009-1645	1.000 ppb
2019-11-13	1225-010-1707	1.20 ppb
2019-11-13	1225-011-1725	1.10 ppb
2019-11-13	1225-012-1409	1.30 ppb
2019-11-13	1225-013-1510	ND
2019-11-21	1225-008-1108	1.70 ppb