Chloroform

Rancho California Water District

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

234

Samples

Samples exceeding legal limit (MCL)

164

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2014	2.48 ppb	30	22	ND - 6.80 ppb
2015	2.82 ppb	47	33	ND - 10.00 ppb
2016	0.675 ppb	11	6	ND - 1.70 ppb
2017	3.66 ppb	55	45	ND - 27.0 ppb
2018	3.46 ppb	62	39	ND - 19.0 ppb
2019	1.54 ppb	29	19	ND - 4.60 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
2014-02-11	4790-801-1023	3.40 ppb
2014-02-11	4790-802-0841	6.10 ppb
2014-02-11	4790-803-0815	1.40 ppb
2014-02-11	4790-804-1056	1.90 ppb
2014-02-11	4790-805-0922	1.20 ppb
2014-02-11	4790-806-1007	2.50 ppb
2014-02-11	4790-807-1039	1.80 ppb
2014-02-11	4790-808-0934	ND
2014-03-11	4790-028-0922	0.950 ppb
2014-03-11	4790-046-0815	ND
2014-04-02	4790-085-1030	2.80 ppb
2014-04-02	4790-086-1100	1.50 ppb
2014-04-03	4790-043-1015	ND
2014-04-03	4790-084-0915	4.50 ppb
2014-05-05	4790-801-0927	5.40 ppb
2014-05-05	4790-802-1115	4.10 ppb
2014-05-05	4790-803-1047	4.90 ppb
2014-05-05	4790-804-1006	5.20 ppb
2014-05-05	4790-805-1205	3.20 ppb
2014-05-05	4790-806-0912	4.50 ppb
2014-05-05	4790-807-0945	6.80 ppb
2014-05-05	4790-808-1150	3.40 ppb
2014-05-08	4790-048-0930	ND
2014-05-23	4790-143-0840	3.30 ppb
2014-06-03	4790-051-1140	ND
2014-08-06	4790-143-0905	2.30 ppb
2014-08-07	4790-095-0905	ND
2014-09-04	4790-059-0935	ND
2014-10-02	4790-029-0940	ND
2014-11-12	4790-143-1045	3.30 ppb
2015-01-07	4790-097-1215	ND
2015-01-29	4790-142-1030	3.90 ppb
2015-02-05	4790-036-1125	1.90 ppb
2015-02-06	4790-042-1100	ND
2015-02-11	4790-801-0915	6.30 ppb
2015-02-11	4790-802-1043	6.90 ppb
2015-02-11	4790-803-1028	5.30 ppb
2015-02-11	4790-804-0955	4.30 ppb
2015-02-11	4790-805-1105	1.20 ppb
2015-02-11	4790-806-0903	4.60 ppb
2015-02-11	4790-807-0935	4.20 ppb
2015-02-11	4790-808-1116	1.30 ppb
2015-04-16	4790-058-1045	1.90 ppb
2015-04-22	4790-053-1200	ND
2015-04-22	4790-142-1015	3.10 ppb
2015-05-06	4790-143-1050	2.60 ppb
2015-05-12	4790-801-1006	5.50 ppb
2015-05-12	4790-802-1144	6.10 ppb
2015-05-12	4790-803-1122	1.20 ppb
2015-05-12	4790-804-1047	0.680 ppb
2015-05-12	4790-805-1213	1.50 ppb
2015-05-12	4790-806-0954	3.00 ppb
2015-05-12	4790-807-1022	3.60 ppb
2015-05-12	4790-808-1243	1.60 ppb
2015-05-14	4790-015-1025	ND
2015-06-02	4790-018-1030	ND
2015-07-01	4790-031-1031	ND
2015-07-02	4790-040-1130	ND
2015-07-14	4790-142-1000	2.50 ppb
2015-07-27	4790-037-1032	ND
2015-08-04	4790-801-1424	9.60 ppb
2015-08-04	4790-802-0921	10.00 ppb
2015-08-04	4790-803-0848	10.00 ppb
2015-08-04	4790-804-1545	6.40 ppb
2015-08-04	4790-805-1102	1.80 ppb
2015-08-04	4790-806-1405	5.40 ppb
2015-08-04	4790-807-1444	9.70 ppb
2015-08-04	4790-808-1127	1.80 ppb
2015-08-05	4790-143-1455	1.80 ppb
2015-08-06	4790-017-1245	1.20 ppb
2015-08-06	4790-019-1210	ND
2015-08-06	4790-025-1140	ND
2015-08-06	4790-038-0945	ND
2015-08-07	4790-027-0840	ND
2015-08-07	4790-035-0930	ND
2015-10-14	4790-142-1045	1.80 ppb
2015-10-22	4790-044-0830	ND
2016-01-20	4790-142-1030	0.910 ppb
2016-02-29	4790-150-1830	1.70 ppb
2016-04-14	4790-142-1100	1.20 ppb
2016-04-22	4790-047-0840	ND
2016-04-22	4790-071-1030	ND
2016-07-25	4790-012-1230	ND
2016-07-27	4790-142-1130	0.820 ppb
2016-08-03	4790-034-1145	ND
2016-08-03	4790-041-0955	ND
2016-10-26	4790-143-1015	1.30 ppb
2016-11-10	4790-153-0935	1.50 ppb
2017-01-18	4790-090-1120	1.20 ppb
2017-02-03	4790-153-1050	2.10 ppb
2017-02-28	4790-801-1129	2.80 ppb
2017-02-28	4790-802-0946	6.30 ppb
2017-02-28	4790-803-1251	ND
2017-02-28	4790-804-1212	1.000 ppb
2017-02-28	4790-805-1017	1.90 ppb
2017-02-28	4790-806-1115	1.10 ppb
2017-02-28	4790-807-1146	1.40 ppb
2017-02-28	4790-808-1031	1.80 ppb
2017-03-09	4790-046-0907	ND
2017-03-23	4790-142-1020	0.870 ppb
2017-04-11	4790-043-0955	ND
2017-04-11	4790-084-0940	2.10 ppb
2017-04-11	4790-085-1040	5.40 ppb
2017-04-12	4790-142-1030	0.830 ppb
2017-04-19	4790-065-1035	ND
2017-04-27	4790-086-1025	27.0 ppb
2017-05-04	4790-153-1005	17.0 ppb
2017-06-09	4790-801-0820	4.00 ppb
2017-06-09	4790-802-0958	12.0 ppb
2017-06-09	4790-803-0943	6.50 ppb
2017-06-09	4790-804-0910	3.80 ppb
2017-06-09	4790-805-1020	8.20 ppb
2017-06-09	4790-806-0807	6.60 ppb
2017-06-09	4790-807-0835	9.20 ppb
2017-06-09	4790-808-1030	9.00 ppb
2017-06-14	4790-051-1130	ND
2017-06-15	4790-048-1053	0.590 ppb
2017-07-13	4790-142-1035	4.50 ppb
2017-08-09	4790-095-1000	ND
2017-08-10	4790-153-1215	2.00 ppb
2017-08-10	4790-801-0853	5.00 ppb
2017-08-10	4790-802-1038	3.20 ppb
2017-08-10	4790-803-1021	2.80 ppb
2017-08-10	4790-804-0950	3.40 ppb
2017-08-10	4790-805-1105	3.60 ppb
2017-08-10	4790-806-0840	3.70 ppb
2017-08-10	4790-807-0919	4.80 ppb
2017-08-10	4790-808-1118	3.80 ppb
2017-09-01	4790-150-0930	0.590 ppb
2017-09-28	4790-059-0943	ND
2017-10-17	4790-029-1101	ND
2017-10-19	4790-142-1020	2.30 ppb
2017-11-08	4790-150-1445	0.680 ppb
2017-11-22	4790-151-1100	ND
2017-11-30	4790-801-1128	5.20 ppb
2017-11-30	4790-802-1033	4.50 ppb
2017-11-30	4790-803-1049	1.90 ppb
2017-11-30	4790-804-1209	3.70 ppb
2017-11-30	4790-805-0948	2.20 ppb
2017-11-30	4790-806-1114	4.40 ppb
2017-11-30	4790-807-1147	5.40 ppb
2017-11-30	4790-808-1004	0.730 ppb
2017-12-06	4790-045-1110	ND
2018-01-04	4790-097-1134	ND
2018-01-04	4790-142-1242	1.40 ppb
2018-01-18	4790-042-0845	ND
2018-02-01	4790-801-0930	15.0 ppb
2018-02-01	4790-802-1152	9.40 ppb
2018-02-01	4790-803-1101	11.0 ppb
2018-02-01	4790-804-1009	7.90 ppb
2018-02-01	4790-805-1230	6.40 ppb
2018-02-01	4790-806-0916	9.50 ppb
2018-02-01	4790-807-0945	16.0 ppb
2018-02-01	4790-808-1304	5.40 ppb
2018-02-05	4790-036-1020	1.50 ppb
2018-02-07	4790-150-1242	2.30 ppb
2018-02-07	4790-151-1148	ND
2018-04-18	4790-053-1025	ND
2018-04-25	4790-152-1135	ND
2018-05-02	4790-801-0954	5.40 ppb
2018-05-02	4790-802-1215	6.60 ppb
2018-05-02	4790-803-1149	5.80 ppb
2018-05-02	4790-804-1105	7.20 ppb
2018-05-02	4790-805-1251	2.80 ppb
2018-05-02	4790-806-0925	5.20 ppb
2018-05-02	4790-807-1014	6.60 ppb
2018-05-02	4790-808-1307	2.00 ppb
2018-05-03	4790-150-1130	2.00 ppb
2018-05-03	4790-151-1235	ND
2018-05-08	4790-015-1006	ND
2018-05-15	4790-024-0942	ND
2018-06-14	4790-018-1020	ND
2018-07-02	4790-031-1110	ND
2018-07-11	4790-037-1045	ND
2018-07-11	4790-040-1231	ND
2018-07-17	4790-152-1045	ND
2018-08-09	4790-035-1205	ND
2018-08-09	4790-151-1000	ND
2018-08-14	4790-038-1220	ND
2018-08-14	4790-150-0914	1.10 ppb
2018-08-15	4790-017-1214	1.000 ppb
2018-08-15	4790-025-0952	ND
2018-08-15	4790-027-1029	ND
2018-08-20	4790-801-0927	6.60 ppb
2018-08-20	4790-802-1143	5.50 ppb
2018-08-20	4790-803-1117	4.90 ppb
2018-08-20	4790-804-1010	5.90 ppb
2018-08-20	4790-805-1209	2.40 ppb
2018-08-20	4790-806-0910	4.90 ppb
2018-08-20	4790-807-0946	5.90 ppb
2018-08-20	4790-808-1236	2.80 ppb
2018-10-03	4790-152-1030	ND
2018-10-08	4790-143-1000	2.90 ppb
2018-10-09	4790-044-1135	ND
2018-10-17	4790-155-1240	ND
2018-11-06	4790-150-0957	1.30 ppb
2018-11-06	4790-151-1116	ND
2018-11-20	4790-801-0900	4.80 ppb
2018-11-20	4790-802-0945	4.60 ppb
2018-11-20	4790-803-0910	4.10 ppb
2018-11-20	4790-804-1015	19.0 ppb
2018-11-20	4790-805-1100	2.60 ppb
2018-11-20	4790-806-0815	2.70 ppb
2018-11-20	4790-807-0930	2.00 ppb
2018-11-20	4790-808-1035	ND
2019-01-09	4790-152-1100	ND
2019-01-09	4790-155-0930	ND
2019-02-07	4790-801-1055	1.60 ppb
2019-02-07	4790-802-0830	4.60 ppb
2019-02-07	4790-803-1245	3.20 ppb
2019-02-07	4790-804-1200	1.000 ppb
2019-02-07	4790-805-0915	2.00 ppb
2019-02-07	4790-806-1030	1.40 ppb
2019-02-07	4790-807-1130	1.30 ppb
2019-02-07	4790-808-0945	2.70 ppb
2019-02-12	4790-153-1201	2.40 ppb
2019-02-19	4790-150-0958	1.20 ppb
2019-02-19	4790-151-0841	ND
2019-04-02	4790-155-1115	ND
2019-04-04	4790-071-1009	ND
2019-04-09	4790-047-0820	ND
2019-05-28	4790-801-0900	1.60 ppb
2019-05-28	4790-802-1305	4.20 ppb
2019-05-28	4790-803-1050	1.40 ppb
2019-05-28	4790-804-1000	2.50 ppb
2019-05-28	4790-805-1140	3.00 ppb
2019-05-28	4790-806-0830	2.30 ppb
2019-05-28	4790-807-0930	1.50 ppb
2019-05-28	4790-808-1210	3.70 ppb
2019-06-04	4790-012-1225	ND
2019-07-22	4790-155-0820	ND
2019-08-14	4790-034-0931	ND
2019-08-14	4790-041-1118	ND
2019-10-17	4790-143-0912	3.10 ppb