Chloroform

Ontario Municipal Utilities 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

233

Samples

Samples exceeding legal limit (MCL)

153

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	1.79 ppb	63	33	ND - 5.80 ppb
2015	2.72 ppb	33	28	ND - 11.0 ppb
2016	2.92 ppb	25	17	ND - 15.0 ppb
2017	5.32 ppb	47	26	ND - 30.0 ppb
2018	4.85 ppb	32	27	ND - 13.0 ppb
2019	5.62 ppb	33	22	ND - 14.0 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
2014-02-20	4790-601-0820	3.60 ppb
2014-02-20	4790-602-0745	0.640 ppb
2014-02-20	4790-603-0855	3.80 ppb
2014-02-20	4790-604-1125	3.90 ppb
2014-02-20	4790-605-1105	3.70 ppb
2014-02-20	4790-606-0800	3.80 ppb
2014-02-20	4790-607-1115	3.60 ppb
2014-02-20	4790-608-0840	3.60 ppb
2014-05-21	4790-601-0820	2.70 ppb
2014-05-21	4790-602-0729	0.760 ppb
2014-05-21	4790-603-0855	2.70 ppb
2014-05-21	4790-604-1145	2.80 ppb
2014-05-21	4790-605-1115	2.80 ppb
2014-05-21	4790-606-0800	2.60 ppb
2014-05-21	4790-607-1130	2.80 ppb
2014-05-21	4790-608-0840	2.80 ppb
2014-07-11	4790-017-0925	ND
2014-07-11	4790-020-1020	ND
2014-07-11	4790-045-0825	ND
2014-07-14	4790-046-0800	ND
2014-07-14	4790-048-0910	ND
2014-07-18	4790-027-0930	ND
2014-07-18	4790-042-0900	ND
2014-07-24	4790-029-0830	ND
2014-07-24	4790-031-0915	ND
2014-07-28	4790-026-0900	ND
2014-07-29	4790-022-1020	ND
2014-07-29	4790-025-0950	ND
2014-07-29	4790-034-0945	ND
2014-07-29	4790-040-1040	ND
2014-08-12	4790-040-0845	ND
2014-08-12	4790-049-0800	ND
2014-08-19	4790-032-0815	ND
2014-08-19	4790-034-0900	ND
2014-08-21	4790-601-0827	5.10 ppb
2014-08-21	4790-602-0758	3.90 ppb
2014-08-21	4790-603-0900	3.50 ppb
2014-08-21	4790-604-1051	5.80 ppb
2014-08-21	4790-605-1116	5.60 ppb
2014-08-21	4790-606-0813	5.40 ppb
2014-08-21	4790-607-1103	5.60 ppb
2014-08-21	4790-608-0845	5.30 ppb
2014-10-15	4790-017-1000	ND
2014-10-15	4790-025-1100	ND
2014-10-16	4790-045-0815	ND
2014-10-16	4790-046-0910	ND
2014-10-16	4790-048-1000	ND
2014-10-28	4790-041-0850	ND
2014-10-28	4790-043-0820	ND
2014-10-28	4790-044-0800	ND
2014-11-06	4790-022-1010	ND
2014-11-06	4790-026-0915	ND
2014-11-07	4790-030-0930	0.750 ppb
2014-11-20	4790-601-0820	3.30 ppb
2014-11-20	4790-602-0730	3.10 ppb
2014-11-20	4790-603-0910	3.20 ppb
2014-11-20	4790-604-1145	2.90 ppb
2014-11-20	4790-605-1125	3.00 ppb
2014-11-20	4790-606-0800	3.40 ppb
2014-11-20	4790-607-1135	3.00 ppb
2014-11-20	4790-608-0840	3.20 ppb
2014-12-04	4790-027-1020	ND
2014-12-04	4790-042-0945	ND
2015-02-19	4790-601-0755	2.40 ppb
2015-02-19	4790-602-0730	0.970 ppb
2015-02-19	4790-603-0825	2.50 ppb
2015-02-19	4790-604-1105	0.920 ppb
2015-02-19	4790-605-1045	0.940 ppb
2015-02-19	4790-606-1125	2.50 ppb
2015-02-19	4790-607-1055	ND
2015-02-19	4790-608-0815	1.20 ppb
2015-05-07	4790-050-1042	ND
2015-05-21	4790-601-0817	4.50 ppb
2015-05-21	4790-602-0744	ND
2015-05-21	4790-603-0852	1.10 ppb
2015-05-21	4790-604-1140	1.40 ppb
2015-05-21	4790-605-1108	ND
2015-05-21	4790-606-0800	4.60 ppb
2015-05-21	4790-607-1125	5.70 ppb
2015-05-21	4790-608-0838	5.50 ppb
2015-08-13	4790-601-0930	7.60 ppb
2015-08-13	4790-602-0753	0.620 ppb
2015-08-13	4790-603-0905	7.20 ppb
2015-08-13	4790-604-1225	1.60 ppb
2015-08-13	4790-605-1207	0.860 ppb
2015-08-13	4790-606-0830	6.60 ppb
2015-08-13	4790-607-1215	11.0 ppb
2015-08-13	4790-608-0915	2.80 ppb
2015-11-19	4790-601-0835	0.840 ppb
2015-11-19	4790-602-0750	ND
2015-11-19	4790-603-0910	0.500 ppb
2015-11-19	4790-604-1210	3.70 ppb
2015-11-19	4790-605-1140	3.70 ppb
2015-11-19	4790-606-0810	1.10 ppb
2015-11-19	4790-607-1155	3.50 ppb
2015-11-19	4790-608-0850	3.80 ppb
2016-02-18	4790-601-0815	1.10 ppb
2016-05-26	4790-601-0750	1.90 ppb
2016-05-26	4790-602-0716	ND
2016-05-26	4790-603-0823	0.520 ppb
2016-05-26	4790-604-1055	15.0 ppb
2016-05-26	4790-605-1034	15.0 ppb
2016-05-26	4790-606-0734	1.30 ppb
2016-05-26	4790-607-1044	15.0 ppb
2016-05-26	4790-608-0806	14.0 ppb
2016-08-25	4790-601-0811	1.10 ppb
2016-08-25	4790-602-0730	1.60 ppb
2016-08-25	4790-603-0841	ND
2016-08-25	4790-604-1115	ND
2016-08-25	4790-605-1134	ND
2016-08-25	4790-606-0749	0.970 ppb
2016-08-25	4790-607-1124	ND
2016-08-25	4790-608-0824	0.630 ppb
2016-11-17	4790-601-0802	1.40 ppb
2016-11-17	4790-602-0715	ND
2016-11-17	4790-603-0847	0.940 ppb
2016-11-17	4790-604-1136	0.730 ppb
2016-11-17	4790-605-1113	ND
2016-11-17	4790-606-0736	1.10 ppb
2016-11-17	4790-607-1123	ND
2016-11-17	4790-608-0820	0.590 ppb
2017-02-01	4790-050-0831	ND
2017-02-23	4790-601-1000	0.860 ppb
2017-02-23	4790-602-0920	0.890 ppb
2017-02-23	4790-603-1040	ND
2017-02-23	4790-604-1105	ND
2017-02-23	4790-605-1135	ND
2017-02-23	4790-606-0945	1.80 ppb
2017-02-23	4790-607-1115	ND
2017-02-23	4790-608-1020	0.650 ppb
2017-04-20	4790-030-0910	ND
2017-05-11	4790-601-0835	6.40 ppb
2017-05-11	4790-602-0745	ND
2017-05-11	4790-603-0925	7.80 ppb
2017-05-11	4790-604-1210	27.0 ppb
2017-05-11	4790-605-1150	26.0 ppb
2017-05-11	4790-606-0810	5.30 ppb
2017-05-11	4790-608-0850	6.80 ppb
2017-05-30	4790-607-1452	30.0 ppb
2017-07-03	4790-042-0910	ND
2017-07-03	4790-043-1110	ND
2017-07-03	4790-044-1015	ND
2017-07-06	4790-025-0955	0.860 ppb
2017-07-12	4790-031-1130	ND
2017-07-12	4790-034-0910	ND
2017-07-12	4790-041-0815	ND
2017-07-12	4790-049-1055	ND
2017-07-19	4790-020-0730	ND
2017-07-19	4790-026-0930	ND
2017-07-19	4790-032-0835	ND
2017-07-19	4790-045-1050	ND
2017-08-03	4790-048-0815	ND
2017-08-10	4790-601-0830	3.10 ppb
2017-08-10	4790-602-0740	ND
2017-08-10	4790-603-0905	1.50 ppb
2017-08-10	4790-604-1200	19.0 ppb
2017-08-10	4790-605-1125	19.0 ppb
2017-08-10	4790-606-0805	4.00 ppb
2017-08-10	4790-607-1140	19.0 ppb
2017-08-10	4790-608-0855	22.0 ppb
2017-11-16	4790-601-0835	5.30 ppb
2017-11-16	4790-602-0740	ND
2017-11-16	4790-603-0920	3.20 ppb
2017-11-16	4790-604-1210	9.20 ppb
2017-11-16	4790-605-1142	9.30 ppb
2017-11-16	4790-606-0805	1.90 ppb
2017-11-16	4790-607-1155	9.10 ppb
2017-11-16	4790-608-0900	10.00 ppb
2018-02-08	4790-601-0820	1.60 ppb
2018-02-08	4790-602-0740	ND
2018-02-08	4790-603-0905	0.720 ppb
2018-02-08	4790-604-1145	0.540 ppb
2018-02-08	4790-605-1120	ND
2018-02-08	4790-606-0800	1.10 ppb
2018-02-08	4790-607-1135	3.20 ppb
2018-02-08	4790-608-0850	7.90 ppb
2018-05-10	4790-601-0825	1.80 ppb
2018-05-10	4790-602-0740	0.550 ppb
2018-05-10	4790-603-0905	ND
2018-05-10	4790-604-1205	12.0 ppb
2018-05-10	4790-605-1135	ND
2018-05-10	4790-606-0805	1.40 ppb
2018-05-10	4790-607-1150	12.0 ppb
2018-05-10	4790-608-0845	12.0 ppb
2018-08-09	4790-601-0850	3.40 ppb
2018-08-09	4790-602-0800	2.40 ppb
2018-08-09	4790-603-0930	1.80 ppb
2018-08-09	4790-604-1235	13.0 ppb
2018-08-09	4790-605-1205	13.0 ppb
2018-08-09	4790-606-0825	5.00 ppb
2018-08-09	4790-607-1220	12.0 ppb
2018-08-09	4790-608-0910	12.0 ppb
2018-11-15	4790-601-0830	5.30 ppb
2018-11-15	4790-602-0740	ND
2018-11-15	4790-603-0910	5.50 ppb
2018-11-15	4790-604-1210	5.40 ppb
2018-11-15	4790-605-1140	5.40 ppb
2018-11-15	4790-606-0800	5.30 ppb
2018-11-15	4790-607-1155	5.30 ppb
2018-11-15	4790-608-0855	5.50 ppb
2019-02-13	4790-601-1130	2.50 ppb
2019-02-13	4790-602-1210	ND
2019-02-13	4790-603-1055	3.30 ppb
2019-02-13	4790-604-1035	13.0 ppb
2019-02-13	4790-605-1010	13.0 ppb
2019-02-13	4790-606-1150	4.70 ppb
2019-02-13	4790-607-1020	13.0 ppb
2019-02-13	4790-608-1110	14.0 ppb
2019-05-09	4790-601-0900	1.50 ppb
2019-05-09	4790-602-0815	ND
2019-05-09	4790-603-0955	ND
2019-05-09	4790-604-1015	12.0 ppb
2019-05-09	4790-605-1045	11.0 ppb
2019-05-09	4790-606-0835	1.20 ppb
2019-05-09	4790-607-1030	12.0 ppb
2019-05-09	4790-608-0935	12.0 ppb
2019-08-15	4790-601-0805	13.0 ppb
2019-08-15	4790-602-0725	7.00 ppb
2019-08-15	4790-603-0850	13.0 ppb
2019-08-15	4790-604-1200	ND
2019-08-15	4790-605-1125	ND
2019-08-15	4790-606-0745	13.0 ppb
2019-08-15	4790-607-1140	ND
2019-08-15	4790-608-0830	ND
2019-10-30	4790-040-0826	ND
2019-11-14	4790-601-0810	7.60 ppb
2019-11-14	4790-602-0735	2.80 ppb
2019-11-14	4790-603-0850	7.50 ppb
2019-11-14	4790-604-1135	ND
2019-11-14	4790-605-1110	ND
2019-11-14	4790-606-0750	6.60 ppb
2019-11-14	4790-607-1125	ND
2019-11-14	4790-608-0825	1.90 ppb