Total trihalomethanes (TTHMs)

City of Bakersfield

Trihalomethanes are cancer-causing contaminants that form during water treatment with chlorine and other disinfectants. The total trihalomethanes group includes four chemicals: chloroform, bromodichloromethane, dibromochloromethane and bromoform. Read More.

Studies conducted in the U.S. and Europe have found that drinking tap water that carries disinfection byproducts increases the risk of developing bladder cancer. In animal studies, all trihalomethanes cause liver, kidney and intestinal tumors. Some human epidemiological studies also reported an association between disinfection byproducts and an increased risk of problems during pregnancy, including spontaneous miscarriage, cardiovascular defects, neural tube defects and low birth weight.

The health guideline of 0.15 parts per billion, or ppb, for the group of four trihalomethanes, or THM4/TTHM, was defined in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level.

Click here to read more about disinfection byproducts.

MORE ABOUT THIS CONTAMINANT

256

Samples

Samples exceeding legal limit (MCL)

192

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2014	3.09 ppb	44	28	ND - 21.3 ppb
2015	3.67 ppb	44	30	ND - 36.7 ppb
2016	10.3 ppb	46	31	ND - 72.0 ppb
2017	13.6 ppb	44	40	ND - 64.0 ppb
2018	13.2 ppb	43	38	ND - 66.5 ppb
2019	15.3 ppb	35	25	ND - 54.2 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.15 ppb

EPA Maximum Contaminant
Level (MCL) 80 ppb

The legal limit for the group of four trihalomethanes, established in 1998, was based on the need for residual disinfectant levels in water served to customers and the cost of treatment. This limit does not fully protect against the risk of cancer due to exposure to trihalomethanes.

ppb = parts per billion

All test results

Date	Lab ID	Result
2014-01-06	5701-111-1420	ND
2014-01-21	5701-900-1255	2.50 ppb
2014-01-21	5701-901-1040	2.00 ppb
2014-01-21	5701-902-1150	ND
2014-01-21	5701-903-1115	2.70 ppb
2014-01-21	5701-904-0955	3.60 ppb
2014-01-21	5701-905-1220	1.60 ppb
2014-01-21	5701-906-1345	2.30 ppb
2014-01-21	5701-907-0935	3.10 ppb
2014-02-10	5701-111-1240	ND
2014-03-03	5701-111-1032	ND
2014-04-02	5701-111-1240	0.500 ppb
2014-04-21	5701-900-1155	4.90 ppb
2014-04-21	5701-901-0950	11.9 ppb
2014-04-21	5701-902-1108	ND
2014-04-21	5701-903-1047	21.2 ppb
2014-04-21	5701-904-1019	1.80 ppb
2014-04-21	5701-905-1129	1.90 ppb
2014-04-21	5701-906-1221	ND
2014-04-21	5701-907-0925	10.4 ppb
2014-05-08	5701-111-1440	ND
2014-06-16	5701-111-0914	ND
2014-07-08	5701-111-0847	ND
2014-07-24	5701-904-1227	3.00 ppb
2014-07-25	5701-900-1102	7.50 ppb
2014-07-25	5701-901-1307	21.3 ppb
2014-07-25	5701-902-1147	ND
2014-07-25	5701-903-1207	5.90 ppb
2014-07-25	5701-905-1122	5.00 ppb
2014-07-25	5701-906-1037	0.700 ppb
2014-07-25	5701-907-1242	5.90 ppb
2014-08-05	5701-111-1004	ND
2014-09-04	5701-111-0939	ND
2014-10-06	5701-111-1007	ND
2014-10-23	5701-900-0945	1.80 ppb
2014-10-23	5701-901-1455	1.60 ppb
2014-10-23	5701-902-1030	ND
2014-10-23	5701-903-1338	4.20 ppb
2014-10-23	5701-904-1255	2.70 ppb
2014-10-23	5701-905-1018	1.20 ppb
2014-10-23	5701-906-0910	ND
2014-10-23	5701-907-1310	4.00 ppb
2014-11-04	5701-111-1010	ND
2014-12-08	5701-111-1156	0.600 ppb
2015-01-07	5701-111-1142	ND
2015-01-22	5701-900-0928	2.60 ppb
2015-01-22	5701-901-0928	1.60 ppb
2015-01-22	5701-902-0928	2.80 ppb
2015-01-22	5701-903-0928	2.40 ppb
2015-01-22	5701-904-0928	6.10 ppb
2015-01-22	5701-905-0928	1.50 ppb
2015-01-22	5701-906-0928	2.10 ppb
2015-01-22	5701-907-0928	8.00 ppb
2015-03-25	5701-111-1319	ND
2015-04-07	5701-111-1222	ND
2015-04-27	5701-900-0925	1.40 ppb
2015-04-27	5701-901-0925	1.40 ppb
2015-04-27	5701-902-0925	ND
2015-04-27	5701-903-0925	3.20 ppb
2015-04-27	5701-904-0925	36.7 ppb
2015-04-27	5701-905-0925	0.600 ppb
2015-04-27	5701-906-0925	0.900 ppb
2015-04-27	5701-907-0925	4.90 ppb
2015-05-12	9590-111-0923	ND
2015-06-04	5701-111-0833	ND
2015-07-01	5701-111-0807	ND
2015-07-23	5701-900-0817	6.30 ppb
2015-07-23	5701-901-0817	9.20 ppb
2015-07-23	5701-902-0817	0.600 ppb
2015-07-23	5701-903-0817	11.2 ppb
2015-07-23	5701-904-0817	2.10 ppb
2015-07-23	5701-905-0817	1.30 ppb
2015-07-23	5701-906-0817	ND
2015-07-23	5701-907-0817	3.50 ppb
2015-08-05	5701-111-0941	ND
2015-09-01	5701-111-1115	ND
2015-10-06	5701-111-1137	ND
2015-10-19	5701-900-0919	4.80 ppb
2015-10-19	5701-901-0919	2.10 ppb
2015-10-19	5701-902-0919	3.80 ppb
2015-10-19	5701-903-0919	16.4 ppb
2015-10-19	5701-904-0919	3.30 ppb
2015-10-19	5701-905-0919	4.80 ppb
2015-10-19	5701-906-0919	1.20 ppb
2015-10-19	5701-907-0919	14.6 ppb
2015-11-03	5701-111-1141	ND
2015-12-02	5701-111-1055	ND
2015-12-21	9590-111-1045	ND
2016-01-04	5701-111-1210	ND
2016-01-19	5701-900-0746	2.20 ppb
2016-01-19	5701-901-0746	1.10 ppb
2016-01-19	5701-902-0746	2.30 ppb
2016-01-19	5701-903-0746	2.50 ppb
2016-01-19	5701-904-0746	2.90 ppb
2016-01-19	5701-905-0746	1.30 ppb
2016-01-19	5701-906-0746	ND
2016-01-19	5701-907-0746	0.900 ppb
2016-02-08	5701-111-1040	ND
2016-03-02	5701-111-1406	ND
2016-04-06	5701-111-1012	ND
2016-04-19	5701-900-0946	22.4 ppb
2016-04-19	5701-901-0946	37.2 ppb
2016-04-19	5701-902-0946	2.70 ppb
2016-04-19	5701-903-0946	50.5 ppb
2016-04-19	5701-904-0946	3.20 ppb
2016-04-19	5701-905-0946	15.6 ppb
2016-04-19	5701-906-0946	0.700 ppb
2016-04-19	5701-907-0946	2.80 ppb
2016-05-04	5701-111-1032	ND
2016-06-09	5701-111-1025	ND
2016-07-18	5810-900-0909	44.0 ppb
2016-07-18	5810-901-1038	46.0 ppb
2016-07-18	5810-902-0948	4.30 ppb
2016-07-18	5810-903-1013	72.0 ppb
2016-07-18	5810-904-1103	62.0 ppb
2016-07-18	5810-905-0925	4.90 ppb
2016-07-18	5810-906-1315	ND
2016-07-18	5810-907-1122	12.0 ppb
2016-07-20	5701-111-1244	ND
2016-07-25	5701-127-1345	ND
2016-08-01	5701-111-0907	ND
2016-09-06	5701-111-1030	ND
2016-09-29	5701-126-1030	ND
2016-10-03	5701-111-1310	0.500 ppb
2016-10-18	5701-900-0928	16.6 ppb
2016-10-18	5701-901-0928	18.5 ppb
2016-10-18	5701-902-0928	1.10 ppb
2016-10-18	5701-903-0928	37.3 ppb
2016-10-18	5701-904-0928	1.30 ppb
2016-10-18	5701-905-0928	1.80 ppb
2016-10-18	5701-906-0928	ND
2016-10-18	5701-907-0928	3.10 ppb
2016-11-14	5701-111-0955	1.20 ppb
2016-12-05	5701-111-1330	ND
2017-01-06	5701-111-1023	0.600 ppb
2017-01-17	5810-900-1005	6.70 ppb
2017-01-17	5810-901-1330	3.00 ppb
2017-01-17	5810-902-1045	9.80 ppb
2017-01-17	5810-903-1115	20.0 ppb
2017-01-17	5810-904-1145	0.740 ppb
2017-01-17	5810-905-1030	ND
2017-01-17	5810-906-0925	ND
2017-01-17	5810-907-1155	2.20 ppb
2017-02-07	9590-111-1335	ND
2017-03-06	5810-111-1405	1.10 ppb
2017-04-03	5701-111-1053	1.50 ppb
2017-04-18	5810-900-1029	40.0 ppb
2017-04-18	5810-901-1435	62.0 ppb
2017-04-18	5810-902-1120	1.40 ppb
2017-04-18	5810-903-1340	63.0 ppb
2017-04-18	5810-904-1139	3.20 ppb
2017-04-18	5810-905-1059	1.10 ppb
2017-04-18	5810-906-1003	5.50 ppb
2017-04-18	5810-907-1358	64.0 ppb
2017-05-01	5701-111-1148	1.50 ppb
2017-06-05	5701-111-1133	1.50 ppb
2017-07-10	5701-111-1235	1.20 ppb
2017-07-17	5810-900-1301	9.70 ppb
2017-07-17	5810-901-1229	37.0 ppb
2017-07-17	5810-902-1150	6.10 ppb
2017-07-17	5810-903-1213	41.0 ppb
2017-07-17	5810-904-0901	1.60 ppb
2017-07-17	5810-905-1043	4.40 ppb
2017-07-17	5810-906-1113	ND
2017-07-17	5810-907-1004	39.0 ppb
2017-08-07	5701-111-1135	1.90 ppb
2017-09-06	5701-111-1255	3.10 ppb
2017-10-02	5701-111-1430	4.20 ppb
2017-10-16	5701-900-0859	1.70 ppb
2017-10-16	5701-901-0859	25.0 ppb
2017-10-16	5701-902-0859	2.30 ppb
2017-10-16	5701-903-0859	33.3 ppb
2017-10-16	5810-904-1255	44.0 ppb
2017-10-16	5810-905-1125	1.50 ppb
2017-10-16	5810-906-1400	0.510 ppb
2017-10-16	5810-907-1235	42.0 ppb
2017-11-02	5701-111-1210	5.30 ppb
2017-12-04	5701-111-1255	6.10 ppb
2018-01-04	5701-111-1045	2.30 ppb
2018-01-18	5810-900-1002	21.0 ppb
2018-01-18	5810-901-1105	13.0 ppb
2018-01-18	5810-902-1026	0.520 ppb
2018-01-18	5810-903-1053	20.0 ppb
2018-01-18	5810-904-1157	33.0 ppb
2018-01-18	5810-905-1219	17.0 ppb
2018-01-18	5810-906-0933	2.00 ppb
2018-01-18	5810-907-1140	6.90 ppb
2018-02-06	5701-111-1111	2.20 ppb
2018-03-06	5701-111-1128	3.00 ppb
2018-04-02	5810-111-1206	2.90 ppb
2018-04-16	5701-900-0904	4.10 ppb
2018-04-16	5701-901-0904	2.20 ppb
2018-04-16	5701-902-0904	0.600 ppb
2018-04-16	5701-903-0904	12.1 ppb
2018-04-16	5701-904-0904	59.6 ppb
2018-04-16	5701-905-0904	0.800 ppb
2018-04-16	5701-906-0904	1.40 ppb
2018-04-16	5701-907-0904	48.1 ppb
2018-05-30	5701-111-0923	1.70 ppb
2018-06-11	5701-111-1045	1.70 ppb
2018-07-10	5810-111-0914	ND
2018-07-17	5701-900-0822	20.9 ppb
2018-07-17	5701-901-0822	50.2 ppb
2018-07-17	5701-902-0822	ND
2018-07-17	5701-903-0822	47.1 ppb
2018-07-17	5701-904-0822	39.0 ppb
2018-07-17	5701-905-0822	0.600 ppb
2018-07-17	5701-906-0822	ND
2018-07-17	5701-907-0822	49.0 ppb
2018-08-08	5701-111-1229	1.20 ppb
2018-09-11	5701-111-0950	1.000 ppb
2018-10-04	5701-111-1036	0.900 ppb
2018-10-17	5701-900-0930	4.10 ppb
2018-10-17	5701-901-0930	1.40 ppb
2018-10-17	5701-902-0930	0.600 ppb
2018-10-17	5701-903-0930	25.8 ppb
2018-10-17	5701-904-0930	ND
2018-10-17	5701-905-0930	0.800 ppb
2018-10-17	5701-906-0930	ND
2018-10-17	5701-907-0930	66.5 ppb
2018-11-06	5701-111-1006	0.900 ppb
2019-01-16	5701-900-0830	5.20 ppb
2019-01-16	5701-901-0830	3.40 ppb
2019-01-16	5701-902-0830	0.600 ppb
2019-01-16	5701-903-0830	28.0 ppb
2019-01-16	5701-904-0830	ND
2019-01-16	5701-905-0830	1.80 ppb
2019-01-16	5701-906-0830	1.90 ppb
2019-01-16	5701-907-0830	11.9 ppb
2019-04-16	5701-900-0825	30.6 ppb
2019-04-16	5701-901-0825	52.6 ppb
2019-04-16	5701-902-0825	2.00 ppb
2019-04-16	5701-903-0825	54.2 ppb
2019-04-16	5701-904-0825	ND
2019-04-16	5701-905-0825	1.20 ppb
2019-04-16	5701-906-0825	13.9 ppb
2019-04-16	5701-907-0825	26.0 ppb
2019-07-16	5701-904-1139	44.1 ppb
2019-07-16	5701-905-1155	ND
2019-07-16	5701-906-1246	ND
2019-07-16	5701-907-1125	40.0 ppb
2019-07-17	5701-900-1012	19.3 ppb
2019-07-17	5701-901-0926	36.0 ppb
2019-07-17	5701-902-1000	0.510 ppb
2019-07-17	5701-903-0944	15.8 ppb
2019-08-17	5701-127-1125	ND
2019-10-22	5701-900-1214	29.5 ppb
2019-10-22	5701-901-1241	30.3 ppb
2019-10-22	5701-902-1012	ND
2019-10-22	5701-903-1101	20.8 ppb
2019-10-22	5701-904-1138	26.3 ppb
2019-10-22	5701-905-1105	ND
2019-10-22	5701-906-0937	ND
2019-10-22	5701-907-1308	40.5 ppb
2019-11-19	5701-126-1335	ND
2019-12-17	5701-111-1153	ND