Total trihalomethanes (TTHMs)

Wailuku

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

173

Samples

Samples exceeding legal limit (MCL)

144

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2014	7.03 ppb	43	35	ND - 32.0 ppb
2015	6.68 ppb	38	34	ND - 24.0 ppb
2016	7.98 ppb	27	21	ND - 35.0 ppb
2017	6.21 ppb	27	20	ND - 27.0 ppb
2018	9.01 ppb	20	17	ND - 29.0 ppb
2019	15.3 ppb	18	17	ND - 32.0 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
2014-02-21	201402260433	ND
2014-02-24	201402260912	ND
2014-02-24	201402260878	ND
2014-02-24	201402260728	ND
2014-02-25	201402280305	ND
2014-02-25	201402280114	9.00 ppb
2014-03-06	201403110749	7.20 ppb
2014-03-06	201403110746	11.0 ppb
2014-03-06	201403110747	8.00 ppb
2014-03-06	201403110751	7.50 ppb
2014-03-06	201403110752	28.0 ppb
2014-03-06	201403110745	6.00 ppb
2014-03-06	201403110748	7.30 ppb
2014-03-06	201403110750	4.80 ppb
2014-03-19	201403210385	ND
2014-03-19	201403210383	2.10 ppb
2014-03-19	201403210381	ND
2014-03-24	201403260368	ND
2014-03-27	201403290120	1.000 ppb
2014-06-05	201406100363	4.70 ppb
2014-06-05	201406100364	21.0 ppb
2014-06-05	201406100361	9.10 ppb
2014-06-05	201406100355	3.60 ppb
2014-06-05	201406100362	3.50 ppb
2014-06-05	201406100356	3.00 ppb
2014-06-05	201406100357	2.60 ppb
2014-06-05	201406100358	8.20 ppb
2014-09-04	201409100080	2.20 ppb
2014-09-04	201409100081	2.60 ppb
2014-09-04	201409100086	24.0 ppb
2014-09-04	201409100082	10.00 ppb
2014-09-04	201409100079	5.90 ppb
2014-09-04	201409100084	5.00 ppb
2014-09-04	201409100083	9.00 ppb
2014-09-04	201409100085	7.00 ppb
2014-12-04	201412110291	18.0 ppb
2014-12-04	201412110292	8.50 ppb
2014-12-04	201412110296	4.00 ppb
2014-12-04	201412110297	6.20 ppb
2014-12-04	201412110293	8.60 ppb
2014-12-04	201412110294	32.0 ppb
2014-12-04	201412110295	6.40 ppb
2014-12-04	201412110298	5.40 ppb
2015-01-14	201501190213	5.10 ppb
2015-01-14	201501190214	3.60 ppb
2015-01-14	201501190215	3.30 ppb
2015-01-14	201501190216	5.10 ppb
2015-01-14	201501190218	7.60 ppb
2015-01-14	201501190219	22.0 ppb
2015-01-15	201501190223	4.80 ppb
2015-01-15	201501190224	3.80 ppb
2015-01-26	201501280565	ND
2015-01-26	201501280741	ND
2015-01-26	201501280752	ND
2015-01-26	201501280753	4.80 ppb
2015-04-09	201504140817	5.50 ppb
2015-04-09	201504140818	4.70 ppb
2015-04-09	201504140819	4.50 ppb
2015-04-09	201504140820	5.10 ppb
2015-04-09	201504140831	12.0 ppb
2015-04-09	201504140832	7.70 ppb
2015-04-09	201504140833	7.80 ppb
2015-04-09	201504140834	23.0 ppb
2015-06-16	201506180519	0.600 ppb
2015-07-22	201507240272	13.0 ppb
2015-07-22	201507240273	3.30 ppb
2015-07-22	201507240274	1.60 ppb
2015-07-22	201507240275	5.10 ppb
2015-07-22	201507240276	4.70 ppb
2015-07-22	201507240277	2.20 ppb
2015-07-22	201507240278	18.0 ppb
2015-07-22	201507240279	2.90 ppb
2015-09-08	201509100855	ND
2015-10-09	201510130316	5.30 ppb
2015-10-09	201510130317	8.70 ppb
2015-10-09	201510130318	5.90 ppb
2015-10-09	201510130319	7.30 ppb
2015-10-09	201510130320	9.60 ppb
2015-10-09	201510130321	6.20 ppb
2015-10-09	201510130322	5.20 ppb
2015-10-09	201510130323	24.0 ppb
2016-01-15		6.70 ppb
2016-01-15		3.70 ppb
2016-01-15		8.60 ppb
2016-01-15		4.60 ppb
2016-01-15		4.40 ppb
2016-01-15		6.10 ppb
2016-01-15		7.10 ppb
2016-01-15		24.0 ppb
2016-02-23		10.00 ppb
2016-02-26		ND
2016-02-26		ND
2016-02-26		ND
2016-04-14		9.60 ppb
2016-04-14		5.80 ppb
2016-04-14		3.10 ppb
2016-04-14		17.0 ppb
2016-07-15		9.60 ppb
2016-07-15		6.20 ppb
2016-07-15		5.30 ppb
2016-07-15		35.0 ppb
2016-09-12		ND
2016-10-06		5.00 ppb
2016-10-06		6.40 ppb
2016-10-06		2.20 ppb
2016-10-06		35.0 ppb
2016-11-30		ND
2016-11-30		ND
2017-01-13		6.10 ppb
2017-01-13		5.10 ppb
2017-01-13		3.30 ppb
2017-01-13		27.0 ppb
2017-01-31		0.780 ppb
2017-01-31		0.560 ppb
2017-01-31		ND
2017-02-24		6.70 ppb
2017-02-24		ND
2017-02-27		ND
2017-02-27		ND
2017-02-27		ND
2017-04-06		5.50 ppb
2017-04-06		4.40 ppb
2017-04-06		3.70 ppb
2017-04-06		26.0 ppb
2017-05-19		0.520 ppb
2017-05-19		ND
2017-07-13		7.80 ppb
2017-07-13		5.40 ppb
2017-07-13		3.50 ppb
2017-07-13		22.0 ppb
2017-09-21		ND
2017-10-06		7.70 ppb
2017-10-06		5.00 ppb
2017-10-06		3.70 ppb
2017-10-06		23.0 ppb
2018-01-11	201801180640	9.50 ppb
2018-01-11	201801180643	7.50 ppb
2018-01-11	201801180642	3.80 ppb
2018-01-11	201801180641	27.0 ppb
2018-01-30	201801030999	ND
2018-01-31	201801030998	4.40 ppb
2018-01-31	201801031000	ND
2018-04-05	201804100503	14.0 ppb
2018-04-05	201804100506	10.00 ppb
2018-04-05	201804100505	3.50 ppb
2018-04-05	201804100504	29.0 ppb
2018-05-17	201805180453	ND
2018-07-02	201807060176	10.00 ppb
2018-07-02	201807060179	3.50 ppb
2018-07-02	201807060178	2.70 ppb
2018-07-02	201807060177	17.0 ppb
2018-10-04	201810090382	5.60 ppb
2018-10-04	201810090385	8.30 ppb
2018-10-04	201810090384	2.30 ppb
2018-10-04	201810090383	22.0 ppb
2019-01-03	201901080077	9.80 ppb
2019-01-03	201901080080	7.30 ppb
2019-01-03	201901080079	5.30 ppb
2019-01-03	201901080078	31.0 ppb
2019-02-04	201902050178	32.0 ppb
2019-03-07	201903120187	ND
2019-04-05	201904090474	10.00 ppb
2019-04-05	201904090477	12.0 ppb
2019-04-05	201904090476	5.00 ppb
2019-04-05	201904090475	31.0 ppb
2019-07-26	201907300338	24.0 ppb
2019-07-26	201907300341	14.0 ppb
2019-07-26	201907300340	5.30 ppb
2019-07-26	201907300339	23.0 ppb
2019-10-03	201910080604	19.0 ppb
2019-10-03	201910080607	14.0 ppb
2019-10-03	201910080606	8.30 ppb
2019-10-03	201910080605	25.0 ppb