Total trihalomethanes (TTHMs)

East Cherry Creek Valley Water and Sanitation District

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

200

Samples

Samples exceeding legal limit (MCL)

184

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2014	31.6 ppb	32	30	ND - 74.5 ppb
2015	31.4 ppb	40	37	ND - 67.7 ppb
2016	18.8 ppb	32	27	ND - 37.5 ppb
2017	35.2 ppb	32	31	ND - 58.2 ppb
2018	36.2 ppb	32	29	ND - 61.0 ppb
2019	34.3 ppb	32	30	ND - 70.4 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	Result
2014-02-13	42.6 ppb
2014-02-13	10.2 ppb
2014-02-13	ND
2014-02-13	50.7 ppb
2014-02-13	55.5 ppb
2014-02-13	19.3 ppb
2014-02-13	58.9 ppb
2014-02-13	13.1 ppb
2014-05-01	38.6 ppb
2014-05-01	37.0 ppb
2014-05-01	46.7 ppb
2014-05-01	22.7 ppb
2014-05-01	45.9 ppb
2014-05-01	39.4 ppb
2014-05-01	34.2 ppb
2014-05-01	42.4 ppb
2014-08-14	23.0 ppb
2014-08-15	19.2 ppb
2014-08-15	20.3 ppb
2014-08-15	32.0 ppb
2014-08-15	19.6 ppb
2014-08-15	20.1 ppb
2014-08-15	15.6 ppb
2014-08-15	20.4 ppb
2014-11-25	74.5 ppb
2014-11-25	32.8 ppb
2014-11-25	ND
2014-11-25	50.6 ppb
2014-11-25	51.1 ppb
2014-11-25	3.00 ppb
2014-11-25	39.5 ppb
2014-11-25	32.4 ppb
2015-02-13	3.80 ppb
2015-02-13	19.6 ppb
2015-02-13	18.4 ppb
2015-02-13	24.5 ppb
2015-02-13	ND
2015-02-13	ND
2015-02-13	26.2 ppb
2015-02-13	22.7 ppb
2015-05-07	25.9 ppb
2015-05-07	24.0 ppb
2015-05-07	25.4 ppb
2015-05-07	25.7 ppb
2015-05-07	22.9 ppb
2015-05-07	24.1 ppb
2015-05-07	20.0 ppb
2015-05-07	20.2 ppb
2015-08-12	25.6 ppb
2015-08-12	ND
2015-08-12	26.1 ppb
2015-08-12	28.8 ppb
2015-08-12	23.1 ppb
2015-08-12	24.4 ppb
2015-08-12	20.8 ppb
2015-08-12	24.4 ppb
2015-11-23	67.7 ppb
2015-11-23	46.6 ppb
2015-11-23	50.9 ppb
2015-11-23	63.3 ppb
2015-11-23	54.8 ppb
2015-11-23	0.500 ppb
2015-11-23	54.2 ppb
2015-11-23	51.9 ppb
2015-11-23	46.6 ppb
2015-11-23	50.9 ppb
2015-11-23	63.3 ppb
2015-11-23	54.8 ppb
2015-11-23	0.500 ppb
2015-11-23	67.7 ppb
2015-11-23	54.2 ppb
2015-11-23	51.9 ppb
2016-02-12	32.5 ppb
2016-02-12	ND
2016-02-12	ND
2016-02-12	31.4 ppb
2016-02-12	19.7 ppb
2016-02-12	2.80 ppb
2016-02-12	8.30 ppb
2016-02-12	28.1 ppb
2016-05-19	32.2 ppb
2016-05-19	ND
2016-05-19	32.6 ppb
2016-05-19	34.1 ppb
2016-05-19	28.7 ppb
2016-05-19	9.30 ppb
2016-05-19	25.7 ppb
2016-05-19	29.2 ppb
2016-08-19	13.4 ppb
2016-08-19	ND
2016-08-19	ND
2016-08-19	15.2 ppb
2016-08-19	14.3 ppb
2016-08-19	7.30 ppb
2016-08-19	11.2 ppb
2016-08-19	9.00 ppb
2016-11-03	37.5 ppb
2016-11-03	28.2 ppb
2016-11-03	30.0 ppb
2016-11-03	35.4 ppb
2016-11-03	29.1 ppb
2016-11-03	6.10 ppb
2016-11-03	24.8 ppb
2016-11-03	26.3 ppb
2017-02-09	42.8 ppb
2017-02-09	37.1 ppb
2017-02-09	40.2 ppb
2017-02-09	45.7 ppb
2017-02-09	44.6 ppb
2017-02-09	3.40 ppb
2017-02-09	42.1 ppb
2017-02-09	43.0 ppb
2017-05-17	41.2 ppb
2017-05-17	3.10 ppb
2017-05-17	ND
2017-05-17	43.0 ppb
2017-05-17	35.2 ppb
2017-05-17	5.30 ppb
2017-05-17	32.0 ppb
2017-05-17	37.7 ppb
2017-08-10	38.8 ppb
2017-08-10	34.1 ppb
2017-08-10	41.7 ppb
2017-08-10	47.2 ppb
2017-08-10	38.8 ppb
2017-08-10	36.2 ppb
2017-08-10	32.6 ppb
2017-08-10	33.7 ppb
2017-11-09	58.2 ppb
2017-11-09	49.1 ppb
2017-11-09	44.8 ppb
2017-11-09	43.2 ppb
2017-11-09	44.0 ppb
2017-11-09	39.9 ppb
2017-11-09	40.3 ppb
2017-11-10	8.20 ppb
2018-02-07	40.3 ppb
2018-02-07	35.6 ppb
2018-02-07	35.2 ppb
2018-02-07	41.8 ppb
2018-02-07	33.0 ppb
2018-02-07	35.7 ppb
2018-02-07	32.7 ppb
2018-02-07	32.4 ppb
2018-05-17	37.4 ppb
2018-05-17	ND
2018-05-17	35.2 ppb
2018-05-17	42.3 ppb
2018-05-17	27.9 ppb
2018-05-17	34.2 ppb
2018-05-17	25.8 ppb
2018-05-17	28.1 ppb
2018-08-15	42.4 ppb
2018-08-15	ND
2018-08-15	ND
2018-08-15	50.6 ppb
2018-08-15	40.5 ppb
2018-08-15	35.8 ppb
2018-08-15	35.5 ppb
2018-08-15	41.4 ppb
2018-11-28	55.4 ppb
2018-11-28	50.7 ppb
2018-11-28	52.3 ppb
2018-11-28	61.0 ppb
2018-11-28	48.8 ppb
2018-11-28	48.6 ppb
2018-11-28	42.9 ppb
2018-11-28	33.6 ppb
2019-02-14	46.8 ppb
2019-02-14	48.9 ppb
2019-02-14	29.3 ppb
2019-02-14	28.5 ppb
2019-02-21	39.0 ppb
2019-02-21	43.8 ppb
2019-02-21	10.9 ppb
2019-02-21	29.8 ppb
2019-05-22	38.4 ppb
2019-05-22	25.0 ppb
2019-05-22	29.4 ppb
2019-05-22	45.2 ppb
2019-05-22	29.4 ppb
2019-05-22	31.6 ppb
2019-05-22	23.5 ppb
2019-05-22	23.4 ppb
2019-08-19	12.0 ppb
2019-08-19	12.0 ppb
2019-08-19	23.0 ppb
2019-08-19	17.0 ppb
2019-08-19	8.90 ppb
2019-08-19	ND
2019-08-19	ND
2019-08-19	12.0 ppb
2019-11-13	70.4 ppb
2019-11-13	59.7 ppb
2019-11-13	66.0 ppb
2019-11-13	69.3 ppb
2019-11-13	62.9 ppb
2019-11-13	60.5 ppb
2019-11-13	53.8 ppb
2019-11-13	47.9 ppb