Total trihalomethanes (TTHMs)

Brownsville Public Utilities Board

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

192

Samples

Samples exceeding legal limit (MCL)

146

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2014	38.2 ppb	32	24	ND - 67.5 ppb
2015	37.6 ppb	32	24	ND - 83.9 ppb
2016	23.6 ppb	32	24	ND - 46.8 ppb
2017	21.6 ppb	32	24	ND - 42.4 ppb
2018	15.3 ppb	32	25	ND - 38.6 ppb
2019	20.2 ppb	32	25	ND - 39.8 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
2014-03-05	AC45671	53.3 ppb
2014-03-05	AC45658	ND
2014-03-05	AC45682	47.1 ppb
2014-03-05	AC45677	48.4 ppb
2014-03-05	AC45679	47.0 ppb
2014-03-05	AC45678	44.6 ppb
2014-03-05	AC45691	47.2 ppb
2014-03-05	AC45692	ND
2014-06-04	AC55990	46.3 ppb
2014-06-04	AC55989	ND
2014-06-04	AC56010	65.6 ppb
2014-06-04	AC56011	61.7 ppb
2014-06-04	AC55996	62.1 ppb
2014-06-04	AC55992	34.0 ppb
2014-06-04	AC56039	29.1 ppb
2014-06-04	AC55988	ND
2014-09-24	AC68141	36.0 ppb
2014-09-24	AC68137	ND
2014-09-24	AC68156	67.5 ppb
2014-09-24	AC68138	48.6 ppb
2014-09-24	AC68144	54.0 ppb
2014-09-24	AC68155	34.0 ppb
2014-09-24	AC68157	67.5 ppb
2014-09-24	AC68158	ND
2014-11-19	AC72442	54.3 ppb
2014-11-19	AC72441	ND
2014-11-19	AC72469	60.2 ppb
2014-11-19	AC72464	57.9 ppb
2014-11-19	AC72467	58.5 ppb
2014-11-19	AC72443	41.2 ppb
2014-11-19	AC72466	55.7 ppb
2014-11-19	AC72468	ND
2015-02-25	AC81870	83.2 ppb
2015-02-25	AC81855	ND
2015-02-25	AC81851	73.8 ppb
2015-02-25	AC81853	83.9 ppb
2015-02-25	AC81857	68.1 ppb
2015-02-25	AC81852	38.6 ppb
2015-02-25	AC81871	45.5 ppb
2015-02-25	AC81854	ND
2015-05-27	AC93481	55.5 ppb
2015-05-27	AC93479	ND
2015-05-27	AC93495	49.1 ppb
2015-05-27	AC93499	63.7 ppb
2015-05-27	AC93497	55.8 ppb
2015-05-27	AC93480	39.7 ppb
2015-05-27	AC93471	44.0 ppb
2015-05-27	AC93482	ND
2015-09-24	AD08468	34.5 ppb
2015-09-24	AD08439	ND
2015-09-24	AD08435	50.5 ppb
2015-09-24	AD08471	47.1 ppb
2015-09-24	AD08425	50.8 ppb
2015-09-24	AD08469	24.5 ppb
2015-09-24	AD08438	44.1 ppb
2015-09-24	AD08470	ND
2015-11-10	AD13143	36.5 ppb
2015-11-10	AD13152	ND
2015-11-10	AD13154	64.8 ppb
2015-11-10	AD13144	53.4 ppb
2015-11-10	AD13141	38.8 ppb
2015-11-10	AD13147	17.6 ppb
2015-11-10	AD13155	40.0 ppb
2015-11-10	AD13146	ND
2016-03-09	AD27842	24.4 ppb
2016-03-09	AD27843	ND
2016-03-09	AD27839	28.8 ppb
2016-03-09	AD27838	30.4 ppb
2016-03-09	AD27844	29.6 ppb
2016-03-09	AD27841	13.9 ppb
2016-03-09	AD27847	21.1 ppb
2016-03-09	AD27846	ND
2016-05-19	AD37469	38.4 ppb
2016-05-19	AD37458	ND
2016-05-19	AD37462	35.9 ppb
2016-05-19	AD37473	36.4 ppb
2016-05-19	AD37463	34.1 ppb
2016-05-19	AD37460	25.6 ppb
2016-05-19	AD37471	32.4 ppb
2016-05-19	AD37457	ND
2016-07-28	AD46101	34.2 ppb
2016-07-28	AD46142	ND
2016-07-28	AD46143	46.8 ppb
2016-07-28	AD46139	39.4 ppb
2016-07-28	AD46099	38.4 ppb
2016-07-28	AD46102	14.3 ppb
2016-07-28	AD46141	29.9 ppb
2016-07-28	AD46098	ND
2016-12-07	AD60852	18.5 ppb
2016-12-07	AD60853	ND
2016-12-07	AD60854	44.2 ppb
2016-12-07	AD60855	41.8 ppb
2016-12-07	AD60856	37.3 ppb
2016-12-07	AD60857	22.5 ppb
2016-12-07	AD60858	37.7 ppb
2016-12-07	AD60859	ND
2017-03-01	AD72734	35.8 ppb
2017-03-01	AD72736	ND
2017-03-01	AD72743	41.1 ppb
2017-03-01	AD72744	39.3 ppb
2017-03-01	AD72730	31.5 ppb
2017-03-01	AD72729	6.60 ppb
2017-03-01	AD72735	36.8 ppb
2017-03-01	AD72731	ND
2017-05-04	AD82747	39.3 ppb
2017-05-04	AD82678	ND
2017-05-04	AD82684	38.8 ppb
2017-05-04	AD82681	36.8 ppb
2017-05-04	AD82682	35.5 ppb
2017-05-04	AD82745	24.9 ppb
2017-05-04	AD82744	39.2 ppb
2017-05-04	AD82679	ND
2017-08-16	AD93220	34.2 ppb
2017-08-16	AD93211	ND
2017-08-16	AD93221	42.4 ppb
2017-08-16	AD93212	37.3 ppb
2017-08-16	AD93214	37.2 ppb
2017-08-16	AD93218	7.20 ppb
2017-08-16	AD93215	36.0 ppb
2017-08-16	AD93217	ND
2017-11-28	AE05927	16.3 ppb
2017-11-28	AE05923	ND
2017-11-28	AE05928	17.9 ppb
2017-11-28	AE05929	20.1 ppb
2017-11-28	AE05932	13.0 ppb
2017-11-28	AE05931	5.90 ppb
2017-11-28	AE05926	17.5 ppb
2017-11-28	AE05924	ND
2018-02-21	AE14666	13.7 ppb
2018-02-21	AE14670	ND
2018-02-21	AE14669	13.0 ppb
2018-02-21	AE14671	14.1 ppb
2018-02-21	AE14667	9.20 ppb
2018-02-21	AE14664	6.30 ppb
2018-02-21	AE14663	12.7 ppb
2018-02-21	AE14665	ND
2018-06-06	AE28845	22.8 ppb
2018-06-06	AE28849	3.20 ppb
2018-06-06	AE28848	24.6 ppb
2018-06-06	AE28847	21.5 ppb
2018-06-06	AE28843	18.7 ppb
2018-06-06	AE28846	6.60 ppb
2018-06-06	AE28842	20.9 ppb
2018-06-06	AE28844	ND
2018-08-07	AE35956	32.4 ppb
2018-08-07	AE35952	ND
2018-08-07	AE35951	38.4 ppb
2018-08-07	AE35959	34.9 ppb
2018-08-07	AE35944	38.6 ppb
2018-08-07	AE35957	18.4 ppb
2018-08-07	AE35949	22.3 ppb
2018-08-07	AE35948	ND
2018-11-13	AE46081	26.3 ppb
2018-11-13	AE46090	ND
2018-11-13	AE46083	24.4 ppb
2018-11-13	AE46085	25.1 ppb
2018-11-13	AE46091	13.6 ppb
2018-11-13	AE46084	12.5 ppb
2018-11-13	AE46088	ND
2018-11-13	AE46086	15.7 ppb
2019-02-04	AE52861	21.2 ppb
2019-02-04	AE52859	ND
2019-02-04	AE52879	22.3 ppb
2019-02-04	AE52882	30.1 ppb
2019-02-04	AE52880	24.3 ppb
2019-02-04	AE52858	11.2 ppb
2019-02-04	AE52881	24.0 ppb
2019-02-04	AE52862	1.10 ppb
2019-05-08	AE65409	23.8 ppb
2019-05-08	AE65407	ND
2019-05-08	AE65408	24.4 ppb
2019-05-08	AE65387	35.0 ppb
2019-05-08	AE65411	20.5 ppb
2019-05-08	AE65410	8.90 ppb
2019-05-08	AE65388	27.3 ppb
2019-05-08	AE65406	ND
2019-07-09	AE73652	33.0 ppb
2019-07-09	AE73661	ND
2019-07-09	AE73630	39.8 ppb
2019-07-09	AE73664	37.7 ppb
2019-07-09	AE73656	38.9 ppb
2019-07-09	AE73634	21.1 ppb
2019-07-09	AE73663	36.2 ppb
2019-07-09	AE73662	ND
2019-10-08	AE85956	30.2 ppb
2019-10-08	AE85950	ND
2019-10-08	AE85960	33.4 ppb
2019-10-08	AE85951	31.0 ppb
2019-10-08	AE85953	25.2 ppb
2019-10-08	AE85957	14.4 ppb
2019-10-08	AE85954	31.6 ppb
2019-10-08	AE85959	ND