Total trihalomethanes (TTHMs)

Suez Water Delaware

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

162

Samples

Samples exceeding legal limit (MCL)

161

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2014	34.9 ppb	32	31	ND - 76.9 ppb
2015	44.1 ppb	31	31	19.9 ppb - 82.9 ppb
2016	38.1 ppb	23	23	12.7 ppb - 75.0 ppb
2017	37.4 ppb	28	28	13.7 ppb - 80.5 ppb
2018	44.6 ppb	32	32	12.9 ppb - 94.4 ppb
2019	40.0 ppb	16	16	11.6 ppb - 80.3 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
2014-03-06	1074953001	19.6 ppb
2014-03-06	1074953002	11.5 ppb
2014-03-06	1074953003	14.1 ppb
2014-03-06	1074953004	20.7 ppb
2014-03-06	1074953005	20.2 ppb
2014-03-06	1074953006	12.3 ppb
2014-03-06	1074953007	8.50 ppb
2014-03-06	1074953008	12.2 ppb
2014-06-11	2013111001 TTHM	45.0 ppb
2014-06-11	2013111002 TTHM	33.6 ppb
2014-06-11	2013111003 TTHM	38.5 ppb
2014-06-11	2013111004 TTHM	48.7 ppb
2014-06-11	2013111005 TTHM	36.6 ppb
2014-06-11	2013111006 TTHM	38.4 ppb
2014-06-11	2013111007 TTHM	43.3 ppb
2014-06-11	2013111008 TTHM	41.3 ppb
2014-09-09	2028983001	67.0 ppb
2014-09-09	2028983002	63.3 ppb
2014-09-09	2028983003	46.9 ppb
2014-09-09	2028983004	76.9 ppb
2014-09-09	2028983005	68.1 ppb
2014-09-09	2028983006	62.2 ppb
2014-09-09	2028983007	56.0 ppb
2014-09-09	2028983008	70.5 ppb
2014-12-18	204252007-TTHM	ND
2014-12-18	2046252001	29.9 ppb
2014-12-18	2046252002-TTHM	16.1 ppb
2014-12-18	2046252003-TTHM	22.8 ppb
2014-12-18	2046252004-TTHM	35.5 ppb
2014-12-18	2046252005-TTHM	21.8 ppb
2014-12-18	2046252006-TTHM	14.2 ppb
2014-12-18	2046252008-TTHM	21.2 ppb
2015-03-11	2059081001 TTHM	49.1 ppb
2015-03-11	2059081002 TTHM	30.9 ppb
2015-03-11	2059081003 TTHM	30.1 ppb
2015-03-11	2059081004 TTHM	40.4 ppb
2015-03-11	2059081005 TTHM	50.9 ppb
2015-03-11	2059081006 TTHM	36.2 ppb
2015-03-11	2059081007 TTHM	39.1 ppb
2015-03-11	2059081008 TTHM	41.3 ppb
2015-06-08	2075686001 TTHM	82.9 ppb
2015-06-08	2075686002 TTHM	57.4 ppb
2015-06-08	2075686003 TTHM	45.8 ppb
2015-06-08	2075686004 TTHM	65.4 ppb
2015-06-08	2075686005 TTHM	61.7 ppb
2015-06-08	2075686006 TTHM	55.2 ppb
2015-06-08	2075686007 TTHM	46.6 ppb
2015-06-08	2075686008 TTHM	44.1 ppb
2015-09-03	2093960002 TTHM	38.8 ppb
2015-09-03	2093960003 TTHM	42.3 ppb
2015-09-03	2093960004 TTHM	59.2 ppb
2015-09-03	2093960005 TTHM	47.5 ppb
2015-09-03	2093960006 TTHM	46.3 ppb
2015-09-03	2093960007 TTHM	33.9 ppb
2015-09-03	2093960008 TTHM	52.9 ppb
2015-12-07	L5949833-1 TTHM	49.8 ppb
2015-12-07	L5949833-2 TTHM	30.1 ppb
2015-12-07	L5949833-3 TTHM	19.9 ppb
2015-12-07	L5949833-4 TTHM	42.2 ppb
2015-12-07	L5949833-6 TTHM	32.9 ppb
2015-12-07	L5949833-7 TTHM	33.6 ppb
2015-12-07	L5949833-8 TTHM	21.1 ppb
2015-12-07	L594983395 TTHM	38.3 ppb
2016-06-10	2151332001 TTHM	51.0 ppb
2016-06-10	2151332002 TTHM	41.1 ppb
2016-06-10	2151332003 TTHM	26.0 ppb
2016-06-10	2151332005 TTHM	44.8 ppb
2016-06-10	2151332006 TTHM	45.6 ppb
2016-06-10	2151332007 TTHM	32.5 ppb
2016-06-10	2151332008 TTHM	39.2 ppb
2016-09-08	2173721001 TTHM	50.4 ppb
2016-09-08	2173721002-TTHM	42.7 ppb
2016-09-08	2173721003-TTHM	34.6 ppb
2016-09-08	2173721004-TTHM	75.0 ppb
2016-09-08	2173721005-TTHM	54.3 ppb
2016-09-08	2173721006-TTHM	46.9 ppb
2016-09-08	2173721007-TTHM	34.8 ppb
2016-09-08	2173721008-TTHM	46.5 ppb
2016-12-08	2194964001 TTHM	26.1 ppb
2016-12-08	2194964002 TTHM	18.0 ppb
2016-12-08	2194964003 TTHM	12.7 ppb
2016-12-08	2194964004 TTHM	43.2 ppb
2016-12-08	2194964005 TTHM	25.7 ppb
2016-12-08	2194964006 TTHM	42.6 ppb
2016-12-08	2194964007 TTHM	15.2 ppb
2016-12-08	2194964008 TTHM	26.9 ppb
2017-03-08	2214632001 TTHM	27.8 ppb
2017-03-08	2214632002 TTHM	15.7 ppb
2017-03-08	2214632003 TTHM	13.7 ppb
2017-03-08	2214632004 TTHM	36.7 ppb
2017-03-08	2214632005 TTHM	22.4 ppb
2017-03-08	2214632006 TTHM	32.0 ppb
2017-03-08	2214632007 TTHM	17.5 ppb
2017-03-08	2214632008 TTHM	17.2 ppb
2017-06-09	2239424001 TTHM	43.3 ppb
2017-06-09	2239424002 TTHM	27.9 ppb
2017-06-09	2239424003 TTHM	29.0 ppb
2017-06-09	2239424004 TTHM	53.6 ppb
2017-06-09	2239424005 TTHM	37.8 ppb
2017-06-09	2239424006 TTHM	55.1 ppb
2017-06-09	2239424007 TTHM	30.0 ppb
2017-06-09	2239424008 TTHM	36.8 ppb
2017-09-07	2260181001 TTHM	77.0 ppb
2017-09-07	2260181002 TTHM	59.6 ppb
2017-09-07	2260181003 TTHM	44.7 ppb
2017-09-07	2260181004 TTHM	65.9 ppb
2017-09-07	2260181005 TTHM	55.8 ppb
2017-09-07	2260181006 TTHM	80.5 ppb
2017-09-07	2260181007 TTHM	35.9 ppb
2017-09-07	2260181008 TTHM	45.7 ppb
2017-12-07	2282095001 TTHM	16.7 ppb
2017-12-07	2282095002 TTHM	22.3 ppb
2017-12-07	2282095003 TTHM	28.0 ppb
2017-12-07	2282095005 TTHM	19.8 ppb
2018-03-08	2300879001	12.9 ppb
2018-03-08	2300879002 TTHM	41.4 ppb
2018-03-08	2300879003 TTHM	22.0 ppb
2018-03-08	2300879004 TTHM	30.9 ppb
2018-03-08	2300879005 TTHM	15.3 ppb
2018-03-08	2300879006 TTHM	16.5 ppb
2018-03-08	2300879007 TTHM	25.5 ppb
2018-03-08	2300879008 TTHM	35.0 ppb
2018-06-07	2319771001 TTHM	37.6 ppb
2018-06-07	2319771002 TTHM	48.9 ppb
2018-06-07	2319771003 TTHM	57.0 ppb
2018-06-07	2319771004 TTHM	54.2 ppb
2018-06-07	2319771005 TTHM	58.6 ppb
2018-06-07	2319771006 TTHM	43.9 ppb
2018-06-07	2319771007 TTHM	29.3 ppb
2018-06-07	2319771008 TTHM	66.4 ppb
2018-09-07	8092132-01 TTHM	68.3 ppb
2018-09-07	8092132-02 TTHM	90.8 ppb
2018-09-07	8092132-03 THM	86.0 ppb
2018-09-07	8092132-04 TTHM	37.4 ppb
2018-09-07	8092132-05 TTHM	94.4 ppb
2018-09-07	8092132-06 TTHM	76.6 ppb
2018-09-07	8092132-07 TTHM	50.8 ppb
2018-09-07	8092132-08 TTHM	49.9 ppb
2018-12-07	8122168-01 TTHM	30.2 ppb
2018-12-07	8122168-02 TTHM	21.7 ppb
2018-12-07	8122168-03 TTHM	21.2 ppb
2018-12-07	8122168-04 TTHM	40.6 ppb
2018-12-07	8122168-05 TTHM	51.6 ppb
2018-12-07	8122168-06 TTHM	26.8 ppb
2018-12-07	8122168-07 TTHM	63.4 ppb
2018-12-07	8122168-08 TTHM	22.6 ppb
2019-06-07	9062660-01 TTHM	49.2 ppb
2019-06-07	9062660-02 TTHM	41.1 ppb
2019-06-07	9062660-03 TTHM	38.2 ppb
2019-06-07	9062660-04 TTHM	68.5 ppb
2019-06-07	9062660-05 TTHM	71.1 ppb
2019-06-07	9062660-06 TTHM	44.6 ppb
2019-06-07	9062660-07 TTHM	80.3 ppb
2019-06-07	9062660-08 TTHM	60.4 ppb
2019-12-09	9122405-01 TTHM	26.0 ppb
2019-12-09	9122405-02 TTHM	18.2 ppb
2019-12-09	9122405-03 TTHM	11.6 ppb
2019-12-09	9122405-04 TTHM	16.0 ppb
2019-12-09	9122405-05 TTHM	29.7 ppb
2019-12-09	9122405-06 TTHM	12.9 ppb
2019-12-09	9122405-07 TTHM	40.1 ppb
2019-12-09	9122405-08 TTHM	32.3 ppb