Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

North Hunt Special Utility 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.

 

48

Samples

2

Samples exceeding legal limit (MCL)

36

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20183.24 ppb83ND - 12.8 ppb
201929.5 ppb85ND - 117.0 ppb
20207.63 ppb881.28 ppb - 24.3 ppb
20217.07 ppb87ND - 22.2 ppb
20224.11 ppb86ND - 9.53 ppb
20239.01 ppb87ND - 18.5 ppb

ppb = parts per billion

State, National, and Health Guidelines for Drinking Water

EWG Health Guideline: 0.15 ppb

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.

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
2018-02-14Q1806240004ND
2018-02-14Q1806240003ND
2018-06-04Q1822050010ND
2018-06-04Q182205000612.8 ppb
2018-08-09Q1831973001ND
2018-08-09Q18319730025.49 ppb
2018-11-06Q1844318003ND
2018-11-06Q18443180047.65 ppb
2019-03-12Q1910237001ND
2019-03-12Q191023700285.3 ppb
2019-05-28Q1928750008ND
2019-05-28Q1928750009117.0 ppb
2019-09-03Q196131100425.4 ppb
2019-09-03Q19613110031.10 ppb
2019-12-12Q1979989003ND
2019-12-12Q19799890047.44 ppb
2020-02-12Q20057100031.28 ppb
2020-02-12Q20057100047.76 ppb
2020-05-07Q20180550013.27 ppb
2020-05-07Q20180550029.68 ppb
2020-09-23Q20377130032.50 ppb
2020-09-23Q203771300424.3 ppb
2020-11-23Q20466210144.56 ppb
2020-11-23Q20466210157.69 ppb
2021-02-08Q2103700009ND
2021-02-08Q21037000106.85 ppb
2021-05-06Q21117680015.60 ppb
2021-05-06Q211176800211.7 ppb
2021-08-04Q21205220031.11 ppb
2021-08-04Q212052200422.2 ppb
2021-10-19Q21293150032.39 ppb
2021-10-19Q21293150046.68 ppb
2022-02-10Q22049370022.88 ppb
2022-02-10Q22049370036.59 ppb
2022-04-25Q22123410024.29 ppb
2022-04-25Q2212341003ND
2022-08-24Q2225213003ND
2022-08-24Q22252130049.53 ppb
2022-11-29Q22353510125.81 ppb
2022-11-29Q22353510133.81 ppb
2023-03-13Q230966800910.2 ppb
2023-03-13Q230966801011.2 ppb
2023-05-30Q2319961003ND
2023-05-30Q23199610041.86 ppb
2023-08-21Q233512100318.5 ppb
2023-08-21Q23351210043.03 ppb
2023-11-28Q235058600115.1 ppb
2023-11-28Q235058600212.2 ppb