Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

Cross Timbers Water Supply Corporation

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

0

Samples exceeding legal limit (MCL)

30

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20186.68 ppb85ND - 12.8 ppb
20199.36 ppb86ND - 14.6 ppb
20205.10 ppb84ND - 13.3 ppb
202113.4 ppb86ND - 36.9 ppb
202215.0 ppb87ND - 35.2 ppb
20232.50 ppb82ND - 10.1 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
2018-01-11Q180161601012.8 ppb
2018-01-11Q180161600911.6 ppb
2018-04-11Q1815188009ND
2018-04-11Q181518800412.1 ppb
2018-07-16Q1828198001ND
2018-07-16Q18281980025.60 ppb
2018-10-09Q184045200111.3 ppb
2018-10-09Q1840452002ND
2019-03-07Q190990900614.3 ppb
2019-03-07Q190990901113.3 ppb
2019-06-05Q1932306014ND
2019-06-05Q193230601511.5 ppb
2019-09-10Q196352400211.4 ppb
2019-09-10Q1963524001ND
2019-12-18Q19808040019.81 ppb
2019-12-18Q198080400214.6 ppb
2020-03-09Q200844700112.2 ppb
2020-03-09Q200844700213.3 ppb
2020-05-18Q2019652009ND
2020-05-18Q20196520104.69 ppb
2020-08-25Q2034098001ND
2020-08-25Q203409800210.6 ppb
2020-10-12Q2039719029ND
2020-10-12Q2039719030ND
2021-03-16Q210676900112.0 ppb
2021-03-16Q210676900221.4 ppb
2021-06-03Q211435200111.2 ppb
2021-06-03Q2114352002ND
2021-08-30Q2123513007ND
2021-08-30Q212351300815.0 ppb
2021-11-08Q213137100511.0 ppb
2021-11-08Q213137100636.9 ppb
2022-02-17Q220596501010.8 ppb
2022-02-17Q220596501110.2 ppb
2022-05-02Q221289400219.9 ppb
2022-05-02Q221289400313.8 ppb
2022-08-22Q222496600110.8 ppb
2022-08-22Q222496600235.2 ppb
2022-11-29Q2235312014ND
2022-11-29Q223531201519.1 ppb
2023-03-02Q2308488019ND
2023-03-02Q23084880209.93 ppb
2023-06-19Q2323082002ND
2023-06-19Q2323082003ND
2023-09-20Q2340862002ND
2023-09-20Q234086200310.1 ppb
2023-11-27Q2350411018ND
2023-11-27Q2350411019ND