Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

Walker Water System

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.

 

128

Samples

0

Samples exceeding legal limit (MCL)

18

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20180.0463 ppb324ND - 0.430 ppb
2019ND320ND
20200.0944 ppb164ND - 0.530 ppb
20210.166 ppb166ND - 0.490 ppb
20220.888 ppb161ND - 14.2 ppb
20230.0944 ppb163ND - 0.540 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
2018-02-02353718880010.430 ppb
2018-02-0235371888002ND
2018-02-0235371888003ND
2018-02-0235371888004ND
2018-02-02353718880010.430 ppb
2018-02-0235371888002ND
2018-02-0235371888003ND
2018-02-0235371888004ND
2018-05-0335390312001ND
2018-05-0335390312002ND
2018-05-0335390312003ND
2018-05-0335390312004ND
2018-05-0335390312001ND
2018-05-0335390312002ND
2018-05-0335390312003ND
2018-05-0335390312004ND
2018-08-0735409811001ND
2018-08-0735409811002ND
2018-08-0735409811003ND
2018-08-0735409811004ND
2018-08-0735409811001ND
2018-08-0735409811002ND
2018-08-0735409811003ND
2018-08-0735409811004ND
2018-11-01354280500010.310 ppb
2018-11-0135428050002ND
2018-11-0135428050003ND
2018-11-0135428050004ND
2018-11-01354280500010.310 ppb
2018-11-0135428050002ND
2018-11-0135428050003ND
2018-11-0135428050004ND
2019-02-1435448843001ND
2019-02-1435448843002ND
2019-02-1435448843003ND
2019-02-1435448843004ND
2019-02-1435448843001ND
2019-02-1435448843002ND
2019-02-1435448843003ND
2019-02-1435448843004ND
2019-05-1535469379001ND
2019-05-1535469379002ND
2019-05-1535469379003ND
2019-05-1535469379004ND
2019-05-1535469379001ND
2019-05-1535469379002ND
2019-05-1535469379003ND
2019-05-1535469379004ND
2019-08-0135486873001ND
2019-08-0135486873002ND
2019-08-0135486873003ND
2019-08-0135486873004ND
2019-08-0135486873001ND
2019-08-0135486873002ND
2019-08-0135486873003ND
2019-08-0135486873004ND
2019-11-0735511062001ND
2019-11-0735511062002ND
2019-11-0735511062003ND
2019-11-0735511062004ND
2019-11-0735511062001ND
2019-11-0735511062002ND
2019-11-0735511062003ND
2019-11-0735511062004ND
2020-02-0635529496001ND
2020-02-06355294960020.530 ppb
2020-02-0635529496003ND
2020-02-0635529496004ND
2020-05-08355488310010.360 ppb
2020-05-08355488310020.320 ppb
2020-05-0835548831003ND
2020-05-08355488310040.300 ppb
2020-08-0635569084001ND
2020-08-0635569084002ND
2020-08-0635569084003ND
2020-08-0635569084004ND
2020-11-0635590483001ND
2020-11-0635590483002ND
2020-11-0635590483003ND
2020-11-0635590483004ND
2021-02-05356100020010.400 ppb
2021-02-0535610002002ND
2021-02-0535610002003ND
2021-02-0535610002004ND
2021-05-0635631659001ND
2021-05-0635631659002ND
2021-05-0635631659003ND
2021-05-06356316590040.440 ppb
2021-08-0535653771001ND
2021-08-0535653771002ND
2021-08-05356537710030.490 ppb
2021-08-0535653771004ND
2021-11-0535676292001ND
2021-11-05356762920020.410 ppb
2021-11-05356762920030.470 ppb
2021-11-05356762920040.440 ppb
2022-02-1035696562005ND
2022-02-1035696562006ND
2022-02-1035696562007ND
2022-02-1035696562008ND
2022-05-0635715922001ND
2022-05-0635715922002ND
2022-05-0635715922003ND
2022-05-0635715922004ND
2022-08-173574119100114.2 ppb
2022-08-1735741191002ND
2022-08-1735741191003ND
2022-08-1735741191004ND
2022-11-0435758151001ND
2022-11-0435758151002ND
2022-11-0435758151003ND
2022-11-0435758151004ND
2023-02-1635781545001ND
2023-02-1635781545002ND
2023-02-1635781545003ND
2023-02-2735782405001ND
2023-05-05357977850010.540 ppb
2023-05-05357977850020.520 ppb
2023-05-0535797785003ND
2023-05-0535797785004ND
2023-08-0235818085001ND
2023-08-02358180850020.450 ppb
2023-08-0235818085003ND
2023-08-0235818085004ND
2023-11-0335839250001ND
2023-11-0335839250002ND
2023-11-0335839250003ND
2023-11-0335839250004ND