Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

City of Blackfoot

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.

 

27

Samples

0

Samples exceeding legal limit (MCL)

11

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2018N/A00N/A
2019ND70ND
2020N/A00N/A
2021N/A00N/A
2022ND80ND
20235.98 ppb1211ND - 9.05 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
2019-10-14VI91012702ND
2019-10-14VI91012703ND
2019-10-14VI91012704ND
2019-10-14VI91012705ND
2019-10-14VI91012706ND
2019-10-14VI91012707ND
2019-10-14VI91012701ND
2022-12-14VI21211807ND
2022-12-14VI21211808ND
2022-12-14VI21211806ND
2022-12-14VI21211805ND
2022-12-14VI21211804ND
2022-12-14VI21211803ND
2022-12-14VI21211802ND
2022-12-14VI21211801ND
2023-06-13DI306221017.97 ppb
2023-06-13DI306221027.79 ppb
2023-06-13DI306221030.870 ppb
2023-06-13DI306221046.61 ppb
2023-07-18DI307252018.29 ppb
2023-07-18DI307252026.20 ppb
2023-07-18DI30725203ND
2023-07-18DI307252040.530 ppb
2023-10-11DI310120018.95 ppb
2023-10-11DI310120029.05 ppb
2023-10-11DI310120036.49 ppb
2023-10-11DI310120049.04 ppb