Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

Vera Water & Power

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.

 

33

Samples

0

Samples exceeding legal limit (MCL)

13

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20180.689 ppb82ND - 4.15 ppb
20191.78 ppb85ND - 6.26 ppb
2020N/A00N/A
20211.24 ppb52ND - 5.64 ppb
20220.481 ppb83ND - 2.45 ppb
20230.308 ppb41ND - 1.23 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
2018-08-16ND
2018-08-16ND
2018-08-164.15 ppb
2018-08-16ND
2018-08-29ND
2018-08-29ND
2018-08-29ND
2018-08-291.36 ppb
2019-09-03ND
2019-09-03ND
2019-09-03ND
2019-09-030.600 ppb
2019-09-301.11 ppb
2019-09-306.26 ppb
2019-09-301.60 ppb
2019-09-304.66 ppb
2021-08-1142007350.570 ppb
2021-10-154195291ND
2021-10-154195290ND
2021-10-1541952925.64 ppb
2021-10-154195289ND
2022-08-314344784ND
2022-08-314344783ND
2022-08-314344785ND
2022-08-3143447860.550 ppb
2022-09-1643563162.45 ppb
2022-09-1643563150.850 ppb
2022-09-164356317ND
2022-09-164356318ND
2023-09-154524750ND
2023-09-1545247521.23 ppb
2023-09-154524751ND
2023-09-154524753ND