Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

Mandeville Water Supply

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.

 

17

Samples

0

Samples exceeding legal limit (MCL)

4

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20180.265 ppb42ND - 0.530 ppb
2019ND40ND
20200.170 ppb31ND - 0.510 ppb
2021ND20ND
2022ND20ND
20230.270 ppb21ND - 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
2018-02-16353748640010.530 ppb
2018-02-16353748640010.530 ppb
2018-08-1035410510001ND
2018-08-1035410510001ND
2019-02-2135450032001ND
2019-02-2135450032001ND
2019-08-1535490976001ND
2019-08-1535490976001ND
2020-02-14355314440010.510 ppb
2020-08-0735568973001ND
2020-08-0735568973002ND
2021-02-0535610005001ND
2021-08-0235652729001ND
2022-02-1135696582001ND
2022-08-0235736643001ND
2023-02-0335776992001ND
2023-08-11358202980010.540 ppb