Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

City of Deridder 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.

 

16

Samples

0

Samples exceeding legal limit (MCL)

6

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20181.15 ppb42ND - 2.30 ppb
20190.440 ppb42ND - 0.880 ppb
2020ND20ND
20210.215 ppb21ND - 0.430 ppb
20220.800 ppb21ND - 1.60 ppb
2023ND20ND

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
2018-08-01354086890012.30 ppb
2018-08-0135408689002ND
2018-08-01354086890012.30 ppb
2018-08-0135408689002ND
2019-08-01354870410010.880 ppb
2019-08-0135487041002ND
2019-08-01354870410010.880 ppb
2019-08-0135487041002ND
2020-08-1135570935001ND
2020-08-1135570935002ND
2021-08-2335659643001ND
2021-08-23356596430020.430 ppb
2022-08-2535742998001ND
2022-08-25357429980021.60 ppb
2023-08-0735819589001ND
2023-08-0735819589002ND