Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

City Of Modesto - Del Rio

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.

 

15

Samples

0

Samples exceeding legal limit (MCL)

0

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2018N/A00N/A
2019ND30ND
2020ND30ND
2021ND30ND
2022ND30ND
2023ND30ND

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
2019-10-08CA5010029_DST_901-201910080830ND
2019-10-08CA5010029_DST_902-201910080755ND
2019-10-08CA5010029_DST_900-201910080740ND
2020-10-13CA5010029_DST_902-202010131127ND
2020-10-13CA5010029_DST_900-202010131150ND
2020-10-13CA5010029_DST_901-202010131107ND
2021-10-14CA5010029_DST_902-202110141050ND
2021-10-14CA5010029_DST_900-202110141105ND
2021-10-14CA5010029_DST_901-202110141030ND
2022-10-11CA5010029_DST_901-202210111218ND
2022-10-11CA5010029_DST_902-202210111154ND
2022-10-11CA5010029_DST_900-202210111140ND
2023-10-10CA5010029_DST_901-202310101107ND
2023-10-10CA5010029_DST_900-202310101035ND
2023-10-10CA5010029_DST_902-202310101050ND