Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

City of Ralls

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.

 

24

Samples

0

Samples exceeding legal limit (MCL)

1

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201811.6 ppb41ND - 46.5 ppb
2019ND40ND
2020ND40ND
2021ND40ND
2022ND40ND
2023ND40ND

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
2018-02-06Q1804612001ND
2018-04-24Q1816512002ND
2018-07-17Q182823100146.5 ppb
2018-11-29Q1848723001ND
2019-03-12Q1910243001ND
2019-05-01Q1917588001ND
2019-08-08Q1952885001ND
2019-10-09Q1972066001ND
2020-03-18Q2011846001ND
2020-05-14Q2019552001ND
2020-08-24Q2033886001ND
2020-11-16Q2044959001ND
2021-03-04Q2105771001ND
2021-04-29Q2110927002ND
2021-08-11Q2121424001ND
2021-12-02Q2133345001ND
2022-03-14Q2208565001ND
2022-06-02Q2215630001ND
2022-09-06Q2226330002ND
2022-12-08Q2236958001ND
2023-02-09Q2305228001ND
2023-04-27Q2315859002ND
2023-08-17Q2334684001ND
2023-10-11Q2343430001ND