Total trihalomethanes (TTHMs)
Woodridge Village
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.
Samples
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2018 | 61.5 ppb | 4 | 4 | 33.0 ppb - 95.7 ppb |
| 2019 | 42.8 ppb | 2 | 2 | 31.9 ppb - 53.7 ppb |
| 2020 | 35.4 ppb | 5 | 5 | 23.9 ppb - 42.0 ppb |
| 2021 | 69.1 ppb | 4 | 4 | 32.0 ppb - 111.0 ppb |
| 2022 | 44.4 ppb | 4 | 4 | 20.6 ppb - 65.0 ppb |
| 2023 | 54.1 ppb | 4 | 4 | 20.3 ppb - 86.0 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 |
|---|---|---|
| 2018-03-01 | DBP J8C0291 | 43.4 ppb |
| 2018-05-10 | DBP J8E0880-01 | 95.7 ppb |
| 2018-07-19 | DBP J8G1736-01 | 73.9 ppb |
| 2018-11-15 | DBP J8K0981-01,2 | 33.0 ppb |
| 2019-02-28 | DBP J9B1399-01 | 31.9 ppb |
| 2019-07-25 | DBP J9G1503-01 | 53.7 ppb |
| 2020-02-05 | DBP S000023319 | 37.8 ppb |
| 2020-05-04 | TTHM S000026501 | 23.9 ppb |
| 2020-07-31 | DBP9 S000032285 | 36.6 ppb |
| 2020-08-03 | DBP9 S000030187 | 36.6 ppb |
| 2020-11-03 | DBP S030182,95 | 42.0 ppb |
| 2021-03-24 | DBP 369667-01 | 32.0 ppb |
| 2021-05-19 | DBP 371299 | 58.0 ppb |
| 2021-08-10 | DBP S062168,57417 | 111.0 ppb |
| 2021-11-03 | DBP S068292,3 | 75.5 ppb |
| 2022-02-08 | DBP S074814 | 20.6 ppb |
| 2022-05-10 | DBP S074282,13 | 65.0 ppb |
| 2022-08-02 | DBP S000074783,910 | 57.9 ppb |
| 2022-11-09 | DBP S0103915,31 | 34.1 ppb |
| 2023-02-08 | DBP S0137412,00 | 20.3 ppb |
| 2023-05-02 | DBP SO137398, 413 | 64.0 ppb |
| 2023-08-10 | DBP S0137399,407 | 86.0 ppb |
| 2023-11-15 | DBP S000166183 | 46.0 ppb |