Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

University of Connecticut - Main Campus

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.

 

119

Samples

0

Samples exceeding legal limit (MCL)

119

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201819.7 ppb24246.80 ppb - 38.3 ppb
201917.6 ppb24249.50 ppb - 32.9 ppb
202018.3 ppb23231.80 ppb - 28.8 ppb
202124.2 ppb16169.50 ppb - 38.1 ppb
202220.9 ppb161614.9 ppb - 29.2 ppb
202319.1 ppb161611.2 ppb - 32.8 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
2018-03-15CA02987TTHM19.7 ppb
2018-03-15CA02988TTHM10.4 ppb
2018-03-15CA02989TTHM25.7 ppb
2018-03-15CA02990TTHM12.5 ppb
2018-06-12CA68568TTHM23.6 ppb
2018-06-12CA68569TTHM20.4 ppb
2018-06-12CA68570TTHM23.8 ppb
2018-06-12CA68571TTHM11.4 ppb
2018-09-19DBP 20050618225.4 ppb
2018-09-19DBP 20050618438.3 ppb
2018-09-19DBP 20050618619.2 ppb
2018-09-19DBP 20050618913.7 ppb
2018-09-25DBP 20050672023.1 ppb
2018-09-25DBP 20050672138.1 ppb
2018-09-25DBP 20050672217.6 ppb
2018-09-25DBP 20050672319.7 ppb
2018-09-26DBP 20050696614.8 ppb
2018-09-27DBP 20050707321.5 ppb
2018-12-04DBP 2005147246.80 ppb
2018-12-04DBP 20051472528.3 ppb
2018-12-04DBP 20051472615.8 ppb
2018-12-04DBP 20051472813.4 ppb
2018-12-17DBP 20051628116.7 ppb
2018-12-17DBP 20051628213.3 ppb
2019-03-18DBP 20052502412.2 ppb
2019-03-18DBP 20052502611.9 ppb
2019-03-18DBP 20052502917.0 ppb
2019-03-18DBP 20052503118.7 ppb
2019-03-18DBP 20052503313.8 ppb
2019-03-18DBP 20052503411.0 ppb
2019-06-24DBP 20053754122.6 ppb
2019-06-24DBP 20053754217.7 ppb
2019-06-24DBP 20053754314.6 ppb
2019-06-25DBP 20053780614.1 ppb
2019-06-25DBP 20053780722.3 ppb
2019-06-25DBP 20053780832.4 ppb
2019-09-16DBP 20054900116.1 ppb
2019-09-16DBP 2005490029.50 ppb
2019-09-16DBP 20054904023.1 ppb
2019-09-16DBP 20054904132.2 ppb
2019-09-16DBP 20054904315.0 ppb
2019-09-16DBP 20054904415.5 ppb
2019-12-09DBP 20055941212.3 ppb
2019-12-09DBP 20055941610.1 ppb
2019-12-09DBP 20055941917.2 ppb
2019-12-09DBP 20055942232.9 ppb
2019-12-09DBP 20055942517.0 ppb
2019-12-09DBP 20055942713.2 ppb
2020-03-10DBP 20056886117.2 ppb
2020-03-10DBP 20056886214.6 ppb
2020-03-10DBP 20056886316.2 ppb
2020-03-10DBP 20056886419.9 ppb
2020-03-10DBP 20056886516.9 ppb
2020-03-10DBP 20056886614.1 ppb
2020-04-28VOC1 2005738851.80 ppb
2020-06-08DBP 20057834816.8 ppb
2020-06-08DBP 20057834921.8 ppb
2020-06-08DBP 20057835014.2 ppb
2020-06-08DBP 20057835127.1 ppb
2020-06-08DBP 20057835217.3 ppb
2020-06-08DBP 20057835314.4 ppb
2020-09-08DBP 20058931028.8 ppb
2020-09-08DBP 20058931128.5 ppb
2020-09-08DBP 20058931222.5 ppb
2020-09-08DBP 20058931314.5 ppb
2020-09-08DBP 20058931428.5 ppb
2020-09-08DBP 20058931513.9 ppb
2020-12-14DBP 20060115614.9 ppb
2020-12-14DBP 20060115721.6 ppb
2020-12-14DBP 20060138520.6 ppb
2020-12-15DBP 20060147514.0 ppb
2021-03-10DBP 20060937914.4 ppb
2021-03-10DBP 20060938018.3 ppb
2021-03-10DBP 2006093819.50 ppb
2021-03-10DBP 20060938218.0 ppb
2021-06-01DBP 20061904232.8 ppb
2021-06-01DBP 20061904426.0 ppb
2021-06-01DBP 20061904616.6 ppb
2021-06-01DBP 20061904833.3 ppb
2021-09-08300054204 30005420929.6 ppb
2021-09-08300054205 30005421129.2 ppb
2021-09-08300054206 30005421312.8 ppb
2021-09-08300054207 30005421538.1 ppb
2021-12-07D300114234 30011423927.7 ppb
2021-12-07D300114235 30011424119.7 ppb
2021-12-07D300114236 30011424325.0 ppb
2021-12-07D300114237 30011424535.6 ppb
2022-03-07CK8043220.4 ppb
2022-03-07CK8043318.2 ppb
2022-03-07CK8043419.5 ppb
2022-03-07CK8043528.1 ppb
2022-06-02CL4681019.0 ppb
2022-06-02CL4681118.8 ppb
2022-06-02CL4681221.4 ppb
2022-06-02CL4681324.3 ppb
2022-09-12CM2852421.3 ppb
2022-09-12CM2852524.9 ppb
2022-09-12CM2852629.2 ppb
2022-09-12CM2852721.1 ppb
2022-12-12CN0252218.2 ppb
2022-12-12CN0252316.5 ppb
2022-12-12CN0252414.9 ppb
2022-12-12CN0252518.6 ppb
2023-03-08CN5528116.0 ppb
2023-03-08CN5528217.5 ppb
2023-03-08CN5528312.5 ppb
2023-03-08CN5528418.8 ppb
2023-06-05CO1917929.3 ppb
2023-06-05CO1918019.3 ppb
2023-06-05CO1918111.2 ppb
2023-06-05CO1918220.9 ppb
2023-09-11CO9421022.2 ppb
2023-09-11CO9421121.8 ppb
2023-09-11CO9421214.4 ppb
2023-09-11CO9421332.8 ppb
2023-12-05CP5986516.4 ppb
2023-12-05CP5986618.3 ppb
2023-12-05CP5986714.7 ppb
2023-12-05CP5986819.2 ppb