Total trihalomethanes (TTHMs)
Danbury Water Department
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.
Testing results - average by year
Year | Average result | Samples taken | Detections | Range of results |
---|---|---|---|---|
2014 | 48.3 ppb | 35 | 35 | 19.0 ppb - 96.0 ppb |
2015 | 42.7 ppb | 32 | 32 | 20.0 ppb - 75.0 ppb |
2016 | 42.9 ppb | 32 | 32 | 19.0 ppb - 78.0 ppb |
2017 | 45.2 ppb | 32 | 32 | 29.2 ppb - 76.0 ppb |
2018 | 43.6 ppb | 32 | 32 | 14.5 ppb - 91.7 ppb |
2019 | 32.9 ppb | 34 | 34 | 13.7 ppb - 55.7 ppb |
ppb = parts per billion
State and national drinking water standards and health guidelines
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 |
---|---|---|
2014-03-11 | E403C94-2TTHM | 34.0 ppb |
2014-03-11 | E403C94-4TTHM | 38.0 ppb |
2014-03-11 | E403C94-7TTHM | 35.0 ppb |
2014-03-12 | E403C94-1TTHM | 44.0 ppb |
2014-03-13 | E403C94-6TTHM | 19.0 ppb |
2014-03-14 | E403C94-8TTHM | 26.0 ppb |
2014-03-17 | E403C94-3TTHM | 26.0 ppb |
2014-03-18 | E403C94-5TTHM | 20.0 ppb |
2014-06-10 | E406G56-4TTHM | 65.0 ppb |
2014-06-10 | E406G56-6TTHM | 51.0 ppb |
2014-06-11 | E406G56-1TTHM | 69.0 ppb |
2014-06-12 | E406G56-2TTHM | 51.0 ppb |
2014-06-12 | E406G56-7TTHM | 63.0 ppb |
2014-06-12 | E406G56-8TTHM | 40.0 ppb |
2014-06-13 | E406G56-5TTHM | 52.0 ppb |
2014-06-16 | E406G56-3TTHM | 33.0 ppb |
2014-09-10 | E409F66-1TTHM | 70.0 ppb |
2014-09-11 | E409F66-4TTHM | 86.0 ppb |
2014-09-11 | E409F66-6TTHM | 58.0 ppb |
2014-09-12 | E409F66-2TTHM | 57.0 ppb |
2014-09-12 | E409F66-8TTHM | 55.0 ppb |
2014-09-15 | E409F66-3TTHM | 54.0 ppb |
2014-09-23 | E409M19-1TTHM | 96.0 ppb |
2014-09-23 | E409M19-2TTHM | 61.0 ppb |
2014-09-23 | E409M19-3TTHM | 85.0 ppb |
2014-09-30 | E409T37-2TTHM | 58.0 ppb |
2014-09-30 | E410021-1TTHM | 75.0 ppb |
2014-12-12 | E412D88-1TTHM | 50.0 ppb |
2014-12-12 | E412D88-7TTHM | 30.0 ppb |
2014-12-12 | E412D88-8TTHM | 28.0 ppb |
2014-12-15 | E412D88-2TTHM | 20.0 ppb |
2014-12-15 | E412D88-3TTHM | 34.0 ppb |
2014-12-15 | E412D88-4TTHM | 54.0 ppb |
2014-12-15 | E412D88-6TTHM | 26.0 ppb |
2014-12-16 | E412D88-5TTHM | 29.0 ppb |
2015-03-12 | E503B60-2TTHM | 34.0 ppb |
2015-03-12 | E503B60-5TTHM | 33.0 ppb |
2015-03-13 | E503B60-1TTHM | 45.0 ppb |
2015-03-13 | E503B60-6TTHM | 24.0 ppb |
2015-03-13 | E503B60-4TTHM | 39.0 ppb |
2015-03-16 | E503B60-3TTHM | 30.0 ppb |
2015-03-25 | E503J77-1TTHM | 28.0 ppb |
2015-03-26 | E503J77-2TTHM | 31.0 ppb |
2015-06-11 | E506H99-5TTHM | 35.0 ppb |
2015-06-12 | E506H99-7TTHM | 52.0 ppb |
2015-06-12 | E506H99-8TTHM | 25.0 ppb |
2015-06-15 | E506H99-4TTHM | 42.0 ppb |
2015-06-15 | E506H99-1TTHM | 52.0 ppb |
2015-06-15 | E506H99-2TTHM | 29.0 ppb |
2015-06-15 | E506H99-3TTHM | 27.0 ppb |
2015-06-16 | E506H99-6TTHM | 39.0 ppb |
2015-09-18 | E509O88-8TTHM | 47.0 ppb |
2015-09-18 | E509O88-6TTHM | 65.0 ppb |
2015-09-21 | E509O88-1TTHM | 73.0 ppb |
2015-09-21 | E509O88-2TTHM | 61.0 ppb |
2015-09-21 | E509O88-3TTHM | 44.0 ppb |
2015-09-22 | E509O88-5TTHM | 74.0 ppb |
2015-09-29 | E509W38-2TTHM | 75.0 ppb |
2015-09-29 | E509W38-1TTHM | 66.0 ppb |
2015-12-17 | E512K74-1-16TTHM | 51.0 ppb |
2015-12-17 | E512K74-2-17TTHM | 20.0 ppb |
2015-12-17 | E512K74-7-15TTHM | 56.0 ppb |
2015-12-17 | E512K74-5-19TTHM | 39.0 ppb |
2015-12-17 | E512K74-4-18TTHM | 43.0 ppb |
2015-12-18 | E512K74-6-20TTHM | 27.0 ppb |
2015-12-18 | E512K74-8-04TTHM | 30.0 ppb |
2015-12-21 | E512K74-3-03TTHM | 31.0 ppb |
2016-03-09 | E603E03-1-16TTHM | 51.0 ppb |
2016-03-09 | E603E03-4-18TTHM | 43.0 ppb |
2016-03-10 | E603E03-5-19TTHM | 29.0 ppb |
2016-03-10 | E603E03-6-20TTHM | 30.0 ppb |
2016-03-10 | E603E03-7-15TTHM | 38.0 ppb |
2016-03-10 | E603E03-2-17TTHM | 19.0 ppb |
2016-03-11 | E603E03-8-04TTHM | 28.0 ppb |
2016-03-14 | E603E03-3-03TTHM | 33.0 ppb |
2016-06-16 | E606O13-1-16TTHM | 60.0 ppb |
2016-06-16 | E606O13-2-17TTHM | 36.0 ppb |
2016-06-16 | E606O13-4-18TTHM | 50.0 ppb |
2016-06-16 | E606O13-5-19TTHM | 37.0 ppb |
2016-06-16 | E606O13-6-20TTHM | 47.0 ppb |
2016-06-16 | E606O13-8-04TTHM | 38.0 ppb |
2016-06-20 | E606O13-7-15TTHM | 52.0 ppb |
2016-06-20 | E606O13-3-03TTHM | 32.0 ppb |
2016-09-08 | 188687CH | 54.5 ppb |
2016-09-09 | 188691CH | 43.2 ppb |
2016-09-13 | 188689CH | 78.0 ppb |
2016-09-13 | 188677CH | 46.2 ppb |
2016-09-13 | 188679CH | 39.2 ppb |
2016-09-13 | 188681CH | 40.3 ppb |
2016-09-13 | 188683CH | 57.1 ppb |
2016-09-14 | 188685CH | 63.2 ppb |
2016-12-12 | 192764CH | 38.8 ppb |
2016-12-13 | 192766CH | 61.6 ppb |
2016-12-13 | 192768CH | 42.9 ppb |
2016-12-13 | 192754CH | 41.6 ppb |
2016-12-13 | 192756CH | 33.9 ppb |
2016-12-13 | 192760CH | 39.1 ppb |
2016-12-13 | 192762CH | 31.1 ppb |
2016-12-14 | 192758CH | 40.3 ppb |
2017-03-09 | 196059GE | 46.7 ppb |
2017-03-09 | 196061GE | 43.5 ppb |
2017-03-09 | 196065GE | 36.3 ppb |
2017-03-13 | 196063GE | 47.5 ppb |
2017-03-14 | 196069GE | 40.7 ppb |
2017-03-15 | 196071GE | 39.8 ppb |
2017-03-15 | 196073GE | 45.9 ppb |
2017-03-15 | 196067GE | 33.6 ppb |
2017-06-13 | 200345GE | 46.0 ppb |
2017-06-13 | 200351GE | 51.3 ppb |
2017-06-14 | 200349GE | 43.8 ppb |
2017-06-14 | 200341GE | 36.1 ppb |
2017-06-14 | 200339GE | 42.6 ppb |
2017-06-15 | 200343GE | 34.4 ppb |
2017-06-15 | 200353GE | 47.6 ppb |
2017-06-15 | 200347GE | 39.1 ppb |
2017-09-12 | 204472GE | 55.7 ppb |
2017-09-12 | 204474GE | 46.2 ppb |
2017-09-12 | 204478GE | 54.8 ppb |
2017-09-12 | 204484GE | 76.0 ppb |
2017-09-12 | 204486GE | 55.6 ppb |
2017-09-13 | 204480GE | 56.0 ppb |
2017-09-13 | 204482GE | 51.7 ppb |
2017-09-13 | 204476GE | 47.1 ppb |
2017-12-11 | 208503GE | 49.2 ppb |
2017-12-11 | 208505GE | 37.5 ppb |
2017-12-12 | 208501GE | 35.5 ppb |
2017-12-12 | 208507GE | 29.2 ppb |
2017-12-12 | 208509GE | 46.6 ppb |
2017-12-12 | 208511GE | 45.4 ppb |
2017-12-12 | 208513GE | 44.2 ppb |
2017-12-12 | 208499GE | 40.9 ppb |
2018-03-14 | 211584GE | 39.8 ppb |
2018-03-14 | 211586GE | 33.7 ppb |
2018-03-14 | 211588GE | 39.3 ppb |
2018-03-14 | 211590GE | 38.8 ppb |
2018-03-14 | 211598GE | 38.5 ppb |
2018-03-15 | 211592GE | 32.2 ppb |
2018-03-15 | 211594GE | 37.1 ppb |
2018-03-15 | 211596GE | 39.4 ppb |
2018-06-19 | 215736GE | 42.7 ppb |
2018-06-19 | 215738GE | 36.9 ppb |
2018-06-19 | 215742GE | 45.5 ppb |
2018-06-19 | 215744GE | 46.2 ppb |
2018-06-19 | 215750GE | 41.8 ppb |
2018-06-20 | 215746GE | 47.8 ppb |
2018-06-20 | 215748GE | 53.0 ppb |
2018-06-20 | 215740GE | 40.4 ppb |
2018-09-14 | DBP 200505484 | 35.3 ppb |
2018-09-14 | DBP 200505486 | 42.7 ppb |
2018-09-14 | DBP 200505491 | 74.0 ppb |
2018-09-14 | DBP 200505493 | 63.5 ppb |
2018-09-14 | DBP 200505495 | 91.7 ppb |
2018-09-14 | DBP 200505497 | 46.1 ppb |
2018-09-14 | DBP 200505499 | 69.6 ppb |
2018-09-17 | DBP 200505658 | 81.3 ppb |
2018-12-14 | DBP 200516093 | 37.9 ppb |
2018-12-14 | DBP 200516094 | 14.5 ppb |
2018-12-14 | DBP 200516095 | 19.7 ppb |
2018-12-14 | DBP 200516096 | 33.5 ppb |
2018-12-14 | DBP 200516097 | 40.9 ppb |
2018-12-14 | DBP 200516098 | 16.7 ppb |
2018-12-14 | DBP 200516099 | 46.7 ppb |
2018-12-14 | DBP 200516100 | 27.8 ppb |
2019-03-14 | DBP 200524760 | 37.1 ppb |
2019-03-14 | DBP 200524761 | 15.9 ppb |
2019-03-14 | DBP 200524762 | 22.5 ppb |
2019-03-14 | DBP 200524763 | 40.7 ppb |
2019-03-14 | DBP 200524764 | 19.8 ppb |
2019-03-14 | DBP 200524765 | 25.7 ppb |
2019-03-14 | DBP 200524766 | 30.7 ppb |
2019-03-14 | DBP 200524767 | 18.8 ppb |
2019-06-20 | DBP 200537265 | 45.8 ppb |
2019-06-20 | DBP 200537266 | 21.8 ppb |
2019-06-20 | DBP 200537267 | 20.2 ppb |
2019-06-20 | DBP 200537268 | 51.5 ppb |
2019-06-20 | DBP 200537269 | 44.0 ppb |
2019-06-20 | DBP 200537270 | 41.8 ppb |
2019-06-20 | DBP 200537271 | 55.7 ppb |
2019-06-20 | DBP 200537272 | 29.9 ppb |
2019-08-15 | VOC1 200545121 | 31.5 ppb |
2019-08-15 | VOC1 200545122 | 31.4 ppb |
2019-09-19 | DBP 200549612 | 44.9 ppb |
2019-09-19 | DBP 200549613 | 21.9 ppb |
2019-09-19 | DBP 200549614 | 25.3 ppb |
2019-09-19 | DBP 200549615 | 47.5 ppb |
2019-09-19 | DBP 200549616 | 47.6 ppb |
2019-09-19 | DBP 200549617 | 48.8 ppb |
2019-09-19 | DBP 200549618 | 52.9 ppb |
2019-09-19 | DBP 200549619 | 36.5 ppb |
2019-12-19 | DBP 200560926 | 34.1 ppb |
2019-12-19 | DBP 200560927 | 14.4 ppb |
2019-12-19 | DBP 200560929 | 13.7 ppb |
2019-12-19 | DBP 200560930 | 24.7 ppb |
2019-12-19 | DBP 200560931 | 36.0 ppb |
2019-12-19 | DBP 200560932 | 33.9 ppb |
2019-12-19 | DBP 200560934 | 19.3 ppb |
2019-12-19 | DBP 200560935 | 32.7 ppb |