Total trihalomethanes (TTHMs)
Scarsdale 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 | 33.4 ppb | 16 | 16 | 8.00 ppb - 46.0 ppb |
2015 | 34.5 ppb | 16 | 16 | 18.0 ppb - 66.0 ppb |
2016 | 38.9 ppb | 16 | 16 | 28.0 ppb - 51.0 ppb |
2017 | 36.1 ppb | 16 | 16 | 26.0 ppb - 45.0 ppb |
2018 | 39.8 ppb | 16 | 16 | 29.0 ppb - 54.0 ppb |
2019 | 34.3 ppb | 16 | 16 | 21.0 ppb - 44.0 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 |
---|---|---|
2014-01-17 | 201401200021DBP | 35.0 ppb |
2014-01-17 | 201401200020DBP | 26.0 ppb |
2014-01-17 | 201401200019DBP | 27.0 ppb |
2014-01-17 | 201401200022DBP | 33.0 ppb |
2014-04-17 | 201404180350DBP | 34.0 ppb |
2014-04-17 | 201404180351DBP | 41.0 ppb |
2014-04-17 | 201404180349DBP | 8.00 ppb |
2014-04-17 | 201404180348DBP | 40.0 ppb |
2014-07-17 | 201407180422DBP | 29.0 ppb |
2014-07-17 | 201407180423DBP | 28.0 ppb |
2014-07-17 | 201407180425DBP | 46.0 ppb |
2014-07-17 | 201407180424DBP | 38.0 ppb |
2014-10-17 | 201410180108 DBP | 34.0 ppb |
2014-10-17 | 201410180109 DBP | 43.0 ppb |
2014-10-17 | 201410180107 DBP | 37.0 ppb |
2014-10-17 | 201410180106 DBP | 36.0 ppb |
2015-01-16 | 201501170042DBP | 25.0 ppb |
2015-01-16 | 201501170043DBP | 29.0 ppb |
2015-01-16 | 201501170045DBP | 31.0 ppb |
2015-01-16 | 201501170044DBP | 54.0 ppb |
2015-04-17 | 201504180152DBP | 36.0 ppb |
2015-04-17 | 201504180151DBP | 66.0 ppb |
2015-04-17 | 201504180149DBP | 28.0 ppb |
2015-04-17 | 201504180150DBP | 30.0 ppb |
2015-07-28 | 201507290515 DBP | 31.0 ppb |
2015-07-28 | 201507290514 DBP | 18.0 ppb |
2015-07-28 | 201507290517 DBP | 20.0 ppb |
2015-07-28 | 201507290516 DBP | 49.0 ppb |
2015-10-15 | 201510160385 DBP | 30.0 ppb |
2015-10-15 | 201510160387 DBP | 32.0 ppb |
2015-10-15 | 201510160388 DBP | 43.0 ppb |
2015-10-15 | 201510160386 DBP | 30.0 ppb |
2016-01-20 | 201601210649 Q1 | 38.0 ppb |
2016-01-21 | 201601210651 DBP | 46.0 ppb |
2016-01-21 | 201601210650 Q1 | 43.0 ppb |
2016-01-21 | 201601210648 DBP | 36.0 ppb |
2016-04-18 | 201604190508 DBP | 46.0 ppb |
2016-04-18 | 201604190509 DBP | 44.0 ppb |
2016-04-18 | 201604190507 DBP | 37.0 ppb |
2016-04-18 | 201604190506 DBP | 44.0 ppb |
2016-07-18 | 201607190661 DBP | 51.0 ppb |
2016-07-18 | 201607190664 DBP | 38.0 ppb |
2016-07-18 | 201607190662 DBP | 28.0 ppb |
2016-07-18 | 201607190663 DBP | 37.0 ppb |
2016-10-17 | 201610180615 DBP | 41.0 ppb |
2016-10-17 | 201610180616 DBP | 34.0 ppb |
2016-10-17 | 201610180614 DBP | 32.0 ppb |
2016-10-17 | 201610180613 DBP | 28.0 ppb |
2017-01-17 | 201701180838 DBP | 37.0 ppb |
2017-01-17 | 201701180837 DBP | 41.0 ppb |
2017-01-17 | 201701180835 DBP | 31.0 ppb |
2017-01-17 | 201701180836 DBP | 33.0 ppb |
2017-04-17 | 201704180814-DBP | 36.0 ppb |
2017-04-17 | 201704180815-DBP | 43.0 ppb |
2017-04-17 | 201704180816-DBP | 39.0 ppb |
2017-04-17 | 201704180813-DBP | 43.0 ppb |
2017-07-17 | 201707180301-DBP | 33.0 ppb |
2017-07-17 | 201707180303-DBP | 26.0 ppb |
2017-07-17 | 201707180302-DBP | 45.0 ppb |
2017-07-17 | 201707180304-DBP | 37.0 ppb |
2017-10-17 | 201710180633-DBP | 27.0 ppb |
2017-10-17 | 201710180635-DBP | 37.0 ppb |
2017-10-17 | 201710180632-DBP | 32.0 ppb |
2017-10-17 | 201710180634-DBP | 38.0 ppb |
2018-01-17 | 201801180352-DBP | 32.0 ppb |
2018-01-17 | 201801180351-DBP | 31.0 ppb |
2018-01-17 | 201801180350-DBP | 29.0 ppb |
2018-01-17 | 201801180349-DBP | 36.0 ppb |
2018-04-17 | 201804180719-DBP | 46.0 ppb |
2018-04-17 | 201804180721-DBP | 40.0 ppb |
2018-04-17 | 201804180722-DBP | 49.0 ppb |
2018-04-17 | 201804180720-DBP | 35.0 ppb |
2018-07-17 | 201807200439-DBP | 42.0 ppb |
2018-07-17 | 201807200435-DBP | 41.0 ppb |
2018-07-17 | 201807200433-DBP | 34.0 ppb |
2018-07-17 | 201807200437-DBP | 43.0 ppb |
2018-10-17 | 201810180781-DBP | 43.0 ppb |
2018-10-17 | 201810180783-DBP | 54.0 ppb |
2018-10-17 | 201810180784-DBP | 45.0 ppb |
2018-10-17 | 201810180782-DBP | 37.0 ppb |
2019-01-17 | 201901180373-DBP | 42.0 ppb |
2019-01-17 | 201901180376-DBP | 44.0 ppb |
2019-01-17 | 201901180374-DBP | 40.0 ppb |
2019-01-17 | 201901180375-DBP | 41.0 ppb |
2019-04-17 | 201904180643-DBP | 37.0 ppb |
2019-04-17 | 201904180641-DBP | 43.0 ppb |
2019-04-17 | 201904180644-DBP | 44.0 ppb |
2019-04-17 | 201904180642-DBP | 21.0 ppb |
2019-07-17 | 201907180459-DBP | 22.0 ppb |
2019-07-17 | 201907180457-DBP | 29.0 ppb |
2019-07-17 | 201907180458-DBP | 28.0 ppb |
2019-07-17 | 201907180460-DBP | 33.0 ppb |
2019-10-17 | 201910180231-DBP | 26.0 ppb |
2019-10-17 | 201910180232-DBP | 29.0 ppb |
2019-10-17 | 201910180230-DBP | 33.0 ppb |
2019-10-17 | 201910180233-DBP | 37.0 ppb |