Total trihalomethanes (TTHMs)
Chautauqua Utility District
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 |
|---|---|---|---|---|
| 2014 | 57.8 ppb | 14 | 14 | 40.2 ppb - 96.3 ppb |
| 2015 | 47.1 ppb | 8 | 8 | 28.4 ppb - 107.3 ppb |
| 2016 | 46.1 ppb | 8 | 8 | 37.9 ppb - 54.5 ppb |
| 2017 | 48.5 ppb | 8 | 8 | 40.8 ppb - 57.5 ppb |
| 2018 | 46.9 ppb | 8 | 8 | 38.0 ppb - 56.0 ppb |
| 2019 | 50.8 ppb | 8 | 8 | 37.0 ppb - 64.0 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 |
|---|---|---|
| 2014-02-13 | FEB2014 WWTP CUD | 96.3 ppb |
| 2014-02-13 | FEB2014 TURNER B | 82.6 ppb |
| 2014-05-15 | MAY2014 TURNER B | 40.2 ppb |
| 2014-05-15 | MAY2014 WWTP | 48.5 ppb |
| 2014-05-15 | MAY2014 TURNER T | 40.2 ppb |
| 2014-05-15 | MAY2014 WWTP TOT | 48.5 ppb |
| 2014-08-14 | AUG 2014 TURNER | 73.1 ppb |
| 2014-08-14 | AUG 2014 WWTP | 63.5 ppb |
| 2014-08-14 | AUG14 TURNER TOT | 74.1 ppb |
| 2014-08-14 | AUG14 WWTP TOTAL | 63.5 ppb |
| 2014-11-06 | NOV14 TURNER-CUD | 41.7 ppb |
| 2014-11-06 | NOV14 TURNER TOT | 41.7 ppb |
| 2014-11-06 | NOV14 CUD WWTP | 47.8 ppb |
| 2014-11-06 | NOV14 WWTP TOTAL | 47.8 ppb |
| 2015-02-19 | FEB15 WWTP-CUD | 28.4 ppb |
| 2015-02-19 | FEB2015 WWTP TOT | 28.4 ppb |
| 2015-02-19 | FEB2015 TURNER B | 31.1 ppb |
| 2015-02-19 | FEB15 TURNER TOT | 31.0 ppb |
| 2015-05-28 | MAY 2015 WWTP DB | 38.4 ppb |
| 2015-05-28 | MAY2015 TURNER B | 43.5 ppb |
| 2015-08-20 | AUG15CUD TURNER | 107.3 ppb |
| 2015-08-20 | AUG15 CUD WWTP | 68.4 ppb |
| 2016-02-24 | FEB16 CUD-TURNER | 37.9 ppb |
| 2016-02-24 | FEB15 CUD-WWTP | 43.1 ppb |
| 2016-05-18 | MAY16 WWTP CUD | 44.6 ppb |
| 2016-05-18 | MAY2016 TURNER B | 39.6 ppb |
| 2016-08-03 | AUG16 TURNER BLD | 51.1 ppb |
| 2016-08-03 | AUG16 WASTEWATER | 47.0 ppb |
| 2016-11-16 | NOV16 TURNER BLD | 51.0 ppb |
| 2016-11-16 | NOV16 WWTP | 54.5 ppb |
| 2017-02-15 | FEB17 WWTP CUD | 44.4 ppb |
| 2017-02-15 | FEB2017 TURNER C | 40.8 ppb |
| 2017-05-03 | MAY17 DBPS CUD # | 57.5 ppb |
| 2017-05-03 | MAY17 DBPS CUD | 53.1 ppb |
| 2017-08-02 | 3RDQT17 WWTP | 57.1 ppb |
| 2017-08-02 | 3RDQT17 TURNER B | 51.0 ppb |
| 2017-11-15 | NOV17 DBP TURNER | 42.4 ppb |
| 2017-11-15 | NOV17 WASTERWATE | 41.5 ppb |
| 2018-02-07 | Q1 CUD 18 WWTP | 48.0 ppb |
| 2018-02-07 | Q1CUD 18 TURNER | 41.0 ppb |
| 2018-05-02 | Q2 CUD 18 TURNER | 42.0 ppb |
| 2018-05-02 | Q2 CUD 18 WWTP | 38.0 ppb |
| 2018-08-01 | Q3 CUD 18 WWTP | 55.0 ppb |
| 2018-08-01 | Q3 CUD 18 TURNER | 56.0 ppb |
| 2018-11-20 | Q4 18 TURNER DBP | 54.0 ppb |
| 2018-11-20 | Q4 18 WWTP DBPS | 41.0 ppb |
| 2019-02-20 | Q1 19 TURNER DBP | 43.0 ppb |
| 2019-02-20 | Q1 19 WWTP DBPS | 37.0 ppb |
| 2019-05-01 | Q2 19 WWTP DBPS | 52.0 ppb |
| 2019-05-01 | Q2 19 TURNER DBP | 49.0 ppb |
| 2019-08-07 | Q3 19 WWTP DBPS | 57.1 ppb |
| 2019-08-07 | Q3 19 TURNER DBP | 64.0 ppb |
| 2019-11-06 | Q4 19 WWTP DBPS | 51.1 ppb |
| 2019-11-06 | Q4 19 TURNER DBP | 53.1 ppb |