Total trihalomethanes (TTHMs)
Clay WDS
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 |
|---|---|---|---|---|
| 2013 | N/A | 0 | 0 | N/A |
| 2014 | 40.6 ppb | 16 | 16 | 22.0 ppb - 62.0 ppb |
| 2015 | 47.0 ppb | 16 | 16 | 19.6 ppb - 80.0 ppb |
| 2016 | 45.4 ppb | 16 | 16 | 28.0 ppb - 58.0 ppb |
| 2017 | 45.8 ppb | 16 | 16 | 27.0 ppb - 65.0 ppb |
| 2018 | 41.4 ppb | 16 | 16 | 27.0 ppb - 54.0 ppb |
| 2019 | 46.5 ppb | 16 | 16 | 33.0 ppb - 67.0 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 |
|---|---|---|
| 2014-02-10 | 1Q2014 FOSTER RD | 43.0 ppb |
| 2014-02-10 | 1Q2014 SHOREVIEW | 22.0 ppb |
| 2014-02-10 | 1Q2014 MOYERS CO | 28.0 ppb |
| 2014-02-10 | 1Q2014 CROSSROAD | 47.0 ppb |
| 2014-05-21 | 2Q2014 FOSTER RD | 62.0 ppb |
| 2014-05-21 | 2Q2014 SHOREVIEW | 32.0 ppb |
| 2014-05-21 | 2Q2014 CROSSROAD | 54.0 ppb |
| 2014-05-21 | 2Q2014 MOYERS CO | 41.0 ppb |
| 2014-08-20 | 3Q2014 MOYERS CO | 48.0 ppb |
| 2014-08-20 | 3Q2014 FOSTER RD | 52.0 ppb |
| 2014-08-20 | 3Q2014 CROSSROAD | 41.0 ppb |
| 2014-08-20 | 3Q2014 SHOREVIEW | 37.0 ppb |
| 2014-12-26 | 4Q2014 CROSSROAD | 37.0 ppb |
| 2014-12-26 | 4Q2014 SHOREVIEW | 27.0 ppb |
| 2014-12-26 | 4Q2014 MOYERS CO | 22.0 ppb |
| 2014-12-26 | 4Q2014 FOSTER RD | 56.0 ppb |
| 2015-03-03 | 1Q2015 SHOREVIEW | 19.6 ppb |
| 2015-03-03 | 1Q2015 CROSSROAD | 54.0 ppb |
| 2015-03-03 | 1Q2015 MOYERS CO | 28.0 ppb |
| 2015-03-03 | 1Q2015 FOSTER RD | 45.0 ppb |
| 2015-06-15 | 2Q2015 MOYERS CO | 45.0 ppb |
| 2015-06-15 | 2Q2015 CROSSROAD | 36.0 ppb |
| 2015-06-15 | 2Q2015 SHOREVIEW | 34.0 ppb |
| 2015-06-15 | 2Q2015 FOSTER RD | 50.0 ppb |
| 2015-09-02 | 3Q2015 CROSSROAD | 47.0 ppb |
| 2015-09-02 | 3Q2015 FOSTER RD | 63.0 ppb |
| 2015-09-02 | 3Q2015 MOYERS CO | 63.0 ppb |
| 2015-09-02 | 3Q2015 SHOREVIEW | 42.0 ppb |
| 2015-12-02 | 4Q2015 SHOREVIEW | 46.0 ppb |
| 2015-12-02 | 4Q2015 CROSSROAD | 51.0 ppb |
| 2015-12-02 | 4Q2015 FOSTER RD | 80.0 ppb |
| 2015-12-02 | 4Q2015 MOYERS CO | 48.0 ppb |
| 2016-03-02 | 1Q2016 SHOREVIEW | 28.0 ppb |
| 2016-03-02 | 1Q2016 MOYERS CO | 37.0 ppb |
| 2016-03-02 | 1Q2016 FOSTER RD | 48.0 ppb |
| 2016-03-02 | 1Q2016 CROSSROAD | 52.0 ppb |
| 2016-06-01 | 2Q2016 MOYERS CO | 58.0 ppb |
| 2016-06-01 | 2Q2016 FOSTER RD | 55.0 ppb |
| 2016-06-01 | 2Q2016 SHOREVIEW | 41.0 ppb |
| 2016-06-01 | 2Q2016 CROSSROAD | 58.0 ppb |
| 2016-09-07 | 3Q2016 CROSSROAD | 35.0 ppb |
| 2016-09-07 | 3Q2016 MOYERS CO | 51.0 ppb |
| 2016-09-07 | 3Q2016 FOSTER RD | 47.0 ppb |
| 2016-09-07 | 3Q2016 SHOREVIEW | 37.0 ppb |
| 2016-12-07 | 4Q2016 SHOREVIEW | 34.0 ppb |
| 2016-12-07 | 4Q2016 CROSSROAD | 53.0 ppb |
| 2016-12-07 | 4Q2016 MOYERS CO | 36.0 ppb |
| 2016-12-07 | 4Q2016 FOSTER RD | 56.0 ppb |
| 2017-03-01 | 1Q2017 MOYERS CO | 34.0 ppb |
| 2017-03-01 | 1Q2017 CROSSROAD | 44.0 ppb |
| 2017-03-01 | 1Q2017 FOSTER RD | 41.0 ppb |
| 2017-03-01 | 1Q2017 SHOREVIEW | 27.0 ppb |
| 2017-06-07 | 2Q2017 CROSSROAD | 47.0 ppb |
| 2017-06-07 | 2Q2017 MOYERS CO | 55.0 ppb |
| 2017-06-07 | 2Q2017 SHOREVIEW | 44.0 ppb |
| 2017-06-07 | 2Q2017 FOSTER RD | 56.0 ppb |
| 2017-09-20 | 3Q2017 CROSSROAD | 61.0 ppb |
| 2017-09-20 | 3Q2017 FOSTER RD | 65.0 ppb |
| 2017-09-20 | 3Q2017 MOYERS CO | 60.0 ppb |
| 2017-09-20 | 3Q2017 SHOREVIEW | 57.0 ppb |
| 2017-12-06 | 4Q2017 SHOREVIEW | 27.0 ppb |
| 2017-12-06 | 4Q2017 FOSTER RD | 45.0 ppb |
| 2017-12-06 | 4Q2017 CROSSROAD | 40.0 ppb |
| 2017-12-06 | 4Q2017 MOYERS CO | 30.0 ppb |
| 2018-03-07 | 1Q2018 CROSSROAD | 36.0 ppb |
| 2018-03-07 | 1Q2018 MOYERS CO | 32.0 ppb |
| 2018-03-07 | 1Q2018 FOSTER RD | 42.0 ppb |
| 2018-03-07 | 1Q2018 SHOREVIEW | 29.0 ppb |
| 2018-06-06 | 2Q2018 CROSSROAD | 54.0 ppb |
| 2018-06-06 | 2Q2018 SHOREVIEW | 37.0 ppb |
| 2018-06-06 | 2Q2018 FOSTER RD | 44.0 ppb |
| 2018-06-06 | 2Q2018 MOYERS CO | 49.0 ppb |
| 2018-09-05 | 3Q2018 SHOREVIEW | 46.0 ppb |
| 2018-09-05 | 3Q2018 FOSTER RD | 54.0 ppb |
| 2018-09-05 | 3Q2018 CROSSROAD | 49.0 ppb |
| 2018-09-07 | 3Q2018 MOYERS CO | 47.0 ppb |
| 2018-12-05 | 4Q2018 FOSTER RD | 49.0 ppb |
| 2018-12-05 | 4Q2018 SHOREVIEW | 27.0 ppb |
| 2018-12-05 | 4Q2018 CROSSROAD | 37.0 ppb |
| 2018-12-05 | 4Q2018 MOYERS CO | 30.0 ppb |
| 2019-03-06 | 1Q2019 FOSTER RD | 48.0 ppb |
| 2019-03-06 | 1Q2019 CROSSROAD | 47.0 ppb |
| 2019-03-06 | 1Q2019 MOYERS CO | 40.0 ppb |
| 2019-03-06 | 1Q2019 SHOREVIEW | 33.0 ppb |
| 2019-06-05 | 2Q2019 SHOREVIEW | 33.0 ppb |
| 2019-06-05 | 2Q2019 FOSTER RD | 47.0 ppb |
| 2019-06-05 | 2Q2019 MOYERS CO | 39.0 ppb |
| 2019-06-05 | 2Q2019 CROSSROAD | 34.0 ppb |
| 2019-09-04 | 3Q2019 FOSTER RD | 67.0 ppb |
| 2019-09-04 | 3Q2019 SHOREVIEW | 51.0 ppb |
| 2019-09-04 | 3Q2019 MOYERS CO | 60.0 ppb |
| 2019-09-04 | 3Q2019 CROSSROAD | 47.0 ppb |
| 2019-12-04 | 4Q2019 MOYERS CO | 42.0 ppb |
| 2019-12-04 | 4Q2019 CROSSROAD | 51.0 ppb |
| 2019-12-04 | 4Q2019 FOSTER RD | 53.0 ppb |
| 2019-12-04 | 4Q2019 SHOREVIEW | 52.0 ppb |