Total trihalomethanes (TTHMs)
Wilmington 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.
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 | 22.5 ppb | 10 | 10 | 5.50 ppb - 53.5 ppb |
| 2015 | 72.0 ppb | 40 | 40 | 8.00 ppb - 132.0 ppb |
| 2016 | 71.0 ppb | 28 | 28 | 10.00 ppb - 88.0 ppb |
| 2017 | 48.3 ppb | 35 | 35 | 12.7 ppb - 85.5 ppb |
| 2018 | 42.3 ppb | 36 | 36 | 11.6 ppb - 81.3 ppb |
| 2019 | 36.8 ppb | 40 | 40 | 8.90 ppb - 79.2 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 |
|---|---|---|
| 2014-04-01 | 1079443001 TTHM | 21.9 ppb |
| 2014-04-01 | 1079443002 TTHM | 53.5 ppb |
| 2014-04-01 | 1079443003 TTHM | 29.9 ppb |
| 2014-04-01 | 1079443004 TTHM | 12.9 ppb |
| 2014-04-01 | 1079443006 TTHM | 5.50 ppb |
| 2014-04-01 | 1079443007 TTHM | 23.6 ppb |
| 2014-04-01 | 1079443008 TTHM | 16.8 ppb |
| 2014-04-01 | 1079443009 TTHM | 23.0 ppb |
| 2014-04-01 | 1079443010 TTHM | 19.4 ppb |
| 2014-04-01 | 1079443011 TTHM | 18.7 ppb |
| 2015-01-05 | 2047942001 TTHM | 8.00 ppb |
| 2015-01-05 | 2047942002 TTHM | 33.4 ppb |
| 2015-01-05 | 2047942003 TTHM | 24.1 ppb |
| 2015-01-05 | 2047942004 TTHM | 19.5 ppb |
| 2015-01-05 | 2047942005 TTHM | 55.8 ppb |
| 2015-01-05 | 2047942006 TTHM | 20.4 ppb |
| 2015-01-05 | 2047942007 TTHM | 20.5 ppb |
| 2015-01-05 | 2047942008 TTHM | 32.2 ppb |
| 2015-01-05 | 2047942009 TTHM | 31.2 ppb |
| 2015-04-14 | 2065266001 TTHM | 19.4 ppb |
| 2015-04-14 | 2065266002 TTHM | 16.6 ppb |
| 2015-04-14 | 2065266003 TTHM | 40.2 ppb |
| 2015-04-14 | 2065266004 TTHM | 33.4 ppb |
| 2015-04-14 | 2065266005 TTHM | 28.8 ppb |
| 2015-04-14 | 2065266006 TTHM | 31.8 ppb |
| 2015-04-14 | 2065266007 TTHM | 48.2 ppb |
| 2015-04-14 | 2065266008 TTHM | 30.9 ppb |
| 2015-04-14 | 2065266009 TTHM | 56.6 ppb |
| 2015-04-14 | 2065266010 TTHM | 38.0 ppb |
| 2015-06-01 | 72.0 ppb* | |
| 2015-06-01 | 72.0 ppb* | |
| 2015-07-08 | 2082331001 TTHM | 57.0 ppb |
| 2015-07-08 | 2082331002 TTHM | 109.5 ppb |
| 2015-07-08 | 2082331003 TTHM | 126.0 ppb |
| 2015-07-08 | 2082331004 TTHM | 93.7 ppb |
| 2015-07-08 | 2082331005 TTHM | 125.0 ppb |
| 2015-07-08 | 2082331006 TTHM | 117.2 ppb |
| 2015-07-08 | 2082331007 TTHM | 72.2 ppb |
| 2015-07-08 | 2082331008 TTHM | 132.0 ppb |
| 2015-07-08 | 2082331009 TTHM | 126.0 ppb |
| 2015-07-08 | 2082331010 TTHM | 37.7 ppb |
| 2015-10-07 | 2100950001 TTHM | 21.1 ppb |
| 2015-10-07 | 2100950003 TTHM | 53.1 ppb |
| 2015-10-07 | 2100950004 TTHM | 42.5 ppb |
| 2015-10-07 | 2100950005 TTHM | 38.0 ppb |
| 2015-10-07 | 2100950006 TTHM | 47.8 ppb |
| 2015-10-07 | 2100950007 TTHM | 51.9 ppb |
| 2015-10-07 | 2100950008 TTHM | 39.9 ppb |
| 2015-10-07 | 2100950009 TTHM | 67.8 ppb |
| 2015-10-07 | 2100950010 TTHM | 49.8 ppb |
| 2016-04-04 | 2134195001 TTHM | 18.1 ppb |
| 2016-04-04 | 2134195003 TTHM | 26.9 ppb |
| 2016-04-04 | 2134195004 TTHM | 30.6 ppb |
| 2016-04-04 | 2134195005 TTHM | 34.9 ppb |
| 2016-04-04 | 2134195006 TTHM | 29.9 ppb |
| 2016-04-04 | 2134195007 TTHM | 29.3 ppb |
| 2016-04-04 | 2134195008 TTHM | 30.1 ppb |
| 2016-04-04 | 2134195009 TTHM | 24.6 ppb |
| 2016-04-04 | 2134195010 TTHM | 31.4 ppb |
| 2016-06-01 | 71.0 ppb* | |
| 2016-06-01 | 71.0 ppb* | |
| 2016-07-26 | 2162107002 | 67.1 ppb |
| 2016-07-26 | 2162107003 | 87.9 ppb |
| 2016-07-26 | 2162107004 | 87.2 ppb |
| 2016-07-26 | 2162107005 | 80.2 ppb |
| 2016-07-26 | 2162107006 | 81.4 ppb |
| 2016-07-26 | 2162107007 | 74.4 ppb |
| 2016-07-26 | 2162107008 | 52.2 ppb |
| 2016-07-26 | 2162107009 | 81.2 ppb |
| 2016-10-03 | 2179446001 TTHM | 14.5 ppb |
| 2016-10-03 | 2179446002 TTHM | 62.3 ppb |
| 2016-10-03 | 2179446003 TTHM | 41.6 ppb |
| 2016-10-03 | 2179446004 TTHM | 39.4 ppb |
| 2016-10-03 | 2179446005 TTHM | 85.5 ppb |
| 2016-10-03 | 2179446006 TTHM | 78.9 ppb |
| 2016-10-03 | 2179446007 TTHM | 44.7 ppb |
| 2016-10-03 | 2179446008 TTHM | 58.7 ppb |
| 2016-10-03 | 2179446009 TTHM | 63.8 ppb |
| 2017-01-04 | 2200080001 TTHM | 12.7 ppb |
| 2017-01-04 | 2200080002 TTHM | 31.4 ppb |
| 2017-01-04 | 2200080003 TTHM | 26.3 ppb |
| 2017-01-04 | 2200080004 TTHM | 23.8 ppb |
| 2017-01-04 | 2200080005 TTHM | 20.1 ppb |
| 2017-01-04 | 2200080006 TTHM | 51.8 ppb |
| 2017-01-04 | 2200080007 TTHM | 22.6 ppb |
| 2017-01-04 | 2200080008 TTHM | 25.6 ppb |
| 2017-01-04 | 2200080009 TTHM | 27.6 ppb |
| 2017-04-04 | 2220361001 TTHM | 18.2 ppb |
| 2017-04-04 | 2220361003 TTHM | 47.2 ppb |
| 2017-04-04 | 2220361004 TTHM | 40.9 ppb |
| 2017-04-04 | 2220361005 TTHM | 31.5 ppb |
| 2017-04-04 | 2220361006 TTHM | 31.7 ppb |
| 2017-04-04 | 2220361007 TTHM | 62.0 ppb |
| 2017-04-04 | 2220361008 TTHM | 37.3 ppb |
| 2017-04-04 | 2220361009 TTHM | 53.4 ppb |
| 2017-04-04 | 2220361010 TTHM | 43.0 ppb |
| 2017-04-05 | 2220361011 TTHM | 25.4 ppb |
| 2017-07-18 | 2247510004 TTHM | 68.0 ppb |
| 2017-07-18 | 2247510006 TTHM | 71.5 ppb |
| 2017-07-18 | 2247510008 TTHM | 61.1 ppb |
| 2017-07-18 | 2247510010 TTHM | 60.4 ppb |
| 2017-07-18 | 2247510012 TTHM | 69.8 ppb |
| 2017-07-18 | 2247510014 TTHM | 57.6 ppb |
| 2017-07-18 | 2247510016 TTHM | 80.4 ppb |
| 2017-07-18 | 2247510018 TTHM | 73.9 ppb |
| 2017-10-03 | 226296008 TTHM | 54.0 ppb |
| 2017-10-03 | 2267296004 TTHM | 62.8 ppb |
| 2017-10-03 | 2267296006 TTHM | 65.1 ppb |
| 2017-10-03 | 2267296010 TTHM | 59.4 ppb |
| 2017-10-03 | 2267296012 TTHM | 71.7 ppb |
| 2017-10-03 | 2267296014 TTHM | 44.2 ppb |
| 2017-10-03 | 2267296016 TTHM | 85.5 ppb |
| 2017-10-03 | 2267296018 TTHM | 73.0 ppb |
| 2018-01-03 | 2287060001 TTHM | 11.6 ppb |
| 2018-01-03 | 2287060004 TTHM | 39.9 ppb |
| 2018-01-03 | 2287060006 TTHM | 39.9 ppb |
| 2018-01-03 | 2287060008 TTHM | 28.3 ppb |
| 2018-01-03 | 2287060010 TTHM | 23.4 ppb |
| 2018-01-03 | 2287060012 TTHM | 50.5 ppb |
| 2018-01-03 | 2287060014 TTHM | 21.4 ppb |
| 2018-01-03 | 2287060016 TTHM | 50.2 ppb |
| 2018-01-03 | 2287060018 TTHM | 36.2 ppb |
| 2018-04-03 | 2306959001 TTHM | 40.0 ppb |
| 2018-04-03 | 2306959003 TTHM | 31.4 ppb |
| 2018-04-03 | 2306959005 TTHM | 15.4 ppb |
| 2018-04-03 | 2306959007 TTHM | 30.8 ppb |
| 2018-04-03 | 2306959009 TTHM | 28.0 ppb |
| 2018-04-03 | 2306959011 TTHM | 27.7 ppb |
| 2018-04-03 | 2306959013 TTHM | 39.9 ppb |
| 2018-04-03 | 2306959015 TTHM | 38.1 ppb |
| 2018-04-03 | 2306959017 TTHM | 25.3 ppb |
| 2018-07-02 | 2324450001 TTHM | 35.9 ppb |
| 2018-07-02 | 2324450003 TTHM | 62.8 ppb |
| 2018-07-02 | 2324450004 TTHM | 70.1 ppb |
| 2018-07-02 | 2324450005 TTHM | 52.8 ppb |
| 2018-07-02 | 2324450006 TTHM | 56.3 ppb |
| 2018-07-02 | 2324450007 TTHM | 65.0 ppb |
| 2018-07-02 | 2324450008 TTHM | 67.1 ppb |
| 2018-07-02 | 2324450009 TTHM | 81.3 ppb |
| 2018-07-02 | 2324450010 TTHM | 60.2 ppb |
| 2018-10-02 | 2342141001 TTHM | 16.7 ppb |
| 2018-10-02 | 2342141004 TTHM | 41.5 ppb |
| 2018-10-02 | 2342141006 TTHM | 35.6 ppb |
| 2018-10-02 | 2342141008 TTHM | 34.8 ppb |
| 2018-10-02 | 2342141010 TTHM | 37.4 ppb |
| 2018-10-02 | 2342141012 TTHM | 76.0 ppb |
| 2018-10-02 | 2342141014 TTHM | 39.7 ppb |
| 2018-10-02 | 2342141016 TTHM | 64.4 ppb |
| 2018-10-02 | 2342141018 TTHM | 46.1 ppb |
| 2019-01-03 | 3009447001 TTHM | 15.0 ppb |
| 2019-01-03 | 3009447004 TTHM | 29.6 ppb |
| 2019-01-03 | 3009447006 TTHM | 22.9 ppb |
| 2019-01-03 | 3009447008 TTHM | 20.8 ppb |
| 2019-01-03 | 3009447010 TTHM | 19.5 ppb |
| 2019-01-03 | 3009447012 TTHM | 46.2 ppb |
| 2019-01-03 | 3009447014 TTHM | 23.4 ppb |
| 2019-01-03 | 3009447016 TTHM | 39.7 ppb |
| 2019-01-03 | 3009447018 TTHM | 26.4 ppb |
| 2019-01-03 | 3009447020 TTHM | 8.90 ppb |
| 2019-04-02 | 3026194001 TTHM | 11.9 ppb |
| 2019-04-02 | 3026194003 TTHM | 27.3 ppb |
| 2019-04-02 | 3026194004 TTHM | 23.7 ppb |
| 2019-04-02 | 3026194005 TTHM | 22.8 ppb |
| 2019-04-02 | 3026194006 TTHM | 18.9 ppb |
| 2019-04-02 | 3026194007 TTHM | 22.6 ppb |
| 2019-04-02 | 3026194008 TTHM | 22.6 ppb |
| 2019-04-02 | 3026194009 TTHM | 34.5 ppb |
| 2019-04-02 | 3026194010 TTHM | 29.4 ppb |
| 2019-04-02 | 3026194011 TTHM | 11.8 ppb |
| 2019-07-01 | 3043203001 TTHM | 31.9 ppb |
| 2019-07-01 | 3043203004 TTHM | 55.8 ppb |
| 2019-07-01 | 3043203006 THHM | 45.0 ppb |
| 2019-07-01 | 3043203008 TTHM | 43.1 ppb |
| 2019-07-01 | 3043203010 TTHM | 51.8 ppb |
| 2019-07-01 | 3043203012 TTHM | 48.7 ppb |
| 2019-07-01 | 3043203014 TTHM | 38.1 ppb |
| 2019-07-01 | 3043203016 TTHM | 71.3 ppb |
| 2019-07-01 | 3043203018 TTHM | 47.3 ppb |
| 2019-07-01 | 3043203020 TTHM | 29.1 ppb |
| 2019-10-02 | 3061934001 TTHM | 33.4 ppb |
| 2019-10-02 | 3061934004 TTHM | 58.1 ppb |
| 2019-10-02 | 3061934006 TTHM | 63.3 ppb |
| 2019-10-02 | 3061934008 TTHM | 49.1 ppb |
| 2019-10-02 | 3061934010 TTHM | 48.9 ppb |
| 2019-10-02 | 3061934012 TTHM | 66.6 ppb |
| 2019-10-02 | 3061934014 TTHM | 44.7 ppb |
| 2019-10-02 | 3061934016 TTHM | 79.2 ppb |
| 2019-10-02 | 3061934018 TTHM | 63.9 ppb |
| 2019-10-02 | 3061934020 TTHM | 23.3 ppb |
* Sample result is taken from the system's CCR report.