Total trihalomethanes (TTHMs)
Regional Water Authority
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.
288
Samples
14
Samples exceeding legal limit (MCL)
288
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2014 | 51.4 ppb | 48 | 48 | 29.0 ppb - 85.6 ppb |
| 2015 | 37.8 ppb | 48 | 48 | 22.9 ppb - 77.3 ppb |
| 2016 | 48.4 ppb | 48 | 48 | 2.10 ppb - 122.7 ppb |
| 2017 | 50.1 ppb | 48 | 48 | 13.6 ppb - 93.3 ppb |
| 2018 | 60.7 ppb | 48 | 48 | 40.8 ppb - 81.9 ppb |
| 2019 | 44.5 ppb | 48 | 48 | 26.1 ppb - 72.1 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 |
|---|---|---|
| 2014-03-04 | DBP 200391954 | 35.2 ppb |
| 2014-03-04 | DBP 200391959 | 38.6 ppb |
| 2014-03-04 | DBP 200391974 | 43.6 ppb |
| 2014-03-05 | DBP 200392092 | 50.5 ppb |
| 2014-03-05 | DBP 200392093 | 55.6 ppb |
| 2014-03-05 | DBP 200392094 | 43.6 ppb |
| 2014-03-06 | DBP 200392152 | 33.0 ppb |
| 2014-03-06 | DBP 200392201 | 53.9 ppb |
| 2014-03-06 | DBP 200392202 | 48.0 ppb |
| 2014-03-07 | DBP 200392306 | 38.7 ppb |
| 2014-03-07 | DBP 200392307 | 63.6 ppb |
| 2014-03-07 | DBP 200392308 | 53.3 ppb |
| 2014-06-02 | DBP 200396948 | 68.2 ppb |
| 2014-06-02 | DBP 200396949 | 62.4 ppb |
| 2014-06-02 | DBP 200396950 | 54.3 ppb |
| 2014-06-03 | DBP 200396959 | 37.7 ppb |
| 2014-06-03 | DBP 200396964 | 38.1 ppb |
| 2014-06-03 | DBP 200396982 | 40.4 ppb |
| 2014-06-03 | DBP 200397073 | 50.3 ppb |
| 2014-06-05 | DBP 200397229 | 50.1 ppb |
| 2014-06-05 | DBP 200397327 | 56.4 ppb |
| 2014-06-05 | DBP 200397328 | 85.6 ppb |
| 2014-06-06 | DBP 200397354 | 81.1 ppb |
| 2014-06-06 | DBP 200397355 | 70.7 ppb |
| 2014-09-02 | DBP 200403272 | 43.3 ppb |
| 2014-09-02 | DBP 200403277 | 46.0 ppb |
| 2014-09-02 | DBP 200403302 | 45.9 ppb |
| 2014-09-03 | DBP 200403470 | 56.1 ppb |
| 2014-09-03 | DBP 200403471 | 41.6 ppb |
| 2014-09-03 | DBP 200403472 | 44.2 ppb |
| 2014-09-04 | DBP 200403517 | 76.7 ppb |
| 2014-09-04 | DBP 200403556 | 47.7 ppb |
| 2014-09-04 | DBP 200403557 | 55.4 ppb |
| 2014-09-04 | DBP 200403558 | 58.2 ppb |
| 2014-09-06 | DBP 200403687 | 69.0 ppb |
| 2014-09-06 | DBP 200403688 | 38.0 ppb |
| 2014-12-02 | DBP 200408683 | 32.0 ppb |
| 2014-12-02 | DBP 200408688 | 37.0 ppb |
| 2014-12-02 | DBP 200408706 | 43.6 ppb |
| 2014-12-02 | DBP 200408748 | 55.8 ppb |
| 2014-12-02 | DBP 200408749 | 64.0 ppb |
| 2014-12-02 | DBP 200408750 | 29.0 ppb |
| 2014-12-03 | DBP 200408856 | 51.9 ppb |
| 2014-12-03 | DBP 200408857 | 84.0 ppb |
| 2014-12-04 | DBP 200408946 | 43.7 ppb |
| 2014-12-04 | DBP 200408968 | 48.8 ppb |
| 2014-12-04 | DBP 200408969 | 55.2 ppb |
| 2014-12-04 | DBP 200408970 | 46.8 ppb |
| 2015-03-02 | DBP 200412851 | 34.3 ppb |
| 2015-03-02 | DBP 200412850 | 29.0 ppb |
| 2015-03-03 | DBP 200412928 | 30.2 ppb |
| 2015-03-03 | DBP 200412929 | 30.5 ppb |
| 2015-03-03 | DBP 200412863 | 22.9 ppb |
| 2015-03-03 | DBP 200412883 | 43.5 ppb |
| 2015-03-03 | DBP 200412870 | 25.8 ppb |
| 2015-03-04 | DBP 200413051 | 38.8 ppb |
| 2015-03-05 | DBP 200413155 | 35.5 ppb |
| 2015-03-05 | DBP 200413154 | 32.7 ppb |
| 2015-03-05 | DBP 200413156 | 35.9 ppb |
| 2015-03-05 | DBP 200413130 | 35.9 ppb |
| 2015-06-01 | DBP 200417605 | 39.4 ppb |
| 2015-06-01 | DBP 200417604 | 36.8 ppb |
| 2015-06-01 | DBP 200417602 | 35.3 ppb |
| 2015-06-01 | DBP 200417603 | 28.6 ppb |
| 2015-06-01 | DBP 200417595 | 37.0 ppb |
| 2015-06-01 | DBP 200417563 | 39.9 ppb |
| 2015-06-02 | DBP 200417699 | 33.4 ppb |
| 2015-06-02 | DBP 200417701 | 34.1 ppb |
| 2015-06-02 | DBP 200417624 | 25.1 ppb |
| 2015-06-02 | DBP 200417629 | 30.1 ppb |
| 2015-06-03 | DBP 200417823 | 44.7 ppb |
| 2015-06-03 | DBP 200417819 | 30.3 ppb |
| 2015-09-01 | DBP 200423869 | 48.4 ppb |
| 2015-09-01 | DBP 200423812 | 28.1 ppb |
| 2015-09-01 | DBP 200423829 | 34.3 ppb |
| 2015-09-01 | DBP 200423807 | 28.7 ppb |
| 2015-09-01 | DBP 200423866 | 45.5 ppb |
| 2015-09-01 | DBP 200423867 | 51.3 ppb |
| 2015-09-01 | DBP 200423821 | 64.0 ppb |
| 2015-09-01 | DBP 200423868 | 34.9 ppb |
| 2015-09-02 | DBP 200424081 | 44.7 ppb |
| 2015-09-02 | DBP 200424082 | 39.6 ppb |
| 2015-09-02 | DBP 200424080 | 37.3 ppb |
| 2015-09-04 | DBP 200424271 | 77.3 ppb |
| 2015-12-01 | DBP 200429601 | 48.9 ppb |
| 2015-12-01 | DBP 200429604 | 30.6 ppb |
| 2015-12-01 | DBP 200429602 | 52.6 ppb |
| 2015-12-01 | DBP 200429541 | 23.0 ppb |
| 2015-12-01 | DBP 200429556 | 31.3 ppb |
| 2015-12-01 | DBP 200429546 | 30.5 ppb |
| 2015-12-02 | DBP 200429752 | 42.3 ppb |
| 2015-12-02 | DBP 200429751 | 49.6 ppb |
| 2015-12-02 | DBP 200429725 | 43.3 ppb |
| 2015-12-03 | DBP 200429877 | 38.4 ppb |
| 2015-12-03 | DBP 200429876 | 47.5 ppb |
| 2015-12-03 | DBP 200429875 | 30.6 ppb |
| 2016-03-01 | DBP 200434420 | 26.8 ppb |
| 2016-03-01 | DBP 200434432 | 20.6 ppb |
| 2016-03-01 | DBP 200434439 | 25.7 ppb |
| 2016-03-01 | DBP 200434518 | 34.3 ppb |
| 2016-03-02 | DBP 200434652 | 29.9 ppb |
| 2016-03-02 | DBP 200434653 | 39.9 ppb |
| 2016-03-03 | DBP 200434705 | 46.3 ppb |
| 2016-03-03 | DBP 200434734 | 52.3 ppb |
| 2016-03-03 | DBP 200434790 | 29.1 ppb |
| 2016-03-03 | DBP 200434791 | 36.6 ppb |
| 2016-03-04 | DBP 200434819 | 37.0 ppb |
| 2016-03-04 | DBP 200434820 | 34.4 ppb |
| 2016-06-01 | DBP 200441025 | 33.9 ppb |
| 2016-06-01 | DBP 200441026 | 36.9 ppb |
| 2016-06-01 | DBP 200441037 | 42.0 ppb |
| 2016-06-01 | DBP 200441054 | 61.5 ppb |
| 2016-06-01 | DBP 200441055 | 53.3 ppb |
| 2016-06-01 | DBP 200441056 | 28.5 ppb |
| 2016-06-01 | DBP 200441057 | 69.0 ppb |
| 2016-06-01 | DBP 200441058 | 37.9 ppb |
| 2016-06-02 | DBP 200441262 | 53.3 ppb |
| 2016-06-02 | DBP 200441297 | 50.6 ppb |
| 2016-06-02 | DBP 200441298 | 56.8 ppb |
| 2016-06-02 | DBP 200441299 | 40.0 ppb |
| 2016-09-06 | DBP 200448969 | 55.4 ppb |
| 2016-09-06 | DBP 200448974 | 58.0 ppb |
| 2016-09-06 | DBP 200449001 | 67.7 ppb |
| 2016-09-06 | DBP 200449014 | 53.6 ppb |
| 2016-09-06 | DBP 200449015 | 76.5 ppb |
| 2016-09-06 | DBP 200449016 | 80.5 ppb |
| 2016-09-07 | DBP 200449214 | 72.1 ppb |
| 2016-09-08 | DBP 200449407 | 80.4 ppb |
| 2016-09-08 | DBP 200449408 | 76.2 ppb |
| 2016-09-09 | DBP 200449500 | 57.8 ppb |
| 2016-09-12 | DBP 200449545 | 89.4 ppb |
| 2016-09-12 | DBP 200449547 | 122.7 ppb |
| 2016-12-05 | DBP 200456081 | 31.9 ppb |
| 2016-12-05 | DBP 200456083 | 44.8 ppb |
| 2016-12-06 | DBP 200456088 | 48.7 ppb |
| 2016-12-06 | DBP 200456110 | 34.4 ppb |
| 2016-12-06 | DBP 200456115 | 37.4 ppb |
| 2016-12-06 | DBP 200456175 | 46.7 ppb |
| 2016-12-07 | DBP 200456358 | 15.2 ppb |
| 2016-12-07 | DBP 200456359 | 47.0 ppb |
| 2016-12-08 | DBP 200456453 | 2.10 ppb |
| 2016-12-08 | DBP 200456460 | 62.6 ppb |
| 2016-12-08 | DBP 200456461 | 47.2 ppb |
| 2016-12-08 | DBP 200456462 | 36.3 ppb |
| 2017-03-01 | DBP 200461496 | 34.6 ppb |
| 2017-03-01 | DBP 200461542 | 35.0 ppb |
| 2017-03-01 | DBP 200461543 | 41.8 ppb |
| 2017-03-01 | DBP 200461544 | 33.7 ppb |
| 2017-03-01 | DBP 200461545 | 42.6 ppb |
| 2017-03-01 | DBP 200461546 | 38.3 ppb |
| 2017-03-02 | DBP 200461650 | 31.6 ppb |
| 2017-03-02 | DBP 200461651 | 33.1 ppb |
| 2017-03-02 | DBP 200461673 | 57.2 ppb |
| 2017-03-02 | DBP 200461674 | 49.2 ppb |
| 2017-03-02 | DBP 200461675 | 17.8 ppb |
| 2017-03-03 | DBP 200461727 | 13.6 ppb |
| 2017-06-05 | DBP 200468420 | 36.9 ppb |
| 2017-06-05 | DBP 200468421 | 49.4 ppb |
| 2017-06-06 | DBP 200468476 | 35.1 ppb |
| 2017-06-06 | DBP 200468481 | 37.6 ppb |
| 2017-06-06 | DBP 200468500 | 49.4 ppb |
| 2017-06-07 | DBP 200468669 | 38.8 ppb |
| 2017-06-07 | DBP 200468670 | 49.4 ppb |
| 2017-06-08 | DBP 200468850 | 29.3 ppb |
| 2017-06-08 | DBP 200468946 | 58.3 ppb |
| 2017-06-08 | DBP 200468947 | 60.6 ppb |
| 2017-06-08 | DBP 200468948 | 46.0 ppb |
| 2017-06-08 | DBP 200468949 | 43.4 ppb |
| 2017-09-05 | DBP 200475785 | 50.3 ppb |
| 2017-09-05 | DBP 200475790 | 52.0 ppb |
| 2017-09-05 | DBP 200475800 | 67.6 ppb |
| 2017-09-07 | DBP 200476104 | 61.3 ppb |
| 2017-09-07 | DBP 200476220 | 86.0 ppb |
| 2017-09-07 | DBP 200476221 | 66.0 ppb |
| 2017-09-07 | DBP 200476222 | 77.0 ppb |
| 2017-09-07 | DBP 200476224 | 81.8 ppb |
| 2017-09-08 | DBP 200476302 | 86.0 ppb |
| 2017-09-08 | DBP 200476304 | 93.3 ppb |
| 2017-09-08 | DBP 200476305 | 54.9 ppb |
| 2017-09-08 | DBP 200476306 | 64.3 ppb |
| 2017-12-05 | DBP 200483376 | 36.8 ppb |
| 2017-12-05 | DBP 200483381 | 41.1 ppb |
| 2017-12-05 | DBP 200483391 | 55.7 ppb |
| 2017-12-07 | DBP 200483770 | 51.9 ppb |
| 2017-12-07 | DBP 200483771 | 58.8 ppb |
| 2017-12-07 | DBP 200483772 | 49.1 ppb |
| 2017-12-07 | DBP 200483773 | 51.1 ppb |
| 2017-12-07 | DBP 200483774 | 57.2 ppb |
| 2017-12-08 | DBP 200483834 | 40.0 ppb |
| 2017-12-08 | DBP 200483843 | 54.6 ppb |
| 2017-12-08 | DBP 200483844 | 55.4 ppb |
| 2017-12-08 | DBP 200483845 | 49.3 ppb |
| 2018-03-06 | DBP 200489268 | 48.3 ppb |
| 2018-03-06 | DBP 200489275 | 49.7 ppb |
| 2018-03-06 | DBP 200489287 | 60.9 ppb |
| 2018-03-07 | DBP 200489537 | 59.4 ppb |
| 2018-03-07 | DBP 200489538 | 59.5 ppb |
| 2018-03-07 | DBP 200489539 | 81.3 ppb |
| 2018-03-07 | DBP 200489540 | 64.9 ppb |
| 2018-03-07 | DBP 200489541 | 49.1 ppb |
| 2018-03-08 | DBP 200489565 | 43.3 ppb |
| 2018-03-09 | DBP 200489701 | 75.7 ppb |
| 2018-03-09 | DBP 200489702 | 79.3 ppb |
| 2018-03-09 | DBP 200489703 | 40.8 ppb |
| 2018-06-05 | DBP 200495984 | 51.4 ppb |
| 2018-06-05 | DBP 200495989 | 54.7 ppb |
| 2018-06-05 | DBP 200496002 | 67.7 ppb |
| 2018-06-06 | DBP 200496235 | 62.0 ppb |
| 2018-06-07 | DBP 200496375 | 42.3 ppb |
| 2018-06-07 | DBP 200496376 | 57.6 ppb |
| 2018-06-07 | DBP 200496417 | 54.0 ppb |
| 2018-06-08 | DBP 200496507 | 72.1 ppb |
| 2018-06-08 | DBP 200496508 | 46.8 ppb |
| 2018-06-08 | DBP 200496509 | 69.3 ppb |
| 2018-06-08 | DBP 200496510 | 69.1 ppb |
| 2018-06-08 | DBP 200496511 | 50.5 ppb |
| 2018-09-04 | DBP 200503732 | 62.8 ppb |
| 2018-09-04 | DBP 200503737 | 64.2 ppb |
| 2018-09-04 | DBP 200503842 | 70.2 ppb |
| 2018-09-04 | DBP 200503912 | 81.9 ppb |
| 2018-09-04 | DBP 200503913 | 81.8 ppb |
| 2018-09-04 | DBP 200503914 | 66.1 ppb |
| 2018-09-05 | DBP 200503981 | 77.6 ppb |
| 2018-09-05 | DBP 200504086 | 52.5 ppb |
| 2018-09-05 | DBP 200504087 | 61.8 ppb |
| 2018-09-06 | DBP 200504185 | 62.8 ppb |
| 2018-09-06 | DBP 200504211 | 68.6 ppb |
| 2018-09-07 | DBP 200504441 | 57.7 ppb |
| 2018-12-03 | DBP 200514372 | 42.6 ppb |
| 2018-12-03 | DBP 200514406 | 52.1 ppb |
| 2018-12-04 | DBP 200514447 | 51.5 ppb |
| 2018-12-04 | DBP 200514452 | 60.3 ppb |
| 2018-12-04 | DBP 200514625 | 74.1 ppb |
| 2018-12-04 | DBP 200514626 | 78.8 ppb |
| 2018-12-04 | DBP 200514627 | 59.1 ppb |
| 2018-12-04 | DBP 200514628 | 48.0 ppb |
| 2018-12-04 | DBP 200514629 | 62.6 ppb |
| 2018-12-05 | DBP 200514952 | 60.8 ppb |
| 2018-12-06 | DBP 200515069 | 49.5 ppb |
| 2018-12-06 | DBP 200515070 | 58.5 ppb |
| 2019-03-04 | DBP 200523215 | 27.0 ppb |
| 2019-03-04 | DBP 200523217 | 33.8 ppb |
| 2019-03-05 | DBP 200523262 | 28.8 ppb |
| 2019-03-05 | DBP 200523269 | 32.7 ppb |
| 2019-03-05 | DBP 200523456 | 33.2 ppb |
| 2019-03-05 | DBP 200523457 | 45.1 ppb |
| 2019-03-05 | DBP 200523458 | 35.4 ppb |
| 2019-03-05 | DBP 200523459 | 32.5 ppb |
| 2019-03-05 | DBP 200523463 | 29.3 ppb |
| 2019-03-07 | DBP 200523884 | 29.5 ppb |
| 2019-03-08 | DBP 200524000 | 26.1 ppb |
| 2019-03-08 | DBP 200524002 | 34.0 ppb |
| 2019-06-03 | DBP 200534373 | 45.5 ppb |
| 2019-06-03 | DBP 200534414 | 54.5 ppb |
| 2019-06-04 | DBP 200534491 | 43.5 ppb |
| 2019-06-04 | DBP 200534496 | 45.7 ppb |
| 2019-06-04 | DBP 200534600 | 41.6 ppb |
| 2019-06-04 | DBP 200534725 | 57.0 ppb |
| 2019-06-04 | DBP 200534727 | 48.9 ppb |
| 2019-06-04 | DBP 200534729 | 56.8 ppb |
| 2019-06-05 | DBP 200535039 | 60.4 ppb |
| 2019-06-05 | DBP 200535041 | 44.6 ppb |
| 2019-06-06 | DBP 200535197 | 46.6 ppb |
| 2019-06-07 | DBP 200535357 | 52.4 ppb |
| 2019-09-03 | DBP 200546988 | 51.1 ppb |
| 2019-09-03 | DBP 200546993 | 59.2 ppb |
| 2019-09-04 | DBP 200547400 | 51.3 ppb |
| 2019-09-04 | DBP 200547402 | 59.5 ppb |
| 2019-09-04 | DBP 200547403 | 59.7 ppb |
| 2019-09-04 | DBP 200547404 | 54.6 ppb |
| 2019-09-04 | DBP 200547405 | 47.6 ppb |
| 2019-09-05 | DBP 200547460 | 72.1 ppb |
| 2019-09-05 | DBP 200547667 | 70.5 ppb |
| 2019-09-06 | DBP 200547826 | 54.7 ppb |
| 2019-09-06 | DBP 200547827 | 64.7 ppb |
| 2019-09-06 | DBP 200547828 | 53.4 ppb |
| 2019-12-02 | DBP 200558405 | 43.1 ppb |
| 2019-12-02 | DBP 200558406 | 37.9 ppb |
| 2019-12-02 | DBP 200558407 | 46.1 ppb |
| 2019-12-03 | DBP 200558454 | 33.8 ppb |
| 2019-12-03 | DBP 200558459 | 38.4 ppb |
| 2019-12-03 | DBP 200558612 | 38.9 ppb |
| 2019-12-04 | DBP 200558916 | 35.7 ppb |
| 2019-12-04 | DBP 200558917 | 39.2 ppb |
| 2019-12-04 | DBP 200558919 | 32.8 ppb |
| 2019-12-05 | DBP 200559073 | 41.5 ppb |
| 2019-12-05 | DBP 200559098 | 30.7 ppb |
| 2019-12-06 | DBP 200559195 | 36.2 ppb |