Chloroform
Metropolitan Utilities District
Chloroform, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Chloroform and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Read More.
In addition to tap water disinfection, chloroform pollution in the environment also comes from industrial discharges from pulp and paper mills, and from urban wastewater effluent. Human studies show that chloroform damages the kidneys, liver and central nervous system. In animals, chloroform causes infertility, birth defects and cancer.
Samples
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2018 | 24.2 ppb | 50 | 50 | 10.3 ppb - 48.6 ppb |
| 2019 | 30.7 ppb | 51 | 50 | ND - 57.6 ppb |
| 2020 | 25.0 ppb | 54 | 51 | ND - 46.1 ppb |
| 2021 | 21.4 ppb | 48 | 48 | 12.0 ppb - 29.7 ppb |
| 2022 | 25.7 ppb | 49 | 49 | 10.9 ppb - 52.4 ppb |
| 2023 | 23.4 ppb | 53 | 52 | ND - 61.3 ppb |
ppb = parts per billion
State, National, and Health Guidelines for Drinking Water
EWG Health Guideline: 0.4 ppb
The EWG Health Guideline of 0.4 ppb for chloroform was based on the California Office of Environmental Health Hazard Assessment's public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer and harm to fetal growth and development.
ppb = parts per billion
All test results
| Date | Lab ID | Result |
|---|---|---|
| 2018-02-06 | 534097 | 15.1 ppb |
| 2018-02-06 | 534092 | 10.3 ppb |
| 2018-02-06 | 534095 | 10.5 ppb |
| 2018-02-06 | 534100 | 14.9 ppb |
| 2018-02-06 | 534094 | 11.8 ppb |
| 2018-02-06 | 534090 | 11.3 ppb |
| 2018-02-06 | 534099 | 17.9 ppb |
| 2018-02-06 | 534096 | 10.6 ppb |
| 2018-02-06 | 534089 | 16.9 ppb |
| 2018-02-06 | 534098 | 16.8 ppb |
| 2018-02-06 | 534091 | 10.3 ppb |
| 2018-02-06 | 534093 | 14.6 ppb |
| 2018-05-07 | 549815 | 29.5 ppb |
| 2018-05-07 | 549816 | 48.5 ppb |
| 2018-05-07 | 549817 | 13.4 ppb |
| 2018-05-07 | 549814 | 42.3 ppb |
| 2018-05-07 | 549819 | 12.2 ppb |
| 2018-05-07 | 549825 | 41.2 ppb |
| 2018-05-07 | 549823 | 48.6 ppb |
| 2018-05-07 | 549821 | 37.8 ppb |
| 2018-05-07 | 549820 | 38.5 ppb |
| 2018-05-07 | 549818 | 31.6 ppb |
| 2018-05-07 | 549824 | 40.9 ppb |
| 2018-05-07 | 549822 | 28.8 ppb |
| 2018-05-14 | 542540 | 25.2 ppb |
| 2018-05-14 | 542539 | 16.2 ppb |
| 2018-08-08 | 567027 | 24.9 ppb |
| 2018-08-08 | 567023 | 25.2 ppb |
| 2018-08-08 | 567022 | 26.5 ppb |
| 2018-08-08 | 567029 | 25.0 ppb |
| 2018-08-08 | 567030 | 24.9 ppb |
| 2018-08-08 | 567024 | 29.1 ppb |
| 2018-08-08 | 567021 | 24.4 ppb |
| 2018-08-08 | 567026 | 23.6 ppb |
| 2018-08-08 | 567020 | 21.5 ppb |
| 2018-08-08 | 567028 | 30.6 ppb |
| 2018-08-08 | 567019 | 38.3 ppb |
| 2018-08-08 | 567025 | 26.1 ppb |
| 2018-11-06 | 583375 | 21.7 ppb |
| 2018-11-06 | 583385 | 25.2 ppb |
| 2018-11-06 | 583379 | 19.5 ppb |
| 2018-11-06 | 583374 | 24.5 ppb |
| 2018-11-06 | 583383 | 22.8 ppb |
| 2018-11-06 | 583378 | 24.0 ppb |
| 2018-11-06 | 583376 | 25.5 ppb |
| 2018-11-06 | 583382 | 25.6 ppb |
| 2018-11-06 | 583380 | 24.7 ppb |
| 2018-11-06 | 583384 | 24.0 ppb |
| 2018-11-06 | 583381 | 18.9 ppb |
| 2018-11-06 | 583377 | 19.9 ppb |
| 2019-02-05 | 595239 | 18.9 ppb |
| 2019-02-05 | 595245 | 20.2 ppb |
| 2019-02-05 | 595238 | 18.7 ppb |
| 2019-02-05 | 595243 | 19.2 ppb |
| 2019-02-05 | 595240 | 17.3 ppb |
| 2019-02-05 | 595237 | 16.5 ppb |
| 2019-02-05 | 595236 | 13.7 ppb |
| 2019-02-05 | 595244 | 19.8 ppb |
| 2019-02-05 | 595241 | 19.8 ppb |
| 2019-02-05 | 595246 | 17.4 ppb |
| 2019-02-05 | 595242 | 21.5 ppb |
| 2019-02-05 | 595247 | 21.6 ppb |
| 2019-04-02 | 604245 | 21.2 ppb |
| 2019-04-22 | 604810 | 14.9 ppb |
| 2019-05-07 | 600564 | 18.6 ppb |
| 2019-05-07 | 600571 | 33.7 ppb |
| 2019-05-07 | 600574 | 53.0 ppb |
| 2019-05-07 | 600567 | 37.2 ppb |
| 2019-05-07 | 600570 | 55.3 ppb |
| 2019-05-07 | 600566 | 45.4 ppb |
| 2019-05-07 | 600573 | 56.2 ppb |
| 2019-05-07 | 600575 | 51.8 ppb |
| 2019-05-07 | 600565 | 20.1 ppb |
| 2019-05-07 | 600568 | 57.6 ppb |
| 2019-05-07 | 600572 | 52.6 ppb |
| 2019-05-07 | 600569 | 51.7 ppb |
| 2019-06-10 | 604811 | ND |
| 2019-08-06 | 622452 | 38.7 ppb |
| 2019-08-06 | 622449 | 41.5 ppb |
| 2019-08-06 | 622450 | 43.0 ppb |
| 2019-08-06 | 622455 | 38.5 ppb |
| 2019-08-06 | 622457 | 40.7 ppb |
| 2019-08-06 | 622459 | 36.7 ppb |
| 2019-08-06 | 622448 | 34.4 ppb |
| 2019-08-06 | 622458 | 40.9 ppb |
| 2019-08-06 | 622451 | 36.9 ppb |
| 2019-08-06 | 622454 | 35.9 ppb |
| 2019-08-06 | 622456 | 30.9 ppb |
| 2019-08-06 | 622453 | 36.8 ppb |
| 2019-11-05 | 644387 | 26.6 ppb |
| 2019-11-05 | 644379 | 22.0 ppb |
| 2019-11-05 | 644378 | 21.5 ppb |
| 2019-11-05 | 644385 | 21.2 ppb |
| 2019-11-05 | 644382 | 26.1 ppb |
| 2019-11-05 | 644381 | 29.3 ppb |
| 2019-11-05 | 644383 | 29.2 ppb |
| 2019-11-05 | 644386 | 35.4 ppb |
| 2019-11-05 | 644380 | 26.2 ppb |
| 2019-11-05 | 644388 | 26.0 ppb |
| 2019-11-05 | 644384 | 21.0 ppb |
| 2019-11-05 | 644389 | 34.9 ppb |
| 2020-02-04 | 656186 | 16.2 ppb |
| 2020-02-04 | 656189 | 20.8 ppb |
| 2020-02-04 | 656190 | 17.9 ppb |
| 2020-02-04 | 656184 | 20.5 ppb |
| 2020-02-04 | 656185 | 18.0 ppb |
| 2020-02-04 | 656187 | 17.9 ppb |
| 2020-02-04 | 656182 | 19.2 ppb |
| 2020-02-04 | 656183 | 22.3 ppb |
| 2020-02-04 | 656193 | 16.4 ppb |
| 2020-02-04 | 656188 | 22.4 ppb |
| 2020-02-04 | 656191 | 20.3 ppb |
| 2020-02-04 | 656192 | 22.1 ppb |
| 2020-04-20 | 667072 | 26.6 ppb |
| 2020-04-20 | 667071 | 17.0 ppb |
| 2020-05-05 | 672108 | 24.0 ppb |
| 2020-05-05 | 672109 | 25.6 ppb |
| 2020-05-05 | 672103 | 24.0 ppb |
| 2020-05-05 | 672106 | 22.0 ppb |
| 2020-05-05 | 672102 | 21.4 ppb |
| 2020-05-05 | 672098 | 28.8 ppb |
| 2020-05-05 | 672107 | 29.6 ppb |
| 2020-05-05 | 672101 | 24.0 ppb |
| 2020-05-05 | 672105 | 17.9 ppb |
| 2020-05-05 | 672099 | 28.1 ppb |
| 2020-05-05 | 672100 | 25.8 ppb |
| 2020-05-05 | 672104 | 29.4 ppb |
| 2020-06-01 | 667076 | ND |
| 2020-06-01 | 667075 | ND |
| 2020-06-01 | 667073 | 2.37 ppb |
| 2020-06-01 | 667074 | ND |
| 2020-08-04 | 681798 | 46.1 ppb |
| 2020-08-04 | 681805 | 38.3 ppb |
| 2020-08-04 | 681796 | 40.3 ppb |
| 2020-08-04 | 681804 | 39.3 ppb |
| 2020-08-04 | 681799 | 39.6 ppb |
| 2020-08-04 | 681795 | 42.1 ppb |
| 2020-08-04 | 681800 | 39.8 ppb |
| 2020-08-04 | 681802 | 37.9 ppb |
| 2020-08-04 | 681801 | 28.7 ppb |
| 2020-08-04 | 681803 | 29.2 ppb |
| 2020-08-04 | 681806 | 40.2 ppb |
| 2020-08-04 | 681797 | 37.1 ppb |
| 2020-11-10 | 706880 | 27.8 ppb |
| 2020-11-10 | 706882 | 23.1 ppb |
| 2020-11-10 | 706889 | 27.4 ppb |
| 2020-11-10 | 706879 | 26.3 ppb |
| 2020-11-10 | 706881 | 24.0 ppb |
| 2020-11-10 | 706883 | 22.9 ppb |
| 2020-11-10 | 706886 | 28.5 ppb |
| 2020-11-10 | 706888 | 26.1 ppb |
| 2020-11-10 | 706878 | 28.2 ppb |
| 2020-11-10 | 706885 | 23.0 ppb |
| 2020-11-10 | 706887 | 26.0 ppb |
| 2020-11-10 | 706884 | 29.2 ppb |
| 2021-02-02 | 719024 | 19.0 ppb |
| 2021-02-02 | 719020 | 13.7 ppb |
| 2021-02-02 | 719019 | 12.0 ppb |
| 2021-02-02 | 719023 | 19.5 ppb |
| 2021-02-02 | 719022 | 14.4 ppb |
| 2021-02-02 | 719025 | 19.3 ppb |
| 2021-02-02 | 719026 | 13.9 ppb |
| 2021-02-02 | 719018 | 12.8 ppb |
| 2021-02-02 | 719017 | 18.5 ppb |
| 2021-02-02 | 719016 | 20.8 ppb |
| 2021-02-02 | 719015 | 13.5 ppb |
| 2021-02-02 | 719021 | 14.7 ppb |
| 2021-05-04 | 733031 | 18.7 ppb |
| 2021-05-04 | 733032 | 21.6 ppb |
| 2021-05-04 | 733028 | 19.8 ppb |
| 2021-05-04 | 733034 | 20.4 ppb |
| 2021-05-04 | 733033 | 21.6 ppb |
| 2021-05-04 | 733026 | 21.7 ppb |
| 2021-05-04 | 733029 | 20.8 ppb |
| 2021-05-04 | 733030 | 19.3 ppb |
| 2021-05-04 | 733027 | 21.5 ppb |
| 2021-05-04 | 733035 | 18.4 ppb |
| 2021-05-04 | 733036 | 16.8 ppb |
| 2021-05-04 | 733037 | 15.0 ppb |
| 2021-08-04 | 753576 | 29.5 ppb |
| 2021-08-04 | 753575 | 26.5 ppb |
| 2021-08-04 | 753580 | 29.7 ppb |
| 2021-08-04 | 753577 | 29.2 ppb |
| 2021-08-04 | 753570 | 26.3 ppb |
| 2021-08-04 | 753571 | 27.3 ppb |
| 2021-08-04 | 753581 | 27.7 ppb |
| 2021-08-04 | 753572 | 25.1 ppb |
| 2021-08-04 | 753578 | 25.7 ppb |
| 2021-08-04 | 753579 | 27.4 ppb |
| 2021-08-04 | 753574 | 29.2 ppb |
| 2021-08-04 | 753573 | 23.3 ppb |
| 2021-11-03 | 770901 | 21.3 ppb |
| 2021-11-03 | 770897 | 19.5 ppb |
| 2021-11-03 | 770898 | 20.8 ppb |
| 2021-11-03 | 770900 | 19.3 ppb |
| 2021-11-03 | 770890 | 22.3 ppb |
| 2021-11-03 | 770892 | 26.1 ppb |
| 2021-11-03 | 770899 | 19.5 ppb |
| 2021-11-03 | 770891 | 24.5 ppb |
| 2021-11-03 | 770894 | 25.4 ppb |
| 2021-11-03 | 770896 | 23.9 ppb |
| 2021-11-03 | 770893 | 25.6 ppb |
| 2021-11-03 | 770895 | 24.3 ppb |
| 2022-02-23 | 782425 | 22.2 ppb |
| 2022-02-23 | 782422 | 12.8 ppb |
| 2022-02-23 | 782428 | 16.5 ppb |
| 2022-02-23 | 782429 | 17.0 ppb |
| 2022-02-23 | 782420 | 12.2 ppb |
| 2022-02-23 | 782427 | 15.9 ppb |
| 2022-02-23 | 782421 | 14.0 ppb |
| 2022-02-23 | 782419 | 10.9 ppb |
| 2022-02-23 | 782423 | 15.3 ppb |
| 2022-02-23 | 782426 | 16.7 ppb |
| 2022-02-23 | 782418 | 12.4 ppb |
| 2022-02-23 | 782424 | 15.4 ppb |
| 2022-04-26 | 793153 | 15.1 ppb |
| 2022-05-03 | 800306 | 19.5 ppb |
| 2022-05-03 | 800313 | 11.4 ppb |
| 2022-05-03 | 800314 | 22.5 ppb |
| 2022-05-03 | 800312 | 12.5 ppb |
| 2022-05-03 | 800305 | 21.5 ppb |
| 2022-05-03 | 800307 | 20.5 ppb |
| 2022-05-03 | 800308 | 22.6 ppb |
| 2022-05-03 | 800309 | 20.5 ppb |
| 2022-05-03 | 800303 | 22.9 ppb |
| 2022-05-03 | 800311 | 23.0 ppb |
| 2022-05-03 | 800304 | 23.7 ppb |
| 2022-05-03 | 800310 | 21.9 ppb |
| 2022-08-03 | 815800 | 46.7 ppb |
| 2022-08-03 | 815794 | 52.4 ppb |
| 2022-08-03 | 815795 | 36.8 ppb |
| 2022-08-03 | 815797 | 51.8 ppb |
| 2022-08-03 | 815803 | 40.9 ppb |
| 2022-08-03 | 815804 | 51.2 ppb |
| 2022-08-03 | 815802 | 48.2 ppb |
| 2022-08-03 | 815801 | 47.3 ppb |
| 2022-08-03 | 815799 | 48.7 ppb |
| 2022-08-03 | 815796 | 40.9 ppb |
| 2022-08-03 | 815793 | 50.2 ppb |
| 2022-08-03 | 815798 | 48.0 ppb |
| 2022-11-08 | 833764 | 19.1 ppb |
| 2022-11-08 | 833766 | 21.3 ppb |
| 2022-11-08 | 833762 | 19.0 ppb |
| 2022-11-08 | 833755 | 23.5 ppb |
| 2022-11-08 | 833757 | 21.5 ppb |
| 2022-11-08 | 833758 | 21.4 ppb |
| 2022-11-08 | 833759 | 26.1 ppb |
| 2022-11-08 | 833760 | 20.6 ppb |
| 2022-11-08 | 833763 | 23.0 ppb |
| 2022-11-08 | 833765 | 21.9 ppb |
| 2022-11-08 | 833761 | 19.5 ppb |
| 2022-11-08 | 833756 | 22.1 ppb |
| 2023-01-17 | 844825 | ND |
| 2023-02-07 | 847425 | 12.0 ppb |
| 2023-02-07 | 847423 | 15.1 ppb |
| 2023-02-07 | 847424 | 9.49 ppb |
| 2023-02-07 | 847415 | 13.0 ppb |
| 2023-02-07 | 847421 | 12.8 ppb |
| 2023-02-07 | 847420 | 9.99 ppb |
| 2023-02-07 | 847418 | 12.0 ppb |
| 2023-02-07 | 847422 | 13.1 ppb |
| 2023-02-07 | 847414 | 15.6 ppb |
| 2023-02-07 | 847419 | 20.2 ppb |
| 2023-02-07 | 847416 | 13.2 ppb |
| 2023-02-07 | 847417 | 13.9 ppb |
| 2023-05-02 | 858550 | 13.1 ppb |
| 2023-05-02 | 858543 | 26.1 ppb |
| 2023-05-02 | 858549 | 13.7 ppb |
| 2023-05-02 | 858548 | 13.7 ppb |
| 2023-05-02 | 858542 | 17.1 ppb |
| 2023-05-02 | 858540 | 25.8 ppb |
| 2023-05-02 | 858539 | 13.2 ppb |
| 2023-05-02 | 858547 | 13.5 ppb |
| 2023-05-02 | 858545 | 26.6 ppb |
| 2023-05-02 | 858541 | 26.0 ppb |
| 2023-05-02 | 858546 | 13.2 ppb |
| 2023-05-02 | 858544 | 25.9 ppb |
| 2023-06-08 | 855997 | 8.06 ppb |
| 2023-06-08 | 855996 | 14.1 ppb |
| 2023-06-12 | 856264 | 42.6 ppb |
| 2023-06-12 | 856263 | 61.3 ppb |
| 2023-08-08 | 879877 | 25.9 ppb |
| 2023-08-08 | 879874 | 28.5 ppb |
| 2023-08-08 | 879878 | 49.0 ppb |
| 2023-08-08 | 879879 | 46.4 ppb |
| 2023-08-08 | 879880 | 28.7 ppb |
| 2023-08-08 | 879885 | 29.9 ppb |
| 2023-08-08 | 879876 | 29.4 ppb |
| 2023-08-08 | 879882 | 27.7 ppb |
| 2023-08-08 | 879875 | 28.6 ppb |
| 2023-08-08 | 879884 | 27.4 ppb |
| 2023-08-08 | 879883 | 52.2 ppb |
| 2023-08-08 | 879881 | 47.6 ppb |
| 2023-11-07 | 891421 | 23.9 ppb |
| 2023-11-07 | 891419 | 23.6 ppb |
| 2023-11-07 | 891420 | 24.8 ppb |
| 2023-11-07 | 891417 | 27.5 ppb |
| 2023-11-07 | 891424 | 33.5 ppb |
| 2023-11-07 | 891425 | 24.6 ppb |
| 2023-11-07 | 891423 | 23.6 ppb |
| 2023-11-07 | 891418 | 23.2 ppb |
| 2023-11-07 | 891427 | 26.5 ppb |
| 2023-11-07 | 891422 | 24.6 ppb |
| 2023-11-07 | 891428 | 23.2 ppb |
| 2023-11-07 | 891426 | 23.6 ppb |