Chloroform
Bcwsa Main Lower South
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 | 33.7 ppb | 32 | 32 | 4.50 ppb - 177.0 ppb |
| 2019 | 23.5 ppb | 32 | 32 | 7.30 ppb - 66.0 ppb |
| 2020 | 39.2 ppb | 65 | 65 | 8.00 ppb - 213.0 ppb |
| 2021 | 34.9 ppb | 96 | 96 | 7.60 ppb - 256.0 ppb |
| 2022 | 26.3 ppb | 97 | 97 | 6.10 ppb - 91.6 ppb |
| 2023 | 28.5 ppb | 96 | 96 | 7.20 ppb - 83.8 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 |
|---|---|---|
| 2018-02-16 | 8022971-01 | 6.60 ppb |
| 2018-02-16 | 8022811-02 | 4.50 ppb |
| 2018-02-16 | 8022811-03 | 6.00 ppb |
| 2018-02-16 | 8022811-04 | 12.5 ppb |
| 2018-02-16 | 8022811-05 | 11.9 ppb |
| 2018-02-16 | 8022811-06 | 21.9 ppb |
| 2018-02-16 | 8022811-07 | 15.0 ppb |
| 2018-02-16 | 8022811-08 | 21.0 ppb |
| 2018-05-17 | 8053554-01 | 12.8 ppb |
| 2018-05-17 | 8053554-02 | 19.1 ppb |
| 2018-05-17 | 8053554-03 | 13.2 ppb |
| 2018-05-17 | 8053554-04 | 18.9 ppb |
| 2018-05-17 | 8053554-05 | 12.9 ppb |
| 2018-05-17 | 8053554-06 | 33.9 ppb |
| 2018-05-17 | 8053554-07 | 21.8 ppb |
| 2018-05-17 | 8053554-08 | 33.1 ppb |
| 2018-08-13 | 8082937-01 | 23.2 ppb |
| 2018-08-13 | 8082937-02 | 38.6 ppb |
| 2018-08-13 | 8082937-03 | 40.8 ppb |
| 2018-08-13 | 8082937-04 | 30.6 ppb |
| 2018-08-13 | 8082937-05RE | 177.0 ppb |
| 2018-08-13 | 8082937-06RE | 149.0 ppb |
| 2018-08-13 | 8082937-07 | 50.1 ppb |
| 2018-08-13 | 8082937-08 | 63.7 ppb |
| 2018-11-12 | 8032032-01RE | 13.5 ppb |
| 2018-11-14 | 8032034-01 | 21.3 ppb |
| 2018-11-14 | 8032035-01 | 29.8 ppb |
| 2018-11-14 | 8032036-01 | 40.4 ppb |
| 2018-11-14 | 8032037-01 | 40.8 ppb |
| 2018-11-14 | 8032038-01 | 44.5 ppb |
| 2018-11-14 | 8032039-01 | 37.5 ppb |
| 2018-11-15 | 8034181-01 | 12.0 ppb |
| 2019-02-13 | 9004485-01 | 10.2 ppb |
| 2019-02-13 | 9004486-01 | 16.5 ppb |
| 2019-02-13 | 9004487-01 | 11.2 ppb |
| 2019-02-14 | 9004483-01 | 7.30 ppb |
| 2019-02-14 | 9004484-01 | 17.7 ppb |
| 2019-02-14 | 9004488-01 | 17.4 ppb |
| 2019-02-14 | 9004489-01 | 13.0 ppb |
| 2019-02-15 | 9004482-01 | 8.00 ppb |
| 2019-05-13 | 9015730-01 | 9.30 ppb |
| 2019-05-13 | 9015731-01 | 9.50 ppb |
| 2019-05-13 | 9015732-01 | 14.2 ppb |
| 2019-05-13 | 9015733-01 | 14.0 ppb |
| 2019-05-13 | 9015734-01 | 36.8 ppb |
| 2019-05-13 | 9015735-01 | 32.8 ppb |
| 2019-05-13 | 9015736-01 | 27.8 ppb |
| 2019-05-13 | 9015737-01 | 26.2 ppb |
| 2019-08-12 | 9028010-01 | 15.7 ppb |
| 2019-08-12 | 9028011-01 | 14.0 ppb |
| 2019-08-12 | 9028012-01 | 25.3 ppb |
| 2019-08-12 | 9028013-01 | 18.0 ppb |
| 2019-08-12 | 9028014-01RE | 66.0 ppb |
| 2019-08-12 | 9028015-01 | 58.6 ppb |
| 2019-08-12 | 9028016-01 | 34.3 ppb |
| 2019-08-12 | 9028017-01 | 33.9 ppb |
| 2019-11-11 | 9112242-01 | 8.30 ppb |
| 2019-11-11 | 9112242-02 | 8.10 ppb |
| 2019-11-11 | 9112242-03 | 21.0 ppb |
| 2019-11-11 | 9112242-04 | 18.9 ppb |
| 2019-11-11 | 9112242-05 | 58.9 ppb |
| 2019-11-11 | 9112242-06 | 44.4 ppb |
| 2019-11-11 | 9112242-07 | 38.5 ppb |
| 2019-11-11 | 9112242-08 | 15.0 ppb |
| 2020-02-12 | 8.00 ppb | |
| 2020-02-12 | 8.20 ppb | |
| 2020-02-12 | 18.4 ppb | |
| 2020-02-12 | 11.9 ppb | |
| 2020-02-12 | 22.6 ppb | |
| 2020-02-12 | 19.4 ppb | |
| 2020-02-12 | 19.0 ppb | |
| 2020-02-12 | 19.0 ppb | |
| 2020-05-13 | 9.90 ppb | |
| 2020-05-13 | 9.70 ppb | |
| 2020-05-13 | 32.9 ppb | |
| 2020-05-13 | 22.3 ppb | |
| 2020-05-13 | 31.5 ppb | |
| 2020-05-13 | 24.9 ppb | |
| 2020-05-13 | 37.5 ppb | |
| 2020-05-13 | 28.9 ppb | |
| 2020-08-14 | 23.7 ppb | |
| 2020-08-14 | 21.2 ppb | |
| 2020-08-14 | 46.3 ppb | |
| 2020-08-14 | 27.2 ppb | |
| 2020-08-14 | 129.0 ppb | |
| 2020-08-14 | 183.0 ppb | |
| 2020-08-14 | 135.0 ppb | |
| 2020-08-14 | 213.0 ppb | |
| 2020-09-04 | 68.5 ppb | |
| 2020-09-08 | 65.8 ppb | |
| 2020-09-11 | 89.5 ppb | |
| 2020-09-15 | 69.1 ppb | |
| 2020-09-15 | 41.7 ppb | |
| 2020-09-18 | 16.8 ppb | |
| 2020-09-18 | 18.3 ppb | |
| 2020-09-18 | 27.0 ppb | |
| 2020-09-18 | 25.2 ppb | |
| 2020-09-18 | 70.0 ppb | |
| 2020-09-18 | 69.7 ppb | |
| 2020-09-18 | 37.3 ppb | |
| 2020-09-18 | 75.1 ppb | |
| 2020-09-22 | 44.6 ppb | |
| 2020-09-22 | 51.4 ppb | |
| 2020-09-29 | 40.7 ppb | |
| 2020-09-29 | 37.4 ppb | |
| 2020-10-14 | 9.90 ppb | |
| 2020-10-14 | 9.80 ppb | |
| 2020-10-14 | 11.1 ppb | |
| 2020-10-14 | 14.5 ppb | |
| 2020-10-14 | 47.2 ppb | |
| 2020-10-14 | 37.4 ppb | |
| 2020-10-14 | 46.8 ppb | |
| 2020-10-14 | 32.7 ppb | |
| 2020-11-13 | 16.8 ppb | |
| 2020-11-13 | 18.8 ppb | |
| 2020-11-13 | 18.7 ppb | |
| 2020-11-13 | 20.5 ppb | |
| 2020-11-13 | 42.5 ppb | |
| 2020-11-13 | 38.0 ppb | |
| 2020-11-13 | 25.0 ppb | |
| 2020-11-13 | 40.6 ppb | |
| 2020-12-11 | 9.50 ppb | |
| 2020-12-11 | 9.10 ppb | |
| 2020-12-11 | 27.2 ppb | |
| 2020-12-11 | 12.6 ppb | |
| 2020-12-11 | 41.4 ppb | |
| 2020-12-11 | 26.9 ppb | |
| 2020-12-11 | 23.8 ppb | |
| 2020-12-11 | 18.5 ppb | |
| 2021-01-15 | 8.70 ppb | |
| 2021-01-15 | 10.00 ppb | |
| 2021-01-15 | 25.8 ppb | |
| 2021-01-15 | 12.7 ppb | |
| 2021-01-15 | 22.8 ppb | |
| 2021-01-15 | 15.0 ppb | |
| 2021-01-15 | 24.8 ppb | |
| 2021-01-15 | 18.5 ppb | |
| 2021-02-12 | 8.20 ppb | |
| 2021-02-12 | 8.50 ppb | |
| 2021-02-12 | 14.3 ppb | |
| 2021-02-12 | 10.00 ppb | |
| 2021-02-12 | 21.4 ppb | |
| 2021-02-12 | 15.4 ppb | |
| 2021-02-12 | 18.8 ppb | |
| 2021-02-12 | 18.6 ppb | |
| 2021-03-11 | 7.60 ppb | |
| 2021-03-11 | 8.20 ppb | |
| 2021-03-11 | 12.5 ppb | |
| 2021-03-11 | 8.70 ppb | |
| 2021-03-11 | 18.7 ppb | |
| 2021-03-11 | 21.1 ppb | |
| 2021-03-11 | 18.6 ppb | |
| 2021-03-11 | 23.8 ppb | |
| 2021-04-12 | 17.9 ppb | |
| 2021-04-12 | 15.0 ppb | |
| 2021-04-12 | 15.9 ppb | |
| 2021-04-12 | 29.8 ppb | |
| 2021-04-12 | 27.2 ppb | |
| 2021-04-12 | 28.3 ppb | |
| 2021-04-12 | 31.4 ppb | |
| 2021-04-16 | 8.70 ppb | |
| 2021-05-12 | 12.1 ppb | |
| 2021-05-12 | 12.7 ppb | |
| 2021-05-12 | 19.3 ppb | |
| 2021-05-12 | 16.5 ppb | |
| 2021-05-12 | 59.0 ppb | |
| 2021-05-12 | 45.3 ppb | |
| 2021-05-12 | 27.8 ppb | |
| 2021-05-12 | 38.2 ppb | |
| 2021-06-11 | 12.3 ppb | |
| 2021-06-11 | 13.4 ppb | |
| 2021-06-11 | 30.0 ppb | |
| 2021-06-11 | 19.2 ppb | |
| 2021-06-11 | 63.9 ppb | |
| 2021-06-11 | 65.3 ppb | |
| 2021-06-11 | 27.9 ppb | |
| 2021-06-11 | 62.1 ppb | |
| 2021-07-28 | 25.0 ppb | |
| 2021-07-28 | 27.5 ppb | |
| 2021-07-28 | 28.8 ppb | |
| 2021-07-28 | 31.8 ppb | |
| 2021-07-28 | 99.4 ppb | |
| 2021-07-28 | 94.8 ppb | |
| 2021-07-28 | 50.4 ppb | |
| 2021-07-28 | 94.5 ppb | |
| 2021-08-13 | 20.4 ppb | |
| 2021-08-13 | 21.6 ppb | |
| 2021-08-13 | 38.7 ppb | |
| 2021-08-13 | 25.7 ppb | |
| 2021-08-13 | 73.1 ppb | |
| 2021-08-13 | 73.7 ppb | |
| 2021-08-13 | 46.7 ppb | |
| 2021-08-13 | 90.4 ppb | |
| 2021-09-10 | 20.3 ppb | |
| 2021-09-10 | 33.2 ppb | |
| 2021-09-10 | 40.2 ppb | |
| 2021-09-10 | 25.5 ppb | |
| 2021-09-10 | 49.4 ppb | |
| 2021-09-10 | 256.0 ppb | |
| 2021-09-10 | 38.1 ppb | |
| 2021-09-10 | 79.1 ppb | |
| 2021-10-15 | 20.1 ppb | |
| 2021-10-15 | 35.2 ppb | |
| 2021-10-15 | 30.8 ppb | |
| 2021-10-15 | 37.9 ppb | |
| 2021-10-15 | 38.6 ppb | |
| 2021-10-15 | 74.2 ppb | |
| 2021-10-15 | 58.6 ppb | |
| 2021-10-15 | 78.4 ppb | |
| 2021-11-12 | 17.2 ppb | |
| 2021-11-12 | 18.8 ppb | |
| 2021-11-12 | 60.1 ppb | |
| 2021-11-12 | 22.1 ppb | |
| 2021-11-12 | 39.7 ppb | |
| 2021-11-12 | 57.9 ppb | |
| 2021-11-12 | 48.6 ppb | |
| 2021-11-12 | 62.1 ppb | |
| 2021-12-10 | 8.10 ppb | |
| 2021-12-10 | 9.00 ppb | |
| 2021-12-10 | 45.5 ppb | |
| 2021-12-10 | 14.0 ppb | |
| 2021-12-10 | 24.2 ppb | |
| 2021-12-10 | 27.1 ppb | |
| 2021-12-10 | 34.1 ppb | |
| 2021-12-10 | 29.3 ppb | |
| 2022-01-14 | 6.10 ppb | |
| 2022-01-14 | 6.30 ppb | |
| 2022-01-14 | 6.90 ppb | |
| 2022-01-14 | 10.4 ppb | |
| 2022-01-14 | 22.3 ppb | |
| 2022-01-14 | 26.4 ppb | |
| 2022-01-14 | 27.2 ppb | |
| 2022-01-14 | 14.1 ppb | |
| 2022-02-11 | 6.60 ppb | |
| 2022-02-11 | 6.50 ppb | |
| 2022-02-11 | 15.6 ppb | |
| 2022-02-11 | 10.7 ppb | |
| 2022-02-11 | 22.8 ppb | |
| 2022-02-11 | 19.0 ppb | |
| 2022-02-11 | 13.5 ppb | |
| 2022-02-11 | 20.6 ppb | |
| 2022-03-11 | 8.00 ppb | |
| 2022-03-11 | 9.50 ppb | |
| 2022-03-11 | 24.3 ppb | |
| 2022-03-11 | 12.1 ppb | |
| 2022-03-11 | 20.3 ppb | |
| 2022-03-11 | 17.8 ppb | |
| 2022-03-11 | 15.3 ppb | |
| 2022-03-11 | 19.1 ppb | |
| 2022-04-15 | 12.0 ppb | |
| 2022-04-15 | 12.3 ppb | |
| 2022-04-15 | 32.8 ppb | |
| 2022-04-15 | 16.6 ppb | |
| 2022-04-15 | 21.9 ppb | |
| 2022-04-15 | 20.1 ppb | |
| 2022-04-15 | 22.6 ppb | |
| 2022-04-15 | 25.8 ppb | |
| 2022-05-13 | 13.3 ppb | |
| 2022-05-13 | 14.3 ppb | |
| 2022-05-13 | 31.9 ppb | |
| 2022-05-13 | 18.0 ppb | |
| 2022-05-13 | 25.8 ppb | |
| 2022-05-13 | 32.0 ppb | |
| 2022-05-13 | 31.8 ppb | |
| 2022-05-13 | 36.7 ppb | |
| 2022-06-10 | 21.1 ppb | |
| 2022-06-10 | 33.2 ppb | |
| 2022-06-10 | 30.2 ppb | |
| 2022-06-10 | 29.0 ppb | |
| 2022-06-10 | 38.3 ppb | |
| 2022-06-10 | 62.7 ppb | |
| 2022-06-10 | 58.9 ppb | |
| 2022-06-10 | 66.9 ppb | |
| 2022-07-15 | 21.8 ppb | |
| 2022-07-15 | 28.5 ppb | |
| 2022-07-15 | 26.0 ppb | |
| 2022-07-15 | 26.8 ppb | |
| 2022-07-15 | 38.0 ppb | |
| 2022-07-15 | 44.5 ppb | |
| 2022-07-15 | 33.7 ppb | |
| 2022-07-15 | 46.0 ppb | |
| 2022-08-12 | 20.1 ppb | |
| 2022-08-12 | 38.1 ppb | |
| 2022-08-12 | 28.4 ppb | |
| 2022-08-12 | 30.4 ppb | |
| 2022-08-12 | 50.3 ppb | |
| 2022-08-12 | 47.3 ppb | |
| 2022-08-12 | 58.4 ppb | |
| 2022-08-12 | 46.7 ppb | |
| 2022-09-16 | 15.7 ppb | |
| 2022-09-16 | 16.1 ppb | |
| 2022-09-16 | 17.0 ppb | |
| 2022-09-16 | 19.8 ppb | |
| 2022-09-16 | 44.0 ppb | |
| 2022-09-16 | 91.6 ppb | |
| 2022-09-16 | 39.0 ppb | |
| 2022-09-16 | 37.7 ppb | |
| 2022-10-14 | 15.8 ppb | |
| 2022-10-14 | 8.50 ppb | |
| 2022-10-14 | 18.8 ppb | |
| 2022-10-14 | 18.9 ppb | |
| 2022-10-14 | 38.8 ppb | |
| 2022-10-14 | 45.6 ppb | |
| 2022-10-14 | 24.8 ppb | |
| 2022-10-31 | 51.8 ppb | |
| 2022-10-31 | 51.8 ppb | |
| 2022-11-11 | 10.4 ppb | |
| 2022-11-11 | 10.2 ppb | |
| 2022-11-11 | 28.4 ppb | |
| 2022-11-11 | 14.2 ppb | |
| 2022-11-11 | 26.3 ppb | |
| 2022-11-11 | 35.2 ppb | |
| 2022-11-11 | 29.3 ppb | |
| 2022-11-11 | 42.2 ppb | |
| 2022-12-16 | 10.3 ppb | |
| 2022-12-16 | 17.1 ppb | |
| 2022-12-16 | 21.3 ppb | |
| 2022-12-16 | 10.00 ppb | |
| 2022-12-16 | 16.6 ppb | |
| 2022-12-16 | 23.2 ppb | |
| 2022-12-16 | 23.0 ppb | |
| 2022-12-16 | 22.3 ppb | |
| 2023-01-13 | 7.20 ppb | |
| 2023-01-13 | 9.40 ppb | |
| 2023-01-13 | 18.9 ppb | |
| 2023-01-13 | 17.6 ppb | |
| 2023-01-13 | 17.7 ppb | |
| 2023-01-13 | 19.9 ppb | |
| 2023-01-13 | 22.7 ppb | |
| 2023-01-13 | 20.7 ppb | |
| 2023-02-10 | 8.60 ppb | |
| 2023-02-10 | 9.50 ppb | |
| 2023-02-10 | 16.4 ppb | |
| 2023-02-10 | 17.6 ppb | |
| 2023-02-10 | 20.8 ppb | |
| 2023-02-10 | 24.0 ppb | |
| 2023-02-10 | 27.4 ppb | |
| 2023-02-10 | 18.0 ppb | |
| 2023-03-10 | 8.30 ppb | |
| 2023-03-10 | 15.5 ppb | |
| 2023-03-10 | 12.6 ppb | |
| 2023-03-10 | 14.4 ppb | |
| 2023-03-10 | 19.0 ppb | |
| 2023-03-10 | 25.9 ppb | |
| 2023-03-10 | 24.6 ppb | |
| 2023-03-10 | 22.9 ppb | |
| 2023-04-14 | 16.8 ppb | |
| 2023-04-14 | 19.9 ppb | |
| 2023-04-14 | 20.3 ppb | |
| 2023-04-14 | 20.8 ppb | |
| 2023-04-14 | 21.2 ppb | |
| 2023-04-14 | 18.7 ppb | |
| 2023-04-14 | 30.8 ppb | |
| 2023-04-14 | 21.5 ppb | |
| 2023-05-12 | 12.7 ppb | |
| 2023-05-12 | 12.9 ppb | |
| 2023-05-12 | 21.0 ppb | |
| 2023-05-12 | 20.9 ppb | |
| 2023-05-12 | 27.0 ppb | |
| 2023-05-12 | 24.1 ppb | |
| 2023-05-16 | 17.9 ppb | |
| 2023-05-16 | 24.8 ppb | |
| 2023-06-16 | 12.8 ppb | |
| 2023-06-16 | 27.3 ppb | |
| 2023-06-16 | 20.6 ppb | |
| 2023-06-16 | 25.1 ppb | |
| 2023-06-16 | 32.9 ppb | |
| 2023-06-16 | 32.4 ppb | |
| 2023-06-16 | 36.6 ppb | |
| 2023-06-16 | 34.1 ppb | |
| 2023-07-14 | 23.5 ppb | |
| 2023-07-14 | 31.1 ppb | |
| 2023-07-14 | 36.7 ppb | |
| 2023-07-14 | 32.0 ppb | |
| 2023-07-14 | 51.2 ppb | |
| 2023-07-14 | 69.1 ppb | |
| 2023-07-14 | 67.4 ppb | |
| 2023-07-14 | 83.8 ppb | |
| 2023-08-16 | 19.8 ppb | |
| 2023-08-16 | 20.7 ppb | |
| 2023-08-16 | 29.5 ppb | |
| 2023-08-16 | 24.8 ppb | |
| 2023-08-16 | 53.8 ppb | |
| 2023-08-16 | 59.8 ppb | |
| 2023-08-16 | 44.4 ppb | |
| 2023-08-16 | 66.6 ppb | |
| 2023-09-15 | 21.7 ppb | |
| 2023-09-15 | 38.0 ppb | |
| 2023-09-15 | 23.2 ppb | |
| 2023-09-15 | 39.7 ppb | |
| 2023-09-15 | 52.7 ppb | |
| 2023-09-15 | 61.8 ppb | |
| 2023-09-15 | 44.6 ppb | |
| 2023-09-15 | 73.5 ppb | |
| 2023-10-16 | 18.5 ppb | |
| 2023-10-16 | 26.2 ppb | |
| 2023-10-16 | 44.7 ppb | |
| 2023-10-16 | 25.4 ppb | |
| 2023-10-16 | 40.8 ppb | |
| 2023-10-16 | 47.8 ppb | |
| 2023-10-16 | 45.4 ppb | |
| 2023-10-16 | 56.7 ppb | |
| 2023-11-13 | 9.00 ppb | |
| 2023-11-13 | 18.9 ppb | |
| 2023-11-13 | 30.6 ppb | |
| 2023-11-13 | 15.0 ppb | |
| 2023-11-13 | 33.1 ppb | |
| 2023-11-13 | 36.8 ppb | |
| 2023-11-13 | 28.2 ppb | |
| 2023-11-13 | 37.3 ppb | |
| 2023-12-12 | 12.2 ppb | |
| 2023-12-12 | 14.4 ppb | |
| 2023-12-12 | 28.1 ppb | |
| 2023-12-12 | 16.0 ppb | |
| 2023-12-12 | 32.3 ppb | |
| 2023-12-12 | 23.3 ppb | |
| 2023-12-12 | 26.0 ppb | |
| 2023-12-12 | 23.0 ppb |