Chloroform
California Water Service (CWS) - King City
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 |
|---|---|---|---|---|
| 2013 | N/A | 0 | 0 | N/A |
| 2014 | 0.488 ppb | 18 | 8 | ND - 2.50 ppb |
| 2015 | 0.504 ppb | 17 | 9 | ND - 1.80 ppb |
| 2016 | 0.393 ppb | 20 | 10 | ND - 1.55 ppb |
| 2017 | 0.494 ppb | 17 | 9 | ND - 1.82 ppb |
| 2018 | 0.764 ppb | 17 | 13 | ND - 2.08 ppb |
| 2019 | 0.133 ppb | 11 | 2 | ND - 0.820 ppb |
ppb = parts per billion
State and national drinking water standards and health guidelines
EWG Health Guideline 0.4 ppb
The EWG Health Guideline of 0.4 ppb for chloroform was proposed in 2018 by the California Office of Environmental Health Hazard Assessment as a one-in-a-million lifetime risk of cancer. Values greater than one-in-a-million cancer risk level can result in increased cancer cases above one in a million people.
ppb = parts per billion
All test results
| Date | Lab ID | Result |
|---|---|---|
| 2014-02-11 | 5701-801-1350 | 0.700 ppb |
| 2014-02-11 | 5701-803-1329 | 0.580 ppb |
| 2014-02-11 | 5701-802-1315 | ND |
| 2014-02-13 | 5701-804-1413 | ND |
| 2014-05-14 | 5701-804-0822 | ND |
| 2014-05-14 | 5701-803-1132 | 0.600 ppb |
| 2014-05-14 | 5701-801-1118 | 1.54 ppb |
| 2014-05-14 | 5701-802-1230 | ND |
| 2014-08-12 | 5701-804-1145 | ND |
| 2014-08-12 | 5701-803-1210 | 0.710 ppb |
| 2014-08-12 | 5701-802-1055 | ND |
| 2014-08-12 | 5701-801-1135 | 2.50 ppb |
| 2014-08-26 | 5701-014-1220 | ND |
| 2014-08-26 | 5701-015-1409 | ND |
| 2014-11-12 | 5701-804-1100 | ND |
| 2014-11-12 | 5701-801-1040 | 1.47 ppb |
| 2014-11-12 | 5701-802-0920 | ND |
| 2014-11-12 | 5701-803-0955 | 0.680 ppb |
| 2015-02-09 | 5701-801-0712 | 1.29 ppb |
| 2015-02-09 | 5701-802-0712 | 0.510 ppb |
| 2015-02-09 | 5701-804-0712 | 0.790 ppb |
| 2015-02-09 | 5701-803-0712 | 0.650 ppb |
| 2015-05-12 | 5701-801-0803 | 1.12 ppb |
| 2015-05-12 | 5701-802-0803 | ND |
| 2015-05-12 | 5701-804-0803 | ND |
| 2015-05-12 | 5701-803-0803 | 0.660 ppb |
| 2015-06-11 | 5701-008-1130 | ND |
| 2015-08-11 | 5701-802-0653 | ND |
| 2015-08-11 | 5701-801-0653 | 1.80 ppb |
| 2015-08-11 | 5701-803-0653 | ND |
| 2015-08-11 | 5701-804-0653 | ND |
| 2015-11-09 | 5701-804-0859 | ND |
| 2015-11-09 | 5701-803-0859 | 0.610 ppb |
| 2015-11-09 | 5701-801-0859 | 1.14 ppb |
| 2015-11-09 | 5701-802-0859 | ND |
| 2016-02-09 | 5701-802-0926 | ND |
| 2016-02-09 | 5701-803-0926 | 0.590 ppb |
| 2016-02-09 | 5701-801-0926 | 1.28 ppb |
| 2016-02-09 | 5701-804-0926 | 0.650 ppb |
| 2016-03-16 | 5701-006-1400 | ND |
| 2016-03-16 | 5701-012-1100 | ND |
| 2016-05-09 | 5701-802-0746 | ND |
| 2016-05-09 | 5701-803-0746 | 0.510 ppb |
| 2016-05-09 | 5701-801-0746 | 0.930 ppb |
| 2016-05-09 | 5701-804-0746 | ND |
| 2016-06-20 | 5701-014-1317 | ND |
| 2016-08-08 | 5701-804-0722 | ND |
| 2016-08-08 | 5701-802-0722 | ND |
| 2016-08-08 | 5701-803-0722 | 0.600 ppb |
| 2016-08-08 | 5701-801-0722 | 1.55 ppb |
| 2016-09-19 | 5701-007-1054 | ND |
| 2016-11-16 | 5701-804-0745 | ND |
| 2016-11-16 | 5701-802-0745 | 0.600 ppb |
| 2016-11-16 | 5701-803-0745 | 0.560 ppb |
| 2016-11-16 | 5701-801-0745 | 0.590 ppb |
| 2017-02-14 | 5810-803-1311 | ND |
| 2017-02-14 | 5810-804-1324 | ND |
| 2017-02-14 | 5810-801-1149 | 1.000 ppb |
| 2017-02-14 | 5810-802-1417 | ND |
| 2017-05-08 | 5701-803-0844 | 0.500 ppb |
| 2017-05-08 | 5701-801-0844 | 1.06 ppb |
| 2017-05-08 | 5701-804-0844 | 0.520 ppb |
| 2017-05-08 | 5701-802-0844 | ND |
| 2017-06-21 | 5701-015-1444 | ND |
| 2017-08-14 | 5810-803-1639 | ND |
| 2017-08-14 | 5810-801-1700 | 1.40 ppb |
| 2017-08-14 | 5810-804-1724 | ND |
| 2017-08-14 | 5810-802-1753 | ND |
| 2017-11-13 | 5701-803-0835 | 0.830 ppb |
| 2017-11-13 | 5701-804-0835 | 0.600 ppb |
| 2017-11-13 | 5701-801-0835 | 1.82 ppb |
| 2017-11-13 | 5701-802-0835 | 0.660 ppb |
| 2018-02-12 | 5810-804-0945 | ND |
| 2018-02-12 | 5810-802-1133 | ND |
| 2018-02-12 | 5810-801-1119 | 1.30 ppb |
| 2018-02-12 | 5810-803-0920 | ND |
| 2018-05-14 | 5701-804-0841 | 0.830 ppb |
| 2018-05-14 | 5701-801-0840 | 2.08 ppb |
| 2018-05-14 | 5701-802-0840 | 0.610 ppb |
| 2018-05-14 | 5701-803-0841 | 0.660 ppb |
| 2018-06-20 | 5701-008-1020 | ND |
| 2018-08-14 | 5701-802-1022 | 0.680 ppb |
| 2018-08-14 | 5701-803-1022 | 0.710 ppb |
| 2018-08-14 | 5701-801-1022 | 1.75 ppb |
| 2018-08-14 | 5701-804-1022 | 0.790 ppb |
| 2018-11-14 | 5701-803-0920 | 0.950 ppb |
| 2018-11-14 | 5701-801-0920 | 1.46 ppb |
| 2018-11-14 | 5701-804-0920 | 0.660 ppb |
| 2018-11-14 | 5701-802-0920 | 0.510 ppb |
| 2019-02-11 | 5810-803-1017 | ND |
| 2019-02-11 | 5810-804-1031 | ND |
| 2019-02-11 | 5810-801-1045 | ND |
| 2019-02-11 | 5810-802-1059 | ND |
| 2019-03-20 | 5810-012-1130 | ND |
| 2019-04-17 | 5701-006-1155 | ND |
| 2019-06-17 | 5701-014-1016 | ND |
| 2019-08-20 | 5701-801-1142 | 0.820 ppb |
| 2019-08-20 | 5701-803-1418 | 0.640 ppb |
| 2019-09-17 | 5701-007-1131 | ND |
| 2019-10-15 | 5701-006-1500 | ND |