Chloroform
Stockton Water Department
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 |
|---|---|---|---|---|
| 2014 | ND | 4 | 0 | ND |
| 2015 | 0.168 ppb | 4 | 4 | 0.0800 ppb - 0.240 ppb |
| 2016 | 0.400 ppb | 2 | 2 | 0.300 ppb - 0.500 ppb |
| 2017 | 0.300 ppb | 2 | 2 | 0.200 ppb - 0.400 ppb |
| 2018 | 0.450 ppb | 4 | 4 | 0.200 ppb - 1.000 ppb |
| 2019 | 0.500 ppb | 2 | 2 | 0.300 ppb - 0.700 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 |
|---|---|---|
| 2014-07-09 | L5104502-1 | ND |
| 2014-07-09 | L5104502-2 | ND |
| 2014-09-30 | L2618479-2 | ND |
| 2014-09-30 | L2618479-1 | ND |
| 2015-09-25 | L5639837-1 | 0.150 ppb |
| 2015-09-25 | L5639790-1 | 0.0800 ppb |
| 2015-09-29 | L5808596-1 | 0.240 ppb |
| 2015-09-29 | L5808596-2 | 0.200 ppb |
| 2016-11-04 | L6440902-1 | 0.500 ppb |
| 2016-11-04 | L6440902-2 | 0.300 ppb |
| 2017-09-07 | L6944960-2 | 0.400 ppb |
| 2017-09-07 | L6944960-1 | 0.200 ppb |
| 2018-07-05 | L7041014-1 | 0.300 ppb |
| 2018-07-05 | L7041054-1 | 0.200 ppb |
| 2018-09-07 | L7062808-2 | 1.000 ppb |
| 2018-09-07 | L7062808-1 | 0.300 ppb |
| 2019-09-10 | L7153740-2 | 0.700 ppb |
| 2019-09-10 | L7153740-1 | 0.300 ppb |