Arsenic
CTWC - Shoreline Region-Guilford System
Arsenic is a potent carcinogen and common contaminant in drinking water. Arsenic causes thousands of cases of cancer each year in the U.S. Click here to read more about arsenic.
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 | ND | 2 | 0 | ND |
| 2019 | ND | 4 | 0 | ND |
| 2020 | ND | 6 | 0 | ND |
| 2021 | ND | 2 | 0 | ND |
| 2022 | ND | 3 | 0 | ND |
| 2023 | ND | 8 | 0 | ND |
ppb = parts per billion
State, National, and Health Guidelines for Drinking Water
EWG Health Guideline: 0.004 ppb
The EWG Health Guideline of 0.004 ppb for arsenic was defined by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer.
EPA Maximum Contaminant
Level (MCL): 10 ppb
The legal limit for arsenic, established in 2001, was based on costs for arsenic removal, as calculated at the time that the standard was set. This limit does not fully protect against the risk of cancer due to arsenic exposure.
ppb = parts per billion
All test results
| Date | Lab ID | Result |
|---|---|---|
| 2018-03-30 | CA11463IOCR | ND |
| 2018-03-30 | CA11466IOC1 | ND |
| 2019-01-30 | IOC1 200520057 | ND |
| 2019-02-27 | IOCR 200523002 | ND |
| 2019-06-24 | IOC1 200537625 | ND |
| 2019-07-10 | IOC1 200539998 | ND |
| 2020-01-20 | IOC1 200563509 | ND |
| 2020-01-21 | IOC1 200563516 | ND |
| 2020-01-28 | IOC1 200564212 | ND |
| 2020-02-11 | IOC1 200565799 | ND |
| 2020-02-11 | IOCR 200565797 | ND |
| 2020-02-25 | IOC1 200567275 | ND |
| 2021-09-30 | I300072093 300072096 | ND |
| 2021-09-30 | R300072099 300072102 | ND |
| 2022-08-15 | CM05636 | ND |
| 2022-08-29 | CM17830 | ND |
| 2022-08-29 | CM17831 | ND |
| 2023-02-13 | CN41858 | ND |
| 2023-02-13 | CN41859 | ND |
| 2023-09-12 | CO95874 | ND |
| 2023-09-12 | CO95875 | ND |
| 2023-09-12 | CO95877 | ND |
| 2023-10-12 | CP23629 | ND |
| 2023-11-28 | CP55320 | ND |
| 2023-11-29 | CP56434 | ND |