Selenium
CTWC - Shoreline Region-Guilford System
Selenium is an essential element in diets. But too much selenium can decrease thyroid hormone production and cause hair loss, skin lesions and brittle fingernails.
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: 30 ppb
The EWG Health Guideline of 30 ppb for selenium 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 hair loss and nail damage.
EPA Maximum Contaminant
Level (MCL): 50 ppb
The legal limit for selenium, established in 1991, was based on human epidemiological studies of populations exposed to naturally occurring selenium in drinking water. This limit does not include any additional consideration of children’s health.
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 |