Selenium
California Water Service - South San Francisco
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 |
|---|---|---|---|---|
| 2013 | N/A | 0 | 0 | N/A |
| 2014 | 0.590 ppb | 14 | 10 | ND - 2.23 ppb |
| 2015 | 0.331 ppb | 18 | 10 | ND - 1.51 ppb |
| 2016 | ND | 30 | 0 | ND |
| 2017 | ND | 4 | 0 | ND |
| 2018 | N/A | 0 | 0 | N/A |
| 2019 | N/A | 0 | 0 | N/A |
ppb = parts per billion
State and national drinking water standards and health guidelines
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 |
|---|---|---|
| 2014-05-05 | 5701-009-1102 | 0.963 ppb |
| 2014-05-05 | 5701-014-1049 | 1.35 ppb |
| 2014-05-05 | 5701-013-1051 | 1.36 ppb |
| 2014-06-04 | 5701-014-0923 | 0.0260 ppb |
| 2014-06-04 | 5701-010-0841 | 0.0320 ppb |
| 2014-08-18 | 5701-009-1118 | 2.23 ppb |
| 2014-08-18 | 5701-010-1145 | 0.488 ppb |
| 2014-08-18 | 5701-013-1121 | 1.25 ppb |
| 2014-09-25 | 5701-014-1403 | ND |
| 2014-10-02 | 5701-010-1107 | ND |
| 2014-10-02 | 5701-009-1103 | 0.203 ppb |
| 2014-10-16 | 5810-007-0952 | ND |
| 2014-11-04 | 5701-013-1107 | ND |
| 2014-11-04 | 5701-009-1105 | 0.370 ppb |
| 2015-01-07 | 5701-009-1058 | 0.212 ppb |
| 2015-01-07 | 5701-010-1106 | 0.0320 ppb |
| 2015-03-03 | 5701-009-1353 | 0.708 ppb |
| 2015-03-03 | 5701-010-1403 | 0.181 ppb |
| 2015-04-07 | 5701-009-1405 | 1.51 ppb |
| 2015-04-07 | 5701-010-1430 | 1.30 ppb |
| 2015-06-02 | 5701-010-1017 | 0.777 ppb |
| 2015-06-25 | 5810-006-1347 | ND |
| 2015-06-25 | 5810-003-1338 | ND |
| 2015-07-21 | 5701-009-0951 | 0.477 ppb |
| 2015-07-21 | 5701-010-1006 | 0.189 ppb |
| 2015-07-21 | 5701-011-0949 | 0.573 ppb |
| 2015-09-08 | 5701-010-1008 | ND |
| 2015-09-08 | 5701-009-0823 | ND |
| 2015-09-08 | 5701-011-0816 | ND |
| 2015-12-01 | 5701-010-1346 | ND |
| 2015-12-01 | 5701-009-1340 | ND |
| 2015-12-01 | 5701-011-1338 | ND |
| 2016-01-26 | 5701-010-1137 | ND |
| 2016-01-26 | 5701-011-1016 | ND |
| 2016-01-26 | 5701-009-1018 | ND |
| 2016-02-02 | 5701-011-1042 | ND |
| 2016-02-02 | 5701-010-1108 | ND |
| 2016-02-02 | 5701-013-1059 | ND |
| 2016-02-02 | 5701-014-1406 | ND |
| 2016-02-02 | 5701-009-1043 | ND |
| 2016-02-16 | 5701-011-0733 | ND |
| 2016-02-16 | 5701-010-0931 | ND |
| 2016-02-16 | 5701-009-0735 | ND |
| 2016-05-05 | 5701-013-1117 | ND |
| 2016-05-05 | 5701-009-1130 | ND |
| 2016-05-05 | 5701-014-1118 | ND |
| 2016-05-05 | 5701-010-1055 | ND |
| 2016-05-05 | 5701-011-1129 | ND |
| 2016-05-17 | 5701-011-0844 | ND |
| 2016-05-17 | 5701-009-0845 | ND |
| 2016-05-17 | 5701-010-0900 | ND |
| 2016-05-23 | 5701-010-1002 | ND |
| 2016-05-23 | 5701-009-0808 | ND |
| 2016-05-23 | 5701-011-0807 | ND |
| 2016-06-06 | 5701-009-1050 | ND |
| 2016-06-06 | 5701-011-1048 | ND |
| 2016-06-06 | 5701-010-1329 | ND |
| 2016-06-07 | 5810-014-1352 | ND |
| 2016-06-07 | 5810-013-1337 | ND |
| 2016-07-21 | 5810-014-1020 | ND |
| 2016-08-24 | 5810-013-1035 | ND |
| 2016-11-29 | 5701-013-1001 | ND |
| 2017-11-28 | 5701-014-1056 | ND |
| 2017-11-28 | 5701-013-1207 | ND |
| 2017-11-28 | 5701-008-1500 | ND |
| 2017-12-05 | 5810-008-1320 | ND |