Mercury (inorganic)
City of San Marcos
Mercury is a potent neurotoxin that also damages the kidneys and other internal organs. Mercury enters drinking water from industrial pollution, mining wastes and coal-fired power plants.
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 | 3 | 0 | ND |
| 2015 | ND | 3 | 0 | ND |
| 2016 | ND | 7 | 0 | ND |
| 2017 | ND | 6 | 0 | ND |
| 2018 | ND | 3 | 0 | ND |
| 2019 | ND | 7 | 0 | ND |
ppb = parts per billion
State and national drinking water standards and health guidelines
EWG Health Guideline 1.2 ppb
The EWG Health Guideline of 1.2 ppb for mercury (inorganic) 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 harm to internal organs.
EPA Maximum Contaminant
Level (MCL) 2 ppb
The legal limit for inorganic mercury, established in 1991, was based on toxicity studies conducted in laboratory animals in the 1970s and 1980s. This limit does not include any additional consideration of children’s health.
ppb = parts per billion
All test results
| Date | Lab ID | Result |
|---|---|---|
| 2014-03-12 | AC46696 | ND |
| 2014-08-12 | AC63050 | ND |
| 2014-08-12 | AC63049 | ND |
| 2015-06-10 | AC95344 | ND |
| 2015-06-10 | AC95343 | ND |
| 2015-06-10 | AC95339 | ND |
| 2016-03-16 | AD29002 | ND |
| 2016-03-16 | AD29003 | ND |
| 2016-06-16 | AD40879 | ND |
| 2016-09-07 | AD48075 | ND |
| 2016-09-07 | AD48074 | ND |
| 2016-12-12 | AD61574 | ND |
| 2016-12-12 | AD61581 | ND |
| 2017-02-22 | AD71448 | ND |
| 2017-05-03 | AD82346 | ND |
| 2017-05-03 | AD82350 | ND |
| 2017-05-03 | AD82349 | ND |
| 2017-05-03 | AD82345 | ND |
| 2017-10-12 | AE00525 | ND |
| 2018-01-25 | AE10438 | ND |
| 2018-01-25 | AE10439 | ND |
| 2018-07-26 | AE34619 | ND |
| 2019-01-16 | AE50027 | ND |
| 2019-01-16 | AE50021 | ND |
| 2019-01-16 | AE50024 | ND |
| 2019-01-16 | AE50023 | ND |
| 2019-01-16 | AE50022 | ND |
| 2019-04-16 | AE62469 | ND |
| 2019-07-09 | AE73591 | ND |