Cyanide
Clear Lake City Water Authority
Cyanide is a toxic chemical that causes central nervous system and thyroid toxicity. Water contamination is generally the result of metal mining and chemical industry waste, runoff from agriculture and road salts used for melting ice.
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 | ND | 5 | 0 | ND |
| 2015 | N/A | 0 | 0 | N/A |
| 2016 | N/A | 0 | 0 | N/A |
| 2017 | 6.00 ppb | 5 | 1 | ND - 30.0 ppb |
| 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 150 ppb
The EWG Health Guideline of 150 ppb for cyanide 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 the brain and nervous system.
EPA Maximum Contaminant
Level (MCL) 200 ppb
The legal limit for cyanide, established in 1992, was based on a 1955 toxicity study conducted in laboratory animals. This limit does not include any additional consideration of children’s health.
ppb = parts per billion
All test results
| Date | Lab ID | Result |
|---|---|---|
| 2014-06-24 | AC57752 | ND |
| 2014-06-24 | AC57744 | ND |
| 2014-06-24 | AC57750 | ND |
| 2014-06-24 | AC57745 | ND |
| 2014-06-24 | AC57751 | ND |
| 2017-01-19 | AD65614 | ND |
| 2017-03-08 | AD73911 | ND |
| 2017-03-08 | AD73921 | ND |
| 2017-03-08 | AD73910 | ND |
| 2017-10-25 | AE02046 | 30.0 ppb |