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Concerning Cyanotoxin Levels Detected at 19 Clear Lake Sites

Danger Level at Ten Locations

Lake County, CA (October 1, 2020) – Clear Lake is a national treasure, and home to some of the finest bass fishing and recreational opportunities available anywhere.  It is also a large and biologically diverse natural body of water, and dynamic in water quality.  During September 15, sampling, concerning levels of Cyanotoxin were detected at 19 Clear Lake sites (see attached map and other resources).

What Are the Risks Associated With Cyanotoxin?
At the “DANGER” and “WARNING” levels (present at 13 sites), toxins from algae in water can harm people and kill animals.  People and pets should stay out of the water in those areas.  Don’t touch scum in the water or on the shore.  Don’t let pets drink the water.  Fish and shellfish from those areas should not be eaten. 

Symptoms of exposure include skin rashes, eye irritation, diarrhea, and vomiting.  Pets who contact the toxin can experience seizures and death.  Contact a medical provider or veterinarian if symptoms due to exposure are suspected.

Much of the aquatic plant growth visible in Clear Lake is harmless, and there is no need to be overly concerned about activities in areas of the lake where algae blooms are not present.

More Water Quality and Cyanotoxin Information
Many thanks to Big Valley Band of Pomo Indians and Elem Indian Colony for their regular monitoring at 30 Clear Lake sites.  For current Cyanotoxin lab results, visit the following webpages:
Further Cyanotoxin resources are available here:

CDC guidance regarding harmful algal blooms can be found here:

This is a challenging time with the fires, poor air quality, and COVID, but harmful algal blooms can cause significant suffering, so we encourage people to be careful and be aware of the risks.

Gary Pace, MD, MPH

Cyanotoxin Map, Signage Information 9/15/20
Table of Microcystin, Anatoxin-a Sampling Results 9/15/20
Cyanotoxin Map 9/15/20

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