Toxicological Summary and Suggested Action Levels to Reduce Potential Adverse Health Effects of Six Cyanotoxins

Worldwide, several species of cyanobacteria produce cyanotoxins that
cause human illnesses and kill pets or livestock. Cyanobacteria bloom in California’s
surface water bodies. These blooms have caused public alarm but local health officials
have lacked a health basis for actions such as posting warning signs. The California
State Water Resources Control Board (SWRCB) contracted with the Office of
Environmental Health Hazard Assessment (OEHHA) to provide risk assessment
support on cyanobacterial toxins. OEHHA conducted a risk assessment to determine
the cyanotoxin concentrations at which no adverse effects are expected to occur. The
risk assessment includes two parts: toxicity assessment and exposure assessment.