Cell Count and Toxin Guide
For protection of human health, the World Health Organization uses a guideline level of greater than 100,000 cells per milliliter (cells/ml) for a high risk health alert in recreational waters.
- <4 parts per billion (ppb): Very low/no risk. Corresponds to World Health Organization Level 1 Recreational Water Guideline. Use common sense practices.
- 4-20 parts per billion (ppb): Low to moderate risk of adverse health affects. Corresponds to World Health Organization Level 2 Recreational Water Guideline. Reduce recreational contact with water.
- >20 parts per billion (ppb): Seriously consider avoiding contact with water until levels of toxin decrease.