Based on the latest scientific information, the U.S. EPA has established recommended water concentrations, at or below which protects public health, for the cyanotoxins microcystins (8 micrograms per liter) and cylindrospermopsin (15 micrograms per liter). EPA’s recommendations are protective of all age groups and are based on peer-reviewed and published science.

https://www.epa.gov/newsreleases/epa-issues-recommendations-recreational-water-quality-criteria-and-swimming-advisories