Microcystins

Cyanobacterial toxins have been shown to be hazardous to humans and animals via direct and indirect routes of exposure such as ingestion of and contact with contaminated water, vegetables, fish/shellfish and through irrigation practices. Microcystins (MCs) are the most commonly encountered cyanotoxins. The toxins produced by Microcystis, Nostoc, Anabaena, Oscillatoria and Planktothrix cyanobacteria are defined by their cyclic heptapeptide structure as well as by the rare amino acids (ADDA or dehydroalanine) that they share. These toxins are potent inhibitors of the eukaryotic protein phosphatase families PP1 and PP2A leading to cell death (apoptosis). Studies have also shown that MCs play a role in liver toxicity and possibly even stimulate the growth of cancer cells following exposure.

More than a dozen countries have developed regulations or guidelines for microcystins in drinking water and recreational waters. Currently there are no mandatory U.S. federal water regulations for cyanotoxins in effect, but in 2015 the EPA issued 10-Day Drinking Water Health Advisories (HAs) for cyanobacterial toxins, microcystins, and cylindrospermopsin to assist managers of public or community water systems in protecting the public from these contaminants.