Evidence of liver damage by toxin from a bloom of the blue-green alga, Microcystis aeruginosa.

Examination of the results of routine assays for hepatic enzymes in plasma has shown a significant elevation of the levels of gamma-glutamyl-transpeptidase, and a lesser elevation of those of alanine aminotransferase, in plasma specimens from a population who obtained drinking water from a reservoir containing a heavy bloom of toxic Microcystis aeruginosa. Such elevations did not occur in the adjacent population who did not use water from this source. They coincided with the occurrence of the algal bloom, and were not present in the corresponding assays during the periods before and after the occurrence of the bloom. Increases in the levels of these enzymes indicate toxic liver injury and could not be attributed to clinical changes in the frequency of acute liver conditions or to variations in the number of plasma samples taken from patients with alcoholism. Therefore, it is concluded that the toxic algae in the water-supply reservoir cause the observed elevation of the levels of hepatic enzymes in the plasma of the consuming population.