Microcystins in water and in microalgae: Do microcystins as microalgae contaminants warrant the current public alarm?

Toxicol Rep. 2018 Aug 3:5:785-792. doi: 10.1016/j.toxrep.2018.07.002. eCollection 2018.


Microcystins have been the subject of increasingly alarming popular and scientific articles, which have taken as their unquestionable foundation the provisional Guideline of 1 μg/L established by the WHO Panel on microcystins levels in water, and mechanically translated by the Oregon government as 1 μg/g of Klamath Aphanizomenon flos aquae microalgae. This article underlines the significant limitations and ultimately scientific untenability of the WHO Guideline on microcystins in water, for being based on testing methodologies which may lead to a significant overestimation of the toxicity of microcystins. I propose criteria for the realization of new experimental studies on the toxicity of microcystins, based on the essential understanding that drinking water is contaminated by whole cyanobacterial microalgae rather than purified microcystins, while it is important to differentiate between water and cyanobacterial supplements. It is indeed a mistake to automatically apply standards that are proper for water to cyanobacterial supplements, as they have different concentrations of the antioxidant substances that inactivate or significantly reduce the toxicity of microcystins, a fact that also require that each cyanobacterial supplement be tested individually and through realistic testing methodologies.

Keywords: Aphanizomenon flos aquae; Chlorella; Cyanobacteria; Klamath algae; Microcystins; Spirulina; Water safety.