The dangers of cyanotoxins in Mexico: Review of national strategies and decision tree proposal for risk assessment in drinking water and continental aquatic ecosystems

Abstract

Background: The study of toxic cyanobacteria in Mexico has gained attraction over the last 20 years due to frequent cases of environmental damage and risks to human health associated with aquatic ecosystems in the center and south of the country. Currently, Mexican regulations only consider four chemical forms of microcystins and one of nodularin, despite approximately 2,000 cyanotoxins recognized; furthermore, treat-ment and elimination procedures are scarcely implemented and the mechanisms of control are practically null. Goals: This work aims to explain the need to incorporate different chemical forms of cyanotoxins into Mexican regulations and to propose diagnosis and intervention strategies using a decision tree protocol for water use, including both human consumption and recreational use. Results: During the review, records were found linking the presence of certain genera of cyanobacteria with the presence of anatoxins, saxitoxins, and cylindrospermopsins in national lakes and rivers that are frequently used without receiving adequate treatment; therefore, they should be included under the law. While standard chemical methods offer accurate information about the presence of some types of cyanotoxins, complementary molecular techniques are recommended to obtain more precise taxonomic and genomic identifi-cations. Conclusions: Herein, we present a decision tree that outlines the available options in the event of a contingency, including the official communication channels that should be activated to monitor and elimi-nate cyanobacterial blooms at different stages of development. In par-ticular, this proposal is focused on empowering communities to make decisions about the environmental quality of aquatic ecosystems and the water resources they use on a daily basis.