Ecotoxicological effects of glyphosate, 2,4 D and atrazine on freshwater systems: concentrations, risk assessment and establishment conditions of a tropical specie

Abstract

Pesticides are agents of global change, since they can be transported to environmental compartments, cause adverse effects on non-target species. The most worldwide used pesticide is glyphosate. Some studies have already shown adverse effects on aquatic species caused by glyphosate, which is triggering global discussions about its legislation and use. Brazil has up to date no prospect of reducing or banning the use of the three most used pesticides in the country, glyphosate, 2,4 D and atrazine. The knowledge on adverse effects of pesticides and other chemical contaminants in tropical species is still scarce, maybe because many do not have defined protocols for ecotoxicological test conditions. The purposes of the each chapter of this study were: (1) to investigate the global glyphosate concentrations in surface freshwaters, to compare the countries laws and to carry out environmental risk assessments; (2) to investigate the Brazilian concentrations of glyphosate, 2,4D and atrazine in surface freshwater, and to assess the potential environmental risks they represent; (3) to describe the steps and the challenges for culturing the tropical test species Chironomus xanthus as well as to discuss its current use in ecotoxicology. Information on glyphosate concentrations in surface freshwater is scarce and known values very irregular among the countries investigated, with 95% of the studied systems showing concentrations that represent a risk to aquatic species. Most countries evaluated did not have restrictive legislation for the glyphosate presence in water resources, resulting in the non-protection of aquatic organisms. There was an increase in the annual sales of 2,4D, atrazine and glyphosate between 2009 and 2018 in Brazil. Although most environment concentrations were below the limit allowed by Brazilian legislation, the observed concentrations represented a medium to high risk for ecosystems in 65%, 72% and 94% of the Brazilian states for 2,4 D, atrazine and glyphosate, respectively. The ecotoxicological effect of pesticides, as well as of other contaminants in freshwater sediments are very often performed with benthic macroinvertebrates. Chironomus xanthus has been increasingly used for the past of years. Therefore, conditions for Chironomus xanthus establishment, maintenance and operation in the laboratory are necessary, due to the absence of protocols for this species.