Toxicidade crônica do herbicida atrazina: impactos na reprodução de peixe-zebra (Danio rerio)

Abstract

Atrazine is one of the most widely used pesticides in Brazil and worldwide, and it is frequently detected in surface waters. However, its adverse effects on environmental and human health at environmentally relevant concentrations (i.e., realistic concentrations) and under long-term exposure remain largely unknown. Given this, the aim of this study was to investigate the effects of chronic atrazine exposure on reproductive parameters and toxicity biomarkers in zebrafish (D. rerio), using test concentrations ranging from the legal limit of this contaminant in drinking water to

environmentally relevant concentrations. For this purpose, animals were sex- separated and exposed for 35 days to two atrazine concentrations, Low (0.4 μg/L)

and High (2 μg/L), or only water (Control). During this period, the fish were allowed to reproduce to assess their spawning frequency and offspring viability. The embryos obtained throughout the exposure were monitored for mortality and malformations over 4 days. At the end of the experiment, animals were euthanized and dissected for gonad removal. Fish and gonads were weighed to calculate relative wet weight (%). The dissected organs were also subjected to enzymatic activity assays (LDH, CAT, GST, and GPx) and measurement of malondialdehyde (MDA) content. Exposed groups showed a significant decrease in egg viability compared with the control. In addition, offspring from exposed groups displayed significant hatching delay. LDH and CAT activities were respectively increased and decreased in exposed males, while GST activity was elevated in females. Relative wet weight of the organs, GPx activity, and MDA accumulation showed no significant differences among treatments. The results demonstrated that environmentally relevant concentrations of atrazine are not safe and are capable of deregulating ROS metabolism in zebrafish. Therefore, Brazilian legislation needs to be revised regarding the maximum permitted limit of atrazine in drinking water, since its presence may pose risks to environmental and possibly human health.