Assess toxicity of mixtures of herbicides in fish

Abstract

Herbicides are widely used is agriculture, known as diffuse source of pollution of surface water and groundwater. The impact of this use on water quality, however, is little known and has been the subject of studies around the world. It has already been observed mutagenic and genotoxic effects in fish exposed to herbicides. The predominant crop in the state of Sao Paulo is the sugarcane, comprising approximately five million hectares. The mixture of herbicides in the spray tank is a common practice among producers, although it is prohibited by law. Therefore, the aim of this study is to evaluate the toxicity of mixtures of tebuthiuron, ametrin and the commercial product Velpar K (diuron and hexazinone), widely used in sugarcane cultivation for zebrafish (Danio rerio), through studies of exposure in short and long term. It will be also evaluated biomarkers related to exposure to herbicides: cholinesterase; glutathione S-transferase; lactate dehydrogenase. The LC50-96h of mixtures will be calculated using the Probit Analysis and the evaluation of biochemical parameters by the module "One Way ANOVA, both of the program STATGRAPHICS PLUS 5. The level of significance will be established as P<0.05. A model parameterization will be performed for assessing effects of mixtures used, by calculating the parameters of the models and their measures of variability, as well as the statistical parameters that allow comparison of different variants and automatic selection of the model and deviations more appropriated to each case. We hope with the present results it is possible to determine the toxicological potential of mixtures of herbicides tested for zebrafish, evaluating, where appropriate, their use in crop management of sugarcane. We also hope that collected data will help the establishment of maximum allowed concentration of contaminants in water compartments in order to protect aquatic communities and public health. The later is a potential consumer of contaminated source of protein supplied by fish. (AU)