The results suggested that sites near the river spring are not appropriate as reference Z-VAD-FMK structure sites to fish genotoxicity bioassays. In addition, based on the monitoring of physicochemical parameters of Sinos River water, Blume et al. [11] have concluded that the sampling sites in the upper course should no longer be used as a reference point in future studies.In the present study, the water samples collected in the summer in the middle course site and in the winter in the three sites have shown genotoxicity in the peripheral blood of H. luetkenii when compared to negative control, confirming the results of other studies that have detected contamination of genotoxic compounds in the Sinos River basin, including the upstream course [12, 13].

Thus, the results of this study indicate that native fish species might be at risk for genotoxic damage in the Sinos River. However, the genotoxic potential of contaminants is an organism-specific and exposure-dependent phenomenon and interspecies variability for toxic responses as a result of differences in uptake, accumulation, metabolism, excretion, and DNA repair efficiency should be considered [8].Many studies investigated the genotoxic effects of rural, industrial, and urban effluents; however, their relative contribution and comprehensive chemical characterization remain a major challenge [26, 28, 29]. Considering the low urban density and the economic activities in the upper Sinos River site (Cara��), this region suffers relatively little influence from domestic and industrial sewage and genotoxic pollutants might come from small farms and livestock.

Contaminants in this region threaten the sustainability of one of the main basins of southern Brazil, responsible for water supply to approximately 1.6 million inhabitants, representing 17% of the population of the Rio Grande do Sul state [24]. Further studies in the upper Sinos River course should be conducted to identify sources of water contaminants so that measures can be taken to reduce or eliminate their negative effects.5. ConclusionPhysicochemical parameters demonstrated decreasing water quality from upstream to downstream of the Sinos River and comet assay in fish showed that the river water may be contaminated with genotoxic pollutants in the upper, middle, and lower courses. Thus, despite good water quality Batimastat of the upper river course, it should no longer be used as a reference site in future genotoxicity studies. Moreover, the results showed that complementing the physicochemical evaluation of river water with bioassays clearly permits acquisition of information that cannot be obtained from the measurement of water quality parameters.