of class 4 cells Ivacaftor synthesis �� 4)] for each fish [22]. Therefore, the total score per individual ranged from 0 (all undamaged) to 400 (all maximally damaged). The damage frequency was calculated as the percentage of damaged cells (e.g., the sum of cells with damage classes 1 to 4).2.4. Physicochemical AnalysisImmediately after collection, water samples were analyzed according to Standard Methods for the Examination of Water and Wastewater [23]. The following parameters were analyzed: pH, chemical oxygen demand (COD), five-day biological oxygen demand (BOD5), conductivity, chlorides, hardness, total nitrogen, ammoniacal nitrogen, phosphorus, aluminum, lead, chromium, copper, nickel, iron, zinc, sodium, total solids, dissolved solids, total volatile solids, nitrite, nitrate, turbidity, dissolved oxygen (DO), total coliforms, and fecal coliforms (Escherichia coli).

2.5. Statistical AnalysisStatistical analysis was performed using ANOVA, followed by Tukey multiple comparison test when appropriate. All analyses were carried out using the Statistical Package for the Social Sciences (SPSS) 15.0 for Windows, considering a significance level of P �� 0.05.3. ResultsThe values of physicochemical variables measured in the three sampling sites during the summer and winter seasons are shown in Table 1. The values were compared to CONAMA Resolution 357/2005 by the Environment National Council [18] for classifying the national water bodies.

In this legislation, the freshwater systems were allocated to five classes (from the class 1 to the class 4, water quality decreases and restrictions to water use as drinking supply increase) and upper limits were fixed for different water variables for each category (some of them for class 2 category are shown in Table 1). Freshwater systems within class 2 category may be used for human supply (after treatment), aquatic biological community protection, recreation, irrigation, aquaculture, and fishing activities.Table 1Physicochemical parameters of water samples from different sites of Sinos River in the summer and winter of 2008. Concerning the nineteen water parameters with reference values defined by CONAMA Resolution n. 357, higher values than standards were observed in sites Parob�� and Sapucaia do Sul. Higher values were observed in Parob�� for aluminum, iron, and fecal coliforms in the two sampling periods, for total phosphorus in summer, and for BOD in winter.

The two water samples of Sapucaia do Sul showed BOD, conductivity, total phosphorus, iron, dissolved oxygen, and fecal coliforms values at odds with the CONAMA resolution, in addition to aluminum and copper in the winter sample. The Cara�� site presented all the physicochemical parameters in accordance with the allowed limits in both AV-951 sampling periods.The results of damage frequency (%) and damage index estimated by the comet assay in the erythrocytes of H.