Evaluation of toxic effects of a triazole fungicide, difenoconazole in a freshwater fish model.

Difenoconazole, a triazole fungicide, is widely used to control fungal infections in agriculture. Due to surface run-off, waterbodies are contaminated by difenoconazole that may cause detrimental effects to non-target aquatic organisms. This study was designed to determine the toxic impacts of difenoconazole on a fish, Pethia conchonius, from the river Teesta using histopathological, biochemical and molecular biomarkers. The 96h-LC₅₀ of 1.886 mg/L for difenoconazole was determined. Based on the 96 h-LC₅₀, three sub-lethal concentrations of difenoconazole, 0.037 mg/L, 0.188 mg/L and 0.377 mg/L, were selected. Histopathological study of the gills showed epithelial lifting, lamellar fusion, curling of secondary lamellae, hypertrophy, aneurysm and necrosis. DNA damage in the exposed groups was significantly higher than in the control, with increasing concentrations and duration of exposure, with a maximum increase of 73% in the Tail DNA. A significant decrease of almost 2-5 times in both catalase (CAT) and superoxide dismutase (SOD) activity along with a 3-5 fold reduction in cat and sod expression was noted in the gills and liver compared to the control in a dose and time-dependent manner. Therefore, this study confirms that difenoconazole adversely affects Pethia conchonius at cellular, enzymatic and DNA levels.