Estimation of median LC50 and toxicity of environmentally relevant concentrations of thiram in Labeo rohita
Sana Alam, Gulnaz Afzal, Riaz Hussain, Hafiz Muhammad Ali, Amtul Sami, Rabbiah Manzoor Malik, Raheela Jabeen, Farid S. Ataya, Kun Li
Abstract
Thiram is a widely used fungicide in agricultural practices as spraying on crops and grains storage but its potential adverse effects on non-target aquatic organisms have raised serious concerns. In this study, firstly LC 50 value of thiram has been determined as 0.744 mg/L for the first time in Labeo rohita and then, the fish were exposed to different sub-lethal concentrations of thiram (40 μg/L, 80 μg/L and 120 μg/L) to evaluate the effects on tissue growth, oxidative stress, anti-oxidant enzymes and histo-pathological parameters at days-20, 40 and 60 of the experiment. There observed a significant ( p < 0.05) decrease in the body weight while a significant increase in the relative ( p < 0.05) and absolute ( p < 0.05) weights of kidneys, heart and brain was found. Hematological analysis showed a significant ( p < 0.05) increase in leukocytes and neutrophils while lymphocytes and monocytes, RBCs and hemoglobin concentration were significantly ( p < 0.05) decreased. Serum biochemical parameters revealed a significant ( p < 0.05) increase in urea and hepatic enzymes while a significant ( p < 0.05) decrease in total proteins, albumin and creatinine were observed at higher doses (80 μg/L and 120 μg/L) of thiram. Oxidative stress parameters; ROS and TBARS were increased significantly ( p < 0.05) while antioxidant enzymes (CAT, SOD, POD, GSH) showed a significant ( p < 0.05) decrease in the treated groups compared to the control. Moreover, comet assay revealed significant ( p < 0.05) DNA damage in the isolated cells of kidneys, heart and brain at higher doses (80 μg/L and 120 μg/L) of thiram that was further confirmed by histo-pathological alterations in these tissues. The findings demonstrate that thiram severely pollute the marine eco-system and is quite hazardous for aquatic species by causing severe health effects even at sub-lethal concentrations and thus, render the apparently clean water to be unfit for animal and human consumption.