The effects of subchronic exposure to terbuthylazine on zebrafish

Terbuthylazine belongs to the group of symmetrical triazine herbicides used extensively in agriculture and non-agricultural sites, primarily to control broadleaf and some grassy weeds that have become ubiquitous contaminants of the environment. The aim of this study was to assess the impact of terbuthylazine in surface waters on fish under experimental conditions. The effects of subchronic exposure to terbuthylazine on fish growth and the development of histopathological changes in selected organs (gill, kidney, liver), and on the activity of some biochemical parameters - glutathione S-transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx) and on the concentration of thiobarbituric acid reactive substances (TBARS) in Danio rerio were investigated during a 28 day toxicity test.

Juvenile growth tests were performed on Danio rerio according to OECD guideline No. 215. Fish at the age of 30 days were exposed for 28 days to a range of sublethal concentrations of terbuthylazine (0.55 - environmental concentration, 150, 400, 700 and 1000 μg/L).

There were no significant differences (p<0.05) between the specific growth rates (r) of the test groups and control group. Histopathological examination revealed pathological changes only in the liver in fish exposed to terbuthylazine at concentrations of 700 and 1000 μg/L. Significant differences (p<0.05) in activities of biochemical markers were found in GST (400, 700 and 1000 μg/L), GR (700 and 1000 μg/L), significant differences (p<0.05) of TBARS concentration were found at 1000 μg/L.

Based on the results of growth rate, the histopathological examination of selected organs, and the results of biochemical parameters, it was found that the environmental concentration of terbuthylazine did not have any effects on juvenile D. rerio. The values of NOEC and LOEC for terbuthylazine for juvenile D. rerio were 150 μg/L and 400 μg/L.