Short communication.: An in vitro approach for ecotoxicity testing of toxic and hazardous wastes

In waste-characterization, chemicals with a low acute toxicity but with a high long-term hazard such as PBTs (persistent, bioaccumulable, and toxic chemicals) are difficult to identify, leading to an inaccurate assessment of their risk to the environment. This study assesses the sensitivity of in vitro assays with rainbow trout cell line RTG-2 as a tool for the ecotoxicological testing of hazardous wastes using a battery of bioassays, including a neutral red (NR) assay for predicting cytotoxicity, a beta-galactosidase (beta gal) assay for predicting cellular defence, and two sub-lethal damage assays: ethoxy resorufin-O-deethylase (EROD) and glutathione S-transferase (GST) to check for induction of cytochrome and for alteration of antioxidant defences respectively. Six samples of complex waste, covering a wide range of liquid (A a C) and solid (1 a 3) matrices were tested. The EC50-values (NR) ranged from 0.09 mL/100 mL (B) to 2.01 mL/100 mL (2). A hormesis effect (beta gal) at low concentrations was observed for the A (0.03-0.18 mL/100 mL), 1 (0.03-0.29 mL/100 mL) and 2 (0.03-0.29 mL/100 mL) samples. A dose-dependent stimulation of enzymatic activity was observed for the B [(EROD (0.58-4.68 mL/100 mL), beta gal (0.58-4.68) and GST (0.14-1.17 mL/100 mL)] and C [(EROD (0.29-4.68 mL/100 mL) and beta gal (2.34-4.68)] samples. No effects were observed at the highest concentration tested (74 mL/100 mL) for sample 3. The in vitro approach can be considered to be an efficient, rapid and cost effective screening system to provide basic information on toxic and hazardous waste for further analysis and risk evaluation.