Detecting genotoxic activity in industrial effluents using the SOS Chromotest microplate assay

Abstract

The SOS Chromotest, a cost-effective short-term bacterial genotoxicity screening assay, was performed to appraise its capacity for detecting the presence of soluble genotoxic activity in industrial effluent samples (organic and inorganic chemical plants, metallurgical plants, pulp and paper mills, municipal wastewater treatment plants). An optimized methodology, based on criteria taking into account β-galactosidase activity (the indicator of SOS gene induction), alkaline phosphatase activity (the indicator of cytotoxicity), and two genotoxicity measurement end points (minimum genotoxic concentration and maximum induction factor), was employed to generate reliable results that overcame the potential interferences inherent to complex wastewaters. Of 48 effluent samples tested, 37 (77%) elicited a significant induction of the Escherichia coli PQ37 SOS response. Effluents from inorganic chemical plants and pulp and paper mills displayed the most potent responses, with and without metabolizing enzymes (S9 mix). In general, chemical data available for some wastewaters supported SOS Chromotest positive responses. The genotoxic activity of whole effluents subjected to a 5-day aeration treatment was as high as that of native (unaerated) samples, suggesting that soluble genotoxicants are relatively recalcitrant to oxidation, although reductions in genotoxic activity did occur. This study indicates that the SOS Chromotest is sufficiently sensitive to screen for the presence of soluble DNA-damaging agents in a wide variety of unconcentrated wastewater samples. © 1996 by John Wiley & Sons, Inc.