Abstract:
Several potential genotoxins found in water samples arise from anthropogenic activities. Acid mine effluent
resulting from coal mining poses serious environment concerns all over the world. The use of toxicity tests
to evaluate the quality of streams add value by providing site-specific toxicological data. Treatment systems
such as the use of natural wetlands (passive) or conventional physical and chemical pH-neutralised processes
(active) are employed mainly to meet certain water quality guidelines. Nonetheless, potential genotoxins or
residues remain which influence the quality of discharged effluents. The objective of this study was to evaluate
the genotoxic potential of acid mine drainage (AMD) released into a natural stream following treatment by
passive and active methods. This study aimed to identify the extent of AMD mutagenicity and genotoxicity
to African Vero monkey kidney cell line and a fish gill cell line (RTgill-W1) using two assays, the Ames test,
and the comet assay, as a rapid and effective screening tool. The Ames test performed without metabolic
activation using Salmonella typhimurium TA98 and TA100 strains showed no indication of mutagenicity in the
water samples tested. Differing results were however obtained for the comet assay using the African Vero
monkey kidney cell line and a fish gill cell line (RTgill-W1), which revealed DNA fragmentation and variations
in morphologies indicative of genotoxicity in the water samples following the two treatment processes. A
significant reduction in DNA damage was observed in water samples following active treatment of the AMD,
evidenced by reduced damage frequency and a lowered comet score. This bioassay confirms the urgency
of integrating high-throughput screening in aquatic toxicity assessment at genetic levels, giving further
evidence that in-vitro bioassays can be incorporated for use in short-term genotoxicity assays. The result
suggests that the comet assay proved sensitive at detecting genotoxicity, supporting the integration of this
into environmental monitoring frameworks targeted at AMD-contaminated sites.
