Ecotoxicological applications and significance of the comet assay

Application of the single-cell gel electrophoresis or comet assay has revolutionized the field of genetic ecotoxicology or eco-genotoxicology. It is a rapid, sensitive and relatively inexpensive method providing the opportunity to study DNA damage (including oxidative damage), repair and cell death (apoptosis) in different cell types without prior knowledge of karyotype and cell turnover rate. The assay has, however, often attracted criticism for its lack of ecotoxicological relevance. In addition, in contrast to genetic toxicology where rapid technical progress has been made to improve cell- and tissue-specific adoption of the assay, only limited advancement has been made to transfer the methodologies to ecotoxicological studies. While reviewing the recent information available in the literature and underscoring the importance of induced genetic damage in natural species, the aims of this article are to (i) highlight and judiciously analyse the ecotoxicological relevance of the assay; (ii) attempt to correlate the comet response with other relevant biological responses or biomarkers; (iii) identify the technical challenges and various factors affecting its application in order to make it reliable, reproducible and robust; (iv) critically compare the technical developments in genetic toxicology and genetic ecotoxicology and (v) evaluate the future developments with respect to applications of the assay. It is suggested that while complementing other ecotoxicological parameters and further improving the methodologies, the comet assay will continue to play an important role in genetic ecotoxicology to determine induced genetic damage, which has significant consequences for short- and long-term survival of the natural or wild species. Information obtained through integrated studies using simultaneous applications of multiple biomarkers on different wild organisms could also provide an holistic dimension of toxicological impact of environmental contaminants for the protection of human health.