Abstract
Landfill leachates contain many kinds of hazardous chemicals, the toxicity of which is evaluated using various bioassays. Alkaline single cell gel electrophoresis (comet assay), a mutagenicity test, enables sensitive detection of DNA damage in eukaryotic cells induced by genotoxic agents. We previously evaluated DNA damage and repair by a comet assay using unicellular green alga Euglena gracilis and demonstrated the usefulness of normalized tail moment as a DNA damage evaluation index. Therefore, we performed an evaluation of DNA damage induced by landfill leachates by the comet assay using E. gracilis and compared the results to the umu test. In the comet assay, sample A and B displayed DNA damage in 40-fold and 10-fold concentration, respectively. Because highly concentrated CODMn (Chemical Oxygen Demand) and T-N (Total Nitrogen) were detected in the samples, the chemicals that caused the DNA damage may be the not-readily biodegradable or biorefractory organics and nitrogen compounds. The DNA damage in sample A was closely related to the indirect mutagens. In sample B, it was influenced by the direct mutagens. These results showed that landfill leachates contain various mutagens difficult to predict from chemical analysis. Moreover, the umu test detected no mutagenicity in any samples. Since the comet assay was more sensitive than the umu test, comet assay is the method of choice for detecting mutagenicity in landfill leachates.
