Solid-phase genotoxicity assay for organic compounds in soil

A genotoxicity assay was developed for samples from environments in which t oxic organic compounds are largely sorbed. The assay entails measurement of the rate of mutation of a strain of Pseudomonas putida to rifampicin resis tance. The ratio of induced to spontaneous mutants was a function of the co ncentration of a test mutagen in soil. In studies of the utility of the ass ay in samples amended with 2-aminofluorene as a test mutagen, the ratio of induced to spontaneous mutants declined with time. The decline paralleled t he disappearance of extractable 2-aminofluorene from the soil. The ratio of induced to spontaneous mutants also fell in four other soils with dissimil ar properties. We suggest that this solid-phase assay is more appropriate f or the estimation of genotoxicants sorbed in soil than assays involving ext ractants or suspensions of soil or sediment samples.