Validation of SOS-lux Microbial Biosensors for Mutagenicity Assessment: Mitomycin-C as a Model Compound AbstractHuman health protection requires relating the bioaccessible concentration of a mutagen with the corresponding likely harm that could be caused through exposure. This requires designating the target receptor in need of protection, and a quantitative understanding of the likely pathways for mutagen availability. In this study, young children were selected as target receptors because of their tendency to directly ingest soils. Most data used to characterise a chemical mutagenicity has been extrapolated from rat-based assays using chemical ingestion or direct injection procedures. Mitomycin C was selected as a relevant model compound and extracted using an established in vitro digestion technique. A range of mutagenic bioassays (i.e. SOS-lux based microbial biosensors and Salmonella mutagenicity assay) were calibrated and optimised in aqueous samples, before being applied to soil extracts. The biosensors were consistently as sensitive and responsive as the traditional Salmonella assay, however, the use of microbial biosensors offered speed and ease of analysis. The data presented confirm that the in vitro digestion bioassay enabled a rapid and inexpensive technique for deriving critical values for the protection of humans exposed to soil borne mutagenic pollutants.