Genotoxicity testing strategies

Genotoxicity tests contribute to the assessment of whether a chemical has the potential to cause somatic or germ-cell effects in animals (i.e. the potential to induce cancer or heritable mutation). Such genotoxicity testing is usually undertaken in a stepwise approach; first an assessment in vitro, to determine intrinsic genotoxic activity, and secondly, an evaluation in vivo to determine whether any such activity is expressed in the whole animal. While this core principle is now generally accepted, there are still different opinions as to when, and how many, in vitro or in vivo assays should be conducted. Such strategies would be simplified and harmonized if testing was carried out based on the knowledge that there was a precedent for that strategy being required to detect a carcinogen or mutagen rather than the possibility that it might.