In Vitro Toxicology and the Test Guidelines

Ethical, economical and scientific considerations should encourage the development of alternative and in vitro test methods. Before their adoption, in vitro methods need to be validated and scientifically justified. Demand for rigorous validation schemes for in vitro tests must be emphasised, even more than in the case of in vivo tests. The OECD has adopted in vitro guidelines for testing genotoxicity; several endpoints and mechanisms can be studied in a cost-effective manner in vitro. Similar advantages could be afforded if acute irritation and corrosion, as well as the non-genotoxic carcinogenic effects of chemicals, could be studied in vitro. Evaluation of the validation status of various methods used to study non-genotoxic carcinogens was begun by the Nordic Working Group on In Vitro Methods for Non-genotoxic Mechanisms in 1996. In some established OECD test guidelines (for example, the dermal irritation/corrosion test), there is already room for the application of in vitro methods which have not been formally validated. In January 1996, the OECD Workshop on Harmonisation of Validation and Acceptance Criteria for Alternative Toxicological Test Methods set the basis for internationally acceptable principles to be followed in the validation of in vitro test methods.