Comment: Defining a “Threshold of Regulation”: The Ultimate Alternative for Safety Assessment?

Robert D. Combes

The ability to eliminate the need for any toxicity testing of a chemical, because its presence in the environment and/or the anticipated maximum level of human exposure is considered to be insignificant as far as human hazard is concerned, would contribute significantly to reducing the numbers of animals that have to be used in the regulatory safety assessment process. This possibility has been the subject of much discussion, prompted by several proposals calling for the establishment and utilisation by regulatory authorities of a “threshold of concern” or “threshold of regulation” for environmental chemicals. The debate has been stirred by potential differences in attitudes to the adoption of the threshold concept exhibited by regulatory agencies in the USA and Europe. These differences were highlighted at a meeting of the European Council’s Scientific Committee for Food (SCF) during 1996 (1), and by publication of a recent paper by Munro et al. (2), which attempted to establish scientific justification for the setting of a general threshold. The present paper reviews the development of the concept and discusses recent proposals and some potential problems in their implementation.