The objective of the workshop was to explore the scientific challenges to the application of TTC as a tool to aid decision-making in chemical safety assessment. TTC is the principle whereby a generic exposure value is established below which there is a low probability of adverse effects to human or environmental health. The concept is based on extrapolation of toxicity data from an available database to a chemical compound for which the chemical structure is known - but for which limited toxicity data is available. The broad approach is potentially applicable to any substance (i.e., intentionally added ingredient or inadvertent contaminants or impurities). The application of TTC in safety assessment is dependent on the quality, quantity and relevance of the underlying toxicity database (i.e., the chemical domain) and the availability of a reliable and relevant estimation of the exposure.
The TTC approach is at present used - amongst others - to evaluate the safety of food contact materials, flavouring agents and genotoxic contaminants in pharmaceuticals. The approach has also been suggested for a number of other applications. Wider acceptance and application of TTC would potentially yield benefits. In particular, it would potentially limit toxicity testing and associated assessment when exposure to a chemical is below a certain level of concern. This would permit a focus of finite resources of time, finance, animal use and human capital on the evaluation of substances with a greater potential to pose risks to human or environmental health.
The workshop participants have:
· Reviewed examples of the application of TTC across different regulatory evaluation frameworks and decision-making programs;
· Identified scientific barriers to broader acceptance of TTC;
· Explored potential opportunities for initiating steps to overcome such barriers.