Uncertainty factors in risk assessment

This advisory report is concerned with scientific developments that are important in relation to the use of so-called ‘uncertainty factors’ for the determination of health-based recommended exposure limits and for toxicological risk assessment. Such factors are used to make allowance for differences between laboratory animal species and humans, for inter-personal sensitivity variations and for shortcomings in the research data.

The report covers various scientific disciplines and methodologies. Toxicological insight into substance kinetics and dynamics is increasing all the time: the absorption, dispersion, metabolism and excretion of substances are increasingly well understood, as are the mechanisms by which substances can be toxic to organisms that are exposed to them. Various molecular analysis techniques, cell culture techniques and computer modelling methods are proving valuable in this context. In more and more cases, such methodologies make it possible to specify the qualitative and quantitative differences between laboratory animals and humans.