Publication - Scientific basis for safety factors under REACH
15 Nov 2016

Assessment factors in human health risk assessment and their associated level of safety

Abstract

Human health risk assessment of chemicals requires solid information on adverse effects after long-term exposure. Because of ethical considerations, human data or even long-term studies with animals are in general scarce. Consequently, reliable assessment factors (AF) are often used in risk assessment to overcome e.g. differences between short-term animal studies and the human situation. In human health risk assessment, usually more than one extrapolation step is required, e.g. the use of factors for interspecies-, intraspecies and time extrapolation. According to Vermeire, the multiplication of several conservative assessment factors – representing worst case assumptions – increases the level of conservatism in the risk assessment. By means of probabilistic distributions for the derivation of an overall assessment factor, the overestimation of risk could be reduced (Vermeire et al. 2001). Furthermore, a discussion about the overall degree of data variability and uncertainty and the confidence of the obtained overall assessment factor cannot be addressed within deterministic safety assessment.