Uncertainty factors in ectotoxicological risk : uncertainty factors in ectotoxicological risk management.

Abstract

Uncertainty factors (also known as extrapolation or safety factors) are widely used in lower tier ecotoxicological risk management in order to allow for sources of variability and uncertainty for which there is only limited information. From the point of view of probabilistic risk assessment, the rationale underlying both the use of uncertainty factors and the specific values chosen is often unclear. On the other hand, uncertainty factors are a convenient approach to lower tier risk assessment. This paper considers the problem of how to improve these lower tier risk assessments without moving completely away from the use of uncertainty factors towards complex probabilistic modelling which often requires calculations using Monte Carlo. It is shown how relatively simple statistical models lead to manageable procedures for computing a single uncertainty factor for multiple sources of uncertainty including inter-species variation, elaborating on ideas and methodology presented in a recent European Food Safety Authority scientific opinion in relation to aquatic risk assessment for pesticides.