Potential impact of prioritisation methods on the outcome of cumulative exposure assessments of pesticides

This report describes the potential impact of a prioritisation method on the outcome of cumulative exposure assessments of pesticides. The method aims to reduce the laborious task of the establishment of cumulative assessment groups (CRAs). The prioritisation method consisted of two steps: 1) identification of low-priority substances and 2) identification of priority organs. The first step aimed to identify low-priority substances based on hazard quotient (HQ) thresholds for single substances relevant for acute effects on the nervous system or chronic effects on the thyroid. For this, probabilistic calculations of chronic and acute HQs were performed for 210 substancesand 10 surveys. Priority pesticides were retained according to four different thresholds, namely an HQ larger than0.1 at the 99th percentile of exposure, or an HQ larger than 0.01, 0.1 or 0.2 at the 99.9th percentile of exposure. In the second step, AGs for the nervous system and the thyroid were compiled and risk metrics obtained for those organs was compared with the risk of higher tier AGs at the specific effect. It was concluded that risk assessment of AGs at the target organ level using critical effects (i.e. using the health-based guidance value of substances) is feasible. The prioritisation thresholds were applied for AGs at the target organ level and for AGs at the specific effect level. The prioritisation threshold of having an HQ larger than 0.1 at 99.9th percentile to retain substances could be used for those AGs. It reduced the number of substances in the AG nervous system to 50% and the number of substances in the AG thyroid to 70% without having a substantialimpact on the total margin of exposure. In conclusion, the prioritisation method could be used to simplify CRA and may contribute to a cost-effective approach whilst still providing a high level of protection.