Pilot study on uncertainty analysis in EFSA Reasoned Opinions on the modification of pesticide maximum residue levels

Applicability of the EFSA Scientific Committee revised draft Guidance on uncertainty in EFSA scientific assessment is tested in the context of an EFSA Reasoned Opinion on the modification of pesticide maximum residue levels (MRLs). EFSA purchased services for the preparation of a non-regulatory Evaluation Report with example non-standard uncertainties related to a fictitious application for the modification of MRLs. The Evaluation Report was assessed by EFSA in the format of a Reasoned Opinion and case-specific examples of non-standard uncertainty in the acute and chronic dietary risk assessments were analysed. Methods were selected from the general framework outlined in the Scientific Committee draft Guidance in order to apply a relatively simple strategy that could be considered for use in a regulatory context. The individual non-standard uncertainties were assessed by sensitivity analysis with iterative back-calculation of the parameter values that would lead to exceedance of the toxicological reference value (exceedance limit calculation), and quantified by subjective probability estimation. Non-standard uncertainties affecting the chronic risk assessment were quantified by subjective upper bound probability percentile estimation and touhe combined estimated non-standard uncertainty calculated by probability bounds analysis. Probability bnds analysis provides a relatively simple approach for calculating the probability related to a combination of uncertainties. The draft Guidance was found to provide a comprehensive range of methods for uncertainty analysis. However, process-specific guidelines and practical procedures may need to be developed in order to implement the uncertainty assessment framework in routine pesticide risk assessments. The uncertainty assessment is intended to provide additional information on how certain the conclusions of the risk assessment are and thereby support the risk-based decision-making process by enabling risk managers to take account of uncertainty. The outcome of the pilot study will inform the EFSA Scientific Committee Working Group on how to further tailor the draft Guidance on uncertainty for the needs of the EFSA panels and units.