RR1204: Uncertainty and sensitivity analysis of the HardSPEC environmental exposure model for pesticide regulatory assessments
Sensitivity and uncertainty analysis of the HardSPEC model
HardSPEC is a realistic but worst-case environmental exposure model used by HSE in regulatory risk assessment of pesticides. It predicts concentrations of pesticides in surface and groundwater following pesticide use for weed control on areas like pavements and roads. The concentrations predicted by the model are used to help determine whether the risk posed by the pesticide use is acceptable.
The model is important in decisions on the authorisation of some pesticide uses. Applicants for pesticide uses sometimes ask HSE to consider a change to the properties of the substance or a change in the model, so the assessment is more appropriate for the use scenarios. HSE wanted to explore how sensitive the model is to changes in the assumptions used in the model. HSE also wanted to understand the uncertainties associated with such changes. In addition, HSE wanted to write the model into a different computer language to enable future development of a more easily maintained model.
The project found that HardSPEC output was most sensitive to substance properties and usage details. Output was also sensitive to a number of parameters built into the standard exposure scenarios within the model. This will help HSE understand the significance of changes requested by applicants.
This report and the work it describes were funded by the Health and Safety Executive. Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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