Modelling the dispersion of volatilised pesticides in air after application for the assessment of resident and bystander exposure

Evaluation of the potential exposure of bystanders and residents to pesticide vapour emitted from treated agricultural fields is an important component of risk assessment in the pesticide approval process. The information available for the development of a revised exposure assessment is reviewed and a new methodology proposed. Dispersion of vapours downwind of the treated field can be successfully modelled using commercially-available software, although there is no agreed method for predicting the emission of pesticide vapours from a treated field. The proposed exposure assessment model separates the emission of pesticide vapour from its downwind dispersion, allowing the latter to be tailored to UK conditions by using representative meteorological data. More work is needed to develop an appropriate model of emissions that can take into account environmental conditions and physico-chemical properties of the formulation.