Exposure Assesment for Bystanders and Residents

The recent BREAM project (Bystander and Resident Exposure Assessment Model) developed a computational model, based on the Silsoe Spray Drift Model, to predict the potential exposure to pesticides for bystanders and residents in the countryside.     It can be used as a tool in risk assessments. The work was concerned with boom sprayers operating over arable crops in a range of conditions relevant to the United Kingdom. Model development and validation was supported by tests in controlled wind tunnel conditions with the overall model predictions validated against full-scale field trials results.

The model developed in the BREAM project is being further developed in the European framework BROWSE project, which aims to review, improve and extend the risk assessment of plant protection products to evaluate the exposure of operators, workers, residents and bystanders. Silsoe Spray Applications Unit is leading the workpackage relating to bystanders and residents.

Other projects, funded by Defra through the Chemicals Regulation Directorate include:

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• improving and extending the spray drift model to take account of the filtering effect of vegetation and to allow extrapolation to a wider range of nozzle sizes and designs

• obtaining data aimed at improving the assessments of exposure to drift from orchard sprayers​

The BREAM2 calculator:

A new calculator for bystander and resident exposure to pesticide spray drift from agricultural applications by a boom sprayer has been developed.
It differs from the original BREAM calculator in the way that the relationship between airborne spray and potential dermal exposure is described, following additional research (Butler Ellis et al, in press). The uncertainty in this relationship is reduced and the variability is more accurately captured in the model. A statistical comparison between the new model and field data shows that BREAM2 is a better predictor of potential dermal exposures.
The predicted 75th and 95th percentiles of potential dermal exposure are reduced compared with BREAM under normal operating conditions.