In 2006, a research project was commissioned by the UK Chemical Regulations Directorate to develop a new model for estimating the exposure of both bystanders and residents to agricultural pesticides. The Bystander and Resident Exposure Assessment Model (BREAM) project aimed to establish
a framework for a predictive model of spray and vapour exposures from boom sprayer applications, then construct and validate the model. Both the model and the data obtained to support it, show clearly that the data on which the existing UK exposure assessment is based, is likely to underestimate
exposure to spray drift in some situations and exposures of more than an order of magnitude greater than the current exposure assessment might be appropriate. The ground deposits predicted by the model are also significantly higher than those currently used in the regulatory exposure assessment.
The BREAM model for exposures to spray drift allows the effect of distance, wind speed, forward speed, boom and crop height on bystander exposure to be explored for a standard flat fan '03' size nozzle, which is a typical nozzle for UK arable applications. Future developments are likely to
include a wider range of nozzles, pressures and the effect of humidity. The reliable prediction of people's exposures to vapours has proven more difficult to achieve. However, limiting volatilisation by applied dose and taking account of UK meteorological conditions in the dispersion calculation
has allowed a more realistic estimate of maximum exposures to be made. The project showed that further investigations into the factors influencing the volatilisation of pesticide from treated fields are required.