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Comparing exposure levels is often the most important step in a bridging exercise. The exposure parameters used in the reference risk assessment should be compared to the expected exposure in the local situation. Almost always, exposures will be (very) different, both for human health and for environmental assessments. However, there is no need for exposure conditions to be identical or even similar; it is only important to assess whether exposure in the local situation is lower, similar or higher than in the reference assessment.
 
Exposure in the reference assessment will often be defined by the model and scenario(s) that were used to estimate exposure levels. It is therefore important that details of the model and scenario(s) are provided in the reference risk assessment report. Exposure in the local situation should be based on the expected conditions of use. These are partly defined in the Good Agricultural Practice (GAP) Table (or the Table of Intended Uses) in the registration dossier; and they partly depend on knowledge by the registration authority about the local pesticide use practices as well as agronomic and environmental conditions.
 
Key parameters that determine exposure, both for human and environmental risks, include the crop, the application rate and frequency of the pesticide, the mode of application and the type of equipment. Additional key factors for human health risk assessments are for instance the personal protective equipment (PPE) used by the farmer or the diet of the consumer. Additional factors that may influence exposure of the environment include weather conditions, use of unsprayed buffer zones, behaviour of non-target organisms, etc.
 
Key exposure parameters differ for the various risks that can be bridged; they are listed in the respective Assessment Summary Tables in the Assessment Methods module of the Toolkit.
 
 
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