DFR trials (GLP)

Risks incurred by workers in contact with a treated crop are often estimated using set calculations. When these calculations are unreliable, i.e. are not a true reflection of reality, a DFR (Dislodgeable Foliar Residue) type study must be conducted.

A DFR study measures residues that can be transferred from the leaf surface to another surface (skin in this case).

The objective of this type of test is to estimate the risk exposure of workers who are in contact with crops at harvest for long periods of time. This is the case of strawberry pickers. The risk is that the product applied to foliage, for example, could be transferred to the skin of workers by repeated contact with leaves during picking.

A puncher called an LPS ("Leaf Punch Sampler") is used to take leaf samples on several different days post application(s). Disc-shaped leaf samples are collected using this device.

Each sample consists of a known number of disks from different plants so that they are representative of the plot. We can thus test the leaf area potentially in contact with pickers. These discs are washed with a special solution to extract any product residue remaining on the leaves which could be transferred to workers. This rinsing process is initiated immediately after taking samples in the field.

The rinsing solutions are then prepared for analysis in the laboratory.

The following snapshots illustrate the different stages of a DFR test.

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