Application for the Reassessment of a Hazardous Substance under ...

and peas 20 minutes after application (Casida et al., 1962; Original not sighted;APVMA, 2008b).5.10 Using the Casida et al. (1962) data a general DFR t (μg/cm 2 /kg a.i./ha) value canbe derived for dichlorvos using the equation (US EPA, 1997):DFR t = (AR x F) x (1-D) t x CF2 x CF3where:AR = application rate (kg/ha);F = fraction of a.i. retained on foliage (unitless);D = fraction of residue that dissipates daily (unitless);t = post-application day on which exposure is being assessed;CF2 = conversion factor to convert the kg a.i. in the application rate to μgfor the DFR value (1 x 10 9 μg/kg);CF3 = conversion factor to convert the surface area units (ha) in theapplication rate to cm 2 for the DFR value (1 x 10 -8 ha/cm 2 if the applicationrate is per hectare).Using Casida et al. data: 5% remains on surface at 20 mins, F = 0.05;D is not needed for these scenarios as the exposure is assumed to occur onthe day of application after residue has dried;DFR t = (1 x 0.05) x 1E9 x 1E-8 = (1 x 0.05) x 10= 0.5 μg/cm 2 per kg a.i./haTransfer coefficient (TC)5.11 The transfer of residues from the plant surface to the clothes or skin of the workercan be regarded as more or less independent of the kind of product applied and thelevel of exposure will depend on the intensity and duration of contact with thefoliage. This is also determined by the nature and duration of the activity duringre-entry. Therefore, it is possible to group various crop habitats and re-entryactivities. The EUROPOEM Group recommended indicative TC values forpotential dermal exposure for four different harvesting scenarios. For other reentryscenarios, TC data may be extrapolated where the scenarios are consideredto be comparable, i.e. the intensity and duration of contact with the foliage issimilar (UK CRD, 2008a).5.12 Three of the TC values in the European guidance documents were applicable todichlorvos use on outdoor crops: tasks in vegetable crops, 2500 cm 2 /hr; tasks infruit trees, 4500 cm 2 /hr; and, tasks in berry crops, 3000 cm 2 /hr.Predicted worker dermal exposures (D)5.13 Predicted dermal exposure for this scenario based on the UK CRD equation(modified by adding a factor for dermal absorption and dividing by the worker‘sbody weight) gives:Dichlorvos reassessment – application Page 310 of 436