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

14, the mixing/loading component of the BBA model was used. Since the BBAmodel does not include indoor scenarios, the outdoor equivalent (hand-heldsprayer: hydraulic nozzles – outdoor, high level target) has been used for themixer/loader component.4.14 Table V also shows the modelled mixer/loader exposures and risks for the indooractivities with hand-held application equipment with dichlorvos (Scenarios 15 &16 - Cymbidium production; use rate: 1800g a.i./ha, with coverage confined to0.2ha/day) based on the BBA model, with PPE and RPE. Note the BBA modeldoes not include indoor scenarios nor application exposure for low level target, sothe outdoor equivalent (hand-held sprayer: hydraulic nozzles – outdoor, high leveltarget) has been used to estimate the operator exposures. The outdoor scenariowill tend to under estimate exposure and risk, whereas the high level target willtend to over estimate exposure and risk.4.15 Scenarios 17-25 consider applications in enclosed (industrial) spaces. Some ofthese use automatic equipment, others hand-held. In the former, occupationalexposure is confined to the mixer/loader, or in the case of gas products,connecting/disconnecting cylinders, as in the green- mushroom house scenarios.In the latter, both mixing/loading and application are included.4.16 In Scenarios 17 & 18 where RTU gas containing 50g a.i./L is triggered remotelyin enclosed spaces of 375, 3750 and 12,500 m 3 at use rates of 0.05g a.i./m 3 , 18.75,187.5 and 625g a.i. are required respectively for each space. These quantities ofactive are contained in 0.375, 3.75 and 12.5 L of gas, i.e. only one 7 L cylinderwould be needed for 375 and 3750, but two 7 L cylinders for 12,500 m 3 . Theproduct labels recommend a higher use rate of 0.15 g a.i./m 3 against certain pests.The higher rates would require 56.25, 562.5 and 975g a.i. respectively for thespaces: 375, 3750 and 12,500 m 3 . The APVMA estimated dermal exposure to0.001 mL/cylinder change (equivalent to 0.0014g dichlorvos, and with 30%dermal absorption, a systemic dose of 0.00042g; glove penetration, 10%), andinhalation exposure at 0.12 mg/cylinder change [see § 4.10 and Appendix 2]. Theresults are presented in Table VI.4.17 In Scenario 19 where RTU gas containing 50g a.i./L is applied using a manualpressure gun in enclosed spaces of 375, 3750 and 12,500 m 3 at use rates of 0.05ga.i./m 3 , the exposure calculated in § 4.15 for cylinder handling is added to thatduring application.4.18 The APVMA (2008b) noted that operators were directed to work away from spraydrift and towards the exit, and avoiding wetting any surfaces. The pressure nozzlewas likely to be held at chest or head height. Dichlorvos volatilisation would bealmost instantaneous and complete on ejection from the nozzle.4.19 The APVMA used a Pesticide Handlers Exposure Database (PHED) exposuremodel for high pressure handwand application, in the absence of any suitablePOEM model (their preferred option). The PHED model was modified to addressthe expectation that the efflux from a manual pressure gun would be significantlyless diffuse and more directional, to estimate dermal exposures during enclosedspace applications. Head/neck, exterior of clothing and hands were assumed to beDichlorvos reassessment – application Page 286 of 436