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

Appendix 2:Occupational Exposure Estimates & Risk Assessment with RTU gas cylinders &EC fogging of indoor spacesA) Worker/loader exposures during RTU gas cylinder changing:In the APVMA re-assessment (APVMA, 2008b) they considered that operators mightbe exposed to dichlorvos when changing cylinders during gas fogging of glass- ormushroom houses (Scenarios 9 & 10) and enclosed (industrial) spaces (Scenarios 17, 18& 19).The APVMA estimated dermal exposure to be 0.001 mL/cylinder (equivalent to0.0014g dichlorvos; relative density, 1.425). Inhalation exposure could also result ifsome of the dichlorvos evaporated into the 1m 3 personal air space around the operator‘sbreathing zone. If 0.005ml of dichlorvos (wt. 7.1mg) was available for inhalation for 1minute, then they would inhale 0.12mg or 0.0017 mg/kg b.w. (70kg)In New Zealand, RTU gases are sold in 7 & 35L cylinders, at 50g a.i./L; and, use rates0.05 or 0.15g a.i./m 3 . For example, to cover 1.25ha at the equivalent of 0.05g a.i./m 3requires approximately 1.6kg (31.25L of product) or five 7L cylinders or one 35L (thisassumes a 2.5m building height).Dermal exposure from cylinder changingThe estimated absorbed dose from dermal exposure after 1 cylinder change would be,noting that gloves are assumed to be worn:And, five cylinder changes:Where:SE(d) = CR x WR x DA x PBWSE(d) = 1.4 x 1 x 0.30 x 0.1 = 0.042 = 0.0006 mg/kg b.w.7070SE(d) = 1.4 x 5 x 0.30 x 0.1 = 0.21= 0.003 mg/kg b.w.7070SE(d) = systemic exposure via the dermal routeCR = contamination rate [1.4 mg/cylinder change]WR = Work Rate [cylinder changes/day]DA = percent dermal absorption [30%]P = Penetration Factor for Clothing [gloves, 10%]BW = body weight [70kg]Dichlorvos reassessment – application Page 354 of 436