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

4OPERATOR EXPOSURE & RISK ASSESSMENT4.1 For occupational situations the main routes of exposure are assumed to be throughthe skin (dermal) or by inhalation. Ingestion of pesticide is not considered inoccupational estimates, as it should not occur in a trained work force. No separateassessment for multiple applications is necessary because the daily exposure isestimated and this is compared to the AOEL which takes into account that theworker may be exposed daily and allows for repeat exposure.4.2 As ERMA New Zealand has no actual exposure data measured in the field underNew Zealand conditions, operator (mixer/loader/applicator) exposures wereestimated by TCL using the United Kingdom Chemicals Regulation Directorate(Pesticides)‘s (UK CRD, 1992) interpretation of the German BBA Model. Thederived values consider both dermal and inhalation exposure routes using thegeometric mean exposure estimates.4.3 The BBA model calculates total systemic exposure or the total absorbed dosefrom both routes. The default assumption is that 100% of the inhaled material isabsorbed, and for dichlorvos this default value is used. However, estimation ofdermal absorption (skin penetration) is usually more complex.4.4 After reviewing the available data, TCL used 30% as the proportion of dichlorvosthat would be absorbed from exposed skin for both concentrate and spray mix, inconcordance with the value used by APVMA, based on studies with rats (Jeffcoat,1990; Original not sighted in APVMA, 2008a). These data were also used by USEPA (2006a; 11%) and Californian Department of Pesticide Regulation (CalDPR,1996; 13%), but these regulators did not use the highest rate of absorption found,but an average.4.5 The BBA model allows exposure estimates to be made with and without a limitedrange of PPE and/or RPE for mixing/loading and application. Mixer/loaderexposures can be modelled with or without gloves, and with or without respirators(either A1P2 or FFP2SL/P2 specification). Applicator exposures can be modelledwith or without head covering (hood + visor or broad-brimmed headgear), glovesand extra body covering (coverall + sturdy footwear), and respirators (either A1P2or FFP2SL/P2 specification). Each item of PPE diminishes exposure to thecovered part of the body by a set protective factor (i.e. allows a percentagetransmission). Similarly, the different RPE mitigate inhalation exposures by setprotective factors. [Note: For some scenarios other models have been used, suchas UK POEM 07, which may present different RPE/PPE options with possiblydifferent protective factors.] The risk assessment is done by calculating the RiskQuotient (RQ = estimated exposure/AOEL). If the RQ for a particular activity isunacceptable (RQ >1) then further exposure mitigation, such as engineeringcontrols, may be considered in the models.4.6 Contained or closed mixing and loading systems can be used, which reduce thedermal exposure to mixers/loaders while readying the application equipment foruse. The US EPA considers that a correctly used and maintained closed systemDichlorvos reassessment – application Page 284 of 436