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

Re-entry into treated glasshouses used for Cymbidium production (Scenarios 13-16)REI for workers ventilating the glasshouse after treatment for Cymbidium production:5.40 The New Zealand use rates in glasshouses for flower production are 52 and 72 mgdichlorvos/m 3 [The use rates are quoted as 1300g a.i./ha for a maximum of 0.1haor 2500m 3 i.e. 1300 / 25000 = 52 mg/m 3 , assuming a 2.5m building height; and1800g a.i./ha for a maximum of 0.2ha or 5000m 3 i.e. 1800 / 25000 = 72 mg/m 3 ].These application rates are approximately 1.58 and 2.18 times the rate (33 mg/m 3 )used in the Brouwer et al. study without ventilation. The regression plotintercepts are adjusted upwards to 4.04 (Log 10 [6900 x 1.58]) and 4.18 (Log 10[6900 x 2.18]) while the same slope (-0.0031/min) has been assumed.5.41 Taking the slowest initial decline in dichlorvos levels, the airborne concentrationof dichlorvos at 240 minutes will be:At 52 mg dichlorvos/m 3 : 10 (4.04 + [-0.0031 x 240]) = 1977 μg/m 3At 72 mg dichlorvos/m 3 : 10 (4.18 + [-0.0031 x 240]) = 2729 μg/m 35.42 Re-entering the treated glasshouse to ventilate it would expose the worker byinhalation at approximately 1.98 or 2.73 mg/m 3 . If the duration of exposure was30 minutes, the worst-case upper limit, the inhalation exposures with various RPEwould be, Table XV:Table XV: Re-entry into glasshouses treated at 52 or 72 mg dichlorvos/m 3 – inhalation exposureat venting (240 minutes after application)Airbornedichlorvosconc.(mg/m 3 )Duration (h)Exposure(mg) aDose (mg/kg b.w.) bRespiratory protection cNone Half-face Full-face Air-hose1.98 0.5 0.99 0.014 0.001 0.0003 Nil2.73 0.5 1.37 0.020 0.002 0.0004 NilabcInhalation rate, 1 m 3 /hour;Body weight, 70kg;Protection factors from APVMA, 2008b: factor of 0.1 for a half face mask and a factor of 0.2 for afull face mask respectively, and no exposure for air-hose (supplied air system) [results rounded].5.43 Predicted dermal exposure for these scenarios when using PPE (hood/visor +overalls over long-sleeved shirt and long-legged trousers + boots + gloves) basedon the UK CRD equation (by adding a factor for dermal exposure and dividing bythe worker‘s body weight) gives:At 52 mg dichlorvos/m 3 (1300g a.i./ha):D = DFR x TC x DA x WR x AR x P / BWD = 0.5 x 5000 x 0.3 x 0.5 x 1.3 x 0.05 / 70 = 24.375 / 70 = 0.348 μg a.s./kg b.w./dayDichlorvos reassessment – application Page 319 of 436