Abstract
In Australia, the registrations of ethyl parathion and methyl parathion are being reviewed under the National Registration Authority's existing pesticide assessment program. A study was conducted in 14 orchards in Victoria to assess the respiratory and dermal exposures of mixer-loader-applicators to both parathions in air blast application, and to compare overseas surrogate (model) data with this real-use situation in Australia. Personal and static air samples were collected through a sampling assembly (modified UKAEA inspirable mass sampler plus adsorbent tube), dermal samples were collected by skin pad dosimetry and glove samplers, and urine samples were collected to determine the p-nitrophenol levels. The 16 workers who participated in this study were potentially exposed to total parathion levels of 0.2 to 305.9 mg/h [geometric mean (GM) = 18.8 mg/h, mean = 92.5 mg/h, 75th percentile = 159.6 mg/h] if polyvinylchloride gloves were not worn. These potential exposures originated predominantly (>99.9%) from the dermal route; only <0.1 percent (GM = 0.006 mg/h) was contributed by respiratory exposure. Of the total potential exposure, 91 percent was contributed by dermal exposure of the hands (GM = 17.1 mg/h, n = 5), whereas 9 percent was from other parts of the body (GM = 1.7 mg/h, n = 17). The mean air concentration was low (GM = 9 μg/m3; range = < 1 to 26 μg/m3, n = 24), and all the results were well below the time-weighted average exposure standards. The use of open tractors or more concentrated sprays (commonly with electrostatic sprayers) has been found to cause higher respiratory and dermal exposures, as compared with the use of air-conditioned cabins or less concentrated sprays (usually with high pressure sprayers). Four workers who had applied concentrated sprays and had prior exposure showed urinary levels of p-nitrophenol in excess of the biological exposure index of 0.5 mg/g creatinine, despite the fact that the concomitant dermal dosimetric measurements would have reduced skin absorption. A good correlation was found between the amount of parathion applied and urinary p-nitrophenol level (r = 0.97). The overall findings are consistent with the results of most overseas studies and with the predicted values extrapolated from the U.K. Predictive Operator Exposure Model and the USA/Canada Pesticide Handlers Exposure Database.