The Effect of the 14-day Agricultural Restricted Entry Interval on Azinphosmethyl Exposures in a Group of Apple Thinners in Washington State

We examined the effect of the 14-day agricultural restricted entry period on absorbed pesticide doses in a group of twenty experienced apple thinners. Thinners entered orchards 1-49 days following azinphosmethyl applications. Urine samples (n=296) collected throughout the thinning season were analyzed for the three dialkylphosphate metabolites of azinphosmethyl to estimate absorbed daily doses. Separate dose distributions were created for samples collected when the interval was <14 days, or 14 days or more; geometric mean doses for these two categories differed by a factor of two (42 and 19 microg/kg/day, respectively; p<0.0001). Dose estimates were compared to US Environmental Protection Agency and California EPA regulatory guidance values for occupational azinphosmethyl risk. None of the doses exceeded the U.S. EPA NOAEL (560 microg/kg/day), but nearly all had a margin of exposure of less than 100. Addition of a 10-fold uncertainty factor to California EPAs NOAEL produced a guidance value of 75 microg/kg/day. Only 2.4% of the doses exceeded this value for re-entry intervals 14 days or more, while 27% exceeded the value for re-entry intervals <14 days. We conclude that the 14-day restricted entry interval provides an appropriate level of worker health protection under the field conditions studied.