Worker reentry study involving phosalone application to citrus groves.

Abstract This study was conducted to provide information for the establishment of a worker reentry period after applying phosalone to citrus groves in California. Fourteen healthy male agricultural workers (volunteers) ranging in age from 18 to 72 years were given physical examinations, including cholinesterase (ChE) determinations, prior to their entry into the phosalone-treated grove; four individuals treated in like manner served as controls. Blood and urine were sampled at the end of each work day. Two separate areas of a citrus grove were treated (6 lb per acre), so that the workers would enter the respective areas 14 or 21 days after the application. Cloth patches were attached to clothing at four sites (chest, shoulder, thigh and back) to collect dislodgeable residues for analysis. Leaf samples were taken to determine the dislodgeable residue of phosalone and its oxon at Day 0 and intervals thereafter. No adverse effects were observed with dislodgeable residues as high as 3.6 μg/cm 2 and no phosalone or its metabolites (phosalone-oxon and 2-amino-5-chlorophenol) were detected in urine. The red blood cell ChE activity of the workers was not significantly different from controls according to the t test on deviations, while the deviations in plasma ChE activity of the workers and controls were significantly different in both the 14- and 21-day studies. Dislodgeable residues on cloth patches were lower in the 14-day study and reflected the differences in dislodgeable residues on leaves for the two reentry periods. On the basis of this study, health scientists recommended a 21-day reentry interval.