G. E. Carman

Worker environment research: Dioxathion (delnav®) residues on and in orange fruits and leaves, in dislodgable particulate matter, and in the soil beneath sprayed trees

Deposits and residues of dioxathion disappear at similar rates on and in the rind of oranges and the leaves of orange trees; dislodgable residues on the leaves dissipate at the same rate as the penetrated residues. This fact is important in evaluating the potential hazard to workers in treated groves because their exposure to pesticide residues is principally through the dislodgable residues. Samples of vapor and particulate matter taken during violent shaking of the trees show that the exposure of workers is almost entirely through contact with, and inhalation of, particulate matter, dermal contact probably being the more important. In one experiment, pickers were used in trees sprayed with dust containing no toxicant to determine the actual weights of dust that are inhaled (using Unico air samplers) and that accumulate on their bare arms (by washing at ten-minute intervals). The data show that several times as much dust is contacted dermally than is inhaled. Washing the entire trees with a dilute detergent solution removes a significant part of the dislodgable residue; as much as 30 percent is removed 46 days after spraying. The data presented in this paper provide a guide for toxicologists to permit the design of tests required to evaluate hazards workers encounter in pesticide-citrus groves.

Pesticide applicator exposure to insecticides during treatment of citrus trees with oscillating boom and airblast units

To obtain relative exposure data for the spray rig driver applying insecticides to California citrus trees, parathion [O,O-diethylO-(4-nitrophenyl) phosphorothioate] and dimethoate [O,O dimethylS-(2-(methylamino)-2-oxoethyl) phosphorodithioate] were applied with oscillating boom and airblast spray units. Spraying conditions were varied to simulate commercial application practices. Test conditions were used which varied from providing no driver protection to that of providing charcoal-filtered air. Both singleand double-side delivery systems were employed. Gauze sponges pinned to the coveralls of the driver were used to indicate dermal exposure potential, and ethylene glycol-containing impinger type air samplers were used to indicate inhalation exposure potential. Urine samples were collected and analyzed for dialkylphosphate and thiophosphate levels.

Post-Application Slough-Off of Pesticide Deposits on Orange Trees

Toxicant loss from fruit and leaf surfaces after a pesticide application was considered by GUNTHER and BLINN (1955) to be composed of 3 separate steps. The first step, occurring immediately after the pesticide spray had dried, was postulated to be a rapid loss within a few hours to a few days of the loosely adhering deposits consisting of pesticide sorbed to formulation carrier and to natural dust on the plant. The following step was a dissipation of toxicant from the more tenaciously adhering deposits through volatilization and decomposition of the compound by the action of sunlight and moisture. The duration of this step could be several days to several weeks. The final step was dissipation of the residues at a greatly reduced rate through a combined action of dislodgment, volatilization, chemical degradation, and penetration into subsurface tissues. The occurrence of the second and final steps, designated on semi-logarithmic plots of pesticide dissipation as the degradation and persistence curves, respectively, was reviewed by GUNTHER (1969) for about 40 insecticides and acaricides on citrus fruit. WESTLAKE et al. (1973) demonstrated this phenomenon on both citrus fruit and foliage for the newer insecticide dioxathion. Much interest has been currently generated with respect to foliar residues because of the current belated emphasis on worker safety in pesticide-treated groves. The visible accumulation of dust on foliage has been recorded by many workers