Levels of exposure to dichlorvos by farmers were investigated during or after the application of the organophorous insecticide to an apple orchard. One farmer applied 500 g of the pesticide as an active ingredient to the 30-are orchard for 20 min with an airblast sprayer. During the spraying work, a large amount of the chemical fell on his head and arms, but the quantities on his trunk and legs were smaller. The operator's dermal exposure level was estimated at 4.4 mg (=56μg/kg of b. w.), or 0.0009% of the total amount of dichlorvos sprayed. At 1 hr and 6 hrs after application, two other farmers entered the orchard for 30 min. They were expected to be systemically exposed to a small amount of the pesticide residues through contact with apple plants first entry, and their estimated exposure levels were 105 to 120μg (1.8-2.3μg/kg). However, it was found that the apple growers were not exposed to the residues during the subsequent reentry. The residue of 331 ng/cm² at the initial entry reduced rapidly thereafter and was not detected on the leaves at 2 days after application. Although the mean level of the pesticide in the air was 13.9μg/m³ at 1 hr, it lowered also rapidly and was not found at 1 day after application. It was considered that the workers in the orchard were not affected at 1 day after the spraying of dichlorvos.

Exposure levels of workers to fenpropathrin were studied during or after the application of the insecticide in a grape orchard. One farmer applied 25 g of the pesticide as an active ingredient to the 30-are orchard for 15 min with an airblast sprayer. The operator was most exposed on his legs, back and head. Consequently, his dermal exposure level was estimated at 783 μg (=12 μg/kg of b. w.), corresponding to 0.003% of the total amount of fenpropathrin sprayed. Another worker entered the orchard for 20 min at reular intervals during the period of 9 days after application. Upon entering 1 hr after application, the farmer was exposed predominantly on his head and to a lesser extent on his arms and back, and his estimated exposure level was 272 μg (=4.7μg/kg). At the subsequent reentries, his exposure level was reduced gradually, and no trace of exposure was recognized at the 9th day. Foliar residues were worked out at about 130ng/cm² 1 to 6 hrs after application, and thereafter decreased to 14ng/cm² at the 9th day. The dissipation of foliar residues of fenpropathrin was expressed in the following regression equation: Y (ng/cm²) =116-0.5 X (hrs). Thus, the half-life of fenpropathrin was estimated at 100 hrs on grape-leaf surfaces. Also, the dermal exposure levels of the reentering worker were correlated with the foliar residues, and when the residues on the leaves were reduced to less than 27 ng/cm², it was suggested that contact with leaves do not cause dermal exposure.

Exposure of applicators to metalaxyl was assessed during the spraying to greenhouse cucumbers by power sprayers. Of four applicators wearing work clothes with a hood, a mask and gloves, two moved forward holding the nozzle in their hands so that they passed through the area sprayed by them. The other two went backward and sprayed both sides. Each of the applicators sprayed 14 to 18 g of metalaxyl during one hour of application. The estimated systemic expoure level in the forward moving group was 1 to 10 mg, 3 to 40 times higher than the exposure level of 0.25 to 0.29 mg in the backward group. But, skin exposure was insignificant or not detected in both groups. Also it was suggested that respiratory exposure was higher in the forward moving group than that in the backward group. In conclusion, when applying metalaxyl by any spraying techniques, the risk of poisoning was thought to be negligible under this research condition. However, the workers should employ the spraying technique moving backward, and be protected with suitable protective gear for preventing acute or chronic pesticide intoxications.

When workers were applying the same volume of a TPN formulation to asparagus fields of the same acreage by a speed sprayer or a conventional power sprayer, their exposure levels to the pesticide were compared. The estimated body exposure level of workers using power sprayer was more than 10 times higher than that of workers using a speed sprayer. The fate of TPN residues in the fields was also assayed. The foliar residues reduced rapidly in one day, but thereafter its reduction rate was very slow, and TPN was expected to remain on the foliage for a long period. However, the airborne TPN concentration was reduced to nil at 1 day after application.