Harvesters exposure, field study

Field studies involving pesticide applicators or mixer-loaders are contrasted with those involving harvesters. The effect of worker methods or work rate on exposure is mentioned. The Influence of the extraction method on the calculated dissipation rate of pesticides from foliar surfaces is discussed. Finally, biological monitoring and statistical problems are outlined. 

For harvesters, there are only a few field experiments described in the literature. The harvesting method and crop have been studied and some reports exist which can be compared. What seems apparent from these reports Is that the exposure process is the same for the harvesting of such tree fruits as citrus and apples. At least, the proportion of harvester exposure to pesticide on the leaf surface Is the same. For other types of crops this proportion may be different. 

Dermal exposure to captan and benomyl by strawberry harvesters has been the subject of several previous studies (1.2.3). This field study was designed to test a number of hypotheses and the reproducibility of dermal exposure rate measurements taken under field conditions. Most of our past studies have not been designed for a particular pesticide but were modified to accommodate the pesticide chosen by the grower to control a certain pest. In this case, the pesticide was carbaryl (1-naphthyl N-methylcarbamate) an insecticide used to control the spittlebug and leafroller. Our results could then he compared with those obtained by Maitlen and co-workers (A) who studied workers exposed to carbaryl in an apple orchard. Furthermore, attempts will be made to test possible positive correlations between age and dermal dose rate versus productivity and dermal dose rate versus age of harvesters. Difference of dermal exposure due to age or... 

A field operator exposure study was designed to accommodate the chemical properties and the use pattern involved in the treatment of potato crops for protection against the Colorado potato beetle. Fifteen farmworkers experienced in the use of tractor-drawn sprayers for application of crop protection materials to crops were selected. All were adult males. To avoid production of a large quantity of treated potato crop prior to registration of the product for sale, the trials were performed on stubble fields after harvest of winter wheat crops in a potato-growing area of southern Ontario. This allowed the use of typical farm spray equipment and a typical duration of exposure for a complete shift of work. 

This assessment included the estimate of the residues of PBO following application at the recommended application rate and at 10 times the single application rate- This incorporates two highly conservative assumptions. First, the I OX rate simulates the maximum number of applications allowed on the label and incorporates the unrealistic assumption that no degradation or dissipation occurs in the field (or all 10 applications are made at the same lime). This is a worst-case scenario considering the degradation predicted by the environmental fate studies and the actual levels of PBO observed in the field, as well as the low likelihood that 1U applications of PBO would ever be made prior to harvest. The second extremely conservative assumption used in this exposure assessment is that I009f- of the avian diet is derived from treated crop,... 

In addition, the 1981 and 1982 studies looked at the exposure received by IPM scouts who frequented the treated fields to make damage assessments. Harvesters were also addressed In the 81-82 work. Tables I-III give an outline of each years monitoring by chemical and devices. Extensive photodocumentation of our programs, particularly of the mixing operations In all four studies, proved Invaluable In Identifying exposure mechanisms. Since reproduction of this media Is not practical here, conceptual observations from this source will be Interjected Into the discussion of the four Individual programs. 

The harvesting operation is heavily mechanized for both commodities, so in this study human subjects are best described as either drivers or crew. Only one cabbage harvester registered any exposure, and that was limited to Systox on one chest patch for a crewman who stood on a platform and culled out small or rotten heads with a pitch fork. Cabbages were harvested from mineral soil fields in our study and there was little airborne dust during the operations. 

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