Carbaryl thinners

The HDE on hands of thinners working in an apple orchard treated with carbaryl correlated with total extractable residues from apple leaves (r=0.99). The loss of residues of carbaryl on apple leaves was found to occur by 2 first-order processes 87% of the residue was lost with a half-life of 8 days, and the rest with a half-life of 45 days. 

Comer et al. (2) therefore evaluated the effect of exposure to carbaryl (1-naphthyl methylcarbamate) on formulating plant workers and on workers applying carbaryl to fruit orchards with a tractor-drawn air-blast sprayer. However, information was still needed on the persistence of carbaryl in apple orchards and on the resultant exposure of workers who re-enter treated orchards. Further, no studies had been done on other types of crops. The present study was undertaken to determine the exposure of agricultural workers to carbaryl as a function of type of formulation, application equipment, application method, and type of work performed (i.e., mixer-loader, applicator, flagman, bystander, and apple thinners). 

Workers associated with the application of carbaryl (applicator, mixer-loader, bystander and aerial flagger) and re-entry workers (apple thinners) were monitored by a modification of the procedure of Durham and Wolfe (3). The workers were fitted with a disposable jacket (Safety and Supply Co., Seattle, WA) to which 10 x 10 cm pads were attached with masking tape. One pad was attached as close to the neck as possible on each shoulder and on the chest and the back of each subject. One pad was also placed on each forearm midway between the elbow and wrist. The pads were constructed by backing an 8 ply gauze compress with two pieces of heavy filter paper and attaching these together in the center with a staple. 

Thinners. Carbaryl is applied to apple trees as a thinning agent, but sometimes it is necessary to send workers into the treated orchard to finish the thinning by hand. For this situation, we studied the relationship between the persistence of carbaryl on apple leaves and the exposure to thinners working in this orchard. 

Figure 2. Residues of carbaryl found on thinners hands (Y) as a function of residues found on leaves (X) for 0.5 and 1.0 lb/100 gal application rates (2.0 lb AI and 4.0 lb Al/acre) (Y — 690X — 45 correlation coefficient (r) = 0.99).

There are, however, several apparent discrepancies. The first is the ratio calculated from literature values dealing with carbaryl exposure to pesticide applicators and fruit thinners in an apple orchard (4) This ratio (about 0.6x10 cm h ) was considerably lower than the range seen in Table IX. The difference may be due to the fact that Maitlen et al. (4) measured total and not dislodgeable foliar residues, thus leading to lower values than those obtained by us and others. 

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