Chlorpyrifos worker exposure data

Use of probability and distributional analysis of chlorpyrifos worker exposure data for the assessment of risks... 

Table 5 presents data on field spike recoveries. Recoveries of chlorpyrifos from "low" spiked substrates in the California studies ranged from 62.5 to 126%, and recoveries of chlorpyrifos from "high" spiked substrates ranged from 93.7 to 133%. In the Florida, Arizona, and Michigan studies, all recoveries ("low" and "high") ranged from 61 to 158%. The field recoveries cited above were found to be reasonable and within the range of field recoveries seen in many worker exposure studies. 

Table 2 summarizes the re-entry exposure data from studies with chlorpyrifos.1 There are fewer replicates for these workers which would seem to be justified by the lower variability in the data sets. There are practically no differences between the arithmetic and geometric means for these data sets. 

When the data in Table 4 were given full evaluation, it was recommended that the 50W formulation of chlorpyrifos no longer be marketed in bags that allowed significant exposure for mixer-loaders of this product. This product was removed from the marketplace and was replaced with one in which the wettable powder (WP) is in water-dissolvable packets. Exposure data on other active ingredients have clearly demonstrated reduced exposure with this type of packaging. The other uses were deemed to present a minimal hazard to users, and only minor protective measures have been recommended to workers. 

In order to determine the dermal exposure of volunteers to chlorpyrifos, the penetration of chlorpyrifos through the outer whole-body dosimeter (coveralls) to the inner body dosimeter (t-shirt and briefs) was measured. The penetration factor was calculated for each volunteer in the study from the experimental data by dividing the amount of chlorpyrifos on the t-shirt and brief sample by the amount of chlorpyrifos on the torso section of the coveralls. This method of calculation assumes that the surface area of the torso section of the coveralls is nearly the same as the surface area of the t-shirt and briefs worn directly under the torso section of the coveralls. A mean penetration factor for each worker type was calculated by averaging all the worker volunteer... 

Assessments of risks associated with the use of chlorpyrifos insecticide products for workers have been made. The assessments are based on the results of field studies conducted in citrus groves, a Christmas tree farm, cauliflower and tomato fields, and greenhouses that utilized both passive dosimetry and biomonitoring techniques to determine exposure. The biomonitoring results likely provide the best estimate of absorbed dose of chlorpyrifos, and these have been compared to the acute and chronic no observed effect levels (NOELs) for chlorpyrifos. Standard margin-of-exposure (MOE) calculations using the geometric mean of the data are performed however, probability (Student s f-test) and distributional (Monte Carlo simulation) analyses are deemed to provide more realistic evaluations of exposure and risk to the exposed population. 

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