Exposure studies, pesticide mixer, loader

Dermal Exposure Levels. Setting acceptable maximum dermal exposure levels to specific pesticides has been difficult. This is primarily due to a lack of specific data on dermal transport rates for specific pesticides as related to adverse effect levels and presumed no-effect levels. We are now requiring such data from the registrants, and our Department has a suggested protocol (1) that is offered to registrants that will provide such information from animal exposure studies. This dermal transport rate information is important in setting minimum field reentry intervals for field workers as well as in evaluating exposure levels of mixers, loaders, and applicators. 

Applicators, mixers, loaders, and others who mix, spray, or apply pesticides to crops face potential dermal and/or inhalation exposure when handling bulk quantities of the formulated active ingredients. Although the exposure periods are short and occur only a few times annually, an estimate of this exposure can be obtained by quantifying the excreted polar urinary metabolites. Atrazine is the most studied triazine for potential human exposure purposes, and, therefore, most of the reported methods address the determination of atrazine or atrazine and its metabolites in urine. To a lesser extent, methods are also reported for the analysis of atrazine in blood plasma and serum. 

Both inner and outer whole-body dosimeters are common tools to measure successfully dermal exposure to pesticide workers and are employed in a variety of ways in mixer-loader/applicator or re-entry studies. 

Another consideration when planning field fortification levels for the matrices is the lowest level for fortification. The low-level fortification samples should be set high enough above the limit of quantitation (LOQ) of the analyte so as to ensure that inadvertent field contamination does not add to and does not drive up the field recovery of the low-fortification samples. Setting the low field fortification level too low will lead to unacceptably high levels of the analyte in low field spike matrix samples if inadvertent aerial drift or pesticide transport occurs in and around where the field fortification samples are located. Such inadvertent aerial drift or transport is extremely hard to avoid since wind shifts and temperature inversions commonly occur during mixer-loader/re-entry exposure studies. 

Mixer, Loader, Applicator Exposure Studies. A major difficulty in making hazard assessments for mixers, loaders, and applicators is the lack of information on how much of the pesticide may be inhaled or may reach the skin under a typical use situation. 

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. 

Until recent years, research devoted to the pesticide exposure of agricultural workers was essentially nonexistent. It has been established that a major source of exposure to toxic chemicals is the use of such chemicals in agricultural production. In general, applicators and mixer/ loaders have the hipest exposure risk. Mary studies have shown the exposure to applicators skin to be well over 90% of their total exposure. The only significant type of barrier available to applicators to reduce dermal contact and hence exposure is protective clothing. 

The actual biological monitoring of workers to detect evidence of exposure such as a drop in blood cholinesterase levels or the presence of a urinary metabolite is superior to the indirect techniques employed in this study. Realizing the difficulties in accurately determining the dermal exposures of mixers, loaders, and applicators to pesticides, the employment of simpler monitoring techniques than the ones performed by CDFA in this report might... 

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