Pesticide mixer, loader, applicator exposure

D.R. Hackathorn and D.C. Eberhart, Database proposal for use in predicting mixer-loader/applicator exposure, in Dermal Exposure Related to Pesticide Use Discussion of Risk Assessment, ed. R.C. Honeycutt, G. Zweig, and N.N. Ragsdale, ACS Symposium Series 273, American Chemical Society, Washington, DC, pp. 341-355 (1985). 

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. 

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. 

Chester, G., Loftus, N.J., Woollen, B.H., and Anema, B.P. (1990b) The effectiveness of protective clothing in reducing dermal exposure to, and absorption of, the herbicide fluazifop-P-butyl by mixer-loader-applicators using tractor sprayers, in Book of Abstracts, Seventh International Congress of Pesticide Chemistry, Vol. Ill, Freshe, H. and Kesseler-Smith, E., Eds., Conway, Hamburg. 

Generally speaking, the equipment that workers use and the type of agricultural work performed while handling pesticides or pesticide-treated commodities have a major impact on the level of exposure a worker receives. Neat work habits generally lead to lower exposure for agricultural workers who handle pesticides. The current Pesticide Handlers Exposure Database (PHED), which is used to predict exposure to mixers/loaders/applicators, is based on this concept. 

Krieger, R.I., C. Blewett, S. Echniston, H.R. Fong, D.D. Meinders, L.P. O Connell, F. Schneider, J. Spencer, T. Thongsinthusak and J.H. Ross (1990). Gauging pesticide exposure of handlers (mixer/loader/applicators) and harvesters in California agriculture. 

Pesticide usage factors include those factors needed to characterize the amount of pesticide an individual is potentially exposed to each day, as well as the duration, frequency and interval of potential exposures. For example, for mixer/loaders/ applicators, this would include hectares typically treated per day, typical application rates, types of equipment used, and whether application is conducted by the farmer or a custom applicator. 

Krieger R (1990) Gauging pesticide exposure of handlers (mixer/loaders/applicators) and harvesters in California agriculture. Proceedings of the Pesticide Workshop. Milan... 

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. 

The purpose of this article is to present a detailed description of the current field methods for collection of samples while measuring exposure of pesticides to farm workers. These current field methods encompass detailed descriptions of the methods for measuring respiratory and also dermal exposure for workers who handle the pesticide products directly (mixer-loaders and applicators) and for re-entry workers who are exposed to pesticide dislodgeable residues when re-entering treated crops. 

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. 

The use of closed systems has been required in California for transfer of toxicity category one liquid pesticides from the manufacturer s container into the mix tank and then into the application vehicle tank. It appears that this process has considerably reduced both dermal and inhalation exposure. The use of probes that are inserted and then removed from containers reduces dermal exposure up to ten-fold it also appears that the use of built-in probes further reduces exposure to the mixer-loader by up to another ten-fold factor in some cases. 

Exposure by workers in the manufacture of agricultural chemical products or by the mixer, loader or applicators who use these products may be considerable. Thus, the risk to these workers may be greater than to the consumer of treated products. The two recognized major routes of exposure are inhalation and topical. However, contrary to what was first believed, topical exposure constitutes the major route and it is for this reason that interest in percutaneous absorption of pesticides has increased to a considerable degree. 

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. 

Applicators and mixer-loaders certainly receive different levels and types of exposure than do harvesters. The mixer-loaders have an opportunity for concentrate as well as drift exposure. The applicator Is primarily exposed Co drift and Che tank mixed material. The harvester Is exposed to a presumably homogeneous application of pesticide on fruit, leaf, and soil surfaces. Both groups may also be exposed by working on or around contaminated machinery and In or around contaminated loading areas. 

There has been some concern over the method of pesticide extraction, particularly for harvester exposure residues. For applicators and mixer-loaders, methods can be developed as needed with defined... 

Applicator and Mixer/Loader Exposure to Pesticides During Ground Boon Spraying Operations," Environnental Protection Agency, 1984. 

Estimates of Field Worker Exposure to Pesticides An example will be presented to show how estimates of lifetime field worker exposure can be made and show how a number of the factors above come into play during such calculations. These calculations apply only to chemicals which demonstrate chronic toxicity predominantly. Shorter term estimates must be made for chemicals showing acute toxicity. For this exercise consider only field crops such as wheat, corn, and soybeans. The example presented here will deal with one application type, i.e., ground boom spray application. Mixer-loaders, cleanup workers and applicators will be considered. Factors such as effectiveness of protective clothing will also be considered. Further, this example will consider only an individual farm operation scenario. 

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. 

Field testing on the efficacy of different types of clothing materials in reducing pesticide exposure to applicators and mixer/loaders. parel six h as coveralls, hats, suits, aprons, hand and foot coverings could be test under actual agricultural use conditions. 

The following are some of the data that may be required by CDFA to assist in making exposure estimates of persons involved in various activities involving the use of pesticides indoor exposure field reentry mixer, loader, and applicator exposure, dermal absorption, and dermal dose response data. 

Appendix One Dermal Exposure Monitoring of Mixers, Loaders, and Applicators of Pesticides in California... 

California regulations require daily provision and use of clean coveralls or other clean outer clothing to mixers, loaders, flaggers, and applicators of any pesticide in toxicity Categories I and II (12). These requirements serve to reduce the potential dermal exposure of workers to pesticides by decreasing the area of bare skin available for contact with the chemicals. 

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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