Field applicators mixer-loaders

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. 

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. 

Dermal Absorption and Dermal Dose-Resnonse. These data are needed in the risk assessment of field workers, mixers/loaders, applicators, and flaggers they may also be used in the development of reentry intervale. The data gathered informs CDFA of how much of the chemical actually enters the body once it comes into contact with the skin. Guides for these types of studies in test animals are available through, and were conducted by, the CDFA. At times, data from human volunteer studies are available when available, this type of information usually takes precedence over animal test data. 

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. 

Observations of the test subjects during the course of the field portion of the worker exposure or re-entry study are extremely important in order to interpret the data that are gathered at the field site and to interpret the final analytical data. There are two schools of thought when making observations of field workers during mixer-loader/applicator worker exposure or re-entry studies. 

The third approach for estimating risk from field data is the use of Monte Carlo simulation. This has been done in this study for the greenhouse mixer/loader/applicators,5 where the model that describes the relationship between the input variables is expressed by the following equation ... 

Oakland, B.G., Schabacker, D.J., Dodd, R.B., and Ross, R.H. (1992b) The evaluation of protective clothing as chemical barriers for mixer/loaders and applicators in agricultural field tests designed to meet FIFRA GLP testing standards, in Performance of Protective Clothing, Vol. 4, McBriarty, J.P and Henry, N.W., Eds., ASTM STP 1133, American Society for Testing and Materials, Philadelphia, PA, pp. 481-495. 

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 workers monitored were the mixer-loader (M) applicator (A) aerial flagger (F), bystander (B) i.e. a field worker near (within 100 feet) the tractor during applications and re-entry thinners (T). 

Ingestion is a possible route of exposure. Prometryn mixers, loaders, and applicators and field workers receive the most exposure by way of skin and eye contact, as well as from inhalation. The product is not available for use by the general public, so exposure to persons other than mixers, loaders, and applicators is limited to exposure by way of ingestion of food crops. However, risk due to ingestion of food is low because allowable residue limits on food crops are low. 

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. 

The purpose of this presentation Is to describe the results of field studies of dermal and Inhalation exposure of applicators and mixer-loaders to the fungicide mancozeb (DITHANE M-45 fungicide, 80Z active Ingredient wettable powder, a product of Rohm and Haas Company, Philadelphia, PA 19105, was used In these studies), a coordination product of zinc Ion and manganese ethyleneblsdlthlo-carbamate, and ethylene thiourea (ETU). The latter compound Is a decomposition product of all EBDC s (mancozeb, maneb, metlram, nabam and zlneb) and also Is produced from EBDC s as an artifact of the analytical procedure for ETU. 

The exposure of mixer-loaders and pilots during the airplane application of mancozeb to potato fields In Michigan, Minnesota and Oregon Is given In Tables VI, Vll and VIII. Mixer-loaders were exposed to mancozeb with forearms being most exposed (1125-9402 yg/body area). Pilots experienced very little exposure, but their hands did range from 58 to 1409 ig/body area. 

Table IX presents the exposure of persons Involved In the ground application of mancozeb by an alrblast sprayer to a tomato field In Ohio. Mixer-loaders again experienced exposure to mancozeb with forearms predominating (2856-3485 iig/body area). Tractor driver—applicators did not experience much exposure, but forearms did range from nondetectable to 1090 yg/body area. Home gardeners using a compressed air sprayer In a homeyard setting experienced little exposure to mancozeb (Table X), except for their ankle and thigh pads (nondetectable-4290 yg/body area).

The dermal and inhalation exposure of applicators and mixer-loaders to ethylenebisdlthlocarbamate and ethylenethlourea (ETU) was determined during field applications of mancozeb by airplanes In Michigan, Minnesota and Oregon, by alrblast sprayers In Ohio and by... 

C. Conrad, D. Cooper, C. Monitoring of Potential Exposures of Mixer-Loaders, Pilots, and Flaggers During Application of tributyl phosphorotrlthloate (DEF) and trlbutyl phosphorotrithl-olte (FOLEX) to Cotton Fields in the San Joaquin Valley of California in 1979. California Department of Food and Agriculture, 1981. 

Segmenting Field Tests Attempts should be aiade to segment a field worker s daily tasks into four areas - mixer-loader, applicator, cleanup worker, and flaggers (where appropriate). This technique allows one to determine which task produces the most exposure. These data can then be used to write precautionary labels directed at specific tasks. Of course, total exposure for workers carrying out combined tasks can be determined by summation. 

Replications Generally, field studies will be replicated 2-3 times. That is, complete studies are done at 2-3 different dates in the crop season. Each new study consists of two replications of each task, i.e., mixer-loader, applicator, cleanup worker. 

Example Estimate exposure of Chemical X (an emulsifiable concentrate) to mixer-loaders-cleanup workers and applicators while treating a field crop such as wheat using a boom sprayer. 

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. 

For applicator, loader-mixer groups we previously discussed sources of experimental variation. For harvesters, different sources of variation exist, but these may not be extreme. Theoretically, harvesters are exposed only to the residues remaining In the field. They are exposed most heavily when working In that field. The experiment appears simple. Pads are placed on the body of Che harvester at various locations, Che residues on leaves, fruit and soil are measured, and Che appropriate correlations are made. 

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