Worker exposure field methods

Izmirova H. 1980. Methods for determination of exposure of agricultural workers to organophosphorus pesticides. In Tordoir WF, Van Heemstra EA, eds. Field worker exposure during pesticide application. New York, NY Elsevier Sci. Publ. Co., 169-172. 

Field methods for performing farm worker exposure and re-entry studies... 

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. 

Current field methods for measuring mixer-loader and re-entry worker exposure to pesticide residues... 

The test substance may be acquired in a number of ways. One common method is to purchase the product from a chemical dealer. This method of acquiring the test substance for a worker exposure or re-entry study allows one to proceed rapidly with the execution of the field portion of the study without the serious delays encountered while waiting for a test substance to be manufactured, assayed, and shipped to the site. Although having a test substance formulation which has been assayed under GLP standards and for which a certificate of analysis has been shipped to the test site is desirable, there are several instances when this is not practical. For example, one may encounter a worker exposure study where the pesticide to be evaluated is sold only in mini-bulk or even large bulk quantities holding as much as 2000 gal. In this case, duplicate 5-10-g or 5-10-mL retainer samples should be taken from the bulk or mini-bulk tanks for assay after the worker exposure study is in progress. 

The industry task forces (ARTF, ORETF, and others) are generating model protocols, efficient and accurate methods of sample collection, and analytical methods of appropriate detectability for use in field-worker exposure studies. Subsequently, the task forces are conducting field studies that will generate data for inclusion in several generic databases. It is understood that the databases will be the property of the member companies who have financed the work of the task forces. It is hoped, however, that the task forces will see fit to publish their protocols, methods, study designs, and other useful information in a volume like this one so that other scientists working in this discipline may access the information. 

Assessment of worker exposure to pesticides through field studies requires collection devices placed on or near the worker, extraction techniques, quantification of the chemical, and statistical analysis. We present an overview of these methods with specific attention given to dermal absorption pads, their proper placement at various body locations, and the statistical variability in pad contamination which commonly results. Use of personal air samplers is reviewed. 

Many of the methods reviewed here have been previously reviewed by Davis. It is our purpose to update that review and to relate our personal experiences with existing devices for monitoring worker exposure in order to assist other prospective researchers with the experimental design of field experiments. 

The previous chapter presented results from field studies in which exposures were measured for workers involved with the use of the insecticide chlorpyrifos in several use scenarios and for persons who might re-enter treated areas. In this chapter, the results from these studies are handled by several methods to demonstrate the advantages of using probability and distributional analyses, rather than single point values, for the characterization of risks to pesticides. 

The NTP has recently completed a series of inhalation studies in rats and mice, including both noncancer and cancer evaluations. The results of these studies will provide valuable new data on the toxicity of this compound in animals. Dr. W. Kilgore (University of California, Davis) is studying methods for detecting exposure of field workers to bromomethane, and is obtaining data on health effects in these workers. 

The Department has developed methods for monitoring the exposure of workers exposed to organophosphate and carbamate pesticides. These methods utilize the determination of plasma and red blood cell cholinesterase activities and urinary alkyl phosphates. Studies are reported vrti ich show that these methods have proven useful in evaluating the safety effectiveness of closed-transfer systems and in determining reentry times for field workers. 

The apparent rate of excretion was slower after dermal exposure than after oral administration, probably due to slower absorption of the 2,4,5-T ester from the skin than 2,4,5-T acid from the gut. This is in agreement with observations made by Feldmann and Maibach for 2,4-D and other pesticides applied to the forearm of human volunteers (13). Calculations by Ramsey et al. using three methods showed that 97% of the 2,4,5-T absorbed by forest workers would be excreted in urine within 7 days following dermal exposure under typical field conditions (16). 

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