Dermal Exposure Related to Pesticide Use - ACS Publications

PREFACE IT

IS G E N E R A L L Y RECOGNIZED that a potential health risk exists for

agricultural

workers

(applicators,

mixer-loaders,

harvesters,

and

field

workers) who are exposed to pesticides. Thus, since 1980, various symposia, including the one upon which this book is based, have been held to examine various parameters involved in the risk assessment of these workers due to

Downloaded by COLUMBIA UNIV on March 9, 2013 | http://pubs.acs.org Publication Date: February 25, 1985 | doi: 10.1021/bk-1985-0273.pr001

dermal exposure from pesticides. Although an abundance of literature has been published on the assessment of agricultural worker exposure, none integrates the three disciplines necessary for a complete risk assessment for field workers exposed to pesticides. These disciplines are dermal absorption, field exposure studies, and toxicology-risk assessment. This volume deals with these three disciplines and shows how they are integrated into a complete risk assessment for agricultural workers from dermal exposure to pesticides. The book is divided into five sections, each dealing with specific topics of risk assessment. The first section deals with the most recent views on dermal absorption of chemicals through human skin and experimental methods and techniques on how to arrive at quantitative absorption data using animal models or in vitro systems. The diversity of methodology presented in this section reflects the quickly evolving state of the art in this field. The

second and third sections are descriptions and results of field

studies with emphasis on methodology and specific compounds or specific applicator sites. The fourth section deals with trends in exposure assessment and protection and reflects some of the more creative approaches and research dealing with predicting exposure and protecting workers against exposure. Chapters 25, 26, and 27 deal with predicting exposure levels for agricultural workers. Although such predictive techniques would be generally welcomed by regulators, industrial scientists, and academicians, the contradictory nature of some of the material in these three chapters reflects the current status of such research, i.e., the final answer on predictive techniques and a generic data base is not in yet. M u c h discussion is needed before moving from these first generation data bases to a common, functional, well-received second generation data base. Furthermore, section four is a discussion of mathematical models and the use of fluorescent tracers in conjunction with television imagery, techniques that are seen by most researchers in the field to have the potential to replace older, more cumbersome, and less precise exposure

evaluation

xi

In Dermal Exposure Related to Pesticide Use; Honeycutt, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

techniques. The areas of the social impact of drift (unintentional exposure) and the use of protective clothing to eliminate exposure are addressed in this section, and they will be extremely important areas for

exposure-risk-

assessment research in the future. The last section is a discussion of the use of experimental data to arrive at risk assessment as recommended by states such as California, Canadian governmental regulatory agencies, and industry. These parties share a common goal, namely to make the workplace safe for agricultural workers who are exposed to pesticides through normal work activities. It is apparent from these last chapters that risk assessment for agricultural workers from dermal exposure to pesticides is an extremely complex


technique that is evolving rapidly and will require considerable

future

resources for it to be refined to a fine science. The editors of this volume, who

were also the organizers

of the

symposium, want to thank all the contributors who gave so generously of their time and experience, and who made this publication a valuable tool for scientists, administrators, and others charged with establishing rules and regulations for the safe use of pesticides. We would also like to thank our symposium session chairpersons, Joe Reinert (EPA), Rhoda Wang ( C D F A ) , Tom Fuhremann (Monsanto), Richard Moraski (EPA), and James Adams (EPA) for their contributions in making this symposium a success. RICHARD C. HONEYCUTT

CIBA-GEIGY GUNTER ZWEIG

University of California, Richmond NANCY RAGSDALE

Department of Agriculture November 1984

xii


INTRODUCTION T H E TWO BASIC DETERMINANTS of human health hazard for toxic chemicals, including pesticides, are exposure (or dosage) and toxicity (or effect). Information on both these determinants of hazard is necessary in arriving at a risk assessment for a particular pesticide or pesticide usage. The exposure parameter is particularly important for agricultural workers because of their


relatively greater contact with pesticides than is true for the general population. A preponderance of past and current health-related research on pesticide chemicals has emphasized study of acute and chronic toxicity, teratology and reproductive effects, genotoxicity, including mutagenic and carcinogenic effects, neurotoxicity, and other modalities of toxicity. Study of these effects undoubtedly represents a most important and necessary step in defining the human health hazard of these agents. However, in order to complete the risk assessment process, it is also necessary to have information on the exposure, or dosage, involved. Exposure to pesticides may occur through ingestion, by inhalation, and from skin contact. The major route of importance for the general population is through ingestion in food and water. Agricultural workers who have contact with pesticides in their occupation are exposed by the dermal and inhalation routes. Previous studies have shown that for most outdoor, fieldtype applications of pesticides dermal exposure is greater than respiratory exposure even when appropriate allowance is made for the greater speed and completeness of absorption by the inhalation pathway. Thus, the decision to target the symposium upon which this book is based to dermal exposure seems appropriate for agricultural workers. Two general types of methods are available for estimating human exposure to pesticides. First, direct entrapment methods involve the use of some mechanism to entrap the toxic material as it comes in contact with the person during an exposure period. The amount of entrapped toxicant, as determined by chemical analysis, is then a direct measure of the particular exposure under study. Further calculations using the kinetics of dermal absorption for the compound and formulation under study are required to arrive at the actual absorbed dose. For the oral and inhalation routes, exposure and absorbed dose are more closely equivalent than for the dermal route. However, for precise data, absorption must be taken into account for these routes, also. Second, indirect methods are based on measurement of some effect of the compound on the exposed individual (such as blood

xiii


cholinesterase level) or determination of the compound or its breakdown product(s) in the tissues or excreta (such as D D T in blood or p-nitrophenol in urine). In comparing these methods, the direct entrapment procedures give the advantage of providing an absolute value for a discrete exposure even within a sequence of repetitive exposures to the same pesticide. They can also be used to differentiate the relative contributions of oral, dermal, and respiratory exposure to the total exposure picture. This book provides an up-to-the-minute picture of the current status of research on measurement and risk assessment of dermal pesticide exposure


for agricultural workers. The chapters also provide an insight into some newer areas (applications of mathematical models, use of fluorescent tracer materials, and extrapolation from a computer data base of generic pesticide exposure data) that will undoubtedly be receiving increased attention in the future. W I L L I A M F. D U R H A M

Environmental Protection Agency Research Triangle Park, North Carolina December 1984

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Dermal Exposure Related to Pesticide Use - ACS Publications

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