Pesticide assessing human exposure

Krieger, R.I., Ross, J.H., and Thongsinthusak, T. (1992) Assessing human exposure to pesticides, Rev. Environ. Contam. Toxicol., 129 1-15. 

It is difficult to assess human exposure to pesticides. Several studies have measured pesticide residues in human fat (MAFF, 1995) or human milk (MAFF, 1997), as both matrices are good indicators of long-term exposure, but they tell little of the subject s exposure to short-lived pesticides such as the OPs or pyrethroids. 

So, what remains is to assess human exposure to the pesticide. While I do not want to discuss exposure asessment extensively today - it is not our topic - I think a brief discussion would clarify how risk assessments based on toxicity data are used in completing a full hazard assessment. Exposure assessment is not a new art. It is, however, an area that requires a lot of work. Most often we do not have monitoring data to precisely describe human exposure, for example. Models are bing used to predict these exposure patterns but no standard process for making these predictions has yet been established. 

Houghton, E.R. Standardized scenarios of pest control situations as a means of assessing human exposure to pesticides. Agriculture Canada, Ottawa, 1978. 

J.N. Seiber and J.E. Woodrow, Airborne residues and human exposure, in Determination and Assessment of Pesticide Exposure, ed. M. Siewierski, Studies in Environmental Science 24, Elsevier, New York, pp. 133-146 (1984). 

Maroni, M. (1986) Organophosphorus pesticides, in Biological Indicators for the Assessment of Human Exposure to Industrial Chemicals, L. Alessio, A. Berlin, M. Boni, and R. Roi (Eds.), Commission of the European Communities (EUR 10704), Brussels, Lusembourg, pp. 51-72. 

Richard C. Honeycutt, Ph.D., was born in Newport News, VA, in 1945. He attended Anderson University in Anderson, IN, from 1963 to 1967 and earned an A.B. in Chemistry. He received his Ph.D. in Biochemistry from Purdue University in 1971 and served as a Postdoctoral Fellow from 1971 to 1973 at the Smithsonian Institution s Radiation Biology Laboratory. Dr. Honeycutt worked as a Senior Chemist at Rohm and Haas Company from 1973 to 1976 and as a Senior Metabolism Chemist at Ciba Geigy from 1976 to 1989. Currently, he is President of the Hazard Evaluation and Regulatory Affairs Company, Inc., which he founded in 1990, and is an analytical biochemist and field research specialist/consultant engaged in exposure assessment of pesticides to humans and the environment. 

The EPA does consider health criteria when determining whether to approve or deny a manufacturer s petition to have a tolerance established. Human health risk assessment practices consider potential human exposure from all registered (and proposed) uses of the pesticide, and if the risk is deemed excessive, the EPA will deny the tolerance petition. In cases where the risks are deemed acceptable, the EPA will establish tolerances, as described in the previous paragraphs. 

In order to assess the potential extent of human exposures and health effects, members of dairy farm families who consumed raw dairy products known to be contaminated with heptachlor epoxide were studied (Stehr-Green et al. 1986). These individuals and an unexposed urban reference population were compared with regard to serum pesticide levels and liver toxicity. The farm family members had significantly higher mean serum levels of heptachlor epoxide (0.81 0.94 ppb), oxychlordane (0.70 0.75 ppb), and transnonachlor (0.79 0.60 ppb) than the unexposed population. This study is limited because exposure level, duration, and frequency of exposure are not known. There was no increase in prevalence of abnormal liver function tests in the dairy farm families... 

Pesticide registrants must also submit environmental fate and effects data to the EPA as part of an application for pesticide registration. The EPA uses such environmental data to characterize the persistence and partitioning of a pesticide in the environment and the pesticide s environmental metabolites and degradates. This information is used by the EPA to assess the potential for human exposure via drinking water contamination and environmental exposure of organisms such as fish, wildlife, and plants to the pesticide or its metabolites. 

Exposure data are important in any assessment of pesticide safety. 2,4-D is a widely used herbicide so that opportunities exist for obtaining reliable quantitative data on exposure levels in several occupational situations. One method of measuring human exposure is by measurement of 2,4-D levels in urine, because most... 

The committee recommends the inclusion of a detailed and accurate exposure analysis for a subset of the biomonitored population in large-scale biomonitoring studies that includes analyses of environmental media in the residence and uses a survey instrument to obtain information on diet, consumer product use, occupational exposures, and other factors relevant to the chemical exposure pathways that are being examined. The exposure assessment can be patterned on protocols used in other exposure analyses, such as the National Human Exposure Assessment Survey (NHEXAS), the Minnesota Children s Pesticide Exposure Study, and Children s Total Exposure to Pesticides and Other Persistent Organic Pollutants. 

Development of Analytical Methodology for Assessment of Human Exposure to Pesticides... 

Assessment of human exposure to pesticides is important for a variety of reasons. In the occupational situation, it is necessary to know the amount of pesticide that an individual is exposed to in order to protect worker health. Formulators, loaders, pickers and pilots can experience high exposures to pesticides. Humans can be exposed to pesticides through environmental routes. The air we breath and the water we drink are but two sources of environmental exposure. 

Measurement of human exposure can be done either directly or indirectly. Direct measurement involves determination of the pesticide level in the media through which the exposure occurs. Examples of this are measurement of pesticides in breathing zone air or pesticides adsorbed onto pads or clothing worn by workers (1, 2). These techniques provide a direct and calculable measure of human exposure under actual conditions. Most often, however, direct measurement is not possible. In these situations indirect methods of exposure assessment must be used. 

In summary, and at the risk of repetition, it must be stressed that the development of analytical methodology for the assessment of human exposure to pesticides is a complex process. Careful attention to planning of the research is of utmost importance. As much information as possible about transformation, storage and excretion of the pesticides of interest should be gathered. Preliminary work should focus on the analytical behavior of parent compounds and metabolites. The combination of these aspects with reliable analytical standards and a sound quality assurance program should yield valid analytical methodology. 

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