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A BRIEF HISTORY OF THE DEVELOPMENT OF EXPOSURE ASSESSMENT METHODS AT US EPA/NERL USING ALVEOLAR BREATH AS THE BIOLOGICAL MEDIUM
Citation:
Pleil, J D. AND A B. Lindstrom. A BRIEF HISTORY OF THE DEVELOPMENT OF EXPOSURE ASSESSMENT METHODS AT US EPA/NERL USING ALVEOLAR BREATH AS THE BIOLOGICAL MEDIUM. Presented at Environmental Sampling and Analysis Seminar, Okinawa, Japan, July 8-22, 2001.
Impact/Purpose:
The objective of this task is to develop state-of-the-art methods for measuring xenobiotic compounds, to include the isolation of the analyte from the appropriate matrix (extraction), preconcentration (typically sorbent-based), and analysis via GC/MS and/or LC/MS. Once established, these methods will be applied in small scale pilot studies or demonstration projects. Particular emphasis will be placed on methods which are readily transferable to other laboratories, including those within the Human Exposure and Atmospheric Sciences Division (HEASD), the National Exposure Research Laboratory (NERL), other EPA Laboratories, Program Offices, Regions, and academic institutions.
Specific objectives of this task include the following:
1) Development of GC/MS and LC/MS methods for the measurement of key xenobiotic compounds and their metabolites (to include the pyrethroid pesticides, perfluorinated organic compounds, and the BFRs) in relevant environmental and biological matrices.
2) Development of efficient low cost methods for the extraction and clean up of these compounds collected from relevant matrices.
3) Determination of xenobiotic compound and metabolite concentrations in samples derived from laboratory and field monitoring studies to help assess exposures and evaluate associated risks.
Description:
Historically, ambient air (and perhaps water, soil, food, etc.) measurements were used to estimate the potential for human exposure to environmental pollutants based on various default assumptions. For instance, if a certain level of benzene was measured in the air, then a typical breathing rate times a typical pulmonary uptake percentage would yield an available blood dose approximation. This would, of course, neglect the potential for additional dermal or ingestion exposure from contaminated water unless these measurements were also made. Philosophically then, a direct measurement of this hypothetical benzene in the exhaled breath (rather than in the ambient air) would not only include the possibility of all exposure routes (inhalation, dermal, ingestion), but would also unambiguously demonstrate that such an exposure had actually occurred. After all, benzene could not come out in the breath if it had not originally entered the body somehow. Additionally, the absolute amount of the benzene in the breath can be directly coupled to the amount in the circulating blood much like blowing into the classic police "breathalizer" instrument for alcohol infers the blood alcohol level. Finally, a series of time dependent measurements during exposure, and later after the exposure is over, can tell the researcher about the chemical's human pharmacokinetics (that is, where in the body and how long a time did the chemical reside).
Researchers at the EPA's National Exposure Research Laboratory have developed and refined alveolar breath collection and analysis techniques over the past six years and have applied them to a variety of environmental investigations. This lecture presents the evolution and application of breath measurement as practiced in the Methods Development group and gives a detailed description of the sampling and analytical strategies. The focus is primarily on the use of rigid stainless steel canisters used for sampling and the methods for subsequent laboratory analysis by gas chromatography - mass spectrometry. The concepts of time dependent measurement and interpretation of the data are explained in the context of extracting valuable biological data such as residence time, target organ dose, and overall dose estimation. Various studies are presented and the results are discussed to demonstrate the utility of breath measurement for practical exposure assessment. Specifically, measurements of environmental exposure to carcinogens or suspected carcinogens such as vinyl chloride, chloroform, bromodichloromethane, benzene, trichloroethylene, and MTBE are presented. Also, the method for assessing exposure to JP-8 jet fuel, a complex mixture of thousands of hydrocarbons, is shown. Further potential applications of breath techniques in future studies are presented and concepts concerning the use of endogenous biomarkers (compounds produced by the body in response to an exposure) are introduced.
This work has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and administrative review process and approved for presentation and publication. Mention of tradenames or commercial products does not constitute endorsement or recommendation for use.