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IMMUNOASSAY HUMAN EXPOSURE STUDIES
Citation:
Van Emon, J M., A W. Reed, AND J. C. Chuang. IMMUNOASSAY HUMAN EXPOSURE STUDIES. Presented at American Chemical Society, Pacifichem 2000, Honolulu, HI, December 14-19, 2000.
Impact/Purpose:
The overall objectives of the task include several components: (1) develop immunochemical methods for compounds difficult to analyze by conventional methodologies; (2) tailor immunochemical methods to support specific human exposure assessment studies; (3) team immunochemical sample preparations with instrumental analysis such as mass spectrometry for in-depth sample characterization; (4) provide methods to support NERL's human exposure and environmental monitoring efforts; (5) provide analytical methods that improve risk assessments by reducing the amount of uncertainity in environmental measurements; (6) provide multimedia analytical methods to support an integrated multimedia approach to assess and characterize risk to human health and the environment; (7) provide sponsorship of annual immunochemistry research meetings as a forum for stimulating interest and discussion on current or emerging bioanalytical methods; (8) develop and incorporate rapid, cost-effective laboratory and field portable immunochemical techniques such as enzyme-linked immunosorbent assay (ELISA) methods into monitoring studies and human exposure field surveys to delineate sub-populations of "highly exposed" individuals for detailed follow-up studies.
Specific method needs have been identified through consultations with client office personnel. This Task strives to fulfill those needs as appropriate. In particular, methods for pyrethroids, e.g., permethrin, cypermethrin, and deltamethrin are being developed and evaluated. Efficient sample preparations are under development for exposure samples using pressurized liquid extraction. Confirmation will be achieved using high performance liquid chromatography (HPLC). A rapid immunoassay approach for the analysis of 2,4-D in urine will be completed and a SOP and report written. Immunoaffinity chromatography sample preparations for the pyrethroids will be developed. Work will continue on the application of antibody replacements such as molecularly imprinted polymers. Additional candidate analytes will be identified for a tiered approach and to guide development of the next Task. Flexibility will be maintained to address methods and measurement issues as they arise during the task period which ends in FY06. The objective of the Task is to develop bioanalytical methods to support exposure monitoring studies during the task period.
Description:
The Human Exposure Research Branch has developed several enzyme-linked immunosorbent assay (ELISA) methods to support human exposure assessment studies. Immunoassays to detect low levels (<10 ng/mL) of chlorpyrifos in food, track-in dirt and house dust have been applied to samples from dietary and indoor exposure surveys. Accelerated solvent extraction procedures followed by cleanup with solid phase extraction have been coupled with a chlorpyrifos ELISA for baby food and dietary samples. Recoveries greater than 90% were achieved for various food matrices. A methanol extraction with sonication followed by ELISA determination provided a streamlined method for analyzing chlorpyrifos from dust and track-in dirt. An immunoassay for the urinary metabolite of chlorpyrifos, 3,5,6-trichloro-2-pyridinol (TCP), has been optimized and evaluated using real-world samples from several monitoring studies. TCP is a major metabolite and environmental degradation product of the insecticide chlorpyrifos and the herbicide triclopyr. Comparative studies with GC/MS indicate a good correlation with the TCP assay at low ppb levels. The least detectable dose estimated for this assay is 0.01 ppb in hydrolyzed and diluted urine samples. Immunoassay results were compared with GC/MS measurements from occupational and nonoccupational exposure studies yielding good correlations (r=0.990 and r=0.970). An advantage of the ELISA method is the capability of rapidly providing exposure data during spray events.
This work has been funded wholly or in part by the U.S. Environmental Protection Agency and has been approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.