Microsystem Technology for On-Site Biological Monitoring of Occupational VOC Exposures

Faculty Researcher: Joseph A. Potkay, PhD, Research Investigator at the Veterans Administration Ann Arbor Healthcare System and Adjunct Research Investigator in the Department of Surgery at the University of Michigan

Cross-section diagram of the μVE demonstrating molecular diffusion of a three compound mixture.

The assessment of occupational exposures to toxic organic compounds remains an essential component of efforts to protect worker health by informing epidemiologic investigations, demonstrating compliance with exposure standards/guidelines, and gathering proactive surveillance data. Measuring contaminants or their metabolites in biological fluids, if properly conducted and interpreted, can provide more relevant information about exposure than merely measuring air concentrations. Doing so in the field with ultra-low-volume samples represents an enticing prospect for advancing occupational exposure science. We propose to develop and test the capabilities of a passive, microfabricated membranemediated device for extracting volatile biomarkers of exposure to various volatile organic compounds (VOC) from ~μL volumes of urine, saliva, and blood. As envisioned, this microscale vapor extractor (μVE) will serve as a disposable front-end interface for a hand-held, battery-powered micro-scale gas chromatograph (μGC) being developed under separate funding. Combining the μVE and μGC will permit rapid field or clinical analyses of biological fluid samples for assessing occupational VOC exposures. The proposed μVE is a derivative of an extant artificial lung technology (Fig. 1), which will be redesigned and repurposed for this application. Devices will be fabricated on campus and then interfaced to a bench-scale GC instrument for initial characterization with respect to extraction efficiency and required sample volumes over ranges of expected target-analyte concentrations in spiked artificial urine, saliva, and blood. The target analytes will comprise a set of 10 VOCs and metabolites for which ACGIH Biological Exposure Indices (BEI) have been established. Following screening experiments, the μVE will be fluidically integrated with one of our μGC prototypes and re-tested to demonstrate feasibility for follow on funding. The successful project would produce an enabling new technology that would facilitate onsite biomonitoring of workers at lower cost by minimally trained OH professionals. This work addresses NORA priorities in the Exposure Assessment Cross-Sector.

Cross-section diagram of the μVE with a close-up of the VOC diffusion interface and equivalent circuit (left and middle). A top-view diagram of the liquid flow channels in the VE (right) showing large diameter routing channels (red and orange) and the array of small diameter extraction microchannels (yellow).