Passive Micro-Sampler with Facilitated On-Site Analysis for Multi-Vapor Worker Exposure Monitoring

Research Trainee/Student Investigator: Changhua (Henry) Zhan, Doctoral Student, Department of Environmental Health Sciences, University of Michigan

Principal Investigator/Faculty Supervisor: Edward T. Zellers, PhD, Professor, Department of Environmental Health Sciences, University of Michigan

Changhua (Henry) Zhan

Changhua (Henry) Zhan

Professor Zellers

Professor Zellers

The adverse health effects of volatile and semi-volatile organic compounds (S/VOCs) can range from mild respiratory tract irritation to severe organ toxicity and cancer. The measurement of exposures to toxic S/VOCs is critical to protecting the health of people at work by defining exposure-response relationships in epidemiologic studies, establishing reasonable workplace exposure limits, and determining compliance with such limits. Since the Permissible Exposure Limits issued by the US Occupational Safety and Health Administration and the Threshold Limit Values (TLV®) of the American Conference of Governmental Industrial Hygienists (ACGIH), require personal sampling to demonstrate that worker exposure complies with the 15-min or 8-hr exposure concentration limits, there is a need for wearable devices to monitor worker exposures. This project concerned the development of a passive, lapel-mountable, Si-microfabricated passive sampler (μPS) capable of collecting, at a known rate, any volatile and semi-volatile organic compounds (S/VOC) in the breathing zone of a worker for exposure periods ranging from 15 minutes to 8 hours. As envisioned the μPS chip would then be inserted into a custom sample-transfer fixture connected (ultimately) to a field-portable or “micro” gas chromatograph (GC or μGC) and heated to desorb/inject captured S/VOCs for immediate, on-site analysis. It could then be replaced on the lapel and reused. We succeeded in finalizing our designs, fabricating devices that incorporate several different design variations, building an exposure chamber and an elaborate exposure testing system, performing fundamental studies of adsorption capacity of the graphitized carbon adsorbents via thermo-gravimetric analysis (TGA), and performing initial performance tests with a high-sampling-rate device.

zellers

Lapel-mountable microscale passive sampler (μPS),

The device (0.8 μ 0.8 cm chip) works well and is providing reproducible results. On-going testing will provide additional verification of performance. We remain optimistic that this approach to measuring exposures could reduce the cost of sampling and analysis and, thereby, increase the quantity, if not the quality, of exposure data available to occupational health scientists for compliance or epidemiologic endpoints. Given their small size, we envision a “suite” of μPS devices, each with slightly different attributes (e.g., sampling rate or adsorbent material), being worn simultaneously, analyzed in rapid succession in the field (perhaps by the worker), and reused indefinitely.

Project Abstract