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Evaluating and Predicting Occupational Exposures to Carbon Nanotubes and Nanofibers

Dahm, Matthew
http://orcid.org/0000-0001-9770-2700
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552379150459669

Abstract Details

2019, PhD, University of Cincinnati, Medicine: Industrial Hygiene (Environmental Health).
Carbon nanotubes and carbon nanofibers (CNT/F) are cylindrical-shaped nanomaterials made of carbon atoms. These materials offer the potential for vast technological breakthroughs in various industrial applications in biomedicine, electronics, as well as high-performance intermediates such as coatings and composites for aerospace, automobiles, and construction. However, as CNT/F have emerged in manufacturing, evidence of potential health effects from animal studies has linked these nanomaterials to effects such as pulmonary inflammation, fibrosis, and granulomas. Although limited human evidence of adverse effects from occupational exposures to CNT/F currently exist, it is recognized that longitudinal studies will be needed due to the long latency periods for many of the health effects of concern. Therefore, the overarching goals of this dissertation, which includes chapters 1-3, were to develop consensus sampling methods to characterize U.S. workplace exposures to CNT/F as well as evaluate alternative methods to estimate exposures for future uses in longitudinal epidemiologic studies. In chapter 1, we measured CNT/F exposures among U.S. workers for use in a dose-response analysis. Full-shift exposures were assessed from participants at 12 facilities for the mass of elemental carbon (EC) at the respirable and inhalable aerosol size fractions, along with the quantitative characterization of CNT/F exposures with transmission electron microscopy (TEM) analysis. The results of this study demonstrated the occurrence of a broad range of workplace exposures to CNT/F. EC mass exposures were generally below the current occupational exposure limit (OEL) of 1 µg/m^3 (as respirable EC mass), but generally above 1 µg/m^3 as inhalable EC mass, which currently does not have an OEL. In chapter 2, we identified workplace determinants that contribute to exposure and developed predictive models to estimate CNT/F exposures for future use in longitudinal studies. An exposure database was created using the exposure metrics collected in chapter 1, which served as the dependent variables for model creation. Regression models were developed and their predictive capabilities were tested through cross-validation. The results demonstrated that company-level determinants were the most important variables associated with increased and decreased exposures. However, it was found that the models were not adequate for predicting workplace exposures and would need to be integrated with other methods. The objective of chapter 3 was to determine if a 25-mm open-faced cassette performed with relative equivalence to a reference inhalable sampler when challenged to CNT/F aerosols. Side-by-side paired sample experiments were conducted within a small chamber using three kinds of CNT/F. The results of this study suggest that the 25-mm OFC collects the inhalable size fraction when sampling CNT/F aerosols and performed within a range of 20% compared to a reference inhalable size-selective sampler. Overall, this dissertation describes the results of a multi-site field study, predictive model development, and laboratory assessment that describe and estimate occupational exposures to CNT/F using a multi-metric approach. The exposure assessment data supports the appropriateness of using the multi-metric approach established in this dissertation for future epidemiologic analyses. Exposure measurement and determinants data should continue to be collected and added to the exposure database for future predictive model development.
Sergey Grinshpun, Ph.D. (Committee Chair)
Stephen Bertke, Ph.D. (Committee Member)
Tiina Reponen, Ph.D. (Committee Member)
Mary Schubauer-Berigan, Ph.D. (Committee Member)
Glenn Talaska, Ph.D. (Committee Member)
151 p.
Occupational Safety
nanomaterials; carbon nanotubes; carbon nanofibers; exposure assessment

Recommended Citations

Citations

  • Dahm, M. (2019). Evaluating and Predicting Occupational Exposures to Carbon Nanotubes and Nanofibers [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552379150459669

    APA Style (7th edition)

  • Dahm, Matthew. Evaluating and Predicting Occupational Exposures to Carbon Nanotubes and Nanofibers. 2019. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552379150459669.

    MLA Style (8th edition)

  • Dahm, Matthew. "Evaluating and Predicting Occupational Exposures to Carbon Nanotubes and Nanofibers." Doctoral dissertation, University of Cincinnati, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552379150459669

    Chicago Manual of Style (17th edition)

ucin1552379150459669
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© 2019, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.