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by
Toni A. Ruda-Eberenz |
Total Records (
2 ) for
Toni A. Ruda-Eberenz |
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M. Eileen Birch
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Bon-Ki Ku
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Douglas E. Evans
and
Toni A. Ruda-Eberenz
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Production of carbon nanofibers and nanotubes (CNFs/CNTs) and their composite products is increasing globally. High volume production may increase the exposure risks for workers who handle these materials. Though health effects data for CNFs/CNTs are limited, some studies raise serious health concerns. Given the uncertainty about their potential hazards, there is an immediate need for toxicity data and field studies to assess exposure to CNFs/CNTs. An extensive study was conducted at a facility that manufactures and processes CNFs. Filter, sorbent, cascade impactor, bulk, and microscopy samples, combined with direct-reading instruments, provided complementary information on air contaminants. Samples were analyzed for organic carbon (OC) and elemental carbon (EC), metals, and polycyclic aromatic hydrocarbons (PAHs), with EC as a measure of CNFs. Transmission electron microscopy with energy-dispersive X-ray spectroscopy also was applied. Fine/ultrafine iron-rich soot, PAHs, and carbon monoxide were production byproducts. Direct-reading instrument results were reported previously [Evans DE et al. (Aerosol monitoring during carbon nanofiber production: mobile direct-reading sampling. Ann Occup Hyg 2010;54:514-31.)] Results for time-integrated samples are reported as companion papers in this Issue. OC and EC, metals, and microscopy results are reported here, in Part I, while results for PAHs are reported in Part II [Birch ME. (Exposure and Emissions Monitoring during Carbon Nanofiber Production-Part II: Polycyclic Aromatic Hydrocarbons. Ann. Occup. Hyg 2011; 55: 1037-47.)]. Respirable EC area concentrations inside the facility were about 6-68 times higher than outdoors, while personal breathing zone samples were up to 170 times higher. |
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M. Eileen Birch
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Toni A. Ruda-Eberenz
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Ming Chai
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Ronnee Andrews
and
Randal L. Hatfield
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Commercially available carbon nanotubes and nanofibers were analyzed to examine possible relationships between their Brunauer-Emmett-Teller
specific surface areas (SSAs) and their physical and chemical properties. Properties found to influence surface area were
number of walls/diameter, impurities, and surface functionalization with hydroxyl and carboxyl groups. Characterization by
electron microscopy, energy-dispersive X-ray spectrometry, thermogravimetric analysis, and elemental analysis indicates that
SSA can provide insight on carbon nanomaterials properties, which can differ vastly depending on synthesis parameters and
post-production treatments. In this study, how different properties may influence surface area is discussed. The materials
examined have a wide range of surface areas. The measured surface areas differed from product specifications, to varying degrees,
and between similar products. Findings emphasize the multiple factors that influence surface area and mark its utility in
carbon nanomaterial characterization, a prerequisite to understanding their potential applications and toxicities. Implications
for occupational monitoring are discussed. |
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