title: Aerosol Emission Monitoring and Assessment of Potential Exposure to Multi-walled Carbon Nanotubes in the Manufacture of Polymer Nanocomposites.
abstract: Recent animal studies have shown that carbon nanotubes (CNTs) may pose a significant health risk to those exposed in the workplace. To further understand this potential risk, effort must be taken to measure the occupational exposure to CNTs. Results from an assessment of potential exposure to multi-walled carbon nanotubes (MWCNTs) conducted at an industrial facility where polymer nanocomposites were manufactured by an extrusion process are presented. Exposure to MWCNTs was quantified by the thermal-optical analysis for elemental carbon (EC) of respirable dust collected by personal sampling. All personal respirable samples collected (n = 8) had estimated 8-h time weighted average (TWA) EC concentrations below the limit of detection for the analysis which was about one-half of the recommended exposure limit for CNTs, 1 µg EC/m(3) as an 8-h TWA respirable mass concentration. Potential exposure sources were identified and characterized by direct-reading instruments and area sampling. Area samples analyzed for EC yielded quantifiable mass concentrations inside an enclosure where unbound MWCNTs were handled and near a pelletizer where nanocomposite was cut, while those analyzed by electron microscopy detected the presence of MWCNTs at six locations throughout the facility. Through size selective area sampling it was identified that the airborne MWCNTs present in the workplace were in the form of large agglomerates. This was confirmed by electron microscopy where most of the MWCNT structures observed were in the form of micrometer-sized ropey agglomerates. However, a small fraction of single, free MWCNTs was also observed. It was found that the high number concentrations of nanoparticles, ~200000 particles/cm(3), present in the manufacturing facility were likely attributable to polymer fumes produced in the extrusion process.
authors.affiliation: Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA;
authors.forename: Drew
authors.initials: D
authors.lastname: Thompson
authors.affiliation: Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA;
authors.forename: Sheng-Chieh
authors.initials: SC
authors.lastname: Chen
authors.affiliation: Institute of Environmental Engineering, ETH Zurich, 8093 Zurich, Switzerland; Department of Analytical Chemistry, Empa, 8600 Dubendorf, Switzerland;
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA; Faculty of Science, The University of Hong Kong, Pokfulam, Hong Kong dyhpui@umn.edu.
authors.forename: David Y H
authors.initials: DY
authors.lastname: Pui
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000395:Air Pollutants, Occupational / Q000032:analysis*; D000818:Animals; D004391:Dust / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D005374:Filtration / Q000295:instrumentation; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis; D008168:Lung / Q000737:chemistry; D066192:Manufacturing Industry; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites; D037742:Nanotubes, Carbon / Q000032:analysis*; D016273:Occupational Exposure / Q000032:analysis*; D010316:Particle Size; D011108:Polymers; D017132:Workplace
chemical_list: D000336:Aerosols; D000395:Air Pollutants, Occupational; D004391:Dust; D037742:Nanotubes, Carbon; D011108:Polymers
keywords: carbon nanotubes; exposure assessment; nanofiller; nanoparticle; polymer extrusion; polymer nanocomposite