title: Exposure Assessment in a Single-Walled Carbon Nanotube Primary Manufacturer.
abstract: This study was aimed at documenting and characterizing occupational exposure to single-walled carbon nanotubes (SWCNTs) generated in a primary manufacturing plant. It also compared various strategies of exposure monitoring.
  
  
  
  A 6-day measurement protocol was scheduled (D1-D6) including both (i) quasi-personal monitoring with an array of direct reading instruments (DRIs) and (ii) offline electron microscopy analyses of surface and breathing zone filter-based samples. The first step (D1 and D2) consisted of contamination screenings resulting from the various SWCNT production tasks using a multimetric approach. Surface sampling was also carried out to assess workplace cross-contamination. The second step (D3-D6) focused on the exposure monitoring during recovery/cleaning task, by comparing three personal elemental carbon (EC) measurements [respirable EC using a cyclone following the NIOSH 5040 method (REC-CYC), respirable and thoracic EC using parallel particle impactors [REC-PPI and TEC-PPI, respectively)] and gravimetric mass concentration measurements.
  
  
  
  DustTrak DRX and electrical low-pressure impactor measurements indicated that particles were released during weighing, transferring, and recovery/cleaning tasks of the manufacturing process. Electron microscopy revealed the presence of agglomerated SWCNTs only during the recovery/cleaning task. REC-CYC concentrations remained under the limits of quantification; REC-PPI showed levels up to 58 µg m-3; and TEC-PPI ranged from 40 to 70 µg m-3. Ratios calculated between gravimetric measurements and estimated DustTrak mass concentrations ranged from 2.8 to 4.9. Cross-contamination appeared to be limited since SWCNTs was only found on surface samples collected close to the reactor in the production room.
  
  
  
  This case study showed that the DustTrak DRX should be the preferred device among DRIs to identify potential exposure to SWCNTs. However, there is a risk of false positive since it is a non-specific instrument; therefore, the actual release of SWCNTs must be confirmed with scanning electron microscopy/transmission electron microscopy analyses. Besides, using EC measurements as a proxy for SWCNT exposure assessments, as suggested by the NIOSH, is still challenging since interferences can occur with other EC sources such as carbon black, which is also present in the workplace.
authors.affiliation: Institut de recherche en santé publique de l'Université de Montréal (IRSPUM), Department of Environmental and Occupational Health, École de santé publique, Université de Montréal, PO Box 6128, Main Station, Montréal, Québec H3C3J7, Canada.
authors.forename: Serge
authors.initials: S
authors.lastname: Kouassi
authors.affiliation: Institut de recherche en santé publique de l'Université de Montréal (IRSPUM), Department of Environmental and Occupational Health, École de santé publique, Université de Montréal, PO Box 6128, Main Station, Montréal, Québec H3C3J7, Canada.
authors.forename: Cyril
authors.initials: C
authors.lastname: Catto
authors.affiliation: Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), 505, Boul. de Maisonneuve Ouest, Montréal, Québec H3A 3C2, Canada.
authors.forename: Claude
authors.initials: C
authors.lastname: Ostiguy
authors.affiliation: École Polytechnique de Montréal, PO Box 6079, Main Station, Montréal, Québec H3C3A7, Canada.
authors.forename: Gilles
authors.initials: G
authors.lastname: L'Espérance
authors.affiliation: Raymor Industries Inc., 3765 Rue la Vérendrye, Boisbriand, Québec QC J7H 1R8, Canada.
authors.forename: Jens
authors.initials: J
authors.lastname: Kroeger
authors.affiliation: Institut de recherche en santé publique de l'Université de Montréal (IRSPUM), Department of Environmental and Occupational Health, École de santé publique, Université de Montréal, PO Box 6128, Main Station, Montréal, Québec H3C3J7, Canada.
authors.forename: Maximilien
authors.initials: M
authors.lastname: Debia
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis; D002244:Carbon / Q000032:analysis*; D004391:Dust / Q000032:analysis; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007221:Industry; D019570:Inhalation Exposure / Q000032:analysis*; D008855:Microscopy, Electron, Scanning / Q000379:methods; D046529:Microscopy, Electron, Transmission / Q000379:methods; D037742:Nanotubes, Carbon / Q000009:adverse effects / Q000032:analysis*; D016273:Occupational Exposure / Q000032:analysis*; D010316:Particle Size; D014481:United States; D017132:Workplace
chemical_list: D000395:Air Pollutants, Occupational; D004391:Dust; D037742:Nanotubes, Carbon; D002244:Carbon
keywords: elemental carbon; exposure assessment; nanoparticle; parallel particle impactors; single-walled carbon nanotubes (SWCNTs); surface sampling