title: Assessment of two portable real-time particle monitors used in nanomaterial workplace exposure evaluations.
abstract: BACKGROUND
  Nanoparticle emission assessment technique was developed to semi-quantitatively evaluate nanomaterial exposures and employs a combination of filter based samples and portable real-time particle monitors, including a condensation particle counter (CPC) and an optical particle counter (OPC), to detect nanomaterial releases. This laboratory study evaluated the results from CPC and OPC simultaneously measuring a polydisperse aerosol to assess their variability and accuracy.
  
  
  RESULTS
  Two CPCs and two OPCs were used to evaluate a polydisperse sodium chloride aerosol within an enclosed chamber. The measurement results for number concentration versus time were compared between paired particle monitors of the same type, and to results from the Scanning Mobility Particle Spectrometer (SMPS) which was widely used to measure concentration of size-specific particles. According to analyses by using the Bland-Altman method, the CPCs displayed a constant mean percent difference of -3.8% (95% agreement limits: -9.1 to 1.6%; range of 95% agreement limit: 10.7%) with the chamber particle concentration below its dynamic upper limit (100,000 particles per cubic centimeter). The mean percent difference increased from -3.4% to -12.0% (range of 95% agreement limits: 7.1%) with increasing particle concentrations that were above the dynamic upper limit. The OPC results showed the percent difference within 15% for measurements in particles with size ranges of 300 to 500 and 500 to 1000 regardless of the particle concentration. Compared with SMPS measurements, the CPC gave a mean percent difference of 22.9% (95% agreement limits: 10.5% to 35.2%); whereas the measurements from OPC were not comparable.
  
  
  CONCLUSIONS
  This study demonstrated that CPC and OPC are useful for measuring nanoparticle exposures but the results from an individual monitor should be interpreted based upon the instrument's technical parameters. Future research should challenge these monitors with particles of different sizes, shapes, or composition, to determine measurement comparability and accuracy across various workplace nanomaterials.
authors.affiliation: Institute of Health Surveillance, Analysis and Protection, Hubei Center for Disease Control and Prevention, Wuhan, Hubei, China; National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Yuewei
authors.initials: Y
authors.lastname: Liu
authors.affiliation: National Institute for Occupational Safety and Health, Division of Surveillance, Hazard Evaluations, and Field Studies, Cincinnati, Ohio, United States of America.
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Beaucham
authors.affiliation: URS Corporation, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Terri A
authors.initials: TA
authors.lastname: Pearce
authors.affiliation: National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Ziqing
authors.initials: Z
authors.lastname: Zhuang
mesh_terms: D000336:Aerosols / Q000032:analysis / Q000737:chemistry; D000395:Air Pollutants, Occupational / Q000032:analysis*; D004867:Equipment Design; D006801:Humans; D049329:Nanostructures / Q000032:analysis*; D016273:Occupational Exposure / Q000032:analysis*; D055095:Optics and Photonics / Q000295:instrumentation* / Q000379:methods; D010316:Particle Size; D017132:Workplace
chemical_list: D000336:Aerosols; D000395:Air Pollutants, Occupational