title: Assessment of Determinants of Emission Potentially Affecting the Concentration of Airborne Nano-Objects and Their Agglomerates and Aggregates.
abstract: Nano-specific inhalation exposure models could potentially be effective tools to assess and control worker exposure to nano-objects, and their aggregates and agglomerates (NOAA). However, due to the lack of reliable and consistent collected NOAA exposure data, the scientific basis for validation of the existing NOAA exposure models is missing or limited. The main objective of this study was to gain more insight into the effect of various determinants underlying the potential on the concentration of airborne NOAA close to the source with the purpose of providing a scientific basis for existing and future exposure inhalation models.
  
  
  
  Four experimental studies were conducted to investigate the effect of 11 determinants of emission on the concentration airborne NOAA close to the source during dumping of ~100% nanopowders. Determinants under study were: nanomaterial, particle size, dump mass, height, rate, ventilation rate, mixing speed, containment, particle surface coating, moisture content of the powder, and receiving surface. The experiments were conducted in an experimental room (19.5 m3) with well-controlled environmental and ventilation conditions. Particle number concentration and size distribution were measured using real-time measurement devices.
  
  
  
  Dumping of nanopowders resulted in a higher number concentration and larger particles than dumping their reference microsized powder (P < 0.05). Statistically significant more and larger particles were also found during dumping of SiO2 nanopowder compared to TiO2/Al2O3 nanopowders. Particle surface coating did not affect the number concentration but on average larger particles were found during dumping of coated nanopowders. An increase of the powder's moisture content resulted in less and smaller particles in the air. Furthermore, the results indicate that particle number concentration increases with increasing dump height, rate, and mass and decreases when ventilation is turned on.
  
  
  
  These results give an indication of the direction and magnitude of the effect of the studied determinants on concentrations close to the source and provide a scientific basis for (further) development of existing and future NOAA inhalation exposure models.
authors.affiliation: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, The Netherlands.|Risk Analysis for Products in Development, TNO, Zeist, The Netherlands.
authors.forename: Cindy
authors.initials: C
authors.lastname: Bekker
authors.affiliation: Risk Analysis for Products in Development, TNO, Zeist, The Netherlands.
authors.forename: Wouter
authors.initials: W
authors.lastname: Fransman
authors.affiliation: Risk Analysis for Products in Development, TNO, Zeist, The Netherlands.
authors.forename: Ruud
authors.initials: R
authors.lastname: Boessen
authors.affiliation: Department for Health Evidence, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Arné
authors.initials: A
authors.lastname: Oerlemans
authors.affiliation: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, The Netherlands.
authors.forename: Ilse B
authors.initials: IB
authors.lastname: Ottenbros
authors.affiliation: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, The Netherlands.
authors.forename: Roel
authors.initials: R
authors.lastname: Vermeulen
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis*; D004784:Environmental Monitoring / Q000295:instrumentation; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis*; D008962:Models, Theoretical; D049329:Nanostructures / Q000706:statistics & numerical data*; D016273:Occupational Exposure; D010316:Particle Size; D012822:Silicon Dioxide / Q000032:analysis; D017132:Workplace
chemical_list: D000395:Air Pollutants, Occupational; D012822:Silicon Dioxide
keywords: NOAA; emission determinants; exposure modelling; occupational exposure