title: Comparative inhalation toxicity of multi-wall carbon nanotubes, graphene, graphite nanoplatelets and low surface carbon black.
abstract: BACKGROUND
  Carbon nanotubes, graphene, graphite nanoplatelets and carbon black are seemingly chemically identical carbon-based nano-materials with broad technological applications. Carbon nanotubes and carbon black possess different inhalation toxicities, whereas little is known about graphene and graphite nanoplatelets.
  
  
  METHODS
  In order to compare the inhalation toxicity of the mentioned carbon-based nanomaterials, male Wistar rats were exposed head-nose to atmospheres of the respective materials for 6 hours per day on 5 consecutive days. Target concentrations were 0.1, 0.5, or 2.5 mg/m3 for multi-wall carbon nanotubes and 0.5, 2.5, or 10 mg/m3 for graphene, graphite nanoplatelets and low-surface carbon black. Toxicity was determined after end of exposure and after three-week recovery using broncho-alveolar lavage fluid and microscopic examinations of the entire respiratory tract.
  
  
  RESULTS
  No adverse effects were observed after inhalation exposure to 10 mg/m3 graphite nanoplatelets or relatively low specific surface area carbon black. Increases of lavage markers indicative for inflammatory processes started at exposure concentration of 0.5 mg/m3 for multi-wall carbon nanotubes and 10 mg/m3 for graphene. Consistent with the changes in lavage fluid, microgranulomas were observed at 2.5 mg/m3 multi-wall carbon nanotubes and 10 mg/m3 graphene. In order to evaluate volumetric loading of the lung as the key parameter driving the toxicity, deposited particle volume was calculated, taking into account different methods to determine the agglomerate density. However, the calculated volumetric load did not correlate to the toxicity, nor did the particle surface burden of the lung.
  
  
  CONCLUSIONS
  The inhalation toxicity of the investigated carbon-based materials is likely to be a complex interaction of several parameters. Until the properties which govern the toxicity are identified, testing by short-term inhalation is the best option to identify hazardous properties in order to avoid unsafe applications or select safer alternatives for a given application.
authors.forename: Lan
authors.initials: L
authors.lastname: Ma-Hock
authors.forename: Volker
authors.initials: V
authors.lastname: Strauss
authors.forename: Silke
authors.initials: S
authors.lastname: Treumann
authors.forename: Karin
authors.initials: K
authors.lastname: Küttler
authors.forename: Wendel
authors.initials: W
authors.lastname: Wohlleben
authors.forename: Thomas
authors.initials: T
authors.lastname: Hofmann
authors.forename: Sibylle
authors.initials: S
authors.lastname: Gröters
authors.forename: Karin
authors.initials: K
authors.lastname: Wiench
authors.forename: Bennard
authors.initials: B
authors.lastname: van Ravenzwaay
authors.forename: Robert
authors.initials: R
authors.lastname: Landsiedel
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000276:immunology; D016207:Cytokines / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015769:Granuloma, Respiratory Tract / Q000139:chemically induced; D006108:Graphite / Q000737:chemistry / Q000633:toxicity*; D018836:Inflammation Mediators / Q000378:metabolism; D019570:Inhalation Exposure / Q000009:adverse effects*; D008168:Lung / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008297:Male; D037742:Nanotubes, Carbon / Q000737:chemistry / Q000633:toxicity*; D017208:Rats, Wistar; D053260:Soot / Q000737:chemistry / Q000633:toxicity*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D015415:Biomarkers; D016207:Cytokines; D018836:Inflammation Mediators; D037742:Nanotubes, Carbon; D053260:Soot; D006108:Graphite