Abstract
BackgroundCarbon 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.MethodsIn 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.ResultsNo 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.ConclusionsThe 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.
Highlights
Carbon nanotubes, graphene, graphite nanoplatelets and carbon black are seemingly chemically identical carbon-based nano-materials with broad technological applications
Graphene has spurred the imagination of engineers and scientists with properties that may in part replace carbon nanotubes (CNT), or replace conventional twodimensional fillers such as clays, promoting development of some unique devices, e.g. in photonics, supercapacitors, or bioapplications [3,4,5]
The fibrillar intermediate structure makes the agglomerates rather spongy in comparison to other MWCNT materials such as NM400 from the OECD sponsorship program, which has a similar outer diameter of 9.5 nm
Summary
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. Engineered nanomaterials have unique physicochemical properties and are commonly used in industrial applications like microelectronics, lightweight materials, functional textiles, or coatings to achieve distinctly improved properties. Graphene has spurred the imagination of engineers and scientists with properties that may in part replace CNTs (e.g. for conductive thin films), or replace conventional twodimensional fillers such as clays (e.g. for barrier properties), promoting development of some unique devices, e.g. in photonics, supercapacitors, or bioapplications [3,4,5]. The implications of a nanomaterials’ dimensionality for their hazard profile have been highlighted recently on the issue of exceptionally high surface to volume ratio of graphene as compared to carbon nanotubes [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
