Up to now, carbon nanotubes (CNTs) are not added to food or cosmetic products. Therefore, the uptake of CNTs via the lung, e.g. at the workplace during production, is the most likely entry path of CNTs into the body. Studies on laboratory animals have shown that carbon nanotubes can size-dependently penetrate into the deeper lungs regions. From there they are either removed by natural clearance processes or they can enter the body through the thin epithelial layer of the pulmonary alveoli.

 

In most studies, carbon nanotubes are applied to laboratory animals in an unusual way, making the relevance of these results for our everyday-life questionable. Carbon nanotubes are either instilled, e.g. as a small amount of a high-dosed liquid suspension of nanomaterial, through the airway directly into the pulmonary alveoli (instillation) or applied by sucking-in of the nanoparticle-containing liquid through the throat (aspiration). Both pathways do not correlate to airborne (nano)particles which are present, e.g. at workplaces, and may be inhaled like fine dust.

In vitro exposure at the air-liquid interface (ALI) with the example of the Karlsruhe exposure system.In vitro exposure at the air-liquid interface (ALI) with the example of the Karlsruhe exposure system.

 

Recent inhalation studies use a more realistic exposure scenario, where carbon nanotubes are exposed to laboratory animals in the breathing air as an aerosol. These studies have shown that carbon nanotubes are able to reach the deeper parts of the lung [1-4].

The results of different studies are partly contradictory and therefore discussed critically. Some research groups observed stress reactions of the lung tissue, which were causing inflammation of the lung, formation of granuloma and a change of the lung function. In contrast to that, other studies describe an altered systemic immune reaction (e.g. in the spleen and lymph nodes) without observing any changes in the lung [5-7].

 

 

These contradictory results can be explained by the different morphologies (modifications) of the applied CNTs, the application method(s) as well as variations within the duration of the studies and the applied doses. Besides these limitations, it is known today that thin, long, biopersistent and fibre-shaped nanomaterials can cause pathogenic effects like inflammation and tumours [8]. For safety reasons carbon nanotubes fulfilling these criteria are no longer in use [9,10].Occupational health & safety measures. © Empa, 2009.Occupational health & safety measures. © Empa, 2009.

 

Today there are only few data available on the concentration of carbon nanotubes at industrial workspaces. First laboratory measurements could detect CNTs in the air under certain experimental conditions (ca. 0.7-53 µg/ml3) [11,12]. Introducing adapted precautionary safety measures, e.g. by the use of laboratory coats and safety equipment such as gloves and respiratory masks, significantly reduces an unintended uptake of nanomaterials.

However, it has yet to be proven especially in case of the CNTs that the critical large and long carbon nanotubes can be taken up via the lung.

 

 

Literature arrow down

  1. Ma-Hock, L et al. (2009), Inhal Toxicol, 21(2): 102-118.
  2. Mitchell, LA et al. (2007), Toxicol Sci, 100(1): 203-214.
  3. Mitchell, LA et al. (2009), Nat Nanotechnol, 4(7): 451-456.
  4. Shvedova, AA et al. (2005), Am J Physiol Lung Cell Mol Physiol, 289(5): L698-708.
  5. Erdely, A et al. (2008), Nano Letters, 9(1): 36-43.
  6. Donaldson, K et al. (2010), Part Fibre Toxicol, 7 5.
  7. Muller, J et al. (2005), Toxicol Appl Pharmacol, 207(3): 221-231.
  8. Marquardt H., Schäfer S. & Barth H. (2013). Toxikologie, Toxikologie - 3., vollständig überarbeitete und erweiterte Auflage 2013., Kapitel 34: Fasern und Nanopartikel, S. 885ff. Wissenschaftliche Verlagsgesellschaft Stuttgart, ISBN 978-3-8047-2876-9.
  9. Warheit, DB et al. (2004), Toxicol Sci, 77(1): 117-125.
  10. Donaldson, K et al. (2011), Nanomedicine (Lond), 6(1): 143-156.
  11. Ruge, CA et al. (2012), PLoS One, 7(7): e40775.
  12. Maynard, AD et al. (2004), J Toxicol Environ Health A, 67(1): 87-107.

 

 

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