At present, carbon nanotubes (CNTs) are not used in food. Only in theory, they can be transported into the gastrointestinal tract through unwanted hand-to-mouth transfer or through swallowing of particles after their clearing process from the respiratory tract. As a rule, particles that have been taken up via the food are excreted via the faeces. Until now, there is no evidence for carbon nanotubes to reach the intestines and enter the body afterwards.

 

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Carbon nanotubes (CNTs) are not accredited for use in foods, and there are no indications for this to happen in the near future. However, it is theoretically possible that e.g. inhaled carbon nanotubes are able to reach the gastro-intestinal tract through coughing followed by swallowing and further distribution within the body. So far, only few analyses exist on this topic.

Single-walled carbon nanotubes (SWCNT) with carbon impurities (spherical deposits highlighted with white arrows).Single-walled carbon nanotubes (SWCNT) with carbon impurities (spherical deposits highlighted with white arrows).

 

Water-soluble carbon nanotubes, which were directly administered into the stomach of mice CNTs, stayed only for a short period in the gastro-intestinal tract before being excreted with the faeces within 12 hours. The carbon nanotubes did neither enter the bloodstream nor cause any biological effects [1]. In case of short or long multi-walled carbon nanotubes (MWCNTs), which were administered directly to the stomach of mice, only long and stiff fibre-shaped CNTs caused inflammation and damages of the upper cell layer. These observed effects (pathogenic reactions) have been known for many years in particular for long and stiff asbestos fibres [2].

 

However, if unmodified carbon nanotubes are injected directly into the bloodstream of laboratory animals, these CNTs are distributed over different internal organs (e.g. liver, spleen, lung) and are excreted only to a small amount via the urine and faeces [3].

 

 

Similar to the uptake of carbon nanotubes via the lung, it is not possible to make a final statement for CNTs in the gastro-intestinal tract. The behaviour of carbon nanotubes strongly depends on the respective modification, the way of administration and their dosage.

 

Literature arrow down

  1. Deng, X et al. (2007), Carbon, 45(7): 1419-1424.
  2. Poland, CA et al. (2008), Nat Nanotechnol, 3(7): 423-428.
  3. Yang, ST et al. (2007), J Phys Chem C, 111(48): 17761-17764.

 

 

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