Currently the use of silver nanoparticles is not permitted in food. But silver in general is approved as a food colouring agent (known as E174) to colour surfaces of sugar-, confectionary and bakery products and has to be labelled appropriately. Due to their antimicrobial activity silver nanoparticles are also used in food contact materials (e.g. packaging foils or plastic storage container) making a transition of silver into the food it possible. But such products are currently not registered in Germany and the EU.

 

Food colouring agent silver (E174) used in edible food varnish. © Lottmann PR.Food colouring agent silver (E174) used in edible food varnish. © Lottmann PR.In a short-term study (14 days) with a commercially available nano silver product the volunteers orally received either a one-time large dose (480 g/day) or repeated smaller doses (100 micrograms/day) of silver nanoparticles. Overall the silver nanoparticles did not cause any clinically relevant negative effects in the test subjects.[11]

Delivering silver nanoparticles in in vivo studies to test animals via the feed resulted in silver being detectable in the blood and in different organs (liver, lung, kidney, stomach, testicles and brain) even after longer periods of time. After uptake within the gastrointestinal tract the silver nanoparticles are transported throughout the body with the help of the blood circulation and accumulate in the above mentioned target organs. The majority of the nano silver, however, is still excreted in the faeces. From these and other studies it has become apparent that it is mostly the ionic form of silver that is bioavailable for the body. In some cases, an accompanying inflammatory response but no acute toxicity has been detected.[6-10,13,17]

In vitro studies in the laboratory, using different cell lines, have shown that silver nanoparticles are taken up into cells of the gastrointestinal tract either in the particulate or ionic form and are even able to pass the intestinal barrier. The induced cellular stress responses are most likely caused by the released silver ions.[4,2,1]

Food packaging with vegetable content. © PhotoSG / fotolia.de

Plastic packaging materials available in the USA and in Asia may contain silver particles that could transfer into the food and consequently be taken up into the body. Studies have proven that predominantly silver ions but also up to 12 % of silver nanoparticles are being released from such packaging materials. However, the detected amounts of nano silver were well below the natural silver load or even below the limit values of 0.05 mg/L silver in water and 0.05 mg/kg of silver in foods as suggested by the European Food Safety Authority (EFSA). Nevertheless the US Environmental Protection Agency (EPA) banned the sale of the investigated plastic containers from this study in March 2014.[3,14,17]

Mandatory Nano labelling in cosmetics, biocides and food

 

 

 

In the EU and in Germany silver is not approved to be used in such antimicrobial packaging materials or as dietary supplement. However, when applied for the decoration of confectionery silver has to be labelled appropriately on the list of ingredients as food colouring agent (E174). Since December 2014 all nanoparticles contained in food and food packaging materials must be labelled with the term "nano" as indicated on the list of ingredients.[15,16,18]

 

 

 

Literature

  1. Boehmert, L et al. (2014). Nanotoxicology, 8(6): 631-642.
  2. Bouwmeester, H et al. (2011). ACS Nano, 5(5): 4091-4103.
  3. Cushen, M et al. (2013). Food Chem, 139(1-4): 389-397.
  4. Gaiser, BK et al. (2013). Toxicol Sci, 131(2): 537-547.
  5. Keil, A et al. (2013). J. Verbr. Lebensm., 8(1-2): 5-16.
  6. Kim, JS et al. (2013). Nanotoxicology, 7(5): 953-960.
  7. Kim, YS et al. (2008). Inhal Toxicol, 20(6): 575-583.
  8. Lee, JH et al. (2013). Part Fibre Toxicol, 10(1): 36.
  9. Liu, J et al. (2012). ACS Nano, 6(11): 9887-9899.
  10. Loeschner, K et al. (2011). Part Fibre Toxicol, 8 18.
  11. Munger M.A. et al. (2014). Nanomedicine, 10(1): 1-9.
  12. Reinhart, A. (2008). J Verbr Lebensm, 3(3): 294-301.
  13. Van Der Zande, M et al. (2012). ACS Nano, 6(8): 7427-7442.
  14. Von Goetz, N et al. (2013). Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 30(3): 612-620.
  15. European Commission (Dec 2014). New EU law on food information to consumers. (last access date: Dec 2014).
  16. Europäische Behörde für Lebensmittelsicherheit (EFSA) (Okt 2014). Topic "Nanotechnology". (last access date: Dec 2014).
  17. Hadrup, N et al. (2014). Regul Toxicol Pharmacol, 68(1): 1-7.
  18. SCENIHR (2014). EC-Report: "Are silver nanoparticles safe? Implications for health, the environment and microbial resistance."
  19. SCENIHR (2014). EC-Report: Opinion on Nanosilver: safety, health and environmental effects and role in antimicrobial resistance. ISBN: 831-4783.
  20. Wijnhoven, SWP et al. (2009), Nanotoxicology, 3(2): 109-U178

 

 

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