Rodent studies show that silver nanoparticles administered in low doses cause no adverse health effects, although silver could be detected in the organs regardless of the route of exposure. Likewise, the first studies on volunteers with commercially available nano silver products displayed no adverse health effects.

 

Possible entry routes of silver nanoparticles into the human body. © Eckhardt et al. (2013), Chem Rev, 113(7): 4708-4754.Possible entry routes of silver nanoparticles into the human body. © Eckhardt et al. (2013), Chem Rev, 113(7): 4708-4754.

To examine the possible entry routes of silver nanoparticles in the body (see section "Uptake") experiments with laboratory animals were performed over longer periods of time (28-90 days). After administering silver nanoparticles to test animals via inhalation, small amounts of silver were detected in the blood and various organs such as liver, kidney, lymph nodes and brain. No definite clinical or histopathological effects were found in rats exposed to nano silver over 28 days. In the course of long-term studies over 90 days the rodents displayed decreased lung function and inflammation in the lungs [7,4,13,14,5,16]

Feeding the laboratory animals with a nano silver supplemented diet over a longer period of time also resulted in silver being detectable in the blood and different organs such as liver, lung, kidneys, stomach, testicles and in the brain. Related to this exposure scenario there occurred gender-related differences in distribution and retention of silver nanoparticles in the body. Twice as much nano silver was found in the kidneys of female rats compared to their male counterparts, whereas the male test animals showed a persistent accumulation of silver in the brain and testes. However, it is still unclear whether either silver ions or (nano) particles are absorbed via the gastrointestinal tract and transported to other areas in the body.

As silver ions are very reactive they usually agglomerate immediately upon release or interact with and bind to other chemical compounds making them more bioavailable for the body. Analyses of the genetic material revealed no DNA-damage to either male or female test animals. Repeated doses of silver nanoparticles in the diet were not toxic to the animal and had no effect on fertility of the rats.[3,7-9,12,15,18]

First-aid box © Olivier DIRSON / fotolia.com

 

Silver nanoparticles used in wound dressing material protect damaged skin (e.g. from skin burns) against excessive bacterial colonisation by the release of silver ions. Studies in rats have shown that the silver nanoparticles can penetrate deep into the damaged skin of rats where they work effectively against microorganisms and promote healing. Another study confirmed that the dermal application of silver nanoparticles only triggered a slight irritation of the skin but no acute toxicity.[6,17]

 

First studies with volunteers using commercially available nano silver containing products (T-shirt, spray, silver nanoparticle solution) showed no adverse health effects on the human body. Taken together small and thus realistic amounts of silver nanoparticles are not toxic for humans and mammals based on the current scientific knowledge.[2,11,10]

 

Literature arrow down

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  2. Hoefer, D et al. (2011). ISRN Dermatol, 2011 369603.
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  4. Ji, JH et al. (2007). Inhal Toxicol, 19(10): 857-871.
  5. Kim, JS et al. (2011). Saf Health Work, 2(1): 34-38.
  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. (2012). J Nanopart Res, 14(9): 1-10.
  9. Loeschner, K et al. (2011). Part Fibre Toxicol, 8 18.
  10. Munger M.A. et al. (2014). Nanomedicine, 10(1): 1-9.
  11. Quadros, ME et al. (2011), Environ Sci Technol, 45(24): 10713-10719.
  12. Song, KS et al. (2013). Nanotoxicology, 7(2): 169-180.
  13. Sung, JH et al. (2008). Inhal Toxicol, 20(6): 567-574.
  14. Sung, JH et al. (2009). Toxicol Sci, 108(2): 452-461.
  15. Van Der Zande, M et al. (2012). ACS Nano, 6(8): 7427-7442.
  16. Wang, X et al. (2014). Small, 10(2): 385-398.
  17. Wu, J et al. (2014). Biomed Mater, 9(3): 035005.
  18. Xue, Y et al. (2012). Appl Toxicol, 32(11): 890-899.
  19. Wijnhoven, SWP et al. (2009), Nanotoxicology, 3(2): 109-U178.
  20. Fries, R et al. (2009). Report: „Nanosilber - NanoTrust Dossier No. 9, April 2009", Wien. ISSN: 1998-7293.
  21. Möller, M et al. (2009)."Nanotechnologie im Bereich der Lebensmittel". TA Swiss, vdf Hoschschulverlag AG, Zürich. ISBN 978-3-7281-3234-5.

 

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