In addition to the handling of silver (powder) at the workplace, silver nanoparticles are also used in sprays. Therefore the lung plays a major role as potential uptake pathway of silver nanoparticles via inhalation, as these ultrafine particles may reach the deeper regions of the lung and enter into the bloodstream.

 

InSchematic exposure set-up for an inhalation study. © Fröhlich E. et al.2014). Int J Mol Sci, 15(3): 4795-4822.Schematic exposure set-up for an inhalation study. © Fröhlich E. et al.2014). Int J Mol Sci, 15(3): 4795-4822.halation studies with laboratory animals have shown that silver nanoparticles are taken up into the bloodstream after inhalation and systemically distributed in the body. The incorporated silver could then be detected in various organs such as liver, kidney, spleen, brain and testes.[1-12]

 

In short-term inhalation studies (28 days), no tissue damage occurred in the experimental animals exposed to sub-acute amounts of 10-15 nm silver nanoparticles, although this was accompanied by a slight inflammatory response. In the course of long-term inhalation experiments (90 days) the test animals were exposed to 18 nm silver nanoparticles for 6 hours per day via the respiratory air and showed a dose-dependent decreased lung function and inflammatory response in the lung. Even at very high doses of silver nanoparticles no genotoxic effects in the bone marrow of the animals could be detected.[1,4,5,8-11]

In vitro exposure at the air-liquid interface (ALI) with the example of the Karlsruhe exposure system. © Vitrocell Systems GmbH & © Lenz et al (2013) Biomed Res Int, 2013 652632.In vitro exposure at the air-liquid interface (ALI) with the example of the Karlsruhe exposure system. © Vitrocell Systems GmbH & © Lenz et al (2013) Biomed Res Int, 2013 652632.

 

Assessing the exposure to substances at the air-liquid interface (ALI) makes it is possible to mimic and simulate the processes happening in the lung in a simplified manner, in a petri dish. Aerosolised 20 nm silver nanoparticles induced only a temporary inflammatory reaction after uptake into the cell whereas only at very high doses could adverse effects be detected. In general small silver nanoparticles trigger stronger effects in in vitro experiments as compared with larger (nano)particles due to their larger specific particle surface area.[2,3]

 

When analysing different spray products that should contain nano silver according to the products' description, silver was only detectable in form of silver chloride and silver agglomerates, but not in nano form in the aerosol. However, even in a worst case scenario the calculated exposure levels were still below the daily WHO (World Health Organisation) exposure limits of 5 micrograms of silver per kg body weight.[7]

 

In general it is possible that silver nanoparticles may enter the body via inhalation. Potential health effects however are mainly dose and time-dependent.

 

Literature arrow down

  1. Chuang, HC et al. (2013). Int J Nanomedicine, 8 4495-4506.
  2. Herzog, F et al. (2013). Part Fibre Toxicol, 10(1): 11.
  3. Holder, AL et al. (2013). Biomed Res Int, 2013 328934.
  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. Munger M.A. et al. (2014). Nanomedicine, 10(1): 1-9.
  7. Quadros, ME et al. (2011), Environ Sci Technol, 45(24): 10713-10719.
  8. Song, KS et al. (2013). Nanotoxicology, 7(2): 169-180.
  9. Stebounova, LV et al. (2011). Part Fibre Toxicol, 8(1): 5.
  10. Sung, JH et al. (2008), Inhal Toxicol, 20(6): 567-574.
  11. Sung, JH et al. (2009), Toxicol Sci, 108(2): 452-461.
  12. Wang, X et al. (2014). Small, 10(2): 385-398.
  13. ATSDR (Dez 1990). Report: "Toxicological Profile for Silver, Agency for Toxic Substances and Disease Registry, U.S. Public Health Service (ATSDR).
  14. ATSDR (1999). Report: "Agency for Toxic Substances and Disease Registry ToxFAQs Silver". CAS#: 7440-22-4

 

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