The precious metal silver occurs naturally in the earth's crust and is present in small amounts in various environmental compartments. In the past, water bodies carried high loads of silver due to waste e.g. from the photographic industry. With the advent of digital photography, however, silver concentrations in water systems have declined drastically. Currently, it is a challenge to nanomaterials in environmental matrices. Furthermore, the natural background of silver complicates the measurement of silver nanoparticles.

 

Sewer & Environmental Pollution. © dmitrimaruta / fotolia.comFor this reason, most studies available on the occurrence of silver nanoparticles in the environment estimate or model environmental concentrations. Production volumes for silver nanoparticles are used as a basis to generate assumptions on their release from products and their subsequent distribution in the environment. The resulting predicted environmental concentrations (PEC value) can be used for risk assessment.

The estimated amounts of nano silver for the different environmental compartments and Europe made in 2009 [1,2] and 2014 [3] show that the estimated silver concentrations were significantly lower in 2014 despite higher production volumes. This is mainly due to an increase in knowledge about the behaviour of silver nanoparticles in the environment. The particles are subject to changes by interaction with other substances and can dissolve. By including such processes in the estimation resulted in much lower calculated concentrations.

 

As mentioned above, the direct measurement of nanomaterials in the environment is difficult, but it is possible to determine the total content of silver in the various environmental compartments. Comparing these measured concentrations with the predicted amounts of nano silver clearly demonstrated that the total silver amount exceeds the amount of silver nanoparticles in all considered environmental systems [3].

Colorful clothes from the washing machine © kalcutta / fotolia.com

 

 

One likely release path for silver nanoparticles is the washing of silver equipped textiles. There is evidence that nano silver is released in varying amounts from textiles, and both the manufacturing and the washing process have an influence on the release behaviour. It is believed that the nano silver release from textiles and plastic products (equivalent to approximately 15 % of the total production of nano silver) is not critical for environmental organisms (see cross-cutting issues - nanoparticles in textiles) [4-7].

 

 

Up-to-now, there exist no real measurement values for silver nanoparticles for the different environmental compartments (water, soil, air). However, estimates show that nano silver represents only a small proportion of the total amount of silver in the environment. Then again, such estimated values allow only a limited evaluation of potential threats nano silver poses for environmental organisms or microbial purification stages of sewage treatment plants.

 

 

Literature arrow down

  1. Gottschalk, F et al. (2009), Environ Sci Technol, 43(24): 9216-9222.
  2. Mueller, NC et al. (2008), Environ Sci Technol, 42(12): 4447-4453.
  3. Sun, TY et al. (2014), Environ Pollut, 185 69-76.
  4. Geranio, L et al. (2009), Environ Sci Technol, 43(21): 8113-8118.
  5. Benn, TM et al. (2008), Environ Sci Technol, 42(11): 4133-4139.
  6. Mitrano, DM et al. (2014), ACS Nano, 8(7): 7208-7219.
  7. Blaser, SA et al. (2008), Sci Total Environ, 390(2–3): 396-409.

 

 

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