The “UMSICHT”-project aimed to better understand behaviour, fate and impact of silver nanoparticles in the environment. Dissolution behaviour, stability, transport and effects of differently made particles on living organisms in inshore waters and soils were investigated under different conditions. Standard procedures as well as optimized or new ones were applied or developed, respectively.
Silver nanoparticles in textiles were studied as an example for consumables – from particle synthesis, production of brins and fibre cloth via abrasion- and washing behaviour to the point of removal in the sewage treatment plant. It became clear that the way of textile fabrication determines whether and to what extent the particles reach the environment: next to nothing (best-case scenario) or almost all (worst-case scenario). As silver nanoparticles are not totally retained in the sewage treatment plant, a smallish part may reach inshore waters – the main part, however, will end up in the soil due to sewage sludge application in agriculture. The nanoparticles, respectively the silver dissolved from these, were highly toxic for almost all tested microbes and higher organisms. On the other hand, the quantities finally reaching the environment are comparatively low. As silver cannot be degraded, however, we cannot exclude that soil organisms will be harmed in the course of decades to centuries. This especially applies to residues from imported products, of which neither kind of fabrication, amount of silver contained, nor the production volume are known. The complexity of the product market proved to be the biggest handicap for reliable predictions.
Conclusion of the project:
For a number of years now, an increasing number of synthetic nanoparticles have been manufactured and incorporated into various products, such as cosmetics. For the first time, a research project at the Technical University of Munich and the Bavarian Ministry of the Environment provides reliable findings on their presence in water bodies.
Nanoparticles can improve the properties of materials and products. That is the reason why an increasing number of nanoparticles have been manufactured over the past several years. The worldwide consumption of silver nanoparticles is currently estimated at over 300 metric tons. These nanoparticles have the positive effect of killing bacteria and viruses. Products that are coated with these particles include refrigerators and surgical instruments. Silver nanoparticles can even be found in sportswear. This is because the silver particles can prevent the smell of sweat by killing the bacteria that cause it.
Previously, it was unknown whether and in what concentration these nanoparticles enter the environment and e.g. enter bodies of water. If they do, this poses a problem. That is because the silver nanoparticles are toxic to numerous aquatic organisms, and can upset sensitive ecological balances.
With the help of this analysis procedure, it is possible to gain new insight into the concentration of nanoparticles in drinking and waste water, sewage sludge, rivers, and lakes. In Bavaria, the measurements yielded good news: The concentrations measured in the water bodies were extremely low. In was only in four of the 13 Upper Bavarian lakes examined that the concentration even exceeded the minimum detection limit of 0.2 nanograms per liter. No measured value exceeded 1.3 nanograms per liter. So far, no permissible values have been established for silver nanoparticles.
Representative for watercourses, the Isar river was examined from its source to its mouth at around 30 locations. The concentration of silver nanoparticles was also measured in the inflow and outflow of sewage treatment plants. The findings showed that at least 94 percent of silver nanoparticles are filtered out by the sewage treatment plants.
This collaborative project comprising 16 partners from academic research institutions, business companies and regulatory authorities was funded by the German Ministry of Education and Research.