Tag Archives: PROSUITE

Silver nanoparticles: we love you/we hate you

We seem to have a love/hate affair with silver nanoparticles. Long recognized as biocides capable of killing bacteria, silver nanoparticles are used both in hospital settings and in sports wear. As the use of silver nanoparticles increases, there are concerns about unintended consequences to the environment and to human health. An Apr. 12, 2013 news item on Nanowerk highlights some research done in Europe in 2011 (Note: Links have been removed),

As part of an EU funded project called Prosuite, Walser [Tobias Walser, researcher at the Institute for environmental engineering at the Swiss Federal Institute of Technology Zürich {ETH}] and colleagues analysed the environmental impact of nanosilver T-shirts during their entire life cycle, from raw material extraction to end-of-life disposal (“Prospective Environmental Life Cycle Assessment of Nanosilver T-Shirts”). This, according to Walser, is the first of its kind for a nanomaterial. The scientists found that the T-shirt’s environmental impact during use would be reduced if they are washed less often than conventional ones, due to their antimicrobial properties. This would even compensate for a slightly higher climate footprint during production. Walser explains: “In comparison to all toxic releases during the life cycle of a T-shirt, the toxic releases from nanosilver from washing appear to be of minor relevance.” [emphasis mine]

The Apr. 11, 2013 article by Constanze Böttcher for Youris.com, which originated the news item, expands on the theme of toxicity, nanosilver, and wastewater (Note: A link has been removed),

Previous studies looked at single impacts of antibacterial textiles. For example, scientists found that nanosilver leaches into the wastewater during washing. According to other studies, this silver may not be that harmful to the environment because it is transformed into a nearly insoluble substance called silver sulphide in wastewater treatments. A study published by the Danish Environmental Protection Agency in 2012 did not find “specific risks” to health or environmental effects of nanosilver textiles available in Denmark.

This finding contrasts with more recent research at Duke University’s CEINT (Center for Environmental Implications of Nanotechnology) mesocosm project where a study did point to adverse responses (noted in my Feb. 28, 2013 posting where I highlighted two nanosilver environmental studies, a Finnish/Estonian research project and the CEINT project),

In experiments mimicking a natural environment, Duke University researchers have demonstrated that the silver nanoparticles used in many consumer products can have an adverse effect on plants and microorganisms.

The main route by which these particles enter the environment is as a by-product of water and sewage treatment plants. [emphasis] The nanoparticles are too small to be filtered out, so they and other materials end up in the resulting “sludge,” which is then spread on the land surface as a fertilizer.

The researchers found that one of the plants studied, a common annual grass known as Microstegium vimeneum, had 32 percent less biomass in the mesocosms treated with the nanoparticles. Microbes were also affected by the nanoparticles, Colman [Benjamin Colman, a post-doctoral fellow in Duke’s biology department and a member of the Center for the Environmental Implications of Nanotechnology (CEINT)] said. One enzyme associated with helping microbes deal with external stresses was 52 percent less active, while another enzyme that helps regulate processes within the cell was 27 percent less active. The overall biomass of the microbes was also 35 percent lower, he said.

As I’ve suggested before, analysing the impact that new products and materials may have on the environment and on our health is a complex process.  From Böttcher’s 2013 article (Note: Links have been removed),

Some experts are concerned about their environmental risks, however. The study “is very relevant” because it “gives a fingerprint” about the impact of such T-shirts, Anders Baun says. But the professor in risk assessment of nanomaterials at the department of environmental engineering at the Technical University of Denmark, based in Lyngby, considers it “a bad idea to distribute silver in the environment”. He points to a study that found evidence for nanosilver accumulating in the food web based on a study of plants and animals of an experimental wetland environment. Moreover, he says, it is unknown how the coating of nanosilver influences its environmental behaviour. Baun has previously criticised the European policies regarding nanosilver and is currently enrolled in a scientific committee on the topic as invited expert. The expert group will publish its opinion later this year, he says.

There’s also the possibility that bacteria will develop resistance with increased use of silver nanoparticles in medical environments and in sportswear and in other applications.

For those who want to conduct their own investigations, here’s a link to and a citation for Walser’s 2011 paper,

Prospective Environmental Life Cycle Assessment of Nanosilver T-Shirts by Tobias Walser, Evangelia Demou, Daniel J. Lang, and Stefanie Hellweg.  Environ. Sci. Technol [Environmental Science and Technology], 2011, 45 (10), pp 4570–4578 DOI: 10.1021/es2001248 Publication Date (Web): April 20, 2011
Copyright © 2011 American Chemical Society

This paper is open access.

A description of PROSUITE (PROspective SUstaInability assessment of TEchnologies project) can be found here and the PROSUITE project website can found here.

ETA Apr. 18, 2013: An Apr. 18, 2013 news item (Barely any nanosilver from consumer products in the water) on Nanowerk provides some insight into why at least one European country views the presence of silver nanoparticles in sewage sludge without any particular alarm,

The study did not examine what happens to nanosilver in the sewage sludge thereafter. In Switzerland, it is not permissible to use sewage sludge on farmland, and most of the sludge is therefore burned. [emphasis mine] The heavy metals separated in this process should not be released into the environment in large quantities.

Here’s a link to and citation for the Swiss study,

Fate and transformation of silver nanoparticles in urban wastewater systems by Ralf Kaegia, Andreas Voegelina, Christoph Orta, Brian Sinneta, Basilius Thalmanna, Jasmin Krismerb, Harald Hagendorferc, Maline Elumelua, and Elisabeth Muellerd. Water Research, http://dx.doi.org/10.1016/j.watres.2012.11.060 Available online 26 March 2013

The article is behind a paywall.