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Toxicity of silver nanoparticles on Arctic soil

While advocating the commercial exploitation of current nanoscience and nanotechnology (for example), Foresight has also supported adequate study of the potential effects of nanoparticles on the environment, health, and safety (EHS) (see Nanoparticle Safety). Such research is especially important because nanoparticles in use and under development represent a great diversity of chemical structures and materials, so that results for one class of nanoparticles will not in general be relevant for different types of nanoparticles. Physorg.com points to this news release from Queen’s University in Canada that reminds us of the need for expanded research on nanoparticle safety “Common nanoparticles found to be highly toxic to Arctic ecosystem“:

Queen’s researchers have discovered that nanoparticles, which are now present in everything from socks to salad dressing and suntan lotion, may have irreparably damaging effects on soil systems and the environment.

“Millions of tonnes of nanoparticles are now manufactured every year, including silver nanoparticles which are popular as antibacterial agents,” says Virginia Walker, a professor in the Department of Biology. “We started to wonder what the impact of all these nanoparticles might be on the environment, particularly on soil.”

The team acquired a sample of soil from the Arctic as part of their involvement in the International Polar Year initiative. The soil was sourced from a remote Arctic site as they felt that this soil stood the greatest chance of being uncontaminated by any nanoparticles.

“We hadn’t thought we would see much of an impact, but instead our results indicate that silver nanoparticles can be classified as highly toxic to microbial communities. This is particularly concerning when you consider the vulnerability of the arctic ecosystem.” …

The researchers first examined the indigenous microbe communities living in the uncontaminated soil samples before adding three different kinds of nanoparticles, including silver. The soil samples were then left for six months to see how the addition of the nanoparticles affected the microbe communities. What the researchers found was both remarkable and concerning.

The original analysis of the uncontaminated soil had identified a beneficial microbe that helps fix nitrogen to plants. As plants are unable to fix nitrogen themselves and nitrogen fixation is essential for plant nutrition, the presence of these particular microbes in soil is vital for plant growth. The analysis of the soil sample six months after the addition of the silver nanoparticles showed negligible quantities of the important nitrogen-fixing species remaining and laboratory experiments showed that they were more than a million times susceptible to silver nanoparticles than other species.

There are three important aspects to this study that the news release does not emphasize. First, the nanoparticles were not already present in the arctic soil samples—they were added by the experimenters, so there is as yet no evidence that silver nanoparticles are widespread in the environment. Second, neither the news release nor the abstract of the research publication correlates the level of silver nanoparticles added to these samples with the levels currently found in other environmental samples. Third, the other two types of nanoparticles (identified in the abstract as copper nanoparticles and silica nanoparticles) showed no evidence of harm.

While there is yet no reason for blanket alarm about the presence of nanoparticles in the environment, the researchers are certainly correct to warn, as they do in the last sentence of their abstract:

Thus, NP contamination of arctic soils particularly by silver NPs is a concern and procedures for mitigation and remediation of such pollution should be a priority for investigation.

One of the worst possible outcomes for the long range development of nanotechnology would be for current nanoparticle commercialization to cause substantial EHS problems as a result of inadequate EHS research and foresight. Some nanoparticles may be of little concern, but others might require special regulation or precautions, or might need to be modified or substituted, or might not be safe for certain applications.

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