Nano-silver: Looking a little tarnished?

The author Neal Stephenson got it wrong—at least, if this week’s nano-news is anything to go by!   In his landmark 1995 novel “The Diamond Age,” Stephenson described a future built on nano-innovation.  But thirteen years later, nanotechnology seems to be ushering in “The Silver Age.”  And to some it’s looking a little tarnished.

First we had Cal Baier-Anderson’s entry on the Environmental Defence Fund nanotech blog, calling claims that bacteria cannot develop resistance to silver “not only false, but dangerous.”  Two days later, the International Center for Technology Assessment (CTA) filed a petition with the USEPA requesting the agency regulate nano-silver products as pesticides.  And to top it all, Washington Post science writer Rick Weiss completed the hat trick with a story on nano-silver in Friday’s edition of the paper.

Silver is currently topping the charts in the Project on Emerging Nanotechnologies consumer products inventory—136 entries out of 610 as of May 2nd.  Nano-silver is clearly a technology of the moment, and manufacturers are flocking to use the antimicrobial nanoscopic particles in anything they can—from socks to toothpastes to fluffy toys.  CTA claim the sole reason for using nano-silver in these products is as an agent for killing microbes and as such, it should be classed as a pesticide. But that would make life difficult for opportunistic manufacturers looking to get onto the nano bandwagon.  Perhaps this is why some companies are using the technology, but being circumspect about who they tell (check out “Benny the bear, and the case of the disappearing nano”).

Silver is a powerful antimicrobial.  Yet widespread and indiscriminate use of silver nanoparticles raises clear concerns: is it harmful to people, will it be released and accumulate in the environment, will it harm environmental organisms, and will it lead to silver-resistant strains of bacteria?  The jury’s still out on most of these questions, which suggests more research is needed—and fast.  A recent study by Paul Westerhoff and Troy M. Benn of Arizona State University demonstrated that ordinary laundering of silver nanoparticle-laden socks can wash the particles out.  But where these particles go and what they do, once out in the environment, is largely unknown.  

And what about microbes building up resistance to nano silver over time?  In a recent article Lucian Lucia, an associate professor of chemistry at North Carolina State University, suggested that bacteria cannot build up resistance to silver nanoparticles as they can to antibiotics: “That’s the beauty of silver… [t]here’s no way to develop a resistance to it.”  Yet Cal Baier-Anderson’s cites a series of convincing studies that challenge this claim.

Silver is a useful weapon in the fight against infection, and nano-silver extends its reach in this arena.  But using it without caution would seem unwise.  Surely it’s time to discover the rules of safe use, and to avoid applications where the benefits are dubious and the risks uncertain.  At least; if we want a nanotechnology age without tarnish.



This post first appeared on the SAFENANO blog in May 2008

One Response to Nano-silver: Looking a little tarnished?

  1. […] is no stranger to the use (and possible abuse) of nanometre-scale silver—products ranging from silver-enhanced socks and toothpaste to plush toys and cure-alls have all appeared in the spotlight recently. With each […]

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