Silver tongues

Apr 17th 2008 | NEW YORK

From The Economist print  edition 

Regulators are looking more closely at nanotechnology claims 



ANCIENT Phoenicians stored their drinking water in silver vessels, but not  

for aesthetic reasons. They discovered that by doing so they remained 

healthier.  The reason for that is now understood: silver has antimicrobial properties. 

 

In the 21st century people have realised that if you fortify Phoenician  

wisdom with a dash of nanotechnology, silver can be made into a far more potent  

bactericide. Companies have quickly seized on this idea to produce a wide  

variety of products, from clothes to soap and even chopsticks, containing silver  

nanoparticles. The claim is that they destroy germs. 

 





But silver can also accumulate in the environment and, at certain levels,  

prove toxic. Nor is the general safety of nanoparticles fully understood, not  

least because they can react in novel ways. Some scientists think more research 

 is needed and perhaps more regulation too. A move in that direction now 

seems to  be under way. 

Silver's natural germ-killing ability stems from its extremely slow release  

of silver ions (electrically charged atoms, or groups of atoms). When made 

into  particles only a few nanometres big—a nanometre is a billionth of a metre—

they  shed a lot more ions and so become more potent. 

America's Environmental Protection Agency (EPA) is  worried about a large 

number of products claiming antimicrobial abilities. One  is “Silver Wash”, a 

washing machine made by Samsung, which claims to employ  nanotechnology to 

release hundreds of billions of silver ions during a wash to  sanitise fabrics.  

The EPA has ruled that ion-generating devices that  claim to kill germs must 

be registered as a pesticide and tested to show they  pose no unreasonable 

risk. The EPA says its intention  is to regulate ion-generating devices rather 

than nanotechnology itself. But it  is hard to draw a distinction. Andrew 

Maynard, chief science adviser for the  Project on Emerging Nanotechnologies at the 

Woodrow Wilson International Centre  for Scholars in Washington, DC, says 

functionality is  an important part of the definition. Turning silver into tiny 

particles that  behave in new ways (for example, by shedding more ions) and 

putting those  particles into new places (such as fabrics) qualifies—or so he 

thinks. 

One consequence of dividing a substance into nanoparticles is that the  

surface area of the material greatly expands. “Nanosilver is so tiny it can go  

right to the surface of an organism and essentially shoot ions into the  organism,

” says Sam Luoma, a research scientist at the John Muir Institute of  the 

Environment at the University of California, Davis. Although this makes  silver 

nanoparticles an extremely effective antimicrobial agent, it also raises  

concerns about humans' ability to withstand relatively high exposures. 

Despite the unknowns, Dr Luoma and others believe there is enormous potential 

 for good from nanosilver. It can, for example, be used in small amounts to 

coat  medical catheters to reduce the possibility of infection without causing  

environmental worries. “We need to separate out the truly beneficial uses,” 

he  adds. 

The EPA will not look at benefit or necessity, but  is determined to make its 

registration stick. It has fined one company more than  $200,000 for making 

unsubstantiated claims about unregistered nanosilver-coated  computer mice and 

keyboards. Firms making claims about nanotechnology need to  watch out







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