The next "it" product is here. Some of you sleep on it. Some of you slap it on cuts. Some of you clean with it. Some babies suck on it. A few people study it, wondering if "it" will be an environmental and health disaster.
Silver nanoparticles lace the insides of mattresses, bandages, washing machines, baby soothers, teddy bears and socks. Long known for its antimicrobial properties, silver is more effective at the nano-scale, particles a billionth of a metre in diameter. It's effective enough that the Environmental Protection Agency in the United States will consider it a pesticide under the Federal Insecticide, Fungicide and Rodenticide Act. Over 500 consumer products in North America hype their nano-sized composition, with silver the nano-star of the moment.
It's such a star that scientists Troy Benn and Paul Westerhoff at Arizona State University took name-brand socks infused with nano-silver and soaked them in a jar of room temperature distilled water. They shook the jars for an hour and tested the water to see if the silver stayed in the fabric. The results were released yesterday at the American Chemical Society meeting in New Orleans.
How small is nano? Look at this way: a sugar molecule is a nanometre wide. It would take about 300 trillion sugar molecules to cover the surface of a penny. DNA is 2.5 nanometres in diameter. A sheet of paper is about 100,000 nanometres thick. A virus measures about 100 nanometres. In Canada, the nanoscale refers to anything less than 100 nanometres.
Nanoscale is a big deal because at that size, a particle has more surface area per volume making it more reactive -- its behaviour is wildly different than at its normal size. That's a good thing, and maybe a bad thing. The question of toxicity and human-engineered nanomaterials is one scientists and regulators struggle to understand. And one that consumers barely know about.
"Consumers are not aware of what's on the market. They are not aware that a substantial amount of consumer products are being sold to them, there's no labelling, there's no information getting to them," explains Elizabeth Nielsen, a consultant for the Consumers Council of Canada (CCC) and author of a report released April 1, Nanotechnology and Its Impact on Consumers.
No clue about exposure level
As a member of the International Organization for Standardization's technical committee on nanotechnology, Dr. Nielsen approached the CCC about exploring the issue on behalf of consumers.
"One of the big areas of concern is cosmetics because there are no risk assessments done on cosmetics here, or in Europe or in the United States, or anywhere. That's something going directly where your exposure is potentially highest," she says from her home in Ottawa. Dr. Nielsen, a chemist, worked for Health Canada on product safety before her retirement.
While scientists know something about a small selection of nanoparticles, no one has a clue about the extent of our exposure.
You probably encounter a nanomaterial every day. To go with your silver-socks, you can use a high-end Babolat tennis racquet that uses carbon nanotubes to make it stronger and lighter than the competition. If you went to Eddie Bauer and bought a wrinkle- and stain-resistant shirt, you're wearing Nano-Tex, a "nanowhiskers" product that's woven onto clothing fibres. You can buy a bed-in-a-box at Canadian Tire that advertises its silver nanoparticles. Walk into any drugstore or natural food store, you might find lotions and potions using nanosilver as the new all-natural germ fighter. You'll definitely find silver-laced bandages.
The questions on scientist's minds are simple: do nanomaterials stay put? If not, where do they go and what do they do?
The carbon nanotubes in the racquet are in a fairly stable matrix -- they're probably not going anywhere, although maybe the nanotubes are released when the racquet is thrown out. The shirt and socks are next to exposed skin, a good barrier against foreign materials, unless you have a cut. Clothes eventually get washed.
The sock experiment is the first time researchers looked at the release of silver from this kind of manufactured clothing. Six pairs from five different brands went through a few washings and released silver at different rates. It suggests that "there may be a manufacturing process that will keep the silver in the socks better," says Benn, a PhD candidate in the civil and environmental engineering department at ASU.
Full Story: http://thetyee.ca/News/2008/04/07/NanoParticles/
