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Science + Tech

Big Worries About Micro Particles

As firms put more nanoparticles in products, science tries to gauge the risks.

Jude Isabella 7 Apr

Jude Isabella is managing editor of YES Mag, a Canadian science magazine for kids. (And grown ups who need to brush up on science basics.)

image atom
Toxic socks? Silver nanoparticles, magnified.

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.

The upside of tiny

Before getting outraged, consider that nanotechnology has great potential to do good. In tests, silver ions neutralize deadly E. coli bacteria and other nasty microbes. Antibiotic-resistant MSRA? High-ho silver to the rescue, in the future maybe. (Some scientists worry about microorganisms developing a resistance to silver as well.) A silver-laced sock, if it really works, is helpful if you have diabetes and at higher risk of foot infections.

Scientists engineer different materials to the nanoscale to get beyond the limitations posed by materials on the macro scale. Some nanomaterials, such as carbon nanotubes, are better at conducting electricity or heat, and especially useful for transistors, the electronic switching devices used in computers. Carbon nanotubes allow these devices to shrink, and computing power to swell -- hello smaller, turbo-laptops that use less energy. Some nanomaterials reflect light better and could hold the key to lower cost solar panels. To be anti-nano is just impossible.

Susan Holtz, a policy analyst with the Canadian Institute for Environmental Law and Policy, has just completed the Second Discussion Paper on a Policy Framework for Nanotechnology for Health Canada.

"There are huge potential benefits in things that I really care about like renewable energy," Holtz says. What CIELAP would like is to slow down the rate at which industry is tossing everything nano on the market. "But slowing down things without putting a dead stop is a complex matter."

What Holtz and Dr. Nielsen are looking for is balance -- that the good is not thrown out because no one anticipated the bad. Research, however, trails behind commercial application.

Tests underway

Last year, scientist Vicki Stone at Napier University in Edinburgh launched the journal Nanotoxicology, a scientific journal with a focus on assessing, evaluating and getting a handle on the risks. Dr. Stone's team began testing silver nanoparticles six months ago in response to the number of nanosilver commercial products popping up on the market. They're not ready to publish any results.

Ask the scientist if silver nanoparticles are worrisome and she answers, "It depends on the product it's being used for. I think for some product applications it will be relatively safe -- if it's incorporated into the interior of a fridge or something like that, or a surface, then it's probably not a problem. But if it's in a formulation that can be released then I think it needs to be carefully tested."

Testing is a truly laborious, if not a daunting affair. Say "nanoparticles" and you're not talking about one thing -- they vary in size, shape and surface structure. Nor are all nanoparticles engineered. Natural nanoparticles are found in the environment, volcanic dust for example. And nanoparticles are incidental, the result of industrial processes.

"Twelve years ago we didn't call them nanoparticles," Dr. Stone says from her Edinburgh office. "We called them ultra fine particles and they were accidentally made from combustion processes like traffic, so they weren't pure, they were contaminated with other things. That literature showed that particle size can influence toxicity in the lungs, and it provided some useful background information to the newly engineered nanoparticles."

Based on those studies, scientists know that nanoparticles created by combustion cause lung inflammation even with low exposure. Obviously, that's bad, but that's exhaust. Engineered nano-sized zinc oxide particles, found in sunscreens, cause no lung inflammation at low doses. At high doses, however, they were more toxic to human immune cells than diesel exhaust particles and silver nanoparticles. In other words, you won't get all the answers by studying one kind of nanoparticle, one dose, or even one size. Gold at 20 nanometres behaves differently than gold at 70 nanometres.

'I certainly worry about it'

So is it wise to imbue socks with silver nanoparticles? Perhaps you won't be affected, directly. But what about the sewage treatment plant that relies on microbial action to breakdown waste, and the aquatic environment -- well, you can follow that to its conclusion. And what about baby bottle nipples, soothers, and stuffed animals? Our mouths hold beneficial flora too. So do our guts. Do silver nanoparticles kill the good guys too? An antimicrobial is an antimicrobial is an antimicrobial.

"Believe me," Holtz says from her home office in Toronto, "everybody who has any kind of scientific background, and paying attention to nano, is aware of all this. I certainly worry about it." The problem, Holtz adds, is that to regulate nanomaterials as potentially toxic substances you need to be able to identify them, classify them, measure them in the environment and test them for health effects and ecological toxicity.

No regulations or standards also mean you don't even know if what you're buying works. You can buy nanosilver health remedies -- labelled as colloidal silver -- that claim to boost your immune system yet efficacy is questionable

"The problem is, just because they label something colloidal silver, you don't know exactly what that means, you don't know how much it contains either," Dr. Stone explains. "You would have to test each sample to determine if it contained any nanosilver particles."

In fact, the socks Benn and Dr. Westerhoff washed contained varying levels of silver.

"Some socks that had a lot of silver did not leach much silver, and some socks had less silver that leached all of it in four washings," Benn says. "The most silver leached from any of the socks was about 1.8 milligrams, after four washings."

What to label 'nano'?

One of the regulatory hurdles is the lack of distinction between a nanoparticle and its bigger version. "Silver," Holtz says, "is already in use. Regulatory authorities have not, so far, identified nano-scale silver as different or treated it as a new substance. In other words, this regulatory loop hole has allowed these materials to proceed directly into various applications."

In early March, a California technology company was fined $208,000 by the EPA for selling unregistered pesticides and making unproven claims about their effectiveness. IOGEAR, a subsiduary of ATEN Inc., was marketing a wireless mouse that killed germs with it "nano shield coating." Silver nanoparticles were part of the germ-free nano recipe.

Dr. Stone adds pure engineered nanoparticles to an organism's environment, algae and fish for example, and then monitors what happens. While the jury is still out on silver, if you start digging, enough tests pop up in a literature search to make you pause and suspiciously eye your tennis racquet. Günter Oberdörster at the University Rochester in 2004 has already shown that nano-sized carbon-13 inhaled by rats can travel from the lungs to the liver in just four hours. They easily passed from the blood vessels' thin walls. In a week they bypassed the blood-brain barrier and were found in the rat's olfactory bulb.

In 2005, Anna Shvedova at the National Institute for Occupational Safety and Health in the U.S. reported that high doses of single-walled carbon nanotubes inhaled by mice caused a rapid inflammatory response, scarring the lungs within seven days.

At the ACS meetings over the next few days, test results from studies of engineered particles on soil, earthworms, and marine life will add to the literature.

Meanwhile, in the real world

Yet even in tests, scientists question how the particles would behave if cultured differently. Real world exposure remains a real mystery. While smashing the ball with your high-end Babolat might be a perfectly safe way of improving your swing, the health of racquet factory workers could be another story.

Forget consumers for a moment, the people most likely to inhale carbon nanotubes or silver nanoparticles work in factories and laboratories. Occupational exposure adds another dimension to the problem, Dr. Nielsen says, "[Workers] are using or developing the products, incorporating them into other products -- that's one of the places where there's the greatest risk, but we don't know right now."

To find an inventory of commercial products in Canada is impossible. Although you can find an inventory in the U.S. As far as manufacturing nanoparticles, it's a given that it's going on in health and other research, and it may be going on in the commercial sector.

"We don't know," Holtz says. "We don't have an inventory here, that's one of the high priority items that would be nice to put in place in overall policy framework." CIELAP suggests at least a dozen topic areas where work needs to proceed at a policy level to develop some kind of oversight, things like measurement standards, terminology, and standardized definitions.

Canada's position on nano

In one way, Canada is ahead of other countries in regulating nanomaterials. Last year, the federal government, under the Canadian Environmental Protection Act, informed manufacturers and importers of nanomaterials that the nano-scale form of a substance on the Domestic Substances List will be considered new if it has a unique molecular arrangement. The advisory explicitly pointed out the nano-material fullerenes (a molecule of carbon spherical or cylindrical in shape, if cylindrical it's called a nanotube) are subject to the same regulatory requirements as chemicals and polymers.

"That probably means negotiating with Environment Canada at this point because we don't even know how to test for them," Holtz says. "As far as I know, that's the first regulatory initiative anywhere in the world that deals with nanomaterials as potentially toxic substances. Everybody's scrambling: the EU, the U.S., Japan, Canada, we're all trying to get a handle on it."

So, are nanosilver socks toxic? After a few washes, maybe to marine life.

"The idea behind our work is that it would provide an estimation to the amount of silver nanoparticles that might be introduced into the environment," Benn explains. "You can combine our work with Dr. Stone's to begin estimating the environmental risk of consumer nanomaterials."

Ask Benn if he would buy silver nanoparticle socks and he says no. "I don't think the benefit outweighs the risk to my own health or the environment." But, again for someone who has a high risk of infection, if the silver worked, it could be a lifesaver. If silver-infused clothes meant we washed our clothes less, maybe the water savings outweighs possible harm.

Benn echoes almost everyone who studies nanotechnology: the biggest concern is that consumers are unaware they are buying products that contain nanoparticles. "Consumers should be informed to make their own judgments of the risks of using these products," he says.

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