Laundering Socks with Nano Particles Possible Health, Environmental Risk

Nanotechnology particles, valued for their antibacterial and odor-fighting properties, are used in a wide range of commercial products such as bandages, washing machines and socks. But researchers from Arizona State University discovered that these socks release silver nanoparticles when washed, raising concerns about the potential impact on environmental and human health.

Researchers Paul Westerhoff and Troy Benn hypothesized in their report, “Fate and transport of ionic and nanoparticle silver released from commercially available socks,” that silver nanoparticles could travel through wastewater treatment systems and enter natural waterways. Once there, they could have unwanted effects on aquatic organisms and possibly humans.

“This is the first report of anyone looking at the release of silver from this type of manufactured clothing product,” said the authors, who presented the report findings April 6 at the national meeting of the American Chemical Society.

Benn and Westerhoff conducted an experiment with six pairs of name brand anti-odor socks impregnated with nanosilver. They soaked the socks in a jar of room temperature distilled water, shook the contents for an hour and tested the water for two types of silver – the harmful “ionic” form and the less-studied nanoparticle variety.

Manufacturing Process May Curb Particle Release

“From what we saw, different socks released silver at different rates, suggesting that there may be a manufacturing process that will keep the silver in the socks better,” said Benn. “Some of the sock materials released all of the silver in the first few washings, others gradually released it. Some didn’t release any silver.”

If sufficient nanosilver leeches out of these socks and escapes waste water treatment systems into nearby lakes, rivers and streams, it could damage aquatic ecosystems, said Benn. Ionic silver, the dissolved form of the element, does not just attack odor-causing bacteria; it also can hijack chemical processes essential for life in other microbes and aquatic animals.

“If you start releasing ionic silver, it is detrimental to all aquatic biota. Once the silver ions get into the gills of fish, it’s a pretty efficient killer,” said Benn. Ionic silver only is toxic to humans at very high levels. The toxicity of nanoparticle silver, said Westerhoff, has yet to be determined.

“The history of silver and silver regulation has been set for decades by the [EPA] — we’re not trying to reexamine or reinvent that,” said Westerhoff.

Public Should Be Informed

Westerhoff and Benn hope to spark a broader examination of the environmental and health consequences of nanomaterials, as well as increasing awareness of nanotechnology’s role in everyday consumer goods.

Silver has been used historically since ancient roman times, though its nanoparticle form has only recently appeared in consumer products. Various nanoparticles increasingly are used to make clothing free of wrinkles and resistant to stains, but not much is known about what happens to nanoparticles in the laundry.

“I’ve spoken with a lot of people who don’t necessarily know what nanotechnology is, but they are out there buying products with nanoparticles in them. If the public doesn’t know the possible environmental disadvantages of using these nanomaterials, they cannot make an informed decision on why or why not to buy a product containing nanomaterials,” Benn said.

The researchers suggest that improved product labeling could help. Westerhoff proposes that clothing labels could appear similar to food packaging labels, complete with a list of “ingredients” like nanosilver.

Westerhoff and Benn expect to expand their experiments to other consumer products imbued with nanomaterials. They hope to find the moment in each product’s life cycle when nanomaterials could be released into the environment, as well as developing better detection methods to characterize nanoparticles in water and air samples.

“Our work suggests that consumer groups need to start thinking about these things,” said Benn. “Should there be other standards for these products?”

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