While the antibacterial and odour-fighting properties of nanoparticle silver has made it a superhit in the retail industry, scientists are concerned because these nanoparticles may have certain unwanted environmental and health consequences.
A report scheduled for the 235th national meeting of the American Chemical Society (ACS) calls for a closer examination of the unforeseen environmental and health consequences that the use of nanosilver in products like odourless socks, bandages, and washing machines may have.
"The general public needs to be aware that there are unknown risks associated with the products they buy containing nanomaterials," Arizona State researchers Paul Westerhoff and Troy M. Benn say in the report.
The researchers are of the opinion that ordinary laundering can wash off substantial amounts of the nanosilver particles from socks impregnated with the material.
They say that the particles, intended to prevent foot odour, could travel through a wastewater treatment system, and enter natural waterways where they might have unwanted effects on aquatic organisms living in the water and possibly humans.
"This is the first report of anyone looking at the release of silver from this type of manufactured clothing product," they write in the report.
In an experiment, Benn and Westerhoff soaked six pairs of name brand anti-odour socks impregnated with nanosilver 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.
"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," they say.
Benn warns that nanosilver escaping waste water treatment systems into nearby lakes, rivers and streams may damage aquatic ecosystems. The researcher says that the dissolved form of iconic silver not only attacks odour-causing bacteria, but it can also 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," says Benn.
Westerhoff, however, concedes that ionic silver is only toxic to humans at very high levels, and that the toxicity of nanoparticle silver has yet to be determined. The researcher also made it clear that the study was not intended at establishing the toxicity of silver.
"The history of silver and silver regulation has been set for decades by the U. S. Environmental Protection Agency - we're not trying to reexamine or reinvent that," says Westerhoff.
The researcher duo has also found that most consumers are unaware of what exactly is nanotechnology.
"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," says Benn.
The researchers recommend improved product labelling for products in which "ingredients" like nanosilver are used.
"Our work suggests that consumer groups need to start thinking about these things. Should there be other standards for these products," says Benn.