Stinky Sock Treatment May Pose Eco Hazard

April 9, 2008 -- The smell from your socks might not be the only toxic thing around. Silver nanoparticles, used for years to kill bacteria and eliminate odors in socks, food containers, medical dressings and even teddy bears, might be a threat to the environment, according to new research.

"People might not even be aware they are buying these things," said Troy M. Benn, an environmental engineer at Arizona State University in Tempe. Benn and his colleagues presented their findings this week at a meeting of the American Chemical Society.

Among an estimated 600 consumer products that contain nanomaterials, at least 20 percent contain silver nanoparticles.

The treated products can be effective since silver is known to have odor-fighting and antibacterial properties. But little is known about how these particles affect waterways once they pass through laundry drains.

To find out, the researchers bought six pairs of commercially available silver nanoparticle-treated socks. They soaked them in water and put them in a washing machine.

After as little as one washing, virtually all of the nanoparticles from two brands of the socks washed out. After four washings, two other brands lost just 1 percent of the silver nanoparticles. That suggested to researchers that it is the manufacturing process of the socks, not the nanoparticles themselves, that caused the silver to disappear down the drain.

The researchers tested waterways for two types of silver: reportedly harmless nanoparticle silver and harmful ionic silver. They found both.

Ionic silver in waterways kills fish and other aquatic creates when it enters their gills, but is harmless to humans.