The petition, filed by the International Center for Technology Assessment and others, also calls on the EPA to require formal pesticide registration of all products containing nanoscale silver, analyze the potential human health and environmental risks of the tiny germ-killing particles, and take regulatory action against existing products that contain the material.

The center said manufacturers are infusing products with nanoscale silver for its enhanced anti-microbial abilities. There are more than 260 nanosilver products currently on the market, including household appliances and cleaners, clothing, cutlery, children's toys and personal care products.

"Nanosilver is an unknown threat not only to the environment but also to human health," center staff attorney George Kimbrell said. "The public has no idea that consumer products contain potentially dangerous nanoparticles because no labeling is currently required."

Kimbrell said silver is toxic to fish, aquatic organisms and microorganisms. A 2008 study showed that washing nanosilver socks released substantial amounts of the nanosilver into laundry discharge water, which will ultimately reach natural waterways, the center said.