Three or four new nanotechnology-based consumer products hit the market every week, according to the Project on Emerging Nanotechnologies, but for the consumer, it's not always easy to know if an item contains nanoparticles.

Shoppers might not be aware, for example, that silver nanoparticles are used in the FresherLonger food storage containers sold by Sharper Image, or in Pure Plushy's mold- and bacteria-resistant teddy bears.

Silver nanoparticles are probably the most popular nanomaterials among manufacturers because of their antimicrobial properties.

Companies such as ARC Outdoors and AgActive in the United Kingdom use nanosilver in socks to keep them odor-free. At Nanoshop.com, customers can find a softener for baby clothes and underwear containing nanosilver, in addition to antimicrobial paint and a shoe deodorizer.

Nano Silver Wholesale offers food storage containers, cosmetics, soap, shampoo, conditioner, dental care, body cleanser, disinfectant spray and pet spray.

And the inventory of nanomaterials in consumer products, held by the Project on Emerging Nanotechnologies, includes nine examples of toothpaste containing gold and silver nanoparticles.

NanoSafeGuard of Seattle, which sells a collection of surface sealants online, does, however, make it clear that their products contain nanoparticles.

"We have nothing to hide," says Kenneth Hansen, company sales director. "There are no new materials in our products; all were listed in the TSCA Inventory before."

Indeed, the nanoparticles in NanoSafeGuard's products are classified as an existing substance by the Environmental Protection Agency. The products contain nanoparticles primarily made of ceramics, glass and titanium dioxide to be used on materials such as wood, stone, glass, leather and metal. The products make it easier to clean the surface.

"There is no need for any harsh chemicals, and you can use up to 80 percent less cleaning detergent," Hansen said.

E-mail Ann Fernholm at afernholm@sfchronicle.com.