Consumer products using extremely small particles of silver to kill germs will need Environmental Protection Agency approval, as part of the U.S. government's first move to regulate the burgeoning nanotechnology industry.

The EPA said Wednesday it was changing federal policy to require that manufacturers provide scientific evidence that their use of nanosilver won't harm waterways or public health.

Environmentalists and others are concerned that after the material is discarded and enters the environment, it may be killing helpful bacteria and aquatic organisms or even pose a risk to humans.

Nanosilver is used to kill germs in shoe liners, food-storage containers, air fresheners, washing machines and other products.

Silver is among the most common type of nanomaterials marketed to consumers, of which more than 200 now exist, according to the Project on Emerging Nanotechnologies, which is funded by the Woodrow Wilson International Center for Scholars and the Pew Charitable Trusts.

But the EPA doesn't plan to oversee most nanomaterials, which can be as small as one-millionth the width of a head of a pin. The Washington Post reported the EPA's decision in Thursday editions. The Washington-based Daily Environment Report published the first story on the decision Tuesday.

The aim of nanotechnology, in the commercial world, is to develop new products and materials by changing or creating materials at the atomic and molecular level. But much of the impact of those developments remains unknown, particularly with regard to possible environmental and health problems.

The Food and Drug Administration also is considering whether to regulate nanotech products.

EPA officials decided a year ago that a major pesticide law, the Federal Insecticide, Fungicide and Rodenticide Act, should not apply to washing machines because they were considered devices.

But after re-examining its decision and regulations, agency officials reversed course and decided "that the release of silver ions in the washing machines is a pesticide, because it is a substance released into the laundry for the purpose of killing pests," EPA spokeswoman Jennifer Wood said in an interview.

"This is now being considered a pesticide," Wood said. "So it does have to be regulated under FIFRA."