The U.S. Food and Drug Administration issued two draft guidelines on Friday calling for more studies, putting, for now, much of the onus for safety on companies.

The FDA also rejected a consumer group's petition from 2006 that urged a separate category of regulation for nanotechnology due to its "unique human health and environmental risks."

Nanotechnology involves designing and manufacturing materials on the scale of one-billionth of a meter - so small it cannot be seen with a regular light microscope.

It is used in hundreds of products in areas ranging from stain-resistant clothing and cosmetics to food additives, but the health effects of nanoparticles are still poorly understood.

Nanoparticles may be able to penetrate the skin, or move between organs, with unknown health effects.

"Understanding nanotechnology remains a top FDA priority," FDA Commissioner Margaret Hamburg said in a statement. "FDA is strengthening the scientific tools and methods for evaluating food products, cosmetics, drugs and medical devices."

The FDA advised companies that use nanotech in food additives or food packaging to consult with the agency and show that the changes are safe before selling their products.

"The consequences (to consumers and to the food industry) of broadly distributing a food substance that is later recognized to present a safety concern have the potential to be significant," the draft guide says.

Makers of most U.S. food additives and ingredients can tell the FDA that their ingredients are "generally recognized as safe" in order to legally sell them.

The FDA said nanotechnology does not automatically fall into this category, meaning companies would have to prove additional safety data before approval.

Erik Olson, director of food programs at Pew Health Group, a consumer advocacy group, said companies can often simply inform the FDA that certain food additives are safe. But the new guidelines for the first time show the FDA thinks nanomaterials deserve greater scrutiny.

"The FDA is essentially saying (to companies), we don't think you can just make your own decision a nanomaterial is safe without telling us," Olson said. "That's a fairly new development."

The International Center for Technology Assessment, which filed the 2006 petition, sued the FDA late last year for being slow to reply.

Jaydee Hanson, policy director at the center, said legal action may have prompted FDA to issue guidance for nanotech in food and cosmetics after a delay of six years.

"It's good that they're making recommendations in this area, but they haven't gone far enough," he said.

The European Union requires companies to prove a nanotech product is safe before it can be sold to consumers, Hanson said, while the FDA has only issued voluntary guidelines for companies.

For cosmetics, the FDA said companies should also do additional testing of products that, for example, use nanotechnology to create smoother-feeling moisturizers or lipstick.

The FDA does not require cosmetic companies to submit safety data before selling their products, and the guidance is unlikely to have a big impact on large cosmetic firms like Avon Products Inc, which already comply with European rules.

Avon said it adds nanomaterials like titanium dioxide or zinc oxide to cosmetic products to boost protection against the sun's ultraviolet rays and let sunscreens rub in without leaving white marks. It said the products were proven safe in the EU.

(Reporting by Anna Yukhananov in Washington, additional reporting by Phil Wahba in New York; Editing by Tim Dobbyn)

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