Sizing Up the Nanometer: Some personal products contain nanoparticles, components less than 100 nanometers in size. To make mineral sunscreens less grainy, companies use particles of titanium dioxide as small as 15 nanometers./ANDY PRESSMAN/RUMORS

By NATASHA SINGER


It sounds like a plot straight out of a science-fiction novel. Toiletry companies formulate new cutting-edge creams and lotions that contain tiny components designed to work more effectively. But those minuscule building blocks have an unexpected drawback: the ability to penetrate the skin, swarm through the body and overwhelm organs like the liver.

Nanophobia is the fear that tiny components engineered on the nanoscale - that is, 100 nanometers or less - could run amok inside the body. A human hair, for example, is 50,000 to 100,000 nanometers in diameter. A nanoparticle of titanium dioxide in a sunscreen could be as small as 15 nanometers. (One nanometer equals a billionth of a meter.)

“The smaller a particle, the further it can travel through tissue, along airways or in blood vessels,”said Dr.Adnan Nasir, a clinical assistant professor of dermatology at the University of North Carolina at Chapel Hill.“Especially if the nanoparticles are indestructible and accumulate and are not metabolized, if you accumulate them in the organs, the organs could fail.”

Indeed, some doctors, scientists and consumer advocates are concerned that many industries are adopting nanotechnology ahead of studies that would establish whether regular ingestion, inhalation or dermal penetration of these particles constitute a health or environmental hazard.

People are already exposed to nanoparticles. Stoves and toaster ovens emit ultrafine particles of 2 to 30 nanometers, according to the National Institute of Standards and Technology; the researchers reported in November that long-term contact with such appliances could constitute a large exposure to the smallest of nanoparticles.

Several products already use nanoengineered materials. There are“nano pants,”stain-resistant chinos and jeans whose fabric contain nano-sized whiskers that repel oil and dirt. And in lotions and creams, the use of nanocomponents may create uniformity or spreadability.

Some ingredients may behave differently as nanoparticles than they do in larger forms. Nano-sized silver, for example, can act as an antibacterial agent on the skin. Larger particles of zinc oxide and titanium dioxide result in white pasty sunscreens; but as nanoparticles, they appear more transparent.

When it comes to beauty products, however, some consumer advocates are concerned that dynamic nanoparticles could pose risks to the skin or, if they penetrate the skin, to other parts of the body. Mineral sunscreens have attracted the most attention.

“Substances that are perfectly benign could be toxic at the nano scale,”said Michael Hansen, a senior scientist at Consumers Union, the company behind Consumer Reports, which puts out product reviews and ratings.“Because they are so small, they could go places in the body that could not be done before.”

But cosmetics industry representatives said there was no evidence that personal care products that contain nano-size components constitute a health hazard. A review of the potential risks of nanomaterials, carried out for the European Center for Toxicology in 2006, concluded that sunscreens with metal nanoparticles were unlikely to penetrate healthy skin, but it did raise the question of whether safety studies should examine if such materials may penetrate damaged skin.

“It’s very difficult to get anything through the skin,”said John Bailey, the executive vice president for science of the Personal Care Products Council, an industry trade group in Washington.“The skin is a very effective barrier.”

Indeed, some nanotechnology researchers said it was illogical to assume that a nano-size component inherently carries greater risk than a larger component.

Last month, a consumer group in London called Which- published a survey it had conducted of 67 cosmetics companies on the prevalence and safety testing of nanomaterials in personal care products. Only 17 companies responded, of which eight acknowledged using nanomaterials.

“When nanotechnology was hot, everybody wanted to talk about ‘nano this, nano that.’Look at the iPod Nano,”said Dr.Hansen of Consumers Union.“But now that the concerns have come out, people are not so sure the word nano is a good thing to be touted.”