It sounds like a plot straight out of a science fiction novel by Michael Crichton. 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.
Humans have long lived in dread of such nightmare scenarios in which swarms of creatures attack. Alfred Hitchcock envisioned menacing flocks in “The Birds.” In the 1990 film “Arachnophobia” a killer spider arrives in the United States, where it attacks and multiplies.
And now comes nanophobia, 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. Personal care products are simply the lowest hanging fruit.
But 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 last month that long-term contact with such appliances could constitute a large exposure to the smallest of nanoparticles.
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.
But cosmetics industry representatives said there was no evidence that personal care products that contain nano-size components constitute a health hazard. Furthermore, no rigorous clinical trials have been published showing that cosmetics with nanocomponents caused health problems. 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. Furthermore, some say cosmetics may contain molecules like a silicone fluid called cyclopentasiloxane that are even smaller than nanomaterials.
“I think it’s a double standard because nanoparticles are less likely to go through the skin than solutions where you are using single molecules,” said Robert S. Langer ScD ’74, a chemical engineering professor at the Massachusetts Institute of Technology in Cambridge. He is developing nanoparticles for the targeted delivery of cancer medications, and is a founder of Living Proof, a cosmetics company that makes hair products. “The molecules in a cream are certainly going to be smaller than a nanoparticle.”