Nanoparticles Are in Our Food, Clothing and Medicine -- And No One Knows for Sure How Dangerous They Might Be
Continued from previous page
So chemistry and physics work differently if you’re a nanoparticle. You’re not as small as an atom or a molecule, but you’re also not even as big as a cell, so you’re definitely not of the macro world either. You exist in an undiscovered country somewhere between the molecular and the macroscopic. Here, the laws of the very small (quantum mechanics) merge quirkily with the laws of the very large (classical physics). Some say nanomaterials bring a third dimension to chemistry’s periodic table, because at the nano scale, long-established rules and groupings don’t necessarily hold up.
These peculiarities are the reason that nanoparticles have seeped into so many commercial products. Researchers can take advantage of these different rules, adding nanoparticles to manufactured goods to give them desired qualities.
Scientists first realized that nanomaterials exhibit novel properties in 1985, when researchers at Rice University in Houston fabricated a Buckminsterfullerene, so named because the arrangement of sixty carbon atoms resembles the geodesic domes popularized by architect Richard Buckminster Fuller. These “Buckyballs” resist heat and act as superconductors. Then, in 1991, a researcher at the Japanese technology company NEC discovered the carbon nanotube, which confers great strength without adding weight. Novel nano materials have been reported at a feverish pace ever since.
With these engineered nanoparticles—not even getting into the more complex nanomachines on the horizon—we can deliver drugs to specific cells, “cloak” objects to make them less visible, make solar cells more efficient, and manufacture flexible electronics like e-paper.
In the household realm, nanosilica makes house paints and clothing stain resistant; nanozinc and nano–titanium dioxide make sunscreen, acne lotions, and cleansers transparent and more readily absorbed; and nanosilicon makes computer components and cell phones ever smaller and more powerful. Various proprietary nanoparticles have been mixed into volumizing shampoos, whitening toothpastes, scratch-resistant car paint, fabric softeners, and bricks that resist moss and fungus.
A recent report from an American Chemical Society journal claims that nano–titanium dioxide (a thickener and whitener in larger amounts) is now found in eighty-nine popular food products. These include: M&Ms and Mentos, Dentyne and Trident chewing gums, Nestlé coffee creamers, various flavors of Pop-Tarts, Kool-Aid, and Jell-O pudding, and Betty Crocker cake frostings. According to a market report, in 2010 the world produced 50,000 tons of nano–titanium dioxide; by 2015, it’s expected to grow to more than 200,000 tons.
At first some in the scientific community didn’t think that the unknown environmental effects of nanotechnology merited CEINT’s research. “The common view was that it was premature,” says CEINT’s director, Mark Wiesner. “My point was that that’s the whole point. But looking at risk is never as sexy as looking at the applications, so it took some time to convince my colleagues.”
Wiesner’s team at CEINT chose to study silver nanoparticles first because they are already commonly added to many consumer products for their germ-killing properties. You can find nanosilver in socks, wound dressings, doorknobs, sheets, cutting boards, baby mugs, plush toys—even condoms. How common is the application of nanoparticles? It varies, but when it comes to socks, for example, hospitals now have to be cautious that the nanosilver in a patient’s footwear doesn’t upset their MRI (magnetic resonance imaging) machines.
Wiesner and his colleagues spent several months designing the experiments that will help them outline some general ecological principles of the unique nanoverse. He knew they wanted to test the particles in a system, but a full-scale ecosystem would be too big, too unmanageable, so they had to find a way to container-ize nature. They considered all sorts of receptacles: kiddie pools (too flimsy), simple holes in the ground (too dirty, too difficult to harvest for analysis), concrete boxes (crack in winter). Finally, they settled upon wooden boxes lined with nonreactive, industrial rubber: cheap to build, easy to reuse, and convenient to harvest.