Sunday, June 1, 2008
You can't see them, but they're everywhere, from stain-resistant pants to antibacterial bandages to deflation-proof tennis balls. They're nanoparticles, microscopic substances less than one one-thousandth the width of a human hair. Though their size gives them unique properties that create handy technologies, concern is growing that some nanoparticles may be bad for the environment, and for you.
One issue is that the explosion of products using nanomaterials has outpaced the research into what happens when the particles escape into the environment or the human body. "Safety studies are dribbling in, but new consumer products are pouring in," says Jane Houlihan, vice president for research at the Environmental Working Group, a nonprofit organization that studies environmental health issues. "The system is backwards."
Arizona State University researchers, for instance, recently presented a study that found that silver nanoparticles used in odor-resistant socks leached into water after just a few washings and that the leaching also produced ionic silver, a toxin.
Silver, one of the most widely used nanomaterials, has potent antibacterial properties, "which can be a good thing or a bad thing," says Ron Turco, professor of agronomy at Purdue University and a leading researcher of nanotechnology's environmental effects. When nanosilver and ionic silver reach wastewater treatment plants, they could kill beneficial bacteria used to remove impurities; if the particles get back into waterways, they could also harm fish and algae. Leftover sewage sludge is also used as agricultural fertilizer; nanosilver remaining there could damage soil used to grow food.
Also of concern to human-health researchers are sunscreens, some of which contain nanoparticles of titanium dioxide and zinc oxide to block ultraviolet rays. Houlihan says studies have proved these sunscreens safe for most people, "but they haven't been well tested on damaged skin and on infants and small children, who have thinner skin."
Nanotechnology does promise technologies to benefit us. Nanoparticles of iron, for instance, are being studied as a way to clean up groundwater pollution. And nanoparticles may be a promising tool in medicine: A nanoparticle loaded with antibodies, for instance, can penetrate the blood-brain barrier to kill a tumor. (Though that advance may be a double-edged sword, as toxic nanoparticles could also reach the human brain.)
Good or bad, nanoparticles are here to stay, which is why they deserve close attention: They're an apt example of how even invisible things can end up having visible ecological consequences. Says Houlihan: "The problem with nanomaterials isn't something we know. It's what's not known."
-- Eviana Hartman