THE DETAILS: When the nonprofit Project on Emerging Nanotechnologies (PEN) started cataloguing products that contained nanoparticles and nanomaterials in 2006, they counted 212. As of August 2009, that number has nearly quadrupled to 1,015, and at least three quarters of those products are designed for the ordinary consumer, despite the fact that the long-term health effects of these particles is completely unknown. The largest group of products, at 605 total, falls into the "health and fitness" category, encompassing cosmetics, clothing, personal-care products, sporting goods, sunscreens, and air and water filters. Nanomaterials are also used in food storage and cookware—even plastic beer bottles and McDonald's clamshell containers—along with electronics, fabric coatings, and household cleaners.
Research on nanotechnology is still in its early stages, but already scientists are sounding alarms. At the recent meeting of the Society of Environmental Toxicology and Chemistry (SETAC), more than 20 studies were presented on the fate of nanoparticles once they enter the environment, and nearly all found that these materials were building up in organisms, such as earthworms, insects, and fish, and having subtle effects on their abilities to survive. Of particular concern are silver nanoparticles, the most ubiquitous nanomaterial in use today, according to PEN. They are used as an antimicrobial in athletic socks and clothing, food containers, and cutting boards due to their effectiveness at killing bacteria without triggering resistance, says Marie-Noële Croteau, PhD, research biologist with the U.S. Geological Survey and author of one of the nanoparticle studies presented at the meeting. At one time, a Samsung brand washing machine was being sold in the U.S. that released nanosilver particles in the wash water as an "ecofriendly" alternative to bleach (the company quit selling them after the Environmental Protection Agency required that the machines be listed as pesticides, due to the harmful affects of silver on wildlife). "In nano form, silver can be potentially toxic," Croteau says, to both animals and people. "Once these particles are in nature, in the water system, they're going to bind to sediment in the water and settle down on the bottom [of lakes and rivers]." Her study found that high levels of metal nanoparticles interfered with aquatic organisms' ability to feed, which has repercussions up the food chain. Another study found that once nanosilver is washed down the drain, it's highly effective at killing the microorganisms used to treat sewage in wastewater treatment plants, which could lead to bigger problems with drinking-water safety.
WHAT IT MEANS: What this tiny technology may be doing to human health is a more complicated question, says Gunter Oberdorster, PhD, professor of toxicology and environmental medicine at the University of Rochester, who takes a more circumspect look at nanoparticles in consumer products. "Different nanoparticles have different effects and they travel differently through the body," he says. "It all depends on the particle type and how they're used." Much of the research done on these particles, he says, simply points out how dangerous they are without considering real-world exposures.
For instance, Oberdorster doesn't see a problem with the use of nanoparticles in creams, despite the fact that the nanomaterials used, namely zinc oxide and titanium dioxide, have been linked in animal studies to brain damage. "No study has shown that zinc oxide or titanium dioxide can penetrate through healthy skin," he says. However, anytime you're dealing with products in powder or aerosolized forms, he says, there's a serious risk that those nanoparticles can penetrate your lungs, causing long-term damage, or get into your brain via inhalation. "Clearly, we need to find out more about the effects of nanoparticles in the conditions that we anticipate will happen for humans," he adds. While generalizing about them could put a damper on technology, "we cannot assume that they are innocuous in the environment," Croteau says.
Concerned about nanoparticles? Here are a few ways to reduce your exposure while science sorts the good from the bad:
• Investigate. Look up your favorite cleaners, cosmetics, clothing, and anything else that might contain nanotechnology at the Project on Emerging Nanotechnologies' Consumer Products Inventory to get a sense of how many of the products you use contain them. While you won't likely get exposed to nanoparticles from a carbon-nanotube bicycle or a nano-sized iPhone computer chip, you could ingest or inhale nanoparticles from cleaners, personal-care products, clothes, and bedding, says Oberdorster, and those are the products best avoided until more research can attest to their safety.
• Screen your sunscreens. While Oberdorster isn't overly concerned about the use of nanoparticles, such as nano titanium dioxide and zinc oxide, in sunblocks and sunscreens, other consumer-health advocates, including Samuel Epstein, MD, Rodale.com advisor and author of the book Toxic Beauty: How Cosmetics and Personal Care Products Endanger Your Health…and What You Can Do About It (Benbella Books, 2009), suggest that they shouldn't be used until more is known about their long-term health effects. And Croteau's research has shown that nano zinc oxide can build up in sediments and interfere with aquatic organisms' feeding behaviors, so your afternoon swim could be hurting the fish. You can see if your favorite sunscreen contains nanoparticles at the database above, and be aware that nanoparticles can hide behind some shady label language. There are no labeling requirements for products containing nano ingredients; they could be listed as "nano," "microfine," or "ultrafine," or simply not mentioned at all. Another good test is to slather some on the back of your hand. If it disappears, it's made with nanoparticles. If it leaves a slightly white sheen, it's nano free. Always avoid spray-on sunscreens that you can inhale, says Oberdorster, since those may contain nanoparticles that pose a serious risk to your lungs.
• Use soap, not silver. If you're tempted to buy nanosilver¬-treated cutting boards, knives, or other appliances, realize that soap is just as effective at killing bacteria without all the nasty side effects. Spray your cutting boards with full-strength white vinegar, followed by full-strength hydrogen peroxide, to kill harmful bacteria. And as for your appliances, a test by scientists in South Korea revealed that Samsung's nanosilver washing machines were no more effective at killing germs than regular machines that clean using hot water.