When Andrew Taton slathers sunscreen on his toddler he knows he's protecting her from the sun's rays, but he's also aware of an invisible magic in sunscreen: nano particles.

Zinc oxide and titanium dioxide, which put the "screen" in sunscreen, used to leave a white film. Now they've been nanosized, made so small that they're invisible. "They're really very super small particles," explained Taton, a chemistry professor at the University of Minnesota who specializes in nanoparticles.

But he's not completely comfortable with the magic. "I'm a scientist, and I have to issue a cautionary note," he said. "Science doesn't really know if they stay on the skin."

Sunscreen isn't the only product using nanotechnology. It's in Behr brand paint at Home Depot, Nano-Tex sheets sold at J.C. Penney, stain-resistant pants from L.L. Bean, the First Response pregnancy test from Walgreens. Even the Metrodome beer hawker is selling nanotechnology in the plastic bottles.

Surprised? You're not alone. Polls show that most Americans have no idea how far this new realm of science and engineering has reached into their lives.

Indeed, some 600 consumer products now contain nanoparticles, according to Project on Emerging Nanotechnologies in Washington, D.C., which maintains an inventory of consumer products using nanomaterials (www.nanotechproject.org/inventories/consumer). Two to three are added daily, according to director David Rejeski -- but that's only a guess. Manufacturers don't have to disclose the use of nanotechnology.

Why are nanoparticles in stores?

Thousands of times smaller than the width of a human hair, roughly 1 to 100 nanometers in dimension, nanoparticles occur naturally in the environment, such as the very minute particles in smoke.

What is new is that we can now create and manipulate them, change their atoms around, make different shapes and sizes. And that's where the magic lies. Carbon, for instance, becomes as light as plastic but many times stronger than steel; aluminum becomes explosive.

Apply these new materials to consumer goods and your socks don't stink (nanosilver), liquids roll right off your trousers (tiny whiskers in cotton) and the urine dipstick changes color if you're pregnant (nano- gold). Thousands of transistors will fit in the space of a hair, making for powerful microelectronic devices. With the right nano-coating, guitar strings last longer and squeak less. Hockey sticks, golf clubs and tennis rackets are lighter yet stronger.

Consumer products are a natural -- and lucrative -- outlet for nanotechnology, but it doesn't stop there.

Nanotechnologies can deliver medicine precisely where needed in cutting-edge chemotherapy. MIT's Institute for Soldier Nanotechnology is creating a battlefield suit that, among other things, detects and neutralizes chemical and biological agents. Nokia's Morph concept is a cell phone that's rigid one moment and flexible the next, so it can be worn around your wrist.

There isn't an aspect of living that won't be affected by nanotechnology, experts predict.

The dark side

Despite the opportunities and promise of nanoscience, many scientists and environmentalists are sounding the alarm.

"We don't know nearly enough about the adverse reactions to any of these materials, environmental or biological," said J. Clarence Davies, a former Environmental Protection Agency official and one of the nation's foremost authorities on environmental regulation and policy.

It was recently discovered, for example, that when some nano-sized carbon material enters the lungs, it acts like asbestos, creating tissue and cell scarring that scientists say could lead to cancer. And some materials go where they're not supposed to. A University of Rochester, N.Y., study found that when rats inhaled nanoparticles, instead of lodging in the nose or lung as expected, the particles also made their way to the rats' brains.

In sunscreens, nanoparticles have been used for the past decade or so, and they're generally believed to be safe. Some watchdog groups, such as the Environmental Working Group, prefer them over sunscreens containing other chemicals such as oxybenzone. They appear to stay on the skin -- unless there's a cut or abrasion, noted Christy Haynes, who is researching nanoparticle toxicology at the University of Minnesota.

If that happens, "nobody has a good answer to where they go in your body and what happens when they're there," she said.

More research needed

Then there's the environmental question. One study shows manufactured nanoparticles in nature could be trouble. A University of Montreal study found nanoparticles of cadmium in shellfish, which caused reproductive and digestive problems.

The silver nanoparticles in socks and lining the inside of some washing machines do a good job of killing bacteria, but they apparently don't stay there. They wash out and enter the wastewater, where they kill beneficial bacteria needed to treat wastewater. The U.S. Environmental Protection Agency (EPA) has been asked to classify these products as pesticides, requiring that they be registered.

What is needed now, Davies says, is more research and oversight.

"Sometimes we want nanomaterial to be toxic, like when it's used in chemotherapy," said Haynes, who is working on studies to develop toxicity guidelines. "But we don't want toxic side effects in nanomaterials that are repelling stains."

Davies hopes the next administration in Washington will fund research and regulation to ensure health and safety for consumers, workers and to protect the nanotechnology industry.

Nanotechnology has incredible potential to cure disease, increase communication and even solve pollution problems and energy dilemmas. But it's important to find out about problem materials before and not after widespread application, Davies said.

"The future of nanotechnology is unimaginable; science fiction looks pale in comparison," he said. "We just need to do it right."

Karen Youso • 612-673-4407