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How safe are nanoparticles?

Boom in nanotechnology points up need to evaluate health risks; latest study suggests asbestoslike effect.

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More than 200 products contain nanosilver, which has been shown to suppress the growth of bacteria. On May 1 a group of citizen-advocacy groups filed a petition with the Environmental Protection Agen­­cy asking that the EPA ban products – with nanosilver. The EPA has the authority to regulate nanosilver as a pesticide, says George Kimbrell, a staff attorney for the nonprofit International Center for Technology Assessment, one of the groups calling for the ban. “We believe very strongly in the consumer’s right to know” that they’ve been exposed to these materials, he says.

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Earlier this year, two researchers at Arizona State University found that socks impregnated with nanosilver particles to kill odor-causing bacteria released the particles into wash water, raising questions about the nanoparticles seeping into the environment. Another study this spring from a researcher at the University of Missouri found that nanosilver particles kill beneficial bacteria needed by wastewater treatment plants to remove ammonia from water.

A nanoparticle is defined as having at least one dimension smaller than 100 nanometers. A sheet of paper or a human hair is about 100,000 nanometers thick. At these sizes, nanoparticles exhibit unusual characteristics. Many of these qualities, such as the ability of nanoparticles to transfer heat efficiently, are what make them so attractive to researchers and manufacturers.

But nanoparticles can become more toxic as well, as is the case with nanosilver particles. “Something that’s safe at a large size suddenly becomes highly active and potentially dangerous when it’s made smaller,” Maynard says.

The problem of determining safety is complicated. In some cases, adequate ways to test the particles have not been found.

“It’s hard to measure anything at that [tiny] scale,” PEN’s Dr. Rejeski says. Nanoparticles that have been bonded to another substance – such as those found in a tennis racket’s frame or an auto fuel line – pose fewer problems. But even then concerns remain: When the product is thrown away, will it degrade over time? Will it be crushed into more mobile particles as part of the disposal process?

Some $88 billion of products incorporating nanotechnology were sold in 2007, according to Lux Research, a research firm specializing in emerging technologies. Last year nanotech start-up companies received $702 million in venture capital in 61 deals, Lux says. By 2014, it estimates, $2.6 trillion in manufactured goods will incorporate na­no­­technology, about 15 percent of the worldwide total. More and more are going into high-profile products. Professional golfer Trevor Immelman won the 2008 Masters tournament with clubs whose shafts had nanoparticles of metals fused onto them. And nanophosphates are the “secret sauce” in the brawny lithium-ion battery that will power GM’s all-electric Volt car.

But this sunny scenario for nanotech’s future relies on continued consumer acceptance. So far, surveys show the US is largely unaware and uninformed, having neither a strongly positive nor negative view.

Dietram Scheufele, a professor of life sciences communication and journalism at the University of Wisconsin in Madison, says public awareness of nanotech hasn’t changed at all since 2004, when he began his surveys. Scientists are more apt to be concerned about health and safety issues than the public is, he says. “Scientists aren’t saying there are problems,” Dr.

Scheufele says. “They’re saying, ‘We don’t know. The research hasn’t been done.’”

In a worst-case scenario, nano­­particles could generate the kind of negative reaction that genetically modified crops have received in Europe, he says.

No bills to specifically regulate nanoparticles are now before Congress, says Matthew Nordan, the president of Lux Research. But the industry is very aware of environmental concerns and wants to know what its liabilities will be, he says.