How safe are nanoparticles?

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

Carbon nanotubes: The tubes (magnified here 40,000 times) are made by rolling sheets of carbon atoms into tiny cylinders.

Small is beautiful when it leads to new products that do great things, like speed up computers or cleanse the environment. But the nanoscale-sized particles (a nanometer is one-billionth of a meter) behind some of these advances are also raising questions about their safety, questions that are not yet thoroughly understood or researched.

In a study published May 20 in the journal Nature Nanotechnology, researchers found that one form of carbon nanotubes – long, thin multiwalled ones, whose shape bears a resemblance to asbestos fibers – appears to act like asbestos, causing damage to the lungs and potential serious illness. The nanotubes were injected into mice, not breathed in, leaving open the question of whether humans breathing in the nanotubes would be exposed to a health risk.

“If the fiber looks like asbestos, it may act like asbestos,” says Kristen Kulinowski, director of the International Council on Nanotechnology at Rice University in Houston, who has seen the paper. “Studies like this point to the need to understand the impacts of nanomaterials on human health and on the environment.”

According to one forecast, nanotube sales are expected to reach $1 billion to $2 billion annually within four to seven years. They are expected to be used in electronics, automobiles, drugs, and energy-efficient batteries.

Early this month, a House science committee approved a bill that would pump billions of dollars in US government funding into research on new applications for nanoparticles. The National Nanotechnology Initiative Amendments Act of 2008 includes a provision for a position within the White House Office of Science and Technology Pol­icy called the Coordinator for societal dimensions of nano­technology, which is expected to urge researchers to consider health, safety, and environmental effects in their research.

But many close observers say that’s not enough, and that the bill ought to include funds earmarked specifically for health and safety research. Outside experts unsuccessfully urged the committee to set aside 10 percent of the funds specifically for environmental, health, and safety research.

“There is a yawning knowledge gap between nanomaterials entering commerce now and what we know about their safety,” said Andrew Maynard, chief science adviser to the nonprofit Project on Emerging Nanotechnologies (PEN) at the Woodrow Wilson Center in Washington, in testimony before the committee in April. “This uncertainty over how to develop nanotechnologies safely is hamstringing regulators, im­­peding nano businesses, and confusing consumers. In short, moving toward the nanotechnology future without a clear understanding of the possible risks, and how to manage them, is like driving blindfolded.”

Dr. Maynard is a coauthor on the carbon-nanotubes study.

Meanwhile, three or four new products containing nanotechnology enter the market every week, according to a study released by the PEN last month. Well over 600 products already advertise their nano-content, viewing it as a marketing plus. But companies aren’t required to label their use of nanomaterials, so that number represents a “significant undercount” of what’s on the market, says David Rejeski, PEN director. Some of the nanomaterials products now on the market include socks, bandages, washing machines, lithium-ion batteries, refrigerators, camera lenses, sunscreens, toothbrushes, baby bottles, plush toys, the Xbox 360, pants, cosmetics, toothpaste, sheets, towels, pillows, and chopsticks.

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.

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.

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