San Francisco Chronicle, May 20, 2008

NEW STUDY SAYS CARBON NANOTUBES MIGHT BE AS HARMFUL AS ASBESTOS

[Rachel's introduction: One of the most promising materials for the future of technology, carbon nanotubes, might be as harmful as asbestos if inhaled.]

By Ann Fernholm

SAN FRANCISCO -- One of the most promising materials for the future of technology, carbon nanotubes, might be as harmful as asbestos if inhaled, according to a new study published today in the scientific journal Nature Nanotechnology.

Animal studies indicate that these long and very thin carbon molecules could cause a cancer called mesothelioma in the lining of the lungs.

"The problem of asbestos was caused when it was released into the air, if it was handled inappropriately or incorrectly. Carbon nanotubes could do the same. With this information we should assume the worst, we should think of them as asbestos. But more research might relax that point of view," said Andrew Maynard, chief science adviser to the Project on Emerging Nanotechnologies in Washington and one of the authors of the study.

Carbon nanotubes, 10,000 times thinner than a human hair, are one of the materials that many scientists believe will be used to build tiny electronics. In 2001, IBM made an array of transistors out of carbon nanotubes. In 2004, General Electric made a carbon nanotube diode, and last year, UC Berkeley scientists used single carbon nanotubes to create the world's smallest radio.

Themost widespread application today is in plastic materials reinforced by carbon nanotubes. Stronger than steel but light as plastic, carbon nanotubes are highly attractive to manufacturers of everything from sporting goods to airplanes. There already are tennis rackets, baseball bats and bicycle frames strengthened by carbon nanotubes available on the market.

"I would be very surprised if it is dangerous to use, let us say, a tennis racket or baseball bat containing carbon nanotubes. But I do not think it is OK to tell people that we think it is safe -- we've got to have evidence," Maynard said.

He said that such products should go through a number of tests investigating, for example, what happens when they break or when the surface is rubbed against the ground. He also wonders what happens when the products are disposed of.

"Is there a chance that the nanotubes will enter the environment?" Maynard said.

The main concern, however, is people processing carbon nanotubes and manufacturing the materials containing them.

The study presented in Nature Nanotechnology used an animal model developed in the 80s to study the development of mesothelioma, which can be caused by asbestos exposure. In this model, the nanotubes were injected into the abdominal cavity of mice, which is lined by the same kind of tissue as the human lung, and which is a sensitive predictor of mesothelioma. After one week, there was an inflammatory response.

"This is a very important study; it is very well done. It shows that you do get an inflammation that is similar to asbestosis. What is not known yet is the long term effect," said Vincent Castranova, involved in the nanotoxicology research at the National Institute for Occupational Safety and Health.

It is also uncertain how this experimental model for mesothelioma translates into reality. Scientists do not know under which circumstances these long carbon nanotubes will form a breathable dust, or if this dust will work its way into the lung.

"Here we run out of information," Maynard said.

Meanwhile, Castranova recommends people working with carbon nanotubes follow NIOSH guidelines for working with engineered nanomaterials, which involve the use of respirators and special filters to clean the air.

E-mail Ann Fernholm at afernholm@sfchronicle.com.

Copyright 2008 Hearst Communications Inc.