Carbon nanotubes are a modern and extremely light material that can add desirable properties to many industrial products, but they may be a health hazard. A new doctoral dissertation at Luleå University of Technology in Sweden shows that extremely small fibers such as carbon nanotubes can make their way far into the lungs, which in the worst case can present an increased risk of developing cancer.

"My research substantiates the concerns about health effects and is one reason we should be careful when handling with these materials," says Sofie Högberg, who now holds a PhD in engineering from the Division of Fluid Mechanics at Luleå University of Technology.

The result of her work indicates that the fibers that are most likely to make their way far into the lungs, perhaps all the way to the alveoli, are those with a diameter of c. 10-100 nanometers (1 nanometer = one billionth of a meter) and a length of 1-10 micrometers. This is a common size for carbon nanotubes.

In her research, she developed equations to describe the movements of a fiber. She then solved these equations numerically for a large number of fibers in a geometry and a flow field that represents the airways, in order to see what proportion of the inhaled fibers might be thought to fasten, depending on parameters like particle size and form.

The field of nanotechnology has been burgeoning in recent years, and today there are more than 1,000 nanoproducts on the market. The technology involves modifying material virtually at the level of the atom. Carbon nanotubes are a popular nanomaterial because of their combination of favorable properties that are desirable in many industrial products. By adding a small amount of carbon nanotubes it's possible to create materials that are strong yet still light in weight. However, with a diameter on the nanoscale and a highly elongated form, this extremely small particle can constitute a health risk.

"There are concerns, among others, that carbon nanotubes may lead to mesothelioma, a cancer form that previously has been associated only with asbestos," says Sofie Högberg.

Our knowledge of how spherical and fiber-shaped particles move can be used in other fields, such as production of composites and paper as well as medicines in aerosols. This means that Sofie Högberg's research has a wide spectrum of applications.

New doctoral dissertation by Sofie Högberg, LTU