Tiny carbon nanotubes are being considered for use in everything from sports equipment to medical applications, but a great deal remains unknown about whether these materials cause respiratory or other health problems. Now a collaborative study from North Carolina State University, The Hamner Institutes for Health Sciences, and the National Institute of Environmental Health Sciences shows that inhaling these nanotubes can affect the outer lining of the lung, though the effects of long-term exposure remain unclear.
Using mice in an animal model study, the researchers set out to determine what happens when multi-walled carbon nanotubes are inhaled. Specifically, researchers wanted to determine whether the nanotubes would be able to reach the pleura, which is the tissue that lines the outside of the lungs and is affected by exposure to certain types of asbestos fibers which cause the cancer mesothelioma. The researchers used inhalation exposure and found that inhaled nanotubes do reach the pleura and cause health effects.
Short-term studies described in the paper do not allow conclusions about long-term responses such as cancer. However, the inhaled nanotubes “clearly reach the target tissue for mesothelioma and cause a unique pathologic reaction on the surface of the pleura, and caused fibrosis,” says Dr. James Bonner, associate professor of environmental and molecular toxicology at NC State and senior author of the study. The “unique reaction” began within one day of inhalation of the nanotubes, when clusters of immune cells (lymphocytes and monocytes) began collecting on the surface of the pleura. Localized fibrosis, or scarring on parts of the pleural surface that is also found with asbestos exposure, began two weeks after inhalation.