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A New Threat to the Lining of the Lungs?

Tuesday, October 27, 2009

By Wade Rawlins

Asbestos mineral fibers gained widespread use in building materials and construction decades before the deadly effects of breathing asbestos fibers became apparent in cases of cancer and fatal respiratory ailments. Today, microscopic carbon nanotubes offer another “miracle” material with extraordinary properties potentially useful in everything from miniaturizing electronics to delivering medicine. But scientists say much more research is needed as to whether carbon nanotubes are as toxic to humans as asbestos.

In a new study using mice, researchers at North Carolina State University set out to determine whether nanotubes, — which are a fraction of the width of a human hair— would reach the lining of the lung if inhaled. The pleura or lining of the lung is one of the tissues that is affected by asbestos fibers, causing development of mesothelioma, a fatal cancer, and asbestosis, a scarring of tissue.

Dr. James Bonner, associate professor of environmental and molecular toxicology at N.C. State and senior author of the study, said the inhaled nanotubes reached the lining of the lungs of mice and caused scarring and a unique pathologic reaction on the surface of the pleura—the target tissue for mesothelioma.

The reaction began within one day of inhalation of the nanotubes, when clusters of immune cells began amassing on the surface of the pleura. Fibrosis, a scarring of the lining the lungs, that also occurs with asbestos exposure, began two weeks after inhalation.

The study shows that the carbon nanotubes can affect the lining of the lungs, the researchers said, though the study was too short in duration to assess whether the mice would eventually develop cancer.

The mice’s immune reaction and scarring disappeared within three months of exposure, but the mice only were exposed once for six hours to carbon nanotubes. “It remains unclear whether the pleura could recover from chronic or repeated exposures,” Bonner said.

The collaborative study by researchers at N.C. State, the Hamner Institutes of Health Sciences and the National Institute of Environmental Health Sciences, is the latest to probe similarities in health responses to asbestos fibers and nanotubes. Scientists have been raising concerns about the potential toxicity of nanotubes in recent years as the material has shown promise for many uses.

A recent article by French researchers in the journal Particle and Fibre Toxicology explored the question of whether asbestos and carbon nanotubes pose similar health risks. The researchers noted that carbon nanotubes resembled asbestos fibers in their needle-like shape and could be inhaled unknowingly and lodge in the lungs. Two recent studies by Japanese researchers showed that occurrence of malignant mesothelioma in mice and rats exposed to carbon nanotubes.

Bonner said more research is needed and it’s not yet known whether inhaled carbon nanotubes cause cancer in the lungs or lining of the lungs. The study suggests that minimizing the inhalation of nanotubes is prudent until further research on the long-term effects is conducted.



N.C. State release

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posted by Wade Rawlins at 2:24 PM
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