Abstract Submitted to the    NANOTUBE'06 Conference:

Pulmonary Response to Aspiration of Single Walled Carbon Nanotubes

Vincent Castranova

National Institute for Occupational Safety and Health (NIOSH)

Vic1@cdc.gov

V. Other Characterization of Nanotubes

Single walled carbon nanotubes are being investigated for applications in microelectronics, structural materials, and bone grafting. It is anticipated that commercial production of single walled carbon nanotubes will grow rapidly. In light of high anticipated production, worker exposure and possible adverse health effects are concerns. Therefore, the potential effects of pulmonary exposure to these nanoparticles was investigated. Mice were exposed by pharyngeal aspiration to purified single walled carbon nanotubes at 10, 20 or 40 $\mu $g/mouse. Pulmonary damage, inflammation, and fibrosis were monitored 1 – 60 days post-exposure. Aspiration generated two size fractions of nanotules (aggregates and more diffuse nanoropes). Pulmonary exposure to nanotubes resulted in an acute damage and inflammatory response, which returned toward the control state after 7 days post-exposure. Deposits of aggregated nanotube material were found in the terminal bronchiolar and proximal alveolar regions. Response at deposition sites of aggregates was the formation of granulomas, characterized by encapsulation of aggregates by epithelioid cells and rapid and progressive fibrosis. In addition diffuse intersitial fibrosis was observed in distal alveolar regions in the absence of visible nanotube aggregates. This interstitial fibrosis was apparent 7 days post-exposure and progressed through 60 days post-exposure. Labeling the nanotube material with gold prior to aspiration allowed deposits of nanoropes to be visualized in these distal alveolar speta. It is concluded that, although exposure to single walled carbon nanotubes did not cause prolonged inflammation, a progressive fibrotic response was observed. In light of such a pulmonary response, it appears prudent to avoid excessive inhalation of this material in the workplace.

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