Carbon nanotubes size classification, characterization and nasal airway deposition

Abstract

Workers and researchers in the carbon nanotubes (CNT)-related industries and laboratories might be exposed to CNT aerosols while generating and handling CNT materials. From the viewpoint of occupational health, it is essential to study the deposition of CNT aerosol in the human respiratory tract to investigate the potential adverse health effects. In this study, a human nasal airway replica and two types of CNT materials were employed to conduct CNT nasal airway deposition studies. The two CNT materials were aerosolized by a nebulizer-based wet generation method, with size classified by three designated classification diameters (51, 101 and 215 nm), and then characterized individually in terms of their morphology and aerodynamic diameter. The nasal deposition experiments were carried out by delivering the size classified CNTs into the nasal airway replica in three different inspiratory flow rates. From the characterization study, it showed that the morphology of the size classified CNTs could be in a variety of complex shapes with their physical dimension much larger than their classification diameter. In addition, it was found that the aerodynamic diameters of the classified CNTs were slightly smaller than their classification diameter. The nasal deposition data acquired in this study showed that the deposition efficiency of CNTs in the nasal airway were generally less than 0.1, which implies that the majority of the CNTs inhaled into the nose could easily penetrate through the entire nasal airway and transit further down to the lower airways, possibly causing adverse health effects.

• Aerosol
• carbon nanotubes
• nasal airway

Acknowledgements

The authors are grateful to Eileen Kuempel and Pramod Kulkarni at NIOSH for developing the concept of this research project; Bean Chen and Bahman Asgharian for useful discussion on the deposition data; and Bon-Ki Ku with special thanks for helping with conducting the APM study.