Estimation of carbon nanotubes deposition in a human respiratory tract replica

• Airborne carbon nanotubes (CNTs) could be size classified by a differential mobility analyzer.
• Human airway replica deposition studies were conducted by size classified CNT aerosols.
• The morphology of size classified stacked-cup carbon nanotube (SCCNT) and single-walled carbon nanotube (SWCNT) aerosols are distinct.
• Deposition efficiencies of CNT aerosols in the human upper airways are generally less than 0.1.

Investigation of the deposition of airborne carbon nanotubes (CNTs) in the human respiratory tract is essential from the occupational health perspective. Due to the dimension of CNTs, it is very difficult to apply traditional deposition experimental methods to CNTs for conducting a deposition study using human airway replicas. In this research, an innovative experimental approach was adopted to estimate the deposition of CNTs in the human respiratory tract. Two types of CNT materials were used as the challenge CNT materials. The deposition experiments were carried out by delivering size classified CNT aerosols into a human airway replica (from the oral cavity down to part of the 4th lung generation). The CNT deposition fractions and efficiencies in the airways were estimated based on the air flow rates, as well as the CNT concentrations measured in associated lung airways. Experimental results acquired showed that CNT deposition fractions in different sections of the airway replica were all smaller than 5%. The CNT deposition efficiency in the tracheobronchial airways was generally less than 0.1. This result implies that the CNTs inhaled into the human respiratory tract could easily penetrate through the upper airways and transit down to the lower airways to cause potential health effects.