Development of a new multi-walled carbon nanotube (MWCNT) aerosol generation and exposure system and confirmation of suitability for conducting a single-exposure inhalation study of MWCNT in rats

Abstract

Because the primary route of human exposure to multi-walled carbon nanotube (MWCNT) is via inhalation, a new dry MWCNT aerosol generation and exposure system for whole-body inhalation exposure using a cyclone and sieve has been developed. The system was tested for operational performance at 0.2, 1 and 5 mg/m³. Additionally, it was examined whether this system can be employed in animal whole-body inhalation studies by exposing rats to MWCNT aerosol for 6 h at 5 mg/m³. The system could consistently provide aerosols with a similar particle size distribution and configuration at all the target exposure concentrations. Almost all MWCNTs were fibrous, and the presence of many well-dispersed, nano-sized particles was confirmed. Additionally, the animal study revealed that large amounts of MWCNTs were inhaled into the lung, resulting in an inflammatory response, with increased LDH and albumin levels, and granulomatous change. Therefore, the aerosol generation and exposure system appears useful for MWCNT inhalation studies using rats.

Keywords::

• multiwall carbon nanotubes
• inhalation toxicity
• aerosol
• rat
• lung deposition

Acknowledgement

The authors are deeply indebted to all members of the committee set up in the Japan Industrial Safety and Health Association to oversee building the system of aerosol generation and inhalation exposure to nanomaterials (chaired by Dr. Norihiko Kohyama, Professor of Toyo University), for their warm support and fruitful discussions throughout the present study. The authors also acknowledge the technical support from Mr. Shigeyuki Hirai, Mr. Masahiro Yamamoto and Mr. Yasutomo Sasaki.