Review; Risk Assessment of Aerosolized SWCNTs, MWCNTs, Fullerenes and Carbon Black

Abstract

In this paper we review the risk assessment of carbonaceous nanomaterials, such as single-wall carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), fullerenes and carbon black, and summarize elemental carbon (EC) analyses for the determination of the those nanomaterials, focusing on the inhalation exposure of airborne nanomaterials. In the reports of hazard assessment, the proposed OELs (Occupational Exposure Limits) of MWCNTs and SWCNTs ranged from 1 to 50 μg/m³. The fullerenes and carbon black seem to be less toxic than the CNTs. In the reports of exposure assessment, the aerosol concentrations of MWCNTs and SWCNTs in work environments were from less than 0.1 to more than 100 μg/m³. The expected minimum concentration of airborne MWCNTs in the EC analyses was around 1 μg/m³, but the concentrations of EC in ambient particulate matters (APM) were more than 1 μg/m³ in urban environments. The EC analysis introduced in this paper is a convenient method to quantify the carbonaceous nanomaterials in the samples, but size-classification of aerosol samples by cascade impactor and observation using electron microscopes are needed to confirm the characteristics of the nanomaterials.