Exposure to Carbon Nanotube Material: Aerosol Release During the Handling of Unrefined Single-Walled Carbon Nanotube Material

Abstract

Carbon nanotubes represent a relatively recently discovered allotrope of carbon that exhibits unique properties. While commercial interest in the material is leading to the development of mass production and handling facilities, little is known of the risk associated with exposure. In a two-part study, preliminary investigations have been carried out into the potential exposure routes and toxicity of single-walled carbon nanotube material (SWCNT)—a specific form of the allotrope. The material is characterized by bundles of fibrous carbon molecules that may be a few nanometers in diameter, but micrometers in length. The two production processes investi-gated use-transition metal catalysts, leading to the inclusion of nanometer-scale metallic particles within unrefined SWCNT material. A laboratory-based study was undertaken to evaluate the physical nature of the aerosol formed from SWCNT during mechanical agitation. This was complemented by a field study in which airborne and dermal exposure to SWCNT was investigated while handling unrefined material. Although laboratory studies indicated that with sufficient agitation, unrefined SWCNT material can release fine particles into the air, concentrations generated while handling material in the field were very low. Estimates of the airborne concen-tration of nanotube material generated during handling suggest that concentrations were lower than 53μg/m³ in all cases. Glove deposits of SWCNT during handling were estimated at between 0.2 mg and 6 mg per hand.

The authors acknowledge the support and assistance of Thomas Reese, Lovely Fotedar, Alice Lee, and Sivaram Arepalli (NASA-JSC), Robert Hauge and Richard Smalley (Rice University), Ken Smith (CNI), Kelsey Seybold Occupational Health Services, and the NASA-JSC Occupational Health and Human Test Support Office.