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 investigated 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 concentration of nanotube material generated during handling suggest that concentrations were lower than 53 microg/m(3) in all cases. Glove deposits of SWCNT during handling were estimated at between 0.2 mg and 6 mg per hand.

Conceptual model for assessment of inhalation exposure to manufactured nanoparticles

“…For example, some powders such as fumed silica with high-specific surface area (B200 g/m 2 ) may be extremely ''fluffy'' and therefore liberate dust at low levels of these forces. Similar behavior is observed during handling of bulk carbon nanotube powders (Maynard et al, 2004). However, this will already, at least, to some extend be covered by the substance emission potential (dustiness).…”

Occupational Nanosafety Considerations for Carbon Nanotubes and Carbon Nanofibers

“…Maynard et al 3 were the first to report aerosolization of CNTs in a laboratory setting upon agitation of SWCNTs during removal of material from the synthesis furnace, transfer of the SWCNTs, or cleaning. Respirable dust concentrations ranged from 0.7 to 53 μg/m 3 , with most airborne particles being agglomerates.…”

Phytotoxicity of multi-walled carbon nanotubes on red spinach (Amaranthus tricolor L) and the role of ascorbic acid as an antioxidant

“…2. Hydroponic exposure for 15 days to CNTs at different concentrations (0, 125, 250, 500 and 1000 mg L −1 ) resulted in toxicity 13 symptoms and retardation of plant growth, leaf number, and size with increasing CNTs concentration compared to control plants (Fig. 3a).…”