Characterizing exposures to nanomaterials.
Toxicologist 2005 Mar; 84(Suppl 1):132-133
Characterizing exposures to particulate matter has always carried with it a unique set of challenges. Unlike bulk materials or gases and vapors, pertinent properties of particles extend beyond the chemistry of the material and encompass physical attributes such as shape and size. As available information on the toxicity of nanometer-scale particles and structures increases, it is apparent that we are being faced with a new set of challenges: Particle number, size, structure, surface area and surface activity are indicated as potentially more relevant than mass concentration and bulk chemistry. As nanotechnology moves closer to widespread commercialization, new methods of characterizing relevant material attributes in toxicity studies and appropriately measuring exposure and dose, are required. Examples are given from two studies: On-line aerosol surface area measurements are becoming increasingly necessary when studying the toxicity of insoluble airborne nanoparticles. Diffusion charging, transmission electron microscopy and scanning mobility particle analysis have been compared for measuring aerosol surface area using particles of various sizes and morphologies. All three techniques give comparable results for particles smaller than 100 nm in diameter. For larger particles, some divergence between the three techniques is observable. Aerosol surface area alone is insufficient to characterize exposures where the bulk nanomaterial is heterogeneous. Research has shown that powders of unprocessed single walled carbon nanotubes (SWCNT) can release nanoscale particles into the air when agitated. The raw material in this case is a matrix of single walled carbon nanotubes, metal catalyst particles and compact carbonaceous material. To further explore the nature of nanoparticles generated while handling unprocessed SWCNT, the mass of single mobility diameter aerosol particles has been measured and effective particle density derived. Current results indicate that compact carbonaceous particles are primarily released into the air during agitation, suggesting that the nanotubes preferentially remain in the bulk material.
Particulates; Surface-properties; Structural-analysis; Toxic-effects; Toxic-materials; Exposure-levels; Exposure-assessment; Airborne-particles; Aerosols; Aerosol-particles; Nanotechnology
Research Tools and Approaches: Exposure Assessment Methods
The Toxicologist. Society of Toxicology 44th Annual Meeting and ToxExpo, March 6-10, 2005, New Orleans, Louisiana