Abstract Number: 163 Working Group: Aerosol Exposure
Abstract Intratracheal instillation test have been considered as a cost-friendly alternative to exposure studies for evaluating the toxicities of nanomaterials. Intratracheal instillation test requires a liquid suspension of solid nanomaterial with a known mass concentration. In this study, dry-dispersed nanomaterials are directly collected into liquid phase from aerosol phase to make suspensions to be used for intratracheal instillation tests. The mass in the collected liquid can be obtained from the measurements in aerosol phase.
Nanomaterial power is fed intermittently to a cylindrical chamber which both ends are covered with a vibrating latex membrane. The powder is aerosolized, and inhalable fraction of the generated particles penetrate through a cyclone. The aerosol is mixed inside a chamber and sampled by aerosol instruments downstream. A nephelometer monitors the mass concentration of aerosol particles, and the concentration is regulated at a fixed value within 5-25 mg/m^3. The sizes of dry-dispersed powder ranged over submicrometer to micrometer range, and the size distributions remained stable during dispersion experiments which are performed continuously for 6 to 8 hours.
Dry-dispersed nanomaterial were collected from aerosol phase directly into liquid phase using a Growth Tube Collector (GTC). Supersaturated water vapour condense onto incoming aerosol particles, and final droplet sizes at the exit of the GTC were about 3 um. These droplets impact onto the surface of liquid contained in a vial. Two kinds of powder material were used; P25-TiO2, JIS standard powder No.8 (Kanto-loam stratum). Collection efficiencies were reasonably high and reproducible. The results suggests that the mass of aerosol particles collected into liquid can be predicted form a mass concentration of aerosol particles, a sampling flowrate of GTC, and a sampling time.