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Cerium Oxide Nanoparticle Nose-Only Inhalation Exposures Using a Low-Sample-Consumption String Generator
Citation:
Ledbetter, A., K. Dreher, AND M. Higuchi. Cerium Oxide Nanoparticle Nose-Only Inhalation Exposures Using a Low-Sample-Consumption String Generator. Presented at American Association for Aerosol Research Meeting, Portland, OR, September 30 - October 04, 2013.
Impact/Purpose:
This abstract will be presented at the American Association for Aerosol Research meeting, September 30 - October 4, 2013, Portland, OR
Description:
There is a critical need to assess the health effects associated with exposure of commercially produced NPs across the size ranges reflective of that detected in the industrial sectors that are generating, as well as incorporating, NPs into products. Generation of stable and low concentrations of size-fractionated nanoscale aerosols in nose-only chambers can be difficult, and when the aerosol agglomerates during generation, the problems are significantly increased. One problem is that many nanoscale aerosol generators have higher aerosol output and/or airflow than can be accommodated by a nose-only inhalation chamber, requiring much of the generated aerosol to be diverted to exhaust. Another problem is that mixing vessels used to modulate the fluctuating output from aerosol generators can cause substantial wall losses, consuming much of the generated aerosol. Other available aerosol generation systems can produce nanoscale aerosols from nanoparticles (NPs), however these NPs are generated in real time and do not approximate the physical and chemical characteristics of NPs that are commercially produced exposing the workers and the public. The health effects associated with exposure to commercial NP production, which are more morphologically and size heterogeneous, is required for risk assessment. To overcome these problems, a low-consumption dry-particulate nanoscale aerosol generator was developed to deliver stable concentrations in the range of 10–5000 µg/m3 to a nose-only exposure chamber using all of the generator output. The generator airflow of 10–15 L/min supplies all the needed air for the exposure chamber, and a 6-h exposure at 10–1500 µg/m3 consumes as little as 200–300 mg of material. The cerium oxide (CeO2) aerosol delivered to the nose-only inhalation exposure chamber has a median number size distribution of 53.2 nm and σg of 1.88. This aerosol reflects the aggregate sizes of CeO2 NPs with primary diameter (5-7 nm) commonly found in diesel exhaust generated with CeO2 NP additive. The generator uses the principle of a continuous feed-string to pick up particles from a small reservoir, carry them through an orifice and into a small chamber where an air jet blows the particles off the string. Then the aerosol is conditioned to remove larger and more highly charged aerosols, leaving less agglomerated nanoscale aerosol for inhalation exposures. In short, this novel string generator is not only low consumption, but more importantly, allows for the generation and modification to nanoscale aerosols of commercially produced NPs. This abstract does not necessarily reflect U.S. EPA policy.