AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Nanoparticle Measurements for the Breathing Zone Model
JEROME GILBERRY, Meaghan McGrath, Jonathan Thornburg, RTI International
Abstract Number: 317 Working Group: Aerosol Exposure
Abstract Human inhalation exposure to nanoparticles may occur in occupational environments during raw nanomaterial production or during product manufacturing. The consumer may be exposed to the nanomaterial in its original nanosize during the use of the product. Exposure assessment strategies, including surveys or direct measurements, are necessary but can quickly become complex and expensive. Exposure modeling that predicts the dispersion and transformation of nanoparticles produced in occupational or consumer environments is a middle tier solution to exposure assessment. A model can bracket the range of potential exposures to inform the user if exposure measurements are necessary to adequately assess risk. RTI developed the Breathing Zone (BZ) model to predict aerosol inhalation exposure to contaminants; however it does not include equations to account for diffusion and coagulation, phenomena specifically applicable to nanoparticles.
The goal of this project was to experimentally validate equations for input to the BZ model for inhalation exposure. SiO2 aerosol nanoparticles were generated in a controlled environmental chamber. The particle concentration and size distribution was measured at various distances from the aerosol source and under quiescent, convective, and thermal conditions. Under quiescent conditions, the distribution was bimodal near the nanoparticle generation source, an indication of coagulation. The concentration decreased and coagulation was not observed with increasing distance. Under convection conditions, the concentration was steadier with increased distance from the generation source and there was no evidence of coagulation. With a thermal body in the generation and sampling area, coagulation was substantial close to the source and remained observable at longer distances. It is apparent that nanoparticle coagulation occurred rapidly after generation as it was not possible to measure particles in a pre-coagulation state with the instrumentation used.