AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Respiratory Dose Assessment for Heterogeneous Ambient Aerosols
CHONG KIM, Jung-il Choi, USEPA
Abstract Number: 605 Working Group: Health Related Aerosols
Abstract Particulate matter (PM) in the ambient air is a complex mixture of particles with different sizes and chemical compositions. Because potential health effects are known to be different for different size particles, specific dose of size-fractionated PM under realistic exposure conditions would be of interest in health risk assessment. We investigated deposition characteristics of typical bi-modal ambient aerosols under three different inhalation exposure conditions: resting, mild exercise and moderate exercise (tidal volume (ml)/ frequency (min-1) = 750/12, 1250/20, 1500/25). Oro-nasal breathing was considered during exercise. Test aerosols were composed with two uni-modal aerosols having the mass median diameter of 0.3 um and 5 um with GSD of 1.8 and 2.0, respectively. Mass ratios (MR = 1st mode distribution/total) were varied from 0-1 with an increment of 0.1. A validated mathematical model was used to calculate total and regional lung deposition (tracheobronchial, TB and alveolar, AL) for three size fractions, Ultrafine (PM0.1), Fine (PM0.1-2.5) and Coarse (PM2.5-10). Results show that for mass deposition both F and C contribute to TB and AL with their respective contribution approximately following MR. During exercise, C increases in TB but decreases in AL while F decreases in both TB and AL. UF is negligible regardless of MR. For surface area, F and UF contribute to both TB and AL more with F. C increases in TB during exercise at MR< 0.5. For number deposition, both UF and F deposit in TB and AL with a respective contribution of approximately 6:4 regardless of exposure conditions. Contribution of C was negligible. In conclusion, for typical bimodal ambient aerosols UF, F and C deposit at the same site of the lung with varying proportions. PM size of dominant deposition varies with deposition site and dose metric.