Citation:

Kim, C. AND J. Choi. Linking Different Exposure Patterns to Internal Lung Dose for Heterogeneous Ambient Aerosols. Presented at American Association for Aerosol Research annual meeting, Portland, OR, September 30 - October 04, 2013.

Impact/Purpose:

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 is important for assessing health risk associated with exposure to ambient PM.

Description:

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. In the present study we investigated deposition characteristics of typical bi-modal distribution 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. The bimodal aerosols were made by combining two uni-modal distributions 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, thus covering a wide range of distribution patterns. Using a validated mathematical model, total and compartmental lung deposition (tracheobronchial, TB and alveolar, AL) were calculated 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 deposit together in TB and AL with their absolute doses per breath being approximately following MR. During exercise, deposition increases particularly in TB with a slight decrease in AL. for C while deposition ofF decreases in both TB and AL. UP contributes minimally in mass deposition regardless of MR. For surface area, F and UF deposit at a ratio of 58:2 in both TB and AL. C contributes substantially only in TB during exercise at MR< 0.5. For number deposition, both UP and F deposit together in both TB and AL at a ratio of approximately 6:4 regardless of exposure conditions. Absolute doses were higher at rest vs. exercise. Contribution of C was negligible. In conclusion, for typical bimodal aerosols UP, F and C deposit together at the same site with varying proportions. Their interactions may be a factor for altering heath risk outcome for multipollutant mixtures. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.

Record Details: