Citation:

Kim, C. AND J. Choi. Respiratory dose analysis for components of ambient particulate matter. Presented at Society of Toxicology meeting, Phoenix, AZ, March 23 - 27, 2014.

Impact/Purpose:

Particulate matter (PM) in the atmosphere is a complex mixture of particles with different sizes and chemical compositions. Although PM is known to induce health effects, specific attributes of PM that may cause health effects are somewhat ambiguous. Because the health effects are directly related to dose, respiratory dose of each specific component of PM together with relevant dose metrics may shed insights into understanding of PM-related health effects.

Description:

Particulate matter (PM) in the atmosphere is a complex mixture of particles with different sizes and chemical compositions. Although PM is known to induce health effects, specific attributes of PM that may cause health effects are somewhat ambiguous. Dose of each specific component of PM together with relevant dose metrics may shed insights into understanding of PM-related health effects. We analyzed the lung deposition doses of typical bimodal ambient aerosols composed of two distinct aerosols with mass median diameter of 0.3 um (A1) and 5.0 um (A2) with geometric standard deviation of 1.8 – 2.0. Mass fractions, MF = A1/(A1+A2), were varied in order to reflect aerosol characteristics of different regions. Lung deposition in the tracheobronchial (TB) and alveolar (AL) regions was calculated by using a mathematical model built upon Weibel’s lung morphology for mass, surface area and number of each of three size fractions, ultrafine (UF, PM0.1), fine (F, PM0.1-2.5) and coarse (C, PM2.5-10) at inhalation patterns mimicking resting and mild to moderate exercise. Overall, mass deposition of C decreases whereas deposition of F increases in both TB and AL as MF increases during normal breathing at rest. Combined deposition of C and F shows a decrease in TB but an increase in AL resulting in a slight increase in TB+AL. Surface area deposition is affected mainly by F with a minor contribution from UF at MF>0.2 whereas number deposition comes from both UF and F at a ratio of 1.5:1. During exercise, mass deposition increases greatly (~140%) in TB but decreases (15%) in AL resulting in a moderate increase of 40% in TB+AL in C whereas F decreases by 15% ~ 40%. This results in variable changes (+/-20%) of F+C as compared with resting condition. Surface area and number deposition shows a decrease of ~20% in a wide range of MF. In conclusion, PM size fractions of ambient aerosols contribute differently to lung deposition dose in terms of mass, surface area and number, and inhalation patterns affect the dose. Significance of roles of each size fraction and their combined effects need to be considered in toxicological and health risk assessment. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.

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