Citation:

Kim, C. AND J. Choi. Respiratory dose analysis for components of ambient particulate matter#. Society of Toxicology, San Antonio, Texas, March 11 - 15, 2018.

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 cause health hazard, specific attributes of PM that may cause health effects are somewhat ambiguous. The dose of each specific component of PM together with relevant dose metrics may shed insights into understanding PM related health effects. This may help set up PM control/regulation strategy that may be more effective.

Description:

Particulate matter (PM) in the atmosphere is a complex mixture of particles with different sizes and chemical compositions. Although PM is known to cause health hazard, specific attributes of PM that may cause health effects are somewhat ambiguous. The dose of each specific component of PM together with relevant dose metrics may shed insights into understanding PM related health effects. We have attempted to analyze lung deposition dose 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 including 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. The 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 resulted 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 at rest and exercise. 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.

Record Details: