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ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED PARTICLES FOR DIFFERENT DOSE METRICS: COMPARISON OF NUMBER, SURFACE AREA AND MASS DOSE OF TYPICAL AMBIENT BI-MODAL AEROSOLS
Citation:
Kim, C. S., S. C. Hu, AND P. Jacques. ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED PARTICLES FOR DIFFERENT DOSE METRICS: COMPARISON OF NUMBER, SURFACE AREA AND MASS DOSE OF TYPICAL AMBIENT BI-MODAL AEROSOLS. Presented at American Thoracic Society Meeting, Atlanta, GA, May 17-22, 2002.
Description:
ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED PARTICLES FOR DIFFERENT DOSE METRICS: COMPARISON OF NUMBER, SURFACE AREA AND MASS DOSE OF TYPICAL AMBIENT BI-MODAL AEROSOLS.
Chong S. Kim, SC. Hu*, PA Jaques*, US EPA, National Health and Environmental Effects Research Laboratory, Research Triangle Park, NC 27711 and *CEMLB, University of North Carolina-Chapel Hill, NC 27599, USA
Although many epidemiological studies have shown a consistent correlation between observed health effects and mass concentration of airborne particulate matter (PM), some evidence suggests that particle number or surface area may also play an important role in PM associated health effects. However, specific quantitative data are lacking for respiratory dose of heterogeneous ambient aerosols and the relationship between different size fractions vs. their relative contributions to the number, surface area and mass deposition. Using the serial bolus delivery method, we measured total as well as detailed regional deposition values in healthy young adults ( n=10, age = 18-40 years) for a series of monodisperse aerosols in the size range of 0.04 -5 m in diameter. Using these data, respiratory deposition of a typical bi-modal ambient aerosol (MMD1 = 0.3 m, MMD2 = 5 m and GSD = 2.0 for each mode) was calculated for four different size fractions (eg, 0.04, 0.1, 1 and 5 m), and deposition was analyzed for mass, number and surface area in different lung regions. At a tidal volume of 500 ml and breathing frequency of 15 breaths/min the results show that 5 m fraction is a dominant contributor for mass deposition followed by 0.1, 1 and 0.04 m fraction. Number deposition was dominated by smaller size fractions. However, surface area deposition peaked at 0.1 m fraction and both 0.04 and 5 m fractions were notable contributors. The results suggest that from the physical dose metric point of view the particle size itself may not be a discriminating factor for PM effects. Chemical composition and other particle properties should be examined along with particle size. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.