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UNIVERSAL RELATIONSHIP OF TOTAL LUNG DEPOSITION OF PARTICLES IN NORMAL ADULTS WITH PARTICLE SIZE AND BREATHING PATTERN
Citation:
KIM, C. S., S. C. HU, AND P. JAQUES. UNIVERSAL RELATIONSHIP OF TOTAL LUNG DEPOSITION OF PARTICLES IN NORMAL ADULTS WITH PARTICLE SIZE AND BREATHING PATTERN. Presented at American Thoracic Society Meeting, San Diego, CA, May 19 - 24, 2006.
Description:
Particulate matter in the air is known for causing adverse health effects and yet estimating lung deposition dose is difficult because exposure conditions vary widely. We measured total deposition fraction (TDF) of monodisperse aerosols in the size range of 0.04 - 5 micron in diameter in nineteen healthy adults at various breathing patterns representing sleep, resting and mild exercise conditions. The tidal volume (Vt) was varied from 350 ml to 1500 ml, respiratory flow rate (Q) from 150 - 1000 ml/s and the breathing frequency from 7.5 to 30 breaths per min. Subjects inhaled test aerosols via the mouthpiece for 10-20 breaths following prescribed breathing patterns displayed on a computer monitor screen. During inhalation, aerosol concentrations were monitored continuously by a laser aerosol photometer for micron size aerosols and a ultrafine condensation particle counter for submicron aerosols. TDF was then analyzed for effects of particle size and breathing pattern parameters. We found that TDF was uniquely correlated with a single composite parameter Xd (=(D.Tm)0.5Vtk) for submicron aerosols (r2 = 0.97) and Xm (= dam Qn Vtp) for micron size aerosols (r2 = 0.98) in the functional form of TDF = 1-1/(1+a X). Here, D and Tm are the diffusion coefficient of particles and mean respiratory time, respectively and da is the aerodynamic particle diameter. For the entire particle size range, TDF = 1-1/(1+a Xd + b Xm) was a good functional form to consolidate the entire TDF data (a and b are constants). In conclusion, a unifying empirical equation for total lung deposition was obtained based on comprehensive human experimental data. The equation will be useful for assessing deposition dose of orally inhaled particles under various inhalation conditions. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.