Continuous Measurements of Ambient Particle Deposition in Human Subjects

The total deposition fraction (TDF) of fine and ultrafine aerosols was measured in a group of six healthy adults exposed to polydisperse ambient aerosols in Boston. Fifteen repeated inhalation-exhalation cycles were conducted during a given exposure session. Deposition efficiency for particles with aerodynamic diameter ranging from 63.5 to 2045 nm was determined using the average concentration of inhaled and exhaled particles measured during these cycles. Deposition efficiencies ranged from 7.3±18.7%(240-275 nm) to 98.6±28.1%(1545-2045 nm). Subjects exhibited similar deposition patterns with minimum efficiencies between 200-400 nm. Results from ANOVA and mixed-model regression analyses showed significant differences (p < 0.05) in particle deposition efficiency by particle size as well as among the subjects. Deposition efficiencies varied most among the subjects for particles between 100 and 1000 nm in size. A comparison with the ICRP model showed good agreement, with best agreement for male subjects and particle sizes <400 nm.

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