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DEPOSITION DISTRIBUTION OF NANO AND ULTRAFINE PARTICLES IN HUMAN LUNGS DURING CONTROLLED MOUTH BREATHING
Citation:
Kim, C. S. AND P. Jaques. DEPOSITION DISTRIBUTION OF NANO AND ULTRAFINE PARTICLES IN HUMAN LUNGS DURING CONTROLLED MOUTH BREATHING. Presented at American Thoracic Society Annual Meeting, San Diego, CA, March 20 - 25, 2005.
Description:
Nano and ultrafine particles are abundant in the atmosphere and the level of human exposure to these tiny particles is expected to increase markedly as industrial activities increase manufacturing nano-sized materials. Exposure-dose relationships and site-specific internal dose are important information needed to assess potential health risk to exposure to these particles. Methods: We measured regional deposition of nano-sized particles (40-100 nm in diameter) in a series of lung compartments in normal adult subjects (N=10) under controlled breathing conditions with the tidal volume (Vt) of 500 and 1000 ml at a constant flow rate of 250 ml/s. Subjects inhaled a bolus aerosol (~45 ml) sandwiched between clean air. Position of the bolus varied sequentially from the beginning to the end of the tidal volume at 50 ml intervals so that the bolus may reach different volumetric regions of the lung. Deposition fractions were obtained from 10-20 different lung compartments for each inhalation condition, and deposition distribution patterns were analyzed. Results: Local deposition fraction (LDF) in each 50 ml compartment formed a skewed arch-shaped curve against the volumetric depth of the lung with a peak LDF between 150-250 ml region regardless of particle sizes and breathing patterns used. LDF decreased steadily from the peak to near zero in the end-tidal compartment. Peak LDF ranged from 0.03 - 0.09 and the value increased with a decrease in particle size for both Vts used. Peak position shifted towards the proximal bound with decreasing particle size. In other words, deposition takes place more proximally with smaller size particles. Deposition dose in each compartment was 1.5 -6.5 times greater and overall tracheobronchial and alveolar deposition dose increased by 1.8 and 3.5 times, respectively with Vt=1000 ml compared with Vt=500 ml. Conclusions: Deposition patterns of nano-sized particles are very uneven within the respiratory tract having peak deposition in the airway-alveolar transition zone. The same region is also known for the primary deposition site of coarse particles. The results suggest that local enhancement of deposition can be a critical factor for adverse health effects associated with particulate matter. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.