Ultrafine particle deposition in humans during rest and exercise.

Ultrafine particles (diameter < 100 nm) may be important in the health effects of air pollution, in part because of their predicted high respiratory deposition. However, there are few measurements of ultrafine particle deposition during spontaneous breathing. The fractional deposition for the total respiratory tract of ultrafine carbon particles (count median diameter = 26 nm, geometric standard deviation = 1.6) was measured in 12 healthy subjects (6 female, 6 male) at rest (minute ventilation 9.0 +/- 1.3 L/min) using a mouthpiece exposure system. The mean +/- SD fractional deposition was 0.66 +/- 0.11 by particle number and 0.58 +/- 0.13 by particle mass concentration, similar to model predictions. The number deposition fraction increased as particle size decreased, reaching 0.80 +/- 0.09 for the smallest particles (midpoint count median diameter = 8.7 nm). No gender differences were observed. In an additional 7 subjects (2 female, 5 male) alternating rest with moderate exercise (minute ventilation 38.1 +/- 9.5 L/min), the deposition fraction during exercise increased to 0.83 +/- 0.04 and 0.76 +/- 0.06 by particle number and mass concentration, respectively, and reached 0.94 +/- 0.02 for the smallest particles. Experimental deposition data exceeded model predictions during exercise. The total number of deposited particles was more than 4.5-fold higher during exercise than at rest because of the combined increase in deposition fraction and minute ventilation. Fractional deposition of ultrafine particles during mouth breathing is high in healthy subjects, and increases further with exercise.

Nitrogen dioxide exposure: effects on airway and blood cells.

This study examined the effects of nitrogen dioxide (NO(2)) exposure on airway inflammation, blood cells, and antiviral respiratory defense. Twenty-one healthy volunteers were exposed on separate occasions to air and 0.6 and 1.5 ppm NO(2) for 3 h with intermittent moderate exercise. Phlebotomy and bronchoscopy were performed 3.5 h after each exposure, and recovered cells were challenged with respiratory viruses in vitro. Blood studies revealed a 4.1% NO(2) dose-related decrease in hematocrit (P = 0.003). Circulating total lymphocytes (P = 0.024) and T lymphocytes (P = 0.049) decreased with NO(2) exposure. Exposure to NO(2) increased the blood lymphocyte CD4(+)-to-CD8(+) ratio from 1.74 +/- 0.11 to 1.85 +/- 0.12 in males but decreased it from 1.88 +/- 0.19 to 1.78 +/- 0.19 in females (P < 0.001 for gender difference). Polymorphonuclear leukocytes in bronchial lavage increased with NO(2) exposure (P = 0.003). Bronchial epithelial cells obtained after exposure to 1.5 ppm NO(2) released 40% more lactate dehydrogenase after challenge with respiratory syncytial virus than with air exposure (P = 0.024). In healthy subjects, exposures to NO(2) at levels found indoors cause mild airway inflammation, effects on blood cells, and increased susceptibility of airway epithelial cells to injury from respiratory viruses.