Distribution of particulate matter and tissue remodeling in the human lung

We examined the relationship between intrapulmonary particle distribution o f carbonaceous and mineral dusts and remodeling of the airways along anatom ically distinct airway paths in the lungs of Hispanic males from the centra l valley of California. Lung autopsy specimens from the Fresno County Coron er's Office were prepared by intratracheal instillation of 2% glutaraldehyd e at 30 cm H2O pressure. Two distinct airway paths into the apico-posterior and apico-anterior portions of the left upper lung lobe were followed. Tis sue samples for histologic analysis were generally taken from the intrapulm onary second, fourth, sixth, and ninth airway generations. Parenchymal tiss ues beyond the 12th airway generation of each airway path were also analyze d. There was little evidence of visible particle accumulation in the larger conducting airways (generations 2-6), except in bronchial-associated lymph oid tissues and within peribronchial connective tissue. In contrast, termin al and respiratory bronchioles arising from each pathway revealed varying d egrees of wall thickening and remodeling. Walls with marked thickening cont ained moderate to heavy amounts of carbonaceous and mineral dusts. Wall thi ckening was associated with increases in collagen and interstitial inflamma tory cells, including dust-laden macrophages. These changes were significan tly greater in first-generation respiratory bronchioles compared to second- and third-generation respiratory bronchioles. These findings suggest that accumulation of carbonaceous and mineral dust in the lungs is significantly affected by lung anatomy with the greatest retention in centers of lung ac ini. Furthermore, there is significant remodeling of this transitional zone in humans exposed to ambient particulate matter.