Autopsies Show Evidence of Particle Damage to Small Airways
Researchers evaluated a series of autopsy lungs from Mexico City, a high-PM locale, and compared them by formal grading analysis to lungs from Vancouver, a region of generally low air pollution.
The small airways in the Mexico City lungs showed markedly higher levels of fibrous tissue and muscle, and microscopic evidence of particle accumulation in the respiratory bronchioles. The study demonstrates that particle pollution penetrates into and is retained in the walls of the small airways. The type of airway wall remodeling found here is associated with chronic airflow obstruction in cigarette smokers and in asthmatics, and may have a similar effect in those exposed to PM.
A related laboratory study has demonstrated that air pollution particles produce airway wall remodeling in rat tracheal tissue maintained in culture. Researchers exposed the tissue to two types of particles — Ottawa urban air particles, and diesel exhaust particles. The study found that exposure to these particles can induce expression of genes involved in fibrogenesis and airway wall fibrosis, suggesting an explanation for the fibrosis and increased muscle observed in human airways subject to chronic exposure to high levels of PM.
Researchers conclude that “PM-induced airway wall remodeling may play an important role in producing airflow obstruction in individuals living in high PM regions.”
Churg, A. Brauer, M., Avila-Casado, M.d.C., Fortoul, T.I., and Wright, J.L. Chronic Exposure to High Levels of Particulate Air Pollution and Small Airway Remodeling. Environmental Health Perspectives. Vol. 111, No. 5, pp. 714-718, May 2003.
The National Institute of Environmental Health Sciences [http://ehis.niehs.nih.gov/] offers the full article online.
Dai, J., Xie, C., Vincent, R., and Churg, A. Air Pollution Particles Produce Airway Wall Remodeling in Rat Tracheal Explants. American Journal of Respiratory Cell Molecular Biology. Vol. 29, pp. 352-358, 2003.
The American Thoracic Society [www.thoracic.org] offers the abstract online.
