Asbestos fibers are inhaled through successively narrower passages, from the trachea through the bronchial tubes to the bronchioles. Fibers embedded in these airways can cause lung cancer. Fibers can reach the clusters of honeycombed air sacs called alveoli, leaving scar tissue. Excessive scarring restricts breathing. This is asbestosis, a condition resulting mainly from occupational exposure.
Fibers can pass through the alveoli and migrate to the pleura, the lining of the chest cavity.
There, they may injure the mesothelial cells and promote malignant tumors. This is mesothelioma, a fairly rare cancer that is usually discovered 25 to 40 years after initial exposure. Nearly all victims die within a year of diagnosis. Mesothelioma sometimes occurs in the peritoneum, the lining of the abdominal cavity.