Asbestosis is a respiratory disease caused by prolonged exposure to asbestos. It causes diffuse pulmonary fibrosis (1). The disease starts when a person inhales asbestos fibers. Most exposure happens as a result of employment in an industry that requires regular contact with asbestos. Family members can be exposed when employees bring asbestos fibers home on their clothing.

During exposure, asbestos fibers travel down through the trachea and into the lungs where some ultimately make it all the way to the alveoli. Alveoli are little pockets in the lungs where oxygen is taken into the blood stream in exchange for carbon dioxide that is then exhaled. When the asbestos fibers get into the alveoli, the alveoli produces cells called macrophages whose job it is to keep the tissue free from foreign substances. Macrophages attack and destroy most particles that reach the lungs, but some asbestos fibers are too long for the macrophage to completely engulf; part of the asbestos fiber sticks out on one or both sides. When this happens, the fluid macrophages use to break down the foreign substance leaks out of the cell and onto the alveoli itself. The fluid irritates the cells it comes in contact with, and if exposure continues, the cells build up scar tissue.

As the scar tissue covers more parts of the lungs, and becomes heavier, it makes the exchange of oxygen for carbon dioxide in the alveoli less and less efficient. The scar tissue also reduces the flexibility and elasticity of the lungs, making it more difficult for them to expand sufficiently to fully inhale. The inflexibility means the muscles have to work harder potentially causing fatigue, blood vessels are under pressure that can cause high blood pressure of the lungs, also known as pulmonary hypertension.