On exposure to asbestos, the larger fibers are filtered in the nasal passage and the upper airways. The minute fibers, in the size range of 3 µm, penetrate the lower airways of the lungs. These fibers are recognized as foreign agents and are, therefore attacked by the macrophages which are components of the body’s immune system.
When the macrophage engulfs the fibers, they get destroyed due to the size of these fibres. The entry of more macrophages to attack the free fibre releases enzymes and free radicals, which has the potential to damage the lung cells. Fibers, with diameters smaller than 3 micrometers, can even penetrate cell membranes.
As a result of damage, the lung tissue gets fibrosed. Initially, the damage is localized and confined to a small area, The person then starts developing symptoms of lung disease. As the exposure to asbestos continues, the fibrosis extends and sometimes the entire lung becomes scarred.
Scarring of the alveoli or air sacs leads to respiratory distress in the affected individuals.