Lungs clearance mechanism or why is chrysotile one of the safest fibers

The profound difference between chrysotile and other asbestos fibers called amphiboles lies in the fact that chrysotile easily dissolves in acids whereas amphiboles are acid-resistant. This has a principally important effect on the potential of a disease.

When we breathe, some dust and bacteria may penetrate through our nose and throat in the air passages. Most of them are then deposited on the walls of bronchi that are covered with sticky mucus and then expectorated, spitted out or otherwise swallowed.

If they penetrate deeper in lungs, then macrophages present in lungs and acting as scavengers clearing the dust and destroying microbes come to the rescue. They either fully engulf and then dissolve the particles or remove them from the air passages.

This is the case for particles, but the problem with fibers is that they can pass through the air passages longitudinally and then reach the lung tissue and alveoli, and are too long to be fully engulfed.

What does all this have to do with chrysotile? When a macrophage engulfs a particle, it tries hard to dissolve it. Remember, one of its most important tasks is to destroy bacteria and for a macrophage a bacterium is like a delicious piece of meat for us. The macrophage produces digestive juices similar to our gastric juice and its juices are highly acidic (pH4).

As far as we know, chrysotile dissolves in acid whereas amphiboles are acid resistant. If it is chrysotile, then some part of the fiber will be successfully destroyed within the macrophage, the remainder will be engulfed by another macrophage, and the process will continue until the fiber is destroyed completely. But if it is a crocidolite, amosite, ceramic or cellulose fiber, then it will persist in the lungs for a long time, up to several years, causing pathological changes.