The toxic effects of asbestos are not due to its chemical make-up, but its structural features: fibers.
Chrysotile is 90% of the world’s asbestos production.
Amosite appears to be the culprit. 5-10% amphiboles which are rod forms associated with malignant mesothelioma even when chrysotile is present.
Chyrsotile breaks down in the body much faster than amphiboles. There is an association between malignant mesothelioma and chrysotile when chrysotile is present at 400 times the lung burden of amosite.
One interesting thing is that animals are affected differently from humans to asbestos fibers. Chrysotile appears to be a more potent inducer of mesothelioma than amphibole fibers. The two types of asbestos break down at similar rates in rodents.
Interestingly, other fibers such as fiberglass are carcinogens in rats but not in humans. Researchers speculate that fiber types may differ in their ability to catalyze reactions between iron ions and oxygen. This reaction could cause free radicals that lead to lipid peroxidation, a fibrosis response, DNA damage, and mutations and cancer.