Mesothelioma is most predominantly caused by asbestos exposure. Asbestos fibers that are inhaled through the mouth and nose may eventually become embedded in the lining of the lungs, causing damage and resulting in lung cancer or asbestosis (scar tissue formation in the lungs). It has also been found that swallowing asbestos fibers could contribute to a form of mesothelioma originating in the abdomen called peritoneal mesothelioma.

Mesothelioma generally results from occupational exposure but there are instances of environmental exposure to asbestos that can cause the disease. Oftentimes second hand exposure of a family member to an asbestos workers dirty work clothes can result in that family member developing mesothelioma.

Asbestos insulation workers appear to have the highest death rate. One study reports that almost six percent of asbestos workers fall victim to mesothelioma and asbestos insulation workers are over 300 times more likely to die from mesothelioma than the general public.