This reaction causes the chest wall lining to permanently thicken. Pleural thickening can be detected by chest x-ray. Asbestos fibers tapped in the pleura can also cause more localized reactions leading to areas of hard scar formation. Over time calcium may be deposited in the scars. The presence of calcified pleural plaques on both sides of the chest is considered to be definite evidence of asbestos exposure and is generally easily detectable on chest x-ray.
Smoking has well known adverse health consequences including being a cause of carcinoma of the lung.
However, asbestos is also known to cause lung cancer even in the absence of smoking. In cases where individuals suffered exposure to asbestos and also smoked cigarettes, careful medical evaluation can often determine whether asbestos, cigarettes, or the combination produced the disease. Some studies have suggested that persons who are exposed to asbestos and who smoked are at least 50 times more likely to develop cancer. Persons who have been exposed to asbestos can reduce their risk of developing lung cancer by quitting smoking. It is never too late to quit smoking .