Asbestos-related diseases persist, because millions of workers have had prior exposure and many industrializing countries continue to use asbestos. Globally, an estimated 107,000 people die annually from lung cancer, malignant mesothelioma, and asbestosis due to occupational asbestos exposure. Malignant mesothelioma and lung cancer are caused by all major types of asbestos. Asbestos causes more lung cancer deaths than malignant mesothelioma of the pleura; most cases of the latter are due to asbestos exposure. The cancer risk increases with cumulative asbestos exposure, with increased risk even at low levels of exposure to asbestos. Based on empirical studies, an estimated cumulative occupational exposure to asbestos of 1 fiber/mL-year substantially raises malignant mesothelioma risk. No safe threshold for asbestos exposure has been established for lung cancer and mesothelioma. The validity of fiber-type risk assessments depends critically on the quality of exposure assessments, which vary considerably, leading to a high degree of uncertainty. Asbestos exposure without asbestosis and smoking increases the risk of lung cancer. The joint effect of asbestos and smoking is supra-additive, which may depend in part on the presence of asbestosis. Asbestos workers who cease smoking experience a dramatic drop in lung cancer risk, which approaches that of nonsmokers after 30 years. Studies to date show that longer, thinner fibers have a stronger association with lung cancer than shorter, less thin fibers, but the latter nonetheless also show an association with lung cancer and mesothelioma. Low-dose chest computed tomographic scanning offers an unprecedented opportunity to detect early-stage lung cancers in asbestos-exposed workers.
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