Mesothelioma and lung cancer mortality: a historical cohort study among asbestosis workers in Hong Kong

Objectives: To investigate the mortality pattern among a cohort of workers with asbestosis in Hong Kong, with special emphases on mesothelioma and lung cancer.

Methods: All 124 male workers with confirmed asbestosis in Hong Kong during 1981-2008 were followed up to December 31, 2008 to ascertain the vital status and causes of death. Standardized mortality ratio (SMR) for each underlying cause of death was calculated by using person-year method. Axelson's indirect method was applied to adjust for the potential confounding effect of cigarette smoking.

Results: A total of 86 deaths were observed after 432.8 person-years of observations. The SMR for overall mortality (6.06, 95% CI: 4.90-7.51) increased significantly. The elevated risk of deaths from all cancers (7.53, 95% CI: 5.38-10.25) was mainly resulted from a significantly excess risk from lung cancer (SMR=7.91, 95% CI: 4.32-13.29, 14 deaths) and mesothelioma (SMR=6013.63, 95% CI: 3505.95-9621.81, 17 deaths). The SMR for lung cancer retained statistically significant after adjustment of smoking. An increased smoking adjusted SMR was also suggested for all heart diseases (2.32, 95% CI: 0.93-4.79, 7 deaths) and acute myocardial infarction (3.10, 95% CI: 0.84-7.94, 4 deaths), though the statistical significance was borderline. We found a positive association with net years of exposure to asbestos for mesothelioma and lung cancer.

Conclusions: Our study provided further evidence on the carcinogenesis of asbestos/asbestosis with the risk of deaths from lung cancer and mesothelioma. This study also provided a preliminary support for a possible link between asbestosis and heart disease, but power is limited.