Objectives This 37-year prospective cohort study was undertaken to provide additional evidence for mortality risks associated with exposure to chrysotile asbestos. Methods 577 asbestos workers and 435 control workers in original cohorts were followed from 1972 to 2008, achieving a follow-up rate of 99% and 73%, respectively. Morality rates were determined based on person-years of observation. Cox proportional hazard models were constructed to estimate HRs of causespecific mortality, while taking into account age, smoking and asbestos exposure level. Results There were 259 (45%) deaths identified in the asbestos cohort, and 96 died of all cancers. Lung cancer (n¼53) and non-malignant respiratory diseases (n¼81) were major cause-specific deaths, in contrast to nine lung cancers and 11 respiratory diseases in the controls. Age and smoking-adjusted HRs for mortality by all causes and all cancers in asbestos workers were 2.05 (95% CI 1.56 to 2.68) and 1.89 (1.25 to 2.87), respectively. The risks for lung cancer and respiratory disease deaths in asbestos workers were over threefold that in the controls (HR 3.31 (95% CI 1.60 to 6.87); HR 3.23 (95% CI 1.68 to 6.22), respectively). There was a clear exposureeresponse trend with asbestos exposure level and lung cancer mortality in both smokers and non-smokers. Conclusion Data from this prospective cohort provide strong evidence for increased mortality risks, particularly from lung cancer and non-malignant respiratory diseases, associated with exposure to chrysotile asbestos, while taking into account of the smoking effect.Asbestos, a recognised hazard in both occupational and environmental settings, has been responsible for millions of deaths worldwide.
This study provides additional evidence for the association between exposure to chrysotile mining dust and excess mortality from digestive cancers, particularly stomach cancer.
Government policies to prevent ARD have been implemented but more actions are necessary to ensure compliance and ultimately, the complete elimination of asbestos to prevent a heavy future disease burden.
Given the substantially increased death risks for lung cancer and nonmalignant respiratory diseases, urgent efforts must be made to implement occupational health and safety regulations and decrease workers' exposures to prevent a future heavier disease burden. Meanwhile, improvements in diagnostics and systematic recording of the incidence and mortality of asbestos-related diseases are needed.
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