Objectives: To examine mortality from digestive cancers in a Chinese miner cohort and to explore the exposure-response relationship between chrysotile mining dust and site-specific digestive cancers.
Methods: A cohort of 1539 asbestos miners was followed for 26 years. Information on vital status and death causes was collected from personnel records and hospitals. Underlying causes of death from cancers were determined by combination of clinical manifestations and pathological confirmation. Individual cumulative dust exposures were estimated based on periodic dust measurements of different workshops, individuals' job title and employment duration, and treated as a time-dependent variable. Standardised mortality ratios (SMR) were calculated according to Chinese national data and stratified by exposure (levels 1-3, from low to high). Cox proportional hazard models were constructed to estimate HRs in relation to cumulative exposure with adjustment of smoking.
Results: Fifty-one deaths from digestive cancers were identified in the cohort, giving an SMR of 1.45 (95% CI 1.10 to 1.90). There was a clear exposure-response relationship between asbestos dust exposure and mortality from stomach cancer, with SMR of 2.39 (95% CI 1.02 to 5.60) and 6.49 (2.77 to 15.20) at exposure levels 2 and 3, respectively. The clear relationship remained in multivariate analysis, in which workers at the highest exposure level had HRs of 12.23 (95% CI 8.74 to 17.12). In addition, excess mortality from oesophageal and liver cancers was also observed at high exposure levels.
Conclusions: This study provides additional evidence for the association between exposure to chrysotile mining dust and excess mortality from digestive cancers, particularly stomach cancer.