title: [Cohort studies on cancer mortality of digestive system among workers exposed to asbestos: a meta-analysis].
abstract: OBJECTIVE
  To determine if there are excessive risks of malignant tumors or not among workers exposed to asbestos by applying a meta-analysis technique.
  
  
  METHODS
  All data meeting the criteria of cohort studies on cancer mortality of digestive system among workers exposed to asbestos would be incorporated into the meta-analysis. The pooled standardized mortality ratios (SMR) and their corresponding 95% confidence intervals (CIs) for main cancer sites of digestive system were calculated by using two approaches of un-weighted ratio and random effects model. The heterogeneity and its sources of the results were examined with a Q-statistic and Z-score test.
  
  
  RESULTS
  69 asbestos-exposed cohorts were summarized. The significantly elevated meta-SMR for all deaths (1.16), all cancers (1.42), cancer of digestive system (1.15) and cancer of stomach (1.20) among workers exposed to chrysotile alone or mixed asbestos were observed (P < 0.01). The stomach cancer SMR was significantly increased in the asbestos cement workers, the screening mine workers and the insulators, (1.27, 1.21 and 2.13 respectively) (P < 0.05). meta-SMR for cancers at other sites of digestive system including esophagus, colon, rectum and liver were not significant.
  
  
  CONCLUSIONS
  There are likely excessive risks of cancer of stomach among workers exposed to asbestos. However, there is likely no convincing indication of an etiological association between asbestos exposure and cancers at other sites of digestive system.
authors.affiliation: Institute of Public Health and Family Medicine, Ningbo College of Health Sciences, Ningbo Zhejiang Province 315100, China.
authors.forename: Tong-da
authors.initials: TD
authors.lastname: Sun
authors.forename: Jian-Er
authors.initials: JE
authors.lastname: Chen
authors.forename: Xiu-Juan
authors.initials: XJ
authors.lastname: Zhang
authors.forename: Xiu-Yang
authors.initials: XY
authors.lastname: Li
mesh_terms: D001194:Asbestos / Q000009:adverse effects*; D002274:Carcinogens, Environmental / Q000009:adverse effects; D015331:Cohort Studies; D004067:Digestive System Neoplasms / Q000139:chemically induced / Q000401:mortality*; D006801:Humans; D016273:Occupational Exposure / Q000009:adverse effects*
chemical_list: D002274:Carcinogens, Environmental; D001194:Asbestos