title: Cohort studies on cancer mortality among workers exposed only to chrysotile asbestos: a meta-analysis.
abstract: OBJECTIVE
  To determine whether there was excessive risk of cancer among workers exposed to chrysotile fiber alone by applying a meta-analysis technique.
  
  
  METHODS
  All data meeting the criteria of cohort studies on cancer mortality among workers exposed only to chrysotile were incorporated into meta-analysis. Pooled standardized mortality ratios (SMRs) and their corresponding 95% confidence intervals (CIs) for main cancer sites were calculated using two approaches of unweighted ratio and random effect model. The heterogeneity and its sources of the results were examined with a Q-statistic and Z-score test. The dose-response effect as reflected in the percentage of all deaths due to mesothelioma served as a proxy measure of chrysotile exposure.
  
  
  RESULTS
  A cohort of twenty six workers exposed to chrysotile alone was summarized. The significantly elevated meta-SMRs for all deaths (1.27), all cancers (1.28), cancers of respiratory organs (2.51), cancers of lung (2.35) and cancers of stomach (1.24) were observed. The significantly elevated meta-SMRs for lung cancer within occupational strata were observed among textile workers (3.55), asbestos product manufacturers (3.30), miners and millers (2.24), cement product workers (1.22), and for stomach cancer among asbestos product manufacturers (1.49). Meta-SMRs for cancers at other sites were not significant. Meta-SMR for lung cancer showed an increasing trend with an elevated percentage of all deaths from mesothelioma, but no such trend for stomach cancer.
  
  
  CONCLUSIONS
  There are excessive risks of lung cancer and mesothelioma among workers exposed to chrysotile fiber alone, and likely no convincing indication of an etiological association between chrysotile exposure and cancers at other sites.
authors.affiliation: Institute of Social Medicine and Family Medicine, Zhejiang University, Hangzhou 310031, Zhejiang, China. lilu@zju.edu.cn
authors.forename: Lu
authors.initials: L
authors.lastname: Li
authors.forename: Tong-Da
authors.initials: TD
authors.lastname: Sun
authors.forename: Xing
authors.initials: X
authors.lastname: Zhang
authors.forename: Rui-Nan
authors.initials: RN
authors.lastname: Lai
authors.forename: Xiu-Yang
authors.initials: XY
authors.lastname: Li
authors.forename: Xue-Jin
authors.initials: XJ
authors.lastname: Fan
authors.forename: Kenji
authors.initials: K
authors.lastname: Morinaga
mesh_terms: D017632:Asbestos, Serpentine / Q000009:adverse effects*; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008175:Lung Neoplasms / Q000209:etiology / Q000401:mortality; D008654:Mesothelioma / Q000209:etiology / Q000401:mortality; D009369:Neoplasms / Q000139:chemically induced / Q000401:mortality*; D016273:Occupational Exposure; D016272:Occupational Health; D018570:Risk Assessment; D013274:Stomach Neoplasms / Q000209:etiology / Q000401:mortality
chemical_list: D017632:Asbestos, Serpentine