A 37-year observation of mortality in Chinese chrysotile asbestos workers

Wang, Xiaorong; Yano, Eiji; Qiu, Hong; Yu, Ignatius; Courtice, Midori N; Tse, L A; Lin, Sihao; Wang, Mianzhen

doi:10.1136/thoraxjnl-2011-200169

A 37-year observation of mortality in Chinese chrysotile asbestos workers

¹Division of Occupational and Environmental Health, School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China
²School of Public Health, Teikyo University School of Medicine, Tokyo, Japan
³Department of Occupational Health, Huaxi School of Public Health, Sichuan University, Chengdu, China

Correspondence to Professor Xiaorong Wang, School of Public Health and Primary Care, The Chinese University of Hong Kong, 4/F School of Public Health, Prince of Wales Hospital, Shatin, N.T., Hong Kong SAR, China; xrwang{at}cuhk.edu.hk

Contributors We assure that all authors included on a paper fulfil the criteria of authorship. There is no one else who fulfils the criteria who has not been included as an author. Professors Wang XR, Yano E, Yu I and Wang MZ worked on the conception and design of the study. Professor Wang XR drafted the manuscript. Dr Qiu H, Lin SH and Tse T worked on data analysis and interpretation and presentation of results. Ms Courtice M participated in critical revision and edition of the manuscript. All authors gave final approval of the revision.

Received 14 March 2011
Accepted 20 July 2011
Published Online First 21 September 2011

Abstract

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 cause-specific 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 (n=53) and non-malignant respiratory diseases (n=81) 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 exposure–response 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.

Footnotes

Funding This study was funded by the Pneumoconiosis Compensation Funding Board, Hong Kong SAR, China.
Competing interests None declared.
Ethics approval Ethics approval was provided by the Research Ethics Committee of the Chinese University of Hong Ko.
Provenance and peer review Not commissioned; externally peer reviewed.