Mortality in Chinese Chrysotile Asbestos Workers

Note: The medical journal Thorax, one of the world's leading respiratory medicine journals, has just published a large, damning 37-year study of mortality among chrysotile asbestos workers in China. The study was carried out by health researchers at the Division of Occupational and Environmental Health, School of Public Health and Primary Care, The Chinese University of Hong Kong, China, at the School of Public Health, Teikyo University School of Medicine, Tokyo, Japan and at the Department of Occupational Health, Huaxi School of Public Health, Sichuan University, Chengdu, China.

The authors found double or triple the mortality rate for "all causes, and all cancers in the asbestos workers, in comparison with the controls... particularly from lung cancer and non-malignant respiratory diseases, associated with exposure to chrysotile asbestos."

This latest study provides yet more compelling evidence that asbestos - be it chrysotile or any other form, and regardless of how carefully or poorly it's handled - is unsafe to use anywhere in the world.

Kathleen Ruff

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

Key messages: What is the key question?

What is the major cause-specific mortality in the cohort of workers who were exposed to chrysotile asbestos, and how strong are the associations between the cause-specific mortality and asbestos exposure?

What is the bottom line?

This 37-year prospective cohort study observed significantly greater mortality of all causes, and all cancers in the asbestos workers, in comparison with the controls. However, the strongest association with asbestos exposure was seen in lung cancer and non-malignant respiratory disease, which showed a clear exposure response trend.

Why read on?

Chrysotile asbestos continues to be mined and used heavily in China, largely because a controversy remains on carcinogenic potency of chrysotile asbestos. This prospective cohort study with the longest observation time to date, and high follow-up rate delivers a strong message that exposure to chrysotile asbestos can cause substantially high mortality risk for lung cancer as well as non-malignant respiratory disease.

Authors: Xiaorong Wang,1 Eiji Yano,2 Hong Qiu,1 Ignatius Yu,1 Midori N Courtice,1 L A Tse,1 Sihao Lin,1 Mianzhen Wang3

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 (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.http://www.blogger.com/img/blank.gif

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

http://thorax.bmj.com/search?fulltext=chrysotile&submit=yes&x=0&y=0