Mortality in chrysotile asbestos workers in China

Our plain-English summary of Mortality in chrysotile asbestos workers in China, by X. Wang, M.N. Courtice, S. Lin (Current Opinion in Pulmonary Medicine, 2013).

The study

• Authors: X. Wang, M.N. Courtice, S. Lin
• Journal: Current Opinion in Pulmonary Medicine
• Published: 2013;19(2):169-73
• Type of article: Review
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose Of Review: China has been the world's top chrysotile asbestos consumer and producer. However, the national mortality rate for asbestos-related diseases, particularly from malignancies, is unknown. This review elaborates recent studies on cancer mortality and nonmalignant respiratory diseases in Chinese chrysotile asbestos workers.

Recent Findings: Studies conducted in asbestos products factory workers and miners have demonstrated strong associations between exposure to chrysotile and mortality rates for lung cancer and nonmalignant respiratory diseases. Mortality rates for lung cancer and nonmalignant respiratory diseases in both asbestos workers and miners are four and three times higher, respectively, than expected, which are greater than those seen in studies from western countries, likely a reflection of heavier exposures and less effective protection for workers. An increased risk of gastrointestinal cancer was also detected in chrysotile miners. There have been surprisingly few reported cases of mesothelioma, however, which could, at least partially, indicate a problem in diagnosis.

Summary: Given the substantially increased death risks for lung cancer and nonmalignant respiratory diseases, urgent efforts must be made to implement occupational health and safety regulations and decrease workers' exposures to prevent a future heavier disease burden. Meanwhile, improvements in diagnostics and systematic recording of the incidence and mortality of asbestos-related diseases are needed.

In plain English

This article was a review, not a new study. The authors summarized recent research on deaths among Chinese chrysotile asbestos workers. It focused on two cohorts studied by one research team: asbestos product factory workers, and miners and millers at China's largest chrysotile mine. The factory study followed 586 male asbestos workers and 599 control workers from 1972 to 2008. Compared with national data, the asbestos workers' lung cancer standardized mortality ratio was 4.08 (95% CI 3.12, 5.33); risk also rose with exposure level. The mine study followed 1539 male workers from 1981 to 2006. Compared with national rates, the 1080 miners had 4.7 times the risk of lung cancer death (95% CI 3.57, 6.21) and 3.5 times the risk of nonmalignant respiratory disease death (95% CI 2.78, 4.48). No mesothelioma was reported in the mine cohort. The authors said both studies lacked historical fibre concentration data. The authors concluded that the studies showed strong associations between chrysotile exposure and deaths from lung cancer and nonmalignant respiratory diseases. They also concluded that the absence of mesothelioma probably reflected problems with diagnosis.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Review of recent cohort studies on mortality in Chinese chrysotile asbestos workers, centred on two cohorts studied by one research group
• Who was studied: Reviewed cohorts: 586 male asbestos product factory workers and 599 control workers, followed 1972 to 2008. Also 1539 male workers at the largest chrysotile mine in China (Qinghai Province), followed 1981 to 2006: 1080 miners and millers and 459 internal controls.
• Exposure: Chrysotile asbestos. The factory used chrysotile from two Sichuan mines with very low amphibole contamination (less than 0.001%) to make asbestos textile, cement and tiles, and rubber boards. At the mine, total dust concentrations ranged between 70 and 400 times the previous national standard.
• Main results:
  • Factory asbestos workers, compared with national mortality data: standardized mortality ratio for lung cancer 4.08 (95% CI 3.12, 5.33), based on 53 observed deaths. For nonmalignant respiratory disease it was 3.38 (95% CI 2.72, 4.21).
  • Factory asbestos workers, compared with the control cohort: lung cancer death risk rose with exposure level. Hazard ratios were 1.94 (0.84, 4.46) at the low level, 3.49 (1.41, 8.67) at the medium level and 6.01 (2.74, 13.19) at the high level.
  • Factory cohort, compared with nonsmoking controls: relative risks of lung cancer were 6.03 (0.75 to 48.21) in smoking controls, 7.52 (0.90 to 62.79) in chrysotile-exposed nonsmokers and 17.35 (2.38 to 126.57) in chrysotile-exposed smokers. The reviewers described this as a joint effect more than additive.
  • Miners, compared with national mortality rates: 4.7 times the risk of lung cancer death (95% CI 3.57, 6.21) and 3.5 times the risk of nonmalignant respiratory disease death (95% CI 2.78, 4.48)
  • Miners, compared with internal controls after adjustment for smoking, age and employment years: 4.6-fold risk for lung cancer, 3.3-fold risk for nonmalignant respiratory disease, and a three-fold risk for gastrointestinal cancer
  • No mesothelioma was reported in the mine cohort, in which 428 deaths were identified
• The authors' conclusion: The authors concluded that the recent Chinese studies showed strong associations between chrysotile exposure and increased mortality from lung cancer and nonmalignant respiratory diseases. They considered that lung cancer rates higher than in western studies likely reflected heavier exposures. They considered that the absence of mesothelioma probably reflected problems with diagnosis.
• Limitations the authors state:
  • Neither reviewed study had historical fibre concentrations or periodic personal samples. This made exposure characterization and comparison with other studies difficult.
  • The absence of mesothelioma may reflect poor diagnostic standards in China rather than a true absence of cases

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile, Lung cancer.

Medical terms in this study, explained in our Lexicon: Chrysotile, Lung Cancer, Mesothelioma.

Related studies

• Analysis of mortality in chrysotile asbestos miners in China — L. Du, X. Wang, et al. (2012)
• Lung cancer mortality from exposure to chrysotile asbestos and smoking: a case-control study within a cohort in China — E. Yano, X. Wang, et al. (2010)
• A 37-year observation of mortality in Chinese chrysotile asbestos workers — X. Wang, E. Yano, et al. (2012)
• Cancer mortality and asbestosis among workers in an asbestos plant in Chongqing, China — F. Zhong, E. Yano, et al. (2008)
• Cause-specific mortality in a Chinese chrysotile textile worker cohort — X. Wang, S. Lin, et al. (2013)
• Exposure to chrysotile mining dust and digestive cancer mortality in a Chinese miner/miller cohort — S. Lin, X. Wang, et al. (2014)

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