Exposure-specific lung cancer risks in Chinese chrysotile textile workers and mining workers

Our plain-English summary of Exposure-specific lung cancer risks in Chinese chrysotile textile workers and mining workers, by X. Wang, S. Lin, E. Yano, et al (Lung Cancer, 2014).

The study

• Authors: X. Wang, S. Lin, E. Yano, I.T. Yu, M. Courtice, Y. Lan, D.C. Christiani
• Journal: Lung Cancer
• Published: 2014;85(2):119-24
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: Whether there is a difference in the exposure-response slope for lung cancer between mining workers and textile workers exposed to chrysotile has not been well documented. This study was carried out to evaluate exposure-specific lung cancer risks in Chinese chrysotile textile workers and mining workers.

Subjects And Methods: A chrysotile mining worker cohort and a chrysotile textile worker cohort were observed concurrently for 26 years. Information on workers' vital status, occupational history and smoking habits were collected, and causes and dates of deaths were verified from death registries. Individual cumulative fiber exposures were estimated based on periodic dust/fiber measurements from different workshops, job title and duration, and categorized into four levels (Q1-Q4). Standardized mortality ratios (SMRs) for lung cancer were calculated and stratified by industry and job title with reference of the national rates. Cox proportional hazard models were fit to estimate the exposure-specific lung cancer risks upon adjustment for age and smoking, in which an external control cohort consisting of industrial workers without asbestos exposure was used as reference group for both textile and mining workers.

Results: SMRs were almost consistent with exposure levels in terms of job titles and workshops. A clear exposure-response relationship between lung cancer mortality and exposure levels was observed in both cohorts. At low exposure levels (Q1 and Q2), textile workers displayed higher death risks of lung cancer than mining workers. However, similarly considerably high risks were observed at higher exposure levels, with hazard ratios of over 8 and 11 at Q3 and Q4, respectively, for both textile and mining workers, after both age and smoking were adjusted.

Conclusion: The chrysotile textile workers appeared to have a higher risk of lung cancer than the mining workers at a relatively low exposure level, but no difference was observed at a high exposure level, where both cohorts displayed a considerably high risk.

Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

In plain English

This study followed 464 male workers at a chrysotile products (textile) factory in Chongqing and 1,539 at a chrysotile mine in Qinghai Province from 1981 to 2006. The authors estimated each worker's cumulative fiber exposure. They compared lung cancer deaths with national rates and with 426 unexposed electronics factory workers. Lung cancer deaths were 6.34 times expected in textile workers (95% CI 4.75 to 8.45) and 4.25 times in mining workers (3.27 to 5.52). Against unexposed workers, adjusted for age and smoking, risk rose with exposure in both groups. At the lowest exposure level (defined separately for each group), hazard ratios were 2.13 (0.82 to 5.52) for textile and 1.01 (0.40 to 2.54) for mining workers; both ranges included 1.0. At the two highest levels, estimates were similar, with wide ranges: 8.47 (3.30 to 21.74) for textile versus 8.50 (3.93 to 21.23) for mining, and 11.69 (4.72 to 34.07) versus 10.68 (4.32 to 30.69). The authors concluded that textile workers appeared to have higher risk at low, but not high, exposure. They acknowledged possible exposure misclassification and less reliable mine estimates.

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: Cohort study comparing two concurrently observed occupational cohorts (chrysotile textile and chrysotile mining workers) against national rates and an external unexposed industrial worker cohort
• Who was studied: 464 male textile workers from an asbestos product factory in Chongqing and 1539 male mining workers from the largest chrysotile mine in China (Qinghai Province), followed January 1, 1981 to December 31, 2006. The comparison group was 426 male workers from an electronics equipment factory in Chongqing with no asbestos exposure.
• Exposure: Chrysotile asbestos with low amphibole contamination. No tremolite was detected at a 0.1% detection limit in the mine, and tremolite contamination of 0.001% was detected in the textile factory. Individual cumulative fiber exposures (fiber-years/ml) were estimated from dust and fiber measurements, workshop, job title and duration.
• Main results:
  • Both groups worked about 27 years on average. Textile workers had higher cumulative fiber exposure (geometric mean 105 f-yrs/ml) than mining workers (58 f-yrs/ml).
  • Textile workers: 46 lung cancer deaths observed versus 7.26 expected from national rates, SMR 6.34 (95% CI 4.75, 8.45).
  • Mining workers: 56 lung cancer deaths observed versus 13.18 expected, SMR 4.25 (95% CI 3.27, 5.52).
  • Among mining workers, millers (the highest-exposed job) had 50 lung cancer deaths versus 4.75 expected, SMR 10.53 (7.99, 13.88).
  • Control (unexposed) workers: lung cancer SMR 1.16 (0.56, 2.40).
  • Asbestosis was recorded in 101 textile workers (21.8%) and 87 mining workers (5.7%).
  • Exposure levels Q1 to Q4 were based on quartiles among lung cancer deaths within each cohort separately, so the cut-offs differ. For example, Q1 was up to 121.62 f-yrs/ml in textile workers and up to 240.90 f-yrs/ml in mining workers.
  • Compared with control workers and adjusted for age and smoking (model 2), the hazard ratio at the lowest level (Q1) was 2.13 (0.82, 5.52) in textile workers and 1.01 (0.40, 2.54) in mining workers. With age adjustment only (model 1), the figures were 2.54 and 1.44.
  • At Q2, adjusted for age and smoking, the hazard ratio was 6.54 (2.53, 16.90) in textile workers and 4.25 (1.67, 10.77) in mining workers.
  • At Q3, adjusted for age and smoking, the hazard ratio was 8.47 (3.30, 21.74) in textile workers and 8.50 (3.93, 21.23) in mining workers.
  • At Q4, adjusted for age and smoking, the hazard ratio was 11.69 (4.72, 34.07) in textile workers and 10.68 (4.32, 30.69) in mining workers. The trend across levels had p less than 0.001 in both cohorts.
  • Treating exposure as continuous (within each cohort, without controls, adjusted for smoking and age), each 100 f-y/ml was associated with a hazard ratio of 1.12 (1.07, 1.17) in textile workers and 1.20 (1.10, 1.32) in mining workers.
  • The exposure-response slopes differed between the two cohorts (heterogeneity test p = 0.006).
• The authors' conclusion: The authors concluded that the data did not support a difference in lung cancer mortality between textile and mining workers at a high exposure level, although textile workers appeared to have a higher risk at a low exposure level.
• Limitations the authors state:
  • Exposure assessment was more reliable for textile workers than for mining workers.
  • The method of estimating individual exposures may have caused exposure misclassification. The authors judged this likely to be non-differential between the cohorts.
  • The difference in exposure data quality might partly explain the different risks observed between textile and mining workers.
  • The authors did not compare their exposure estimates with those of other studies.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Chrysotile, Occupational History, Habit, standardized mortality ratio (SMR), Asbestos Exposure, Hazard Ratio.

Related studies

• Cause-specific mortality in a Chinese chrysotile textile worker cohort — X. Wang, S. Lin, et al. (2013)
• Cancer mortality among Chinese chrysotile asbestos textile workers — X.R. Wang, I.T. Yu, et al. (2012)
• Exposure to chrysotile mining dust and digestive cancer mortality in a Chinese miner/miller cohort — S. Lin, X. Wang, et al. (2014)
• Respiratory cancer in chrysotile textile and mining industries: exposure inferences from lung analysis — P. Sebastien, J.C. McDonald, et al. (1989)
• Mortality in a Chinese chrysotile miner cohort — X. Wang, S. Lin, et al. (2012)
• Cancer mortality in Chinese chrysotile asbestos miners: exposure-response relationships — X. Wang, E. Yano, et al. (2013)

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