Cancer mortality among Chinese chrysotile asbestos textile workers

Our plain-English summary of Cancer mortality among Chinese chrysotile asbestos textile workers, by X.R. Wang, I.T. Yu, H. Qiu, et al (Lung Cancer, 2012).

The study

• Authors: X.R. Wang, I.T. Yu, H. Qiu, M.Z. Wang, Y.J. Lan, L.Y. Tse, E. Yano, D.C. Christiani
• Journal: Lung Cancer
• Published: 2012;75(2):151-5
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To determine mortality associated with exposure to chrysotile asbestos, a cohort of asbestos workers from an asbestos textile factory in China was followed prospectively from 1972 to 2008. A total 577 workers were successfully followed, achieving a follow-up rate of 98.5% over 37 years. Employment data and smoking information were obtained from factory and individual workers. Vital status was ascertained from factory personnel records and the municipal death registry. Workers were categorized into high, medium and low exposure groups in terms of their job titles and workshops. Follow-up generated 17,508 person-years, with 259 deaths from all causes, 96 all cancers and 53 lung cancers and 2 mesotheliomas. The highest cancer mortality was observed in the high exposure group, with 1.5-fold age-adjusted mortality from all cancers and 2-fold from lung cancer compared to the low exposure group. Age and smoking adjusted hazard ratio in the high exposure group was 2.99 (95%CI, 1.30, 6.91) for lung cancer and 2.04 (1.12, 3.71) for all cancers. Both smokers and nonsmokers at the high exposure level had a high death risk of lung cancer, with a clearer exposure-response trend seen in smokers. This study confirmed increased mortality from lung cancer and all cancers in asbestos workers, and the cancer mortality was associated with exposure level.

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In plain English

This study enrolled 586 male workers registered on January 1, 1972 at an asbestos textile factory in China where, according to factory records, only chrysotile was used. Tests of chrysotile samples found very low tremolite contamination. By the end of 2008, 577 workers (98.5%) had been traced. Workers were sorted by job and workshop into high (raw material and textile), medium and low (office and administration) exposure groups, and the groups were compared with each other. There were 259 deaths, including 96 from all cancers, 53 from lung cancer and 2 from mesothelioma (one pleural, one peritoneal). After adjusting for age at entry, smoking and exposure duration, the high exposure group had a lung cancer hazard ratio of 2.99 (95% CI 1.30 to 6.91) and an all-cancer hazard ratio of 2.04 (1.12 to 3.71) compared with the low group. Asbestosis-related deaths were also higher in the high group. Gastrointestinal cancer showed no trend. The authors concluded that lung cancer, all-cancer and all-cause mortality were increased and associated with exposure level. They noted possible exposure misclassification, and that only about half of cancers were pathologically confirmed.

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: Prospective cohort study (37-year follow-up) with internal comparison of mortality between exposure groups
• Who was studied: 586 male workers registered at an asbestos textile factory in China on January 1, 1972, with no sign of malignant tumors; 577 were followed to the end of 2008 (98.5%). Female workers were not included.
• Exposure: Chrysotile only, according to factory records, with very low tremolite contamination in tested samples. Products were asbestos textiles, friction materials, rubber products, heat resistant materials and asbestos cement products. Workers were grouped by job and workshop: high (raw material and textile sections), medium (rubber, cement, maintenance, ancillary and cleaning) and low (office and administration). Personal samples taken in 2006 averaged 2.30 f/cm3 in the textile section, 1.95 f/cm3 in the raw material section and 0.74 f/cm3 in the rubber plate section.
• Main results:
  • Whole cohort: 259 deaths in total, of which 96 were from all cancers and 53 from lung cancer.
  • Whole cohort: 2 workers died from mesothelioma, one pleural and one peritoneal.
  • High exposure group compared with low exposure group: the age-adjusted all-cancer mortality rate was over 1.5-fold and the lung cancer rate was 2.2-fold (630.87 versus 283.10 deaths per 100,000 person-years).
  • Lung cancer, adjusted for age at entry, smoking and exposure duration: hazard ratio 2.99 (95% CI 1.30 to 6.91) in the high exposure group and 1.18 (0.49 to 2.80) in the medium group, compared with the low group. The authors describe these as 199% and 18% higher risk.
  • All cancers, with the same adjustment: hazard ratio 2.04 (95% CI 1.12 to 3.71) in the high exposure group and 1.21 (0.67 to 2.18) in the medium group, compared with the low group.
  • Asbestosis-related deaths (39 in total): adjusted hazard ratio 3.80 (95% CI 1.29 to 11.22) in the high exposure group and 1.52 (0.50 to 4.64) in the medium group, compared with the low group.
  • Gastrointestinal cancer (29 deaths): no trend with exposure level. The adjusted hazard ratio in the high exposure group was 0.64 (0.22 to 1.93).
  • Joint effect analysis (371 subjects; reference group was low exposure nonsmokers): the hazard ratio for lung cancer was 6.63 (0.89 to 49.22) in high exposure smokers and 5.78 (0.64 to 51.93) in high exposure nonsmokers. These results were not statistically significant.
  • The synergy index for high exposure combined with smoking was 1.39 (95% CI 0.36 to 11.25). The authors read this as more than additive, but it was not statistically significant.
• The authors' conclusion: The authors concluded that mortality from lung cancer, all cancers and all causes was increased in these workers and was associated with the level of asbestos exposure. They added that because the comparison was made among exposed employees, actual risks could be greater compared with unexposed nonsmokers.
• Limitations the authors state:
  • Exposure misclassification was possible. Some workers changed jobs, and some office staff in the low exposure group visited the dusty workshops.
  • The effect of smoking could not be evaluated precisely because the amount smoked was unavailable.
  • The small number of nonsmokers may have weakened the analysis of interaction between smoking and asbestos.
  • Only about half of the malignant tumors were confirmed pathologically.
  • Nine workers were lost to follow-up.

Topics

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

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

Related studies

• Cause-specific mortality in a Chinese chrysotile textile worker cohort — X. Wang, S. Lin, et al. (2013)
• Exposure-specific lung cancer risks in Chinese chrysotile textile workers and mining workers — X. Wang, S. Lin, et al. (2014)
• Cause-specific mortality in relation to chrysotile-asbestos exposure in a Chinese cohort — S. Lin, X. Wang, et al. (2012)
• Follow-up study of chrysotile asbestos textile workers: cohort mortality and case-control analyses — J.M. Dement, D.P. Brown, et al. (1994)
• Cancer mortality in Chinese chrysotile asbestos miners: exposure-response relationships — X. Wang, E. Yano, et al. (2013)
• Increased lung cancer mortality among chrysotile asbestos textile workers is more strongly associated with exposure to long thin fibres — D. Loomis, J.M. Dement, et al. (2012)

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