Cause-specific mortality in a Chinese chrysotile textile worker cohort

Our plain-English summary of Cause-specific mortality in a Chinese chrysotile textile worker cohort, by X. Wang, S. Lin, I. Yu, et al (Cancer Science, 2013).

The study

• Authors: X. Wang, S. Lin, I. Yu, H. Qiu, Y. Lan, E. Yano
• Journal: Cancer Science
• Published: 2013;104(2):245-9
• Cited by: 45 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Chrysotile asbestos has continued to be mined and used in China, but its health effects on exposed workers have not been well documented. This study was conducted to give a complete picture about cause-specific mortality in Chinese asbestos workers. A cohort of 586 males and 279 females from a chrysotile textile factory were prospectively followed for 37 years. Their vital status was identified, and the date and underlying cause of death were verified from death registry. Cause-specific standardized mortality ratios by gender were computed with nationwide gender- and cause-specific mortality rates as reference. Male workers were 11 years older, and had 6 years longer exposure duration than females; 79% in males and 1% in females smoked. In males, the mortality rate of all cancers doubled; both larynx and lung cancer were four-fold, and mesothelioma was 33-fold. In females, there was slightly excess mortality from lung cancer and all cancers, and significant increase in mesothelioma and ovarian cancer. Other significantly increased mortality was seen from cancers of thymus, small intestine and penis in males, and cancers of bone and bladder in females. In addition to asbestosis, mortality from pulmonary heart disease was significantly elevated in both genders. The data confirmed significantly excess mortality from mesothelioma in either gender, lung and larynx cancers in males, and ovarian cancer in females. A gender difference in mortality from lung cancer and all cancers could be mainly due to the discrepancies in age, exposure duration and smoking between the male and female workers.

© 2012 Japanese Cancer Association.

In plain English

This study followed 586 men and 279 women who had worked for at least a year at a chrysotile asbestos textile factory in China, from 1972 through 2008. The authors compared their deaths with expected numbers based on national Chinese death rates. Men had 96 cancer deaths, about twice the expected number (SMR 2.09; 95% CI 1.71 to 2.55). Lung cancer (53 deaths) and larynx cancer (2 deaths) were each about four times the expected rate, and mesothelioma (2 deaths) about 33 times. Among women, deaths from all cancers (10) and from lung cancer (2) were slightly above expected but not statistically significant. One peritoneal mesothelioma death and one ovarian cancer death in women were each significantly above expected. Asbestosis caused 37 deaths in men and 3 in women, and pulmonary heart disease deaths were significantly raised in both sexes. Several findings rested on only one or two deaths. The authors concluded that the higher cancer mortality in men could be mainly explained by differences in age, exposure duration and smoking: 79% of men smoked, against 1% of women.

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 comparing observed deaths with expected deaths from national Chinese mortality rates (standardized mortality ratios, SMRs), by gender
• Who was studied: 586 male and 279 female workers who had been employed for at least 1 year by the start of 1972 at an asbestos textile factory in China, followed from 1 January 1972 to the end of December 2008. Men were on average about 40 years old at entry and women about 29. Nine men and two women were lost to follow-up.
• Exposure: Chrysotile asbestos only, used at the factory since 1958 to make asbestos textiles, friction and rubber materials, and construction materials such as asbestos cement and tiles. Chrysotile samples showed a very low level of tremolite contamination. In 2002, air samples measured 18 f/cm3 in the raw material section and 6 f/cm3 in the textile section. Men averaged 25.5 years of employment and women 19.4 years.
• Main results:
  • Men: 96 deaths from all cancers against 45.96 expected, SMR 2.09 (95% CI 1.71–2.55).
  • Men: 53 deaths from trachea, bronchus and lung cancer against 13.00 expected, SMR 4.08 (95% CI 3.12, 5.33).
  • Men: 2 deaths from larynx cancer against 0.47 expected, SMR 4.26 (95% CI 1.17, 15.52).
  • Men: 2 mesothelioma deaths (one pleural, one peritoneal) against 0.06 expected, SMR 33.33 (95% CI 9.14, 121.55). The mesothelioma SMR was computed from the 2004–2005 national survey only.
  • Women: 10 deaths from all cancers against 7.47 expected, SMR 1.34 (95% CI 0.73, 2.46). Lung cancer: 2 deaths, SMR 1.23 (95% CI 0.34, 4.50). Neither was statistically significant.
  • Women: one peritoneal mesothelioma death, SMR 166.67 (95% CI 29.42, 944.18), and one ovarian cancer death, SMR 7.69 (95% CI 1.36, 43.58). Both were statistically significant.
  • Significantly raised mortality from cancers of the thymus, small intestine and penis in men, and of bone and bladder in women, each based on one case.
  • Asbestosis deaths: 37 men (SMR 100.00; 95% CI 72.55, 137.83) and 3 women (SMR 78.95; 95% CI 26.85, 232.14). Expected numbers were based on national pneumoconiosis rates.
  • Pulmonary heart disease: 36 deaths in men (SMR 13.09; 95% CI 9.46, 18.12) and 2 deaths in women (SMR 8.33; 95% CI 2.29, 30.39).
  • All causes of death combined: significantly raised in men (SMR 1.31; 95% CI 1.16–1.48), but not in women (SMR 0.82; 95% CI 0.56, 1.21).
  • Men: lung cancer deaths made up 17% (22 of 127) of men with asbestosis and 7% (31 of 450) of men without asbestosis. No lung cancer death occurred among women with asbestosis.
  • Men: lung cancer deaths occurred in 10% of smokers (47 of 452) and 5% of nonsmokers (6 of 125).
  • Smoking: 79% of men smoked, while 3 women (1%) did.
• The authors' conclusion: The authors concluded that the data confirmed significantly excess mortality from mesothelioma in both genders, from lung and larynx cancers in men, and from ovarian cancer in women, although case numbers for some cancers were limited. They also concluded that the gender difference in mortality from lung cancer and all cancers could be mainly explained by differences between men and women in age, exposure duration and smoking.
• Limitations the authors state:
  • Many of the elevated cancer SMRs were based on only one or two cases.
  • The national population used as the reference had different smoking rates from the workers. Lung cancer SMRs may therefore be overestimated in men and somewhat underestimated in women.
  • No national asbestosis death rate was available, so national pneumoconiosis rates were used to calculate expected asbestosis deaths.
  • Mesothelioma was not coded before ICD-10, so its SMR was based on the 2004–2005 national survey only.

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, standardized mortality ratio (SMR), Lung Cancer, Mesothelioma, Ovarian Cancer, Laryngeal Cancer.

Related studies

• Cause-specific mortality in relation to chrysotile-asbestos exposure in a Chinese cohort — S. Lin, X. Wang, et al. (2012)
• Cancer mortality among Chinese chrysotile asbestos textile workers — X.R. Wang, I.T. Yu, et al. (2012)
• Exposure-specific lung cancer risks in Chinese chrysotile textile workers and mining workers — X. Wang, S. Lin, et al. (2014)
• Exposure to chrysotile mining dust and digestive cancer mortality in a Chinese miner/miller cohort — S. Lin, X. Wang, et al. (2014)
• Mortality in a Chinese chrysotile miner cohort — X. Wang, S. Lin, 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)

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