Mortality from a Chinese asbestos plant: overall cancer mortality

Our plain-English summary of Mortality from a Chinese asbestos plant: overall cancer mortality, by Z.C. Pang, Z. Zhang, Y. Wang, et al (American Journal of Industrial Medicine, 1997).

The study

• Authors: Z.C. Pang, Z. Zhang, Y. Wang, H. Zhang
• Journal: American Journal of Industrial Medicine
• Published: 1997;32(5):442-4
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The cancer mortality in a Chinese asbestos plant using only chrysotile was studied. Opened in the 1950s, all workers with at least 1 year of employment by 1972 were followed through 1994. Most workers were female. Excess cancer mortality, compared to local city data, was found for lung cancer, including many cases among nonsmoking women, and stomach cancer. Plant asbestos levels have been high in the past but have consistently come down over the decades.

In plain English

This study followed 530 workers (160 men, 370 women) through 1994. All had worked at least one year by 1972 at a Qingdao, China, asbestos plant that used only chrysotile. The plant made brake shoes, textiles and rope. Deaths were compared with Qingdao's general population. The text reports 22 cancers causing 21 deaths, though the table lists 22 cancer deaths against 11.17 expected. Lung cancer deaths exceeded expectations in men (3 observed, 0.59 expected; standardized mortality ratio 5.1) and women (6 observed, 0.88 expected; ratio 6.8). All three men with lung cancer smoked. All six women with lung cancer were nonsmokers. All nine lung cancers occurred in the highest-exposure jobs: raw material handling, carding and spinning. All five stomach cancers were in men, where 0.63 were expected (ratio 7.9 for men, 4.4 for all workers). Dust levels, measured by weight rather than fiber counts, were extremely high at first and fell over the decades. The authors concluded the study supports a link between asbestos exposure and stomach cancer. They could not determine how many workers were lost to follow-up.

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: Historical prospective (retrospective cohort) mortality study, comparing deaths with the general population of Qingdao (standardized mortality ratios)
• Who was studied: 530 workers (160 males, 370 females) with at least one year of employment by 1972 at an asbestos plant in Qingdao, China, followed through 1994; 3,366 male and 7,973 female person-years
• Exposure: Chrysotile asbestos only, mostly Chinese chrysotile with small amounts of Canadian chrysotile, used to make brake shoes, textiles and rope. Jobs included raw material handling, carding, spinning, brake manufacturing, repair, stockroom work and loading/unloading.
• Main results:
  • Whole cohort: the text reports 22 malignancies leading to 21 deaths, while the table lists 22 cancer deaths observed versus 11.17 expected in total (males 12 vs 3.69; females 10 vs 7.48).
  • Mortality table, all cancer: males 12 observed vs 3.69 expected; females 10 vs 7.48; total 22 vs 11.17
  • Lung cancer: males SMR 5.1 (3 observed, 0.59 expected); females SMR 6.8 (6 observed, 0.88 expected); both reported as significant at P less than 0.01
  • All nine lung cancers occurred among workers in the highest-exposure job classifications (raw material handling, carding, spinning)
  • All three male lung cancers were in smokers; all six female lung cancers were in nonsmokers (all females in the cohort were nonsmokers)
  • Stomach cancer: all five cases were among the 160 males, with 0.63 expected; SMR 7.9 for males and 4.4 for all workers, both reported as significant at P less than 0.01
  • No lung cancers occurred with less than 15 years of employment, and no cancers of any type occurred with less than 10 years; time from first employment to any cancer ranged from 15 to 43 years
  • Air sampling (dust mass) showed exposure levels falling continually over time from extremely high early levels
• The authors' conclusion: The authors concluded that the study supports a relationship between asbestos exposure and gastrointestinal tract cancers, specifically stomach cancer. They also stated that malignancy appeared highest among the most highly exposed workers and that past exposure levels in the plant had been too high.
• Limitations the authors state:
  • The number of workers lost to follow-up could not be determined
  • Exposure was measured as dust mass rather than fiber counts, and the two correlate poorly

Topics

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

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

Related studies

• Cancer mortality among Chinese chrysotile asbestos textile workers — X.R. Wang, I.T. Yu, et al. (2012)
• Cause-specific mortality in relation to chrysotile-asbestos exposure in a Chinese cohort — S. Lin, X. Wang, 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)
• Cause-specific mortality in a Chinese chrysotile textile worker cohort — X. Wang, S. Lin, et al. (2013)
• 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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