Mortality among shipbreaking workers in Taiwan--a retrospective cohort study from 1985 to 2008

Our plain-English summary of Mortality among shipbreaking workers in Taiwan--a retrospective cohort study from 1985 to 2008, by W.T. Wu, Y.H. Lu, Y.J. Lin, et al (American Journal of Industrial Medicine, 2013).

The study

• Authors: W.T. Wu, Y.H. Lu, Y.J. Lin, Y.H. Yang, H.S. Shiue, J.H. Hsu, C.Y. Li, C.Y. Yang, S.H. Liou, T.N. Wu
• Journal: American Journal of Industrial Medicine
• Published: 2013;56(6):701-8
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Shipbreaking workers are typically exposed to a wide range of hazardous chemicals. However, long-term follow-up studies of their mortality patterns are lacking. This study examined mortality among shipbreaking workers over a 24-year follow-up period.

Methods: A total of 4,962 shipbreaking workers were recruited from the database of the Kaohsiung Shipbreaking Workers Union. The data were then linked to the Taiwan National Death Registry from 1985 to 2008. The mortality ratios-standardized for age and calendar years-(SMRs) for various causes of deaths were calculated with reference to the general population of Taiwan.

Results: Among men workers, a statistically significant increased SMR was observed for all causes (SMR = 1.28), all cancers (SMR = 1.26; particularly noteworthy for lesions of oral and nasopharyngeal: SMR 2.03, liver: SMR 4.63, and lung: SMR 1.36), cirrhosis of the liver (SMR = 1.32), and accidents (SMR = 1.91). A statistically significant increase in mortality was observed for respiratory system cancer (SMR = 1.87) and lung cancer (SMR = 1.91) among workers with a longer duration of employment (≥7 years). The result also showed that among shipbreaking workers who were still alive, two people had mesothelioma and 10 people have asbestosis.

Conclusions: Those employed in shipbreaking industries experienced an increase in mortality from all causes. The increased SMR for lung cancer was probably related to asbestos, metals, and welding fume exposure.

Copyright © 2013 Wiley Periodicals, Inc.

In plain English

This retrospective cohort study followed 4,962 members of the Kaohsiung Shipbreaking Workers Union in Taiwan through the national death registry from 1985 to 2008. By the end, 939 had died. Death rates were compared with Taiwan's general population as standardized mortality ratios (SMRs). Exposure was not measured; length of employment and job type were used instead. Among men, deaths were higher than expected from all causes (SMR 1.28), all cancers (1.26), liver cancer (4.63), oral and nasopharyngeal cancer (2.03), lung cancer (1.36, 95% CI 1.00 to 1.79), cirrhosis of the liver (1.32) and accidents (1.91). Among men employed 7 years or more, the lung cancer SMR was 1.91 (1.30 to 2.69). For shorter employment it was 1.14, which was not statistically significant. No SMR among women was statistically significantly raised or lowered. One male flame cutter died of pleural mesothelioma. Outpatient health insurance records listed two living workers with mesothelioma and 10 with asbestosis. The authors concluded that the lung cancer excess was probably related to asbestos, metals and welding fumes. They noted that they had no data on smoking, alcohol or diet.

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: retrospective cohort study (mortality follow-up using the national death registry, with standardized mortality ratios against the general population of Taiwan); an extension of the authors' earlier 13-year follow-up
• Who was studied: 4,962 shipbreaking workers who were registered members of the Kaohsiung Shipbreaking Workers Union in Taiwan as of 1985 (first employed from as early as 1975). The tables give 4,157 men and 805 women. Followed for deaths from January 1, 1985 to December 31, 2008, giving 128,102 person-years and 939 deaths. Job groups: 2,861 flame cutters, 876 lifters, 999 odd-jobbers, 226 supervisors and others.
• Exposure: Work in shipbreaking. Jobs included flame cutting, lifting, and odd jobs that included dismantling asbestos materials. Asbestos fiber types were not specified. No exposure measurements were made. Duration of employment (less than 7 years vs 7 years or more) was used as a proxy for exposure level, alongside job category.
• Main results:
  • Men: all-cause mortality was higher than in Taiwan's general population, SMR 1.28 (860 observed vs 669.8 expected deaths; 95% CI 1.20 to 1.37). All cancers SMR 1.26 (95% CI 1.11 to 1.43).
  • Men: SMR 2.03 for oral and nasopharyngeal cancer (56 deaths), 4.63 for liver cancer (65 deaths), and 1.36 for lung cancer (49 observed vs 36.1 expected; 95% CI 1.00 to 1.79).
  • Men: SMR 1.32 for cirrhosis of the liver and 1.91 for accidents.
  • Men employed 7 years or more: statistically significant SMRs of 1.87 for respiratory system cancer (95% CI 1.29 to 2.63) and 1.91 for lung cancer (32 deaths; 95% CI 1.30 to 2.69). Men employed less than 7 years: 1.09 and 1.14, which were not statistically significant.
  • Male flame cutters: lung cancer SMR 1.68 (27 observed vs 16.1 expected; 95% CI 1.11 to 2.44).
  • Women: no SMR was statistically significantly raised or lowered. Cancers were non-significantly increased (all cancers SMR 1.09, 95% CI 0.73 to 1.56; all causes SMR 1.02, 95% CI 0.81 to 1.28). No mesothelioma deaths were recorded among women.
  • One male flame cutter died of pleural mesothelioma. No cause-specific SMR was calculated for mesothelioma.
  • Linkage to outpatient health insurance records (1989 to 2008) found two people with mesothelioma (ICD-9 code 163) and 10 with asbestosis (ICD-9 code 501) among workers still alive.
• The authors' conclusion: The authors concluded that shipbreaking workers in Taiwan had increased mortality from all causes. They judged that the increased lung cancer SMR was probably related to asbestos, metals and welding fume exposure, and that tobacco use might not fully explain the lung cancer excess.
• Limitations the authors state:
  • No exposure assessment. Exposures were complex and poorly documented.
  • No information on smoking, alcohol or diet.
  • Follow-up may not have been long enough to observe mesothelioma, given its long latency.
  • The excess of accidental deaths among workers employed less than 7 years (a competing cause of death) may have led to cancer being underestimated.
  • A healthy worker effect was judged to still be present.

Topics

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

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

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