Increased Standardised Incidence Ratio of Malignant Pleural Mesothelioma in Taiwanese Asbestos Workers: A 29-Year Retrospective Cohort Study

Our plain-English summary of Increased Standardised Incidence Ratio of Malignant Pleural Mesothelioma in Taiwanese Asbestos Workers: A 29-Year Retrospective Cohort Study, by C.K. Lin, Y.Y. Chang, J.D. Wang, et al (BioMed Research International, 2015).

The study

• Authors: C.K. Lin, Y.Y. Chang, J.D. Wang, L.J. Lee
• Journal: BioMed Research International
• Published: 2015;2015:678598
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: This paper aimed to determine the standardised incidence ratio (SIR) of malignant pleural mesothelioma (MPM) in workers exposed to asbestos in Taiwan.

Methods: All workers employed in asbestos-related factories and registered by the Bureau of Labour Insurance between 1 March, 1950, and 31 December, 1989, were included in the study and were followed from 1 January, 1980, through 31 December, 2009. Incident cases of all cancers, including MPM (ICD-9 code: 163), were obtained from the Taiwan Cancer Registry. SIRs were calculated based on comparison with the incidence rate of the general population of Taiwan and adjusted for age, calendar period, sex, and duration of employment.

Results: The highest SIR of MPM was found for male workers first employed before 1979, with a time since first employment more than 30 years (SIR 4.52, 95% CI: 2.25-8.09). After consideration of duration of employment, the SIR for male MPM was 5.78 (95% CI: 1.19-16.89) for the workers employed for more than 20 years in asbestos-related factories.

Conclusions: This study corroborates the association between occupational asbestos exposure and MPM. The highest risk of MPM was found among male asbestos workers employed before 1979 and working for more than 20 years in asbestos-related factories.

In plain English

This retrospective cohort study followed 160,640 workers from asbestos-related factories in Taiwan, identified through labour insurance records. It tracked new cancers in the Taiwan Cancer Registry from 1980 to 2009 and compared their rates with those of Taiwan's general population. Exposure was not measured for individual workers. Instead, the time each worker was insured stood in for the amount of exposure. Among men, 17 cases of malignant pleural mesothelioma were found, a standardised incidence ratio of 2.65 (95% CI 1.54 to 4.25). The ratio was 4.52 (95% CI 2.25 to 8.09) for men first employed between 1950 and 1979 with more than 30 years since first employment. It was 5.78 (95% CI 1.19 to 16.89, 3 cases) for men employed more than 20 years. No case appeared within 20 years of first employment. Men's overall cancer and lung cancer rates were below expected. One woman developed mesothelioma, a result that was not statistically significant. The authors concluded that minimal asbestos exposure with long latency is enough to increase mesothelioma risk. They noted they lacked data on asbestos type and smoking, and that follow-up may have been too short.

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 comparing cancer incidence (standardised incidence ratios) with the Taiwanese general population
• Who was studied: 160,640 workers (121,883 men, 38,757 women) employed in asbestos-related factories in Taiwan and registered with labour insurance. Total follow-up was 4,021,078 person-years. Only workers first employed before 1989 were counted, and cancers were tracked from 1980 to 2009.
• Exposure: Employment in 389 factories listed by the Taiwan EPA as asbestos-related, in seven groups: asbestos-cement, asbestos friction, asbestos thermal insulation, industries using serpentine, those that applied to use asbestos, those that applied but did not use it, and not classified. There was no individual exposure measurement. Total labour insurance coverage time was used as a proxy for the amount of exposure.
• Main results:
  • Men: 17 cases of malignant pleural mesothelioma were observed, a standardised incidence ratio of 2.65 (95% CI 1.54 to 4.25), statistically significant.
  • Men first employed before 1979: SIR 3.68 (95% CI 2.10 to 5.98). Men employed after 1979: SIR 0.62 (95% CI 0.00 to 3.48).
  • Men first employed 1950 to 1979, more than 30 years since first employment: 11 cases, SIR 4.52 (95% CI 2.25 to 8.09).
  • Men employed more than 20 years: SIR 5.78 (95% CI 1.19 to 16.89), based on 3 cases.
  • Men employed less than 1 year: overall SIR 2.61 (95% CI 1.05 to 5.39). All of these cases had more than 20 years of latency.
  • No case of malignant pleural mesothelioma was found within 20 years of first employment. Among the 17 male cases, the median latency was 33.2 years.
  • Among the 17 male cases, the median duration of employment was 1.7 years (range 0.1 to 30 years).
  • Of the 17 male cases, 16 worked in the 'not classified' factory category and one in the insulation industry.
  • Men overall: 6,544 cancers, below expectation (SIR 0.48, 95% CI 0.47 to 0.49). The authors also reported no increased risk of lung cancer among the workers.
  • Women: one case of malignant pleural mesothelioma, SIR 1.67 (95% CI 0.04 to 9.29). This was not statistically significant.
  • Women: cervical cancer was statistically significantly higher than expected, SIR 1.73 (95% CI 1.57 to 1.91), 412 cases. The authors judged a causal link with asbestos less likely because the result was not consistent across employment periods.
• The authors' conclusion: The authors concluded that risk of malignant pleural mesothelioma was higher among men first employed before 1979, especially those employed more than 20 years. They said their findings support the view that minimal asbestos exposure with long latency is enough to increase risk.
• Limitations the authors state:
  • The study had no detailed exposure assessment, and no data on which type of asbestos each factory used.
  • There were no data on cigarette smoking among the workers.
  • Follow-up from 1980 to 2009 may be too short given mesothelioma's long latency, and more cases are expected after 2009.
  • The Taiwan EPA roster may not include all factories that used asbestos, and employment may have been underreported.
  • ICD-9 coding underestimates malignant mesothelioma, because it has no specific code.
  • Including factories that applied to use asbestos but did not use it may have diluted, and underestimated, the risk of all cancers.

Topics

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

Medical terms in this study, explained in our Lexicon: Standardized Incidence Ratio (SIR), Pleural Mesothelioma, Cohort Study, Cancer Registry, Incidence, Asbestos Exposure.

Related studies

• Increased Risk of Gastric Cancer in Asbestos-Exposed Workers: A Retrospective Cohort Study Based on Taiwan Cancer Registry 1980-2015 — Y.J. Fang, H.Y. Chuang, et al. (2021)
• Cancer incidence of Taiwanese shipbreaking workers who have been potentially exposed to asbestos — W.T. Wu, Y.J. Lin, et al. (2014)
• Mortality among shipbreaking workers in Taiwan--a retrospective cohort study from 1985 to 2008 — W.T. Wu, Y.H. Lu, et al. (2013)
• Standardized Incidence Ratio and Standardized Mortality Ratio of Malignant Mesothelioma in a Worker Cohort Using Employment Insurance Database in Korea — E.A. Kim (2021)
• Upcoming epidemic of asbestos-related malignant pleural mesothelioma in Taiwan: A prediction of incidence in the next 30 years — R.T. Lin, Y.Y. Chang, et al. (2019)
• Incidence of Cancer and Asbestos-Related Diseases among Residents Living near Abandoned Asbestos Mines in South Korea: A Retrospective Cohort Study Using National Health Insurance Database — K. Kwak, K.E. Zoh, et al. (2021)

Browse more research in BioMed Research International, or return to medical research.