Historical cohort study of US man-made vitreous fiber production workers: II. Mortality from mesothelioma

Our plain-English summary of Historical cohort study of US man-made vitreous fiber production workers: II. Mortality from mesothelioma, by G.M. Marsh, M.J. Gula, A.O. Youk, et al (Journal of Occupational and Environmental Medicine, 2001).

The study

• Authors: G.M. Marsh, M.J. Gula, A.O. Youk, J.M. Buchanich, A. Churg, T.V. Colby
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2001;43(9):757-66
• Type of article: Case report
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

As part of our ongoing mortality surveillance program for the US man-made vitreous fiber (MMVF) industry, we examined mortality from malignant mesothelioma using data from our 1989 follow-up of 3478 rock/slag wool workers and our 1992 follow-up of 32,110 fiberglass workers. A manual search of death certificates for 1011 rock/slag wool workers and 9060 fiberglass workers revealed only 10 death certificates with any mention of the word "mesothelioma." A subsequent review of medical records and pathology specimens for 3 of the 10 workers deemed two deaths as definitely not due to mesothelioma and one as having a 50% chance of being caused by mesothelioma. Two other deaths, for which only medical records were available, were given less than a 50% chance of being due to mesothelioma. Eight of the 10 decedents had potential occupational asbestos exposure inside or outside the MMVF industry. We also estimated the mortality risk from malignant mesothelioma in the cohort using two cause-of-death categorizations that included both malignant and benign coding rubrics. Using the more comprehensive scheme, we observed overall deficits in deaths among the total cohort and fiberglass workers and an overall excess among rock/slag wool workers. The excess in respiratory system cancer is largely a reflection of elevated lung cancer risks that we attributed mainly to confounding by smoking, to exposures outside the MMVF industry to agents such as asbestos, or to one or more of the several co-exposures present in many of the study plants (including asbestos). The second scheme, which focused on pleural mesothelioma in time periods when specific malignant mesothelioma coding rubrics were available, classified only one cohort death as being caused by malignant mesothelioma, compared with 2.19 expected deaths (local county comparison). We conclude that the overall mortality risk from malignant mesothelioma does not seem to be elevated in the US MMVF cohort.

In plain English

This historical cohort study examined deaths from malignant mesothelioma among US man-made vitreous fiber production workers. The cohort was 32,110 fiberglass workers from 10 plants and 3478 rock/slag wool workers from 6 plants, all employed at least one year between 1945 and 1978. The authors found 10 deaths possibly due to mesothelioma, 8 among fiberglass and 2 among rock/slag wool workers. Two pathologists reviewed tissue for three of them: one was a solitary fibrous tumor, one a carcinoma, and one might have been either mesothelioma or carcinoma. Records for five others could not be obtained. Most of the 10 had potential asbestos exposure. A broad group of death codes that could hide mesothelioma, mostly other cancers, gave 192 deaths against about 204 expected. Within it, rock/slag wool workers had an excess that was not statistically significant, which the authors linked mainly to respiratory cancer. A narrower pleural mesothelioma scheme found one death against 2.19 expected locally, and that tumor was judged definitely not mesothelioma. The authors concluded that mesothelioma risk did not seem elevated.

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 cohort mortality study with review of death certificates, medical records and pathology specimens; deaths compared with US and local county rates as standardized mortality ratios (SMRs)
• Who was studied: 32,110 fiberglass workers from 10 plants and 3478 rock/slag wool workers from 6 US plants, employed at least 1 year between 1945 and 1978; follow-up 1946 to 1989 (rock/slag wool) and 1946 to 1992 (fiberglass)
• Exposure: Respirable man-made vitreous fibers (fiberglass and rock/slag wool) and several workplace co-exposures, including asbestos
• Main results:
  • 10 deaths possibly due to malignant mesothelioma were identified from death certificates and ICD codes: 2 in the rock/slag wool cohort and 8 in the fiberglass cohort
  • Pathology review was possible for three cases, and both pathologists reached the same diagnoses. Case 1 was a malignant solitary fibrous tumor, which the article describes as not related to malignant mesothelioma. Case 2 was a carcinoma, possibly arising in the lung or mediastinum. Case 3 was a high-grade tumor that might be either an epithelial mesothelioma or a carcinoma.
  • For cases 4 and 5 only written medical records were available. The authors reported clinical evidence against mesothelioma in both: case 4 apparently survived at least 5 years after diagnosis, and case 5 presented with a mediastinal mass. An earlier panel review of case 5 slides determined it was not malignant mesothelioma.
  • Three decedents (cases 4, 5, 10) had potential asbestos exposure during their MMVF employment. Proxy interviews indicated potential asbestos exposure inside or outside the industry for cases 1, 2, 5, 6, 7, 9 and 10.
  • Among the decedents with exposure data, respirable fiber exposures were absent or low
  • The broad UPitt scheme (malignant codes only, 1946 to 1992) covered many ICD codes that could possibly contain mesothelioma, including other cancers. For the total cohort, 192 deaths were observed against 203.89 expected by US rates: SMR 0.94, 95% CI 0.81 to 1.08.
  • Under the UPitt scheme, fiberglass workers showed an 11% deficit (164 deaths; SMR 0.89, 95% CI 0.76 to 1.04, US comparison)
  • Under the UPitt scheme, rock/slag wool workers had 28 deaths, a not statistically significant excess: SMR 1.43 (95% CI 0.95 to 2.06) by US rates and 1.38 (95% CI 0.91 to 1.99) by local county rates
  • Respiratory system cancer made up 15 (53.6%) of the 28 rock/slag wool deaths in the UPitt scheme. The authors attributed respiratory cancer excesses in this group mainly to higher smoking rates and/or asbestos exposure outside the industry.
  • Under the narrower Xu et al pleural mesothelioma scheme (1968 to 1992), the combined cohort had 1 observed death. Expected deaths were 2.53 by US rates (SMR 0.39, 95% CI 0.01 to 2.20) and 2.19 by local county rates (SMR 0.46, 95% CI 0.01 to 2.54).
  • That single death was the male rock/slag wool worker in case 2, whose tumor was judged definitely not mesothelioma on pathology review
• The authors' conclusion: The authors concluded that the overall mortality risk from malignant mesothelioma does not seem to be elevated in the US MMVF cohort
• Limitations the authors state:
  • The authors stated that the main weakness was the inability to identify mesothelioma accurately from death certificates and/or ICD codes, which affects both the cohort deaths and the comparison population rates
  • Medical records and pathology specimens could not be obtained for five of the 10 deaths, mostly because relatives refused to release them

Topics

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

Medical terms in this study, explained in our Lexicon: Cohort Study, Vitreous, Mesothelioma, Death Certificate, Pathology, Asbestos Exposure, Lung Cancer, Confounding.

Related studies

• Historical cohort study of US man-made vitreous fiber production workers: I. 1992 fiberglass cohort follow-up: initial findings — G.M. Marsh, A.O. Youk, et al. (2001)
• Man-made vitreous fibers and risk of respiratory system cancer: a review of the epidemiologic evidence — I.M. Lee, C.H. Hennekens, et al. (1995)
• Mortality among a cohort of US man-made mineral fiber workers: 1985 follow-up — G.M. Marsh, P.E. Enterline, et al. (1990)
• Cancer mortality among man-made vitreous fiber production workers — C.E. Rossiter, H.G. Grimm (1998)
• Cytotoxic and oxidative effects induced by man-made vitreous fibers (MMVFs) in a human mesothelial cell line — D. Cavallo, A. Campopiano, et al. (2004)
• Lung cancer and exposure to man-made vitreous fibers: results from a pooled case-control study in Germany — H. Pohlabeln, K.H. Jöckel, et al. (2000)

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