Historical cohort study of US man-made vitreous fiber production workers: II. Mortality from mesothelioma
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G M Marsh1, M J Gula, A O Youk
1Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA. gmarsh@pitt.edu
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.
Insights
Mortality surveillance of US man-made vitreous fiber (MMVF) workers found no elevated risk of malignant mesothelioma. Most potential mesothelioma deaths were linked to asbestos exposure outside the MMVF industry.
Area of Science:
- Occupational epidemiology
- Environmental health
- Cancer research
Background:
- Ongoing mortality surveillance of the US man-made vitreous fiber (MMVF) industry is crucial for understanding worker health.
- Previous studies have raised concerns about potential asbestos-related diseases in MMVF workers.
Observation:
- A review of death certificates for rock/slag wool and fiberglass workers identified only 10 mentions of mesothelioma.
- Medical record reviews and pathology specimen analyses confirmed few, if any, mesothelioma deaths within the cohort.
- Most identified cases had potential occupational asbestos exposure unrelated to MMVF production.
Findings:
- Using comprehensive cause-of-death categorizations, deficits in overall deaths were observed in the total cohort and fiberglass workers, with an excess in rock/slag wool workers.
- Elevated respiratory cancer risks were largely attributed to smoking or external exposures like asbestos, not MMVF production.
- A focused analysis on pleural mesothelioma identified only one death, compared to 2.19 expected deaths.
Implications:
- The study suggests that the US MMVF industry does not have an elevated mortality risk from malignant mesothelioma.
- Findings highlight the importance of considering confounding factors like smoking and external occupational exposures in epidemiological studies.
- This research contributes to a clearer understanding of the health impacts associated with MMVF production and occupational exposures.
