Systematic review and meta-analysis of epidemiological literature evaluating the association between exposure to man-made vitreous fibers and respiratory tract cancers

Our plain-English summary of Systematic review and meta-analysis of epidemiological literature evaluating the association between exposure to man-made vitreous fibers and respiratory tract cancers, by N. Suder Egnot, S.M. Benson, M.F. Vater, et al (Regulatory Toxicology and Pharmacology, 2020).

The study

• Authors: N. Suder Egnot, S.M. Benson, M.F. Vater, R. Hazan, O. Patel, G.M. Marsh
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2020;112:104585
• Type of article: Meta-analysis, Systematic review
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We conducted a systematic review and meta-analysis of epidemiological studies that evaluated occupational exposure to man-made vitreous fibers (MMVF) including glass, rock, and slag wools, and respiratory tract cancers (RTC) including cancers of the larynx, trachea, bronchus, and lung. The MEDLINE/PubMed and Web of Science databases were searched in order to identify epidemiological studies that evaluated the association between occupational MMVF exposure and RTCs. We performed random-effects meta-analyses of relevant studies identified by our literature search, and evaluated sources of between-study heterogeneity. The pooled relative risk (RR) of RTC among workers exposed to MMVFs was 1.09 (95% CI = 0.97, 1.22). The RR was closer to 1.0 when limiting the analysis to effect estimates from studies that accounted for the main a priori risk factors for RTC, asbestos exposure and smoking (RR = 1.03, 95% CI = 0.90, 1.18). Overall, our synthesis of the epidemiological literature suggests that occupational MMVF exposure is not associated with risk of RTC.

Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.

In plain English

This article was a systematic review and meta-analysis, which pools results from earlier studies. In May 2019 the authors searched two databases and combined 19 studies (nine cohort and 10 case-control studies) of workers exposed on the job to man-made vitreous fibers, mainly glass wool and rock/slag wool, and cancers of the larynx, trachea, bronchus and lung. Asbestos was not the exposure studied; along with smoking, it was treated as another risk factor to account for. Across all studies the pooled relative risk was 1.09 (95% confidence interval 0.97 to 1.22). In estimates that accounted for both asbestos and smoking it was 1.03 (0.90 to 1.18). Cohort studies pooled to 0.97 (0.86 to 1.09). Case-control studies pooled to a statistically significant 1.41 (1.12 to 1.79), and lung cancer estimates alone pooled to 1.25 (1.07 to 1.47). The authors said the limitations of the case-control studies, including reliance on self-reported work histories, kept them from treating that elevation as a valid association. The authors concluded that the studies provided no consistent or credible evidence of an association.

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: Systematic review and random-effects meta-analysis of published cohort and case-control studies
• Who was studied: 19 published studies identified by searching PubMed and Web of Science in May 2019, plus earlier studies found through the 2002 IARC Monograph and reference lists. Five studies were from North America (Canada and US), 13 from European countries and one from Asia (China).
• Exposure: Occupational exposure to man-made vitreous fibers (MMVF), specifically glass wool (GW) and rock/slag wool (RSW). Asbestos exposure and smoking were treated as a priori risk factors to be accounted for. The outcomes were respiratory tract cancers: larynx, trachea, bronchus and lung.
• Main results:
  • Overall pooled relative risk (meta-RR) for MMVF exposure and respiratory tract cancer, all studies: 1.09 (95% CI 0.97, 1.22)
  • Pooled estimate among studies adjusted for both asbestos exposure and smoking: meta-RR 1.03 (95% CI 0.90, 1.18)
  • Pooled estimate for cohort studies only: meta-RR 0.97 (95% CI 0.86, 1.09)
  • Pooled estimate for case-control studies only: statistically significant meta-RR 1.41 (95% CI 1.12, 1.79). It was 1.32 (95% CI 1.14, 1.53) when limited to estimates that accounted for asbestos exposure and smoking.
  • By fiber type: glass wool meta-RR 0.96 (95% CI 0.83, 1.00); rock/slag wool meta-RR 1.11 (95% CI 0.84, 1.46). The authors reported no associations.
  • After adjustment for smoking, glass wool exposure showed a statistically significant deficit in respiratory tract cancer mortality: SMR 0.86 (95% CI 0.76, 0.99)
  • Lung cancer-specific estimates pooled from 17 studies: statistically significant meta-RR 1.25 (95% CI 1.07, 1.47)
  • Laryngeal cancer estimates pooled from five studies: meta-RR 1.22 (95% CI 0.90, 1.65), not statistically significant
  • The funnel plot and Egger test (p = 0.445) did not suggest publication bias. The Tse et al. (2012) study was excluded from this analysis as an outlier.
• The authors' conclusion: The authors concluded that the studies published since 2002, particularly the cohort studies, provide no consistent or credible evidence of an association between MMVF exposure and respiratory tract cancer, a conclusion they said was supported by their overall meta-analysis.
• Limitations the authors state:
  • The authors stated that the limitations of the case-control studies prevented them from treating the elevated pooled case-control estimate as a valid association.
  • The case-control studies published since 2002 assigned exposure from self-reported work histories, which the authors said may cause exposure misclassification and recall bias.
  • The cohort studies published since 2002 mainly lacked statistical adjustment for smoking and other occupational exposures.
  • Most of the recent studies included only men, which the authors said limits how widely the results apply.
  • The included studies differed in design and analysis.

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: Systematic Review, Meta-Analysis, Vitreous, Occupational Exposure, Bronchus, Relative Risk, Asbestos Exposure.

Related studies

• Respiratory cancer and exposure to man-made vitreous fibers: a systematic review — D. Berrigan (2002)
• 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)
• Historical cohort study of US man-made vitreous fiber production workers: II. Mortality from mesothelioma — G.M. Marsh, M.J. Gula, et al. (2001)
• Respiratory health effects of man-made vitreous (mineral) fibres — P. De Vuyst, P. Dumortier, et al. (1995)
• Deposition of inhaled asbestos and man-made mineral fibres in the respiratory tract — A. Morgan (1995)
• Cytotoxic and oxidative effects induced by man-made vitreous fibers (MMVFs) in a human mesothelial cell line — D. Cavallo, A. Campopiano, et al. (2004)

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