Respiratory health effects of man-made vitreous (mineral) fibres

Our plain-English summary of Respiratory health effects of man-made vitreous (mineral) fibres, by P. De Vuyst, P. Dumortier, G.M. Swaen, et al (The European Respiratory Journal, 1995).

The study

• Authors: P. De Vuyst, P. Dumortier, G.M. Swaen, J.C. Pairon, P. Brochard
• Journal: The European Respiratory Journal
• Published: 1995;8(12):2149-73
• Type of article: Review
• Cited by: 40 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The group of man-made mineral or vitreous fibres (MMMFs or MMVFs) includes glass wool, rock wool, slag wool, glass filaments and microfibres, and refractory ceramic fibres (RCFs). Experimental observations have provided evidence that some types of MMVF are bioactive under certain conditions. The critical role of size parameters has been demonstrated in cellular and animal experiments, when intact fibres are in direct contact with the target cells. It is, however, difficult to extrapolate the results from these studies to humans since they bypass inhalation, deposition, clearance and translocation mechanisms. Inhalation studies are more realistic, but show differences between animal species regarding their sensibility to tumour induction by fibres. Fibre biopersistence is an important factor, as suggested by recent inhalation studies, which demonstrate positive results with RCF for fibrosis, lung tumours and mesothelioma. There is no firm evidence that exposure to glass-, rock- and slag wool is associated with lung fibrosis, pleural lesions, or nonspecific respiratory disease in humans. Exposure to RCF could enhance the effects of smoking in causing airways obstruction. An elevated standard mortality ratio for lung cancer has been demonstrated in cohorts of workers exposed to MMVF, especially in the early technological phase of mineral (rock slag) wool production. During that period, several carcinogenic agents (arsenic, asbestos, polycyclic aromatic hydrocarbons (PAH)) were also present at the workplace and quantitative data about smoking and fibre levels are lacking. It is not possible from these data to determine whether the risk of lung cancer is due to the MMVFs themselves. No increased risk of mesothelioma has been demonstrated in the cohorts of workers exposed to glass-, slag- or rock wool. There are in fact insufficient epidemiological data available concerning neoplastic diseases in RCF production workers because of the small size of the workforce and the relatively recent industrial production.

In plain English

This article was a review, not a new study. The authors summarized published cell, animal and human research on man-made vitreous fibres, including insulation wools and refractory ceramic fibres (RCFs). They reported that recent animal inhalation studies gave positive results with RCFs for fibrosis, lung tumours and mesothelioma. In the Geneva rat inhalation studies, glass wool and slag wool produced no significant fibrosis or tumours. Rock wool produced minimal lung fibrosis only in the two highest exposure groups, without excess tumours. When all glass wool inhalation data were combined, however, a significant increase in lung tumours was found. Pooled analyses of US, European and Canadian worker cohorts found raised lung cancer mortality, highest in early rock and slag wool production. During that early period, arsenic, asbestos and polycyclic aromatic hydrocarbons were also present, and quantitative data on smoking and fibre levels were lacking. The authors concluded that the role of the fibres themselves in lung cancer could not be definitively proved or ruled out. No increase in mesothelioma was demonstrated in glass, slag or rock wool workers. Human data on RCF workers were insufficient.

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: Narrative review of in vitro, animal (injection and inhalation) and human epidemiological and clinical studies
• Who was studied: Reviewed literature. The human data came mainly from three cohorts of MMVF production workers: a Canadian cohort of 2,557 workers from one plant (1955-1984), a US cohort of 16,661 workers from 17 plants (1945-1985), and a European IARC cohort of 21,967 workers from 14 plants (1953-1981). The review also covered animal and cell studies.
• Exposure: Man-made vitreous (mineral) fibres: glass wool, rock wool, slag wool, glass filaments and microfibres, and refractory ceramic fibres. Co-exposures in early production included asbestos, arsenic and PAH.
• Main results:
  • Recent animal inhalation studies reviewed by the authors gave the highest positive results seen for any MMVF with refractory ceramic fibres (fibrosis, lung tumours, mesothelioma).
  • In the reviewed Geneva rat inhalation studies, no significant fibrosis or tumours were reported for glass wool and slag wool at exposures of 25 to 225 fibres per mL.
  • In the same Geneva studies, minimal lung fibrosis from rock wool was reported for the two highest exposure groups (150 and 225 fibres per mL), with no significant excess of tumours.
  • When all glass wool inhalation data were gathered, a significant increase in lung tumours was found.
  • In pooled estimates from the three cohorts for workers followed up 20 years or more, lung cancer SMRs for glass wool and for mineral (rock/slag) wool were significantly elevated compared with regional rates.
  • The US and European cohorts gave similar lung cancer SMRs: 113.5 and 111.4 respectively for glass wool, and 134.2 and 139.9 for mineral (rock/slag) wool.
  • A recent follow-up of the European cohort (Boffetta et al.) reported lung cancer SMRs of 132 for the whole cohort, 137 for rock/slag wool and 127 for glass wool (all p less than 0.05).
  • The highest lung cancer SMRs, as high as 257, were reported in subcohorts of workers exposed in the early technological phase.
  • In a nested case-control study (Wong et al.) of 55 lung cancer cases and 98 controls within the US cohort of slag wool workers, the relationship between fibre exposure and lung cancer disappeared after adjustment for smoking.
  • No increase in mesothelioma risk was demonstrated in the cohorts of glass, slag or rock wool workers. In the US study, two deaths were coded as mesothelioma against 1.45 expected.
  • In one reviewed series of refractory ceramic fibre manufacturing workers, 3.4% had pleural changes considered as pleural plaques. The figure was 11.4% among those whose first RCF production job was more than 20 years earlier.
  • In the largest lung tissue study reviewed (131 deceased glass, rock and slag wool workers and 112 referents), most exposed workers had no MMVFs in their lung tissue.
• The authors' conclusion: The authors concluded that there is no firm evidence linking glass, rock and slag wool exposure to mesothelioma, lung fibrosis, pleural disease or nonspecific respiratory disease. Lung cancer SMRs were elevated in early mineral wool production, where other carcinogens were present, so it was not possible to definitively prove or rule out the role of MMVFs in lung cancer. Data on ceramic fibre workers were insufficient.
• Limitations the authors state:
  • The epidemiological cohort studies could not control confounders such as smoking and other carcinogens, and they lacked quantitative data such as fibre levels.
  • For the early production period, quantitative data about smoking and fibre levels were lacking.
  • There were insufficient data on ceramic fibre production workers, because the workforce is small and production is relatively recent.
  • Human lung data were too restricted to draw general conclusions about how long MMVFs persist in the human lung.
  • The authors said it is difficult to extrapolate cell and animal results to humans. Injection tests bypass inhalation and clearance, and inhalation studies differ between animal species.

Topics

Medical terms in this study, explained in our Lexicon: Vitreous, Deposition, Translocation, biopersistence, Fibrosis, Mesothelioma, Lung Cancer, Carcinogenic.

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• Respiratory cancer and exposure to man-made vitreous fibers: a systematic review — D. Berrigan (2002)
• Deposition of inhaled asbestos and man-made mineral fibres in the respiratory tract — A. Morgan (1995)
• Man-made mineral fibers and interstitial lung diseases — E. Fireman (2014)
• EV@LUTIL: An open access database on occupational exposures to asbestos and man-made mineral fibres — E. Orlowski, S. Audignon-Durand, et al. (2015)
• Systematic review and meta-analysis of epidemiological literature evaluating the association between exposure to man-made vitreous fibers and respiratory tract cancers — N. Suder Egnot, S.M. Benson, et al. (2020)

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