Man-made vitreous fibers and workers' health. An overview of the epidemiologic evidence

Our plain-English summary of Man-made vitreous fibers and workers' health. An overview of the epidemiologic evidence, by R. Saracci, L. Simonato (Scandinavian Journal of Work, Environment & Health, 1982).

The study

• Authors: R. Saracci, L. Simonato
• Journal: Scandinavian Journal of Work, Environment & Health
• Published: 1982;8(4):234-42
• Read it: PubMed · Publisher

In plain English

This review, by two International Agency for Research on Cancer researchers, examined epidemiologic evidence on man-made vitreous fibers (slagwool, rockwool, glasswool and continuous filament) and workers' health. It covered ten cross-sectional studies, seven mortality studies and one autopsy study, all of production workers, plus one study of building industry workers. For chronic respiratory disease, 11 of 19 studies were negative; eight showed some association. One well-conducted study linked only borderline X-ray abnormalities, among current smokers only, probably to the fibers. For respiratory cancer, four of nine investigations were negative; five showed some association. In one large US study, slagwool/rockwool workers had a ratio of 1.6 (45 observed, 28.1 expected; p less than 0.01). Neither large cohort study found a relation with exposure duration or intensity. Smoking and other exposures could not be controlled. The authors concluded that no long-term effects had been detectable in production workers under exposure conditions of roughly the first 20 years after first exposure. They judged later indications insufficient to show a causal role but enough to require further investigation, and the single user study inadequate for generalizations.

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: Review (overview) of published and conference-reported epidemiologic studies, reflecting the authors' own interpretation
• Who was studied: Studies of workers producing man-made vitreous fibers: ten cross-sectional studies (United States, United Kingdom, Italy, Yugoslavia, Sweden), seven mortality studies (United States, Canada and seven European countries) and one autopsy study. One further study covered Swedish building industry workers who used the products. The authors put the total number of workers observed at more than 40,000.
• Exposure: Man-made vitreous fibers (also called man-made mineral fibers): slagwool, rockwool, glasswool and continuous filament. Some slagwool/rockwool plants in one US study, and one rockwool plant in the European study, may have had some asbestos exposure or use.
• Main results:
  • Chronic respiratory disease, all morbidity and mortality studies combined: results were negative in 11 of 19 studies.
  • The other eight studies showed some association between chronic respiratory disease and work involving man-made vitreous fibers. The authors said confounding or bias could not be ruled out with any confidence.
  • One well-conducted study (Weill et al) linked only borderline chest X-ray abnormalities (small opacities), and only among current smokers, to an effect probably due to the fibers.
  • Respiratory cancer: of nine investigations, four were negative and five showed some association with work involving man-made vitreous fibers.
  • In the US study of 17 plants (Enterline and Marsh), slagwool/rockwool workers had an overall respiratory cancer ratio of 1.6 (45 observed against 28.1 expected; p less than 0.01). Glass fiber workers in the same study had 202 observed deaths against 203.5 expected.
  • In the European study (Saracci et al, 13 plants in seven countries), respiratory cancer ratios over the whole observation period were 1.1 (42 observed against 38.7 expected) for rockwool workers, 0.9 (30 against 39.9) for glasswool workers and 1.4 (15 against 10.5) for continuous filament workers. None was statistically significant.
  • In neither large cohort study, and for no production type, was respiratory cancer related to exposure duration or exposure intensity.
  • In the Swedish building industry case-referent study (320 lung cancer cases, 1,390 referents), the relative risk for 'heavy exposure' to man-made vitreous fibers was 3.64 (p less than 0.05), adjusted for smoking, place of residence and asbestos exposure. The authors noted that separating fiber exposure from asbestos exposure was only partially solved in that study.
  • On the possible occasional asbestos exposure in the US slagwool/rockwool plants, the authors noted that no mesothelioma deaths had been detected, which argued against any substantial asbestos exposure.
• The authors' conclusion: The authors concluded that, in the industry producing man-made vitreous fibers, no long-term harmful effects on workers' health had been detectable under the exposure conditions of roughly the first 20 years after first exposure. They judged that indications of respiratory effects 20, 30 or more years after first exposure were insufficient to show a causal role for the fibers, but sufficient to require full attention and further investigation. For users, they judged the one available study inadequate to allow generalizations.
• Limitations the authors state:
  • In all the mortality studies, smoking, workers' exposures before entering the industry, and other exposures in the plants could not be controlled. Weak associations could be partly explained by these uncontrolled confounders.
  • Little information was available for 30 or more years after first exposure, when some long-term effects may appear.
  • All the cross-sectional studies examined only workers still employed ('survivors').
  • About half of the negative studies had limited sensitivity (small samples, short exposure or short observation).
  • In the building industry study, separating exposure to man-made vitreous fibers from exposure to asbestos was only partially solved.
  • For users of the products, only one study was available, and its data were inadequate to allow generalizations.

Topics

Medical terms in this study, explained in our Lexicon: Vitreous.

Related studies

• 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: I. 1992 fiberglass cohort follow-up: initial findings — G.M. Marsh, A.O. Youk, et al. (2001)
• Respiratory health effects of man-made vitreous (mineral) fibres — P. De Vuyst, P. Dumortier, et al. (1995)
• Solubility of asbestos and man-made mineral fibers in vitro and in vivo: its significance in lung disease — A. Morgan, A. Holmes (1986)
• Lung dust analysis in the assessment of past exposure of man-made mineral fibre workers — J.C. McDonald, B.W. Case, et al. (1990)
• Occupational exposure to asbestos and man-made vitreous fibers, and risk of lung cancer: evidence from two case-control studies in Montreal, Canada — J. Pintos, M.E. Parent, et al. (2008)

Browse more research in Scandinavian Journal of Work, Environment & Health, or return to medical research.