Health aspects of man-made mineral fibres. A review

Our plain-English summary of Health aspects of man-made mineral fibres. A review, by J.W. Hill (The Annals of Occupational Hygiene, 1977).

The study

• Author: J.W. Hill
• Journal: The Annals of Occupational Hygiene
• Published: 1977;20(2):161-73
• Type of article: Review
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Man-made mineral fibres (MMMF) have been in production for over 40 years. The diameter of the fibres has in general been too large to cause a high concentration of respirable fibrous dust during manufacturing or use. Medical studies in several countries of groups of workers exposed for lengthy periods to glass fibre have produced evidence of the absence of lung fibrosis or respiratory impairment, and have not shown an excess risk of lung or other cancers. Reports of a few individuals with respiratory disease and an exposure to MMMF have not clearly indicated the fibres as a cause of the disease. Limited pathological studies of lungs of workers with long term exposures to glass fibre have shown no evidence of lung damage. Animal inhalation studies in general confirm that MMMF are not fibrogenic. Following injection of fibres into the pleura, the incidence of tumours produced is related to the dose, diameter and length of the fibres. Further research is needed to enlarge the number and diversity of the epidemiological studies; also to look more critically at the biological effects of small diameter fibres which may arise as a result of changes in technology of production and use of MMMF.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This article reviewed published evidence on the health effects of man-made mineral fibres, made from glass, natural rock or slag. The author contrasted these with crystalline asbestos. Measured respirable fibre levels in the production industry averaged about 0.03 to 0.2 fibres/ml. One sample from making very fine fibres reached 44 fibres/ml. Worker studies using chest X-rays and lung function tests revealed no evidence of disease attributable to them. One reviewed study traced 1448 glass wool workers. It found no overall excess mortality and no case of mesothelioma, but an excess of non-malignant respiratory deaths excluding pneumonia and influenza; the author questioned that finding's significance. In reviewed rat experiments, fibres placed in the chest or abdomen, including glass fibres, could induce mesotheliomas. The author concluded that worker evidence was adequate to exclude a risk of pneumoconiosis (dust-related lung disease) for practical purposes. The author added that mesothelioma evidence came from small groups and did not cover newer very fine fibres. A discussion printed with the article reported six respiratory cancers against 2.6 expected among over 500 workers in Norway, still under follow-up.

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 of published literature (case reports, worker studies, animal experiments and cell culture studies)
• Who was studied: Published studies on man-made mineral fibres (glass, rock and slag wools): case reports, worker groups in several countries, animal and cell experiments. No new study population.
• Exposure: Man-made mineral fibres made from glass, natural rock or slag, which the author describes as amorphous silicates, in contrast with crystalline asbestos
• Main results:
  • Respirable fibre concentrations in the production industry averaged between about 0.03 and 0.2 fibres/ml. The author compared this with the then Threshold Limit Value of 2 fibres/ml for asbestos generally and 0.2 fibres/ml for crocidolite.
  • For production of very fine fibres (less than 1 micrometre in diameter), a level as high as 44 fibres/ml was reported. The author notes this was a single sample of one operation.
  • The reviewed worker studies of chest X-rays, lung function and bronchitis symptoms revealed no evidence of disease attributable to man-made mineral fibres.
  • In a reviewed study (Bayliss et al., 1976) of 1448 workers employed at least five years between 1940 and 1949 in a glass wool plant, there was no overall excess mortality, no excess of cancer deaths and no case of mesothelioma.
  • In the same study, the only positive finding was an excess of deaths in the category of non-malignant respiratory deaths excluding pneumonia and influenza. The author criticised the choice of the US population as the comparison group.
  • The author considered the significance of that excess open to doubt, citing some workers' prior exposure to dusty trades and the difficulty of classifying these diseases.
  • In a reviewed study of 416 retired glass fibre workers (Enterline, 1975), retirements due to bronchitis were three observed against 0.5 expected.
  • The author summarised animal inhalation experiments as showing that glass fibres produce a minimal tissue response in the lungs.
  • In reviewed experiments where fibres were placed in the pleural or peritoneal space of rats, a fibrous shape conferred the potential for inducing mesotheliomas, whatever the chemical nature of the fibre.
  • In reviewed intrapleural work in rats (Wagner et al.), glass fibres at or below 0.5 micrometres in diameter produced mesotheliomas, while fibres more than 3 micrometres in diameter had a much reduced effect.
  • In the report of discussion printed with the article, a group of over 500 workers in Norway had six cases of cancer of the respiratory organs against 2.6 expected. The group was being followed further.
• The authors' conclusion: The author concluded that the epidemiological evidence was substantially negative and adequate to exclude a risk of pneumoconiosis for practical purposes. The author also called for larger prospective studies because of mesothelioma's rarity and possibly long latency.
• Limitations the authors state:
  • For very rare tumours such as mesothelioma, the evidence is retrospective and comes from groups too small to detect such an increase in risk.
  • The available epidemiological evidence does not relate to fibres with nominal diameters of 1 micrometre or less, which were produced commercially only in the previous 10 years or so.
  • Doses in the intrapleural experiments were very great compared with probable human exposures, and the author says there is no scientific basis for quantifying risk from them.

Topics

Medical terms in this study, explained in our Lexicon: Fibrosis, Fibrogenic, Pleura.

Related studies

• Lung dust analysis in the assessment of past exposure of man-made mineral fibre workers — J.C. McDonald, B.W. Case, et al. (1990)
• Respiratory cancer incidence in Swedish construction workers exposed to man-made mineral fibres and asbestos — G. Engholm, A. Englund, et al. (1987)
• Respiratory health effects of man-made vitreous (mineral) fibres — P. De Vuyst, P. Dumortier, et al. (1995)
• The ability of mineral dusts and fibres to initiate lipid peroxidation. Part I: parameters which determine this ability — M. Gulumian (1999)
• Solubility of asbestos and man-made mineral fibers in vitro and in vivo: its significance in lung disease — A. Morgan, A. Holmes (1986)
• Carcinogenesis and mineral fibres — J.C. Wagner, G. Berry, et al. (1980)

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