Mineral fibres, fibrosis, and asbestos bodies in lung tissue from deceased asbestos cement workers

Our plain-English summary of Mineral fibres, fibrosis, and asbestos bodies in lung tissue from deceased asbestos cement workers, by M. Albin, L. Johansson, F.D. Pooley, et al (British Journal of Industrial Medicine, 1990).

The study

• Authors: M. Albin, L. Johansson, F.D. Pooley, K. Jakobsson, R. Attewell, R. Mitha
• Journal: British Journal of Industrial Medicine
• Published: 1990;47(11):767-74
• Cited by: 43 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 003781).

Abstract

Lung tissue from 76 deceased asbestos cement workers (seven with mesothelioma) exposed to chrysotile asbestos and small amounts of amphiboles, has been studied by transmission electron microscopy, together with lung tissue from 96 controls. The exposed workers with mesothelioma had a significantly higher total content of asbestos fibre in the lungs than those without mesothelioma, who in turn, had higher concentrations than the controls (medians 189, 50, and 29 x 10(6) fibres/g (f/g]. Chrysotile was the major type of fibre. The differences were most pronounced for the amphibole fibres (62, 4.7, and 0.15 f/g), especially crocidolite (54, 1.8 and less than 0.001 f/g), but were evident also for tremolite (2.9, less than 0.001, and less than 0.001 f/g) and anthophyllite (1.7, less than 0.001, and less than 0.001 f/g). For amosite, there was no statistically significant difference between lungs from workers with and without mesothelioma; the lungs of workers had, however, higher concentrations than the controls. Strong correlations were found between duration of exposure and content of amphibole fibres in the lungs. Asbestos bodies, counted by light microscopy, were significantly correlated with the amphibole but not with the chrysotile contents. Fibrosis was correlated with the tremolite but not the chrysotile content in lungs from both exposed workers and controls. Overall, similar results were obtained using fibre counts and estimates of mass.

In plain English

This study from Lund, Sweden measured mineral fibres by transmission electron microscopy in lung tissue from 76 deceased asbestos cement workers. Their plant used mainly chrysotile (over 95%), with small amounts of crocidolite and amosite. Seven of the workers had pleural mesothelioma. Their lungs were compared with tissue from 96 matched controls. Median total asbestos content was 189, 50 and 29 million fibres per gram of dry lung tissue in workers with mesothelioma, workers without mesothelioma and controls. Chrysotile was the main fibre, but the largest differences were in amphiboles, especially crocidolite. Workers with mesothelioma did not have significantly more chrysotile or amosite than other workers. Amphibole content rose with length of employment. Asbestos bodies were correlated with amphibole but not chrysotile content. No correlation was found between measured lung chrysotile content and fibrosis. Tremolite showed a relation with fibrosis in the workers; amphiboles and tremolite were significantly correlated with fibrosis in the controls. The authors concluded that tremolite and the commercial amphiboles may be more fibrogenic than chrysotile. They noted that few workers had high exposure to crocidolite and amosite.

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: Lung tissue (fibre burden) study comparing deceased exposed workers with matched controls, using tissue collected retrospectively from routine autopsies and analysed by transmission electron microscopy and light microscopy
• Who was studied: 76 deceased asbestos cement workers: 69 without mesothelioma, whose matched controls (89) came from an earlier histology study, and 7 with pleural mesothelioma, each with one matched control. That makes 96 controls in total. Authors were based in Lund, Sweden; the plant operated 1907-77.
• Exposure: Work in asbestos cement production. Chrysotile made up over 95% of the asbestos used. Small amounts of crocidolite were used until 1966 (often under 1%, never over 3 to 4%) and amosite until 1956. Mean cumulative exposure was 26 fibre-years/ml (range 0 to 230) for workers without mesothelioma and 49 (range 14 to 162) for workers with mesothelioma.
• Main results:
  • Fibre concentrations were measured per gram dry weight of lung tissue. Median total asbestos fibre content was 189 x 10^6 fibres/g in workers with mesothelioma, 50 x 10^6 in workers without mesothelioma, and 29 x 10^6 in controls.
  • Median amphibole content was 62, 4.7 and 0.15 (x 10^6 fibres/g) in the same three groups. For crocidolite the medians were 54, 1.8 and less than 0.001.
  • Workers with mesothelioma had significantly more crocidolite (p = 0.003) and tremolite (p = 0.005) than workers without mesothelioma.
  • Workers with mesothelioma did not have significantly higher chrysotile (p = 0.08) or amosite (p = 0.08) concentrations than workers without mesothelioma.
  • In a rough matched analysis of workers employed more than 20 years, the worker without mesothelioma had lower amphibole counts than the mesothelioma case in 6 of 7 pairs (p = 0.04).
  • Among the 76 workers, duration of employment was correlated with the sum of amphibole fibres (rank correlation 0.4, p less than 0.001).
  • Among the 76 workers, for chrysotile there was only a non-significant tendency for content to rise with duration of employment (0.1, p = 0.06).
  • Among the 69 workers without mesothelioma, asbestos body counts were significantly correlated with amphibole content but not with chrysotile or non-asbestos fibres. No significant correlations were found among controls.
  • No correlation was found between the measured chrysotile or non-asbestos fibre content of the lungs and fibrosis, in either the exposed workers or the controls.
  • Among exposed workers, rank correlations between fibre content and fibrosis grade were not statistically significant. In logistic regression, however, tremolite content showed a clear relation with presence of fibrosis (chi-square 4.9, p printed as 0.003).
  • Among the 89 controls, total amphibole content (rank correlation 0.15, p = 0.04) and tremolite content (0.21, p = 0.01) were significantly correlated with fibrosis grade.
• The authors' conclusion: The authors concluded that tremolite, as well as the commercial amphiboles amosite and crocidolite, may have a stronger fibrogenic effect than chrysotile. They also concluded that the amphibole differences between workers with and without mesothelioma were only partly explained by background factors such as duration of exposure.
• Limitations the authors state:
  • Tissue came from routine autopsies, often without information on which part of the lung was sampled.
  • Fibre loss or splitting of fibre bundles can occur during preparation, and results cannot be directly compared with other laboratories.
  • Few workers had high exposure to crocidolite and amosite, which limited the assessment of these fibres' effect on fibrosis.
  • The data cannot show whether fibres accumulated first and caused fibrosis, or whether fibrosis came first and reduced clearance of fibres.
  • Total dust was not analysed, so the relation between total retained material and tremolite content could not be assessed.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Mesothelioma, Tremolite.

Medical terms in this study, explained in our Lexicon: Fibrosis, Asbestos Bodies, Asbestos-Cement, Mesothelioma, Chrysotile, Amphibole Group, Transmission Electron Microscopy (TEM), Crocidolite.

Related studies

• Retention patterns of asbestos fibres in lung tissue among asbestos cement workers — M. Albin, F.D. Pooley, et al. (1994)
• Ferruginous bodies and pulmonary fibrosis in dead low to moderately exposed asbestos cement workers: histological examination — L.G. Johansson, M.P. Albin, et al. (1987)
• Asbestos-induced visceral pleural fibrosis reduces pulmonary compliance — E.H. Valkila, M.M. Nieminen, et al. (1995)
• Fibre type and concentration in the lungs of workers in an asbestos cement factory — B. Gylseth, G. Mowé, et al. (1983)
• Fibrogenesis by mineral fibres: an in-vitro study of the roles of the macrophage and fibre length — M. Aalto, A.G. Heppleston (1984)
• Sumas Mountain chrysotile induces greater lung fibrosis in Fischer344 rats than Libby amphibole, El Dorado tremolite, and Ontario ferroactinolite — J.M. Cyphert, A. Nyska, et al. (2012)

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