Distribution and characteristics of amphibole asbestos fibres, measured with the light microscope, in the left lung of an insulation worker

Our plain-English summary of Distribution and characteristics of amphibole asbestos fibres, measured with the light microscope, in the left lung of an insulation worker, by A. Morgan, A. Holmes (British Journal of Industrial Medicine, 1983).

The study

• Authors: A. Morgan, A. Holmes
• Journal: British Journal of Industrial Medicine
• Published: 1983;40(1):45-50
• Cited by: 34 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Concentrations of uncoated and coated amphibole fibres were measured postmortem in samples taken from the periphery of both upper and lower lobes of the left lung of an insulation worker. Similar measurements were made on a more limited range of samples from elsewhere in the lung and on a hilar lymph node. The mean concentration of uncoated fibres in the upper lobe was twice that in the lower. Significant differences were observed in the mean concentration of uncoated fibres in different regions of the periphery, the diaphragmatic region having the lowest value. Variations in the concentrations of both uncoated and coated fibres in the costal region of the lower lobe may have been related to the effect of rib structures on ventilation. Concentrations of fibrous and non-fibrous dust were well correlated in the peripheral samples. The length distributions of uncoated and coated fibres were also measured and differences detected in fibres from the various regions of the lung. This work emphasises the care required in sampling lung tissue in order to obtain representative material for the determination of fibre concentration.

In plain English

This study examined the left lung of one man, a 57-year-old insulation engineer exposed to asbestos for 37 years. He died of squamous cell carcinoma of the bronchus that had spread to the pleura. He had no mesothelioma and had fairly substantial asbestosis. The authors used a light microscope to count coated and uncoated amphibole fibres in tissue blocks from the outer edge of the upper and lower lobes, in cross-sections through each lobe, and in one hilar lymph node. The fibre type was not identified, though the authors suggested amosite exposure may have occurred. The average uncoated fibre concentration in the upper lobe was almost twice that in the lower lobe. In the lower lobe, the concentration of uncoated fibres was statistically significantly higher at the costal (rib-side) pleura than at the diaphragmatic pleura. Concentrations fell sharply at the tips of each lobe. The highest concentration of uncoated fibres was 21 times the lowest in the upper lobe and 26 times the lowest in the lower lobe. The authors concluded that lung tissue must be sampled carefully to obtain representative fibre concentrations.

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: Postmortem laboratory analysis of fibres in a single lung (one case), using light microscopy, with electron microscopy on three samples
• Who was studied: One 57-year-old man, an insulation engineer exposed to asbestos for 37 years. He died of poorly differentiated squamous cell carcinoma of the bronchus with secondary spread to the pleura, had no evidence of mesothelioma, and had fairly substantial asbestosis. The lung was provided by City Hospital, Nottingham (UK).
• Exposure: Occupational asbestos exposure as an insulation engineer. The amphibole fibres in the lung were not identified. Because the fibres were thicker than those seen in crocidolite-exposed gas-mask factory workers, the authors suggested exposure to amosite may have occurred.
• Main results:
  • The overall average concentration of uncoated fibres in the upper lobe was almost twice that in the lower lobe. The difference was less pronounced for coated fibres.
  • In the lower lobe, the mean uncoated fibre concentration at the costal pleura was statistically significantly greater than at the diaphragmatic pleura. The p-value is printed in the scanned text as "p < 0 05", with the decimal point lost.
  • Concentrations of both uncoated and coated fibres fell sharply at the extremities (tips) of each lobe.
  • In the costal region of the lower lobe, there was a pattern of alternating peaks and troughs in the concentrations of both uncoated and coated fibres.
  • The ratio of the highest to the lowest uncoated fibre concentration was 21 in the upper lobe and 26 in the lower lobe.
  • In the peripheral tissue, there were about 10 times as many optically visible uncoated fibres as coated fibres.
  • In peripheral samples, uncoated and coated fibre concentrations were closely and significantly correlated. The coefficients are printed with a hyphen in place of the decimal point, as "r = 0-93, p < 0-001".
  • The proportion of fibres that were coated is printed as "9 3%" for the upper lobe and "11 3%" for the lower lobe. Central samples had a significantly lower percentage of coated fibres than peripheral samples.
  • The average count median length of uncoated fibres is printed as "8 4" micrometres in the upper lobe and "9 4" micrometres in the lower lobe.
  • The average count median length of coated fibres was 29 micrometres in the upper lobe and 32 micrometres in the lower lobe.
  • Uncoated fibres in the hilar lymph node were considerably shorter than in any other sample. The authors suggested this may reflect easier transfer of short fibres to the lymphatics.
  • In peripheral samples, total fibre concentrations were closely correlated with levels of non-fibrous dust. In central samples the correlation was weaker.
  • Compared with electron microscopy, the light microscope detected nearer 50% of fibres in this case, against 10 to 15% in crocidolite-exposed cases.
  • In peripheral lower-lobe samples, the estimated probability that fibres 20 to 40 micrometres long were coated ranged from 14% to 56%, with a mean of 26%.
• The authors' conclusion: The authors concluded that care is required in sampling lung tissue to obtain representative material for measuring fibre concentration. They saw an advantage in sampling the periphery of the lung but advised avoiding the extremities, and recommended taking samples from predetermined sites, analysed individually or pooled.
• Limitations the authors state:
  • The amphibole fibre type in the lung was not identified.
  • Light microscopy detects only part of the fibres present, and few if any chrysotile fibres.
  • Non-fibrous dust levels were scored subjectively on an arbitrary scale of one to six.
  • The study did not discuss how fibre concentrations relate to lung disease.

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Asbestos, Insulator, Amphibole Group.

Related studies

• Electron microscope characteristics of inhaled chrysotile asbestos fibre — F.D. Pooley (1972)
• The distribution and characteristics of asbestos fibers in the lungs of Finnish anthophyllite mine-workers — A. Morgan, A. Holmes (1984)
• A study of the size distributions of airborne amosite fibres in the manufacture of asbestos insulation boards — S.T. Beckett, J.L. Jarvis (1979)
• Determination of mineral fibre in human lung tissue by light microscopy and transmission electron microscopy — A.J. Rogers (1984)
• Light microscope studies on the effects of chrysotile asbestos and fiber glass on the morphology and reticulin formation of cultured lung fibroblasts — R.J. Richards, F. Jacoby (1976)
• Chemical characterization of uncoated asbestos fibers from the lungs of asbestos workers by electron microprobe analysis — A.M. Langer, I.B. Rubin, et al. (1972)

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