Alveolar fiber load in asbestos workers and in subjects with no occupational asbestos exposure: an electron microscopy study

Our plain-English summary of Alveolar fiber load in asbestos workers and in subjects with no occupational asbestos exposure: an electron microscopy study, by G. Chiappino, K.H. Friedrichs, G. Rivolta, et al (American Journal of Industrial Medicine, 1988).

The study

• Authors: G. Chiappino, K.H. Friedrichs, G. Rivolta, A. Forni
• Journal: American Journal of Industrial Medicine
• Published: 1988;14(1):37-46
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000201).

Abstract

The alveolar fiber load was evaluated by bronchoalveolar lavage and by scanning and transmission electron microscopy (SEM and TEM) in 50 subjects with or without occupational exposure to asbestos. The concentration of asbestos fibers in bronchoalveolar lavage was significantly higher in the groups of people currently and formerly occupationally exposed, compared to the concentration found in people only exposed environmentally, despite wide interindividual variation within the groups. Nonasbestos inorganic fibers were present in all groups, but the concentrations did not differ significantly. Both in people occupationally exposed and in those only environmentally exposed, the alveolar load consisted mainly of ultrashort and ultrathin fibers, which can be studied only with TEM. In fact, the percentage of fibers greater than 5 micron long was only around 15% in the occupationally exposed and was minimal in those only environmentally exposed. The geometric mean diameters of asbestos fibers retained in the alveoli ranged from 0.05 micron for chrysotile to 0.15 micron for amphiboles.

In plain English

This study, from the Institute of Occupational Health at the University of Milan with electron microscopy done in Düsseldorf, examined fluid washed out of the lungs (bronchoalveolar lavage) of 50 people. Thirty-five had worked in jobs with significant asbestos exposure, such as asbestos-textile, asbestos-cement, insulation, mining, friction products, and carpentry or welding aboard ships. Of these, 17 were still working and 18 had stopped 2 to 33 years earlier. The 15 comparison subjects were 10 male industrial workers in jobs apparently without asbestos exposure and 5 men without industrial work. Using scanning and transmission electron microscopy, the authors found that asbestos fiber concentrations differed significantly across the four groups and were higher in the occupationally exposed, with wide variation between individuals. Other mineral fibers did not differ significantly. Most fibers were ultrashort and ultrathin, and only transmission microscopy could fully evaluate them. Fibers longer than 5 micrometres made up around 15% in the occupationally exposed and were minimal in the others. The authors concluded that group differences persist long after exposure stops.

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: Comparison of groups using lung-washing (bronchoalveolar lavage) fluid examined by scanning and transmission electron microscopy and by light microscopy. The 50 subjects were chosen from a larger group undergoing lavage.
• Who was studied: 50 subjects undergoing bronchoalveolar lavage at the Institute of Occupational Health, University of Milan, Italy. Group 1: 17 currently exposed workers. Group 2: 18 workers who had stopped asbestos work 2 to 33 years earlier. The 35 exposed workers were 29 men and 6 women. Group 3: 10 male industrial workers in jobs apparently not associated with asbestos exposure. Group 4: 5 males not in industrial work, undergoing lavage for various respiratory disorders. Of the 35 exposed workers, 22 had lung and/or pleural changes on X-ray attributable to asbestos.
• Exposure: Occupational asbestos exposure in 8 asbestos-textile workers, 6 asbestos-cement workers, 4 insulation workers, 3 miners, 3 friction product workers, 6 carpenters or welders aboard ships, and 5 people in various jobs. Most had been exposed for 7 to 37 years; five for only 2 to 4 years. Fibers analysed included chrysotile and amphiboles, as well as non-asbestos inorganic fibers.
• Main results:
  • Geometric mean asbestos fiber concentrations in lavage fluid differed significantly across the four groups by both microscopes (F = 5.348, p less than .01 for scanning; F = 5.212, p less than .01 for transmission).
  • Concentrations of fibers other than asbestos did not differ significantly among the four groups (F = 1.349 for scanning; F = 0.776 for transmission; p greater than .05).
  • Within the groups, asbestos fiber concentrations varied widely from person to person.
  • By light microscopy, 32 of the 35 occupationally exposed subjects had asbestos bodies in lavage fluid, compared with less than one-third by electron microscopy. One-third of the environmentally exposed subjects (groups 3 and 4) also had asbestos bodies by light microscopy, at very low concentrations.
  • Most fibers were very short. Half of all fibers were shorter than 1.4 micrometres by transmission microscopy and shorter than 2.8 micrometres by scanning microscopy. Fibers longer than 5 micrometres made up around 15% in the occupationally exposed and were minimal in the environmentally exposed. The difference between exposed and nonexposed groups was significant at the 5% level, with one exception: scanning-microscopy results for group 2 in the 5.1 to 10 micrometre range.
  • Geometric mean length of chrysotile fibers differed significantly across the groups (F = 5.684, p less than .01) and was shorter in the nonexposed groups. Amphibole length also differed significantly (F = 4.249, p less than .01), but the trend was less evident.
  • Geometric mean diameters of asbestos fibers retained in the alveoli ranged from 0.05 micrometres for chrysotile to 0.15 micrometres for amphiboles.
  • Chrysotile and amphiboles were present in similar concentrations in the occupationally exposed, while chrysotile seemed to prevail in the nonexposed. The detailed ratio was not reported.
  • Unexpectedly, some subjects who had not been occupationally exposed for 15 to 20 years had high alveolar asbestos fiber concentrations. The authors said the cause could not at present be stated.
• The authors' conclusion: The authors drew three conclusions. First, most fibers retained in the alveoli are ultrashort and ultrathin and can be completely evaluated only by transmission electron microscopy. Second, groups with different intensity of asbestos exposure differ significantly in asbestos fiber concentrations in lavage fluid, and the difference persists long after occupational exposure stops. Third, the mean length of asbestos fibers, mainly chrysotile, is significantly higher in the occupationally exposed groups. They also said fiber size distribution should be reported when assessing fiber concentrations.
• Limitations the authors state:
  • Lavage may not remove the whole alveolar content, and the amount recovered may vary because of fiber distribution in the lung, fiber type and shape, tissue reactions and other factors.
  • Scanning electron microscopy cannot analyse fibers thinner than 0.2 micrometres, so it underestimates asbestos concentration, especially for chrysotile.
  • Because of wide variation between individuals, exposed and nonexposed subjects can be distinguished on a group basis.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Bronchoalveolar Lavage (BAL), Transmission Electron Microscopy (TEM), Occupational Exposure, Alveoli, Chrysotile, Amphibole Group.

Related studies

• Morphologic characterization of alveolar macrophages from subjects with occupational exposure to inorganic particles — T. Takemura, W.N. Rom, et al. (1989)
• The utility of electron microscopy in detecting asbestos fibers and particles in BALF in diffuse lung diseases — T. Kido, Y. Morimoto, et al. (2017)
• The sensitivity of lavage analysis by light and analytical electron microscopy in correlating the types of asbestos from a known exposure setting — R.F. Dodson, M. O'Sullivan, et al. (2003)
• Scanning electron microscopical investigations of broncho-alveolar casts after intratracheal asbestos fibre instillation — B. Voss, T. Kerenyi, et al. (2000)
• The ability of inflammatory bronchoalveolar leucocyte populations elicited with microbes or mineral dust to injure alveolar epithelial cells and degrade extracellular matrix in vitro — K. Donaldson, J. Slight, et al. (1988)
• The relationship between large airway and alveolar space inflammation and airway metaplasia — W.W. Merrill, D. Carter, et al. (1992)

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