Chrysotile and tremolite asbestos fibres in the lungs and parietal pleura of Corsican goats

Our plain-English summary of Chrysotile and tremolite asbestos fibres in the lungs and parietal pleura of Corsican goats, by P. Dumortier, F. Rey, J.R. Viallat, et al (Occupational and Environmental Medicine, 2002).

The study

• Authors: P. Dumortier, F. Rey, J.R. Viallat, I. Broucke, C. Boutin, P. De Vuyst
• Journal: Occupational and Environmental Medicine
• Published: 2002;59(9):643-6
• Cited by: 23 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background And Aims: Environmental exposures to chrysotile and tremolite from the soil cause pleural plaques and mesothelioma in northeast Corsica. Goats grazing in the contaminated areas inhale asbestos fibres. We used this natural animal model to study whether these exposures actually result in increased fibre burdens in the lungs and parietal pleura.

Methods: Ten goats from areas with asbestos outcrops and two from other areas were slaughtered. Fibre content of lung and parietal pleural samples was determined by analytical transmission electron microscopy.

Results: Both chrysotile and tremolite fibres were detected. In the exposed goats, the geometric mean concentrations of asbestos fibres longer than 1 microm were 0.27 x 10(6) fibres/g dry lung tissue and 1.8 x 10(6) fibres/g dry pleural tissue. Asbestos fibres were not detected in the lungs of the two control goats. Chrysotile fibres shorter than 5 microm were predominant in the parietal pleura. Tremolite fibres accounted for 78% and 86% of the fibres longer than 5 microm in lung and parietal pleural samples, respectively.

Conclusions: Environmental exposure in northeast Corsica results in detectable chrysotile and tremolite fibre loads in the lung and parietal pleura of adult goats. Tremolite fibres of dimensions with a high carcinogenic potency are detected in the parietal pleura.

In plain English

This short report studied goats in northeast Corsica, where the soil contains chrysotile and tremolite asbestos. The authors slaughtered ten goats that had grazed in asbestos areas around the villages of Rutali and Laporta, plus two unexposed goats from Arro in south Corsica. They counted asbestos fibres in the lung and in the parietal pleura (the lining of the chest wall) by electron microscopy. No pleural plaques or tumours were seen. Chrysotile and tremolite were the only asbestos types found. Asbestos fibres were detected in the lungs of all exposed goats and of neither control goat. For fibres longer than 1 micrometre, the exposed goats had geometric means of 0.27 million fibres per gram of dry lung and 1.8 million per gram of dry pleura. One control goat had 0.66 million short fibres per gram in its pleura. Pleural fibres were shorter and thinner than lung fibres and were mostly short chrysotile. Tremolite made up 78% (lung) and 86% (pleura) of fibres longer than 5 micrometres. The authors concluded that this environmental exposure produced detectable fibre loads in adult goats, including pleural tremolite fibres of dimensions with high carcinogenic potency.

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: Animal study (short report) using naturally exposed goats as a model; fibre burden analysis of lung and parietal pleura by analytical transmission electron microscopy
• Who was studied: Ten exposed goats from asbestos areas in northeast Corsica (8 from Rutali, 2 from Laporta), mean age 6.4 years (range 6 to 8), and two unexposed control goats aged 9 and 12 years from Arro village in south Corsica. Study dates not given.
• Exposure: Environmental (natural) exposure to chrysotile and tremolite asbestos while grazing in areas with asbestos outcrops in the soil of northeast Corsica
• Main results:
  • Chrysotile and tremolite were the only asbestos fibre types detected; a few asbestos bodies, all formed on long chrysotile fibres, were found in some lung samples.
  • No macroscopic pleural lesions (pleural plaques, tumours, or black spots) were found at autopsy.
  • Asbestos fibres were detected in the lungs of all exposed goats but in none of the two control goats.
  • In exposed goats, mean lung concentrations were below one million fibres/g dry lung in every goat: geometric mean 0.27 × 10^6 f/g (GSD 2.8), range 0.055 to 0.84 × 10^6 f/g, for fibres longer than 1 µm. The highest concentration was 1.8 × 10^6 f/g dry lung.
  • In exposed goats, the geometric mean concentration of asbestos fibres longer than 1 µm in parietal pleura was 1.8 × 10^6 fibres/g dry tissue (GSD 3.6, range 0.333 to 19.2 × 10^6 f/g). Concentrations were above one million f/g dry pleura in five exposed goats.
  • In exposed goats, concentrations of both tremolite and chrysotile were significantly higher in the parietal pleura than in the lungs for fibres longer than 1 µm (p = 0.005). The difference was not significant for fibres longer than 5 µm (p = 0.32).
  • The pleural asbestos fibre burden did not correlate with the lung burden or with the age of the goats.
  • One of the two unexposed control goats had a mean pleural fibre concentration of 0.66 × 10^6 fibres/g, all shorter than 5 µm.
  • The ratio of chrysotile to tremolite concentrations was significantly higher in the parietal pleura than in the lung (3.2 v 1.1, p = 0.016). Chrysotile and tremolite fibres were significantly thinner and shorter in the pleura than in the lung.
  • In exposed goats, 90% of chrysotile fibres in the lung and 99% in the pleura were shorter than 5 µm; for tremolite these proportions were 62% and 81%.
  • Tremolite fibres accounted for 78% of fibres longer than 5 µm in lung samples and 86% in parietal pleural samples.
• The authors' conclusion: The authors concluded that environmental exposure in northeastern Corsica results in increased fibre loads in the lungs and parietal pleura of adult goats. They found that fibres retained in the pleura are shorter than those in the lungs and that short chrysotile fibres predominate in the pleura, but that tremolite fibres of dimensions with a high carcinogenic potency are also detected. They suggested that tissue from local animals may be useful indicators of environmental exposure when human samples are unavailable or scarce.
• Limitations the authors state:
  • Fibre breakage during sample preparation affects chrysotile fibre number and dimensions more than amphibole fibres; the authors took precautions to limit this.
  • Fibre distribution in the pleura was highly heterogeneous in some goats; the authors used large and multiple samples to minimise this effect.
  • It remains unknown whether the size and type differences between pleura and lung come from segregation during fibre migration or from fibre breakage in the pleura.
  • Some asbestos fibres were found in air samples from control villages, which might explain the short fibres found in the pleura of one control goat.
  • The authors suggested that sampling sites along the pleural fluid pressure gradient (highest in the sternal region in goats) might be more advisable than the sites they used.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Tremolite, Parietal Pleura, Environmental Exposure, Pleural Plaques, Mesothelioma, Analytical Transmission Electron Microscopy (ATEM), Carcinogenic.

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• Comparison of Calidria chrysotile asbestos to pure tremolite: final results of the inhalation biopersistence and histopathology examination following short-term exposure — D.M. Bernstein, J. Chevalier, et al. (2005)
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