Asbestos bodies in the sputum of asbestos workers: correlation with occupational exposure

Our plain-English summary of Asbestos bodies in the sputum of asbestos workers: correlation with occupational exposure, by C. Paris, F. Galateau-Salle, C. Creveuil, et al (The European Respiratory Journal, 2002).

The study

• Authors: C. Paris, F. Galateau-Salle, C. Creveuil, R. Morello, C. Raffaelli, J.C. Gillon, M.A. Billon-Galland, J.C. Pairon, L. Chevreau, M. Letourneux
• Journal: The European Respiratory Journal
• Published: 2002;20(5):1167-73
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A cross-sectional medical survey including collection of three consecutive sputum samples was carried out among 270 retired workers of a textile and friction materials factory, in order to investigate the relationship between asbestos body identification and asbestos exposure. The individual cumulative asbestos exposure, determined by means of a plant-specific job-exposure matrix based on asbestos air measurements in the workshops, proved to be heavy with a mean cumulative exposure of 217 fibres x mL(-1) x yr. Macrophages and asbestos bodies were identified in sputum samples by light microscopy. The lung origin of the sputum, suggested by the presence of macrophages and/or asbestos bodies, was confirmed in 82.6% of subjects, and 53% of these samples were positive for asbestos bodies. The prevalence of asbestos bodies was not related to sex, smoking status or latency. Conversely, multivariate analysis showed a positive relationship with cumulative exposure, duration and intensity of exposure to asbestos, as well as age and time since retirement. These findings suggest that sputum analysis for asbestos bodies may remain a relevant and noninvasive marker of heavy occupational exposure to asbestos, even years after retirement. Owing to the new perspectives in lung cancer screening, it might contribute to the identification of high-risk subjects.

In plain English

This cross-sectional survey examined 270 retired workers from an asbestos textile and friction material factory, enrolled in a medical surveillance programme in Caen and Flers, Normandy, France. Chrysotile was the only asbestos used in the friction workshops, while several textile workshops also used a smaller amount of crocidolite. Each worker's exposure was estimated from workshop air measurements, and the average cumulative exposure was 217 fibres per millilitre-years. Workers gave sputum (coughed-up mucus), which was examined by light microscopy. Sputum was judged to come from the lungs in 223 of 270 workers (82.6%), and 118 of these 223 (53%) contained at least one asbestos body. Asbestos bodies were not significantly related to sex or smoking. They were more common when exposure included crocidolite (77.0% versus 37.5% with chrysotile only). They were also more common with higher cumulative exposure, longer and more intense exposure, older age and longer time since retirement. The authors concluded that asbestos bodies in sputum can reflect occupational exposure even when it stopped many years earlier. They added that the test is often negative even after heavy exposure, so only positive results should be taken into account.

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: cross-sectional medical survey with collection of three consecutive sputum samples per subject
• Who was studied: 270 retired workers from an asbestos textile and friction material factory, included in a medical surveillance programme for retired asbestos workers at hospitals in Caen and Flers (Normandy, France); survey dates not stated
• Exposure: Occupational asbestos exposure in one factory: chrysotile only in friction material workshops (brake and clutch linings); chrysotile plus a smaller amount of crocidolite (20%) in several textile workshops. Cumulative exposure was estimated with a plant-specific job-exposure matrix based on workshop air measurements, averaging 217 fibres per millilitre-years.
• Main results:
  • Sputum was considered to come from the lung in 223 of 270 subjects (82.6%)
  • 118 subjects had at least one asbestos body in sputum, 53% of the lung-derived samples (118 of 223)
  • In univariate analysis, the presence of asbestos bodies was not significantly related to sex or smoking status
  • Univariate: asbestos bodies were present in 37.5% of the 136 chrysotile-only subjects and in 77.0% of the 87 chrysotile plus crocidolite subjects (relative risk 2.1, 95% CI 1.6 to 2.6)
  • Univariate: asbestos bodies were present in 37.6% of subjects with cumulative exposure of 0 to 200 fibres per mL-years (n=125), 62.1% at 200 to 400 (n=58; relative risk 1.7, 95% CI 1.2 to 2.2), and 87.5% above 400 (n=40; relative risk 2.3, 95% CI 1.8 to 3.0)
  • Multivariate: cumulative exposure above 400 fibres per mL-years versus 0 to 200 had an adjusted odds ratio of 9.1 (95% CI 3.1 to 26.8)
  • Multivariate: exposure to chrysotile plus crocidolite versus chrysotile only had an adjusted odds ratio of 5.1 (95% CI 2.5 to 10.4)
  • Multivariate: age 68 or over versus 55 to 60 had an adjusted odds ratio of 5.9 (95% CI 2.3 to 15.0)
  • Multivariate: 12 or more years since retirement versus 1 to 6 years had an adjusted odds ratio of 6.5 (95% CI 2.6 to 15.9)
  • Multivariate: exposure duration of 25 years or more had an adjusted odds ratio of 2.4 (95% CI 1.2 to 4.8); exposure intensity above 12 fibres per mL had an adjusted odds ratio of 2.8 (95% CI 1.2 to 6.6)
  • In multivariate analysis, latency (time since onset of exposure) was no longer significantly related to asbestos bodies (p=0.09)
  • Among retired workers exposed to chrysotile only, 37% had asbestos bodies in sputum
  • Transmission electron microscopy on several samples with high levels of asbestos bodies showed that, in textile workers, all asbestos bodies were formed on amphibole fibres, mainly amosite and crocidolite
• The authors' conclusion: The authors concluded that the presence of asbestos bodies in sputum is correlated with the intensity of asbestos exposure and can reflect occupational contact with asbestos even many years after it stopped. They also concluded that sputum analysis is noninvasive, can be proposed in retired subjects, and may help identify subjects at high risk of lung cancer.
• Limitations the authors state:
  • The test has poor sensitivity: a negative sputum examination cannot exclude even high occupational exposure, and only positive results should be taken into account
  • Odds ratios are not good estimates of relative risks here, because asbestos bodies in sputum were not rare in this population
  • The fibre type at the core of asbestos bodies could not be determined in the few samples from friction workers that were analysed by electron microscopy

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Bodies, Sputum, Occupational Exposure, Asbestos Body Formation, Asbestos Exposure, Cumulative Exposure, Macrophage, Latency.

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• Sputum asbestos bodies and radiographic changes in residents of Wittenoom, Western Australia — A.W. Musk, J.E. Baker, et al. (1983)
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• Perls' Prussian Blue Stains of Lung Tissue, Bronchoalveolar Lavage, and Sputum — A.J. Ghio, V.L. Roggli (2021)

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