Limitations in drawing etiologic inferences based on measurement of asbestos fibers from lung tissue

Our plain-English summary of Limitations in drawing etiologic inferences based on measurement of asbestos fibers from lung tissue, by D.B. Baker (Annals of the New York Academy of Sciences, 1991).

The study

• Author: D.B. Baker
• Journal: Annals of the New York Academy of Sciences
• Published: 1991;643:61-70
• Type of article: Review
• Cited by: 19 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. 004496).

Summary of the article

This paper examined the methodological limitations of using measurements of asbestos fibers and asbestos bodies in lung tissue to estimate past asbestos exposure and to draw inferences about disease causation. The author reviewed published lung fiber burden studies within an epidemiologic framework of selection bias, information bias, confounding and random variation, and then reviewed technical sources of error in preparing and counting tissue specimens. Cited studies showed that fiber concentrations varied several-fold from site to site within a lung. Light microscopy was estimated to visualize only 5% of crocidolite, 26.5% of amosite and 0.14% of chrysotile fibers present in lung tissue. Ratios of amosite fibers to ferruginous bodies ranged from 11:1 to 30,000:1 among 12 former asbestos workers. The author noted that chrysotile tends to be cleared from the lung more rapidly than amphiboles, that laboratories produced markedly different absolute values, and that studies based on few cases had low statistical power. The author concluded that lung fiber burden analyses cannot reliably give quantitative estimates of past exposure or cumulative dose, though they may allow ranking of exposure within cohorts with known high occupational exposure. They cannot be used to estimate past chrysotile exposure or relative exposure to different asbestos types, and absence of chrysotile fibers cannot rule out exposure. Light microscopy and asbestos body counts cannot be used to estimate exposure. Nonsignificant findings should be considered inconclusive rather than negative.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This paper was a methodological review, not a new study. The author examined the limits of inferring past exposure and disease cause from lung fiber and asbestos body counts. The author argued that autopsy subjects do not represent general-population deaths and that counts vary several-fold within one lung. Laboratory methods also differ, the author added, and most studies are too small for adequate statistical power. Citing others' work, the author noted that light microscopy misses most fibers, especially chrysotile. In one cited study of 14 asbestos workers with interstitial fibrosis, body counts correlated well with amphibole and poorly with chrysotile fibers; the author stated that body counts cannot estimate individual amphibole concentrations. Chrysotile, the author noted, clears from the lung faster than amphiboles. The author stated that a causal link between lung parenchyma fibers and pleural or peritoneal mesothelioma had not been demonstrated. The author concluded that fiber burden cannot reliably estimate past dose or chrysotile exposure. The author added that absent chrysotile fibers cannot rule out exposure and nonsignificant findings should be considered inconclusive, not negative.

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: Methodological review and commentary on lung fiber burden studies; no new data were collected
• Who was studied: No study subjects; the author reviewed published studies that measured asbestos fibers and bodies in human lung tissue
• Exposure: Asbestos fibers and asbestos (ferruginous) bodies retained in lung tissue, including chrysotile and amphiboles (amosite, crocidolite, tremolite)
• Main results:
  • The author stated that fiber burden studies cannot estimate past exposure to chrysotile, or relative exposure to different asbestos types, because fibers persist and move differently in lung tissue
  • The author stated that a causal relationship between fibers in lung parenchyma and malignant mesothelioma of the pleura or peritoneum had not been demonstrated
  • Selection bias: the author noted that autopsy-series specimens do not represent the general population of people who die
  • Methodologic studies cited by the author found that fiber counts vary several-fold within the same lung
  • An inter-laboratory trial by Gylseth et al., cited by the author, found large differences between laboratories in absolute fiber counts
  • A study by Pooley, cited by the author, suggested that light microscopy visualizes only small fractions of lung fibers: 5% of crocidolite, 26.5% of amosite and 0.14% of chrysotile
  • Studies cited by the author found that no more than 1% of the lung's total fiber burden becomes coated as asbestos bodies
  • In a study by Warnock and Wolery of 14 asbestos workers with interstitial fibrosis, cited by the author, asbestos body counts correlated well with amphibole fibers (r = 0.94) but poorly with chrysotile fibers (r = 0.29)
  • The author stated that, given wide ranges in amphibole-fiber-to-body ratios, individual amphibole fiber concentrations cannot be estimated from asbestos body counts; body counts may give only a relative indication of past exposure to long amphibole fibers
  • Using a study by Churg et al. (five pleural mesothelioma cases compared with nine controls) as an example of low precision, the author noted that standard deviations were about as large as, or larger than, the means
  • The author stated that chrysotile found in lung tissue shows past exposure, but the absence of chrysotile fibers cannot rule exposure out
  • The author suggested that fiber burden analyses may be able to rank past exposure in order within cohorts with known high occupational exposure
• The authors' conclusion: The author concluded that fiber burden cannot reliably give quantitative estimates of past exposure or cumulative dose. The author added that, because of low statistical power, nonsignificant findings in such studies should be considered inconclusive rather than negative.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Bodies, Asbestos Exposure, Causation, Fiber Burden, Selection Bias, Confounding, Crocidolite, Amosite.

Related studies

• Asbestos exposure among Finnish lung cancer patients: occupational history and fiber concentration in lung tissue — A. Karjalainen, S. Anttila, et al. (1993)
• Characterization of asbestos fibers in lungs and mesotheliomatous tissues of baboons following long-term inhalation — K. Hiroshima, Y. Murai, et al. (1993)
• Measurements of asbestos burden in tissues — R.F. Dodson, M.A. Atkinson (2006)
• Mineral fiber concentration in lung tissue of mesothelioma patients in Finland — T. Tuomi, M. Segerberg-Konttinen, et al. (1989)
• Asbestos fiber burdens in lung tissues of Hong Kong Chinese with and without lung cancer — Y. Liu, P. Zhang, et al. (2001)
• The association among ferruginous body, uncoated fibers, asbestos and non-asbestos fibers in lung tissue in terms of length — T. Suzuki, Y. Sakakibara, et al. (2016)

Browse more research in Annals of the New York Academy of Sciences, or return to medical research.