Epidemiological significance of mineral fiber persistence in human lung tissue

Our plain-English summary of Epidemiological significance of mineral fiber persistence in human lung tissue, by J.C. McDonald (Environmental Health Perspectives, 1994).

The study

• Author: J.C. McDonald
• Journal: Environmental Health Perspectives
• Published: 1994;102 Suppl 5(Suppl 5):221-4
• Type of article: Review
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

For the experimentalist, mineral fiber persistence may provide clues to disease mechanisms, for the epidemiologist, to the measurement of exposure. Qualitatively, this can be valuable when unsuspected exposures have been demonstrated as, for example, MMMF workers exposed to amosite or chrysotile workers to tremolite. Quantitatively, the potential of lung burden analyses to assess lifetime mineral fiber exposure has yet to be achieved with confidence. The difficulties are 2-fold, the first related to sampling and the second to the dynamics of biopersistence. Until some noninvasive method is found to identify and quantify numerically inorganic fibers in human tissue during life, epidemiological studies must depend on lung samples obtained at autopsy or thoracic surgery. This source is inevitably subject to seriously large and indefinable bias of various kinds. Of equal importance is the present uncertain state of knowledge concerning factors that determine what is present in the lung at any time. These determinants clearly include the dimensional features of airborne environmental particulates and characteristics that affect their durability in tissue.

In plain English

This article, a review presented at a 1992 workshop in Lyon, France, discussed what lung-tissue fibers can tell epidemiologists about past exposure. The author reviewed six surveys by the author's group. These covered Quebec chrysotile miners and millers; 100 Canadian men who died violent or unexplained deaths, examined to estimate general-population levels; mesothelial tumor cases and matched controls; Charleston, South Carolina, chrysotile textile workers; and American man-made mineral fiber (MMMF) production workers. In the Quebec miners, tremolite and chrysotile were found in roughly equal amounts, both correlating with accumulated dust exposure. The case-control surveys found much higher amphibole concentrations in cases than controls, but little difference for chrysotile. In one mineral wool plant, amosite at more than 1.0 fibers per microgram was found in four of six workers but in none of their matched controls. The author stressed that autopsy and surgical samples are unrepresentative and that fibers differ widely in how long they persist. The author concluded that research is needed on how well tissue levels reflect lifetime exposure, particularly for low-persistence fibers such as chrysotile and most MMMF.

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: Review and discussion paper (workshop presentation) summarizing six lung-burden surveys previously carried out by the author's group, with one additional matched-pair analysis of earlier data
• Who was studied: The reviewed surveys were:
• 55 lung samples from Quebec chrysotile miners.
• 100 Canadian males whose lungs were collected in 1983 to 1984 from 25 forensic centers (86% violent deaths, the rest unexplained causes). This survey was designed to estimate lung burden in the general population.
• Mesothelial tumor cases and matched controls: 99 pairs in the first survey, 78 pairs in the second.
• 161 samples from Charleston textile workers (72) and Quebec miners and millers (89).
• 145 American MMMF production workers, with matched controls for 124 of them.
• Exposure: Mineral fibers retained in lung tissue, including chrysotile, tremolite and other amphiboles, amosite, and man-made mineral fibers. The jobs involved were chrysotile mining and milling, chrysotile textile work, and MMMF production.
• Main results:
  • In the Quebec chrysotile miners survey, tremolite and chrysotile were found in approximately equal quantities. Counts correlated with accumulated dust exposure: chrysotile 0.40 (p = 0.005) and tremolite 0.49 (p = 0.0005).
  • In the survey of Canadian males from forensic centers, samples from larger cities had higher counts of asbestos bodies and amphibole fibers, but not of chrysotile fibers. Concentrations increased with age.
  • Both mesothelial tumor case-control surveys found much higher concentrations of amphibole fibers in cases than in controls, but little difference for chrysotile.
  • In the comparison of Charleston textile workers with Quebec miners and millers, concentrations of both tremolite and chrysotile correlated with cumulative dust exposure in both series.
  • Findings in the American MMMF production workers:
• Only 26% of the workers' lungs contained any MMMF.
• MMMF were slightly more frequent in cases than in controls, but not significantly so.
• In a mineral wool plant with a lung cancer SMR of 200 and a probable mesothelioma, amosite at more than 1.0 fibers per microgram was found in four of six workers and in none of their matched controls.
  • In 13 matched pairs taken from the 55 Quebec lung analyses, tremolite-to-chrysotile ratios were:
• Asbestos: 0 to 8.3 (mean 1.5, median 0.7).
• Thetford: 0 to 9.0 (mean 4.9, median 1.7).
  This suggested tremolite exposure at Thetford Mines may have been two or three times higher than at Asbestos.
• The authors' conclusion: The authors concluded that research should establish how far tissue fiber concentrations correlate with lifetime or work-related exposure, especially for low-persistence fibers such as chrysotile and most MMMF. Without such evidence, using tissue analyses in epidemiology may be premature. Where such evidence exists, carefully matched case-control studies appear reasonably reliable.
• Limitations the authors state:
  • Lung tissue is available almost only from autopsy or major surgery, so serious selection bias is virtually unavoidable.
  • In the first Quebec prevalence survey, overall sampling success was only 7%, so the findings could be misleading.
  • The accident victims in the Canadian forensic survey may not have been wholly representative of the general population.
  • Results from one laboratory are unlikely to be directly comparable with those from another, or with the same laboratory at another time.
  • Fibers differ widely in biopersistence; chrysotile, for example, appears to clear faster than tremolite. Lung concentrations therefore do not simply reflect exposure.
  • The textile-versus-mining comparison was hard to analyze because the two groups differed greatly in age and in exposure timing. Only 32 pairs met the matching criteria.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Amosite, Chrysotile, Tremolite, biopersistence, Autopsy, Thoracic Surgery.

Related studies

• Electron microscopy analysis of mineral fibers in human lung tissue — K.H. Friedrichs, M. Brockmann, et al. (1992)
• Solubility of asbestos and man-made mineral fibers in vitro and in vivo: its significance in lung disease — A. Morgan, A. Holmes (1986)
• Significance of durability of mineral fibers for their toxicity and carcinogenic potency in the abdominal cavity of rats in comparison with the low sensitivity of inhalation studies — F. Pott, M. Roller, et al. (1994)
• Binding of environmental carcinogens to asbestos and mineral fibres — G. Harvey, M. Pagé, et al. (1984)
• The detection and localization of mineral fibers in tissue — C. Berkley, J. Churg, et al. (1965)
• Solubility of chrysotile asbestos and basalt fibers in relation to their fibrogenic and carcinogenic action — F.M. Kogan, O.V. Nikitina (1994)

Browse more research in Environmental Health Perspectives, or return to medical research.