Biopersistence of respirable synthetic fibers and minerals: the point of view of the epidemiologist

Our plain-English summary of Biopersistence of respirable synthetic fibers and minerals: the point of view of the epidemiologist, by P. Boffetta (Environmental Health Perspectives, 1994).

The study

• Author: P. Boffetta
• Journal: Environmental Health Perspectives
• Published: 1994;102 Suppl 5(Suppl 5):11-3
• Type of article: Review
• Read it: PubMed · Publisher · Free full text

Abstract

Biopersistence of fibers and minerals in human respiratory tissues is an important aspect of the toxicity of these agents. However, few data are available from human studies. Although a number of studies have measured the lung burden of asbestos and other minerals in exposed humans, few presented information relevant to biopersistence of these agents. The studies analyzing asbestos lung burden in workers at different intervals following cessation of exposure suggest a linear decrease in concentration over time, that is independent of duration of exposure. However, the available evidence on asbestos is too sparse to allow a firm conclusion; almost no data are available on other minerals.

In plain English

This article was presented at a 1992 workshop in Lyon, France. In it, an epidemiologist reviewed what human studies showed about how long asbestos and other mineral fibers persist in the lungs. The author noted that no study had specifically addressed this question. Instead, the author reviewed a few studies that measured asbestos in the lungs of miners, textile workers, asbestos cement workers and amosite plant workers at different times after their exposure ended. In one of these, covering South Carolina textile workers and Quebec miners and millers exposed to chrysotile, chrysotile and tremolite levels appeared to fall with time since exposure ended among workers exposed for 200 months or more. The author also reanalyzed data from three smaller studies. All three linked lung fiber levels to how long workers had been exposed. Two showed a negative correlation with time since exposure ended; the Texas amosite study did not. The author concluded that the sparse evidence pointed toward less fiber in the lungs after exposure stops, at least for asbestos. A precise rate could not be estimated.

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 of published human lung fiber burden studies, presented at a workshop, including the author's own univariate and multivariate regression reanalysis of data from three of those studies
• Who was studied: Reviewed studies: 161 lung tissue samples from South Carolina asbestos textile workers and Quebec asbestos miners and millers (Sebastien et al.); 20 asbestosis cases among Canadian chrysotile miners, 16 with detectable fibers (Pooley); four mesothelioma and four lung cancer cases from a Norwegian asbestos cement plant (Gylseth et al.); 12 workers from a Texas amosite plant (Dodson et al.); Vermont granite workers (bronchoalveolar lavage study)
• Exposure: Occupational asbestos exposure, mainly chrysotile (with tremolite measured in the Sebastien study) and amosite in the Texas plant, examined by duration of exposure, time since first exposure and time since cessation of exposure; also minerals in granite workers
• Main results:
  • In the Sebastien et al. study, a decrease in both chrysotile and tremolite lung concentration with time since cessation of employment was suggested among textile workers and miners exposed for 200 months or more. Results for workers exposed for a shorter period were less easily interpretable.
  • In the author's regression analyses of the Pooley, Gylseth et al. and Dodson et al. data, all three studies showed a correlation between lung fiber concentration and duration of exposure.
  • The Pooley and Gylseth et al. data showed a negative correlation between lung fiber concentration and time since cessation of exposure. The Dodson et al. (Texas amosite) data did not show any correlation.
  • Table 1 p-values for time since cessation of exposure were 0.04 (univariate) and 0.04 (multivariate) for Pooley, 0.06 and 0.06 for Gylseth et al., and 0.80 and 0.46 for Dodson et al. For duration of exposure, the p-values were 0.02 and 0.04 (Pooley), 0.01 and 0.07 (Gylseth et al.), and 0.01 and 0.02 (Dodson et al.).
  • In a reviewed study of Vermont granite workers, no effect of retirement was shown on bronchoalveolar lavage mineral levels. Detailed data were not shown in that study.
• The authors' conclusion: The author concluded that, at least for asbestos, the sparse epidemiologic evidence points toward a reduction in lung fiber content after exposure ends. The author added that cumulative exposure may not be an appropriate indicator of biologically effective dose, and that dose rate and time since cessation of exposure should be taken into account.
• Limitations the authors state:
  • A precise disappearance rate could not be estimated from the available data, and clearance mechanisms such as dissolution or migration to the pleura could not be distinguished.
  • Differences between study results may reflect different fiber types, exposure patterns, analytic methods and the statistical imprecision of small sample sizes.
  • Human studies on minerals other than asbestos are lacking.

Topics

Medical terms in this study, explained in our Lexicon: biopersistence.

Related studies

• Biopersistence of respirable synthetic fibers and minerals: point of view of the chest physician — P. De Vuyst (1994)
• An experimental approach to the evaluation of the biopersistence of respirable synthetic fibers and minerals — D.M. Bernstein, R. Mast, et al. (1994)
• Introduction: INSERM-IARC-CNRS workshop on biopersistence of respirable synthetic fibers and minerals — J. Bignon, R. Saracci, et al. (1994)
• Patterns of histopathological change determined by the point counting method and its application for the hazard assessment of respirable dust — A. Ogami, Y. Morimoto, et al. (2004)
• In vitro assays to predict the pathogenicity of mineral fibers — B.T. Mossman, A.M. Sesko (1990)
• The chemiluminescent response of human phagocytic cells to mineral dusts — I.P. Gormley, M.J. Kowolik, et al. (1985)

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