Migration of ingested asbestos

Our plain-English summary of Migration of ingested asbestos, by J.H. Kaczenski, W.H. Hallenbeck (Environmental Research, 1984).

The study

• Authors: J.H. Kaczenski, W.H. Hallenbeck
• Journal: Environmental Research
• Published: 1984;35(2):531-51
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Tissue samples from one test and one control baboon were analyzed by transmission electron microscopy for the presence of chrysotile and crocidolite asbestos. The test animal had been gavaged with cumulative doses of 800 mg each of chrysotile and crocidolite asbestos. An earlier evaluation of these tissues led to the conclusion that ingested asbestos fibers do not penetrate the gastrointestinal tract of the baboon and migrate systemically. However, the present study involved more sensitive methodology, and penetration and migration were clearly demonstrated by the recovery of significant levels of asbestos from test stomach, heart, spleen, pancreas, and blood samples.

In plain English

This animal experiment re-examined frozen tissues from an earlier study of two baboons. One test baboon had been gavaged (fed by tube) with cumulative doses of 800 mg each of chrysotile and crocidolite asbestos. A second baboon served as a control. The earlier analysis of these tissues had concluded that swallowed fibers did not pass through the gut and spread through the body. This time the authors used a more sensitive electron microscopy method, which lowered the detection limit from 220 to an average of 24 fibers per mg of dry tissue. Compared with the control, the test animal's stomach, heart, pancreas and blood taken at sacrifice had significantly higher chrysotile fiber and mass levels (P = 0.028). No control spleen was available, so the test spleen was compared with blank filters, and its chrysotile levels were higher. Amphibole fibers were significantly raised only in fiber counts from the heart, from blood taken at the last gavage, and from the spleen. Kidney, lung and liver did not differ significantly from the control. The authors concluded that penetration and migration of chrysotile was demonstrated, and that amphibole migration may not have occurred to a great extent. They noted that only part of each organ was analyzed.

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 experiment: a reanalysis, by transmission electron microscopy and with a more sensitive method, of stored tissues from one test and one control baboon in an earlier study
• Who was studied: One test baboon and one control baboon. Tissues analyzed were stomach, heart, pancreas, blood (taken at sacrifice and at last gavage), kidney, lung, liver and spleen; there was no control spleen. The tissues had been frozen and stored at the end of an earlier study. Location and dates are not given.
• Exposure: The test baboon was gavaged with cumulative doses of 800 mg each of chrysotile and crocidolite asbestos. Fibers recovered were classified as chrysotile or amphibole.
• Main results:
  • The minimum detection limit was reduced from 220 fibers/mg in the original study to an average of 24 fibers/mg dry tissue.
  • In the recovery test using chrysotile added to pig kidney, the authors estimated that true fiber recovery probably lay between 61% and 100%.
  • In the test stomach, chrysotile fiber and mass concentrations were significantly greater than in the control stomach (P = 0.028).
  • In the test heart, chrysotile fiber and mass concentrations were significantly greater than in the control heart (P = 0.028).
  • In the test pancreas and in test blood taken at sacrifice, chrysotile fiber and mass concentrations were significantly greater than in the matching control samples (P = 0.028).
  • In test blood taken at the last gavage, the chrysotile fiber concentration was significantly greater than in the control (P = 0.020), but the mass concentration was not significantly different.
  • Because no control spleen was available, the test spleen was compared with its blank. Its chrysotile fiber and mass concentrations were significantly greater than the blank (P = 0.028).
  • In the test heart, the amphibole fiber concentration was significantly greater than in the control (P = 0.028). On a mass basis, the heart amphibole concentration was not significantly different from the control.
  • In test blood taken at the last gavage, the amphibole fiber concentration was significantly greater than in the control (P < 0.001).
  • Amphibole was found only in the fiber count data, and only in the test heart, blood taken at last gavage, and spleen. There was no indication that amphibole penetrated the stomach wall.
  • In the test pancreas and test blood taken at sacrifice, amphibole fiber and mass concentrations were not significantly different from the controls.
  • In kidney, lung and liver, test chrysotile and amphibole fiber and mass concentrations were not significantly different from the control.
  • About 73% of chrysotile fibers recovered from the test stomach, heart, pancreas, sacrifice blood and spleen were 0.2 to 1.0 micrometres long. By comparison, about 62% of the fibers given by gavage were in that length range.
  • In the test stomach, heart, pancreas, sacrifice blood and spleen, chrysotile concentrations averaged 6100 fibers per mg tissue.
• The authors' conclusion: The authors concluded that their sample preparation method was sensitive and did not destroy asbestos fibers. They concluded that penetration and migration of chrysotile after gavage was demonstrated by both fiber count and mass data in the test stomach, heart, pancreas, sacrifice blood and spleen. Amphibole penetration and migration was indicated only by fiber count data in the heart, blood taken at last gavage, and spleen. The authors suggested amphibole may not have migrated to a great extent because amphibole fibers are larger than chrysotile fibers.
• Limitations the authors state:
  • Where test and control concentrations were equal, migration may have occurred without being detected. This is because less than the whole organ was analyzed, and fibers may not be spread evenly through an organ.
  • Some control tissues had more asbestos than their blanks. The authors suggested this may have come from environmental sources.
  • No control spleen was available, and only 2.5 g wet weight of test spleen was available.
  • For some tissues, mass-based statistical analysis was not possible because fiber clusters occurred in the samples.

Topics

Medical terms in this study, explained in our Lexicon: Transmission Electron Microscopy (TEM), Chrysotile, Crocidolite, Cumulative Dose.

Related studies

• Presence of asbestos bodies in organs other than the lung — O. Auerbach, A.S. Conston, et al. (1980)
• Analyses of tissue, blood, and urine samples from a baboon gavaged with chrysotile and crocidolite asbestos — W.H. Hallenbeck, D.R. Markey, et al. (1981)
• Letter: Penetration of asbestos through the digestive tract of rats — R.D. Pontefract, H.M. Cunningham (1973)
• The dose-dependent effects of ingested chrysotile on DNA synthesis in the gastrointestinal tract, liver, and pancreas of the rat — D.E. Amacher, A. Alarif, et al. (1975)
• Ingested mineral fibers. Do they penetrate tissue or cause cancer? — P. Gross, R.A. Harley, et al. (1974)
• Effects of ingested chrysotile on DNA synthesis in the gastrointestinal tract and liver of the rat — D.E. Amacher, A. Alarif, et al. (1974)

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