Penetration of cells by asbestos fibers

Our plain-English summary of Penetration of cells by asbestos fibers, by J.M. Davis, R.E. Bolton, J. Garrett (Environmental Health Perspectives, 1974).

The study

• Authors: J.M. Davis, R.E. Bolton, J. Garrett
• Journal: Environmental Health Perspectives
• Published: 1974;9:255-60
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Studies on the behavior of asbestos fibers within tissues have shown that the only cells that regularly contain asbestos are macrophages and their derivatives. However, these cells actively incorporate the asbestos fibers by the process of phagocytosis, and there is little evidence of direct penetration. Examination of the gut lining after prolonged asbestos ingestion has shown no evidence of dust penetration either through or between the epithelial cells. The structure and arrangement of these cells is discussed, and it is suggested that they are exceptionally well adapted to prevent penetration by any solid material.

In plain English

This short paper discussed how asbestos fibers get into cells and reported early results from a rat feeding experiment that was still under way. The authors noted that their survey of the previous ten years of literature indicated asbestos fibers were extremely rarely found in any cells other than phagocytes, the cells that engulf particles. In their experiment, rats were given butter mixed with chrysotile or crocidolite asbestos (5 mg per gram of butter) along with normal food pellets. Each rat ate on average about 20 g of butter, roughly 100 mg of asbestos, a week. Stomach, small intestine, colon and mesenteric lymph node tissue was examined by electron microscopy, but so far this had not gone beyond rats killed after 3 months of feeding. All cells examined appeared normal and no asbestos penetration was seen. The authors described the closely packed microvilli and firmly joined cells of the gut lining as a likely barrier. They concluded that these early results suggested ingested asbestos did not damage or penetrate the rat gut lining, but that completed studies were needed to be definite.

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: Short discussion paper reporting preliminary results of an ongoing animal feeding experiment, with gut tissue examined by electron microscopy
• Who was studied: Rats fed chrysotile or crocidolite asbestos; tissue blocks from stomach, small intestine, colon and mesenteric lymph nodes. The number of rats is not stated.
• Exposure: Chrysotile (UICC sample A) or crocidolite mixed into butter at 5 mg of asbestos per gram of butter. The butter was available freely alongside normal food pellets. On average each rat ate about 20 g of butter a week, about 100 mg of asbestos.
• Main results:
  • Background from the authors' survey of other studies, not this experiment: asbestos fibers were extremely rarely found in any cells other than phagocytes.
  • In rats fed chrysotile or crocidolite and examined by electron microscopy (up to 3 months of feeding), all cells examined appeared normal and no sign of asbestos penetration was seen.
  • The authors described the gut lining cells as having closely packed microvilli (the brush border) and as being firmly bound together. They suggested this structure was a formidable barrier to penetration by particles.
• The authors' conclusion: The authors concluded that their early results suggested asbestos fibers ingested with normal quantities of food did not damage the gut lining in rats or penetrate the gut epithelial cells, but said completed studies were needed to be definite.
• Limitations the authors state:
  • The results were preliminary, and completed studies would be needed to be definite.
  • Although feeding had run for 6 months, electron microscope examination had not gone beyond animals killed after 3 months of feeding.
  • The authors said little was known about how rigid microvilli are.

Topics

Medical terms in this study, explained in our Lexicon: Macrophage, Phagocytosis.

Related studies

• Pulmonary cell interactions with asbestos fibers in vivo and in vitro — A.R. Brody (1986)
• Cigarette smoke increases the penetration of asbestos fibers into airway walls — D. McFadden, J. Wright, et al. (1986)
• The short-term effects of chronic asbestos ingestion in rats — R.E. Bolton, J.M. Davis (1976)
• Effects of asbestos and man-made vitreous fibers on cell division in cultured human mesothelial cells in comparison to rodent cells — K. Pelin, P. Kivipensas, et al. (1995)
• Scavengers of active oxygen species prevent cigarette smoke-induced asbestos fiber penetration in rat tracheal explants — A. Churg, J. Hobson, et al. (1989)
• Review of published studies on gut penetration by ingested asbestos fibers — P.M. Cook (1983)

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