Identification of a particular amphibole asbestos fiber in tissues of persons exposed to a high oral intake of the mineral

Our plain-English summary of Identification of a particular amphibole asbestos fiber in tissues of persons exposed to a high oral intake of the mineral, by R.E. Carter, W.F. Taylor (Environmental Research, 1980).

The study

• Authors: R.E. Carter, W.F. Taylor
• Journal: Environmental Research
• Published: 1980;21(1):85-93
• Cited by: 23 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Samples of liver, jejunum, and lung tissue from each of 32 persons with long-term, high-level oral exposure to a ferromagnesium silicate amphibole asbestos were ashed, and the residue was analyzed by means of transmission electron microscopy with selected area electron diffraction, and energy dispersive X-ray analytic techniques. Fibers of the type ingested were identified in the tissues of 29 of the 32 persons. Among ?I controls, the tissues of only 2 subjects contained this type of fiber-in each, a single fiber from a single tissue specimen. Chrysotile asbestos fibers were found in all tissues in most of the subjects studied.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This autopsy study looked for one particular asbestos fiber, a ferromagnesium silicate amphibole (Cummingtonite-Grunerite), in people who had swallowed it in drinking water. The fiber was in Lake Superior, the water supply of Duluth, Minnesota, and came from tailings discharged by a taconite processing plant. Using electron microscopy, the authors examined lung, liver and jejunum (small intestine) samples taken at autopsy in 1973 and 1974. The samples came from 32 Duluth residents with no industrial asbestos exposure and 21 control cases from Minneapolis-Saint Paul or Houston. The amphibole was found in tissues of 29 of the 32 Duluth residents. In all, 60 of 96 Duluth specimens contained at least one such fiber, compared with 2 of 61 control specimens. The control levels were about the same as in blank laboratory samples, and the authors attributed them to contamination. Chrysotile fibers were found in lung tissue from all controls and from 30 of 32 Duluth cases. The authors concluded that the tissue burden presumably came from uptake through the intestine. They stated that too few years had passed to draw any conclusions about ultimate risk.

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: Autopsy tissue study comparing exposed residents with controls; cases chosen blind and at random from a pool of autopsy cases, with tissue examined by transmission electron microscopy
• Who was studied: 32 Duluth, Minnesota residents autopsied in 1973 and 1974 (33 were selected; one was excluded for using well water). 23 were female, average age 72 years (range 52 to 89), and none had industrial asbestos exposure. There were 21 control cases from Minneapolis-Saint Paul or Houston, Texas: 12 female, average age 56 years (range 17 to 77).
• Exposure: Long-term oral exposure, through Duluth tap water drawn from Lake Superior, to a ferromagnesium silicate amphibole (Cummingtonite-Grunerite) from taconite processing tailings, for up to 15 years. Chrysotile fibers in tissue were also counted.
• Main results:
  • The ingested amphibole fiber type was identified in the tissues of 29 of the 32 Duluth residents. Among the controls, only 2 subjects had this fiber, each a single fiber in a single tissue specimen.
  • 60 of 96 tissue specimens from Duluth residents had 1 or more amphibole fibers, compared with 2 of 61 tissue specimens from control cases (P less than 0.001).
  • Among Duluth cases, the share of specimens with at least one amphibole fiber was 66% for lung, 63% for liver and 59% for jejunum. These percentages did not differ significantly from one another.
  • The amphibole concentration in control tissues was about the same as in the blank laboratory grids, which the authors considered due to contamination alone.
  • In 65 blank grids (300 grid squares) used to check laboratory contamination, 401 chrysotile fibers and only one amphibole fiber were found.
  • Chrysotile fibers were found in lung tissue from all control cases and from 30 of 32 Duluth cases. The apparent excess of lung chrysotile in Duluth cases was not statistically significant.
  • Jejunum and liver samples from Duluth cases had significantly less chrysotile than those from control cases (P less than 0.01). The Duluth levels did not differ significantly from the blank grids.
  • In an age-matched reanalysis (22 Duluth and 14 control subjects aged 50 through 79), amphibole fibers were found in 44 of 66 Duluth tissue specimens. Among controls, one fiber was found in a single tissue from each of two subjects (P less than 0.001).
• The authors' conclusion: The authors concluded that the amphibole tissue burden in Duluth residents presumably resulted from uptake of the fibers through the intestinal lining.
• Limitations the authors state:
  • Control cases were younger than the Duluth cases. The authors said this did not invalidate the results and reanalysed the data using age-matched cases.
  • Individual measures of fiber concentration were very crude, so only averages could be used for meaningful comparisons.
  • The data could not show whether amphibole levels in Duluth residents' tissues were steadily increasing or had reached a steady state.
  • Too few years had passed since oral exposure began to draw any conclusions about ultimate risk.
  • The authors had no explanation for the low chrysotile levels in liver and jejunum from Duluth subjects.

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Asbestos, Silicate, Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), Chrysotile.

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• Ingested mineral fibers. Do they penetrate tissue or cause cancer? — P. Gross, R.A. Harley, et al. (1974)
• The reliability of measures of amphibole fiber concentration in water — A.L. Brown, W.F. Taylor, et al. (1976)
• Mineral fiber concentration in lung tissue of mesothelioma patients in Finland — T. Tuomi, M. Segerberg-Konttinen, et al. (1989)
• Asbestos fibers in human pulmonary and extrapulmonary tissues — J. Huang, N. Hisanaga, et al. (1988)

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