Placental transfer of asbestos

Our plain-English summary of Placental transfer of asbestos, by H.M. Cunningham, R.D. Pontefract (Nature, 1974).

The study

• Authors: H.M. Cunningham, R.D. Pontefract
• Journal: Nature
• Published: 1974;249(453):177-8
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This animal experiment asked whether asbestos injected into pregnant rats could cross the placenta into the unborn young. Chrysotile asbestos was injected into a vein of pregnant Wistar rats at 1 to 3 mg every two days, beginning on day 10 to 14 of pregnancy. Other rats served as uninjected controls. There were two experiments. Caesarean removal the day before birth was planned, but in the first experiment two injected rats gave birth 2 to 3 hours after their third dose; those young were killed immediately. Foetal livers and lungs were examined for fibres by electron microscopy. In both, fibre levels in young from injected rats varied widely, some extremely high, especially in the liver. In the second experiment, control young had low levels, all but one below the detection limit. The authors concluded that the many very high values in injected rats, versus very low control levels, added considerable evidence that asbestos fibres can cross the placenta. They said how this happens had yet to be determined, and that the variable results were very difficult to analyse statistically.

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 (two experiments in pregnant rats, with uninjected controls), using electron microscopy to count fibres in foetal tissue
• Who was studied: Pregnant Wistar rats weighing 300 g, at the Health Protection Branch, Department of Health and Welfare, Ottawa, Canada. Experiment 1 had four rats given 3 mg doses plus controls. Experiment 2 had four controls, four rats given four 1 mg injections, and four rats given five 2 mg injections. Livers from two foetuses and lungs from three foetuses per rat were analysed.
• Exposure: Chrysotile asbestos injected into the femoral vein of the mother at 1 to 3 mg per dose, at 2-day intervals, beginning on the 10th to 14th day of gestation
• Main results:
  • Experiment 1: extremely high fibre values were found in the foetal liver and lungs from rat 7 and the foetal liver from rat 8. Fibre levels in the foetal tissues from treated rats 5 and 6 were close to the higher values in the control rats.
  • Experiment 1: two of the four rats given 3 mg doses gave birth about 2 to 3 hours after the third dose, apparently because of the stress of the injection. Their young were killed immediately rather than removed by Caesarean section. In preliminary experiments, higher doses were usually fatal, with the rats having difficulty breathing.
  • Experiment 2, control rats: values were low, with all but one below the detection level. That level was equivalent to 0.45 × 10⁶ fibres per gram in liver, or about half that in lungs.
  • Experiment 2, asbestos-injected rats: foetal liver and lung values were again highly variable, with extremely high values in the livers of several rats' foetuses (rats 18 and 19 are named).
• The authors' conclusion: The authors concluded that the number of very high values in the young of asbestos-injected rats, compared with very low levels in the young of controls, added considerable evidence to the theory that asbestos fibres can cross the placenta. They said the way this occurs (individual fibres penetrating, a mass breakthrough, or both) had yet to be determined.
• Limitations the authors state:
  • The results were so variable that they were very difficult to analyse statistically.
  • The livers and lungs analysed were chosen at random and could have come from different foetuses in the same uterus. This meant the authors could not check whether a single foetus had high levels in all its organs.
  • How the fibres cross the placenta was not determined.

Related studies

• Asbestos in organs and placenta of five stillborn infants suggests transplacental transfer — A.K. Haque, M.G. Mancuso, et al. (1992)
• Transplacental transfer of asbestos in pregnant mice — A.K. Haque, D.M. Vrazel (1998)
• Chrysotile asbestos fibers detected in the newborn pups following gavage feeding of pregnant mice — A.K. Haque, I. Ali, et al. (2001)
• Teratogenicity of asbestos in mice — T. Fujitani, M. Hojo, et al. (2014)
• Assessment of asbestos burden in the placenta and tissue digests of stillborn infants in South Texas — A.K. Haque, D.M. Vrazel, et al. (1998)
• Tissue distribution of a coelomic-epithelium-related antigen recognized by the monoclonal antibody OC125 — S.E. Kabawat, R.C. Bast, et al. (1983)

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