Asbestos and embryonic development

Our plain-English summary of Asbestos and embryonic development, by U. Schneider, R.R. Maurer (Teratology, 1977).

The study

• Authors: U. Schneider, R.R. Maurer
• Journal: Teratology
• Published: 1977;15(3):273-9
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Chrysotile asbestos was administered to pregnant CD-1 mice in their drinking water and to Day 4 blastocysts during culture. Administration to pregnant mice did not affect embryo survival. In vitro administration of asbestos did not interfere with embryo implantation upon transfer of blastocysts to recipient females but did result in a decrease in postimplantation survival. These studies did not demonstrate asbestos to be teratogenic whether administered to the dam or to the blastocyst in vitro.

In plain English

In this animal experiment, the authors tested whether chrysotile asbestos affected embryo development in CD-1 mice. Pregnant mice drank water containing 0, 1.43, 14.3 or 143 micrograms of asbestos per millilitre on Days 1 to 15 of pregnancy. Separately, Day 4 embryos (blastocysts) were cultured with 0, 1, 10 or 100 micrograms of asbestos per millilitre and then transferred to recipient females. In the drinking-water study, asbestos did not change water consumption, maternal health signs or weight gain. Only the number of implants at the lowest dose differed, which the authors judged not likely due to asbestos. In the culture study, implantation was not significantly altered except in one group. The authors reported a dose-related increase in dead and resorbed fetuses (P = 0.063 and P = 0.054 in the two recipient groups). Malformation rates were not related to dose. Electron microscopy showed fibers stayed outside the zona pellucida, a coat surrounding the embryo, and entered its trophoblastic cells only when that coat was removed. The authors concluded the studies did not demonstrate asbestos to be teratogenic, meaning causing birth defects.

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: chrysotile asbestos given to pregnant mice in drinking water, and added to cultures of Day 4 mouse blastocysts that were then transferred to recipient females
• Who was studied: Naturally mated CD-1 female mice aged 8 to 10 weeks, in four groups of 10 to 12 animals each, replicated three times. Separately, blastocysts from superovulated virgin CD-1 mice were transferred to pseudopregnant recipient mice on Day 3 or Day 4. Study at the National Institute of Environmental Health Sciences, North Carolina.
• Exposure: Chrysotile asbestos fibers (No. 7RF02, Johns Manville). Drinking water contained 0, 1.43, 14.3 or 143 micrograms per ml on Days 1 to 15 of gestation. In the culture experiment, blastocysts received 0, 1, 10 or 100 micrograms of asbestos per 1 ml of medium for four hours.
• Main results:
  • Drinking-water study: asbestos did not change daily water consumption in any dose group.
  • Drinking-water study: the pregnant females showed no adverse effects in cardinal signs or maternal weight gain.
  • Drinking-water study: only the number of implants in the 1.43 microgram per ml group differed significantly (P less than 0.10). The authors judged this not likely due to asbestos, because the higher doses showed no such effect and one such result was about what chance would produce.
  • Culture study: exposure did not significantly alter implantation rate, except in Day 3 recipients given blastocysts exposed to 10 micrograms of asbestos.
  • Culture study: the authors reported a significant dose-related response in dead and resorbed fetuses (Jonckheere test, P = 0.063 in Day 4 recipients and P = 0.054 in Day 3 recipients).
  • Day 4 recipients showed an increase in postimplantation mortality in all exposed groups, but without a dose relationship. Day 3 recipients showed a dose-related increase.
  • Culture study: neither fetal weight nor the incidence of stunted fetuses was affected by asbestos exposure.
  • Culture study, Day 3 and Day 4 recipients combined: malformations were 1.7%, 0.9%, 0% and 2.8% for the 0, 1, 10 and 100 microgram groups, and were not related to dose (P greater than 0.10).
  • Electron microscopy of six control and six exposed blastocysts: fibers attached only to the outside of the zona pellucida (the coat surrounding the embryo) of intact blastocysts.
  • When the zona pellucida was removed, fibers were found in vacuoles inside the trophoblastic cells.
  • Blastocysts without zonae pellucidae were exposed and transferred to five recipients, of which three became pregnant. None of the seven resulting fetuses showed adverse effects.
• The authors' conclusion: The authors concluded that asbestos added to the culture of blastocysts decreased postimplantation survival. They also concluded that the studies did not demonstrate asbestos to be teratogenic, whether given to the mother or to the blastocyst in vitro.
• Limitations the authors state:
  • The authors said the lack of effect in the drinking-water study might be due to three things: asbestos may change its activity in water suspension; its effects may appear only after long exposure; or the doses used may have been outside the range that affects this test system.
  • The authors noted it had not been shown that ingested asbestos reaches the embryo, which is why they also exposed blastocysts directly.

Topics

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

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