Assessment of asbestos burden in the placenta and tissue digests of stillborn infants in South Texas

Our plain-English summary of Assessment of asbestos burden in the placenta and tissue digests of stillborn infants in South Texas, by A.K. Haque, D.M. Vrazel, T. Uchida (Archives of Environmental Contamination and Toxicology, 1998).

The study

• Authors: A.K. Haque, D.M. Vrazel, T. Uchida
• Journal: Archives of Environmental Contamination and Toxicology
• Published: 1998;35(3):532-8
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The primary aim of this prospective study was to examine the tissues and placentas of autopsied stillborn infants for presence of asbestos fibers. Asbestos burden of lung, liver, skeletal muscle, and placenta digests of 82 stillborn infants was determined using standard bleach digestion technique. The digests were examined by electron microscopy, and the types of fibers determined using energy dispersive x-ray analysis and selected area diffraction analysis. Digests of 45 placentas collected from deliveries of liveborn healthy infants were processed and examined similarly as controls. Asbestos fibers were detected in 50% of the fetal digests and 23% of the placental digests of stillborn infants. Of the fibers present, 88% were chrysotile, 10% were tremolite, and 2% were actinolite and anthophyllite. Fibers measured 0.5-16.73 microgram in length (mean 1.55 microgram), and 0.03-0.8 microgram in width (mean 0.098 microgram). Lungs were most frequently positive for fibers (50%), followed by muscle (37%), placenta (23%), and liver (23%). Mean fiber counts were highest in the liver (58,736 f/g), followed by placenta (52,894 f/g), lungs (39,341 f/g), and skeletal muscle (31,733 f/g). Digests of 15% of the control placentas also showed asbestos fibers, although in very small numbers. The mean fiber count of the stillborn placentas (52,894 f/g) was significantly higher than the mean fiber count of the control placentas (mean 19 f/g) (p = 0.001). A highly significant association was found between fiber presence in stillborns and a maternal history of previous abortions (p = 0.007). A significant association was also found between fiber presence and placental diseases (p = 0.041). An association was suggested between working mothers and fiber presence (p = 0.19), although it did not reach statistical significance. The study documents the presence of small and thin asbestos fibers in stillborn fetal tissues and placenta. Significantly higher number of fibers were found in stillborn tissues compared to controls (liveborn placenta). The absence of a maternal history of asbestos-related occupations suggests that the fibers may have been acquired through environmental exposure.

In plain English

This prospective study looked for asbestos fibers in lung, liver, skeletal muscle and placenta from 82 stillborn infants autopsied in Galveston, Texas. It also examined 45 placentas from healthy, full-term liveborn infants as controls. Sixty of the 82 stillborn infants had fibers in at least one tissue. Most fibers were chrysotile (88%); 10% were tremolite and 2% were actinolite and anthophyllite. Fibers were found in 19 stillborn placentas and in seven of the 45 control placentas (15%). Among these fiber-positive placentas, mean counts were 52,894 fibers per gram (stillborn) and 19 fibers per gram (control), a significant difference (p = 0.001). In stillborn digests, one fiber seen equalled an average of 11,000 fibers per gram of wet tissue. Among stillborns, fiber presence was associated with a maternal history of previous abortions (odds ratio 9.4, 95% CI 1.6 to 56.0) and with placental disease (odds ratio 2.8, 95% CI 1.0 to 7.8). No mother's listed job was known to involve asbestos, and the authors concluded this suggested possible environmental exposure. They noted that the groups differed in disease, gestational age, tissues sampled and microscope used.

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: Prospective tissue-analysis study comparing autopsied stillborn infants with placentas from liveborn infants. Fibers were counted and typed by electron microscopy with energy dispersive x-ray analysis and selected area diffraction.
• Who was studied: 82 stillborn infants autopsied at the University of Texas Medical Branch Hospital at Galveston between September 1990 and August 1992, with gestational age 18 to 42 weeks (average 26.7). Controls were 45 placentas from healthy, full-term liveborn infants delivered at the same university hospitals in the same period. The study includes 30 stillborn infants the authors had reported earlier.
• Exposure: Asbestos fibers measured in tissue digests; no known maternal occupational asbestos exposure. The most common maternal jobs were cashier, clerk, waitress and housekeeper, and the authors did not systematically ask about other sources of exposure.
• Main results:
  • 22 of the 82 stillborn infants had no detectable fibers in either fetal or placental digests (that is, 60 had fibers in at least one).
  • In stillborn infants, the proportion of samples negative for fibers was 77% of livers, 62% of muscle, 68% of placentas and 50% of lungs. By Table 2, the positive samples were 41 lungs, 19 livers, 30 muscles and 19 placentas.
  • Mean fiber counts in stillborn tissues are for fiber-positive samples (each range starts above zero):
• liver: 58,736 fibers/g (range 12,000 to 397,000)
• placenta: 52,894 fibers/g (range 12,000 to 252,000)
• lung: 39,341 fibers/g (range 8,000 to 265,000)
• skeletal muscle: 31,733 fibers/g (range 12,000 to 196,000)
  • In stillborn digests, one fiber found was equivalent to an average of 11,000 fibers per gram of wet tissue.
  • Fibers in stillborn tissues were 88% chrysotile, 10% tremolite, and 2% actinolite and anthophyllite. Length was 0.5 to 16.73 micrometers (mean 1.55) and width 0.03 to 0.8 micrometers (mean 0.098).
  • Control placentas:
• 7 of 45 (15%) had fibers.
• Those 7 had 10 to 28 fibers/g (mean 19 fibers/g).
• The fibers were longer and thicker than in the stillborn group.
• Four of the seven fibers were compatible with chrysotile and three with amosite.
  • The mean fiber count of fiber-positive stillborn placentas (52,894 f/g, 19 placentas) was significantly higher than that of fiber-positive control placentas (mean 19 f/g, 7 placentas), p = 0.001.
  • Among stillborn infants, fiber presence was associated with a maternal history of previous abortions (p = 0.007). The odds ratio was 9.4 (95% confidence interval 1.6 to 56.0).
  • Among stillborn infants, fiber presence was associated with placental diseases (placental infarcts, chorioamnionitis, abruptio placenta), p = 0.041. The odds ratio was 2.8 (95% confidence interval 1.0 to 7.8).
  • No association was found between fiber presence and intrauterine fetal demise (p = 0.69). The other seven variables tested, including maternal occupation, were not statistically significant (p 0.17 to 0.93).
  • Mean gestational age was 26.5 weeks in fiber-positive stillborns and 28.8 weeks in fiber-negative stillborns; the difference was not statistically significant (p = 0.18).
• The authors' conclusion: The authors concluded that the absence of a known maternal occupational exposure suggests possible environmental exposure of the mothers, with circulation, accumulation in the placenta and transfer of fibers across the placenta. They called for further studies to clarify links between maternal asbestos exposure and pregnancy outcomes.
• Limitations the authors state:
  • The stillborn group had a high rate of maternal, fetal and placental disease; the control group had practically none.
  • Controls provided only placentas, not lung, liver or muscle.
  • Average gestational ages differed between the groups (most controls term or near term).
  • Most control placentas were collected late in the study over a short period.
  • Two different electron microscopes were used. The authors said this might partly explain the fiber-size difference between groups, and they were re-examining the control placentas.
  • Control placenta samples were larger (average 3 to 5 g) than stillborn placenta samples (1 to 2 g).
  • Sources of maternal exposure, including housing, were not systematically investigated.
  • The sample size was small, so associations (such as with intrauterine fetal demise) may be hard to demonstrate.

Topics

Medical terms in this study, explained in our Lexicon: Tissue Digestion, Chrysotile, Tremolite, Actinolite, Anthophyllite, Statistical Significance, Environmental Exposure.

Related studies

• Asbestos in organs and placenta of five stillborn infants suggests transplacental transfer — A.K. Haque, M.G. Mancuso, et al. (1992)
• Tissue burden of asbestos in nonoccupationally exposed individuals from east Texas — R.F. Dodson, M.G. Williams, et al. (1999)
• Asbestos and embryonic development — U. Schneider, R.R. Maurer (1977)
• Retrospective exposure assessment of airborne asbestos related to skilled craftsmen at a petroleum refinery in Beaumont, Texas (1940-2006) — P. Williams, D. Paustenbach, et al. (2007)
• Placental transfer of asbestos — H.M. Cunningham, R.D. Pontefract (1974)
• Numbers of asbestos bodies on iron-stained tissue sections in relation to asbestos body counts in lung tissue digests — V.L. Roggli, P.C. Pratt (1983)

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