Modeled exposure to tetrachloroethylene-contaminated drinking water and the occurrence of birth defects: a case-control study from Massachusetts and Rhode Island

Our plain-English summary of Modeled exposure to tetrachloroethylene-contaminated drinking water and the occurrence of birth defects: a case-control study from Massachusetts and Rhode Island, by A. Aschengrau, L.G. Gallagher, M. Winter, et al (Environmental Health, 2018).

The study

• Authors: A. Aschengrau, L.G. Gallagher, M. Winter, L. Butler, M. Patricia Fabian, V.M. Vieira
• Journal: Environmental Health
• Published: 2018;17(1):75
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Residents of Massachusetts and Rhode Island were exposed to tetrachloroethylene-contaminated drinking water from 1968 through the early 1990s when it leached from the vinyl lining of asbestos cement water distribution pipes. While occupational exposure to solvents during pregnancy has consistently been linked to an increased risk of certain birth defects, mixed results have been observed for environmental sources of exposure, including contaminated drinking water. The present case-control study was undertaken to examine further the association between prenatal exposure to tetrachloroethylene-contaminated drinking water and the risk of central nervous system defects, oral clefts and hypospadias.

Methods: Cases were comprised of live- and stillborn infants delivered between 1968 and 1995 to mothers who resided in 28 Massachusetts and Rhode Island cities and towns with some PCE-contaminated water supplies. Infants with central nervous system defects (N = 268), oral clefts (N = 112) and hypospadias (N = 94) were included. Controls were randomly selected live-born, non-malformed infants who were delivered during the same period and geographic area as cases (N = 771). Vital records and self-administered questionnaires were used to gather identifying information, birth defect diagnoses, and other relevant data. PCE exposure during the first trimester was estimated using water distribution system modeling software that incorporated a leaching and transport model. Prenatal PCE exposure was dichotomized as "high" or "low" exposure at the level corresponding to an estimated average concentration of 40 μg/L, the criterion for remediation when PCE contamination was discovered in 1980.

Results: Mothers with "high" levels of exposure to PCE-contaminated drinking water during the first trimester (> 40 μg/L) had increased odds of having a child with spina bifida (OR: 2.0, 95% CI: 0.8-5.4), cleft lip with or without cleft palate (OR: 3.8, 95% CI: 1.2-12.3) and hypospadias (OR: 2.1, 95% CI:0.5-8.3). No increases in the odds of other defects were observed in relation to "high" exposure levels.

Conclusions: The results of the present study suggest that mothers with "high" PCE exposure levels during the first trimester have increased odds of having a child with spina bifida, cleft lip with or without cleft palate, and hypospadias. These findings support several prior studies that observed an increased risk of selected birth defects following prenatal exposure to solvents in occupational and environmental settings. Even though PCE contamination from vinyl lined pipes was remediated many years ago, it remains a widespread contaminant across the U.S and so environmental regulations must be guided by a precautionary perspective that safeguards pregnant women and their offspring.

In plain English

This case-control study examined tetrachloroethylene (PCE), a solvent that leached into drinking water from vinyl-lined asbestos cement pipes. Asbestos itself was not studied. Cases were live- and stillborn infants delivered 1968 through 1995 to residents of 24 Massachusetts and four Rhode Island towns: 268 with central nervous system defects, 112 with oral clefts, 94 with hypospadias. Controls were 771 liveborn infants without defects. Because historical water samples were scarce, first-trimester exposure was estimated with a water-system model. Exposure above 40 μg/L was called "high." Any exposure showed no meaningful increase in most defects. Cleft lip with or without cleft palate was the exception (adjusted odds ratio 2.1, 95% confidence interval 1.1 to 4.0). High exposure was linked to higher odds of that defect (3.8, interval 1.2 to 12.3), spina bifida (2.0, 0.8 to 5.4) and hypospadias (2.1, 0.5 to 8.3). The intervals for spina bifida and hypospadias included 1. The authors concluded high exposure was associated with these defects. They noted that few mothers were highly exposed, making results unstable, and that the model estimated PCE delivered to homes, not personal intake.

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: Case-control study. Infants with birth defects found in vital records were compared with randomly selected infants without defects, and odds ratios were estimated with logistic regression
• Who was studied: Cases were live- and stillborn infants delivered 1968 through 1995 to residents of 24 Massachusetts and 4 Rhode Island cities and towns with some vinyl-lined asbestos cement pipes: 268 with central nervous system defects, 112 with oral clefts and 94 with hypospadias. Controls were 771 liveborn infants without malformations, born in the same period to residents of the same area
• Exposure: Tetrachloroethylene (PCE) that leached into drinking water from the vinyl lining of asbestos cement distribution pipes. Because historical sampling data were scant, first-trimester exposure was estimated with a leaching and transport model in water distribution software. Exposure was split into "high" (above 40 μg/L, the 1980 remediation criterion, equal to 1.136 g per month) and lower exposure
• Main results:
  • Share of mothers with some PCE exposure in the first trimester: 68.3% of central nervous system defect cases, 72.3% of oral cleft cases, 61.7% of hypospadias cases and 67.8% of control mothers
  • Any first-trimester PCE exposure was not associated with meaningful increases in the adjusted odds of central nervous system defects combined, neural tube defects, anencephaly, spina bifida, other central nervous system defects or hypospadias
  • Cleft lip with or without cleft palate: the adjusted odds ratio was 2.1 (95% CI 1.1 to 4.0) for any exposure, rising to 3.8 (95% CI 1.2 to 12.3) for exposure above 40 μg/L
  • Spina bifida with and without hydrocephalus, high exposure: adjusted odds ratio 2.0 (95% CI 0.8 to 5.4)
  • Hypospadias (male infants only), high exposure: adjusted odds ratio 2.1 (95% CI 0.5 to 8.3)
  • Cleft palate alone: only one case had high exposure, so no odds ratio was estimated for that level. Any exposure gave an adjusted odds ratio of 1.4 (95% CI 0.7 to 2.7)
  • The results did not change meaningfully in sensitivity analyses. These used first-trimester addresses for mothers who moved, and separately excluded families with a history of defects, cases with multiple defects, and cases from the authors' prior cohort study
• The authors' conclusion: The authors concluded that their results suggest pregnant women with "high" exposure (above 40 μg/L) had increased odds of a child with spina bifida, cleft lip or hypospadias. They also wrote that, because PCE remains a common U.S. drinking water contaminant, regulations should take a precautionary approach.
• Limitations the authors state:
  • The findings are statistically unstable, with wide confidence intervals, because few mothers were exposed above the remediation cut point
  • The model estimated the mass of PCE delivered to the home, not personal exposure. The authors wrote that misclassification from model-based estimates likely weakened the associations
  • Vital records used to identify cases and controls likely suffered from mis-reporting and under-reporting of defects
  • Pregnancies lost before birth were not studied, which may have led to underestimating the effect

Topics

Medical terms in this study, explained in our Lexicon: Case-Control Study, Asbestos-Cement, Occupational Exposure.

Related studies

• Evaluation of the Webler-Brown model for estimating tetrachloroethylene exposure from vinyl-lined asbestos-cement pipes — L.A. Spence, A. Aschengrau, et al. (2008)
• Concentrations of asbestos fibers and metals in drinking water caused by natural crocidolite asbestos in the soil from a rural area — B. Wei, B. Ye, et al. (2013)
• Evidence of arsenic release promoted by disinfection by-products within drinking-water distribution systems — S.S. Andra, K.C. Makris, et al. (2014)
• Quantitative analysis of asbestos in drinking water and its migration in mice using fourier-transform infrared spectroscopy and inductively coupled plasma optical emission spectrometry — B. Zheng, L. Zang, et al. (2019)
• Asbestos-contaminated drinking water: its impact on household air — J.S. Webber, S. Syrotynski, et al. (1988)
• Exposure to chlorinated solvents and lung cancer: results of the ICARE study — F. Mattei, F. Guida, et al. (2014)

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