Modeled exposure to tetrachloroethylene-contaminated drinking water and the risk of placenta-related stillbirths: a case-control study from Massachusetts and Rhode Island

BACKGROUND: Residents of Massachusetts and Rhode Island were exposed to tetrachloroethylene (PCE)-contaminated drinking water from 1968 through the early 1990s when the solvent was used to apply a vinyl liner to drinking water mains to address taste and odor problems. Few studies have examined the risk of fetal death among women exposed to solvent-contaminated drinking water. Two previous investigations found moderate increases in the risk of stillbirth among highly exposed women; however, these results were based on a small number of cases. The present case-control study was undertaken to examine further this association with a large number of stillbirths. METHODS: Cases were comprised of stillborn infants delivered between 1968 and 1995 to mothers who resided in 28 Massachusetts and Rhode Island cities and towns with some affected water mains (N = 296). Cases were included if the cause of death was placental abruption and/or placental insufficiency. Controls were randomly selected live-born infants who were delivered in the same time period and geographic area (N = 783). Data on confounding variables were gathered from vital records and questionnaires. PCE exposure was estimated using a leaching and transport model integrated into water system software. RESULTS: Mothers with any PCE exposure had a 1.7-fold increase in the adjusted odds of placenta-related stillbirth (95% CI: 1.2–2.4). The adjusted odds ratio (OR) increased as a woman’s exposure level increased: in comparison to unexposed mothers, ORs were 1.5 (95% CI: 1.0–2.3) for low exposure (> 0-median), 1.7 (95% CI: 1.1–2.5) for moderate exposure (>median-90th percentile) and 1.9 (95% CI: 1.1–3.2) for high exposure (>90th percentile) (p value for trend = 0.02). A similar pattern was observed when PCE exposure was dichotomized at 40 μg/L, the suggested action guideline for remediation (OR = 1.5, 95% CI: 1.1–2.2 and OR = 2.6, 95% CI: 1.4–4.8, respectively, for PCE exposure <=40 μg/L and > 40 μg/L) (p value for trend = .003). CONCLUSIONS: We observed a linear dose-dependent increase in the odds of stillbirth due to placental abruption and placental insufficiency with prenatal exposure to PCE contaminated drinking water. Because PCE remains a common drinking water contaminant, these findings highlight the importance of considering pregnant women when monitoring, regulating and remediating drinking water supplies.