Background: There is concern about possible effects of disinfection by-products on reproductive outcomes. The purpose of this study was to evaluate the association between maternal exposure to chlorination by-products and the risk of delivering a small for-gestational-age (SGA) neonate.
Methods: We conducted a population-based case-control study in the Québec City (Canada) area. Term newborn cases with birth weights <10th percentile (n = 571) were compared with 1925 term controls with birth weights ≥10th percentile. Concentrations of trihalomethanes and haloacetic acids in the water-distribution systems of participants were monitored during the study period, and a phone interview on maternal habits was completed within 3 months after childbirth. We estimated chlorination by-products ingestion during the last trimester of pregnancy and trihalomethanes doses resulting from inhalation and dermal exposure. We evaluated associations between chlorination by-products in utero exposure and SGA by means of unconditional logistic regression with control of potential confounders.
Results: When total trihalomethanes and the 5 regulated haloacetic acids concentrations were divided into quartiles, no clear dose-response relationship was found with SGA. However, increased risk was observed when haloacetic concentrations were above the fourth quartile and when either trihalomethanes or haloacetic acids concentrations were above current water standards (adjusted OR= 1.5 [95% confidence interval = 1.1–1.9] and 1.4 [1.1–1.9], respectively). Inhalation and dermal absorption of trihalomethanes did not contribute to this risk, but a monotonic dose-response was found with haloacetic acids ingestion.
Conclusion: Oral exposure to high levels of chlorination by-products in drinking water could be a risk factor for term SGA.
From the aInstitut national de santé publique du Québec, Québec, Canada; bDépartement de médecine sociale et préventive, Université Laval, Québec, Canada; cCentre de recherche du Centre Hospitalier Universitaire de Québec, Québec, Canada; dCentre de recherche en aménagement et développement, Université Laval, Québec, Canada; and eDépartement de santé environnementale et santé au travail, Université de Montréal, Montréal, Canada.
Submitted 14 June, 2011; accepted 13 December, 2011.
Supported by the Canadian Institutes of Health Research through an operating grant. The authors reported no financial interests related to this research.
Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com). This content is not peer-reviewed or copy-edited; it is the sole responsibility of the author.
Correspondence: Patrick Levallois, Institut national de santé publique du Québec, 945, avenue Wolfe, Québec, Canada G1V 5B3. E-mail: Patrick.Levallois@msp.ulaval.ca.