Associations Between Craniofacial Birth Defects and Disinfection By-Product Exposures in Massachusetts, USA

Abstract

Epidemiological studies suggest that women exposed to disinfection by-products (DBPs) in treated water have an increased risk of delivering babies with some birth defect types, though evidence for craniofacial defects (CFDs) and specific DBPs is limited. We used a case-control design of birth defects in Massachusetts from 2000-2004 with complete trihalomethane (THM) and haloacetic acid (HAA) data. We randomly matched each case (n=371) to 10 controls based on week of conception. We used first trimester DBP exposures weight-averaged across quarterly water sampling locations linked to individuals based on residence at birth. Adjusted odds ratios (aORs) were calculated for four CFDs in relation to 13 DBP exposures categorized based on available data distributions, including chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), dichloroacetic acid (DCA), trichloroacetic acid (TCA), THM4 (sum of bromoform, TCM, BDCM, DBCM), HAA5 (sum of DCA, TCA, monochloroacetic, monobromoacetic, and dibromoacetic acids) and DBP9 (sum of THM4 and HAA5). Comparing highest to lowest exposure groups, we detected elevated aORs for cleft palate (n=131) for quintiles of DBP9 (aOR=6.36; 95%CI: 1.55-26.10) and THM4 (aOR=2.54; 95%CI: 0.60-10.74), quartiles of DCA (aOR=2.25; 95%CI: 0.68-7.42) and TCA (aOR=2.10; 95%CI: 0.64-6.89), BDCM tertiles (aOR=1.32; 95%CI: 0.65-2.71), the upper DBCM decile (aOR=1.30; 95% CI: 0.57-2.99), and a positive exposure-response relationship for HAA5 quintiles (aOR range: 1.53-3.30). We detected elevated aORs for eye defects (n=67) with THM4 tertiles (aOR=3.81; 95%CI: 0.74-19.52), TCA quartiles (aOR=4.05; 95%CI: 0.52-31.59), and the upper BDCM decile (aOR=2.64; 95%CI: 0.66-10.58). No elevated aORs were detected for cleft lip or ear defects. Though our analyses were limited by small case numbers, this is the first study to examine HAAs with CFDs, and the third to examine brominated DBPs, thus adding specificity to previous research.