Periconceptional Exposure to Trihalomethanes in Drinking Water and the Risk of Neural Tube Defects

Abstract

Trihalomethanes (THMs) are disinfection by-products found in drinking water that result when chlorine reacts with organic matter. An association between THMs and neural tube defects (NTDs) has been suggested in other studies. Using a case-control design, this study investigated the relation between NTDs and THMs in offspring of Mexican-American women living in the 14 Texas counties bordering Mexico. Participants in the study, 184 case-women with an NTD-affected pregnancy and 225 control-women, were interviewed about their environmental and occupational exposures during the periconceptional period. Public drinking water monitoring data was matched to the mother’s residence at the time of conception. Odds ratios were suggestive of an association among women with an NTD-affected pregnancy and periconceptional exposure to drinking water with THM levels greater than or equal to 50 (ig/liter (OR=2.36); however, 95% confidence intervals were consistent with unity. Odds ratios for THM levels > 50 |j,g/liter were also elevated for women who ingested tap water as opposed to bottled water (OR= 3.6,95% Cl 1.1-12.3). Logistic regression models examining THMs and other potential risk factors were not significant (p> 0.05). The study was limited by sparse drinking water THM monitoring data with very few caseand control-women in the high exposure categories. Further studies are warranted to investigate individual compounds of THMs as opposed to total THMs in an attempt to understand if individual compounds render exposed women more susceptible to NTDaffected pregnancies in this study population. The relation between THM exposure and source of drinking water (tap versus bottled water) also deserves further exploration.