Drinking water disinfection by-products during pregnancy and child neuropsychological development in the INMA Spanish cohort study

Abstract

BackgroundDisinfection by-products (DBPs) constitute a complex mixture of prevalent chemicals in drinking water and there is evidence of neurotoxicity for some of them. ObjectivesWe evaluated the association between estimates of DBP exposure during pregnancy and child neuropsychological outcomes at 1 and 4–5years of age. MethodsWe conducted a population-based mother-child cohort study in Spain with recruitment at first trimester of gestation (INMA Project, 2003–2008). Neuropsychological development was measured at 1year of age using the Bayley Scales of Infant Development and at 4–5years with the McCarthy Scales of Children's Abilities. Modeled tap water concentrations of trihalomethanes (THM) were combined with personal ingestion, showering and bathing habits to estimate exposure as ingestion uptake, all route (showering, bathing, ingestion) uptake (μg/day) and crude levels (μg/l) in the residence. Chloroform, brominated THMs (bromodichloromethane, dibromochloromethane, bromoform) and total THMs (chloroform and brominated THMs) were analysed separately. Nine haloacetic acids levels were available in one of the areas. Linear regression was used to estimate associations in 1855 subjects adjusting for covariables. ResultsThe median concentration of total THMs, chloroform, brominated THMs, total haloacetic acids, dichloroacetic acid, and trichloroacetic acid were, respectively 30.3μg/L, 9.4μg/L, 11.6μg/L, 10.5μg/L, 2.7μg/L, and 3.1μg/L. The associations between THM exposure and neuropsychological outcomes were null, except for total and brominated THM uptake though all routes and the general cognitive score at 4–5years, with a decrease in −0.54 points (95%CI −1.03, −0.05) and −0.64 (95%CI −1.16, −0.12), respectively, for doubling total and brominated THM uptake. A positive association found between dichloroacetic acid and the mental score at 1year did not persist at 4–5years. ConclusionsMinor associations observed between DBP exposure during gestation and child neuropsychological development at 1year disappeared at 4–5years. Although a suggestive association is identified for exposure to brominated THMs and the cognitive score at 4–5years, chance cannot be ruled out.