Relationship between Environmental Phthalate Exposure and the Intelligence of School-Age Children

Abstract

BackgroundConcern over phthalates has emerged because of their potential toxicity to humans.ObjectiveWe investigated the relationship between the urinary concentrations of phthalate metabolites and children’s intellectual functioning.MethodsThis study enrolled 667 children at nine elementary schools in five South Korean cities. A cross-sectional examination of urine phthalate concentrations was performed, and scores on neuropsychological tests were obtained from both the children and their mothers.ResultsWe measured mono-2-ethylhexyl phthalate (MEHP) and mono(2-ethyl-5-oxohexyl)phthalate (MEOHP), both metabolites of di(2-ethylhexyl)phthalate (DEHP), and mono-n-butyl phthalate (MBP), a metabolite of dibutyl phthalate (DBP), in urine samples. The geometric mean (ln) concentrations of MEHP, MEOHP, and MBP were 21.3 μg/L [geometric SD (GSD) = 2.2 μg/L; range, 0.5–445.4], 18.0 μg/L (GSD = 2.4; range, 0.07–291.1), and 48.9 μg/L (GSD = 2.2; range, 2.1–1645.5), respectively. After adjusting for demographic and developmental covariates, the Full Scale IQ and Verbal IQ scores were negatively associated with DEHP metabolites but not with DBP metabolites. We also found a significant negative relationship between the urine concentrations of the metabolites of DEHP and DBP and children’s vocabulary subscores. After controlling for maternal IQ, a significant inverse relationship between DEHP metabolites and vocabulary subscale score remained. Among boys, we found a negative association between increasing MEHP phthalate concentrations and the sum of DEHP metabolite concentrations and Wechsler Intelligence Scale for Children vocabulary score; however, among girls, we found no significant association between these variables.ConclusionControlling for maternal IQ and other covariates, the results show an inverse relationship between phthalate metabolites and IQ scores; however, given the limitations in cross-sectional epidemiology, prospective studies are needed to fully explore these associations.

Circulating phthalates during critical illness in children are associated with long-term attention deficit: a study of a development and a validation cohort

“…This assumption was based on the fact that many patients were admitted after exposure to extracorporeal circuits for surgery [19] and on the number of indwelling medical devices that typically diminishes throughout PICU stay, taking into account the half-life of the metabolites (between 5-15h) [20]. The available evidence suggests that both the concentration of circulating DEHP metabolites to which the brain is exposed and the duration of this exposure determine any eventual long-term neurocognitive harm [21,22] within a concept of "threshold" toxicity [23]. Therefore, we decided to consider the product of the last day plasma concentration and the duration of PICU stay as that exposure to circulating phthalates during PICU stay that was minimally present for each patient, further referred to as the phthalate "exposure".…”

“…In vitro studies, animal studies and observational reports in humans suggest that chronic exposure to DEHP may deleteriously affect neurocognitive development [19][20][21][22][23]. Specifically, a toxic effect on dopaminergic neurons was suggested to contribute to an increased incidence of attention-deficit disorders in young children exposed to environmental phthalates [24,25].…”

Exposure to phthalates: Reproductive outcome and children health. A review of epidemiological studies

“…Another study performed in South Korea among 667 elementary schools children evaluated a relationship between the urine concentrations of the metabolites of DEHP and DBP and children's vocabulary scores. Among boys, but not girls, a negative association was found between increasing MEHP phthalate concentrations and the sum of DEHP metabolite levels and vocabulary score [59]. The association of prenatal phthalate exposure with behavior and executive functioning at 4-9 years of age was examined in multiethnic prenatal population in New York City.…”

“…Animal studies have also revealed that the phthalate might cause hyperactivity similar to the clinical syndrome of attention-deficit/hyperactivity disorder (ADHD) found in children [56]. Exposures to phthalates have been examined in relation to neurodevelopment among neonates 5 days after birth in United States [57], in Korea in children from elementary schools [58,59] and in United States both among children 4-9 years [60] and 3.6-6.4 years of age [61] (Table 4). …”

“…The observed risks are generally presumed to be related to the endocrine altering properties of these chemicals [57,61]. In all those studies, exposure to phthalates was associated with neurodevelopmental disorders reflected by significantly poorer scores on conduct problems [60], quality of alertness among girls [57], decreased (less masculine) composite score in boys [61] and lower concentrations and vocabulary score among boys [59] as well as attention deficit hyperactivity disorder (ADHD) [58].…”