Academic journal article Environmental Health Perspectives

Prenatal Phthalate Exposures and Neurobehavioral Development Scores in Boys and Girls at 6-10 Years of Age

Academic journal article Environmental Health Perspectives

Prenatal Phthalate Exposures and Neurobehavioral Development Scores in Boys and Girls at 6-10 Years of Age

Article excerpt

Introduction

Phthalates are human-made chemicals used globally in production of commercial and industrial goods (Meeker et al. 2009). Phthalates are primarily used as plasticizers in the manufacture of flexible vinyl and polyvinyl chloride plastic, but are also used in personal care products, pharmaceuticals, textiles, medical supplies, and many other products [U.S. Environmental Protection Agency (EPA) 2007]. Because they are not covalently bound to the product matrix, phthalates can leach into the surrounding environment (U.S. EPA 2007). Exposure to phthalates can occur through ingestion, inhalation, intravenous, or dermal exposure (Meeker et al. 2009; Sathyanarayana 2008). Because of their widespread use, phthalates are ubiquitous in the environment, and nationally representative studies have demonstrated widespread exposure to multiple phthalates in the U.S. population [Centers for Disease Control and Prevention (CDC) 2012a; Silva et al. 2004a].

Concern has been raised over potential endocrine-disrupting properties of phthalates (Crisp et al. 1998; U.S. EPA 2007), particularly evidence suggesting anti-androgenic effects during prenatal development (Meeker et al. 2009; Swan et al. 2005). A less studied area of public health importance is the potential neurobehavioral effects of prenatal exposure to phthalates. Fetal brain development is tightly regulated by the maternal endocrine system (Moore and Persaud 2003). Phthalates and other endocrine-disrupting chemicals may perturb this hormonal balance and disrupt fetal brain development (Zoeller and Crofton 2000).

Two studies of prenatal phthalate exposure and neonatal behavior have focused on infants 5 days and 5 weeks after delivery, respectively (Engel et al. 2009; Yolton et al. 2011). Both studies suggest that phthalate metabolite concentrations may be associated with alertness, motor control, arousal, and other behaviors, and lend support to examining these relationships in older children. To date, two studies have examined relationships between prenatal phthalate exposure and neurobehavioral development during childhood. A 2010 study reported that among 171 children 4-9 years of age, higher prenatal urine concentrations of low-molecular weight phthalates [including di-w-butyl phthalate (DnBP) and diisobutyl phthalate (DiBP) (referred therein as dibutyl phthalates; DBPs) and diethyl phthalate (DEP)] were associated with higher scores for aggression, conduct problems, and depressive symptoms, but lower scores for emotional control, attention, and executive function based on parental surveys (Engel et al. 2010). Sex-stratified analyses revealed elevated coefficients among males for several of these outcome scores. More recently, Whyatt set al. (2012) reported that prenatal urinary concentrations of phthalate metabolites were associated with higher scores for emotional reactivity, somatic complaints, withdrawn behavior, and a summary measure of internalizing behavior in 3-year old children (Whyatt et al. 2012). These associations varied between boys and girls; specifically, metabolites of DBPs were associated with higher scores for emotional reactivity, somatic complaints, and withdrawn behavior in boys, whereas greater concentrations of a benzylbutyl phthalate (BzBP) metabolite were associated with higher scores for anxiety/depressive behavior, somatic complaints, and withdrawn behavior in girls. Somatic complaints and withdrawn behavior were positively associated with mono-w-butyl phthalate (MBP) in boys and girls.

In summary, results from the few published studies suggest associations between prenatal phthalate exposure and children's neurodevelopment. However, given the variety of study populations, age groups, and neurobehavioral instruments employed in these studies, additional investigation is warranted. Therefore, in this analysis we examined associations between urinary prenatal phthalate metabolites concentrations and neurobehavioral scores among children 6-10 years of age. …

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