Content area
Full text
Introduction
Polychlorinated biphenyls (PCBs) have been widely used in, for example, hydraulic equipment, dyes, plasticizers, capacitors, transformers and flame retardants. Dichlorodiphenyltrichloroethane (DDT) has been used primarily as a pesticide and for vector control. Even though PCBs and DDT were banned from use in most Western countries in the 1970s and 1980s, DDT continues to be used for disease vector control in some developing countries (van den Berg 2009), and both are persistent and ubiquitous substances found in the environment (Ibarluzea et al. 2011).
The main exposure routes of organochlorine compounds such as PCBs and DDT and its breakdown product dichlorodiphenyldichloroethylene (DDE) are through food consumption and breastfeeding, and given their lipophilic properties and long half-lives of 5 to 10 y, they bioaccumulate within human adipose tissue (Glynn et al. 2007; Malarvannan et al. 2013; Ribas-Fitó et al. 2005). These compounds may also cross the placental barrier, potentially resulting in fetal exposures decades after maternal exposure (Glynn et al. 2007; Vizcaino et al. 2014). Environmental pollutants such as pesticides, solvents, and organochlorines may act as developmental neurotoxins, inducing brain injury during early-life development at doses much lower than those required for adverse effects in adults, with potential long-term implications for the child (Grandjean and Landrigan 2006; Rosas and Eskenazi 2008).
Based on concentrations measured in cord serum, prenatal exposures to PCBs and DDE were found to be associated with attention deficit hyperactivity disorder (ADHD)-related behaviors in 573 U.S. children at 8 y of age (Sagiv et al. 2010). Verner et al. (2015) used a pharmacokinetic model to estimate postnatal exposures in the same cohort and reported positive associations between postnatal PCB exposures and ADHD-related behaviors that were weaker than associations with prenatal exposures. PCB concentrations in maternal blood samples were also negatively associated with attention deficit disorders in 117 German children at 8–9 y of age (Neugebauer et al. 2015). However, other studies have not found associations between behavior outcomes and PCB or DDE exposures (Grandjean et al. 2012; Ribas-Fitó et al. 2007b; Strøm et al. 2014).
In the present prospective cohort study, we investigated associations between prenatal and early-life exposures to organochlorine compounds, specifically 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p′-DDE), and abnormal behavior scores among children at 5–9 y of age.
Methods
Study Population
The study...