Prenatal exposure to polybrominated diphenyl ethers and child attention problems at 3–7 years
Prenatal exposure to some flame retardants that have been widely-used in consumer products is associated with attention problems in children ages three through seven, according to a study by researchers at the Columbia Center for Children’s Environmental Health, within Columbia’s Mailman School of Public Health, ccceh reports.
Polybrominated diphenyl ethers (PBDEs) comprise a class of halogenated compounds used extensively as flame retardant chemicals in consumer products resulting in nearly ubiquitous human exposure. Mounting evidence suggests that PBDEs are developmental neurotoxicants; however, associations between early life exposure and child behavior have been largely limited to a single developmental time point.
The study population consists primarily of white, black and Chinese women who were pregnant on 11 September 2001 and delivered at 1 of 3 downtown New York City hospitals. Maternal–child pairs were followed through age 7 years. Cord blood was collected at delivery and PBDE plasma levels for 210 samples were analyzed by the U.S. Centers for Disease Control and Prevention. The Child Behavior Checklist, a validated maternal-report instrument used for assessing child behavior, was administered annually between the ages of 3 and 7 years. We analyzed the association between natural log-transformed and dichotomized (low vs. high) PBDEs and attention problems using multivariable adjusted negative binomial regression.
We detected 4 PBDE congeners in more than 50% of samples, with concentrations highest for BDE-47 (median ± IQR: 11.2 ± 19.6 ng/g). In adjusted analyses, we detected associations between BDE-47 (1.21, 95% CI: 1.00, 1.47), and BDE-153 (1.18, 95% CI: 1.00, 1.39) in cord plasma and increased attention problems among children at age 4 (n = 109) but not 6 (n = 107) years.
Our findings demonstrate a positive trend between prenatal PBDE exposure and early childhood attention problems, and are consistent with previous research reporting associations between prenatal PBDE exposure and disrupted child behaviors.
You are what you eat, and drink
Components used in plastics, such as phthalates, bisphenol A (BPA), polybrominated diphenyl ethers (PBDE) and tetrabromobisphenol A (TBBPA), are detected in humans. In addition to their utility in plastics, an inadvertent characteristic of these chemicals is the ability to alter the endocrine system. Phthalates function as anti-androgens while the main action attributed to BPA is oestrogen-like activity. PBDE and TBBPA have been shown to disrupt thyroid hormone homeostasis while PBDEs also exhibit anti-androgen action. Experimental investigations in animals indicate a wide variety of effects associated with exposure to these compounds, causing concern regarding potential risk to human health. For example, the spectrum of effects following perinatal exposure of male rats to phthalates has remarkable similarities to the testicular dysgenesis syndrome in humans. Concentrations of BPA in the foetal mouse within the range of unconjugated BPA levels observed in human foetal blood have produced effects in animal experiments. Finally, thyroid hormones are essential for normal neurological development and reproductive function. Human body burdens of these chemicals are detected with high prevalence, and concentrations in young children, a group particularly sensitive to exogenous insults, are typically higher, indicating the need to decrease exposure to these compounds.
Exposure of humans to pharmaceuticals is deliberate, with the intention of achieving a desired effect. Development and testing of medications involves a series of evaluations culminating in human clinical trials before marketing is approved. This is quite different from the situation with chemicals, whose presence in biota and humans is inadvertent. In the field of toxicology, information regarding potential human health effects is mainly derived from experimental studies and, when available, from epidemiological studies. Difficulties are not only encountered with extrapolation from animal models to humans, but epidemiological studies are also thwarted by drawbacks such as controlling for confounding factors. In particular, subjects are exposed to an assortment of chemicals on a daily basis and, often, lack of data regarding the extent of exposure at what may have been the critical time frame. One of the goals of toxicology is to identify effects in animal models with the aim to lower the risks of negatively impacting human health. Implicit in this task is that toxicological data, derived from animal studies indicating a potential for adverse effects, serve as a basis to limit exposure before effects appear or are confirmed in humans. The evidence from animal studies on single exposures to the chemicals discussed here suggests the potential for risk to human health. Moreover, data derived from co-exposure studies support the contention that the assortment of chemicals to which we are exposed on a daily basis increases the likelihood of health effects. The high prevalence of body burdens of these chemicals and simultaneous exposure to a number of substances, in conjunction with the fact that the highest concentrations have been demonstrated in the developing young, a sensitive subpopulation of society, indicate the need to decrease the exposure to these compounds.
Read the full study (free access) on NCBI PubMed, 2009 Jul 27.
Exposure to polybrominated diphenyl ethers (PBDEs) and child behavior: Current findings and future directions
2018 Study Highlights
- Prenatal PBDEs are associated with executive function impairments and inattention.
- Prenatal and postnatal PBDE exposures increase externalizing problems in children.
- PBDEs’ association with internalizing, adaptive, and social behaviors is not clear.
- PBDE exposure adversely affects behavioral development in children.
Polybrominated diphenyl ethers (PBDEs) are recognized neurotoxicants, but the extent to which PBDEs influence various domains of behavior in children is not fully understood.
As such, we reviewed epidemiologic studies published to date to provide an overview of the current state of knowledge on PBDEs’ potential role in behavioral development.
We identified 19 epidemiologic studies reporting on associations of prenatal and childhood concentrations of PBDEs with behaviors assessed in children from 1 to 12 years, including executive function, attention, externalizing and internalizing behaviors, adaptive skills, and social behaviors/Autism Spectrum Disorder (ASD).
While the mechanisms of PBDE neurotoxicity in humans are still not clearly elucidated, findings from this review indicate that PBDE exposure during fetal development is associated with impairments in executive function and poorer attentional control in children. Results from large prospective cohorts demonstrate that prenatal and postnatal PBDE exposure adversely impacts externalizing behavior (e.g., hyperactivity and conduct problems). Additional studies are needed to determine whether PBDEs are associated with internalizing problems, adaptive skills, and social behaviors/ASD in children.
Future studies will help better understand the potential neurotoxic effects of PBDE exposures during adolescence, possible sex-dependent effects, and the impact of exposure to BDE-209 and alternative flame retardants. Future studies should also examine chemical mixtures to capture real-world exposures when examining PBDEs and their impact on various behavioral domains in the context of multiple chemical exposures.