Analysis of Polybrominated Diphenyl Ethers and Lipid Composition in Human Breast Milk and Their Correlation with Infant Neurodevelopment

Systematic review on Endocrine Disrupting Chemicals in breastmilk and neuro-behavioral development: Insight into the early ages of life

Breast milk (BM) is the main nutrition source for infants that plays a key role on growth and development. Human milk composition includes endogenous and exogenous substances, including endocrine disrupting chemicals (EDCs). EDCs are man-made environmental chemicals present in everyday environment and food that can disrupt the programming of endocrine signalling pathways during development, resulting in adverse effects that may not be apparent until much later in life. The presence of single and/or mixtures of EDCs in BM has been shown to be associated with impairment of reproductive, metabolic, immunologic system and neurobehavioral developmental outcomes. This systematic review discusses the current knowledge about the presence of EDCs in BM, and their potential effects on infant outcomes during the first six years of life. Following PRISMA guidelines, we made a systematic evaluation of the literature on the effects of single and mixtures EDC on (i) mental and psychomotor development; (ii) socio-communicative and behavioral development. Negative association between EDC exposure and developmental areas considered emerged highlighting: (i) BM as a potential key matrix for the monitoring of EDC exposure (ii) the short- and long-term negative effect on infant neuro-behavioral outcomes, and (iii) the importance of public health efforts to reduce maternal and infant EDC exposure. However, heterogeneous results found emphasizes the need to further longitudinal studies to consider factors that can lower EDC exposure or exert a protective role on infant neurodevelopment, and to better understand the mechanism behind the EDCs and its effects on infant development.

Association between pre- and postnatal exposure to endocrine-disrupting chemicals and birth and neurodevelopmental outcomes: an extensive review

Endocrine-disrupting chemicals (EDCs) are natural or synthetic chemicals that mimic, block, or interfere with the hormones in the body. The most common and well- studied EDCs are bisphenol A, phthalates, and persistent organic pollutants including polychlorinated biphenyls, polybrominated diphenyl ethers, per- and polyfluoroalkyl substances, other brominated flame retardants, organochlorine pesticides, dioxins, and furans. Starting in embryonic life, humans are constantly exposed to EDCs through air, diet, skin, and water. Fetuses and newborns undergo crucial developmental processes that allow adaptation to the environment throughout life. As developing organisms, they are extremely sensitive to low doses of EDCs. Many EDCs can cross the placental barrier and reach the developing fetal organs. In addition, newborns can be exposed to EDCs through breastfeeding or formula feeding. Pre- and postnatal exposure to EDCs may increase the risk of childhood diseases by disrupting the hormone-mediated processes critical for growth and development during gestation and infancy. This review discusses evidence of the relationship between pre- and postnatal exposure to several EDCs, childbirth, and neurodevelopmental outcomes. Available evidence suggests that pre- and postnatal exposure to certain EDCs causes fetal growth restriction, preterm birth, low birth weight, and neurodevelopmental problems through various mechanisms of action. Given the adverse effects of EDCs on child development, further studies are required to clarify the overall associations.

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

Has Regulatory Action Reduced Human Exposure to Flame Retardants?

Flame retardant (FR) exposure has been linked to several environmental and human health effects. Because of this, the production and use of several FRs are regulated globally. We reviewed the available records of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDDs) in human breast milk from literature to evaluate the efficacy of regulation to reduce the exposure of FRs to humans. Two-hundred and seven studies were used for analyses to determine the spatial and temporal trends of FR exposure. North America consistently had the highest concentrations of PBDEs, while Asia and Oceania dominated HBCDD exposure. BDE-49 and -99 indicated decreasing temporal trends in most regions. BDE-153, with a longer half-life than the aforementioned isomers, typically exhibited a plateau in breast milk levels. No conclusive trend could be established for HBCDD, and insufficient information was available to determine a temporal trend for BDE-209. Breakpoint analyses indicated a significant decrease in BDE-47 and -99 in Europe around the time that regulation has been implemented, suggesting a positive effect of regulation on FR exposure. However, very few studies have been conducted globally (specifically in North America) after 2013, during the time when the most recent regulations have been implemented. This meta-analysis provides insight into global trends in human exposure to PBDEs and HBCDD, but the remaining uncertainty highlights the need for ongoing evaluation and monitoring, even after a compound group is regulated.

7,10,13,16-Docosatetraenoic acid impairs neurobehavioral development by increasing reactive oxidative species production in Caenorhabditis elegans

AIMS

To investigate human breast milk (HBM) lipids that may adversely affect infant neurodevelopment.

MAIN METHODS

We performed multivariate analyses that combined lipidomics and psychologic Bayley-III scales to identify which HBM lipids are involved in regulating infant neurodevelopment. We observed a significant moderate negative correlation between 7,10,13,16-docosatetraenoic acid (omega-6, C₂₂H₃₆O₂, the common name adrenic acid, AdA) and adaptive behavioral development. We further studied the effects of AdA on neurodevelopment by using Caenorhabditis elegans (C. elegans) as a model. Worms from larval stages L1 to L4 were supplemented with AdA at 5 nominal concentrations (0 μM [control], 0.1 μM, 1 μM, 10 μM, and 100 μM) and subjected to behavioral and mechanistic analyses.

KEY FINDINGS

Supplementation with AdA from larval stages L1 to L4 impaired neurobehavioral development, such as locomotive behaviors, foraging ability, chemotaxis behavior, and aggregation behavior. Furthermore, AdA upregulated the production of intracellular reactive oxygen species. AdA-induced oxidative stress blocked serotonin synthesis and serotoninergic neuron activity and inhibited expression of daf-16 and the daf-16-regulated genes mtl-1, mtl-2, sod-1, and sod-3, resulting in attenuation of the lifespan in C. elegans.

SIGNIFICANCE

Our study reveals that AdA is a harmful HBM lipid that may have adverse effects on infant adaptive behavioral development. We believe this information may be critical for AdA administration guidance in children's health care.

Potential Health Risk to Brazilian Infants by Polybrominated Diphenyl Ethers Exposure via Breast Milk Intake

Polybrominated diphenyl ethers (PBDEs) are ubiquitous flame retardants and are environmentally persistent. PBDEs show endocrine disruption, neurotoxicity, and lower birth weight in infants, and their human body burden has become a public health concern. The infants' exposure begins in the prenatal period and continues via breast milk ingestion, although, little is known about the factors that may influence this exposure. In this study, PBDE levels in Brazilian breast milk were assessed in 200 lactating women. The risk assessment of infants' exposure to PBDE was performed through the estimated daily intake (EDI) calculation. The geometric mean (GM) of ∑_PBDEs levels was 2.33 (0.14-6.05) ng/g wet weight. At least one PBDE congener was detected in the samples, and the 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) showed a 100% of detection rate (GM of 1.05 ng/g). Location of residence, maternal level education, monthly salary, and race were positively associated with PBDE levels (p < 0.05). The EDI of BDE-47 was higher in Belo Horizonte (8.29 ng/kg/day) than in Viçosa (6.36 ng/kg/day), as well as for the ∑_PBDEs (19.77 versus 12.78 ng/kg/day) (p < 0.05). Taking the high detection rate of PBDEs in breast milk and their toxicity, continuous studies on infant exposure, fetal growth, and child neurodevelopment are requested.

Triiodothyronine or Antioxidants Block the Inhibitory Effects of BDE-47 and BDE-49 on Axonal Growth in Rat Hippocampal Neuron-Glia Co-Cultures

We previously demonstrated that polybrominated diphenyl ethers (PBDEs) inhibit the growth of axons in primary rat hippocampal neurons. Here, we test the hypothesis that PBDE effects on axonal morphogenesis are mediated by thyroid hormone and/or reactive oxygen species (ROS)-dependent mechanisms. Axonal growth and ROS were quantified in primary neuronal-glial co-cultures dissociated from neonatal rat hippocampi exposed to nM concentrations of BDE-47 or BDE-49 in the absence or presence of triiodothyronine (T3; 3-30 nM), N-acetyl-cysteine (NAC; 100 µM), or α-tocopherol (100 µM). Co-exposure to T3 or either antioxidant prevented inhibition of axonal growth in hippocampal cultures exposed to BDE-47 or BDE-49. T3 supplementation in cultures not exposed to PBDEs did not alter axonal growth. T3 did, however, prevent PBDE-induced ROS generation and alterations in mitochondrial metabolism. Collectively, our data indicate that PBDEs inhibit axonal growth via ROS-dependent mechanisms, and that T3 protects axonal growth by inhibiting PBDE-induced ROS. These observations suggest that co-exposure to endocrine disruptors that decrease TH signaling in the brain may increase vulnerability to the adverse effects of developmental PBDE exposure on axonal morphogenesis.