Organohalogens are persistent organic pollutants that have a wide range of chemical application. There is growing evidence that several of these chemical compounds interfere with human development in various ways. The aim of this review is to provide an update on the relationship between various persistent organic pollutants and childhood neurodevelopmental outcome from studies from the past 10 years. This review focuses on exposure to polychlorinated biphenyls (PCBs), hydroxylated PCBs (OH-PCBs), polybrominated diphenyl ethers (PBDEs) and dichlorodiphenyldichloroethylene (DDE), and in addition on exposure to phthalates, bisphenol A, and perfluorinated compounds and their associations with neurodevelopmental outcome in childhood, up to 18 years of age. This review shows that exposure to environmental chemicals affects neurodevelopmental outcome in children. Regarding exposure to PCBs and OH-PCBs, most studies report no or inverse associations with neurodevelopmental outcomes. Regarding exposure to PBDEs, lower mental development, psychomotor development and IQ were found at preschool age, and poorer attention at school age. Regarding exposure to DDE, most studies reported inverse associations with outcome, while others found no associations. Significant relations were particularly found at early infancy on psychomotor development, on attention and ADHD, whereas at school age, no adverse relationships were described. Additionally, several studies report gender-related vulnerability. Future research should focus on the long-term effects of prenatal and childhood exposure to these environmental chemicals, on sex-specific and combined exposure effects of environmental chemicals, and on possible mechanisms by which these chemicals have their effects on neurodevelopmental and behavioral outcomes.

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Polychlorinated biphenyls (PCBs) are environmental chemicals which are potentially toxic to the developing brain. Their hydroxylated metabolites (OH-PCBs) are suggested to be even more toxic. Knowledge about the health effects of prenatal OH-PCB exposure is limited. We aimed to determine whether prenatal background exposure to PCBs and OH-PCBs is associated with neurological functioning in 3-month-old boys and girls. In a Dutch observational cohort study, we measured 10 PCBs and 6 OH-PCBs in maternal blood samples of 98 pregnant women. We assessed their infants neurologically with Touwen examination at 3 months and calculated an Optimality Score (OS, range 0-53, low-high optimality). We calculated correlation coefficients between compound levels and OS. Subsequently, we tested whether levels were associated with specific clusters and whether levels differed between infants with "normal" (dysfunction on ≤1 cluster) and "non-optimal" development (dysfunction on ≥2 clusters). The mean OS was 48 (range 44-52). Higher exposure to PCB-146 correlated significantly with higher OS (r = 0.209; p = 0.039). In boys, higher exposure to 4-OH-PCB-107 correlated with lower OS (r = -0.305; p = 0.030). Higher exposure to 9 PCBs and the sum of all PCBs was associated with better visuomotor and/or better sensorimotor function. Infants classified as "non-optimal" (n = 36) had significantly lower prenatal exposure to 6 PCBs and the sum of all PCBs (p < 0.05) compared with infants classified as "normal" (n = 62). In conclusion, higher prenatal exposure to Dutch background PCB levels is associated with better neurological functioning in 3-month-old infants. Prenatal exposure to 4-OH-PCB-107 is associated with less optimal neurological functioning in boys.

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Objective: To obtain reference data on the early motor repertoire of very preterm infants compared with healthy term infants at three months' post-term age. Study design: In this observational study, using Prechtl's method on the assessment of the early motor repertoire, we compared the quality of fidgety movements and the concurrent motor optimality scorerevised of infants with a gestational age <30 weeks and/or a birth weight <1000 g with healthy infants with a gestational age of 37e42 weeks. Results: One hundred eighty very preterm and 180 healthy term infants participated. The median motor optimality scores -revised of very preterm infants were significantly lower in comparison to those of term infants, with scores of 24 (25th-75th percentiles: 23e26) and 26 (25th-75th percentiles: 26e28), respectively. Fidgety movements were aberrant (abnormal or absent) more often in very preterm infants than in term infants. The odds ratio was 4.59 (95% CI, 1.51e13.92). Compared with term infants, very preterm infants had poorer scores on the subscales age-adequate movement repertoire, observed postural patterns, and movement character with odds ratios 2.97. We found no differences regarding observed movement patterns. Conclusion:This study provides reference data on the early motor repertoire of very preterm and healthy term infants. It demonstrates that the early motor repertoire of very preterm infants is poorer than that of term infants, a finding consistent with existing knowledge that prematurity increases the risk of poor neurodevelopment.

Prenatal background exposure to several POPs can influence neuropsychological outcomes in 13- to 15-year-old Dutch adolescents, although exposure to most compounds does not have clinically relevant consequences at adolescence.

Several chemical compounds are resistant to degradation and end up in the food chain. One group of these chemicals is polychlorinated biphenyls (PCBs) which are used as flame retardants and plasticizers. Although PCBs were banned several decades ago, PCBs are still found in environmental media, including in the body of humans. PCBs are transferred from mother to fetus via the placenta during pregnancy. Considering that the prenatal period is a sensitive period during which essential developmental processes take place, exposure to environmental chemicals might have considerable and permanent consequences for outcomes in later life. The aim of this review is to provide an update on the latest insights on the effects of prenatal exposure to PCBs on neurological, sexual and pubertal development in children. We give an overview of recent literature, and discuss it in the light of the findings in a unique Dutch birth cohort, with data on both neurological and pubertal development into adolescence. The findings in the studies included in this review, together with the findings in the Dutch cohort, demonstrate that prenatal exposure to PCBs can interfere with normal child development, not only during the perinatal period, but up to and including adolescence. Higher prenatal exposure to PCBs was found to be both negatively and positively associated with neurodevelopmental outcomes. Regarding pubertal development, higher prenatal PCB exposure was found to be associated with more advanced pubertal development, also in the Dutch cohort, whereas other studies also found delayed pubertal development. These findings raise concern regarding the effects of man-made chemical compounds on child development. They further contribute to the awareness of how environmental chemical compounds can interfere with child development and negatively influence healthy ageing.

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