Prenatal and childhood phthalate exposure and attention deficit hyperactivity disorder traits in child temperament: A 12-year follow-up birth cohort study

Early childhood exposures to phthalates in association with attention-deficit/hyperactivity disorder behaviors in middle childhood and adolescence in the ReCHARGE study

BACKGROUND

Early-life exposure to phthalates alters behaviors in animals. However, epidemiological evidence on childhood phthalate exposure and attention-deficit/hyperactivity disorder (ADHD) behaviors is limited.

METHODS

This study included 243 children from the ReCHARGE (Revisiting Childhood Autism Risks from Genetics and Environment) study, who were previously classified as having autism spectrum disorder (ASD), developmental delay, other early concerns, and typical development in the CHARGE case-control study. Twenty phthalate metabolites were measured in spot urine samples collected from children aged 2-5 years. Parents reported on children's ADHD symptoms at ages 8-18 years using Conners-3 Parent Rating Scale. Covariate-adjusted negative binomial generalized linear models were used to investigate associations between individual phthalate metabolite concentrations and raw scores. Weighted quantile sum (WQS) regression with repeated holdout validation was used to examine mixture effects of phthalate metabolites on behavioral scores. Effect modification by child sex was evaluated.

RESULTS

Among 12 phthalate metabolites detected in >75% of the samples, higher mono-2-heptyl phthalate (MHPP) was associated with higher scores on Inattentive (β per doubling = 0.05, 95% confidence interval [CI]: 0.02, 0.08) and Hyperactive/Impulsive scales (β = 0.04, 95% CI: 0.00, 0.07), especially among children with ASD. Higher mono-carboxy isooctyl phthalate (MCiOP) was associated with higher Hyperactivity/Impulsivity scores (β = 0.07, 95% CI: -0.01, 0.15), especially among typically developing children. The associations of the molar sum of high molecular weight (HMW) phthalate metabolites and a phthalate metabolite mixture with Hyperactivity/Impulsivity scores were modified by sex, showing more pronounced adverse associations among females.

CONCLUSION

Exposure to phthalates during early childhood may impact ADHD behaviors in middle childhood and adolescence, particularly among females. Although our findings may not be broadly generalizable due to the diverse diagnostic profiles within our study population, our robust findings on sex-specific associations warrant further investigations.

Postnatal nighttime light exposure and infant temperament at age 12 months: mediating role of genus Akkermansia

The gut microbiome has been reported to be associated with nighttime light (NTL) exposure and temperament. However, the specific role of infant gut microbiome plays in NTL exposure and temperament is unclear. This study investigated the potential mediating role of infants' gut microbiome in correlations between NTL exposure and temperament. Demographic information, stool samples, and temperament scores were collected from 40 infants. Temperament was evaluated using the Infants Behavior Questionnaire-Revised (IBQ-R). The gut microbiota was analyzed using 16S rRNA sequencing. Cumulative and lagged effects of NTL exposure were calculated based on residential address (NTLpoint) and a concentric 1 km radius buffer zone around the address (NTL1000m), respectively. Mediation models were utilized for assessing the mediating effects of the gut microbiome. The gut microbiome of infants with higher fear scores was characterized by a higher abundance of Akkermansia and Clostridium_sensu_stricto_1 and a lower abundance of Bacteroides. Mediation models indicated Akkermansia played a full mediating role in associations between NTLpoint, NTL1000m and fear in specific time periods. Genus Akkermansia explained 24.46% and 33.50% of associations between fear and cumulative exposure to NTLpoint and NTL1000m, respectively. This study provides evidence for the mediating role of Akkermansia between NTL exposure and fear. However, further experimental is required to elucidate the mechanisms through which the gut microbiome mediates between NTL exposure and temperament in infants.

Phthalate Exposure and Neurotoxicity in Children: A Systematic Review and Meta-analysis

Objectives: This systematic review aims to assess the relationship between prenatal and childhood exposure to phthalates and neurodevelopmental outcomes, identifying periods of heightened susceptibility. Data sources considered studies examining repeated phthalate exposure during pregnancy and childhood on neurodevelopment. Methods: Evaluation included bias risk and study quality criteria. Evidence was synthesized by groups of low and high phthalate molecular weight and exposure measured prenatally and postnatally and outcome measured in childhood. Beta coefficients and their standard errors were extracted, leading to meta-analyses of various neurodevelopmental outcomes: cognition, motor skills, language, behavior, and temperament. Results: Eleven pregnancy and birth cohort studies were identified as relevant. For each phthalate group and outcome combination, there was low or very low evidence of an association, except for prenatal and postnatal phthalate exposure and behavioral development and postnatal exposure and cognition. Conclusion: The estimated effects sizes were relatively small and strong evidence for periods of heightened susceptibility could not be elucidated. No distinction between phthalates of low molecular weight and those of high molecular weight with regards to the outcomes was found.

Early childhood exposure to environmental phenols and parabens, phthalates, organophosphate pesticides, and trace elements in association with attention deficit hyperactivity disorder (ADHD) symptoms in the CHARGE study

BACKGROUND

A growing body of literature investigated childhood exposure to environmental chemicals in association with attention-deficit/hyperactivity disorder (ADHD) symptoms, but limited studies considered urinary mixtures of multiple chemical classes. This study examined associations of concurrent exposure to non-persistent chemicals with ADHD symptoms in children diagnosed with autism spectrum disorder (ASD), developmental delay (DD), and typical development (TD).

METHODS

A total of 549 children aged 2-5 years from the Childhood Autism Risks from Genetics and Environment (CHARGE) case-control study were administered the Aberrant Behavior Checklist (ABC). This study focused on the ADHD/noncompliance subscale and its two subdomains (hyperactivity/impulsivity, inattention). Sixty-two chemicals from four classes (phenols/parabens, phthalates, organophosphate pesticides, trace elements) were quantified in child urine samples, and 43 chemicals detected in > 70% samples were used to investigate their associations with ADHD symptoms. Negative binomial regression was used for single-chemical analysis, and weighted quantile sum regression with repeated holdout validation was applied for mixture analysis for each chemical class and all chemicals. The mixture analyses were further stratified by diagnostic group.

RESULTS

A phthalate metabolite mixture was associated with higher ADHD/noncompliance scores (median count ratio [CR] = 1.10; 2.5th, 97.5th percentile: 1.00, 1.21), especially hyperactivity/impulsivity (median CR = 1.09; 2.5th, 97.5th percentile: 1.00, 1.25). The possible contributors to these mixture effects were di-2-ethylhexyl phthalate (DEHP) metabolites and mono-2-heptyl phthalate (MHPP). These associations were likely driven by children with ASD as these were observed among children with ASD, but not among TD or those with DD. Additionally, among children with ASD, a mixture of all chemicals was associated with ADHD/noncompliance and hyperactivity/impulsivity, and possible contributors were 3,4-dihydroxy benzoic acid, DEHP metabolites, MHPP, mono-n-butyl phthalate, and cadmium.

CONCLUSIONS

Early childhood exposure to a phthalate mixture was associated with ADHD symptoms, particularly among children with ASD. While the diverse diagnostic profiles limited generalizability, our findings suggest a potential link between phthalate exposure and the comorbidity of ASD and ADHD.

Prenatal Di-methoxyethyl phthalate exposure impairs cortical neurogenesis and synaptic activity in the mice

Di-methoxyethyl phthalate (DMEP) is a well-known environmentally prevalent endocrine disruptor and may be associated with neurodevelopmental disorders including attention deficit/hyperactivity disorder and intellectual disability. However, the regulatory mechanisms leading to these neurodevelopmental disorders are still poorly understood. Here, we demonstrate that prenatal DMEP exposure causes abnormal brain morphology and function in the mice. DMEP (50 mg/kg) was chronically administered to pregnant mice orally once a day starting on embryonic day 0 (E0) to breast-feeding cessation for the fetus. We found that prenatal DMEP exposure significantly reduced the number of neurons in the parietal cortex by impairing neurogenesis and gliogenesis during the developing cortex. Moreover, we found that prenatal DMEP exposure impaired dendritic spine architectures and synaptic activity in the parietal cortex. Finally, prenatal DMEP exposure in mice induces hyperactivity and reduces anxiety behaviors. Altogether, our study demonstrates that prenatal DMEP exposure leads to abnormal behaviors via impairment of neurogenesis and synaptic activity.

The role of estrogen receptors (ERs)-Notch pathway in thyroid toxicity induced by Di-2-ethylhexyl phthalate (DEHP) exposure: Population data and in vitro studies

BACKGROUND

This study aimed to assess the exposure level and risk of Di-2-ethylhexyl Phthalate (DEHP) among adults in Jilin Province, China, clarify the impact of DEHP on human thyroid function, and to explore the role of estrogen receptors (ERs)-Notch signaling pathway in the effect of DEHP metabolites on thyroid hormones based on population data and in vitro experiments.

METHODS

312 adults participated in this study. Urinary DEHP metabolites were determined by high performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS). Two pharmacokinetic models were used to evaluate the estimated daily intake (EDI) and hazard quotient (HQ) of the adults. Multiple linear regression and mediating effect models were used to evaluate the target associations. In cell experiments, thyroid follicular epithelial (Nthy-ori3-1) cells were exposed to mono (2-ethylhexyl) phthalate (MEHP) for testing. The inhibitions of ERα and Notch pathway were conducted by siRNA and Notch pathway inhibitor DAPT.

RESULTS

The detection rate of five DEHP metabolites was 97.1∼100.0%. The HQ value of 0.3% of adults was higher than 1. The levels of urinary DEHP metabolites were significantly correlated with thyrotropin (TSH), thyrotropin-releasing hormone (TRH), total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3) and free thyroxine (FT4) and gene (estrogen receptor α (ERα), Notch1, Dll4) levels. The ERα-Notch pathway played a mediating role in the association between DEHP metabolite levels and FT4. The cell results showed, the levels of FT3 and FT4 in cell supernatant decreased after MEHP exposure, and the downward trend was reversed after ERα and notch pathways were inhibited, notch pathway genes also decreased after ERα inhibition.

CONCLUSION

Adults in the Jilin Province of China were widely exposed to DEHP. ERs-Notch pathway played an important role in the effect of DEHP metabolites on thyroid hormones.

Maternal concentrations of phthalates and Attention-Deficit Hyperactivity Disorder (ADHD-) related symptoms in children aged 2 to 4 years from Odense child cohort

BACKGROUND

Phthalates are endocrine disrupting chemicals used in everyday consumer products. Several epidemiological studies have examined the association between prenatal phthalate concentration and Attention-Deficit Hyperactivity Disorder (ADHD) in offspring, but the findings have been inconclusive.

OBJECTIVES

To investigate the association between maternal urinary concentrations of phthalate metabolites during pregnancy and ADHD related symptoms in children at 2 to 4 years in a large prospective cohort.

METHODS

In the Odense Child Cohort from Denmark were women recruited in early pregnancy from 2010 to 2012. Phthalate concentrations were measured in urine samples collected in 3rd trimester and separated into low and high weight phthalates. Parents filled in the Child Behavior Checklist for ages 1.5 to 5 years (CBCL/1½-5), including a 6-item ADHD symptom scale at children aged 2 to 4 years. Data were analysed by use of adjusted negative binomial regression.

RESULTS

A total of 658 mother-child pairs were included. Urinary phthalate metabolite concentrations were generally low compared to previous cohorts. A doubling in maternal concentration of the low-weighted phthalate metabolite MCPP was significantly associated with lower ADHD symptoms score in children (IRR: 0.95 (95 % CI 0.91-0.98)), strongest in girls (IRR: 0.92 (0.87-0.98)). Sex differences were observed. High maternal phthalate metabolite concentrations were associated with lower ADHD symptom score in girls, significant trends across tertile of MCPP and MnBP (p = 0.018, p = 0.038, respectively). In boys, maternal concentrations of high-molecular-weight phthalates (MBzP, ∑DiNP and ∑DEHP) were associated with an almost significantly higher ADHD symptom score (IRR for a doubling in concentration: 1.04 (95 % CI: 0.99-1.10), IRR: 1.05 (95 % CI: 0.97-1.13), IRR: 1.04 (95 % CI: 0.99-1.10), respectively).

CONCLUSION

Maternal concentration of the low-weighted phthalate metabolite MCPP was significantly associated with a lower ADHD symptom score in children, strongest in girls. Maternal concentrations of high-molecular-weight phthalates were associated with non-significant increase in ADHD symptom score in boys.

Associations of urinary phthalate metabolites with household environments among mothers and their preschool-age children

Phthalates have become a matter of public health concern due to their extensive use worldwide and negative health effects. The evaluation of potential sources of phthalate exposure is crucial to design prevention strategies, especially for vulnerable populations. This study included 528 mother-child pairs in the Taiwan Mother Infant Cohort Study who were followed up at ages 3-6 years between 2016 and 2020. Each mother was interviewed by using a structured questionnaire containing questions on demographic characteristics and household environment factors, such as the use of plastic food packaging, residential visible mold, insecticide sprays, and electric mosquito repellents. Eleven phthalate metabolites were analyzed in urine samples simultaneously collected from the mother-child pairs. The phthalate metabolite urinary concentrations were higher among the children than among their mothers, except those of mono-ethyl phthalate (MEP) and mono-2-ethylhexyl phthalate (MEHP). Multiple linear regression analyses showed that urine samples collected during the summer showed higher concentrations of phthalate metabolites than those collected during the winter. Family income levels had negative associations with the concentrations of MnBP and metabolites of di-2-ethylhexyl phthalate (DEHP) in children. The use of plastic food packaging was positively associated with mono-n-butyl phthalate (MnBP) and metabolites of DEHP in mothers. Residential visible mold or mold stains were significantly associated with higher MnBP and DEHP metabolite concentrations in children. The use of insecticide sprays was positively associated with MnBP concentrations in children. Significant associations between household environmental factors and phthalate exposure were mostly found in children, potentially indicating different exposure pathways between mothers and their children. Findings from this study provide additional information for the design of prevention strategies to protect the health of children and women.

Urinary di-(2-ethylhexyl) phthalate metabolites are independently related to serum neurofilament light chain, a biomarker of neurological diseases, in adults: results from NHANES 2013-2014

Di (2-ethylhexyl) phthalate (DEHP) is a chemical commonly used in the manufacturing of plastics and can pose human health risks, including endocrine disruption, reproductive toxicity, and potential carcinogenic effects. Children may be particularly vulnerable to the harmful effects of DEHP. Early exposure to DEHP has been linked to potential behavioral and learning problems. However, there are no reports to date on whether DEHP exposure in adulthood has neurotoxic effects. Serum neurofilament light chain (NfL), a protein released into the blood after neuroaxonal damage, has been shown to be a reliable biomarker for many neurological diseases. To date, no study has examined the relationship between DEHP exposure and NfL. For the present study, we selected 619 adults (aged ≥ 20 years) from the 2013-2014 National Health and Nutrition Examination Survey (NHANES) to examine the association between urinary DEHP metabolites and serum NfL. We reported higher urinary levels of ln-mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), ln-mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and ln-mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), and ln-ΣDEHP levels were associated with higher serum levels of ln-NfL (ΣDEHP: β-coefficient = 0. 075; S.E. = 0.026; P = 0.011). When we divided ΣDEHP into quartiles, mean NfL concentrations increased with quartiles of MEHHP (P for trend = 0.023). The association was more pronounced in males, non-Hispanic white race, higher income, and BMI < 25. In conclusion, higher DEHP exposure was positively associated with higher serum NfL in adults from NHANES 2013-2014. If this finding is causal, it is possible that DEHP exposure in adulthood may also induce neurological damage. Although the causality of this observation and the clinical significance are uncertain, our findings suggest that additional research is needed on DEHP exposure, serum NfL, and neurological disease in adults.

Co-exposure to toxic metals and phthalates in pregnant women and their children's mental health problems aged four years - Taiwan Maternal and Infant Cohort Study (TMICS)

BACKGROUND

Childhood and adolescent mental health problems may increase the global burden of disease. Neurotoxic metals are associated with inflammation and cytotoxicity in the brain. In addition, prenatal phthalate ester (PAE) exposure is associated with cognitive function deficits. However, the effect of co-exposure to toxic metals, PAEs, and their association with child behavior is less well studied. Hence, we aimed to investigate prenatal co-exposure to the metals and PAEs and the consequent behavioral outcomes in early childhood.

METHODS

We followed pregnant women and their newborns from the Taiwan Maternal and Infant Cohort Study between 2015 and 2017, with a focus on women from the central, southern, and eastern areas of Taiwan. We quantified maternal urinary concentrations of metals and metabolites of PAEs as surrogates of prenatal exposure. We recorded the Child Behavior Checklist scores according to caregiver reports at 4 years of age, and identified Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)-oriented problems.

RESULTS

Ultimately, 408 children were included in the statistical analysis. Maternal urinary copper levels were significantly associated with depressive problems (odds ratio [OR] = 2.13) in children. Maternal urinary concentrations of mono-n-butyl phthalate (MnBP) and mono-isobutyl phthalate (MiBP) were also significantly associated with depressive symptoms (odds ratio [OR] = 1.51 and 1.53, respectively). Further analysis considering prenatal co-exposure to metals and PAEs showed that co-exposure to these materials was significantly associated with autism spectrum problems (OR = 3.11).

CONCLUSIONS

We observed that prenatal single exposure or co-exposure to metals and PAEs may play a role in some DSM-5-oriented problems in children at 4 years of age. Reduction of exposure to toxic metals and PAEs in pregnancy is suggested to prevent increased mental health problems in children.

Associations between maternal phthalate exposure and neonatal neurobehaviors: The Taiwan maternal and infant cohort study (TMICS)

Previous studies have shown associations between prenatal phthalate exposure and neurobehavioral changes in children. However, few studies have focused on neonatal neurobehavioral development. This study aimed to examine the associations between prenatal phthalate exposure and neonatal neurobehavioral development in the early days of life after birth. This cohort study included 283 mother-infant pairs who participated in the Taiwan Mother Infant Cohort Study during 2012-2015. Each mother was interviewed, and urine samples were collected during the third trimester of pregnancy (weeks 29-40). Eleven common phthalate metabolites in maternal urine were analyzed. The Chinese version of the Neonatal Neurobehavioral Examination was used to evaluate early infant neurobehavioral development within five days of birth. We performed multiple linear regressions to explore the associations between phthalate exposure and neonatal neurobehavioral development. Sex differences in the association between phthalate metabolites and neonatal neurobehaviors were noted. Among girls, tertiles of phthalate metabolite concentrations were associated with worse behavioral responses and tone and motor patterns in the high-molecular-weight phthalate (HMW) and low-molecular-weight phthalate (LMW) groups. Girls in the highest tertile of di-2-ethylhexyl phthalate (DEHP) and mono-isobutyl phthalate (MiBP) had a negative association with tone and motor patterns. Girls in the highest tertile of mono-n-butyl phthalate (MnBP) and MiBP showed a negative association with behavioral responses. In contrast, tertiles of phthalate metabolite exposure were associated with improved neurobehaviors in mono-methyl phthalate (MMP) among boys. The highest tertile of MMP was positively associated with behavioral responses, primitive reflexes, and tone and motor patterns. Our findings suggest that maternal phthalate exposure affects neonatal neurobehavioral development in a sex-specific manner. Despite the relatively small sample size, our findings add to the existing research linking maternal phthalate exposure to neonatal neurobehavioral development. Additional research is needed to determine the potential long-term effects of prenatal phthalate exposure on children.

Early childhood exposure to environmental phenols and parabens, phthalates, organophosphate pesticides, and trace elements in association with attention deficit hyperactivity disorder (ADHD) symptoms in the CHARGE study

Background

Agrowing body of literature investigated childhood exposure to environmental chemicals in association with attention deficit hyperactivity disorder (ADHD) symptoms, but limited studies considered urinary mixtures of multiple chemical classes. This study examined associations of concurrent exposure to non-persistent chemicals with ADHD symptoms in children diagnosed with autism spectrum disorder (ASD), developmental delay, and typical development.

Methods

A total of 574 children aged 2-5 years from the Childhood Autism Risks from Genetics and Environment (CHARGE) case-control study was administered the Aberrant Behavior Checklist (ABC). This study focused on the Hyperactivity subscale and its two subdomains (hyperactivity/impulsivity, inattention). Sixty-two chemicals from four classes (phenols/parabens, phthalates, organophosphate pesticides, trace elements) were quantified in child urine samples, and 43 chemicals detected in >70% samples were used in statistical analyses. Weighted quantile sum regression for negative binomial outcomes with repeated holdout validation was performed to investigate covariate-adjusted associations between mixtures and ABC scores in 574 children. The mixture analyses were further restricted to 232 children with ASD.

Results

Phthalate metabolite mixtures, weighted for mono-n-butylphthalate (MNBP), mono-2-heptyl phthalate, and mono-carboxy isononyl phthalate, were associated with the Hyperactivity subscale (mean incidence rate ratio [mIRR] = 1.11; 2.5th, 97.5th percentile: 1.00, 1.23), especially the hyperactivity/impulsivity subdomain (mIRR = 1.14; 2.5th, 97.5th percentile: 1.06, 1.26). These associations remained similar after restricting to children with ASD. The inattention subdomain was associated with a phenols/parabens mixture, weighted for several parabens and bisphenols (mIRR = 1.13; 2.5th, 97.5th percentile: 1.00, 1.28) and a total mixture, weighted for 3,4-dihydroxy benzoic acid, MNBR and mono-(2-ethyl-5-carboxypentyl) phthalate (mIRR = 1.11; 2.5th, 97.5th percentile: 1.01,1.25) only among children with ASD.

Conclusions

Concurrent exposure to phthalate mixtures was associated with hyperactivity in early childhood. Though causal inference cannot be made based on our cross-sectional findings, this study warrants further research on mixtures of larger number of chemicals from multiple classes in association with ADHD-related behaviors in young children.

Impact of endocrine disrupting chemicals on neurodevelopment: the need for better testing strategies for endocrine disruption-induced developmental neurotoxicity

INTRODUCTION

Brain development is highly dependent on hormonal regulation. Exposure to chemicals disrupting endocrine signaling has been associated with neurodevelopmental impairment. This raises concern about exposure to the suspected thousands of endocrine disruptors, and has resulted in efforts to improve regulation of these chemicals. Yet, the causal links between endocrine disruption and developmental neurotoxicity, which would be required for regulatory action, are still largely missing.

AREAS COVERED

In this review, we illustrate the importance of two endocrine systems, thyroid hormone and retinoic acid pathways, for neurodevelopment. We place special emphasis on TH and RA synthesis, metabolism, and how endocrine disrupting chemicals known or suspected to affect these systems are associated with developmental neurotoxicity.

EXPERT OPINION

While it is clear that neurodevelopment is dependent on proper hormonal functioning, and evidence is increasing for developmental neurotoxicity induced by endocrine disrupting chemicals, this is not grasped by current chemical testing. Thus, there is an urgent need to develop test methods detecting endocrine disruption in the context of neurodevelopment. Key to this development is further mechanistic insights on the involvement of endocrine signaling in neurodevelopment as well as increased support to develop and validate new test methods for the regulatory context.

Interrelationships among growth hormone, thyroid function, and endocrine-disrupting chemicals on the susceptibility to attention-deficit/hyperactivity disorder

Abnormal growth hormones and thyroid function may be linked to pathophysiology of attention-deficit/hyperactivity disorder (ADHD). Phthalates and bisphenol-A (BPA), two endocrine-disrupting chemicals (EDCs), may affect the human endocrine system. In this study, we aimed to perform a comprehensive investigation of whether growth hormone, thyroid function, and EDCs exhibited differential levels between ADHD patients and healthy controls. In total, 144 children with ADHD and 70 healthy control subjects were enrolled. Their endocrine systems were evaluated using the serum levels of insulin-like growth factor-1 (IGF-1), IGF-binding protein-3 (IGFBP-3), thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), and Free T4. The urinary levels of EDCs, including monoethyl phthalate (MEP), mono-methyl phthalate (MMP), monoethylhexyl phthalate (MEHP), mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBzP), and BPA, were also examined. Patients with ADHD had lower IGF-1 levels than healthy controls (p = 0.003), but we observed no significant difference in IGFBP-3, TSH, T3, T4, or Free T4. Compared to the control group, patients with ADHD demonstrated higher MEHP levels (p = 0.043), MnBP (p = 0.033), and MBzP (p = 0.040). Furthermore, MEHP levels (p < 0.001) and BPA levels (p = 0.041) were negatively correlated with IGF-1 levels, while IGF-1 levels were negatively correlated with principal components consisting of ADHD clinical symptoms and neuropsychological performance variables. We suggest that MEHP exposure may be associated with decreased serum levels of IGF-1 and increased risk of ADHD. The mechanism underlying this association may be important for protecting children from environmental chemicals that adversely affect neurodevelopment.

Phasing out DEHP from plastic indwelling medical devices used for intensive care: Does it reduce the long-term attention deficit of critically ill children?

BACKGROUND

Children who have been critically ill face long-term developmental impairments. Iatrogenic exposure to di(2-ethylhexyl)phthalate (DEHP), a plasticizer leaching from plastic indwelling medical devices used in the pediatric intensive care unit (PICU), has been associated with the pronounced attention deficit observed in children 4 years after critical illness. As concerns about DEHP toxicity increased, governmental authorities urged the phase out of DEHP in indwelling medical devices and replacement with alternative plasticizers. We hypothesized that exposure to DEHP decreased over the years, attenuating the pronounced long-term attention deficit of these vulnerable children.

METHODS

We compared plasma concentrations of 3 oxidative DEHP metabolites (5cx-MEPP, 5OH-MEHP, 5oxo-MEHP) on the last PICU day in 216 patients who participated in the Tight Glucose Control study (2004-2007) and 334 patients who participated in the PEPaNIC study (2012-2015) and survived PICU stay. Corresponding minimal exposures to these metabolites (plasma concentration multiplied with number of days in PICU) were also evaluated. In patients with 4-year follow-up data, we compared measures of attention (standardized reaction times and consistency). Comparisons were performed with univariable analyses and multivariable linear regression analyses adjusted for baseline risk factors.

RESULTS

In the PEPaNIC patients, last PICU day plasma concentrations of 5cx-MEPP, 5OH-MEHP, 5oxo-MEHP and their sum, and corresponding minimal exposures, were reduced to 17-69% of those in the Tight Glucose Control study (p < 0.0001). Differences remained significant after multivariable adjustment (p ≤ 0.001). PEPaNIC patients did not show better attention than patients in the Tight Glucose Control study, also not after multivariable adjustment for risk factors.

CONCLUSION

Exposure of critically ill children to DEHP in the PICU decreased over the years, but the lower exposure did not translate into improved attention 4 years later. Whether the residual exposure may still be toxic or whether the plasticizers replacing DEHP may not be safe for neurodevelopment needs further investigation.

Effects of Prenatal Phthalate Exposure and Childhood Exercise on Maternal Behaviors in Female Rats at Postpartum: A Role of Oxtr Methylation in the Hypothalamus

Both the detrimental effect of prenatal exposure to di-(2-ethylhexyl)-phthalate (DEHP) and the beneficial effects of physical exercise on brain functions have been reported. The oxytocin pathway has been implicated in the onset of maternal behaviors. Epigenetic modification of the oxytocin receptor gene (OXTR) through DNA methylation has been associated with the pathogenesis of neuropsychiatric disorders. The purpose of this study was to investigate the effects of prenatal DEHP exposure on oxytocin-regulated maternal behaviors and to examine the protective effect of exercise. Pregnant rats (F0) were fed with vehicle or DEHP during gestation and the offspring females (F1) were assessed for their maternal behaviors by pup retrieval test at postpartum. The results showed that reduced pup retrieval activities without significant alteration of stress responses were observed in the prenatally DEHP-exposed females. Prenatal DEHP exposure decreased the expressions of oxytocin, Oxtr mRNA, and oxytocin receptor, and increased Oxtr methylation in the hypothalamus of postpartum female rats. There were no significant effects of exercise on behavioral, biochemical, and epigenetic measurements. These results suggest that prenatal DEHP exposure has a long-term adverse effect on maternal behaviors; Oxtr hyper-methylation may be a potential epigenetic mechanism for this alteration, which cannot be prevented by physical exercise during childhood.

The effects of phthalate ester exposure on human health: A review

Phthalate esters (PAEs) are one of the most widely used plasticizers in polymer products and humans are increasingly exposed to them. The constant exposure to PAEs-contained products has raised some concerns against human health. Thus, the impacts of PAEs and their metabolites on human health require a comprehensive study for a better understanding of the associated risks. Here, we attempt to review eight main health effects of PAE exposure according to the most up-to-date studies. We found that epidemiological studies demonstrated a consistent association between PAE exposure (especially DEHP and its metabolites) and a decrease in sperm quality in males and symptom development of ADHD in children. Overall, we found insufficient evidence and lack of consistency of the association between PAE exposure and cardiovascular diseases (hypertension, atherosclerosis, and CHD), thyroid diseases, respiratory diseases, diabetes, obesity, kidney diseases, intelligence performance in children, and other reproductive system-related diseases (anogenital distance, girl precocious puberty, and endometriosis). Future studies (longitudinal and follow-up investigations) need to thoroughly perform in large-scale populations to yield more consistent and powerful results and increase the precision of the association as well as enhance the overall understanding of potential human health risks of PAEs in long-term exposure.

Gestational and peripubertal phthalate exposure in relation to attention performance in childhood and adolescence

The prevalence of Attention Deficit/Hyperactivity Disorder (ADHD) has been increasing. Research suggests that exposure to endocrine disrupting chemicals such as phthalates may play a role, but studies of in utero phthalate exposure and ADHD-related symptoms beyond early childhood are limited. We investigated associations between measures of in utero phthalate exposure and ADHD symptoms, such as inattention and impulsivity, in childhood (age 6-11 years, n = 221) and in adolescence (age 9-18 years, n = 200), as well as cross-sectional relationships between phthalate exposure and ADHD symptoms in adolescence (n = 491) among participants in the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) cohort. Women provided urine samples up to three times during pregnancy and adolescents provided a urine sample at 9-18 years of age for phthalate metabolite measurement. We administered the Conners' Continuous Performance Test (CPT) when children were age 6-11 years and again at 9-18 years of age. We used multivariable linear regression to examine associations between the geometric mean of phthalate metabolite levels across pregnancy and CPT scores in childhood or adolescence separately, adjusting for age, years schooling (at 9-18 only), maternal education, and specific gravity. Although average in utero phthalate concentrations were not associated with CPT scores in childhood, interquartile range (IQR) increases of in utero MBzP, MCPP, and MBP were associated with 4.2%, 4.7%, and 4.5% (p < 0.05) higher Omissions scores in adolescence, respectively, indicating higher inattention. In utero MiBP levels were also associated with higher Inter-Stimulus Interval (ISI) and Variability scores (5.4% and 5.5% per IQR, p < 0.05) in adolescence. In addition, urinary DEHP metabolite levels during adolescence were cross-sectionally associated with poorer scores on several CPT indices indicating greater inattention. These findings suggest that in utero phthalate exposure may have adverse effects on attention, but these effects may not appear until adolescence, a period of extensive neurodevelopment. Future research investigating the long-term effects of in utero phthalate exposure on attention and ADHD in adolescence, as well as identification of potential mechanisms involved, is needed.

Associations among phthalate exposure, DNA methylation of TSLP, and childhood allergy

BACKGROUND

Dysregulation of thymic stromal lymphopoietin (TSLP) expressions is linked to asthma and allergic disease. Exposure to phthalate esters, a widely used plasticizer, is associated with respiratory and allergic morbidity. Dibutyl phthalate (DBP) causes TSLP upregulation in the skin. In addition, phthalate exposure is associated with changes in environmentally induced DNA methylation, which might cause phenotypic heterogeneity. This study examined the DNA methylation of the TSLP gene to determine the potential mechanism between phthalate exposure and allergic diseases.

RESULTS

Among all evaluated, only benzyl butyl phthalate (BBzP) in the settled dusts were negatively correlated with the methylation levels of TSLP and positively associated with children's respiratory symptoms. The results revealed that every unit increase in BBzP concentration in the settled dust was associated with a 1.75% decrease in the methylation level on upstream 775 bp from the transcription start site (TSS) of TSLP (β =  - 1.75, p = 0.015) after adjustment for child's sex, age, BMI, parents' smoking status, allergic history, and education levels, PM_2.5, formaldehyde, temperature; and relative humidity. Moreover, every percentage increase in the methylation level was associated with a 20% decrease in the risk of morning respiratory symptoms in the children (OR 0.80, 95% CI 0.65-0.99).

CONCLUSIONS

Exposure to BBzP in settled dust might increase children's respiratory symptoms in the morning through decreasing TSLP methylation. Therefore, the exposure to BBzP should be reduced especially for the children already having allergic diseases.

Phthalate pollution: environmental fate and cumulative human exposure index using the multivariate analysis approach

A comprehensive review was performed on the environmental fate, environmental occurrence, toxicity, physical-chemical properties, abiotic and biotic removal and degradation of phthalate esters (PAEs) to compute the overall phthalate exposure and their impact on human beings. The removal and degradation of these wide spread pollutants by abiotic processes such as hydrolysis and photodecomposition are very slow and insignificant. On the other hand, the breakdown of PAEs by microorganisms is considered to be one of the major routes of environmental degradation for these widespread pollutants. Numerous microbial strains have been reported to degrade these compounds under aerobic, anaerobic and facultative conditions. Concurrently, the environmental fate, transport and transformation/degradation of these compounds under natural conditions are highly dependent on their physical and chemical properties. In order to understand the relationship between the concentrations of PAEs of different environmental compartments and human exposure prospects, a novel average phthalate pollution index (PPI) and cumulative phthalate exposure index (PEI) were proposed using the multivariate analysis approach. These indices were computed on the basis of relative importance, environmental occurrence, toxicity, physical-chemical properties, abiotic and biotic removal and degradation of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP) and diethyl-hexyl phthalate (DEHP). At present, the average PPI and cumulative PEI of 29 countries were evaluated using the concentrations of PAEs reported in the literature. These indices signify the overall phthalate pollution, human exposure and their interrelation. According to the index, Slovakia, Canada, Taiwan, Sweden and South Africa are among the top five countries in terms of cumulative phthalate exposure as per the existing data. The exposure percentage of total PAEs significantly varies between 23 and 44% since many environmental compartments are not directly exposed to human beings and they are degraded under natural conditions.

Environmental toxicology wars: Organ-on-a-chip for assessing the toxicity of environmental pollutants

Environmental pollution is a widespread problem, which has seriously threatened human health and led to an increase of human diseases. Therefore, it is critical to evaluate environmental pollutants quickly and efficiently. Because of obvious inter-species differences between animals and humans, and lack of physiologically-relevant microenvironment, animal models and in vitro two-dimensional (2D) models can not accurately describe toxicological effects and predicting actual in vivo responses. To make up the limitations of conventional environmental toxicology screening, organ-on-a-chip (OOC) systems are increasingly developing. OOC systems can provide a well-organized architecture with comparable to the complex microenvironment in vivo and generate realistic responses to environmental pollutants. The feasibility, adjustability and reliability of OCC systems make it possible to offer new opportunities for environmental pollutants screening, which can study their metabolism, collective response, and fate in vivo. Further progress can address the challenges to make OCC systems better investigate and evaluate environmental pollutants with high predictive power.

Phthalates exposure and attention-deficit/hyperactivity disorder in children: a systematic review of epidemiological literature

Epidemiological studies have proven that children mental health can be affected by environmental pollutants which are believed to be visible in the form of psychological disorder later in their childhood. Moreover, the effects of children mental health are evidently clear in the case of phthalates which have been observed to increase psychological disorder, specifically attention-deficit hyperactivity disorder (ADHD). Hence, the present study aims to conduct a systematic review and provide an overview of the existing literature on the association between urinary phthalate metabolite concentrations and ADHD symptoms among children by emphasizing the confounding factors and limitations. Additionally, this review addressed the possible phthalate mechanism insights in human body including its impact on ADHD symptoms. In this case, 16 epidemiological studies (five cross-sectional, nine cohort and two case control studies) that met all the inclusion criteria were selected out of the total of 427 papers screened to show varying quantitative associations between phthalate exposure and ADHD symptoms among children with confounding factors and limitations in the existing studies in regard to the exposure and outcomes. This review also attempted to present possible explanation on phthalate mechanism in children body and its connection on neurodevelopment and ADHD symptom development which remains unclear in most of the studies. Finally, it is highly recommended for further research to carefully design cohort studies from prenatal to later childhood development with a complete sample size in order to understand phthalate impacts on children health.

Gestational and childhood exposure to phthalates and child behavior

BACKGROUND

Early-life phthalate exposures may adversely influence neurodevelopment by disrupting thyroid hormone homeostasis, altering brain lipid metabolism, or reducing gonadal hormone concentrations. Previous literature examining gestational phthalate exposure and child behavior were inconclusive and few prospective studies have examined childhood phthalate exposure, particularly phthalate mixtures. We investigated whether gestational and childhood phthalate exposures were associated with child behavior.

METHODS

We used data from 314 mother-child pairs in the HOME Study, a longitudinal pregnancy and birth cohort that enrolled pregnant women from Cincinnati, Ohio. We quantified urinary concentrations of 11 phthalate metabolites in samples collected twice during gestation from women and six times from their children when they were ages 1, 2, 3, 4, 5, and 8 years. We assessed children's behavior at ages 2, 3, 4, 5, and 8 years using the Behavioral Assessment System for Children-2. Using linear mixed models, we estimated covariate-adjusted associations of measurement-error-corrected gestational and childhood phthalate metabolite concentrations (per interquartile range increase) with repeated child behavior assessments. We used Weighted Quantile Sum (WQS) regression to estimate the association of phthalate mixtures with child behavior.

RESULTS

Gestational mono(3-carboxypropyl) phthalate (MCPP) concentrations were associated with more problem behaviors (internalizing: β = 0.9, 95% confidence interval [CI] = -0.1, 1.9; externalizing: β = 1.0, 95%CI = -0.1, 2.0; behavioral symptoms index [BSI]: β = 1.1, 95%CI = 0.1, 2.1). Higher childhood monobenzyl phthalate (MBzP) (β = 1.4; 95%CI = 0.0, 2.7), monocarboxynonyl phthalate (MCNP) (β = 3.2; 95%CI = 1.6, 4.8), monocarboxyoctyl phthalate (MCOP) (β = 0.9; 95%CI = 0.0, 1.7), MCPP (β = 1.8; 95%CI = 0.2, 3.5), and monoethyl phthalate (MEP) (β = 1.6; 95%CI = 0.1, 3.1) concentrations were associated with higher BSI composite scores. Consistent with this, the weighted childhood phthalate index was associated with more problem behaviors (internalizing: β = 1.5, 95%CI = -0.2, 3.1; externalizing: β = 1.7, 95%CI = 0.1, 3.5; BSI: β = 1.7, 95%CI = 0.2, 3.2); MBzP, MCNP, and MEP largely contributed to these associations.

CONCLUSION

Our findings suggest that childhood exposure to phthalate mixtures may be associated with children's problem behaviors.

Early exposure to food contaminants reshapes maturation of the human brain-gut-microbiota axis

Early childhood growth and development is conditioned by the consecutive events belonging to perinatal programming. This critical window of life will be very sensitive to any event altering programming of the main body functions. Programming of gut function, which is starting right after conception, relates to a very well-established series of cellular and molecular events associating all types of cells present in this organ, including neurons, endocrine and immune cells. At birth, this machinery continues to settle with the establishment of extra connection between enteric and other systemic systems and is partially under the control of gut microbiota activity, itself being under the densification and the diversification of microorganisms’ population. As thus, any environmental factor interfering on this pre-established program may have a strong incidence on body functions. For all these reasons, pregnant women, fetuses and infants will be particularly susceptible to environmental factors and especially food contaminants. In this review, we will summarize the actual understanding of the consequences of repeated low-level exposure to major food contaminants on gut homeostasis settlement and on brain/gut axis communication considering the pivotal role played by the gut microbiota during the fetal and postnatal stages and the presumed consequences of these food toxicants on the individuals especially in relation with the risks of developing later in life non-communicable chronic diseases.

Recovery of BDNF and CB1R in the Prefrontal Cortex Underlying Improvement of Working Memory in Prenatal DEHP-Exposed Male Rats after Aerobic Exercise

Early-life exposure to di-(2-ethylhexyl)-phthalate (DEHP) has been suggested to relate to hyperactivity, lack of attention, and working memory deficits in school-age children. Brain-derived neurotrophic factor (BDNF) and endocannabinoids are induced by aerobic exercises to provide beneficial effects on brain functions. This study investigated the mechanisms underlying working memory impairment and the protective role of exercise in prenatal DEHP-exposed male rats. Sprague Dawley dams were fed with vehicle or DEHP during gestation. The male offspring were trained to exercise on a treadmill for 5 weeks, which was followed by an assessment of their working memory with a T-maze delayed non-match-to-sample task. The expressions of BDNF, dopamine D1 receptor (D1R), cannabinoid receptor 1 (CB1R), and fatty acid amide hydrolase (FAAH) in the prefrontal cortex were detected by Western blot. The results showed that DEHP-exposed rats exhibited working memory impairments without significant alterations in locomotor activities. The reduced expressions of prefrontal BDNF and CB1R were obtained in the DEHP-exposed rats, while D1R and FAAH were barely affected. Importantly, aerobic exercise during childhood-adolescence prevented the impairment of working memory in the DEHP-exposed rats by recovering the BDNF and CB1R expressions in the prefrontal cortex. These findings suggest that exercise may provide beneficial effects in ameliorating the impairment of working memory in the prenatal DEHP-exposed male rats at late adolescence.

The association between prenatal endocrine-disrupting chemical exposure and altered resting-state brain fMRI in teenagers

Many studies have reported that prenatal exposure to endocrine-disrupting chemicals (EDCs) can cause adverse behavioral effects or cognitive dysfunction in children. This study aimed to investigate a relationship of the concentration of prenatal EDCs and brain function in teenagers. We recruited 59 mother-child pairs during the third trimester of pregnancy, and collected and examined the concentration of EDCs, such as heavy metals, phthalates and perfluoroalkyl substances (PFASs), in maternal urine and serum. Resting-state functional magnetic resonance imaging (rs-fMRI) data were collected in teenagers 13-16 years of age, and fractional amplitude of low-frequency fluctuation (fALFF) and regional homogeneity (ReHo) were performed to find the association between maternal EDC concentrations and the functional development of the teenage brain. We found a correlation between MBP concentration and activity in the superior frontal gyrus, middle frontal gyrus, middle temporal gyrus and inferior temporal gyrus in the combined group of boys and girls. We also observed a correlation between MBzP concentration and activity in the anterior cingulum gyrus and insula in girls. We found a correlation between lead concentration and activity in the cuneus in the combined group. We also observed a correlation between MeHg concentration and activity in the superior temporal gyrus, caudate nucleus and putamen in the combined group. The PFOS results revealed a negative relationship between activity in the right putamen in boys, girls and the combined group after phthalate or heavy metals were applied as covariates. The PFNA results showed a negative correlation between activity in the left/right putamen and left caudate nucleus in boys, girls and the combined group after phthalate, heavy metals or PFOS were applied as covariates. We examined the correlations between maternal EDC concentrations and brain development and found that the associations with resting-state teenage brains in some circumstances are sex-related.