Mercury, APOE, and child behavior

Genetic Susceptibility to Neurotoxicity Related to Prenatal Inorganic Arsenic Exposure in Young Spanish Children

We explored the influence of child and maternal single nucleotide polymorphisms (SNPs) in genes related to neurological function and arsenic metabolism (i.e., ABCA1, ABCB1, PON1, CYP3A, BDNF, GSTP1, MT2A, and APOE as well as AS3MT) on the association between prenatal arsenic (As) exposure and methylation efficiency and neuropsychological development in 4-5-year-old children. Participants were 549 mother-child pairs from the INMA (Environment and Childhood) Spanish Project. We measured inorganic arsenic (iAs) and the metabolites monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in urine samples collected during pregnancy. Neuropsychological development was assessed at the age of 4-5 years using the McCarthy Scales of Children's Abilities (MSCA). Several SNPs were determined in maternal and child DNA; AS3MT and APOE haplotypes were inferred. The median ∑As (sum of iAs, DMA, and MMA) was 7.08 μg/g creatinine. Statistically significant interactions for children's APOE haplotype were observed. Specifically, ε4-carrier children had consistently lower MSCA scores in several scales with increasing ∑As and MMA concentrations. These results provide evidence regarding the neurotoxic effects of early life exposure to As, observing that the APOE ε4 allele could make children more vulnerable to this exposure.

The Contribution across Three Generations of Mercury Exposure to Attempted Suicide among Children and Youth in Grassy Narrows First Nation, Canada: An Intergenerational Analysis

BACKGROUND

For 60 y, the people of Asubpeeschoseewagong Anishinabek (Grassy Narrows First Nation) have endured the effects of massive mercury (Hg) contamination of their river system, central to their traditions, culture, livelihood, and diet. In the years following the Hg discharge into the English-Wabigoon River system by a chloralkali plant in the early 1970s, there was a dramatic increase in youth suicides. Several authors attributed this increase solely to social disruption caused by the disaster.

OBJECTIVE

This research examined the possible contribution of Hg exposure across three generations on attempted suicides among today's children (5-11 y old) and youth (12-17 y old), using a matrilineal intergenerational paradigm.

METHODS

Information from the 2016-2017 Grassy Narrows Community Health Assessment (GN-CHA) survey was merged with Hg biomonitoring data from government surveillance programs (1970-1997). Data from 162 children/youth (5-17 years of age), whose mothers (n=80) had provided information on themselves, their parents, and children, were retained for analyses. Direct and indirect indicators of Hg exposure included a) grandfather had worked as a fishing guide, and b) mother's measured and estimated umbilical cord blood and childhood hair Hg and her fish consumption during pregnancy with this child. Structural equation modeling (SEM) was used to examine significant links from grandparents (G0) to mothers' exposure and mental health (G1) and children/youth (G2) risk for attempted suicide.

RESULTS

Mothers' (G1) median age was 33 y, 86.3% of grandmothers (G0) had lived in Grassy Narrows territory during their pregnancy, and 52.5% of grandfathers (G0) had worked as fishing guides. Sixty percent of children (G2) were <12 years of age. Mothers reported that among teenagers (G2: 12-17 years of age), 41.2% of girls and 10.7% of boys had ever attempted suicide. The SEM suggested two pathways that significantly linked grandparents (G0) to children's (G2) attempted suicides: a) through mothers' (G1) prenatal and childhood Hg exposure and psychological distress, and b) through maternal fish consumption during pregnancy (G1/G2), which is an important contributor to children's emotional state and behavior.

DISCUSSION

Despite minimal individual information on G0 and G1 past life experiences, the findings support the hypothesis that Hg exposure over three generations contributes to the mental health of today's children and youth. The prevalence of Grassy Narrows youth ever having attempted suicide is three times that of other First Nations in Canada. https://doi.org/10.1289/EHP11301.

ALAD and APOE polymorphisms are associated with lead and mercury levels in Italian pregnant women and their newborns with adequate nutritional status of zinc and selenium

The impacts of single-nucleotide polymorphisms (SNPs) in ALAD and VDR genes on Pb health effects and/or kinetics are inconclusive at low exposure levels, while studies including APOE SNPs are rare. In this study, we examined the associations of ALAD, VDR and APOE SNPs with exposure biomarkers of Pb and other trace elements (TEs) in Italian pregnant women (N = 873, aged 18-44 years) and their newborns (N = 619) with low-level mixed-element exposure through diet, the environment or endogenously. DNA from maternal peripheral venous blood (mB), sampled during the second and third trimesters, was genotyped for ALAD (rs1800435, rs1805313, rs1139488, rs818708), VDR (rs2228570, rs1544410, rs7975232, rs731236) and APOE (rs429358, rs7421) using TaqMan SNP assays. Personal and lifestyle data and TE levels (mB, maternal plasma, hair and mixed umbilical cord blood [CB]) from the PHIME project were used. Multiple linear regression models, controlling for confounding variables, were performed to test the associations between SNPs and TEs. The geometric means of mB-Pb, mB-Hg, mB-As and mB-Cd (11.0 ng/g, 2.16 ng/g, 1.38 ng/g and 0.31 ng/g, respectively) indicated low exposure levels, whereas maternal plasma Zn and Se (0.72 μg/mL and 78.6 ng/g, respectively) indicated adequate micronutritional status. Variant alleles of ALAD rs1800435 and rs1805313 were negatively associated with mB-Pb levels, whereas a positive association was observed for rs1139488. None of the VDR SNPs or their haplotypes had any association with Pb levels. Regarding APOE, the ϵ4 allele was associated with lower mB-Hg and CB-Hg, while a positive association was found with the ϵ2 allele and CB-Pb when the model included only newborn girls. The observed associations indicate possible modification effects of ALAD and APOE SNPs on Pb or Hg kinetics in women and their newborns with low exposure to non-essential TEs, as well as an adequate nutritional status of Zn and Se.

Mercury Ion Binding to Apolipoprotein E Variants ApoE2, ApoE3, and ApoE4: Similar Binding Affinities but Different Structure Induction Effects

Mercury intoxication typically produces more severe outcomes in people with the APOE-ε4 gene, which codes for the ApoE4 variant of apolipoprotein E, compared to individuals with the APOE-ε2 and APOE-ε3 genes. Why the APOE-ε4 allele is a risk factor in mercury exposure remains unknown. One proposed possibility is that the ApoE protein could be involved in clearing of heavy metals, where the ApoE4 protein might perform this task worse than the ApoE2 and ApoE3 variants. Here, we used fluorescence and circular dichroism spectroscopies to characterize the in vitro interactions of the three different ApoE variants with Hg(I) and Hg(II) ions. Hg(I) ions displayed weak binding to all ApoE variants and induced virtually no structural changes. Thus, Hg(I) ions appear to have no biologically relevant interactions with the ApoE protein. Hg(II) ions displayed stronger and very similar binding affinities for all three ApoE isoforms, with K _D values of 4.6 μM for ApoE2, 4.9 μM for ApoE3, and 4.3 μM for ApoE4. Binding of Hg(II) ions also induced changes in ApoE superhelicity, that is, altered coil-coil interactions, which might modify the protein function. As these structural changes were most pronounced in the ApoE4 protein, they could be related to the APOE-ε4 gene being a risk factor in mercury toxicity.

Methylmercury and Polycyclic Aromatic Hydrocarbons in Mediterranean Seafood: A Molecular Anthropological Perspective

Eating seafood has numerous health benefits; however, it constitutes one of the main sources of exposure to several harmful environmental pollutants, both of anthropogenic and natural origin. Among these, methylmercury and polycyclic aromatic hydrocarbons give rise to concerns related to their possible effects on human biology. In the present review, we summarize the results of epidemiological investigations on the genetic component of individual susceptibility to methylmercury and polycyclic aromatic hydrocarbons exposure in humans, and on the effects that these two pollutants have on human epigenetic profiles (DNA methylation). Then, we provide evidence that Mediterranean coastal communities represent an informative case study to investigate the potential impact of methylmercury and polycyclic aromatic hydrocarbons on the human genome and epigenome, since they are characterized by a traditionally high local seafood consumption, and given the characteristics that render the Mediterranean Sea particularly polluted. Finally, we discuss the challenges of a molecular anthropological approach to this topic.

Mechanisms of oxidative stress in methylmercury-induced neurodevelopmental toxicity

Methylmercury (MeHg) is a long-lasting organic environmental pollutant that poses a great threat to human health. Ingestion of seafood containing MeHg is the most important way by which it comes into contact with human body, where the central nervous system (CNS) is the primary target of MeHg toxicity. During periods of pre-plus postnatal, in particular, the brain of offspring is vulnerable to specific developmental insults that result in abnormal neurobehavioral development, even without symptoms in mothers. While many studies on neurotoxic effects of MeHg on the developing brain have been conducted, the mechanisms of oxidative stress in MeHg-induced neurodevelopmental toxicity is less clear. Hitherto, no single process can explain the many effects observed in MeHg-induced neurodevelopmental toxicity. This review summarizes the possible mechanisms of oxidative stress in MeHg-induced neurodevelopmental toxicity, highlighting modulation of Nrf2/Keap1/Notch1, PI3K/AKT, and PKC/MAPK molecular pathways as well as some preventive drugs, and thus contributes to the discovery of endogenous and exogenous molecules that can counteract MeHg-induced neurodevelopmental toxicity.

Altered functional activations of prefrontal brain areas during emotional processing of fear in Inuit adolescents exposed to environmental contaminants

Exposure to mercury, lead and polychlorinated biphenyls (PCBs) have been associated with emotional dysregulation, but their neuronal correlates have yet to be examined. Inuit from Nunavik (Northern Quebec, Canada) face internalizing problems and are among the most exposed individuals to these environmental contaminants in the world. The aim of this study was to examine the link between pre- and postnatal exposure to these contaminants and brain fear-circuitry in Inuit adolescents. Facial expression stimuli were presented to participants (mean age = 18.3 years) in a magnetic resonance imaging (MRI) scanner. Fear conditioning and extinction tasks included neutral faces as the conditioned threat and safety cues and a fearful face paired with a shrieking scream as the unconditioned stimulus. Functional MRI data were gathered at the conditioning phase (n = 71) and at the extinction phase (n = 62). Mercury, lead and PCB 153 concentrations were measured in blood samples at birth (cord blood) and at the time of the adolescent testing to estimate pre- and postnatal exposure, respectively. For each time point, exposures were categorized in tertiles (low, moderate and high exposed groups). Mixed analyses of variance were conducted for each contaminant of interest controlling for sex, age, socioeconomic status, drug/alcohol use, food insecurity and contaminant co-exposure. Results revealed greater differential activation during the conditioning phase in the right orbitofrontal cortex in participants with moderate and high concentrations of cord blood PCB 153 compared to those in the low exposure group. During the extinction phase, the high prenatal mercury exposed group showed a lower differential activation in the right and left anterior cingulate cortex compared to those in the low-exposed group; whereas there was a higher differential activation in right dorsolateral prefrontal cortex in the high postnatal lead exposed group compared to the moderate- and low-exposed groups. Our study is the first to show alterations in the prefrontal brain areas in fear conditioning and extinction tasks in relation to environmental contaminant exposures. The observed brain correlates may advance our understanding of the emotional problems associated with environmental chemical toxicity.

Associations of metals and neurodevelopment: a review of recent evidence on susceptibility factors

PURPOSE OF REVIEW

Epidemiologic evidence exists that many metals are associated with adverse neurobehavioral effects in young children, including lead (Pb), methylmercury (meHg), manganese (Mn) and arsenic (As)5-8. Importantly, chemical insult can vary depending on host factors and exposure circumstance. This systematic review summarizes the recent literature investigating modifying factors of the associations between metals and neurodevelopment, including immutable traits (sex or genetics) or exposure conditions (timing or co-exposures).

RECENT FINDINGS

Of the 53 studies included in this review, the number investigating modification of exposure effects were: 30 for sex, 21 for co-exposures, 12 for timing of exposure, and six for genetic modifiers. Sex-specific effects of metal-neurobehavioral associations were inconclusive for all metals, likely due to the heterogeneity of outcome domains assessed and the exposure time points measured. Seven studies evaluated both sex and exposure timing as modifying factors using deciduous teeth or other biomarkers with repeated measures to characterize metals exposure over time. Only five studies used statistical methods for mixtures to evaluate associations of more than two metals with neurobehavioral domains.

SUMMARY

Despite the expansion of research on susceptibility to the neurodevelopmental effects of metals exposure, considerable gaps remain. This work remains critical, as characterizing susceptible subpopulations can aid in identifying biological mechanisms and is fundamental for the protection of public health.

Risk factors associated with developing anxiety in Inuit adolescents from Nunavik

This study aimed to examine the relation between anxiety among the at-risk population of Inuit adolescents and diverse developmental risk factors including exposure to environmental chemicals, a subject of concern in Nunavik. Anxiety was assessed in 89 Inuit participants (mean age = 18.4 years; range = 16.2-21.9) with the Screen for Child Anxiety Related Emotional Disorders (SCARED) and the State-Trait Anxiety Inventory (STAI). Potential risk factors for anxiety were documented at birth, 11 years of age and 18 years of age, including blood levels of chemicals (mercury, lead, PCBs) and nutrients, as well as age, sex, estimated IQ, drug and alcohol use, bullying, exposure to domestic violence, food insecurity, crowding and socio-economic status. Results showed that participants scored high on both measures of anxiety, particularly the SCARED, for which the mean score was above the clinical threshold. Multiple regression results show that significant risk predictors obtained from the SCARED scores were female sex (β = 0.32), higher current blood mercury concentration (β = 0.26), food insecurity (β = 0.26) and bullying experiences in the last year (β = 0.21). The significant predictors for the STAI trait anxiety were food insecurity (β = 0.25) and lower estimated IQ (β = -0.31), whereas food insecurity (β = 0.21), lower blood levels of vitamin E (β = -0.25) and higher cord blood mercury concentrations (β = 0.25) were found for STAI situational anxiety. Further regression analyses suggested that the adolescent-related variables were the most important risk factors. Our findings show that Inuit adolescents are at risk for anxiety via multiple contributing factors, particularly current exposure to mercury, food insecurity and female sex.

Toxicity of mercury: Molecular evidence

Minamata disease in Japan and the large-scale poisoning by methylmercury (MeHg) in Iraq caused wide public concerns about the risk emanating from mercury for human health. Nowadays, it is widely known that all forms of mercury induce toxic effects in mammals, and increasing evidence supports the concern that environmentally relevant levels of MeHg could impact normal biological functions in wildlife. The information of mechanism involved in mercurial toxicity is growing but knowledge gaps still exist between the adverse effects and mechanisms of action, especially at the molecular level. A body of data obtained from experimental studies on mechanisms of mercurial toxicity in vivo and in vitro points to that disruption of the antioxidant system may play an important role in the mercurial toxic effects. Moreover, the accumulating evidence indicates that signaling transduction, protein or/and enzyme activity, and gene regulation are involving in mediating toxic and adaptive response to mercury exposure. We conducted here a comprehensive review of mercurial toxic effects on wildlife and human, in particular synthesized key findings of molecular pathways involved in mercurial toxicity from the cells to human. We discuss the molecular evidence related mercurial toxicity to the adverse effects, with particular emphasis on the gene regulation. The further studies relying on Omic analysis connected to adverse effects and modes of action of mercury will aid in the evaluation and validation of causative relationship between health outcomes and gene expression.

Environmental toxic agents: The impact of heavy metals and organochlorides on brain development

Exposure to environmental toxicants can have deleterious effects on the development of physical, cognitive, and mental health. Extensive laboratory and clinical studies have demonstrated how the developing brain is uniquely sensitive to toxic agents. This chapter focuses on the main neurologic impairments linked to prenatal and postnatal exposure to lead, methylmercury, and polychlorinated biphenyls, three legacy environmental contaminants whose neurotoxic effects have been extensively studied with respect to cognitive and behavioral development. The main cognitive, emotion regulation, sensory, and motor impairments in association with these contaminants are briefly reviewed, including the underlying neural mechanisms such as neuropathologic damages, brain neurotransmission, and endocrine system alterations. The use of neuroimaging as a novel tool to better understand how the brain is affected by exposure to environmental contaminants is also discussed.

Mercury and Alzheimer's Disease: Hg(II) Ions Display Specific Binding to the Amyloid-β Peptide and Hinder Its Fibrillization

Brains and blood of Alzheimer's disease (AD) patients have shown elevated mercury concentrations, but potential involvement of mercury exposure in AD pathogenesis has not been studied at the molecular level. The pathological hallmark of AD brains is deposition of amyloid plaques, consisting mainly of amyloid-β (Aβ) peptides aggregated into amyloid fibrils. Aβ peptide fibrillization is known to be modulated by metal ions such as Cu(II) and Zn(II). Here, we study in vitro the interactions between Aβ peptides and Hg(II) ions by multiple biophysical techniques. Fluorescence spectroscopy and atomic force microscopy (AFM) show that Hg(II) ions have a concentration-dependent inhibiting effect on Aβ fibrillization: at a 1:1 Aβ·Hg(II) ratio only non-fibrillar Aβ aggregates are formed. NMR spectroscopy shows that Hg(II) ions interact with the N-terminal region of Aβ(1-40) with a micromolar affinity, likely via a binding mode similar to that for Cu(II) and Zn(II) ions, i.e., mainly via the histidine residues His6, His13, and His14. Thus, together with Cu(II), Fe(II), Mn(II), Pb(IV), and Zn(II) ions, Hg(II) belongs to a family of metal ions that display residue-specific binding interactions with Aβ peptides and modulate their aggregation processes.

Mercury speciation in prenatal exposure in Slovenian and Croatian population - PHIME study

In recent years, several studies have addressed the issue of prenatal exposure to methylmercury (MeHg); however, few have actually analysed MeHg blood concentrations. Our study population included mothers and their new-borns from Slovenia (central region; N = 584) and Croatia (coastal region; N = 234). We have measurements of total Hg (THg) and MeHg in maternal hair, maternal peripheral blood, and cord blood. Cord blood Hg concentrations were low to moderate (median THg = 1.84 ng/g and MeHg = 1.69 ng/g). The proportion of THg as MeHg (%MeHg) in maternal and cord blood varied between 4% and 100% (coefficient of variation, CV = 32%) and between 8% and 100% (CV = 20%), respectively. Our data shows that variability of %MeHg was higher at lower blood THg levels. Concentrations of MeHg in maternal blood and cord blood were highly correlated (R_s = 0.943), in the case of inorganic Hg correlation was significant but weaker (R_s = 0.198). MeHg levels in maternal blood and cord blood were positively associated with seafood intake, maternal age, and negatively associated with pre-pregnancy BMI. Additionally, MeHg in maternal blood was positively associated with plasma selenium levels, and cord blood MeHg was negatively associated with parity. The results of multiple linear regression models showed that speciation analysis provides more defined estimation of prenatal exposure in association modelling. Associations between Hg exposure and cognitive performance of children (assessed using Bayley Scales of Infant and Toddler development) adjusted for maternal or child Apolipoprotein E genotypes showed higher model R² and lower p-values when adjusted for MeHg compared to THg. This study demonstrates that Hg speciation improves the association between exposure and possible negative health effects.

Very low-level prenatal mercury exposure and behaviors in children: the HOME Study

BACKGROUND

Mercury is toxic to the developing brain, but the lowest concentration associated with the development of behavior problems is unclear. The purpose of this study was to examine the association between very low-level mercury exposure during fetal development and behavior problems in children.

METHODS

We used data from 389 mothers and children in a prospective pregnancy and birth cohort study. We defined mean prenatal mercury concentration as the mean of total whole blood mercury concentrations in maternal samples collected at 16- and 26-weeks of gestation, delivery, and neonatal cord blood samples. We assessed parent-reported child behavior up to five times from two to 8 years of age using the Behavioral Assessment System for Children (BASC-2). At 8 years of age, we assessed self-reported child anxiety using the Spence Children's Anxiety Scale (SCAS). We used multiple linear mixed models and linear regression models to estimate the association between mean prenatal mercury concentrations and child behavior and anxiety, respectively.

RESULTS

The median prenatal total blood mercury concentrations was 0.67 μg/L. Overall, we did not find statistically significant associations between mean prenatal mercury concentrations and behavior problems scores, but a 2-fold increase in mercury concentrations at 16-weeks gestation was associated with 0.83 point (95% CI: 0.05, 1.62) higher BASC-2 anxiety scores. Maternal and cord blood mercury concentrations at delivery were associated with parent-reported anxiety at 8 years.

CONCLUSION

We found limited evidence of an association between very-low level prenatal mercury exposure and behaviors in children, with an exception of anxiety.

Multiple low-level exposures: Hg interactions with co-occurring neurotoxic substances in early life

All chemical forms of Hg can affect neurodevelopment; however, low levels of organic Hg (methylmercury-MeHg and ethylmercury-EtHg in Thimerosal-containing vaccines, hereafter 'TCV') exposures during early life (pregnancy and lactation) co-occur with other environmental neurotoxic substances. These neurotoxicants may act in parallel, synergistically, or antagonistically to Hg. Nevertheless, the risks of neurotoxicity associated with multiple neuro-toxicants depend on type, time, combinations of exposure, and environmental and/or genetic-associated factors. Neurological developmental disorders, delays in cognition and behavioral outcomes associated with multiple exposures (which include Hg) may show transient or lasting outcomes depending on constitutional and/or environmental factors that can interact to neutralize, aggravate or attenuate these effects; often these studies are challenging to interpret. During pregnancy and lactation, fish-MeHg exposure is frequently confounded with the opposing effects of neuroactive nutrients (in fish) that lead to positive, negative, or no effects on neurobehavioral tests. In infancy, exposures to acute binary mixtures (TCV- EtHg and Al-adjuvants in infant immunizations) are associated with increased risks of tics and other developmental disorders. Despite the certitude that promulgates single environmental neurotoxicants, empirical comparisons of combined exposures indicate that Hg-related outcome is uneven. Hg in combination with other neurotoxic mixtures may elevate risks of neurotoxicity, but these risks arise in circumstances that are not yet predictable. Therefore, to achieve the goals of the Minamata treaty and to safeguard the health of children, low levels of mercury exposure (in any chemical form) needs to be further reduced whether the source is environmental (air- and food-borne) or iatrogenic (pediatric TCVs).

Genetic Susceptibility to Neurodegeneration in Amazon: Apolipoprotein E Genotyping in Vulnerable Populations Exposed to Mercury

Human exposure to mercury is a serious problem of public health in Amazon. As in other vulnerable populations throughout the world, Amazonian riverine populations are chronically exposed to this metal and some symptoms of mercury intoxication were already detected in these populations. However, studies on the genetic susceptibility to mercury toxicity in the Amazon are scarce, and they tested a limited number of individuals. In this context, apolipoprotein E gene (APOE) is a key element with a well-established association among their alleles and the neurodegenerative consequences of mercury intoxication. However, no studies have addressed APOE genotyping in Amazonian exposed populations. Additionally, epidemiological studies with APOE genotyping in Amazon have been restricted to indigenous populations. Therefore, this work analyzed for the first time the genotypic and allelic profiles of APOE in Amazonian riverine populations chronically exposed to mercury. Eight hundred and twenty three individuals were enrolled in our study donating blood (794) and/or hair (757). APOE genotyping was analyzed by real-time PCR. Total mercury and mercury species were quantified by ICP-MS and GC-pyro-AFS, respectively. Genomic ancestry markers were evaluated by multiplex-PCR reaction, separated by capillary electrophoresis on the ABI 3130 Genetic Analyzer instrument and analyzed on GeneMapper ID v3.2. The 𝜀3 and 𝜀3/𝜀3 were the most frequent allele and genotype, respectively, followed by 𝜀4 allele and 𝜀3/𝜀4 genotype. Only 𝜀2/𝜀2 genotype was not found, suggesting that the absence of this genotype is a generalized phenomenon in Amazon. Also, our data supported an association between the presence of APOE4 and the Amerindian origin in these populations. Fifty-nine individuals were identified at maximum risk with levels of mercury above 10 μg/g and the presence of APOE4. Interestingly, among individuals with high mercury content, APOE4-carriers had high mercury levels than APOE2-carriers, pointing to a different heavy metal accumulation according to the APOE allele. These data suggest that APOE4, in addition to a possible pharmacodynamic effect, may influence pharmacokinetically the mercury exposure causing its higher accumulation and leading to worse deleterious consequences. Our results may aid in the development of prevention strategies and health policy decision-making regarding these at-risk vulnerable populations.

Selective mercury ion recognition using a methyl red (MR) based silatrane sensor

A methyl red based silatrane (MR-APS) sensor has been synthesized and applied for Hg²⁺ ion recognition by UV-Visible spectrophotometery.

Children's environmental health based on birth cohort studies of Asia

Numerous studies have explored the associations between environmental pollutants and pediatric health. Recent studies have investigated the issue in Asia, but no systematic review has been published to date. This study aims to elucidate the issue by summarizing relevant epidemiologic evidence for cohorts in Asia, using information from the Birth Cohort Consortium of Asia (BiCCA). Environmental pollutants include mercury, environmental tobacco smoke (ETS), polychlorinated biphenyls (PCB), perfluoroalkyl substances (PFAS) and phthalates. This study sought to classify the effects of such compounds on fetal growth and pregnancy outcomes, neurodevelopment and behavioral problems, allergic disease and immune function and the endocrine system and puberty. These evidences showed ETS has been associated with infant birth weight, children's neurodevelopment and allergy disease; mercury and PCB have been shown to affect children's neurodevelopment; phthalate has effects on endocrine function; PFAS alters children's neurodevelopment, the endocrine system, and the allergic response. However, more consistent and coordinated research is necessary to understand the whole picture of single environmental and/or co-exposure and children's health. Therefore, harmonization and international collaboration are also needed in Asia.

Associations of prenatal and early childhood mercury exposure with autistic behaviors at 5years of age: The Mothers and Children's Environmental Health (MOCEH) study

BACKGROUND

Although mercury is an established neurotoxin, only few longitudinal studies have investigated the association between prenatal and early childhood mercury exposure and autistic behaviors.

METHODS

We conducted a longitudinal cohort study using an ongoing prospective birth cohort initiated in 2006, wherein blood mercury levels were measured at early and late pregnancy; in cord blood; and at 2 and 3years of age. We analyzed 458 mother-child pairs. Autistic behaviors were assessed using the Social Responsiveness Scale (SRS) at 5years of age. Both continuous SRS T-scores and T-scores dichotomized by a score of ≥60 or <60 were used as outcomes.

RESULTS

The geometric mean of mercury concentrations in cord blood was 5.52μg/L. In adjusted models, a doubling of blood mercury levels at late pregnancy (β=1.84, 95% confidence interval [CI]: 0.39, 3.29), in cord blood (β=2.24, 95% CI: 0.22, 4.27), and at 2years (β=2.12, 95% CI: 0.54, 3.70) and 3years (β=2.80, 95% CI: 0.89, 4.72) of age was positively associated with the SRS T-scores. When the SRS T-scores were dichotomized, we observed positive associations with mercury levels at late pregnancy (relative risk [RR]=1.31, 95% CI: 1.08, 1.60) and in cord blood (RR=1.28, 95% CI: 1.01, 1.63).

CONCLUSION

We found that blood mercury levels at late pregnancy and early childhood were associated with more autistic behaviors in children at 5years of age. Further study on the long-term effects of mercury exposure is recommended.

Genetic Aspects of Susceptibility to Mercury Toxicity: An Overview

Human exposure to mercury is still a major public health concern. In this context, children have a higher susceptibility to adverse neurological mercury effects, compared to adults with similar exposures. Moreover, there exists a marked variability of personal response to detrimental mercury action, in particular among population groups with significant mercury exposure. New scientific evidence on genetic backgrounds has raised the issue of whether candidate susceptibility genes can make certain individuals more or less vulnerable to mercury toxicity. In this review, the aim is to evaluate a new genetic dimension and its involvement in mercury risk assessment, focusing on the important role played by relevant polymorphisms, located in attractive gene targets for mercury toxicity. Existing original articles on epidemiologic research which report a direct link between the genetic basis of personal vulnerability and different mercury repercussions on human health will be reviewed. Based on this evidence, a careful evaluation of the significant markers of susceptibility will be suggested, in order to obtain a powerful positive “feedback” to improve the quality of life. Large consortia of studies with clear phenotypic assessments will help clarify the “window of susceptibility” in the human health risks due to mercury exposure.

Prenatal mercury exposure, neurodevelopment and apolipoprotein E genetic polymorphism

The aim of the present study was to evaluate the association between prenatal exposure to mercury (Hg) and neurodevelopment of the child, taking into account genetic polymorphism of apolipoprotein E (Apoe) and other relevant confounders. Six hundred and one mother-child pairs were recruited from the central Slovenia region and 243 from Rijeka, on the Croatian coast of the northern Adriatic. The total Hg in cord blood, Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) assessment at 18 months of age and Apoe genotyping was performed on 361 children; 237 of them were from Slovenia and 124 from Croatia. The results showed negative association between low-to-moderate Hg exposure in children with normal neurodevelopmental outcome and cognitive and fine motor scores at 18 months of age as assessed by Bayley III. The Hg-related decrease in cognitive score was observed only in children carrying at least one Apoe ε4 allele, while the decrease in fine motor scores was independent of the Apoe genotype. Adjusting for selenium (Se) and lead (Pb) levels, a positive association between Se and the language score and a negative association between Pb and the motor score was observed, but not in the subgroup of children carrying the ε4 allele.

Gene-environment interactions in development and disease

Developmental geneticists continue to make substantial jumps in our understanding of the genetic pathways that regulate development. This understanding stems predominantly from analyses of genetically tractable model organisms developing in laboratory environments. This environment is vastly different from that in which human development occurs. As such, most causes of developmental defects in humans are thought to involve multifactorial gene-gene and gene-environment interactions. In this review, we discuss how gene-environment interactions with environmental teratogens may predispose embryos to structural malformations. We elaborate on the growing number of gene-ethanol interactions that might underlie susceptibility to fetal alcohol spectrum disorders. WIREs Dev Biol 2017, 6:e247. doi: 10.1002/wdev.247 For further resources related to this article, please visit the WIREs website.

Scientific foundations of fish-consumption advice for pregnant women: Epidemiological evidence, benefit-risk modeling, and an integrated approach

BACKGROUND

Pregnant women need fish consumption advice that increases seafood intake and simultaneously reduces methylmercury (MeHg) exposure. Two disciplines, epidemiology and benefit-risk modeling, can support such advice. Some current models suggest that fish consumption during pregnancy has only net beneficial effects. In contrast, many recent epidemiological studies have associated adverse effects on cognitive development with ordinary fish intake and MeHg doses routinely encountered by up to one in six US women of childbearing age. Proposed federal fish-consumption advice is based solely on a benefit-risk model. A more complete assessment integrating both types of evidence is needed.

OBJECTIVES AND METHODS

The goal of this paper is to use a model to rank seafood items by their relative benefits and risks, producing consumer seafood choice recommendations that are also consistent with epidemiological observations. Recent epidemiological studies and benefit-risk models are reviewed, and model results are compared with one another and with epidemiological observations to identify commonalities that support inter-calibration.

RESULTS AND CONCLUSIONS

Both approaches quantify MeHg doses at which harm slightly exceeds benefit. A model from the US Food and Drug Administration (FDA) predicts adverse effects at fish intakes containing, on average, more than 16 times the the US Reference Dose (RfD) for MeHg. Epidemiological results indicate that the RfD itself approximates a minimal adverse dose. This conceptual similarity allows FDA's model to be calibrated with the epidemiological results to generate fish intake recommendations that both the model and the epidemiology suggest should have substantially positive public health impacts.

[Recent Epidemiological Studies on Methylmercury, Mercury and Selenium]

More than sixty years has passed since the outbreak of Minamata disease, and high-level methylmercury contaminations now seem nonexistent in Japan. However, mercury has been continuously discharged from natural sources and industrial activities, and the health effects on children susceptible to methylmercury exposure at low levels, in addition to mercury contamination from mercury or gold mining areas in developing countries, become a worldwide concern. In this article, we provide a recent overview of epidemiological studies regarding methylmercury and mercury. The following findings were obtained. (1) Many papers on exposure assessment of methylmercury/mercury have been published since the Minamata Convention on Mercury was adopted in 2013. (2) The most crucial problem is child developmental neurotoxicity resulting from prenatal exposure to methylmercury, but its precise assessment seems to be difficult because most of such effects are neither severe nor specific. (3) Several problems raised in birth cohort studies (e.g., whether IQ deficits due to prenatal methylmercury exposure remain when the children become adults, or whether the postnatal exposure at low levels also causes such adverse effects in children) remain unsolved. (4) Concurrent exposure models of methylmercury, lead, polychlorinated biphenyls, aresenic, and organochlorine pesticides, as well as possible antagonists such as polyunsaturated fatty acids and selenium, should be considered in the study design because the exposure levels of methylmercury are extremely low in developed countries. (5) Further animal experiments and molecular biological studies, in addition to human studies, are required to clarify the mechanism of methylmercury toxicity.