Prenatal exposure to mercury and neurobehavioral development of neonates in Zhoushan City, China

Neurodevelopmental associations of prenatal and postnatal methylmercury exposure among first-grade children in the Kinan region, Japan

The most severe effects of methylmercury (MeHg) exposure during child development are thought to result from exposure during fetal life and childhood. However, comparing the neurodevelopmental effects of prenatal and postnatal MeHg exposure (PreMeHg and PostMeHg, respectively) remains unclear. We aimed to investigate the associations between neurodevelopmental indicators and PreMeHg or PostMeHg. The participants were 134 children in the first grade of elementary schools aged 7-8 years from the Kinan region, an area with high consumption of MeHg-rich whales and tunas in Japan. We measured MeHg levels in preserved umbilical cord tissues and total mercury (T-Hg) levels in children's hair to estimate PreMeHg and PostMeHg levels, respectively. Neuropsychological (intelligence quotient testing and Boston Naming Test) and neurophysiological (brainstem auditory evoked potential [BAEP], visual evoked potential [VEP], and color vision tests) studies were performed to evaluate the neurodevelopmental status. Multiple regression analyses were conducted according to sex. The geometric mean MeHg levels in preserved umbilical cord tissues and T-Hg levels in children's hair were 0.11 μg/g and 2.94 μg/g, respectively. Neither PreMeHg nor PostMeHg was related to neuropsychological indicators. Some associations between MeHg exposure and neurophysiological results were observed only in boys. N145 latency in VEPs was significantly prolonged with increasing PreMeHg (β: 12.01, 95% confidence interval [CI]: 0.648, 23.38). The III-V interpeak intervals in BAEP were significantly prolonged with increasing PreMeHg or PostMeHg (β [95% CI]: 0.142 [0.041, 0.243] and 0.159 [0.052, 0.265], respectively). After adjusting for PreMeHg, the association between PostMeHg and BAEP latencies disappeared. In conclusion, the latency in the auditory and visual pathways was significantly prolonged with increasing PreMeHg in boys. These findings suggest that male fetuses may be more susceptible to MeHg exposure.

Temporal changes of blood mercury concentrations in Chinese newborns and the general public from 1980s to 2020s

Mercury (Hg) is a global pollutant that threatens the environment and human health. As a major producer, emitter and consumer of Hg, China is currently taking different measures to curb mercury pollution in accordance with the requirements of the Minamata Convention on Mercury. Blood Hg can reflect the human body's recent exposure to Hg. This review summarized the temporal changes in blood Hg concentrations in newborns and the general public in China from 1980 s to 2020 s. It was shown that the blood Hg concentrations of newborns showed the downward trend, although it was not significant. The general public Hg concentrations showed a trend of first increase and then decrease trend. Most of the cord blood Hg and venous blood Hg concentrations in China were lower than the USEPA reference concentration of 5.8 µg/L. Since low-dose prenatal Hg exposure can affect fetal and neonatal development, continuous attention needs to be paid to reduce maternal and neonatal Hg exposure. The information provided in this review may lay a basis for the effectiveness evaluation on the implementation of Minamata Convention on Mercury.

Fish consumption habits of pregnant women in Itaituba, Tapajós River basin, Brazil: risks of mercury contamination as assessed by measuring total mercury in highly consumed piscivore fish species and in hair of pregnant women

The Tapajós River basin in the Amazon region, Brazil is one of the most active gold mining areas in the world. In this study, we evaluated fish consumption habits and mercury exposure in 110 pregnant women in the city of Itaituba by measuring their total hair mercury concentrations. In addition, we investigated seasonal differences in mercury concentrations in two highly consumed piscivorous fish species, tucunaré (Cichla spp.) and pescada (Plagioscion squamosissimus). Total fish mercury concentrations (THg) during the dry season were 0.62±0.07 mg/kg for Cichla spp. and 0.73±0.08 mg/kg for P. squamosissimus. During the rainy season they were 0.39±0.04 and 0.84±0.08 mg/ kg, respectively. Of our participants 44 % declared that they ate Cichla spp. and 67 % P. squamosissimus. Mean mercury concentration in their hair was 1.6±0.2 mg/kg and was above the US Environmental Protection Agency (US EPA) reference dose of 1 mg/kg in 48 % of them. Mean fish THg concentrations were also above the joint Food and Drug Administration and US EPA safety limit of 0.5 mg/kg for P. squamosissimus during both seasons and for Cichla spp. during the dry season only. These results show that pregnant women should avoid consumption of these piscivorous fish species during pregnancy and call for a regular programme to monitor Hg levels in that area.

Heavy metals and neurodevelopment of children in low and middle-income countries: A systematic review

BACKGROUND

The presence of harmful environmental exposures, which disproportionately affects low-and-middle income countries (LMICs), contributes to >25% of deaths and diseases worldwide and detrimentally affects child neurodevelopment. Few resources succinctly summarize the existing literature on this topic. Our objective is to systematically review and characterize the evidence regarding the relationship between heavy metals and neurodevelopment of children in LMICs.

METHODS

We conducted a medical librarian-curated search on multiple online databases to identify articles that included individuals <18 years living in a LMIC, quantitatively measured exposure to a heavy metal (either prenatal or postnatal), and used a standardized measurement of neurodevelopment (i.e. cognitive, language, motor, and behavior). Reviews, editorials, or case studies were excluded. Results were analyzed qualitatively, and quality was assessed.

RESULTS

Of the 18,043 screened articles, 298 full-text articles were reviewed, and 100 articles met inclusion criteria. The included studies represented data from 19 LMICs, only one of which was classified as a low-income country. Ninety-four percent of postnatal lead and all postnatal manganese studies showed a negative association with metal exposure and neurodevelopment, which were the strongest relationships among the metals studied. Postnatal exposure of mercury was associated with poor neurodevelopment in only half of studies. Limited data on postnatal arsenic and cadmium suggests an association with worse neurodevelopment. Findings were mixed for prenatal arsenic and lead, although some evidence supports that the neurotoxicity of lead was amplified in the presence of manganese.

CONCLUSIONS AND POTENTIAL IMPACT

We found that lead and manganese appear to consistently have a detrimental effect on the neurodevelopment of children, and more evidence is needed for mercury, arsenic, and cadmium. Better characterization of these effects can motivate and inform prioritization of much needed international policies and programs to reduce heavy metal exposures for young children within LMICs.

Prenatal exposure to metal mixtures and newborn neurobehavior in the Rhode Island Child Health Study

Background:

Prenatal exposure to metals can affect the developing fetus and negatively impact neurobehavior. The associations between individual metals and neurodevelopment have been examined, but little work has explored the potentially detrimental neurodevelopmental outcomes associated with the combined impact of coexisting metals. The objective of this study is to evaluate prenatal metal exposure mixtures in the placenta to elucidate the link between their combined effects on newborn neurobehavior.

Method:

This study included 192 infants with available placental metal and NICU Network Neurobehavioral Scale data at 24 hours–72 hours age. Eight essential and nonessential metals (cadmium, cobalt, copper, iron, manganese, molybdenum, selenium, zinc) detected in more than 80% of samples were tested for associations with atypical neurobehavior indicated by NICU Network Neurobehavioral Scale using logistic regression and in a quantile g-computation analysis to evaluate the joint association between placental metal mixture and neurobehavioral profiles.

Results:

Individually, a doubling of placental cadmium concentrations was associated with an increased likelihood of being in the atypical neurobehavioral profile (OR = 2.39; 95% CI = 1.05 to 5.71). In the mixture analysis, joint effects of a quartile increase in exposure to all metals was associated with 3-fold increased odds of newborns being assigned to the atypical profile (OR = 3.23; 95% CI = 0.92 to 11.36), with cadmium having the largest weight in the mixture effect.

Conclusions:

Prenatal exposure to relatively low levels of a mixture of placental metals was associated with adverse newborn neurobehavior. Examining prenatal metal exposures as a mixture is important for understanding the harmful effects of concomitant exposures in the vulnerable populations.

Sex-specific neurotoxic effects of heavy metal pollutants: Epidemiological, experimental evidence and candidate mechanisms

The heavy metals lead (Pb), mercury (Hg), and cadmium (Cd) are ubiquitous environmental pollutants and are known to exert severe adverse impacts on the nervous system even at low concentrations. In contrast, the heavy metal manganese (Mn) is first and foremost an essential nutrient, but it becomes neurotoxic at high levels. Neurotoxic metals also include the less prevalent metalloid arsenic (As) which is found in excessive concentrations in drinking water and food sources in many regions of the world. Males and females often differ in how they respond to environmental exposures and adverse effects on their nervous systems are no exception. Here, we review the different types of sex-specific neurotoxic effects, such as cognitive and motor impairments, that have been attributed to Pb, Hg, Mn, Cd, and As exposure throughout the life course in epidemiological as well as in experimental toxicological studies. We also discuss differential vulnerability to these metals such as distinctions in behaviors and occupations across the sexes. Finally, we explore the different mechanisms hypothesized to account for sex-based differential susceptibility including hormonal, genetic, metabolic, anatomical, neurochemical, and epigenetic perturbations. An understanding of the sex-specific effects of environmental heavy metal neurotoxicity can aid in the development of more efficient systematic approaches in risk assessment and better exposure mitigation strategies with regard to sex-linked susceptibilities and vulnerabilities.

Effect of combined pharmacological, behavioral, and physical interventions for procedural pain on salivary cortisol and neurobehavioral development in preterm infants: a randomized controlled trial

Repeated procedural pain may lead to increased secretion of cortisol and future neurobehavioral development disorders in preterm infants. Changes in the cortisol level may mediate the effect of neonatal repetitive procedural pain on altered childhood neurobehavioral development in preterm infants. However, few studies have investigated the effect of combined pharmacological, behavioral, and physical interventions over repeated painful procedures on pain response, cortisol level, and neurobehavioral development. This study examined (1) the efficacy and safety of sucrose combined with massage, music, non-nutritive sucking, and gentle human touch to treat preterm infants with repeated procedural pain; (2) the cortisol level at discharge from the neonatal intensive care unit (NICU); (3) neurobehavioral development at 40 weeks' corrected gestational age; and (4) the potential mediating effect of the cortisol level in the combined interventions on neurobehavioral development. Stable preterm infants (n = 76) were randomized to receive routine care or combined interventions across repeated painful procedures throughout their NICU stay. The Premature Infant Pain Profile scores in the early, middle, and late periods of the NICU stay were measured, as were the basal salivary cortisol level at admission and discharge, the Neonatal Behavioral Neurological Assessment score at 40 weeks' corrected gestational age, and the incidence of adverse effects during the study period. Our findings indicated that the combined interventions remained efficacious and safe for reducing repeated procedural pain, decreased the cortisol level at discharge, and promoted early neurobehavioral development in preterm infants. This effect may have been mediated through decreased cortisol levels and reduced repeated procedural pain.

Impact of dietary mercury intake during pregnancy on the health of neonates and children: a systematic review

CONTEXT

Growing evidence suggests that prenatal exposure to methyl mercury through the maternal diet could have great influence on the neurological and physical development of neonates and young children.

OBJECTIVE

The aim of this review was to evaluate the clinical repercussions of maternal exposure to methyl mercury during pregnancy on the health of fetuses, neonates, and children up to 8 years of age.

DATA SOURCES

The Web of Science, PubMed, CINAHL, Scopus, and Dialnet Plus databases were searched for articles published in English or Spanish from 1990 to 2020.

STUDY SELECTION

Original articles published in English or Spanish from 1990 to 2020 were eligible for inclusion. All study designs were eligible. Animal studies were excluded. Two authors independently screened studies for inclusion. From the 971 records initially identified, 19 studies were included in the systematic review.

DATA EXTRACTION

PRISMA guidelines were followed. Outcomes extracted included maternal dietary exposure to methyl mercury during pregnancy, possible health repercussions in offspring up to 8 years of age, and quantitative measurement of mercury in a biological sample. All studies met the requirements established for assessing both study quality and risk of bias.

RESULTS

Prenatal exposure to mercury was consistently associated with lower birth weight, but only one study reported a negative association with length at birth. Higher mercury levels were also related to lower scores in various neuropsychological and developmental tests.

CONCLUSION

The literature shows clear evidence of the adverse effects of maternal methyl mercury exposure on anthropometric variables and cognitive or physical development in children. It is noteworthy, however, that mercury toxicity may sometimes be mitigated by other essential nutrients in the maternal diet, such as polyunsaturated fatty acids.

Temporal variation of total mercury levels in the hair of pregnant women from the Maternal-Infant Research on Environmental Chemicals (MIREC) study

Prenatal exposure to total mercury (T-Hg) comes from both natural and anthropogenic sources. T-Hg can cross the blood-brain and placental barriers, and may be associated with future neurological and physiological dysfunctions. Scalp hair is an optimal and non-invasive indicator of chronic T-Hg exposure. As part of the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, hair samples from 350 women were collected within weeks after giving birth, to determine temporal variations in T-Hg levels from preconception to delivery, and to compare these levels to corresponding levels measured in other matrices (maternal and umbilical cord blood, and infant's meconium). A maximum of 12 one-cm hair segments were cut starting at the scalp; segments closer to the scalp reflected recent exposure (within the last month). For proper comparison, the hair segments were matched with the collection dates for other matrices. GM hair T-Hg levels greatly decreased during pregnancy, from 0.26 μg g^-1 (preconception or full-length hair) to 0.18 μg g^-1 (at delivery or segments closer to the scalp). A similar decreasing trend was found for T-Hg in maternal blood: 1st trimester (0.60 μg L^-1) to 3rd trimester (0.47 μg L^-1). The median hair-to-blood ratios of T-Hg levels varied from 364 (1st trimester), to 408 (3rd trimester), to 229 (cord blood). Very low T-Hg levels were detected in meconium. Mercury levels in blood and hair correlated with consumption of large predatory fish.

Temporal trends of urinary mercury in Chinese people from 1970s to 2010s: A review

Mercury (Hg) is one of the most toxic heavy metals. It can migrate around the globe and magnify through the food chain, ultimately harming human health. Urinary Hg reflects recent exposure of Hg, which reflects the status of environmental contamination by Hg. This review summarized the levels and presented temporal trends of urinary Hg in Chinese people (both the general public and the occupationally exposed people) reported from 1970s to 2010s. It was found that urinary Hg levels in 92.3% of the reported population were less than the reference value (10.0 µg/L) recommended by Chinese health authority, while 76.9% were less than the reference value (4.0 µg/L) recommended by World Health Organization (WHO) in the general public in China. For the temporal trend from 1970s to 2010s, the urinary Hg levels in the general public in China were found to decrease gradually. In the occupationally exposed people, the urinary Hg levels generally exceeded the reference value (10.0 µg/L) for the general public, and about half of them were higher than the occupational exposure limit (35.0 µg/g creatinine) set by Chinese Occupational Health Standard (WS/T 265 - 2006). From 1970s to 2010s, the urinary Hg levels in occupationally exposed population increased first and then decreased slowly. Hg miners in Guizhou were found to have the highest urinary Hg levels, while workers in Anhui, Chongqing, Qinghai and Shanxi also had high levels of urinary Hg. In all, the urinary Hg levels in both the general public and the occupationally exposed people decreased from 1970s to 2010s, especially in recent decades. Attention should be paid to occupationally exposed people since high levels of urinary Hg were found in them. The message provided in this review can help better understand the situation of Hg burden in Chinese people and lay a basis for the coming effectiveness evaluation on the implementation of Minamata Convention on Mercury. Capsule abstract: The urinary Hg levels in both the general public and the occupationally exposed people in China are decreasing.

Effects of low-level mercury exposure on brain-derived neurotrophic factor in preschool children

OBJECTIVES

Mercury (Hg), a ubiquitous heavy metal, could affect the neurodevelopment of the children, however, these associations are still equivocal. Brain derived neurotrophic factor (BDNF) plays an essential role in the central nervous system development in children. This study aimed to investigate the effects of low-level mercury exposure on serum BDNF levels and the influence of sex and dietary intake on these relationships in children.

METHODS

In this cross-sectional study, a total of 541 pre-school children were recruited, the blood mercury concentrations and serum BDNF levels were measured. The background information on demographic characteristics and dietary habits of the children was collected through questionnaires. Multivariable linear models after adjustment for potential confounders were used to evaluate the associations between mercury exposure and levels of BDNF in children.

RESULTS

The GMs of blood mercury concentrations and serum BDNF levels were 1.06 μg/L, 20.4 ng/mL, respectively. A significant positive association between blood mercury concentrations and serum BDNF levels was found. After stratification by sex, the blood mercury concentrations in children were positive associated with serum BDNF levels in girls but not in boys. However, these associations were attenuated when we further adjusted the children's dietary intake variables.

CONCLUSIONS

Our findings suggest that low-levels of mercury exposure may have sex-specific effects on BDNF levels in young children and that dietary intake may be potential confounders in these relationships. However, further studies are warranted to investigate the role of BDNF in the effects of mercury on neurodevelopment.

Brain Development in Infants of Mothers With Gestational Diabetes Mellitus: A Diffusion Tensor Imaging Study

OBJECTIVE

The objective of this study was to investigate clinical neurocognitive performance and microstructural white matter (WM) alterations in infants of mothers with gestational diabetes mellitus (GDM) using diffusion tensor imaging.

MATERIALS AND METHODS

Infants (corrected gestational age, 33.42-36.00 weeks) of mothers with GDM (n = 31) and gestational age- and sex-matched unexposed controls (n = 31) accomplished 3-T diffusion tensor imaging scans and neurocognitive tests. Diffusion tensor imaging measures, mainly referring to fractional anisotropy (FA) values, were compared between 2 groups, and within-group analysis of correlation between FA values and neurocognitive testing outcomes in GDM-exposed infants was conducted subsequently.

RESULTS

Fractional anisotropy was significantly decreased in the splenium of corpus callosum, posterior limb of internal capsule, thalamus in infants of mothers with GDM when compared with controls (P < 0.05), reflecting microstructural WM abnormalities in the GDM group. Decreased FA was associated with worse neurocognitive performance in the exposed group (P < 0.05).

CONCLUSIONS

Individuals of mothers with GDM showed microstructural WM abnormalities in different brain regions, which were significantly related to worse neurocognitive performance. This might reveal that GDM directly insults the brain development of the offspring.

Impact of low-level mercury exposure on intelligence quotient in children via rice consumption

Wanshan is a city in southwest China that has several inactive mercury (Hg) mines. The local population are exposed to methylmercury (MeHg) due to the consumption of Hg contaminated rice. The relationship between Hg exposure and the cognitive functions of local children is unknown. This study investigated the relationship between hair Hg concentrations and the intelligence quotient (IQ) of 314 children aged 8-10 years, recruited from three local primary schools in Wanshan area in 2018 and 2019. IQ was evaluated using Wechsler Intelligence Scale for Children - Fourth Edition (WISC-IV). The average THg concentration in children's hair samples was 1.53 μg g^-1 (range: 0.21-12.6 μg g^-1), and 65.6% exceeded the United States Environment Protection Agency (USEPA) recommended value of 1 μg g^-1. Results of logistic regression analysis showed that children with hair Hg ≥ 1 μg g^-1 were 1.58 times more likely to have an IQ score <80, which is the clinical cut-off for borderline intellectual disability (R² = 0.20, p = 0.03). Increasing of 1 μg g^-1 hair Hg resulted in 1 point of IQ loss in Wanshan children, which was.much higher than that via fish consumption. The economical cost due to Hg exposure was estimated to be $69.8 million (9.43% of total GDP) in the Wanshan area in 2018.

Sex-specific influence of prenatal air pollutant exposure on neonatal neurobehavioral development and the sensitive window

Increasing evidence indicates the adverse effect of air pollution exposure during pregnancy on neurologic development among children. However, the impact on neurobehavioral development in fetus remains unknown. In 2017, a total of 1193 mother-newborns pairs were enrolled in a birth cohort study in Changsha, China. Exposures to PM_2.5, PM_10, SO₂, CO and NO₂ were determined by using inverse distance weighted method based on local monitoring station data. Neurobehavioral measure was administered at 48-72 h postpartum by utilizing the neonatal behavioral neurological assessment (NBNA). Basic information and covariates were collected by face to face interview. Generalized linear regression and multivariable restricted cubic spline function were performed to explore the trimester-specific association and dose-response relationship of maternal air pollution exposure with NBNA score, respectively. In adjusted three-pollutant model, PM_2.5 exposure in trimester 2 was negatively associated with behavior score (β, -0.003; 95% CI, -0.006, -0.001) and the inverse relation was more pronounced in male infants. In addition, PM_2.5 level in the 2nd trimester was negatively related to activetone score (β, -0.012; 95% CI, -0.021, -0.002) in a dose-dependent manner for both genders. Collectively, our results demonstrated that prenatal exposure to PM_2.5 was linked to poor neurobehavioral performance of newborns. The second trimester was the most sensitive time window for the developments of behavior and activetone, and male subject was more vulnerable as compared to females.

Association between mercury in cord serum and sex-specific DNA methylation in cord tissues

Prenatal exposure to mercury in utero causes abnormal foetal growth and adverse outcomes. DNA methylation is currently considered a possible mechanism through which this occurs. However, few studies have investigated the association between prenatal exposure to mercury and DNA methylation in detail. This study aimed to clarify the relationship between prenatal exposure to total mercury (Hg) and DNA methylation and its associations with sex-specific characteristics in male and female offspring. In a birth cohort study known as the Chiba study of Mother and Child Health, the DNA methylation status in cord tissue and Hg concentrations in cord serum were examined. A total of 67 participants (27 males and 40 females) were analysed based on Spearman's correlations, adjusted by a false discovery rate of the sex of each offspring. Only one methylated locus was positively correlated with Hg concentrations in cord serum in male offspring, but not in female offspring, and was annotated to the haloacid dehalogenase-like hydrolase domain-containing protein 1 (HDHD1) gene on chromosome X. This locus was located in the intron of the HDHD1 gene body and is a binding site for the zinc finger protein CCCTC-binding factor. One of the other loci, located in HDHD1, was highly methylated in the group with higher mercury concentrations, and this locus was in the gene body of HDHD1. Our results suggest that prenatal exposure to Hg might affect the epigenetic status of male foetuses.

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.

Pregnancy exposome and child psychomotor development in three European birth cohorts

Characterization of the exposome, the totality of all environmental factors that one is exposed to from conception onwards, has been recommended to better evaluate the role of environmental influences on developmental programming and life-course vulnerability to major chronic diseases. In the framework of the Health and Environment-wide Associations based on Large population Surveys (HEALS) project we considered the pregnancy exposome exploiting two databases (PHIME and REPRO_PL) that include birth cohorts from three EU countries (Croatia, Slovenia and Poland). The databases contained information on several chemical exposures, socio-demographic, lifestyle and health related factors from conception to child birth, and neuropsychological scores assessed by the Bayley Scales of Infant and Toddler Development in the first two years of life. Our main goal was to assess consistency of environmental influences on neurodevelopment, if any, across European countries differing for geographical, socio-demographic characteristics and levels of chemical exposures to metals such as lead (Pb), mercury (Hg), cadmium (Cd) and trace elements, including micronutrients such as zinc (Zn) and selenium (Se). To this aim, we first selected variables common to the different databases, then applied univariate and multivariate regression analyses to identify factors linked to neurodevelopment, and finally performed meta-analysis to detect potential heterogeneity among cohorts and pooled estimates. Significant differences in exposure levels among the three sub-cohorts were observed as for Hg and Se; exposure levels under study were relatively low and within the range described in existing EU biomonitoring studies. The univariate analyses did not show any common pattern of association as only in the Polish cohort chemical exposure had an impact on neuropsychological outcome. In the meta-analysis, some consistent trends were evident, relative to the adverse influence of Pb on children's language and cognition and the positive influence of Se on language abilities. The effects of the neurotoxic metal Hg positively influenced the motor scores in the Polish cohorts, while it decreased the motor scores in the Slovenia and Croatian sub-cohorts. The only socio-demographic factor consistently associated to the outcome among cohorts was child's sex, with females performing better than males on cognitive and language scores. These findings point to the need of harmonizing existing cohorts or creating prospective study designs that facilitate comparisons in the exposome over time, places and kind of environmental exposures.

Prenatal polycyclic aromatic hydrocarbons metabolites, cord blood telomere length, and neonatal neurobehavioral development

BACKGROUND

Prenatal exposure to polycyclic aromatic hydrocarbon (PAH) is a potential risk factor for child neurobehavioral development. Telomere length (TL) has important implications for health over the life course.

OBJECTIVE

In this study, we aimed to investigate whether prenatal urinary PAH metabolites were associated with adverse neonatal neurobehavioral development and altered cord blood TL and to explore whether the change of TL was a predictor of neonatal neurobehavioral development.

METHOD

We enrolled 283 nonsmoking pregnant women in Taiyuan city. Eleven PAH metabolites were measured in maternal urine samples. TL in cord blood was measured by real time quantitative polymerase chain reaction. Neonatal behavioral neurological assessment (NBNA) tests were conducted when the infants were three days old. Multiple linear regression models were used to analyze the associations of maternal urinary PAH metabolites with NBNA scores and cord blood TL, and restricted cubic spline models were further used to examine the shapes of dose-response relationships. A mediation analysis was also conducted.

RESULT

We observed dose-response associations of maternal urinary 2-hydroxyfluorene (2-OHFlu) and 2-hydroxyphenanthrene (2-OH Phe) with decreased active tone scores, sum of NBNA scores, and cord blood TL (P for trend<0.05). Each 1 unit increase in urinary levels of Ln (2-OH Flu) or Ln (2-OH Phe) was associated with a 0.092 or 0.135 decrease in the active tone scores and a 0.174 or 0.199 decrease in the sum of NBNA scores. Mediation analysis showed TL could explained 21.74% of the effect of sum of NBNA scores change related to prenatal exposure to 2-OH Phe (P for mediator = 0.047).

CONCLUSION

Our data indicates maternal urinary specific PAH metabolites are inversely associated with neonatal neurobehavioral development and cord blood TL. TL mediates the associations of 2-OH Phe with neonatal neurobehavioral development and partly explains the effect of 2-OH Phe on neonatal neurobehavioral development.

Relation of prenatal low-level mercury exposure with early child neurobehavioral development and exploration of the effects of sex and DHA on it

BACKGROUND

The extent to which low-level, in utero mercury exposure affects child neurobehavioral development during early childhood has been inconclusive. In addition, the effects of sex and docosahexaenoic acid (DHA) on these relationships remain unclear and controversial.

OBJECTIVES

This study aimed to explore the associations between prenatal low-level mercury exposure and child neurobehavioral development during the neonatal and toddler periods and to examine the potential confounding or interactive effects of sex and DHA status on these relationships.

METHODS

This longitudinal study included 286 mother-child pairs in Shanghai, China, whose cord blood samples were analyzed for total mercury, DHA, other nutrients and coexposure contaminants possibly due to maternal consumption of seafood. Children's neurobehavioral development was assessed with the Neonatal Behavioral Neurological Assessment (NBNA) three days after birth and the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III) at 18 months of age.

RESULTS

Cord blood mercury concentration, with geometric mean of 2.00 μg/l, was related to poorer NBNA performance but unrelated to BSID-III scores with adjustment for DHA and other covariates. Cord serum DHA was positively associated with motor development assessed by the BSID-III. The interaction was found between mercury and DHA on the NBNA score, and the inverse relation of cord blood mercury with NBNA was significant only among the children with lower DHA levels (<45.54 μg/ml). Additional adjustment for DHA didn't change the associations between cord blood mercury and neurodevelopmental outcomes substantially. The mercury by sex interaction for language of BSID-III was borderline significant.

CONCLUSIONS

Our research provides initial evidence for the negative effects of prenatal low-level mercury exposure on neonates' neurobehavioral development. Prenatal DHA status may modify the relationship between cord blood mercury level and neonatal neurobehavioral development, but the confounding effects of DHA were not observed. Further studies are warranted before the causality of the observed associations can be determined.

Human Biological Monitoring of Mercury Through Hair Samples in China

Mercury (Hg) is a global pollutant that affects environmental and human health. Considering the high toxicity of Hg, it is required to assess the exposure of Hg in human body for appropriate risk management. In this review paper, we summarized data obtained through regional and small-scaled human biomonitoring (HBM) program for Hg in hair samples in China, which can deliver scientific data to make decisions on environmental health policy. Besides, the major conclusions got from this study and perspectives for future works through these HBM program in China were presented. To better understand the current situation of hair Hg levels in China, a well-coordinated and designed national HBM program is urgently needed considering the requirements of the Minamata Convention on Mercury for effectiveness evaluation.

Effects of lead, mercury, aluminium and manganese co-exposure on the serum BDNF concentration of pre-school children in Taizhou, China

Previous studies have shown that toxic metal exposure can have adverse effects on the nervous system of children, but the toxicology of metal co-exposure on neurodevelopment remains to be clarified. Brain derived neurotrophic factor (BDNF) plays an important role in nervous system development, but the possible effects of metal co-exposure on the serum BDNF concentrations of children remain unknown. A total of 561 children living in Taizhou City, China were recruited to participate in our cross-sectional multicenter survey. We measured their blood Pb, Hg, Al and Mn levels and serum BDNF concentrations as well as determined their associations in the total and within sex subgroups. The geometric means of the blood Pb, Hg, Al and Mn levels in all the participants were 67.18 μg/L, 1.01 μg/L, 52.03 μg/L and 18.26 μg/L, respectively. The serum BDNF concentration in children was 19.45 ng/mL. After adjusting for confounders, the blood Pb levels were significantly negatively associated with the serum BDNF concentrations in all the subjects and boys but not in girls. In addition, a significantly negative interaction between blood Pb and blood Hg and a positive interaction between blood Pb and blood Al on serum BDNF concentrations were also observed in boys but not in girls. Our findings highlight the toxic effects of metal co-exposure on serum BDNF levels in pre-school children and indicate that these effects might differ by gender, which suggest that special attention should be paid to the sex-specific effects of metal exposure.

First-trimester blood concentrations of drinking water trihalomethanes and neonatal neurobehavioral development in a Chinese birth cohort

Toxicological evidence indicates that exposure to drinking water trihalomethanes (THMs) can impair neural development. However, no epidemiologic study to date has evaluated the relation of trihalomethanes exposure with neonatal neurobehavioral development. Here we aimed to evaluate if prenatal exposure to THMs during early pregnancy is associated with neonatal neurobehavioral development in 451 Chinese mother-child pairs. First trimester blood THMs [chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM)] were determined by solid phase micro-extraction gas chramatography. Neonatal neurobehavioral development was assessed using neonatal behavioral neurological assessment (NBNA) on the third day after birth. Multivariable linear regression models and restricted cubic spline models were constructed to evaluate the associations between blood THMs and neonatal neurological development scores. Blood concentrations of BDCM, whether modeled as continuous or categorical variables, were inversely associated with total NBNA score of newborns based on the multivariable linear regression. The association was further confirmed in the cubic spline model, and a linear dose-response relationship was observed. Stratified analysis showed that the inverse association between blood BDCM and total NBNA score was more evident in male infants than females. Our findings suggest that exposure to THMs during early pregnancy may be associated with impaired neonatal neurobehavioral development.

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.

Placental concentrations of essential, toxic, and understudied metals and relationships with birth outcomes in Chattanooga, TN

BACKGROUND

Comprehensive examinations of placental metal concentrations and correlations with infant parameters are under-investigated. Chattanooga, Tennessee's consistently high incidence of low birth weight and potential for metal exposure provides an ideal opportunity to investigate potential correlations.

OBJECTIVES

To investigate the associations between a wide variety of metals in placental tissue and multiple infant parameters.

METHODS

A total of 31 elements were screened via ICP-MS in 374 individual placental samples. Of those, 14 were quantifiable in > 86% of the samples. We examined correlations between metal concentrations and infant parameters (birth weight, gestational age, birth weight centile, placental weight, birth length and head circumference). We fit multivariable regression models to estimate the covariate-adjusted associations of birth weight with ln-transformed concentrations of each of the 14 metals and used generalized additive models to examine nonlinear relationships.

RESULTS

Some of the strongest relationships with infant parameters came from several lesser-studied metals. Placental rhodium concentrations were negatively correlated with almost all infant parameters. In the fully adjusted regression model, birth weight was significantly associated with several metals. On an IQR (25th to the 75th percentile) basis, estimated changes in birthweight were: for cobalt (82.5 g, IQR=6.05 µg/kg, p = 0.006), iron (-51.5 g, IQR = 171800 µg/kg, p = 0.030), manganese (-27.2 g, IQR=152.1 µg/kg, p = 0.017), lead (-72.7 g, IQR=16.55 µg/kg, p = 0.004) and rhodium (-1365.5 g, IQR = 0.33 µg/kg, p < 0.001). Finally, a generalized additive model showed significant nonlinear relationships between birth weight and concentrations of Co and Rh.

CONCLUSIONS

Our comprehensive examination of placental metals illustrate many strong associations between lesser-studied metals and infant parameters. These data, in combination with our correlations of well-studied metals, illustrate a need to consider in utero exposure to a broad array of metals when considering fetal development.

Prenatal exposure to arsenic and neurobehavioral development of newborns in China

The link between arsenic exposure and deficits in children's neurodevelopment has been suggested, but it remains unclear regarding the arsenic-related effects on the developing brain in early life. To investigate the associations of in utero arsenic exposure with neonatal neurobehavioral development, we conducted a cross-sectional study of 892 mother-infant pairs from 10 hospitals of different levels in Shanghai, China. The concentrations of arsenic were determined in cord blood samples. Neurobehavioral measures were administered at 3 days postpartum in full-term newborns using the neonatal behavioral neurological assessment (NBNA). Logistic regression models were used to estimate odds ratios for dichotomous NBNA outcomes. After adjusting for potential confounders, a natural log unit (ln-unit) increase in cord blood arsenic was associated with 90% increased odds of low NBNA score (95% confidence interval [CI]: 1.62, 2.23). As for clusters, each ln-unit arsenic increase was associated with 47% increased odds of low score for behavior (95% CI: 1.31, 1.66) and 36% increased odds of low score for passive muscle tone (95% CI: 1.23, 1.51). Odds ratios comparing extreme tertiles were 8.62 (95% CI: 4.19, 17.8) for total scale, 3.69 (95% CI: 2.35, 5.82) for behavior, and 3.32 (95% CI: 2.21, 4.97) for passive tone (all p-trend < 0.001). Stratified analyses showed that these associations were strengthened in newborns of mothers over 29 years of age. Our results provide evidence for an inverse association between low-level prenatal arsenic exposure and neurobehavioral performance of newborns, particularly among those born to older mothers. Further studies are warranted to confirm these findings and to determine whether such decrements in early neurodevelopment persist in later childhood.

Distribution and predictors of 20 toxic and essential metals in the umbilical cord blood of Chinese newborns

Early-life exposure to heavy metals and/or trace metal imbalances can have negative developmental effects. Here we sought to characterize exposure profiles for 20 heavy metals and trace elements in umbilical cord blood plasma and identify demographic predictors of exposure. Twenty metals were measured in cord plasma from 357 Chinese infants using ICP-MS. Relationships between demographic variables and metals were analyzed using generalized linear models and logistic regression. Ten metals (antimony [Sb], cobalt [Co], cesium [Cs], copper [Cu], lead [Pb], molybdenum [Mo], rubidium [Rb], selenium [Se], strontium [Sr], titanium [Ti], zinc [Zn]) were detected in all samples. Season of birth was the strongest predictor of metals in cord blood across analyses. Infants born in the spring had 0.1-0.2 μg L-1 higher logAs and logCo in their cord blood (β [95%CI] = 0.22 [0.01,0.42], p = 0.04; 0.11 [0.01,0.22], p = 0.04), while infants born in the summer had higher Sb, logB, logHg, and logZn (β [95%CI] = 0.74 [0.24,1.24], p = 0.004; 0.11 [0.00,0.21], p = 0.04; 0.29 [0.08,0.49], p = 0.007; 0.18 [0.06,0.31], p = 0.005), compared to those born in fall/winter. Prenatal heavy metal exposure and/or trace metal deficiencies are global concerns because of increasing awareness of downstream developmental effects.

Methylmercury Exposure and Developmental Outcomes in Tohoku Study of Child Development at 18 Months of Age

Seafood is an important component in a healthy diet and may contain methylmercury or other contaminants. It is important to recognize the risks and benefits of consuming seafood. A longitudinal prospective birth cohort study has been conducted to clarify the effects of neurotoxicants on child development—the Tohoku Study of Child Development (TSCD) in Japan. TSCD comprises two cohorts; a polychlorinated biphenyls (PCB) cohort (urban area) and a methylmercury cohort (coastal area). Our previous results from the coastal area showed prenatal methylmercury exposure affected psychomotor development in 18-month-olds, and boys appear to be more vulnerable to the exposure than girls. In this report, we have added the urban area cohort and we reanalyzed the impact of prenatal exposure to methylmercury, which gave the same results as before. These findings suggest prenatal exposure to low levels methylmercury may have adverse effects on child development, especially in boys.

Prenatal mercury exposure and child neurodevelopment outcomes at 18 months: Results from the Mediterranean PHIME cohort

INTRODUCTION

Neurotoxicity due to acute prenatal exposure to high-dose of mercury (Hg) is well documented. However, the effect of prenatal exposure to low Hg levels on child neurodevelopment and the question about "safety" of fish-eating during pregnancy remain controversial. International comparisons of Hg concentrations in mother-child biological samples and neurodevelopmental scores embedded in birth cohort studies may provide useful evidence to explore this issue.

MATERIALS AND METHODS

The Mediterranean (Italy, Slovenia, Croatia, and Greece) cohort study included 1308 mother-child pairs enrolled in the Public Health Impact of long-term, low-level, Mixed Element exposure in a susceptible population EU Sixth Framework Programme (PHIME). Maternal hair and venous blood, cord blood and breast milk samples were collected, and total Hg (THg) levels were measured. Demographic and socioeconomic information, lifestyles and nutritional habits were collected through questionnaires at different phases of follow-up. Children at 18 months of age underwent neurodevelopmental testing using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). Multivariate linear and logistic regressions were performed, for each country, to assess the association between THg and BSID-III scores, obtaining adjusted β coefficients and odds ratios (ORs). These values were used to conduct a meta-analysis, to explore possible heterogeneity among countries and to obtain combined estimates of the association between THg exposure and BSID-III scores.

RESULTS

Median THg (ng/g) was: 704 in maternal hair, 2.4 in maternal blood, 3.6 in cord blood, and 0.6 in breast milk. THg concentrations were highest in Greece and lowest in Slovenia. BSID-III neurodevelopmental scores were higher in Croatia and Slovenia. The meta-analysis of multivariate linear models found an overall positive association between language composite score and receptive communication scaled score and increasing THg in maternal hair (n = 1086; β = 0.55; 95%CI: 0.05-1.05 and n = 1075; β = 0.12; 95%CI: 0.02-0.22, respectively). The meta-analysis of logistic regression models showed that the overall adjusted OR between THg in cord blood and suboptimal gross motor score was borderline significant (n = 882; OR = 1.03; 95%CI: 1.00-1.07). Heterogeneity was found across the four sub-cohorts for language composite score in maternal blood, and for fine motor scaled score in cord blood and breast milk. Language composite score and THg concentrations in maternal venous blood were positively related (n = 58; β = 4.29; CI95% (-0.02, 8.60)) in Croatia and an increase of 1 ng/g of THg in maternal venous blood was associated with a reduced risk for children to fall in the lowest quintile of language score by 31% (n = 58; OR = 0.69; CI 95%: 0.37, 1.01). The comparison of β coefficients obtained by multiple linear regression model showed an inverse association between fine motor score and THg concentrations in cord blood for Croatia (n = 54; β = -0.53; CI 95%: -1.10, 0.04) and Slovenia (n = 225; β = -0.25; CI 95%: -0.49, -0.01). In Slovenia THg level in breast milk was associated with suboptimal fine motor performance (n = 195; OR = 5.25; CI 95%: 1.36, 21.10).

CONCLUSIONS

This study showed an inverse relation between THg levels and developmental motor scores at 18 months, although the evidence was weak and partially internally and externally inconsistent. No evidence of detrimental effects of THg was found for cognitive and language outcomes at these concentrations and age.

Prenatal co-exposure to neurotoxic metals and neurodevelopment in preschool children: The Environment and Childhood (INMA) Project

We sought to determine whether prenatal co-exposure to As, Cd, Hg, Mn, and Pb was associated with impaired neurodevelopment in preschool children from the Spanish Environment and Childhood (INMA) Project, using the placenta as exposure matrix. We measured metal levels in placenta tissue samples randomly selected from five of the seven population-based birth cohorts participating in the INMA Project, collected between 2000 and 2008. Neuropsychological assessment of cognitive and motor function was carried through the use of the McCarthy Scales of Children's Abilities (MSCA) at the age of 4-5years. Data on placental metal levels, MSCA scores, and relevant covariates was available for 302 children. Mn was detected in all placental samples, Cd in nearly all placentas (99%) and As, Hg, and Pb in 22%, 58%, and 17% of the placentas, respectively. After adjusting for potential confounders, detectable As levels were associated with decrements in global and verbal executive functions and quantitative abilities; detectable Hg was associated with lower scores on the verbal function of posterior cortex in a dose-response manner, and non-linearly related to poorer motor function and gross motor skills; and Mn levels were associated with decrement in perceptual-performance skills in a dose-response manner but with better memory span and quantitative skills. A synergistic interactive effect was found between As and Pb with respect to the general cognitive score, whereas an antagonistic interaction was found between Mn and Hg. Prenatal exposure to As and Hg may be a risk factor for cognitive and motor impairment in children, while the effects of Cd and Mn on neurodevelopment are less clear. Future studies should examine combined and interactive effects of exposure to multiple metals during vulnerable periods of brain development prospectively.

Dietary human exposure to mercury in two artisanal small-scale gold mining communities of northwestern Colombia

Artisanal and small-scale gold mining (ASGM) is the largest anthropogenic source of mercury pollution worldwide, posing a grave threat to human health. The present study identifies current levels of mercury in the human population from mining areas of the Chocó Department, Colombia, through total mercury (THg) and methylmercury (MeHg) measurements in human hair. Mercury exposure of the local population was assessed in two towns affected by ASGM and was related to different variables of interest. Concentrations of THg in human hair ranged from 0.06 to 17.54ppm and the mean value for the subjects under study was 2.48ppm. Men had significantly higher levels than women in both towns (3.29ppm vs. 0.77ppm). Fish consumption was related to a marked increase of THg in hair, with mean values close to five times higher in frequent fish consumers (5-7 times/week) than in non-fish consumers (4.80ppm vs. 0.90ppm). A multiple linear regression model was fitted successfully (R=0.671) and reveals that gender, fish consumption and location of residence were significant indicators of Hg levels in hair, while no significant relationship was found for age. Approximately 60% of subjects tested had THg levels that exceeded the U.S. Environmental Protection Agency reference dose of 1.0ppm, while 25% surpassed that of the World Health Organization (2.2ppm).

Persistent DNA methylation changes associated with prenatal mercury exposure and cognitive performance during childhood

Prenatal exposure to mercury, a known neurotoxic metal, is associated with lower cognitive performance during childhood. Disruption of fetal epigenetic programming could explain mercury’s neurodevelopmental effects. We screened for epigenome-wide methylation differences associated with maternal prenatal blood mercury levels in 321 cord blood DNA samples and examined the persistence of these alterations during early (n = 75; 2.9–4.9 years) and mid-childhood (n = 291; 6.7–10.5 years). Among males, prenatal mercury levels were associated with lower regional cord blood DNA methylation at the Paraoxonase 1 gene (PON1) that persisted in early childhood and was attenuated in mid-childhood blood. Cord blood methylation at the PON1 locus predicted lower cognitive test scores measured during early childhood. Methylation at the PON1 locus was associated with PON1 expression in an independent set of cord blood samples. The observed persistent epigenetic disruption of the PON1 gene may modulate mercury toxicity in humans and might serve as a biomarker of exposure and disease susceptibility.

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.

Prenatal low-level mercury exposure and infant neurodevelopment at 12 months in rural northern China

Although MeHg is a confirmed neurotoxin at sufficiently high dosages, the effect of prenatal low-level Hg exposure on infant neurodevelopment is still unknown. Four hundred ten mother-infant pairs were recruited in rural northern China from September 2010 to September 2012. We investigated maternal diet during pregnancy, collected maternal and umbilical blood samples, and tested infant neurodevelopment using Gesell developmental schedules (GDS) at the age of 1 year old. The geometric means (GM) of Hg exposure in maternal and umbilical blood were 0.72 and 1.2 μg/L, respectively. Positive associations between Hg levels and the frequency of total fish consumption were found (Spearman's correlation, r = 0.09 for maternal Hg, r = 0.14 for umbilical Hg, p < 0.01). After adjusting for confounding factors, we found a log-unit increase in umbilical blood Hg levels was associated with a 4.22-point (95 % confidence interval (95 %CI) 0.77 to 7.67) increase in the adaptive domain and a 4.06-point (95 %CI 0.51 to 7.62) increase in the social domain. No significant association has been found between other domains and Hg levels in our study. In further analysis, we noticed the positive correlation between the developmental quotient (DQ) scores of the adaptive domain and frequencies of total fish consumption (p = 0.04). Our results failed to indicate the adverse effects between prenatal Hg exposure and infant neurodevelopment. However, given the low-level Hg exposure and its predominant source, the potential positive associations in our study may be attributed to the beneficial nutrients of fish consumption.

Cord Blood Methylmercury and Fetal Growth Outcomes in Baltimore Newborns: Potential Confounding and Effect Modification by Omega-3 Fatty Acids, Selenium, and Sex

BACKGROUND

Methylmercury (MeHg) may affect fetal growth; however, prior research often lacked assessment of mercury speciation, confounders, and interactions.

OBJECTIVE

Our objective was to assess the relationship between MeHg and fetal growth as well as the potential for confounding or interaction of this relationship from speciated mercury, fatty acids, selenium, and sex.

METHODS

This cross-sectional study includes 271 singletons born in Baltimore, Maryland, 2004-2005. Umbilical cord blood was analyzed for speciated mercury, serum omega-3 highly unsaturated fatty acids (n-3 HUFAs), and selenium. Multivariable linear regression models controlled for gestational age, birth weight, maternal age, parity, prepregnancy body mass index, smoking, hypertension, diabetes, selenium, n-3 HUFAs, and inorganic mercury (IHg).

RESULTS

Geometric mean cord blood MeHg was 0.94 μg/L (95% CI: 0.84, 1.07). In adjusted models for ponderal index, βln(MeHg) = -0.045 (g/cm(3)) × 100 (95% CI: -0.084, -0.005). There was no evidence of a MeHg × sex interaction with ponderal index. Contrastingly, there was evidence of a MeHg × n-3 HUFAs interaction with birth length [among low n-3 HUFAs, βln(MeHg) = 0.40 cm, 95% CI: -0.02, 0.81; among high n-3 HUFAs, βln(MeHg) = -0.15, 95% CI: -0.54, 0.25; p-interaction = 0.048] and head circumference [among low n-3 HUFAs, βln(MeHg) = 0.01 cm, 95% CI: -0.27, 0.29; among high n-3 HUFAs, βln(MeHg) = -0.37, 95% CI: -0.63, -0.10; p-interaction = 0.042]. The association of MeHg with birth weight and ponderal index was affected by n-3 HUFAs, selenium, and IHg. For birth weight, βln(MeHg) without these variables was -16.8 g (95% CI: -75.0, 41.3) versus -29.7 (95% CI: -93.9, 34.6) with all covariates. Corresponding values for ponderal index were -0.030 (g/cm(3)) × 100 (95% CI: -0.065, 0.005) and -0.045 (95% CI: -0.084, -0005).

CONCLUSION

We observed an association of increased MeHg with decreased ponderal index. There is evidence for interaction between MeHg and n-3 HUFAs; infants with higher MeHg and n-3 HUFAs had lower birth length and head circumference. These results should be verified with additional studies.

Prenatal Maternal Occupational Exposure and Postnatal Child Exposure to Elemental Mercury

OBJECTIVES

Young children are highly vulnerable to elemental mercury toxicity, and elementary mercury exposure in young children in China unfortunately occurs regularly because of the wide use of fluorescent lamps, glass thermometers, and other mercury-contained items. This study aimed to summarize such recent cases in a referral clinic and to make recommendations for postexposure treatment and prevention of future exposure.

METHODS

Patients were evaluated between January 2007 and December 2009 in environmental health facilities throughout China and were referred to our clinic. A total of 6 children younger than 4 years with significant elemental mercury exposure were included in this case series analysis. The total mercury content in blood and hair (fetal hair if necessary) and average 24-hour urine mercury concentrations were analyzed. Meso-2,3-dimercaptosuccinic acid or surgery was prescribed for the patient if necessary.

RESULTS

Young children were found to be exposed in 3 ways as follows: prenatal exposure through maternal occupational contact in compact fluorescent-lamp factories (2 cases), broken thermometers (3 cases), and other causes of accidental inhalation of mercury vapor during the embryonic and lactation periods (1 case). For 3 cases caused by broken thermometers, x-ray images helped to identify the position of mercury residues. Local excision was used to remove mercury from the floor of the mouth in 1 case. One child was prescribed oral meso-2,3-dimercaptosuccinic acid, and a good response was received.

CONCLUSIONS

Substitution of mercury-in-glass thermometers and vigilance to prevent women of childbearing age from occupational mercury exposure were suggested. Treatment selection should vary according to patient situations.

Mercury levels assessment and its relationship with oxidative stress biomarkers in children from three localities in Yucatan, Mexico

Mercury (Hg) is a global pollutant that is released into the environment from geologic and anthropogenic sources. Once it enters an organism, it generates several toxicity mechanisms and oxidative stress has been proposed as the main one. Metal susceptibility is greater in children, which is a result of their physiology and behavior. In Yucatan, Mexico, burning of unregulated garbage dumps and household trash, ingestion of top marine predators, and pottery manufacturing are among the conditions that could promote Hg exposure. However, for Yucatan, there are no published studies that report Hg levels and associated oxidative stress status in children. Therefore, this study aimed to assess Hg levels in blood and urine and oxidative stress biomarkers levels in a sample of 107 healthy children from three localities in Yucatan, Mexico, as well as investigate the relationship between these parameters. Hg was detected in 11 (10.28%) of blood samples and 38 (35.51%) of urine samples collected from the participating children. Fourteen subjects showed Hg above recommended levels. The oxidative stress biomarkers were slightly elevated in comparison with other studies and were statistically different between the sampling sites. No linear correlation between Hg levels and oxidative stress biomarkers was found. Nevertheless, exploratory univariate and multivariate analysis showed non-linear relations among the measured variables. Globally, the study provides, for the first time, information regarding Hg levels and their relationship with oxidative stress biomarkers in a juvenile population from Mexico's southeast (Yucatan) region. In agreement with worldwide concern about Hg, this study should stimulate studies on metal monitoring in humans (especially children) among scientists working in Mexico, the establishment of polices for its regulation, and the reduction of human health risks.

A brain proteome profile in rats exposed to methylmercury or thimerosal (ethylmercury)

Exposure to organomercurials has been associated with harmful effects on the central nervous system (CNS). However, the mechanisms underlying organomercurial-mediated neurotoxic effects need to be elucidated. Exposure to toxic elements may promote cellular modifications such as alterations in protein synthesis in an attempt to protect tissues and organs from damage. In this context, the use of a "proteomic profile" is an important tool to identify potential early biomarkers or targets indicative of neurotoxicity. The aim of this study was to investigate potential modifications in rat cerebral cell proteome following exposure to methylmercury (MeHg) or ethylmercury (EtHg). For MeHg exposure, animals were administered by gavage daily 140 µg/kg/d of Hg (as MeHg) for 60 d and sacrificed 24 h after the last treatment. For EtHg exposure, 800 µg/kg/d of Hg (as EtHg) was given intramuscularly (im) in a single dose and rats were sacrificed after 4 h. Control groups received saline either by gavage or im. After extraction of proteins from whole brain samples and separation by two-dimensional electrophoresis (2-DE), 26 differentially expressed proteins were identified from exposed animals by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF/TOF). Both MeHg and EtHg exposure induced an overexpression of calbindin, a protein that acts as a neuroprotective agent by (1) adjusting the concentration of Ca(2+) within cells and preventing neurodegenerative diseases and (2) decreasing expression of glutamine synthetase, a crucial protein involved in regulation of glutamate concentration in synaptic cleft. In contrast, expression of superoxide dismutase (SOD), a protein involved in antioxidant defense, was elevated in brain of MeHg-exposed animals. Taken together, our data provide new valuable information on the possible molecular mechanisms associated with MeHg- and EtHg-mediated toxicity in cerebral tissue. These observed protein alterations may be considered as biomarkers candidates for biological monitoring of organomercurial poisoning.

Placental Epigenetics in Children's Environmental Health

There is a growing interest in understanding the mechanisms that drive the developmental origins of health and disease, and the role of epigenetic regulation has risen to the forefront of these studies. In particular, the placenta may be a model organ to consider as a mediator of the impact of the environment on developmental programming of children's health, as this organ plays a critical role in directing development and regulating the fetal environment. Several recent studies have begun to examine how environmental toxicant exposures can impact the placental epigenome, focusing on studies of DNA methylation and microRNA expression. This review highlights several of these studies and emphasizes the potential the placenta may hold on the broader understanding of the impact of the intrauterine environment on long-term health.

Assessing pre/post-weaning neurobehavioral development for perinatal exposure to low doses of methylmercury

Fetuses and neonates are known to be high-risk groups for Methylmercury (MeHg) exposure. MeHg can be transferred to the fetus through the placenta and to newborn offspring through breast milk. The aim of the present study was to investigate the neurotoxic effects of low doses of MeHg (1 and 5μg/mL in drinking water) administration, from gestational day 1 to postnatal day (PND) 21, on the neurobehavioral development of rats. The results showed that the no-observed-effect level of MeHg is somewhere in the range of 1-4μg/mL. Neurobehavioral development analysis revealed a delayed appearance of cliff drop and negative geotaxis reflexes in the 5μg/mL MeHg exposure group. Developmental exposure to MeHg affected locomotor activity functions for the females, but not for the males, implying that the female pups were more vulnerable than the male pups. All pups exposed to 5μg/mL of MeHg showed a significant deficit in motor coordination in the rotarod test compared with controls, and the highest accumulated concentrations of Hg were found in the cerebellum, followed by the hippocampus and cerebral cortex, indicating that the cerebellum is a possible target for MeHg toxicity. We demonstrated adverse effects of developmental exposure to MeHg associated with tissue concentrations very close to the current human body burden of this persistent and bioaccumulative compound.

Placental DNA Methylation Related to Both Infant Toenail Mercury and Adverse Neurobehavioral Outcomes

BACKGROUND

Prenatal mercury (Hg) exposure is associated with adverse child neurobehavioral outcomes. Because Hg can interfere with placental functioning and cross the placenta to target the fetal brain, prenatal Hg exposure can inhibit fetal growth and development directly and indirectly.

OBJECTIVES

We examined potential associations between prenatal Hg exposure assessed through infant toenail Hg, placental DNA methylation changes, and newborn neurobehavioral outcomes.

METHODS

The methylation status of > 485,000 CpG loci was interrogated in 192 placental samples using Illumina's Infinium HumanMethylation450 BeadArray. Hg concentrations were analyzed in toenail clippings from a subset of 41 infants; neurobehavior was assessed using the NICU Network Neurobehavioral Scales (NNNS) in an independent subset of 151 infants.

RESULTS

We identified 339 loci with an average methylation difference > 0.125 between any two toenail Hg tertiles. Variation among these loci was subsequently found to be associated with a high-risk neurodevelopmental profile (omnibus p-value = 0.007) characterized by the NNNS. Ten loci had p < 0.01 for the association between methylation and the high-risk NNNS profile. Six of 10 loci reside in the EMID2 gene and were hypomethylated in the 16 high-risk profile infants' placentas. Methylation at these loci was moderately correlated (correlation coefficients range, -0.33 to -0.45) with EMID2 expression.

CONCLUSIONS

EMID2 hypomethylation may represent a novel mechanism linking in utero Hg exposure and adverse infant neurobehavioral outcomes.

Low-level prenatal mercury exposure in north China: an exploratory study of anthropometric effects

In order to investigate anthropometric effects of mercury (Hg) exposure, we examined the status of human prenatal exposure to Hg species, including total mercury (THg), methylmercury (MeHg) and inorganic mercury (IHg), in North China, as well as their potential effects on fetal and infant growth. Hg concentrations in various bioindicators were measured from 50 Chinese women and newborns in 2011. The participants were followed for 12 months to collect anthropometric information. Linear and two-level regression analyses were performed to determine the associations between Hg levels and body growth. The geometric mean levels of THg in the placenta, cord blood, fetal hair, and maternal blood, hair, and urine were 25.88 μg/kg dry wt, 2.73 μg/L, 572.98 μg/kg, 2.29 μg/L, 576.54 μg/kg, and 0.58 μg/g creatinine, respectively. Nearly 100% of Hg presented as IHg in urine, and the percentage of IHg in other bioindicators was 14.86-48.73%. We observed significantly negative associations between Hg levels in some matrixes and anthropometry of neonates (weight and height) and infants (height) (p < 0.05). THg levels in maternal hair were also negatively associated with infant growth rate of weight during 12 months after delivery (p = 0.017). This study suggests that low-level prenatal Hg exposure could play a role in attenuating fetal and infant growth, and the effects of MeHg and IHg are different.

Prenatal exposure to manganese at environment relevant level and neonatal neurobehavioral development

BACKGROUND

Effects of prenatal Manganese (Mn) exposure at an environmental relevant level on neonatal neurodevelopment remains unclear.

OBJECTIVES

In the multi-center study, we assessed the impact of low level prenatal Mn exposure on neonatal behavioral neurological assessments (NBNA), and explore a threshold umbilical cord blood Mn on neonatal neurological development.

METHODS

We investigated 933 mother-newborn pairs in Shanghai, China, from 2008 through 2009. Umbilical cord serum concentrations of Mn were measured and NBNA tests were conducted. The NBNA contains five clusters: behavior, active tone, passive tone, primary reflexes and general assessment with a maximal total score of 40. The score<37 is defined as low.

RESULTS

The median serum Mn concentration was 4.0 μg/L. Of the 933 infants, 44 (4.7%) had low NBNA. After adjusting for potential confounders, a high level of Mn (≥ 75th percentile ) was associated with a lower NBNA score (adjusted ß=-1.1, 95% CI: -1.4-0.7, p<0.01) and a higher risk of low NBNA (adjusted OR=9.4, 95% CI: 3.4-25.7, p<0.01). A nonlinear relationship was observed between cord serum Mn and NBNA after adjusting for potential confounders. NBNA score decreased with increasing Mn levels after 5.0 μg/L(LgMn ≥ 0.7). The cord serum Mn ≥ 5.0 μg/L had adverse effects on behavior, active tone and general reactions of clusters (p<0.001).

CONCLUSIONS

High prenatal Mn exposure even at an environmental relevant level, is associated with poor fetal neurobehavioral development in a nonlinear pattern. A threshold cord serum Mn of 5.0 μg/L existed for lower neonatal behavioral neurological assessments.

Body burden of Hg in different bio-samples of mothers in Shenyang city, China

Hg is an accumulative and neuro-toxic heavy metal which has a wide range of adverse effects in human health. However, few studies are available on body burden of Hg level in different bio-samples of pregnant women in Chinese population. Therefore, this study evaluated Hg levels in different maternal bio-samples in Shenyang city, China and investigated the correlation of Hg levels in different bio-samples. From October to December 2008, 200 pregnant women about to deliver their babies at ShengJing Hospital (Shenyang city, northeast of China) participated in this study. The geometric mean (GM) of Hg levels in cord blood, maternal venous blood, breast milk, and maternal urine were 2.18 µg/L, 1.17 µg/L, 1.14 µg/L, and 0.73 µg/L, respectively, and the GM of maternal hair Hg level was 404.45 µg/kg. There was a strong correlation between cord blood and maternal blood total Hg level (r = 0.713, P<0.001). Frequency of fish consumption more than or equal to 3 times per week during pregnancy was suggested as a significant risk factor of prenatal Hg exposure (unadjusted OR 3.5, adjusted OR 2.94, P<0.05). This study provides evidence about Hg burden of mothers and the risk factors of prenatal Hg exposure in Shenyang city, China.

The neurological effects of prenatal and postnatal mercury/methylmercury exposure on three-year-old children in Taiwan

This study attempts to elucidate the relationship between neurological effects and mercury/methylmercury concentrations in various biomarkers, including meconium, hair, fingernail, and toenail. Eight-three mother-infant pairs were recruited between August 2008 and December 2009, and follow-up examinations on these children were completed after three years. The Bayley Scales of Infant and Toddler Development (Bayley-III) for evaluating the cognitive, language, and motor development of three-year-old children were calculated and validated. The geometric mean of the total mercury concentration in meconium was 89.6 ng g(-1). The methylmercury concentrations in hair, fingernail, and toenail samples were 1.96, 0.64, and 0.55 μg g(-1), respectively. Seventy percent of children had hair methylmercury concentrations exceeding the U.S. environmental protection agency (EPA) reference of 1 μg g(-1). A significantly positive correlation was obtained between methylmercury levels in hair, fingernail, and toenail. These methylmercury levels were also significantly positively correlated with the children's fish intake and negatively correlated with a Bayley-III scale score of expressive language. The prenatal mercury exposure, however, did not show significant influence on neurological development. High fish consumption appears to be a critical risk factor for methylmercury levels in children and may cause a lower expressive language score.

Global methylmercury exposure from seafood consumption and risk of developmental neurotoxicity: a systematic review

OBJECTIVE

To examine biomarkers of methylmercury (MeHg) intake in women and infants from seafood-consuming populations globally and characterize the comparative risk of fetal developmental neurotoxicity.

METHODS

A search was conducted of the published literature reporting total mercury (Hg) in hair and blood in women and infants. These biomarkers are validated proxy measures of MeHg, a neurotoxin found primarily in seafood. Average and high-end biomarkers were extracted, stratified by seafood consumption context, and pooled by category. Medians for average and high-end pooled distributions were compared with the reference level established by a joint expert committee of the Food and Agriculture Organization (FAO) and the World Health Organization (WHO).

FINDINGS

Selection criteria were met by 164 studies of women and infants from 43 countries. Pooled average biomarkers suggest an intake of MeHg several times over the FAO/WHO reference in fish-consuming riparians living near small-scale gold mining and well over the reference in consumers of marine mammals in Arctic regions. In coastal regions of south-eastern Asia, the western Pacific and the Mediterranean, average biomarkers approach the reference. Although the two former groups have a higher risk of neurotoxicity than the latter, coastal regions are home to the largest number at risk. High-end biomarkers across all categories indicate MeHg intake is in excess of the reference value.

CONCLUSION

There is a need for policies to reduce Hg exposure among women and infants and for surveillance in high-risk populations, the majority of which live in low-and middle-income countries.

Prenatal exposure to organophosphate pesticides and neurobehavioral development of neonates: a birth cohort study in Shenyang, China

Background

A large amount of organophosphate pesticides (OPs) are used in agriculture in China every year, contributing to exposure of OPs through dietary consumption among the general population. However, the level of exposure to OPs in China is still uncertain.

Objective

To investigate the effect of the exposure to OPs on the neonatal neurodevelopment during pregnancy in Shenyang, China.

Methods

249 pregnant women enrolled in the Central Hospital Affiliated to Shenyang Medical College from February 2011 to August 2012. A cohort of the mothers and their neonates participated in the study and information on each subject was obtained by questionnaire. Dialkyl phosphate (DAP) metabolites were detected in the urine of mothers during pregnancy to evaluate the exposure level to OPs. Neonate neurobehavioral developmental levels were assessed according to the standards of the Neonatal Behavioral Neurological Assessment (NBNA). Multiple linear regressions were utilized to analyze the association between pregnancy exposure to OPs and neonatal neurobehavioral development.

Results

The geometric means (GM) of urinary metabolites for dimethyl phosphate (DMP), dimethyl thiophosphate (DMTP), diethyl phosphate (DEP), and diethyl thiophosphate (DETP) in pregnant women were 18.03, 8.53, 7.14, and 5.64 µg/L, respectively. Results from multiple linear regressions showed that prenatal OP exposure was one of the most important factors affecting NBNA scores. Prenatal total DAP concentrations were inversely associated with scores on the NBNA scales.?Additionally, a 10-fold increase in DAP concentrations was associated with a decrease of 1.78 regarding the Summary NBNA (95% CI, −2.12 to −1.45). And there was an estimated 2.11-point difference in summary NBNA scores between neonates in the highest quintile of prenatal OP exposure and the lowest quintile group.

Conclusion

The high exposure of pregnant women to OPs in Shenyang, China was the predominant risk factor for neonatal neurobehavioral development.

Selenium protects neonates against neurotoxicity from prenatal exposure to manganese

Manganese (Mn) exposure can affect brain development. Whether Selenium (Se) can protect neonates against neurotoxicity from Mn exposure remains unclear. We investigated this issue in 933 mother-newborn pairs in Shanghai, China, from 2008 through 2009. Umbilical cord serum concentrations of Mn and Se were measured and Neonatal Behavioral Neurological Assessment (NBNA) tests were conducted. The scores <37 were defined as the low NBNA. The median concentrations of cord serum Mn and Se were 4.0 µg/L and 63.1 µg/L, respectively. After adjusting for potential confounders, the interaction between Se and Mn was observed. Cord blood Mn levels had different effects on NBNA scores stratified by different cord blood Se levels. With Se Collapse

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MESH Headings

• Analysis of Variance
• Female
• Humans
• Infant, Newborn
• Male
• Manganese/toxicity
• Maternal Exposure/adverse effects
• Neuroprotective Agents/pharmacology
• Pregnancy
• Prenatal Exposure Delayed Effects/prevention & control
• Selenium/pharmacology

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Affiliation(s)

Xin Yang MOE-Shanghai Key Lab of Children’s Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
YiXiao Bao Department of Pediatrics, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
HuanHuan Fu MOE-Shanghai Key Lab of Children’s Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
LuanLuan Li MOE-Shanghai Key Lab of Children’s Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
TianHong Ren MOE-Shanghai Key Lab of Children’s Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
XiaoDan Yu MOE-Shanghai Key Lab of Children’s Environmental Health, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China

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