Maternal and fetal mercury and n-3 polyunsaturated fatty acids as a risk and benefit of fish consumption to fetus

Maternal n-7 Unsaturated Fatty Acids Protect the Fetal Brain from Neuronal Degeneration in an Intrauterine Hyperglycemic Animal Model

We previously reported that glycation induces insulin resistance in the hearts of newborn pups from a gestational diabetes mellitus (GDM) rat model. Administration of n-3 unsaturated fatty acids suppressed glycation and improved signaling in GDM rat pups. In this study, we investigated their effects on cranial neurons using the GDM rat model and PC12 cells derived from rat adrenal pheochromocytomas. Additionally, we examined whether n-3 and n-7 unsaturated fatty acids (cis-palmitoleic acid [CPA] and trans-palmitoleic acid [TPA]) ameliorate the detrimental effects of high glucose exposure on rats. In the neonatal cerebrum of GDM rats, increased levels of advanced glycation end products (AGEs) inhibited Akt phosphorylation; however, CPA and TPA intake during pregnancy ameliorated these abnormalities. Furthermore, exposure to high-glucose-induced apoptosis in PC12 cells compared to the cells cultured in control glucose. PC12 cells exposed to high-glucose with fatty acids exhibited reduced AGE production and apoptosis induction compared to the high-glucose group. These findings suggest that a hyperglycemic environment during pregnancy promotes AGE formation in brain neuronal proteins and induces apoptosis. Both TPA and CPA mitigated these abnormalities; however, CPA is cytotoxic, highlighting its safety in pregnant women.

Total mercury and fatty acids content in selected fish marketed in Quito - Ecuador. A benefit-risk assessment

Total mercury and fatty acids contents were determined in muscles of croaker, snapper, dolphinfish, blue marlin, and shark, from different markets in the Metropolitan District of Quito, Ecuador. Fifty-five samples were collected and analyzed for total mercury using cold vapor atomic fluorescence spectrometry, and the fatty acids were analyzed using gas chromatography equipped with a flame ionization detector. The lowest total mercury levels were found in snapper [0.041 µg·g^-1 wet weight (ww)] while blue marlin showed the highest (5.883 µg·g^-1 ww). EPA + DHA ranged from 1.0 mg·g^-1 in snapper to 2.4 mg·g^-1 in shark. A high omega-3/omega-6 ratio was found for all fish types; however, the HQ_EFA for the benefit-risk ratio was above 1, suggesting an evident risk to human health. Based on our results, consumption of croaker and dolphinfish is recommended up to one serving per week, considering the importance of EFAs intake and avoiding fish with elevated MeHg content. Therefore, Ecuadorian authorities could enhance public standards for seafood safety and develop consumer advice for pregnant women and young children to determine good fish choices or those to avoid.

Association between maternal fish consumption during pregnancy and preterm births: the Japan Environment and Children's Study

BACKGROUND

Fish are a rich source of essential nutrients that protect against preterm birth. However, as fish can absorb environmental pollutants, their consumption can also increase the risk of preterm birth. This study aimed to assess whether maternal fish consumption during pregnancy is associated with preterm birth in a nationwide large Japanese cohort that consumed relatively high amounts and many types of fish.

METHODS

This study included 81,428 mother-child pairs enrolled in a nationwide prospective Japanese birth cohort study. Fish consumption was assessed using a validated food frequency questionnaire. Multivariate logistic regression was used to investigate the association of total consumption of fish, fatty fish and lean fish, fish paste, and seafood and clams with preterm birth, adjusted for potential confounders.

RESULTS

There was no association between overall fish consumption and preterm births. However, the highest quintile of fish paste consumption was significantly associated with an increased risk of preterm birth (odds ratio [OR]: 1.11; 95% confidence interval [CI: 1.04, 1.17]). The consumption of baked fish paste at least three times per week was significantly associated with preterm birth (OR: 1.20; 95% CI: 1.03, 1.40). Consumption of other types of fish, except fish paste, was not significantly associated with preterm birth risk.

CONCLUSIONS

Fish paste consumption may increase the risk of preterm birth. Further studies are required to confirm this association.

Mercury Contamination in Fish and Its Effects on the Health of Pregnant Women and Their Fetuses, and Guidance for Fish Consumption-A Narrative Review

As a principal source of long-chain omega-3 fatty acids (3FAs), which provide vital health benefits, fish consumption also comes with the additional benefit of being rich in diverse nutrients (e.g., vitamins and selenium, high in proteins and low in saturated fats, etc.). The consumption of fish and other seafood products has been significantly promoted universally, given that fish is an important part of a healthy diet. However, many documents indicate that fish may also be a potential source of exposure to chemical pollutants, especially mercury (Hg) (one of the top ten chemicals or groups of chemicals of concern worldwide), and this is a grave concern for many consumers, especially pregnant women, as this could affect their fetuses. In this review, the definition of Hg and its forms and mode of entrance into fish are introduced in detail and, moreover, the bio-accumulation of Hg in fish and its toxicity and action mechanisms on fish and humans, especially considering the health of pregnant women and their fetuses after the daily intake of fish, are also reviewed. Finally, some feasible and constructive suggestions and guidelines are recommended for the specific group of pregnant women for the consumption of balanced and appropriate fish diets in a rational manner.

PM2.5 as a potential risk factor for autism spectrum disorder: Its possible link to neuroinflammation, oxidative stress and changes in gene expression

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by behavioral deficits including impairments in social communication, social interaction, and repetitive behaviors. Because the etiology of ASD is still largely unknown, there is no cure for ASD thus far. Although it has been established that genetic components play a vital role in ASD development, the influence of epigenetic regulation induced by environmental factors could also contribute to ASD susceptibility. Accumulated evidence has suggested that exposure to atmospheric particulate matter (PM) in polluted air could affect neurodevelopment, thus possibly leading to ASD. Particles with a size of 2.5 μm (PM_2.5) or less have been shown to have negative effects on human health, and could be linked to ASD symptoms in children. This review summarizes evidence from clinical and animal studies to demonstrate the possible linkage between PM_2.5 exposure and the incidence of ASD in children. An attempt was made to explore the possible mechanisms of this linkage, including changes of gene expression, oxidative stress and neuroinflammation induced by PM_2.5 exposure.

Prenatal exposure to mercury and precocious puberty: a prospective birth cohort study

STUDY QUESTION

Is in utero exposure to mercury associated with the risk of precocious puberty?

SUMMARY ANSWER

Prenatal exposure to high levels of mercury was associated with increased risk of precocious puberty, which was strengthened by concomitant maternal cardiometabolic conditions and adverse birth outcomes.

WHAT IS KNOWN ALREADY

The developing fetus is sensitive to mercury, a well-known endocrine disruptor which impacts the endocrine and reproductive system.

STUDY DESIGN, SIZE, DURATION

This study included 1512 mother-child pairs from the Boston Birth Cohort, a longitudinal cohort which recruited at birth and followed prospectively up to 21 years of age.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Mother-child pairs, from a predominantly urban minority population, were enrolled from 2002 to 2013. Prenatal exposure was assessed by maternal mercury concentration in red blood cells (RBCs) collected at 1-3 days after delivery. Precocious puberty was defined based on International Classification of Disease codes. Cox proportional hazards models were applied to the association between maternal mercury concentrations and the risk of precocious puberty.

MAIN RESULTS AND THE ROLE OF CHANCE

The median (interquartile range) of maternal mercury concentrations among children with and without precocious puberty were 3.4 (1.9-4.6) µg/l and 2.0 (1.0-3.7) µg/l, respectively. Compared to those in the lowest tertile for mercury, the highest tertile was associated with increased risk of precocious puberty, with an adjusted hazard ratio (HR) of 2.41, 95% CI: 1.16-5.03. In addition, concomitant maternal cardiometabolic conditions and adverse birth outcomes strengthened the effects of mercury on the risk of precocious puberty. The highest risk of precocious puberty was observed among children who had adverse birth outcomes and whose mothers had high RBC-mercury concentrations along with cardiometabolic conditions, with an HR of 4.76 (95% CI: 1.66-13.60) compared to children with favorable profiles of all three risk factors.

LIMITATIONS, REASONS FOR CAUTION

Precocious puberty was defined based on medical records, not on a direct assessment, which may have led to underdiagnosis and the inability to make a subclassification. The study included a predominately urban, low-income, minority population and as such our findings may not be widely generalizable.

WIDER IMPLICATIONS OF THE FINDINGS

Prenatal Hg exposure was associated with an increased risk of precocious puberty. This risk was strengthened by concomitant maternal cardiometabolic conditions during pregnancy and adverse birth outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the NIH/National Institute of Environmental Health Sciences, NIH/Eunice Kennedy Shriver National Institute of Child Health and Human Development and the Health Resources and Services Administration of the U.S. Department of Health and Human Services. The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Human mercury exposure levels and fish consumption at the French Riviera

Humans are exposed to methylmercury (MeHg), a bioaccumulative neurotoxin, mainly through the consumption of marine fish. Several studies showed that high MeHg exposure can lead to neurological damage. This is particularly relevant for pregnant women, because MeHg exposure negatively impacts foetal development. Populations living near the sea are generally at increased exposure risk due to higher consumption of fish and seafood. Here, we present the first study of MeHg exposure levels of the population living at the French Riviera, using mercury (Hg) concentrations in hair as a proxy for MeHg exposure. We found that older people that consume more fish presented the highest hair Hg concentrations. Compared to other Mediterranean bordering countries and other European countries, the southern France population is among those with high MeHg exposure (median for women of childbearing age is 0.56 μg g^-1). A global implementation of the Minamata Convention is necessary to lower MeHg exposure of the population.

Using carbon and nitrogen stable isotope modelling to assess dietary mercury exposure for pregnant women in Baja California Sur, Mexico

INTRODUCTION

Previous studies of mercury (Hg) in pregnant women in the area of La Paz, Baja California Sur (BCS), Mexico found a proportion of individuals had concentrations of total Hg ([THg]) above some thresholds of concern set by health agencies. The [THg] were associated with fish and seafood consumption as well as other factors; although it was unclear which marine diet items could potentially be contributing to the concentrations observed.

METHOD

We examined [THg] and monomethylmercury concentration ([MeHg⁺]) in the archived hair of 70 pregnant women from BCS as well as in diet items including fish, shellfish, and staple items (rice, beans, corn, and flour). We measured stable isotopes of carbon and nitrogen and employed a Bayesian stable isotope mixing model to investigate the proportion of fish and seafood in the isotopic profiles of archived hair samples.

RESULTS

Concentrations of Hg species were low in staple foods and ranged from below detection limit to 5.71 parts per billion (ppb) wet weight. In hair, geometric mean [THg] was 658 ppb and [MeHg⁺] was 395 ppb, which were lower than previous reports. Percent MeHg⁺ was positively correlated with higher δ¹⁵N values.

CONCLUSIONS

The largest carbon contributors to the diet of the study participants were corn and rice, and our analysis of fish contribution to diet varyingly agreed with the self-reported fish consumption. This report highlights the ability to discriminate potential sources of Hg from a diverse diet and the limitations of dietary recall studies.

Sustainable Seafood and Vegetable Production: Aquaponics as a Potential Opportunity in Urban Areas

Global population growth will increase pressures on current food systems in order to supply adequate protein and produce to the increasingly urban world population. The environmental impact of food production is a critical area of study as it influences water and air quality, ecosystem functions, and energy consumption. Aquaponics (in which seafood and vegetables are grown in a closed-loop system) has the potential to reduce the environmental impact of food production. A review of the current environmental and economic considerations is provided in order to identify current research gaps. Research gaps exist with respect to 1) diversity of aquatic and plant species studied; 2) inconsistent bounds, scope, and lifetime across studies; 3) diverse allocation of the environmental and economic impacts to the coproducts; 4) scale of systems considered; 5) transportation of produced food; and 6) presence of heavy metals, pests, and pathogens with human health implications. These aspects require increased attention to close the existing gaps prior to widescale deployment of these systems for increased sustainable food production toward satisficing human needs. Integr Environ Assess Manag 2019;00:1-12. © 2019 SETAC.

Rethinking the Dental Amalgam Dilemma: An Integrated Toxicological Approach

Mercury (Hg) has been identified as one of the most toxic nonradioactive materials known to man. Although mercury is a naturally occurring element, anthropogenic mercury is now a major worldwide concern and is an international priority toxic pollutant. It also comprises one of the primary constituents of dental amalgam fillings. Even though dental mercury amalgams have been used for almost two centuries, its safety has never been tested or proven in the United States by any regulatory agency. There has been an ongoing debate regarding the safety of its use since 1845, and many studies conclude that its use exposes patients to troublesome toxicity. In this review, we present in an objective way the danger of dental amalgam to human health based on current knowledge. This dilemma is addressed in terms of an integrated toxicological approach by focusing on four mayor issues to show how these interrelate to create the whole picture: (1) the irrefutable constant release of mercury vapor from dental amalgams which is responsible for individual chronic exposure, (2) the evidence of organic mercury formation from dental amalgam in the oral cavity, (3) the effect of mercury exposure on gene regulation in human cells which supports the intrinsic genetic susceptibility to toxicant and, finally, (4) the availability of recent epidemiological data supporting the link of dental amalgams to diseases such as Alzheimer’s and Parkinson.

Endocrine Disruptors and Autism Spectrum Disorder in Pregnancy: A Review and Evaluation of the Quality of the Epidemiological Evidence

Exposure to environmental contaminants during pregnancy has been linked to adverse health outcomes later in life. Notable among these pollutants are the endocrine disruptors chemicals (EDCs), which are ubiquitously present in the environment and they have been measured and quantified in the fetus. In this systematic review, our objective was to summarize the epidemiological research on the potential association between prenatal exposure to EDCs and Autism Spectrum Disorder (ASD) published from 2005 to 2016. The Navigation Guide Systematic Review Methodology was applied. A total of 17 studies met the inclusion criteria for this review, including: five cohorts and 12 case-control. According to the definitions specified in the Navigation Guide, we rated the quality of evidence for a relationship between prenatal exposure to EDCs and ASD as "moderate". Although the studies generally showed a positive association between EDCs and ASD, after considering the strengths and limitations, we concluded that the overall strength of evidence supporting an association between prenatal exposure to EDCs and later ASD in humans remains "limited" and inconclusive. Further well-conducted prospective studies are warranted to clarify the role of EDCs on ASD development.

[Mercury as a Global Pollutant and Mercury Exposure Assessment and Health Effects]

Mercury and its compounds are classified into three main groups: metallic mercury (Hg⁰), inorganic mercury (Hg²⁺), and organic mercury (methyl mercury: CH₃Hg⁺, etc.). Metallic mercury is the only metal that is liquid at ambient temperature and normal pressure, which readily forms an amalgam with other metals. Therefore, mercury has long been used for refining various metals, and mercury amalgam has been used for dental treatment. Mercury has also been used in measuring instruments such as thermometers, barometers and blood pressure monitors, as well as electric appliances such as lighting equipment and dry batteries. Large amounts of metallic mercury are still used in other countries as a catalyst in the production of caustic soda by electrolysis. In addition, mercury compounds have been used in various chemicals such as mercurochrome, agricultural chemicals, and mildew-proofing agents. However, the use of mercury has also caused health problems for people. Minamata disease in Japan is a typical example. Also, since mercury is highly volatile, it is discharged as a product of industrial activities or derived from volcanoes, and it has been concluded on the basis of the findings of the United Nations Environment Program (UNEP) that it is circulating globally. Therefore, with the aim of establishing an internationally legally binding treaty for the regulation of mercury use to reduce risk, an intergovernmental negotiating committee was established in 2009. Japan actively contributed to this negotiation owing to its experience with Minamata disease, which led to the Convention on the regulation of mercury use being discharged as the "Minamata Convention on Mercury" and the treaty came into force on August 16, 2017. In this review, we introduce 1) the Global Mercury Assessment by UNEP; 2) mercury kinetics, exposure assessment and toxicity of different chemical forms; 3) large-scale epidemics of methylmercury poisoning; 4) methylmercury exposure assessment and health survey in whale-eating populations; 5) elemental mercury exposure assessment and health survey of mercury mine workers in China.

A likely placental barrier against methylmercury in pregnant rats exposed to fish-containing diets

Methylmercury (MeHg) taken up through fish consumption can be transferred from the mother to the fetus during pregnancy. In the present study, pregnant rat mothers were contaminated with environmentally relevant doses of 36 and 76 ng MeHg/g of food using diets containing naturally mercury-containing fish. Young female rats fed with fish-containing food after weaning showed decreased locomotion in Y maze for accumulated concentrations in brain as low as 75 ng Hg/g dry weight (15 ng Hg/g wet weight). Young female rats fed the control diet after weaning yet borne by mothers fed the diet containing 76 ng MeHg/g, presented a 58% reduced activity in the open-field labyrinth, meaning that the maternal exposure to fish-containing food exerted an effect in utero that lasted several weeks after birth. Newborns were protected against Hg exposure by the placental barrier since in newborns from mothers fed the diet containing 76 ng MeHg/g of food, the concentrations of Hg in brain, kidney, liver and skeletal muscles represented 12, 3, 21 and 18% of those of their mother's tissues, respectively. These results suggest the existence, at least in rats, of a threshold level in terms of MeHg exposure above which the placental barrier collapses.

Health Impacts and Biomarkers of Prenatal Exposure to Methylmercury: Lessons from Minamata, Japan

The main chemical forms of mercury are elemental mercury, inorganic divalent mercury, and methylmercury, which are metabolized in different ways and have differing toxic effects in humans. Among the various chemical forms of mercury, methylmercury is known to be particularly neurotoxic, and was identified as the cause of Minamata disease. It bioaccumulates in fish and shellfish via aquatic food webs, and fish and sea mammals at high trophic levels exhibit high mercury concentrations. Most human methylmercury exposure occurs through seafood consumption. Methylmercury easily penetrates the blood-brain barrier and so can affect the nervous system. Fetuses are known to be at particularly high risk of methylmercury exposure. In this review, we summarize the health effects and exposure assessment of methylmercury as follows: (1) methylmercury toxicity, (2) history and background of Minamata disease, (3) methylmercury pollution in the Minamata area according to analyses of preserved umbilical cords, (4) changes in the sex ratio in Minamata area, (5) neuropathology in fetuses, (6) kinetics of methylmercury in fetuses, (7) exposure assessment in fetuses.

Placental transfer and levels of mercury, selenium, vitamin E, and docosahexaenoic acid in maternal and umbilical cord blood

Methylmercury (MeHg) is a neurotoxicant known to affect the developing fetal brain as a sensitive target organ. As most mercury (Hg) in blood is MeHg, total mercury (THg) levels in blood are used to estimate the body burden of MeHg. The nutrients selenium (Se), vitamin E, and docosahexaenoic acid (DHA) are protective against MeHg toxicity. We compared maternal and cord blood concentrations of biochemical substances, THg and Se, vitamin E, DHA, and other elements, fatty acids, and amino acids in 54 Japanese mother-newborn pairs to elucidate the fetal risk of MeHg toxicity. Cord blood had higher hematocrit and amino acid values and lower concentrations of lipid components, including fatty acids compared with maternal blood. THg levels in cord blood (7.26ng/g) were 1.9 times higher than levels in maternal blood (3.79ng/g). Se concentrations in cord blood (176ng/g) were slightly higher than concentrations in maternal blood (156ng/g). Levels of vitamin E (0.31mg/dL) and DHA (58.8μg/mL) in cord blood were much lower than levels in maternal blood (1.38mg/dL and 147μg/mL, respectively). The ratios of Se/THg, vitamin E/THg, and DHA/THg in cord blood were lower than ratios in maternal blood. These results suggest that fetuses are at higher risk to MeHg toxicity.

Mercury in Children: Current State on Exposure through Human Biomonitoring Studies

Mercury (Hg) in children has multiple exposure sources and the toxicity of Hg compounds depends on exposure routes, dose, timing of exposure, and developmental stage (be it prenatal or postnatal). Over the last decades, Hg was widely recognized as a threat to the children’s health and there have been acknowledgements at the international level of the need of a global policy intervention—like the Minamata treaty—aimed at reducing or preventing Hg exposure and protecting the child health. National human biomonitoring (HBM) data has demonstrated that low levels of exposure of Hg are still an important health concern for children, which no one country can solve alone. Although independent HBM surveys have provided the basis for the achievements of exposure mitigation in specific contexts, a new paradigm for a coordinated global monitoring of children’s exposure, aimed at a reliable decision-making tool at global level is yet a great challenge for the next future. The objective of the present review is to describe current HBM studies on Hg exposure in children, taking into account the potential pathways of Hg exposure and the actual Hg exposure levels assessed by different biomarkers.

Stable and episodic/bolus patterns of methylmercury exposure on mercury accumulation and histopathologic alterations in the nervous system

The main purpose of the present study was to compare the blood and brain mercury (Hg) accumulation and neurological alterations in adult male and pregnant female/fetal rats following stable and episodic/bolus patterns of methylmercury (MeHg) exposure. In addition, MeHg accumulation in the human body was estimated by a one-compartment model using three different patterns of MeHg exposure. In the adult male rat experiment, doses of 0.3 and 1.5mg MeHg/kg/day were orally administered to the stable groups for 5 weeks, while 7-fold higher doses of 2.1 and 10.5mg MeHg/kg/once a week were administered to the bolus groups. The blood Hg levels increased constantly in the stable groups, but increased with repeated waves in the bolus groups. At completion of the experiment, there were no significant differences in the brain Hg concentrations or neurological alterations between the stable and bolus groups, when the total doses of MeHg were the same. In the pregnant female rat experiment, a dose of 1mg MeHg/kg/day was administered orally to the stable group for 20 days (until 1day before expected parturition), while a 5-fold higher dose of 5mg MeHg/kg/once every 5 days was administered to the bolus group. In the brains of the maternal/fetal rats, there were no significant differences in the Hg concentrations and neurological alterations between the stable and bolus groups. The mean Hg concentrations in the fetal brains were approximately 2-fold higher than those in the maternal brains for both stable and bolus groups. Using the one-compartment model, the Hg accumulation curves in humans at doses of 7µg MeHg/day, 48µg MeHg/once a week, and 96µg MeHg/once every 2 weeks were estimated to be similar, while the bolus groups showed dose-dependent amplitudes of repeated waves. These results suggest that stable and episodic/bolus patterns of MeHg exposure do not cause differences in Hg accumulation in the blood and brain, or in neurological alterations, when the total doses are the same.

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.

[Effects of Prenatal Methylmercury Exposure: From Minamata Disease to Environmental Health Studies]

Methylmercury, the causative agent of Minamata disease, can easily penetrate the brain, and adult-type Minamata disease patients showed neurological symptoms according to the brain regions where the neurons, mainly in the cerebrum and cerebellum, were damaged. In addition, fetuses are exposed to methylmercury via the placenta from maternal fish consumption, and high-level exposure to methylmercury causes damage to the brains of infants. Typical patients with fetal-type Minamata disease (i.e., serious poisoning caused by in utero exposure to methylmercury) were born during the period of severe methylmercury pollution in 1955-1959, although they showed no abnormality during gestation nor at delivery. However, they showed difficulties in head control, sitting, and walking, and showed disturbances in mental development, these symptoms that are similar to those of cerebral palsy, during the growth periods after birth. The impaired development of fetal-type Minamata disease patients was one of the most tragic and characteristic feature of Minamata disease. In this review, we first summarize 1) the effects of prenatal methylmercury exposure in Minamata disease. Then, we introduce the studies that were conducted mainly by Sakamoto et al. as follows: 2) a retrospective study on temporal and regional variations of methylmercury pollution in Minamata area using preserved umbilical cord methylmercury, 3) decline in male sex ratio observed in Minamata area, 4) characteristics of hand tremor and postural sway in fetal-type Minamata disease patients, 5) methylmercury transfer from mothers to infants during gestation and lactation (the role of placenta), 6) extrapolation studies using rat models on the effects of prenatal methylmercury exposure on the human brain, and 7) risks and benefits of fish consumption.

Implications of mercury concentrations in umbilical cord tissue in relation to maternal hair segments as biomarkers for prenatal exposure to methylmercury

In this study, we investigated how mercury (Hg) concentrations in umbilical cord tissue are correlated with those in biomarkers for prenatal exposure to methylmercury (MeHg). Total Hg (T-Hg) concentrations were measured in 54 mother-child paired samples of maternal blood, umbilical cord tissue, cord blood, and maternal hair segments (1-cm incremental segments from the scalp) collected at parturition. MeHg concentrations were also measured in the cord tissue. Median T-Hg and MeHg concentrations in cord tissue on a dry-weight basis (d.w.) were 62.2ng/g and 56.7ng/g, respectively. Proportions of MeHg to T-Hg were approximately 95%. Both T-Hg and MeHg in cord tissue (d.w.) showed better correlations with T-Hg in cord blood than did T-Hg in cord tissue on a wet-weight basis (w.w.). Median T-Hg concentrations in maternal blood, cord blood, and maternal hair (0-1cm from the scalp) were 3.79ng/g, 7.26ng/g, and 1.35 μg/g, respectively. Median T-Hg concentration in cord blood was 1.92 times higher than that in maternal blood. T-Hg in cord tissue (d.w.) showed a strong correlation with that in cord blood (r=0.912, p<0.01). Among the hair segments, T-Hg in cord tissue (d.w.) showed the strongest correlation (r=0.854, p<0.01) with that in maternal hair at 0-1cm from the scalp, reflecting growth for approximately 1 month before parturition. Based on the present results, T-Hg and MeHg concentrations in cord tissue may be useful biomarkers for prenatal MeHg exposure of the fetus, especially reflecting the maternal MeHg body burden during late gestation. The conversion factors for T-Hg and MeHg concentrations in cord tissue (d.w.) to T-Hg concentrations in maternal hair (0-1cm from the scalp) were calculated to be 22.37 and 24.09, respectively. This information will be useful for evaluating maternal MeHg exposure levels in retrospective studies using preserved umbilical cord tissue.

Within-person reproducibility of red blood cell mercury over a 10- to 15-year period among women in the Nurses' Health Study II

Most epidemiologic studies of methylmercury (MeHg) health effects rely on a single measurement of a MeHg biomarker to assess long-term exposures. Long-term reproducibility data are, therefore, needed to assess the reliability of a single measure to reflect long-term exposures. In this study, we assessed within-person reproducibility of red blood cell (RBC) mercury (Hg), a marker of methyl-mercury, over 10-15 years in a sample of 57 women. Fifty-seven women from the Nurses' Health Study II provided two blood samples 10-15-years apart (median: 12 years), which were analyzed for mercury levels in the red blood cells (B-Hg*). To characterize within-person reproducibility, we estimated correlation and intraclass correlation coefficients (r and ICC) across the two samples. Further, we compared different prediction models, including variables on fish and seafood consumption, for B-Hg* at the first sample, using leave-one-out cross-validation to assess predictive ability. Overall, we observed strong correlations over 10-15 years (r=0.69), as well as a high ICC (0.67; 95% CI: 0.49, 0.79). Fish and seafood consumption reported concurrently with the first B-Hg* sample accounted for 26.8% of the variability in that B-Hg*, giving a correlation of r=0.52. Despite decreasing B-Hg* levels over time, we observed strong correlations and high ICC estimates across B-Hg* measured 10-15 years apart, suggesting good relative within-person stability over time. Our results indicate that a single measurement of B-Hg* likely is adequate to represent long-term exposures.

Mercury and Lead Contamination in Three Fish Species and Sediments from Lake Rukwa and Catchment Areas in Tanzania

BACKGROUND

Mining activity in the catchment area of Tanzania's Lake Rukwa is suspected of adding to the lake and connected rivers' heavy metal load. There has been no study done, however, on the levels of mercury (Hg) and lead (Pb) in lake sediment and fish muscle, and what the results could mean for human health.

OBJECTIVES

This study investigated the concentration of Hg and Pb in lake sediment and in the muscles of African sharptooth catfish (Clarias gariepinus), Lake Rukwa tilapia (Oreochromis rukwaensis) and Singida tilapia (Oreochromis esculentus) from Tanzania's Lake Rukwa and connected rivers.

METHODS

Concentrations of Hg and Pb in fish muscle and lake sediment were measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and mercury analyzers, respectively.

RESULTS

Levels of Pb and Hg from C. gariepinus ranged between 0.01 to 1.9 μg/g and 0.03 to 0.33 μg/g, respectively. Pb and Hg in O. esculentus varied between 0.02 to 1.4 μg/g and <0.01 to 0.29 μg/g, respectively. Pb and Hg levels in O. rukwaensis ranged from 0.12 to 0.88 μg/g and 0.12 to 0.88 μg/g, respectively. On the other hand, concentrations of Pb and Hg in the sediment samples ranged between 0.02 to 16.23 μg/g and from 0.01 to 1.43 μg/g, respectively. Concentrations of Hg in the muscles of C. gariepinus and O. esculentus were above World Health Organization (WHO) permissible limits, indicating that they are not safe for human consumption. Concentrations of Pb in fish muscle samples were below WHO permissible limits and United States Environmental Protection Agency (USAEPA) provisional tolerable weekly intake (PTWI) standards. Furthermore, Hg and Pb in sediment were below the threshold value of Environment Canada and Florida's 'No effect level'.

CONCLUSIONS

Although levels of Pb in fish samples and Hg and Pb levels in sediment were below international standards, it is important to consider that fish forms an important source of animal protein for local inhabitants, who are likely to consume more fish than considered by these standards. The study recommends further research on the levels of mercury and lead in humans, especially children and pregnant women.

Mercury, APOE, and child behavior

Methylmercury (MeHg) is a neurotoxicant and may have an adverse impact on child behavior. However, this impact was found to be inconsistent in fish-eating populations. Although the positive effects of the nutrients provided by a fish diet may overcome the effect of MeHg, the possibility of genetic variants influencing an individual's response to MeHg has also been discussed. The role of the Apolipoprotein E (APOE) epsilon 4 allele (ε4) on MeHg related neurotoxicity is still unclear. In the present study, we investigated the role of APOE variants in the relationship between cord blood mercury (Hg) and child behavior. A total of 166 subjects were recruited at delivery, and their cord blood was collected for laboratory analyses of Hg and the APOE genotype. The Child Behavior Checklist (CBCL) was administered to the subjects when they reached the age of two years. An increase in cord blood Hg concentrations in APOE ε4 carriers was consistently associated with an increased score for all CBCL syndromes. After controlling for potential confounding factors, the group of ε4 carriers with an elevated cord blood Hg concentration had significantly higher scores in the syndrome categories of general internalizing, emotionally reactive, and anxiety/depression as well as CBCL total scores. Furthermore, general externalizing and aggressive syndromes were borderline significantly higher in this group. In conclusion, we suggest that APOE may modify the toxicity of MeHg. APOE ε4 carriers may be more vulnerable to the effects of MeHg on child behavior at the age of two years.

Associations of dietary intake and plasma concentrations of eicosapentaenoic and docosahexaenoic acid with prenatal depressive symptoms in Japan

The association between depression and omega-3 polyunsaturated fatty acids, including eicosapentaenoic and docosahexaenoic acid, continues to gain focus. In this study, we examined whether dietary intakes and plasma concentrations of eicosapentaenoic and docosahexaenoic acid were associated with depressive symptoms during pregnancy. Healthy Japanese women with singleton pregnancies were recruited at a university hospital in Tokyo between 2010 and 2012. The depressive-symptom group included participants with Edinburgh Postnatal Depression Scale scores greater than eight. Of the 329 participants, 19 (5.8%) had depressive symptoms. Lower plasma docosahexaenoic acid concentration was significantly associated with prenatal depressive symptoms. Women with depressive symptoms had a higher rate of pregnancy-associated nausea than those with non-depressive symptoms (52.6% vs 28.7%, respectively). Although we adjusted for the presence of pregnancy-associated nausea, dietary fatty acid intake was not associated with depressive symptoms in the multiple logistic regression analyses. Further large studies would be required to examine any preventive effect of dietary fatty acid intake on depressive symptoms among pregnant women.

Persistent organic pollutants (POPs) and metals in primiparous women: a comparison from Canada and Mexico

Under the North American Commission for Environmental Cooperation (CEC) and its Sound Management of Chemicals (SMOC) program, a tri-national human contaminant monitoring initiative was completed to provide baseline exposure information for several environmental contaminants in Canada, Mexico and the United States (U.S). Blood samples were collected from primiparous women in Canada and Mexico, and were analysed for a suite of environmental contaminants including polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene(p,p'-DDE),beta-hexachlorocyclohexane (β-HCH), mercury and lead. A multiple stepwise linear regression analysis was conducted using data from Canadian and Mexican primiparous mothers, adjusting for ethnicity group, age, pre-pregnancy BMI, years at current city and ever-smoking status. Concentrations of p,p'-DDE, β-HCH, and lead were found to be higher among Mexican participants; however, concentrations of most PCBs among Mexican participants were similar to Canadian primiparous women after adjusting for covariates. Concentrations of total mercury were generally higher among Mexican primiparous women although this difference was smaller as age increased. This initial dataset can be used to determine priorities for future activities and to track progress in the management of the selected chemicals, both domestically and on a broader cooperative basis within North America.

Associations of prenatal maternal blood mercury concentrations with early and mid-childhood blood pressure: a prospective study

BACKGROUND

Childhood blood pressure (BP) is an important determinant of adult cardiovascular disease. Prenatal exposure to methylmercury through maternal fish consumption has been reported to increase the BP of children years later.

METHODS

Mother-child pairs were enrolled from Project Viva, a prospective cohort study in Massachusetts. From second trimester maternal blood samples, we measured erythrocyte mercury concentration. Systolic BP in children, measured up to 5 times per visit in early and mid-childhood (median ages 3.2 and 7.7 years), was the primary outcome. We used mixed-effect regression models to account for variation in the number of BP measurements and to average effects over both time points.

RESULTS

Among 1103 mother-child pairs, mean (SD) second trimester total erythrocyte mercury concentration was 4.0 (3.9)ng/g among mothers whose children were assessed in early childhood and 4.0 (4.0)ng/g for children assessed in mid-childhood. Mean (SD) offspring systolic BP was 92.1 (10.4)mm Hg in early childhood and 94.3 (8.4)mm Hg in mid-childhood. After adjusting for mother and infant characteristics, mean second trimester blood mercury concentration was not associated with child systolic BP (regression coefficient, 0.1mm Hg; 95% CI, -1.3 to 1.5 for quartile 4 vs. quartile 1) at either time period. Further adjusting for second trimester maternal fish consumption, as well as docosahexaenoic acid and eicosapentaenoic acid consumption, did not substantially change the estimates.

CONCLUSIONS

The results of this study demonstrate an absence of association between childhood blood pressure and low-level mercury exposure typical of the general US population.

Effect of hemoglobin adjustment on the precision of mercury concentrations in maternal and cord blood

The cord-blood mercury concentration is usually considered the best biomarker in regard to developmental methylmercury neurotoxicity. However, the mercury concentration may be affected by the binding of methylmercury to hemoglobin and perhaps also selenium. As cord-blood mercury analyses appear to be less precise than suggested by laboratory quality data, we studied the interrelationships of mercury concentrations with hemoglobin in paired maternal and cord blood samples from a Faroese birth cohort (N=514) and the Mothers and Children's Environmental Health study in Korea (n=797). Linear regression and structural equation model (SEM) analyses were used to ascertain interrelationships between the exposure biomarkers and the possible impact of hemoglobin as well as selenium. Both methods showed a significant dependence of the cord-blood concentration on hemoglobin, also after adjustment for other exposure biomarkers. In the SEM, the cord blood measurement was a less imprecise indicator of the latent methylmercury exposure variable than other exposure biomarkers available, and the maternal hair concentration had the largest imprecision. Adjustment of mercury concentrations both in maternal and cord blood for hemoglobin improved their precision, while no significant effect of the selenium concentration in maternal blood was found. Adjustment of blood-mercury concentrations for hemoglobin is therefore recommended.

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.

Mercury, APOE, and children's neurodevelopment

The benefit of the nutritious elements in fish is insufficient for explaining the controversial finding regarding prenatal mercury (Hg) exposure and neurodevelopment; the varying frequency of susceptible genes among these populations may shed light on these observations. However, limited studies have been reported on the association between genetic susceptibility of prenatal Hg exposure and child development. Apolipoprotein E (APOE, protein; Apoe, gene) is a major protein transporter expressed in the brain. The Apoe epsilon 4 (ε4) allele is associated with poor neural repair function and is a risk factor associated with Alzheimer disease. We conducted a prospective cohort study in 2004 and 2005. In this study, 168 subjects were recruited at delivery and followed up at two years of age, and genetic polymorphisms of Apoe were included to assess genetic susceptibility and to determine the relationship between Hg concentrations in cord blood and neurodevelopment. The results showed that adverse effects on neurodevelopment were consistently associated with prenatal Hg exposure in all subtests of Comprehensive Developmental Inventory for Infants and Toddlers (CDIIT) among ε4 carriers as assessed by both simple linear and multiple linear regression models. After controlling for confounding factors, statistical significance was found in the subtests of cognition tests (β=-8.47, 95% confidence interval (CI)=-16.10 to -0.84), social tests (β=-11.02, 95% CI=-20.85 to -1.19) and the whole test of CDIIT (β=-10.45, 95% CI=-17.36 to -3.54) in a multiple linear regression model. Additionally, the interaction effect between gene polymorphisms of Apoe and Hg levels was significant in the whole test CDIIT and subtests of cognition, language and fine motor tests. In conclusion, Apoe modifies the adverse effects of cord blood Hg on neurodevelopment at the age of two years.

A human pluripotent carcinoma stem cell-based model for in vitro developmental neurotoxicity testing: effects of methylmercury, lead and aluminum evaluated by gene expression studies

The major advantage of the neuronal cell culture models derived from human stem cells is their ability to replicate the crucial stages of neurodevelopment such as the commitment of human stem cells to the neuronal lineage and their subsequent stages of differentiation into neuronal and glial-like cell. In these studies we used mixed neuronal/glial culture derived from the NTERA-2 (NT-2) cell line, which has been established from human pluripotent testicular embryonal carcinoma cells. After characterization of the different stages of cell differentiation into neuronal- and glial-like phenotype toxicity studies were performed to evaluate whether this model would be suitable for developmental neurotoxicity studies. The cells were exposed during the differentiation process to non-cytotoxic concentrations of methylmercury chloride, lead chloride and aluminum nitrate for two weeks. The toxicity was then evaluated by measuring the mRNA levels of cell specific markers (neuronal and glial). The results obtained suggest that lead chloride and aluminum nitrate at low concentrations were toxic primarily to astrocytes and at the higher concentrations it also induced neurotoxicity. In contrast, MetHgCl was toxic for both cell types, neuronal and glial, as mRNA specific for astrocytes and neuronal markers were affected. The results obtained suggest that a neuronal mixed culture derived from human NT2 precursor cells is a suitable model for developmental neurotoxicity studies and gene expression could be used as a sensitive endpoint for initial screening of potential neurotoxic compounds.

Recent advances in evaluation of health effects on mercury with special reference to methylmercury-A minireview

Mercury is a metal that has long been used because of its many advantages from the physical and chemical points of view. However, mercury is very toxic to many life forms, including humans, and mercury poisoning has repeatedly been reported. The main chemical forms of mercury are elemental mercury (Hg(0)), divalent mercury (Hg(2+)) and methylmercury (CH(3)-Hg(+)), the toxicities and metabolisms of which differ from each other. Methylmercury is converted from divalent mercury and is a well-known neurotoxicant, having been identified as the cause of Minamata disease. It bioaccumulates in the environment and is biomagnified in the food web. Human exposure to methylmercury is mainly through fish and seafood consumption. Methylmercury easily penetrates the blood-brain barrier and causes damage to the central nervous system, particularly in fetuses. In this paper, we summarize the global mercury cycle and mercury metabolism, toxicity and exposure evaluation, and the thresholds for the onset of symptoms after exposure to different chemical forms of mercury, particularly methylmercury.

Factors affecting hand tremor and postural sway in children

OBJECTIVES

It is crucial to consider covariates relevant for outcome variables in developing dose-effect relations of environmental hazardous toxins. The aim of this study was to clarify the covariates affecting hand tremor and postural sway in children.

METHODS

Hand tremor and postural sway, as well as hair mercury concentrations, were measured in 155 boys and 148 girls at age 7 years.

RESULTS

Current mercury concentrations in child hair ranged from 0.35 to 6.32 μg/g (geometric mean, 1.71 μg/g for boys and 1.58 μg/g for girls), and were not significantly correlated with the neuromotor parameters. All hand tremor and postural sway parameters, except for tremor intensity at 1-6 Hz with non-dominant hand, were significantly larger in the boys than in the girls. Using multiple regression analysis, some postural sway parameters were related negatively to age in the boys and girls (p<0.05), and positively to height (p<0.05). Similarly, hand tremor parameters were positively related to age, height and heart rate either in the boys or in the girls (p<0.05). Also, there were positive relationships between tremor intensity at 1-6 Hz and transversal and sagittal sways at 1-2 Hz and 2-4 Hz (p<0.05).

CONCLUSIONS

Heart rate and postural sway, together with age, sex, and height, should be considered in interpreting hand tremor in children. Hand tremor or postural sway may not be so sensitive or specific to methylmercury exposures at levels of less than 7 μg/g in hair.

Effects of hair treatment on hair mercury-The best biomarker of methylmercury exposure?

OBJECTIVES

Exposure misclassification is a major obstacle to obtain accurate dose-response relationships. In order to solve this problem, the impact of hair treatment on total mercury in hair was assessed in Japanese women.

METHODS

A cross-sectional study was carried out among 327 women at age 24-49 years to determine hair mercury levels and estimate daily mercury intakes from seafood by using a food frequency questionnaire.

RESULTS

Hair mercury levels in the women and daily mercury intake ranged from 0.11 to 6.86 (median 1.63) μg/g and from 0.77 to 144.9 (median 15.0) μg/day, respectively. The hair mercury was positively correlated with the daily mercury intake (p<0.001). When the women were divided into two subgroups based on artificial hair-waving, hair coloring/dyeing, residence (non-fishing and fishing areas), and working status, a significant difference in the hair mercury level was observed between the women with and without artificial hair-waving only (p<0.001). The multiple regression analysis showed that the log-transformed hair mercury level was significantly related to the log-transformed daily mercury intake (standardized regression coefficient βs=0.307) and artificial hair-waving (βs=-0.276); but not to hair coloring/dyeing, residence, working status or age. Permanent hair treatment was estimated to reduce total mercury in hair by approximately 30%, after adjusting for daily mercury intake and other possible factors.

CONCLUSIONS

These findings suggest that hair mercury is not the best biomarker of methylmercury exposure when a study population includes women with artificial hair-waving.

Changes in body burden of mercury, lead, arsenic, cadmium and selenium in infants during early lactation in comparison with placental transfer

The developing brains of both fetuses and infants are susceptible to environmental contaminants. However, the contribution of breast-feeding to the element body burden in infants remains unclear. The main objective of this study was to investigate the changes in body burden of elements such as methylmercury, lead, arsenic, cadmium, and selenium in infants during a 3-month breast-feeding period compared with placental transfer of the elements. Element concentrations were measured in maternal and umbilical cord (fetus) red blood cells (RBCs) at parturition and in infant RBCs at 3 months. Most of the mercury in RBCs is in the methyl form, and the total mercury concentration in RBCs reflects methylmercury exposure. The mercury level in cord RBCs was approximately 1.5 times higher than that in mothers, while in infants, it declined by approximately 60% after 3-months' breast-feeding. The cord selenium level was similar to the maternal level, but declined approximately 75% after 3-months' breast-feeding in infants. Lead and arsenic concentrations in cord RBCs were about 60% of the maternal levels, and remained constant until the 3-month study period. The cadmium level in cord RBCs was about 20% of that in maternal RBCs, and remained almost constant until the end of the 3-month study period. In conclusion, although pregnant women should pay attention to avoid high methylmercury exposure, element exposure through breast-feeding does not pose any great concern in this population.

Mercury and docosahexaenoic acid levels in maternal and cord blood in relation to segmental maternal hair mercury concentrations at parturition

Fish is a major source of harmful methylmercury (MeHg) and beneficial docosahexaenoic acid (DHA) in the developing brain. In this study, we investigated the correlations among maternal and umbilical cord (cord) MeHg and DHA levels at parturition, and mercury (Hg) concentration in 1-cm incremental segments hair samples which grew during gestation representing monthly MeHg exposure levels throughout the period. Whole blood Hg and plasma DHA levels were measured in blood sample pairs collected from 54 mothers at early gestation and parturition, and in cord blood. Maternal hair samples were collected at parturition, and Hg concentrations were measured in 1-cm incremental segments. Hg level in mothers at parturition was slightly lower than that at early gestation and the level in cord blood were approximately 1.9 times higher than that in mothers at parturition. On the other hand, DHA level in mothers at parturition was approximately 2.3 and 1.6 times higher than those in mothers at early gestation and in cord plasma, respectively. These results indicate that kinetics of these chemicals in mothers during gestation and placental transfer are completely different. However, Hg and DHA levels had significant positive correlation in fetal circulation. The cord blood Hg showed the strongest correlation with maternal hair Hg in the first 1-cm segment from the scalp at parturition (r=0.87), indicating that fetal MeHg level reflects maternal MeHg burden at late gestation. In contrast, maternal and cord plasma DHA concentrations at parturition showed the highest correlation coefficients with Hg in the fifth (r=0.43) and fourth (r=0.38) 1-cm hair segments, suggesting that maternal and fetal DHA levels reflects maternal fish intake during mid-gestation.

Mercury exposure assessment in Iranian pregnant women's hair with respect to diet, amalgam filling, and lactation

Our aim for carrying out this study was to estimate the levels of mercury in the hair of pregnant women and its association with fish consumption and amalgam fillings. From November 2007 to January 2008, 100 hair samples were collected randomly from three groups of pregnant women: Ahvaz in the south of Iran, Noushahr in the north, and the countryside of Noushahr. Significant differences were found in these three groups of pregnant women's samples (p>0.05). The mean mercury level in women's hair was found to be 0.37 μg/g (range, 0.11-3.57 μg/g). Only in 2 % of collected hair samples did the total mercury (THg) level exceed the United States Environmental Protection Agency-recommended 1.0 μg/g. In addition, there was a positive correlation of THg content in Ahvaz group's samples with respect to fish consumption (r=0.41, p=0.02) and a negative correlation of THg content in those who consumed vegetables and fruit. The level of education also played an indicating factor in this group. Moreover, significant association was found between the residence time and Hg concentration of women's hair samples collected from Noushahr (p>0.05). Similarly, the same correlations were found between hair mercury levels and the time since the first filling, number of dental fillings, pregnancy interval, and lactating period.

Translating neurobehavioural endpoints of developmental neurotoxicity tests into in vitro assays and readouts

The developing nervous system is particularly vulnerable to chemical insults. Exposure to chemicals can result in neurobehavioural alterations, and these have been used as sensitive readouts to assess neurotoxicity in animals and man. Deconstructing neurobehaviour into relevant cellular and molecular components may allow for detection of specific neurotoxic effects in cell-based systems, which in turn may allow an easier examination of neurotoxic pathways and modes of actions and eventually inform the regulatory assessment of chemicals with potential developmental neurotoxicity. Here, current developments towards these goals are reviewed. Imaging genetics (CB) provides new insights into the neurobiological correlates of cognitive function that are being used to delineate neurotoxic mechanisms. The gaps between in vivo neurobehaviour and real-time in vitro measurements of neuronal function are being bridged by ex vivo measurements of synaptic plasticity (RW). An example of solvent neurotoxicity demonstrates how an in vivo neurological defect can be linked via the N-methyl-d-aspartate (NMDA)-glutamate receptor as a common target to in vitro readouts (AB). Axonal and dendritic morphology in vitro proved to be good correlates of neuronal connectivity and neurobehaviour in animals exposed to polychlorinated biphenyls and organophosphorus pesticides (PJL). Similarly, chemically induced changes in neuronal morphology affected the formation of neuronal networks on structured surfaces. Such network formation may become an important readout for developmental neurotoxicity in vitro (CvT), especially when combined with human neurons derived from embryonic stem cells (ML). We envision that future in vitro test systems for developmental neurotoxicity will combine the above approaches with exposure information, and we suggest a strategy for test system development and cell-based risk assessment.

Balancing the benefits of n-3 polyunsaturated fatty acids and the risks of methylmercury exposure from fish consumption

Fish and shellfish are widely available foods that provide important nutrients, particularly n-3 polyunsaturated fatty acids (n-3 PUFAs), to many populations globally. These nutrients, especially docosahexaenoic acid, confer benefits to brain and visual system development in infants and reduce risks of certain forms of heart disease in adults. However, fish and shellfish can also be a major source of methylmercury (MeHg), a known neurotoxicant that is particularly harmful to fetal brain development. This review documents the latest knowledge on the risks and benefits of seafood consumption for perinatal development of infants. It is possible to choose fish species that are both high in n-3 PUFAs and low in MeHg. A framework for providing dietary advice for women of childbearing age on how to maximize the dietary intake of n-3 PUFAs while minimizing MeHg exposures is suggested.

Neurobehavioral effects of prenatal exposure to methylmercury and PCBs, and seafood intake: neonatal behavioral assessment scale results of Tohoku study of child development

As factors affecting neonatal neurodevelopment, methylmercury, polychlorinated biphenyls (PCBs), and maternal seafood intake reflecting n-3 polyunsaturated fatty acids (PUFAs) are believed to have adverse or beneficial effects, but there are a few reports addressing such factors simultaneously. We carried out a birth cohort study to clarify the effects of these three factors on the Neonatal Behavioral Assessment Scale (NBAS), administered 3 days after birth. In a total of 498 mother-neonate pairs, the total mercury level (median, 1.96microg/g) in maternal hair at parturition and the summation operatorPCB level (45.5ng/g-lipid) in cord blood were analyzed, and maternal seafood intake was estimated using a semi-quantitative food frequency questionnaire. A negative relationship between the hair mercury level and the motor cluster of NBAS was observed, even after adjusting for PCBs, maternal seafood intake, and possible confounders such as maternal age, birth weight, and parity. The summation operatorPCB level was negatively correlated with the motor cluster, but this association was attenuated after adjusting for mercury and the confounders. There was seen to be a positive association between maternal seafood intake and the motor cluster when considering the effects of mercury and PCBs. In conclusion, our data suggest that prenatal exposure to methylmercury adversely affects neonatal neurobehavioral function; in contrast, maternal seafood intake appears to be beneficial. The neurobehavioral effect of prenatal exposure to PCBs remains unclear in our study. Further research is necessary to elucidate interactive effects of methylmercury, PCBs, and n-3 PUFAs, originating from fish, on child neurodevelopment.

Hair mercury levels in pregnant women in Mahshahr, Iran: fish consumption as a determinant of exposure

MeHg is a well-documented neurotoxicant even at low levels of exposure. Developing brain, in particular, is vulnerable to that. Through bioaccumulating to differing degrees in various fish species, it can have serious adverse effects on the development and functioning of the human central nervous system, especially during prenatal exposure. Therefore, the purpose of this study was to investigate mercury concentration in hair samples of pregnant women living in Mahshahr located in Khuzestan province, Iran. It assessed the association between fish consumption and specific characteristics that can influence exposure. From April to June 2008, 149 pregnant women were invited to participate in this study. An interview administered questionnaire was used to collect information about age, body weight, height, fish (fresh, canned and shrimp) consumption, pregnancy stage, residence duration, education level, family income and number of dental amalgam fillings. The obtained results showed that the geometric mean and range for hair total Hg concentration was 3.52 microg/g (0.44-53.56 microg/g). About 5.4% of mothers had hair total Hg levels in excess of 10 microg/g. Maternal hair mercury level was less than threshold level of WHO (5 microg/g). As expected, there was a clear increase in hair Hg with reported fresh marine fish consumption (p=0.04). The highest mean for hair mercury level in a group who consumed fish several times per week, was 4.93 microg/g. Moreover, a significant effect of age and residential time on Hg concentration in the hair of the women was found. Pregnant women in Mahshahr consumed large amounts of fish; consequently, most of their offspring were prenatally exposed to moderately high levels of mercury. The results found suggest that pregnant women should decrease their fish consumption.

Retrospective study on temporal and regional variations of methylmercury concentrations in preserved umbilical cords collected from inhabitants of the Minamata area, Japan

The present study was conducted to investigate the historical time-course changes and regional distribution of methylmercury concentrations in preserved umbilical cords collected from Minamata-area inhabitants born between 1947 and 1989. The data from Miyazaki, Tottori, Akita, Tsushima (Nagasaki), Fukuoka and Tokyo were used as controls. A total of 325 data were analyzed to estimate the temporal and spatial distribution of methylmercury among inhabitants born in the Minamata area. Elevated methylmercury concentrations (>or=1 microg/g) were mainly observed in inhabitants born between 1947 and 1968. That peak coincided with the peak of acetaldehyde production in Minamata. The methylmercury concentrations started to decrease in keeping with the decline of acetaldehyde production, which ceased in 1968, and thereafter the methylmercury levels gradually decreased to the control levels. Elevated methylmercury concentrations were first observed in the districts of Minamata, followed by Izumi, Tsunagi and Ashikita, indicating the time-course-dependent regional distributions of methylmercury pollution.

The impact of environmental and occupational exposures on reproductive health

Environmental exposures during critical periods of susceptibility in utero may result in lifelong or intergenerational adverse health effects. Most chemicals in commercial use in the United States have not been tested for possible developmental toxicity to fetuses, infants, and children. Environmental and occupational exposures can result in adverse effects on female and male reproduction. Nurses can identify at-risk patients, provide education about the impact of chemical toxicants, and empower women to take precautionary action.

Methylmercury exposure and health effects from rice and fish consumption: a review

Methylmercury (MeHg) is highly toxic, and its principal target tissue in humans is the nervous system, which has made MeHg intoxication a public health concern for many decades. The general population is primarily exposed to MeHg through consumption of contaminated fish and marine mammals, but recent studies have reported high levels of MeHg in rice and confirmed that in China the main human exposure to MeHg is related to frequent rice consumption in mercury (Hg) polluted areas. This article reviews the progress in the research on MeHg accumulation in rice, human exposure and health effects, and nutrient and co-contaminant interactions. Compared with fish, rice is of poor nutritional quality and lacks specific micronutrients identified as having health benefits (e.g., n-3 long chain polyunsaturated fatty acid, selenium, essential amino acids). The effects of these nutrients on the toxicity of MeHg should be better addressed in future epidemiologic and clinical studies. More emphasis should be given to assessing the health effects of low level MeHg exposure in the long term, with appropriate recommendations, as needed, to reduce MeHg exposure in the rice-eating population.

An ignored risk factor in toxicology: The total imprecision of exposure assessment

Quality assurance of exposure biomarkers usually focuses on laboratory performance only. Using data from a prospective birth cohort study in the Faroe Islands, we have assessed the total imprecision of exposure biomarkers. As biomarkers of prenatal methylmercury exposure, mercury concentrations were determined in cord blood, cord tissue, and maternal hair. We determined their mutual correlations and their associations with the child's neurobehavioral effect variables at age 7 years. The exposure biomarkers correlated well with one another, but the cord blood mercury concentration showed the best associations with neurobehavioral deficits. Because at least three exposure parameters were available, factor analysis and structural equation modeling could be applied to determine the total imprecision of each biomarker. For the cord-blood parameter, the total imprecision was 25-30%, and almost twice as much for maternal hair. The total imprecision of these biomarkers much exceeded the normal laboratory variability of less than 5%. Such imprecision can cause underestimation of dose-related toxicity, and data analysis should therefore include sensitivity analyses that take this factor into account. Ignoring preanalytical imprecision may cause serious bias.

Mercury and heavy metal profiles of maternal and umbilical cord RBCs in Japanese population

Mercury (Hg) and other heavy metal profiles, namely, lead (Pb), arsenic (As), cadmium (Cd), and selenium (Se) were investigated in maternal and umbilical cord (cord) red blood cells (RBCs) at parturition in Japanese population. Correlation coefficients of Hg, Pb, As, Cd, and Se between maternal and cord RBCs were 0.91, 0.79, 0.89, 0.31, and 0.76, respectively, and the respective means of cord/maternal RBCs ratios were 1.63, 0.52, 0.62, 0.12, and 1.18. These results indicate that fetal exposure to these metals (excluding Cd) strongly reflected each maternal exposure level. Among these metals, the placental transfer of methylmercury (MeHg) seemed to be extremely high but that of Cd to be limited. Hg showed positive correlations with Se in maternal RBCs but not in cord RBCs, and the Se/Hg molar ratio was lower in the latter, suggesting that the protective effects of Se against MeHg are less expected in fetuses than in mothers.