Human milk as a source of methylmercury exposure in infants

Evaluating the relationship between the nutrient intake of lactating women and their breast milk nutritional profile: a systematic review and narrative synthesis

Maternal diet influences breast milk nutritional profile; however, it is unclear which nutrients and contaminants are particularly responsive to short- and long-term changes in maternal intake, and the impact of specific exclusion diets, such as vegan or vegetarian. This study systematically reviewed the literature on the effects of maternal nutrient intake, including exclusion diets, on both the nutrient and contaminant content of breast milk. The electronic databases, PubMed, CENTRAL, Web of Science and CINALH were systematically searched until 4 June 2023, with additionally searches of reference lists (PROSPERO, CRD42020221577). The quality of the studies was examined using Cochrane Risk of Bias tool and Newcastle-Ottawa scale. Eighty-eight studies (n 6577) met the search criteria. Due to high heterogeneity, meta-analysis was not possible. There was strong evidence of response to maternal intakes for DHA and EPA, vitamins A, E and K, iodine and Se in breast milk composition, some evidence of response for α-linolenic acid, B vitamins, vitamin C and D, ovalbumin, tyrosine and contaminants, and insufficient evidence to identify the effects arachidonic acid, Cu, Fe, Zn and choline. The paucity of evidence and high heterogeneity among studies reflects the need for more high-quality trials. However, this review identified the importance of maternal intake in the nutritional content of breast milk for a wide range of nutrients and supports the recommendation for supplementation of DHA and vitamin B12 for those on restrictive diets.

Characterization of the internal working-life exposome using minimally and non-invasive sampling methods - a narrative review

During recent years, we are moving away from the 'one exposure, one disease'-approach in occupational settings and towards a more comprehensive approach, taking into account the totality of exposures during a life course by using an exposome approach. Taking an exposome approach however is accompanied by many challenges, one of which, for example, relates to the collection of biological samples. Methods used for sample collection in occupational exposome studies should ideally be minimally invasive, while at the same time sensitive, and enable meaningful repeated sampling in a large population and over a longer time period. This might be hampered in specific situations e.g., people working in remote areas, during pandemics or with flexible work hours. In these situations, using self-sampling techniques might offer a solution. Therefore, our aim was to identify existing self-sampling techniques and to evaluate the applicability of these techniques in an occupational exposome context by conducting a literature review. We here present an overview of current self-sampling methodologies used to characterize the internal exposome. In addition, the use of different biological matrices was evaluated and subdivided based on their level of invasiveness and applicability in an occupational exposome context. In conclusion, this review and the overview of self-sampling techniques presented herein can serve as a guide in the design of future (occupational) exposome studies while circumventing sample collection challenges associated with exposome studies.

Mercury Exposure in Women of Reproductive Age in Rondônia State, Amazon Region, Brazil

Environmental contamination by mercury (Hg) is a problem of global scale that affects human health. This study's aim was to evaluate Hg exposure among women of reproductive age residing in the Madeira River basin, in the State of Rondônia, Brazilian Amazon. This longitudinal cohort study used linear regression models to assess the effects on Hg levels of breastfeeding duration at 6 months, and of breastfeeding duration and number of new children at 2-year and 5-year. Breastfeeding duration was significantly associated with maternal Hg levels in all regression models (6 months, 2 years and 5 years) and no significant association was observed between the number of children and the change in maternal Hg levels in the 2-year and 5-year models. This longitudinal cohort study evaluated Hg levels and contributing factors among pregnant women from different communities (riverine, rural, mining and urban) in Rondônia, Amazon Region, for 5 years. A well-coordinated and designed national biomonitoring program is urgently needed to better understand the current situation of Hg levels in Brazil and the Amazon.

Breast milk contribution to tissue mercury levels in rat pups examined by cross-fostering at birth

The developing perinatal brain is vulnerable to methylmercury (MeHg) exposure. The contribution of breast milk to tissue MeHg levels in offspring is a significant public health concern because breast milk contains a certain amount of MeHg. Here, the contribution of MeHg transferred via breast milk to the Hg levels in the tissues of pups (Wistar rats) was investigated. Mated maternal rats were fed a MeHg (2 ppm)-supplemented or a control diet during pregnancy. Following parturition, male neonates from each group were cross-fostered between exposed or control dams, and they were further raised by dams fed a MeHg-supplemented diet or a control diet during lactation. Consequently, we evaluated three pup groups, which were raised by dams exposed to MeHg during pregnancy (P pups), lactation (L pups), or pregnancy and lactation (PL pups). Total mercury (THg) concentrations in the tissues of the offspring were measured at birth (postnatal day 0 [PD0]), during lactation (PD6, PD12, and PD19), and after weaning (PD29 and PD36). Blood and brain THg levels in the P and PL pups declined dramatically during lactation, however, there were no considerable differences between the two groups at PD6 and PD12. In contrast, blood and brain THg levels in the L pups increased slightly during lactation. The increase in the THg levels in the blood and brain of L pups at PD12 were approximately 3.3% and 1.5%, respectively, compared to the corresponding THg levels in the neonates in the P and PL groups. Our results suggest that if the MeHg exposure level during pregnancy is not high enough to cause neuronal development defects in the fetus, the exposure via breast milk is not a significant concern.

Marine pollutant exposures and human milk extracellular vesicle-microRNAs in a mother-infant cohort from the Faroe Islands

BACKGROUND/AIMS

Early life exposures to marine contaminants can adversely impact child health but modes of action are unclear. Human milk contains extracellular vesicles (EVs) that can transport biologically relevant cargo from mother to infant, including microRNAs (miRNAs), and may partly mediate the effects of pollutants on child health. However, the role of marine pollutants on miRNA expression in milk EVs is unexplored.

METHODS

We isolated EV RNA from 333 milk samples collected between 2 and 74 days postpartum from a Faroese birth cohort born 1997-2000 and sequenced 2083 miRNAs using a targeted library preparation method. We quantified five perfluoroalkyl substances (PFAS), pesticide metabolite p,p'-dichlorodiphenyldichloroethylene (DDE), and the sum of three major polychlorinated biphenyls (ΣPCBs) in maternal serum at 34 weeks of gestation and maternal hair total mercury (Hg) at birth. We used negative binomial regressions to estimate associations between individual pollutants and 418 reliably expressed EV-miRNAs adjusted for potential confounders. We performed sparse principal components (PCs) analysis to derive the first four components of the EV-miRNA data and examined associations between pollutants and PCs using Bayesian kernel machine regression (BKMR).

RESULTS

We observed no associations between pollutants and individual EV-miRNA expression after controlling the false discovery rate at 0.1. However, BKMR suggested that Hg was positively associated with PC1 and negatively associated with PC3, while ΣPCBs was negatively associated with PC3, and two PFAS were associated with PC4. Exploration of PC loadings followed by pathway analyses suggested that miRNAs in PC1 (miR-200b-3p, miR-664a-3p, miR-6738-5p, miR-429, miR-1236-5p, miR-4464, and miR-30b-5p) may be related to Hg neurotoxicity, while remaining PCs require further research.

CONCLUSIONS

Our findings suggest that groups of milk EV-miRNAs may better serve as environmental biomarkers than individual miRNAs. Future studies are needed to elucidate the role of milk EV-miRNAs in child health following prenatal exposures.

An Assessment of Health Outcomes and Methylmercury Exposure in Munduruku Indigenous Women of Childbearing Age and Their Children under 2 Years Old

In line with the 1000-day initiative and the Sustainable Development Goals (SDG) 2 and 3, we present a cross-sectional analysis of maternal health, infant nutrition, and methylmercury exposure within hard-to-reach indigenous communities in the state of Pará, Brazilian Amazon. We collected data from all women of childbearing age (i.e., 12-49) and their infants under two years old in three Munduruku communities (Sawré Muybu, Sawré Aboy, and Poxo Muybu) along the Tapajos River. We explored health outcomes through interviews, vaccine coverage and clinical assessment, and determined baseline hair methylmercury (H-Hg) levels. Hemoglobin, infant growth (Anthropometric Z scores) and neurodevelopment tests results were collected. We found that 62% of women of childbearing age exceeded the reference limit of 6.0 μg/g H-Hg (median = 7.115, IQR = 4.678), with the worst affected community (Sawré Aboy) registering an average H-Hg concentration of 12.67 μg/g. Half of infants aged under 24 months presented with anemia. Three of 16 (18.8%) infants presented H-Hg levels above 6.0 µg/g (median: 3.88; IQR = 3.05). Four of the 16 infants were found to be stunted and 38% of women overweight, evidencing possible nutritional transition. No infant presented with appropriate vaccination coverage for their age. These communities presented with an estimated Infant Mortality Rate (IMR) of 86.7/1000 live births. The highest H-Hg level (19.6 µg/g) was recorded in an 11-month-old girl who was found to have gross motor delay and anemia. This already vulnerable indigenous Munduruku community presents with undernutrition and a high prevalence of chronic methylmercury exposure in women of childbearing age. This dual public health crisis in the context of wider health inequalities has the potential to compromise the development, health and survival of the developing fetus and infant in the first two critical years of life. We encourage culturally sensitive intervention and further research to focus efforts.

Antioxidative Molecules in Human Milk and Environmental Contaminants

Breastfeeding provides overall beneficial health to the mother-child dyad and is universally recognized as the preferred feeding mode for infants up to 6-months and beyond. Human milk provides immuno-protection and supplies nutrients and bioactive compounds whose concentrations vary with lactation stage. Environmental and dietary factors potentially lead to excessive chemical exposure in critical windows of development such as neonatal life, including lactation. This review discusses current knowledge on these environmental and dietary contaminants and summarizes the known effects of these chemicals in human milk, taking into account the protective presence of antioxidative molecules. Particular attention is given to short- and long-term effects of these contaminants, considering their role as endocrine disruptors and potential epigenetic modulators. Finally, we identify knowledge gaps and indicate potential future research directions.

Exposure to total and methylmercury among pregnant women in Suriname: sources and public health implications

Previous research has found that women and children living in rural, interior communities in Suriname have high concentrations of mercury in hair. Freshwater fish from these areas also have high concentrations of mercury. Artisanal and small-scale gold mining operations in parts of the country use elemental mercury to extract gold from soils and sediments. Total mercury and methylmercury concentrations have been determined in hair and blood from pregnant women across the country. Pregnant women from interior communities have significantly higher concentrations of both total and methylmercury in hair (median total mercury in hair 3.64 µg/g) compared with pregnant women from two urban coastal cities, Paramaribo (0.63 µg/g) and Nickerie (0.74 µg/g). Total and methylmercury concentrations in blood and hair are highly correlated (r = 0.986, r = 0.974) with methylmercury making up 86% of the total in blood and 97% of the total in hair. Most women in the interior regions rely heavily on local fish as part of their regular diet, and many live outsides of areas with active ASGM operations. This study demonstrates that diet and fish consumption largely govern mercury exposures in pregnant women in Suriname.

Blood and Urine Inorganic and Organic Mercury Levels in the United States from 1999 to 2016

BACKGROUND

Mercury is an environmental hazard. Organic mercury is biologically more toxic than inorganic mercury. Therefore, we studied recent trends in the blood levels of organic and inorganic mercury in the United States.

METHODS

A total of 56,445 participants that had blood mercury and urine mercury measurements in National Health and Nutrition Examination Survey (NHANES) 1999-2016 were included. The organic mercury level was obtained by subtracting the inorganic mercury level from the total mercury level. Results were analyzed using SPSS complex sample module version 25. Pregnant women, children ages <20 years, and different ethnicities were analyzed as subgroups.

RESULTS

Blood organic mercury level increased from (geometric mean [95% confidence interval]) 0.08 [0.07-0.10] to 0.17 [0.16-0.18] µg/L during 1999-2016. It increased significantly (P <0.001) from 0.03 [0.02-0.03] to 0.07 [0.06-0.07] µg/L in children ages <20 and from 0.14 [0.09-0.21] to 0.36 [0.16-0.83] µg/L in pregnant women in this period (P <0.001). In 2013-2016, non-Hispanic Asians had the highest blood organic mercury level among different ethnicities, 0.93 [0.82-1.05] µg/L (P <0.001). Blood inorganic mercury level decreased from 0.31 [0.31-0.31] in 1999-2000 to 0.21 [0.21-0.22] µg/L in 2015-2016 (P <0.001). Urine mercury level decreased from 0.75 [0.71-0.80] in 1999-2000 to 0.16 [0.16-0.17] µg/L in 2015-2016 (P <0.001).

CONCLUSION

Blood organic mercury increased over the period 1999-2016 in the US population, including children and pregnant women, whereas there was a steady decline in both blood inorganic mercury and urine mercury levels.

Infants and mothers levels of mercury in breast milk, urine and hair, data from an artisanal and small-scale gold mining area in Kadoma / Zimbabwe

In Kadoma (Zimbabwe) gold is extracted from ore based on a simple technology using mercury. Women are exposed whilst living in an exposed area, or even more working directly with mercury. Breast fed infants are exposed via mercury contaminated milk and the general environmental mercury exposure. The aim of the study was to measure infants and mothers levels of mercury in urine and hair, as well as in breast milk. In 2006, an environmental epidemiological field study with 120 mother - child pairs was conducted. A non exposed control group (n = 42) was compared with a medium exposed group (n = 51) and a high exposed group (occupational exposure, n = 27). Urine and hair samples from mother and infants plus breast milk samples were analyzed for total mercury. 120 breast milk samples were analyzed, median (maximum) concentrations [μg Hg/l] were (i) control group < 0.50 (1.55), (ii) medium exposed group 1.10 (10.48), (iii) high exposed group 1.20 (24.80) (p < 0,001). Urine and hair results were distributed similarly for infants and mothers, with higher levels according to the exposure subgroup. All specimen results correlated very well with another, indicating there is a pathway between breast milk and infant's level of mercury. The daily uptake of mercury via breast milk was calculated. The reference dose of 0.3°[μg Hg/kg BW/d] was used to compare the burden of the infants. No infant from the control group, but 17.6% of the medium and 18.5% of the high exposed group were above the reference dose. Mercury in breast milk is generally higher in artisanal and small scale gold mining areas. Breast fed infants were burdened with toxic mercury via breast milk and via the general environment, both are important public health issues.

Concentration of mercury, cadmium, and lead in breast milk from Norwegian mothers: Association with dietary habits, amalgam and other factors

Mercury (Hg), cadmium (Cd), and lead (Pb) are of great concern for food safety and infants are especially sensitive to exposure to the maternal body burden. We quantified these elements in breast milk from Norwegian mothers and determined their association with dietary habits, maternal amalgam fillings, and smoking. Breast milk (n = 300) from the Norwegian Human Milk Study (HUMIS) was analyzed using triple quadrupole inductively coupled plasma mass spectrometry, after an acidic decomposition using microwave technique. We used multiple linear regression to examine predictors of Hg and Cd in breast milk, and logistic regression to test predictors of Pb above the quantification limit. The median breast milk concentrations (minimum - maximum) were 0.20 μg Hg/kg (<0.058-0.89), 0.057 μg Cd/kg (0.017-1.2), and <0.67 μg Pb/kg (<0.2-7.5). Cadmium showed no significant relation with any exposure variable investigated. Lead was associated with intake of liver and kidneys from game. For Hg concentration in breast milk, number of amalgam fillings and high fish consumption were significant predictors (p < 0.001). We detected a significant association (p < 0.01) between Hg in breast milk and maternal consumption of Atlantic halibut, lean fish, mussels and scallops and lifetime consumption of crab. Seafood intake alone explained 10% of variance, while together with amalgam explained 46% of variance in Hg concentration in breast milk. Our findings emphasize the importance of following consumer advice with respect to fish and seafood and points to amalgam as an important source for Hg exposure.

Occurrence of Methylmercury in Rice-Based Infant Cereals and Estimation of Daily Dietary Intake of Methylmercury for Infants

Recent reports of elevated levels of methylmercury (MeHg) in rice revealed the possible occurrence of MeHg in infant rice cereals, leading to potential MeHg exposure through cereal consumption. Total mercury (THg) and MeHg levels in 119 infant cereal samples commonly marketed in the United States and China and estimated daily intake of MeHg through cereal consumption were determined. Concentrations of THg and MeHg in the tested cereal samples ranged from 0.35 to 15.9 μg/kg and from 0.07 to 13.9 μg/kg with means of 2.86 and 1.61 μg/kg, respectively. Rice-based cereals contained MeHg levels significantly higher than those of nonrice cereals, indicating that MeHg in rice could be source of MeHg in cereals. Cereal consumption could be a potential pathway of MeHg exposure for infants, as the EDI through cereal consumption amounted to 4-122% of the MeHg reference dose, suggesting the necessity of further evaluation of the potential health risk of dietary MeHg exposure to infants.

Heavy metals (Pb, Cd, As and MeHg) as risk factors for cognitive dysfunction: A general review of metal mixture mechanism in brain

Human exposure to toxic heavy metals is a global challenge. Concurrent exposure of heavy metals, such as lead (Pb), cadmium (Cd), arsenic (As) and methylmercury (MeHg) are particularly important due to their long lasting effects on the brain. The exact toxicological mechanisms invoked by exposure to mixtures of the metals Pb, Cd, As and MeHg are still unclear, however they share many common pathways for causing cognitive dysfunction. The combination of metals may produce additive/synergetic effects due to their common binding affinity with NMDA receptor (Pb, As, MeHg), Na⁺ - K⁺ ATP-ase pump (Cd, MeHg), biological Ca⁺² (Pb, Cd, MeHg), Glu neurotransmitter (Pb, MeHg), which can lead to imbalance between the pro-oxidant elements (ROS) and the antioxidants (reducing elements). In this process, ROS dominates the antioxidants factors such as GPx, GS, GSH, MT-III, Catalase, SOD, BDNF, and CERB, and finally leads to cognitive dysfunction. The present review illustrates an account of the current knowledge about the individual metal induced cognitive dysfunction mechanisms and analyse common Mode of Actions (MOAs) of quaternary metal mixture (Pb, Cd, As, MeHg). This review aims to help advancement in mixture toxicology and development of next generation predictive model (such as PBPK/PD) combining both kinetic and dynamic interactions of metals.

Mercury Exposure in Healthy Korean Weaning-Age Infants: Association with Growth, Feeding and Fish Intake

Low-level mercury (Hg) exposure in infancy might be harmful to the physical growth as well as neurodevelopment of children. The aim of this study was to investigate postnatal Hg exposure and its relationship with anthropometry and dietary factors in late infancy. We recruited 252 healthy Korean infants between six and 24 months of age from an outpatient clinic during the 2009/2010 and 2013/2014 seasons. We measured the weight and height of the infants and collected dietary information using questionnaires. The Hg content of the hair and blood was assessed using inductively coupled plasma mass spectroscopy. The geometric mean Hg concentration in the hair and blood was 0.22 (95% confidence interval: 0.20–0.24) µg/g and 0.94 (n = 109, 95% confidence interval: 0.89–0.99) µg/L, respectively. The hair Hg concentration showed a good correlation with the blood Hg concentration (median hair-to-blood Hg ratio: 202.7, r = 0.462, p < 0.001) and was >1 µg/g in five infants. The hair Hg concentration showed significant correlations with weight gain after birth (Z-score of the weight for age—Z-score of the birthweight; r = −0.156, p = 0.015), the duration (months) of breastfeeding as the dominant method of feeding (r = 0.274, p < 0.001), and the duration of fish intake more than once per week (r = 0.138, p = 0.033). In an ordinal logistic regression analysis with categorical hair Hg content (quartiles), dietary factors, including breastfeeding as the dominant method of feeding in late infancy (cumulative odds ratio: 6.235, 95% confidence interval: 3.086–12.597, p < 0.001) and the monthly duration of fish intake more than once per week (cumulative odds ratio: 1.203, 95% confidence interval: 1.034–1.401; p = 0.017), were significantly associated with higher hair Hg content. Weight gain after birth was not, however, significantly associated with hair Hg content after adjustment for the duration of breastfeeding as the dominant method of feeding. Low-level Hg exposure through breastfeeding and fish intake as a complementary food did not directly affect anthropometry in this population. If prolonged breastfeeding is expected, however, the Hg exposure through fish intake may need to be monitored for both mothers and infants.

Methylmercury in the breast milk of Japanese mothers and lactational exposure of their infants

The human fetus is known to be exposed to methylmercury (MeHg), but little is known about the risk of infant exposure via breast milk. To evaluate the lactational exposure to MeHg via breast milk in Japanese infants, the levels of total mercury (THg) and MeHg were determined in breast milk and maternal blood using samples from a birth cohort study at the Tohoku Study of Child Development. Maternal blood and breast milk were collected one day postpartum and one month after delivery, respectively. The median THg (and MeHg) concentrations in maternal RBCs, plasma and breast milk were 17.8 ng g(-1) (17.8 ng g(-1)), 1.51 ng g(-1) (1.33 ng g(-1)) and 0.81 ng g(-1) (0.45 ng g(-1)), respectively (n=27). The median percentage of MeHg in THg was 54% in breast milk. Breast milk contained substantial amounts of MeHg, which was strongly associated with the internal accumulation of MeHg and the lipid content of the milk (r=0.684). The range of lipid contents in milk varied widely from 0.50 to 6.60 g/100 g of milk, with a median of 3.60 g/100 g. The median (range) weekly average intake of MeHg via breast milk was estimated to be 0.63 μg kg(-1) (0.08-1.68 μg kg(-1)) BW/week. Because the MeHg and lipid contents in milk substantially fluctuate, an investigation of the variations of MeHg and lipid content in breast milk may be required for a more precise risk assessment.

Milestone achievement and neurodevelopment of rural Amazonian toddlers (12 to 24 months) with different methylmercury and ethylmercury exposure

Neurological outcomes (Gesell development schedules [GDS]), age of walking, and age of talking were studied in 299 toddlers (12 to 24 mo) in relation to environmental (fish consumption and tin mining) exposure. Exposure to fish methylmercury (MeHg) consumption and iatrogenic ethylmercury (EtHg) in Thimerosal-containing vaccines (TCV) was quantified in toddlers from two rural villages (n = 91, Itapuã; n = 218, Bom Futuro) respectively populated by fishers and cassiterite miners. Median total hair Hg (HHg) concentrations of infants from Itapuã (3.5 μg/g) were significantly higher than those of infants from Bom Futuro (2.2 μg/g). Median EtHg exposure from TCV was also significantly higher in toddlers from Itapuã (137.5 μg) than in those from Bom Futuro (112.5 μg). There were no significant differences between groups for any of the Gesell schedules; however, there were proportionally more compromised toddlers (GDS < 70) in Itapuã than Bom Futuro. Median age of talking was not statistically different but median age of walking was significantly higher in Bom Futuro. In toddlers from both villages, of fishers and miners, HHg concentrations were significantly correlated with family fish consumption. A logistic regression model was applied to all infants after classification into two groups: above or below the median Gesell schedules. Overall, there was no distinctive pattern of neurodevelopment associated with either HHg or EtHg exposure; however, nutritional status was significantly associated with GDS. In conclusion, milestone achievement was delayed in toddlers from tin-ore mining communities. Despite significantly higher exposure to both forms of organic Hg (MeHg from maternal fish consumption, and EtHg from TCV) in toddlers from the fishing village, significant differences were seen only among the proportions of most severely affected toddlers (GDS < 70).

Mercury transfer during pregnancy and breastfeeding: hair mercury concentrations as biomarker

Hair mercury (HHg) concentration is a biomarker of exposure that is widely used to assess environmental contamination by fish methylmercury and neurodevelopment in children. In the Rio Madeira basin (Brazilian Amazon), total HHg concentrations in 649 mother-infant pairs were measured at birth (prenatal exposure) and after 6 months of exclusive breastfeeding; these mother-infant pairs were from high fish-eating communities (urban, n = 232; rural, n = 35; and Riverine, n = 262) and low fish-eating tin-miner settlers (n = 120). Differences in kinetics were seen between Hg exposure from fish consumption and environmental exposure to a tin-ore mining environment. Overall maternal HHg concentrations (at childbirth and after 6 months of lactation) were higher than those of infant HHg. However, the relative change in HHg after 6 months of lactation showed that mothers decreased HHg while infants increased HHg. The relative change showed a consistently higher increase for girls than boys with a statistical significance only in high fish-eating mothers. The correlation coefficients between maternal and newborn hair were high and statistically significant for mothers living in urban (r = 0.66, p < 0.001), rural (r = 0.89, p < 0.001), and Riverine (r = 0.89, p < 0.001) communities not for tin miner settlers (r = 0.07, p = 0.427). After 6 months of exclusive breastfeeding, correlation coefficients showed high correlation coefficients and statistical significance for all groups (urban, r = 0.73, p < 0.001; rural, r = 0.88, p < 0.001; Riverine, r = 0.91, p < 0.001) except for Tin miners (r = -0.07, p = 0.428). A linear model analysis was used to assess the longitudinal associations of maternal total HHg and total HHg at birth (0 days) and 6 months of age in exclusively breastfed infants. Regression analysis significantly predicted HHg in newborn from maternal HHg for high fish-eating maternal-infant pairs.

CONCLUSION

The concentration of mercury accumulated in newborn tissues (in utero and during breastfeeding) relevant to both, maternal sources and infant exposure, can be reliably assessed from maternal hair.

Long-lasting neurotoxic effects of exposure to methylmercury during development

Amongst environmental chemical contaminants, methylmercury (MeHg) remains a major concern because of its detrimental effects on developing organisms, which appear to be particularly susceptible to its toxicity. Here, we investigated the effects of low MeHg levels on the development of the nervous system using both in vitro and in vivo experimental models. In neural stem cells (NSCs), MeHg decreased proliferation and neuronal differentiation and induced cellular senescence associated with impairment in mitochondrial function and a concomitant decrease in global DNA methylation. Interestingly, the effects were heritable and could be observed in daughter NSCs never directly exposed to MeHg. By chronically exposing pregnant/lactating mice to MeHg, we found persistent behavioural changes in the male offspring, which exhibited depression-like behaviour that could be reversed by chronic treatment with the antidepressant fluoxetine. The behavioural alterations were associated with a decreased number of proliferating cells and lower expression of brain-derived neurotrophic factor (Bdnf) mRNA in the hippocampal dentate gyrus. MeHg exposure also induced long-lasting DNA hypermethylation, increased histone H3-K27 tri-methylation and decreased H3 acetylation at the Bdnf promoter IV, indicating that epigenetic mechanisms play a critical role in mediating the long-lasting effects of perinatal exposure to MeHg. Fluoxetine treatment restored the Bdnf mRNA expression levels, as well as the number of proliferating cells in the granule cell layer of the dentate gyrus, which further supports the hypothesis that links depression to impaired neurogenesis. Altogether, our findings have shown that low concentrations of MeHg induce long-lasting effects in NSCs that can potentially predispose individuals to depression, which we have reported earlier to occur in experimental animals exposed to MeHg during prenatal and early postnatal development.

Semen quality and reproductive hormones in Faroese men: a cross-sectional population-based study of 481 men

OBJECTIVES

To determine semen quality and reproductive hormone levels in young Faroese men.

DESIGN

Descriptive cross-sectional study of Faroese men compared with Danish men.

SETTING

Faroese one-centre study.

PARTICIPANTS

481 men born from 1981 to 1987 and investigated from 2007 to 2010.

OUTCOME MEASURES

Sperm concentration, semen volume, total sperm count, sperm motility, sperm morphology and reproductive hormone levels.

RESULTS

Sperm concentrations for the Faroese men were lower than for the Danish men (crude median 40 vs 48 mill/ml, p<0.0005). Semen volume was higher, and thus the total sperm counts did not differ (159 vs 151 mill, p=0.2). Motility and morphology did not differ between the Faroese and Danes. The inhibin B/follicle-stimulating hormone ratios for the Faroese men were lower than for the Danes (64 vs 76, p=0.001). Similarly, lower total testosterone/luteinising hormone (LH) ratio (4.6 vs 6.0, p<0.0005) and lower calculated free-testosterone/LH ratio (94 vs 134, p<0.0005) were detected for the Faroese men.

CONCLUSIONS

Semen quality among the Faroese men is at the same low level as reported for Danish men, and the reproductive hormone levels furthermore indicated a lower Leydig cell capacity for testosterone production. The influence of environmental exposure and genetic factors on semen quality has to be studied further.

Consumption of tomato products is associated with lower blood mercury levels in Inuit preschool children

Some evidence suggests that various diet components and nutrients, including vegetables, fruit and food-derived antioxidants, could mitigate contaminant exposure and/or adverse health effects of contaminants. To examine the effect of the consumption of tomato products on blood mercury levels in Inuit preschool children, 155 Inuit children (25.0±9.1months) were recruited from 2006-2008 in Nunavik childcare centers (northern Québec, Canada). Food frequency questionnaires were completed at home and at the childcare center, and total blood mercury concentration was measured by inductively coupled plasma-mass spectrometry. Multivariate regression analysis was performed after multiple imputation. The median blood concentration of mercury was 9.5nmol/L. Age, duration of breastfeeding, annual consumption frequency of seal meat, and monthly consumption frequency of tomato products were significant predictors of blood mercury levels, whereas annual consumption frequencies of beluga muktuk, walrus, Arctic char, and caribou meat were not. Each time a participant consumed tomato products during the month before the interview was associated with a 4.6% lower blood mercury level (p=0.0005). All other significant predictors in the model were positively associated with blood mercury levels. Further studies should explore interactions between consumption of healthy store-bought foods available in Arctic regions and contaminant exposure.

Neurodevelopment of Amazonian infants: antenatal and postnatal exposure to methyl- and ethylmercury

Neurodevelopment as Gesell development scores (GDSs) in relation to mercury exposure in infants (<6 months of age) of one urban center and two rural villages, respectively, of fisherman and cassiterite miners. Mean total hair-Hg (HHg) concentrations of infants from Itapuã (3.95 ± 1.8 ppm) were statistically (P = 0.0001) different from those of infants from Porto Velho (3.84 ± 5.5 ppm) and Bom Futuro (1.85 ± 0.9 ppm). Differences in vaccine coverage among these populations resulted in significantly higher (P = 0.0001) mean ethylmercury (EtHg) exposure in urban infants (150 μg) than in infants from either village (41.67 μg, Itapuã; 42.39 μg, Bom Futuro). There was an inverse significant (Spearman r = −0.2300; P = 0.0376) correlation between HHg and GDS for infants from Porto Velho, but not for the rural infants from Bom Futuro (Spearman r = 0.1336; P = 0.0862) and Itapuã (Spearman r = 0.1666; P = 0.5182). Logistic regression applied to variables above or below the median GDS showed that EtHg exposure (estimated probability = −0.0157; P = 0.0070) and breastfeeding score (estimated probability = −0.0066; P = 0.0536) score were significantly associated with GDS. Conclusion. In nurslings whose mothers are exposed to different levels of fish-MeHg (HHg), a higher score of neurological development at six months was negatively associated with exposure to additional TCV-EtHg. Results should be interpreted with caution because of unaccounted variables.

Rescue of neuronal migration deficits in a mouse model of fetal Minamata disease by increasing neuronal Ca2+ spike frequency

In the brains of patients with fetal Minamata disease (FMD), which is caused by exposure to methylmercury (MeHg) during development, many neurons are hypoplastic, ectopic, and disoriented, indicating disrupted migration, maturation, and growth. MeHg affects a myriad of signaling molecules, but little is known about which signals are primary targets for MeHg-induced deficits in neuronal development. In this study, using a mouse model of FMD, we examined how MeHg affects the migration of cerebellar granule cells during early postnatal development. The cerebellum is one of the most susceptible brain regions to MeHg exposure, and profound loss of cerebellar granule cells is detected in the brains of patients with FMD. We show that MeHg inhibits granule cell migration by reducing the frequency of somal Ca(2+) spikes through alterations in Ca(2+), cAMP, and insulin-like growth factor 1 (IGF1) signaling. First, MeHg slows the speed of granule cell migration in a dose-dependent manner, independent of the mode of migration. Second, MeHg reduces the frequency of spontaneous Ca(2+) spikes in granule cell somata in a dose-dependent manner. Third, a unique in vivo live-imaging system for cell migration reveals that reducing the inhibitory effects of MeHg on somal Ca(2+) spike frequency by stimulating internal Ca(2+) release and Ca(2+) influxes, inhibiting cAMP activity, or activating IGF1 receptors ameliorates the inhibitory effects of MeHg on granule cell migration. These results suggest that alteration of Ca(2+) spike frequency and Ca(2+), cAMP, and IGF1 signaling could be potential therapeutic targets for infants with MeHg intoxication.

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.

Allergy and sensitization during childhood associated with prenatal and lactational exposure to marine pollutants

BACKGROUND

Breast-feeding may affect the risk of developing allergy during childhood and may also cause exposure to immunotoxicants, such as polychlorinated biphenyls (PCBs), which are of concern as marine pollutants in the Faroe Islands and the Arctic region.

OBJECTIVES

The objective was to assess whether sensitization and development of allergic disease is associated with duration of breast-feeding and prenatal or postnatal exposures to PCBs and methylmercury.

METHODS

A cohort of 656 singleton births was formed in the Faroe Islands during 1999-2001. Duration of breast-feeding and history of asthma and atopic dermatitis were recorded at clinical examinations at 5 and 7 years of age. PCB and mercury concentrations were determined in blood samples obtained at parturition and at follow-up. Serum from 464 children (71%) at 7 years of age was analyzed for total immunoglobulin E (IgE) and grass-specific IgE.

RESULTS

The total IgE concentration in serum at 7 years of age was positively associated both with the concomitant serum PCB concentration and with the duration of breast-feeding. However, the effect only of the latter was substantially attenuated in a multivariate analysis. A raised grass-specific IgE concentration compatible with sensitization was positively associated with the duration of breast-feeding and inversely associated with prenatal methylmercury exposure. However, a history of asthma or atopic dermatitis was not associated with the duration of breast-feeding, although children with atopic dermatitis had lower prenatal PCB exposures than did nonallergic children.

CONCLUSIONS

These findings suggest that developmental exposure to immunotoxicants may both increase and decrease the risk of allergic disease and that associations between breast-feeding and subsequent allergic disease in children may, at least in part, reflect lactational exposure to immunotoxic food contaminants.

Mercury exposure and children's health

Acute or chronic mercury exposure can cause adverse effects during any period of development. Mercury is a highly toxic element; there is no known safe level of exposure. Ideally, neither children nor adults should have any mercury in their bodies because it provides no physiological benefit. Prenatal and postnatal mercury exposures occur frequently in many different ways. Pediatricians, nurses, and other health care providers should understand the scope of mercury exposures and health problems among children and be prepared to handle mercury exposures in medical practice. Prevention is the key to reducing mercury poisoning. Mercury exists in different chemical forms: elemental (or metallic), inorganic, and organic (methylmercury and ethyl mercury). Mercury exposure can cause acute and chronic intoxication at low levels of exposure. Mercury is neuro-, nephro-, and immunotoxic. The development of the child in utero and early in life is at particular risk. Mercury is ubiquitous and persistent. Mercury is a global pollutant, bio-accumulating, mainly through the aquatic food chain, resulting in a serious health hazard for children. This article provides an extensive review of mercury exposure and children's health.

Mercury exposure and children's health

Acute or chronic mercury exposure can cause adverse effects during any period of development. Mercury is a highly toxic element; there is no known safe level of exposure. Ideally, neither children nor adults should have any mercury in their bodies because it provides no physiological benefit. Prenatal and postnatal mercury exposures occur frequently in many different ways. Pediatricians, nurses, and other health care providers should understand the scope of mercury exposures and health problems among children and be prepared to handle mercury exposures in medical practice. Prevention is the key to reducing mercury poisoning. Mercury exists in different chemical forms: elemental (or metallic), inorganic, and organic (methylmercury and ethyl mercury). Mercury exposure can cause acute and chronic intoxication at low levels of exposure. Mercury is neuro-, nephro-, and immunotoxic. The development of the child in utero and early in life is at particular risk. Mercury is ubiquitous and persistent. Mercury is a global pollutant, bio-accumulating, mainly through the aquatic food chain, resulting in a serious health hazard for children. This article provides an extensive review of mercury exposure and children's health.

Methylmercury-induced neurotoxicity and apoptosis

Methylmercury is a widely distributed environmental toxicant with detrimental effects on the developing and adult nervous system. Due to its accumulation in the food chain, chronic exposure to methylmercury via consumption of fish and sea mammals is still a major concern for human health, especially developmental exposure that may lead to neurological alterations, including cognitive and motor dysfunctions. Mercury-induced neurotoxicity and the identification of the underlying mechanisms has been a main focus of research in the neurotoxicology field. Three major mechanisms have been identified as critical in methylmercury-induced cell damage including (i) disruption of calcium homeostasis, (ii) induction of oxidative stress via overproduction of reactive oxygen species or reduction of antioxidative defenses and (iii) interactions with sulfhydryl groups. In vivo and in vitro studies have provided solid evidence for the occurrence of neural cell death, as well as cytoarchitectural alterations in the nervous system after exposure to methylmercury. Signaling cascades leading to cell death induced by methylmercury involve the release of mitochondrial factors, such as cytochrome c and AIF with subsequent caspase-dependent or -independent apoptosis, respectively; induction of calcium-dependent proteases calpains; interaction with lysosomes leading to release of cathepsins. Interestingly, several pathways can be activated in parallel, depending on the cell type. In this paper, we provide an overview of recent findings on methylmercury-induced neurotoxicity and cell death pathways that have been described in neural and endocrine cell systems.

Longitudinal mercury monitoring within the Japanese and Korean communities (United States): implications for exposure determination and public health protection

BACKGROUND

Estimates of exposure to toxicants are predominantly obtained from single time-point data. Fish consumption guidance based on these data may be incomplete, as recommendations are unlikely to consider impact from factors such as intraindividual variability, seasonal differences in consumption behavior, and species consumed.

OBJECTIVES/METHODS

We studied populations of Korean (n = 108) and Japanese (n = 106) women living in the Puget Sound area in Washington State to estimate mercury exposure based on fish intake and hair Hg levels at two and three time points, respectively. Our goals were to examine changes in hair Hg levels, fish intake behavior, and Hg body burden over time; and to determine if data from multiple time points could improve guidance.

RESULTS/CONCLUSION

More than 50 fish species were consumed, with eight species representing approximately three-fourths of fish consumed by the Japanese and 10 species representing approximately four-fifths of fish intake by the Koreans. Fish species responsible for most Hg intake did not change over time; < 10 species accounted for most of the Hg body burden in each population. Longitudinal variability of hair Hg levels changed slowly across the study period. Japanese with hair Hg levels > 1.2 ppm (mean, 2.2 ppm) consumed approximately 150% more fish than those with levels < or = 1.2 ppm (mean, 0.7 ppm). However, because many participants consumed substantial amounts of fish while having hair-Hg levels < or = 1.2 ppm, the nutritional benefits offered from fish consumption should be obtainable without exceeding the RfD. We observed a 100% difference in fish intake between open-ended and 2-week recall fish consumption surveys. Open-ended survey data better represent Hg intake as determined from hair Hg levels. Single time-point fish intake data appear to be adequate for deriving guidance, but caution is warranted, as study is required to determine the significance of the different outcomes observed using the two survey time frames.

Postnatal exposure to methyl mercury from fish consumption: a review and new data from the Seychelles Child Development Study

BACKGROUND

Fish is an important source of nutrition worldwide. Fish contain both the neurotoxin methyl mercury (MeHg) and nutrients important for brain development. The developing brain appears to be most sensitive to MeHg toxicity and mothers who consume fish during pregnancy expose their fetus prenatally. Although brain development is most dramatic during fetal life, it continues for years postnatally and additional exposure can occur when a mother breast feeds or the child consumes fish. This raises the possibility that MeHg might influence brain development after birth and thus adversely affect children's developmental outcomes. We reviewed postnatal MeHg exposure and the associations that have been published to determine the issues associated with it and then carried out a series of analyses involving alternative metrics of postnatal MeHg exposure in the Seychelles Child Development Study (SCDS) Main Cohort.

METHODS

The SCDS is a prospective longitudinal evaluation of prenatal MeHg exposure from fish consumption. The Main Cohort includes 779 subjects on whom recent postnatal exposure data were collected at the 6-, 19-, 29-, 66-, and 107-month evaluations. We examined the association of recent postnatal MeHg exposure with multiple 66- and 107-month outcomes and then used three types of alternative postnatal exposure metrics to examine their association with the children's intelligence quotient (IQ) at 107 months of age.

RESULTS

Recent postnatal exposure at 107 months of age was adversely associated with four endpoints, three in females only. One alternative postnatal metric was beneficially associated with 9-year IQ in males only.

CONCLUSIONS

We found several associations between postnatal MeHg biomarkers and children's developmental endpoints. However, as has been the case with prenatal MeHg exposure in the SCDS Main Cohort study, no consistent pattern of associations emerged to support a causal relationship.

Human developmental neurotoxicity of methylmercury: impact of variables and risk modifiers

Methylmercury (MeHg) is a widespread environmental and food toxicant which has long been known to affect neurodevelopment in both humans and experimental animals. Risk assessment for MeHg is mainly based on human data coming from the massive episodes of poisoning in Japan and Iraq, as well as from large scale epidemiological studies concerning childhood development and neurotoxicity in relation to in utero exposure in various fish eating communities around the world. Despite the extensive literature and research, the threshold dose for MeHg neurotoxic effects is still unclear, in particular when it comes to subtle effects on neurobehaviour. In this article clinical and epidemiological findings concerning the neurodevelopmental toxicity of MeHg are reviewed. Much attention is focussed on the potential impact of factors, such as diet and nutrition, gender, pattern of exposure and co-exposure to other neurotoxic pollutants, which may modulate MeHg toxic effects. These factors, together with the notion that some symptoms may ensue or exacerbate with aging, contribute to the difficulties in the definition of safe levels for developmental exposure.

Proximity to point sources of environmental mercury release as a predictor of autism prevalence

The objective of this study was to determine if proximity to sources of mercury pollution in 1998 were related to autism prevalence in 2002. Autism count data from the Texas Educational Agency and environmental mercury release data from the Environmental Protection Agency were used. We found that for every 1000 pounds of industrial release, there was a corresponding 2.6% increase in autism rates (p<.05) and a 3.7% increase associated with power plant emissions(P<.05). Distances to these sources were independent predictors after adjustment for relevant covariates. For every 10 miles from industrial or power plant sources, there was an associated decreased autism Incident Risk of 2.0% and 1.4%, respectively (p<.05). While design limitations preclude interpretation of individual risk, further investigations of environmental risks to child development issues are warranted.

Mercury exposure from fish consumption within the Japanese and Korean communities

Public health guidance pertaining to fish consumption requires that we be cognizant of the health concerns associated with eating contaminated fish and the nutritional benefits obtained from fish consumption. In doing so, a need exists for an improved understanding of the extent of contamination within various fish species consumed by populations of concern and the extent of exposure to contamination by these populations. As part of the Arsenic Mercury Intake Biometric Study involving the Japanese and Korean communities, it was possible to obtain fish intake data, determine mercury (Hg) fish tissue concentrations for various species consumed, and examine hair for Hg levels of study participants. This longitudinal study (n = 214) included 106 Japanese and 108 Korean women of childbearing age. Hair Hg levels for the two populations and weight-normalized, species-specific, individual-consumption pattern data that estimated Hg intake levels were compared with published National Health and Nutrition Examination Survey (NHANES) data. Sensitivity analyses and population-specific probabilistic assessments of exposure were conducted. The estimated Hg intake levels for the Japanese (0.09 microg/kg/d) and Koreans (0.05 microg/kg/d) were above the NHANES estimates (0.02 microg/kg/d), as were the hair Hg levels (1.23, 0.61, 0.2 ppm, respectively). Results indicate that (1) there are significant differences between the fish-species-consumption behavior of these two populations; (2) even when fish-consumption rates are equal between two populations, Hg intakes between them can vary significantly; and (3) these population and Hg intake differences present public health challenges when attempting to provide fish consumption guidance.

Neurobehavioural and molecular changes induced by methylmercury exposure during development

There is an increasing body of evidence on the possible environmental influence on neurodevelopmental and neurodegenerative disorders. Both experimental and epidemiological studies have demonstrated the distinctive susceptibility of the developing brain to environmental factors such as lead, mercury and polychlorinated biphenyls at levels of exposure that have no detectable effects in adults. Methylmercury (MeHg) has long been known to affect neurodevelopment in both humans and experimental animals. Neurobehavioural effects reported include altered motoric function and memory and learning disabilities. In addition, there is evidence from recent experimental neurodevelopmental studies that MeHg can induce depression-like behaviour. Several mechanisms have been suggested from in vivo- and in vitro-studies, such as effects on neurotransmitter systems, induction of oxidative stress and disruption of microtubules and intracellular calcium homeostasis. Recent in vitro data show that very low levels of MeHg can inhibit neuronal differentiation of neural stem cells. This review summarises what is currently known about the neurodevelopmental effects of MeHg and consider the strength of different experimental approaches to study the effects of environmentally relevant exposure in vivo and in vitro.

Mercury exposure and public health

Mercury is a metal that is a liquid at room temperature. Mercury has a long and interesting history deriving from its use in medicine and industry, with the resultant toxicity produced. In high enough doses, all forms of mercury can produce toxicity. The most devastating tragedies related to mercury toxicity in recent history include Minamata Bay and Niagata, Japan in the 1950s, and Iraq in the 1970s. More recent mercury toxicity issues include the extreme toxicity of the dimethylmercury compound noted in 1998, the possible toxicity related to dental amalgams, and the disproved relationship between vaccines and autism related to the presence of the mercury-containing preservative, thimerosal.

Maternal mercury exposure and neuro-motor development in breastfed infants from Porto Velho (Amazon), Brazil

Fish is an important item in the diet of Amazonians, and per se is their best single source of essential nutrients. Rapid urbanization and migration are bringing changes in dietary habits of Amazonians. Exposure to fish-Hg during pregnancy and lactation were studied in 100 women and newborns from Porto Velho. Tissue-Hg concentrations and neurodevelopment (Gesell Developmental Schedules) were assessed at birth and at 6 months in exclusively breastfed infants. Maternal mean frequency of fish consumption was low (<2 meals/week; range 0->7 meals/week) compared to Amazonian standards. Women consuming <2 fish meals/week showed less median hair-Hg (3.5 microgg-1) than women that consumed 2 fish meals/week (5.7 microgg). Median total Hg in maternal hair (5.4 microgg-1) was higher than in newborns (1.6 microgg-1). Significant correlation was observed between maternal hair-Hg and infant hair-Hg at birth (r=0.353; p<0.01) and at six months (r=0.510; p<0.01). Placenta-Hg was also significantly correlated to maternal hair-Hg (r=0.321; p<0.01), newborn hair-Hg (r=0.219; p<0.05), maternal blood-Hg (r=0.250; p<0.01) and to umbilical cord-Hg (r=0.857; p<0.01). Most infants (74%) had normal Gesell Schedules but among the 26% showing neuro-motor development delays only six (7%) had multiple (motor, language, and adaptative) delays. The infants with multiple delays were born from mothers with range of hair-Hg comparable to mothers of normally developed infants. Coincidentally, mothers of infants with multiple delays also showed the lowest range of income and level of education. Fish consumption, income, and level of education varied greatly among these breastfeeding urban mothers. It seems that development delays of exclusively breastfed infants are a component of the health inequalities that accompanies socioeconomic disadvantages.

Assessing and managing methylmercury risks associated with power plant mercury emissions in the United States

Until the Clean Air Mercury Rule was signed in March 2005, coal-fired electric utilities were the only remaining, unregulated major source of industrial mercury emissions in the United States. Proponents of coal-burning power plants assert that methylmercury is not a hazard at the current environmental levels, that current technologies for limiting emissions are unreliable, and that reducing mercury emissions from power plants in the United States will have little impact on environmental levels. Opponents of coal-burning plants assert that current methylmercury exposures from fish are damaging to the developing nervous system of infants, children, and the fetus; that current technology can significantly limit emissions; and that reducing emissions will reduce exposure and risk. One concern is that local mercury emissions from power plants may contribute to higher local exposure levels, or "hot spots." The impact of the Mercury Rule on potential hot spots is uncertain due to the highly site-specific nature of the relationship between plant emissions and local fish methylmercury levels. The impact on the primary source of exposure in the United States, ocean fish, is likely to be negligible due to the contribution of natural sources and industrial sources outside the United States. Another debate centers on the toxic potency of methylmercury, with the scientific basis of the US Environmental Protection Agency's (EPA's) recommended exposure limit questioned by some and defended by others. It is likely that the EPA's exposure limit may be appropriate for combined exposure to methylmercury and polychlorinated biphenyls (PCBs), but may be lower than the available data suggest is necessary to protect children from methylmercury alone. Mercury emissions from power plants are a global problem. Without a global approach to developing and implementing clean coal technologies, limiting US power plant emissions alone will have little impact.

Trends in mercury in hair of Greenlandic polar bears (Ursus maritimus) during 1892-2001

Mercury concentrations in hair from 397 Greenland polar bears (Ursusmaritimus) sampled between 1892 and 2001 were analyzed for temporal trends. In East Greenland the concentrations showed a significant (p < 0.0001, n = 27) increase of 3.1%/year in the period 1892-1973. In Northwest Greenland, a similar (p < 0.0001, n = 69) increase of 2.1%/year was found, which continued until 1991, when the most recent samples were obtained. In East Greenland, a significant (p = 0.009, n = 322) decrease of 0.8%/year was observed after 1973. Two Northwest Greenland samples from 1300 A.D. had a mean value of 0.52 mg/kg of dry weight, which can be considered as a baseline level. The Hg concentration during 1985-1991 from Northwest Greenland (mean value of 7.45 mg/kg of dry weight) was more than 14-fold higher than the assumed baseline level from 1300 A.D. from the same region (i.e., about 93% anthropogenic). Although a decrease was found in East Greenland after 1973, the concentration is still ca. 11-fold higher than the baseline level (i.e., about 90% anthropogenic).

Transport of methylmercury and inorganic mercury to the fetus and breast-fed infant

It is well established that methylmercury (MeHg) and mercury vapor pass the placenta, but little is known about infant exposure via breast milk. We measured MeHg and inorganic mercury (I-Hg) in blood of Swedish mothers (n = 20) and their infants, as well as total mercury (T-Hg) in breast milk up to 13 weeks postpartum. Infant blood MeHg was highly associated with maternal blood MeHg at delivery, although more than twice as high. Infant MeHg decreased markedly until 13 weeks of age. Infant blood I-Hg was associated with, and about as high as, maternal blood I-Hg at delivery. Infant I-Hg decreased until 13 weeks. In breast milk, T-Hg decreased significantly from day 4 to 6 weeks after delivery but remained unchanged thereafter. At 13 weeks, T-Hg in breast milk was associated with infant MeHg but not with maternal MeHg. Conversely, T-Hg in breast milk was associated with maternal I-Hg but not with infant I-Hg. From the findings of the present study in which the exposure to both MeHg and I-Hg was low, we conclude that the exposure to both forms of mercury is higher before birth than during the breast-feeding period, and that MeHg seems to contribute more than I-Hg to infant exposure postnatally via breast milk.

Effects of breast feeding on neuropsychological development in a community with methylmercury exposure from seafood

Breastfeeding has been associated with an advantage to infant neurobehavioral development, possibly in part due to essential nutrients in breast milk. However, breast milk may be contaminated by environmental neurotoxicants, such as methylmercury. In the Faroe Islands, where maternal consumption of pilot whale may cause transfer of marine toxicants into breast milk, a cohort of 1022 consecutive singleton births was generated during 1986-87. Methylmercury exposure was assessed from mercury concentrations in cord blood and in the hair of the child at age 12 months, and the duration of breastfeeding was recorded. At approximately 7 years of age, 917 (90%) of the children underwent detailed neurobehavioral examination. After adjustment for confounders, breastfeeding was associated with only marginally better neuropsychological performance on most tests. These associations were robust even after adjustment for cord-blood and hair mercury concentration at age 1 year. Thus, in this cohort of children with a relatively high prenatal toxicant exposure and potential exposure to neurotoxicants through breast milk, breastfeeding was associated with less benefits on neurobehavioral development than previously published studies though not associated with a deficit in neuropsychological performance at age 7. Although the advantage may be less, Faroese women can still safely breastfeed their children.

Cadmium, lead and mercury in human milk from Slovakia

The objective of this study was to investigate Cd, Pb, and Hg levels in the breast milk of 158 lactating healthy women who were not occupationally exposed and living in eight environmentally different polluted locations of the Slovak Republic. Levels of these metals were examined in relation to selected parameters, such as: location, mother's age, parity, number of mother's teeth fillings, newborn's gender and birth weight, and smoking habits in the family. Cd and Pb levels in human milk and reconstituted infant formula were determined by GFAAS. Hg levels were measured by amalgamation technique AAS. The average concentrations of Cd, Pb and Hg in breast milk samples, taken on the 4th postpartum day, were 0.43, 4.7 and 0.94 microg/kg, respectively, and those in infant formula (n = 10) were 0.40, 5.0 and 0.25 microg/kg, respectively. Dietary weekly intakes of Cd, Pb, and Hg from breast milk and infant formula in newborn babies were also estimated. Whereas the calculated average dietary intakes of Cd, Pb, and Hg in newborn babies from breast milk and infant formula were all far lower than the appropriate PTWI values recommended by WHO/FAO, two individual breast milk samples for Pb and one breast milk sample for Hg exceeded the PTWI values. Regarding the studied parameters, only the active/passive smoking of the mother at home significantly increased Pb levels in breast milk and amalgam teeth fillings increased Hg levels in breast milk.