Children's health and mercury exposure

Blood mercury concentrations in preschool children and potential risk factors in São Paulo, Brazil

Environmental exposure of preschool children to mercury can elevate blood mercury levels (BML) and negatively affect their health. This study aimed to determine BML in preschool children from Brazil's largest city and explore potential associated risk factors. Blood samples were collected in 2013 from 2436 children (age 1-5 years) attending 50 daycare centers (DCC) located in São Paulo, Brazil. Parents or guardians answered questionnaires collecting information on sociodemographics and potential risk factors. BML was determined by Cold Vapor Atomic Absorption Spectrophotometry (CV-AAS) and categorized using a cutoff point of 2.77 μg L⁻1, corresponding to the 75th percentile. Multiple logistic regression was performed (p < 0.05). Data were georeferenced and associations with air pollution, wind frequency and direction were evaluated. The results showed a geometric mean for BML of 1.65 μg L⁻1 (95% CI: 1.60-1.70), arithmetic mean of 2.15 μg L⁻1 (95% CI: 2.09-2.22), 75th percentile of 2.77 μg L⁻1 (95% CI: 2.67-2.91) and 95th percentile of 5.51 μg L⁻1 (95% CI: 5.18-5.92). DCCs located in the Northwest and East zones (p < 0.001) and fish consumption in the past two days (p = 0.04) were associated with high BML. The elevated BML observed in children living in the eastern zone might be attributed to the southeasterly winds passing through a petrochemical complex located nearby. The 95th percentile of BML in this study exceeded the U.S. 95th percentile by five times. BML in São Paulo preschool children was associated with individual and environmental risk factors. This finding highlights the need to identify and control hot spots in São Paulo, Brazil, especially in peripheral and surrounding areas, where individuals are more vulnerable. Further research is needed in Latin America to identify additional sources of urban environmental mercury exposure and guide interventions for protecting the environment and safeguarding children's health.

Neurobehavioral effects of cinnabar and the cinnabar-containing pediatric prescription, Yi-Nian-Jin, in juvenile rats

BACKGROUND

Cinnabar, a mercury-containing mineral medicine, has long been widely used in pediatric prescriptions. The safety of cinnabar-containing prescriptions, particularly for children, is drawing increasing attention worldwide. However, whether cinnabar and these pediatric prescriptions have adverse effects on neurobehavior is unknown. Yi-Nian-Jin (YNJ), a classic pediatric prescription, contains 5.66% (w/w) cinnabar, along with other four herbs. YNJ is widely prescribed to promote digestion, eliminate phlegm, and prevent constipation in children (aged 0-6 years). In this study, we used YNJ as an example of cinnabar-containing pediatric prescriptions to determine mercury absorption, distribution, and accumulation and further investigate its potential neurotoxicity in juvenile rats.

MATERIAL AND METHODS

Low (67.9 mg/kg), middle (169.8 mg/kg), and high dose (339.6 mg/kg) of cinnabar, and low (1.2 g/kg), middle (3.0 g/kg), and high dose (6.0 g/kg) of YNJ were used in this study, corresponding to 3, 7.5, and 15 times the clinically equivalent dose, respectively. Juvenile rats were orally administered different doses of cinnabar or YNJ for 14 consecutive days. The mercury content in rat blood and tissues (brain, liver, and kidney) and serum biochemical changes on day 14 of consecutive administration and on day 14 after cessation were measured. Moreover, a series of behavioral assays (open field, elevated plus-maze, and Morris water maze assays) were performed after 14 consecutive days of administration.

RESULTS

The mercury absorption, distribution, and accumulation of cinnabar and YNJ in juvenile rats were substantially different. Mercury in cinnabar was absorbed to a greater extent than that in YNJ, and the mercury content in cinnabar high-dose group (cinnabar-H) was approximately seven times higher than that in YNJ high-dose group (YNJ-H) on day 14 of administration. In contrast, compared with that of cinnabar, the mercury content in YNJ accumulated more in the tissues, especially in the brain and kidney. Repeated administration of cinnabar or YNJ did not affect liver function, renal function, learning, and memory in juvenile rats. However, repeated administration of YNJ at a high dose (6.0 g/kg) affected locomotor activity in juvenile rats. Repeated administration of cinnabar (339.6 mg/kg) or YNJ (>1.2 g/kg) induced anxiety-related behavior in juvenile rats.

CONCLUSIONS

Mercury in YNJ exhibited lower absorption but higher accumulation in tissues than those of the mercury in cinnabar. Consecutive oral administration of cinnabar or YNJ had no impact on liver function, renal function, learning, and memory, but could cause motor dysfunction and anxiety in juvenile rats.

Identification of Mercury Emissions in Soot with the Quadrant Method on Combustion of Gold in Aceh Jaya District

BACKGROUND: Gold mining, especially by the community, causes many problems. One of the problems is the increase in mercury pollution. The amalgamation technique involving mercury in the gold processing process is still widely used by miners and has the potential to threaten the health of workers and the surrounding community. AIM: This study aimed to identify mercury levels in soot at the location of a traditional gold processing plant in Paya Seumantok Village, Krueng Sabee District, Aceh Jaya District. METHODS: This research was conducted at the Environmental Quality Analysis laboratory, Chemical Engineering Department, Syiah Kuala University, Banda Aceh, in May–August 2021. The sample in this study was soot caught on cloth attached to the gold kiln location by amalgamation using the quadrant method. The soot sample was obtained from the people’s gold processing unit in Gampong Paya Seumantok, Krueng Seabee District; then, the fabric sample containing soot was destroyed using HNO3 in the microwave. Measurement of mercury levels, using AAS Perkin-Elmer Analyst 600, equipped with Graphite Furnace (AAS) Technique. RESULTS: The results of the identification show that the mercury level in the first stage of measurement found the highest mercury concentration at a distance of 10 cm with a concentration of 41.90 (±21.64) g-Hg/g, a distance of 5 cm was obtained at 28.71 (±11. 0.98) g-Hg/g, and at a distance of 15 cm obtained 28.20 (±2.85) g-Hg/g. Furthermore, in the measurement of samples in stages 2 and 3, the mercury concentration in soot is influenced by distance, where the closer the distance, the higher the mercury concentration. Stage 2 measurement at a distance of 5 cm, the mercury concentration obtained is 26.84 (±21.05) g-Hg/g, a distance of 10 and 15 cm each has a concentration of 9.25 (±1.26) g-Hg/g and 9.91 (±3.59) g-Hg/g, and in the third stage of the test, the highest concentration located at a distance of 5 cm with a concentration of 20.27 (±3.57) g-Hg/g. CONCLUSION: The average value of mercury concentration in soot obtained far exceeds the threshold set by the World Health Organization, which is 1 g-Hg/gram. Mercury levels that have exceeded the threshold need to be filtered in an enclosed space before the smoke from burning gold spreads into the free air.

Methylmercury-Induced Toxicopathologic Findings in Salivary Glands of Offspring Rats After Gestational and Lactational Exposure

Methylmercury (MeHg) is one of the main global pollutants. The vulnerability of fetus and newborn to MeHg-induced changes is extensively reported, making relevant investigation possible for alternative sample matrix for human biological monitoring for at this stage of life. This study aimed to characterize tissue change effects of environmental-experimental MeHg on salivary glands of offspring rats after pre- and postnatal exposure. For this, pregnant Wistar rats were orally exposed to MeHg (40 μg/kg BW/day) or only vehicle (control group), from the gestational period to the end of the lactation period. Salivary glands (SG) were collected from the offspring to analyze possible Hg levels and main findings by histopathological evaluations and CK19 and α-SMA immunostaining. The results indicated that Hg levels in SG of intoxicated offspring were associated with histologic abnormalities, such as acinar atrophy and an increase in the intercellular matrix among the acini, as well as damages in the architecture of epithelium and myoepithelial cells, evidenced by a decrease in immunostaining area. Thus, this is the first study to show in the literature the toxicopathologic findings on SG of offspring after pre- and postnatal exposure to MeHg. Moreover, it presents the SG as an attractive target to futures studies, mainly in children exposed to environmentally relevant doses.

Improving Human Health in China Through Alternative Energy

In this study, we estimate the health benefits of more stringent alternative energy goals and the costs of reducing coal-fired power plant pollution in China projected in 2030. One of our two overarching alternative energy goals was to estimate the health benefits of complete elimination of coal energy, supplemented by natural gas and renewables. The second was a policy scenario similar to the U.S. 2013 Climate Action Plan (CAP), which played a pivotal role leading up to the 2015 Paris Climate Agreement. We used the Greenhouse Gas and Air Pollution Interactions and Synergies (GAINS) model created by the International Institute for Applied Systems Analysis for our model simulations. We found that 17,137–24,220 premature deaths can be avoided if coal energy is completely replaced by alternative energy, and 8,693–9,281 premature deaths can be avoided if coal energy is replaced by alternatives in a CAP-like scenario. A CAP-like scenario using emission-controls in coal plants costs $11–18 per person. Reducing coal energy in China under a CAP-like scenario would free up $9.4 billion in the annual energy budget to spend on alternatives, whereas eliminating the cost of coal energy frees up $32 billion. This study's estimates show that more stringent alternative energy targets in China are worth the investment in terms of health.

Mercury Exposure in Artisanal and Small-Scale Gold Mining Communities in Sukabumi, Indonesia

BACKGROUND

Artisanal and small-scale gold mining (ASGM) is one of the largest sources of mercury (Hg) pollution in Indonesia. In West Java Province, ASGM is found in Bogor, Cianjur, and Sukabumi Regencies.

OBJECTIVES

The present study aimed to evaluate Hg contamination effects and socioeconomic factors in communities living around ASGM operations in Sukabumi Regency.

METHODS

A quantitative method was used to describe socioeconomic ASGM communities. The concentrations of total mercury (T-Hg) in hair were measured in 71 respondents. This study also assessed perception of the use of Hg in the gold ore processing and their impact on the environment.

RESULTS

The population of gold miners in the studied three villages was 1300 households (25.77% from a total of 5044 households). Artisanal and small-scale gold mining involves both men and women employed as miners and gold amalgam processors, respectively. The average monthly income generated as much as Indonesian Rupiah (IDR) 272 000-2 000 000 (about 19-140 USD). Total Hg analysis was conducted for hair samples of 71 respondents (38 men, 33 women). The results showed an average T-Hg in men of 3.27±2.89 ppm, and women of 5.91±4.69 ppm. The level of T-Hg in the respondents was associated with distance to the ball mills and not related to distance to the mine site.

PARTICIPANT CONSENT

Obtained.

ETHICS APPROVAL

This study was approved by Ministry of Environment and Forestry of the Republic of Indonesia.

COMPETING INTERESTS

The authors declare no competing financial interests.

Soil toxicants that potentially affect children's health

Soil pollution is a global phenomenon, and children are uniquely susceptible to the wide range of toxicants that persist in topsoil. Given their increased exposure through mouthing activities, increased body surface area, likelihood of breathing air closer to soil, and immature immune and elimination systems, it is essential to understand the mechanisms of children's exposure and the potential health effects of toxicants found in soil. Here we describe the sources and toxicological profiles of a range of inorganic and organic soil contaminants, including arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), benzene, toluene, ethylbenzene and xylenes, chlorinated dibenzo-p-dioxins, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), per and polyfluoroalkyl substances (PFAS), as well as agricultural and domestic sources of pollution. The aim of this article is to increase awareness regarding the risks and health impacts of contaminated soil, and to encourage further research and efforts aimed at mitigating children's exposure.

The Fluorescent Quenching Mechanism of N and S Co-Doped Graphene Quantum Dots with Fe3+ and Hg2+ Ions and Their Application as a Novel Fluorescent Sensor

The fluorescence intensity of N, S co-doped graphene quantum dots (N, S-GQDs) can be quenched by Fe3+ and Hg2+. Density functional theory (DFT) simulation and experimental studies indicate that the fluorescence quenching mechanisms for Fe3+ and Hg2+ detection are mainly attributed to the inner filter effect (IFE) and dynamic quenching process, respectively. The electronegativity difference between C and doped atoms (N, S) in favor to introduce negative charge sites on the surface of N, S-GQDs leads to charge redistribution. Those negative charge sites facilitate the adsorption of cations on the N, S-GQDs' surface. Atomic population analysis results show that some charge transfer from Fe3+ and Hg2+ to N, S-GQDs, which relate to the fluorescent quenching of N, S-GQDs. In addition, negative adsorption energy indicates the adsorption of Hg2+ and Fe2+ is energetically favorable, which also contributes to the adsorption of quencher ions. Blue fluorescent N, S-GQDs were synthesized by a facile one-pot hydrothermal treatment. Fluorescent lifetime and UV-vis measurements further validate the fluorescent quenching mechanism is related to the electron transfer dynamic quenching and IFE quenching. The as-synthesized N, S-GQDs were applied as a fluorescent probe for Fe3+ and Hg2+ detection. Results indicate that N, S-GQDs have good sensitivity and selectivity on Fe3+ and Hg2+ with a detection limit as low as 2.88 and 0.27 nM, respectively.

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.

Mercury pollution in vegetables, grains and soils from areas surrounding coal-fired power plants

Mercury contamination in food can pose serious health risks to consumers and coal-fired power plants have been identified as the major source of mercury emissions. To assess the current state of mercury pollution in food crops grown near coal-fired power plants, we measured the total mercury concentration in vegetables and grain crops collected from farms located near two coal-fired power plants. We found that 79% of vegetable samples and 67% of grain samples exceeded the PTWI's food safety standards. The mercury concentrations of soil samples were negatively correlated with distances from the studied coal-fired power plants, and the mercury contents in lettuce, amaranth, water spinach, cowpea and rice samples were correlated with the mercury contents in soil samples, respectively. Also, the mercury concentrations in vegetable leaves were much higher than those in roots and the mercury content of vegetable leaves decreased significantly after water rinses. Our calculation suggests that probable weekly intake of mercury for local residents, assuming all of their vegetables and grains are from their own farmland, may exceed the toxicologically tolerable values allowed, and therefore long-term consumptions of these contaminated vegetables and grains may pose serious health risks.

Urgent need to reevaluate the latest World Health Organization guidelines for toxic inorganic substances in drinking water

The World Health Organization (WHO) has established guidelines for drinking-water quality that cover biological and chemical hazards from both natural and anthropogenic sources. In the most recent edition of Guidelines for Drinking-water Quality (2011), the WHO withdrew, suspended, did not establish, or raised guidelines for the inorganic toxic substances manganese, molybdenum, nitrite, aluminum, boron, nickel, uranium, mercury, and selenium. In this paper, we review these changes to the WHO drinking-water guidelines, examining in detail the material presented in the WHO background documents for each of these toxic substances. In some cases, these WHO background documents use literature reviews that do not take into account scientific research published within the last 10 or more years. In addition, there are instances in which standard WHO practices for deriving guidelines are not used; for example, rounding and other mathematical errors are made. According to published meeting reports from the WHO Chemical Aspects Working Group, the WHO has a timetable for revising some of its guidelines for drinking-water quality, but for many of these toxic substances the planned changes are minimal or will be delayed for as long as 5 years. Given the limited nature of the planned WHO revisions to the inorganic toxic substances and the extended timetable for these revisions, we suggest that governments, researchers, and other stakeholders might establish independent recommendations for inorganic toxic substances and possibly other chemicals to proactively protect public health, or at the very least, revert to previous editions of the Guidelines for Drinking-water Quality, which were more protective of public health.

Evaluación de la capacidad acumuladora de mercurio del ají (Capsicum annuum)

<p><strong>Objetivo</strong> Evaluar la capacidad acumuladora de mercurio por parte la planta de ají (<em>Capsicum annuum</em>), en suelos contaminados procedentes del corregimiento Mina Santa Cruz, Sur de Bolívar, Colombia, con el propósito de establecer el riesgo para la salud de la población consumidora.</p><p><strong>Materiales y Métodos </strong>Se tomaron muestras de tejidos (raíces, tallos y hojas) de plantas de <em>C. annuum</em> sembradas en dos suelos contaminados con mercurio y un suelo control, durante sus primeros cinco meses de crecimiento para determinar mercurio total mediante la técnica de espectrofotometría de absorción atómica por vapor frio. Se determinó mercurio total en muestras de frutos de ají consumido en Mina Santa Cruz.</p><p><strong>Resultados</strong> Las concentraciones medias de mercurio total en raíces fueron mayores en comparación con tallos y hojas. Los niveles de mercurio en suelos y el tiempo influyeron en la acumulación en tejidos. Las concentraciones de mercurio en frutos de <em>C.</em> <em>annuum </em>fueron bajas en relación a la ingesta tolerable semanal dispuesta por la OMS.<strong></strong></p><p><strong>Conclusión </strong>Los porcentajes de translocación de mercurio a las partes aéreas de la planta fueron bajos tanto en el suelo control como en los suelos contaminados. A pesar de los bajos niveles de mercurio en este alimento se debe disminuir al máximo el consumo de alimentos contaminados con dicho metal.</p>

Chronic exposure to low mercury chloride concentration induces object recognition and aversive memories deficits in rats

This work examines the effects of chronic exposure to low inorganic mercury (mercury chloride, HgCl(2)) concentration on the recognition and aversive memories. Forty male Wistar rats were divided into 4 groups treated during 30 or 60 days with saline (control) or HgCl(2) doses. After treated the animals were tested considering object recognition and inhibitory avoidance behavioral memory paradigms. Elevated plus maze, open field and tail flick tests were used to assess anxiety, locomotor and exploratory activity and pain thresholds. Only exposure for 60 days to HgCl(2) induced in memory deficits quantified in the object recognition task. In the inhibitory avoidance all the animals exposed to mercury (for 30 or 60 days) presented worst performance than control animals. Our results suggest that chronic exposure to low mercury chloride concentrations impairs memory formation.

Advances in carcinogenic metal toxicity and potential molecular markers

Metal compounds such as arsenic, cadmium, chromium, cobalt, lead, mercury, and nickel are classified as carcinogens affecting human health through occupational and environmental exposure. However, the underlying mechanisms involved in tumor formation are not well clarified. Interference of metal homeostasis may result in oxidative stress which represents an imbalance between production of free radicals and the system's ability to readily detoxify reactive intermediates. This event consequently causes DNA damage, lipid peroxidation, protein modification, and possibly symptomatic effects for various diseases including cancer. This review discusses predominant modes of action and numerous molecular markers. Attention is paid to metal-induced generation of free radicals, the phenomenon of oxidative stress, damage to DNA, lipid, and proteins, responsive signal transduction pathways with major roles in cell growth and development, and roles of antioxidant enzymatic and DNA repair systems. Interaction of non-enzymatic antioxidants (carotenoids, flavonoids, glutathione, selenium, vitamin C, vitamin E, and others) with cellular oxidative stress markers (catalase, glutathione peroxidase, and superoxide dismutase) as well as certain regulatory factors, including AP-1, NF-κB, Ref-1, and p53 is also reviewed. Dysregulation of protective pathways, including cellular antioxidant network against free radicals as well as DNA repair deficiency is related to oncogenic stimulation. These observations provide evidence that emerging oxidative stress-responsive regulatory factors and DNA repair proteins are putative predictive factors for tumor initiation and progression.

Mercury hair concentrations and dietary exposure among Inuit preschool children in Nunavut, Canada

There is concern that the traditional diet is a source of mercury exposure among Inuit in the Canadian Arctic. Mercury exposure in utero and in early childhood presents a risk to neurodevelopment. The objectives of the present study were to assess the dietary mercury exposure from traditional food among Inuit children 3 to 5 years of age in Nunavut, and evaluate the association between estimated dietary mercury intake and body burden. A cross-sectional Nunavut Inuit Child Health Survey was conducted in 2007 and 2008 which included assessment of dietary habits and children's hair mercury (Hg) levels. Further, an Inuit Adult Health Survey was conducted in the same years which included assessment of dietary habits and whole blood mercury concentrations. Traditional food samples were collected during this study and previously from the Canadian Arctic. Daily mercury intake from traditional food was calculated. Body mercury burden was determined using the hair mercury concentration. The geometric mean of children's hair Hg was 0.66 μg/g and varied by region. Nearly 25% of children had hair Hg concentrations equal to or higher than 2 μg/g (WHO reference level). There was a significant correlation between mercury levels in children's hair and that of the adults in the same household. For children, beluga muktuk, narwhal muktuk, ringed seal liver, fish, caribou meat and ringed seal meat were the major dietary sources of mercury. These food items together accounted for over 95% of total daily dietary mercury intake. A positive linear regression relationship between children's hair mercury levels and estimated dietary mercury intake was observed. Estimated intake in Baffin decreased by 30% compared to 20 years ago. Some traditional food items were significant sources of mercury to Inuit children in Nunavut. Although a reduction in the consumption of these diet items may be a way to reduce mercury intake, the nutritional, social and cultural benefits of traditional food and countervailing risks must be taken into account in risk mitigation.

Does background postnatal methyl mercury exposure in toddlers affect cognition and behavior?

Because the toxicological effects of mercury (Hg) are more serious in the developing central nervous system of children than adults, there are growing concerns about prenatal and early childhood Hg exposure. This study examined postnatal methylmercury (MeHg) exposure and cognition and behavior in 780 children enrolled in the Treatment of Lead (Pb)-exposed Children clinical trial (TLC) with 396 children allocated to the succimer and 384 to the placebo groups. Mercury exposure was determined from analyses of blood drawn 1 week before randomization and 1 week after treatment began when succimer had its maximal effect on blood Pb (PbB). The baseline MeHg concentrations were 0.54 microg/L and 0.52 microg/L and post-treatment concentrations were 0.51 microg/L and 0.48 microg/L for placebo and succimer groups, respectively. Because the baseline characteristics in the two groups were balanced and because succimer had little effect on MeHg concentration and no effect on the cognitive or behavioral test scores, the groups were combined in the analysis of MeHg and neurodevelopment. The children's IQ and neurobehavioral performance were tested at age 2, 5 and 7 years. We saw weak, non-significant but consistently positive associations between blood MeHg and IQ test scores in stratified, spline regression and generalized linear model data analyses. The behavioral problem scores were constant or decreased slightly with increasing MeHg concentration. Additional adjustment for PbB levels in multivariable models did not alter the conclusion for MeHg and IQ scores, but did confirm that concurrent PbB was strongly associated with IQ and behavior in TLC children. The effects of MeHg on neurodevelopmental indices did not substantially differ by PbB strata. We conclude that at the present background postnatal MeHg exposure levels of US children, adverse effects on children's IQ and behavior are not detectable.

Effect of PCBs on the lactational transfer of methyl mercury in mice: PBPK modeling

MeHg and PCB exposure to lactating mice were analyzed and a physiologically-based pharmacokinetic (PBPK) model was developed to describe the lactational transfer of MeHg in mice. The influence of albumin on the lactational transfer of MeHg was incorporated into the PBPK model. Experimental results with lactating mice and their pups showed that co-exposure with PCB congeners increased the lactational transfer of MeHg to the pups, which was associated with the rise of albumin levels in maternal blood. Observed results were matched with PBPK model simulations conducted under the assumptions that (1) MeHg bound to plasma albumin is transferred to maternal milk, and (2) PCB congeners may increase the lactational transfer of MeHg by escalating albumin levels in maternal blood. Further refinement of PBPK model quantitatively described the pharmacokinetic changes of MeHg by co-exposure with PCBs in pup's tissues.

Neurobehavioral assessment of rats exposed to low doses of PCB126 and methyl mercury during development

Epidemiological and laboratory studies have suggested that polychlorinated biphenyls (PCBs) and methyl mercury (MeHg) may have additive or synergistic effects on CNS function. Aim of this study was to characterize the effects of exposure to low levels of MeHg (0.5mg/kgday in drinking water) and PCB126 (100ng/kgday in food), alone and in combination, on neurobehavioral development in Wistar rats. Dams were treated from gestational day 7 to post-natal day (PND) 21. Animals were tested for developmental landmarks and reflexes (PND1-21), attention deficits (PND40), locomotor activity (PND30, 110), spatial learning (PND75), coordination and balance (PND90), object discrimination (PND80), anxiety (PND100), and conditioned learning (PND110). Parameters related to pregnancy, sex ratio at birth, and physical development (at weaning) did not differ among groups, though PCB126 decreased number of pups at birth. A slight delay in negative geotaxis was found in female rats in all treatment groups. No significant effects were seen in attention, coordination and balance, object discrimination, and spatial and conditioned learning. Increased motor activity was present in PCB126-treated male and in MeHg+PCB-treated female rats in the elevated plus maze test, and in PCB126-treated male rats in the open field test (PND110). The results do not support the hypothesis that co-exposure to MeHg and PCB126 results in additive or synergistic effects. This finding is in agreement with more recent in vitro and in vivo studies.

Changes in children hair-Hg concentrations during the first 5 years: Maternal, environmental and iatrogenic modifying factors

Children are exposed to Hg from mothers (via placenta and lactation), environment (food), and in many parts of the world by thimerosal-containing vaccines (TCV) during immunization. Neurodevelopment studies based on infant hair-Hg (HHg) have been designed without explicit attention to the factors associated with changes in infant physiology and Hg sources of exposure. A longitudinal study of changes in HHg concentrations from birth to 5 years was done in a sample of children from Porto Velho (Rondonia), Brazilian Amazonia. The study extracted information from the asymmetry associated with maternal and infant HHg changes at specified sampling: birth (fetal exposure), 6 months of exclusive breastfeeding, 36 months (weaning) and 60 months (pre-school). The distribution of HHg in breastfed infants followed a pattern different from their mothers. While mothers had the highest HHg concentrations at childbirth, infants showed the highest HHg values at 6 months after the recommended full schedule (six shots) of immunization with TCV; after that, the downward trend in HHg shown by children coincided with both weaning and less frequent vaccination period (5 years). Extended lactation (up to 36 months) was not significantly associated with HHg of infants or mothers; however, significant association (Spearman's r) between maternal and infant HHg concentration was seen at birth (r=0.3534; P=0.001), 6 months (r=0.4793; P<0.0001), 3 years (r=0.0122; P=0.012) and 5 years (r=0.0357; P=0.005). Maternal postpartum metabolic changes, infant development and transitional diets and possibly Hg from TCV contribute to the asymmetry of HHg changes between mothers and children.