Assessment of chronic mercury exposure within the U.S. population, National Health and Nutrition Examination Survey, 1999–2006

Mercury, natural fertility and outcomes of assisted reproduction: A systematic review

The primary route of mercury exposure for the general population is through consumption of contaminated seafood. There is a biological basis for an adverse effect of mercury exposure on human fertility. The goal of this review was to evaluate the existing literature on the association between mercury and pregnancy, among men and women attempting to conceive with and without assisted reproductive technology (ART). Systematic searches were performed in PubMed, EMBASE, Scopus and Web of Science for papers published up to March 2023 with no early date restriction, only including studies with a biomarker measurement of mercury exposure. We identified 11 studies examining mercury and natural fertility and 12 studies examining mercury and outcomes of assisted reproduction (implantation or clinical pregnancy). The accumulated evidence provides some support for a null association between bodily mercury concentrations and natural fertility among women, however, a large proportion of studies did not report adjusted estimates or were extremely imprecise. The majority of studies of natural fertility were also cross-sectional in nature. There was no evidence for an inverse or null association between mercury and natural fertility among men, or mercury and ART outcomes among men or women. In spite of biological plausibility, the existing evidence includes studies that are imprecise and often conflicting and does not allow us to make definitive conclusions on the associations of mercury exposure with successful pregnancy. Additional, larger studies are warranted, especially among individuals with high concentrations of mercury exposure as these individuals may be underrepresented in the current literature.

Combining computational tools and experimental studies towards endocrine disruptors mitigation: A review of biocatalytic and adsorptive processes

The endocrine disruptors (EDCs) are an important group of emerging contaminants, and their mitigation has been a huge challenge due to their chemistry complexity and variety of these compounds. The traditional treatments are inefficient to completely remove EDCs, and adsorptive processes are the major alternative investigated on their removal. Also, the use of EDCs degrading enzymes has been encouraged due to ecofriendly approach of biocatalytic processes. This paper highlights the occurrence, classification, and toxicity of EDCs with special focus in the use of enzyme-based and adsorptive technologies in the elimination of EDCs from ambiental matrices. Numerous prior reviews have focused on the discussions toward these technologies. However, the literature lacks theoretical discussions about important aspects of these methods such as the mechanisms of EDCs adsorption on the adsorbent surface or the interactions between degrading enzymes - EDCs. In this sense, theoretical calculations combined to experimental studies may help in the development of more efficient technologies to EDCs mitigation. In this review, we point out how computational tools such as molecular docking and molecular dynamics have to contribute to the design of new adsorbents and efficient catalytic processes towards endocrine disruptors mitigation.

Blood lead and mercury levels are associated with low resting heart rate in community adolescent boys

While the neurotoxic effects of heavy metals at even low levels have been well-studied, few studies have examined the cardiovascular effects of heavy metals on resting heart rate and these have focused on adult populations. The present study aimed to examine the association between low-level environmental lead and mercury exposure and resting heart rate in community adolescents. As part of the China Jintan Cohort Study, 532 adolescents aged 12 years (SD = 0.6) were tested for blood levels of lead (BLL) and mercury (BML) and resting heart rate (RHR). Generalized linear models were conducted to test the relationship between BLL and BML and RHR, controlling for children's sex, age, and socioeconomic status. Analyses were clustered at the preschool level when the children were recruited to adjust for standard error. The mean (SD) BLL and BML were 3.14 (SD = 1.19) μg/dL and 1.26 (SD = 0.68) μg/L at age 12 years, respectively. After adjusting for confounders, we found a significant interaction between BML and BLL in predicting RHR in boys (B = -1.27, SE = 0.49, p < 0.01, n = 289). We created BLL and BML groups in boys based on median cut-offs. Boys in the High BLL/High BML group had significantly lower RHR (mean = 84.22 beats per minute [bpm], SD = 8.77, n = 61) than boys in the Low BLL/Low BML group (mean = 89.03 bpm, SD = 10.75, n = 69; p < 0.05). BML and BLL did not interact to predict RHR in girls (B = -0.18, SE = 0.88, p > 0.05, n = 242). Combined high BLL and BML were associated with low RHR in community adolescent boys. Low RHR is an indication of chronic under-arousal and has been implicated in psychopathology, particularly for externalizing behavior. Our findings may stimulate further communication and research in this area.

Elevated blood mercury level has a non-linear association with infertility in U.S. women: Data from the NHANES 2013-2016

Mercury is a ubiquitous toxic heavy metal associated with an increased risk of female infertility; however, the evidence supporting this is limited and controversial. We aimed to explore the relationship between the total blood mercury and infertility in 1796 selected participants from the National Health and Nutrition Examination Survey (NHANES) (2013-2016). We found no significant association between mercury and infertility based on a fully-adjusted model (OR 1.04; 95 % CI 0.91, 1.19), and the results remained robust in a series of sensitive analysis. However, a non-linear relationship was detected. By a two-piecewise linear regression model and recursive algorithm, we identified an inflection point of 5.278 μg/L, when blood mercury was >5.278 μg/L, a 1-unit increase in mercury (log2) was associated with 157 % greater adjusted odds of infertility (OR 2.57; 95 % CI 1.12, 5.87). Our findings provide new insights to advance the research of the link between mercury and infertility.

Exposure to mercury and human reproductive health: A systematic review

BACKGROUND

Evidences from human and animal studies suggest that reproductive function may be affected by mercury. The aim of this review was to explore the mercury influence on human fertility.

METHODS

A systematic search was made in PubMED for papers published between 1975-2017, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Increased mercury levels were associated with infertility or subfertility status. Further, infertile subjects with unexplained infertility showed higher levels of mercury in hair, blood and urine than fertile ones. Mercury exposure induced sperm DNA damage and abnormal sperm morphology and motility. Additionally, mercury levels were related with higher incidence of menstrual and hormonal disorders and increased rates of adverse reproductive outcomes.

CONCLUSIONS

Our review showed that mercury negatively impacts human reproduction, affecting the reproductive and endocrine systems in both male and female. However, the molecular mechanisms underlying the mercury-associated decline on fertility remains unknown.

Mercury-associated diagnoses among children diagnosed with pervasive development disorders

Nelson and Bauman (Pediatrics 111:674-679, 2003) previously hypothesized that pervasive developmental disorder (PDD) was not associated with mercury (Hg) exposure because the medical conditions associated with Hg exposure were not associated with PDD. A hypothesis-testing longitudinal case-control study evaluated the frequency of medically diagnosed conditions previously associated with Hg poisoning, including: epilepsy, dysarthria, failure to thrive, cerebral palsy, or contact dermatitis and other eczema among children preceding their eventual PDD diagnosis (cases) compared to controls. A retrospective examination of medical records within the Vaccine Safety Datalink (VSD) was undertaken. Cases diagnosed with PDD (n = 534) were born from 1991 to 2000 and continuously enrolled until their PDD diagnosis. Controls (n = 26,367) were born from 1991 to 1993 and continuously enrolled from birth for 7.22 years. Within the first 5 years of life, cases compared to controls were significantly (p < 0.0001) more likely to be assigned a diagnosis of contact dermatitis and other eczema (odds ratio (OR) = 2.033), dysarthria (OR = 23.992), epilepsy (OR = 5.351), failure to thrive (OR = 25.3), and cerebral palsy (OR = 4.464). Similar results were observed when the data were separated by gender. Overall, the results of the present study and recently published studies provide direct evidence supporting a link in twelve of twelve categories (100%) of Hg poisoning associated symptoms as defined by Nelson and Bauman (Pediatrics 111:674-679, 2003) and symptoms observed in those with a PDD diagnosis. The results of this study support the biological plausibility of Hg poisoning to induce PDD diagnoses and rejection of the Nelson and Bauman (Pediatrics 111:674-679, 2003) hypothesis because those with a PDD diagnosis have an increased frequency of conditions previously associated with Hg poisoning.

Mercury (II) impairs nucleotide excision repair (NER) in zebrafish (Danio rerio) embryos by targeting primarily at the stage of DNA incision

Mercuric ion (Hg²⁺) is the most prevalent form of inorganic Hg found in polluted aquatic environment. As inhibition of DNA damage repair has been proposed as one of the mechanisms of Hg²⁺-induced genotoxicity in aquatic animals and mammalian cells, this study explored the susceptibility of different stages of nucleotide excision repair (NER) in zebrafish (Danio rerio) embryos to Hg²⁺ using UV-damaged DNA as the repair substrate. Exposure of embryos at 1h post fertilization (hpf) to HgCl₂ at 0.1-2.5μM for 9h caused a concentration-dependent inhibition of NER capacity monitored by a transcription-based DNA repair assay. The extracts of embryos exposed to 2.5μM Hg²⁺ almost failed to up-regulate UV-suppressed marker cDNA transcription. No inhibition of ATP production was observed in all Hg²⁺-exposed embryos. Hg²⁺ exposure imposed either weak inhibitory or stimulating effects on the gene expression of NER factors, while band shift assay showed the inhibition of photolesion binding activities to about 40% of control in embryos treated with 1-2.5μM HgCl₂. The damage incision stage of NER in zebrafish embryos was found to be more sensitive to Hg²⁺ than photolesion binding capacity due to the complete loss of damage incision activity in the extracts of embryos exposed to 1-2.5μM Hg²⁺. NER-related DNA incision was induced in UV-irradiated embryos based on the production of short DNA fragments matching the sizes of excision products generated by eukaryotic NER. Pre-exposure of embryos to Hg²⁺ at 0.1-2.5μM all suppressed DNA incision/excision in UV-irradiated embryos, reflecting a high sensitivity of DNA damage incision/excision to Hg²⁺. Our results showed the potential of Hg²⁺ at environmental relevant levels to disturb NER in zebrafish embryos by targeting primarily at the stage of DNA incision/excision.

Exposure to endocrine disruptors during adulthood: consequences for female fertility

Endocrine disrupting chemicals are ubiquitous chemicals that exhibit endocrine disrupting properties in both humans and animals. Female reproduction is an important process, which is regulated by hormones and is susceptible to the effects of exposure to endocrine disrupting chemicals. Disruptions in female reproductive functions by endocrine disrupting chemicals may result in subfertility, infertility, improper hormone production, estrous and menstrual cycle abnormalities, anovulation, and early reproductive senescence. This review summarizes the effects of a variety of synthetic endocrine disrupting chemicals on fertility during adult life. The chemicals covered in this review are pesticides (organochlorines, organophosphates, carbamates, pyrethroids, and triazines), heavy metals (arsenic, lead, and mercury), diethylstilbesterol, plasticizer alternatives (di-(2-ethylhexyl) phthalate and bisphenol A alternatives), 2,3,7,8-tetrachlorodibenzo-p-dioxin, nonylphenol, polychlorinated biphenyls, triclosan, and parabens. This review focuses on the hypothalamus, pituitary, ovary, and uterus because together they regulate normal female fertility and the onset of reproductive senescence. The literature shows that several endocrine disrupting chemicals have endocrine disrupting abilities in females during adult life, causing fertility abnormalities in both humans and animals.

Associations of blood mercury, inorganic mercury, methyl mercury and bisphenol A with dental surface restorations in the U.S. population, NHANES 2003-2004 and 2010-2012

The potential adverse health effects of mercury from amalgam and bisphenol A (BPA) from composite resin have been significant concerns. It is unclear whether dental restorative materials significantly contribute to mercury or BPA levels. The purpose of this study is to use NHANES data including 14,703 subjects (2003-2004: n=7514; 2011-2012: n=7189) to examine the association between Dental Surface Restorations (DSR) and blood total mercury (THg), inorganic mercury (IHg), methyl mercury (MeHg) and urinary BPA through the stratification of covariates and multivariate analysis. Subjects were divided into three groups based on the number of dental surface restorations (DSRs, 0, 1-8, >8). Blood THg and IHg in 2003-2004 were significantly higher in the subjects with DSR (geometric mean of 0.48, 0.69 and 1.17μg/l for THg; 0.32, 0.33 and 0.39μg/l for IHg with DSR 0, 1-8 and >8). Similarly, increases of THg, IHg and MeHg were also observed in 2013-2014 (geometric mean of 0.51, 0.69 and 0.99μg/l for THg; 0.40, 0.49 and 0.66μg/l for MeHg; 0.20, 0.22 and 0.29μg/l for IHg with DSR 0, 1-8 and >8). Linear regression model analysis revealed blood THg and IHg in 2003-2004 and THg, IHg and MeHg in 2011-2012 were quantitatively associated with the number of DSRs. A dramatic decrease in urinary BPA from 2003 to 2004-2011-2012 was observed, but no significant increase with DSRs in either period of study. In conclusion, significant increases in blood THg, IHg, and MeHg in the subjects with DSRs are confirmed in a nationally representative population, a critical step in assessing the potential risk of adverse effects from dental restorative materials, but no association between dental fillings and urinary BPA was found.

Trace metal imaging in diagnostic of hepatic metal disease

The liver is the most central organ and the largest gland of the body that influences and controls a variety of metabolic and catabolic processes. It produces inconceivable many essential proteins, is responsible for the recovery of various food components, degrades toxins, mediates the bile production, and is involved in the excretion of unwanted metabolites. Several of these anabolic or catabolic functions of the liver depend on trace elements. These are either integral part of enzymes, cofactors, or act as chemical catalysts. Therefore, a lack of trace elements can lead to organ failure or systemic illness. Conversely, excessive hepatic trace element deposition resulting from genetic disorders, intoxication, extensive dietary supply, or long-term parenteral nutrition may cause hepatic inflammation, fibrosis, cirrhosis, and even hepatocellular carcinoma. Although specific serum parameters currently allow rough assessment of metal deficit and excess, the precise quantification of hepatic metal content in liver is presently only possible by different titration or staining techniques of biopsy specimens. Recently, novel innovative metal imaging techniques were developed that are on the way to replace these traditional methods. In the present review, we summarize the function of different trace elements in liver health and disease and discuss the present knowledge on how quantitative biometal imaging techniques such as synchrotron X-ray fluorescence microscopy, secondary ion mass spectrometry, and laser ablation inductively coupled plasma mass spectrometry enrich diagnostics in the detection and quantification of hepatic metal disorders. We will further discuss sample preparation, sensitivity, spatial resolution, specificity, quantification strategies, and potential future applications of metal bioimaging in experimental research and clinical daily routine. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 35:666-686, 2016.

Thimerosal exposure and increased risk for diagnosed tic disorder in the United States: a case-control study

A hypothesis testing, case-control study evaluated automated medical records for exposure to organic-Hg from Thimerosal-containing hepatitis B vaccines (TM-HepB) administered at specific intervals in the first six-months-of-life among cases diagnosed with a tic disorder (TD) or cerebral degeneration (CD) (an outcome not biologically plausibly linked to TM exposure) in comparison to controls; both cases and controls were continuously enrolled from birth (born from 1991-2000) within the Vaccine Safety Datalink (VSD) database. TD cases were significantly more likely than controls to have received increased organic-Hg from TM-HepB administered within the first month-of-life (odds ratio (OR)=1.59, p<0.00001), first two-months-of-life (OR=1.59, p<0.00001), and first six-months-of-life (OR=2.97, p<0.00001). Male TD cases were significantly more likely than male controls to have received increased organic-Hg from TM-HepB administered within the first month-of-life (OR =1.65, p<0.0001), first two-months-of-life (OR=1.64, p<0.0001), and first six months-of-life (OR=2.47, p<0.05), where as female TD were significantly more likely than female controls to have received increased organic-Hg from TM-HepB administered within the first six-months-of-life (OR=4.97, p<0.05). By contrast, CD cases were no more likely than controls to have received increased organic-Hg exposure from TM-HepB administered at any period studied within the first six-months-of-life. Although routine childhood vaccination is considered an important public health tool to combat infectious diseases, the present study associates increasing organic-Hg exposure from TM-HepB and the subsequent risk of a TD diagnosis.

Thimerosal-containing Hepatitis B Vaccine Exposure is Highly Associated with Childhood Obesity: A Case-control Study Using the Vaccine Safety Datalink

BACKGROUND

Obesity among children and adolescents in the United States has tripled since 1980, and has become a major public health concern.

AIMS

The purpose of this study was to evaluate the potential relationship between exposure to organic mercury from Thimerosal-containing hepatitis B vaccines and the children's subsequent risk of an obesity diagnosis.

MATERIALS AND METHODS

A hypothesis-testing, case-control study was undertaken to evaluate exposure to organic mercury from Thimerosal-containing hepatitis B vaccines, which were administered at specific intervals in the first 6 months of life, among cases diagnosed with childhood obesity and controls by examining automated medical records for children born from 1991 to 2000 who were continuously enrolled in the Vaccine Safety Datalink database.

RESULTS

This study found highly significant associations as follows. Cases diagnosed with obesity were significantly (P < 0.00001) more likely to have received greater exposure to organic mercury from Thimerosal-containing hepatitis B vaccines administered within the first month of life (odds ratio (OR) =1.511), first 2 months of life (OR = 1.486), and first 6 months of life (OR = 3.795) than the controls. Similar outcomes were observed when the overall data were separated by gender. In a dose-response manner, cases diagnosed with obesity were significantly more likely than controls to have received greater exposure to organic mercury from Thimerosal-containing hepatitis B vaccines, which were administered within the first 6 months of life (OR = 1.0375 per μg of mercury, P < 0.00001).

CONCLUSIONS

In a dose-response manner, the present study associates an increased organic mercury exposure from Thimerosal-containing hepatitis B vaccines with an increased risk of obesity diagnosis, and suggests that Thimerosal is an obesogen. The results are biologically plausible and future studies are needed to examine this phenomenon.

Thimerosal-Preserved Hepatitis B Vaccine and Hyperkinetic Syndrome of Childhood

(1) BACKGROUND: Hyperkinetic syndrome of childhood (HKSoC) is an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9) category in which the majority of the children are also diagnosed under the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR), where the umbrella term is "Attention-Deficit and Disruptive Behavior Disorders". The diagnostic criteria for HKSoC are developmentally inappropriate inattention, hyperactivity, and impulsivity. Some studies have implicated mercury (Hg) exposure as a risk factor. (2) METHODS: This hypothesis testing study; using the Vaccine Safety Datalink; assessed the toxicological effects of bolus exposure to organic-Hg from Thimerosal-containing vaccines (TCVs) by examining the relationship between Thimerosal-preserved hepatitis B vaccines (TM-HepB) given at varying levels and at specific intervals in the first six months after birth and the risk of a child being diagnosed with HKSoC. (3) RESULTS: Children diagnosed with HKSoC were significantly more likely to be exposed to increased organic-Hg from TM-HepB doses given within the first month (odds ratio = 1.45; 95% confidence interval (CI) = 1.30-1.62); within the first two months (odds ratio = 1.43; 95% CI = 1.28-1.59); and within the first six months (odds ratio = 4.51; 95% CI = 3.04-6.71) than controls. (4) CONCLUSION: The results indicate that increasing organic-Hg exposure from TCVs heightens the risk of a HKSoC diagnosis.

Shared Brain Connectivity Issues, Symptoms, and Comorbidities in Autism Spectrum Disorder, Attention Deficit/Hyperactivity Disorder, and Tourette Syndrome

The prevalence of neurodevelopmental disorders, including autism spectrum disorder (ASD), attention deficit/hyperactivity disorder (ADHD), and Tourette syndrome (TS), has increased over the past two decades. Currently, about one in six children in the United States is diagnosed as having a neurodevelopmental disorder. Evidence suggests that ASD, ADHD, and TS have similar neuropathology, which includes long-range underconnectivity and short-range overconnectivity. They also share similar symptomatology with considerable overlap in their core and associated symptoms and a frequent overlap in their comorbid conditions. Consequently, it is apparent that ASD, ADHD, and TS diagnoses belong to a broader spectrum of neurodevelopmental illness. Biologically, long-range underconnectivity and short-range overconnectivity are plausibly related to neuronal insult (e.g., neurotoxicity, neuroinflammation, excitotoxicity, sustained microglial activation, proinflammatory cytokines, toxic exposure, and oxidative stress). Therefore, these disorders may a share a similar etiology. The main purpose of this review is to critically examine the evidence that ASD, ADHD, and TS belong to a broader spectrum of neurodevelopmental illness, an abnormal connectivity spectrum disorder, which results from neural long-range underconnectivity and short-range overconnectivity. The review also discusses the possible reasons for these neuropathological connectivity findings. In addition, this review examines the role and issue of axonal injury and regeneration in order to better understand the neuropathophysiological interplay between short- and long-range axons in connectivity issues.

Association between serum mercury concentration and leukocyte differential count in children

There have been a number of animal studies on the immunological effects of mercury. However, there is a lack of studies investigating the effects of mercury in children. We investigated the association between serum mercury and leukocyte differential count in Korean children. The relationship between mercury and leukocyte differential count (segment, lymphocyte, monocyte, basophil, and eosinophil counts) was analyzed by multivariate linear analysis adjusted for sex, BMI, parental smoking, lead, cadmium, and allergic sensitization in 311 children. Mercury showed a positive correlation with lymphocyte count (coefficient 113.8, 95% confidence interval 26.7-200.9). However, mercury was not associated with total leukocyte, segment, monocyte, basophil, or eosinophil count. Mercury was associated with the increased of lymphocyte count in Korean children. Further studies will be required to ascertain the clinical significance of this association.

Assessing metal exposures in a community near a cement plant in the Northeast U.S

Cement production is a major source of metals and metalloids in the environment, while exposures to metals and metalloids may impact human health in the surrounding communities. We recruited 185 participants living in the vicinity of a cement plant in the northeast U.S., and measured the levels of aluminum (Al), arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and selenium (Se) in blood and Hg in hair samples from them. A questionnaire was used to assess potential sources of Hg exposure. Multivariate regressions and spatial analyses were performed to evaluate the relative importance of different routes of exposures. The metal concentrations in blood or hair samples of our study participants were comparable to the U.S. general or regional population. Smoking contributed significantly to Cd and Pb exposures, and seafood consumption contributed significantly to Hg and As exposures, while variables related to the cement plant were not significantly associated with metal concentrations. Our results suggest that our study population was not at elevated health risk due to metal exposures, and that the contribution of the cement plant to metal exposures in the surrounding community was minimal.

A longitudinal study of mercury exposure associated with consumption of freshwater fish from a reservoir in rural south central USA

Methylmercury (MeHg) exposure through fish consumption is a worldwide health concern. Saltwater fish account for most dietary MeHg exposure in the general U.S. population, but less is known about seasonal variations in MeHg exposure and fish consumption among millions of freshwater anglers. This longitudinal study examined associations between MeHg exposure and fish consumption in a rural, low-income population relying on a freshwater reservoir (Oklahoma, USA) for recreational and subsistence fishing. We interviewed 151 participants, primarily anglers and their families, seasonally for one year using 90-day recall food frequency questionnaires to assess general and species-specific fish consumption, and tested hair biomarker samples for total mercury (THg hair). Mean THg hair was 0.27 μg/g (n=595, range: 0.0044-3.1 μg/g), with 4% of participants above U.S. EPA's guideline for women of childbearing age and children. Mean fish consumption was 58 g/d (95% CI: 49-67 g/d), within the range previously reported for recreational freshwater anglers and above the national average. Unlike the general U.S. population, freshwater species contributed the majority of fish consumption (69%) and dietary Hg exposure (60%) among participants, despite relatively low THg in local fish. THg hair increased with fish consumption, age, and education, and was higher among male participants and the lowest in winter. Our results suggest that future studies of anglers should consider seasonality in fish consumption and MeHg exposure and include household members who share their catch. Efforts to evaluate benefits of reducing Hg emissions should consider dietary patterns among consumers of fish from local freshwater bodies.

Blood inorganic mercury is directly associated with glucose levels in the human population and may be linked to processed food intake

Background:

The goals of the study were (1) to determine the impact of inorganic mercury exposure on glucose homeostasis; and (2) to evaluate the effectiveness of two community-based interventions in promoting dietary changes among American Indian college students to reduce risk factors for Type-2 Diabetes including fasting glucose, insulin, and mercury levels, weight, and body mass index.

Methods:

To accomplish goal one, the National Health and Nutrition Examination Survey (NHANES) dataset was analyzed using a previously published method to determine if there is a relationship between inorganic blood mercury and fasting glucose. To accomplish goal two, ten college students were recruited and randomly assigned to a group receiving the online macroepigenetics nutrition course and the support group for eliminating corn sweeteners. Participants in both groups were assessed for diet patterns, weight, body mass index (BMI), fasting glucose, insulin, and mercury levels. The interventions were implemented over a 10-week period.

Results:

Analysis of the NHANES data (n=16,232) determined a direct relationship between inorganic mercury in blood and fasting glucose levels (p<0.001). The participants who took the online macroepigenetics nutrition intervention course significantly improved their diets (p<0.01), and fasting blood glucose levels (p<0.01) while having lower levels of inorganic mercury in their blood compared to the subjects in the group who eliminated corn sweeteners from their diet and participated in the support group. The trend in lower blood inorganic mercury was strong with p=0.052. The participants in the support group who eliminated corn sweeteners from their diet achieved significant weight loss (p<0.01) and reduced their body mass index (p<0.01).

Conclusion:

Total blood mercury levels may be influenced by dietary intake of highly processed foods and lower inorganic mercury levels are associated with lower fasting glucose levels. Alternative community-based interventions emphasizing the role food ingredients and toxic substances play in gene modulation and the development of diseases can result in significant dietary improvements and reductions in risk factors associated with type-2 diabetes. A healthier diet can be promoted among community members using a novel online nutrition course. Consumption of corn sweeteners may be a risk factor in the development of obesity.

Thimerosal-containing hepatitis B vaccination and the risk for diagnosed specific delays in development in the United States: a case-control study in the vaccine safety datalink

Background:

Within the first 3 years of life, the brain develops rapidly. Its development is characterized by critical developmental periods for speech, vision, hearing, language, balance, etc.; and alteration in any of the processes occurring in those critical periods can lead to specific delays in development.

Aims:

The present study evaluated the potential toxic effects of organic-mercury exposure from Thimerosal (49.55% mercury by weight) in childhood vaccines and its hypothesized possible relationship with specific delays in development.

Materials and Methods:

A hypothesis testing case-control study was undertaken to evaluate the relationship between exposure to Thimerosal-containing hepatitis B vaccines administered at specific intervals in the first 6 months among cases diagnosed with specific delays in development and controls born between 1991-2000, utilizing data in the Vaccine Safety Datalink database.

Results:

Cases were significantly more likely than controls to have received increased organic-mercury from Thimerosal-containing hepatitis B vaccine administered in the first, second, and sixth month of life.

Conclusion:

Though routine childhood vaccination may be an important public health tool to reduce the morbidity and mortality associated with infectious diseases, the present study supports an association between increasing organic-mercury exposure from Thimerosal-containing childhood vaccines and the subsequent risk of specific delays in development among males and females.

60-Day chronic exposure to low concentrations of HgCl2 impairs sperm quality: hormonal imbalance and oxidative stress as potential routes for reproductive dysfunction in rats

Mercury is a toxic and bio-accumulative heavy metal of global concern. While good deals of research have been conducted on the toxic effects of mercury, little is known about the mechanisms involved in the pathogenesis of male reproductive dysfunction induced by mercury. Therefore, the purpose of this study was to assess the effects and underlying mechanisms of chronic mercury exposure at low levels on male reproductive system of rats. Three-month-old male Wistar rats were divided into two groups and treated for 60 days with saline (i.m., Control) and HgCl2 (i.m. 1st dose: 4.6 µg/kg, subsequent doses 0.07 µg/kg/day). We analyzed sperm parameters, hormonal levels and biomarkers of oxidative stress in testis, epididymis, prostate and vas deferens. Mercury treatment decreased daily sperm production, count and motility and increased head and tail morphologic abnormalities. Moreover, mercury treatment decreased luteinizing hormone levels, increased lipid peroxidation on testis and decreased antioxidant enzymes activities (superoxide dismutase and catalase) on reproductive organs. Our data demonstrate that 60-day chronic exposure to low concentrations of HgCl2 impairs sperm quality and promotes hormonal imbalance. The raised oxidative stress seems to be a potential mechanism involved on male reproductive toxicity by mercury.

Novel oral detoxification of mercury, cadmium, and lead with thiol-modified nanoporous silica

We have developed a thiol-modified nanoporous silica material (SH-SAMMS) as an oral therapy for the prevention and treatment of heavy metal poisoning. SH-SAMMS has been reported to be highly efficient at capturing heavy metals in biological fluids and water. Herein, SH-SAMMS was examined for efficacy and safety in both in vitro and in vivo animal models for the oral detoxification of heavy metals. In simulated gastrointestinal fluids, SH-SAMMS had a very high affinity (Kd) for methyl mercury (MeHg(I)), inorganic mercury (Hg(II)), lead (Pb(II)), and cadmium (Cd(II)) and was superior to other SAMMS with carboxylic acid or phosphonic acid ligands or commercially available metal chelating sorbents. SH-SAMMS also effectively removed Hg from biologically digested fish tissue with no effect on most nutritional minerals found in fish. SH-SAMMS could hold Hg(II) and MeHg(I) tightly inside the nanosize pores, thus preventing bacteria from converting them to more absorbable forms. Rats fed a diet containing MeHg(I), Cd(II), and Pb(II) and SH-SAMMS for 2 weeks had blood Hg levels significantly lower than rats fed the metal-rich diet only. Upon cessation of the metal-rich diet, continued administration of SH-SAMMS for 2 weeks facilitated faster and more extensive clearance of Hg than in animals not continued on oral SH-SAMMS. Rats receiving SH-SAMMS also suffered less weight loss as a result of the metal exposure. Retention of Hg and Cd in major organs was lowest in rats fed with SH-SAMMS throughout the entire four weeks. The reduction of blood Pb by SH-SAMMS was significant. SH-SAMMS was safe to intestinal epithelium model (Caco-2) and common intestinal bacteria (Escherichia coli). Altogether, it has great potential as a new oral drug for the treatment of heavy metal poisoning. This new application is enabled by the installation of tailored interfacial chemistry upon nontoxic nanoporous materials.

Redox Regulation and the Autistic Spectrum: Role of Tryptophan Catabolites, Immuno-inflammation, Autoimmunity and the Amygdala

The autistic spectrum disorders (ASD) form a set of multi-faceted disorders with significant genetic, epigenetic and environmental determinants. Oxidative and nitrosative stress (O&NS), immuno-inflammatory pathways, mitochondrial dysfunction and dysregulation of the tryptophan catabolite (TRYCATs) pathway play significant interactive roles in driving the early developmental etiology and course of ASD. O&NS interactions with immuno-inflammatory pathways mediate their effects centrally via the regulation of astrocyte and microglia responses, including regional variations in TRYCATs produced. Here we review the nature of these interactions and propose an early developmental model whereby different ASD genetic susceptibilities interact with environmental and epigenetic processes, resulting in glia biasing the patterning of central interarea interactions. A role for decreased local melatonin and N-acetylserotonin production by immune and glia cells may be a significant treatment target.

Blood mercury concentration among residents of a historic mercury mine and possible effects on renal function: a cross-sectional study in southwestern China

This cross-sectional study aimed to investigate blood mercury (B-Hg) concentration of residents living in the vicinity of Chatian mercury mine (CMM) in southwestern China and to assess the possible effects on renal function. It evaluates the effects of gender and age (children, <18 years; adults, 18-60 years; elderly, >60 years) on the B-Hg and serum creatinine (SCR) and serum urea nitrogen (SUN) levels. In the CMM, elevated levels were found for B-Hg, SCR, and SUN with mean values at 6.09 μg/L, 74.21 μmol/L, and 13.26 mmol/L, which were significantly higher than those in the control area, respectively. Moreover, the coefficients between paired results for B-Hg and SCR and SUN levels were positive at statistical significance (B-Hg vs. SCR, r = 0.45, p < 0.01; B-Hg vs. SUN, r = 0.20, p < 0.05). The aforementioned results revealed that mercury exposure can cause human renal function impairment. B-Hg, SCR, and SUN can also be useful biomarkers to assess the extent of mercury exposure among residents in areas with extensive mining activities. Furthermore, data analysis revealed that there was a tendency for higher B-Hg, SCR, and SUN levels in females than in males, and the levels of B-Hg, SCR, and SUN increased among the older residents. We conclude that females and the elderly in the mining area were more susceptible to mercury exposure, and therefore, they deserve further research.

Web-based environmental health education: fish facts

Nurses and other health professionals are often asked about the benefits and risks of fish consumption. The combination of conflicting media messages about these risks and benefits and limited knowledge has led to confusion about how to properly advise people about safe fish consumption. "Fish Facts for Health Professionals" was the result of a collaborative effort of environmental, public health, medical, nursing, and media experts to create a web-based educational series to address the need for reliable information on fish consumption. Using interviews and real case studies, the 3- to 5-minute media modules provided a strong visual element while remaining conversational. The modules were viewed worldwide, and 121 participants successfully completed the requirements for professional continuing education credit.

Chemical form matters: differential accumulation of mercury following inorganic and organic mercury exposures in zebrafish larvae

Mercury, one of the most toxic elements, exists in various chemical forms each with different toxicities and health implications. Some methylated mercury forms, one of which exists in fish and other seafood products, pose a potential threat, especially during embryonic and early postnatal development. Despite global concerns, little is known about the mechanisms underlying transport and toxicity of different mercury species. To investigate the impact of different mercury chemical forms on vertebrate development, we have successfully combined the zebrafish, a well-established developmental biology model system, with synchrotron-based X-ray fluorescence imaging. Our work revealed substantial differences in tissue-specific accumulation patterns of mercury in zebrafish larvae exposed to four different mercury formulations in water. Methylmercury species not only resulted in overall higher mercury burdens but also targeted different cells and tissues than their inorganic counterparts, thus revealing a significant role of speciation in cellular and molecular targeting and mercury sequestration. For methylmercury species, the highest mercury concentrations were in the eye lens epithelial cells, independent of the formulation ligand (chloride versusl-cysteine). For inorganic mercury species, in absence of l-cysteine, the olfactory epithelium and kidney accumulated the greatest amounts of mercury. However, with l-cysteine present in the treatment solution, mercuric bis-l-cysteineate species dominated the treatment, significantly decreasing uptake. Our results clearly demonstrate that the common differentiation between organic and inorganic mercury is not sufficient to determine the toxicity of various mercury species.

Amelioration of Acute Mercury Toxicity by a Novel, Non-Toxic Lipid Soluble Chelator N,N'bis-(2-mercaptoethyl)isophthalamide: Effect on Animal Survival, Health, Mercury Excretion and Organ Accumulation

The toxic effects of mercury are known to be complex with specific enzyme inhibitions and subsequent oxidative stress adding to the damaging effects. There are likely other factors involved, such as the development of impaired metal ion homeostasis and depletion of thiol and selenium based metabolites such as cysteine and selenium. Much of the toxicity of mercury occurs at the intracellular level via binding of Hg(2+) to thiol groups in specific proteins. Therefore, amelioration of mercury toxicity by the use of chelation would likely be enhanced by the use of a chelator that could cross the cell membrane and the blood brain barrier. It would be most favorable if this compound was of low toxicity, had appropriate pharmacokinetics, bound and rendered mercury cation non-toxic and had antioxidant properties. Herein we report on such a chelator, N,N'-bis(2-mercaptoethyl)isophthalamide (NBMI), and, using an animal model, show that it prevented the toxic effects associated with acute exposure induced by injected mercury chloride.

Inorganic mercury exposure in prairie voles (Microtus ochrogaster) alters the expression of toll-like receptor 4 and activates inflammatory pathways in the liver in a sex-specific manner

Environmental exposure to mercury can cause a number of adverse effects in humans including the disruption of endocrine function that may result in sex-specific effects. The present study was designed to characterize sex-specific effects of chronic inorganic mercury exposure on toll-like receptor (TLR) 2 and TLR4 and inflammatory signaling in the liver of prairie voles (Microtus ochrogaster). Following 10 weeks of exposure to mercury via drinking water, effects on protein expression levels of TLR2 and TLR4 and the downstream p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor-kappa (NF-κB) signaling pathways were assessed. Using immunoblot analysis, we found that mercury exposure significantly enhanced the expression of TLR4 and activated p38 MAPK and NF-κB pathways in vole livers. This is the first report indicating that TLR4 may serve as a sensor for chronic mercury exposure in the liver. Further, compared to females, mercury-treated male voles exhibited significant increases in activated p38 MAPK and a greater extent of liver damage. Together, these findings establish sex-specific liver immunomodulation and cellular signaling following chronic inorganic mercury exposure. Furthermore, this study also supports the use of voles as biomarkers of environmental mercury contamination and offers a promising in vivo tool to test various therapeutic strategies for mercury detoxification.

Coexposure to mercury increases immunotoxicity of trichloroethylene

We have shown previously that chronic (32 weeks) exposure to occupationally relevant concentrations of the environmental pollutant trichloroethylene (TCE) induced autoimmune hepatitis (AIH) in autoimmune-prone MRL+/+ mice. In real-life, individuals are never exposed to only one chemical such as TCE. However, very little is known about the effects of chemical mixtures on the immune system. The current study examined whether coexposure to another known immunotoxicant, mercuric chloride (HgCl(2)), altered TCE-induced AIH. Female MRL+/+ mice were treated for only 8 weeks with TCE (9.9 or 186.9 mg/kg/day in drinking water) and/or HgCl(2) (260 μg/kg/day, sc). Unlike mice exposed to either TCE or HgCl(2) alone, mice exposed to both toxicants for 8 weeks developed significant liver pathology commensurate with early stages of AIH. Disease development in the coexposed mice was accompanied by a unique pattern of anti-liver and anti-brain antibodies that recognized, among others, a protein of approximately 90 kDa. Subsequent immunoblotting showed that sera from the coexposed mice contained antibodies specific for heat shock proteins, a chaperone protein targeted by antibodies in patients with AIH. Thus, although TCE can promote autoimmune disease following chronic exposure, a shorter exposure to a binary mixture of TCE and HgCl(2) accelerated disease development. Coexposure to TCE and HgCl(2) also generated a unique liver-specific antibody response not found in mice exposed to a single toxicant. This finding stresses the importance of including mixtures in assessments of chemical immunotoxicity.

Toxicity biomarkers among US children compared to a similar cohort in France: a blinded study measuring urinary porphyrins

The purpose of this blinded study was to evaluate potential environmental toxicity in a cohort of neurotypical children (n = 28) living in a suburban area of north-central Texas in the United States (US) with a comparable age- and gender-matched cohort of neurotypical children (n = 28) living in a suburban area of southeastern France using urinary porphyrin testing: uroporphyrin (uP), heptacarboxyporphyrin (7cxP), hexacarboxyporphyrin (6cxP), pentacarboxyporphyrin (5cxP), precoproporphyrin (prcP), and coproporphyrin (cP). Results showed significantly elevated 6cxP, prcP (an atypical, mercury-specific porphyrin), and cP levels, and increasing trends in 5cxP levels, among neurotypical children in the USA compared to children in France. Data suggest that in US neurotypical children, there is a significantly increased body-burden of mercury (Hg) compared to the body-burden of Hg in the matched neurotypical children in France. The presence of lead contributing to the higher levels of cP also needs to be considered. Further, other factors including genetics can not be completely ruled out.

Is dental amalgam safe for humans? The opinion of the scientific committee of the European Commission

It was claimed by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR)) in a report to the EU-Commission that "....no risks of adverse systemic effects exist and the current use of dental amalgam does not pose a risk of systemic disease..." [1, available from: http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_016.pdf].SCENIHR disregarded the toxicology of mercury and did not include most important scientific studies in their review. But the real scientific data show that:(a) Dental amalgam is by far the main source of human total mercury body burden. This is proven by autopsy studies which found 2-12 times more mercury in body tissues of individuals with dental amalgam. Autopsy studies are the most valuable and most important studies for examining the amalgam-caused mercury body burden.(b) These autopsy studies have shown consistently that many individuals with amalgam have toxic levels of mercury in their brains or kidneys.(c) There is no correlation between mercury levels in blood or urine, and the levels in body tissues or the severity of clinical symptoms. SCENIHR only relied on levels in urine or blood.(d) The half-life of mercury in the brain can last from several years to decades, thus mercury accumulates over time of amalgam exposure in body tissues to toxic levels. However, SCENIHR state that the half-life of mercury in the body is only "20-90 days".(e) Mercury vapor is about ten times more toxic than lead on human neurons and with synergistic toxicity to other metals.(f) Most studies cited by SCENIHR which conclude that amalgam fillings are safe have severe methodical flaws.

Mercury in the Tapajós River basin, Brazilian Amazon: a review

This paper presents a review about mercury contamination and human exposure in the Tapajós River basin (Brazil), one of the major tributaries of the Amazon impacted by traditional gold mining from the mid 1980s. The most recent review in this region was published more than ten years ago and since then many articles about environment and especially human populations have revealed new aspects of mercury toxicology. Additionally, new biomarkers of mercury exposure and toxicity have been studied in these populations. However, there are still many open, about both mercury's biogeochemical cycle and mercury health risks. Further environmental and human risk research directions are proposed.

Luteinizing hormone provides a causal mechanism for mercury associated disease

Previous studies have demonstrated that the pituitary is a main target for inorganic mercury (I-Hg) deposition and accumulation within the brain. My recent study of the US population (1999-2006) has uncovered a significant, inverse relationship between chronic mercury exposure and levels of luteinizing hormone (LH). This association with LH signifies more than its presumed role as bioindicator for pituitary neurosecretion and function. LH is the only hormone with a rare and well characterized, high affinity binding site for mercury. On its catalytic beta subunit, LH has the structure to preferentially bind inorganic mercury almost irreversibly, and, by that manner, accumulate the neurotoxic element. Thus, it is likely that LH is an early and significant target of chronic mercury exposure. Moreover, due to the role of LH in immune-modulation and neurogenesis, I present LH as a central candidate to elucidate a causal mechanism for chronic mercury exposure and associated disease.