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Environmental Health Perspectives Nov 1987The nervous system is the principal target for a number of metals. Inorganic compounds of aluminum, arsenic, lead, lithium, manganese, mercury, and thallium are well... (Review)
Review
The nervous system is the principal target for a number of metals. Inorganic compounds of aluminum, arsenic, lead, lithium, manganese, mercury, and thallium are well known for their neurological and behavioral effects in humans. The alkyl derivatives of certain metals--lead, mercury and tin--are specially neurotoxic. Concern over human exposure and in some cases, outbreaks of poisoning, have stimulated research into the toxic action of these metals. A number of interesting hypotheses have been proposed for the mechanism of lead toxicity on the nervous system. Lead is known to be a potent inhibitor of heme synthesis. A reduction in heme-containing enzymes could compromise energy metabolism. Lead may affect brain function by interference with neurotransmitters such as gamma-amino-isobutyric acid. There is mounting evidence that lead interferes with membrane transport and binding of calcium ions. Methylmercury produces focal damage to specific areas in the adult brain. One hypothesis proposes that certain cells are susceptible because they cannot repair the initial damage to the protein sythesis machinery. The developing nervous system is especially susceptible to damage by methylmercury. It has been discovered that microtubules are destroyed by this form of mercury and this effect may explain the inhibition of cell division and cell migration, processes that occur only in the developmental stages. These and other hypotheses will stimulate considerable experimental challenges in the future.
Topics: Animals; Calcium; Central Nervous System; Humans; Lead Poisoning; Methylmercury Compounds
PubMed: 3319566
DOI: 10.1289/ehp.877559 -
Bulletin of the World Health... Apr 2014To examine biomarkers of methylmercury (MeHg) intake in women and infants from seafood-consuming populations globally and characterize the comparative risk of fetal... (Review)
Review
OBJECTIVE
To examine biomarkers of methylmercury (MeHg) intake in women and infants from seafood-consuming populations globally and characterize the comparative risk of fetal developmental neurotoxicity.
METHODS
A search was conducted of the published literature reporting total mercury (Hg) in hair and blood in women and infants. These biomarkers are validated proxy measures of MeHg, a neurotoxin found primarily in seafood. Average and high-end biomarkers were extracted, stratified by seafood consumption context, and pooled by category. Medians for average and high-end pooled distributions were compared with the reference level established by a joint expert committee of the Food and Agriculture Organization (FAO) and the World Health Organization (WHO).
FINDINGS
Selection criteria were met by 164 studies of women and infants from 43 countries. Pooled average biomarkers suggest an intake of MeHg several times over the FAO/WHO reference in fish-consuming riparians living near small-scale gold mining and well over the reference in consumers of marine mammals in Arctic regions. In coastal regions of south-eastern Asia, the western Pacific and the Mediterranean, average biomarkers approach the reference. Although the two former groups have a higher risk of neurotoxicity than the latter, coastal regions are home to the largest number at risk. High-end biomarkers across all categories indicate MeHg intake is in excess of the reference value.
CONCLUSION
There is a need for policies to reduce Hg exposure among women and infants and for surveillance in high-risk populations, the majority of which live in low-and middle-income countries.
Topics: Adult; Biomarkers; Environmental Exposure; Female; Global Health; Hair; Humans; Infant; Infant, Newborn; Male; Methylmercury Compounds; Neurotoxicity Syndromes; Pregnancy; Rivers; Seafood; Water Pollutants, Chemical; Young Adult
PubMed: 24700993
DOI: 10.2471/BLT.12.116152 -
Environmental Health Perspectives Oct 2002This article discusses three examples of delay (latency) in the appearance of signs and symptoms of poisoning after exposure to methylmercury. First, a case is presented... (Review)
Review
This article discusses three examples of delay (latency) in the appearance of signs and symptoms of poisoning after exposure to methylmercury. First, a case is presented of a 150-day delay period before the clinical manifestations of brain damage after a single brief (<1 day) exposure to dimethylmercury. The second example is taken from the Iraq outbreak of methylmercury poisoning in which the victims consumed contaminated bread for several weeks without any ill effects. Indeed, signs of poisoning did not appear until weeks or months after exposure stopped. The last example is drawn from observations on nonhuman primates and from the sequelae of the Minamata, Japan, outbreak in which low chronic doses of methylmercury may not have produced observable behavioral effects for periods of time measured in years. The mechanisms of these latency periods are discussed for both acute and chronic exposures. Parallels are drawn with other diseases that affect the central nervous system, such as Parkinson disease and post-polio syndrome, that also reflect the delayed appearance of central nervous system damage.
Topics: Acute Disease; Chronic Disease; Food Contamination; Humans; Iraq; Kinetics; Mercury Poisoning; Methylmercury Compounds; Neurodegenerative Diseases; Time Factors
PubMed: 12426145
DOI: 10.1289/ehp.02110s5851 -
Environmental Pollution (Barking, Essex... Nov 2022Mercury (Hg) is a widespread heavy metal causing various damages to health, while insufficient studies assessed its exposure risk across China. This study explored...
Mercury (Hg) is a widespread heavy metal causing various damages to health, while insufficient studies assessed its exposure risk across China. This study explored concentrations in food items and dietary exposure risks across China by comprehensively analyzing the researches on total Hg (THg) in eight food items and methylmercury (MeHg) in aquatic foods published between 1980 and 2021. According to the included 695 studies, the average THg concentration in all food items was 0.033 mg/kg (ranging from 0.004 to 0.185 mg/kg), with the highest concentration in edible fungi. The average daily dietary THg exposure from all foods was 12.9 μg/day. Plant-based foods accounted for 62.7% of the dietary THg exposure. Cereals and vegetables were the primary source of THg exposure. The MeHg concentration in aquatic foods was 0.08 mg/kg, and the average dietary exposure was 3.8 μg/day. Monte Carlo simulations of the dietary exposure risk assessment of THg and MeHg showed that approximately 6.4 and 7.0% of residents exceeded the health-based guidance value set by the European Food Safety Authority, with higher exposure risk in Southwest and South China. The nationwide target hazard quotient index of THg was greater than 1, suggesting that the non-carcinogenic risk of dietary exposure to THg needed further concern. In summary, this study has a comprehensive understanding of dietary Hg exposure risks across China, which provide a data basis for Hg exposure risk assessment and policy formulation.
Topics: China; Dietary Exposure; Environmental Monitoring; Food Contamination; Mercury; Metals, Heavy; Methylmercury Compounds; Risk Assessment
PubMed: 36029907
DOI: 10.1016/j.envpol.2022.120026 -
Journal of Trace Elements in Medicine... Apr 2014Early methylmercury (MeHg) exposure can have long-lasting consequences likely arising from impaired developmental processes, the outcome of which has been exposed in... (Review)
Review
Early methylmercury (MeHg) exposure can have long-lasting consequences likely arising from impaired developmental processes, the outcome of which has been exposed in several longitudinal studies of affected populations. Given the large number of newborns at an increased risk of learning disabilities associated with in utero MeHg exposure, it is important to study neurobehavioral alterations using ecologically valid and physiologically relevant models. This review highlights the benefits of using the MeHg drinking water exposure paradigm and outlines behavioral outcomes arising from this procedure in rodents. Combination treatments that exacerbate or ameliorate MeHg-induced effects, and possible molecular mechanisms underlying behavioral impairment are also discussed.
Topics: Animals; Behavior, Animal; Drinking Water; Environmental Exposure; Female; Methylmercury Compounds; Pregnancy; Prenatal Exposure Delayed Effects; Rodentia
PubMed: 24210169
DOI: 10.1016/j.jtemb.2013.09.008 -
Nihon Eiseigaku Zasshi. Japanese... 2018Mercury and its compounds are classified into three main groups: metallic mercury (Hg), inorganic mercury (Hg), and organic mercury (methyl mercury: CHHg, etc.).... (Review)
Review
Mercury and its compounds are classified into three main groups: metallic mercury (Hg), inorganic mercury (Hg), and organic mercury (methyl mercury: CHHg, etc.). Metallic mercury is the only metal that is liquid at ambient temperature and normal pressure, which readily forms an amalgam with other metals. Therefore, mercury has long been used for refining various metals, and mercury amalgam has been used for dental treatment. Mercury has also been used in measuring instruments such as thermometers, barometers and blood pressure monitors, as well as electric appliances such as lighting equipment and dry batteries. Large amounts of metallic mercury are still used in other countries as a catalyst in the production of caustic soda by electrolysis. In addition, mercury compounds have been used in various chemicals such as mercurochrome, agricultural chemicals, and mildew-proofing agents. However, the use of mercury has also caused health problems for people. Minamata disease in Japan is a typical example. Also, since mercury is highly volatile, it is discharged as a product of industrial activities or derived from volcanoes, and it has been concluded on the basis of the findings of the United Nations Environment Program (UNEP) that it is circulating globally. Therefore, with the aim of establishing an internationally legally binding treaty for the regulation of mercury use to reduce risk, an intergovernmental negotiating committee was established in 2009. Japan actively contributed to this negotiation owing to its experience with Minamata disease, which led to the Convention on the regulation of mercury use being discharged as the "Minamata Convention on Mercury" and the treaty came into force on August 16, 2017. In this review, we introduce 1) the Global Mercury Assessment by UNEP; 2) mercury kinetics, exposure assessment and toxicity of different chemical forms; 3) large-scale epidemics of methylmercury poisoning; 4) methylmercury exposure assessment and health survey in whale-eating populations; 5) elemental mercury exposure assessment and health survey of mercury mine workers in China.
Topics: Animals; Environmental Exposure; Environmental Pollutants; Fishes; Global Health; Humans; Mercury Compounds; Mercury Poisoning, Nervous System; Methylmercury Compounds; Occupational Exposure; Risk Assessment
PubMed: 30270289
DOI: 10.1265/jjh.73.258 -
Archives of Toxicology Jan 2017Mercury exists in the environment in various forms, all of which pose a risk to human health. Despite guidelines regulating the industrial release of mercury into the... (Review)
Review
Mercury exists in the environment in various forms, all of which pose a risk to human health. Despite guidelines regulating the industrial release of mercury into the environment, humans continue to be exposed regularly to various forms of this metal via inhalation or ingestion. Following exposure, mercuric ions are taken up by and accumulate in numerous organs, including brain, intestine, kidney, liver, and placenta. In order to understand the toxicological effects of exposure to mercury, a thorough understanding of the mechanisms that facilitate entry of mercuric ions into target cells must first be obtained. A number of mechanisms for the transport of mercuric ions into target cells and organs have been proposed in recent years. However, the ability of these mechanisms to transport mercuric ions and the regulatory features of these carriers have not been characterized completely. The purpose of this review is to summarize the current findings related to the mechanisms that may be involved in the transport of inorganic and organic forms of mercury in target tissues and organs. This review will describe mechanisms known to be involved in the transport of mercury and will also propose additional mechanisms that may potentially be involved in the transport of mercuric ions into target cells.
Topics: Absorption, Physiological; Animals; Biological Transport; Blood-Brain Barrier; Environmental Pollutants; Female; Humans; Male; Maternal-Fetal Exchange; Mercury Compounds; Mercury Poisoning; Methylmercury Compounds; Models, Biological; Organomercury Compounds; Pregnancy; Tissue Distribution; Toxicokinetics
PubMed: 27422290
DOI: 10.1007/s00204-016-1803-y -
International Journal of Molecular... Oct 2022Methylmercury (MeHg) is a well-known environmental contaminant, particularly harmful to the developing brain. The main human dietary exposure to MeHg occurs through...
Methylmercury (MeHg) is a well-known environmental contaminant, particularly harmful to the developing brain. The main human dietary exposure to MeHg occurs through seafood consumption. However, seafood also contains several nutrients, including selenium, which has been shown to interact with MeHg and potentially ameliorate its toxicity. The aim of this study was to investigate the combined effects of selenium (as selenomethionine; SeMet) and MeHg on mercury accumulation in tissues and the effects concomitant dietary exposure of these compounds exert on the hippocampal proteome and transcriptome in mice. Adolescent male BALB/c mice were exposed to SeMet and two different doses of MeHg through their diet for 11 weeks. Organs, including the brain, were sampled for mercury analyses. Hippocampi were collected and analyzed using proteomics and transcriptomics followed by multi-omics bioinformatics data analysis. The dietary presence of SeMet reduced the amount of mercury in several organs, including the brain. Proteomic and RNA-seq analyses showed that both protein and RNA expression patterns were inversely regulated in mice receiving SeMet together with MeHg compared to MeHg alone. Several pathways, proteins and RNA transcripts involved in conditions such as immune responses and inflammation, oxidative stress, cell plasticity and Alzheimer's disease were affected inversely by SeMet and MeHg, indicating that SeMet can ameliorate several toxic effects of MeHg in mice.
Topics: Male; Adolescent; Animals; Humans; Mice; Methylmercury Compounds; Selenomethionine; Transcriptome; Selenium; Proteome; Proteomics; Mice, Inbred BALB C; Mercury; Diet; Antioxidants; Hippocampus; RNA
PubMed: 36293098
DOI: 10.3390/ijms232012242 -
Environment International May 2017Methylmercury (MeHg) is a known developmental neurotoxicant present in fish, yet the impact of childhood exposure is uncertain, especially in children with poor...
BACKGROUND
Methylmercury (MeHg) is a known developmental neurotoxicant present in fish, yet the impact of childhood exposure is uncertain, especially in children with poor nutrition.
OBJECTIVES
To evaluate associations of MeHg exposure with cognitive abilities and behavior in children from a poor rural area in Bangladesh.
METHODS
The MeHg exposure was assessed in 1434 ten-year-old children by measuring mercury concentrations in hair (hair-Hg), using inductively coupled plasma mass spectrometry. Cognitive abilities were assessed with the Wechsler Intelligence Scale for Children (4th edition), and behavior by the parent-report Strengths and Difficulties Questionnaire.
RESULTS
Children's median hair-Hg was 674μg/kg (range 70-17,561μg/kg). Concentrations did not differ by distance from scalp, indicating a similar exposure over time. No multivariable-adjusted associations were observed between the children's hair-Hg and their cognitive abilities. However, children in the highest tertile of hair-Hg had a lower prevalence of hyperactivity (OR: 0.61, 95% CI: 0.45-0.83) and peer relationship problems (OR: 0.58, 95% CI: 0.44-0.76), compared to children in the lowest tertile. The corresponding ORs were slightly stronger in children from families with lower socioeconomic status (OR: 0.56, 95% CI: 0.34-0.90 and OR: 0.48, 95% CI: 0.30-0.74) than in children from families with higher socioeconomic status (OR: 0.73, 95% CI: 0.49-1.08 and OR: 0.72, 95% CI: 0.51-1.02). Similar stronger ORs were observed in underweight children.
CONCLUSION
MeHg exposure was not associated with cognitive function, but inversely associated with certain adverse behavior. More studies are needed concerning the risk-benefit of different fish consumption in rural Bangladesh.
Topics: Animals; Bangladesh; Child; Child Behavior; Cognition; Environmental Exposure; Female; Fishes; Hair; Humans; Male; Methylmercury Compounds; Risk Assessment; Rural Population; Social Class; Water Pollutants, Chemical; Wechsler Scales
PubMed: 28216013
DOI: 10.1016/j.envint.2017.02.004 -
International Journal of Environmental... Jun 2023Minamata disease, which happened during the 1950s and 1960s in Minamata, Japan, is a well-known case of food poisoning caused by methylmercury-contaminated fish....
Minamata disease, which happened during the 1950s and 1960s in Minamata, Japan, is a well-known case of food poisoning caused by methylmercury-contaminated fish. Although many children were born, in the affected areas, with severe neurological signs after birth (known as congenital Minamata disease (CMD)), few studies have explored the possible effects of low-to-moderate methylmercury exposure in utero, probably at lower levels than in CMD patients, in Minamata. We, therefore, recruited 52 participants in 2020: 10 patients with known CMD; 15 moderately exposed residents; and 27 non-exposed controls. The average umbilical cord methylmercury concentrations were 1.67 parts per million (ppm) for CMD patients and 0.77 ppm for moderately exposed participants. After conducting four neuropsychological tests, we compared the functions among the groups. Compared with the non-exposed controls, both the CMD patients and moderately exposed residents had worse scores in the neuropsychological tests, although the score decline was more severe in the CMD patients. For example, even after adjusting for age and sex, the CMD patients and moderately exposed residents had 16.77 (95% CI: 13.46 to 20.08) and 4.11 (95% CI: 1.43 to 6.78) lower scores in the Montreal Cognitive Assessment, respectively, than the non-exposed controls. The present study indicates that residents of Minamata who experienced low-to-moderate prenatal methylmercury exposure also have neurological or neurocognitive impairments.
Topics: Animals; Foodborne Diseases; Japan; Mercury Poisoning, Nervous System; Methylmercury Compounds; Neurologic Examination; Humans
PubMed: 37372760
DOI: 10.3390/ijerph20126173