Mercury poisoning | |
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Other names | Mercury toxicity, mercury overdose, mercury intoxication, hydrargyria, mercurialism |
The bulb of a mercury-in-glass thermometer | |
Specialty | Toxicology |
Symptoms | Muscle weakness, poor coordination, numbness in the hands and feet [1] |
Complications | Kidney problems, decreased intelligence [2] |
Causes | Exposure to mercury [1] |
Risk factors | Consumption of fish, which may contain mercury [3] |
Diagnostic method | Difficult [3] |
Prevention | Decreasing use of mercury, low mercury diet [4] |
Medication | Acute poisoning: dimercaptosuccinic acid (DMSA), dimercaptopropane sulfonate (DMPS) [5] |
Mercury poisoning is a type of metal poisoning due to exposure to mercury. [3] Symptoms depend upon the type, dose, method, and duration of exposure. [3] [4] They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashes, anxiety, memory problems, trouble speaking, trouble hearing, or trouble seeing. [1] High-level exposure to methylmercury is known as Minamata disease. [2] Methylmercury exposure in children may result in acrodynia (pink disease) in which the skin becomes pink and peels. [2] Long-term complications may include kidney problems and decreased intelligence. [2] The effects of long-term low-dose exposure to methylmercury are unclear. [6]
Forms of mercury exposure include metal, vapor, salt, and organic compound. [3] Most exposure is from eating fish, amalgam-based dental fillings, or exposure at a workplace. [3] In fish, those higher up in the food chain generally have higher levels of mercury, a process known as biomagnification. [3] Less commonly, poisoning may occur as a method of attempted suicide. [3] Human activities that release mercury into the environment include the burning of coal and mining of gold. [4] [7] Tests of the blood, urine, and hair for mercury are available but do not relate well to the amount in the body. [3]
Prevention includes eating a diet low in mercury, removing mercury from medical and other devices, proper disposal of mercury, and not mining further mercury. [4] [2] In those with acute poisoning from inorganic mercury salts, chelation with either dimercaptosuccinic acid (DMSA) or dimercaptopropane sulfonate (DMPS) appears to improve outcomes if given within a few hours of exposure. [5] Chelation for those with long-term exposure is of unclear benefit. [5] In certain communities that survive on fishing, rates of mercury poisoning among children have been as high as 1.7 per 100. [4]
Common symptoms of mercury poisoning are peripheral neuropathy, presenting as paresthesia or itching, burning, pain, or even a sensation that resembles small insects crawling on or under the skin (formication); skin discoloration (pink cheeks, fingertips and toes); swelling; and desquamation (shedding or peeling of skin). [8]
Mercury irreversibly inhibits selenium-dependent enzymes (see below) and may also inactivate S-adenosyl-methionine, which is necessary for catecholamine catabolism by catechol-O-methyl transferase. Due to the body's inability to degrade catecholamines (e.g. adrenaline), a person with mercury poisoning may experience profuse sweating, tachycardia (persistently faster-than-normal heart beat), increased salivation, and hypertension (high blood pressure). [9]
Affected children may show red cheeks, nose and lips, loss of hair, teeth, and nails, transient rashes, hypotonia (muscle weakness), and increased sensitivity to light. Other symptoms may include kidney dysfunction (e.g. Fanconi syndrome) or neuropsychiatric symptoms such as emotional lability, memory impairment, or insomnia. [10]
Thus, the clinical presentation may resemble pheochromocytoma or Kawasaki disease. Desquamation (skin peeling) can occur with severe mercury poisoning acquired by handling elemental mercury. [11]
Historically, medicines could contain mercury and thus do more harm than good to patients. The popular Victorian medicine calomel contained mercury. In her 1859 autobiography, Scottish seamstress Elizabeth Storie describes her life as a disabled woman due to severe mercury poisoning when a doctor attempted to treat a mild childhood disease with prolonged administration of calomel. [12] In 1862 a soldier in the American civil war, Carleton Burgan, suffered a similar disfigurement when he was treated with calomel for an infection. [13]
Today, consumption of fish containing mercury is by far the most significant source of ingestion-related mercury exposure in humans, although plants and livestock also contain mercury due to bioconcentration of organic mercury from seawater, freshwater, marine and lacustrine sediments, soils, and atmosphere, and due to biomagnification by ingesting other mercury-containing organisms. [14] Exposure to mercury can occur from breathing contaminated air, [15] from eating foods that have acquired mercury residues during processing, [16] [17] from exposure to mercury vapor in mercury amalgam dental restorations, [18] and from improper use or disposal of mercury and mercury-containing objects, for example, after spills of elemental mercury or improper disposal of fluorescent lamps. [19]
All of these, except elemental liquid mercury, produce toxicity or death with less than a gram. Mercury's zero oxidation state (Hg 0) exists as vapor or as liquid metal, its mercurous state (Hg+) exists as inorganic salts, and its mercuric state (Hg2+) may form either inorganic salts or organomercury compounds. [20] [21] [22]
Consumption of whale and dolphin meat, as is the practice in Japan, is a source of high levels of mercury poisoning. [23] Tetsuya Endo, a professor at the Health Sciences University of Hokkaido, has tested whale meat purchased in the whaling town of Taiji and found mercury levels more than 20 times the acceptable Japanese standard. [24]
Human-generated sources, such as coal-burning power plants [25] emit about half of atmospheric mercury, with natural sources such as volcanoes responsible for the remainder. A 2021 publication investigating the mercury distribution in European soils found that high mercury concentrations are found close to abandoned mines (such as Almadén (Castilla-La Mancha, Spain), Mt. Amiata (Italy), Idrija (Slovenia) and Rudnany (Slovakia)) and coal-fired power plants. [26] An estimated two-thirds of human-generated mercury comes from stationary combustion, mostly of coal. Other important human-generated sources include gold production, nonferrous metal production, cement production, waste disposal, human crematoria, caustic soda production, pig iron and steel production, mercury production (mostly for batteries), and biomass burning. [27]
Small independent gold-mining operation workers are at higher risk of mercury poisoning because of crude processing methods. [28] Such is the danger for the galamsey in Ghana and similar workers known as orpailleurs in neighboring francophone countries. While no official government estimates of the labor force have been made, observers believe 20,000–50,000 work as galamseys in Ghana, a figure including many women, who work as porters. Similar problems have been reported amongst the gold miners of Indonesia. [29]
Some mercury compounds, especially organomercury compounds, can also be readily absorbed through direct skin contact. Mercury and its compounds are commonly used in chemical laboratories, hospitals, dental clinics, and facilities involved in the production of items such as fluorescent light bulbs, batteries, and explosives. [30]
Many traditional medicines, including ones used in Ayurvedic medicine, [31] [32] [33] [34] and in Traditional Chinese medicine, [35] contain mercury and other heavy metals.
Organic compounds of mercury tend to be much more toxic than either the elemental form or the salts. These compounds have been implicated in causing brain and liver damage. The most dangerous mercury compound, dimethylmercury, is so toxic that even a few microliters spilled on the skin, or even on a latex glove, can cause death. [36] [37]
Methylmercury is the major source of organic mercury for all individuals. [38] Due to bioaccumulation, it works its way up through the food web and thus biomagnifies, resulting in high concentrations among populations of some species. Top predatory fish, such as tuna or swordfish, are usually of greater concern than smaller species. The US FDA and the EPA advise women of child-bearing age, nursing mothers, and young children to completely avoid swordfish, shark, king mackerel and tilefish from the Gulf of Mexico, and to limit consumption of albacore ("white") tuna to no more than 170 g (6 oz ) per week, and of all other fish and shellfish to no more than 340 g (12 oz) per week. [39] A 2006 review of the risks and benefits of fish consumption found, for adults, the benefits of one to two servings of fish per week outweigh the risks, even (except for a few fish species) for women of childbearing age, and that avoidance of fish consumption could result in significant excess coronary heart disease deaths and suboptimal neural development in children. [40]
Because the process of mercury-dependent sequestration of selenium is slow, the period between exposure to methylmercury and the appearance of symptoms in adult poisoning cases tends to be extended. The longest recorded latent period is five months after a single exposure, in the Dartmouth case (see History); other latent periods in the range of weeks to months have also been reported. When the first symptom appears, typically paresthesia (a tingling or numbness in the skin), it is followed rapidly by more severe effects, sometimes ending in coma and death. The toxic damage appears to be determined by the peak value of mercury, not the length of the exposure. [41]
Methylmercury exposure during rodent gestation, a developmental period that approximately models human neural development during the first two trimesters of gestation, [42] [43] has long-lasting behavioral consequences that appear in adulthood and, in some cases, may not appear until aging. Prefrontal cortex or dopamine neurotransmission could be especially sensitive to even subtle gestational methylmercury exposure [44] and suggests that public health assessments of methylmercury based on intellectual performance may underestimate the impact of methylmercury in public health.
Ethylmercury is a breakdown product of the antibacteriological agent ethylmercurithiosalicylate, which has been used as a topical antiseptic and a vaccine preservative (further discussed under Thiomersal below). Its characteristics have not been studied as extensively as those of methylmercury. It is cleared from the blood much more rapidly, with a half-life of seven to ten days, and it is metabolized much more quickly than methylmercury. It is presumed not to have methylmercury's ability to cross the blood–brain barrier via a transporter, but instead relies on simple diffusion to enter the brain. [38] Other exposure sources of organic mercury include phenylmercuric acetate and phenylmercuric nitrate. These compounds were used in indoor latex paints for their antimildew properties, but were removed in 1990 because of cases of toxicity. [38]
Mercury occurs as salts such as mercuric chloride (HgCl2) and mercurous chloride (Hg2Cl2), the latter also known as calomel. Because they are more soluble in water, mercuric salts are usually more acutely toxic than mercurous salts. Their higher solubility lets them be more readily absorbed from the gastrointestinal tract. Mercury salts affect primarily the gastrointestinal tract and the kidneys, and can cause severe kidney damage; however, as they cannot cross the blood–brain barrier easily, these salts inflict little neurological damage without continuous or heavy exposure. [45] Mercuric cyanide (Hg(CN)2) is a particularly toxic mercury compound that has been used in murders, as it contains not only mercury but also cyanide, leading to simultaneous cyanide poisoning. [46] The drug n-acetyl penicillamine has been used to treat mercury poisoning with limited success. [47]
Quicksilver (liquid metallic mercury) is poorly absorbed by ingestion and skin contact. Its vapor is the most hazardous form. Animal data indicate less than 0.01% of ingested mercury is absorbed through the intact gastrointestinal tract, though it may not be true for individuals with ileus. Cases of systemic toxicity from accidental swallowing are rare, and attempted suicide via intravenous injection does not appear to result in systemic toxicity, [41] though it still causes damage by physically blocking blood vessels both at the site of injection and the lungs. Though not studied quantitatively, the physical properties of liquid elemental mercury limit its absorption through intact skin and in light of its very low absorption rate from the gastrointestinal tract, skin absorption would not be high. [48] Some mercury vapor is absorbed dermally, but uptake by this route is only about 1% of that by inhalation. [49]
In humans, approximately 80% of inhaled mercury vapor is absorbed via the respiratory tract, where it enters the circulatory system and is distributed throughout the body. [50] Chronic exposure by inhalation, even at low concentrations in the range 0.7–42 μg/m3, has been shown in case–control studies to cause effects such as tremors, impaired cognitive skills, and sleep disturbance in workers. [51] [52]
Acute inhalation of high concentrations causes a wide variety of cognitive, personality, sensory, and motor disturbances. The most prominent symptoms include tremors (initially affecting the hands and sometimes spreading to other parts of the body), emotional lability (characterized by irritability, excessive shyness, confidence loss, and nervousness), insomnia, memory loss, neuromuscular changes (weakness, muscle atrophy, muscle twitching), headaches, polyneuropathy (paresthesia, stocking-glove sensory loss, hyperactive tendon reflexes, slowed sensory and motor nerve conduction velocities), and performance deficits in tests of cognitive function. [48]
The toxicity of mercury sources can be expected to depend on its nature, i.e., salts vs. organomercury compounds vs. elemental mercury.
The primary mechanism of mercury toxicity involves its irreversible inhibition of selenoenzymes, such as thioredoxin reductase (IC50 = 9 nM). [53] Although it has many functions, thioredoxin reductase restores vitamins C and E, as well as a number of other important antioxidant molecules, back into their reduced forms, enabling them to counteract oxidative damage. [54] Since the rate of oxygen consumption is particularly high in brain tissues, production of reactive oxygen species (ROS) is accentuated in these vital cells, making them particularly vulnerable to oxidative damage and especially dependent upon the antioxidant protection provided by selenoenzymes. High mercury exposures deplete the amount of cellular selenium available for the biosynthesis of thioredoxin reductase and other selenoenzymes that prevent and reverse oxidative damage, [55] which, if the depletion is severe and long lasting, results in brain cell dysfunctions that can ultimately cause death.
Mercury in its various forms is particularly harmful to fetuses as an environmental toxin in pregnancy, as well as to infants. Women who have been exposed to mercury in substantial excess of dietary selenium intakes during pregnancy are at risk of giving birth to children with serious birth defects, such as those seen in Minamata disease. Mercury exposures in excess of dietary selenium intakes in young children can have severe neurological consequences, preventing nerve sheaths from forming properly.
Exposure to methylmercury causes increased levels of antibodies sent to myelin basic protein (MBP), which is involved in the myelination of neurons, and glial fibrillary acidic protein (GFAP), which is essential to many functions in the central nervous system (CNS). [56] This causes an autoimmmune response against MBP and GFAP and results in the degradation of neural myelin and general decline in function of the CNS. [57]
Diagnosis of elemental or inorganic mercury poisoning involves determining the history of exposure, physical findings, and an elevated body burden of mercury. Although whole-blood mercury concentrations are typically less than 6 μg/L, diets rich in fish can result in blood mercury concentrations higher than 200 μg/L; it is not that useful to measure these levels for suspected cases of elemental or inorganic poisoning because of mercury's short half-life in the blood. If the exposure is chronic, urine levels can be obtained; 24-hour collections are more reliable than spot collections. It is difficult or impossible to interpret urine samples of people undergoing chelation therapy, as the therapy itself increases mercury levels in the samples. [58]
Diagnosis of organic mercury poisoning differs in that whole-blood or hair analysis is more reliable than urinary mercury levels. [58]
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Pollution |
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Mercury poisoning can be prevented or minimized by eliminating or reducing exposure to mercury and mercury compounds. To that end, many governments and private groups have made efforts to heavily regulate the use of mercury, or to issue advisories about the use of mercury. Most countries have signed the Minamata Convention on Mercury.
The export from the European Union of mercury and some mercury compounds has been prohibited since 15 March 2011. [59] The European Union has banned most uses of mercury. [60] Mercury is allowed for fluorescent light bulbs because of pressure from countries such as Germany, the Netherlands and Hungary, which are connected to the main producers of fluorescent light bulbs: General Electric, Philips and Osram. [61]
The examples and perspective in this article may not represent a worldwide view of the subject.(February 2019) |
Country | Regulating agency | Regulated activity | Medium | Type of mercury compound | Type of limit | Limit |
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US | Occupational Safety and Health Administration | occupational exposure | air | elemental mercury | Ceiling (not to exceed) | 0.1 mg/m3 |
US | Occupational Safety and Health Administration | occupational exposure | air | organic mercury | Ceiling (not to exceed) | 0.05 mg/m3 |
US | Food and Drug Administration | eating | sea food | methylmercury | Maximum allowable concentration | 1 ppm (1 mg/L) |
US | Environmental Protection Agency | drinking | water | inorganic mercury | Maximum contaminant level | 2 ppb (0.002 mg/L) |
The United States Environmental Protection Agency (EPA) issued recommendations in 2004 regarding exposure to mercury in fish and shellfish. [63] The EPA also developed the "Fish Kids" awareness campaign for children and young adults [64] on account of the greater impact of mercury exposure to that population.
Mercury thermometers and mercury light bulbs are not as common as they used to be, and the amount of mercury they contain is unlikely to be a health concern if handled carefully. However, broken items still require careful cleanup, as mercury can be hard to collect and it is easy to accidentally create a much larger exposure problem. [65] If available, powdered sulfur may be applied to the spill, in order to create a solid compound that is more easily removed from surfaces than liquid mercury. [66]
Identifying and removing the source of the mercury is crucial. Decontamination requires removal of clothes, washing skin with soap and water, and flushing the eyes with saline solution as needed.
Before the advent of organic chelating agents, salts of iodide were given orally, such as heavily popularized by Louis Melsens and many nineteenth and early twentieth century doctors. [67] [68]
Chelation therapy for acute inorganic mercury poisoning, a formerly common method, was done with DMSA, 2,3-dimercapto-1-propanesulfonic acid (DMPS), D-penicillamine (DPCN), or dimercaprol (BAL). [38] Only DMSA is FDA-approved for use in children for treating mercury poisoning. However, several studies found no clear clinical benefit from DMSA treatment for poisoning due to mercury vapor. [69] No chelator for methylmercury or ethylmercury is approved by the FDA; DMSA is the most frequently used for severe methylmercury poisoning, as it is given orally, has fewer side-effects, and has been found to be superior to BAL, DPCN, and DMPS. [38] α-Lipoic acid (ALA) has been shown to be protective against acute mercury poisoning in several mammalian species when it is given soon after exposure; correct dosage is required, as inappropriate dosages increase toxicity. Although it has been hypothesized that frequent low dosages of ALA may have potential as a mercury chelator, studies in rats have been contradictory. [70] Glutathione and N-acetylcysteine (NAC) are recommended by some physicians, but have been shown to increase mercury concentrations in the kidneys and the brain. [70]
Chelation therapy can be hazardous if administered incorrectly. In August 2005, an incorrect form of EDTA (edetate disodium) used for chelation therapy resulted in hypocalcemia, causing cardiac arrest that killed a five-year-old autistic boy. [71]
Experimental animal and epidemiological study findings have confirmed the interaction between selenium and methylmercury. Instead of causing a decline in neurodevelopmental outcomes, epidemiological studies have found that improved nutrient (i.e., omega-3 fatty acids, selenium, iodine, vitamin D) intakes as a result of ocean fish consumption during pregnancy improves maternal and fetal outcomes. [72] For example, increased ocean fish consumption during pregnancy was associated with 4-6 point increases in child IQs.
Some of the toxic effects of mercury are partially or wholly reversible provided specific therapy is able to restore selenium availability to normal before tissue damage from oxidation becomes too extensive. [73] Autopsy findings point to a half-life of inorganic mercury in human brains of 27.4 years. [74] Heavy or prolonged exposure can do irreversible damage, in particular in fetuses, infants, and young children. Young's syndrome is believed to be a long-term consequence of early childhood mercury poisoning. [75]
Mercuric chloride may cause cancer as it has caused increases in several types of tumors in rats and mice, while methyl mercury has caused kidney tumors in male rats. The EPA has classified mercuric chloride and methyl mercury as possible human carcinogens (ATSDR, EPA)
Mercury may be measured in blood or urine to confirm a diagnosis of poisoning in hospitalized people or to assist in the forensic investigation in a case of fatal over dosage. Some analytical techniques are capable of distinguishing organic from inorganic forms of the metal. The concentrations in both fluids tend to reach high levels early after exposure to inorganic forms, while lower but very persistent levels are observed following exposure to elemental or organic mercury. Chelation therapy can cause a transient elevation of urine mercury levels. [76]
Infantile acrodynia (also known as "calomel disease", "erythredemic polyneuropathy", and "pink disease") is a type of mercury poisoning in children characterized by pain and pink discoloration of the hands and feet. [106] The word is derived from the Greek, where άκρο means end or extremity , and οδυνη means pain. Acrodynia resulted primarily from calomel in teething powders and decreased greatly after calomel was excluded from most teething powders in 1954. [107] [108]
Acrodynia is difficult to diagnose; "it is most often postulated that the etiology of this syndrome is an idiosyncratic hypersensitivity reaction to mercury because of the lack of correlation with mercury levels, many of the symptoms resemble recognized mercury poisoning." [109]
Mercury was once prescribed as a purgative. [110] Many mercury-containing compounds were once used in medicines. These include calomel (mercurous chloride), and mercuric chloride.
In 1999, the Centers for Disease Control (CDC) and the American Academy of Pediatrics (AAP) asked vaccine makers to remove the organomercury compound thiomersal (spelled "thimerosal" in the US) from vaccines as quickly as possible, and thiomersal has been phased out of US and European vaccines, except for some preparations of influenza vaccine. [111] The CDC and the AAP followed the precautionary principle, which assumes that there is no harm in exercising caution even if it later turns out to be unwarranted, but their 1999 action sparked confusion and controversy that thiomersal was a cause of autism. [111]
Since 2000, the thiomersal in child vaccines has been alleged to contribute to autism, and thousands of parents in the United States have pursued legal compensation from a federal fund. [112] A 2004 Institute of Medicine (IOM) committee favored rejecting any causal relationship between thiomersal-containing vaccines and autism. [113] Autism incidence rates increased steadily even after thiomersal was removed from childhood vaccines. [114] Currently there is no accepted scientific evidence that exposure to thiomersal is a factor in causing autism. [115]
Dental amalgam is a possible cause of low-level mercury poisoning due to its use in dental fillings. Discussion on the topic includes debates on whether amalgam should be used, with critics arguing that its toxic effects make it unsafe.
Some skin whitening products contain the toxic mercury(II) chloride as the active ingredient. When applied, the chemical readily absorbs through the skin into the bloodstream. [116] The use of mercury in cosmetics is illegal in the United States. However, cosmetics containing mercury are often illegally imported. Following a certified case of mercury poisoning resulting from the use of an imported skin whitening product, the United States Food and Drug Administration warned against the use of such products. [117] [118] Symptoms of mercury poisoning have resulted from the use of various mercury-containing cosmetic products. [41] [119] [120] The use of skin whitening products is especially popular amongst Asian women. [121] In Hong Kong in 2002, two products were discovered to contain between 9,000 and 60,000 times the recommended dose. [122]
Fluorescent lamps contain mercury, which is released when bulbs break. Mercury in bulbs is typically present as either elemental mercury liquid, vapor, or both, since the liquid evaporates at ambient temperature. [123] When broken indoors, bulbs may emit sufficient mercury vapor to present health concerns, and the U.S. Environmental Protection Agency recommends evacuating and airing out a room for at least 15 minutes after breaking a fluorescent light bulb. [124] Breakage of multiple bulbs presents a greater concern. A 1987 report described a 23-month-old toddler who had anorexia, weight loss, irritability, profuse sweating, and peeling and redness of fingers and toes. This case of acrodynia was traced to exposure of mercury from a carton of 8-foot fluorescent light bulbs that had broken in a potting shed adjacent to the main nursery. The glass was cleaned up and discarded, but the child often used the area to play in. [125]
Mercury has, allegedly, been used at various times to assassinate people. In 2008, Russian lawyer Karinna Moskalenko claimed to have been poisoned by mercury left in her car, [126] while in 2010 journalists Viktor Kalashnikov and Marina Kalashnikova accused Russia's FSB of trying to poison them. [127]
In 2011, German Christoph Bulwin was poisoned with a mercury compound from a syringe attached to an umbrella.
Selenium is a chemical element; it has the symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure ore compounds in Earth's crust. Selenium was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium.
A toxic heavy metal is a common but misleading term for a metal-like element noted for its potential toxicity. Not all heavy metals are toxic and some toxic metals are not heavy. Elements often discussed as toxic include cadmium, mercury and lead, all of which appear in the World Health Organization's list of 10 chemicals of major public concern. Other examples include chromium and nickel, thallium, bismuth, arsenic, antimony and tin.
Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. Thus, the longer the biological half-life of a toxic substance, the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high. Bioaccumulation, for example in fish, can be predicted by models. Hypothesis for molecular size cutoff criteria for use as bioaccumulation potential indicators are not supported by data. Biotransformation can strongly modify bioaccumulation of chemicals in an organism.
Thiomersal (INN), or thimerosal, also sold under the name merthiolate is an organomercury compound. It is a well-established antiseptic and antifungal agent.
Dimethylmercury is an extremely toxic organomercury compound with the formula (CH3)2Hg. A volatile, flammable, dense and colorless liquid, dimethylmercury is one of the strongest known neurotoxins. Less than 0.1 mL is capable of inducing severe mercury poisoning resulting in death.
Chelation therapy is a medical procedure that involves the administration of chelating agents to remove heavy metals from the body. Chelation therapy has a long history of use in clinical toxicology and remains in use for some very specific medical treatments, although it is administered under very careful medical supervision due to various inherent risks, including the mobilization of mercury and other metals through the brain and other parts of the body by the use of weak chelating agents that unbind with metals before elimination, exacerbating existing damage. To avoid mobilization, some practitioners of chelation use strong chelators, such as selenium, taken at low doses over a long period of time.
Dimercaprol, also called British anti-Lewisite (BAL), is a medication used to treat acute poisoning by arsenic, mercury, gold, and lead. It may also be used for antimony, thallium, or bismuth poisoning, although the evidence for those uses is not very strong. It is given by injection into a muscle.
This discussion of the dental amalgam controversy outlines the debate over whether dental amalgam should be used. Supporters claim that it is safe, effective and long-lasting, while critics argue that amalgam is unsafe because it may cause mercury poisoning and other toxicity.
Methylmercury (sometimes methyl mercury) is an organometallic cation with the formula [CH3Hg]+. It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environmental toxicant with a 50-day half-life. Methylmercury is the causative agent of the infamous Minamata disease.
Ethylmercury (sometimes ethyl mercury) is a cation composed of an organic CH3CH2— species (an ethyl group) bound to a mercury(II) centre, making it a type of organometallic cation, and giving it a chemical formula C2H5Hg+. The main source of ethylmercury is thimerosal.
Erethism, also known as erethismus mercurialis, mad hatter disease, or mad hatter syndrome, is a neurological disorder which affects the whole central nervous system, as well as a symptom complex, derived from mercury poisoning. Erethism is characterized by behavioral changes such as irritability, low self-confidence, depression, apathy, shyness and timidity, and in some extreme cases with prolonged exposure to mercury vapors, by delirium, personality changes and memory loss. People with erethism often have difficulty with social interactions. Associated physical problems may include a decrease in physical strength, headaches, general pain, and tremors, as well as an irregular heartbeat.
Concerns about thiomersal and vaccines are commonly expressed by anti-vaccine activists. Claims relating to the safety of thiomersal, a mercury-based preservative used in vaccines, are refuted, but still subject to fearmongering, notably claims it could cause neurological disorders such as autism, leading to its removal from most vaccines in the US childhood schedule. This had no effect on the rates of diagnosis of pervasive developmental defects, including autism. Extensive scientific research shows no credible evidence linking thiomersal to such conditions.
Metal toxicity or metal poisoning is the toxic effect of certain metals in certain forms and doses on life. Some metals are toxic when they form poisonous soluble compounds. Certain metals have no biological role, i.e. are not essential minerals, or are toxic when in a certain form. In the case of lead, any measurable amount may have negative health effects. There is a popular misconception that only heavy metals can be toxic, but lighter metals such as beryllium and lithium can be toxic too. Not all heavy metals are particularly toxic, and some are essential, such as iron. The definition may also include trace elements when abnormally high doses may be toxic. An option for treatment of metal poisoning may be chelation therapy, a technique involving the administration of chelation agents to remove metals from the body.
Mercury is a chemical element; it has symbol Hg and atomic number 80. It is also known as quicksilver and was formerly named hydrargyrum from the Greek words hydor'water' and argyros'silver', from which its chemical symbol is derived. A heavy, silvery d-block element, mercury is the only metallic element that is known to be liquid at standard temperature and pressure; the only other element that is liquid under these conditions is the halogen bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature.
The presence of mercury in fish is a health concern for people who eat them, especially for women who are or may become pregnant, nursing mothers, and young children. Fish and shellfish concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organomercury compound. This element is known to bioaccumulate in humans, so bioaccumulation in seafood carries over into human populations, where it can result in mercury poisoning. Mercury is dangerous to both natural ecosystems and humans because it is a metal known to be highly toxic, especially due to its neurotoxic ability to damage the central nervous system.
Mercury regulation in the United States limit the maximum concentrations of mercury (Hg) that is permitted in air, water, soil, food and drugs. The regulations are promulgated by agencies such as the Environmental Protection Agency (EPA) and Food and Drug Administration (FDA), as well as a variety of state and local authorities. EPA published the Mercury and Air Toxics Standards (MATS) regulation in 2012; the first federal standards requiring power plants to limit emissions of mercury and other toxic gases.
Selenium is an essential micronutrient for animals, though it is toxic in large doses. In plants, it sometimes occurs in toxic amounts as forage, e.g. locoweed. Selenium is a component of the amino acids selenocysteine and selenomethionine. In humans, selenium is a trace element nutrient that functions as cofactor for glutathione peroxidases and certain forms of thioredoxin reductase. Selenium-containing proteins are produced from inorganic selenium via the intermediacy of selenophosphate (PSeO33−).
Mercury is a heavy metal that cycles through the atmosphere, water, and soil in various forms to different parts of the world. Due to this natural mercury cycle, irrespective of which part of the world releases mercury it could affect an entirely different part of the world making mercury pollution a global concern. Mercury pollution is now identified as a global problem and awareness has been raised on an international action plan to minimize anthropogenic mercury emissions and clean up mercury pollution. The 2002 Global Mercury Assessment concluded that "International actions to address the global mercury problem should not be delayed". Among many environments that are under the impact of mercury pollution, the ocean is one which cannot be neglected as it has the ability to act as a "storage closet" for mercury. According to a recent model study the total anthropogenic mercury released into the ocean is estimated to be around 80,000 to 45,000 metric tons and two-thirds of this amount is estimated to be found in waters shallower than 1000m level where much consumable fish live. Mercury can bioaccumulate in marine food chains in the form of highly toxic methylmercury which can cause health risks to human seafood consumers. According to statistics, about 66% of global fish consumption comes from the ocean. Therefore, it is important to monitor and regulate oceanic mercury levels to prevent more and more mercury from reaching the human population through seafood consumption.
Mercury is a poisonous element found in various forms in Canada. It can be emitted in the atmosphere naturally and anthropogenically, the main cause of mercury emission in the environment. Mercury pollution has become a sensitive issue in Canada for the past few decades and many steps have been taken for prevention at local, national, and international levels. It has been found to have various negative health and environmental effects. Methylmercury is the most toxic form of mercury which is easily accessible as well as digestible by living organisms and it is this form of mercury causing serious harm to human and wildlife health.
Mercury contamination in Grassy Narrows was an uncontrolled discharge of between 9,000 kilograms (20,000 lb) and 11,000 kilograms (24,000 lb) of mercury from the Dryden Mill's chloralkali plant in Dryden into the headwaters of the Wabigoon River in the Kenora District of Northwestern Ontario from 1962 until 1970. It was described as "one of the worst cases of environmental poisoning in Canadian history." The contamination poisoned many people in the Grassy Narrows First Nation and Whitedog First Nation communities.
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