Methylmercury(1+)

If material involved in fire: Use water in flooding quantities as fog. Use "alcohol" foam, dry chemical, or carbon dioxide. Apply water from as far a distance as possible. /Mercury compounds, liquid, n.o.s./

Use dry chemical, carbon dioxide, water spray, or alcohol foam extinguishers ... If material or contaminated runoff enters waterways, notify downstream users of potentially contaminated waters. Nofity local health and fire officials and pollution control agencies. From a secure, explosion-proof location, use water spray to cool exposed containers. If cooling streams are ineffective (venting sound increases in volume and pitch, tank discolors or shows any signs of deforming), withdraw immediately to a secure position. /Mercury alkyl compounds/

Wear appropriate chemical clothing. Wear positive pressure self-contained breathing apparatus /Mercury compounds, liquid, n.o.s./

PRECAUTIONS FOR "CARCINOGENS": Storage site should be as close as practical to lab in which carcinogens are to be used, so that only small quantities required for ... expt need to be carried. Carcinogens should be kept in only one section of cupboard, an explosion-proof refrigerator or freezer (depending on chemicophysical properties ...) that bears appropriate label. An inventory ... should be kept, showing quantity of carcinogen & date it was acquired ... Facilities for dispensing ... should be contiguous to storage area. /Chemical Carcinogens/

These compounds should be stored in a refrigerator or a cool dry place away from oxidizers. A regulated, marked area should be established where this chemical is handled, used, or stored ... /Mercury alkyl compounds/

PRECAUTIONS FOR "CARCINOGENS": A high-efficiency particulate arrestor (HEPA) or charcoal filters can be used to minimize amt of carcinogen in exhausted air ventilated safety cabinets, lab hoods, glove boxes or animal rooms ... Filter housing that is designed so that used filters can be transferred into plastic bag without contaminating maintenance staff is avail commercially. Filters should be placed in plastic bags immediately after removal ... The plastic bag should be sealed immediately ... The sealed bag should be labelled properly ... Waste liquids ... should be placed or collected in proper containers for disposal. The lid should be secured & the bottles properly labelled. Once filled, bottles should be placed in plastic bag, so that outer surface ... is not contaminated ... The plastic bag should also be sealed & labelled. ... Broken glassware ... should be decontaminated by solvent extraction, by chemical destruction, or in specially designed incinerators. /Chemical Carcinogens/

Environmental considerations - land spill: Dig a pit, pond, lagoon, holding area to contain liquid or solid material. /SRP: If time permits, pits, ponds, lagoons, soak holes, or holding areas should be sealed with an impermeable flexible membrane liner./ Cover solids with a plastic sheet to prevent dissolving in rain or fire fighting water. Dike surface flow using soil, sand bags, foamed polyurethane, or foamed concrete. Absorb bulk liquid with fly ash, cement powder, or commercial sorbents. /Mercury compounds, liquid, n.o.s./

Environmental considerations - water spill: Use natural barriers or oil spill control booms to limit spill travel. Use natural deep water pockets, excavated lagoons, or sand bag barriers to trap material at bottom. Remove trapped material with suction hoses. /Mercury compounds, liquid, n.o.s./

Environmental considerations - air spill: Apply water spray or mist to knock down vapors. /Mercury compounds, liquid, n.o.s./

For more Cleanup Methods (Complete) data for Methylmercury Cation (7 total), please visit the HSDB record page.

Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number D009, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste.

Chemical treatment: The mercury-carbon bond of organomercury cmpd is remarkably stable; it is very resistant to both oxidation and hydrolysis. Thus, the chemical evidence indicates that practical methods could be devised for converting organomercury cmpd to inorganic mercury cmpd, for example, chlorination. However, no recommendation can be made until specific experiments are performed to demonstrate the reliability of such techniques.

PRECAUTIONS FOR "CARCINOGENS": There is no universal method of disposal that has been proved satisfactory for all carcinogenic compounds & specific methods of chem destruction ... published have not been tested on all kinds of carcinogen-containing waste. ... summary of avail methods & recommendations ... /given/ must be treated as guide only. /Chemical Carcinogens/

PRECAUTIONS FOR "CARCINOGENS": ... Incineration may be only feasible method for disposal of contaminated laboratory waste from biological expt. However, not all incinerators are suitable for this purpose. The most efficient type ... is probably the gas-fired type, in which a first-stage combustion with a less than stoichiometric air:fuel ratio is followed by a second stage with excess air. Some ... are designed to accept ... aqueous & organic-solvent solutions, otherwise it is necessary ... to absorb soln onto suitable combustible material, such as sawdust. Alternatively, chem destruction may be used, esp when small quantities ... are to be destroyed in laboratory. /Chemical Carcinogens/

For more Disposal Methods (Complete) data for Methylmercury Cation (7 total), please visit the HSDB record page.

If material not on fire and not involved in fire: Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. Build dikes to contain flow as necessary. Attempt to stop leak if without undue personnel hazard. /Mercury compounds, liquid, n.o.s./

Personnel protection: Keep upwind ... Do not handle broken packages unless wearing appropriate personal protective equipment. /Mercury compounds, liquid, n.o.s./

Contact lenses should not be worn when working with this chemical. //SRP: Contact//

PRECAUTIONS FOR "CARCINOGENS": Smoking, drinking, eating, storage of food or of food & beverage containers or utensils, & the application of cosmetics should be prohibited in any laboratory. All personnel should remove gloves, if worn, after completion of procedures in which carcinogens have been used. They should ... wash ... hands, preferably using dispensers of liq detergent, & rinse ... thoroughly. Consideration should be given to appropriate methods for cleaning the skin, depending on nature of the contaminant. No standard procedure can be recommended, but the use of organic solvents should be avoided. Safety pipettes should be used for all pipetting. /Chemical Carcinogens/

For more Preventive Measures (Complete) data for Methylmercury Cation (12 total), please visit the HSDB record page.

PRECAUTIONS FOR "CARCINOGENS": ... Dispensers of liq detergent /should be available./ ... Safety pipettes should be used for all pipetting. ... In animal laboratory, personnel should ... wear protective suits (preferably disposable, one-piece & close-fitting at ankles & wrists), gloves, hair covering & overshoes. ... In chemical laboratory, gloves & gowns should always be worn ... however, gloves should not be assumed to provide full protection. Carefully fitted masks or respirators may be necessary when working with particulates or gases, & disposable plastic aprons might provide addnl protection. ... Gowns ... /should be/ of distinctive color, this is a reminder that they are not to be worn outside the laboratory. /Chemical Carcinogens/

Protective equipment: Wear protective gloves and clothing to prevent any possibility of skin contact ... Wear chemical goggles and face shield unless full facepiece respiratory protection is worn. Employees should wash immediately with soap when skin is wet or contaminated. Provide emergency showers and eyewash. /Methyl mercury compounds/

Guidance for Industry: Action Levels for Poisonous or Deleterious Substances in Human Food and Animal Feed ... Commodity: Fish, shellfish, crustaceans, other aquatic animals (fresh, frozen or processed); Action Level: 1 ppm methylmercury in edible portion.

Mercury (Hg) has been reported in breast milk in women exposed to methylmercury from fish and from bread contaminated with methylmercury fungicides in the 1971-72 outbreak in Iraq.

Human hair is accepted as the best indicator for assessment of contamination in populations exposed to methylmercury(1). In 1992, abnormally high levels of mercury (mean range of 7.3-49.8 with an high of 132.6 ppm) were found in human hair from Jacareacanga and Brasilia Legal located near the main gold mining area in the Tapajos river basin, Brazil, as well as from Tres Bocas facing the lake in Amapa state, whereas the levels were much lower in Ponta de Pedras, a long way downstream(2). Hair from people in different Mediterranean areas: 9 controls (negligible to moderate fish consumption), methylmercury concentration range 0.01-0.55 ug/g, avg concentration 0.16 ug/g; 26 people, residents of a coastal areas, concentration range 0.39-36.0 ug/g, avg concentration 3.68 ug/g(3). Hair of a Papua New Guinean population, 114 samples, methymercury concentration range 3.2-50.5 ug/g, avg concentration 15.5 ug/g; a nearby control group who consumed a similar amount of fish, 51 samples, methylmercury concentration range 0.62-25.7 ug/g, avg concentration 6.4 ug/g; and a control group who consumed fish much less frequently, 45 samples, methylmercury concentration range 0.33-9.0 ug/g, avg concentration 2.4 ug/g(4). Peruvian population chronically exposed to methylmercury due to long-term, heavy consumption of fish (70% of dietary protein came from fish), mean methylmercury blood level - 82 ng/mL(5). Human placentae, Italy, 22 samples, mean total organic mercury content 0.076 ug/g dry wt(6). In fishermen from two south Atlantic coastal areas of Spain, mean methylmercury ion content in hair was 8.28 ug/g and 6.72 ug/g(7). The concentration of methylmercury ion in seafood consumed by the fisherman were: Scrobicularia plana, 1.20 ug/g; Tapes decussatus, 0.039 ug/g(7).

In humans, after high oral intake of methylmercury for 2 months, the following values were reported (percentage of total mercury in tissues as inorganic mercury): whole blood, 7%; plasma, 22%; breast milk, 39%; urine, 73%; liver 16-40%(1).

Methylmercury levels in 17 hair samples from pregnant women in New Jersey ranged from <0.2 to 9.1 ug/mercury/gm hair, from a study conducted between July 1995 and April 1997(1). Mercury levels in 143 blood samples from this same population ranged from <0.5 to 32.0 ug/g, with only 15% of samples having concentrations above the detection limit of 0.5 ug/L. Participants reported on average 83 fish meals/year(1). Methylmercury levels in pregnant Swedish women ranged from 0.07-1.5 mg/kg hair and 0.10 to 5.7 ug/L cord blood; reported fish consumption was 6.7 times/month(2). Methyl mercury in hair of the riverine population of the Negro River, Amazon Basin ranged from 0 to 56.79 ug/g, in samples taken March 1998 from 149 individuals(3).

... This study investigated the effects of prenatal exposure to MeHg and Hg vapor on Hg concentrations in the brain of neonatal rats. Female Long-Evans hooded rats were exposed to MeHg (0, 3, 6, or 9 ppm as drinking solution), Hg vapor (0, 300, or 1,000 ug/cu m for 2 hr/day), or the combination of both, from 30 days before breeding through gestational day 18. On postnatal day 4, whole brains were taken from one male and one female from each of four litters in each treatment group to assess organic and inorganic Hg in the brain by cold vapor atomic absorption spectrometry. Statistical analysis using linear mixed effects models showed that MeHg dose was the primary determinant of both organic and inorganic brain Hg levels. For both outcomes, ... significant interactions between MeHg and Hg vapor exposure /were found/...

Complexing with L-cysteine or glutathione has particular toxicological significance. In rats, injection of L-cysteine with methylmercury changed the short-term distribution of the latter by decreasing the plasma concentration and increasing the concentrations in brain, liver, and kidney. D-Cysteine had similar effects but did not increase the concentration of mercury in brain ... GSH had less effect on the brain uptake of methylmercury than L-cysteine ... Increased uptake by brain was also achieved by administration of a cysteine-supplemented diet ... The stimulatory effect of L-cysteine may be due to the structural similarity between the methylmercury-cysteine complex and L-methionine, which permits use of the same L-amino acid transport system ... L-Cysteine can also increase the biliary excretion of methylmercury, after a delay for conversion to GSH ...

/Glutathione/ (GSH) plays a key role in biliary secretion of methylmercury. Consequently, compounds that deplete GSH decrease and compounds that stimulate glutathione S-transferase increase the biliary excretion of both GSH and methylmercury ... This effect is modulated by the transport molecule ligandin (a glutathione S-transferase): the biliary excretion of methylmercury was inhibited by indocyanine green, a non-substrate ligand for ligandin ... trans-Stilbene oxide, which induces glutathione S-transferase activity, had no effect on the biliary excretion of GSH or methylmercury ... but potentiated the effect of GSH in rats ... The excreted methylmercury is attached to GSH ... or to its metabolic product ...

/Glutathione/ (GSH) also affects the renal handling of methylmercury. Depletion of hepatic GSH by 1,2-dichlorobenzene resulted in a reduced blood GSH concentration and a reduced renal content of methylmercury. Inhibition of renal gamma-glutamyl-transpeptidase, a membrane enzyme that catalyzes the breakdown of GSH, decreased the renal deposition and increased the urinary excretion of methylmercury. The sex difference in the renal handling of methylmercury in some mouse strains may also depend on the concentration and metabolism of renal GSH ...

For more Interactions (Complete) data for Methylmercury Cation (27 total), please visit the HSDB record page.

Mercury mainly affects the nervous system. Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys, and developing fetus. Effects on brain functioning may result in irritability, shyness, tremors, changes in vision or hearing, and memory problems. Acrodynia, a type of mercury poisoning in children, is characterized by pain and pink discoloration of the hands and feet. Mercury poisoning can also cause Hunter-Russell syndrome and Minamata disease. (L7)

EC50; Species: Callinectes sapidus (Blue crab, embryo, stage 3); Conditions: saltwater, static, 28 °C; Concentration: 0.1 ug/L until hatch; Effect: decreased hatching

EC50; Species: Callinectes sapidus (Atlantic blue crab, embryo, stage 4): Conditions: static, 28 °C; Concentration 0.3 ug/L for 5-6 days; Effect: decreased hatching

LC50; Species: Oncorhynchus mykiss (Rainbow trout, embryo); Conditions: freshwater, renewal, 12-14 °C, pH 7.0-7.8, hardness 90-105 mg/L CaCO3; Concentration: 5 ug/L for 4 days post-hatch /total mercury ion/

Environmental factors influence net amt of methylmercury in an ecosystem by shifting equilibrium of the opposing methylation and demethylation processes. Methylation is result of mercuric ion (Hg++) interference with biochemical C-1 transfer reactions. Demethylation is brought about by nonspecific hydrolytic and reductive enzyme processes. Studies have demonstrated a strong negative correlation between salinity of anaerobic sediments and their ability to form methylmercury from Hg++.

TERRESTRIAL FATE: Volatilization of methylmercury ion from moist soil surfaces is not expected to be an important fate process given it is in the cation state and cations do not volatilize(SRC). Methylmercury ion is part of the biogeochemical cycle of mercury(1). Where mercury is found in soil, methylmercury ion may also be found since it is both produced and destroyed by microbial processes involving mercury compounds. Since mercury is cannot be destroyed under environmental conditions it remains available for transformation into methylmercury ion(2-4).

AQUATIC FATE: Inorganic mercury introduced as a pollutant into natural waters is scavanged by particulate matter and deposited into bottom sediments. Free Hg++ is gradually released from this pool of slightly soluble inorganic mercury and is then transformed by microbial activity into methylmercury ion. Methylmercury ion diffuses into the water column and is taken up by fish and other organisms (either directly through water or through the food chain), and accumulated in their tissue. Rates of methylmercury ion production and bioaccumulation depend not only on the abundance of inorganic mercury but also on a complex assortment of environmental variables which affect the activities and species composition of the microflora and the availability of inorganic mercury for methylation. Stimulation of microbial growth by nutrients such as readily metabolized organic matter tends to promote methylation of the available (free bivalent) fraction of the inorganic mercury, although this tendency is counteracted to a greater or lesser extent by other microbial processes such as microbial breakdown (demethylation) of methylmercury ion and the formation of sulfides. The effects of environmental variables are complex and mercury transformation processes are highly dependent upon the characteristics of the system(1). Methylmercury ion, added to a river water system containing sediment, was sorbed onto the sediments reaching a maximum in 7 days. At first no conversion of methylmercury ion occurred, but after 7 days 35% inorganic mercury was produced and in 28 days 55% was produced(2).

AQUATIC FATE: Volatilization of methylmercury ion from water surfaces is not expected to be an important fate process given it is in the cation state and cations do not volatilize(SRC). Methylmercury ion is susceptible to abiotic photodegradation in epilimnetic lake water(1). Bioaccumulation occurs because mercury, when methylated, enters the food chain by rapid diffusion and tight binding to proteins in aquatic biota(2). The older an organism is, and the higher its position in the food chain, the greater the fraction of total mercury existing as methylmercury(2).

The mean methylmercury (as the chloride) concentration in broilers and hens from Greece was (wet weight): breast (broilers) 0.9 ppb, leg (broilers) 0.7 ppb, liver (broilers) 2.6 ppb; breast (hens) 1.8 ppb, leg (hens) 1.4 ppb, liver (hens) 6.1 ppb(1). Methylmercury concentrations in Swedish foods in 1966 were as follows (mg of Hg/kg): ox meat, 0.068; poultry, 0.17; pig liver, 0.75-0.95; egg yolk, 0.005-0.009; egg white, 0.009-0.011; perch, 0.20-2.99; pike, 0.55-3.11; and cod, 0.022-0.055(2).

Methylmercury levels in boiled whale livers purchased between 1999 and 2001 from Japanese food retail outlets were as follows (ug/g wet gram): Risso's dolphin, 7.43-15.3; pilot whale, 9.83-14.8; striped/bottlenose/common dolphin, 3.01-23.5; minke whale, 0.12-20.3. Levels in boiled whale lungs were as follows (ug/g wet gram): Risso's dolphin, 0.20-2.43; pilot whale, 0.50-2.08; striped/bottlenose/common dolphin, 1.6-9.93; minke whale, 0.12-1.80. Levels in boiled whale kidneys were as follows (ug/g wet gram): Risso's dolphin, 1.59-2.76; striped/bottlenose/common dolphin, 0.62-21.0; minke whale, 0.01-1.54. Levels in whale red meat were as follows (ug/g wet gram): Risso's dolphin, 0.09-9.21; pilot whale, 5.38-13.8; striped/bottlenose/common dolphin, 2.17-63.4; Baird's beaked whale, 1.48-5.30. Levels in whale red meat from mysticetes were as follows (ug/g wet gram): minke whale, 0.04-0.12; Bryde's whale, 0.09(1).

Methylmercury is excreted in breast milk ... The ratio of mercury in breast milk to mercury in whole blood was approximately 1:20 in women exposed to methylmercury via contaminated grain in Iraq between 1971 and 1972 ... Evidence from the Iraqi poisoning incident also showed that lactation decreased blood mercury clearance halftimes from 75 days in males and nonlactating females to 42 days in lactating females; the faster clearance due to lactation was confirmed in mice ... In mice, of the total mercury in the breast milk, approximately 60% was estimated to be methylmercury. /It was/ found that 16% of mercury in human breast milk is methylmercury. Studies in animals indicate that the mercury content of breast milk is proportional to the mercury content of plasma.

In humans, after high oral intake of methylmercury for 2 months, the following values were reported (percentage of total mercury in tissues as inorganic mercury): ... breast milk, 39% ... .

The general population is primarily exposed to methymercury through the diet. However, air and water, depending upon the level of contamination, can contribute significantly to the daily intake of total mercury. ... Fish and fish products are the dominant source of methylmercury in the diet ... Methylmercury in the human diet is almost completely absorbed into the bloodstream and distributed to all tissues within about 4 days. ... Methylmercury is converted to inorganic mercury in experimental animals and humans. ... The rate of excretion of mercury in both laboratory animals and humans is directly proportional to the simultaneous body burden and can be described by a single-compartment model with a biological half-time, in fish-eating humans, of 39-70 days ... In every animal species studied, the nervous system is a target of methylmercury, fetuses appearing to be at higher risk than adults. ... Methylmercury is fetotoxic in mice (single dose of 2.5-7.5 mg/kg); teratogenic in rats, and adversely affects the behavior of monkey offspring (mercury doses of 50-70 ug/kg per day before and during pregnancy). It also affects spermatogenesis in mice .... The clinical and epidemiological evidence indicates that prenatal life is more sensitive to the toxic effects of methylmercury than in adult life. The inhibition of protein synthesis is one of the earliest detectable biochemical effects in the adult brain ... Methylmercury can also react directly with important receptors in the nervous system, as shown by its effect on acetylcholine receptors in the peripheral nerves. In the case of prenatal exposure ... it affects normal neuronal development, leading to altered brain architecture, heterotopic cells and decreased brain size. Methylmercury may also be exerting an effect, perhaps through inhibition of the microtubular system, on cell division during critical stages in the formation of the central nervous system. ... No adverse effects /in adults/ have been detected with long-term daily methylmercury intakes of 3-7 ug/kg body weight (hair mercury concentrations of approximately 50-125 ug/g). Pregnant women may suffer effects at lower methylmercury exposure levels than non-pregnant adults, suggesting a greater risk for pregnant women. Severe derangement of the developing central nervous system can be caused by prenatal exposure to methylmercury. ... Evidence of pyschomotor retardation (delayed achievement of developmental milestones, a history of seizures, abnormal reflexes) was seen ... at maternal hair levels below those associated with severe effects. ... CONCLUSIONS: ... Certain groups with a high fish consumption may attain a blood methylmercury level ... associated with a low (5%) risk of neurological damage to adults. The fetus is at particular risk. ... There is a need for epidemiological studies on children exposed in utero to levels of methylmercury that result in peak maternal hair mercury levels below 20 ug/g, in order to screen for those effects only detectable by available psychological and behavioral tests.

ATMOSPHERIC INTAKE: 0.14 ug/day total mercury (elemental and methylmercury) (assuming an avg ambient concentration 7 ng/cu m)(1). FOOD INTAKE: 16.3 ug/day total mercury (assuming avg mercury concentration in fish, 0.4 ug/g and an avg concentration in other foods, 0.004 ug/g(1)).

AIR INTAKE: 0.008 ug/day; FOOD INTAKE: 2.4 ug/day (fish); 0 ug/day (non-fish); WATER INTAKE: 0 ug/day(1).

/BIRDS and MAMMALS/ In birds, foraging efficiency and learning may be sensitive endpoints for sublethal methylmercury toxicity, and these endpoints also may be biologically relevant at the population level. In the present study, groups of wild-caught, prefledgling white ibises (Eudocimus albus) were raised in a free-flight, open-air aviary on diets that approximated the measured range of methylmercury exposure in the Everglades ecosystem (0, 0.05, 0.1, and 0.3 mg/kg/day). The effect of methylmercury exposure on group foraging efficiency was examined by allowing birds to forage on 200 fathead minnows (Pimephales promelas) in artificial ponds for 15 min by straining the arenas' contents through a seine net and counting all remaining prey. Additionally, we varied the difficulty of foraging by these tactile feeding birds by adding multiple levels of structural complexity (e.g., increased vegetation and prey refugia) to the pond. Structural complexity affected both foraging efficiency and the rate of increase in efficiency over time (improvement). Methylmercury exposure affected foraging efficiency (p = 0.03). It did not affect foraging improvement in the face of increasingly challenging environments, however, and the dose-response relationship was nonlinear (e.g., the control and high-exposure groups were the least efficient foragers). Evidence for an effect of methylmercury on foraging efficiency therefore was inconclusive because of unpredicted results and no interaction with time or habitat complexity. These data suggest a nonlinear dose-response relationship at low levels of methylmercury exposure ... This appears to be the first experimental demonstration of the effects of habitat complexity on foraging efficiency in long-legged wading birds.

/BIRDS and MAMMALS/ Methylmercury (MeHg) is a globally distributed neurotoxin, endocrine disruptor, and teratogen, and its effects on birds are poorly understood, especially within an environmentally relevant exposure range. In an effort to understand the potential causal relationship between MeHg exposure and endocrine development, we established four dietary exposure groups (0 [control], 0.05, 0.1, and 0.3 mg/kg wet wt/day of MeHg) of postfledging white ibises (Eudocimus albus) in a divided, free-flight aviary that spanned the estimated range of environmental exposure for this species. Fecal samples were collected from individually identified ibises over six months in 2005 and processed for hormone evaluation. Significant sex-related differences in fecal estradiol concentrations, though unpredicted in direction, suggest that this steroid could be related to juvenile development in this species. Using repeated-measures general linear models, we tested a set of candidate models to explain variation in endocrine expression. We found that MeHg exposure led to significant differences in fecal estradiol concentrations between the control and medium-dose groups, whereas differences in fecal corticosterone concentrations were observed between the control and both the low- and high-dose groups. These results suggest highly nonlinear dose-response patterns for MeHg. Many endocrine-disrupting contaminants are theorized to affect multiple endpoints in a nonlinear manner, making results difficult to interpret using a traditional toxicological approach.

D009; A solid waste containing mercury may or may not become characterized as a hazardous waste when subjected to the Toxicity Characteristic Leaching Procedure listed in 40 CFR 261.24, and if so characterized, must be managed as a hazardous waste. /Mercury/

Listed as a hazardous air pollutant (HAP) generally known or suspected to cause serious health problems. The Clean Air Act, as amended in 1990, directs EPA to set standards requiring major sources to sharply reduce routine emissions of toxic pollutants. EPA is required to establish and phase in specific performance based standards for all air emission sources that emit one or more of the listed pollutants. Methylmercury is included on this list.

Methyl mercury has no industrial uses; it is formed in the environment from the methylation of the inorganic mercurial ion.

Fungicide-treatment for grains. /Former use/

In laboratory-based research

Used in treating seeds for fungi and seedborne diseases, as timber preservatives, and disinfectants. /Methyl mercury compounds/

Methylmercury is a pollutant producted by the burning of fossil fuels and wastes containing inorganic mercury. It bioaccumulates in aquatic systems and exposure can result from ingesting contaminated fish. (L260)

/Former use:/ ... Of alkyl mercury compounds, ethyl and methyl compounds have been used as pesticides. Methyl mercury was available in the form of several salts: each sold under one or more proprietary names incl bis-methylmercuric sulfate (Cerewet), cyanoguanidine or dicyanodiamide (Agrosol, Morsodren, Panogen, (anospray), nitrile (Chipcote), and propionate (Metasol MP). /Alkyl mercury compounds/

Alkyl mercury compounds have been used as seed disinfectants and for fungicides. They have also been used in organic synthesis. /Mercury alkyl compounds/

Conditions for methylation by sediment microorganisms are strict and occur only within narrow pH range. Rate of synthesis of methylmercury also depends on redox potential, composition of microbial population, availability of Hg2+ and temp. Vitamin B12 derivatives are believed to be methylating agents ...

Methylmercury is formed in the environment from the methylation of the inorganic mercurial ion.

The general term "methylmercury" is used throughout this text to represent monomethylmercury compounds. In many cases, the precise identity of these compounds is not known except that the methylmercury cation, CH3Hg+, is associated either with a simple anion, like chloride, or a large molecule, for example protein, with negative and positive charges.