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The background information page contains information and concepts that will be useful in understanding some of the issues surrounding the NPI. It is strongly recommended that you read this before reading the information presented below.
For an explanation of some of the terms used in this page, see the Glossary
Substance name | Mercury & compounds |
CASR number | 7439-97-6 |
Molecular formula | Mercury (Hg): 7439-97-6; Mercury bichloride (HgCl2): 7487-94-7; Methyl Mercury (CH3Hg+): 22967-92-6 |
Synonyms | Mercury: Quick Silver, Liquid silver, hydragyrum. Mercury bichloride: Mercuric bichloride, mercuric chloride, Bichloride of Mercury, Corrosive Sublimate, Mercury perchloride, Mercury (II) Chloride, Mercury chloride, perchloride of mercury, sublimate |
Physical and chemical properties Physical properties: Mercury, a naturally occurring element, is an odourless, very heavy, silver white, liquid metal. Mercuric chloride is an odourless, white powder or crystal. Both mercury and mercuric chloride are slightly volatile at ordinary temperatures. Mercury: Melting Point (°C): -39 Boiling Point (°C:): 357 Specific Gravity: 13.6 Vapour Pressure (mm Hg/21°C): 0.0012 Mercuric chloride: Melting Point (°C): 277 Boiling Point (°C:): 320 Specific Gravity: 5.4 Vapour Pressure (MM Hg/21°C): 1.3 Chemical properties: |
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Common uses Mercury is used in its pure form in thermometers and barometers. Many batteries contain mercury. It is used in floodlights, streetlights, and other outdoor or powerful lights. It is also used as a catalyst in the chemical manufacturing industry. It is used to conduct electricity (i.e. thermostats). Mercury is used in dental amalgams. It is also used in the mining industry to extract gold and silver ores. Mercuric chloride is used in the manufacture of disinfectants, other chemicals, and as a catalyst. Mercuric chloride is used in photography and embalming. Bacteria in the water and the soil primarily produce methyl mercury. |
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Sources of emissions Point sources Fossil fuel power plants emit to air, precious metal mining operations may emit to water or land, metal smelters may emit to air, cement manufacture may emit to air. Municipal landfills, sewage, metal refining, and chemical manufacturing are also significant potential emitters of mercury to land and water. Diffuse sources, and point sources included in aggregated emissions data Burning of fossil fuels (home heating oil, petrol) emits to air, disposal of batteries, thermometers and other mercury containing products may emit to land, and photographic processing facilities may emit mercury to water. Natural sources Mercury is a naturally occurring element that is found in rocks and ores. Mercury is released into the atmosphere by evaporating from soils, from volcanic activity, and from burning of fossil fuels (coal, oil, petrol, asphalt, etc.). Mobile sources The combustion of petrol releases small amounts of mercury to air. Consumer products which may contain Mercury and compounds Batteries, thermometers, barometers, thermostats, and mercury lights are some of the consumer products that contain mercury. Photographic toners contain mercuric chloride. |
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Health effects How might I be exposed to Mercury and compounds? Mercury can be absorbed through the skin. Workers in the industries that use or produce mercury and its compounds (mercury mines and refineries, chemical manufacturing, dental/health fields, metal smelters) are at risk of exposure. Workers in fossil fuel power plants and in cement manufacturing may be exposed to mercury compounds if they are exposed to gaseous process emissions. Consumers can be exposed to mercury and its compounds by exposure to air from production and processing facilities using mercury and its compounds, by eating fish or shellfish contaminated with methyl mercury. People can also be exposed to mercury from dental work and medical treatments. By what pathways might Mercury and compounds enter my body? Mercury and mercury containing products will enter the body if we breathe in contaminated air, drink contaminated water, eat contaminated food, or have our skin come into contact with it. Mercury may be absorbed through the skin. Mercury released into the environment is converted into methyl mercury by bacteria. The methyl mercury will then build up in the tissues of fish and shellfish. Humans (and other animals) may also be poisoned by eating these fish or shellfish. Relative health hazard On a health hazard spectrum of 0 - 3 Mercury and compounds registers 1.7. A score of 3 represents a very high hazard to health, 2 represents a medium hazard and 1 is harmful to health. Factors that are taken into account to obtain this ranking include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the evaluation of its tendency to cause, or not cause cancer and/or birth defects. It does not take into account exposure to the substance. Human exposure is reflected in the NPI rank given to this substance (see comparative data below). A substance that scores highly as a health hazard is arsenic at 2.3 and one of the lowest scores is ammonia at 1.0. Health guidelines Worksafe Australia: the eight hour time weighted average (TWA) exposure limit is 0.05 mg/m3. Mercury bichloride is also considered to be toxic by inhalation, skin contact, or swallowing. Australian Drinking Water Guidelines (NHMRC and ARMCANZ, 1996): Maximum of 0.001 mg/L (i.e. 0.000001 g/L) See the Additional Information page for current health information. The Australian NOHSC National Exposure Standards Database link is probably the most useful source of information. Note that the emissions data in the NPI database is not directly comparable with these guidelines. What effect might Mercury and compounds have on my health? The nervous system is very sensitive to all forms of mercury. Methyl mercury and mercury metal vapours are especially harmful, because more mercury reaches the brain. Exposure to high levels of any types of mercury can permanently damage the brain, kidneys, and developing foetus. Effects on brain functions may result in irritability, shyness, tremors, changes in vision or hearing and memory problems. High exposures of mercury vapour may cause chest pain, shortness of breath, and a build up of fluids in the lungs (pulmonary oedema). This can cause death. Long term exposures may cloud the eye. Contact with mercuric chloride can cause burns to the skin and permanent damage to the eyes. Mercury accumulates in the body. |
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Environmental effects Environmental Fate When mercury enters the environment from emissions in the air, water or soil, it oxidises into other compounds of mercury. These other forms of mercury form methyl mercury, through either chemical or biological (bacteria) processes. Methyl mercury builds up in the tissues of fish and shellfish. In areas of mercury contamination, larger and older fish tend to have higher levels of mercury. Mercury emitted to the environment will remain for years. Environmental Transport Mercury chloride will act as a particle, following wind patterns, and being deposited by rain. Elemental mercury may be a gas in the atmosphere. Emissions of mercury and or mercury compounds can produce elevated, but still low level concentrations in the atmosphere around the source. Elemental mercury can evaporate from both soil and water into the atmosphere. Relative hazard to the environment On an environmental spectrum of 0 - 3 Mercury and compounds registers 2. A score of 3 represents a very high hazard to the environment and 0 a negligible hazard. Factors that are taken into account to obtain this ranking include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the measure of its ability to remain active in the environment and whether it accumulates in living organisms. It does not take into exposure to the substance. Environmental exposure is reflected in the NPI rank for this substance (see comparative data below). A substance that scores highly as an environmental hazard is oxides of nitrogen at 3.0 and one of the lower scores is carbon monoxide at 0.8. Environmental guidelines Australian Water Quality Guidelines for Fresh and Marine Waters: (ANZECC, 1992): Maximum of 0.0001 mg/L (i.e. 0.0000001 g/L) See the Additional Information page for current environmental guidelines. Note that the emissions data in the NPI database is not directly comparable with these guidelines. What effect might Mercury and compounds have on the environment? Both mercury and its compounds have high acute (short-term) toxicity on aquatic life. They also have high chronic (long-term) toxicity on aquatic life. Eating fish contaminated with mercury has caused poisoning in humans; birds and land animals exposed in the same manner could also be subject to the same effects. There is not sufficient data to determine the acute toxicity of mercury and its compounds on plants, birds or land animals. Mercury and its compounds are highly persistent in water and the environment. Mercury, and its compounds will bioaccumulate or concentrate in the tissues of fish. These concentrations will be considerably higher than the water from which the fish is taken. |
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Comparative data NPI Rank Approximately 400 substances were considered for inclusion on the NPI reporting list. A risk ranking was given based on health and environmental hazard identification and human and environmental exposure to the substance. Some substances were grouped together at the same rank with 208 ranks in total. Mercury and compounds was ranked as 35 out of the 208 ranks. Total hazard score (human health + environmental criteria) = 3.7. |
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Sources of information used in preparing this article
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Additional information provides more details on information sources.
Last Updated: Wednesday, 23-Oct-2002 13:44:43 EST |