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Mercury and the Environment

Mercury and the Environment. Bio Sci 2B. Mercury : The Element. Liquid at room temperature Atomic #: 80 Atomic Mass: 200.59 g “Quicksilver” Density: 13.6 g/mL. The Different Forms of Mercury. Exists in different forms: elemental, inorganic, and organic mercury

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Mercury and the Environment

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  1. Mercuryand the Environment Bio Sci 2B

  2. Mercury: The Element • Liquid at room temperature • Atomic #: 80 • Atomic Mass: 200.59 g • “Quicksilver” • Density: 13.6 g/mL

  3. The Different Forms of Mercury • Exists in different forms: elemental, inorganic, and organic mercury • Mercury alloys easily with other metals such as gold, silver, and tin (amalgams). • Important mercury salts include HgCl2, Hg2Cl2, Hg(ONC)2, and HgS (vermillion). • Metallic mercury is used in thermometers, barometers, and fluorescent light bulbs.

  4. How Mercury Enters the Environment • Mercury can enter the environment through human activities such as coal burning and product manufacturing. Mercury can also enter the environment from natural sources such as volcanoes. • Globally, 4800 – 8300 tons of mercury are deposited per year due to both natural and human generated causes.

  5. Bioaccumulation of Mercury • Bioaccumulation of mercury begins when bacteria in soils convert the mercury to methylmercury, a highly toxic form. • The concentrations of methylmercury in large fish can be over a million-fold larger than in the surrounding water. • The methylmercury is concentrated further up the food chain.

  6. Overview of Mercury Health Effects • Almost all people have at least trace amounts of mercury in their tissues. People may be exposed to mercury in any of its forms under different situations. • The effects of mercury exposure can be very severe, subtle, or may not occur at all. • Because young children and unborn fetuses are still developing, they are particularly sensitive to the effects of methylmercury on the nervous system. • Because young children and unborn fetuses are still developing, they are particularly sensitive to the effects of methylmercury on the nervous system.

  7. Methylmercury Effects & Exposure • Organic mercury, such as methyl mercury is more toxic than inorganic mercury. • Symptoms of methylmercury poisoning may include: impairment of the peripheral vision, disturbances in sensations, lack of coordination of movements, impairment of speech, hearing, walking, and muscle weakness. • Methylmercury exposure in the womb, which can result from a mother's consumption of fish and shellfish that contain methylmercury, can adversely affect a baby's growing brain and nervous system. • Impacts on cognitive thinking, memory, attention, language, and fine motor and visual spatial skills have been seen in children exposed to methylmercury in the womb.

  8. Statistics and Details • The reference dose the EPA uses is 0.1 µg/kg body weight/day as an exposure without recognized adverse effects. This is equivalent to about 5.8 µg/L of whole blood. • The EPA estimated that 7% of women of childbearing age would have blood mercury concentrations greater than those equivalent to the reference dose (1997). • It is estimated that more than 300,000 newborns each year may have increased risk of learning disabilities associated with in utero exposure to methylmercury.

  9. Effects of Other Mercury Compounds • Elemental (metallic) mercury primarily causes health effects when it is breathed as a vapor where it can be absorbed through the lungs. • With large acute exposures to metallic mercury vapor, the lungs may be permanently damaged. • High exposures to inorganic mercury may result in damage to the gastrointestinal tract, and the nervous system. • Long term exposure to inorganic mercury affects the kidneys and can cause tubular necrosis. • Organic mercury compounds are more readily absorbed via ingestion than inorganic mercury compounds.

  10. Reducing Mercury Exposure • Fish consumption advisories in 44 states have limited or eliminated the fishing of certain highly mercury contaminated fish. • The FDA maximum permissible level is 1 part of methyl mercury in a million parts of seafood (1ppm). • On March 15th, 2005. the EPA issued the Clean Air Mercury Rule to reduce mercury emissions from coal-fired power plants. This rule will hopefully reduce emissions by 33 tons, nearly 70% when fully implemented. • Medical waste incinerators, which emitted about 50 tons of mercury per year into the air in 1990, have gone down 95% since the EPA issued emission standards for these medical waste incinerators in 1997.

  11. Bibliography • www.epa.gov/mercury/ • www.ems.org/mercury/fish.html • www.lenntech.com/Periodic-chart-elements/Hg-en.htm • www.wicca.com/celtic/ stones/images/cinnabar.jpg

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