mercury contaminated fish and minamat bay incident


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mercury contaminated fish and Minamata bay incident, M.Nadeem Ashraf

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mercury contaminated fish and minamat bay incident

  1. 1. “TOXICITY THROUGH MERCURY CONTAMINATED FISH” M. Nadeem Ashraf M.Sc.(Hons.) Soil Science Soil And Environmental Sciences, UAF 2013-ag-10
  2. 2. INTRODUCTION  Mercury only metal on Earth that can be found in a liquid form at room temperature.  High density  High rate of thermal expansion  Used in Barometer and thermometer  Use in lamps  Industrial production of chloride and NaOH.  Cosmetics etc.
  3. 3. SOURCE OF MERCURY EMISSION  Mercury vapour is emitted to the atmosphere through:  Natural sources  Anthropogenic sources.
  4. 4. NATURAL SOURCES  Natural sources of mercury vapour include volcanoes, as well as rocks, soils and water surfaces.  Mercury is also found naturally in cinnabar, the major ore for the production of mercury. (Clarkson & Magos, 2006)  About 1,000 tons of mercury per year is emitted to the atmosphere by natural sources. (Honda et al., 2006)
  5. 5. ANTHROPOGENIC SOURCES  Anthropogenic sources of mercury vapour include emissions from coal-burning power plants, municipal incinerators, and through the recycling of auto-mobiles.  It is estimated that 50 to 70 percent of the total emission of mercury to the environment is a result of human activity.  About 2,600 tons mercury, is emitted from anthropogenic sources. (Honda et al., 2006)
  6. 6. TYPES OF MERCURY 1) Mercury exists in several forms that differ in toxicity; exposure potential and environmental fate. 2) All toxic and of concern.
  7. 7. ELEMENTAL MERCURY  Routes of exposure  Inhalation: Readily absorbed through lungs  Ingestion : poorly absorbed (<1%)  Dermal: moderate absorption  Sources of exposure  Spills (broken products)  Cultural uses  Dental fillings  Key Toxicities  CNS; kidney
  8. 8. ORGANIC MERCURY  Routes of exposure  Ingestion/ inhalation: >90% absorption  Dermal: well absorbed; % depends on contact time  Sources of exposure  Primarily via ingestion of methyl mercury from fish  Occupational exposures to other forms  Some via inhalation  Key Toxicities  CNS; neurodevelopmental
  9. 9. INORGANIC FORMS: HG+1, +2  Routes of Exposure  Absorption varies depending on precise form  typically low-moderate (5-10%) absorption by inhalation/ingestions. Less via dermal.  Sources of exposure  Minor source of mercury exposure to general population.  Combustion emissions, occasionally in groundwater  Major Toxicities  Skin hypersensitvity (e.g. pinks disease due to calomel)  Kidney; CNS
  10. 10.  For example, sardines contain about 0.01 ppm of mercury while sharks contain from 1 ppm to as much as 4 ppm. (EPA, 2006).
  11. 11. HEALTH HAZARDS OF METHYL MERCURY  Methyl-mercury accumulate in body through fish and shell fish.  Methyl-mercury is easily absorbed in the digestive tract, where it forms a complex with the amino acid cysteine.  This complex enters the blood stream, methyl mercury will accumulate in the brain and cause damage to the central nervous system(CNS).
  12. 12. SYMPTOMS OF METHY-LMERCURY EXPOSURE  Paraesthesia (tingling or numbness is felt in the hands, arms, legs, or feet ).  Ataxia (stumbling or clumsy gait) and generalized weakness.  Higher doses of methyl-mercury poisoning may lead to dysarthria, loss of vision and hearing, tremor, and finally, coma and death. (Shea et al., 2004).
  13. 13. MERCURY LEVELS IN COMMONLY CONSUMED FISH AND SHELLFISH Species fish Mercury concentration (ppm) Shark 0.988 Trout (Freshwater) 0.072 Sardine 0.016 Species - Shellfish Mercury concentration (ppm) Lobster 0.31 Crab 0.06 Oyster 0.013 Source: CFSAN, US FDA, Feb. 2006
  14. 14. MINAMATA BAY INCIDENT  In 1950,s the most severe incident of industrial pollution, mercury poisoning occurred in the small seaside town of Minamata, Japan.  A local petrochemical and plastics company, Chisso Corporation, dumped an estimated 27 tons of methyl- mercury into the Minamata Bay over a period of 37 years.
  15. 15.  Residents of Minamata, who relied heavily on fish for food.  It leads to severe neurological damage and killed more than 900 people.  An estimated 2 million people from the area suffered health problems or were left permanently disabled from the contamination.  This form of toxicity in humans is now called Minamata disease. (McCurry, 2006)
  16. 16. CONTROL  In 1977, the Japanese government took on the huge task of cleaning the sediments in the bay by vacuuming up 1.5 million cubic meters of mercury-contaminated sludge.  After $359 million dollars and 14 years, the project was completed in 1997. (McCurry, 2006)