Wednesday, April 30, 2014

Mercury: Pollution and Poisoning

       
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Mercury is a heavy metal that is commonly recognized by its symbol “Hg” and atomic number 80.  The
element appears silver in color, is liquid at room temperature and evaporates readily.  It is naturally contained within a variety of rocks, including cinnabar deposits, limestone and coal.  And though it does occur in nature, it is very toxic to plants, animals and humans once it enters the environment, at which point it persists for long periods of time.  This can happen via fossil fuel combustion (specifically coal), production of cement and metal and mining (small-scale gold). 
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The World Health Organization considers mercury to be “highly toxic to human health.”  If the element is inhaled or ingested it may be detrimental to a variety of organ systems; these include the immune, digestive and nervous systems.  Minor indications of poisoning include headaches, weakness, and a continuous bitter taste in the mouth.   Because it does affect individuals neurologically, mercury is sometimes referred to as a neurotoxin.  Mainly damage is done to the cerebellum, which is responsible for motor control (coordination, balance).  Those affected typically display signs of stumbling, tremors and difficult speaking and/or swallowing.  The inorganic salts that form are able to breakdown cellular components of the skin, eyes and gastrointestinal tract.  Most of these damages, especially neurological, that humans experience are permanent.     
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      As mentioned before, mercury is released into the environment through a variety of industrial processes.  The two most common methods are coal burning and small-scale gold mining.  The combustion of fossil fuels is the number one contributor to global mercury pollution.  Artisanal small-scale gold mining is the second largest source of emissions.  There are nearly seventy countries that practice mining.  These unregulated operations contain between ten and fifteen million miners in the world.  Individuals obtain a muddy sample and add mercury.  This allows for the binding of the molecule to gold particles, resulting in a compound known as amalgram.  Finally, it is boiled or burned which allows for the extraction of gold.  There are a number of environmentally friendly practices that use less mercury or none at all, however many miners are of lower socioeconomic status and cannot afford these methods.   
 
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       Mercury pollution is considered an issue in most parts of the world.  Asia produces approximately fifty percent of the world’s emissions, whereas North America adds seven percent and Europe and North Africa together only result in twelve percent.  The emissions from China’s coal plants severely affect those living in higher elevations in different parts of the world.  These individuals may not contribute as much but are still experiencing the pollution.  It is also more likely for people living closer to mining sites to be exposed to increased levels of mercury.  In 2012, a study was performed in which hair samples from 1029 individuals within twenty-four communities of Lima, Peru were tested for the toxic element.  Data showed that natives living near the Wildcat Alluvial Gold Mining Industry were 2.3 times more likely to have high (five times higher than acceptable) levels of mercury than non-indigenous people.  It is also likely that these individuals are being affected by their greater fish intake.  In the Amazon nearly sixty percent of fish species are contaminated with unacceptable levels mercury.  Indonesia is another relatively polluted area and is known for the “Minamata Disease,” also referred to as mercury poisoning or intoxication.  There is an even larger issue within this location due to the combination of mercury and cyanide.  The latter substance aids in removing mercury.  However, if it is not handled correctly it will form methyl mercury.  This form is even more toxic and is responsible for the Minatama disease.  Other Asian countries follow this similar process and have ended up contaminating their rice paddy fields, thus introducing methyl mercury to their food.       
       
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A number of
approaches are being implemented to attempt to reduce current levels of mercury and prevent future pollution.  In 2011, the European Union banned the exportation of the element and published rules and regulations concerning the storage and use of mercury in other products.  For example, thermometers no longer contain the element but are instead made with alcohol.  The EU continues to debate the issue of battery and dental filling material being manufactured with mercury.  In the United States, mercury bans were introduced in January of 2013 which prohibited exportation.  Furthermore, the Environmental Protection Agency has launched new regulations for coal burning.  It is not yet complete but the idea is that controlling emissions such as nitrogen oxide and sulfur dioxide will result in an overall decrease of mercury.  This has been referred to as a “co-benefit” and may be advantageous for Asia due to its lack of mercury control and large number of coal plants.  In Indonesia the Assistant Deputy Minister of the Environment, Halimah Syafrul, is attempting to cease all illegal mercury imports.  Finally, more than 140 countries around the world, including Norway, Switzerland and Japan, have adopted and support the United Nations’ Mercury Emissions Treaty, also known as the Minamata Convention.  The goal of the treaty is to eliminate mercury used in mining, power plants and within certain products and other industrial procedures.  Limits are to be set that may not be exceeded, while communities are encouraged to use eco-friendly alternatives.




 

2 comments:

  1. In the developing world, our food supply is the most likely concentrated source of mercury. While we are figuring out how to reduce the emissions that contaminate aquatic food chains (and especially top-predator species such as tuna), it may be a good idea to moderate (not stop, if you are a sushi/seafood fan) fish consumption, and to learn about which fish species are less contaminated.
    http://www.health.harvard.edu/blog/make-smart-seafood-choices-minimize-mercury-intake-201404307130

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  2. Here's another set of fish consumption guidelines:
    http://www.nrdc.org/health/effects/mercury/guide.asp

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