Mercurial salts nervous system

Mercury exists in the environment in three main chemical forms elemental mercury (Hg°), inorganic mercurous (Hg+) and mercuric (Hg2+) salts, and organic methylmer-cury (CH3Hg) and dimethylmercury (CH3HgCH3) compounds. Elemental mercury, in the form of mercury vapor, is almost completely absorbed by the respiratory system, whereas ingested elemental mercury is not readily absorbed and is relatively harmless. Once absorbed, elemental mercury can cross the blood-brain barrier into the nervous system. Most exposure to elemental mercury tends to be from occupational sources. 

Mercury can exist in several forms and all of them are toxic. Thus the element itself is poisonous because hquid mercury vaporizes and the vapour can be inhaled and absorbed. It can enter the brain in this state and cause damage there. The salts of mercury (inorganic mercury) can also be absorbed from the gut and can damage the kidneys. Finally, mercury can exist as organomercury in which it is part of an organic compound. These are also very toxic and damage the brain and nervous system. Mercury is... 

Breathing in or swallowing large amounts of methylmercury also results in some of the mercury moving into the brain and affecting the nervous system. Inorganic mercury salts, such as mercuric chloride, do not enter the brain as readily as methylmercury or metallic mercury vapor. 

Inorganic salts of mercury do not readily cross the blood-brain barrier or the placenta. They are, therefore, ultimately less toxic to the central nervous system and the developing fetus than either absorbed metallic mercury or organic mercury compounds. Metallic mercury is more readily oxidized to... 

The most sensitive end point following oral exposure of any duration to inorganic salts of mercury appears to be the kidneys. Liquid metallic mercury can volatilize at ambient temperatures. The absorption of metallic mercury vapors from lungs is high (about 80%) (Hursh et al. 1976), and the most sensitive target following inhalation exposure to metallic mercury is the central nervous system. 

A variety of effects have been observed in animals treated with toxic doses, but some of these, such as renal damage and anorexia, have not been observed in humans exposed to high doses. The primary tissues of concern in humans are the nervous system and particularly the developing brain, and these have been the main reason for the wide range of epidemiologial studies. Methylmercury passes about ten times more readily through the placenta than other mercury compounds. The dermal absorption of methylmercury is similar to that of inorganic mercury salts. 

The term biocide is not used much in the scientific literature. It may be used for a substance that is toxic and kills several different life-forms. Mercury salts (Hg++) may be called biocides because they are toxic for microorganisms, animals, and many other organisms, whereas DDT is not a biocide because of its specificity toward organisms with a nervous system (animals). 

Elemental mercury is mainly hazardous as the vapor. There is less danger of absorbing the metal for the digestive tract. Like the alkylmercurials, elemental Hg affects the central nervous system, accompanied with such symptoms as tremors, irritability, and sleeplessness. Kidney damage is also reported as a result of the influence of inorganic mercury salts due to a complexation of mercury by the protein metallothionein, which accumulates in the renal tubules. 

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