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Diseases » Mercury poisoning » Wikipedia
 

Mercury poisoning in Wikipedia

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Mercury poisoning". (Source - Retrieved 2006-09-07 15:53:07 from http://en.wikipedia.org/wiki/Mercury_poisoning)

Introduction

Mercury poisoning, also known as mercuralism, is the phenomenon of toxication by contact with mercury.

The main dangers associated with elemental mercury are that at standard conditions for temperature and pressure, mercury tends to oxidize forming mercury(II) oxide, and that if dropped or disturbed, mercury will form microscopic drops, increasing its surface area dramatically.

Mercury is known to cause birth defects among herring living in Fremont glacier.

Air saturated with mercury vapor at room temperature is at a concentration many times the toxic level, despite the high boiling point (the danger is increased at higher temperatures).

Watersheds tend to concentrate mercury through erosion of mineral deposits and atmospheric deposition. Plants absorb mercury when wet but may emit it in dry air. Plant and sedimentary deposits in coal contain various levels of mercury. Like plants, mushrooms can also accumulate mercury from the soil.

Human activities, like the application of agricultural fertilizers and industrial wastewater disposal, are examples of how humans release mercury directly into the soil or water. The mercury that is released in the environment ends up in surface water or soils eventually. When the pH values in acidic surface waters are between five and seven, the mercury concentrations in the water will increase. This is due to the mobilization of mercury in the ground near a water source.

Microorganisms are able to convert the mercury that reaches the surface water to methyl mercury and most organisms absorb this substance quickly. Methyl mercury is also known to cause nerve damage. Fish are among the organisms that absorb methyl mercury in great amounts from water. As a consequence, methyl mercury accumulates in fish and passes into the food chain. The deleterious effects of mercury consumed by animals that eat fish include reproductive failure, damage to intestines, stomach disruption, DNA alteration, and kidney damage.

Effects in humans

Mercury is a bioaccumulative toxicant that is easily absorbed through the skin, respiratory and gastrointestinal tissues.

Mercury attacks the central nervous system and endocrine system and adversely affects the mouth, gums, and teeth. High exposure over long periods of time will result in brain damage and ultimately death. (The term "Mad as a hatter" is thought to relate to occupational insanity caused by exposure to mercury compounds in the manufacture of felt hats in the 19th century). Mercury also can have severe effects on fetuses and infants. Mothers who have taken in high levels of mercury have given birth to children with birth defects. Due to this risk, with the exception of some Influenza (flu) vaccines, none of the vaccines used in the U.S. to protect preschool children against 12 infectious diseases contain thimerosal as a preservative.$[1]$

Mercury exposure in very young children can have severe neurological consequences, as a result of the failure of nerve sheaths to form properly. Research has been done that demonstrates the inhibitory effect that mercury has on myelin, the building block protein that forms nerve sheaths.$[2]$$[3]$ Mercury intoxication in the young is suspected by some (for example Mark Geier) as a possible cause of autistic behaviors, although Geier has admitted there is no conclusive evidence to support his suspicion.$[4]$$[5]$

Humans or animals poisoned with mercury or its compounds often manifest excessive salivation, a condition called mercurial ptyalism.

Minamata disease is a form of mercury poisoning.

Another case of widespread mercury poisoning occurred in rural Iraq in 1971-1972, when grain treated with a methyl-mercury-based fungicide, intended for planting, was used instead by the rural population to make bread.

In their policy paper written in 2005, "Mercury in Health Care", The World Health Organization confirmed that "mercury contained in dental amalgam is the greatest source of mercury vapour in non-industrialized settings, exposing the concerned population to mercury levels significantly exceeding those set for food and for air".$[6]$

The possible adverse health effects of dental amalgams containing mercury is an ongoing scientific controversy.

Toxicity of mercury compounds

Elemental, liquid mercury is slightly toxic, while its vapor, compounds and salts are highly toxic and have been implicated as causing brain and liver damage when ingested, inhaled or contacted.

  • The most dangerous mercury compound, dimethylmercury, is so toxic that even a few microliters spilled on the skin, or even a latex glove, can cause death. One of the chief targets of the toxin is the enzyme pyruvate dehydrogenase (PDH). The enzyme is irreversibly inhibited by several mercury compounds, the lipoic acid component of the multienzyme complex binds mercury compounds tightly (mercury binds to the sulfur atoms in lipoic acid) and thus inhibits PDH.
  • Through bioaccumulation, methylmercury in the environment works its way up the food chain, reaching high concentrations among populations of some species such as tuna. Mercury poisoning in humans will result from persistent consumption of tainted foodstuffs. Larger species of fish, such as tuna or swordfish, are usually of greater concern than smaller species, since the mercury accumulates up the food chain. The U.S. Food and Drug Administration (FDA) advises women of child-bearing age and children to completely avoid swordfish, shark, king mackerel and tilefish and to limit consumption of King Crab, Snow Crab, albacore tuna and tuna steaks to 6 oz. or less per week. However, there is no evidence that moderate consumption of fish in the U.S. poses a health hazard. In fact, a recent Harvard Medical School study of mothers and their infants suggests that the nutritional benefits of fish outweigh the effects of methylmercury.$[7]$ In the HMS study, each additional weekly serving of fish consumed by the mother during pregnancy was associated with an increase in infant cognition.
  • Ethylmercury is a breakdown product of the antibacteriological agent thimerosal which has effects similar but not identical to methylmercury.
  • Even though it is far less toxic than its organic compounds, elemental mercury still poses significant environmental pollution and remediation problems due to the fact that mercury forms such organic compounds inside living organisms. Inorganic mercury is less toxic than organic compounds (molecules containing carbon).

Treatment

The Standard of Care for mercury poisoning is chelation therapy. Conventional medicine makes use of DMSA (US) along with DMPS and ALA (Ex-Soviet Union, Europe).

Alternative medicine makes use of these same substances along with others, such as EDTA and "high sulfur foods". Homeopaths also claim to have approaches to the symptoms of mercury poisoning. While these practitioners believe that their approaches can support the body's own ability to heal itself, and can thus help with the symptoms of mercury poisoning, the human body is incapable of removing mercury or other heavy metals from the brain.

Since chelators move heavy metals, and since heavy metals are neuro-toxins, any use of such substances either conventional or alternative, should be well considered.

References

  1. http://www.cdc.gov/nip/vacsafe/concerns/thimerosal/default.htm
  2. http://movies.commons.ucalgary.ca/showcasetv/mercury
  3. http://www.cem.msu.edu/~reusch/VirtTxtJml/lipids.htm
  4. http://www.generationrescue.org/pdf/bernard.pdf
  5. http://www.the7thfire.com/AuBernard.htm
  6. http://www.who.int/water_sanitation_health/medicalwaste/mercurypolpaper.pdf
  7. Maternal Fish Consumption, Hair Mercury, and Infant Cognition in a U.S. Cohort
 

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