Mercury poisoning

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 oxidizeforming mercury oxide, and that if dropped or disturbed, mercury will form microscopic drops, increasing its surface area dramatically.

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).

Watershedstend 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.

Effects in humans

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

Mercury attacks the central nervous systemand endocrine systemand 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). It can pose a major health risk to an unborn fetus.

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

Minamata diseaseis a form of mercury poisoning.

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

Toxicity of mercury compounds

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

• One of the most dangerous mercury compounds, dimethylmercury, is so toxic that even a few microliters spilled on the skin 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 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.

• Ethylmercury is a breakdown product of the antibacteriological agent thimerosalwhich 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 pollutionand remediationproblems due to the fact that mercury forms such organic compounds inside living organisms. Inorganic mercury is less toxic than organic compounds (molecules containing carbon).

External links

• GotMercury.Org, a mercury-in-fish calculator, which uses FDA mercury data with the EPA's formula to determe your safe exposure levels of mercury in fish.
• National Pollutant Inventory - Mercury and compounds Fact Sheet
• NIH
• eMedicine
• Trees
• NRDC: Mercury Contamination in Fish

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Mercury+poisoning Wikipedia article Mercury poisoning.