TOXICITY OF SOME COMMON CONTAMINANTS
RADIONUCLIDES
Caesium
Regardless of the mode of exposure, 137Cs is rapidly absorbed into the bloodstream and distributes throughout the active tissues of the body. Metabolically, 137Cs behaves as an analogue of potassium. Distribution of caesium throughout the body and energetic b and c radiation from the decay progeny, 137mBa, result in essentially whole body irradiation.
Radium
Radium, as a metabolic analogue of calcium, is readily absorbed through the gastrointestinal tract or the lungs into the bloodstream and subsequently is deposited in the bones. Values for fractional absorption through the gastrointestinal tract have been observed in the range from 0.15 to 0.21. During the first few days after intake, radium becomes heavily concentrated on bone surfaces, and then gradually shifts its primary deposition site to bone volume. A large percentage of subjects exposed to high doses of radium have developed bone cancer.
Lead
Lead is a chemical element in the carbon group with symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft and malleable metal, which is regarded as a heavy metal and poor metal. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid.
Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield. Lead has the highestatomic number of all of the stable elements, although the next higher element, bismuth, has a half-life that is so long (much longer than the age of the universe) that it can be considered stable. Its four stable isotopes have 82 protons, a magic number in thenuclear shell model of atomic nuclei.
If ingested, lead is poisonous to animals, including humans. It damages the nervous system and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones.
Mercury
Mercury is a chemical element. Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion, a pure form of mercuric sulfide, is mostly obtained by reaction of mercury (produced by reduction from cinnabar) with sulfur. Cinnabar is highly toxic by ingestion or inhalation of the dust. Mercury poisoning can also result from exposure to water-soluble forms of mercury (such as mercuric chloride ormethylmercury), inhalation of mercury vapor, or eating seafood contaminated with mercury.
Arcenic
Arsenic is a heavy metal that exists in three metallic forms, alpha or yellow, beta or black and gamma or grey. It also exists in compounds that may be organic or inorganic. Poisoning can occur by ingestion, inhalation and dermal absorption. Inorganic compounds are much more toxic than organic compounds. Elemental arsenic is least toxic. Trivalent arsenic is well absorbed through the skin and is 60 times more toxic than pentavalent arsenic, which is well absorbed by the gut.[1] Arsine gas is highly toxic.
Toxicity is due to arsenic's effect on many cell enzymes, which affect metabolism and DNA repair. Arsenic is excreted in urine, but can also accumulate in many body tissues.[2]
Arsenic has been used in medicines, as a pigment, a pesticide, and as a weapon of murder. It shares many toxic features with the other heavy metals like mercury and lead. It is used in the production of glass and semiconductors. It is found in some water supplies and seafood, and is used in various industries.
Toxicity is due to arsenic's effect on many cell enzymes, which affect metabolism and DNA repair. Arsenic is excreted in urine, but can also accumulate in many body tissues.[2]
Arsenic has been used in medicines, as a pigment, a pesticide, and as a weapon of murder. It shares many toxic features with the other heavy metals like mercury and lead. It is used in the production of glass and semiconductors. It is found in some water supplies and seafood, and is used in various industries.
Cyanide
| Cyanide | |
|---|---|
 | |
| Properties | |
| Molecular formula | CN− |
| Molar mass | 26.007 g mol-1 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
A cyanide is any chemical compound that contains monovalent combining group CN. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogenatom.[1]
In inorganic cyanides, such as sodium cyanide, NaCN, this group is present as the negatively-charged polyatomic cyanide ion (CN-); these compounds, which are regarded as salts of hydrocyanic acid, are highly toxic. The cyanide ion is isoelectronic with carbon monoxide and with molecular nitrogen.[2][3] Most cyanides are highly toxic.[4]
Organic cyanides are usually called nitriles; in these, the CN group is linked by a covalent bond to a carbon-containing group, such as methyl (CH3) in methyl cyanide (acetonitrile).
Hydrocyanic acid, also known as hydrogen cyanide, or HCN, is a highly volatile liquid used to prepare acrylonitrile, which is used in the production of acrylic fibers, synthetic rubber, and plastics. Cyanides are employed in a number of chemical processes, includingfumigation, case hardening of iron and steel, electroplating, and the concentration of ores.
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