World iodine

The thyroid hormones T3 and T4 are unique in that iodine (as iodide) is an essential component of both. In most parts of the world, iodine is a scarce component of soil, and for that reason there is htde in food. A complex mechanism has evolved to acquire and retain this cmcial element and to convert it into a form suitable for incorporation into organic compounds. At the same time, the thyroid must synthesize thyronine from tyrosine, and this synthesis takes place in thyroglobuhn (Figure 42-11). 

In the United States and most parts of the world, iodine is obtained com-merciaUy from brine wells. Many subsurface brines have iodine concentrations in the range of 10 to 100 mg/L. Various extraction processes are known including (i) precipitation with silver nitrate, (ii) oxidation with chlorine, and (hi) ion exchange. In the chlorine oxidation process, natural subsurface brine first is acidified with sulfuric acid and then treated with chlorine. Chlorine hberates iodine from the brine solution. Iodine is blown out into a counter-current stream of air. It is dissolved in a solution of hydriodic acid and sulfu-... 

Between 1982 and 1986, the world iodine production remained fairly stable and amounted to approximately 12 500 tons per year. Japan accounted for 57% of the world s production, followed by Chile (23%) and the former Soviet Union (15%). In Japan, iodine is produced entirely as a byproduct of natural gas production. Chile has large reserves of iodine associated with sodium nitrate deposits (Lyday 2002). 

Mali is a landlocked country in West Africa, and is one of the poorest countries in the world. Iodine deficiency disorders (IDD) have been prevalent in several areas of the country, especially in the southern part. This chapter provides a historic overview of the changes in IDD over time, and of the various strategies that have been implemented to combat IDD. While the national total goiter rate was estimated to be 30% in 1974, a nationwide survey in 2005 found a total goiter rate of 8%, with 88% of the households using iodized salt. The latest figures indicate that Mali still suffers from iodine deficiency, and that efforts must continue in order to reach the goal of universal salt iodization. 

Mineral Deposits. The only iodine obtained from minerals has been a by-product of the processing of nitrate ores in Chile. CaUche occurs in the Atacama desert of Northern Chile and west of the Andes mountains. The Atacama desert is known as the driest of the world s deserts, where measurable (>1 mm) rainfalls may be as infrequent as once every 5—29 years (58). The caUche deposits occur in an area averaging 700 km (north—south) by 30 km (east—west). The iodine may total over 5 x 10 t (59). 

Brines. About 65% of the iodine consumed in the world comes from brines processed in Japan, the United States, and the former Soviet Union (see Chemicals frombrine). The predorninant production process for iodine from brines is the blow-out process, which was first used in Japan. Iodine is present in brines as iodide, and its concentration varies from about 10 to 150 ppm. As shown in Figure 3, the recovery process can be divided into brine clean-up, iodide oxidation to iodine followed by air blowing out and recovery, and iodine finishing. 

Not considering the former USSR, world production of iodine was ca 13,500 metric tons in 1992. Japan provided about 45% of the world total, compared to 44% from Chile and 11% from the United States. An annual output of 2300 t from 1976 to 1979 was estimated by the U.S. Bureau of Mines (66) but was revised to 2000 tons in 1981. No official data are available for the former USSR where iodine production is reported to be produced from iodine—bromine brines. Two areas have been mentioned the Neftechalinki field in the Slavianski-Triotskoe area near the Black Sea, and a plant in the Baku area in Azerbaidzhan on the Caspian Sea where ca 1400 metric tons was estimated for 1990 production. 

It is difficult to define the normal range of iodine intake in humans, and despite efforts to provide iodine supplementation in many geographic areas of the world, endemic iodine deficiency and attendant goiter remain a world health problem (147). Exposure to excess iodine may sometimes lead to the development of thyroid disease. This unusual type of iodide-induced goiter has been found, for example, in 10% of the population of a Japanese island where fishermen and their families consume large quantities of an iodine-rich seaweed and have an iodine intake as high as 200 mg/d (148). 

Iodized Salt. Iodized table salt has been used to provide supplemental iodine to the U.S. population since 1924, when producers, in cooperation with the Michigan State Medical Society (24), began a voluntary program of salt iodization in Michigan that ultimately led to the elimination of iodine deficiency in the United States. More than 50% of the table salt sold in the United States is iodized. Potassium iodide in table salt at levels of 0.006% to 0.01% KI is one of two sources of iodine for food-grade salt approved by the U.S. Food and Dmg Administration. The other, cuprous iodide, is not used by U.S. salt producers. Iodine may be added to a food so that the daily intake does not exceed 225 p.g for adults and children over four years of age. Potassium iodide is unstable under conditions of extreme moisture and temperature, particularly in an acid environment. Sodium carbonate or sodium bicarbonate is added to increase alkalinity, and sodium thiosulfate or dextrose is added to stabilize potassium iodide. Without a stabilizer, potassium iodide is oxidized to iodine and lost by volatilization from the product. Potassium iodate, far more stable than potassium iodide, is widely used in other parts of the world, but is not approved for use in the United States. 

The main metals in brines throughout the world are sodium, magnesium, calcium, and potassium. Other metals, such as lithium and boron, are found in lesser amounts. The main nonmetals ate chloride, sulfate, and carbonate, with nitrate occurring in a few isolated areas. A significant fraction of sodium nitrate and potassium nitrate comes from these isolated deposits. Other nonmetals produced from brine ate bromine and iodine. 

Occurrence. Iodine [7553-56-2] is widely distributed in the Hthosphere at low concentrations (about 0.3 ppm) (32). It is present in seawater at a concentration of 0.05 ppm (33). Certain marine plants concentrate iodine to higher levels than occur in the sea brine these plants have been used for their iodine content. A significant source of iodine is caUche deposits of the Atacama Desert, Chile. About 40% of the free world s iodine was produced in Japan from natural gas wells (34), but production from Atacama Desert caUche deposits is relatively inexpensive and on the increase. By 1992, Chile was the primary world producer. In the United States, underground brine is the sole commercial source of iodine (35). Such brine can be found in the northern Oklahoma oil fields originating in the Mississippian geological system (see Iodine and iodine compounds). 

A large reserve of caUche ore bearing iodine is being processed in the Atacama Desert. Production of iodine there is relatively inexpensive. About 40% of the world supply of iodine is made from these Chilean deposits. The process consists of leaching the caUche with water. Brine is stripped of iodine using an organic solvent. The iodine is then removed from the solvent to form a slurry. SoHd-phase iodine is separated from the slurry in conventional flotation cells, dried, and packaged. Details of the process are proprietary. 

Economic Aspects and Uses. Most of the iodine used in the United States comes from Japan and Chile. The United States produces 10% of the world supply but consumes 30%. Production in Chile appears to be relatively low cost, and the product there presently controls prices. Iodine is produced in Woodward and Vici, Oklahoma. These two locations produce about 30% of the 4000 tons used yearly in the United States. Total world consumption is 10,000 to 12,000 tons per year. Prices range from 20.00/kg in 1988 to 12.5/kg in 1991. 

The first iodine-containing mineral (Agl) was discovered in Mexico in 1825 but the discovery of iodate as an impurity in Chilean saltpetre in 1840 proved to be more significant industrially. The Chilean nitrate deposits provided the largest proportion of the world s iodine until overtaken in the late 1960s by Japanese production from natural brines (pp. 796, 799). 

The newest process to be developed oxidizes the brine with CI2 and then treats the solution with an ion-exchange resin the iodine is adsorbed in the form of polyiodide which can be eluted with alkali followed by NaCl to regenerate the column. About 65% of the iodine consumed in the world comes from brines. 

World production of I2 in 1992 approached 15 000 tonnes, the dominant producers being Japan 41%, Chile 40%, USA 10% and the former Soviet Union 9%. Crude iodine is packed in double polythene-lined fibre drums of 10-50-kg capacity. Resublimed iodine is transported in lined fibre drums (11.3 kg) or in bottles containing 0.11, 0.45 or 2.26 kg. The price of I2 has traditionally fluctuated wildly. Thus, because of acute over-supply in 1990 the price for I2 peaked at 22/kg in 1988, falling to 12/kg in 1990 and 9.50/kg in 1992. Unlike CI2 and Br2, iodine has no predominant commercial outlet. About 50% is incorporated into a wide variety of organic compounds and about 15% each is accounted for as resublimed iodine, KI, and other inorganics. The end uses include catalysts for synthetic rubber manufacture, animal- and fowl-feed supplements. 

The amino acid tyrosine is the starting point in the synthesis of the catecholamines and of the thyroid hormones tetraiodothyronine (thyroxine T4) and triiodothyronine (T3) (Figure 42-2). T3 and T4 are unique in that they require the addition of iodine (as T) for bioactivity. Because dietary iodine is very scarce in many parts of the world, an intricate mechanism for accumulating and retaining T has evolved. 

Knoche, K.F. et al, Second law and cost analysis of the oxygen generation step of the general atomic sulfur-iodine cycle, in Proc. 5th World Hydrogen Energy Conf, Toronto, 2, 487, July, 1984. 

Situated between the solid and gaseous states as the only non-metallic element liquid at ambient temperature, bromine is sandwiched in the periodic table between the ubiquitous chlorine and the rather rare iodine. In terms of production volumes it is neither a bulk commodity chemical like chlorine, nor a speciality chemical like iodine. And commercially, bromine is beset by uncertainty. Until the 1970s, the major market forbromine was in dibromoethane - a co-additive for leaded petrol. The phase-out of lead in petrol could have spelled the collapse of the bromine industry, but alternative bromine markets developed and the industry both rationalised and flourished. However, although world bromine production continues to increase slowly, fresh environmental concerns have emerged and the industry is once more under threat. Details are given. 19 refs. 

Elements and compounds constitute the world of pure substances. An element is a substance that cannot be decomposed by any chemical reaction into simpler substances. Elements are composed of only one type of atom and all atoms of a given type have the same properties. Pure substances cannot be separated into other kinds of matter by any physical process. We are familiar with many pure substances water, iron, mercury, iodine, helium, rust, diamond, table salt, sugar, gypsum, and so forth. Among the pure substances listed above, iron, mercury, iodine, diamond (pure carbon), and helium are elements. We are also familiar with mixtures of pure substances. These include the air that we breathe, milk, molasses, beer, blood, coffee, concrete, egg whites, ice cream, dirt, steel, and so on. 

WHO. WHO assessment of iodine deficiency disorders and monitoring their elimination. A guide for programme managers. 2nd ed. Geneva (Switzerland) World Health Organization 2001. 

WHO/UNICEF/ICCIDD. Iodized oil during pregnancy. Safe use of iodized oil to prevent iodine deficiency in pregnant women. Geneva (Switzerland) World Health Organization 1996. (WHO/NUT/96.5). 

Worldwide, the most common thyroid disorder is hypothyroidism resulting from dietary iodine deficiency. In iodine-replete areas of the world, most thyroid disorders are the result of autoimmune disease. The symptoms manifested in hypothyroid and hyperthyroid states are largely independent of any underlying disorder of the thyroid gland itself they are a function of the degree of hormone deficiency or excess. 

A second dietary trace element, selenium, is also essential for normal thyroid hormone metabohsm. Selenium in the form of selenocysteine is a required component for three enzymes that remove iodide from thyroid hormones. Deiodination is the major metabohc pathway by which T4 and T3 are cleared from the system. After secretion by the thyroid gland, T4 may be deiodinated to yield either T3 or the physiologically inactive reverse Tj (3,3, 5 -triiodothyronine, or rX3). T3 and rTj are further deiodinated to form less active metabolites. Selenium, like iodine, is deficient in many areas of the world. 

An adequate dietary intake of iodine is essential to prevent hypothyroidism. In many areas of the world, dietary iodine intake is insufficient and must be supplemented. There is another element in which a dietary intake may be insufficient that is also associated with thyroid hormone metabolism. This element is... 

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