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Suggested Citation:"'IODINE'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
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Page 25
Suggested Citation:"'IODINE'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
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Page 26
Suggested Citation:"'IODINE'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
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Page 27

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TABLE 9 Estimated Total Fluoride Emissions from Major Industrial Sources in the United States, I96SO Source Phosphate fertilizer industry Aluminum industry Steel industry Welding operations Nonfenous metal foundries Ceramics industry (brick, tile, glass, etc.) Combustion of coal Fluorocarbon Atmospheric Emissions, tons/yr 18,700 16,000 40,100 2,700 4,000 21,200 16,000 45,000 a Adapted from Table 2·1, p. 9 (Committee on Biologic Effects of Atmospheric Pollutants, 1971). facilities. Laboratory studies (Henrikson et al., 1970; Moore, 1969a,b) have demonstrated that such marine organisms as oysters and crabs do accumulate fluoride in proportion to concentrations in water, and concentrations above 20- 30 mg/1 result in acute detrimental effects on the survival and growth of the marine invertebrates studied. Investiga- tions on the chronic. effects of low levels of fluoride expo· sure to marine organisms of commercial importance are urgently needed. The fluoridation of public water supplies in many munic· ipalities, now including the water supplies of about half the population of the United States, has greatly affected levels of intake in man, and appreciable amounts are added to human intake by the use of fluoride-containing dentifrices. RECOMMENDATIONS FOR RESEARCH I. Additional detailed studies are needed of the health of human and animal populations exposed to high concen· trations of airborne fluorides. 2. The gross effects of fluoride on plants and animals have been studied, but much needs to be done on the basic biochemical lesions induced by fluoride, and on dietary factors affecting fluoride uptake by man. 3. The very large emission of fluorocarbons (freons) and their rapidly increasing use require study of their distribu· tion, rate of degradation, and possible effects on plants, animals, and humans. 4. Waste waters of high fluoride content have been re- leased from phosphate processing and from the aluminum industry, with detrimental effects to such marine organisms as oysters and crabs. Possible chronic effects from expo- sure of such organisms to lower levels of fluoride need study. 5. In view of the high fluoride content reported to exist in some fish-protein concentrates used as food supplements, the possible impact of this added source of fluoride in the diet should be further investigated. Fluorine 25 6. Methods of sampling and separating gaseous and par· ticulate forms of airborne fluorine need study and stan· dardization. 7. Further work is needed on the relation of the uptake of fluorine by plants to its concentration in the air. 8. Study of the form of fluorine in plants is highly de· sirable, especially the nature of fluorine bonding in plant tissue and its solubility in aqueous solutions. 9. More data are needed on the relation of the fluoride content of ground waters to the mineralogical and chemical composition of the source rocks. REFERENCES Committee on Biologic Effects of Atmospheric Pollutants. 1971. Fluorides. National Academy of Sciences, Washington, D.C. 295 pp. Dymling, J. F. 1964. Calcium kinetics in ostcopenia and parathyroid disease. Acta. Med. Scand. Suppl. 408:1-62. Fleischer, Michael, and W. 0 . Robinson. 1963. Some problems of the geochemistry of fluorine. R. Soc. Can. Spec. Publ. 6:58-75. Henrikson, P. A., L. Lutwalt, L. Krook, R. Skogerboe, F. Kallfelz, L. F. Belanger, J. R. Marier, B. E. Sheffy, B. Romanus, and C. Hirsch. 1970. Fluoride and nutritional osteoporosis: Physico- chemical data on bones from an experimental study on dogs. J. Nutr. 100:631-642. Jowsey, J., B. L. Riggs, P. J. Kelly, and D. L. Hoffman. 1972. Effect of combined therapy with sodium fluoride, vitamin D and cal· cium in osteoporosis. Am. J. Med. 53 :43-49. Ke, P. J., H. E. Power, and L. W. Regier. 1970. Fluoride content of fiSh protein concentrate and raw fish. J. Sci. Food Agric. 21: 108-109. Kister, L. R., S. G. Brown, H. H. Schumann, and P. W. Johnson. 1966. Maps, showing fluoride content and salinity of ground- water in the Willcox Basin, Graham and Cochise Counties, Arizona. U.S. Geol. Surv. Hydro!. Invest. Atlas HA-214. pp. 1-6. Krook, Lennart, L. Lutwalt, P. A. Henrikson, F. Kallfelz, C. Hirsch, B. Romanus, L. F. Belanger, J. R. Marier, and B. E. Sheffy. 1971. Reversibility of nutritional osteoporosis: physico-chemical data on bones from an experimental study on dogs. J . Nutr. 101 : 233-246. Messer, H. H., W. D. Armstrong, and L. Singer. 1972. Fertility im· painnent in mice on a low fluoride intake. Science 177:983-984. Moore, D. J. 1969a. The uptake and concentration of fluoride by the blue crab, Cllllinectes ~t~pldus. PhD thesis, North Carolina State University, Rale;p. 41 pp. Moore, D. J. 1969b. A field and laboratory study of fluoride uptake by oysters. N.C. State Univ. Water Resour. 1nst. Rept. 20:1-13. Saville, P. D., and Lennart Kroolt. 1969. Gravimetric and isotope studies in nutritional hyperparathyroidism in beagles. Clin. Orthop. 43:15- 24. Schwan, K. 1971. Trace elements newly identified as essential to animals. Press release, meeting of the American Association for the Advancement of Science, Philadelphia, Pa., December 28, 1971. Schwan, K., and D. B. Milne. 1972. Fluorine requirement for growth in the rat. Bioinorg. Chem. 1:331-l38. World Health Organization. 1970. Fluorides and human health. WHO Monogr. Ser. No. 5. World Health Organization, Geneva. p. 364.

III Iodine MICHAEL FLEISCHER, Chairman Richard M. Forbes, Robert C. Harriss, Lennart Krook, Joe Kubota The geochemical distribution of iodine and the occurrence of endemic goiter in man represents one of the first recog- nized associations between geochemical environment and health and disease. A dietary deficiency of iodine results in goiter, which, in iodine-deficient areas, can be prevented by iodine supplements. Furthermore, there is now a con- cern about other environmental factors that can result in conditioned deficiencies of iodine, even though analysis indicates that the diet contains normal concentrations of iodine. Neither what constitutes an adequate intake of iodine, nor what the potential is for interference with its utilization, appear to be fully understood at this time (World Health Organization, 1960; Scrimshaw, 1964). CHARACTERISTIC GEOCHEMISTRY AND SOURCES Iodine has atomic number 53 and an atomic weight of 126.90. The natural occurrence of iodine, the least abun- dant of the halogen elements, has not been studied ex- tensively, but its concentration in most igneous and sedi- mentary rocks has generally been given as 0.2-5.8 ppm, with 5-10-times these amounts in shales rich in organic matter, in soils, and in coals (Chilean Iodine Educational Bureau, 1956; Vought et al., 1970). Recent determinations indicate that these values may be too low (Becker et al., 1972). Known iodine minerals include iodiqes of silver and 26 copper and iodates of calcium, copper, and lead. Surface waters contain about 0.002 ppm, presumably present as iodide. Ocean waters contain 0.06 ppm, on the average, present mainly as iodate but partly as iodide. Appreciable amounts of iodine are carried over land as spray derived from the ocean. More information is needed about the chemical speciation of iodine in water, but improved ana- lytical methods must first be devised. Plants Most terrestrial plants are low in iodine, averaging less than 1 ppm (dry wt) (Shacklette and Cuthbert, 1967). Marine plankton and red and brown algae concentrate iodine from 30 to I ,500 ppm, many times the concentration in seawater. The mechanism of uptake by plankton and algae is not understood, nor has the relation of iodine content in soils to its uptake by terrestrial plants been adequately investi- gated. Animals and Man Iodine appears to be unique among the mineral elements essential for animals in that it functions in a single class of organic compounds (iodothyronines) readily synthesized in a discrete tissue, where the inorganic moiety is incorpo- rated into the organic structure. The greatest concentration

of iodine, normally 0.2-0.5 percent of the dry matter (8- 12 mg), is in the thyroid gland. This amount constitutes 70-80 percent of the total content of iodine in the body. The remaining 20-30 percent of iodine is distributed widely in the soft tissues. EFFECTS ON HEALTH The o~y known role of iodine is in the synthesis of the thy- roid hormones, thyroxine and triiodothyronine. These hor- mones are prime regulators of the rate of overall metabolism and are essential for normal growth differentiation of devel- oping tissues. They have regulatory roles in neuromuscular functioning, and are necessary for development and mainte- nance of male and female reproductive functions. Failure to supply adequate amounts of iodine in the diet or interfer- ence with absorption or utilization results in simple goiter. Deficiency of iodine in fetal or early postnatal life can re- sult in cretinism (Scrimshaw, 1964). Areas of endemic goiter in the world are shown in Figure 3. Accurate minimum-requirement fJgUres have not been established, but man remains euthyroid when the diet con- tains about 0.2-0.4 ppm (dry wt). In human adults, this is estimated to be 130-199 p.g/day (Wood, 1970), but the average consumption in the United States may be 2- to 7- times this amount (Oddie et al., 1970; Vought, 1972). Animals are relatively tolerant of iodine many times in excess of the probable requirement of about 300 J.tg. None- theless, toxic effects of large excesses ingested over pro- longed periods can inhibit uptake of iodine by the thyroid •• - ----- - - - - .• 4.'-"-•!1\. - - -- •• - - - - - --- I"ACIFIC OCEAN Iodine 21 gland and, hence, may precipitate a syndrome resembling iodine deficiency. Levels of iodine in the diet required to produce this effect approximate 1,000 ppm or more. Re- covery from excess dosage is rapid when the intake is restored to a normal level. Certain plants contain factors that interfere with iodine utilization by men and animals. These so-called goitrogens are of several general types. One, identified as 5-vinyl-2- thiooxazolidine, inhibits thyroidal peroxidase and thus prevents formation of thyroxine. This material occurs in the brassicae and its effect cannot be counteracted by sup- plementary iodine. A second type of goitrogen, the cyano- genetic glucoside, is found in a number of other plants, such as white clover. This type of goitrogen inhibits the uptake of iodine by the thyroid gland, and its effects can be offset by supplemental iodine. A possible third type of goitrogen, a sulfated unsaturated hydrocarbon, has been isolated from drinking water in Colombia, South America (Gaitan et al., 1972). POLLUTION This has not yet been regarded as a problem, although some evidence has been submitted to suggest that intakes of io- dine by persons in the United States may be several times greater than the normal requirement. The release of radio- active 131 I may need consideration in the future, and iodine intake from fortified salt, bread, and vitamin-mineral prep- arations should be assessed for its possible effect on health . . • . - f•_r:• r INDIAN O(('EA.N \.l- s. ~- lit. ,- -- FIGURE 3 World map, showing occurrence of endemic goiter. Black areas indicate where endemic goiter has been found (Underwood, 1971).

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