Abstract
Iodine is an effective, simple, and cost-efficient means of water disinfection for people who vacation, travel, or work in areas where municipal water treatment is not reliable. However, there is considerable controversy about the maximum safe iodine dose and duration of use when iodine is ingested in excess of the recommended daily dietary amount. The major health effect of concern with excess iodine ingestion is thyroid disorders, primarily hypothyroidism with or without iodine-induced goiter. A review of the human trials on the safety of iodine ingestion indicates that neither the maximum recommended dietary dose (2 mg/day) nor the maximum recommended duration of use (3 weeks) has a firm basis. Rather than a clear threshold response level or a linear and temporal dose-response relationship between iodine intake and thyroid function, there appears to be marked individual sensitivity, often resulting from unmasking of underlying thyroid disease. The use of iodine for water disinfection requires a risk-benefit decision based on iodine's benefit as a disinfectant and the changes it induces in thyroid physiology. By using appropriate disinfection techniques and monitoring thyroid function, most people can use iodine for water treatment over a prolonged period of time.
Full text
PDF





Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Boyages S. C., Bloot A. M., Maberly G. F., Eastman C. J., Li M., Qian Q. D., Liu D. R., van der Gaag R. D., Drexhage H. A. Thyroid autoimmunity in endemic goitre caused by excessive iodine intake. Clin Endocrinol (Oxf) 1989 Oct;31(4):453–465. doi: 10.1111/j.1365-2265.1989.tb01269.x. [DOI] [PubMed] [Google Scholar]
- Braverman L. E. Iodine and the thyroid: 33 years of study. Thyroid. 1994 Fall;4(3):351–356. doi: 10.1089/thy.1994.4.351. [DOI] [PubMed] [Google Scholar]
- Braverman L. E., Roti E. Effects of iodine on thyroid function. Acta Med Austriaca. 1996;23(1-2):4–9. [PubMed] [Google Scholar]
- Cooper D. S. Subclinical thyroid disease: a clinician's perspective. Ann Intern Med. 1998 Jul 15;129(2):135–138. doi: 10.7326/0003-4819-129-2-199807150-00016. [DOI] [PubMed] [Google Scholar]
- Corvilain B., Van Sande J., Dumont J. E., Bourdoux P., Ermans A. M. Autonomy in endemic goiter. Thyroid. 1998 Jan;8(1):107–113. doi: 10.1089/thy.1998.8.107. [DOI] [PubMed] [Google Scholar]
- Dunn J. T. What's happening to our iodine? J Clin Endocrinol Metab. 1998 Oct;83(10):3398–3400. doi: 10.1210/jcem.83.10.5209. [DOI] [PubMed] [Google Scholar]
- Ericsson C. D., DuPont H. L. Travelers' diarrhea: approaches to prevention and treatment. Clin Infect Dis. 1993 May;16(5):616–624. doi: 10.1093/clind/16.5.616. [DOI] [PubMed] [Google Scholar]
- Freund G., Thomas W. C., Jr, Bird E. D., Kinman R. N., Black A. P. Effect of iodinated water supplies on thyroid function. J Clin Endocrinol Metab. 1966 Jun;26(6):619–624. doi: 10.1210/jcem-26-6-619. [DOI] [PubMed] [Google Scholar]
- Georgitis W. J., McDermott M. T., Kidd G. S. An iodine load from water-purification tablets alters thyroid function in humans. Mil Med. 1993 Dec;158(12):794–797. [PubMed] [Google Scholar]
- Harjai K. J., Licata A. A. Effects of amiodarone on thyroid function. Ann Intern Med. 1997 Jan 1;126(1):63–73. doi: 10.7326/0003-4819-126-1-199701010-00009. [DOI] [PubMed] [Google Scholar]
- Helfand M., Redfern C. C. Clinical guideline, part 2. Screening for thyroid disease: an update. American College of Physicians. Ann Intern Med. 1998 Jul 15;129(2):144–158. doi: 10.7326/0003-4819-129-2-199807150-00020. [DOI] [PubMed] [Google Scholar]
- Hollowell J. G., Staehling N. W., Hannon W. H., Flanders D. W., Gunter E. W., Maberly G. F., Braverman L. E., Pino S., Miller D. T., Garbe P. L. Iodine nutrition in the United States. Trends and public health implications: iodine excretion data from National Health and Nutrition Examination Surveys I and III (1971-1974 and 1988-1994) J Clin Endocrinol Metab. 1998 Oct;83(10):3401–3408. doi: 10.1210/jcem.83.10.5168. [DOI] [PubMed] [Google Scholar]
- Jubiz W., Carlile S., Lagerquist L. D. Serum thyrotropin and thyroid hormone levels in humans receiving chronic potassium iodide. J Clin Endocrinol Metab. 1977 Feb;44(2):379–382. doi: 10.1210/jcem-44-2-379. [DOI] [PubMed] [Google Scholar]
- Khan L. K., Li R., Gootnick D. Thyroid abnormalities related to iodine excess from water purification units. Peace Corps Thyroid Investigation Group. Lancet. 1998 Nov 7;352(9139):1519–1519. doi: 10.1016/s0140-6736(98)00058-0. [DOI] [PubMed] [Google Scholar]
- Konno N., Makita H., Yuri K., Iizuka N., Kawasaki K. Association between dietary iodine intake and prevalence of subclinical hypothyroidism in the coastal regions of Japan. J Clin Endocrinol Metab. 1994 Feb;78(2):393–397. doi: 10.1210/jcem.78.2.8106628. [DOI] [PubMed] [Google Scholar]
- Koutras D. A. Control of efficiency and results, and adverse effects of excess iodine administration on thyroid function. Ann Endocrinol (Paris) 1996;57(6):463–469. [PubMed] [Google Scholar]
- LeMar H. J., Georgitis W. J., McDermott M. T. Thyroid adaptation to chronic tetraglycine hydroperiodide water purification tablet use. J Clin Endocrinol Metab. 1995 Jan;80(1):220–223. doi: 10.1210/jcem.80.1.7829615. [DOI] [PubMed] [Google Scholar]
- Liel Y., Alkan M. 'Travelers' thyrotoxicosis'. Transitory thyrotoxicosis induced by iodinated preparations for water purification. Arch Intern Med. 1996 Apr 8;156(7):807–810. doi: 10.1001/archinte.156.7.807. [DOI] [PubMed] [Google Scholar]
- MORGAN D. P., KARPEN R. J. Test of chronic toxicity of iodine as related to the purification of water. U S Armed Forces Med J. 1953 May;4(5):725–728. [PubMed] [Google Scholar]
- Martino E., Safran M., Aghini-Lombardi F., Rajatanavin R., Lenziardi M., Fay M., Pacchiarotti A., Aronin N., Macchia E., Haffajee C. Environmental iodine intake and thyroid dysfunction during chronic amiodarone therapy. Ann Intern Med. 1984 Jul;101(1):28–34. doi: 10.7326/0003-4819-101-1-28. [DOI] [PubMed] [Google Scholar]
- Mizukami Y., Michigishi T., Nonomura A., Hashimoto T., Tonami N., Matsubara F., Takazakura E. Iodine-induced hypothyroidism: a clinical and histological study of 28 patients. J Clin Endocrinol Metab. 1993 Feb;76(2):466–471. doi: 10.1210/jcem.76.2.8432791. [DOI] [PubMed] [Google Scholar]
- Mueller B., Diem P., Bürgi U. "Travelers' thyrotoxicosis" revisited. Arch Intern Med. 1998 Aug 10;158(15):1723–1723. doi: 10.1001/archinte.158.15.1723. [DOI] [PubMed] [Google Scholar]
- NAGATAKI S., INGBAR S. H. RELATION BETWEEN QUALITATIVE AND QUANTITATIVE ALTERATIONS IN THYROID HORMONE SYNTHESIS INDUCED BY VARYING DOSES OF IODIDE. Endocrinology. 1964 May;74:731–736. doi: 10.1210/endo-74-5-731. [DOI] [PubMed] [Google Scholar]
- Nagata K., Takasu N., Akamine H., Ohshiro C., Komiya I., Murakami K., Suzawa A., Nomura T. Urinary iodine and thyroid antibodies in Okinawa, Yamagata, Hyogo, and Nagano, Japan: the differences in iodine intake do not affect thyroid antibody positivity. Endocr J. 1998 Dec;45(6):797–803. doi: 10.1507/endocrj.45.797. [DOI] [PubMed] [Google Scholar]
- Nagataki S., Shizume K., Nakao K. Thyroid function in chronic excess iodide ingestion: comparison of thyroidal absolute iodine uptake and degradation of thyroxine in euthyroid Japanese subjects. J Clin Endocrinol Metab. 1967 May;27(5):638–647. doi: 10.1210/jcem-27-5-638. [DOI] [PubMed] [Google Scholar]
- Namba H., Yamashita S., Kimura H., Yokoyama N., Usa T., Otsuru A., Izumi M., Nagataki S. Evidence of thyroid volume increase in normal subjects receiving excess iodide. J Clin Endocrinol Metab. 1993 Mar;76(3):605–608. doi: 10.1210/jcem.76.3.8445017. [DOI] [PubMed] [Google Scholar]
- Nauman J., Wolff J. Iodide prophylaxis in Poland after the Chernobyl reactor accident: benefits and risks. Am J Med. 1993 May;94(5):524–532. doi: 10.1016/0002-9343(93)90089-8. [DOI] [PubMed] [Google Scholar]
- PARIS J., McCONAHEY W. M., OWEN C. A., Jr, WOOLNER L. B., BAHN R. C. Iodide goiter. J Clin Endocrinol Metab. 1960 Jan;20:57–67. doi: 10.1210/jcem-20-1-57. [DOI] [PubMed] [Google Scholar]
- Paul T., Meyers B., Witorsch R. J., Pino S., Chipkin S., Ingbar S. H., Braverman L. E. The effect of small increases in dietary iodine on thyroid function in euthyroid subjects. Metabolism. 1988 Feb;37(2):121–124. doi: 10.1016/s0026-0495(98)90004-x. [DOI] [PubMed] [Google Scholar]
- Pennington J. A. A review of iodine toxicity reports. J Am Diet Assoc. 1990 Nov;90(11):1571–1581. [PubMed] [Google Scholar]
- Robison L. M., Sylvester P. W., Birkenfeld P., Lang J. P., Bull R. J. Comparison of the effects of iodine and iodide on thyroid function in humans. J Toxicol Environ Health A. 1998 Sep 25;55(2):93–106. doi: 10.1080/009841098158539. [DOI] [PubMed] [Google Scholar]
- SAXENA K. M., CHAPMAN E. M., PRYLES C. V. Minimal dosage of iodide required to suppress uptake of iodine-131 by normal thyroid. Science. 1962 Oct 19;138(3538):430–431. doi: 10.1126/science.138.3538.430. [DOI] [PubMed] [Google Scholar]
- Stanbury J. B., Ermans A. E., Bourdoux P., Todd C., Oken E., Tonglet R., Vidor G., Braverman L. E., Medeiros-Neto G. Iodine-induced hyperthyroidism: occurrence and epidemiology. Thyroid. 1998 Jan;8(1):83–100. doi: 10.1089/thy.1998.8.83. [DOI] [PubMed] [Google Scholar]
- Sternthal E., Lipworth L., Stanley B., Abreau C., Fang S. L., Braverman L. E. Suppression of thyroid radioiodine uptake by various doses of stable iodide. N Engl J Med. 1980 Nov 6;303(19):1083–1088. doi: 10.1056/NEJM198011063031903. [DOI] [PubMed] [Google Scholar]
- Surks M. I., Ocampo E. Subclinical thyroid disease. Am J Med. 1996 Feb;100(2):217–223. doi: 10.1016/s0002-9343(97)89462-4. [DOI] [PubMed] [Google Scholar]
- Suzuki H., Higuchi T., Sawa K., Ohtaki S., Horiuchi Y. "Endemic coast goitre" in Hokkaido, Japan. Acta Endocrinol (Copenh) 1965 Oct;50(2):161–176. [PubMed] [Google Scholar]
- Tajiri J., Higashi K., Morita M., Umeda T., Sato T. Studies of hypothyroidism in patients with high iodine intake. J Clin Endocrinol Metab. 1986 Aug;63(2):412–417. doi: 10.1210/jcem-63-2-412. [DOI] [PubMed] [Google Scholar]
- Thomas W. C., Jr, Malagodi M. H., Oates T. W., McCourt J. P. Effects of an iodinated water supply. Trans Am Clin Climatol Assoc. 1979;90:153–162. [PMC free article] [PubMed] [Google Scholar]
- Vagenakis A. G., Downs P., Braverman L. E., Burger A., Ingbar S. H. Control of thyroid hormone secretion in normal subjects receiving iodides. J Clin Invest. 1973 Feb;52(2):528–532. doi: 10.1172/JCI107212. [DOI] [PMC free article] [PubMed] [Google Scholar]
- WILLIAMS E. D., SANDLER M. The classification of carcinoid tum ours. Lancet. 1963 Feb 2;1(7275):238–239. doi: 10.1016/s0140-6736(63)90951-6. [DOI] [PubMed] [Google Scholar]
- WOLFF J., CHAIKOFF I. L. The temporary nature of the inhibitory action of excess iodine on organic iodine synthesis in the normal thyroid. Endocrinology. 1949 Nov;45(5):504-13, illust. doi: 10.1210/endo-45-5-504. [DOI] [PubMed] [Google Scholar]
- Wolff J. Iodide goiter and the pharmacologic effects of excess iodide. Am J Med. 1969 Jul;47(1):101–124. doi: 10.1016/0002-9343(69)90245-9. [DOI] [PubMed] [Google Scholar]