Abstract
White rats of 30 gram weight were placed on a diet containing about or less than .006 milligram of iodin in 50 grams of dry foodstuff in addition to distilled water. Controls were placed on the same diet except for one day a week when they drank water containing .01 per cent. iodin. At the end of about three months those receiving the iodin had thyroid glands one-half to two-thirds the weight of those receiving no iodin.
The United States is divided into four zones based on the number of goiters too large for wearing military collars per 1,000 drafted men. The amount in parts per billion of iodin in drinking water is also given:
Zone I—Goitre, 1-30. Iodin, 0.1-1. Washington, Oregon, Wyoming, Montana, parts of Utah, Minnesota, Wisconsin, and Michigan.
ZONE II-Goitre, 5-15. Iodin, .015-1.2. Nevada, Colorado, North Dakota, Iowa, Ohio, Indiana, West Virginia, parts of California, Utah, South Dakota, Minnesota, Wisconsin, Michigan, Pennsylvania.
ZONE III-Goitre, 1-5. Iodin, .06-9. Nebraska, Kansas, Missouri, Illinois, Kentucky, Tennessee, parts of California, Arizona, New Mexico, South Dakota, South Carolina, North Carolina, Virginia, Maryland, Pennsylvania, New York.
ZONE IV-Goitre, 0.1. Iodin, 1.4-9.7. Texas Indian Territory, Arkansas, Louisiana, Mississippi, Georgia, Alabama, Florida, parts of Arizona, New Mexico, South Oarolina, and a strip along the Atlantic seaboard.
These zones run from east to west but are diverted southward in the mountainous regions and northward in the Great Plains area which contained a large salt lake centering in Kansas during the Permian period. The goiter-free southern states were submerged beneath the sea even as late as the Pliocene period.
In order to determine the iodin in drinking water quantitatively very large samples are necessary, in fact the smallest sample from Zone I must be at least 25 gallons; Zone II, 15 gallons; Zone III, 10 gallons; Zone IV, 5 gallons.
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