What is exposure to iodine-131?
Between 1951 and 1963, the United States conducted about one hundred above-ground nuclear weapons tests at the Nevada Test Site. These tests released radioactive materials, including iodine-131 (I-131), mainly during 1952, 1953, and 1957. I-131 released from the tests was carried by the wind and deposited on soil and vegetation throughout the United States. The areas most affected were downwind of the test site, to the north and east of Nevada. The areas least affected were on the West Coast of the United States. Because I-131 breaks down quickly, most exposure occurred within three months after each test. The most common way people came in contact with I-131 was through contaminated milk. This was because the I-131 fell onto pasture grasses eaten by cows and goats, and was absorbed into their milk. The I-131 concentrated in the thyroid glands of people who drank milk. Children usually drink larger amounts of milk, so young children absorbed more I-131 than adults did. Children’s thyro
