First scene: Iodine I-131 ( I-131) was among the radioactive materials released by the atomic bomb tests. (military observers watch mushroom cloud rise above desert.)

Second scene: It was carried thousands of miles away from the test areas on the winds. Because of wind and rainfall patterns, the distribution of fallout varied widely after each test. Therefore, although all areas of the U.S. received fallout from at least one nuclear weapons test, certain areas of North America received more fallout than others. (jet stream disperses I-131, shown as pulsing red dots, across the United States.)

Third scene: I-131 traveled to all states, particularly those in the Midwestern, Eastern, and Northeastern United States, where it fell with the rain. (rain contaminated with I-131 falls on a wheat field.)

Fourth scene: Some of the I-131 collected on pastures and on grasses, where it was consumed by cows and goats. (two grazing cows graze in a field contaminated by rain carrying I-131 particles.)

Fifth scene: When consumed by cows or goats, I-131 collects in the animals' milk. Eating beef from cows exposed to I-131 carried little risk. (a dairy farmer milks a cow. I-131 particles are seen in the pail of fresh milk.)

Sixth scene: Much of the health risk associated with I-131 occurred among milk-drinkers-usually children. (a child is shown drinking milk containing I-131 particles.)

Seventh scene: From what is known about thyroid cancer and radiation, scientists think that people who were children during the period of atomic bomb testing are at higher risk for developing thyroid cancer. (the scene zooms in to the child's neck, continuing to zoom in to show a strand of DNA. a particle of I-131 strikes the DNA, mutating it. the mutated DNA replicates, causing thyroid cancer.)