The finger of blame pointed to the same bomb tests in Nevada. NCI focused on thyroid cancer among children, since this is a signature disease of fallout exposure. They now find that children's exposure across the U.S. was 10 to 100 times worse than official estimates at the time of the bomb tests. That was four to 10 times the expected levels. These high levels in the U.S. West exceed those that Russian children near Chernobyl got after the 1986 accident there.
Nuclear tests produce radioactive iodine as one of their many radioactive by-products.
The iodine spreads on dusts and through fallout to grasslands, then the cows eat the grass and concentrate the radioactive chemicals in their milk. When children drink the radioactive milk, the iodine goes directly to the thyroid glands in their necks and is stored there. Every eight days, half of the iodine radiation is deposited in the tissue of the thyroid and cancerous lesions may develop. These victims must take drugs for the rest of their lives to replace the hormones their bodies no longer produce. These are only a small percentage of the roughly 1,000 people who die each year from this cancer.