The first signs of trouble came from the sheep. Local ranchers observed sheep with signs of burns, bleeding lips, hide that sloughed off with a touch. Lambs were born with severe birth defects, and consequently died. The ranchers were convinced radiation from nuclear testing was the cause; the Atomic Energy Commission denied all accusations. In 1956, Utah ranchers took the federal government to court, alleging the loss of more than 4,000 animals. They lost.
In subsequent years, communities in southern Utah began to notice a troubling phenomenon — friends, neighbors, and relatives were being diagnosed with cancer. Cancer clusters were emerging in different communities, with relatively rare cancers such as thyroid cancer and leukemia showing up even among children.
When a nuclear bomb is detonated, it releases a variety of different radioactive materials, such as cesium-137, iodine-131, strontium-90, barium-140, among others. Some of these radioactive isotopes can remain in the human body for decades (cesium-137 has a radioactive half-life of 30 years) but even radioactive isotopes with shorter half-lives can cause problems. One such isotope is iodine-131. In the same way that mercury collects in aquatic animals at the top of their food chain, such as tuna, iodine-131 collected in the thyroid glands of children living in southern Utah — children who drank milk from local cows that had grazed on grass on which nuclear fallout containing iodine-131 had landed.