On Jul. 29, 1997, the National Cancer Institute (NCI) released information that nuclear testing during the 1950s could be a cause of thyroid cancer and as many as 10,000 to 75,000 people, exposed to the 1950’s fallout as children, could develop thyroid cancer.

During the Cold War in the mid-1940s through early 1960s, the U.S. government conducted about 100 nuclear weapons (atomic bomb) tests in the atmosphere at a test site in Nevada, more than 100 in the Pacific, and one—the first ever—in New Mexico. The radioactive substances released by these tests are known as “fallout.” They were carried thousands of miles away from the test site by winds. As a result, people living in the United States at the time of the testing were exposed to varying levels of radiation.

Among the numerous radioactive substances released in fallout, there has been a great deal of concern about and study of one radioactive form of iodine–called iodine-131, or I-131. I-131 collects in the thyroid gland. People exposed to I-131, especially during childhood, may have an increased risk of thyroid disease, including thyroid cancer.