Nevada Test Site and the downwinders

On January 27, 1951, an Air Force bomber dropped a one kiloton device on Frenchman Flat, the first test at what became the Nevada Test Site, about 105 kilometers northwest of Las Vegas. Between 1951 and 1958 the United States exploded 100 nuclear weapons in the open air there. Winds carried the radioactive clouds east over ranches and towns in southern Utah, Nevada and northern Arizona, and fallout reached much of the country. The Atomic Energy Commission told the people living downwind, who came to call themselves downwinders, that the levels were harmless, and urged them not to worry when dust fell on their homes.¹²

In 1953, thousands of sheep died after the Upshot-Knothole tests, and the AEC blamed malnutrition; court records later showed its scientists had suspected radiation. Communities reported clusters of leukemia and other cancers. A 1997 National Cancer Institute study estimated that iodine-131 from the tests, absorbed mainly through milk, could cause thousands of thyroid cancers nationwide. In 1990 Congress passed the Radiation Exposure Compensation Act, offering payments to downwinders in designated counties, and in 2025 it extended and widened the program.²³