Silent Fallout: The Green Run Plume

In 1949, a classified experiment at the Hanford Site released a radioactive cloud over the Pacific Northwest. The public wasn’t warned. The documents weren’t declassified until decades later.

This episode of Unsettled: The Hidden Record investigates The Green Run, a top-secret Cold War operation in which U.S. scientists intentionally released iodine-131 and xenon-133 into the atmosphere to study how Soviet fallout might behave. The test blanketed populated areas—schools, farms, entire towns—with radioactive material.

No one was told. There was no evacuation, no advisory, and no long-term study of the affected communities until the 1980s. And even then, most people never knew why their cancer rates were so high.

What happens when national security overrides human safety? And what else was never disclosed?

This is the story of a silent plume—and the invisible line it crossed.