Who is spreading radiation poisoning, and how is it being done?

The radiation poisoning travels with the wind. They believe it's traveling from Tallahassee.

"Lucky east wind," Randy said, and then was surprised at his words. The danger of radiation was still there, and might increase. Long before this day scientists had been worried about tests of nuclear weapons, even when conducted in uninhabited areas under rigid controls. Now the danger obviously was infinitely greater, but since there were other and more immediate dangers, dangers that you could see, feel, and hear-radiation had become secondary. He wasn't thinking of its effect upon future generations. He was concerned with the present. He wasn't exercised over the fallout blanketing Tallahassee from the attack on Jacksonville. He was worried about Fort Repose.