delayed fallout

Fallout refers to the deposition of radioactive materials from the atmosphere onto Earth. This can originate from natural causes, nuclear explosions, or atomic reactor operations.1

Nuclear explosions produce three types of fallout:
* Local fallout: Larger radioactive particles deposited near the explosion site, intense but short-lived.1
* Tropospheric fallout: Finer particles enter the lower atmosphere and are deposited later over a wider area, typically within a month.1
* Stratospheric fallout: Extremely fine particles in the upper atmosphere can travel worldwide and deposit years later, usually from large nuclear weapons.1

Residual radiation, emitted more than a minute after detonation, includes fallout. Early fallout occurs within 24 hours, while delayed fallout arrives after the first day, dispersed globally. The radioactivity decreases significantly over time; for instance, after seven hours, it drops to about 10 percent of its amount at one hour. Long-lived isotopes like strontium-90 are significant in stratospheric fallout due to their extended half-lives.213