How was nuclear fallout discovered?

Nuclear fallout was discovered in the aftermath of nuclear bomb tests conducted during the late 1940s and early 1950s. Scientists observed radioactive particles and isotopes in the environment, particularly after atmospheric tests. The fallout was identified as a significant health hazard when studies showed increased radiation levels in areas downwind from test sites, leading to concerns about the effects on human health and the environment. This prompted further research and monitoring of radioactive materials released during nuclear detonations.