The Goiânia caesium-137 blue glow
In September 1987, scavengers in Goiânia, Brazil, took a radiotherapy unit from an abandoned clinic and sold it to scrapyard owner Devair Alves Ferreira, who found the caesium-137 powder inside glowing blue and shared it with family and neighbors. His six-year-old niece, Leide das Neves Ferreira, ate with the powder on her hands and was one of four people who died. Hundreds more were contaminated, over 100,000 were screened, and whole houses were demolished as radioactive waste.