Hot particles in the form of alpha-emitting plutonium (Pu-238) were released from the Fukushima nuclear power plant in Japan after it was compromised by the earthquake/tsunami on March 11, 2011.
“Alpha radiation from plutonium and other alpha-emitting radionuclides can be blocked by skin or even a piece of paper but it is the most biologically destructive form of ionizing radiation when the alpha-emitting substance is deposited in the soft tissue of internal organs like the lung. The alpha tracks shown here were captured over a two-day period.” Lawrence Radiation Laboratory, Berkeley California, September 1982.
The following link from the Department of Nuclear Engineering at UC Berkeley takes up the same subject in one of their blogs:
Cancer causing ‘Hot Particles’ detected in Seattle