Research will probe effects of radioactive dust on internal exposure in Hiroshima bombing

by Michiko Tanaka, Staff Writer

Research into the effects of radioactive dust on internal exposure to radiation will be launched by Masaharu Hoshi, 64, professor emeritus at Hiroshima University. The atomic bomb that was dropped on Hiroshima made dust radioactive, too. Based on soil samples obtained from various places in the city, Professor Hoshi, an expert in radiation biology and physics, will seek to grasp how far the dust was spread and estimate the amount of radiation.

Radiation risk assessment is currently conducted based on the amount of radiation at the time the atomic bomb exploded. When exposed to the bomb’s strong neutron rays, soil in the city was also made radioactive. However, internal exposure through the inhalation of radioactive dust has not been taken into account in the assessment. For the most part, the effects of radioactive dust have yet to be determined.

In November, soil samples will be collected at several points within one kilometer of the hypocenter. At each point, several samples will be taken between 0.2 and 1 centimeter below the surface using special equipment. The sizes of the grains will be analyzed, and simulations will be carried out on how the dust flew in the air at the time of the bombing. Researchers will try to estimate the dose of internal radiation in each area.

Professor Hoshi will conclude his research and report the findings by the end of this fiscal year. “There are cases in which people who were far from the hypocenter came down with the same symptoms, such as hair loss or diarrhea, as those who were close to the hypocenter,” he said. “It’s hard to explain all these cases based only on the initial dose of radiation at the time of the explosion. We need to conduct a thorough investigation into the effects of dust on internal exposure.”

(Originally published on October 19, 2012)