5 Juin 2017
June 5, 2017
Radiation doses 29% higher than thought indoors after A-bombs
By SONOKO MIYAZAKI/ Staff Writer
HIROSHIMA--People who were indoors when the atomic bombs struck Hiroshima and Nagasaki may have been exposed to a radiation dose 29 percent higher than previously believed, a study group said June 4.
At an atomic bomb disease research meeting here, the group cited the overestimation of the shield effect of structures as a reason for the underestimated radiation levels.
In the study, the group reanalyzed the causal link between the frequency of chromosomal abnormalities of atomic bomb survivors--1,980 in Hiroshima and 1,062 in Nagasaki--and their exposed doses, which had been released by Radiation Effect Research Foundation, a Japan-U.S. joint research organization.
After the re-evaluation, the group concluded that radiation levels of indoor survivors had been underestimated when taking into consideration their chromosome abnormalities.
It also found that chromosome abnormalities occurred among atomic bomb victims who had been indoors at a 40 percent higher frequency than those who had been outdoors at the time of the atomic bombing in Hiroshima on Aug. 6, 1945.
This might have been caused by internal exposure to dust and other substances that entered the buildings and were not subsequently dispersed, the group pointed out.
The initial radiation released at the time of atomic bomb explosions had been previously used for calculating doses and the health hazard for people who were indoors were considered small in general.
“The damage caused by radiation cannot be explained by only looking at the initial radiation,” said a member of the group.
The scientific team included Megu Otaki, a professor emeritus of statistics at Hiroshima University, who has been involved in many studies on the effects of the atomic bombs.