Answer to Question #1495 Submitted to "Ask the Experts"

Q

A 14-year-old gentleman was on a train that drove through Hiroshima 18 months after the atomic bomb. The train drove slowly through town; it took about 20 minutes to a half hour to drive through. He doesn't remember whether or not his window was open, though he could have opened it. How much radiation might he have been exposed to, and is it possible he may yet see the effects?

A

It is very unlikely that the 14-year-old gentleman to whom you refer received any significant radiation dose, certainly not a dose that would likely result in any biological effects now or in the future. Remember that people had been living in Hiroshima continuously for all those months after the atomic bombing and hence had a very much longer exposure time to any residual radioactivity from the bombings than the gentleman you mention. Long-term follow-up studies of these people do not indicate any significant effects at the dose levels they incurred from the residual activity.

So what dose did the gentleman incur from his 20-to-30-minute train trip through the city? Likely a very small fraction of the dose he would normally receive from cosmic rays and natural radioactivity in the environment in a year, and really too small to be distinguished from the variations in the natural radiation environment. Or, by way of another comparison, very much less than the dose from a chest x ray. Tell the man, who would now be nearly 60 years old, not to worry.

Ron Kathren, CHP