Calculating Risk

An Old and Prized Cherry Tree Behind Gumyoji Kannon

Below is an excerpt from May issue of Bungeishinju magazine. The title of this interview-styled article is “The Truth Is It Takes A Year,” and the subtitle is “Erroneous Reports on Radiation.”



Interviewer: Koichi Okamoto, specialized in Crisis Psychology, Professor at Toyo-Eiwa Women College, a specialist member of Nuclear Energy Safety Committee and Nuclear Energy Committee

Interviewee: Masayori Ishikawa, Professor of the Graduate School of Hokkaido University
Studied and worked at Kyoto University Nuclear Reactors Research Center, Tokyo University Nuclear Power Research General Center, Hokkaido Hospital,

The Petals of the Cherry Blossoms 

On page 209, this is what the interviewee said.




“To evaluate the amount of radiation, we have to add how much exposure we collected throughout our lifetime, not just in days.”


A friend of mine has recently told me that after the Hiroshima bomb, the radiation fall out onto the Kanto region--Tokyo and Yokohama included, was 10,000 times more than the previous norm. I didn’t know that. My parent died without knowing it.


“This is based on the current statistics. If our accumulated amount passed 100 mili sieverts, and if we added more, per 1000 mili sievert (1 siervert), the cancer rate would possibly go up 5 %. Therefore, if a person were exposed to 100 mili sieverts so far in her or his life, and also the probability of that person to afflict with a cancer were 50 %, then the rate becomes 50.5 %.

Today, one person out of two gets cancer, and one out of three dies by cancer. Being aware of these facts and the accumulated amount of our own radiation exposure and risks, we can choose the way we live.”


So far, I know the Japanese average is 1.45 mili sierverts a year. The Hiroshima and Nagasaki bombs happened before I was born. My mother and aunt must have exposed to the 10,000-times-over-the-norm radiation, and the descendants like us are I’m sure affected. I moved to the U.S. in 1970. So, I want to know the U.S. average by state, city, and town. My mother died of liver cancer at age 76, but my aunt moved to the U.S. around 1955, and she is 87 and has dementia, but as far as I know, she doesn’t have cancer.

I hope this helps.