I get antsy whenever I hear young women in Fukushima Prefecture bemoaning their dismal marriage prospects following the nuclear accident there.
Many people fear that their exposure to radiation could be passed down to their children, grandchildren and later generations.
Their anxiety is understandable, given repeated statements that the implications of low-level radiation exposure have yet to be fully understood.
That said, there seems to be little to warrant their concern about genetic defects due to the reactor meltdowns last year at the Fukushima No. 1 nuclear power plant. There is plenty of research literature on this subject.
Studies in Hiroshima and Nagasaki following the 1945 atomic bombings found that children were affected if their mothers were exposed to radiation at levels of 200 millisieverts or more during the early stage of pregnancy.
But few children suffered abnormalities when readings were below that level.
Those who were not pregnant at a time of their exposure added no risk when they gave birth later in their lives.
Cases documented around the world show that women, if they were treated with radiation therapy for cancer when they were young children, did not suffer any major problems when they gave birth as adults.
Studies in Denmark show that even a heavy dose of radiation, taken as part of cancer treatment, does not increase the risk of a chromosomal disorder in the offspring of the patients.
The research involved children of cancer survivors who underwent radiation therapy and children of their siblings who did not have the disease.
Japanese people were alarmed about the genetic effects of radiation after the atomic bombings of Hiroshima and Nagasaki because it was already known at that time flies mutate after they are irradiated.
After World War II, researchers in the United States conducted an experiment involving millions of mice to study the impact of radiation.
They examined the correlation between the frequency of mutations taking place in the mice offspring and the dose of radiation.
Researchers found that mutations are unlikely to occur if radiation exposure was incremental or exposure occurred at intervals.
The International Commission on Radiological Protection said in a 2007 report that the likelihood of genetic impact is 0.2 percent per dose of 1,000 millisieverts.
Michiaki Kai, a professor of risk analysis of radiation at Oita University of Nursing and Health Sciences and a member of the ICRP, said the figure was based on the mice field tests.
The ICRP report is not without its critics.
But it carries weight because the figure was based on the results of an extensive investigation and scientists around the world agreed with the findings.
A recent survey of 10,000 Fukushima Prefecture residents showed that most of them have been exposed to no more than 20 millisieverts. In fact, the readings for a great number of these people were less than 2 millisieverts.
As for the level of internal radiation exposure, the figure was much smaller.
Research to unravel the mechanism of heredity made great strides in the late 20th century.
People are born with numerous DNA mutations. There are no exceptions.
I dearly hope that women will not limit their choices in life and let prejudice about radiation exposure influence their decisions.
* * *
Mariko Takahashi is a senior staff writer of The Asahi Shimbun.
- « Prev
- Next »