26.04.2011 I was dismayed to learn that the Ministry of Education, Culture, Sports, Science and Technology earlier this week increased the allowable dose of ionizing radiation for children in Fukushima Prefecture.
The dose they set, 3.8 microsieverts per hour, equates to more than 33 millisieverts (mSv) over a year. This is to apply to children in kindergartens, nursery, primary and junior high schools. Let me try to put this in perspective.
Widely accepted science tells us that the health risk from radiation is proportional to the dose -- the bigger the dose the greater the risk, and there is no level without risk.
The International Commission on Radiological Protection recommends that all radiation exposure be kept as low as achievable, and for the public, on top of background radiation and any medical procedures, should not exceed 1 mSv per year.
For nuclear industry workers, they recommend a maximum permissible annual dose of 20 mSv averaged over five years, with no more than 50 mSv in any one year.
In Japan the maximum allowed annual dose for workers, 100 mSv, was already higher than international standards. This has been increased in response to the Fukushima disaster to 250 mSv.
The U.S. National Academy of Sciences BEIR VII report estimates that each 1 mSv of radiation is associated with an increased risk of solid cancer (cancers other than leukemia) of about 1 in 10,000; an increased risk of leukemia of about 1 in 100,000; and a 1 in 17,500 increased risk of dying from cancer.
But a critical factor is that not everyone faces the same level of risk. For infants (under 1 year of age) the radiation-related cancer risk is 3 to 4 times higher than for adults; and female infants are twice as susceptible as male infants.
Females' overall risk of cancer related to radiation exposure is 40 percent greater than for males. Fetuses in the womb are the most radiation-sensitive of all.
The pioneering Oxford Survey of Childhood Cancer found that X-rays of mothers, involving doses to the fetus of 10-20 mSv, resulted in a 40 percent increase in the cancer rate among children up to age 15.
In Germany, a recent study of 25 years of the national childhood cancer register showed that even the normal operation of nuclear power plants is associated with a more than doubling of the risk of leukemia for children under 5 years old living within 5 kilometers of a nuclear plant.
Increased risk was seen to more than 50 km away. This was much higher than expected, and highlights the particular vulnerability to radiation of children in and outside the womb.
In addition to exposure measured by typical external radiation counters, the children of Fukushima will also receive internal radiation from particles inhaled and lodged in their lungs, and taken in through contaminated food and water.
A number of radioactive substances are concentrated up the food chain and in people. As a parent, as a physician, the decision to allow the children of Fukushima to be exposed to such injurious levels of radiation is an unacceptable abrogation of the responsibility of care and custodianship for our children and future generations.