Strontium 90 in Japan

U.S. daily press reports have indicated that radioactive strontium 90 from the fallout of thermonuclear explosions is nothing to worry about. Japanese scientists do not agree. On April 8 scientists working under Japan's Atomic Energy Commission will present a report to the United Nations Radiation Committee. Its gist: strontium 90 should be studied carefully, and much more must be known about it before it can be written off as harmless to the human species.

The Japanese scientists tested a long list of objects, from spinach to deer horns, for strontium 90, and found a wide variation. Tea plants, for instance, contained 30 "units"* while spinach had only 3.8. Rice, all important in Japan, was comparatively high (10.4 units), but shellfish from Tokyo Bay had only .04 units. Highest count was from tuna caught in Bikini waters in 1956: 53.5 units. The scientists also examined the ashes of 20 persons, taken from burial urns, and found that their strontium 90 count varied from .06 units for an elderly man who lived in Niigata, to 4.1 units for a survivor of the Nagasaki bombing who died in 1955.

None of this proves, say the reporting scientists, that the earth's present "burden" of strontium 90 is an immediate peril, but neither does it prove the contrary. They suspect that the average human being contains about eight times more strontium 90. than was reported in the U.S. (TIME, Feb. 18), and they note that the amount is increasing, and may be increasing rapidly. They insist that no one knows how much is needed to damage health.

Said Dr. Masao Tsuzuki, director of Tokyo's Red Cross Central Hospital: "Speaking as a scientist, I can make no evaluation of the strontium 90 danger. Too much work is still to be done. We do not know how much gets down to earth or how long that takes. We do not know how much then enters the human body, or at what rate, or what the mechanism of transfer from food to animals and humans is. I do not believe that strontium 90 will be permanently harmful at its present level, but if experimental explosions continue at the present rate, there will come a time when the human body will be seriously harmed. It will then be too late to do anything about it."

*Each unit is one micromicrocurie (millionth of a millionth of a curie) or radioactivity owing to strontium 90 per gram of calcium.

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