Fallout with the Daffodils

In the atomic age, March winds and April showers also bring fallouts from the thin upper air. As spring crept over the Northern Hemisphere last week, scientists everywhere deployed their Geiger count ers, sure that radioactivity would rise with the daffodils.

First measurements came from radio sensitive Japan, where radioactivity had sunk to a comfortably low winter level after last fall's Russian tests in Novaya Zemlya. In December the index figure was an insignificant 6.77 millimicrocuries.* Radioactivity stayed low during January and February, but since then it has climbed steeply. By March it had reached 29-48 millimicrocuries, and scientists of Japan's Meteorological Institute estimate that it will reach about 50 millimicrocuries for the month of April. After the notably "dirty" Soviet tests of 1958, the figure peaked at 94.45 in May of 1959. Japanese meteorologists point out that their last winter was very dry with rainfall registering only about half that of three years ago. They predict that when the heavy spring rains arrive, they will pull down enough fallout to equal or exceed the 1959 peak.

In the U.S., where fallout watchers are neither as prompt with their reports as the Japanese nor as frank, few figures have been released. But radioactivity is known to be showing its expected spring rise. In the Northern states cows are still feeding mostly on fodder gathered last fall before the Soviet tests, and their milk is still low in radioactivity. But Southern cows are already grazing on green grass, and the spring fallout that has collected on it is passing into their milk. As spring moves north and the grass greens up in Vermont and Wisconsin, the radioactivity of Northern milk will increase too.

U.S. authorities, including the Atomic Energy Commission, the Public Health Service and the Weather Bureau, feel sure that the 1962 fallout will probably equal or exceed the 1959 peak, but they are not alarmed. The fission energy yield of the Soviet 1958 tests was 10 to 15 megatons. The total energy of last fall's Soviet tests was much greater (170 mega tons), but most of it came from nuclear fusion, which creates little fallout. Only about 25 megatons came from nuclear fission of uranium or plutonium, and since many of the Russian tests were exploded at high altitudes, their dangerous fission products will presumably stay aloft for longer periods of time and lose more of their activity by natural decay before they come down.

Even if the 1962 spring fallout sets a new record, says the Public Health Service, it is not likely to endanger health.

The highest levels reached in 1959 were only about 25% of the amount that would have made protective measures worth the trouble.

*Gross radioactivity is measured in millimicrocuries per minute per square meter.

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