CORRELATION BETWEEN PRECIPITATION
AND AMOUNT OF !37Cs IN MILK IN NORWAY
KJELL MADSHUS* and AKSEL STRO@MMET
*Norsk Hydros Institute for Cancer Research, Oslo, Norway
+The Norwegian Radium Hospital, Oslo, Norway |
INTRODUCTION
The distribution of radioactive fallout has been nonuniform in different
parts of the world, Because of atmospheric movements, turbulence and
diffusion in the stratosphere, and prevailing west to east winds in the
troposphere, most of the fallout from a nuclear explosion descends on
the hemisphere in which the explosion occurred. The northern hemiSphere therefore is the most contaminated since most nuclear tests
have been made in it. Some radioactive particles come down as dry
debris,’ but mostly they are brought down by rain or snow. The
regional climate, precipitation type and rate, and topographical pecu-
liarities, to a high degree, determine the amount of fallout.
The main routes of radioactive particles from the atmosphere and
the soil to man are through plants and animal products. Among the
various radioactive nuclides present in fallout, 1370s is one of the most
important from a medical point of view. About half of the body burden
of this nuclide in man is often considered to come from milk intake,
although it has been shown?’? that this is not always the case. In Western
Europe, however, a considerable part of the body burden of **"Cs in
man does come from this source.
The minimum concentration of radioactive nuclides in milk is in
Spring, when cows are kept in sheds and partly fed uncontaminated
fodder. The biological half-life of !°°Cs in cows is only about 20 days;‘
therefore the body burden of this nuclide in cows is rapidly reduced
when they are partly fed uncontaminated fodder,
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