STRONTIUM 90 TESTS

Press, Volume C, Issue 29680, 25 November 1961, Page 16

STRONTIUM 90 TESTS

Reasons For Using Milk

The programme for the measurement of strontium 90 in milk had been established not because milk was a source of danger but because it was one of the safest avenues for the detection for this chemical, which was similar to calcium, said the atcing-director of the Dominion X-ray and Radium Laboratory (Mr H. J. Yeabsley) in an address on radioactive fallout to the Canterbury branch of the Royal Society of New Zealand iast evening. Radioactivity was not new. Man had eaten radioactive food and drunk radioactive water all during his existence, Mr Yeabsley said. Strontium 90 had not been present in the soil before the testing of nuclear bombs but radium, which was 20 times more lethal than strontium, had always been present in radiations from soil and space, he said. Strontium was considered the most lethal product of nuclear fission because it was produced in large amounts in nuclear reactions, because it could easily enter human bodies and be assimilated into the system, because it attacked a particular part of the human structure—bones, and because its “half life” of about 30 years was long enough to enable it to spread widely, and short enough for it to operate within the normal life span, Mr Yeabsley said. Contamination from strontium was largely from affected rainfall, he said. In this way it entered the soil, was assimilated in growth such as grass from which cows manufactured milk—a mam source of calcium. In this way cows acted as a sieve. Only a quarter of the amount of strontium taken in food was assimilated into -the system, so by the time it was absorbed by persons the amount was an eighth of the quantity in the original vegetation, he said. This was infinitesimal as the initial degree of contamination was itself negligible. The total amount of radioactivity at present was not more than the quantity emitted by the many luminous wrist-watch dials worn today. Present radiation could probably be blamed for causing fatal leukemia in about 10 persons during the next 70 years, he said. Persons should be more concerned with such things as deficient brakes and the careless labelling and storing of poisonous materials, said Mr Yeabsley, as these mundane matters constituted far greater hazards than atomic radiation.