- 63 chemically similar elements. of strontium and calcium, The abundance in sea water which is chemically similar to strontium, is part of the reason that S$r90 is not abundant in marine organisms (Table IV). Another factor is the lew specific activity for Sr9° in sea water due to mixing and dilutien by ocean waters. The low level of csl47 in marine organisms cannot be accounted for entirely for the same reasons, because the stable isotopes of cesium are scarce in the sea. However, potassium, an element chemically similar to cesium, is abundant (Table IV) and also, the specific activity for Csl37 in sea water is low. The Sr9° in canned tuna fish and salmon has been determined by the Health and Safety Laboratory of the U.S. Atomic Energy Commission. In 48 analyses of samples re- ceived between April 20, 1956 and August 8, 1957, the highest value was ,.004 wuc/g, wet weight (U. S. Atomic Energy Commission report HASL 42 1958). Because the values were very low and there seemed to be no trend in time or location, arily. from the the sampling was discontinued tempor- The health hazard from sr9° which is determined ratio of gr90 to calcium is low for fish because

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