- 64of the low uptake of gr9° and normal values for calcium,
For conditions of equal fallout, the Sr90-calcium ratio
is a good deal less for fish than for such calcium-rich
terrestrial food products as milk (Schaefer 195%).
Tne principal radioisotopes found in fish are nonfission products,
of whieh Zn 65 appears at this time to
present the greatest potential hazard (Table V).
In
samples from the western Pacific and from the United
States, Zn°5 was identified in tuna muscle (Kawabata 1956b;
Hiyama 1957) and has been found in trace quantities in
foods analyzed by Murthy et al.
(1959).
The values re-
ported by Murthy et al. were higher for oysters and clams
than for land crops and,
Chesapeake Bay oysters,
in terms of wuc/kg were as follows:
January 1959,
178;
Chesapeake Bay
oysters, March 1958, 1245 and East Coast hard-shelled
clams, May 1958, 40.
The MPC for gn5, 106 upc/kg, as
caiculated from Handbook 69,
is considerably greater than
the present values for oysters and clams.
The concentration
of gn©5 was not unexpected as Chipman (1959) found that
oysters,
zinc,
clams and scallops concentrate large amounts of
thousands of times above its level in sea water.
Because the local fallout in the vicinity of the