A study was undertaken to estimate the actual concentration of gamma-active isotopes in vegetables, tea. tobacco, powdered milk, wheat, rice, fish, etc., which are available in Bombay, India. A large-size NaI(Tl) crystal scintillator and a thirty-channel pulse-height analyser were used to identify and to estimate the concentration of the radioisotopes. The studies were carried out over a period of about 15 months which is broadly divided as (1) the year following the stoppage of nuclear weapon tests (in October 1958), (2) the month before the French atomic weapon test in Sahara desert on February 13, 1960, and (3) the month after this test. In addition to the presence of natural radioactivity of K40, fission product activities such as Zr95-Nb95, Ru103 I131, Cs137, Ba140-La140 Ce141 and Ce144 were noticed, but in varying amounts in different materials. The very high activities of Zr95-Nb95 and Ce144 in tea were found to be chemically bound in its leaves preventing this uptake by human beings. The presence of Zr95-Nb95 in carrots suggests its preferential pick up through the roots. The radioisotope Zn65 was detected in fish and prawns. The analysis of certain vegetables during the month following the French test clearly indicated the presence of short-lived fission products which should have originated in the test. The degree of contamination is found to depend upon the total surface offered to the fallout and its roughness to hold the activity.
©1962Health Physics Society