A STUDY ON SOME STABLE ELEMENTS AND RADIONUCLIDES IN HUMAN-MILK

The behaviour of radioactive Sr was studied together with that of Ca, and the behaviour of radioactive Cs with that of K, as Ca and K are co nsidered reference standards in studying radionuclide transfers from o ne compartment of the environment or of the human body to another. Rad ioactive Cs and K were determined by gamma spectrometry, whereas radio active Sr was first separated via ion exchange resin and then beta mea sured. Ca, K, and Sr measurements were carried out by Inductively Coup led Plasma Atomic Emission Spectrometry. Sr-90/Ca and Sr-90/Sr ratios were determined in some tens of human milk samples from two different Italian zones and different periods. The mean values of Sr-90/Ca were found to be 46+/-35 and 39+/-25 mBq/g, whereas those of Sr-90/Sr 200+/ -170 and 191+/-96 Bq/g. K and K-40 concentrations were measured in som e human milk samples and for comparison in some cow and sheep milk sam ples. In all the three cases the K-40-to-K ratio (28-36 Bq/g) showed t o be in good agreement with the isotopic ratio in natural K (0.0118%).