ESTIMATION OF CHANGE DYNAMICS OF MILK CONTAMINATION WITH 90SR AND 137CS IN LITHUANIA IN 1965–2003

Abstract

The paper describes the trends of concentrations of 90Sr and 137Cs in milk in Lithuania in 1965–2003. Sampling of milk was performed in five regions of the biggest cities of Lithuania, and since 1976 ‐ also in the region of possible impact of Ignalina Nuclear Power Plant (NPP). Data of production and consumption of milk are taken from Lithuanian statistical yearbooks. Activity concentrations of radionuclides were measured at Radiation Protection Centre. Daily diet products are connected with different components of the environment ‐ soil, air and water. For this reason food contamination reflects pollution of the environment. This paper describes estimation of trends of activity concentrations of 90Sr and 137Cs in one of the food products ‐ in milk. Comparison applies to two periods ‐ the so‐called before Chernobyl period (1965–1985) and that after the accident in Chernobyl NPP up to now (1986–2003). Contamination of milk was analysed using correlation tests. Though the trend of average annual activity concentrations is complicated, during the two periods plenty of high enough correlation ratio values were calculated (0,63–0,74). Regression curves using 3–6 degree of polynoms show the decrease of 90Sr and 137Cs activity concentrations during the periods analysed. Factors of influence on the value of an average annual effective dose for an inhabitant of Lithuania based on activity concentrations of 90Sr and 137Cs in milk were evaluated. Estimation shows that accuracy of calculating an average annual effective dose due to 90Sr and 137Cs in milk does not exceed 60%.