NATURAL AND FALLOUT RADIOACTIVITY IN MILK AND DIET SAMPLES IN BOMBAY AND POPULATION DOSE-RATE ESTIMATES

The results of radioactivity measurements of Sr-90, Cs-137 and K-40 in milk as well as Sr-90, Cs-137, K-40, Pb-210, Ra-226 and Th-228 in composite diet samples collected in Bombay from 1965 to 1990 are presented in this paper. The activity levels of K-40 in milk samples were almost constant. In diet samples, Ra-226 and Th-228 levels were low, whereas K-40 levels varied widely. In the case of fallout radionuclides (Sr-90 and Cs-137), the average concentration levels in milk as well as in diet varied between < 0.005 and 0.442 Bq\(l or diet). By using the measured average concentrations of natural and fallout radionuclides in milk and diet samples as well as by taking the mean consumption of 100 ml of milk and two diets per day, the daily intake of fallout and natural radionuclides for the people of Bombay has been assessed. Based on the intake values, the annual effective ingestion dose to the Bombay population has been estimated. It has ranged between 79 and 177 muSv/y with an average of 110 muSv/y; additionally, K-40 which is in homeostatic equilibrium in the body is estimated to give rise to a dose of 189 muSv/y to the Indian population. The main contribution to the ingestion dose is from natural radionuclides.