Determination of 40K concentration in milksamples consumed in Tehran-Iran and estimationof its annual effective dose

Background: since 40k is the most important natural radionuclide in the environment, its concentration was measured for all milk and milk powder samples consumed in tehran-iran. milk was chosen, since because it is a reliable indicator of the general population intake of certain radionuclide, and many environmental programs have been applied for its safety. materials and methods: measurements was done using a canberra gamma spectrometer model no. s100. forty one milk and milk powder samples were choosen for the gamma spectroscopy analysis. results: the average activity concentrations for 40k in the samples were calculated, 31.0 ± 6.1 and 17.1 ± 3.3 bq.kg-1, in milk and milk powder respectively. these data correspond to the effective dose of 14 ìsv.year-1 for adults and in the range of 6.4-15.9 ìsv.day-1 for children. conclusion: consider- ing the obtained data from liquid milk samples, an almost uniform distribution of 40k can also be obtained. furthermore, the calculated effective doses were too low to induce important health hazards; however, the data useful for monitoring.