ABSTRACT
The existence of some radionuclides in soil and some building materials produce a beta - gamma radiation field, which in some regions the exposure of these radionuclides to human is high. The air-absorbed dose, indoor and outdoor annual effective dose of soil and some building material samples [ceramic, granite, gypsum, etc.]. The samples were collected from 35 different regions in the northwest of Iran were calculated. Specific activity of natural radionuclides [226]Ra, [232]Th and [40]K were measured by using a beta - gamma spectrometer consisted of NaI[Tl] and organic scintillators. The analysis of measured spectra was based on maximum likelihood estimation. The calculated data were compared with world's mean values. It is found that the specific activity of 40K ranges from 573.8 to 1392 Bqkg[-1], for [232]Th ranges from 6 to 54.6 Bqkg[-1] and for [226]Ra ranges from and 5.1 to 36.2 Bqkg-1. In some regions, the concentrations of natural radionuclides [[40]K, [232]Th, [226]Ra] were higher than standard level. Experimental results related to specific activity, indoor and outdoor annual effective doses of [226]Ra, [232]Th and [40]K revealed that radionuclide concentration in soil and some building material samples of some regions of northwest of Iran are of some radiological importance