ABSTRACT
Objective To measure the current environmental radioactivity levels in some districts of Yunnan Province,and to estimate the external doses to local residents.Methods The surface soil,aerosol and water samples were collected and analyzed by HPGe gamma spectrometry.Based on the estimation model selected by Ministry of Health in the nationwide soil survey,the doses to local residents from 238U,226Ra,232Th,40K and 137Cs in environmental samples were estimated.CARI-6 software issued by FAA (Federal Aviation Administration ) was used to estimate cosmic radiation dose to the local population.Results The external annual dose rate to the local people was 1.13 mSv per year,of which 0.52 mSv per year was contributed by natural radionuclides in soil,0.6 μ Sv per year by 137 Cs in soil and 0.61 mSv per year by cosmic radiation.Conclusions The cosmic radiation and natural radionuclides in soil might contribute 99.95％ of external exposure dose,while artificial radionuclide 137Cs contribute 0.05％ of external exposure dose.