Natural background radiation and exposure to general public in Beijing

Natural radioactive isotope concentrations in air, soil, drinking water, food-stuff, building materials, coal, fuel gases, body tissue samples from Beijing area and the external exposure rates from terrestrial radioactivity and cosmic radiation were measured. The results of estimation show that the per caput annual effective dose equivalent from natural sources in Beijing area is 2.43 mSv/a, and the external dose and the internal dose make up 32% and 68% of the total dose respectively. The inhalation of short-lived decay products of radon (Rn-222) and thoron (Rn-220) accounts for 55% of the effective dose equivalent from all natural sources of radiation, and the ingestion accounts for 13% of the total. The indoor and outdoor doses account for 73% and 14% respectively. The radionuclides of uranium series, thorium series, K-40 and cosmic-ray charged particles account for 54%, 19%, 17% and 10% respectively. The estimated annual collective effective does equivalent commitment from natural background for the general public is 2.39 x 104 man·Sv/a