YUAN Yong-ling, H. Morishima, SHEN Hong et al
Objective The purposes is to estimate the average annual effective dose of the inhabitants and absorbed dose in some human tissues and organs arising from natural radiation sources in the High Background Radiation Area (HBRA) of Yangjiang and in the neighboring Control Area (CA).In order to provide more effective evidence for analyzing the dose-effect relationships among the cohort members in the investigated areas, we divided the local inhabitant into different dose-groups.Methods We measured the environmental gamma external radiation levels and individual accumulated doses of 5 293 people in the investigated areas.The concentrations for 222Rn, 220Rn and their decay products in air were also surveyed.We estimated the internal doses of natural radionuclides based on the Results obtained from measurements in food, in drinking water, in human teeth, in several human tissues, in human placenta, and in activity concentration of exhaled 222Rn and 220Rn of the residents living in the investigated areas.Results The estimation of average annual effective doses in HBRA and CA based on the data of environmental measurements of radiation level respectively are 2.12±0.29 mSv a-1 and 0.69±0.09 mSv a-1.The sources of higher background radiation in HBRA are mainly contributed from terrestrial gamma radiation.The estimation of average annual effective doses to the residents arising from inhalation of 222Rn, 220Rn and their decay products was 3.28 mSv a-1 in HBRA, while that in CA was 1.03 mSv a-1.The values of the absorbed dose of the residents in their trachea-bronchial tree and lung in HBRA arising from inhalation of 222Rn, 220Rn and their decay products are 5.40 mGy a-1 and 1.08 mGy a-1 respectively, which are about four times of the values of the absorbed dose in CA.The estimation of average annual effective doses to the inhabitants caused by 226Ra and 228Ra in HBRA and CA were 281.88 μSv a-1 and 84.54 μSv a-1 respectively.The annual absorbed doses to red bone marrow and bone lining cells of the inhabitants in HBRA were estimated to be 25.54 μGy a-1 and 140.46 μGy a-1 respectively for 226Ra and 228Ra respectively, while in CA were estimated 7.68 μGy a-1 and 42.25 μGy a-1 respectively.Conclusion The values of the effective dose of the inhabitants arising from natural radiation sources in HBRA and CA are 5.9 mSv a-1 and 2.0 mSv a-1 respectively.The value of the effective dose of the inhabitants arising from natural radiation sources in HBRA is about three times of the value in CA.There are 23718 individuals whose effective dose is 7 mSv a-1.The values of the effective dose caused by internal radiation and external radiation in HBRA are 3.76 mSv a-1 and 2.12 mSv a-1 respectively.The amount of the effective dose of the residents arising from inhalation of 222Rn, 220Rn and their decay products consists of about 88 percent of the total amount of the internal radiation dose of the residents in HBRA.The estimate of average annual effective dose the residents arising from inhalation of 222Rn and its decay products in HBRA was 1.53 mSv a-1.The average annual effective dose of the residents arising from 220Rn and its decay products in HBRA is 17.5 mSv a-1, which is 17.5 times of the worldwide average value 0.10 mSv a-1.Thus, the 220Rn and its decay products are one of the main sources to cause the internal radiation dose of the inhabitants living in HBRA.
