| YUAN Yongling,SHEN Hong,SUN Quanfu,et al.Estimation of individual doses from external exposures and dose group classification of cohort members in high background radiation area in Yangjiang, China[J].Chinese Journal of Radiological Medicine and Protection,1999,19(2):99-103 |
| Estimation of individual doses from external exposures and dose group classification of cohort members in high background radiation area in Yangjiang, China |
| Received:September 20, 1998 Revised:January 13, 1999 |
| DOI： |
| KeyWords:Kerma Effective dose Dose group classification Mis classification |
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| Abstract:: |
| Objective In order to estimate annual effective doses from external exposures in the high background radiation area(HBRA)and in the control area(CA),we measured absorbed dose rates in air from terrestrial gamma radiation with different dosimeters.A dose-group classification was an important step for analyzing the dose-effects relationship among the cohort members in the investigated areas.We used the hamlet specific average annual effective doses of all the 526 hamlets in the investigated areas.A classification of four dose groups was made for the cohort members(high,moderate,low and control).Methods For the purpose of studying the dose effect relationships among the cohort members in HBRA and CA,it would be ideal that each subject has his own record of individual accumulated doses received before the evaluation.However,it is difficult to realize it in practice (each of 106517 persons should wear TLD for a long time).Thus we planned two sets of measurements.Firstly,to measure the environmental dose rates(outdoor,indoor,over the bed)in every hamlet of the investigated area (526 hamlets),considering the occupancy factors for males and females of different age groups to convert to the annual effective dose from the data of dose-rates.Secondly,to measure the individual cumulative dose with TLD for part of the subjects in the investigated areas.Results Based on the two sets of measurements,the estimeates of average annual effective doses in HBRA were 211.86 and 206.75×10-5 Sv/a,respectively,68.60 and 67.11×10-5 Sv/a,respectively(gamma radiation only).The intercomparison between these two sets of measurement showed that they were in good correlation.Thus we are able to yield the equations of linear regression:Y=0.9937+6.0444,r=0.9949.Conclusiones We took the value obtained from direct measurement as “standard”,and 15% for uncertainty of measurement.Since the estimates of individual annual effective dose for the cohort members were based on hamlet average dose and occupancy factors for males and females of different age groups,there were uncertainties in the classification of dose groups.Thus we analyzed the probability of mis classification of dose groups.The results of analysis showed that the probability of mis-classification would not influence significantly the function classification. |
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