阳江高本底辐射地区的个人外照射剂量估算和人员的剂量分组

Estimation of individual doses from external exposures and dose group classification of cohort members in high background radiation area in Yangjiang,China.

目的为了更好地进行剂量与效应关系的分析，将高本底辐射地区（ＨＢＲＡ）的人员按村平均的环境γ外照射水平及各自的居留因子估算的村平均有效剂量分成“高”、“中”、“低”三个剂量组和相邻的正常本底地区（ＣＡ）的一个对照组。方法在进行辐射剂量与效应关系的研究时，采用环境γ外照射辐射水平（卧室、室内、外和田野）的测量和个人累积剂量（ＴＬＤ）的两种测量方法给出ＨＢＲＡ和ＣＡ各组人员平均有效剂量。结果这两种方法的测量结果：ＨＢＲＡ分别是２１１８６×１０－５Ｓｖ·ａ－１和２０６７５×１０－５Ｓｖ·ａ－１；ＣＡ分别是６８６０×１０－５Ｓｖ·ａ－１和６７１１×１０－５Ｓｖ·ａ－１。两种不同测量方法所估算的村平均有效剂量有很好的相关性，它们的直线回归方程为Ｙ＝０．９３３７Ｘ＋６．０４４４，相关系数ｒ＝０．９９４９。结论环境γ外照射辐射水平测量方法的总的不确定度为１５％。作者分析了引起人员误分组的原因，并认为人员的误分组的可能性不会超过１％，它不会影响分组作用的有效性。

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.Conclusions 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.