阳江高本底放射地区1979～1995年恶性肿瘤死亡调查分析

Cancer mortality in high background radiation area of Yangjiang, China, 1979-1995

目的探索平均年有效剂量为６４ｍＳｖ的广东省阳江地区天然高本底放射的致癌危险。方法对１９７９～１９８６年的恶性肿瘤死亡资料通过前瞻性调查从一个动态队列来收集，对１９８７～１９９５年资料通过回顾性调查和（或）前瞻性调查从一个固定人群队列获得。恶性肿瘤死亡资料现场调查分队列成员追踪和死因确认两步骤。个人累积剂量估算包括内照射和外照射。按以村平均的居民年外照射剂量水平，将研究人群分为４个剂量组进行比较分析。相对危险（ＲＲ）和超额相对危险系数（ＥＲＲ／Ｓｖ）及其９５％可信区间（ＣＩ）采用Ｅｐｉｃｕｒｅ中的ＡＭＦＩＴ程序计算。结果１９７９～１９９５年共观察１２５０７９人，累积观察１６９８３５０人年。期间，总死亡１０４１５例，其中因恶性肿瘤死亡者１００３例。整个高本底放射地区全部恶性肿瘤经性别年龄组调整后的ＲＲ（９５％ＣＩ）为０９９（０８７～１１４）。就肿瘤系统而言，胃癌、结肠癌、肝癌、肺癌、骨癌、甲状腺癌及女性乳腺癌的ＲＲ小于１；而鼻咽癌、食管癌、直肠癌、胰腺癌、皮肤癌、宫颈癌、脑和中枢神经系统其他部位恶性肿瘤、白血病及淋巴肉瘤的ＲＲ大于１，但除食管癌外均差异无显著意义（Ｐ＞００５）。对全部恶性肿瘤及部位别恶?

Objective To estimate cancer risk associated with the low level radiation exposure of average annual effective dose of 6.4 mSv in HBRA the high background radiation area (HBRA) of Yangjiang, China. Methods The cancer mortality data of 19791986 were collected from a dynamic cohort by prospective survey. The data of 19871995 were obtained from a fixed cohort by retrospective and/or prospective survey. The mortality investigation on the spot consisted of two steps, i.e. the followup of the members in the cohort and the ascertainment of the death causes. The estimate of cumulative individual dose of the cohort members included that of the exposure from natural external and internal sources. Both direct (TLD measurement) and indirect (environmental measurement and occupancy pattern) approaches were used for individual external dose estimate. On the basis of the hamletspecific average annual external dose, the cohort members were classified into four groups for internal comparison: high, medial and low dose groups from HBRA and control group from control area (CA). Relative risk (RR) and excess relative risk coefficient (ERR per sievert) and its 95% confidence interval (CI) was estimated using AMFIT program in Epicure. Results During the period 19791995, there were 10 415 total deaths and 1003 cancer deaths among 1 698 350 personyears at risk in the cohort of 125 079 subjects. The adjusted RR (95% CI) with sex and age group for all cancers of whole HBRA was 0.99 (0.871.14). As for the sitespecific cancer of whole HBRA, the RRs of cancers of stomach, colon, liver, lungs, bone, female breast, and thyroid were less than one, while the RRs of cancers of nasopharynx, esophagus, rectum, pancreas, skin, cervix uterus, brain and central nervous system, leukemia and lymphoma were larger than one. However, all of them except for esophagus cancer were not different statistically from one (P>0.05). The homogeneity tests of RRs for all cancers and for sitespecific cancer among the three dose groups in HBRA revealed that the RRs in these dose groups were not different statistically (P>0.05) for all. The ERR (95% CI)/Sv of all cancers for both sexes and all ages was -0.10 (-0.67, 0.69). Conclusion An increased cancer risk associated with the high levels of natural radiation in HBRA was not found. On the contrary, the mortality of all cancers in HBRA was generally lower than that in CA, but not significant statistically.