阳江高本底地区恶性肿瘤死亡调查1987～1995年资料分析

目的 本项研究是高本底辐射研究组的一项专题，始于１９７２年，旨在探索平均年有效剂量国６．４ｍＳｖ的阳江天然放射性高本底辐射照射的致癌危险，１９９１年起中日两国科学家合作继续研究，以累积更多观察人年数，提高统计学精度，并检验以往研究的可重复性，方法 合作研究后所获１９８７～１９９５年恶性肿瘤死亡资料是通过回顾性调查或／和前瞻性调查从定群队列中获得。恶性肿瘤死亡现场调查分为队列成员追踪和死因确认两步骤

Analysis of data (1987-1995) from investigation of cancer mortality in high background radiation area of Yangjiang, China

Objective This investigation is a special project of High Background Radiation Research Group.The objective of the cancer mortality study in the high background radiation area (HBRA) of Yangjiang,China,which was started in 1972,was to estimate cancer risk associated with the low level radiation exposure of average annual effective dose of 6.4 mSv in HBRA.Since 1991,the study has been conducted collaboratively by Chinese and Japanese scientists with the purpose of accumulating further person years (Pyr) of observation for improving the statistical precision and seeing the reproducibility of the previous results. Methods The cancer mortality data of 1987-1995 covered in the current cooperative study were collected by a retrospective and/or prospective survey from a fixed cohort.The mortality investigation on the spot consisted of two steps,i.e.the follow-up of members in the cohort and the ascertainment of the death causes.Based on the hamlet specific average annual external dose,the members of the cohort in HBRA were classified into three groups:high,medial and low dose groups.Risk comparisons between each of the three dose groups with the control group from control area (CA) were conducted by means of relative risk (RR).The RR and the excess relative risk coefficient (ERR per sievert) and their 95% confidence interval (CI) were estimated using AMFIT program in Epicure. Results During the period 1987 1995,there were 5161 total deaths and 557 cancer deaths among 926238 Pyr at risk in the cohort of 106517 subjects.The RR (95% CI) adjusted for sex and age group for all cancers of whole HBRA was 0.96 (0.80- 1.15).As for the site specific cancer of whole HBRA,the RRs for leukemia,cancers of nasopharynx,esophagus and intestine were larger than one,while the RRs for cancers of stomach,liver,lungs,female breast,thyroid and lymphoma were less than one.However,all of them were not statistically different from one (P >0.05 for all).The homogeneity tests of RRs for all cancers and for site specific cancer among the three dose groups in HBRA revealed that the RRs among the dose groups were not different statistically ( P >0.05 for all).The results of RR estimation based on the combined data of 1979-1995,which included 125079 subjects,and total deaths of 10415 and cancer deaths of 1003 among 1698350 Pyr at risk,were generally consistent with those based on the data of 1987 1995 mentioned above.The RR (95%CI) for all cancers of whole HBRA was 0.99 (0.87 1.14) and the ERR (95%CI)/Sv of all cancers for both sexes and all ages was 0.10(-0.67,0.69) resulting from the combined data. Conclusione The results from data of different periods demonstrated that an increased cancer risk associated with the high levels of natural radiation in HBRA was not found;on the contrary,there was a trend that the mortality of all cancers in HBRA was generally lower than that in CA,but not significantly different statistically.