Yangjiang High Background Radiation Carcinogenic Hazard Analysis And The Residents Of Immune Function

The objective of the study is to examine whether the cancer risk elevated or not with the high levels of natural radiation exposures occurring in the high background radiation area. The observation of person years and the number of cancer death increased gradually in the cohort study collected from different follow-up period. In the aspect of controlling confounding factor, individual confounding factor was not considered in the analysis of cancer risk associated with low dose radiation exposure besides age and sex confounding factor. This study mainly added the new data of follow-up and death causes from 1999 to 2002 and the individual smoking data of each subjects in the fixed cohort study obtained by interviewing subjects or the relative. So this study firstly analyzed the cancer risk associated with low dose radiation from 1999 to 2002, and further estimated the cancer risk associated with low dose radiation from 1979 to 2002 after merging with the data of follow-up and death causes collected from 1979 to 1998 to increase the statistic power. After adjusting the individual smoking factor, cancer risk associated with low dose radiation was reestimated. This study carried out serum epidemiology study again and explored immune function change of healthy people due to chronic low dose radiation exposure.The cohort study was applied in the health study of the resident in HBRA. The subjects were followed up in different stages, and the data of cancer mortality for the deceased were collected by the prospective study in each stage. The main point of this study was adding the new data of cohort follow-up and ascertainment of death cause from 1999 to 2002. This study firstly estimated the risk of cancer mortality with EPICURE software from 1999 to 2002 in HBRA, then using the follow-up data from 1999 to 2000 updated the data collected by HBRA research group from 1979 to 1998. The relative risk (RR) and excess relative risk coefficient (ERR/Sv) of cancer mortality from 1979 to 2002 before and after adjusting smoking were estimated with Poisson regress model in AMFIT mode. The person year was calculated with DATAB mode in EPICURE software.The subjects of immune function study must be male healthy people age from 40 to 65 years in HBRA. All subjects were interviewed by face-to-face questionare inquiry to obtain the basic information, inhabitancy/ migrant history, health status and living habit, et al. For the subjects of satisfying the include criterions, 5 mL of peripheral blood was collected without anti-coagulant in order to separate the serum. Serum was centrifuged using standard method to measure the soluble interleukin 2 receptor with sandwich Enzyme Linked-Immuno-Sorbent Assay (ELISA) and evaluate immune function of the subjects who expose chronic low dose radiation. All experiment data were keyed into the computer with Epidata software and Excel software, the statistic analyses were completed with STATA 9.0 statistic analysis software.The follow-up of 76 264 subjects, which were available for the analysis, resulted in the accumulation of 300 523 person-years of observation and the identification of 2267 deaths during the period of 1999-2002. Cancer deaths yielded a total of 239, making up 10.5% of all causes of death. The sex and age-adjusted RR of mortality of all cancers in the entire HBRA comparing with the control areas (CA) was 0.95 (95% CI, 0.73-1.24), showing no statistically significant difference between HBRA and CA. The follow-up of 125 079 subjects resulted in the accumulation of 2 292 490 person-years of observation and the identification of 14711 total deaths, among them 1441 cancer deaths, during the period of 1979-2002. The sex and age-adjusted RR of mortality of all cancers in the entire HBRA comparing with the control areas (CA) was 0.99 (95% CI, 0.89-1.11), showing no statistically significant difference between HBRA and CA. The value of excess relative risk coefficient (ERR/Sv) associated with cumulative individual lifetime external and internal doses for all cancers was -0.01 (95% CI, -0.50-0.64). After adjusting smoking, RR of all cancers mortality in the entire HBRA comparing with CA was 1.00 (95% CI, 0.87-1.15), showing no statistically significant difference. The RRs of all cancer mortality in different dose-rate groups in the HBRA did not show statistically significant difference from the control group. After adjusting smoking, the value of ERR/Sv for all cancers was 0.01 (95% CI, -0.56-0.81).85 healthy persons were selected from HBRA and CA respectively to measure the serum sIL-2R concentration. The average age of subjects in HBRA and CA was (52.2±8.0) years and (50.4±6.2) years respectively, showing no statistic significant difference (P=0.1025). The average serum sIL-2R concentration in HBRA and CA was (2151.1±692.1) pg/mL and (2181.9±919.5) pg/mL respectively, showing no statistic significant difference. The results of covariance analysis showed that the concentration of serum sIL-2R increased statistic significantly with age after adjusting area, smoking, drinking and X ray exposure (P=0.0003).In conclusion, the results of this study are in accordance with those of the previous study conducted in HBRA, confirming the creditability of the follow-up study data from 1999 to 2002. Through the merge of the data in both studies, the accumulative person-years observation increased, which resulted in the improvement of the statistical power of the radiation risk cancer. It was not found out that the cancer risk associated with chronic low dose radiation increased in HBRA through the combined analysis. After adjusting smoking, there was still no statistic difference in all cancer mortality between HBRA and CA, but excess relative risk increased slightly. The immune function of healthy male subjects in HBRA was probably higher than that in CA, especially for the healthy over 50-year-old people.