natural background radiation dosimetry in the highest altitude region of Iran

The natural background radiation has been measured in one of the highest altitude regions (Zagros Mountains), Chaharmahal and Bakhtiari province, in the south west of Iran. The outdoors-environmental monitoring exposure rate of radiation was measured in 200 randomly chosen regions using portable Geiger-Muller and scintillation detectors. Eight measurements were made in each region and an average value was used to calculate the exposure rate from natural background radiation. The average exposure rate was found to be 0.246 microGy/h and the annual average effective dose equivalent was found to be 0.49 mSv. An overall population-weighted mean outdoor dose rate was calculated to be 49 nGy/h, which is higher than the world-wide mean value of 44 nGy/h, as reported by UNSCEAR in 1998, and is comparable to the annual effective dose equivalent of 0.38 mSv. A good correlation between the altitude and the exposure rate was observed, as the higher altitude regions have higher natural background radiation levels.     

Epidemiological studies of radiation workers: preliminary communication.

British Nuclear Fuels Limited has embarked on a study of the mortality data among those of its workforce who were employed prior to 1 January 1976. The study covers a total population of about 41 000 current and ex-employees, but is initially concerned with a radiation worker cohort of 7500 at the Sellafield establishment where the highest radiation doses are received. Tracing of the health status of ex-employees has been undertaken using the services provided by the Office of Population Censuses and Surveys (OPCS) and the Department of Health and Social Security (DHSS) and it is expected that ultimately the level of trace will be better than 97%. Mortality data not specifically related to radiation workers are included and relate to male deaths among serving staff and pensioners during the years 1962-1978. Those observed deaths (O) are compared on an age standardized basis with those expected (E) from the general population, the ratio O/E being about 1 for all cancers and less than 1 for non-cancer deaths. This pattern is consistent with the well known 'healthy worker' effect seen in industry.     

Adaptive response of blood lymphocytes of inhabitants residing in high background radiation areas of ramsar- micronuclei, apoptosis and comet assays

The hot springs in certain areas of Ramsar contain (226)Ra and (222)Rn. The effects of natural radiation on the inhabitants of these areas and the inhabitant's radiosensitivity or adaptive responses were studied. One group of volunteers from areas with high natural background radiation and another group from areas with normal background radiation were chosen as the case and control group respectively. The frequency of micronuclei, apoptosis, and DNA damage in peripheral blood mononuclear cells were measured following gamma irradiation (4 Gy). The incidence of micronuclei in the case group was significantly lower than that in the control group while their frequency of apoptosis was higher (P < 0.05). However, the rates of induced DNA damage and repair were significantly higher in the case group (P < 0.05). Smaller number of micronuclei and higher levels of apoptosis in the case group could be the result of higher resistance to radiation stress and a more rigorous checkpoint at cell division. However, regarding the alkaline labile sites, the individuals in the case group are more sensitive and susceptible to DNA damage. The results of micronuclei, apoptosis and repair studies suggest that an adaptive response might be induced in people residing in areas with high background radiation.     

阳江高本底地区肺癌与室内氡暴露巢式病例-对照研究

目的研究居室氡暴露与肺癌危险的关系。方法采用巢式病例-对照研究设计,病例与对照为1∶2个体配比。以面访的方式访问调查对象的家属或其他知情人。用固体核径迹探测器方法,对调查对象曾住房屋的氡浓度进行累积测量。结果成功访问了63例肺癌病例和125例对照,病例与对照的平均死亡年龄分别为60.1岁和60.6岁。病例和对照所在室内氡的平均浓度分别为40.1和39.2 Bq/m3。单因素条件logistic回归分析氡暴露与肺癌危险的关系,比值比[(OR)95%可信限(95%CI)]为1.25(0.63~2.52)。不同程度氡暴露,肺癌危险有增加趋势,但差异无统计学意义(P>0.05)。在100 Bq/m3氡浓度时,氡暴露的超额比值比(EOR)为0.30(95%CI:-0.53~14.93),调整钍射气贡献后,EOR=0.14。结论未发现室内氡暴露与肺癌危险有统计学意义的关联。     

阳江天然放射性高本底地区居民血清免疫学调查研究

目的调查广东省阳江天然高本底地区（High Background Radiation Areas,HBRA）健康居民血清免疫学指标的表达情况,探讨慢性低剂量辐射免疫生物学效应及作用机制。方法采用随机抽样方法分别从高本底地区的阳西县塘口镇和对照地区（ControlAreas,cA）的阳西县横陂镇各选取125名健康男性居民。应用常规EI。ISA方法检测其中20名居民血清IL-2的表达水平,85名居民血清sIL-2R的表达水平,剩余20名检测p53的表达水平。实验数据由SPSS16．0统计软件完成。两地区居民血清IL2、sIL2R、p53表达差异进行独立样本t检验,检验水准a=0．05．协方差分析观察高本底辐射、年龄、吸烟、饮酒和医疗照射对IL-2、sIL-2R表达的影响。非条件多因素logistic回归分析地区、年龄和吸烟对p53表达率的影响。结果高本底地区健康居民血清1I。2的浓度略高于对照地区,分别为（13．65±10．96）和（12．18±11．61）ng／I。;对照地区居民血清sIL2R的浓度略高于高本底地区,分别为（2181．9±919．5）和（2151．1±692．1）ng／L,高本底和对照地区居民血清p53浓度分别为（6．26±8．01）和（9．81±7．18）U／ml。上述三个指标的统计结果在两地区之间差异无统计学意义。调整地区,吸烟,饮酒和医用照射因素后,发现年龄对两地区居民血清sIL2R表达水平影响最大,F=13．61,P=0．0003。对地区、年龄和吸烟三因素进行logistic回归分析,结果显示地区是对p53表达率有统计学意义的影响因素,Z=-2．56,P=0．010。结论天然放射性高本底地区居民的免疫功能略强于对照地区,提示长期慢性低剂量电离辐射有增强机体免疫的趋势,但有待进一步探索。     

高本底辐射地区居民热休克蛋白70表达水平研究

目的探讨小剂量慢性长期持续性照射对居民周围血热休克蛋白(HSP)70mRNA、痰样HSP70蛋白表达的影响。方法选择我国广东阳江天然高本底辐射地区(HBRA)的53名50～59岁男性居民作为研究对象,另选择广东恩平市横陂镇(CA)出生并长大的年龄相仿的男性居民作为对照人群。分别抽取周围血5ml、连续3d痰样,并测定周围血HSP70mRNA、痰样HSP70蛋白的水平。结果在HBRA和CA居民周围血HSP70mRNA水平分别为血清中(0.551±0.358)和(0.584±0.400),痰样HSP70为(1.439±0.851)和(1.925±0.719)。与CA组比较,HBRA组人群周围血HSP70mRNA、痰样HSP70水平较低,差异无统计学意义(P>0.05)。结论天然高本底辐射长期作用于人体,其周围血、痰样HSP70表达有一定降低,尚不能判断长期低剂量辐射与HSP70表达高低的关系。     

Epidemiological studies on disturbances of human fetal development in areas with various doses of natural background radiation. II. Relationship between incidences of hydatidiform mole, malignant hydatidiform mole, and chorionepithelioma and gonad dose equivalent rate of natural background radiation

The relationships between gonad dose equivalent rates and incidences of chorionic disease (i.e., hydatidiform mole, malignant hydatidiform mole, and chorionepithelioma) were analyzed with Kendall's rank correlation and regression methods. Data used were from 11 prefectures of Japan with various dose rates of natural background ionizing radiation between the years 1974 to 1976. The results suggested an association of the incidence of chorionic disease with the radiation dose rate in the very low dose-rate range.     

阳江高本底地区部分居民营养状况调查

目的 比较广东阳江高本底地区和对照地区居民营养状况,评价营养在高本底地区对辐射致癌的混杂作用.方法 分别从高本底地区和对照地区各3个镇中随祝抽取居民各150人,调查近1个月家庭及个人的膳食平均摄入量及家庭基本情况,测量身高、体质量,测量血清总蛋白、三酰甘油、胆固醇、高低密度脂蛋白、肌酐、尿素氮等.结果 2地区居民体质量指数(BMI)分布对照地区(22.06±3.15)高于高本底地区(20.19±2.47,P＜0.01),2地区居民部分营养素摄入水平有差异,对照地区偏高(P＜0.01);血生化指标平均值均在正常参考值范围,对照地区低密度脂蛋白、白蛋白、总蛋白等均高于高本底地区(P＜0.05).结论 高本底地区和对照地区居民营养状况有一定差异,对照地区居民营养状况总体好于高奉底地区.     

Lens opacity prevalence among the residents in high natural background radiation area in Yangjiang,China

The aim of the study was to evaluate the risk and threshold doses of lens opacity among residents exposed to low-dose radiation. Residents aged ≥45 years were recruited from a high natural background radiation (HNBR) area in Yangjiang City and a control area selected from nearby Enping City. Lens opacities (LOPs) were classified according to the Lens Opacities Classification System (LOCS) III system. Face-to-face interviews were conducted to collect information on lifestyles, migration and medical history. Life-time cumulative doses were estimated using gender, age, occupancy factors and environmental radiation doses received indoors and outdoors. Logistic regression analyses were conducted to estimate the dose response and determine thresholds. In the HNBR area, among 479 study participants, 101 (21.1%), 245(51.1%) and 23 cases (4.8%), respectively, of cortical, nuclear and posterior subcapsular (PSC) LOPs were found. In the control area, those types of LOPs were identified among 58 cases (12.6%), 206 cases (51.2%) and 6 cases (1.3%) of 462 examinees, respectively. Cumulative eye lens dose was estimated to be 189.5 ± 36.5 mGy in the HNBR area. Logistic analyses gave odds ratios at 100 mGy of 1.26 [95% confidence interval (CI) 1.00–1.60], 0.81 (95% CI 0.64–1.01) and 1.73 (95% CI 1.05–2.85) for cortical, nuclear and PSC LOPs, respectively. For cortical LOPs, a logistic analysis with a threshold dose gave a threshold estimate of 140 mGy (90% CI 110–160 mGy). The results indicated that population exposed to life-time, low-dose-rate environmental radiation was at an elevated risk of cortical and PSC LOPs. A statistically significant threshold dose was obtained for cortical LOPs and no threshold dose for PSC LOPs.     

Epidemiological studies on disturbances of human fetal development in areas with various doses of natural background radiation. I. Relationship between incidences of Down's syndrome or visible malformation and gonad dose equivalent rate of natural background radiation

The relationship between environmental radiation (mSv X a-1) to the gonads and incidences of Down's syndrome and visible malformation was analyzed using Kendall's rank correlation method. The subjects, studied during a 3-yr period (1979-1981), were inhabitants of 46 prefectures in Japan that had various dose rates (mu R/h) of natural background ionizing radiation. Results showed that the natural background very low-dose radiation rate was not a predominant factor responsible for inducing Down's syndrome or other visible malformations.     

Exposure to high background radiation level in the tin mining area of Jos Plateau, Nigeria.

The present work deals with the radioactivity of samples of tin tailings collected from a mining site in Jos, Nigeria. The activity concentrations of the samples were measured using a gamma-ray spectrometer with a hyper-pure germanium detector. In situ dose rates at the site were also measured using a precalibrated survey meter. Potassium-40 was not detected in any of the studied samples. The activity concentrations of (238)U and (232)Th ranged from 17.1 x 10(2) to 16.6 x 10(3) Bq kg(-1) and from 52.9 x 10(2) to 47.5 x 10(3) Bq kg(-1), with mean values of 72.2 x 10(2) and 16.8 x 10(3) Bq kg(-1), respectively. The absorbed dose rates were between 4.0 and 36.3 microGy h(-1), with a mean value of 13.5 microGy h(-1), which is much higher than the world average of 0.06 microGy h(-1) for soil. The calculated effective dose rates varied between 2.8 and 25.4 microSv h(-1), with a mean value of 9.4 microSv h(-1), whereas the effective dose rates obtained for the in situ measurement varied between 6.0 and 28.0 microSv h(-1). The annual gonadal dose equivalent was calculated as 92.4 mSv. This is much higher than the world average dose equivalent rate to individuals from soil (0.30 mSv y(-1)).     

高本底辐射居民机体抗氧化水平研究

群抗氧化能力.     

高本底放射性饮水对小鼠细胞遗传学指标的影响

目的　观察放射性水平不同的饮水对小鼠遗传性状的影响。方法　昆明种幼鼠随机分为 3组 ,分别喂养至第 5 0、10 0、15 0天时进行动物骨髓细胞微核试验及染色体畸变分析。结果　两处理组与对照组不同时相点的实验结果基本一致 (P >0 .0 5 )。结论　该实验浓度的高本底放射性饮水未观察到遗传毒性效应