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PubMed2006

High background radiation areas of Ramsar in Iran: evaluation of DNA damage by alkaline single cell gel electrophoresis (SCGE).

The hot springs in special areas in Ramsar, a northern coastal town in Iran, contain (226)Ra and (222)Rn. The natural radiation effects, radiosensitivity or adaptive responses, on the inhabitants of high natural radiation in Ramsar were studied. The single cell gel electrophoresis was used to monitor DNA damages. Three groups of volunteers were selected, one from high natural background radiation areas as the case group and two from normal background radiation areas as controls (control 1 and control 2). The latter one had the similar living situation to case group while the other (control 2) had different living situation from the other groups. Peripheral blood mononuclear cells (PMNCs) were separated and irradiated by (60)Co source at five different gamma doses. It was found that the spontaneous level of DNA damage and the induced DNA damage in all challenging doses in case group was considerably higher than control groups (p < 0.05). On the other hand, the repair rate in those volunteers, who received less than 10.2 mSv/y was significantly more than the control groups. In the contrary, individuals who live in homes with more than 10.2 mSv/y had incomplete repair. Additionally the plasma and urinary levels of vitamin C were measured spectrophotometrically. Although the concentration of vitamin C of plasma was equal in case and control 1 groups, the urinary level of vitamin C was found to be lower in the case group.

Ascorbic Acid↗
PubMedDate not supplied

Background radiation, electrical work, and some other exposures associated with acute myeloid leukemia in a case-referent study.

The effect of potential risk factors for acute myeloid leukemia was evaluated in a case-referent study encompassing 59 cases and 354 referents, all of whom were alive. Information on exposure was obtained through a questionnaire mailed to the subjects. The possible effect of background radiation was evaluated by means of a gamma radiation index, which accounted for the differences between cases and referents in this respect, i.e., in time spent in concrete buildings both at home and at work places. In the 20-54 yr old age group, there was an association between leukemia morbidity and index of background radiation. X-ray treatment and electrical work were also associated with increased rate ratios. With regard to solvents, only styrene appeared as a risk factor, but the number of exposed subjects was small. Other exposures were less clearly associated with increased risks.

Adult↗
PubMed1996

[Epidemiological survey in a high background radiation area in Yangjiang, China].

The results of the health survey in a high background radiation area (HBRA) from 1972 to 1990, in Yangjiang, China, are presented in this paper. Radiological measurements of the environmental and human bodies with different methods revealed that 330 mR/a in HBRA and 114 mR/a in the control area (CA) were the doses that annually an individual exposure to the external environmental gamma radiation and effective doses to whole body are 6.4 mSv in HBRA and 2.4 mSv in CA annually. The carcinogenic and mutagenic factors were surveyed. The Results showed that these factors in the two areas were similar. Up till now, no harmful impact induced by natural radiation, based on the data as: cancer mortality from 1,008,769 person-years in HBRA and 995,070 person-years in CA; hereditary diseases and congenial malformations from 13,425 subjects in HBRA and 13,087 subjects in CA; human chromosome aberrations, and immune function of the inhabitants, was found. In addition, in this paper the authors discussed the results of cancer mortality, of chromosome aberrations and of immune function, and analyzed the possible relationship among them. The carcinogenic risk induced by low dose radiation was also estimated and discussed.

Background Radiation↗
PubMed1990

Thyroid nodularity and chromosome aberrations among women in areas of high background radiation in China.

Thyroid nodularity following continuous low-dose radiation exposure in China was determined in 1,001 women aged 50-65 years who resided in areas of high background radiation (330 mR/yr) their entire lives, and in 1,005 comparison subjects exposed to normal levels of radiation (114 mR/yr). Cumulative doses to the thyroid were estimated to be of the order of 14 cGy and 5 cGy, respectively. Personal interviews and physical examinations were conducted, and measurements were made of serum thyroid hormone levels, urinary iodine concentrations, and chromosome aberrations in circulating lymphocytes. For all nodular disease, the prevalences in the high background and control areas were 9.5% and 9.3%, respectively. For single nodules, the prevalences were 7.4% in the high background area and 6.6% in the control area (prevalence ratio = 1.13; 95% confidence interval = 0.82-1.55). There were no differences found in serum levels of thyroid hormones. Women in the high background region, however, had significantly lower concentrations of urinary iodine and significantly higher frequencies of stable and unstable chromosome aberrations. Increased intake of allium vegetables such as garlic and onions was associated with a decreased risk of nodular disease, which seems consistent with experimental studies suggesting that allium compounds can inhibit tumor growth and proliferation. The prevalence of mild diffuse goiter was higher in the high background radiation region, perhaps related to a low dietary intake of iodine. These data suggest that continuous exposure to low-level radiation throughout life is unlikely to appreciably increase the risk of thyroid cancer. However, such exposure may cause chromosomal damage.

Autoantibodies↗
PubMed2000

An introductory overview of the epidemiological study on the population at the high background radiation areas in Yangjiang, China.

The epidemiological study on the residents of the high background radiation areas in Yangjiang, China was started by Chinese scientists in 1972 and continued until 1986. In 1991, Japanese scientists recognized the importance of the work and a joint feasibility study was conducted with revised protocols. The feasibility study matured to a cooperative project involving both Chinese and Japanese scientists in 1992, which currently is still in progress. The project was divided into three phases; the first being from 1992 to 1995, the second from 1995-1998 and the third from 1998 to 2001. The results of the first phase were reported previously in 1996. The present paper is a historical overview of the studies before the cooperation and the first two phases. Remarks are made on the detailed data on dosimetry, cytogenetic studies and cancer epidemiology of a series of the papers in this supplemental issue. Some problems such as paradoxical observations between cytogenetic results and cancer mortality, and the importance of the high background study in risk assessment are discussed.

Background Radiation↗
PubMed2000

Excess relative risk of solid cancer mortality after prolonged exposure to naturally occurring high background radiation in Yangjiang, China.

A study was made on cancer mortality in the high-background radiation areas of Yangjiang, China. Based on hamlet-specific environmental doses and sex- and age-specific occupancy factors, cumulative doses were calculated for each subject. In this article, we describe how the indirect estimation was made on individual dose and the methodology used to estimate radiation risk. Then, assuming a linear dose response relationship and using cancer mortality data for the period 1979-1995, we estimate the excess relative risk per Sievert for solid cancer to be -0.11 (95% CI, -0.67, 0.69). Also, we estimate the excess relative risks of four leading cancers in the study areas, i.e., cancers of the liver, nasopharynx, lung and stomach. In addition, we evaluate the effects of possible bias on our risk estimation.

Adolescent↗
PubMed2002

Influence of a low background radiation environment on biochemical and biological responses in V79 cells.

We present the results of an experiment aimed at comparing the effects of different background radiation environments on metabolism and responses to gamma-rays and cycloheximide of cultured mammalian cells. Chinese hamster V79 cells were maintained in exponential growth in parallel for up to 9 months at the Istituto Superiore di Sanità (ISS) and at the INFN-Gran Sasso underground Laboratory (LNGS) where exposure due to gamma-rays and to radon was reduced by factors of about 70 and 25, respectively. After 9 months the cells grown at the LNGS (cumulative gamma dose about 30 microGy, average radon concentration around 5 Bq/m(3)), compared to the cells grown at the ISS (cumulative gamma-ray dose about 2 mGy, average radon concentration around 120 Bq/m(3)), exhibited i). a significant increase of the cell density at confluence, ii). a significantly higher capacity to scavenge organic and inorganic hydroperoxides but a reduced scavenging capacity towards superoxide anions and iii). an increase in both the basal hprt mutation frequency and sensitivity to the mutagenic effect of gamma-rays. The cells grown at the LNGS also showed a greater apoptotic sensitivity starting at the third month of culture, that was no longer detected after 9 months. Overall, these data suggest a role of background ionizing radiation in determining an adaptive response, although they cannot be considered conclusive.

Air Pollution, Indoor↗
PubMedDate not supplied

[Possible effect of natural background radiation on the development of mammals].

The deceleration of the development of young rats during the postnatal ontogenesis under conditions of a low-background chamber (a 10-fold decrease in the natural radiation background) was detected using the criterion of individual growth of the body weight for 10 days of observation. The administration, to the low-background chamber, of uranium salts which restore the natural background (all other experimental conditions being retained) removed the effect observed.

Animals↗
PubMed2000

Measurements of Rn-222, Rn-220 and their decay products in the environmental air of the high background radiation areas in Yangjiang, China.

For the renewal of dose estimation from internal irradiation in the high background radiation areas (HBRA) of Yangjiang, the measurements of radon, thoron and their decay products in the environmental air were conducted, including: (1) integrating measurements of Rn-222 and Rn-220 concentrations; (2) eqilibrium factor F for Rn-222 and alpha-potential energy value of Rn-220; (3) external gamma radiation in places where radon measurements were undertaken; (4) cumulative exposure to indoor radon for each family in a case-control study on lung cancer. The Rn-Tn cup monitor method was used for the integrating measurement of Rn-222 and Rn-220 concentration. An alpha track detector was used for the integration measurement of Rn-222 concentration in the case-control study on lung cancer. The results of measurements show that although the investigated areas are located between the Equator and the Tropic of Cancer, and that people live in well-ventilated dwellings, the concentrations of radon, especially of Rn-220 are significantly higher in the indoor air of HBRA than those in the control area. The value of equilibrium factors for Rn-222, the alpha potential energy of decay products from Rn-222 and Rn-220 are determined.

Air↗
PubMed1987

Influence on cell proliferation of background radiation or exposure to very low, chronic gamma radiation.

Investigations carried out on the protozoan Paramecium tetraurelia and the cyanobacteria Synechococcus lividus, which were shielded against background radiation or exposed to very low doses of gamma radiation, demonstrated that radiation can stimulate the proliferation of these two single-cell organisms. Radiation hormesis depends on internal factors (age of starting cells) and external factors (lighting conditions). The stimulatory effect occurred only in a limited range of doses and disappeared for dose rates higher than 50 mGy/y.

Animals↗
PubMed2002

Study of natural radionuclide concentrations in an area of elevated radiation background in the northern districts of Bangladesh.

The activity concentrations of naturally occurring radioactive materials in soil samples from an elevated radiation background area of three northern districts of Bangladesh were determined using gamma ray spectrometry. The outdoor and indoor external effective dose rates and the radiation hazard indices from these soil activities were evaluated. The dose rates were found to be about four times higher than the reported world average value. The concentration of natural radionuclides, derived radium equivalent activities and the representative level indices were also found to be higher. Recommendations on radiological and dosimetric measures have been suggested with an aim of minimising the harmful effects of ionising radiation to the population of the area concerned.

Background Radiation↗
PubMed1999

Spatial variations in natural background radiation: absorbed dose rates in air in Colorado.

Large and small-scale spatial variations in natural ambient background radiation dose rates in Colorado were investigated at 1,150 specific locations with particular attention to 40 of the more populated areas along the Front Range of the Rocky Mountains. Total dose rates (including cosmic and terrestrial components) in Front Range communities below 2,000 m elevation averaged 135 nGy h(-1). Terrestrial dose rates had a coefficient of variation of 17%. Communities above 2,000 m had a mean total dose rate of 196 nGy h(-1), and a terrestrial dose rate coefficient of variation of 17%. Across all Front Range communities, the coefficient of variation for terrestrial dose rates was 22%. Within individual communities, coefficient of variation values for terrestrial dose rates ranged from 3 to 21%. Smaller-scale spatial variability (to within a few meters) was relatively small (coefficient of variation values generally ranged from 3 to 7%). A significant linear relationship (r2 = 0.83) between the size of area surveyed (km2) and coefficient of variation value for terrestrial dose rates was found. West of the Continental Divide, the terrestrial component accounted for roughly 60% of total measured dose rates, while east of the Continental Divide, where enriched granitic source rocks and associated soils are prevalent, the terrestrial component generally accounted for two-thirds or more of total dose rates.

Air Pollutants, Radioactive↗
PubMed1999

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

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 1979-1986 were collected from a dynamic cohort by prospective survey. The data of 1987-1995 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 follow-up 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 hamlet-specific 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 1979-1995, there were 10,415 total deaths and 1003 cancer deaths among 1,698,350 person-years 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 (0.87-1.14). As for the site-specific 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 site-specific 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.

Background Radiation↗
PubMed2000

Chromosome translocation in residents of the high background radiation areas in southern China.

We performed a cytogenetical study using chromosome painting analysis on 9 residents of the naturally high background radiation areas (HBRA) and 8 residents of the control areas in southern China. The estimated dose (air kerma) of each resident measured by an electric pocket dosimeter showed 2.20-4.23 mGy/year in HBRA and 0.56-0.70 mGy/year in the control areas. A total of 14,096 cells (1,566 cells/case) in the former and 17,522 cells (2,190 cells/case) in the latter were analyzed. Children, both in HBRA and in the control areas, had translocations at low frequencies. The frequency of translocations among elder individuals varied widely and it was not possible to detect dose effect although it was detected in dicentrics. The effect of radiation on the induction of chromosome aberrations, which have a statistically potential risk of causing malignant or congenital diseases, seems to be less significant than those of metabolic factors and/or mutagenic agents (excluding radiation) even in HBRA in China.

Aged↗
PubMed2003

Electromagnetic wave collapse in a radiation background.

The nonlinear interaction, due to quantum electrodynamical (QED) effects between an electromagnetic pulse and a radiation background, is investigated by combining the methods of radiation hydrodynamics with the QED theory for photon-photon scattering. For the case of a single coherent electromagnetic pulse, we obtain a Zakharov-like system, where the radiation pressure of the pulse acts as a driver of acoustic waves in the photon gas. For a sufficiently intense pulse and/or background energy density, there is focusing and the subsequent collapse of the pulse. The relevance of our results for various astrophysical applications are discussed.

Journal Article↗
PubMed2000

Dose-effect relationship of dicentric and ring chromosomes in lymphocytes of individuals living in the high background radiation areas in China.

Chromosomes of 39 healthy family members (3 generations from 13 families) living both in the high-level background radiation areas (HBRA) and the control areas (CA) were studied. Cumulative dose from birth to the time of blood sampling was estimated by calculating measured exposure rate in each individual. The cumulative doses ranged 30.9-358.9 and 6.0-59.2 mGy for HBRA and CA, respectively. Peripheral lymphocyte chromosome preparations were made according to our improved method. Dicentric and ring chromosomes (Dic + Rc) were scored in average 2,527 cells per individual in HBRA and 2,694 cells in CA under a microscope equipped with an automated stage. A positive correlation between Dic + Rc and age was found in HBRA, while no such dose relationship was clear in CA. The frequency of Dic + Rc linearly increases over lifetime due to chronic low dose exposure and it is likely that the activation of repair enzymes is not triggered in the present HBRA. Threshold dose (rate) of the induction of chromosome aberrations, if any, is below the present dose (rate) level.

Adult↗