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PubMed2000

Cancer mortality in the high background radiation areas of Yangjiang, China during the period between 1979 and 1995.

The objective of the present study was to estimate cancer risk associated with the low-level radiation exposure of an average annual effective dose of 6.4 mSv (including internal exposure) in the high background-radiation areas (HBRA) in Yangjiang, China. The mortality survey consisted of two steps, i.e., the follow-up of cohort members and the ascertainment of causes of death. The cohort members in HBRA were divided into three dose-groups on the basis of environmental dose-rates per year. The mortality experiences of those three dose groups were compared with those in the residents of control areas by means of relative risk (RR). During the period 1987-1995, we observed 926,226 person-years by following up 106,517 subjects in the cohort study, and accumulated 5,161 deaths, among which 557 were from cancers. We did not observe an increase in cancer mortality in HBRA (RR = 0.96, 96% CI, 0.80 to 1.15). The combined data for the period 1979-95 included 125,079 subjects and accumulated 1,698,316 person-years, observed 10,415 total deaths and 1,003 cancer deaths. The relative risk of all cancers for whole HBRA as compared with the control area was estimated to be 0.99 (95% CI, 0.87 to 1.14). The relative risks of cancers of the stomach, colon, liver, lung, bone, female breast and thyroid within whole HBRA were less than one, while the risks for leukemia, cancers of the nasopharynx, esophagus, rectum, pancreas, skin, cervix uteri, brain and central nervous system, and malignant lymphoma were larger than one. None of them were significantly different from RR = 1. Neither homogeneity tests nor trend tests revealed any statistically significant relationship between cancer risk and radiation dose. We did not find any increased cancer risk associated with the high levels of natural radiation in HBRA. On the contrary, the mortality of all cancers in HBRA was generally lower than that in the control area, but not statistically significant.

Adolescent↗
PubMedDate not supplied

[The effect of the biochemical adaptations in the Manchu alder (Duschecia fruticosa (Rupr)) to an elevated natural radiation background on the survivability of seedlings and on the radiosensitivity of its seeds].

Seeds and sprouts of bushy alder existing for long under the condition of the enhances natural radiation background (ENRB; from 1.4 to 72.0 mCu/(kg.s)) have been examined to determine biochemical adaptations to permanent low-level irradiation. To achieve this goal a combined cytological and biochemical technique for the assessment of the activity of genome of the sprout root meristem in response to translation, replication and reparation has been applied. The activity of antioxidant systems has been studied. The data obtained allow us to reveal mechanisms of alder bush biochemical adaptations to various ENRB rates and their effect upon seeds radiosensitivity and sprouts survival. It is determined that the increase in sprout vitality and high radioresistance of seeds ripened under the conditions of low-level natural radiation is due to the content of low molecular antioxidants and activation of systems of genome reparation.

Adaptation, Physiological↗
PubMed2006

Genomic instability of the DYZ1 repeat in patients with Y chromosome anomalies and males exposed to natural background radiation.

We assessed genomic instability of 3.4 kb DYZ1 repeat arrays in patients encompassing prostate cancer (PC), cases of repeated abortion (RA) and males exposed to natural background radiation (NBR) using real-time PCR and fluorescence in situ hybridization (FISH). Normal males showed DYZ1 copies ranging from 3000 to 4300, RA, 0-2237; PC, 550; and males exposed to NBR, 1577-5700. FISH showed organizational variation of DYZ1 in these samples substantiating the data obtained from real-time PCR. Of the 10 RA samples, 7 were found to be affected of which, 5 showed deletion of 265 bp from nt 25 to 290 and 773 bp from 1347 to 2119 and 2 showed deletion of 275 bp from nt 3128 to 3402. Copy number variation of DYZ1 in these males correlated with genetic constrains/anomalies. Although precise mechanisms of genomic instability of DYZ1 remains unclear, we construe that this repeat plays a critical role in maintaining the structural integrity of the Y chromosome, possibly by absorbing the load of mutations. This may be used as a marker system to analyze genetic integrity of the DYZ1 repeat array(s) across the spectrum of patients.

Abortion, Induced↗
PubMed1985

Outdoor natural background radiation in The Netherlands.

As part of the SAWORA-project the outdoor natural background radiation was investigated by the National Institute of Public Health and Environmental Hygiene and by the Netherlands Energy Research Foundation. Measurements were carried out with an ionization detector at more than 1000 locations evenly distributed throughout the country. After correction for the contribution of the cosmic radiation, the exposure rates were plotted on a map. Results show that the gamma radiation originating from the soil in The Netherlands varies between 1.1 and 7.2 microR/h (79 and 516 fC/(kg.s)). Comparison of the radiation map with a geological one indicates that "high" values of the exposure rates correspond to areas with silty deposits. The "low" exposure rates correspond to areas with sandy deposits. Gamma spectrometric analysis of the radiation at some locations shows that the terrestrial radiation is mainly caused by natural radionuclides.

Environmental Exposure↗
PubMed1998

[Effect of an increased radiation background on mice, carrying lethal t-haplotypes].

To study the effect of a high radiation background on the structure and function of the T-complex, we used laboratory mice carrying t-haplotypes of four complementation groups (t0, t12, tw1, and tw5). In 1987-1989, the animals were kept each year for a month within a 30-kilometer zone of Chernobyl Nuclear Power Station in regions with different degrees of pollution. Subsequent genetic analysis revealed a decrease in fertility, fecundity, and the index of preferable transmission of t-carrying chromosomes in radiated animals and some of their progeny. The effect of different radiation doses on these parameters was different in animals with various t-haplotypes. A lack of complementation or a decrease in the complementation effect was revealed in a number of crosses involving the progeny of irradiated animals. The frequency of complementation distortion was about 8 x 10(-2), which is more than an order higher than the usual recombination frequency characteristic of these t-haplotypes.

Animals↗
PubMedDate not supplied

[Monitoring of tundra vole (Microtus oeconomus Pall.) population inhabiting areas with increased radiation background].

The data of complex examinations of morphophysiological state of Tundra vole (Microtus oeconomus Pall.), the lipid peroxidation (LPO) processes and the energy exchange in their organs, the cytogenetic analysis of marrow cells and the process of multiplication in populations inhabiting areas with increased natural radiation background more 50 years are generalized. The data obtained support the existence of qualitative differences of Tundra vole subpopulations inhabiting control and radioactive nuclide contaminating areas. They allow to suppose that the process of adaptation to chronic low intensity radiation effect of Tundra vole in natural conditions involves the transition of the LPO and another regulatory systems to different level of function and is directed on population survival and homeostasis maintenance in changing radioecological conditions.

Animals↗
PubMed1988

Modeling estimates of the effect of acid rain on background radiation dose.

Acid rain causes accelerated mobilization of many materials in soils. Natural and anthropogenic radionuclides, especially 226Ra and 137Cs, are among these materials. Okamoto is apparently the only researcher to date who has attempted to quantify the effect of acid rain on the "background" radiation dose to man. He estimated an increase in dose by a factor of 1.3 following a decrease in soil pH of 1 unit. We reviewed literature that described the effects of changes in pH on mobility and plant uptake of Ra and Cs. Generally, a decrease in soil pH by 1 unit will increase mobility and plant uptake by factors of 2 to 7. Thus, Okamoto's dose estimate may be too low. We applied several simulation models to confirm Okamoto's ideas, with most emphasis on an atmospherically driven soil model that predicts water and nuclide flow through a soil profile. We modeled a typical, acid-rain sensitive soil using meteorological data from Geraldton, Ontario. The results, within the range of effects on the soil expected from acidification, showed essentially direct proportionality between the mobility of the nuclides and dose. This supports some of the assumptions invoked by Okamoto. We conclude that a decrease in pH of 1 unit may increase the mobility of Ra and Cs by a factor of 2 or more. Our models predict that this will lead to similar increases in plant uptake and radiological dose to man. Although health effects following such a small increase in dose have not been statistically demonstrated, any increase in dose is probably undesirable.

Background Radiation↗
PubMed1998

Estimation of environmental gamma background radiation levels in Pakistan.

For the purpose of preparing an environmental gamma radiation map of Pakistan, the geological materials exposed in the country were divided into eight different classes. Using average 238U, 232Th, and 40K content of these materials, total absorbed dose rate in these rocks was calculated. The dose rate in the environment ranged from 1 nGy h(-1) to 97 nGy h(-1) with a mean value of 59 nGy h(-1). These data are presented as a dose rate map of Pakistan. This map provides a usable regional picture of environmental gamma background radiation levels excluding cosmic radiation in Pakistan.

Background Radiation↗
PubMed1985

Biological effects of background radiation: mutagenicity of 40K.

The naturally occurring radioactive isotope 40K is the single largest contributor to the internal background radiation dose in living organisms. We examined cell growth and mutation rate or frequency in several strains of Escherichia coli in (i) media containing the natural content of 40K, (ii) media containing potassium from which essentially all of the 40K had been removed by isotope separation, and (iii) media highly enriched in 40K. Growth rates (doubling times) were identical in the present or absence of 40K. In more than 40 chemostat experiments, we were unable to detect any significant differences in mutation rate to bacteriophage T5 resistance or in mutation frequency to valine resistance or tryptophan prototrophy attributable to 40K. We conclude that, in the bacterial systems we have studied, 40K does not make a significant contribution to spontaneous mutation.

Dose-Response Relationship, Radiation↗
PubMed1997

The variations in long term TLD measurements of environmental background radiation at locations in southeastern New York state and northern New Jersey.

The variations of the measured dose rate in air should be recognized especially where background radiation is used as a comparative benchmark to assess radiation surveillance and environmental remediation work. In this note, the natural variations of the combined gamma and cosmic-ray background air-dose rate as measured by lithium fluoride thermoluminescence dosimeters are reported. The dosimeters were deployed monthly at locations within 150 km of the Environmental Measurements Laboratory in New York City. Urban and suburban stations were established with simultaneous indoor and outdoor measurements at some locations. Measurements were obtained over 10 to 18 years. The mean air-dose rates from the six outdoor and four indoor stations vary from 50.8 to 123.1 nGy h(-1). The range of the annual dose rates expressed as a percent-difference of the minimum and maximum is 5.3 to 18.0%. Commonly, 1-mo deviations from the long term mean of about +/-10 to +/-25% are observed. An abrupt decrease in the annual dose rate at one of the measurement sites was attributed to a minor relocation of a dosimeter. Structural shielding factors for the first and second floors of a residence are reported. The ground level location of a dosimeter inside another residence apparently resulted in a very high shielding factor. Finally, a gradual decrease of the dose rate at most of the stations is shown to exist (approximately -0.3 nGy h(-1) y(-1) for the outdoor stations). Plausible causes of this trend are briefly discussed.

Air Pollution, Indoor↗
PubMed2004

Heritable anomalies among the inhabitants of regions of normal and high background radiation in Kerala: results of a cohort study, 1988-1994.

In a genetic epidemiological and fertility survey among 70,000 inhabitants in a high-background radiation region (HBRR) and normal radiation region (NRR) in Kerala, India, 985 persons were found to have heritable anomalies. Suggested etiologies for the anomalies were chromosomal and Mendelian, 15 percent; multifactorial, 60 percent; and congenital, 25 percent. There was a statistically significant increase of Down syndrome, autosomal dominant anomalies, and multifactorial diseases and an insignificant increase of autosomal recessive and X-linked recessive anomalies in the HBRR. The total fertility rate was 3.85 per couple; 9 percent of live-born children were reported dead. The rate of untoward pregnancy outcome--death of the offspring or presence of an anomaly in a living child--was 6.4 percent among the unrelated couples in the NRR, with one spouse born outside the area of current residence ("migrant"). Considering this as the base, the excess relative risks in the other groups are: "NRR-nonmigrant," 35 percent; "HBRR-nonmigrant," 69 percent; "NRR-consanguineous," 76 percent; and "NBRR-consanguineous," 157 percent. Ionizing radiation, consanguinity, and nearness of birthplace of the spouse are risk factors for the death of offspring and for anomalies. The higher risk among the "nonmigrant" couples may be due to geographic inbreeding. The findings are suggestive of an autosomal recessive etiology for the majority of the multifactorial anomalies.

Abnormalities, Multiple↗
PubMed1998

Natural background radiation and cancer death in Rocky Mountain states and Gulf Coast states.

Calculations based on data from NCRP reports show that the average level of natural background radiation (NBR) in Rocky Mountain states is 3.2 times that in Gulf Coast states. However, data from the American Cancer Society show that age-adjusted overall cancer death in Gulf Coast states is actually 1.26 times higher than in Rocky Mountain states. The difference from proportionality is a factor of 4.0. This is a clear negative correlation of NBR with overall cancer death. It is also shown that, comparing 3 Rocky Mountain states and 3 Gulf Coast states, there is a strong negative correlation of estimated lung cancer mortality with natural radon levels (factors of 5.7 to 7.5).

Alabama↗
PubMed2004

Environmental 238U and 232Th concentration measurements in an area of high level natural background radiation at Palong, Johor, Malaysia.

Concentrations of uranium-238 and thorium-232 in soil, water, grass, moss and oil-palm fruit samples collected from an area of high background radiation were determined using neutron activation analysis (NAA). U-238 concentration in soil ranged from 4.9 mg kg(-1) (58.8 Bq kg(-1)) to 40.4 mg kg(-1) (484.8 Bq kg(-1)), Th-232 concentration ranged from 14.9 mg kg(-1) (59.6 Bq kg(-1)) to 301.0 mg kg(-1) (1204 Bq kg(-1)). The concentration of U-238 in grass samples ranged from below the detection limit to 0.076 mg kg(-1) (912 mBq kg(-1)), and Th-232 ranged from 0.008 mg kg(-1) (32 mBq kg(-1)) to 0.343 mg kg(-1) (1.372 Bq kg(-1)). U-238 content in water samples ranged from 0.33 mg kg(-1) (4.0 Bq L(-1)) to 1.40 mg kg(-1) (16.8 Bq L(-1)), and Th-232 ranged from 0.19 mg kg(-1) (0.76 Bq L(-1)) to 0.66 mg kg(-1) (2.64 Bq L(-1)). It can be said that the concentrations of environmental U-238 and Th-232 in grass and water samples in the study area are insignificant. Mosses were found to be possible bio-radiological indicators due to their high absorption of the heavy radioelements from the environment.

Bryophyta↗