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At least 505 records · Page 28Linked to original sources
PubMed1993

Estimate of excess uranium in surface soil surrounding the Feed Materials Production Center using a requalified data base.

A conservative estimate of the excess total uranium in the top 5 cm of soil surrounding the former Feed Materials Production Center was made using a data base compiled by the International Technology Corporation in 1986, and the requalification of that data base was completed in 1988. The results indicate that within an area of 8 km2, extending 2 km both northeast and southwest of the Feed Materials Production Center, the uranium concentration is between 2 and 5 times greater than average natural background radiation levels. More than 85% of this excess uranium is deposited within 1 km of the site boundary. The presence of any excess uranium outside of this area is indistinguishable from the natural background contribution.

Databases, Factual↗
PubMedDate not supplied

[The stimulating action of low doses of ionizing radiation on glucokinase synthesis in the liver of developing rats].

Taking spontaneous glucokinase synthesis as an example the authors showed an increase in the rate of enzymatic differentiation against the insignificantly increased natural radiation background, which might serve as a supporting evidence of the previously obtained data confirming the necessity of the natural radioactive background for the development of mammals.

Animals↗
PubMed1984

An assessment of health risk from radiation exposures.

A methodology has been developed to assess potential hazards from low-level exposures to radioactive pollutants. Estimates of dose rates to reference organs from internal and external exposure pathways (inhalation of contaminated air, ingestion of contaminated food or water, immersion in contaminated air, and exposure to contaminated ground surfaces) are computed with contemporary dosimetric models. These dose rates are used in a life-table analysis to estimate the radiation-induced cancer deaths and resultant years of life lost in an exposed cohort of 100,000 persons, all simultaneously liveborn and subject to the same risks of dying from competing causes (including natural background radiation). Estimates of the potential health risk are tabulated for approx. 150 radionuclides for each of the exposure pathways; results are summarized in terms of the probability of premature radiation-induced death for a member of the cohort due to incremental radiation exposure, and the average number of years of life lost per incremental fatality. The estimates of radiation-induced mortality generated by these methods provide a useful means of quantifying radiation risk; however, these estimates may be subject to large uncertainties, and can be best interpreted as a measure of the relative degree of hazard associated with exposures to various radionuclides through several exposure pathways.

Actuarial Analysis↗
PubMed2000

Mortality among the residents of the Three Mile Island accident area: 1979-1992.

The largest U.S. population exposed to low-level radioactivity released by an accident at a nuclear power plant is composed of residents near the Three Mile Island (TMI) Plant on 28 March 1979. This paper (a collaboration of The University of Pittsburgh and the Pennsylvania Department of Health) reports on the mortality experience of the 32,135 members in this cohort for 1979-1992. We analyzed standardized mortality ratios (SMRs) using a local comparison population and performed relative risk regression modeling to assess overall mortality and specific cancer risks by confounding factors and radiation-related exposure variables. Total mortality was significantly elevated for both men and women (SMRs = 109 and 118, respectively). All heart disease accounted for 43.3% of total deaths and demonstrated elevated SMRs for heart disease of 113 and 130 for men and women, respectively; however, when controlling for confounders and natural background radiation, these elevations in heart disease were no longer evident. Overall cancer mortality was similar in this cohort as compared to the local population (male SMR = 100; female SMR = 101). In the relative risk modeling, there was a significant effect for all lymphatic and hematopoietic tissue in males in relation to natural background exposure (p = 0.04). However, no trend was noted. We found a significant linear trend for female breast cancer risk in relation to increasing levels of TMI-related likely [gamma]-exposure (p = 0.02). Although such a relationship has been noted in other investigations, emissions from the TMI incident were significantly lower than in other documented studies. Therefore, it is unlikely that this observed increase is related to radiation exposure on the day of the accident. The mortality surveillance of this cohort does not provide consistent evidence that radioactivity released during the TMI accident has a significant impact on the mortality experience of this cohort to date. However, continued follow-up of these individuals will provide a more comprehensive description of the morbidity and mortality experience of the cohort.

Adolescent↗
PubMed1990

A-bomb radiation and evidence of late effects other than cancer.

Cancer risk coefficients for ionizing radiation are currently based on the assumption that, after the bombing of Hiroshima and Nagasaki, there were no late effects of early selection (survival of the fittest) or acute marrow damage. These negative findings were the result of applying a linear model of relative risk to the deaths of 5-y survivors. By applying a linear-quadratic model to these deaths (i.e., a model with more than one degree of freedom), we have obtained evidence of longstanding competition between selection effects of the early deaths and other radiation effects, and also evidence that late effects of radiation include marrow damage as well as cancer. Consequently, the present method of risk estimation--by linear extrapolation of high dose effects--should no longer be used for estimating the cancer effects of occupational exposures or background radiation.

Humans↗
PubMed1994

Database requirements for epidemiological estimates of radiation risks in continuously exposed populations.

Using the revised risk coefficients recommended by the 1990 report of the International Commission of Radiological Protection (ICRP), computations have been made on the minimum databases required for detecting radiogenic cancer excesses from epidemiological surveys of populations exposed to low level radiations. The computations have been made separately for Indian and Western populations using their representative demographic data. The western database requirements are generally found to be about half the Indian requirement. For the exposures in high background radiation areas at the rate of say 5 mSv/y, the minimum required database is 121,500 person years, in the Indian case. Similarly, for Indian occupational workers exposed at the rate of say, 10 mSv/y, it is required to observe 30,000 persons for the first 40 years or 3600 persons over their entire lifetime for obtaining statistically significant results.

Environmental Exposure↗
PubMed1997

[Radiotherapy after radical prostatectomy: indications, results and side effects].

BACKGROUND: Radiation therapy following radical prostatectomy in locally progressed prostate carcinoma has become increasingly important in the last few years as both adjuvant therapy in patients with pT3-tumors with or without positive margins and treatment for a PSA increase in local recurrence of disease. The background for this is the knowledge gained by using PSA that up to 60% of the patients with histopathologically confirmed pT3/4 tumors or involvement of the lymph nodes are systemically and/or locally progressive after 3 to 5 years if only surgical or radiation therapy was performed. RESULTS: A number of studies, albeit exclusively retrospective, substantiated a significantly high local tumor control by radiotherapy after radical prostatectomy. This holds true for adjuvant therapy with a PSA in the "zero range" as well as with a PSA increase from the "zero range", whereby it must be taken into consideration that a certain percentage of treated patients with a PSA in the "zero-range" with or without positive margins actually do not need further therapy. Two retrospective studies demonstrated a significant better lengthening of "freedom from treatment failure" that is local and systemic progression of disease. Lengthening the survival time has, however, not yet been proven. With an increase in the PSA from the "zero range" after radical prostatectomy, there are indications that systemic metastatic spread already occurs with values higher than 2.5 to 4 ng/ml and the radiotherapy no longer has any curative intention. CONCLUSIONS: Adjuvant RT following radical prostatectomy gives better local control rates and probably better rates of "freedom from treatment failure" in patients with locally advanced prostate cancer with positive margins and probably in patients with negative margins. However, in retrospective studies no advantage in overall survival was shown.

Follow-Up Studies↗
PubMed1997

Chromosome aberrations in Syrian hamsters following very low radiation doses in vivo.

This paper addresses a report of a large increase (approximately 6- to 11-fold) in chromosome aberrations in lymphocytes of persons in Salzburg attributed to their exposure to fallout from the Chernobyl cloud. Their additional exposure, approximately 0.3 mGy in 1 year, comprised about a 30% increase in their normal background radiation dose. The report has attracted considerable attention because, if correct, it seriously challenges assumptions of linearity in the low-dose response for chromosomal damage and, by implication, the linear, no-threshold hypothesis for risk of induced cancer. An experiment has been carried out with Syrian hamsters treated with caesium-137 to produce a range of doses comparable with those calculated for the persons in Salzburg. No significant elevation in lymphocyte aberration yields was found in the hamsters, thus arguing against the conclusions of the Salzburg study.

Animals↗
PubMed2004

Effect of low-level radiation on the low temperature acoustic behavior of a-SiO2.

We report on the mechanical behavior of an a-SiO2 84 kHz torsional oscillator operated between 100> or =T> or =1.0 mK. Below 10 mK we observed well-differentiated transient responses which we attribute to the interaction with low-level background radiation (gamma quanta and cosmic ray micro) and which can be modeled in terms of a change in the spring constant.

Journal Article↗
PubMed1993

Caffeine enhanced measurement of mutagenesis by low levels of gamma-irradiation in human lymphocytes.

The well-known action of caffeine in synergizing mutagenesis (including chromosome aberrations) of agents like ionizing radiation by inhibition of cellular repair processes has been incorporated into a rapid procedure for detection of mutagenicity with high sensitivity. Effects of 5-10 rads of gamma-irradiation, which approximate the human lifetime dose accumulation from background radiation, can be detected in a two-day procedure using an immortalized human WBC culture. Chromosomally visible lesions are scored on cells incubated for 2 h after irradiation in the presence and absence of 1.0 mg/ml of caffeine. An eightfold amplification of scorable lesions is achieved over the action of radiation alone. This approach provides a closer approximation to absolute mutagenicity unmitigated by repair processes, which can vary in different situations. It is proposed that mutagenesis testing of this kind, using caffeine or other repair-inhibitory agents, be employed to identify mutagens in their effective concentrations to which human populations may be exposed; to detect agents such as caffeine that may synergize mutagenic actions and pose epidemiologic threats; and to discover effective anti-mutagens. Information derived from the use of such procedures may help prevent cancer and newly acquired genetic disease.

Caffeine↗
PubMed1999

Nurture with ionizing radiation: a provocative hypothesis.

Whole body exposure to low-dose ionizing radiation appears to decrease overall cancer incidence. The data come from at least eight large studies of populations exposed to various forms of radioactive material and from more limited studies of occupational and environmental exposures to plutonium, radium, and radon. Earlier experiments in animals strongly support the protective effect that is apparent in humans. Also, experimental reports from invertebrates kept in radiation-deficient conditions suggest that ionizing radiation is essential for optimal growth and development. The combined evidence points to the presence of no-adverse-effect thresholds and of hormesis or beneficial effects at doses below those thresholds. Furthermore, according to the geological record, the high background radiation under which life first evolved has progressively attenuated up to the present. Thus it is intriguing to postulate that modern humans may live under conditions of partial deficiency of ionizing radiation; low doses of ionizing radiation may likely function as inducers of repair and detoxification mechanisms, much as low-level antigenic challenges are responsible for enhanced immune competence. This hypothesis runs contrary to the prevailing consensus of regulatory default assumptions, which negate the possibility of no-effect thresholds for agents that are carcinogenic at certain levels of exposure. Still, those are dogmatic policy assumptions without scientific or even empirical justification, whereas the hypothesis advanced here has consistent observational and experimental support. The implication is that a partial deficiency of ionizing radiation could be remedied by a safe supplementation, possibly through dietary means. Dose-response data from studies of nuclear workers and populations subjected to unusual exposures suggest that safe supplementation with about 0.4 cGy/mo would be beneficial and conservative.

Animals↗
PubMedDate not supplied

[The demonstration of environmental radioactive contamination by its gametocidal action].

Two Viola matutina Klok. populations growing in two areas of the thirty-kilometer zone of Chernobyl varying in gamma radiation background have been studied. Stable, repeated (during a period of 1987-1988) differences between the populations with respect to the amount of sterile pollen and the pattern of anther distribution curves have been revealed. It is suggested that the increased radiation loading is the cause of the increased occurrence of sterile pollen in one of the populations.

Accidents↗
PubMed1977

Comparison of two independent methods for determining the neutron/gamma sensitivity of a dosemeter.

Results obtained with two independent methods for measuring the n/gamma sensitivity of non-hydrogenous dosemeters are compared for the neutron beam produced by 8.3 MeV deuterons on beryllium. In one method, a pure neutron field is simulated by taking the difference between measurements made at diffrent angles in a mixed field with an isotropic gamma-ray component. In the second method, the mixed (n+gamma) beam is purified by lead filtration. An assumption in the lead filtration method is that the background radiation is invariant under three different beam conditions. This assumption was found not be be valid in our experimental arrangement; and caused the values obtained for the n/gamma sensitivity to be systematically high. A modification was made in the lead filtration method so that the dosemeter response to background could be determined for each beam condition. Good agreement was obtained between the results of the spectral difference and modified lead filtration methods.

Air↗
PubMed2001

Comparison between direct ion storage and thermoluminescence dosimetry individual monitoring systems, and Internet reporting.

A new electronic direct ion storage (DIS) dosemeter allows accumulated personal dose equivalent Hp(d) at depths of 10 mm and 0.07 mm to be monitored in a few seconds by inserting the dosemeter into a local reader without deleting the accumulated dose. The DIS system meets general requirements on individual monitoring of hospital personnel using ionising radiation. It differs greatly from off-line thermoluminescence dosimetry systems and offers many additional benefits. The non-volatile reading takes only 5 s, is taken as often as needed, and the data are collected into a dose database, where background radiation is subtracted. Individual personnel doses are reported in Intranet as well as on the Internet at regular intervals to the National Regulatory Authorities.

Air Pollutants, Radioactive↗
PubMedDate not supplied

[The action of atomic radiation in low doses on the biota].

The radiobiological studies carried out in conditions of lower and slightly increased natural radiation background have prompted an idea of "low doses" in radiobiology which is proposed for discussion. The author emphasizes that the difference between the leading molecular and cellular mechanisms that come into play under the effect of high- and low-level atomic radiation makes it incorrect to assess the risk from low radiation doses on the basis of the regularities obtained with high doses.

Animals↗
PubMed2004

NEMA NU 2 performance tests for scanners with intrinsic radioactivity.

Performance tests on lutetium oxyorthosilicate (LSO)-based PET scanners cannot be conducted strictly according to the National Electrical Manufacturers Association (NEMA) NU 2 standards because of the presence of intrinsic radioactivity within the LSO crystal scintillator material. This background radiation gives rise mainly to random coincidence events but also to a small number of true coincidences, which cannot be eliminated from measurements on such scanners and must therefore be corrected for in the data analysis. The current NU 2 standards do not take account of these backgrounds and hence can lead to erroneous results on LSO-based machines. Nevertheless, the intent of the standards can be met with appropriate modifications to the acquisition and processing procedures. In this paper, we propose certain changes to the NEMA specifications to accommodate this class of scanners. These changes affect mainly the estimation of sensitivity, scatter, randoms, and count losses. Using these modified procedures, the NU 2 performance of LSO-based systems can accurately be measured.

Gamma Cameras↗
PubMed1996

Regional variation in radionuclide concentrations and radiation dose in caribou (Rangifer tarandus) in the Canadian Arctic; 1992-94.

Gamma-emitting radionuclides and 210Po, an alpha-emitting product of the 238U decay chain, were analysed in tissues from 16 caribou (Rangifer tarandus) collections in the Canadian North between 1992 and 1994. The study was conducted to determine the regional variability of anthropogenic and natural radionuclides in Canadian caribou, and to estimate the background radiation dose to caribou tissues. 137Cs, 40K, 210Pb and 210Po were consistently found in most herds. Mean muscle 137Cs varied from below detection limits on Banks Island to 231 Bq kg-1 wet weight (ww) in the Beverly herd in the central Arctic. Comparison of 1992-94 levels with published values from the 1960s and 1980s showed that 137Cs in caribou is declining with an effective half-life (Teff) of 9.9 years. The highest mean bone and liver 210Pb activities were observed on south Baffin Island, which included one bone sample with 3800 Bq kg-1 ww of 210Pb and 3070 Bq kg-1 ww of 210Po. The distribution of 137Cs and 210Pb between herds was attributed to higher atmospheric deposition rates between 60 and 65 degrees N, and changes in plant community structure and lichen species composition. The highest mean absorbed dose (30 mGy year-1) was observed in 1993 in the liver of caribou from Lake Harbour. This dose translated into a weighted absorbed dose of 300 mGy year-1, assuming a radiation weighting factor (wR) of 10 to account for the increased biological efficiency of alpha particles for deterministic effects. The Lake Harbour site also had the highest individual weighted absorbed dose in bone (810 mGy year-1) and liver (530 mGy year-1) in the study. There was no significant relationship between bone 210Pb activity and age for individual or pooled herds, indicating that the estimated doses are probably present throughout the lifetime of the caribou. Because some herds number several hundred thousand individuals, collective doses may also be very high. As yet, there have been no reports of observable effects due to these relatively high exposures and many of the herds continue to thrive and increase in size.

Analysis of Variance↗