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At least 19 recordsLinked to original sources
PubMed2005

Biomarkers of space radiation risk.

Radiation risk estimates are based on epidemiological data obtained on Earth for cohorts exposed predominantly to acute doses of gamma rays, and the extrapolation to the space environment is highly problematic and error-prone. The uncertainty can be reduced if risk estimates are compared directly to space radiation-induced biological alterations, i.e. by detecting biomarkers in astronauts. Chromosomal aberrations in peripheral blood lymphocytes are the only biomarker that can provide simultaneous information on dose, dose equivalent and risk, and they have been measured extensively in astronauts during the past 10 years. Individual relative risks calculated from chromosomal aberration measurements in crew members after single space missions in low-Earth orbit fall in the same range as the estimates derived from physical dosimetry, suggesting that the current system for radiogenic risk evaluation is essentially sound. However, the output of the biomarker test is dependent upon the sampling time. Recent results show a fast time-dependent decay of chromosomal aberrations in blood lymphocytes after space flight and a lack of correlation between translocations and cumulative dose in astronauts involved in two to five space missions. This "time factor" may reflect individual variability and time dependence in the risk produced by exposure to cosmic radiation during the flight. Biomarkers may be superior to dose in predicting space radiation risk, pending technical improvements in sensitivity, and validation by epidemiological studies.

Biomarkers↗
PubMedDate not supplied

[Evaluation of the radiation risk of determinate effects from space radiation in a piloted mission to Mars].

Solar cosmic rays (SCR) are one of the sources of radiation risk specific to space flights. On Earth, occupational exposure has a regular character and radiation risk is an attribute of nothing else but stochasticity of radiobiological effects. In space flight, SCR impart stochasticity to the radiation environment and, therefore, probability to all, including determinate, radiobiological effects. The most dangerous effect is radiation disease the dosimetric functional of which is an equivalent dose to the blood-forming organs. In addition, this radiation pathology is modulated by reparative processes in the blood-forming tissue which must be also taken into account during radiation risk evaluation. Using the speculated mission to Mars as an example, it was shown that radiation risk of determinate effects defined as probability of death by radiation disease in consequence of exposure to SCR can be comparable in value to the risk from stochastic effects.

Cosmic Radiation↗
PubMed2001

Mechanistic bases for modelling space radiation risk and planning radiation protection of astronauts.

The approaches generally adopted for planning radiation protection in ground-based facilities cannot be applied straightforward for astronaut protection in space. Indeed in such extreme conditions, modelling methods and shielding design must be based on a detailed mechanistic knowledge of the peculiar astronauts irradiation conditions. Great help can derive from mechanistic modelling, generally aimed to better understand the intermediate steps leading from the initial energy depositions to different biological endpoints, up to organ and organism level. In the present work, criteria will be illustrated for using mechanistic approaches in developing practical tools for astronauts radioprotection, once the external field and the interaction cross sections with the spacecraft walls are known; particular attention will be given to the treatment of mixed fields. Techniques for integrating into condensed-history codes stochastic information provided by event-by-event simulations will be presented.

Aerospace Medicine↗
PubMed2002

Thyroid cancer incidence among liquidators of the Chernobyl accident. Absence of dependence of radiation risks on external radiation dose.

The increase of thyroid cancer incidence rate among children living in the Chernobyl contaminated territories of Belarus, Russia and Ukraine has widely been accepted. Our current work deals with thyroid cancer incidence in the cohort of liquidators (99024 persons) living in 6 regions of Russia: North-West, Volgo-Vyatsky, Central-Chernozemny, Povolzhsky, North-Caucasus and Urals. In the period 1986-1998, a total of 58 thyroid cancer cases were detected in this cohort. We found a statistically significant increase of the thyroid cancer incidence rate in liquidators as compared to the baseline (male population of Russia) level (SIR=4.33, 95% CI: 3.29; 5.60). It was demonstrated that there is no dependence of incidence rates due to external radiation exposure (ERR/Gy=-2.23, 95% CI: -4.67; 0.22).

Adolescent↗
PubMed2000

Radiation risks in perspective: radiation-induced cancer among cancer risks.

The majority of the public in industrial countries believes that pollution and low doses of radiation are threats to good health. As a matter of fact, when these putative risks are compared to those originating from lifestyle, they appear very small. In particular, the risks associated with low doses of irradiation, even when they are assessed with the most pessimistic models, appear extremely small. Public anxiety is fuelled by the uncertainty regarding the magnitude of this risk and the use of the linear no threshold (LNT) hypothesis, which gives credence to the concept that even the smallest doses are harmful. There are a number of scientific and epidemiological data currently under debate that are not consistent with the LNT hypothesis. For example, no difference in the incidence of cancers or of birth defects has been observed between regions with low or high natural irradiation. This inconsistency between perceptions and data underlines the role of psychological factors studied since 1957 which should be placed in the perspective of the public's present attitude toward risk and technology. Social amplification or attenuation of risk may occur in several ways. Fearful concern about radiation began in 1955, with the beginning of the Cold War, when the possibility of a nuclear holocaust appeared very real. Analysis of the data shows that these fears of technology could have a detrimental effect; they should therefore be investigated and understood.

Cause of Death↗
PubMed2002

Routine screening mammography: how important is the radiation-risk side of the benefit-risk equation?

The potential radiation hazards associated with routine screening mammography, in terms of breast cancer induction, are discussed in the context of the potential benefits. The very low energy X-rays used in screening mammography (26-30 kVp) are expected to be more hazardous, per unit dose, than high-energy X- or gamma-rays, such as those to which A-bomb survivors (from which radiation risk estimates are derived) were exposed. Based on in vitro studies using oncogenic transformation and chromosome aberration end-points, as well as theoretical estimates, it seems likely that low doses of low-energy X-rays produce an increased risk per unit dose (compared with high energy photons) of about a factor of 2. Because of the low doses involved in screening mammography, the benefit-risk ratio for older women would still be expected to be large, though for younger women the increase in the estimated radiation risk suggests a somewhat later age than currently recommended--by about 5-10 years--at which to commence routine breast screening.

Adult↗
PubMed1986

Cataract analysis and the assessment of radiation risk in space.

Radiation cataract, a non-stochastic effect on the lens, is readily amenable to non-invasive analysis. Thus, it provides the means to assess radiation risk in space and for long-term monitoring of those who frequent that environment. The importance of such evaluations are underscored by the uncertainties associated with the assignment of quality factors for the effects of heavy charged particles constituting cosmic and solar radiation. Experimental studies were conducted using albino rats to evaluate the cataractogenic potential of 570 MeV/amu Argon ions administered as both single and protracted doses. The cataract studies and investigations of quantitative cytopathological changes associated with them indicate that as the dose of heavy particles decreases, the relative biological effectiveness, compared to X rays, increases. Fractionating the exposures not only failed to reduce the cataractogenic effect but caused a dose-dependent enhancement in the time of onset of opacification. Cytopathologically, the damage caused by heavy particles, when compared to low-LET radiation was found to be quantitatively dissimilar but qualitatively identical. In addition, damage which might be consistent with microlesions was not evident. The data indicates that as regards the cataractogenic potential of heavy particles at low doses an assignment of a Quality Factor (QF) of at least 40 may be in order.

Animals↗
PubMed1985

[Current aspects in the evaluation of radiation risk: from the risk to organs to total injury risk (effective equivalent doses)].

For the estimation of the health risks of radiation in man by low radiation doses as well as to compare the man-made radiation exposure with the natural one, it is proved useful and necessary to estimate the effective dose-equivalent. It is not sufficient to take only into consideration the radiation exposure of bone marrow and gonads. Due to an external irradiation source as well as by incorporation of radioactive materials, various tissues and organs in the human body will simultaneously be exposed. This is best illustrated by the component of the "natural" radiation exposure with radon, attributable more or less to our living conditions. The incorporation of radon and its daughters in the lung with its cancer causing risk is not evaluated in the determination of the gonads and bone marrow dose. The effective dose-equivalent is being estimated for the evaluation of possible radiation risk by the carcinogenic and mutagenic effectiveness of radiation (stochastic radiation risk) with weighting factors. For the genetic risk solely 25% and for the somatic risk 75% are granted, whereas the risk factor "breast tissue" dominates.

Dose-Response Relationship, Radiation↗
PubMed1976

[Trends and new findings in the assessment of the somatic radiation risk (author's transl)].

New findings are described which enable a more precise estimation of the leukemia and cancer risk by radiation. They concern the risk ratio of cancer to leukemia after whole body irradiation, the shape of the dose-risk-relationship and the time factor problem. Finally a balance of the somatic radiation risk from whole body irradiation is set up and the consequences for the establishment of dose limits are discussed.

Dose-Response Relationship, Radiation↗
PubMed1995

Application of the HSEF to assessing radiation risks in the practice of radiation protection.

The primary risk coefficients upon which exposure limits for radiation protection purposes are currently based are derived almost exclusively from cancer-induction data obtained from human populations exposed to radiations of low linear energy transfer. The question of higher linear energy transfer radiations is handled by means of quality factors derived from values for relative biological effectiveness obtained from animal data. However, the advent of microdosimetry has made it possible to establish hit size effectiveness functions from single-cell systems, both in vitro and in vivo. This type of function can substitute completely for the concept of relative biological effectiveness, Q and equivalent dose. A common basis for risk coefficients and the hit size effectiveness function lies in the fact that human cancers are monoclonal and thus single cell in origin. The present communication utilizes this common base as a means of extending the present low-linear energy transfer based risk coefficients to include carcinogenic responses from exposure in radiation fields of any one or mixed qualities, extending from the smallest to the largest linear energy transfers of practical consequence. In doing so, risks from ionizing radiations of any linear energy transfer may be predicted more accurately than at present.

Biophysical Phenomena↗
PubMed2004

Solar cosmic rays as a specific source of radiation risk during piloted space flight.

Solar cosmic rays present one of several radiation sources that are unique to space flight. Under ground conditions the exposure to individuals has a controlled form and radiation risk occurs as stochastic radiobiological effects. Existence of solar cosmic rays in space leads to a stochastic mode of radiation environment as a result of which any radiobiological consequences of exposure to solar cosmic rays during the flight will be probabilistic values. In this case, the hazard of deterministic effects should also be expressed in radiation risk values. The main deterministic effect under space conditions is radiation sickness. The best dosimetric functional for its analysis is the blood forming organs dose equivalent but not an effective dose. In addition, the repair processes in red bone marrow affect strongly on the manifestation of this pathology and they must be taken into account for radiation risk assessment. A method for taking into account the mentioned above peculiarities for the solar cosmic rays radiation risk assessment during the interplanetary flights is given in the report. It is shown that radiation risk of deterministic effects defined, as the death probability caused by radiation sickness due to acute solar cosmic rays exposure, can be comparable to risk of stochastic effects. Its value decreases strongly because of the fractional mode of exposure during the orbital movement of the spacecraft. On the contrary, during the interplanetary flight, radiation risk of deterministic effects increases significantly because of the residual component of the blood forming organs dose from previous solar proton events. The noted quality of radiation responses must be taken into account for estimating radiation hazard in space.

Cosmic Radiation↗
PubMed2001

[Assessment of usefulness and risk of mammography screening with exclusive attention to radiation risk].

In Germany, a vivid debate is still going on concerning the implantation of preventive mammographic screening into the national health care system. Before launching such a programme, benefits and risks have to be carefully assessed. The risk of radiation induced breast cancer was calculated in terms of mortality per 100.000 women using the risk estimates of BEIR. The radiation dose was assumed to be 8 mSv per examination (2 mGy per view, 2 views; RBE = 2, to be on the safe side). From the current literature regarding the benefits of screening, the number of deaths avoided per 100.000 women was estimated. Under the assumptions made in the model, screening from age 40 to 50 (six examinations at 2 years intervals, discontinuing at later age) might be associated with a benefit/risk ratio of about 6, whereas for women in the age group from 50 to 60 years the benefit/risk ratio was shown to be about 25. For a screening programme starting at the age of 50, the radiation risk involved does not appear to be a crucial issue. For performing mass screening with mammography beginning at the age of 40, radiation risks might have to be considered among a number of other risks associated with this age group.

Adult↗
PubMed1999

[An algorithm to compute the radiation risk during interplanetary space flights].

The algorithm of estimation of the radiation risk to cosmonauts on long-term interplanetary missions stems from new approaches to the estimation of radiation hazard, calculation of generalized dose inputs from various space radiations, hypothesized probability of human death due to exposure to varying doses of standard radiation. These data allow calculation of radiation risk from deterministic sources along the flight trajectory and stochastically distributed in time solar flares. Results of this calculation can be further used to correlate the in-flight radiation risk with mission length, shield thickness, solar cycle, and age of cosmonauts. They may be additionally used to compare the in-flight radiation risk with the national demographic risk of male lethality over a similar period.

Adult↗
PubMed2003

The impact of the new biology on radiation risks in space.

Radiation is considered to be one of three or four major hazards for personnel in space and has emerged as the most critical issue to be resolved for long-term missions, both orbital and interplanetary. Space habitats are stressful and dangerous environments. Health and medical consequences arising from microgravity, stress, and trauma include weakened immune systems, increased viral activity, and loss of bone mass. The greatest risks from radiation are generally assumed to be cancers and possibly damage to the central nervous system. Synergistic effects arising from the other environmental hazards along with abscopal and exogenic factors are likely. Space programs represent an exceptional opportunity for examining the biological consequences of low-dose exposures of humans to radiation at every level of progression. Although astronauts are a relatively small population, they are healthy, physically active volunteers who undergo extensive testing and medical examinations before, during, and after protracted exposures with periodic follow-up examinations. The radiation environments along with other hazards are likewise monitored and documented. Extensive international research programs are in progress. Seven years ago the U.S. National Aeronautics and Space Administration established the National Space Biomedical Research Institute through a cooperative agreement with a consortium of research and academic institutions in order to address radiation issues through a concerted, programmatic effort. Advanced technologies are rapidly being incorporated into these programs to determine the significance of new biological data and to evaluate the interplay among the different medical hazards. Programmatic in vivo and in vitro studies of the processes leading to carcinogenesis are in progress. Drugs and dietary supplements are being examined at the cellular and in vivo levels to assess their potential as dose-modifying agents. The infrastructure of this new approach, recent results, and research in progress are reviewed and discussed.

Academies and Institutes↗
PubMed1993

On communication and comparison of radiation risks.

Comparison with other risks helps to put a radiation risk into perspective and facilitates communication of radiation risk to the public. Twelve recommendations for risk comparisons are given, and some guidelines for risk communication are discussed.

Communication↗