Radiation protection of the environment: anthropocentric and eco-centric principles

The second half of the XX century was dominated in the field of radiation protection of the environment by the anthropocentric concept stated by the International Commission on Radiological Protection (ICRP). According to this concept "if man is adequately protected by radiological standards then biota are also adequately protected". At the end of the XX--beginning of the XXI centuries in the area of area of radiation protection of nature an ecocentric strategy is beginning to develop where emphasis has swung to the protection of biota in their environment. Inadequacy of ICRP's anthroposentric concept is reported. Issues are discussed such as ecological dosimetry, nonequidosal irradiation of man and biota, criteria for estimating radiation induced changes in biota and man, as well as the need to harmonize permissible exposure doses to man and biota. An urgent need is stressed to develop a single (synthetic) concept of radiation protection which simultaneously ensures protection of human health and biota well-being in their environment. This concept is to be based on the recognition of the integrity of socio-natural ecosystems where man and biota are considered as a unity.     

Radiation injury: some aspects of the oncogenic effects.

The late effects or irradiation stem from cell killing, mutation, and malignant transformation. Cancer is the major somatic late effect of exposure to low dose levels of radiation, and estimates of risk of cancer in man after irradiation are based entirely on human experience. The data for dose-response relationships for the induction of tumors by external irradiation in man have been obtained from a single exposure or a small number of exposures delivered at high dose rates. In contrast, exposure to environmental irradiation is mainly protracted over a long period of time and is delivered at a low dose rate. As yet no allowance has been made for the effect of protraction of the exposure time in estimating the risk of cancer, although an adjustment has been made in the case of estimates of genetic risk. Incidence of tumors has been the only parameter used for risk estimates, but latent period and degree of malignancy, which are probably both dose and dose-rate dependent, influence the nature of the risk from radiation. As the knowledge about the effects of low-level radiation has been accumulated and assimilated over the last 70 years, so has the concern for reasonable standards of safety. There are still problems in the estimation of radiation risks, but at least many of the relevant questions can now be framed. The problems of estimating risks for chemical carcinogens are clearly greater, but the experience gained from radiation studies should help in the design of the necessary experiments.     

Genotoxicity and toxicity assay of water sampled from the underground nuclear explosion site in the north of the Perm region (Russia)

The results of our study revealed a local biologically relevant surface water contamination in the radionuclide anomaly in the north of Russia (Perm region) by means of Allium shoenoprasum L. the anaphase-telophase chromosome aberration assay. This radionuclide anomaly was formed in 1971 as a result of an underground nuclear explosion with soil excavation. Specific activities of main dose-forming radionuclides in all examined reservoirs are below intervention levels officially adopted in Russia for drinking water. We found that 90Sr significantly contribute to induction of cytogenetic disturbances. Our previous and described here data suggest that metal ions and radionuclides combined exposure on the various biota species (with the dose below permissible exposure limits for human) may cause substantial biological effects in part be due to synergic response. The findings described here indicated that development of a new concept of radiation protection for humans and biota should be based on the clear understanding of biological effects of low doses of radiation in chronic exposure to multi-pollutant mixtures.     

The individual prognosis of the gravity and of the outcome of acute radiation disease based on immunological indexes

The information significance of the immunological indexes for the prognosis of gravity of course and of outcome of an acute radiation disease for the people after the exposure of ionizing radiation in clinically significant doses is studied. The value of indexes of the C-reactive protein contents, of the complement contents and of the titer of haemagglutinins in serum of a blood of 147 patients damaged at Chernobyl NPP accident as a result of external radiation gamma-exposure in combination with internal irradiation from the incorporation in an organism predominantly beta-emitting radionuclides were compared to the weight of acute radiation disease and its outcome (survival or loss). Was determined, that indexes of the contents of C-reactive protein in a peripheral blood during primary reactions on the irradiation (1-2 day after irradiation) and in latent period of disease (3-9 day after irradiation), and also titer of a complement on 3-9 day after irradiation can serve a source of information for the prognosis of probable gravity of a radiation injury and its outcome at irradiation of the man in clinically significant doses.     

Chernobyl and the environment

Analyzed information which describes a wide spectrum of the consequences of radioactive contamination of natural ecosystems by the Chernobyl accident. The main regularities of radionuclide migration in the environment was been considered and scales of radiation damage to biota assessed. The area where signs of direct damage to biota are visible is shown to be noticeably smaller in size that the area where radionuclide concentration in environmental objects is above the permissible levels. The importance of the impact of radioactive contamination of natural ecosystems is assessed in terms of formation of exposure doses to the population. The conclusion was made that the detriment from all the factors is larger for humans (direct irradiation, limitation of the economic activity, etc.) than for biota.     

The significance of cytogenetic investigation for the estimation of Chernobyl accident consequences

The results of the cytogenetic investigation of people, which were exposed to radiation in the result of the Chernobyl NPP accident, were presented. Also the possibilities of the application of cytogenetic findings for dose estimations and for the prediction of the radiation influence consequences were examined. During the period of time since 1986 till 2004 the cytogenetic investigations of 1724 liquidators participating in the liquidation works after the Chernobyl accident were carried out. The radiation dose estimated by the frequency of dicentrics in 1986 was about 0.16 Gy. The doses for liquidators were determined by the frequency of translocations (FISH method) during the period from 1992 till 1995. For liquidators who worked in Chernobyl only in 1986 the average dose of radiation was about 0.19 Gy and for liquidators who worked repeatedly during the period from 1986 till 1995 - 0.39 Gy. There was shown that during the whole period of investigation (1986-2004) the frequency of dicentrics in peripheral blood lymphocytes was significantly higher than the control level. The cytogenetic investigation of Bryansk region inhabitants which was carried out in 1992-1994 discovered heightened value in 5 times than the control one. Findings are of great importance for the prediction of ill effects of radiation and for the development of sensitive criterions for early exposure disturbances in state of health.     

Morphometric Indices of Scots Pine Needle under Chronic Radiation Exposure

We have studied the morphometric indices of needles in Scots pine populations that grow in Bryansk oblast in sites with radioactive contamination long after the Chernobyl accident. The variability in needle weight and length, as well as the fluctuating asymmetry indices and occurrence of necroses and morphoses, were studied in four contaminated and two reference populations of Scots pine in 2011, 2013, and 2014. The exposure of needles in radioactively contaminated sites varied from 7 to 130 mGy/yr. We found brachyblasts with three needles in contaminated Scots pine populations; this morphosis was absent in the reference populations. A dependence of the occurrence of needles damaged by necrosis on the levels of radiation exposure in 2011 was found. However, it was statistically insignificant in other years. The length and weight of needles in contaminated populations differed from the control values; however, the dependence of these indices on the level of radiation exposure was not revealed in the studied range of doses. In 2011 and 2013, the index of fluctuating asymmetry in needle length exceeded the control levels in sites where the absorbed doses were 90 and 130 mGy; this index also tended to grow (statistically significantly in 2011) with an increase in the characteristics of radioactive contamination of the studied plots: the exposure dose rate and the specific activity of ⁹⁰Sr and ¹³⁷Cs in cones and of ¹³⁷Cs in the soil. Therefore, one can observe the consequences of chronic radiation exposure at the organismic level in populations of Scots pine (one of the most radiosensitive plant species) even 25 years after the accident. The data that we obtained in natural habitats confirm the international estimates, according to which the annual chronic radiation exposure of 100 mGy can be considered the limit of safe radiation exposure of natural populations according to morphological and ontogenetic parameters.     

The effects of non-human species irradiation after the Chernobyl nuclear accident

Data are presented on the effects of irradiation of different biota species after the Chernobyl accident.     

Radiation Hazards Control in Survival Operations in the Event of a Nuclear War

The concepts of radiation protection in survival operations are explained, and procedures devised to control radiation hazards for the protection of the population and maintenance of the operating efficiency of survival operations personnel are presented.Radiation protection is a command function. The medical responsibility is to provide advice on the probable effects of radiation exposure in the light of existing knowledge of these effects in man.The major hazard is that of external exposure to penetrating gamma radiation. Radiation exposure guides indicate that persons may be exposed to not more than 100 r whole body radiation in a six-week period, or 200 r whole body radiation in a period in excess of six weeks, without loss of operational efficiency. Beta radiation from fallout deposited on skin or clothing may produce burns, but these injuries will not be incapacitating and can be controlled by simple procedures.The internal hazard is mainly from ingestion of food or water contaminated with radioactive material. For protection, only canned or packaged foods and water from covered or deep wells are consumed during the early days after a nuclear attack.     

Long-term follow-up cytogenetic survey and biological dosimetry in persons evacuated from 30-km Chernobyl NPP zone

The paper presents the results of the follow-up cytogenetic survey and biological dosimetry carried out in inhabitants of Pripiat' town and nearby villages, who were departured from the Chernobyl NPP 30-km exclusive zone during first days after the Chernobyl catastrophe. The unstable chromosome aberration level in inhabitants were significantly increased above control in terms up to 1 year after evacuation and declined gardually during next 14 years. In early period the cytogenetic damage frequency in evacuees showed no dependence on gender. The chromosome type aberration level appeared to be lower in young persons comparing with adults. The dicentrics plus centric rings yield had a positive correlation with duration of staying at Chernobyl zone. The average doses of protracted exposure were calculated from the dicentrics and centric rings yields; the dose estimations appeared to be 1.4 times higher in persons evacuated 3-11 days after the accident than that of in persons with shorter departure time. Uing the Bayesian analysis the probabilistic distribution of biological doses was constructed for the studied evacuees group. This distribution was characterized by a mean dose of 360 mGy, the modal doses of 200-450 mGy and 80% of probability density within the dose range 0-1000 mGy, that seems to be sufficient for considering the increased risk of late somatic radiation effects for this cohort.     

Pollinators and Other Flying Insects inside and outside the Fukushima Evacuation Zone

Following the accident at the Fukushima Daiichi nuclear power plants in 2011, a large evacuation zone was imposed in an area where residents had historically managed forests and farmlands. Thus, the human activities that had maintained biodiversity and ecosystem services in the zone were discontinued. Such change can affect insects, a biodiversity component that is relatively tolerant to radiation exposure. In this study, we investigated flying insects, including pollinators, important ecosystem providers inside and outside the zone, using Malaise traps. The results showed that the number of individuals of Xylocopa appendiculata, the largest Apidae species in the region, was significantly lower inside the evacuation zone than outside it, whereas those of other insects were not lower significantly. Although we suggest that flying insects and their ecosystem services (i.e., benefits from them such as pollination) 3 years after the disaster were not critically impacted, it is important to monitor the long-term effects of the evacuation in the future.     

Genomic damage in children accidentally exposed to ionizing radiation: a review of the literature

During the last decade, our knowledge of the mechanisms by which children respond to exposures to physical and chemical agents present in the environment, has significantly increased. Results of recent projects and programmes focused on children's health underline a specific vulnerability of children to environmental genotoxicants. Environmental research on children predominantly investigates the health effects of air pollution while effects from radiation exposure deserve more attention. The main sources of knowledge on genome damage of children exposed to radiation are studies performed after the Chernobyl nuclear plant accident in 1986. The present review presents and discusses data collected from papers analyzing genome damage in children environmentally exposed to ionizing radiation. Overall, the evidence from the studies conducted following the Chernobyl accident, nuclear tests, environmental radiation pollution and indoor accidental contamination reveals consistently increased chromosome aberration and micronuclei frequency in exposed than in referent children. Future research in this area should be focused on studies providing information on: (a) effects on children caused by low doses of radiation; (b) effects on children from combined exposure to low doses of radiation and chemical agents from food, water and air; and (c) specific effects from exposure during early childhood (radioisotopes from water, radon in homes). Special consideration should also be given to a possible impact of a radiochemical environment to the development of an adaptive response for genomic damage. Interactive databases should be developed to provide integration of cytogenetic data, childhood cancer registry data and information on environmental contamination. The overall aim is to introduce timely and efficient preventive measures, by means of a better knowledge of the early and delayed health effects in children resulting from radiation exposure.     

Monosodium glutamate for accidental,retrospective, and medical dosimetry using electron spin resonance

The risk of a radiation episode has increased in the last years due to several reasons. In case of a nuclear incident, as with the use of an improvised nuclear device, determination of the radiation doses received by the victims is of utmost importance to define the appropriate medical treatment or to monitor the late effects of radiation. Dose assessment in case of accidents can be performed using commonplace materials found in the accident area. In this paper, the dosimetric properties of monosodium glutamate are investigated by electron spin resonance spectroscopy (ESR), for retrospective and accidental dosimetry. The spectroscopic parameters were optimized to achieve higher signal intensity and better signal-to-noise ratio. As a result, the lowest detectable dose was 0.1 Gy, and monosodium glutamate showed a linear dose–response curve for doses ranging from 0.1 Gy to 10 kGy. The dosimetric signal was monitored from minutes right after irradiation, until 1 year. No changes in the signal intensity were observed over this period, meaning that doses could be assessed immediately after radiation exposure and can still be reconstructed long after the accident. This property also implies that late effects due to victim’s radiation exposure could be better monitored and understood. ESR signal intensity for samples irradiated with a photon energy below 100 keV was decreased by only 27% and no dose-rate dependence was noticed. Therefore, the ability to measure doses as low as 0.1 Gy, the high stability of the dosimetric signal, as well as independence on dose rate, tissue equivalence, low-cost, and wide commercial availability make monosodium glutamate a very good dosimetric material not only for retrospective and accidental but also for medical dosimetry.     

Analysis of blood lymphocyte subsets in children living around Chernobyl exposed long-term to low doses of cesium-137 and various doses of iodine-131

Epidemiological studies have found that children living around Chernobyl have rates of respiratory tract illness that are higher than those seen in the area before the Chernobyl accident. The present study investigates the possible effects of radiation exposure on the composition of peripheral blood lymphocyte subsets in children living around Chernobyl. Two hundred nineteen healthy children and children suffering from recurrent respiratory diseases aged 6-14 years who received both low doses of radiation to the whole body from (137)Cs and various doses of radiation to the thyroid from (131)I as fallout from the accident were assessed 5 (1991) and 8-10 years (1994-1996) after the accident. A total of 148 healthy children and children suffering from recurrent respiratory diseases living in noncontaminated areas were also evaluated as controls. Children with recurrent respiratory diseases who lived around Chernobyl had a significantly lower percentage of T cells and a higher percentage of NK cells compared to control children with recurrent respiratory diseases during the study period. In contrast to the findings in 1991, a significant decrease in the percentage of helper-inducer cells was observed in children with recurrent respiratory diseases in 1994-1996. In contrast to 1991, there is a positive correlation between the percentage of helper-inducer cells, the helper-inducer/cytotoxic-suppressor cell ratio, and the dose of radiation to the thyroid of healthy children from (131)I in 1994-1996. There was a positive correlation between the dose of radiation to the thyroid from (131)I and the percentage of helper-inducer cells in children with recurrent respiratory diseases 5 years (1991) after the accident. Further, the dose of radiation to the thyroid from (131)I correlated negatively with the percentage of T and B cells and positively with the percentage of NK cells in children with recurrent respiratory diseases 8-10 years (1994-1996) after the accident. These results raise the possibility that long-term exposure to low doses of (137)Cs may have altered the composition of the T-cell subsets and NK cells in children with recurrent respiratory diseases. The differences in the composition of the peripheral blood lymphocyte subsets between healthy children and those with recurrent respiratory diseases may be attributed to long-term low-dose exposure of the whole body to radiation from (137)Cs and exposure of the thyroid to radiation from (131)I subsequent to the Chernobyl accident.     

Man's sensitivity to bone marrow failure following whole body exposure to low LET ionising radiation: inferences to be drawn from animal experiments

Evidence concerning the sensitivity of man to bone marrow failure following exposure to brief but substantial doses of ionising radiation is sparse. There is, however, a relatively substantial body of information on such effects in large animals. Reported experiments on six species where exposure to low LET radiation was uniform to the whole body and of brief duration (exposure times of the order of one hour or less) have been reanalysed both in terms of exposure and of midline tissue dose. The results indicate a marked lack of homogeneity among values for LD50 within species thus questioning the applicability of LD50 as a species dependent constant. It is, however, suggested that on a purely empirical basis these large animal data suggest that the dose killing 'most' (where 'most' is between 90 and 95 per cent) is about twice that killing 'few' (where 'few' is between 5 and 10 per cent). For man, where there is evidence that the dose killing few is unlikely to be less than 3 Gy, this relationship might indicate a gradient of mortality with dose between 3 and 6 Gy.     

Interrelationships amongst radiation-induced genomic instability, bystander effects, and the adaptive response

Over the past two decades, our understanding of radiation biology has undergone a fundamental shift in paradigms away from deterministic "hit-effect" relationships and towards complex ongoing "cellular responses". These responses include now familiar, but still poorly understood, phenomena associated with radiation exposure such as bystander effects, genomic instability, and adaptive responses. All three have been observed at very low doses, and at time points far removed from the initial radiation exposure, and are extremely relevant for linear extrapolation to low doses; the adaptive response is particularly relevant when exposure is spread over a period of time. These are precisely the circumstances that are most relevant to understanding cancer risk associated with environmental and occupational radiation exposures. This review will provide a synthesis of the known, and proposed, interrelationships amongst low-dose cellular responses to radiation. It also will examine the potential importance of non-targeted cellular responses to ionizing radiation in setting acceptable exposure limits especially to low-LET radiations.     

Trends in childhood leukaemia in the Nordic countries in relation to fallout from atmospheric nuclear weapons testing.

OBJECTIVE--To obtain further information about the risks of childhood leukaemia after exposure to ionising radiation at low doses and low dose rates before or after birth or to the father''s testes shortly before conception. DESIGN--Observational study of trends in incidence of childhood leukaemia in relation to estimated radiation exposures due to fallout from atmospheric nuclear weapons testing during the 1950s and 1960s. SETTING--Nordic countries. SUBJECTS--Children aged under 15 years. MAIN OUTCOME MEASURES--Incidence rates of leukaemia by age at diagnosis, sex, country, and calendar year of diagnosis or year of birth; exposure category; relation between leukaemia and exposure for children aged 0-14 and 0-4 separately. RESULTS--During the high fallout period the average estimated dose equivalent to the fetal red bone marrow was around 140 mu Sv and the average annual testicular dose 140 mu Sv. There was little evidence of increased incidence of leukaemia among children born in these years. Doses to the red bone marrow of a child after birth were higher, and during the high exposure period children would have been subjected to an additional dose equivalent of around 1500 mu Sv, similar to doses received by children in several parts of central and eastern Europe owing to the Chernobyl accident and about 50% greater than the annual dose equivalent to the red bone marrow of a child from natural radiation. leukaemia incidence and red marrow dose was not related overall, but rates of leukaemia in the high exposure period were slightly higher than in the surrounding medium exposure period (relative risk for ages 0-14: 1.07, 95% confidence interval 1.00 to 1.14; for ages 0-4: 1.11, 1.00 to 1.24). CONCLUSIONS--Current predicted risks of childhood leukaemia after exposure to radiation are not greatly underestimated for low dose rate exposures.     

Long-term cytogenetic effects in children prenatally-exposed to radiation as a result of the accident at the Chernobyl Atomic Energy Station

Forty-two children exposed to ionizing radiation in prenatal period and 15 children of control group were examined in the remote terms after the accident using the method of differential G-staining of chromosomes in lymphocytes of peripheral blood. It was found that the average group rate of aberrant cells and chromosome aberrations was reliably higher in the children exposed in utero compared to control. Long-term cytogenetic consequences of the pre-natal exposure were characterized by prevalence of aberrations of a chromosome type, mainly stable chromosome lesions. At chronic exposure to low doses of ionizing radiation the increase in the rate both stable and unstable chromosome aberrations.