P. Strand

Environmental protection : transfer parameters for reference animals and plants

In Publication 103 (ICRP, 2007), the Commission included a section on the protection of the environment, and indicated that it would be further developing its approach to this difficult subject by way of a set of Reference Animals and Plants (RAPs) as the basis for relating exposure to dose, and dose to radiation effects, for different types of animals and plants. Subsequently, a set of 12 RAPs has been described in some detail (ICRP, 2008), particularly with regard to estimation of the doses received by them, at a whole-body level, in relation to internal and external radionuclide concentrations; and what is known about the effects of radiation on such types of animals and plants. A set of dose conversion factors for all of the RAPs has been derived, and the resultant dose rates can be compared with evaluations of the effects of dose rates using derived consideration reference levels (DCRLs). Each DCRL constitutes a band of dose rates for each RAP within which there is likely to be some chance of the occurrence of deleterious effects. Site-specific data on Representative Organisms (i.e. organisms of specific interest for an assessment) can then be compared with such values and used as a basis for decision making. It is intended that the Commissions approach to protection of the environment be applied to all exposure situations. In some situations, the relevant radionuclide concentrations can be measured directly, but this is not always possible or feasible. In such cases, modelling techniques are used to estimate the radionuclide concentrations. This report is an initial step in addressing the needs of such modelling techniques. After briefly reviewing the basic factors relating to the accumulation of radionuclides by different types of biota, in different habitats, and at different stages in the life cycle, this report focuses on the approaches used to model the transfer of radionuclides through the environment. It concludes that equilibrium concentration ratios (CRs) are most commonly used to model such transfers, and that they currently offer the most comprehensive data coverage. The report also reviews the methods used to derive CRs, and describes a means of summarising statistical information from empirical data sets. Emphasis has been placed on using data from field studies, although some data from laboratory experiments have been included for some RAPs. There are, inevitably, many data gaps for each RAP, and other data have been used to help fill these gaps. CRs specific to each RAP were extracted from a larger database, structured in terms of generic wildlife groups. In cases where data were lacking, values from taxonomically-related organisms were used to derive suitable surrogate values. The full set of rules which have been applied for filling gaps in RAP-specific CRs is described. Statistical summaries of the data sets are provided, and CR values for 39 elements and 12 RAP combinations are given. The data coverage, reliance on derived values, and applicability of the CR approach for each of the RAPs is discussed. Finally, some consideration is given to approaches where RAPs and their life stages could be measured for the elements of interest under more rigorously controlled conditions to help fill the current data gaps.

Prediction of 137Cs deposition from atmospheric nuclear weapons tests within the Arctic

A method of predicting the spatial distribution of 137Cs deposition in fallout in the Arctic from atmospheric nuclear weapons testing, developed during the Arctic Monitoring and Assessment Programme (AMAP), is described. The method uses a relationship between deposition and precipitation at Tromso (Norway) calculated for each year since 1955, which is spread over the Arctic using a global precipitation data set within a geographical information system. The advantages of this approach include the ability to cover the whole Arctic area and to predict 137Cs deposition, either integrated or decay corrected (cumulative), for any 0.5×0.5° unit for any year. For land north of 60°N, the areas with the lowest estimated ground 137Cs deposition from nuclear weapons testing are the Russian far north east, north Greenland and northern Canada. The highest estimated ground deposition occurred in the coastal areas of Alaska, the southern tip of Greenland, western Canada, Iceland and the western coast of Norway. Predicted differences in the spatial distribution of global fallout are generally consistent with the trends observed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and with reported measurements in the region above 60°N. A comparison of the predicted cumulative 137Cs deposition with measured values gave a significant correlation (p<0.001). However, the current predicted deposition would probably underestimate global fallout deposition in areas receiving little precipitation and areas close to the test site.

Radioactive contamination from dumped nuclear waste in the Kara Sea — results from the joint Russian-Norwegian expeditions in 1992–1994

Russian-Norwegian expeditions to the Kara Sea and to dumping sites in the fjords of Novaya Zemlya have taken place annually since 1992. In the fjords, dumped objects were localised with sonar and ROV equipped with underwater camera. Enhanced levels of 137Cs, 60Co, 90Sr and 239,240Pu in sediments close to dumped containers in the Abrosimov and Stepovogo fjords demonstrated that leaching from dumped material has taken place. The contamination was inhomogeneously distributed and radioactive particles were identified in the upper 10 cm of the sediments. 137Cs was strongly associated with sediments, while 90Sr was more mobile. The contamination was less pronounced in the areas where objects presumed to be reactor compartments were located. The enhanced level of radionuclides observed in sediments close to the submarine in Stepovogo fjord in 1993 could, however, not be confirmed in 1994. Otherwise, traces of 60Co in sediments were observed in the close vicinity of all localised objects. Thus, the general level of radionuclides in waters, sediments and biota in the fjords is, somewhat higher or similar to that of the open Kara Sea, i.e. significantly lower than in other adjacent marine systems (e.g. Irish Sea, Baltic Sea, North Sea). The main sources contributing to radioactive contamination were global fallout from atmospheric nuclear weapon tests, river transport from Ob and Yenisey, marine transport of discharges from Sellafield, UK and fallout from Chernobyl. Thus, the radiological impact to man and the arctic environment of the observed leakages from dumped radioactive waste today, is considered to be low. Assuming all radionuclides are released from the waste, preliminary assessments indicate a collective dose to the world population of less than 50 man Sv.

Radiation-induced effects on plants and animals: findings of the United Nations Chernobyl Forum.

Several United Nations organizations sought to dispel the uncertainties and controversy that still exist concerning the effects of the Chernobyl accident. A Chernobyl Forum of international expertise was established to reach consensus on the environmental consequences and health effects attributable to radiation exposure arising from the accident. This review is a synopsis of the subgroup that examined the radiological effects to nonhuman biota within the 30-km Exclusion Zone. The response of biota to Chernobyl irradiation was a complex interaction among radiation dose, dose rate, temporal and spatial variation, varying radiation sensitivities of the different taxons, and indirect effects from other events. The radiation-induced effects to plants and animals within the 30-km Exclusion Zone around Chernobyl can be framed in three broad time periods relative to the accident: an intense exposure period during the first 30 d following the accident of 26 April 1986; a second phase that extended through the first year of exposure during which time the short-lived radionuclides decayed and longer-lived radionuclides were transported to different components of the environment by physical, chemical and biological processes; and the third and continuing long-term phase of chronic exposure with dose rates <1% of the initial values. The doses accumulated, and the observed effects on plants, soil invertebrates, terrestrial vertebrates and fish are summarized for each time period. Physiological and genetic effects on biota, as well as the indirect effects on wildlife of removing humans from the Chernobyl area, are placed in context of what was known about radioecological effects prior to the accident.

Contribution of fungi to radiocaesium intake by rural populations in Russia

Abstract In a study of transfer of Chernobyl radiocaesium to man, dietary surveys and whole body monitoring were conducted at two sites in the Bryansk Region of the Russian Federation. Radiocaesium activity concentrations in wild food products, especially mushrooms, were higher than those in agricultural products. The surveys revealed that consumption of highly contaminated wild mushrooms provided a significant contribution to ingested radiocaesium, accounting for 20–40% of the variability of radiocaesium activity concentrations in rural populations 8–9 years after the 1986 accident. Consumption of mushrooms was also the main reason for a 60–70% mean increase in radiocaesium activity concentrations in humans in autumn. Long term dose assessments after accidental releases of radiocaesium should therefore consider the potential contribution by mushrooms to ingested dose.

Survey of artificial radionuclides in the Barents Sea and the Kara Sea

The concentrations of radionuclides have been measured in water, sediments and biota from the Barents and Kara Seas. The survey was undertaken to identify the contribution to the anthropogenic radionuclides in the environment from nuclear waste dumped by the USSR in these areas from 1962 to the present day. The concentration in seawater was in the range 3.3- 20.4 Bq m −3 for 137 Cs, 3.0-12.1 Bq m −1 for 90 Sr and < 1.8-16.0 MBQ M −3 for 239,240 Pu. The concentrations in sediments (0-10 cm) were in the range 120-910 Bq m −2 for 137 Cs and 2.5-135 Bq m −2 for 239,240 Pu. The influence of radioactivity from dumped nuclear waste has not had a significant impact on the general levels of anthropogenic radioactivity

Accumulation and long term behaviour of radiocaesium in Norwegian fungi

Abstract The accumulation and long term behaviour of radiocaesium in mushrooms were studied at selected sites in Norway. A large variation in transfer factors from soil to mushroom were found with the lowest value of 0.002 m 2 /kg for Leccinum versipelle up to 0.5 m 2 /kg for species of Amanita fulva and Amanita vaginata. Rozites caperata and Cortinarius armillatus were also found to accumulate radiocaesium very efficiently. For the study of long term behaviour of radiocaesium in mushrooms the same species were collected from the same location from 1989 to 1995. Two of four data sets showed a significant decrease in activity levels in the study period with an estimated effective ecological half-life in the range of 1.5–8 years, while a non-significant decrease and no decrease were indicated by the other two.

Radioactive contamination in the Arctic--sources, dose assessment and potential risks.

Arctic residents, whose diets comprise a large proportion of traditional terrestrial and freshwater foodstuffs, have received the highest radiation exposures to artificial radionuclides in the Arctic. Doses to members of both the average population and selected indigenous population groups in the Arctic depend on the rates of consumption of locally-derived terrestrial and freshwater foodstuffs, including reindeer/caribou meat, freshwater fish, goat cheese, berries, mushrooms and lamb. The vulnerability of arctic populations, especially indigenous peoples, to radiocaesium deposition is much greater than for temperate populations due to the importance of terrestrial, semi-natural exposure pathways where there is high radiocaesium transfer and a long ecological half-life for this radionuclide. In contrast, arctic residents with diets largely comprising marine foodstuffs have received comparatively low radiation exposures because of the lower levels of contamination of marine organisms. Using arctic-specific information, the predicted collective dose is five times higher than that estimated by UNSCEAR for temperate areas. The greatest threats to human health and the environment posed by human and industrial activities in the Arctic are associated with the potential for accidents in the civilian and military nuclear sectors. Of most concern are the consequences of potential accidents in nuclear power plant reactors, during the handling and storage of nuclear weapons, in the decommissioning of nuclear submarines and in the disposal of spent nuclear fuel from vessels. It is important to foster a close association between risk assessment and practical programmes for the purposes of improving monitoring, formulating response strategies and implementing action plans.

The impact of the Fukushima nuclear accident on marine biota: Retrospective assessment of the first year and perspectives

An international study under the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was performed to assess radiological impact of the nuclear accident at the Fukushima-Daiichi Nuclear Power Station (FDNPS) on the marine environment. This work constitutes the first international assessment of this type, drawing upon methodologies that incorporate the most up-to-date radioecological models and knowledge. To quantify the radiological impact on marine wildlife, a suite of state-of-the-art approaches to assess exposures to Fukushima derived radionuclides of marine biota, including predictive dynamic transfer modelling, was applied to a comprehensive dataset consisting of over 500 sediment, 6000 seawater and 5000 biota data points representative of the geographically relevant area during the first year after the accident. The dataset covers the period from May 2011 to August 2012. The method used to evaluate the ecological impact consists of comparing dose (rates) to which living species of interest are exposed during a defined period to critical effects values arising from the literature. The assessed doses follow a highly variable pattern and generally do not seem to indicate the potential for effects. A possible exception of a transient nature is the relatively contaminated area in the vicinity of the discharge point, where effects on sensitive endpoints in individual plants and animals might have occurred in the weeks directly following the accident. However, impacts on population integrity would have been unlikely due to the short duration and the limited space area of the initially high exposures. Our understanding of the biological impact of radiation on chronically exposed plants and animals continues to evolve, and still needs to be improved through future studies in the FDNPS marine environment.

Protection of the environment in the 21st century: radiation protection of the biosphere including humankind. Statement of the International Union of Radioecology.

In order to draw the attention of EEIU and IUR members, as well as others interested in the ecological/envi- ronmental aspects of radioactivity as related to ethics, science and politics, ESEP presents the key IUR Statement Protection of the environment in the 21st century: radiation protection of the biosphere including humankind (Brechignac et al. 2003), which is currently in press with the Journal of Environmental Radioactivity. More information about the IUR is available at www.iur-uir.org.