The Derivation of Transfer Parameters in the Assessment of Radiological Impacts on Arctic Marine Biota

The initial stage of an environmental impact assessment requires quantification of radionuclide transfer in the study area. This paper evaluates the robustness of the concentration factor (CF) approach in assessing radiological impact on reference Arctic marine biota. By comparing region-specific data sets with recommended generic values for CFs, we tested the hypothesis that transfers to Arctic biota differ from transfers observed in temperate areas for 90Sr, 137Cs, 239, 240Pu and 99Tc. Despite the general paucity of data and great uncertainty regarding radionuclide CFs in reference biota, we conclude that the use of Arctic-specific CFs for Sr and Pu can be justified in some cases where differences from generic CFs seem apparent. Where CF data are absent, a biokinetic modelling approach with allometric considerations might be used to bridge data gaps. Such an approach has been used here to estimate the trophic transfer of 137Cs and 239Pu in a marine food chain consisting of four trophic levels. For the simulation concerning 137Cs, the preliminary results suggest that it takes more than five years to attain equilibrium for higher trophic levels (polar cod and harp seal). Biomagnification appears to occur at the lower trophic levels, but not at the highest (seal). For 239Pu, transfer to successively higher trophic levels is low: there is a fall of several orders of magnitude between primary producers, represented by phytoplankton, and polar cod, representing trophic levels 3 and 4. However, the model predicts that this decreasing trend in activity concentrations along the food chain is reversed for the highest trophic level, represented by seal. The simulated results for seal display equilibrium activity concentrations about two orders of magnitude higher than those observed for polar cod (one of its prey species). However, equilibrium (165 years) is not reached during the life span of a seal. The equilibrium 137Cs CFs are approximately 50 l/kg for zooplankton, 130l/kg for polar cod, and 70 l/kg for seal. The predicted equilibrium 239Pu CFs are 2.5·10³ l/kg for zooplankton and 25 l/kg for polar cod. For seal, following a one-year equilibration period, a CF of approximately 75 l/kg is predicted.Le stade initial d'une étude d'impact environnemental nécessite une évaluation quantitative du transfert de radionucléides dans la zone d'étude. Cet article évalue la robustesse de la méthode du facteur de concentration (FC) pour déterminer l'impact radiologique sur un biote marin arctique de référence. En comparant des ensembles de données spécifiques à une région avec des valeurs génériques recommandées pour les facteurs de concentration, on a testé l'hypothèse selon laquelle les transferts au biote arctique diffèrent des transferts observés dans des régions tempérées pour 90Sr, 137Cs, 239,240Pu et 99Tc. Malgré la pénurie générale de données et un haut niveau d'incertitude concernant les FC des radionucléides dans le biote de référence, on conclut que l'utilisation de FC spécifiques à l'Arctique pour Sr et Pu peut être justifiée dans certains cas où les différences d'avec les FC génériques semblent apparentes. Là où il n'existe pas de données sur les FC, on peut recourir à la modélisation biocinétique tenant compte des éléments allométriques afin de combler les lacunes dans les données. C'est cette approche que l'on a utilisée ici pour estimer le transfert trophique de 137Cs et de 239Pu dans une chaîne alimentaire marine comprenant quatre niveaux trophiques. Pour la simulation relative à 137Cs, les résultats préliminaires suggèrent qu'il faut plus de cinq ans pour atteindre l'équilibre aux niveaux trophiques supérieurs (morue polaire et phoque annelé). La bioamplification semble se produire aux niveaux trophiques inférieurs, mais pas au plus élevé (phoque). Pour 239Pu, le transfert aux niveaux trophiques supérieurs est faible: on constate une baisse de plusieurs ordres de grandeur entre les producteurs primaires, représentés par le phytoplancton, et la morue polaire, qui représente les niveaux trophiques 3 et 4. Le modèle prédit toutefois que cette tendance à la baisse dans l'activité volumique le long de la chaîne alimentaire s'inverse au niveau trophique le plus élevé, représenté par le phoque. Les résultats simulés pour le phoque affichent des activités volumiques à l'équilibre environ deux ordres de grandeur plus élevées que celles observées chez la morue polaire (l'une des espèces-proies du phoque). L'équilibre (165 ans) n'est cependant pas atteint durant la durée de vie du phoque. Les FC de 137Cs à l'équilibre sont environ de 50 l/kg pour le zooplancton, de 130 l/kg pour la morue polaire et de 70 l/kg pour le phoque. Les FC de 239Pu projetés à l'équilibre sont de 2,5·10³ l/kg pour le zooplancton et de 25 l/kg pour la morue polaire. Pour le phoque, après une période d'équilibre d'une année, on prédit un FC d'environ 75 l/kg

Geographical variation in radiological services: a nationwide survey

BACKGROUND: Geographical variation in health care services challenges the basic principle of fair allocation of health care resources. This study aimed to investigate geographical variation in the use of X-ray, CT, MRI and Ultrasound examinations in Norway, the contribution from public and private institutions, and the impact of accessibility and socioeconomic factors on variation in examination rates. METHODS: A nationwide survey of activity in all radiological institutions for the year 2002 was used to compare the rates per thousand of examinations in the counties. The data format was files/printouts where the examinations were recorded according to a code system. RESULTS: Overall rates per thousand of radiological examinations varied by a factor of 2.4. The use of MRI varied from 170 to 2, and CT from 216 to 56 examinations per 1000 inhabitants. Single MRI examinations (knee, cervical spine and head/brain) ranged high in variation, as did certain other spine examinations. For examination of specific organs, the counties' use of one modality was positively correlated with the use of other modalities. Private institutions accounted for 28% of all examinations, and tended towards performing a higher proportion of single examinations with high variability. Indicators of accessibility correlated positively to variation in examination rates, partly due to the figures from the county of Oslo. Correlations between examination rates and socioeconomic factors were also highly influenced by the figures from this county. CONCLUSION: The counties use of radiological services varied substantially, especially CT and MRI examinations. A likely cause of the variation is differences in accessibility. The coexistence of public and private institutions may be a source of variability, along with socioeconomic factors. The findings represent a challenge to the objective of equality in access to health care services, and indicate a potential for better allocation of overall health care resources. PREVIOUS PUBLICATION: The data applied in this article was originally published in Norwegian in: Børretzen I, Lysdahl KB, Olerud HM: Radiologi i Noreg – undersøkingsfrekvens per 2002, tidstrendar, geografisk variasjon og befolkningsdose. StrålevernRapport 2006:6. Østerås: The Norwegian Radiation Protection Authority. The Norwegian Radiation Protection Authority has given the authors permission to republish the data

Biological transfer of radionuclides in marine environments - identifying and filling knowledge gaps for environmental impact assessments

Methodologies have been developed to allow impacts of ionising radiation on marine ecosystems to be evaluated within selected geographical settings. The stages in the assessment require initial information about unit concentrations of radionuclides in reference media to be collated. Activity concentrations for reference groups of flora and fauna and for representatives of these groups are then derived using an equilibrium concentration factor approach. Following this, dose-rates can be calculated using relevant dose conversion factors. Impacts on the environment are evaluated by comparison with dose-rates at which selected biological effects are known to occur and the natural radiation background. This paper focuses mainly on the transfer part of the assessment drawing attention to gaps in information that have been identified through review and providing an outline of methods that may be used to fill these gaps. Biokinetic models parameterised using allometric relationships have shown their utility in this respect. Initial work looking into the application of such models has met with some success with model predictions comparing favourably with the few empirical data available. Further work will be needed to validate the models for a large range of radionuclides and to consider uncertainty in model estimates through probabilistic analyses

PRSS2 remodels the tumor microenvironment via repression of Tsp1 to stimulate tumor growth and progression

Tsp-1 in the tumor microenvironment is known to suppress tumor growth and progression. Here the authors show that PRSS2 represses Tsp-1 by binding to lipoprotein receptor-related protein 1 and suggest targeting PRSS2 mediated Tsp-1 repression as a potential therapeutic strategy

CT radiation dose in children: a survey to establish age-based diagnostic reference levels in Switzerland

This work aimed at assessing the doses delivered in Switzerland to paediatric patients during computed tomography (CT) examinations of the brain, chest and abdomen, and at establishing diagnostic reference levels (DRLs) for various age groups. Forms were sent to the ten centres performing CT on children, addressing the demographics, the indication and the scanning parameters: number of series, kilovoltage, tube current, rotation time, reconstruction slice thickness and pitch, volume CT dose index (CTDI(vol)) and dose length product (DLP). Per age group, the proposed DRLs for brain, chest and abdomen are, respectively, in terms of CTDI(vol): 20, 30, 40, 60 mGy; 5, 8, 10, 12 mGy; 7, 9, 13, 16 mGy; and in terms of DLP: 270, 420, 560, 1,000 mGy cm; 110, 200, 220, 460 mGy cm; 130, 300, 380, 500 mGy cm. An optimisation process should be initiated to reduce the spread in dose recorded in this study. A major element of this process should be the use of DRLs