WG 5: Exposure and effects to wildlife Biota exposures and effects modelling: models for assessing radiation effects on populations of wildlife Jordi Vives i Batlle (SCK • CEN, Belgium) Nick Beresford (CEH, UK) IAEA International Atomic Energy Agency
Why was the WG5 group introduced • The revised BSS require the consideration of the radiological impact on the environment when planning and applying for an authorization for new nuclear facilities. • explicit demonstration of the protection of the environment • The aim of radiological protection of biota is related to higher organizational levels of populations of species and communities of different species. • The estimation of possible consequences to populations is an important step in exploring the ecological relevance of dose estimates for flora and fauna. IAEA
Exposure - Aims and Objectives • Demonstrate fit for purpose regulatory models • Validate, test, improve models for different applications • Good practice guidance IAEA
Issue 1: animal – environment exposure modelling Spatial modelling • Estimating soil Animal-environment interaction contamination in modelling started in MODARIA home ranges of different species IAEA
Moose scenario • Compare seasonal GPS data of moose migration in a heterogeneously-contaminated fallout area (Lapland) Comparison of predicted to observed data (kBq m -2 ) for Cs in terms of geometric means IAEA
Applying approaches from other area - EcoSpace • Compartmentalised modelling to look at the frequency of migration based on environmental quality parameters Grey = no go Pale blue = non-preferred Other = 3 types of preferred habitat ” no go ” cells = 21.6% of matrix IAEA
Reindeer exercise • Dosimetry detectors in collars of reindeer in Norway • Correlating doses with known activity concentration data • Coupling with GPS installed on different individuals • Estimating exposure based on animal movement Vågå IAEA Activity depositions of Cs-137 in soil in 1986 (data from NRPA)
New transfer data obtained from various sites – to be added to Wildlife Transfer Database early 2020 [and used in ICRP reports] Alligator Rivers Region IAEA
Exposure - ‘ Lessons learnt ’ paper • Capabilities of openly available assessment models • Parameter values • Dosimetry/voxels/geometries - organisms • Coping with heterogeneous media distributions • Radionuclide specific issues (decay series, Ar, Kr etc.) • How to sample/analyse for wildlife assessment • Extending allometric capabilities Final draft need ‘ tarting-up ’ 1.00E+07 using new approach (Bq/kg f.m.) Predicted activity concentration 1.00E+06 1.00E+05 1.00E+04 1.00E+03 1.00E+02 1.00E+01 1.00E+00 1.00E-01 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 IAEA Predicted activity concentration using traditional CR approach (Bq/kg f.m.)
Effects subgroup - Aims and Objectives • Apply population models to different exposure situations. • Learn from these applications: spatial effects (migration, inhomogeneity of contamination), historical doses. • Identify new experimental evidence against which to test models: Non-targeted effects (NTEs) and historical doses • Review of population modelling approaches in chemicals regulation • Provide guidance on the use of population models in evaluating regulatory benchmarks. • The word Guidance has to be understood as a set of general recommendations, not as a guide aiming to replace any international guidance, standards or benchmarks IAEA
Questions that IAEA would like addressed • What is the dose rate at which we can start seeing effects at the population(s) / ecosystem level in the presence of other stressors? • What percentage of the population needs to be affected in order for the effect to affect the whole population? • How robust are the existing benchmarks for exposure to biota populations? IAEA
Chernobyl vole population model • Set up population model of Chernobyl red forest field voles in ecological context • Identify population phenomena that may increase sensitivity enough to potentially affect benchmarks • Planned output: advice on the extent to which historical doses and other ecological factors may influence different exposure modelling scenarios • Some caveats: • Models are conceptual and can ’ t be fully validated - indicative guidance • DCRLs are for planned exposures so most guidance will be for such • We have not enough basis for suggesting changes to benchmarks IAEA
Final version of model Monte_dose_function[1..3] DoseRate[1..3] Dose_step_function[1..3] 100𝑓 −ln 2 𝑢 Fecundity[1..3] RepairPool[1..3] 91.25 + Migration[1..3] 0.125𝑓 − ln 2 𝑢 10950 (Monte, 2019) HealthyAdaptation[1..3] Healthy[1..3] InitiaPopulValue[1..3] CarryingCapMax[1..3] Adapted[1..3] AdaptedHealing[1..3] Radiation_damage[1..3] SickAdapt[1..3] SickRepair[1..3] Parameters CarryingCap[1..3] Sick[1..3] H_death[1..3] A_death[1..3] MinViable[1..3] S_death[1..3] Migration_switch TotalSick TotalHealthy Dead[1..3] IAEA TotalAdapted TotalAlive
Some results – historical dose effect Dose applied for 2000 days, two unequal patches with migration Historical dose effect IAEA
Publications • Key findings on the basis of models done so far: • Bigger size and longevity higher population vulnerability in chronic exposures • Tipping points for population survival at doses higher than the benchmarks • In isolation, the benchmarks seem to be fit for purpose IAEA
Sazykina model from mice to elephant IAEA 16
Impacts of non targeted effects (NTE) and historic dose • Long term effects could include historic dose component • NTE from acute historic exposure? • Effect of chronic accumulated dose? • Impact of current ambient dose? • Are these separate components? • Can the help explain laboratory/field effects discrepancies? • Are they relevant to “ harm ” ? • How do we quantify them? • Ongoing literature and data search during the project to produce guidance. IAEA https://present5.com/bystander-effect-n-the-bystander-effect-refers/
Historical dose concept • Stimulation of the system by low dose/dose rate exposure which becomes harmful as the dose increases • Important because it provides 2 “ no effect levels ” in the dose response curve but the dose(rate) at which stimulation occurs is highly variable • Also important because hormetic doses are often in the range of environmental concern! IAEA
Student project • To source data sets from Chernobyl and Fukushima as well as lab studies on lethal mutations, genomic and chromosomal instability, and other evidence of trans- generational instability to determine how widespread these are after different acute historic doses IAEA
Comparing radiological modelling approach with chemicals • How has population modelling influenced benchmarks for chemicals? • Two pieces of work produced: review of chemicals and ecotox models • Check consistency of approach in population modelling for regulation • Opening an exchange with the ecotox modelling community • Visit to Prof. Karel de Schamphelaere at the U of Gent - • Expert on ecotoxicology and of the ecological impact of chemicals • Feedback received: • Joint interest in not complicating the system • Need to ensure that models maintain the right level of conservatism • General finding: Ecotox community trying to extrapolate from individual to population level as well, for mostly the same reasons. • Link between radio- and chemotoxicity - Radiation itself is a source for chemical pollution (radiolysis products in air, soil and water) IAEA
How has population modelling influenced benchmarks with regards to chemicals? Overall: limited requirements and benchmarks are generally not set • based on populations In general, the goals (ecosystem) of Directives do not align with the data • requirements and data requirements do not align between Directives Benchmarks are set by looking at data from individuals, or by looking at • limited SSD for critical group or main non-target species Usually relies on standard tests (e.g. OECD) • Very little guidance on use (and need) of higher-tier assessment • (population or ecosystem modelling). However, in practice often performed anyway by assessors. Has population modelling influenced benchmarks? Not yet • Radiation protection is actually ahead in the game (on some aspects) • IAEA
Existing models (Galic et al . 2010 – SETAC) 149 publications > 90 models in DB, most models for aquatic environment • 63 exposure models + 27 exclusively deal with ecological processes • Majority are structured population-level models in aquatic environment • 81 out of 90 deal with extrapolation to population level • Analysis of models regarding applicability in protection aims & data needs • IAEA
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