IAEAInternational Atomic Energy Agency

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

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.

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Exposure - Aims and Objectives

• Demonstrate fit for purpose regulatory models

• Validate, test, improve models for different applications

• Good practice guidance

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Spatial modelling

• Animal-environment interaction

modelling started in MODARIA

Estimating soil

contamination in

home ranges of

different species

Issue 1: animal – environment exposure

modelling

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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

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Applying approaches from other area -

EcoSpace

Grey = no goPale blue = non-preferredOther = 3 types of preferred habitat”no go” cells = 21.6% of matrix

• Compartmentalised modelling to

look at the frequency of migration

based on environmental quality

parameters

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• 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

Reindeer exercise

Vågå

Activity depositions of Cs-137 in soil in 1986

(data from NRPA)

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New transfer data obtained from various sites – to

be added to Wildlife Transfer Database early 2020

[and used in ICRP reports]

Alligator

Rivers

Region

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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-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

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

Pre

dic

ted

activity c

on

ce

ntr

ation

u

sin

g n

ew

ap

pro

ach

(B

q/k

g f.m

.)

Predicted activity concentration using traditional CR approach (Bq/kg f.m.)

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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

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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?

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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

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Healthy[1..3]InitiaPopulValue[1..3]

Dead[1..3]

H_death[1..3]Sick[1..3]

Radiation_damage[1..3]

RepairPool[1..3]

SickRepair[1..3]

Fecundity[1..3]

S_death[1..3]

DoseRate[1..3]

TotalHealthy TotalSick

TotalAlive

CarryingCapMax[1..3]

Migration_switchMinViable[1..3]

Migration[1..3]

TotalAdapted

Adapted[1..3]

A_death[1..3]

AdaptedHealing[1..3]

SickAdapt[1..3]

HealthyAdaptation[1..3]

CarryingCap[1..3]Parameters

Monte_dose_function[1..3] Dose_step_function[1..3]

Final version of model

100𝑒−ln 2 𝑡91.25 +

0.125𝑒−ln 2 𝑡

10950

(Monte, 2019)

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Some results – historical dose effect

Historical dose effect

Dose applied for 2000 days,

two unequal patches with

migration

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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

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Sazykina model from mice to elephant

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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.

https://present5.com/bystander-effect-n-the-bystander-effect-refers/

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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!

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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

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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)

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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)

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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

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Projected output

• We will produce concise

guidance accompanied with

examples of ecological

phenomena influencing effects

• Starting with ICRP DCRLs, vary

modelled dose rates until

population impacts occur

• Identify population phenomena

that may increase sensitivity

enough to potentially affect benchmarks

• Link TO doses in real situations where there is a need to

regulate, testing for effects at agreed benchmark levels.

• Enable discussions with stakeholders about the relevance of

benchmarks for populations

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Caveats

• The models are conceptual and cannot be fully validated so the guidance is

indicative

• The ICRP DCRLs are for planned exposures so most of the guidance will

be for such

• For existing and emergency exposures we can still evaluate current

thinking and come up with some expert advice

• Considering validity of benchmarks - not making an assessment!

Exposure

situation

Phenomena to consider Outcome or goal Experimental

evidence

Planned

and existing

situations

Struggle for limited resources,

Interaction between organism

and environmental factors,

species competition,

migration issues, spatial

issues

Benchmark

testing/validation

What kind of effects

may be expected

Give here an

overview of the

experimental

evidence for the

phenomena

Emergency (acute phase)

In emergency situations we can only evaluate current thinking and explain

to the IAEA the relevant developments, because DCRLs do not apply to

emergency situations.

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Latest developments and conclusions

• Exposures latest developments

• Lessons learned progressing to publication.

• Further, a comparison of model applications for U-facilities from EMRAS II (Beaverlodge

paper) has started to make progress.

• Started to collate data to improve tissue to whole-body activity concentration corrections

• Inputs from exposures subgroup to update the Wildlife Transfer Database by early 2020

• Effects latest developments

• Synthesis of all the work (vole modelling, historical and NTE effects, population models for

chemicals) is well advanced (tasks assigned, substantial drafting during this week).

• Vole modelling study progressing to scientific publication by early 2020

• Working on the production of the guidance report Plans for reporting – for exposures,

produce short summary report covering EMRAS II to MODARIA II – can be

combined with ‘effects’ report or kept separate (discussion within group).

• Conclusion: We have worked to meet our objectives set in MODARIA II to produce

improved fit for purpose methodology and data on biota exposures and effects,

ready to translate into good practice guidance for IAEA.

IAEA

Reporting plans for WG5 biota group

• Almost all work finished and working on reports is advancing

• For exposures, short summary report covering EMRAS II to MODARIA II

• For effects, short summary of MODARIA I combined with MODARIA II

• Probably aiming at two reports (exposures and effects), but clearly

stating they are joint reports of the biota working group

• For exposures, we will have a final videoconference in late March

2020 to ensure last modelling results feed correctly into the guidance

part of the report

• For exposures report, need to discuss plans with Nick Beresford

• First full draft exposures report for review around August 2020

IAEA

Dr Abu Bakr Ramadan – in memoriam