Acknowledgements Most of the following slides have been borrowed from previous presentations of other C5 members If there are –mistakes, they are mine –overstatements, they are also mine If I got it completely right, it is because of the brilliance of my C5 colleagues
ICRP Committee 5 membership RJ Pentreath (chair)UK CM Larsson (vice-chair)Sweden K Higley (secretary)USA P Strand Norway A JohnstonAustralia A RealSpain F BrechignacFrance K SakaiJapan G PröhlGermany
ICRP C5 Concerned with radiological protection of the environment. Aim: development and application of approaches to environmental protection that are: –Compatible with those for radiological protection of man, and –With those for protection of the environment from other potential hazards.
Directions of C5 Work Develop a framework for the assessment of radiation exposure and effects on non-human species: –For planned, existing, and emergency exposure situations. –That will serve as a benchmark for international and individual national approaches to environmental protection –And that will parallel the framework for human radiation protection. Done in an open and transparent manner.
Commonalities, RP (hum) and RP (env) Reference Person Environmental radionuclide concentration(s) Reference Animals and Plants Dose limits, constraints, reference levels Decision-making regarding public health and environment for the same environmental situation Derived Consideration Levels Planned, existing and emergency exposure situations
C5 Four Year Plan, Major Documents Reference Animals and Plants (2007) –Supporting database (transfer, background, etc) –Radiation dosimetry –Radiation effects Radiation weighting factors (2008) Commonality of RAPs approach to other environmental protection efforts (2008-9) Will build on updated scientific information and recent methodological achievements (EC projects, UNSCEAR……
High Level Overview
A reference animal or plant is a hypothetical entity, With the assumed basic characteristics of a specific type of animal or plant, as described to the generality of the taxonomic level of family, With precisely defined anatomical, physiological, and life-history properties That can be used for the purposes of relating exposure to dose, and dose to effects, for that type of living organism. Reference Animals and Plants
Deer Rat Bee Earthworm Duck Frog Trout Marine Flatfish Crab Pine Tree Grass Seaweed
Criteria for Selection of RAPs
Consideration of Exposure Situations and Computation of DCCs Small burrowing mammal exposed from a planar source at the surface of the soil Computational animal with liver and testes
Overview of FRED(ERICA) Effects Data; Access via Ecosystem References # Data%Effect Total Number %ExternalInternalOther Terrestrial (579) 19, Acute12, Chronic6, Transitory Not Stated Freshwater (195) Acute4, Chronic1, Transitory Not Stated Marine (45) Acute Chronic Transitory00000 Not Stated10001
Natural Background* ECOSYSTEM NON- WEIGHTED µGy h -1 WEIGHTED a µGy h -1 Marine0.04 – – 9.9 Freshwater0.09 – Terrestrial – 0.09 (external) a Includes weighting factors for high LET radiation *Brown et al.; Gomez-Ros et al Journal of Radiological Protection, 24:4A, pp
STATUS: Existing Information on Radiation Effects for RAPs
Data on RAPS organism available Data on RAPS-related organism available No data available Preliminary Data Survey
Availability of Acute Data Reference Organism MorbidityMortality Reproductive Capacity Mutation Deer Rat Duck Frog Trout Marine Flatfish Bee Crab Earthworm Pine Tree Grass Seaweed =data available = related data maybe available = no data available
Availability of Chronic Data Reference Organism MorbidityMortality Reproductive Capacity Mutation Deer Rat Duck Frog Trout Marine Flatfish Bee Crab Earthworm Pine Tree Grass Seaweed =data available = related data maybe available = no data available
Data on RAPS organism available Data on RAPS-related organism available No data available How to Proceed Scaling functions?
STATUS: Dosimetry for RAPS
Objectives Select approach to estimate Dose Per Unit Concentration (DPUC) –Kinetics not taken into account –Doses to organs not explicitly considered –Consider simple geometries Spheres, ellipsoids, cylinders Calculate DPUC values for ICRP RAPs –Average dose rate for the whole body per unit activity concentration In the organisms, or Surrounding media.
Dose Concept Absorbed dose –Dose equivalent and effective doses as used for humans not applicable –Radiation weighting factors under discussion Absorbed fraction –Fraction of energy emitted by a radiation source that is absorbed within the target tissue, organ or organism Homogeneous medium, organism immersed in water –D int = E * AF(E) –D ext = E * [1-AF(E)]
Influence of shape Internal exposure –AF spheres –AF for various shapes –Interpolation Shape Mass Energy => Enables estimations for a wide range of ellipsoids External exposure –DCCs for spheres –etc.
Absorbed fractions for photons as a function of mass and energy for spheres
Absorbed fractions for electrons as a function of mass and energy for spheres
AF for non-spherical organisms: 10 keV photons and electrons
AF for non-spherical organisms: 100 keV photons and electrons
External exposure Terrestrial RAPs –Based and detailed MC calculations for specified geometries On-soil: –Planar source on the soil with a surface roughness of 3 mm, –Volume source with a thickness of 10 cm, In-soil: Middle of a volume source with a thickness of 50 cm Aquatic –In-water –On-water
Derived Consideration Concentrations (DCCs) In Progress All RAPs –Partly for different habitats 75 radionuclides –Daughters included if half-life < 10 d External and internal exposure
STATUS: Supporting Database Concentration and transfer data used in the derivation of external and internal dose-rates for RAPs
Objective Derive a reference set of –Values for naturally occurring radionuclides in sea water, freshwater, sediment and soil from which to calculate the reference external background dose rates for RAPs. –Values for naturally occurring nuclides on a whole body basis from which to calulate internal reference background dose rates for RAPs. –Transfer factors for anthropogenic radionuclides to allow whole body activity concentrations and thereby internal dose rates to be derived for RAPs.
Selection of radionuclides For artificial radionuclides, equilibrium concentration ratios (CRs) have been derived for the following: –Ag, Am, C, Cd, Ce, Cl, Cm, Co, Cs, Eu, H, I, Mn, Nb, Ni, Np, P, Pu, Ru, S, Sb, Se, Sr, Tc, Zr For naturally-occurring radionuclides, activity concentrations in RAPs and their environment were derived for all radionuclides in U-238 and Th-232 decay chains with half-life > 10 days; and for other important primordial and cosmogenic radionuclides
Terrestrial CRs for RAPs – data coverage
Natural radionuclides considered * Assumed for dosimetric purposes for progeny with t 1/2 less than 10 days.
ACTION 1 : External dose-rates from naturally occurring radionuclides
External dose-rates from naturally occurring radionuclides Marine – Raw data collated. Preliminary typical values derived. Terrestrial – Work in progress –e.g. World generic soil values (UNSCEAR, 2000) Freshwater – Work in progress. Data available J.E. Brown, S.R. Jones, R. Saxén, H.Thørring and J. Vives i Batlle (2004). Radiation doses to aquatic organisms from natural radionuclides. Journal of Radiological Protection, 24, pp. A63-A77. UNSCEAR (2000).Sources and effects of ionising radiation
Concentrations of naturally occuring radionuclides in seawater (Bq/m 3 ) Review based on Bowen (1979), IAEA (1988a), IAEA (1988b), IAEA (1990), Cherry & Shannon (1974), Woodhead (1973), Brown et al (2004)
Activity concentrations depend on underlying sediment type, e.g. clay content strongly influences K-40 concentrations. Separate sediments into sand, silt, clay where appropriate and data coverage sufficient ? Review based on : Baxter (1983); BNFL(1994); Bowen(1979); Brown (1997); Brown et al. (2004); Grøttheim (1999); Hamilton et al. (1994); Holm & Fukai (1986); IAEA (1988a); Kershaw et al. (1992); McCartney et al. (1990); McDonald et al. (1991);Van der Heijde et al. (1990);Walker & Rose (1990). Concentrations of naturally occuring radionuclides in marine sediment (Bq/kg d.w.)
Marine – seawater and sediments Broader review necessary ? –Focus on nuclides important from an exposure perspective ? Summarised or generic values can be derived –(statistically) summarised values difficult to derive because original information often provided as typical or representative values.
ACTION 2 : Set of natural radionuclide concentrations for internal dose rates
Set Of Natural Radionuclide Concentrations For Internal Dose Rates Marine – Starting from data collated for Brown et al. (2004). Database further developed and expanded Contains approximately 1500 data. –Macroalgae (n=669), –Crustaceans (n=374), –Fish (n=373) Most data are Po-210 Terrestrial and freshwater not considered here
All compiled data (RO coverage)
Marine RAPs Jklfhd-lsdgfsjd Hj.hsdjkgfhksd = data available (In brackets – only limited amount of data n<3) RO= data available for ERICA reference organisms (but not RAPs) - = No data Macroalgae Crustaceans Fish
Available data (example) Concentrations of Polonium-210 (Bq/kg FW) in corresponding ERICA reference organisms (ROs) Concentrations of Polonium-210 (Bq/kg FW) in RAPs
ACTION 3: CRs for Deriving Internal Activity Concentrations of Artificial Radionuclides
CRs for Deriving Internal Activity Concentrations of Artificial Radionuclides Marine – Comprehensive database created by NRPA Terrestrial – Preliminary summary table provided by CEH. NRPA working on database in conjunction with CEH Freshwater – Data made available from STUK. Further work necessary (Data not presented here).
Marine CRs – Macroalgae Red, green and brown macroalgae Brown algae
Marine CRs - Crustaceans All crustaceans Cancer pagarus
Marine CRs - Fish All fish types Flatfish
Example Cs-137 CF values (Bq/kg FW) for ICRP Raps Cs-137 CF values (Bq/kg FW) for corresponding ERICA reference organisms
Marine CRs – Fish egg and Fish larvae Fish egg Fish larvae The available data is very limited Fish egg: n = 45 Fish larvae: n = 39
Available data (example) Sr Concentration factor values for fish egg and fish larvae for all fish types and turbot.
Terrestrial CRs for RAPs
Terrestrial CRs for RAPs – data coverage
Terrestrial CRs for RAPs - comments There are few RAP specific values Data are for 'adult stage'; ERICA considers terrestrial bird eggs and has some values derived from terrestrial bird CRs combined with hen diet-egg transfer information (not reported in ICRP database) The ERICA CR summary database contains a value for every RO-radionuclide combination. Where data are lacking these were derived using various guidance options. The values derived by this guidance are NOT included in the ICRP summary - i.e. this contains data derived from empirical values only FOR H, C, S, P CR defined as whole body activity concentration (fresh weight) to the activity concentration in air (Bq/m 3 ); model derived.
General discussion (CRs) Technologically-enhanced radionuclides : CR values e.g. U-238, Ra-226, Po-210, C-14 and H-3 may be useful in a regulatory context. –Can be extracted from existing databases. Use RAP specific values or generic RO values ? Data gap filling methodology (ERICA) – relevant here ?
STATUS: Commonality of RAPS with other approaches
Bottom-up, toxicological approach Based upon individuals System structured around some reference(s) Dose-driven (weighted to allow for additivity) HumanEnvironment (RAPs) Single effect endpoint: cancer induction Several effect endpoints: mortality, morbidity, reproduction, chromosome damage Stochastic effects of major concern, LNT model assumption Deterministic effects of major concern F. Bréchignac – ICRP Committee 5 Meeting, Corvallis, Oregon, USA, August 2006 Raps Approach Consistent With Human Radioprotection
STATUS - OVERALL
Progress to Date Two major meetings –Geneva, Sept 05 –Corvallis, Aug 06 –Next in Germany, 07 Task groups –Dosimetry –Other??