PROTECT: First Proposed Levels for Environmental Protection against Radioactive Substances Definitio

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PROTECT First Proposed Levels for Environmental
Protection against Radioactive Substances
Definitions, Derivation Methods to Determine
Thresholds, Available Effects Data, Preliminary
Reasoning and Results
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Reminder of PROTECT objective within WP3

• To derive and propose numerical target values for
  an extended list of ecological targets and
  protection levels,

explore the possibility for the application of
advanced statistical methods that (1) allow
the best use of the available knowledge when
this is represented by small data sets, (2)
allow quantification of the associated
uncertainty, (3) easily allow revision of
resultant values when new knowledge becomes
available.
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Definition
Ecosystem structure function

• Protection goals
• For the ecological target(s) of interest,
  combination of
• the targeted level of biological organisation
• (e.g., a population of a given ecosystem,
  taxonomic group, species)
• (2) the targeted level of protection that may
  take into account legal requirements
• (e.g., each individual for an endangered
  species, 95 of species for a taxonomic group or
  a community)

Communities Populations of species
Species Population
Individual (sub)
-gt a range of protection goals can be listed -gt
a range of numerical thresholds can be derived to
assure compliance to those environmental
protection goals
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Numerical Thresholds (1/3)

• Definition
• a limit quantifying the interface between an
  acceptable stressor level (e.g., in a given
  medium, in biota) and an unacceptable level
   acceptable  being related to the protection
  goal
• Applications
• Ecological Risk Assessment used as Screening
  Values, associated with a tiered RA scheme
• Exceeding means  do more  to better understand
  the risk
• (e.g., the screening value in ERICA)
• (2) Regulation used as Action Values, i.e.
   legally  binding criteria (or standards) to
  meet the  legal  requirements
• Exceeding means  act 
• (e.g., an EQS)

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Numerical Thresholds (2/3)

• Application
• Planned and existing situations for which
  environmental impact/risk needs to be assessed
  (e.g., chronic (routine) releases).
• Existing situations such as contaminated sites,
  for which a threshold may be defined to identify
  serious risk level triggering an immediate
  action/intervention (e.g., clean up a site).

• Unit
• Dose Rates in Gy per unit time (e.g., µGy/h)
  that may be converted into activity
  concentrations in media (water, sediment, soil,
  air)

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Numerical Thresholds (3/3)In Summary

• Screening Values-gt to trigger further
  investigation in a tiered risk assessment
• Action Values -gt to make a final decision about
  acceptability, trigger a regulatory action
• Both categories of thresholds may be
• (1) Applied to the context of chronic
  radioactive substances releases due to planned
  or existing situations.
• (2) Designed to be protective at a pre-defined
  level, of different ecological targets that are
  potentially exposed to radioactive substances
  (ecosystems (terrestrial, marine and
  freshwater), communities or wildlife taxonomic
  groups, populations of a species, individuals of
  a specific population of a species).

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Methods for deriving thresholds (1/5)

• Existing (chemical) approaches are based on
  available critical ecotoxicity data, typically
  ED50 for acute exposure conditions (short-term)
  and EDR10 for chronic exposure conditions
  (long-term).

Exposure-response relationship from ecotoxicity
tests (stressor, species, endpoint)

Effect ()
100
Observed data
Regression model
50
10
Dose (Gy) Dose Rate (µGy/h)
ED50 EDR50
ED10 EDR10
EDR10 Dose Rate giving 10 effect in the
exposed group in comparison to the control
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Methods for deriving thresholds (2/5)

• Methods recommended by EC for chemicals
  (Technical Guidance Document (2003)) easily
  adaptable to radioactive substances when ED50 or
  EDR10 are available

(1) The Assessment Factor Method for small data
sets
Case not used Problem of Unit
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Methods for deriving thresholds (3/5)
(2) The Species Sensitivity Distribution (SSD)
Method
statistical extrapolation models to address
variation between species in their sensitivity to
a stressor.
The species for which results are known are
representative, in terms of sensitivity, of the
totality of the species in the ecosystem. The
endpoints measured in laboratory tests are
indicative of effects on populations in the field.
PAF ()
100
80
EDR10
60
40
Dose Rate (µGy/h)
20
0
1
10
100
1000
10000
10
Methods for deriving thresholds (4/5)
(3) a weight of evidence approach using data from
field exposures (field measurements of
biodiversity indexes co-occurring with
stressor(s) levels) -gtConcerning radioactive
substances, such data series may be available for
some specific sites (e.g., uranium mining sites
and long-term ecological surveillance SQGs for
ERA of metals and radionuclides)
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Methods for deriving thresholds (5/5)

• In summary
• 3 main methodologies may be used (combined) for
  deriving thresholds (methods 1 2
  reviewed/compared during ERICA)
• (1) the Assessment Factor method when few
  ecotoxicity data are available, or
• (2) the Species Sensitivity Distribution (SSD)
  approach associated with an arbitrary cut-off
  value, which is usually set at a protection level
  of 95 of the species when the available data set
  is more robust.
• (3) a weight of evidence approach using data from
  field exposures
• based on critical ecotoxicity values - i.e.,
  stressor level in a given medium giving 10
  effect in the exposed group in comparison to the
  control group for chronic exposure (or 50 effect
  for acute exposure conditions).

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Chronic effects data from FREDERICA

• To apply any of the methods in a robust way,
  comparable critical ecotoxicity endpoints are
  needed i.e. EDR10 for chronic exposure.
• To meet this aim, a meta-analysis of effects data
  has been initiated and applied in ERICA to
  reconstruct dose-effect relationships exhibiting
  a logistic pattern.

• Only data devoted to effects induced by external
  irradiation pathway were quantitatively adequate
  to be mathematically structured in terms of
  dose-effect relationships.
• In Protect, we have included an analysis of
  dose-effects relationships exhibiting an hormetic
  pattern.

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Dose-effect relationships reconstruction(examples
)
Sus scrofa (mammal, pig) Response reproduction
(number of germ cells in female of
control) (ID629)
Synechococcus lividus (Cyanobacteria) Response
growth (number of cells) (ID804)
Logistic
Hormetic
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Data set (EDR10 in µGy/h) obtained for chronic g
external exposure
Hormetic relationship
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Chronic critical radiotoxicity valuesSummary and
 possible  SSD-cases

• Only obtained for g external exposure conditions

• EDR10 geometric means per species and effect
  category and per model (logistic/hormetic)

Total number of EDR10 80 (logistic) 8
(hormetic) Total number of geometric means 24
6 Number of species 18 3
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First Proposed Thresholds Reasoning for use

• Protection goals
• Ecosystem (structure function)
• 95 of species
• AF for a high degree of conservatism
• Taxonomic groups (one or several) 95 of species
• AF for small datasets

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HDR5
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First Proposed Thresholds (1/3)

• Ecological target Ecosystem (structure
  function)

All data (n30)
HDR5 45 µGy/h CI 95 8.8207
Proposed Screening value Application of a max AF
(5) -gt 10 or 20 µGy/h
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Taxonomic groups without enough chronic data
First Proposed Thresholds (2/3)
HDR5 (µGy/h) Best estimate and CI95
800
700
600
500
400
300
200
100
0
Aquatic Plants
Terrestrial Plants
Aquatic Vertebrates
Generic Ecosystem
Aquatic Ecosystem
Aquatic Invertebrates
Terrestrial Ecosystem
Terrestrial Invertebrates
Terrestrial Vertebrates
without the lowest data
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First Proposed Thresholds (3/3)
Lowest value included
Action Values (AV) Application of AF (1-5)
possible
Screening Values (SV) Application of AF of 5
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Issues for discussion (not exhaustive!)

• Application of an additional AF to generate
  Screening values for ecosystems (SVltltAV)
• Application of a taxonomic weight on Plants,
  Invertebrates and vertebrates to establish the
  SSD at the ecosystem-level
• Use of extrapolation empirical models to fill the
  gaps for taxonomic groups (Acute-to-Chronic
  relationships on sensitivity distributions)
• Use of other groupings (e.g., plants,
  invertebrates)
• Use of an additional standard for  contaminated
  sites  to trigger a remediation action (i.e.
  HDR50 or dose rate affecting 50 of species to a
  10 effect)
• e.g., HDR50 SSD-All EDR10 - Ecosystem 4.2
  mGy/h