Presentation on theme: "PROTECTFP6-036425 PROTECT: First Proposed Levels for Environmental Protection against Radioactive Substances Definitions, Derivation Methods to Determine."— Presentation transcript:
PROTECTFP PROTECT: First Proposed Levels for Environmental Protection against Radioactive Substances Definitions, Derivation Methods to Determine Thresholds, Available Effects Data, Preliminary Reasoning and Results
PROTECTFP 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.
PROTECTFP Definition Protection goals: For the ecological target(s) of interest, combination of : (1)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) -> a range of protection goals can be listed -> a range of numerical thresholds can be derived to assure compliance to those environmental protection goals Ecosystem: structure & function Communities: Populations of species Species: Population Individual (sub)
PROTECTFP 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 : (1)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)
PROTECTFP 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)
PROTECTFP Numerical Thresholds (3/3) In Summary Screening Values-> to trigger further investigation in a tiered risk assessment Action Values -> 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).
PROTECTFP Existing (chemical) approaches are based on available critical ecotoxicity data, typically ED 50 for acute exposure conditions (short-term) and EDR 10 for chronic exposure conditions (long- term). Methods for deriving thresholds (1/5) Exposure-response relationship from ecotoxicity tests (stressor, species, endpoint) Effect (%) Regression model 100 % 50 % 10 % ED 10 EDR 10 Dose (Gy) Dose Rate (µGy/h) ED 50 EDR 50 Observed data EDR 10 : Dose Rate giving 10% effect in the exposed group in comparison to the control
PROTECTFP Methods recommended by EC for chemicals (Technical Guidance Document (2003)) – easily adaptable to radioactive substances when ED 50 or EDR 10 are available (1) The Assessment Factor Method for small data sets Methods for deriving thresholds (2/5) Case not used Problem of Unit
PROTECTFP 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. (2) The Species Sensitivity Distribution (SSD) Method Dose Rate (µGy/h) PAF (%) 5% HDR 5% : Dose rate giving 5% of the species affected to a 10% effect Calculation of a dose rate that is assumed to protect a given % of species In the Technical Guidance Document (2003): the agreed concentration is the hazardous concentration affecting 5 % of species to a 10%. When it remains other extrapolation issues, the TGD recommends to apply an additional AF (1-5) Methods for deriving thresholds (3/5) EDR 10
PROTECTFP (3) a weight of evidence approach using data from field exposures (field measurements of biodiversity indexes co-occurring with stressor(s) levels) ->Concerning 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) Methods for deriving thresholds (4/5)
PROTECTFP 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).
PROTECTFP Chronic effects data from FREDERICA 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. To apply any of the methods in a robust way, comparable critical ecotoxicity endpoints are needed i.e. EDR 10 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.
PROTECTFP Dose-effect relationships reconstruction (examples) EDR10 = 7.42 Synechococcus lividus (Cyanobacteria) Response : growth (number of cells) (ID:804) EDR10 = Sus scrofa (mammal, pig) Response : reproduction (number of germ cells in female %of control) (ID:629) Logistic Hormetic
PROTECTFP Data set (EDR 10 in µGy/h) obtained for chronic external exposure Hormetic relationship
PROTECTFP Chronic critical radiotoxicity values Summary and « possible » SSD-cases Only obtained for external exposure conditions EDR 10 – geometric means per species and effect category and per model (logistic/hormetic) Total number of EDR 10 : 80 (logistic) + 8 (hormetic) Total number of geometric means: Number of species:
PROTECTFP 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 5% HDR 5% Application Category of threshold HDR 5 – protective criterion in µGy/h ERA Screening Values Highly Conservative values. HDR 5 + AF of 5 from SSD- EDR 10 ecosystems. BELOW -> Stop ABOVE -> Refine the risk assessment (exposure, effect and risk) Potential Regulation Action Values Realistic values. HDR 5 + AF of 5 (or 1-5) from SSD- taxonomic groups. BELOW-> Manage the risk (e.g., monitoring) ABOVE -> Act to reduce the dose rate
PROTECTFP First Proposed Thresholds (1/3) Ecological target : Ecosystem (structure & function) HDR 5 = 45 µGy/h CI 95% = [8.8;207] All data (n=30) Proposed Screening value: Application of a max AF (5) -> 10 or 20 µGy/h HDR 5 = 109 µGy/h CI 95% = [36;374] Without the lowest data (n=29)
PROTECTFP Generic Ecosystem Terrestrial Ecosystem Aquatic Ecosystem Terrestrial Plants Aquatic Plants Terrestrial Invertebrates Aquatic Invertebrates Terrestrial Vertebrates Aquatic Vertebrates HDR 5 (µGy/h) Best estimate and CI 95% Taxonomic groups without enough chronic data without the lowest data First Proposed Thresholds (2/3)
PROTECTFP First Proposed Thresholds (3/3) HDR 5 SV Generic Ecosystems Terrestrial Ecosystems12725 Aquatic Ecosystems HDR 5 =AV if AF=1AV if AF=5 Terrestrial Plants Aquatic Plants All Plants Terrestrial Invertebrates Aquatic Invertebrates All Invertebrates399 Terrestrial Vertebrates347 Aquatic Vertebrates All Vertebrates337 Screening Values (SV) Application of AF of 5 Action Values (AV) Application of AF (1-5) possible Lowest value included
PROTECTFP Issues for discussion (not exhaustive!) Application of an additional AF to generate Screening values for ecosystems (SV<