Considering the Environment When Applying the System of Radiological Protection
Abstract
This publication broadens the Reference Animals and Plants (RAP) and Derived
Consideration Reference Levels (DCRL) approach outlined in Publication 108. It introduces
a methodology for establishing additional DCRLs at higher taxonomic levels to complement
the existing DCRLs which are defined at the family level. A transparent, data-driven
approach for assessing the effects of ionising radiation on non-human species in their natural
environment is described. By integrating comprehensive radiation effects data, documented
models, and considering the underlying assumptions, the methodology enhances
transparency, reproducibility, and improves the ability of assessors to address complex
environmental impact assessments.
The broadened RAP approach extends beyond the twelve RAP families defined in
Publication 108 by incorporating higher taxonomic levels such as class, phylum, and broad
non-human species groups (vertebrates, invertebrates, and plants). This expansion improves
the representativeness and applicability of the RAP approach in radiological environmental
impact assessments. The approach applies two statistical models: the Acute-to-Chronic
Transformation of Radiation Effects (ACTR) model, which extrapolates chronic effects from
acute data, and the Endpoint Sensitivity Distribution (ESD) model, which synthesises chronic
and acute effects data across taxonomic groups. The additional DCRLs are derived using the
5 th percentile of the ESD, with a multi-criteria Extrapolation Factor (EF) applied to establish
the lower boundary, and accounting for data gaps and uncertainties.
As simple guidance, the DCRLs (family) from Publication 108 are the benchmarks
recommended for environmental impact assessments. The additional DCRLs introduced in
this publication provide complementary reference points, particularly in cases where dose
rates approach or exceed DCRL Family values. This broadened approach where benchmarks can
be used in conjunction, is especially relevant for complex impact assessments, such as
evaluations of large facilities, post-accident scenarios, and protected ecosystems. It also
allows flexibility in applying different ESD percentiles to identify an acceptable level of
protection in consultation with stakeholders or to incorporate site-specific data for refined
assessments.
Irrespective of the DCRLs used, the guidance from Publication 124 applies: the lower
boundary of the relevant DCRL should be applied in planned exposure situations, while in
existing exposure scenarios or post-accident long-term assessments, DCRLs help guide
optimisation of radiological protection of non-human species. Additionally, in emergencies,
at the time where the focus shifts to environmental recovery, the acute ESD models for
classes or phyla, or broad species groups can support stakeholder discussions providing
retrospective information on the likely ecological consequences of radiation exposure.
By broadening the RAP approach, this publication strengthens the scientific basis for
environmental radiological protection, facilitates stakeholder engagement, and contributes to
support decision-making in environmental impact assessments. The additional DCRLs at
higher taxonomic levels introduced in this publication provide an important complement in
complex cases as it offers the possibility of a more refined assessment and a transparent
evaluation of the level of confidence. The methodology and underpinning data enable
assessors to adapt their assessments to specific contexts, make informed judgments, and
reduce uncertainties in evaluating radiation impact or risk to non-human species. Further
guidance on the application of the DCRLs within the system of radiological protection will be
provided as Part 2 in this series of publications ‘Considering the Environment When
Applying the System of Radiological Protection Part 2: Integration within the system,
including practical use of Derived Consideration Reference Levels’.