ILCD Handbook: Framework and requirements for LCIA models and ...

ILCD Handbook: Framework and requirements for LCIA models and indicators First edition
RESPIRATORY INORGANICS Check the following:
Final recommendation
4.5 Ionizing Radiation
4.5.1 Framework and scope
Threshold
(Minimum
score)
Importance
(H-N)
The same framework for human toxicity and ecotoxicity applies for ionizing radiation: the
modelling starts with releases at the point of emission, expressed as Becquerel (Bq), and
calculates the radiative fate and exposure, based on detailed nuclear physics knowledge.
For human toxicity, the exposure analysis calculates the dose that a human actually
absorbs, given the radiation levels that are calculated in the fate analysis. The measure for
the effective dose is the Sievert (Sv), based on human body equivalence factors for the
different ionising radiation types ( -radiation, neutrons: 1 Sv = 1 J/kg body weight).
Data expressed in Sievert include physical data on energy doses and biological data on
the sensitivities of different body tissues. Man Sievert (Man-Sv) is the collective dose,
calculated by multiplying the average individual dose representative of the population, by the
number of people affected and integrating it over a specified time horizon. An intermediate
stage in the calculations of doses is often expressed as Gray (Gy). This is the measure of
absorbed dose without considering the different reaction types of body tissues.
For ecosystem impacts, the ecotoxicity framework is based on Hazardous Concentration
affecting 50% of species (HC50) at their 50% effect (EC50) and on the concept of the change
in the potentially affected fraction (PAF), adapted to radioactive substances. The
ecotoxicological effect factor is calculated by converting the dose rates into the
corresponding medium concentration (i.e. water and sediment for freshwaters). For a given
radionuclide r, this conversion from dose rate endpoint (HDR50 in µGy/h) to corresponding
medium concentration (HC50r) needs to implement:
A transfer sub-model to take on board all potential exposure pathways (external and
internal irradiation);
A dosimetric sub-model to calculate the energy absorbed by the organism from each
radionuclide source, including water, sediment and the organism itself.
The relationship between the activity concentration of an organism or media, and internal
or external absorbed dose rates is described by the dose conversion coefficient (DCC):
µGy/h per Bq/kg fresh weight that is organism (o) and radionuclide (r) specific as
described by Beaugelin et al. (2006). Therefore:
HC50r,o = HDR50 / DDCr,o.
4.5.1.1 Environmental Mechanism (cause-effect chain)
Figure 4-6 describes the framework for human toxicity while Figure 4-7 describes the
framework for ecotoxicity.
4 Requirements for specific impact categories 49