WP3

Task 3.1 Quantification of the effect of smoking on absorbed doses from radon exposure

Leader: IRSN, partners: MTA EK, RPI (M1-M30)

The aim of this task is to separate the effects of smoking from that of radon gas and radon progeny. For this purpose, deposition of inhaled cigarette smoke particles, primarily the combustion products (tar), will be simulated by the recently developed ADiC model implemented into the Monte Carlo deposition model IDEAL. The comparison between the predicted smoke deposition patterns with the pathologically observed distribution of bronchial carcinomas in smokers’ lungs will allow us to establish a baseline for the additional effect of radon-induced lung cancers. Both morphometric (e.g. increased mucus layer thickness), respiratory (e.g. change in breathing frequency) and other physiological (e.g. change in mucus layer velocity) effects induced by smoking will be taken into account. Because of the widely differing experimental information on the effects of smoking on lung morphometry, respiratory physiology and mucus clearance, a thorough review of the existing literature prior to the simulations will be required to establish reasonable modelling scenarios.

Task 3.2 Dosimetric calculations for epidemiological studies

Leader: PHE, partners: IIRSN, BfS, RPI (M1-M48)

The aim of this task is to calculate annual absorbed doses to the lung and to systemic organs (red bone marrow, liver, kidney, stomach, colon, brain, heart, posterior nasal passages, pharynx and larynx) of individual miners within the cohorts considered. Annual absorbed doses arising from exposure to radon gas, radon progeny, long-lived radionuclides (LLR) in the uranium ore and to the external gamma radiation will be calculated (alpha radiation alone as well as the total absorbed doses). Calculations will be performed with the new ICRP biokinetic and dosimetric models published in the Occupational Intake of Radionuclides (OIR) document series. In collaboration, with the epidemiologists of Task 4.2, model parameter data for the miner cohorts will be reviewed. Based on this review, appropriate model parameter values will be assumed including different aerosol parameter values for different exposure conditions and different breathing rates depending upon type of job. Specific software tools will be developed for cohorts or group of cohorts taking into account the nature, format and amount of data in each cohort. Organ doses to members of the public will be considered for the residential studies in Task 3.3.

Task 3.3 Dose assessment for specific subgroups of the population

Leader: BfS, other partners: EK, RPI (M1-M54)

The aim of this task is to assess doses to specific human subpopulations with potentially higher sensitivity to radiation exposure or with higher public concern.

A comprehensive model for the dose to embryo and foetus will be developed. Starting from the most recent biokinetic model structures presented in the latest ICRP publications, the transfer of radioisotopes from the mother to the unborn child through the placenta and their distribution in the organs of embryo/foetus at different stages of pregnancy will be taken into account. Specific model for assessing doses to lactating infants due to incorporation of radionuclides present in mother’s milk after exposure to radon and its progeny will also be developed.

Dosimetric peculiarities of children of different ages will be analysed. Age-specific sizes of organs, morphology, breathing rate may largely affect the absorbed doses especially in case of inhalation of radionuclides. The airway geometry specific to different ages will be numerically modelled based on available morphometric data.

The effects of lung diseases on absorbed doses and dose distributions in the lungs will be quantified. Computer models of airways of asthmatic and COPD patients with different degrees of disease severity will be developed considering specific breathing patterns, airway remodelling, change in the calibre of the airways, and composition and thickness of the lung epithelium.

The task is split in 3 subtasks:

Subtask 3.3.1 A comprehensive model for the dose to embryo and foetus

Subtask 3.3.2 Dosimetric peculiarities of children of different ages

Subtask 3.3.3 The effects of lung diseases on absorbed dose and dose distribution in the lung

Task 3.4 Assessment of uncertainties affecting dosimetric calculations

Leader: KIT, other partners: BfS, IRSN, RPI (M1-M60)

The main aim of this task is to gain insights on the uncertainty affecting the dose attributed to cohort members which will help to define better the uncertainties affecting the dose-effect relationship. Biokinetic and dosimetric will be applied in the dose calculations and uncertainty analysis. The task will look at the uncertainty in dose estimates that arises from the uncertainties in the model parameters. A literature review of the models and their parameter values will be performed to derive prior distributions from which parameter values will be sampled for Monte Carlo simulations. Uncertainties of the annual absorbed doses and the total committed doses will be calculated for the target organs and models defined in Task 3.2. The contribution of the different radiation types to the dose and its uncertainty will also be considered in this work package. Uncertainties arising from exposure, biokinetic, dosimetric models will be studied separately and then combined. Quality assurance of the calculations will be performed by comparison of computer codes used by partner institutions.
This task is split into 2 subtasks:

Subtask 3.4.1 Dosimetric equations and prior distributions for epidemiological studies in WP4

Subtask 3.4.2 The interference of thoron on radon dose calculations

Task 3.5 Computational microdosimetry supporting the preparation and evaluation of experiments

Leader: EK, other partners: IRSN, PTB (M1-M36)

The general aim of this task is to support the biological experiments performed in WP4. The specific aims are
(i) to quantify the in vivo dose distributions in human lungs in order to provide realistic exposure conditions for in vitro experiments with cell cultures and organotypic tissue models, (ii) to quantify the dose distribution in rat and mice lungs in order to support the retrospective rat study in WP4, (iii) to quantify the specific energy and hit distributions in the in vitro experiments with cells and organotypic tissue models exposed to radon, solid alpha-sources, and a charged particle microbeam. For these purposes, computational microdosimetry will be applied. For the quantification of in vivo dose distributions, airway geometry of rats and mice will be modelled based on available morphometric data. Numerical particle tracking will be performed to quantify the deposited radioactivity and the dose distribution upon exposure to radon and NORM.

Task 3.6 Comparison of the effects of homogeneous and inhomogeneous dose distributions

Leader: EK, other partners: GSI (M1-M60)

The aim of this task is (i) to compare the health and biological effects of homogeneous and inhomogeneous exposures resulting in the same tissue dose, and (ii) to explore ways how differences can be considered in the system of radiation protection. For this purpose, we review the existing epidemiological and biological data about the biological and health effects of hot particles and other heterogeneous exposures including exposure to radon progeny. Particular attention will be paid on experimental results on the effects of spatially inhomogeneous dose distributions in organotypic lung models. The Local Effect Model, a biophysical model capable to predict the relative biological effectiveness for various radiation types, will be applied to describe the carcinogenic potential of complex radiation fields in dependence on dose. This leads to an estimate for the effect weighted dose in dependence on the composition of the radiation field for carcinogenesis related endpoints.