Annals of ICRP v. 24, No 1-3, Pergamon, 1994. 462 p.
This report describes a revision of the model used in ICRP Publication 30 to calculate radiation doses to the respiratory tract of workers resulting from the intake of airborne radionuclides. This revision was motivated by the availability of increased knowledge of the anatomy and physiology of the respiratory tract and of the deposition, clearance, and biological effects of inhaled radioactive particles, and by greatly expanded dosimetry requirements.
In addition, large differences in radiation sensitivity among the respiratory tract tissues and the doses they receive from inhaled radionuclides argue for calculating radiation doses to specific tissues of the respiratory tract. (The current model leads to calculation of doses averaged over the total mass of blood-filled lungs.) To use these tissue doses effectively for radiation protection purposes, they must be compatible with the ICRP dosimetric system in ICRP Publication 60.
Addressing all of these requirements has resulted in a dosimetry model that is more complex than previous models. This complexity is reflected in the structure of this report, which includes chapters on respiratory tract morphometry, physiology, and radiation biology or health detriment. Other chapters deal with the deposition and clearance of inhaled radioactive particles, inhalation of radioactive gases, and application of the model to estimate respiratory tract doses. The model provides most of the flexibility needed to calculate doses to the respiratory tract for a wide range of exposure conditions and for specific individuals. This flexibility also allows for revision of reference parameter values as new information becomes available without changing the model. The wide availability of personal computers allows for the easy use of the model.
The model is described in Chapters 2 through 8, beginning with the morphometric model, important respiratory physiology parameters, consideration of the biological effects of inhaled radionuclides, deposition and clearance models, inhalation of radioactive gases and vapours, and concluding with methodology for calculating radiation doses to respiratory tract tissues. The scientific background for these chapters and the tabulation of values to be used with the model are to be found in Annexes A-H. Chapter 9 addresses the application of the model, contains recommended parameter values for reference populations, and includes an example of a dose calculation with this respiratory tract model using information in the report. Chapter 10 is a summary description of the respiratory tract dosimetry model.
GLOSSARY
INTRODUCTION
MORPHOMETRIC MODEL
Introduction
The Extrathoracic Region (ET)
The Bronchial Region (BB)
The Bronchiolar Region (bb)
Alveolar-Interstitial Region (AI)
Scaling of Airway Dimensions for Age and Gender
Masses of Target Tissues
PHYSIOLOGICAL PARAMETERS
Introduction
Reference Values for Workers
Reference Values for Members of the General Population
RADIATION BIOLOGY CONSIDERATIONS
Introduction
Respiratory Tract Cancers
Progenitor Cells of Respiratory Tract Cancers
Partition of Detriment
DEPOSITION MODEL
Deposition Compartments
Model Derivation
Form of the Recommended Model
Specification of Filtration Efficiencies
Parameters of the Deposition Model
Recommended Deposition Formulae
Estimates of Variability in Regional Deposition
Application of the Model
Reference Values of Regional Deposition
GASES AND VAPOURS
Introduction
Models of Gas Uptake
Regional Gas Uptake
Three Classes of Gas Uptake Pattern
Uptake Model Gases and Vapours
Integration with the Deposition and Clearance Model
CLEARANCE MODEL
Introduction
Compartment Model for Respiratory Tract Clearance
Absorption into Blood
Modifying Factors
Radioactive Decay Products
DOSIMETRY
Introduction
Dosimetric Principles
Specific Absorbed Fractions for Photons
Dosimetry of Short-Range Alpha, Electron and Beta-Emitters
Scaling for Age and Gender
Absorbed Fractions for Short-Range Alpha, Electron and Beta-Emitters
Implementation of the Dosimetry Model
Calculation of Number of Transformations
Factors for Apportionment of Radiation Detriment
APPLICATION OF THE MODEL
Introduction
Model Reliability
Use of Respiratory Tract Model for Calculating Effective Dose
Example Calculation of Respiratory Tract Doses
SUMMARY DESCRIPTION OF RESPIRATORY TRACT DOSIMETRY MODEL
Introduction
Respiratory Tract Morphometry
Physiology
Deposition
Clearance
Dose Calculations
REFERENCES
ANNEXES
ANATOMY AND MORPHOLOGY OF THE RESPIRATORY TRACT
Introduction
General Aspects
The Normal Structure
Variations
Modifying Factors
Deposition and Clearance Pathways
Respiratory Tract Model Considerations
References
RESPIRATORY PHYSIOLOGY
Introduction
General Aspects
Normal Breathing Dynamics
Variabilities
Modifying Factors
Model Considerations: Parameters for ICRP Respiratory Tract Dosimetric Model
References
EFFECTS OF RADIATION ON THE RESPIRATORY TRACT
Nonstochastic Risk
Basic Epidemiology of Respiratory Tract Cancers
Tumour Type, Histogenesis, and Target Tissues
Modifying Factors
References
DEPOSITION OF INHALED PARTICLES
Introduction
Inhalability
Breathing Habit
Empirical Modelling of Deposition Data
Nasal Deposition: Human Data and Models
Oropharyngeal-Laryngeal Deposition: Human Data and Models
Lung (Thoracic) Deposition: Human Data and Models
Theoretical Model of Regional Lung Deposition
Data and Model for Hygroscopic Aerosols
Reference Aerosol and Exposure Parameters
References
CLEARANCE OF PARTICLES FROM THE RESPIRATORY TRACT
Glossary
Introduction
Clearance Mechanisms
The Clearance Model
The Extrathoracic Airways
The Alveolar-Interstitial Region
The Lymph Nodes
REFERENCE VALUES FOR REGIONAL DEPOSITION
SPECIFIC ABSORBED FRACTIONS OF PHOTON ENERGY
ABSORBED FRACTIONS FOR ALPHA, ELECTRON, AND BETA EMISSIONS
