2005 RECOMMENDATIONS OF ICRP

Transcription

1 IRPA th International Congress of the International Radiation Protection Association May 2004, Madrid, Spain 2005 RECOMMENDATIONS OF ICRP ROGER H CLARKE CHAIRMAN

2 FEATURES OF RECOMMENDATIONS Volume 35 Issue ? Quantities in Radiological Protection Biological Aspects General System of Protection Quantitative Recommendations Optimization of Protection Medical Exposures Potential Exposures PUBLICATION 100? 2005 Recommendations of the International Commission on Radiological Protection Exclusion from the Recommendations Radiological Protection of the Environment

3 EFFECTIVE DOSE E = Σ w T Σ w R T R D T,R The major changes are: New values of w R are proposed following a review of RBE data -for protons w R is reduced from 5 to 2 -for neutrons < 1 MeV w R is reduced by ~ 2 and recommended in the form of a continuous curve. New values of w T are proposed following a review of risk data for somatic and hereditary defects -for gonads risk is reduced by ~ 4 following UNSCEAR 2001

4 PROPOSED w R FOR NEUTRONS ICRP 60 function ICRP 60 histogram 2005 Proposed function w R = exp[-(ln E n ) 2 /6]... for E n < 1 Mev = exp[-(ln 2 En) 2 /6]...for E n >1 MeV

5 PROPOSED w T VALUES Gonads 0.20 Bone marrow 0.12 Bone marrow 0.12 Breast Colon Colon Lung Lung Stomach Stomach Bladder 0.05 Bladder 0.05 Liver Liver Oesophagus Oesophagus Thyroid Thyroid Breast Gonads Skin 0.01 Skin 0.01 Bone surface Bone surface Brain Kidney Salivary glands Remainder 0.05 Remainder 0.1

6 TREATMENT OF REMAINDER TISSUES The w T of 0.1 is given to the dose averaged equally over the following 14 tissues or organs Adipose tissue, Adrenals, Connective tissue, ET region a, Gall bladder, Heart wall, Lymphatic nodes, Muscle, Pancreas, Prostate, SI Wall, Spleen, Thymus, Uterus/cervix. a As defined in ICRP Publication 66, includes anterior (ET1) and posterior nasal passages, larynx, pharynx and mouth (ET2).

7 BIOLOGICAL ASPECTS Induction of tissue reactions RBE-weighted absorbed dose (Gy-Eq) DNA mutation Cancer Mechanisms Epidemiology Hereditary effects Embryo and fetus Genetic susceptibility Non-cancer diseases

8 DETRIMENT COEFFICIENTS (% Sv -1 ) Exposed population Lethality adjusted cancer risk Lethality adjusted heritable effects Detriment 2005 Detriment Pub.60 Whole population Adult workers

9 THE 2005 SYSTEM OF PROTECTION JUSTIFICATION QUANTITATIVE RECOMMENDATIONS OPTIMIZATION

10 JUSTIFICATION OF NEW CONTROLLABLE SOURCES Justifying net benefit is primarily for the appropriate authorities Radiological considerations are only one input ICRP recommendations apply to practices only when declared justified and to natural controllable sources Patient exposures need separate consideration

11 THE 2005 SYSTEM OF PROTECTION JUSTIFICATION QUANTITATIVE RECOMMENDATIONS OPTIMIZATION

12 THE PUBLIC IS PROTECTED - FROM A SINGLE SOURCE IN NORMAL, EMERGENCY, AND CONTROLLABLE EXPOSURE SITUATIONS BY THE DOSE CONSTRAINTS FROM ALL REGULATED SOURCES ONLY IN NORMAL SITUATIONS BY THE DOSE LIMITS

13 THE WORKER IS PROTECTED - FROM A SINGLE SOURCE IN NORMAL, EMERGENCY, AND CONTROLLABLE EXPOSURE SITUATIONS BY THE DOSE CONSTRAINTS FROM ALL REGULATED SOURCES ONLY IN NORMAL SITUATIONS BY THE DOSE LIMITS

14 THE 2005 SYSTEM OF PROTECTION JUSTIFICATION QUANTITATIVE RECOMMENDATIONS SOURCE CONSTRAINTS Restrictions are established for the most exposed individuals -set by ICRP, and by International Agencies OPTIMIZATION

15 CONSTRAINTS IN 2005 Fewer can be set but from existing numerical values -which maintains continuity They can be explained in terms of multiples or fractions of background -which achieves simplicity They are a necessary, but not sufficient criterion for protection -which requires optimization

16 ICRP s NEED FOR ACTION HIGH INCREASING DECREASING 100 msv/yr NATURAL BACKGROUND AROUND 1 msv/yr 0.01 msv/yr LOW

17 MAXIMUM CONSTRAINTS EFFECTIVE DOSE IN A YEAR (msv) Emergency workers Evacuation or relocation in emergencies High levels of existing controllable exposures Information, training, monitoring NO INDIVIDUAL/SOCIETAL BENEFIT ABOVE Occupational exposure Sheltering, stable iodine, in emergencies Existing exposures such as radon Comforters and carers to patients Information, training, monitoring or assessment DIRECT OR INDIRECT BENEFIT TO THE INDIVIDUAL Normal situations No information or training No individual dose assessment SOCIETAL, BUT NO INDIVIDUAL DIRECT BENEFIT 0.01 Minimum value of any constraint

18 RADON-222 Recommendations in Publication 65 are adapted for 2005 Constraints set where action is almost always warranted Home Work 600 Bq m Bq m -3 NATIONAL AUTHORITY establishes a lower level- Below which, at work, exposures are NOT subject to the system of protection And, no action to reduce levels in homes

19 THE 2005 SYSTEM OF PROTECTION JUSTIFICATION QUANTITATIVE RECOMMENDATIONS INDIVIDUAL LIMITS Already exist in Basic Safety Standards No individual is exposed to unacceptable regulated risk in normal situations OPTIMIZATION

20 DOSE LIMITS FOR PRACTICES PUBLIC 1 msv in a year -exceptionally, 1mSv/yr averaged over 5 years WORKERS 20 msv per year averaged over 5 years -100 msv in 5 years and less than 50 msv in one year Organ or tissue Radiation weighted dose (msv/yr) Occupational Public Lens of the eye The skin Hands and feet 500 -

21 THE 2005 SYSTEM OF PROTECTION JUSTIFICATION QUANTITATIVE RECOMMENDATIONS OPTIMIZATION There is a duty to reduce doses to achieve a higher level of protection -the responsibility of operators and national authorities

22 SAFETY CULTURE Optimization of protection is part of a successful radiological protection programme It necessitates co-operation operation between all parties involved who must subscribe to safety culture as defined in the BSS- The assembly of characteristics and attitudes in organizations and individuals which establishes that, as an overriding priority, protection and safety issues receive the attention warranted by their significance

23 STAKEHOLDER INVOLVEMENT It may be better to consult the most directly concerned, including representatives of those exposed, in determining or negotiating, optimized protection ICRP can give guidance, but it is a Task for Operators and National Authorities

24 THE PROTECTION OF GROUPS Collective dose is defined as E max S = E(t) dn de dt t=0 E=0 =0 de It is of limited utility as it aggregates information excessively For decision-aiding, the information should be presented as disaggregated data-the the Dose Matrix For the workforce, the minimum information is the number of workers and their mean dose

25 EXCLUSION LEVELS ICRP recommends that its system of protection is not applied to materials with activity concentrations below- Artificial Radionuclides α-emitters 0.01 Bq g -1 β/γ emitters 0.1 Bq g -1 Natural radionuclides 238 U, Th 1 Bq g K 10 Bq g -1

26 PROTECTION OF THE PATIENT GENERIC JUSTIFICATION The radiological procedure must provide the necessary information to improve diagnosis or treatment JUSTIFY THE INDIVIDUAL REFERRAL Application of the procedure to an individual Patient should be justified OPTIMIZATION Diagnostic Reference Levels are indicators of good practice CONSTRAINTS Needed for comforters and carers

27 POTENTIAL EXPOSURES Dose constraint Risk constraint Risk = probability of incurring dose x Lifetime conditional probability of attributable death from that dose Effective dose should not be used if it is greater than 100 msv, as there can be tissue reactions in organs Therefore only option is to restrict the probability of the event occurring Hot particles also addressed

28 PROTECTION OF THE ENVIRONMENT Aim: to develop a policy and a framework for environmental radiological protection. A A Reference Environment Derived Consideration Levels based on background A common system for human and non-human species

29 PROPOSED TIMESCALES Release of text on web Supporting documents finalized by ICRP Committees Consideration of comments June 2004 October 2004 April 2005 FINAL TEXT