THE ICRP APPROACH TO LOW LEVEL RADIATION RISK

1
THE ICRP APPROACH TO LOW LEVEL RADIATION RISK

• Caroline SCHIEBER
• 2nd International ILK Symposium
• Munich, 28-29 October 2003

2
THE RECOGNITION OF RADIATION RISK (1)

• First part of 20th Century
• Recognition of the existence of deterministic
  effects
• Quantification of dose thresholds for these
  effects
• Set up of dose limits to avoid deterministic
  effects ("maximum tolerable doses")
• In the same time, first signs of existence of
  medium and long term effects (leukaemia, genetic
  effects)

3
THE RECOGNITION OF RADIATION RISK (2)

•  The Fifties "first step of precaution"
•  ICRP 1954
• "In view of the incomplete evidence on which the
  values are based, coupled with the knowledge that
  certain radiation effects are irreversible and
  cumulative,
• it is strongly recommended that every effort be
  made to reduce exposure to all types of ionising
  radiations to the lowest possible level.
• The Commission will continually review the
  recommended permissible levels as new information
  becomes available"

4
THE RECOGNITION OF RADIATION RISK (3)

•  ICRP 1 (1958)
• " The most conservative approach would be to
  assume that there is no threshold and no
  recovery, in which case even low doses would
  induce leukaemia in some susceptible individuals,
  and the incidence might be proportional to the
  accumulated dose"
• "The Commission recommends that all doses be kept
  as low as practicable, and
• that any unnecessary exposure be avoided"

5
THE RECOGNITION OF RADIATION RISK (4)

•  ICRP 9 (1965)
• Dose-effect relationship "clearly established
  after doses of more than 100 rads", but "it is
  unknown whether a threshold of dose exists"
• Because of the lack of knowledge of the nature of
  the dose-effect relationship, the Commission sees
  no practical alternative, for the purpose of
  radiological protection, to assuming a linear
  relationship between dose and effect, and that
  doses act cumulatively."
• "The Commission recommends that any unnecessary
  exposure be avoided, and that all doses be kept
  as low as is readily achievable, economic and
  social considerations being taken into account."

6
THE MANAGEMENT OF RADIATION RISK (1)

• Since the Fifties
• Development of scientific research in
  radiobiology and epidemiology
• Reduction of uncertainty
• the risk coefficient is progressively delimited
• the dose level above which epidemiology
  demonstrates a significant risk is progressively
  reduced
• 1965 1 Sv - 1980 0.5 Sv - 1990 0.2 Sv -
• 2000 0.1 Sv
• results from radiobiology do not invalidate nor
  conflict with the linear non threshold
  dose-effect relation-ship

7
THE MANAGEMENT OF RADIATION RISK (2)

• Development of a "philosophy of action" for a
  responsible risk management
• Three principles
• Justification of risk activities
• Avoid all unnecessary exposure or exposures non
  justified according to a detriment/benefit
  balance
• Optimisation of radiation protection (ALARA)
• Search for the acceptable and accepted level of
  risk according to each exposure situation
• Limitation of individual exposures
• Boarder of the unacceptable levels of risks

8
Conclusion

• The early adoption of the precautionary principle
  didn't stop the development of radiation risk
  activities
• It allowed to develop a responsible management of
  the radiation risk
• The main challenge remains in the process to be
  adopted to reach the acceptable levels of risk
  according to the exposure situations
• After a first period focussed on the
  "cost-benefit model", there is a trend for giving
  more importance to stakeholder involvement
  processes for both public and worker exposures in
  complex situations