The Ministry of Health has approved the decision of the ASN to reduce the threshold for stable iodine intake in the event of a nuclear accident

Published on 29/12/2009 at 14:56

Information notice

On 18 August 2009, the nuclear safety authority adopted a decision lowering the intervention level for the intake of stable iodine (potassium iodide) in the event of a nuclear accident.

Stable iodine tablets should now be taken where a thyroid dose of 50 millisievert (mSv) is likely to be reached (as against 100mSv previously). This decision improves the protection of the most susceptible populations (foetuses and young people under 18) and brings French practice into line with that of neighbouring countries.

 The decision was approved by ministerial decree on 20 November 2009.

 The ingestion of stable iodine: a simple way to protect the population

 In conjunction with the sheltering of the population, the ingestion of a stable iodine tablet is an effective means of protecting the thyroid against the effects of radioactive releases.

 In the event of a nuclear accident, radioactive iodine from the nuclear reactor can be discharged into the environment. If breathed in or swallowed, this radioactive iodine settles in the thyroid gland and can then increase the risk of thyroid cancer, especially in the youngest.

 Taking a stable iodine tablet before the occurrence of such discharges protects the thyroid by preventing radioactive iodine from concentrating there. The iodine tablet must be taken only when so instructed by the prefect and immediately the instruction is issued.

 In France stable iodine distribution campaigns take place regularly in areas surrounding the nuclear installations concerned. The latest campaign is currently in progress in the vicinity of EDF nuclear power stations. For more information visit:

 ASN will lauch together a working group in the near future, to study the impact of this new intervention level on the management of emergency situations and the possible improvements to be made to the Orsec plans (organisation for civil defence response).

Date of last update : 03/09/2021