Nuclear risk: why are iodine tablets distributed to protect the French ?

Risque nucléaire : pourquoi des pastilles d’iode sont-elles distribuées autour des centrales ?

Une campagne de distribution de pastille d’iode stable a débuté en septembre en France à proximité de plusieurs centrales nucléaires. A quoi servent ces pastilles et comment fonctionnent-elles ?

A new campaign for the preventive distribution of stable iodine tablets was launched in September. The tablets can be collected from pharmacies in each municipality located within a 10 km radius of certain French nuclear sites. Individuals, establishments open to the public, businesses and communities are concerned. To find out if you are affected, click here.

What is iodine ?

It's for thyroid hormones. It is found in everyday foods such as fortified salt, seafood, fish and seaweed. But also in the meat of farmed animals fed with iodine-enriched feed.

What are iodine tablets used for ?

The tablets are indicated in the event of radioactive iodine being released into the atmosphere during a nuclear accident. Stable iodine is used to protect populations exposed to radioactive iodine.

Stable or radioactive, iodine naturally binds to the thyroid, which does not differentiate. When breathed in or swallowed, radioactive iodine released into the environment binds to the thyroid and increases the risk of thyroid cancer. The idea with taking stable iodine is to saturate the thyroid gland so that radioactive iodine cannot attach itself to it.

People at highest risk

The preventive distribution campaign is aimed at the entire population. However, certain groups of people are at greater risk of developing thyroid cancer:

Newborns and children whose thyroid is still developing Pregnant and breastfeeding women (risks for the fetus and baby)

Fetuses, newborns and children are in fact more exposed because in adults, the gland fixes 25 to 30% of the iodine incorporated. In children, the dose delivered is higher. “About 6,500 cases of thyroid cancer in children were documented in Chernobyl. For adults, the thyroid, more mature, has a very slow natural development and the risk of thyroid cancer is therefore much lower”, explains Inserm.

If preventive distribution is aimed at all populations, Inserm stressed in 2022 that the massive intake of stable iodine after the age of 40 could have negative effects greater than the benefits. “Indeed, it can lead to deregulation of the organ and its hormone production. For example, by making the thyroid overactive (hyperthyroidism), heart rate and blood pressure disorders can occur as well as excess anxiety or hot flashes,” explains the scientific research organization.

When should you take the iodine tablet ?

Stable iodine should only be ingested when instructed to do so by the prefect. It should be taken a few hours before the passage of a radioactive cloud, and no later than eight hours after. If taken too long before, the medication loses its effectiveness completely and no longer protects the thyroid.

“In France, in line with the recommendations of the IAEA – International Atomic Energy Agency – and the WHO, the threshold at which the thyroid must be protected is set at 50 millisieverts. When the experts' predictions exceed this threshold, the prefect gives the order to take the pill,” explains the Institute for Radiological Protection and Nuclear Safety (INRS). If you take the tablet too early, the thyroid will no longer be saturated when the cloud passes.