"It is only necessary to take an iodine tablet if there is a nuclear accident and the person is close to the scene of the accident. However, the radiation level in Estonia and Europe, in general, has not increased, nor has there been a nuclear accident. The nuclear power plants operating in Ukraine are also so far away from Estonia that it is by no means necessary to take iodine tablets in Estonia," said Rainer Vakra, Director General of the Environmental Board.
It is important to distinguish between non-radioactive iodine, which is essential for human life, and the radioactive isotopes of iodine that are released during a nuclear accident.
THE RADIATION MONITORING BUREAU OF THE ENVIRONMENTAL BOARD PROVIDES EXPLANATIONS ABOUT IODINE AND ITS RADIOACTIVE ISOTOPES.
1) Iodine does not protect against radiation in general.
2) Iodine protects against the radioactive isotopes of only one specific substance, iodine itself, of which iodine-131 (I-131) is the only relevant isotope in the context of a nuclear accident.
3) The half-life of iodine-131, i.e., the time during which the substance is halved during radioactive decay, is eight days. This time is short enough for the substance to deplete relatively quickly (1024-fold in 80 days), but still long enough to travel by wind far from the scene of the accident for hours and days.
4) Iodine-131 is only produced in a working nuclear reactor. When the chain reaction in the reactor ends, the formation of iodine-131 will soon stop. Only the decay process of iodine-131 follows.
5) Due to the above, iodine-131 is not present in the territory of the Chernobyl nuclear power plant or in any radioactive waste repository. The chain reaction cannot occur again in these places. A working reactor is required for a new chain reaction to occur.
6) Iodine-131 is released during an accident with a running reactor and spreads to where it is carried by the wind. Initially, the concentration of iodine in the cloud is high. The farther away, the thinner the cloud becomes. As the cloud expands twofold, the density decreases eightfold. If the size is tenfold, the density is already a thousand times smaller, and so on. When it gets to the areas where it rains, the rain brings most of the radioactive substance to the ground, and less of it spreads farther away.
7) If a person appears to be downwind from the scene of the accident, he or she may be exposed to the cloud for some time. The farther away this happens, the more sparse the cloud, the less I-131 reaches the human body by inhalation and the smaller its potential impact. Some of the I-131 that enters the body is excreted in the process of metabolism; some will affect a person for a long time.
8) Human iodine reserve is stored in the thyroid gland. If a person inhales iodine-131, it is also stored in the thyroid gland.
9) To prevent radioactive iodine from being stored in the thyroid gland, the thyroid gland must be saturated with non-radioactive iodine beforehand. The storage of iodine-131 in the thyroid gland can be prevented by taking a special iodine tablet a few hours before being exposed to a radioactive iodine cloud. It is only necessary to take an iodine tablet if you are close to the scene of the accident.
The effect of the iodine tablet remains only for 24-36 hours, therefore it is necessary to take the tablet only when the authorities have ordered to do so.
The iodine rich foods (e.g., iodized salt or water) have such low iodine concentrations that their consumption is not sufficient to saturate the thyroid gland. The iodine content of the iodized salt is a few tens of micrograms per gram, the iodine content in the iodized water is about 150 micrograms per litre. One hundred milligrams of iodine, necessary for an adult to saturate the thyroid gland, corresponds to several kilograms of salt or 700 liters of water.
10) The so-called iodine prophylaxis or taking iodine tablets is necessary up to a few dozens of kilometers from the accident site, depending on the size of the accident and the weather conditions on the way of movement of the cloud. From there, up to a hundred kilometers away, the need to take iodine tablets becomes less and less likely.
