A single iodine dose provides protection for one day and some protection on the second day after taking it. The iodine dose should be taken 1–6 hours before exposure to radioactive iodine in order to provide full protection. The later the iodine dose is taken, the greater the reduction in the protective effect. The iodine dose is of no use if the radioactive substances were inhaled more than 12 hours before taking the dose. To ensure correct timing, the iodine tablet should only be taken as instructed by the authorities.

No link has been found between exposure to radioactive iodine and thyroid cancer in adults. This is why the World Health Organisation (WHO) does not recommend iodine tablets for people over 40 years of age in emergency situations. Exceptions are pregnant women and workers at risk. The most vulnerable group in a radiological emergency are young children and foetuses. The risk of adverse effects from an extra dose of iodine also increases with age, as does the incidence of thyroid disease.

The public health care distributes iodine products to newborns that can be accurately dosed for children under 3 years of age or under one month of age. Some pharmacies also offer 65 mg iodine tablets, which can be divided into doses small enough for children under 3 years of age. The iodine tablet is a medicine. Medicines must be administered in doses specified by the manufacturer in the package leaflet. 

The most commonly available iodine tablets in pharmacies, with a strength of 130 mg (Jodix), cannot be reliably divided into doses small enough for children under 3 years of age. The instructions in the iodine preparation package leaflet do not contain any information about giving the iodine tablet to a child under the age of 3.

It is especially important that children and pregnant women take iodine tablets as instructed by the authorities in a radiation hazard situation. The thyroid glands of children and the foetuses are more sensitive to radiation than those of adults. It is also recommended that pregnant women with a thyroid condition take the iodine tablet to protect the foetus. If necessary, talk to your treating physician about taking iodine tablets.

The iodine tablet taken at the right time saturates the thyroid gland with normal non-radioactive iodine and thus prevents the accumulation of radioactive iodine in the thyroid gland. Radioactive iodine will be quickly eliminated from the body by the kidneys. The protective effect of the tablet is reduced if the tablet is taken too early or too late.

A serious nuclear power plant accident may release radioactive iodine into the atmosphere, and this typically builds up in the thyroid gland after entering the body by inhalation, for example. The primary protective measure is sheltering indoors. The build-up of radioactive iodine in the thyroid gland can be reduced by taking an iodine tablet. The efficiency of this measure depends on correct timing. The tablets must therefore only be taken when instructed by the authorities. Instructions for using the iodine tablet are provided via radio and television. Guidance can also be found by following the authorities' communications on their websites and social media channels.

The situation in Ukraine has no impact on the radiation situation in Finland. The authorities recommend that iodine tablets should be available at homes and workplaces as part of basic preparedness, but there is no need to purchase them separately due to the situation in Ukraine. Above all, iodine tablets must not be taken without instructions from the authorities. You should never take an iodine tablet ‘just in case’, as it is important to take the iodine tablet at the right time. The protective effect of the tablet is reduced if the tablet is taken too early or too late.

The distance impacts of the use of a nuclear weapon are very difficult to estimate as they depend on the size of the weapon and the height at which it is detonated. In order for the effects of the weapon to reach Finland, the nuclear weapon would need to be very large. Even this would not have an immediate effect: the direct heat and pressure effect of even a really big nuclear bomb extends over some dozens of kilometres at worst. Modern nuclear weapons designed to be used in combat are smaller so-called tactical nuclear weapons.  The radiation effect is not the main destructive mechanism of a nuclear weapon, but the nuclear bomb also produces an extensive explosion. This means that damage is primarily caused by the effects of heat and pressure. At the moment, nuclear weapons do not represent a threat to Finland.

A meltdown of a nuclear reactor in Ukraine could cause large local discharges if the containment building around the reactor was damaged at the same time. However, there would be no significant dispersion of radioactive materials over a radius of more than 100 km from the accident. Therefore, immediate health effects could only occur near the plant. In practice, nothing related to possible radioactive materials or nuclear power plants in Ukraine can cause a situation that would require immediate radiation protection in Finland. Finland could be subject to restrictions on the use of certain foodstuffs if there was a nuclear accident or a nuclear attack in Ukraine. These kinds of actions would protect people from the long-term effects of radiation.

If radioactive substances were released from an operational nuclear power plant or Chernobyl in Ukraine, the effects would be mostly local and regional. People in Finland would not need to shield against radiation.
Finnish authorities use extremely precise and sensitive methods for detecting radioactivity in outdoor air and fallout, which is why trace activity concentrations might be detected in Finland as well. The concentration depends greatly on wind directions and the altitude of the release. A strong wind (more than 10 meters per second) blowing directly northwards from Ukraine toward Finland would carry the release to Finland in approximately two days. The release would of course become diluted on the way, as it would get mixed with air and a part of it would settle on the ground. Even in this case, people in Finland would not need to shield against radiation.

Despite the fact that the Chernobyl accident was very serious, the accident did not have any health effects in Finland. Radiation levels rose also in Finland, but not to such an extent that protection measures for people would have been necessary. Protective measures for food production were started immediately in Finland, so that short-lived radioactive substances would not be transferred to humans via food. Chernobyl fallout continues to increase the radiation dose received by Finns, but the amount is very small, less than a hundredth of our annual average dose of 5.9 millisieverts. According to a study conducted by STUK, which was published in 2013, the Cancer Registry and the National Institute for Health and Welfare (THL), the fallout caused by the Chernobyl nuclear power plant accident has not noticeably increased the number of cancers in Finland.

More information

• The effects of the Chernobyl nuclear power plant accident on people​​​​​​​​​​​​​​
• Chernobyl fallout and cancer incidence in Finland 1988–2007 (julkari.fi)

An accident such as the one in Chernobyl in 1986 is not possible. The reactor destroyed in Chernobyl was of a different type than the reactors in the current operating nuclear power plants in Ukraine. There was a design flaw in the Chernobyl reactor and the security systems had also been shut down before the explosion. The Chernobyl reactor used graphite as the moderator, the combustion of which raised radioactive substances high into the air and subsequently spread them over a very large area through the air currents.

STUK monitors the situation in Ukraine from the point of view of nuclear and radiation safety and reports, for example, on the situation of Ukraine's nuclear power plants and possible effects of the radiation situation on Finland on its website and social media channels. We do not take a position on energy, geopolitical or security policy issues. We also do not provide advice on medicines, illnesses or allergies. For example, for individual questions related to iodine tablets, please contact your physician or pharmacist.

The Finnish Ministry of Foreign Affairs (um.fi) is closely monitoring the situation in Ukraine and providing reliable information related to the crisis. STUK publishes information related to nuclear and radiation safety on its website and social media channels. It is especially important to be media and source critical during crises and serious events. Not all information shared online is reliable, and children, for example, must be protected from war material shared on social media.

UV radiation is classified by wavelength. UV-A radiation ranges from 315–400 nm, and UV-B from 280–315 nm (nm = nanometers). The main differences between UV-A and UV-B are their effects on the skin, how deeply they penetrate, and how the atmosphere filters them.

UV-B radiation penetrates only the outer layers of the skin. It increases surface cell production and pigmentation. UV-B can burn the skin and increase the risk of skin cancer. About 90% of solar UV-B is absorbed by ozone, water vapor, oxygen, and carbon dioxide in the atmosphere.

UV-A radiation penetrates the deepest layers of the skin, darkens existing pigment, and accelerates skin aging. It can also contribute to skin cancer. UV-A is barely filtered by the atmosphere.

Yes, although tanning occurs more slowly than without sunscreen. When used correctly, sunscreens can prevent sunburn, but they do not entirely block the effects of UV radiation. Small amounts of UV still reach the skin even if the recommended protection time has not been exceeded. As a result, the skin will tan and, in the worst case, even burn despite using sunscreen.
 

Fair, easily burning skin, freckles, numerous moles, and family history of skin cancer are risk factors. Although many moles increase melanoma risk, skin cancer often appears on skin without moles. Therefore, exposing any skin area to high UV radiation is risky regardless of moles. People with multiple risk factors should take extra care. Monitor your moles and consult a doctor if you notice changes like growth, itching, color change, or bleeding.
 

In autumn and winter, UV radiation levels in Finland are so low that protection is not needed. 

Snow-free land reflects UV radiation poorly, but snow reflects UV radiation well. This is why it is important to protect your face and eyes from UV radiation during long outdoor stays in spring, even if the UV index has not yet exceeded 3.

UV radiation affects the body even at lower index levels. The recommendation to protect at index values over 3 is based on the risk of skin burning.

The amount of UV radiation depends on season, time of day, location, altitude, cloudiness, and ozone layer thickness. About half of the daily UV dose occurs between 11 a.m. and 3 p.m. Radiation is strongest when the sun is highest in the sky.