What is the current risk of radiation-related health problems in Japan to those near the reactor at the time, and those in other parts of Japan?
The actions proposed by the Government of Japan are in line with the existing recommendations based on public health expertise. The government is asking people living within 20 km of the Fukushima Daiichi nuclear power plant to evacuate and those between 20 km and 30 km away from the plant are asked to stay indoors in unventilated rooms. People living farther away are at lower risk than those who live nearby.
This assessment can change if there are further incidents at these plants and WHO is following the situation closely. However, radiation-related health consequences will depend on exposure. Exposure in turn is dependent on the amount of radiation released from the reactor, weather conditions such as wind and rain at the time of the exposure, the distance someone is from the plant, and the amount of time someone is in irradiated areas.
What is ionizing radiation?
When certain atoms disintegrate, either naturally or in man-made situations, they release a type of energy called ionizing radiation (IR). This energy can travel as either electromagnetic waves (gamma or X-rays) or as particles (neutrons, beta or alpha).
The atoms that emit radiation are called radionuclides.
The time required for the energy released by a radionuclide to decrease by half (i.e., the half-life) range from tiny fractions of a second to millions of years depending on the type of atoms.
Are people normally exposed to ionizing radiation?
Human beings are exposed to natural radiation on a daily basis. The radiation comes from space (cosmic rays) as well as natural radioactive materials found in the soil, water and air. Radon gas is a naturally formed gas that is the main natural source of radiation.
People can also be exposed to radiation from human-made sources. Today, the most common man-made source of ionizing radiation are certain medical devices such as X-ray machines.
The radiation dose can be expressed in units of Sievert (Sv). On average, a person is exposed to approximately 3.0 mSv/year of which, 80% (2.4 mSv) is due to naturally-occurring sources (i.e., background radiation), 19.6 % (almost 0.6 mSv) is due to the medical use of radiation and the remaining 0.4% (around 0.01 mSv) is due to other sources of human-made radiation.
In some parts of the world, levels of exposure to natural radiation differ due to differences in the local geology. People in some areas can be exposed to more than 200 times the global average.
How are people exposed to ionizing radiation?
Ionizing radiation may result from sources outside or inside of the body (i.e. external irradiation or internal contamination).
Internal contamination may result from breathing in or swallowing radioactive material or through contamination of wounds.
External irradiation is produced when a person is exposed to external sources such as X-rays or when radioactive material (e.g. dust, liquid, aerosols) becomes attached to skin or clothes, resulting in external contamination.
External contamination can often be washed off the body.
What type of radiation exposure could occur in a nuclear power plant accident?
If a nuclear power plant does not function properly, radioactivity may be released into the surrounding area by a mixture of products generated inside the reactor (”nuclear fission products”). The main radionuclides representing health risk are radioactive caesium and radioactive iodine. Members of the public may be exposed directly to such radionuclides in the suspended air or if food and drink are contaminated by such materials.
Rescuers, first responders and nuclear power plant (NPP) workers may be exposed to higher radiation doses due to their professional activities and direct exposure to radioactive materials inside the power plant.
What is the WHO travel advice for Japan?
At this time, WHO is not advising general restrictions on travel to Japan.
However, travellers should avoid travel to the areas most affected by the earthquake and tsunami because of disruptions to essential services, such as transport and electric power, and the ongoing disaster relief activities, including the nuclear power plant emergency response and control activities, will make travel difficult and could consume resources needed by relief worker and residents. Moreover, as indicated by the Japanese authorities, travel within the evacuation and exclusion zones surrounding the Fukushima Daiichi nuclear power plant is prohibited.
In general, travellers who do not have essential reasons to travel should give careful consideration to deferring travel to any areas where there has been considerable disruption to the normal infrastructure and where authorities are responding to urgent humanitarian needs.
What are the precautions when travelling in Japan?
Travellers should also be aware of the risk of further earthquakes across Japan. Moreover, there may be areas of power, fuel, food and water shortages.
Travellers in Japan should monitor local media, follow the advice and instructions issued by local authorities and register their travel and location details with their respective embassy or consulate. Information on the status of the nuclear facilities in Fukushima can be found on Japan’s Nuclear and Industrial Safety Agency (NISA) website and on the International Atomic Energy Agency (IAEA) website. Additional information can be found on the WHO web site.
Do travellers returning from Japan represent a health risk for others?
At this time, only those involved in the emergency response near the plant remain in the area where there are higher levels of radioactivity. For their own safety, all personnel in these areas should undergo decontamination procedures when they leave the site. Travellers returning from Japan who have come from the 20 km evacuation zone surrounding the Fukushima Daiichi nuclear power plant and who have undergone proper screening and decontamination procedures, and travellers from all other areas, do not pose a radioactive health risk to others.
What are the acute health effects of radiation exposure?
If the dose of radiation exceeds a certain threshold level, then it can produce acute effects, such as skin redness, hair loss, radiation burns, and acute radiation syndrome (ARS1).
In a nuclear power plant accident, the general population is not likely to be exposed to doses high enough to cause such effects.
Rescuers, first responders and nuclear power plant workers are more likely to be exposed to doses of radiation high enough to cause acute effects.
What long-term effects can be expected from radiation exposure?
Exposure to radiation can increase the risk of cancer. Among the Japanese atomic bomb survivors, the risk of leukaemia increased a few years after radiation exposure, whereas the risks of other cancers increased more than 10 years after the exposure.
Radioactive iodine can be released during nuclear emergencies. If breathed in or swallowed, it will concentrate in the thyroid gland and increase the risk of thyroid cancer. Among persons exposed to radioactive iodine, the risk of thyroid cancer can be lowered by taking potassium iodide pills, which helps prevent the uptake of the radioactive iodine.
The risk of thyroid cancer following radiation exposure is higher in children and young adults.
1 ARS is a set of signs and symptoms that may develop after whole-body doses above 1 Sv (i.e. about 300 times the annual dose to background radiation). It is related to the damage of the bone marrow, where the blood cells are produced. At higher doses (>10 Sv) other organs may be affected (e.g. gastrointestinal, cardiovascular).
Which public health actions are most important to take?
Health effects can only occur if someone is exposed to radiation, thus the main protective action someone can take is to prevent exposure. Those closest to the radiation are at greatest risk of exposure and the greater the distance away, the lower the risk. This is why when a nuclear accident occurs, the recommended public health actions involve evacuation and sheltering of those near the site.
These necessary actions depend on the estimated exposure (i.e. the amount of radioactivity released in the atmosphere and the prevailing meteorological conditions such as wind and rain). The actions include steps such as evacuation of people within a certain distance of the plant, providing shelter to reduce exposure and providing iodine pills for people to take to reduce the risk of thyroid cancer.
If warranted, steps such as restricting the consumption of vegetables and dairy products produced in the vicinity of the power plant can also reduce exposure.
Only competent authorities who have conducted a careful analysis of the emergency situation are in a position to recommend which of these public health measures should be taken.
How can I protect myself?
Keep you and your family informed by obtaining accurate and authoritative information (for example, information from authorities delivered by radio, TV or the Internet) and following your government’s instructions.
The decision to stockpile or take potassium iodide tablets should be based on information provided by national health authorities who will be in the best position to determine if there is enough evidence to warrant these steps.
If I have been exposed to high levels of radiation, what should I do?
If you are coming indoors after radiation exposure, undress in the doorway to avoid further contamination in your home or shelter. Remove clothing and shoes and place them in a plastic bag. Seal the bag and place it in safe location, away from living areas, children, and pets.
Shower or bathe with warm, not scalding hot, water and soap.
Notify authorities that you may have contaminated clothing and personal belongings to be handled appropriately and disposed of according to accepted national procedures.
When people are advised to stay indoors, what does this mean?
When a radiological or nuclear event occurs, public health authorities may order residents in the affected areas to stay indoors rather than to evacuate. You may be advised to take shelter at home, at work, or in public shelters. The recommendation is usually issued to protect people from exposure to radiation.
If you are advised to stay indoors, you should find the safest room in your house or office building that has no windows or doors. Ventilation systems, such as heating and cooling systems, should be shut down.
In sub-zero temperatures, it is important to keep warm. If you have been instructed to shelter in your home, office, or other structure, it may not safe to burn fuelssuch as gas, coal, or woodto keep warm. Carbon monoxide poisoning may occur in rooms that are not properly ventilated and should not be used in this circumstance. If available, electrical forms of heating would be safer.
Shelter can provide protection from both external and internal irradiation, as well as from inhalation of radioactive material.
Taking shelter is a simple and protective action that can be implemented promptly during the early phase of an incident.
What are potassium iodide pills?
Potassium iodide pills are a source of stable (i.e. non-radioactive) iodine. The thyroid gland requires iodine to produce thyroid hormones. The presence of stable iodine in the body in an appropriate amount blocks the thyroid from absorbing radioactive iodine (radioiodine), reducing the risk of thyroid cancer which may follow from exposure to radioiodine.
Potassium iodide pills are not “radiation antidotes”. They do not protect against external radiation, or against any other radioactive substances besides radioiodine. They may also cause medical complications for some individuals with poorly functioning kidneys. Potassium iodide should be taken only when there is a clear public health recommendation.
When and why should I take potassium iodide?
You should only take potassium iodide when it is recommended by public health authorities. If you are at risk or have been exposed to radioiodine, potassium iodide pills may be given to protect the thyroid gland from uptake of radioiodine. This can reduce the risk of thyroid cancer in the long run, when given before or shortly after exposure.
Should I take iodized salt to protect myself from radiation?
No, you should not take iodized salt to protect yourself from radiation. It is dangerous to take large amounts of iodized salt in order to increase the amount of stable iodine in the body.
Increasing one’s daily intake of iodized salt will cause more harm than good. The main ingredient of iodized salt is sodium chloride, which is linked with hypertension (high blood pressure) and other medical disorders. The iodine content in iodized salt is too low to prevent uptake of radioiodine.
Sodium chloride is acutely toxic in large amounts: even tablespoon quantities of salt repeatedly taken over a short period of time could cause poisoning.
Can I take other forms of iodine?
No, you should not take products that contain iodine, other than medicines recommended by public health authorities.
Iodine is found in a number of different household and industrial products. For example, iodine may be found in some disinfectants, antiseptics, and water-sterilizing solutions. These products should not be taken as an alternative to potassium iodide pills, because such products contain other ingredients that can be harmful if swallowed.
Can pregnant women take potassium iodide pills?
Yes, most pregnant women can take potassium iodide pills, following the instructions of public health authorities. Potassium iodide will cross the placenta and protect the thyroid of the growing foetus, as well as the mother.
Can breastfeeding women take potassium iodide?
Yes, most breastfeeding women can take potassium iodide, following the instructions of public health authorities.
Is it safe to eat food imported from Japan?
Food that was dispatched before the emergency situation would not be affected. Food safety concerns are restricted to food from the affected zone around the Fukushima Daiichi nuclear power plant. Given the reported safety measures, the winter conditions, and the earthquake and resulting tsunami, it is unlikely that food production or harvesting intended for export is taking place in that area. Japanese authorities have instituted monitoring of food for radionuclide contamination.
How can food products become radioactive?
Foods can be contaminated with radioactive materials as the result of a nuclear or radiological emergency. The surface of foods like fruits and vegetables or animal feed can become radioactive by deposit of radioactive materials falling on it from the air or through rain water. Over time, radioactivity can also build up within food, as radionuclides are transferred through soil into crops or animals, or into rivers, lakes and the sea where fish and shellfish could take up the radionuclides. The severity of the risk depends on the radionuclide mix and the level of contaminant released.
Radioactivity cannot contaminate food that is packaged; for example, tinned or plastic-wrapped food is protected from radioactivity as long as the food is sealed.
What are the potential health effects of consuming contaminated food ?
Food contaminated with radioactive material will not appear spoiled, but consuming such food will increase the amount of radioactivity a person is exposed to and could increase the health risks associated with exposure. For example, it could increase prevalence of certain cancers in the future. The exact effects on specific organs will depend on which radionuclides have been ingested and the amount being ingested.
What general advice can be given to food consumers and producers in the event of a nuclear emergency?
The response to an emergency involving radioactivity should be the same as the response to any emergency involving any hazardous material contaminating food. In the early stages of an emergency, and if it is safe to do so, it is possible to take immediate actions to prevent or minimize the contamination of food by radiological materials. For example, it is possible to do the following:
protect growing vegetables and animal fodder; cover with plastic sheets or tarpaulins;
Many other short-, medium- and long-term actions need to be considered in areas confirmed to be seriously contaminated, such as:
avoid consumption of locally produced milk or vegetables;
Additional information on emergency preparedness and response Joint FAO/IAEA Programme
Are there rules for radioactivity in foods for international trade?
There are internationally agreed Guideline Levels (GLs) for radionuclide levels in internationally traded food following a nuclear or radiological emergency. These GLs are published by the Joint FAO/WHO Codex Alimentarius Commission.
Food below these GLs is safe for people to eat. When the GLs are exceeded, national governments must decide whether and under what circumstances the food should be allow to be distributed within their territory or jurisdiction.
Guideline Levels (GLs) for radionuclide levels Joint FAO/WHO Codex Alimentarius Commission
What is WHO’s role in nuclear emergencies?
In accordance with its Constitution and the International Health Regulations, WHO is mandated to assess public health risks and provide technical consultation and assistance in association with public health events, including those associated with radiation events. In doing so, WHO is working with independent experts and other UN agencies.
WHO’s work is supported by a global network comprising more than 40 specialized institutions in radiation emergency medicine. The network, the Radiation Emergency Medical Preparedness and Assistance Network (REMPAN), provides technical assistance for radiation emergency preparedness and response.