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Factbox: WHO issues guidelines on radiation exposure

In the wake of Japan's nuclear crisis, the World Health Organization (WHO) issued fresh guidelines on how to minimize exposure to radiation that can cause cancers, especially in children and young adults.
/ Source: Reuters

In the wake of Japan's nuclear crisis, the World Health Organization (WHO) issued fresh guidelines on how to minimize exposure to radiation that can cause cancers, especially in children and young adults.

The United Nations agency said measures taken by Japan so far meet its public health recommendations, including evacuating people within 20 km of the crippled Fukushima nuclear power plant and asking those within 30 km to stay indoors.

There was no indication of food safety risks due to imports of food products from Japan. It was also unlikely food production or harvesting in the affected area was taking place, but it said crops and livestock in the area should be protected.

Following is a list of the main WHO recommendations:

* The main radionuclides released in a nuclear power plant accident 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," the WHO said.

* If radioactive iodine is breathed in or swallowed, it will concentrate in the thyroid gland and increase the risk of thyroid cancer. This risk can be lowered by taking potassium iodide pills which saturate the thyroid gland and help prevent the uptake of the radioactive material. "When given before or shortly after exposure, this step can reduce the risk of cancer in the long term," it said. National authorities are best placed to determine if it is warranted to take the tablets.

* If a dose of radiation exceeds a certain threshold level, then it can produce skin redness, hair loss, radiation burns and acute radiation syndrome. Due to their work, rescuers and nuclear power plant workers may be exposed to higher radiation doses than the general population.

* Exposure to radiation can increase the risk of cancer. Among the survivors in Japan of U.S. atomic bombs dropped in August 1945, the risk of leukemia increased a few years after radiation exposure, while the risks of other cancers increased more than 10 years after the exposure.

* The risk of thyroid cancer following radiation exposure is higher in children and young adults.

* 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.

* "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 a safe location, away from living areas, children, and pets," it said.

* "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," the WHO said.

* "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," the agency said.

* Foods can be contaminated with radioactive materials as a 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.

* "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," the WHO said.

* In the early stages of an emergency, and if it is safe to do so, vegetables and animal fodder can be protected with plastic sheets or tarpaulins. "Bring livestock in from pasture; move animals into a shed or barn. Harvest any ripe crops and place under cover," it said.

* Avoid consumption of locally produced milk or vegetables, avoid slaughtering animals and avoid fishing, hunting or gathering mushrooms or other forest foods.