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Editor’s note:

A massive 9.0-magnitude earthquake struck the Pacific coastal areas of northeastern Japan, triggering an enormous tsunami. The number of dead, missing and sick continues to rise as the country faces a catastrophic nuclear crisis.

People are desperate for information on loved ones and fearful of the enduring nuclear crisis. Aside from the live updates of Japan’s quake aftermath, we will also give our readers in-depth background information on natural catastrophes, as well as advice, facts and information to help reduce the growing sense of panic around the world.

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Major nuclear accidents around the world

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The No 3 nuclear reactor of the Fukushima Daiichi nuclear plant at Minamisoma is seen burning after a blast following an earthquake and tsunami in this handout satellite image taken March 14, 2011. [Photo/Agencies]

The Fukushima No 1 nuclear power plant in northeast Japan started to leak radioactive material after an hydrogen explosion, which was caused by a devastating earthquake and ensuring tsunamis, occurred Saturday afternoon.

The following table shows the major nuclear accidents around the world since the former Soviet Union set up the world's first nuclear power plant in 1954.

When Where Consequences
Oct 10, 1957 Windscale nuclear reactor (later renamed Sellafield) in northwest England Sale of milk and other produces from nearby farms were banned for a month. Scores of people later developed cancer and died because of exposure to radiation.
March 28, 1979 Three Mile Island in the United States Evacuation of at least 150,000 local residents.
April 26, 1986 Chernobyl nuclear plant in the former Soviet Union Explosion killed 30 people on the spot, released more than eight tons of highly radioactive material, contaminated 60,000 square km of land, and caused more than 3.2 million people to be affected by radiation.
April 6, 1993 Tomsk-7 Reprocessing Complex in the Siberian region of Russia A total of 10 square km of land was contaminated by radioactive material and a number of nearby villages were evacuated.
Sept 30, 1999 Tokai village, Ibaraki prefecture, Japan Nuclear accident killed two workers, exposed dozens of people to radiation and forced the evacuation of local residents.
Aug 9, 2004 No 3 reactor at Kansai Electric's Mihama power plant, Japan. Four workers were killed and seven others injured.

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Key facts on Chernobyl nuclear accident

Unlike the nuclear crisis in Japan which was caused by a natural disaster, the explosion and fire at the Chernobyl power plant on April 26, 1986 -- the world's worst nuclear accident -- was caused by human error.

Facility operators, in violation of safety regulations, had switched off important control systems at the Ukrainian plant's reactor number four and allowed it to reach unstable, low-power conditions, according to a United Nations report. A power surge led to a series of blasts, at 1:24 am, which blew off the reactor's heavy steel and concrete lid and sent a cloud of radioactive dust billowing across northern and western Europe, reaching as far as the eastern United States. more

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3D diagrams explaining the 1986 Chernobyl nuclear disaster and planned 20,000 ton steel case to cover its aged and crumbling Sarcophagus. [Photo/Agencies]

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Radiation and its effects on humans

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A man is screened for radiation levels at a makeshift facility in Nihonmatsu, northern Japan, March 14, 2011. [Photo/Agencies]

The following photo shows a girl isolated at a makeshift facility looks at her dog

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through a window in Nihonmatsu, northern Japan, March 14, 2011.

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A man is scanned for radiation at a gymnasium in Fukushima Prefecture, northern Japan March 17, 2011. [Photo/Agencies]

Health effects of radiation exposure


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. more

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A technician in protective gear scans for signs of radiation on a child at a makeshift facility in Nihonmatsu, northern Japan March 14, 2011. [Photo/Agencies]

Human exposure to radiation


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. more


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.

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.

These necessary actions depend on the estimated exposure. The actions include steps such as evacuation of people, providing shelter to reduce exposure and providing iodine pills for people to take to reduce the risk of thyroid cancer. more


Other infomation that may be helpful

INES Scale

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What are potassium iodide pills?

In the setting of a nuclear power plant accident, potassium iodide pills are given to saturate the thyroid gland and prevent the uptake of radioactive iodine. When given before or shortly after exposure, this step can reduce the risk of cancer in the long term.

Can pregnant women take potassium iodide pills?

Pregnant women should take potassium iodide pills only when instructed by the competent authorities because the thyroid of a pregnant woman accumulates radioactive iodine at a higher rate than other adults and because the thyroid of the fetus is also blocked by giving potassium iodide pills to the mother.

Current risk of radiation-related health problems in Japan

The actions proposed by the Government of Japan are in line with the existing recommendations based on public health expertise.


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Houses are swept by water following a tsunami and earthquake in Natori City in northeastern Japan March 11, 2011. A massive 8.9 magnitude quake hit northeast Japan on Friday, causing many injuries, fires and a ten-metre (33-ft) tsunami along parts of the country's coastline. [Photo/Agencies]

What is earthquake?

An earthquake is what happens when two blocks of the earth suddenly slip past one another. The surface where they slip is called the fault or fault plane. more

What causes earthquakes?

The earth has four major layers: the inner core, outer core, mantle and crust. The crust and the top of the mantle make up a thin skin on the surface of our planet. But this skin is not all in one piece -- it is made up of many pieces like a puzzle covering the surface of the earth. more

Relationship between earthquakes, tsunamis

A tsunami is a series of destructive waves, sometimes tens of meters high, caused by the displacement of a large volume of water, usually an ocean. With gigantic energy and fast movement, the waves are catastrophic to the affected coastal areas. more

Tsunamis triggered by major earthquakes globally in recent years

When Where Consequences
June, 2001 Southern Peru At least 78 people were killed by a tsunami caused by a magnitude-8.4 earthquake in southern Peru. The direct economic loss reached about $300 million.
Dec 26, 2004 Indonesian island of Sumatra A 9.0 magnitude earthquake struck off the Indonesian island of Sumatra, triggering a tsunami that killed tens of thousands of people in several countries.
July 17, 2006 Indonesia's West Java A magnitude 6.8 earthquake occurred off the coast of Indonesia's West Java, triggering a tsunami that killed 668 people, injured at least 1,438 and left about 74,000 people homeless.
Jan 13, 2007 Disputed four-island chain known as the Northern Territories in Japan and the Kuril Islands in Russia A magnitude 8.3 earthquake near the disputed four-island chain known as the Northern Territories in Japan and the Kuril Islands in Russia triggered tsunami warnings, sending thousands fleeing to higher ground.
April 2, 2007 Solomon Islands More than 50 people died and thousands of people were evacuated in the Solomon Islands when it was hit by a tsunami caused by a magnitude-8.0 earthquake.
Sept 29, 2009 Samoa A strong earthquake measuring 8.0 on the Richter scale struck the Pacific island nation of Samoa, causing a tsunami that killed at least 184 people.
Jan 4, 2010 Western part of the Solomon Islands Two powerful earthquakes measuring 6.5 and 7.2 on the Richter scale hit the western part of the Solomon Islands, followed by a number of smaller quakes. It triggered a tsunami that left about 1,000 homeless.
Feb 27, 2010 Chile An 8.8-magnitude earthquake hit Chile, triggering tsunami warnings along the coasts of the Pacific Ocean.
Oct 25, 2010 Sumatra, Indonesia At least 509 people were killed and 21 others went missing after a tsunami unleashed by a 7.2 magnitude quake jolted the island of Sumatra, Indonesia.

How to protect yourself during an earthquake?

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