Japanese emperor 'deeply worried'

By Richard Warry BBC News
 

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Prof Malcolm Sperrin, a medical physicist, on the Japan quake health risks

The Japanese authorities say radiation levels from the Fukushima Daiichi nuclear plant climbed to potentially harmful levels for a brief interval on Tuesday.

Residents living within 30km (18 miles) of the plant have been advised to leave the area, or to stay indoors, and try to make their homes airtight.
Experts have stressed that swift action should be able to minimise any impact on human health.

What are the immediate health effects of exposure to radiation?

Exposure to moderate levels of radiation - above one gray - can result in radiation sickness, which produces a range of symptoms.
Nausea and vomiting often begin within hours of exposure, followed by diarrhoea, headaches and fever.
After the first round of symptoms, there may be a brief period with no apparent illness, but this may be followed within weeks by new, more serious symptoms.
At higher levels of radiation, all of these symptoms may be immediately apparent, along with widespread - and potentially fatal - damage to internal organs.
Exposure to a radiation dose of four gray will typically kill about half of all healthy adults.
For comparison, radiation therapy for cancer typically involves several doses of between one and seven gray at a time - but these doses are highly controlled, and usually specifically targeted at small areas of the body.

 How is radiation sickness treated?

The first thing to do is to try to minimise further contamination by removing clothes and shoes, and gently washing the skin with soap and water.
Drugs are available that increase white blood-cell production to counter any damage that may have occurred to the bone marrow, and to reduce the risk of further infections due to immune-system damage.
There are also specific drugs that can help to reduce the damage to internal organs caused by radioactive particles.

How does radiation have an impact on health?

Radioactive materials that decay spontaneously produce ionising radiation, which has the capacity to cause significant damage to the body's internal chemistry, breaking the chemical bonds between the atoms and molecules that make up our tissues. The body responds by trying to repair this damage, but sometimes it is too severe or widespread to make repair possible. There is also a danger of mistakes in the natural repair process.
Regions of the body that are most vulnerable to radiation damage include the cells lining the intestine and stomach, and the blood-cell producing cells in the bone marrow.
The extent of the damage caused is dependent on how long people are exposed to radiation, and at what level.

What are the most likely long-term health effects?

Cancer is the biggest long-term risk. Usually when the body's cells reach their "sell-by date" they commit suicide. Cancer results when cells lose this ability, and effectively become immortal, continuing to divide and divide in an uncontrolled fashion.
The body has various processes for ensuring that cells do not become cancerous, and for replacing damaged tissue.
But the damage caused by exposure to radiation can completely disrupt these control processes, making it much more likely that cancer will result.
Failure to properly repair the damage caused by radiation can also result in changes - or mutations - to the body's genetic material, which are not only associated with cancer, but may also be potentially passed down to offspring, leading to deformities in future generations. These can include smaller head or brain size, poorly formed eyes, slow growth and severe learning difficulties.

Are children at greater risk?

Potentially yes. Because they are growing more rapidly, more cells are dividing, and so the potential for things to go wrong is greater. Following the Chernobyl nuclear reactor accident in the Ukraine in 1986, the World Health Organization recorded a dramatic increase in thyroid cancer among children in the vicinity.
This was because the radioactive materials released during the accident contained high levels of radioactive iodine, a material that accumulates in the thyroid.

What risk does Fukushima pose currently?

The Japanese authorities have recorded a radiation level of up 400 millisieverts per hour at the nuclear plant itself. A sievert is essentially equivalent to a gray, but tends to be used to measure lower levels of radiation, and for assessing long-term risk, rather than the short-term acute impact of exposure.
Professor Richard Wakeford, an expert in radiation exposure at the University of Manchester, said exposure to a dose of 400 millisieverts was unlikely to cause radiation sickness - that would require a dose of around twice that level (one sievert/one gray). However, it could start to depress the production of blood cells in the bone marrow, and was likely to raise the lifetime risk of fatal cancer by 2-4%. Typically, a Japanese person has a lifetime risk of fatal cancer of 20-25%.

Prof Wakeford stressed only emergency workers at the plant were at risk of exposure to such a dose - but it was likely that they would only be exposed for short periods of time to minimise their risk.
The level of exposure for the general population, even those living close to the plant, was unlikely to be anywhere near as high.

How can the Japanese authorities minimise the cost to human health?

Prof Wakeford said that provided the Japanese authorities acted quickly, most of the general population should be spared significant health problems.
He said in those circumstances the only people likely to be at risk of serious health effects were nuclear workers at the plant or emergency workers exposed to high levels of radiation.
He said the top priority would be to evacuate people from the area and to make sure they did not eat contaminated food. The biggest risk was that radioactive iodine could get into their system, raising the risk of thyroid cancer.

To counter that risk, people - in particular children - could be given tablets containing stable iodine which would prevent the body absorbing the radioactive version.
The Japanese already have a lot of iodine in their natural diet, so that should help too.

How does Fukushima compare to Chernobyl?

Professor Gerry Thomas, who has studied the aftermath of the Chernobyl disaster, said: "It is very unlikely that this will turn into anything that resembles Chernobyl.
"In Chernobyl you had a steam explosion which exposed the reactor core, which meant you had a lot of radiation shooting up into the atmosphere."
Prof Thomas said although the Chernobyl disaster had led to a rise in thyroid cancer cases, the only people affected were those living in the immediate area of the explosion and who were young at the time.

Japan fears nuclear plant meltdown

Blast reported at nuclear plant as safety panel worries that reactor can no longer cool radioactive substances.

Last Modified: 12 Mar 2011 09:16 GMT



Japanese nuclear authorities say there is a possibility that nuclear fuel rods at a reactor in Fukushima prefecture may be melting.
The cooling system of the plant was damaged in the massive earthquake that struck northeastern Japan and triggered a tsunami, killing at least 703 people.
Masato Abe, a Fukushima Prefecture official, said there was shaking and a trail of white smoke at the quake-hit plant on Saturday. He said the cause was under investigation, and it was unclear whether there was an explosion.
Jiji news agency quoted reported that several workers were injured and that radioactivity had risen 20-fold outside.
Television channels warned nearby residents to stay indoors, turn off air-conditioners and not to drink tap water. People going outside were also told to avoid exposing their skin and to cover their faces with masks and wet towels.
Kyodo News agency said radioactive caesium had been detected near the plant, citing the Japanese nuclear safety commission.

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Parts of the No. 1 reactor's nuclear fuel rods were briefly exposed to the air on Saturday after cooling water levels dropped and a fire engine was pumping water into the reactor, Jiji Press reported.
Tokyo Electric Power, the operator of the plant, said water levels were recovering, according to Jiji.
Peter Hayes, the executive director of the Nautilus Institute for Security and Sustainable development in Melbourne, described the situation as "dire".
"It's still possible that the reactor workers can stabilise the situation is power is brought back, if coolant is brought into the reactor," he told Al Jazeera, but warned that "we're really right at the precipice of a massive nuclear crisis".
State of emergency
A state of emergency has been declared for five nuclear reactors at two different sites in Fukushima, located about 250 kilometres northeast of greater Tokyo.

Nuclear expert Peter Hayes discusses possible scenarios for the quake-hit nuclear plants

Steam containing low-level radiation were released to relieve pressure and tens of thousands of residents have been evacuated from surrounding areas.
Radiation 1,000 times above normal was detected in the control room of one plant, although authorities said levels outside the facility's gates were only eight times above normal, spelling "no immediate health hazard".
The 8.9 quake and the tsunami cut the supply of off-site power to the plant and diesel generators intended to provide back-up electricity to the cooling system.
"The events that occurred at these plants, which is the loss of both offsite power and onsite power, is one of the rarest events to happen in a nuclear power plant, and all indications are that the Japanese do not have the situation under control," "Edwin Lyman, a nuclear expert at the Union of Concerned Scientists, a US-based nonprofit organisation, said.
'No Chernobyl possible'
However, Naoto Sekimura, a professor at the University of Tokyo, said a major radioactive disaster was unlikely.
"No Chernobyl is possible at a light water reactor. Loss of coolant means a temperature rise, but it also will stop the
reaction," he said.
"Even in the worst-case scenario, that would mean some radioactive leakage and equipment damage, but not an explosion. If venting is done carefully, there will be little leakage. Certainly not beyond the 3 km radius."
Prime Minister Naoto Kan said securing the nuclear plants was Japan's top priority. Early on Saturday morning, he left on a helicopter ride to Fukushima to assess the situation at the plants operated by Tokyo Electric Power, and in other areas in the disaster zone.
When Friday's quake hit, the plants immediately shut down, along with others in quake-hit parts of Japan, as they are designed to do - but cooling systems at some reactors failed, the government said.
When reactors shut down, cooling systems must kick in to bring down the very high temperatures. This is key to prevent a "nuclear meltdown" and radioactive release. Japan's network of advanced nuclear power plants are designed to shut down as soon as the earth shakes.
The quake was one of the strongest ever recorded and triggered a devastating tsunami, up to 10-metre-high along parts of the country's northeastern coastline.

Media reports estimate at least 1,300 people may have been killed, most of whom appeared to have drowned by churning waters.
"The damage is so enormous that it will take us much time to gather data," an official at the national police agency said.
Massive destruction
The Japanese army has deployed about 50,000 troops for search and rescue operations.
A towering wall of water, generated by the quake, pulverised the northeastern city of Sendai, where 200-300 bodies have reportedly been found on the coast.
The wave of black water sent shipping containers, cars and debris crashing through the streets of Sendai and across open farmland, while a tidal wave of debris-littered mud destroyed everything in its path.
The northeastern Japanese city of Kesennuma, with a population of 74,000, was hit by widespread fires and one-third of the city was under water, Jiji news agency said.

Al Jazeera's meteorologist explains Japan's quake

More than eight million homes lost power, mobile and landline phone systems broke down for many and gas was cut to more than 300,000 homes, meaning many people could not heat their dark homes during the cold night.
The unfolding natural disaster prompted offers of search and rescue help from 50 countries.
Australia pledged to throw "anything and everything" to help Japan.
China said rescuers were ready to help with quake relief, while President Barack Obama mobilised US military might to provide emergency aid after the disaster which he described as "simply heartbreaking."
The United States, which has nearly 40,000 military personnel in Japan, has ordered a flotilla including two aircraft carriers and support ships to the region to provide aid following the tsunami.
The towering wave set off alerts across the Pacific, sparking evacuations in Hawaii and the US West Coast, and devastating at least one California port.
Chile said it was evacuating coastal areas and Ecuador's state oil company announced it had suspended crude oil exports due to risks posed by the tsunami.
Unfolding disaster
More than 300 houses were destroyed in the remote city of Ofunato and a dam broke in the northeast prefecture of Fukushima, with homes washed away.
In Tokyo, office workers who were stranded in the city after the quake forced the subway system to close early slept alongside the homeless at one station.
Scores of men in suits lay on newspapers, using their briefcases as pillows. Kyodo said at least 116,000 people in Tokyo had been unable to return home on Friday evening due to transport disruption.
There was major disruption to air travel and bullet train services. A passenger train with an unknown number of people aboard was unaccounted for on a line outside Sendai, Kyodo News reported.
The quake, which hit at 05:46 GMT and lasted about two minutes, rattled buildings in greater Tokyo, the world's largest urban area and home to about 30 million people. It was felt in Beijing, some 2,500 km away.
The first quake struck just under 400km northeast of Tokyo, the US Geological Survey said. It was followed by more than 70 powerful aftershocks, one as strong as 7.1.
Japan sits on the "Pacific Ring of Fire" and Tokyo is in one of its most dangerous areas, where three continental plates are slowly grinding against each other, building up enormous seismic pressure.
The government has warned of a 70 per cent chance that a magnitude-eight quake will strike within the next 30 years in the Kanto plains, home to Tokyo's vast urban sprawl.