Japan nuclear leak - health risks 3
"The situation is definitely more serious". That is how the government's Chief Scientist has summed up the rapidly developing crisis at Fukushima. Professor John Beddington altered his assessment of the situation because of the loss of water covering spent fuel rods stored in ponds close to the reactors.
In this rapidly developing crisis, this is causing "considerable concern" according to Professor Beddington, speaking in a TV interview. American, French and British nuclear experts who are monitoring the situation believe that the pond in Reactor 4 is all but gone.
He explained that the worst case scenario is that the fuel rods could start to burn and emit substantial amounts of nuclear material into the atmosphere. Professor Beddington said he was also "extremely worried" that the fuel tanks in Reactors 5 and 6 are leaking and if open to the air might emit significant amounts of radiation which would undermine the ability of the Japanese emergency workers to continue their efforts to control the situation.
So what does this mean for the potential health risks? Up to now Professor Beddington had supported the line taken by the Japanese authorities, that any danger was confined to within a 30 kilometre (18 mile) radius of the reactors.
Now he believes: "The situation is definitely more serious both within the area and further afield". The Scientific Advice Group for Emergencies (SAGE) which advises the government, have looked at "plausible worst case scenarios". For days that has been a potential meltdown of some of the reactor nuclear material but now a potential fire and release of radioactive material from the fuel rods has to be added in. Professor Beddington said if both these things happened and there were unfavourable winds, then radioactive material could affect Tokyo.
But he added this caveat: "Even in that situation we think the level of radiation that would come into the Tokyo area would be such that you could mitigate against it with relatively straightforward and simple measures - such as staying indoors with the windows closed."
British nationals are being advised to stay at least 80 kilometres (50 miles) from the nuclear plant, and to consider leaving Tokyo.
"We are right to be worried by need to put the risks in context" said Gerry Thomas, Professor of Medical Pathology at Imperial College London. She is concerned that the dangers to human health are being exaggerated by some in the international media and could cause "psychological damage" to the Japanese.
She said that, even in the worst-case scenario, with a large release of radioactive material from Fukushima, the health dangers would be minimal.
"The Japanese are doing the right things - giving people iodine tablets, setting up an exclusion zone and asking people to stay indoors". Even if radiation from Fukushima reached Tokyo she believes the long-term health risks would be minimal.
Gerry Thomas is an expert in the health effects of radiation and has been studying tissue samples from many of the cancer patients affected by the Chernobyl disaster. Like other experts she said Fukushima was in no way as serious as Chernobyl and she urged those reporting the situation not to overplay the situation.