Professor Wade Allison from the University of Oxford is one of the world’s top experts in radiation physics – and his recent talk to Tokyo’s Foreign Correspondents Club of Japan should be required viewing for anyone who genuinely wants to understand the consequences of the disaster at Fukushima.

Professor Allison argues that the radiation and radioactivity levels that have been set for mandatory evacuations are up to 1,000 times below the level we know to be safe, causing unnecessary hardship and stress to the population. The video can be found here:

For those with prohibitively short attention spans, here is a quick summary:

* We know that PET and CT scans safely give people whole body doses of 15 millisieverts of radiation and radioactivity from external and internal sources – so 15 millisieverts is not a level regarded as dangerous.

* In Japan, you would need to eat 2000 kilograms of beef per month at the regulatory level of 500 becquerels per kilogram to achieve a radiation level similar to a CT scan. This is equivalent to about 16 kilograms of beef per day. This tells us that food standards in Japan for radiation are well within the boundaries of what we regard as safe.

* No worker at Chernobyl who received a dose of less than 2000mSv of radiation died of acute radiation sickness. By comparison, at Fukushima, 30 workers have received between 100 and 250mSv – mostly about one tenth or less of the lowest radiation dose necessary to cause a death.

* It can safely be assumed, therefore, that no-one around Fukushima will die of radiation sickness.

* At Hiroshima, people who received sudden radiation doses of 160mSv had their risk of dying of cancer increased by a factor of about one in 15, but below 100mSv, there was no added risk of dying of cancer.

* Extrapolating these results, it is possible that one in 150 of the workers at Fukushima who received high doses could die of cancer within the next 50 years because of the accident, but there is a good chance that none of them will die, because fewer than 30 have received these levels of radiation.

* At Fukushima, anyone considered at risk of receiving 20mSv or more over a year has been evacuated. However experience from radiotherapy tells us that over the same period, people can withstand 20,000mSv of radiation.

* Professor Allison proposes new limits as high as 100mSv for a single dose or as a monthly maximum, and 5000mSv as a lifetime exposure.