Our colleague Paddy Regan has been on all the networks from the BBC to Aljazeera, talking about the Fukushima reactors and the dangers from the radiation. Radioactivity is not my field, Paul knows more than I, see the previous post, but I saw this very nice chart. It illustrates in one image, doses from that from eating a banana, 0.1 μSv, to the dose that will quickly kill you, 10 Sv.
I think the chart is very useful in helping you think about the numbers involved. For instance if I eat a banana I get 0.1 μSv, where 1 μSv is one millionth of a Sv = Sievert. See here for a definition of a Sievert but really you don’t need to know what it is (but a friend, Paul Glover will show you in a very clear way).
You can just look at the chart and see what doses you have had, and what things you would want to avoid, and compare that to the doses people in Japan have been exposed to. For instance I like bananas so clearly I am not going to worry about 0.1 μSv. However, clearly if I got 100 million bananas then between there would be a enough radioactivity for a lethal dose. Incidentally, by coincidence people are proposing container ships with a capacity for 860 million bananas or enough radioactivity to kill 8 people. However, even if I live to be quite old then that is only around 30,000 days, and at 10 bananas a day that is 300,000 bananas – it is just not possible to eat 100 million bananas, even in a lifetime.
The chart also shows up the dose from flying – planes are high up in the atmosphere where you are more exposed to radiation from space. A long distance flight is around 400 bananas worth of radiation.
Finally, the chart shows that the United States limit (the chart is American) for someone working in a place like a nuclear powerplant is around 1000 long distance flights worth of radiation. I guess this means that long-haul pilots and cabin crew must get doses at least as large as workers in the nuclear industry. With these figures in mind I think it is easier to understand what is going on and to decide to worry, or not to worry.