As you probably know, there have been disturbing incidents at several reactors in Fukushima, Japan lately. I’m not sure how the mass media in your country handle the issue, but those here in Germany are certainly going completely insane over it, to an extent that even Germans start to think they might be in danger.

Don’t get me wrong, this is a terrible incident and I don’t support nuclear energy (mostly because storing nuclear waste worries me). Nonetheless, as educated human beings, we should approach such events factual, not emotional.

So what is radiation? I’m no physicist, but I know that radiation is not some rare, deadly poison – it’s everywhere. Sure, in very large doses, it can damage your health, so can pretty much anything on this planet. As Paracelsus put it:

All things are poison, and nothing is without poison; only the dose permits something not to be poisonous.

So it’s the dose we should talk about, not the fact that there is radiation near Fukushima, because radiation is everywhere. XKCD posted a very nice chart comparing radiation doses from various sources.

So how much radiation is there around Fukushima? Greenpeace published their monitoring results. The problem with data is that we have to find some we can trust. I consider Greenpeace a sufficiently trustworthy source on this matter.

Now we can get ourselves an idea of how bad the situation in Fukushima is. When looking at the Greenpeace data right now, I see some dark red bubbles north west of Fukushima. Since that colour indicates the highest readings, we can infer that 11 µSv/h is the highest radiation dose around Fukushima. So that’s 264 µSv/day and 96.36 mSv/year. According to the XKCD chart, this is twice the allowed dose for US radiation workers, which is 50 mSv/year.

That’s certainly not good. But how bad is it? Another look at the XKCD chart reveals that the lowest yearly dose clearly linked to increased cancer risk is 100 mSv/year. That’s awefully close, so these people might in fact suffer from an increased cancer risk if exposed to this amount of radiation for a whole year. And how big would that cancer risk actually be? Probably lower than that caused by smoking, according to Nature News.

That was the worst region in the area, how about those south of Fukushima, further away (about 1/3 on the way to Tokyo)? The readings say 0.4 µSv/h, which is 6.9 µSv/day and 3.5 mSv/year. I don’t think that’s a dose to worry about.

I’m no radiation expert, so both my data and my analysis could be wrong. If you’re sceptical, do some research on your own and see what you can find out. And, as Douglas Adams wisely put it in (and, in fact, on) The Hitchhiker’s Guide to the Galaxy:

Don’t panic.

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