Radiation - Fukushima 1 year later (Part 4)

For people just joining us, this is the fourth post in a series of reflections on the series of disasters that started last year with the earthquake on March 11th. As always, I encourage anyone who would like to leave their comments below the post to do so. Especially in this post, some discussion might be helpful.

Today I am going to talk a bit about radiation. I was going to jump into data about what I’d found checking for radiation around the northern Chiba, Tokyo, Ibaraki and other areas, but before that I think the subject itself needs a few minutes.

This is going to be a long post, so bear with me, but I think the info here is very important to know. And before going on I strongly recommend you head to Wikipedia and look up details on the sievert (abbreviated as Sv). There is also a useful online conversion tool you can get here that lets you switch around units relatively quickly (go here for a tool that lets you input the isotope type, and it'll tell you how to switch between Bq and uSv with a little tweaking).

Now let’s get down to business.

When people talk about rads or microsieverts (usually written as μSv or uSv), they are talking about how dangerous the radiation is. In most cases, radiation under 0.2 uSv/hr is considered “normal,” but unfortunately it gets confusing very quickly.

You see, radiation isn’t like heat. It doesn’t go from safe to dangerous after doubling or tripling. In order to be in true danger you need to get a dose in the range of several sieverts (1 Sv = 1 million uSv). So since radioactive sources are listed as a number of uSv per hour, you can see that something measuring around 0.3 uSv/hr or 3 uSv/hr or even 300 uSv/hr will take a long time to get dangerous. It takes a place radiated like the insides of the destroyed nuke plants (sorry link only in JP) giving off levels in the 100s of millisieverts (mSv, and 1 mSv = 1,000 uSv) to give you a truly dangerous dose after tens of hours or a few days.

Does that mean a hot spot I found giving off 2.0 uSv/hr in a gutter is safe? Not exactly, because if you spend a lot of time there, weeks or months or years, it will build up and could get dangerous. How dangerous is still up to speculation, but let’s say you did put up a tent on the spot I found and lived there 24/7. After a year you have a dose of 17,520 uSv, or about 17.5 millisieverts. Most people are said to get around 2 millisieverts per year, meaning you got almost 9x the normal amount. It’s also way over what the IAEA recommends as the max dose for civilians. How dangerous, though, is hard to say.

Current official data suggests that a dose of 100 mSv in a year will increase your chances of getting cancer. To get this much you would need an average dose of 11.5 uSv/hr for a whole year, much higher than any spot I’ve seen in Japan so far. The increased chance of getting cancer is considered to be very low even after this exposure level (though some research suggests a higher risk). But the data is still far from concrete. At any rate, though, thankfully none of the areas I've checked in northern Chiba, Tokyo or Ibaraki have had even close to that dose. A friend of mine said he found a gutter filled with sludge giving off 12uSv/hr, but that's the worst I've heard of in this area.

Now all that might sound reassuring, but there is still internal exposure to worry about. Radiation in soil and water can be taken in by plants and livestock, in some cases in high concentrations. Just walking around in an area hit by a "small" amount of radioactive cesium may give you almost no external exposure, but eat a potato or some rice grown there and the cesium in the produce goes into you, and you continuously get hit by that radiation until it's expelled from your body. In some cases your body can confuse cesium for calcium and incorporate it into muscle tissue. Not fun.

But even then it's not necessarily fatal. You could suffer no effect at all, and will probably not even notice it was there. If it's not too big of an amount.

And that's the key. Getting hit by big doses of radiation in the air, or eating food with high concentrations of it can be really nasty, leading to cancers, heart problems and leukemia. But getting small doses, even over an extended period will often have no effect.

And that's where I'm going to end this post (on a hopeful note). With regular testing of foods for radiation and the watchful eyes of the public on the government and producers, I think a major catastrophe of people dying from radiated foods can be averted. Would this have been possible if not for the "crazies" like me freaking out about radiation on blogs, twitter and other social networks? Would the government be testing around town and monitoring foods served in school lunches without "crazy" mothers calling to ask about safety? I doubt it. But thankfully there are a lot of people in this country with cash and a love of gadgets, and our watchful monitoring of data is the best way to keep things on the right path.