Obviously an ongoing concern for many people in Japan, both in the environment and in the food chain, is that of radiation levels. To be honest, around our area most independent checks (such as by Safecast drive-bys) show a level of around 0.107 micro sieverts/hour, which seems to be pretty much a background level for the area generally.
In February I believe, our local City Hall started offering some radiation monitoring devices for free half-day loans. We expected these things to be booked out for months, but when we asked, they said anytime was OK, and when we picked it up we saw we were only the fourth people to borrow it. That somewhat surprised me.
The device in question was a Horiba PA-1000. I’m still looking around to see what kind of reputation this has, but it seemed to work and at least be consistent.
We were asked to use it in it’s bag, playing it in one place, 5cm above the ground, for 60 seconds, and repeat the test five times, and calculate an average. So that’s what we did.
Around our small house, averaged readings ran from 0.037 to 0.068, with a highest average at the nearest street drain (in front of our neighbours house) at 0.073. We also went to take some readings in the local park, which ranged from 0.04 in the general kids play area, with one anomaly, a bush in the corner, at 0.172. Hmm. Odd.
However, all of these are by most definitions ‘safe‘. The City Hall had asked us to inform them if anything regularly topped 0.19 and they’d come and check.
I wont claim this is awesomely scientific, and that one set of readings one morning is in any way conclusive – nor to we have a baseline from before March 10th 2011 to compare this against. However, we’re going to repeat this quarterly, hopefully, and just see if their is any variance over time from now (We took photos of location and device positioning for repeatability).
For some international contrast, Safecast and others have rated the micro sieverts/hour in Hong Kong at 0.22, Seoul at 0.14, and Dublin and New York around 0.12.