Tuesday, 28 June 2011
Geiger Counters & Barium Meals
Last week, one of the THJ guys, Murooka-san, brought along a handheld geiger counter up to Fukushima. There’s a 6-8 week waiting list for them in Japan these days but it had finally arrived. In Tokyo before we left it was reading around 0.15 microSieverts/hour, which seems to be around average. It’s hard to find data on the web that isn’t provided by the nuclear companies but according to Wikipedia, the average individual background radiation dose is 0.23μSv/h (0.00023mSv/h); 0.17μSv/h for Australians and 0.34μSv/h for Americans. (scroll down to the bit about hourly dose examples here)
Up at the volunteer centre in Iwaki City which is about 50 kms from the reactor, it was reading about 0.25 microSieverts/hour. When we got to the cleanup location a bit further North just under 40kms from the reactor and where people are still living, it read between 0.25 and 0.42, and peaked at 0.57 microSieverts/hour as the rain came down. We'll check again this weekend but basically, what we saw agreed with the official readings available online.
To extrapolate the per-hour readings to per-year values, you’d think just multiply the hourly reading by 24, then multiply by 365, but sometimes the figure is adjusted down because people spend a lot of time indoors sleeping etc where the levels are lower than outdoors. Some say the max recommended level is 1 milliSievert per year, some say it’s 5 milliSieverts per year, others say it’s up to 20. Either way, looking at our worst case exposure, the max we saw of 0.57 microSieverts/hour works out to an annual dose of 5 milliSieverts per year. That’s a full year of standing outside, 24 hours a day, less than 40kms from the plant. Since we’re only up there for 7-hours once a week or so, we got much, much less.
On the way home, I started thinking about my annual health check. Unusually for the rest of the world, in Japan most company health-checks include a barium meal, probably because stomach cancer is the most common cancer in Japan. The readings I found online for a barium meal varied from 2 milliSieverts on the NHS site to a whopping 15 milliSieverts on a private page written by what could have been the dubiously named Dr.Geoff Pain. Not knowing who to believe, again, I checked with the Medical Centre where I had my annual checkup only a few weeks ago. The nurse there was very helpful but had no idea and disappeared for 10 minutes to look up how many milliSieverts was in one dose.
She came back looking shocked saying it was actually between 10 and 20 milliSieverts (10,000 and 20,000 microSieverts) in one hit! Dr Pain was right on the money. Whether it was 10 or 20 varied depending on your body type and how long your body took to get rid of it.
Although one big concentrated hit of radiation is not the same as prolonged exposure at a much lower level, depending on what Fukushima reading you took, and depending on how your body handles it, one medical checkup packed the equivalent punch of standing outside, 24 hours a day, less than 40kms from the nuclear plant, for between 2 to 10 YEARS!! And I’ve had four of the buggers!
They’re not even that reliable. A friend of mine had a barium meal in February 2010 and got the all-clear. He was then diagnosed with stomach cancer three months later and had to have ¾ of his stomach removed. Luckily he’s over it now and fitter than me these days.
Stomach camera option for me next year!