I have been collaborating on some research to assess levels of internal exposure to Cesium in residents of Minamisoma, Fukushima prefecture, and today the results have been published in the Journal of the American Medical Association (paywalled), along with news reports in the Washington Post amongst other media outlets.

Minamisoma is a small town located mostly just inside the 20-30 km “stay-indoors” zone around the Fukushima power plant, and is one of the closest towns to the plant that isn’t under a long-term evacuation order. Minamisoma Municipal General Hospital began to assess internal exposure to Cesium in August last year, and we report on the first year’s assessment of just over 8000 residents, finding most had no measurable levels of exposure (38% of adults and 16% of children). Those who were exposed had generally low levels of exposure. Although calculating the equivalent dose of internal exposure is a bit tricky and controversial, the lead author estimated the maximum at about 1mSv, and suggests this is about the equivalent of half a chest X-ray. The linked Washington Post article describes some other comparisons and gives the opinions of other experts in the field who know more about these kinds of calculations than I do. We also observe that the levels of exposure less than one year after the Fukushima disaster are much lower than those observed even several years after Chernobyl, despite the fact that supposedly similar amounts of radionuclides were released into the atmosphere. Our suggestion is that the combination of early evacuation and comprehensive food monitoring and control were key to containing the effects of the disaster.

These results suggests that in many ways, the Fukushima Daiichi nuclear plant explosion is far from the worst aspect of the disaster that hit Fukushima prefecture on the 11th March, 2011. I have visited Minamisoma before and previously put up a post describing the destruction at the seaside and some of the difficulties the town faces, and I hope that this research will serve to give some perspective to the severity of the various problems the town faces. I have now been given a two year grant by the Toyota Foundation to continue research (in collaboration with the local hospital), monitoring the radiation exposure of the residents and conducting a broader needs assessment of their health needs and the ways in which their mortality risks have changed since the earthquake. As I said in my previous post, the experience of these communities in Japan is of value to other countries with a similar aging problem that might experience similar disasters, including possible nuclear accidents, and it’s important both for the people of Minamisoma and for other communities at risk of earthquake, tsunami and nuclear accident that we more clearly understand the best potential policy both for preparing and responding to these kinds of disasters. Hopefully this research will benefit both the town’s residents, and policy-makers in other places who face the potential of similar catastrophes.

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