So, clearly there was a good reason why IAEA went to measure the radiation levels in Nihonmatsu City, Fukushima Prefecture when they came in March 2011 right after the March 11 nuclear accident.
From Jiji Tsushin (1/19/2012):
The Ministry of the Environment announced on January 19 that 43,780 becquerels/kg of radioactive cesium was detected from the ashes in a wood stove used in a personal residence in Nihonmatsu City, Fukushima Prefecture.
Ashes are used as soil amendment.
The safety standards for firewood and charcoal were not even in place until November last year. According to the Forestry Agency, the safety limit for firewood is 40 becquerels/kg of radioactive cesium, and 280 becquerels/kg for charcoal so that the resultant ashes would not contain more than 8,000 becquerels/kg of radioactive cesium.
The Agency's Q&A says:
From the incineration tests, when 1 kg of firewood is burned it results in 5 grams of ashes, and 1 kg of charcoal in 30 grams of ashes, with 90% of radioactive cesium remaining in the ashes.
That means radioactive cesium density in 1 kg of ashes is 182 times as much as that of 1 kg of firewood, and 28 times as much as that of 1 kg of charcoal.
2% of radioactive cesium in firewood/charcoal, when used in cooking, was transferred to the food.
Oh wait a minute. 10% of radioactive cesium that is in the wood/charcoal is released in the air when burned?
Reading further, the Agency openly encourage the bundling of radioactive firewood/charcoal that exceed the safety limit with those without any cesium detected:
It is OK to bundle firewood or charcoal that exceed the safety standard with firewood or charcoal that does not exceed the safety standard, and sell the bundle as long as it is not shipped across the prefectural border. [What's the point of that?]
To dispose the ashes of unknown radioactive cesium density, do not use as soil amendment in gardens and farmlands. Dispose them appropriately as waste products.
The Agency does not say. I don't think ANY seller of firewood or charcoal is measuring the radioactivity, and I don't think any user of wood stove who gets the wood from the mountains in their backyard is measuring it either.
They say that's how the soil contamination after the Chernobyl accident remained high - cut the woods that were doused with radioactive materials, burn them in stoves for heat and cooking, use the ashes as soil amendment to grow food.
That's happening in Japan now, thanks partly to bureaucrats in the government ministries but also to the general public who still don't connect the March 11 Fuku I accident with radioactive materials all around them.