Cs137 contamination occured in the most areas of eastern Japan
If the contamination is measured up to 5 cm in depth in soil, 1Bq/kg is equal to 100MBq/sq. km. In the case of Chernobyl, highly contaminated area was defined as more than 1Ci (37000MBq/sq.km ), that is, 370Bq/kg of the soil contamination level. From Iwate Pref down to Tochig and Ibaraki Pref, that is, in the areas 200km or so north and south of the accident site, the high contamination seems to have spreaded if this estimation is correct.
We should keep in mind that this estimation is the least level possible since it was based on the fallout data from Mar 20 for one month to the exclusion of the fallout occured by the explosion of the plant around Mar 15. There have been contamination to the ocean going on, if the level is now very low, and the underground water could be also contaminated with the cooling water poured to the plants.
So what should we say? The most important lesson is that the nuclear power plant could give rise to this kind of serious accident. It should leave the devastating contamination over the vast area which could affect the next generation for the decades. The nuclear power, if it is used for peaceful purposes, should be abondoned immediately so far as it is not controllable by technology.