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Source : Japan's Nuclear Safety Commission
This shows accumulated dose in the immediate area without protection. It also shows the two area stretching to 40 km away with significant contamination, and that some areas 15km away are not affected as much.
This dose came from the short-lived radioactive nucleotides released in the first few days. Unfortunately, they also show where the dangerous Iodine-134, and the long-term problem Cesium-134 is as well.
So no green leafy vegetables grown inside the 5 boundary should be harvested for at least 30 years or so. Most should be relatively safe-ish (if checked) within 18 months. Just not grass, cabbage etc.
But then... the salt-contaminated soils in the whole of the tsunami region will be affected anyway, with all sorts of chemicals and heavy metals disturbed from their safe deposition by the tsunami. Plus the benzenes from the wrecked oil refineries etc. There will be birth defects and cancers from these far in excess of those caused by radiation, unfortunately, and not just confined to a small stretch of coast, but all the towns and cities along hundreds of kilometres of coastline.
The scale of the total received dose as of one week ago, I found shocking. Not so much the 10Sv (100% fatal dose) at the reactor site, but the extent of the 1/2 Sv (50 Rem) area. Although actual dose might be at most 1/2 and often 1/10 of this, they didn't evacuate any too soon: and the evacuation radius should be extended to 40km.