Based on the latest radiation measures by Prof. Hayakawa[jp], I estimated the following "no go" zones in Japan based on the radioactive cesium found in the "black dust" (dirt in the roadside, often hotspots of radiation):
|My opinion: the red areas are a no-go zone (but many millions live in them)|
No specifics strict terminology can be applied because there is no absolute rule on how radiation affects you considering only on becquerels per kilogram. But based on the notion that Japan considered, prior to the accident, that 100 Bq/kg to be radioactive waste, then I would say that the colors could mean:
- Fukushima: don't go at all: killer zone. The westernmost part of the department would be however in the red zone (still very bad).
- Red Zone: avoid it all you can, bring food and water from the outside, try not to live there, very specially not children nor pregnant women. Roadside hotspots here typically have 1000-10,000 Bq/kg, 10x to 100x what used to be considered nuclear waste, sometimes even much more. In some cases, specially in Greater Tokyo, the measures are almost as high as in Fukushima.
- Orange Zone: less dangerous, with roadside hotspots often above the 100 Bq/kg "nuclear waste" measure but nothing >1000 Bq/kg.
- Yellow areas: some >100 Bq/kg hotspots and often >30 Bq/kg ones but generally within safety levels.
- Not colored: either unknown of clearly low radioactivity.
Special acknowledgement to Ex-SKF (I don't speak Japanese so I could have missed a lot of information without his explanations in English).
Note: at the time of writing this note, I could not open the first map (radiation fallout contours for April 2011), which gave me a 404 error, but here there is another link (3.3 MB, jpg format).
Special warning on Japanese food: while these maps reflect environmental radioactive risk, the Japanese government is applying a criminal policy of forcing people to eat radioactive food, apparently because they just do not want to evacuate Fukushima so they pretend it's all alright (when it's obviously not), and often the origin of products is criminally mislabeled. Hence all Japanese food and products are suspect and potentially dangerous and you may well be unlucky enough to eat the wrong sushi snack and get radiation poisoning, while another dish may be perfectly edible. Personally, in the current conditions of lack of control, I would not eat anything Japanese if I can help it, nor seafood nor mushrooms from anywhere in all the North Pacific basin.