A Post on the Greenpeace Campaign Blog, ‘Fukushima evacuation zone expanded’ (Blogpost by Jessica Miller – April 11, 2011 at 13:16):
–> has the link that gives access to their impressive compilation of location- and time-specific radioactivity measurements outside the Fukuchima Daiichi evacuation zone, including soil and food samples in Bq/Kg (Becquerel per kilogram), and air background radiation levels in µSv/h (microSievert per hour):
To get an idea of how severe some of the food and soil contamination is well outside the evacuation zone, compare to maximum allowable levels (for Canada, but they’re similar worldwide), on my Radiation Food Standards blogpost from last week. For help interpreting units or doses, see my pages ‘Radiation Units’ and ‘Exposure Health Effects’. (top bar).
–> One thing that is clear from these field measurements is that radioactive contamination can differ hugely from one spot to another in the same general area of a fallout zone. This is probably due to weather conditions, effects of microclimates, topography, vegetation type and soil conditions, and it underscores the importance of a vast monitoring network if you want to have truly reliable data about background radiation levels and radionuclide pollution. This is a screen-shot of a zoom-in of the above map, shows variations in background radiation within the city of Fukushima, Fukushima Perfecture, Japan.