The NY Times has published a map of the estimated potential exposures around Fukushima area from a simulation, along with expected symptoms of exposure to those levels. Also listed is the population living in those area before the earthquake. From the site:
The American Embassy recommended on Wednesday that Americans within 50 miles of the Fukushima reactors evacuate, based on an analysis by the Nuclear Regulartory Commission. The recommendation was based on a model that predicts potential radiation levels depending on whether the containment vessels remain intact, weather patterns, and other factors. Here are the results of the model on March 16.
Nuclear Regulatory Commission;
Environmental Protection Agency;
Robert Meck, health physicist, Science and Technology Systems;
LandScan 2009 population dataset/UT-Battelle (population estimates)