From Jiji Tsushin (2/20/2012):
The Fukushima prefectural government and Fukushima Medical University announced on February 20 that the maximum external radiation exposure in the first 4 months after the March 11, 2011 accident was 23.0 millisieverts among the residents who are not radiation workers. Total 10,000 residents of Fukushima have been surveyed.
The survey, with Dr. Shunichi "Damashita" Yamashita in charge, consists of detailed questions for the residents in order to estimate the radiation exposure. The residents have to fill out the pages with information on their whereabouts, on what day, for how long, what they were doing, etc. Dr. Yamashita's group considers the information with the SPEEDI simulation done specifically for Fukushima Prefecture to figure out the radiation doses in Fukushima in the early days of the nuclear accident.
The press conference is on-going in Fukushima right now, and the information has not been uploaded on the Fukushima government website yet.
(UPDATE) Jiji has filled in more details:
10,468 residents in Namie-machi, Iitate-mura, Kawamata-machi Yamakiya District
- Highest (23 millisieverts) from a woman who lived in the planned evacuation zone [no mention of which town]
2 people exceeded 20 millisieverts
58.0% of people tested: less than 1 millisievert
99.1% of people tested: less than 10 millisieverts
71 people exceeded 10 millisieverts
Max for radiation workers: 47.2 millisieverts
"It is difficult to imagine there would be an effect on health", says the Fukushima prefectural government.
If you recall, over 30% of 3,765 children from the same towns tested for thyroid abnormalities were found with lumps/nodules and/or cysts.