According to Mainichi Shinbun (linked and translated below), the group of Japanese Communist Party assemblymen in Matsudo City in Chiba Prefecture released the result of their radiation survey of 144 locations in the city, and found 37 locations with over 1 microsievert/hour radiation. The highest was 7 microsieverts/hour. If you stand on the spot 24 hours a day for one year, you would get 61 millisieverts of external radiation.
Matsudo City, located on the western edge of Chiba Prefecture, are one of the cities and towns that have relatively high overall radiation in Kanto. (The map (version 4) is by Professor Yukio Hayakawa of Gunma University. Matsudo City is circled in red.)
The Communist Party assemblymen in the Tokyo Metropolitan Assembly did the similar survey of Tokyo back in May, which helped force the Tokyo government to start monitoring radiation in more details.
From Mainichi Shinbun (10/20/2011):
The group of Japanese Communist Party assemblymen in Matsudo City in Chiba Prefecture announced on October 20 the result of the air radiation survey of 144 locations in the city. The locations included parks, private residences, and nursery schools. They measured up to 25 points in one location, and the highest radiation was recorded at the side of an agricultural greenhouse, at 7 microsieverts/hour. More than 1 microsievert/hour radiation was measured at 37 locations.
1,830 Matsudo City residents also participated in the survey that was carried out from September 7 to October 17. The radiation was measured at 5 centimeters off the ground at each location. The group says it will not reveal the details of the location that measured 7.0 microsieverts/hour radiation for the fear of "baseless rumors". The highest measurement in parks was recorded at the sand box of Nishinoshita Park, at 3.42 microsieverts/hour. The group notified the city, who decontaminated the sand pit. The radiation was reduced to 0.3 microsievert/hour after decontamination.
The city has already carried out emergency decontamination at 10 locations after confirming the radiation measurements done by the city residents. It will conduct a more detailed survey in parks.
Localized, high radiation contamination has been consistently found in places like sand boxes. The group says, "We are surprised at the very high numbers in locations that have been considered relatively safe. We should make it an urgent task to conduct a more detailed survey."