"Contaminated Zone" in Chiba

Radiation spread reaches Chiba, Saitama prefectures - AJW by The Asahi Shimbun

» In Chiba Prefecture, the highest levels of cesium-137, between 30,000 and 60,000 becquerels per square meter, were detected in northern areas, such as Kashiwa, Matsudo, Abiko and Nagareyama. Cesium-137 has a half-life of 30 years.
In the 1986 Chernobyl nuclear accident, areas with 37,000 becquerels or more of radioactivity per square meter were designated contaminated zones, while levels of 555,000 becquerels or more required forcible relocation.
In Chiba and Saitama prefectures, the highest radiation levels were 0.2 to 0.5 microsievert per hour. In most other areas, the radiation levels were 0.1 microsievert or less.

http://ajw.asahi.com/article/0311disaster/fukushima/AJ2011093012746