The following quotes are from a cesium-137 soil contamination study reviewed in July, and published in October 2011, just months after the Fukushima Daiichi nuclear disaster began.

“The soils around Fukushima NPP [nuclear power plant] and neighboring prefectures have been extensively contaminated with depositions of more than 100,000 and 10,000 MBq km^-2…”

“…around 90% of the total deposition of ¹³⁷Cs occurs with precipitation.”

“…most of the eastern parts of Japan were effected by a total ¹³⁷Cs deposition of more than 1,000 MBq km^-2.”

“Airborne and ground-based survey measurements jointly carried out by MEXT and the US Department of Energy (DOE) (21) show high ¹³⁷Cs deposition amounts were observed northwestward and up to a distance of 80 km from Fukushima NPP. It was estimated from the first measurement that by April 29, more than 600,000 MBq km^-2 had been deposited in the area, which is greater than our estimate of less than 500,000 MBq km^-2…”

“Overall, however, the highest potential deposition occurred over the Pacific Ocean…”

The study used soil samples taken by Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT), U.S. DOE and independent sources. Again, this was during the first few months of the ongoing the nuclear disaster.

The study is titled Cesium-137 deposition and contamination of Japanese soils due to the Fukushima nuclear accident.