It took about 15 to 16 months for the Ministry of Education and Science or MEXT (the very name is a joke at this point) to announce radioactive strontium (Sr-90) was widely dispersed from the broken reactors at Fukushima I Nuclear Power Plant last year in 10 prefectures in Kanto and Tohoku, to the levels last seen in the Chernobyl accident.
Caveat is that it excludes Fukushima and Miyagi, probably the two most contaminated with radioactive fallout from the Fukushima accident. MEXT's excuse is that the stations in these prefectures have been damaged by the earthquake/tsunami.
From the press release by Ministry of Education and Science on July 24, 2012, "Analysis of Strontium-90 in the monthly environmental radioactivity levels (fallout)" (in Japanese; labels added by me):
Asahi Shinbun has a chart that tries to put these numbers in perspective. The bump this time looks slightly bigger than the one after the Chernobyl accident. But Asahi, either in its scientific illiteracy or on purpose to minimize the latest bump, uses the normal scale on the Y-axis instead of a log scale which would make it easier to discern the fluctuations in smaller numbers:
Looking for a historical chart on a log scale, I went to the site maintained by the Japan Chemical Analysis Center. I searched the database, and the 2011 data is already in the database. Here's the chart I created using the graph function at the site. I added the thin red line later to compare the 2011 level with that after the Chernobyl accident. It does look it is ever so slightly higher. The chart is a log scale, and the data is from all prefectures:
I wonder what the levels would be if Fukushima and Miyagi's data were to be added. Back to the level during the atmospheric nuclear testing? Or would it exceed that level?