I'm no "atomic troll" and radioactive contamination at Fukushima is potentially a significant problem. But the detected plutonium levels are almost insignificant compared to the detected Cs-137 contamination (whose half-life is 30 years, not months):
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/im... (Pu) http://www.mext.go.jp/component/english/__icsFiles/afieldfil... (Cs-137)
The activity of Cs-137 is orders of magnitude greater.