Japanese Science Ministry has finished a survey of Fukushima Prefecture.  They were looking for evidence of strontium 90, they found plenty.

Strontium 90 is created during nuclear fission.  It has a half life of 29 years, and can cause bone cancer.

Samples were taken at 11 locations, all 11 tested positive.  The furthest location from the damaged Fukushima Daiichi nuke plant, that tested positive, is Fukushima City at 60 km (37 miles) away.  The highest reading was 250 becquerels per kilogram, at Namie City.