Via NHK News, excerpt :
" Japan's science ministry says small amounts of radioactive strontium have been detected in soil and plants outside the 30-kilometer zone around the Fukushima plant where the government has advised people to stay indoors. Strontium could cause cancer.
The ministry has been monitoring the level of radioactive substances in soil and weeds in Fukushima Prefecture.
It found 3.3 to 32 becquerels of strontium 90 per kilogram of soil in samples taken from 3 locations in Namie Town and Iitate Village, 30 kilometers from the plant.
An extremely small amount of strontium was also found in plants taken from Motomiya City, Ono Town and Otama and Nishigo Villages. The areas are 40 to 80 kilometers from the Fukushima plant.
Strontium 90 has a half-life of 29 years. It tends to accumulate in bones and could cause cancer."