Close Window
Strontium-90 Radioactivity Found Near Tokyo October 14, 2011
Japan radiation map
Radiation levels in 10 prefectures surrounding the Fukushima No. 1 Nuclear Power Plant. Areas in red indicate over 3 million becquerels of cesium per square meter. Light brown shows less than 10,000.
Heavy radioactive contamination from Japan’s March 11 tsunami-nuclear disaster may have reached metropolitan Tokyo due to the discovery of strontium-90 in nearby Yokohama.

About 195 becquerels of the radioactive isotope, believed to be from the crippled Fukushima nuclear plant, was discovered in dust on top of an apartment building in the port of Yokohama, about 15 miles south of Tokyo.

Strontium-90 has a half-life of 29 years and had been detected in concentrations roughly between 10 and 20 becquerels at various locations across Japan prior to the explosions at the Fukushima reactors.

This is the first time strontium at a concentration of over 100 becquerels per kilogram has been found beyond 60 miles of the Fukushima power plant.

Strontium can accumulate in bones if inhaled or ingested, and is believed to cause bone cancer and leukemia.

Graphic: (Japan) Ministry of Science