Yokohama finds high strontium-90 levels

http://search.japantimes.co.jp/cgi-bin/nn20111013a3.html

YOKOHAMA — Radioactive strontium exceeding normal levels has been detected in sediment from atop an apartment building in Yokohama, some 250 km from the Fukushima No. 1 nuclear power plant, city officials said Wednesday.

While the discovery of 195 becquerels of strontium-90 in the rooftop sediment fueled concerns that leaked radiation may have spread farther than the central government expected, the officials said the city is carefully examining where the isotope came from.

If the substance is from the Fukushima plant, it will be the first time strontium at a concentration of more than 100 becquerels per kilogram has been found beyond 100 km from the troubled plant.

The strontium-90 was detected by a private agency that conducted the test at the request of a resident.

and continue to be dangerous?

Not that this is an example of spreading... in fact it's just the opposite (concentrating).

As for "continue to be dangerous"... wouldn't the levels in the area have to get UP to "dangerous" before they can continue to be dangerous?

100 Bq/kg is not a level for concern. You face levels like that all the time.

And the article doesn't even say how much of the stuff there was. Is there even a single kilogram?

Bone cancer.

Still buying food imported from Japan? Why?

PB

And Strontium 90 is a bone-seeker

Which makes it more dangerous than comparable activity from other sources, but there still has to be enough of it to matter.

Strontium 90 is a beta emitter - which is therefore more dangerous as an internal emitter than something outside of your body. You would obviously like to limit that internal exposure.

If you're a human male that weighs about 200 pounds, then you have roughly 22 milligrams of Potassium 40 and 29 nanograms of Carbon 14 in your body all day long. Both are beta emitters. Together they account for roughly 10,500 Bq of internal beta emissions on an ongoing basis.

Are you really concerned about eating enough muck from a ceiling drain at 45 Bq per pound to impact that 10,500?