Plutonium scare in Japan: Are we at risk?

(CBS) First it was radioactive iodine and cesium, and now Japan's crippled nuclear plant is said to be leaking plutonium. That news sent shock waves across Japan - after all, plutonium was the stuff that powered the atomic bomb that fell on Nagasaki in 1945.

But given the tiny amounts of plutonium involved, health experts downplayed any risk to humans.

"This does not pose any (threat) to human health," an official of the Nuclear Industrial Safety Agency in Tokyo said Monday, the Japan Times reported.

Just what is plutonium anyway? It's a highly toxic silvery-gray metal that comes in at least 15 different forms (isotypes), all of which are radioactive. Traces of plutonium-238, -239, and -240 were found in and around the power plant, according to the Times. Even before Japan's nuclear crisis, it was possible to find plutonium-239 - the stuff used to make nuclear weapons - in soil all around the world, the result of radioactive fallout from nuclear weapons tests in the atmosphere conducted in the 1950s and 1960s.

External exposure to plutonium poses little health risk, and most plutonium swallowed is quickly excreted. But inhaling plutonium-tainted dust is a serious health hazard. Once in the bloodstream, plutonium generally remains in the body for decades, exposing organs and tissues to cancer-causing radiation.

For more on plutonium and its health effects, see the EPA website.