Radioactive plume

On Thursday, Japanese military fire trucks began spraying water onto spent fuel rods at the Fukushima Daiichi Nuclear Power Station in northeast Japan, which was damaged in last Friday's 9.0 magnitude earthquake.

Japanese officials have been working non-stop to try to bring the temperature of the overheated reactors down, using various methods including, most recently, dumping sea water onto the reactor from helicopters.

However, as radiation continues to leak, experts remain worried that it will build into a "radioactive plume," which could be carried through the air, potentially thousands of kilometers away. As the plume is carried, its potency dissipates.

As a precaution, the United States government has announce that it is deploying additional radiation monitors on Hawaii and other US Pacific territories, including the Aleutian Islands and Guam.

"All the available information continues to indicate Hawaii, Alaska, the US Territories and the US West Coast are not expected to experience any harmful levels of radioactivity," the United States Nuclear Regulatory Commission said in a statement posted on its website on Wednesday.

Small radioactive particles, high risk

According to Mojib Latif, a meteorologist and climate scientist at the Leibniz Institute of Marine Sciences at Kiel University in Germany, the impact of a radioactive plume can happen quickly.

"This is essentially radioactive particles. One can imagine (a situation) such as when dust is whirled," he told Deutsche Welle.

One major difference, he pointed out, is that radioactive plumes are not visible, as normal clouds.

He added that Europe was too far away from Japan to be affected by a radioactive plume. The World Health Organization has made similar assurances.

"The World Health Organization would like to assure governments and members of the public that there is no evidence at this time of any significant international spread from the nuclear site," said Michael O'Leary, WHO's representative in China, in a statement.

Rain and snow could be a factor

But, Latif noted, such plumes could have a devastating impact in Japan, especially if it rains or snows more in the affected areas.

"If it rains, then these particles fall out," he said. "That is, they are washed out."

Fittingly, experts call this phenomenon a "rain out" or "wash out."

Cesium, strontium and iodine isotopes can trickle down into the soil, plants, livestock, and can get into the food supply and can take decades to dissipate.

For example, cesium-137 has a half-life of 30 years and continues to impact the environment during that period, as evidenced in the disaster area surrounding the Chernobyl nuclear plant.

"In many, many years, even for decades, the area [will be] contaminated, polluted or worse," said Latif.

He added that at this point, it's almost impossible to calculate the effects of a radioactive plume on the affected areas in Japan - which will be determined to some degree by the efforts to contain the disaster, how much radiation is let loose and weather events.

Latif said that it would not necessarily be ideal if the plume were to dissipate over the Pacific Ocean.

"The direct burden on the people on land is avoided, but of course the marine ecosystems are affected as well," he said. “In the end (humans can still be affected) through the food chain."

Autor: Nicole Scherschun / cjf
Editor: Nathan Witkop