It will be another week before scientists in British Columbia can assess if a dramatic increase in radiation detected in Japan will result in any radioactive risk in North America.

The radiation threat at the damaged Fukushima nuclear reactors were set to "maximum alert" Tuesday after highly toxic plutonium was found seeping into the soil outside the power plant.

"We clearly see from the data we have there is on the order of seven days between the releases in Fukushima and the radiation reaching us here," said Simon Fraser University scientist Kris Starosta.

"We can monitor the situation in Japan and know ahead of time of any releases, and we'll have our window to react and prepare for that."

Tests on rainwater and seaweed show radiation from the Fukushima plant made its way to B.C.'s shores about seven days after radioactive steam blew off from the reactors there.

Also monitoring for cesium

So far, B.C. scientists have said local radiation levels that can be linked to the Japanese reactor are minuscule and pose no health risk to the public.

Starosta said researchers will continue to keep an eye on radioactive iodine 131 — a key component of nuclear power plant radiation — but also on cesium 137.

"Cesium is harder to detect than iodine 131," Starosta said.

Iodine 131 also decays rapidly, he said, lessening the risk. Cesium can remain in the atmosphere for 30 years.

Starosta said whether the leaking plutonium at Fukushima will appear in B.C is also a question, because it's unclear if it travels the same way the other radioactive elements do.

With files from the CBC's Priya Ramu