Detectable amounts of Fukushima radiation have already washed up on the shore of Washington State. After the Chernobyl disaster, detectable levels were in the air over the US.

Although they were detectable, the amounts were insignificant and posed no danger. After all, we're bombarded with background radiation every day.

The carbon 14 in all organic material is radioactive. That's why radiocarbon dating works.

Or for water contaminated with radioactive materials, for instance, it's routine at La Hague.

https://en.wikipedia.org/wiki/La_Hague_site

Of course the particulars matter quite a lot, I'm have no idea whether the planned release at Fukushima is comparable to the releases at La Hague.