Kelp may be all that is available (and it is going fast) for iodine supplements to protect against radioactive iodine, which is supposed to arrive here on the West Coast from Japan today. Most pharmacies here are sold out of potassium iodide.
The most serious effects of radiation are to children, whose tissues are still developing. Us geezers will die from something else, before we can get cancer from the fall out.
Information and logic would seem to counsel us that the fall-out from Japan will be light, but the drama in Fukushima isn't over yet. A larger explosions, would send greater amounts of radiation.