With all that is going on in Japan, just a couple of thoughts:
1. People in the US, stop freaking out... and for heaven's sake, stop hoarding potassium iodide pills.
2. Let's pretend that all the reactors blew up and a radioactive cloud goes into the air...
- the cloud will follow the wind currents
- there will be settling of materials (things with mass will fall because of gravity) so this means a lot of it will be deposited in the ocean.
- Rain could make the radioactive particles deposit on the ground or sea
- by virtue of being airborne it will disperse and the concentration will decrease (kind of like LA's smog floating west and by the time it reaches Las Vegas, the smog concentration is low)
- It is good that they are on the coast and there is a lot of ocean
3. Environmentalists: what is more damaging? Oil refinery, natural gas, coal, and chemical plant sludge, fires, and spills into the environment or some radiation? I'm sorry, I would go with the sludge.
4. Don't believe most of what you hear in the media.
There's just so much to say and so little time. Generally, we as Americans are stupid when it comes to science... especially when you mention "radiation." This is why I love my job! But, the reactors in Japan are having real difficulty (you would to if you just got hit with a 9.0 and a tsunami destroyed your equipment). Hope for the best and pray for those 150 or so nuke plant workers. Those guys are heroes.