The plume of radiation emanating from Japan's crippled nuclear reactors is slowly swirling its way across the Pacific Ocean and is expected to permeate California's airspace as early as tomorrow (the Times, as it often does, has a cool interactive map). Though this seems like it might be an appropriate time to freak out, experts say that by the time the plume gets Stateside, the radiation will barely be any more harmful than the smog Californians are used to breathing on a daily basis.
Health and nuclear experts emphasize that radiation in the plume will be diluted as it travels and, at worst, would have extremely minor health consequences in the United States, even if hints of it are ultimately detectable. In a similar way, radiation from the Chernobyl disaster in 1986 spread around the globe and reached the West Coast of the United States in 10 days, its levels measurable but minuscule ....
The chairman of the Nuclear Regulatory Commission, Gregory B. Jaczko, said Monday that the plume posed no danger to the United States. “You just aren’t going to have any radiological material that, by the time it traveled those large distances, could present any risk to the American public,” he said in a White House briefing.
Many Californians don't necessarily believe this analysis, however, as demonstrated by the spike in Google searches there for potassium iodide — which protects against thyroid cancer from exposure to nuclear radiation — over the past few days.