But it has been well dispersed by ocean currents, according to marine chemist Ken Buesseler at the Woods Hole Oceanographic Institution in Massachusetts.

WSJ: In Japan, Relief at Radiation's Low Toll

Mr. JEFF SHORT (Research Chemist, National Marine Fishery Service): Oil spills are a lot more damaging than we thought.

NPR: Valdez: The Damage Persists, 17 Years Later