Fukushima Diary alerts me of this video-simulation of the spread of Cesium-137 in the North Pacific Ocean published by the German newspaper Süddeutsche Zeitung[ge]:
Credit: Geomar (oceanic institute of Kiel, Germany).
The values are not absolute but relative to those initially released at Japan, whose exact measure is unknown to me, but the bright red zones are just 1/1000 of what was released near Fukushima.
Low enough? The Alaskan seals would not agree. According to the model, the area was then only touched by some 1 billionth of what Fukushima released if anything at all but the seals were eating fish which was maybe contaminated in other parts of the Pacific.
Still the high levels (one thousandth rel. to Fukushima) of radioactive cesium appear to reach North America only some five years after the catastrophe (i.e. in 2016), so the worst is probably yet to happen to the North American Pacific shores.
That assuming that nothing even worse happens in Fukushima Daiichi, what, considering the lack of control that TEPCO, Japan and the IAEA have on the ongoing quadruple China syndrome, is probably not the case.