[ohgodplsno]

The pacific's radiation levels have increased by about 0%. The total releases from all of Fukushima was on the order of 30 PBq. Water has a natural radioactivity of 13 Bq/L. So, if you want to only double the natural radioactivity of water (which is still basically nothing), you need to dilute ask this radiation in 2e15 L of water.

The entire pacific is 7.10e20 L of water. Even the area around Japan is thousands of times more liters of water. To give you an idea, in 2011, 41% of caught marine species on the coast of Fukushima had Cs137 concentrations higher than the normal limits (100bq/kg, which is still really damn low). In 2015, that was 0.05%

So, no, the pacific doesn't give a damn about Fukushima. And so do the people. You're exposed to about 2100Bq in a year.

[jcranmer]

It's worth noting that oceanic water is actually very poorly mixed, with only the first 200m or so mixing well with the atmosphere, so the radioactive emissions likely wouldn't increase in the deep ocean water. On the other hand, that basically only lops a zero off your number.