Of course, Bq's (the rate of decay) are just one facet of the risk. It depends on what is decaying, what is emitted during the decay, bioconcentration, etc.
A better approach would have been to compare the 40E12 Bq of H-3 to the amount of naturally produced H-3 in the Pacific Ocean, which is about 4E17 Bq.
In other words, the new concentration is 4.0004E17 Bq. An increase, but a RELATIVELY small one.
For some reason I'm reminded of this: