Tuna and Mercury

Does anyone know how much Tuna you have to get toxic levels of mercury? I eat a can a day - is this too much?

This has been discussed before on the forum.

I believe the consensus was that there is nothing to worry about because

a: The age of the tuna commonly used in canning is fairly young therefore not much mercury in it and

b: In general the levels are pretty low and so unless you are eating ten cans a day, no big deal.