I have read reports of canned fish found in sunken ships from the 1700's and early 1800's were loaded with mercury. Its always been there. Just one of those things. I have eaten fish all my life and I don't glow. I am a feisty 73 and still going strong.
I remember reading about some expedition to the frozen north that failed to make it. Graves were discovered with the bodies having expressions of agony. It was determined that the lids of the canned food had been sealed with lead, which poisoned the crew.
