In a weeks worth of experiments we recently conducted, we tested all sorts of substances for mercury vapor using a $15,000 piece of lab equipment that we rented. On the last day, we tested tuna and found well over 100 ug/m3 (micrograms per cubic meter) coming off of a newly-opened can of tuna (that's a lot). We have this all on video and will be posting it here shortly. Fish-related cat food also showed large amounts of mercury vapor. Although I love fish, I generally stay away from it because I do experience mercury symptoms when I eat it unless I take a bunch of algin with it, in which case, I have virtually no symptoms. Hope this helps.