Methyl mercury in fish is not as effectively retained by humans who eat it, as is the ethyl mercury (from vaccines) or the inorganic mercury (from dental amalgams or air). Inorganic mercury (Hg2+) is made from elemental mercury (hg) vapor from dental amalgams by action of the enzyme catalase. This is the major source of mercury found in the bodies of those with dental amalgams.
The major difference between these forms of mercury exposure to humans is not methyl versus ethyl mercury. Both are very toxic in their pure forms. However, methyl mercury from a diet of fish has already reacted with the protective proteins and compounds in the fish and is much less likely to be taken up and retained by the human body—it is mostly excreted. This is why individuals from the Faroe Islands, where they eat mostly fish, do not have excessive mercury toxicity problems. Also, this mercury passes through the intestines where the bulk of one of our major protective proteins against heavy metals (metallothionein) exists, which binds the mercury and enables it to be excreted in the feces without most of it ever entering the body.
In contrast, inhaled mercury vapor and injected ethyl mercury (thimerosal) bypasses this intestinal protection and is highly retained in the body since this mercury has never reacted with any other biological system prior to a human's being exposed to it.
In my opinion, there is no comparison between the toxicity of injected pure ethyl mercury (thimerosal) and that of ingested fish protein with bound methyl mercury.
Dr. Haley is Professor of Chemistry/Biochemistry at the University of Kentucky and has spent the past 17 years researching the biochemistry of Alzheimer's disease and its relationship to mercury toxicity. Dr. Haley has testified before numerous government agencies at the federal and state levels on the effects of mercury toxicity from dental amalgams and vaccines.