Although methyl mercury (tuna fish) and ethyl mercury (vaccines) are not molecularly similar they are compared to each other by our health authorities, scientist and researchers. This professional body finds them to be similar enough to not study the toxic threshold of ethyl mercury and only go off what we know regarding methyl mercury.
If we look at the science when comparing ingestion of methyl mercury and injection of ethyl mercury we see that the ethyl mercury monkeys had higher levels of mercury in the kidneys when compared to the methyl mercury monkeys. Ethyl mercury clears the blood at a higher rate but both mercury compounds uptake in tissues about the same (~4-7 ng/g and ~10 ng/g, respectively). The concentration of total inorganic mercury in the brain of the thimerosal-exposed monkeys was much higher.
Here is the study: Burbacher, "Comparison of Blood and Brain Mercury Levels in Infant Monkeys Exposed to Methylmercury or Vaccine containing Thimerosal", Environmental Health Perspectives, Aug 2005.
Excerpt from study:
The concentration of total inorganic mercury in the brains of the thimerosal-exposed monkeys is up to 4.6 times higher than in the blood at 2 days after the last injection. The ratio increased as the sacrifices were performed at longer duration from the last dose.
Also they discovered that thimerosal injected monkeys had higher uptake of disposition fate of INORGANIC MERCURY PARTICULARLY IN THE BRAIN that was associated with microglia activation. Inorganic mercury can stay in the brain for the duration of a patients life!
Microglia activation via thimerosal injection is also big deal because this causes neural damage or inflammation.
Further pregnant women are injected with flu vaccines containing 25mcg of thimerosal (RfD of 0.1 ug/kg body weight/day), which exceeds EPA standards.