Overview

Thimerosal (50% mercury by weight) is used as preservative in vaccines. Thimerosal is made with ethlymercurrichloride. The concentration of this material in many vaccines is 0.01% thimerosal. This is equivalent to 100,000 ppb thimerosal or 50,000 ppb mercury in the original vaccine vial. We now know that primates exposed to injected thimerosal, as opposed to equal amounts of ingested methylmercury, accumulate twice as much of the inorganic fraction of mercury in the brain (Burbacher et.al.). Inorganic mercury has a half-life of over 700 days in the brain and has been identified as the primary toxic agent following the dealkylation of ethyl and methyl mercury (Charleston et. al). This process leads to neuroinflamation and brain injury and has recently been identified in autistic patients who have been exposed to multiple doses of thimerosal (Vargas et. al).

The FDA is working to reduce or eliminate the use of thimerosal in vaccines (see FDA Thimerosal in Vaccines) and Institute of Medicine as reviewed the use of thimerosal and found evidence on the health effects of thimerosal inconclusive (see the IOM web site).

References

Charleston J, Body R, Bolender R, Mottet N, Vahter M, Burbacher T 1996. Changes in the number of astrocytes and microglia in the thalamus of the monkey Macaca fascicularis following long-term subclinical methylmercury exposure. Neurotoxicology 17:127-138

Wolfgang S, Mrak R, Griffin W 2004. Microglia and neuroinflamation: a pathological perspective. Journal of Neuroinflamation 1:14

Vargus DL, Nascimbene C, Krishnan C, Zimmerman AW, Pardo Ca. 2005 Neuroglial activation and neuroinflamation in the brain of patients with autism. Annals of Neurology 57:67-81.

Burbacher T, Shen D, Liberato N, Grant K, Cernichiari E, Clarkson T. 2005. Comparison of blood and brain mercury levels in infant monkeys exposed to methylmercury or vaccines containing thimerosal. Environmental Health Perspectives. 113:1015-1021