Article evaluates danger of mercury in vaccines

An article published last year in the journal NeuroToxicology (2001;22:691-697) reviews the evidence linking exposure to mercury from immunizations and developmental disorders in children. The authors of the article also have a website at where related information can be found.

Daily exposure to low levels of mercury was shown to have neurodevelopmental effects in infants, particularly in the domains of language, attention and memory. As a result, the EPA established reference exposure limits considered acceptable, recently adjusting them to 0.1 micrograms per kilogram (2.2 lbs) of weight per day. For example, the EPA limits would result in a maximum daily exposure of 0.9 micrograms of mercury for a twenty-pound child.

Thimerosal is a preservative utilized in the production of biological and pharmaceutical products, including vaccines, that contains roughly 50% mercury. Each dose of vaccine containing this preservative delivers 12.5 to 25 micrograms of mercury directly into an infant’s body. Since several vaccines are typically administered at once, it is possible for infants to have a bolus exposure of 50 to 62.5 micrograms at 2, 4, and 6 months of age with a cumulative maximum exposure of 187.5 micrograms in the first 6 months of life.

Little is known regarding the capability of infants’ bodies to excrete mercury, and several studies suggest that neonates up to 6 months of age do not excrete mercury at all due to immature liver function. Other factors may also determine the degree of mercury toxicity at a given level of exposure. For example, one study found a synergistic effect between low doses of mercury and “stress” caused by concurrent viral infections, other environmental factors and internal physiological states.

The article concludes that there is sufficient evidence to support the likelihood that mercury in vaccines may affect nervous system development in children. “These concerns are heightened by a recent report that found statistically significant associations between cumulative exposure to mercury-containing vaccines at 2 months of age and unspecified developmental delay; cumulative exposure at three months of age and tics; cumulative exposure at 1, 3 and 6 months of age and neurodevelopmental delays in general; and cumulative exposure at 6 months of age and attention deficit disorder.”

While mercury in vaccines has not been banned, it is gradually being phased out.

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