THURSDAY, Feb. 5, 2004 (HealthDayNews) -- Exposure to certain neurodevelopmental toxins, including the vaccine additive thimerosal, may increase the risk of autism and attention-deficit hyperactivity disorder, says a study in the April issue of Molecular Psychiatry.
This research is the first to offer a possible explanation for possible causes of these two increasingly common childhood disorders.
The researchers found that exposure to toxins such as ethanol and heavy metals (including lead, aluminum and the ethylmercury-containing preservative thimerosal) interrupt growth factor signaling. This adversely impacts methylation reactions such as the transfer of carbon atoms. Methylation is critical to proper neurological development in infants and children.
"Scientists certainly acknowledge that exposure to neurotoxins like ethanol and heavy metals can cause developmental disorders but, until now, the precise mechanisms underlying their toxicity have not been known," researcher and pharmacy professor Richard Deth of Northeastern University says in a prepared statement.
"The recent increase in the incidence of autism led us to speculate that environmental exposures, including vaccine additives, might contribute to the triggering of this disorder," Deth says.
Starting in 2000, the United States and Europe largely phased out thimerosal, often used as a preservative in multi-dose units of vaccines for diseases such as hepatitis, whooping cough, tetanus and diptheria.
Now, most vaccines in the United States and Europe contain only trace amounts of thimerosal. However, multi-dose flu vaccines still contain thimerosal. The same is true of many larger, multi-dose vials of vaccines shipped to and used in developing countries.
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