News - Mercury in Vaccines Different, Study Shows.html

April 21, 2005

News - Mercury in Vaccines Different, Study ShowsThey really can't

measure the amount of mercury in the brain, so the statement near the end of

this article about brain concentrations of total mercury being less by

three-fold in vaccine-exposed infants than in those exposed to methyl mercury

from fish or the environment ought to be challenged. After all, we know that

Prozac is concentrated in the brain at something like 20 times the blood

concentration. And despite the similarity between humans and primates, as

mammals, when all is said and done, babies are not monkeys, and vice versa.

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Mercury in Vaccines Different, Study Shows

1 hour, 2 minutes ago

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - The mercury contained in some vaccines is processed

differently in the body and is possibly less toxic to children than mercury

found in pollution and fish, U.S. researchers reported on Thursday.

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Tests in monkeys showed that the ethyl mercury contained in the vaccine

preservative thimerosal is cleared quickly by the body, while methyl mercury

persists much longer.

This suggests that current Environmental Protection Agency guidelines on

mercury exposure should not apply to the type of mercury in vaccines -- and

could help answer doubts about the safety of some vaccines, the researchers

wrote in this week's issue of Environmental Health Perspectives.

" The current debate linking the use of thimerosal in vaccines to autism

and other developmental disorders has led many families to question whether the

potential risks associated with early childhood immunizations may outweigh the

benefits, " Burbacher of the University of Washington in Seattle and

colleagues wrote in their report.

The Institute of Medicine, an independent body that advises the federal

government, has said there is no evidence of any link between vaccines and

autism. It has advised researchers looking for the causes of autism to look

elsewhere.

This has enraged autism activists, who fear a cover-up.

Burbacher's team said it would make sense to study more closely the

effects of thimerosal, a mercury-based preservative once widely used in

vaccines. It has been removed from most childhood vaccines because of the furor.

Thimerosal remains in the influenza vaccine and in some vaccines used

outside the United States.

Current government advice on vaccine exposure limits are based on studies

done on people who were exposed to methyl mercury from industrial accidents. It

can clearly cause long-term brain and nervous system damage.

An earlier study calculated that children receive 187.5 micrograms of

ethyl mercury from thimerosal-containing vaccines given over the first 14 weeks

of life. This can exceed EPA guidelines for methyl mercury exposure during

pregnancy.

Some experts have argued that thimerosal breaks down into a different form

of mercury in the body -- ethyl mercury -- and that this is cleared more

quickly.

Tests on human infants suggest this does happen, but their brains cannot

be directly examined.

Burbacher's team tested 41 newborn monkeys, feeding them either methyl

mercury or giving them shots of thimerosal in doses comparable to those given

vaccinated human infants. The mercury from the vaccines was cleared out of the

body much more quickly than was methyl mercury, they said.

It took just over eight days to completely clear mercury from thimerosal,

while it took 21 days to clear methyl mercury from the blood, they found.

" Brain concentrations of total mercury were significantly lower by about

three-fold for the thimerosal-exposed infants when compared to the methyl

mercury infants, " they wrote.

The researchers said this does not mean thimerosal is harmless and urged

more research.

" This information is critical if we are to respond to public concerns

regarding the safety of childhood immunizations, " they wrote.

" This study emphasizes that thimerosal and methyl mercury behave

differently in the body. Given that we routinely inject thimerosal into millions

of infants, the study authors' call for more in-depth research on the subject is

the right way to go, " said Dr. Jim Burkhart, science editor for the journal.

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April 21, 2005