June 18. 2003 — Mercury has been fingered in a study as a possible cause of autism, the British weekly New Scientist reports in its upcoming issue on Saturday.
A US team compared mercury levels in hair that had been kept from 139 babies when they had their first haircuts, when they were around 18 months old.
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Mercury levels among 94 children who were later diagnosed as autistic was 0.47 parts per million (ppm), while among the 45 other children who developed normally, the levels were eight times higher, at 3.63 ppm.
The lower the level of mercury, the worse the degree of autism, the scientists found.
The results are remarkable but until more work is carried out, the conclusions are open to dispute, New Scientist says.
The clear implication is that autistic children have a genetic flaw that makes them vulnerable in their exposure to essential or toxic metals.
It could be that these children cannot get rid of mercury via their faeces and urine, which means that the toxic metal may accumulate in their brain cells and affect their neurological development.
Alternatively, mercury may not be to blame. The difference in mercury levels in the hair could be an indicator of a general problem these children may have in dealing with metals.
Autistic children, according to this line of thinking, may be deficient in processing zinc, iron and copper and other metals essential for brain development.
The research, led by Louisiana doctor Amy Holmes, will be published in September in the International Journal of Toxicology, New Scientist said.
Parents of autistic children have filed lawsuits in North America, blaming vaccines containing a mercury-based preservative called thimerosal for their child's plight.
Other parents, notably in Britain, blame a triple vaccine for measles, mumps and rubella (MMR) for causing their child's autism. However, this vaccine does not contain any mercury at all, and most scientists say that in any case the evidence against the vaccine is not convincing.
Holmes' study said the children's only significant source of mercury came from their mothers while they were in the womb.
A check on the family's background, health and eating habits found the biggest sources were the mother's mercury amalgam fillings; immunoglobulin injections containing thimerosal for women whose blood-group was Rhesus negative; and heavy consumption of fish, defined as more than five fish meals a month.
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