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Vaccines that contain
thimerosal, a mercury-containing preservative, may not contribute
to elevated levels of mercury in the blood, according to a
recent study.
The study involved
40 infants who had received thimerosal-containing vaccines
and 21 who had received vaccines without the substance. When
urine, blood and stool samples were looked at, the highest
blood mercury level found was 4.11 ng/ml and most of the children
had levels of 1 or 2 ng/ml. All participants had mercury levels
below the U.S. Environmental Protection Agency’s public
safety limit for mercury, which is 5.8 ng/ml.
Additionally, researchers
believe that thimerosal mercury is eliminated from the blood,
primarily through the stool, up to six times faster than methyl
mercury. While it was thought that the mercury had a half-life
in the blood of 45 days, they now say that the half-life is
six or seven days. This would mean that the mercury would
be close to eliminated from the body by the time a child received
his or her next round of mercury-containing vaccines.
Investigators noted
that, if vaccines were changed to be thimerosal-free, millions
of children in developing countries would not be vaccinated
due to the costliness of the venture.
The
Lancet November 30, 2002 Full Text Article
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