Mercury in Vaccines Leaves Blood Fast
Study Shows Ethyl Mercury in Thimerosal Leaves Blood Quickly
WebMD News Archive
Jan 30, 2008 -- Ethyl mercury from the vaccine preservative thimerosal
leaves the blood 10 times faster than methyl mercury, on which current risk
assessments are based.
Only trace levels of thimerosal can be found in U.S. vaccines, except in
multi-dose vials of flu
vaccine (single-dose flu vaccine has no thimerosal). But the inexpensive
vaccines that allow poorer nations to afford to immunize their children still
use thimerosal to prevent bacterial contamination.
Major studies of children who received thimerosal-preserved vaccines fail to
find a link between these vaccines and health problems. But because
thimerosal's active ingredient is a kind of mercury -- and because mercury can
be highly toxic -- there is a belief among many parents of autistic children
that thimerosal caused their children's disease.
Nearly everything known about the toxic effects of mercury is based on
studies of a form of mercury called methyl mercury. That's the kind of mercury
found in large ocean fish -- and the kind that causes developmental problems in
children exposed to mercury through environmental disasters. But astonishingly
little is known about the real risks of ethyl mercury itself.
A new study by University of Rochester researcher Michael E. Pichichero, MD,
and colleagues now sheds some light on this mystery. Pichichero's team studied
ethyl mercury levels in the blood, urine, and stools of Argentinean newborns
and infants before and after they received multiple childhood immunizations
with thimerosal-preserved vaccines.
"While our study is not a direct evaluation of neurological disorders
and autism, it shows that mercury levels in infants' blood
after vaccination with thimerosal-containing vaccines are 10 times lower -- and
go away 10 times faster -- than if they'd received the same amount of methyl
mercury," Pichichero tells WebMD.
One of the few researchers who studies the effects of ethyl mercury is
Thomas Burbacher, PhD, professor of environmental and occupational health
sciences and director of the infant primate research lab at the National
Primate Research Center, University of Washington, Seattle. Burbacher's studies
of ethyl mercury and thimerosal in primates are cited by both sides of the
Burbacher says that just because ethyl mercury is gone from an infant's
blood soon after it receives a dose of thimerosal -- a half-life of just 3.7
days in the Pichichero study -- doesn't mean it's gone from the body.
"Just because it came out of the blood doesn't mean it is excreted from
the body. It could have gone to the brain," Burbacher tells WebMD.
"Although total mercury levels in the blood are lower following thimerosal
exposure [than following methyl mercury exposure], mercury in the blood from
thimerosal has an easier time getting to the brain than methyl
Pichichero agrees with Burbacher on this but he says the current findings
are relevant to thimerosal risk.