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FOR IMMEDIATE RELEASE
Safe Minds and Mercury Policy Project Statement on "Mercury
concentrations and metabolism in infants receiving vaccines
containing mercury: a descriptive study"
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Washington, DC, Nov. 29 -/E-Wire/-- According to Safe Minds and Mercury
Policy Project, few, if any, definitive conclusions can be drawn from this
latest thimerosal study.
”An initial analysis of the Pichichero et al. study of blood mercury
concentrations in infants after vaccination with thimerosal-containing vaccines
clearly demonstrates that this is a poorly designed study”, said Sallie
Bernard, president of Safe Minds.
Nevertheless, in the article and accompanying commentary, the authors make the
following sweeping statements:
1. "Overall, the results of this study show that amounts of mercury in the
blood of infants receiving vaccines formulated with thiomersal are well below
concentrations potentially associated with toxic effects."
2. "Administration of vaccines containing thimerosal does not seem to raise
blood concentrations of mercury above safe values in infants."
3. "This study gives comforting reassurance about the safety of ethyl mercury
as a preservative in childhood vaccines."
“This report looks very much like agenda research and not an unbiased study,”
said Michael Bender of the Mercury Policy Project.
According to the groups, these statements cannot be supported by the study
design and results, for the following reasons.
1. The blood mercury concentrations found in the study are not
necessarily below the established safety limits: the authors cite a 1994 study
by Grandjean to provide a safety level for methylmercury of 29 ppb (parts per
billion) and state that this level is ten times lower than the mercury level
needed to see a decrease in cognitive performance in children. However, this
comparison does not utilize the latest safety data research. In 1998, Grandjean
published an article (Grandjean et al., "Cognitive performance of children
prenatally exposed to "safe" levels of methylmercury", Environmental Research,
1998) in which he rejected the conclusions of his earlier research and found
performance declines when the average cord blood mercury concentration was 59
ppb. His later study was validated as the "gold standard" by the National
Academy of Science in their 2000 report "Toxicological Effects of
Methylmercury" in which they found that the lowest dose for which adverse
neurological effects are found is when cord blood is 58 ppb. In the Pichichero
study, there was one infant out of 33 (3%) in which blood mercury was measured
who has a mercury concentration of 20.55 ppb. This infant was exposed to 37.5
micrograms of mercury, and the blood draw was taken on day 5. The authors state
that the half life of ethylmercury is probably about 6-7 days. Thus, this
infant's peak mercury concentration would be much higher than 20.55 ppb. Many
infants in the 1990s were exposed to 62.5 micrograms of mercury at age 2
months, or nearly double what the study infant recieved. Therefore, it is
probable that the blood levels of some infants given the full regimen of
thimerosal vaccines in the 1990s would exceed the 58 ppb threshhold for adverse
effects. THerefore, the results from the Pichichero study can hardly be seen
as "reassuring" to any parent.
2. Samples of blood were taken at various time points after exposure,
but each study subject only had one apparent blood draw. Standard study design
for a parmacokinetic study, even a simple one, is to obtain multiple draws from
each subject. Otherwise, it is not possible to make definitive statements about
distribution, elimination, and half life, which this study seems to do.
3. The reference point that they use to establish safety levels for
thimerosal is methylmercury, a different compound than the ethylmerucry in
thimerosal. Simply because a compound is similar does not mean it is as safe.
A good example is thalidomide, a sedative drug that was prescribed to pregnant
women from 1957 into the early 60's. It was present in at least 46 countries
under different brand names. When taken during the first trimester of
pregnancy, Thalidomide prevented the proper growth of the foetus, resulting in
horrific birth defects in thousands of children around the world. The reason is
the Thalidomide molecule is chiral, with left and right-handed versions. The
drug that was marketed was a 50/50 mixture. One of the molecules was a
sedative, whereas the other was found later to cause foetal abnormalities. The
tragedy could have been avoided had the physiological properties of the
individual thalidomide [molecules] been tested prior to commercialization.
Molecules that look almost exactly alike can behave very differently. The FDA
is very rigid about testing the precise molecule being approved.
4. The conclusions are based on blood draws from 33 exposed children,
which is a small sample upon which to draw far reaching conclusions. It is also
a convenience sample without random assignment of subjects and not even an
attempt to make sure that comparison groups were age-sex matched.
5. There was variability in the thimerosal doses given, and little
attempt to incorporate dose differences in the half life model or safety
assessment.
6. With a claimed half life of 6-7 days, it is remiss that there is no
collection within 3 days of exposure, when peak mercury levels would be
obtained. It would be impossible to make any conclusions about safety without
these measures.
For these reasons alone, Safe Minds and the Mercury Policy Project believe that
the conclusions of this study should not be used in deliberations of thimerosal
safety. Rather, more and better research is needed.
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