http://www.quackwatch.org/03HealthPromotion/immu/thimerosal.html
Misconception: Thimerosal Causes Autism: Chelation Therapy Can Cure It
A few physicians have been promoting the idea that the mercury content
of vaccines is a cause of autism and that autistic children should
undergo chelation therapy to be detoxified. Lawsuits have been filed,
and several attorneys are advertising on the Internet for more clients.
The situation arose because until recently, certain vaccines contained
thimerosal, a mercury-containing preservative that is no longer used in
tmost of the vaccines not recommended for children. However, there are
several reasons why concerns about the use of thimerosal in vaccines
are misguided:
• The amounts of mercury involved were very small.
• No link between mercury and autism has been proven.
• There is no logical reason to believe that autism has a toxic
cause.
Thimerosal has been used as preservative in biologics and vaccines
since the 1930s because it prevents bacterial and fungal contamination,
particularly in multidose containers. In 1999, an FDA review noted that
with the increased number of vaccines then recommended for infants, the
total amount of mercury in vaccines containing thimerosal might exceed
the levels recommended by other federal agencies [1]. The mercury
limits imposed by these agencies have a wide margin of safety; and
there was no information suggesting that any infant had been harmed.
Nevertheless, to be super-cautious, the U.S. Public Health Service
(PHS) and the American Academy of Pediatrics (AAP) asked doctors to
minimize exposure to thimerosal-containing vaccines and manufacturers
to remove thimerosal from vaccines as soon as possible [2].
By mid-2000, thimerosal-free vaccines against hepatitis B and bacterial
meningitis were widely available. A combination vaccine for diphtheria,
pertussis, and tetanus is also available today without thimerosal.
Measles/mumps/rubella (MMR), chickenpox, inactivated polio, and
pneumococcal conjugate vaccines have never contained thimerosal. Thus,
except for some influenza vaccine, none of the vaccines now used to
protect preschool children against 12 infectious diseases contain
thimerosal as a preservative. Certain flu vaccines and
tetanus-diphtheria vaccines (Td) given to children age 7 and older
still contain thimerosal as a preservative.
Before the recent reductions, the maximum cumulative exposure to
mercury via routine childhood vaccinations during the first six months
of life could have been 187.5 micrograms (which averages to about 1
microgram per day. With the newly formulated vaccines, the maximum
cumulative exposure during the first six months of life should now
total no more than 3 micrograms of mercury [3]. No studies have shown
that either the old or the new amounts have any toxic effect.
The U.S. Centers for Disease Control and Prevention has compared the
incidence of autism with the amount of thimerosal received from
vaccines. Preliminary results indicated no change in autism rates
relative to the amount of thimerosal a child received during the first
six months of life (from 0 micrograms to greater than 160 micrograms).
A weak association was found with thimerosal intake and certain
neurodevelopmental disorders (such as attention deficit hyperactivity
disorder) in one study, but was not found in a subsequent study [4].
Additional studies are planned, but it is unlikely that any significant
association will be found.
An Institute of Medicine (IOM) committee, which issued a comprehensive
report in October 2001, found no proof of a link between
thimerosal-containing vaccines and autism, attention
deficit-hyperactivity disorder, speech or language delays, or other
neurodevelopmental disorders [5].
A study published in 2002 of infants who were 6 months of age or
younger compared the levels of mercury in the blood, hair, urine, and
stool of 40 who received vaccines containing thimerosal and 20 who
received vaccines without thimerosal. The study found:
• Mercury levels in blood and urine were low in all infants
studied
and in many cases too small to measure. There was no observed
dose-dependent relationship between the level of thimerosal received
through vaccination and the level of mercury in the body.
• Mercury levels in blood did not exceed, at any time, the
blood
levels that correspond to Environmental Protection Agency guidelines
for exposure.
• Mercury levels in the stool of infants receiving vaccines
containing thimerosal were relatively high compared to mercury levels
in the stool of infants who were not exposed to thimerosal, providing
evidence that mercury from thimerosal is eliminated in the stool of
infants.
The researchers concluded that, "Administration of vaccines containing
thiomersal does not seem to raise blood concentrations of mercury above
safe values in infants." [6].
The use of chelation therapy to treat autistic children is completely
bogus. One lawsuit has been filed by parents who believe they were
victimized in this way [7].
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