neurotoxicology

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1: Neurotoxicology 2001 Oct;22(5):691-7 Books, LinkOut

Predicted mercury concentrations in hair from infant immunizations:

cause

for concern.

Redwood L, Bernard S, Brown D.

Coalition for Safe Minds, Cranford, NJ 07016, USA.

tlredwood@...

Mercury (Hg) is considered one of the worlds most toxic metals. Current

thinking suggests that exposure to mercury occurs primarily from seafood

contamination and rare catastrophic events. Recently, another common

source

of exposure has been identified. Thimerosal (TMS), a preservative found

in

many infant vaccines, contains 49.6% ethyl mercury (EtHg) by weight and

typically contributes 25 microg of EtHg per dose of infant vaccine. As

part

of an ongoing review, the Food and Drug Administration (FDA) announced

in

1999 that infants who received multiple TMS-preserved vaccines may have

been

exposed to cumulative Hg in excess of Federal safety guidelines.

According

to the centers for disease control (CDC) recommended immunization

schedule,

infants may have been exposed to 12.5 microg Hg at birth, 62.5 microg

EtHg

at 2 months, 50 microg EtHg at 4 months, 62.5 microg EtHg at 6 months,

and

50 microg EtHg at approximately 18 months, for a total of 237.5 microg

EtHg

during the first 18 months of life, if all TMS-containing vaccines were

administered. Neurobehavioral alterations, especially to the more

susceptible fetus and infant, are known to occur after relatively low

dose

exposures to organic mercury compounds. In effort, to further elucidate

the

levels of ethyl mercury resulting from exposure to vaccinal TMS, we

estimated hair Hg concentrations expected to result from the recommended

CDC

schedule utilizing a one compartment pharmacokinetic model. This model

was

developed to predict hair concentrations from acute exposure to

methymercury

(MeHg) in fish. Modeled hair Hg concentrations in infants exposed to

vaccinal TMS are in excess of the Environmental Protection Agency (EPA)

safety guidelines of 1 ppm for up to 365 days, with several peak

concentrations within this period. More sensitive individuals and those

with

additional sources of exposure would have higher Hg concentrations.

Given

that exposure to low levels of mercury during critical stages of

development

has been associated with neurological disorders in children, including

ADD,

learning difficulties, and speech delays, the predicted hair Hg

concentration resulting from childhood immunizations is cause for

concern.

Based on these findings, the impact which vaccinal mercury has had on

the

health of American children warrants further investigation.

PMID: 11770890 [PubMed - in process]

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