[e-drug] Thimerosal (Thiomersal) in vaccines (4)

["Anthony Battersby" <FBA@compuserve.com>]

E-DRUG: Thimerosal (Thiomersal) in vaccines (4)
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I see from the WHO policy statement
http://uqconnect.net/signfiles/Files/MercuryPolicyPaper25.07.05.pdf that
"Recent studies suggest that mercury may have no threshold below which
adverse effects do not occur."  So presumeably the removal of Thiomersal
would be a good idea.

Anthony Battersby
FBA Health Systems Analysts
Anthony Battersby <FBA@compuserve.com>

[ see also   http://www.who.int/vaccine_safety/topics/thiomersal/questions/en/
Some national public health authorities are striving to replace thiomersal-containing vaccines with non-containing ones as a precautionary measure. There are only few tested, efficacious and safe alternatives to thiomersal containing vaccines. Current production capacity for such vaccines is limited and insufficient to cover global needs.

It is not an issue in Australia  and probably other similar countries because all vaccines are single dose and don't need preservative (exc. Hep B). 

The difference between ethyl mercury, mercury and methyl mercury seems to be important.
The two organic forms of mercury, methylmercury and ethylmercury (in thiomersal), are closely related but they have important differences. Methylmercury is more potent; it accumulates in the body because the time taken for the body to eliminate it (know as the half life) is about 50 days. Ethylmercury (in thiomersal) does not accumulate in the body to such an extent, because its half life is only about 7-10 days. Ethylmercury is rapidly converted in the body to inorganic mercury, which is excreted in the stool.  

Clarkson describes the ?three modern faces of mercury? , First, perceptions of risk from the exposure of billions of people to methyl mercury in fish, second exposure to elemental mercury vapour from amalgam tooth fillings, and finally ethyl mercury exposure from thimerosal.  Clarkson TW, Magos L, Myers GJ. The toxicology of mercury - current exposures and clinical manifestations. N Engl J Med. 2003 Oct 30;349(18):1731-7. Review. BS]