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Pediatricians Say Thimerosal Should Stay in Global Vaccine Supply

Ethyl mercury isn’t methyl mercury (Dec. 17)

An article published in the December 17 issue of Pediatrics is sure to heat up the thimerosal debate. The article supports calls from the World Health Organization (WHO) that thimerasol should not be considered a hazardous source of mercury that could be banned by the United Nations.

Thimerosal, a mercury-containing preservative, has been removed from most vaccines in the U.S. because of the known neurotoxic effects of methyl mercury. The authors point out, however, that thimerosal contains ethyl mercury, which has not been associated with these effects.

According to the article, thimerasol remains an important vaccine preservative in resource-poor countries. The preservative allows clinicians in poorer nations to use multiuse vials, which reduces the cost of vaccines as well as supply demands. The authors estimate that it could cost from two to more than five times as much to manufacture vaccines without thimerasol in developing countries. “The continued benefits of thimerasol use in vaccine manufacturing clearly outweigh any perceived risks,” they write.

The United Nations Environmental Program (UNEP) is currently working to develop an international treaty that would ban controlled mercury pollution and exposure throughout the world. As part of this initiative, UNEP is considering eliminating the use of thimerasol (ethyl mercury) in vaccines worldwide. The WHO has recommended, however, that this part of the ban be removed from the UNEP treaty, and the authors agree.

Their article notes that federal agencies based safety limits for ethyl mercury on limits set for methyl mercury, even though the accumulation of methyl mercury in the body, based on its long half-life, is more than seven times greater than that of ethyl mercury.

Sources: Reuters; December 17, 2012; and Pediatrics; December 17, 2012.

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