What is ethylmercury and what is ethylmercury toxicity and effects on human neural cells?

Answer 1

Ethylmercury (sometimes ethyl mercury) is a cation composed of an ethyl group and a mercury atom; its chemical formula is C2H5Hg+. The term 'ethylmercury' is sometimes used as a generic term to describe organomercury compounds which include ethylmercury such as ethylmercury chloride and ethylmercury urea. The CAS registry number for ethylmercury chloride is [107-27-7] [1].

Ethylmercury is one of the metabolites of thiomersal, which is used as a preservative in some vaccines. For this application, the ethylmercury salt sodium ethylmercuric thiosalicylate is used. Thimerosal (C9H9HgNaO2S) is made from the combination of ethyl mercuric chloride, thiosalicylic acid, sodium hydroxide and ethanol.

Unlike methylmercury, ethylmercury has not been found to bioaccumulate[1]. The toxicity of ethylmercury is not well studied, however exposure standards based on methylmercury (such as those currently recommended by the EPA) are not demonstrated to be equivalent for ethylmercury[2].

The Food and Drug Administration (FDA) Modernization Act of 1997 called for a review and risk assessment of all mercury-containing food and drugs.[6] Vaccine manufacturers responded to FDA requests for December 1998 and April 1999 to provide detailed information about the thimerosal content of their preparations. From the early 1970s until present day, the number of vaccines regularly received by children in the US before the age of four has risen from two or three to up to twenty-two.

Through its Center for Biologics Evaluation and Research (CBER), the FDA studied the results and found regularly vaccinated young children were injected with up to 187.5 mcg of ethylmercury by the time they were six months old. When trying to assess whether this dosage was likely to cause damage, the CBER could not find guidelines for ethylmercury.

The FDA recognized that some children who receive thimerosal-containing vaccines may have, over time, exceeded federal guidelines for bolus (single-dose) mercury exposure, based on methylmercury (but not ethylmercury) studies. The United States Public Health Service (PHS), American Academy of Pediatrics (AAP) and vaccine manufacturers agreed that thimerosal-containing vaccines should be removed as soon as possible because of the potential risk of adverse effects from mercury exposure.[7] Similar conclusions were reached by the European Medicines Agency.[8]

In June of 1999, Dr. Neal A. Halsey, director of the Johns Hopkins University Institute for Vaccine Safety, Former Chairman of the American Academy of Pediatrics and a vocal supporter of the vaccination policy, was apprised of the results of the CBER study.[9] Dr. Halsey enlisted Dr. Walter Orenstein, the director of the Centers for Disease Control's (CDC) National Immunization Program for advice. Along with leaders of the American Academy of Pediatrics, the group advised a cautious stance by informing physicians about the findings.[10] Negotiations within the AAP resulted in a press release calling for a delay of Hepatitis B vaccines under certain circumstances.[11]

Due to the concerns that were raised, the Centers for Disease Control and the National Institutes of Health (NIH) asked the National Academy of Science's (NAS) Institute of Medicine (IOM) to establish an independent expert committee to review hypotheses about existing and emerging immunization safety concerns. In 2001 the IOM committee concluded that the hypothesis was biologically plausible; however, the evidence was inadequate to accept or reject a causal relationship between thimerosal exposures from childhood vaccines and neurodevelopmental disorders.[12][13][14][15]

The IOM panel reconvened in 2004 and concluded the evidence that was presented favored a rejection of a causal relationship between thimerosal-containing vaccines and autism; and that hypotheses generated to date concerning a biological mechanism for such causality are theoretical only. The IOM went on to recommend the termination of additional research into the subject, stating clearly that, "Further research to find the cause of autism should be directed toward other lines of inquiry". The IOM committee chair stated, "Available funding for autism research should be channeled to the most promising areas, of which the link with vaccines does not appear to be one."[16][17]

Answer 2

Ethylmercury is a cation composed of an ethyl group and a mercury atom; its chemical formula is C2H5Hg+.

Ethylmercury is one of the metabolites of thiomersal, which is used as a preservative in some vaccines. For this application, the ethylmercury salt sodium ethylmercuric thiosalicylate is used.

Unlike methylmercury, ethylmercury has not been found to bioaccumulate. The toxicity of ethylmercury is not well studied, however exposure standards based on methylmercury (such as those currently recommended by the EPA) are not demonstrated to be equivalent for ethylmercury.