Concern has been expressed over the possibility that the mercury-containing compound thimerosal in vaccines may cause autism.1–4 Thimerosal is sodium ethylmercury thiosalicylate, an organic compound of ethyl mercury, included in certain vaccines to protect multiple dose ampules from bacterial and fungal contamination. Mercury in sufficient dose is neurotoxic, and probably more toxic in the immature brain. It is reasonable to ask whether thimerosal in childhood vaccine increases risk of chronic childhood neurologic disability and specifically of autism. The available data with which to address the question are very limited and largely inferential. Most of the information we have about mercury toxicity is related to exposure to methyl rather than ethyl mercury.
Bernard et al1 offered an hypothesis that autism is an expression of mercury toxicity resulting from thimerosal in vaccines. They base this hypothesis on their views2 that the clinical signs of mercury toxicity are...
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