Thimerosal

Updated: March 11th, 2010 |

HEALTH CONCERNS
Is this chemical a carcinogen?	No.
How can it affect me?	Thimerosal contains ethylmercury, not methylmercury. When all the discussions about thimerosal began in 1999, there were very little data about ethylmercury toxicity. Because little information about ethylmercury toxicity was available in 1999, public health authorities worried that ethylmercury toxicity might be similar to that of methylmercury. If that were the case, exposure levels of young infants to mercury from thimerosal might theoretically be close to the safe intake level (the maximum amount to which an infant can safely be exposed on a daily basis, which is about ten times lower than where it might be neurotoxic). While methylmercury and ethylmercury sound similar, they are very different—just as are methyl alcohol (wood alcohol, a poison used in antifreeze) and ethyl alcohol (found in wine and beer). Except when used as a preservative, the final concentration of thimerosal in the vaccine is very small. In this case, the vaccine is labeled as containing “trace amounts” of thimerosal. The thimerosal content of vaccines either from the manufacturing process or as preservative can be found at the FDA Web site.
Are there controversial issues?	Methylmercury is NOT present in vaccines but it is in some of the food we eat. Methylmercury is well established as a neurotoxin—that is, it can damage the brain and cause developmental disabilities in young infants. Concerns that children with autism spectrum disorders had symptoms similar to methylmercury poisoning did not stand up to scientific scrutiny by the Institute of Medicine nor to side by side comparisons by neuroscientists. In their 2004 report, the Institute of Medicine said “… autism has never been documented as a consequence of high-dose mercury exposure…” Thimerosal in vaccines does not cause autism. Despite this, many parents, and some scientists and doctors, believe there is a connection. Parents may first become aware of autistic symptoms in their child around the same time of a routine vaccination begins, and parental concern about vaccines has led to a decreasing uptake of childhood immunizations and an increasing likelihood of measles outbreaks. The lack of a link between Thimerosal in vaccines and autism is the conclusion reached by The Institute of Medicine's Immunization Safety Review Committee in its 2004 report, Vaccines and Autism.  The report stated that the evidence favors "rejection of a causal relationship between thimerosal-containing vaccines and autism." Additional studies since then have continued to find no association.