evidence: If you look up some vaccine ingredients on the internet you may read that they could be harmful, but most of them are present in vaccines in amounts that are completely normal for our bodies. Even common salt (sodium chloride), which is essential for the normal functioning of the body, is harmful in large quantities. [...] Thiomersal is a mercury-based preservative used in tiny quantities in some vaccines to prevent the growth of bacteria and fungi which can contaminate from the environment when the vaccine is opened. [...] In the US, UK and Europe, thiomersal was removed from vaccines as a precaution. This was in line with the global goal of reducing environmental exposure to mercury from all sources. However, there was no evidence that thiomersal in vaccines caused harm. Thiomersal contains a compound called ethyl mercury, but concern about mercury in the environment has centred on a different compound called methyl mercury, which accumulates in the food chain and in the human body. More detailed information can be found on the US National Institute of Allergy and Infectious Disease website. A study from 2008 showed that the ethyl mercury in thiomersal does not appear to accumulate in the bodies of even very small babies. It is cleared from the blood in 30 days, and the evidence suggests that it is passed out in the baby’s stool (poo).