Breathing in mercury is extremely bad and can have consequences for your whole remaining life.

It's the property of mercury to evaporate at room temperature, which is why it can get harmful so easily. Evaporated mercury gets breathed in, which then gets into the blood which then gets into the brain and can result in sleep dissorders, paralysis and so on.

But when it gets injected directly into the body - it gets directly into the blood and into the brain - what can be the causes of that? Or how harmful can it be when mercury gets injected (even in very small dosis)?

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    What is the difference between 10mg mercury injected into your veins vs. 10mg absorbed in the capillaries of your lung? None at all. So the effects would be exactly the same as via the airways (apart from the damage the mercury dealt on its way in). What are you asking? Do you want to know the lethal dosage of mercury and the side effects of high doses?
    – Narusan
    Oct 24, 2018 at 14:48
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    How or why would mercury be injected? Are you referring to the thimerosal used in some vaccines?
    – Carey Gregory
    Oct 24, 2018 at 15:09
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    @Narusan exactly what I thought. I would like to know how harmful even a small dosis can be (as Carey wrote in his comment: thimerosal in vaccines), and what effects can occur. And if thimerosal isn't harmful, well, why is mercury harmful then?
    – watchme
    Oct 24, 2018 at 17:10
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    Consider methy alcohol (methanol) and ethyl alcohol (ethanol). They're both alcohol, but methanol is extremely toxic while we consume ethanol freely every time we have a glass of beer, wine or spirits. Mercury comes in methyl and ethyl forms too, and that explains why thimerosal isn't the hazard anti-vaxxers love to claim it is. I'll write a proper answer later.
    – Carey Gregory
    Oct 24, 2018 at 17:21
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    I would remind people that comments are intended to improve and clarify questions/answers. If you would like to debate the merits of vaccines and medical interventions that cause some degree of harm in the interest of a better good (i.e. broken ribs vs death), please do so in chat.
    – JohnP
    Oct 24, 2018 at 18:32

1 Answer 1


The problem here is the over-simplified (and inaccurate) idea that Thiomersal = mercury, it's not, rather it is a compound (chemical formula: C9H9HgNaO2S) that has mercury atoms in it's molecules, the mercury vapors (Hg) are a different thing, chemically speaking.

This means that mercury and Thiomersal will behave very differently in chemical terms, Thiomersal is metabolised by the body into ethylmercury (C2H5Hg+) which is eliminated from both the body and the brain relatively quickly and does not bioaccumulate. Unlikle methylmercury (CH3Hg+) which is the organic mecury formed from inorganic mercury sources such as the aforementioned mercury vapors or ingesting liquid mercury) which stays in the body up to five times longer (offering significant opportunity for bioaccumulation in the food chain - most human exposure to methylmercury comes from eating fish such as swordfish, big-eye tuna and king mackerel).

While Thiomersal itself can be quite toxic itself (which of course is exactly why it works so well as a preservative) as the old axiom states "the dose maketh the poison" and you need much higher doses that what is contained in vaccines to create adverse health effects in humans. And with the fact that it is eliminated completely from the body and doesn't bioaccumulate it's not a case that you need to worry about any cumulative effects.

The removal of Thiomersal from childhood vaccines (it's still in single-vial forms of some flu vaccines) in the US/Europe (some other countries still use the variant of MMR that contains Thiomersal) was prompted (at least in part) by a mistaken presumption that ethylmercury would behave in the body in the same way that methylmercury does. Which we now know not to be the case.

If you were to inject elemental mercury, then you'd be in the same situation as breathing in the vapors - even small doses can be dangerous because it metabolizes in to methylmercury and bioaccumulates.

NB: On a related note the distinction between ethyl- and methylmercury is what makes the chelation therapy some quacks/scam artists prescribe for autism to be doubly ineffective (not to mention it's potentially lethal effects!) because not only is autism not caused by mercury-poisoning but the mercury they are trying to chelate out is no longer even in the body in the first place!


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