Today I read an interesting article about some recent research carried out at the University of Illinois where they demonstrated that the best way to convince parents to vaccinate their children might be to show them the results of the diseases the vaccines prevent. (This, by the way, contradicts some research published in 2014 which showed that this tactic didn’t work. For an excellent discussion of the two, see here.)

Then, because I am just one of those people who can’t resist poking at ulcers with my tongue (you know what I mean) I had a quick look at some of the comments regarding that article. Reassuringly, most people were weighing in on the “yeah, vaccinate!” side of the argument. But not surprisingly there was also a small group of people posting the traditional anti-vaccine arguments. And then, this appeared:

Well, it did make be go “hmmmmm”, but for the reason you might imagine.

No, you see, what I thought was: “hmmmmm, someone else who has, possibly deliberately, failed to understood the difference between elements and compounds, and how chemical bonding changes properties.”

Allow me to start at the beginning. If you went to a school in the UK (and I would hope it’s similar elsewhere in the world) you learned about elements, compounds and mixtures when you were about 13 years old – if not before. You might have forgotten it since, but I can absolutely, categorically guarantee you that lesson happened. In fact, it was probably a few lessons.

One experiment much beloved of chemistry teachers since year dot is to take a mixture of sulfur (a yellow powder) and some iron filings (grey) and show that they can be separated with a magnet. Then heat the mixture up so that the two react, with a rather beautiful red glow, to form iron sulfide. This is a blackish solid which is in theory not magnetic (but in practice almost always is) and demonstrate that now the two elements cannot be separated.

Thus we have demonstrated that elements (the iron and the sulfur) have different properties to the compound they formed (iron sulfide), and also that mixtures can be separated fairly easily, whereas breaking compounds up into their constituent elements is much harder. Lovely. Job done.

And yet… so many people seem to have been asleep that day. Or perhaps just didn’t grasp it well enough to continue to apply the principle to other things.

For example, mercury. Mercury, the element (the runny, silvery stuff that you used to find in thermometers) is a heavy metal. Like most of its compatriots, such as cadmium, lead and arsenic, it’s toxic. It can be absorbed through the skin and mercury vapour can be inhaled, so containers need to be tightly sealed. The increasing awareness of the toxicity of mercury is why older readers might remember seeing it ‘in the flesh’, so to speak, at school, whereas younger ones will not – these days it’s rarely even used in thermometers for fear of breakages.

That said, it does occur naturally in the environment, particularly as the result of volcanic eruptions – and very low levels aren’t considered harmful. The dose, as they say, makes the poison. It also occurs as the result of industrial processes, particularly coal-fired power plants and gold production, and occupational exposure is a genuine concern. In particular, chronic exposure is known to cause cogitative impairment. It might the source of the ‘mad dentist’ myth. It’s almost certainly the origin of the phrase ‘mad as a hatter‘.

So in summary, don’t mess about with elemental mercury; it’s not good for your health.

However, as I took some pains to establish, elements and compounds are different things. So what about compounds which contain mercury?

This is where vaccines come in. There is a substance that used to be used as a preservative in (some) vaccines called thiomersal (or thimerosal, in the U.S). You may have heard its name; it comes up quite a lot. Incidentally, it hasn’t just been used in vaccines, but also in various other things including skin-test antigens and tattoo inks.

Now, to be clear, thiomersal IS potentially toxic, however it’s quickly metabolised in the body to ethyl mercury (C₂H₅Hg⁺) and thiosalicylate and, although ethyl mercury does, clearly, still contain atoms of mercury, it does not bioaccumulate. In other words, your body gets rid of it. At very low doses (such as those in vaccines) there is no good evidence that thiomersal is harmful.

Still, due to continuing public health concerns, thiomersal has been phased out of most U.S. and European vaccines. In the UK, thiomersal is no longer used in any of the vaccines routinely given to babies and young children in the NHS childhood immunisation programme. And at the moment, all routinely recommended vaccines for U.S. infants are available only as thimerosal-free formulations or contain only trace amounts of thimerosal (≤1 than micrograms mercury per dose).

Let me just say that again. The evidence suggests it’s safe, but it’s been removed anyway as a precaution. If you live in the UK, it’s not in your child’s vaccines, and that includes the new nasal-spray vaccine for flu which has been rolled out over the last few years. If you live in the U.S. it’s probably not, and thimerosal (thiomersal) free versions exist. It does turn up most often in flu vaccines (hence the meme image at the start) but thiomersal-free versions of those also exist in the U.S.

So chances are it’s not in your vaccines. Not in there. Got it? Ok.

Now, you may have heard about mercury in seafood. It is an issue, particularly for women who are pregnant, trying to become pregnant or breastfeeding, and is the reason such women are advised not to eat shark and swordfish, and to keep their tuna consumption low. But here’s the thing: it’s a different kind of mercury. In this case, it’s methyl mercury (remember, thiomersal breaks down to ethyl mercury, which is not the same).

Methyl mercury is more toxic than ethyl mercury. Methyl mercury binds to parts of amino acids much more readily than its ethyl cousin, and it’s able to pass through the blood brain barrier and into nerve cells where it causes damage. In addition, ethyl mercury is much more quickly eliminated from the body than methyl mercury. Because of all this, methyl mercury does bioaccumulate (build up in the body), and that’s why large top-of-the-food-chain fish like shark and tuna can have significant levels of it, and why certain groups of people should be careful about eating them.

The FDA’s action level (the limit at or above which FDA will take legal action) for methyl mercury in fish is 1000 ppb (1 ppm). But remember, that’s for the much more dangerous methyl mercury, not ethyl mercury. I’ve been unable to find an equivalent figure for the UK, but I’d imagine it’s similar.

So, where does the 200 ppb mercury figure in the image at the top come from? Well the Environmental Protection Agency does indeed set a ‘maximum contaminant level goal’ for inorganic mercury of 0.002 mg/L or 2 ppb in water supplies. Methyl and ethyl mercury are not inorganic mercury; compounds that fall into this category include mercuric chloride, mercuric acetate and mercuric sulfide, which largely get into water as the result of industrial contamination.

In summary, that meme image at the start is basically comparing apples and oranges. The EPA limit isn’t relevant to vaccines, because it’s for inorganic mercury, which the substance in vaccines isn’t. While we’re about it, the levels applied to fish don’t apply either, because that’s methyl mercury, not ethyl mercury. They’re not the same thing. And all that aside, it’s highly unlikely (if you live in the UK, no chance at all) that there are 50,000 ppb of ethyl mercury in your flu vaccine anyway. AND, let’s not forget, there’s no evidence that the tiny quantities of thiomersal used in vaccines are harmful in the first place.

Phew.

You may note that I’ve studiously avoided the word ‘autism’ in this post so far. But yes, that’s the big concern; that exposure to thiomersal in vaccines could cause autism. Despite multiple, huge, studies in several countries looking for possible links between vaccines and autism, none have been found. Vaccines don’t cause autism. It’s time we stopped wasting enormous amounts of time and resources on this non-link and spent it instead on finding out what does cause it. Wouldn’t that be far more useful and interesting?

Now… if you’re hardcore anti-vaccine and you’ve read this far, and you’re about to hit the comment button and tell me that all this research is just Big Pharma covering things up so they can make money from the ‘million(/billion/trillion) dollar vaccine industry’, just wait a moment.

Stop.

Think about this: how much money could the medical industry make from people actually catching measles, mumps, polio, TB, whooping cough and all the others? Just think of all the money they could make selling antivirals and antibiotics, all the money to be made from painkillers, antipyretics, drugs to treat respiratory symptoms of one kind or another, and everything else? Believe me, it would be much, much more than they make from a single 2 ml dose of vaccine. Why ‘cover up’ research that’s, if anything, reducing their profits?

All these diseases are horrible, and some can be fatal or have genuinely life-changing consequences. That’s proven. Please vaccinate your children, and yourself.

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