... or not
As my readers* may be aware, my recent skeptical focus has been all over the anti-vaccination lobby, a bunch of rabid, idiotic fringe-dwellers who think vaccines are the sole cause of everything bad in the world.
One of the oft-repeated canards of the antivaxers is that vaccines contain thimerosal, which contains mercury, and that mercury is the
second most toxic substance known to man.
But is it?
Liam Skoda, over at the
Stop The AVN Facebook group, took up the challenge of this question and in short order demolished this piece of antivax nonsense.
Liam simply looked up some known lethal dose information, the measure by which toxicity is measured out here in the real world, and found some surprising information on Thimerosal, the mercury compound used in vaccines as a preservative **
Thimerosal's LD50 is examined here.
As you can see, the highest toxicity is intravenously in mice, and that stands at 30mg/kg. Or, in less sciencey terms, A dose of 30mg per kilogram of bodyweight is sufficient to kill 50% of a given group of mice.
So, Thimerosal, 30mg/kg ivn-mus
I executed a
really quick search on the same database to see what other substances were listed with IVN-MUS figures, to get a fair comparison
Zinc Chloride has an LD50 IVN-MUS of 9mg/kg
Selenium Dioxide also comes in at 9mg/kg
Hydrogen Cyanide rocks it up at 1mg
Arterenol Free Base checks in at a fantastic 0.55mg/kg
As a gauge, something you may be more familiar with, especially in large doses, Caffeine, checks in at 109mg/kg IVN in rats.
So already we've demonstrated that the antivaxers' sloppy line that
"The use of any product containing mercury [Thimerosal] has been or is in the process of being banned. It is the second most toxic substance to man behind plutonium." is, frankly, utter bullshit.
Now, let's examine where the antivaxers got this from originally. You'll notice that "thimerosal" is in braces. The original quote seems to originate from the American Chronicle, specifically
this article by Alan E. Moses****. You'll note that the word "thimerosal" is absent from the original sentence.
So the antivaxers added it.
This is what we've come to expect.
So now we adjust our search a little. The original sentence appears to be sloppily comparing element with element. perhaps it means that Mercury
the element is the second most toxic after
the element plutonium? Maybe Alan just messed up when he used the word substance, because we KNOW that's untrue. Well, it's difficult to find LD50 figures on Mercury and Plutonium, because let's face it, who goes around injecting mice with elemental mercury these days?
However, wikipedia has a good jumping point in their article on
toxic metals. Going from there, we read in the
Plutonium article:
Wait, what?
Is it possible that entire assertion was also bullshit?
Well, it contains a grain of truth. Plutonium is definitely toxic, and definitely a fucking dangerous metal, and most certainly not something you want hanging around the house, but not the #1 most toxic element?
Well, no. Polonium checks in at an LD50 of 4.5 sieverts. Plutonium is known to have killed humans at around 5.1 sieverts. I'm not even going to do a full poll of toxic metals, because frankly my work here is done, but let's just say the Alan E Moses sentence is busted.
- There is no ban in the pipeline on the use of all products containing mercury
- Mercury is not the second most toxic substance on earth
- Mercury isn't even the most toxic element
- And neither is plutonium
So, back to mercury and Thimerosal.
Just how toxic is Thimerosal really?
Let's get something straight before we begin. We NEED Thimerosal to have toxicity in order for it to be useful. In vaccines, it is used to kill bacteria. If we replaced it, it'd probably be with something else toxic. But just how toxic is it?
Well, again, let's do some back-of-a-beermat maths and match it with Caffeine. This time, an LD50 based on oral administration in rats.
Thimerosal: 75mg/kg
Caffeine: 192mg/kg
I'm about 100kg in weight, give or take. To kill me (or technically, to kill 50% of a representative sample of guys like me), you're gonna need 19200mg of caffeine. Or 19g.
According to Health Canada, you get about 300mg of caffeine from two decent sized cups of coffee, so 150mg from a single cup. Doing the math, I'd have to have something like 1300 cups of coffee to get a lethal dose.
HOLY CRAP! I drink a couple of cups a day. that means I'd have to increase my consumption by less than a thousandfold, and I'd be dead as.
But what about thimerosal? Thimerosal is, and let's be charitable in our rounding, about three times as toxic as caffeine
Well, the FDA provides a
useful table of thimerosal content in vaccines here. Let's look at the flu vaccine as an example.
The flu vaccine gives you about 25
micrograms of mercury per dose. Thimerosal is about 50% mercury by weight, so we make that 50 micrograms of thimerosal per dose. We've established we need about 7500mg, or 7.5g of thimerosal to kill me, so... let me just fire up Google and use the handy calculator function
Ah. there we go:
Yes, you just read that right. I'd need the thimerosal content of 150,000 doses of flu vaccine to kill 50% of a group of guys like me.
Holy crap. I have one flu shot a year! So I'd only have increase my one-off, once-a year flu vaccine consumption by
150,000 fold to be in some serious trouble!
Wait, hang on....
That makes no sense.
Surely I'm not eating the flu vaccine? Surely I'm injecting it? Oh, OK, let's be nice to the antivaxers and replace out the oral LD50 of 75mg/kg with the more toxic IVN-MUS LD50 of 30mg/kg - the highest toxicity in the table at 2/5ths that of the ORL-RAT - and we still get a figure of
60,000 flu shots to reach LD50 in a representative group of adults***
So, where was I?
Oh yes.
I think the flu vaccine, in terms of thimerosal's toxicity at least, is pretty safe. One flu shot contains about 1/60,000th of a lethal human dose of the scary ingredient. One cup of coffee contains 1/1300th of the lethal dose of caffeine.
And I also think that next time an antivaxxer tells you that vaccines are unsafe because mercury is the second most toxic substance on earth, you can feel quite justified in stabbing them in the eye with the nearest sharp implement you can find. In fact, I'd recommend it.
* all two of you
** or not surprising at all, if you're familiar with the usual standard of evidence employed by antixavers
*** I was purposefully fast and loose with the administration method here. I consciously wanted to match LD50 methods and ORL-RAT was the only method out of oral or intravenous that appeared on both lists. It also made the calculations much neater to understand, in the end, with a 2/5ths divide being applied after the big numbers rather than at the start
**** Alan E. Moses is on Twitter. Someone needs to alert him to his mistake and maybe rip him a new one over his terrible grammar and orthography
posted @ Monday, September 21, 2009 12:19 PM