Anti-vaxxers can’t do math

A posting at a “newspaper” (I use the term loosely here) called the Canadian entitled ” America’s Toxic Flu shots: 250 times EPA mercury limit” has been getting a bit of attention (and ridicule) lately. The same article appears to be posted at another site under the name “Flu Shots Contain More than 250 Times the EPA’s Safety Limit for Mercury“, both by someone called Anthony Gucciardi. The article is riddled with factual errors, and actually identifies well-known quack Russel Blaylock as a “leading neurologist”. But without even going into all the factual errors, which have been pointed out elsewhere (such as here), the article has fundamental math errors that  make it even more laughable.

The article claims that because influenza vaccines have 25 ug of thimerasol, they exceed the EPA exposure limit by a factor of 250 times. He then goes on to claim that if someone gets annual vaccinations for 10 years they’d exceed the limit by 2500 times. The exposure limit he is talking about is the US EPA chronic oral reference dose of 0.1 ug per kilogram body weight per day for methylmercury.

Even ignoring the fact that thimerasol (ethylmercury) is much less toxic than methylmercury and has a much shorter half-life in the body, and therefore using the methylmercury reference dose is completely inappropriate, and also ignoring the fact that very few flu vaccines have that much thimerasol, the author doesn’t seem to get either the “per kilogram body weight” part or the “lifetime average” part.

Assuming someone gets 1 flu shot per year, the actual chronic dose would be 0.068 ug per day thimerasol. We still have to adjust for body weight though. Even an infant weighing only 5 kg (which since the vaccine isn’t given to babies under 6 months is pretty low) would have an annual dose-equivalent of 0.014 ug/kg/day – about an order of magnitude below this “limit”, and it drops over time as the person’s body weight increases, so the lifetime average exposure would end up about an order of magnitude or so below that (2 orders of magnitude below the limit). So even if you consider ethylmercury to be as toxic as methylmercury (which it isn’t), you still end up about 100 times below the US EPA limit, or 10 times below even if you don’t amortize over a lifetime and just look at infant exposure.

In reality you shouldn’t even be comparing an acute (short-term) dose to a reference dose based on average lifetime exposure, but if you’re going to do that at least get the math right. It’s apparent that Anthony Gucciardi is completely without a clue on this subject (and from a quick look also on the other topics he writes about) and that “the Canadian” is not even remotely credible as a source of news. The flu vaccine is quite safe.

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