The tuna argument smells fishy

“The amount in flu vaccines is much less than the daily limit recommended – for example a can of tuna fish has more mercury than the thimerosal in the H1N1 flu vaccine.”
— Public Health Agency of Canada website page

In an effort to reduce public fear related to thimerosal in the H1N1 vaccine, some Canadian government authorities have been using what I call the “tuna argument.” An example of this is above.

I’ve given it its own little name now (with air quotes of course) because it is turning into a pet peeve of mine. Since its first use, media sources have picked up on it and it’s been repeated in several print and online articles. Add this to its repetition from people I meet in the grocery store to my facebook friends, and this argument for the safety of thimerosal in vaccines is now irking me.

Now, before I proceed. Let’s keep in mind that I have not stated whether I am pro-vaccine or anti-vaccine or neutral on the whole thing. That’s because REGARDLESS of your stance, you’ve got to admit this tuna argument smells fishy.

Here’s why:

• Tuna is digested, not injected directly into the blood stream.
• I would not feed my 16-month-old child a whole can of tuna.
• According to Health Canada guidelines, this same child should only consume a maximum of 75 g of canned tuna/week to limit mercury exposure. One can of tuna weights 170g net.
• And last but not least, the type of mercury found in a can of tuna is methyl mercury (an FDA explanation is available here.) Thimersol, on the other hand, contains ethyl mercury.

It’s this last point on the type of mercury that makes the whole tuna argument so annoying to me. The form of mercury (methyl) found in tuna is far more dangerous than the form of mercury found in thimerosal (ethyl). Not only does the use of the “tuna argument” to allay fears seem just plain silly, it also seems counter-intuitive to the goal here.

Why not skip the tuna argument altogether and and just explain the difference between ethyl and methyl mercury?

Wouldn’t that be simpler? More clear? I don’t know … maybe it’s no big deal. Maybe I just ate too much tuna for lunch and I’m getting worked up for nothing.

In case you want to read the difference between the two types of mercury, here is an overview.