Mercury in Seafood

On the hunt for swordfish.

Introduction to Mercury; Not The Planet
By Carl Safina

And we care about mercury because…? Because if you’re eating seafood, it’s got mercury. And because mercury poisoning is rare, but the risks are real. And mainly because if you understand the risks—you don’t have to worry.

Richard Gelfond is the CEO of IMAX movie theaters. A few years ago he noticed that when he was running, he was suddenly having trouble with balance. He dismissed it until he began having difficulty even walking. His wife had to hold his hand while stepping off curbs. He thought it was stress, until one day—he simply fell down.

Mr. Gelfond’s doctors couldn’t figure out what his problem was. First they suspected a brain tumor. Then they simply suspected that Mr. Gelfond was lying when he insisted he wasn’t an alcoholic. Months of frustration and worsening health ensued.

It was an article in the New York Times—not the physician’s training—that finally caused his frustrated doctor to ask his frustrated patient, “Do you eat a lot of fish?”

“What kind of question is that?,” Gelfond thought. He replied that in fact he had a very healthy diet—he ate fish about 14 times a week. The doctor arranged for yet another blood test; this time, they’d be looking for mercury. A blood mercury concentration over 5 milligrams per liter is cause for concern; Mr. Gelfond’s was 76. Diagnosis: severe mercury poisoning.

And yet, Mr. Gelfond could not locate a doctor in all of New York City who knew what to do for him. The only thing they could offer was, “Don’t eat any more fish; you’ll probably get better.”

(Scroll down to see: “Medical Masquerade: One Man’s Experience with Methylmercury Poisoning” –  Mr. Gelfond begins at 4 minutes.)

So part of the reason we’re interested in mercury is to help create a better-informed medical community, and to spread the word to nutritionists and seafood lovers to be on the lookout for mercury, to understand about mercury in seafood, and to stay healthy.

Another reason: it’s close to home for me too. As a lifelong avid fisherman, 30 years ago I started eating fish I caught instead of buying meat. It was a big part of my diet; I ate fish probably five or six nights a week. And because I caught a lot, I served large portions.

As my fishing skills improved I sought bigger and bigger fish, until a very large proportion of my diet was tuna steaks and shark—some of the highest-mercury fish around. But at the time, I didn’t know much about mercury. Then I noticed that when I was driving, I was having trouble staying in the lane even on straight roads. I had to really concentrate, and do a lot of correcting with the wheel.

Like Mr. Gelfond’s physicians, I simply did not think about mercury poisoning, or make the connection between my driving and what I was eating. The problem went undiagnosed, but it’s likely that I’d given myself mercury poisoning.

Over time my fishing and eating habits changed; I went back to catching smaller fish. About 10 years after those weird driving episodes, I found myself talking to the physician who was quoted in the article that first alerted Mr. Gelfond’s doctor to the possibility of mercury. He tested my hair and found a mercury concentration of 1.3 parts per million. That’s a lot higher than most people’s, which usually ranges from about 0.3 to 0.8 parts per million, but it was well below the level at which most people would become sick. (The concentration in hair can’t be compared to that in blood; the levels differ and are measured differently).

The thing is, when I got my hair tested I was probably still eating fish several times a week. But I was eating small fish, one-to-two pounders that I caught from my kayak along the shore. That’s a lot different than eating big, open-ocean fish that were 100 times larger; because with mercury, size matters. It makes the difference; the bigger the fish, the bigger the mercury dose.

And a big part of what I hope you get from all this is: it’s not about avoiding fish; it’s about avoiding mercury.

We’ve put together a report intending to shed light on a topic that can seem confusing. I hope you find it enlightening and clarifying. And I hope it helps to keep you healthy. –Carl Safina

For more advice, read on: 

The Safina Center’s Mercury Video Tutorial (below.)