heavy metals

Seafood Lover’s Mercury Monitor

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By J. E. Hinners, MD MPH SeafoodLove seafood + hate mercury?

Me too.

Sometimes ignorance is bliss.

I remember when I first learned that many seafoods contain the neurotoxic, heavy metal of mercury, I was quite devastated and began internally banning seafood from my food choices, as a result.

After all, the body is believed to absorb over 95% of the methymercury found in seafood, letting the metal freely flow through your blood stream to tissues and organs. Mercury toxicity in humans can affect brain and nerve health, and there have also been some questionable links to cancer.

Salmon ok?

Later, however, I had read that salmon was one of the few seafoods with lower mercury levels. So I upgraded my seafood allowance to include the occasional dish of salmon.

But then I learned about the dangers of farm-raised salmon, and my heart sank. I now had to be vigilant even about the one occasional seafood allowance I had been giving myself. And when I did have the occasional splurge of any other seafood, I couldn’t get rid of my awareness and guilt over the fact that I was probably just adding mercury to my body’s system with every bite I took.

This is no fun!

I love the taste of seafood, and there’s no other food I prefer particularly when I have the luxury of dining at a coastal restaurant.

 I am a believer of allowing occasional “unhealthy food” splurges in moderation–but when it comes to mercury levels in seafood, what does a “safe level of moderation” mean?

Blissful ignorance may be dangerous, but having only a partial knowledge of something can be equally–if not exceedingly–dangerous.

Why write off most of my beloved seafood altogether if perhaps a better understanding of the varying mercury levels might let me still safely enjoy the occasional seafood dish–and maybe even more frequently than I had previously allowed myself?

Seafood: a healthy or unhealthy food?

On a side note, I would not go so far as labeling all seafood “unhealthy” overall–on the contrary, there are many health benefits of seafood, including brain health from omega-3’s and improved wound recovery from argnine, among other things.

But in cases where the health hazards from consuming seafood would outweigh the health benefits, I would categorize that particular seafood or level of seafood consumption as “unhealthy.”

By identifying seafood mercury levels and conservatively estimating safe dose limits, we will better be able to determine the point up until which we can more freely enjoy consuming seafood before the health hazards begin to outweigh the health benefits.

Conservative estimation of safe dose limits

The Natural Resources Defense Council has put out a very helpful and specific guide for safe dose limits for pregnant women that I will be directly using in the lists below. The guidance assumes a 6 oz. serving of cooked fish for a woman of 130 lbs (60 kg) who is either pregnant or planning to become pregnant, since such women are at greater risk from mercury toxicity compared to non-pregnant women. These guidelines are therefore conservative estimates for both women who are not pregnant as well as for men (but not for children, however).

The specific mercury concentration mean (ppm) values provided below following each seafood item have been obtained from the FDA’s database of mercury levels in commercial fish and shellfish.

LOWEST Mercury Level Seafood


Lowest mercury level seafood (safest)

Recommended servings per month: No specified restrictions

  • Anchovies, 0.017
  • Butterfish, 0.058
  • Catfish, 0.025
  • Clam, 0.009
  • Domestic Crab, 0.065
  • Crawfish/Crayfish, 0.033
  • Atlantic Croaker, 0.065
  • Flounder, 0.056
  • Atlantic Haddock, 0.055
  • Hake, 0.079
  • Herring, 0.084
  • N. Atlantic/Chub Mackerel, 0.05/0.088
  • Mullet, 0.05
  • Oyster, 0.012
  • Ocean Perch, 0.121
  • Plaice, 0.056
  • Pollock, 0.031
  • Canned Salmon*, 0.008
  • Fresh Salmon*, 0.022
  • Sardine, 0.013
  • Scallop, 0.003
  • American Shad, 0.045
  • Shrimp, 0.009
  • Pacific Sole, 0.056
  • Calamari/Squid, 0.023
  • Tilapia, 0.013
  • Freshwater Trout, 0.071
  • Whitefish, 0.089
  • Whiting, 0.051

*Farmed salmon, however, is not recommended, as it contains harmful chemicals

 MODERATE Mercury Level Seafood


Moderate Levels

Recommended servings per month: 6 or less

  • Striped/Black Bass, 0.152
  • Carp, 0.11
  • Alaskan Cod, 0.111
  • White Pacific Croaker, 0.287
  • Atlantic Halibut, 0.241
  • Pacific Halibut, 0.241
  • Silverside Jacksmelt, 0.081
  • Lobster, 0.166
  • Mahi Mahi, ?
  • Monkfish, 0.181
  • Freshwater Perch, 0.15
  • Sablefish, 0.361
  • Skate, 0.137
  • Snapper, 0.166
  • Canned Chunk Light Tuna, 0.128
  • Skipjack Tuna, 0.144
  • Sea Trout Weakfish, 0.235

 HIGH Mercury Level Seafood


High levelsRecommended servings per month: 3 or less

  • Bluefish, 0.368
  • Grouper, 0.448
  • Spanish/Gulf Mackerel, 0.454
  • Chilean Sea Bass, 0.354
  • Canned Albacore Tuna, 0.35
  • Yellowfin Tuna, 0.354

HIGHEST Mercury Level Seafood


Highest levels

Recommended servings per month: Avoid these foods altogether, if possible

  • King Mackerel, 0.73
  • Marlin, 0.485
  • Orange Roughy, 0.571
  • Shark, 0.979
  • Swordfish, 0.995
  • Gulf of Mexico Tilefish, 1.45
  • Bigeye/Ahi Tuna, 0.689

Smaller tends to be safer

If you’re in a restaurant, and you’re blanking out on which seafoods to avoid, you can generally more safely order a seafood item that’s of a smaller size; these foods tend to have less mercury.

The reason for the lower levels in the smaller seafoods is that mercury is accumulated in seafood as a result of industrial mercury emissions, which have slowly increased over time and are projected to continue to increase.

Sea animals feed on tiny plants and other animals containing mercury, thereby acquiring mercury in their own tissues. Since the larger sea creatures eat more quantities of these mercury-containing creatures over longer periods of time, mercury accumulates in much larger levels than in the smaller sea creatures.

Curious about your mercury consumption last week?

Try out the more personalized mercury calculator by the National Resources Defense Council.

Eat up!

So next time you’re feeling paranoid about consuming mercury through seafood, perhaps these conservative monthly dose limits can help set you free to eat up wisely and enjoy!

Er…maybe just be sure your regular dose of seafood isn’t coming from Japan 🙂