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Food Safety: How Much Mercury is Safe in Seafood?

Pregnant Women, Child-Bearing Women, and Children

What is mercury?

Mercury, also known as quicksilver, is a heavy metal like cadmium or lead, that exists in various chemical forms.

It primarily enters the atmosphere from coal-burning electric utilities. It later becomes more toxic when bacteria in lakes and oceans convert it into methylmercury, which fish and shellfish absorb into their tissues. Larger predatory fish — like sword fish— will likely harbor more methylmercury due to its size.

Pregnant Women

Methylmercury is especially dangerous to pregnant women, nursing mothers, and young children. Even small amounts can effect the developing brain and have neurological and behavioral effects. In addition, dietary methylmercury may increase the risk of heart disease in some adults.

Seafood is not only delicious, but also nutritious. It is low in saturated-fat, has high-quality protein, and is rich in heart-healthy omega-3 fatty acids. It’s no wonder why many public health experts are eager to decide the amount of mercury that can be safely consumed in seafood.

Based on the current FDA guidelines, women of childbearing age, especially if they are already pregnant or nursing, and young children should avoid the following seafood:

  • Shark

  • Marlin

  • Orange roughy

  • Big eye tuna

  • Swordfish

  • King mackerel

  • Tile fish

In addition, you should limit yourselves to 12 oz (340 g) of any other fish or seafood per week.

Seafood that is lowest in mercury:

  • Catfish

  • Flounder

  • Salmon

  • Shrimp

  • Haddock

  • Pollock (used in frozen fish products)

  • Sardines

  • Crab

  • Scallops

Helpful Tips

When selecting canned tuna, choose “light” over “white” varieties.


  1. Berkoff, F. G., & Schwarcz, J. (2018). Foods that harm, foods that heal: What to eat to beat disease and live longer. Reader’s Digest.

  2. Mercury. Mercury: 1. What is mercury? (n.d.).


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