Arsenic in Seafood and Seaweed

Arsenic in fish is almost always harmless. But to be safe, find out whether the fish, shellfish and seaweed you like to eat has arsenic that could be harmful to you and your family, particularly if you are exposed to arsenic through private well water, other foods or other sources.

Should you be concerned about arsenic in seafood and seaweed?

It depends. The arsenic in most seafood is usually harmless. Some types of seaweed have high inorganic arsenic, which is the most harmful to people. Shellfish from some areas can also have higher levels of inorganic arsenic. Vary what you eat and avoid eating one kind of food all the time if it has higher levels of arsenic. If you could be exposed to arsenic from well water, other foods or other sources, make sure to reduce your total exposure.


  • Don’t eat Hijiki seaweed. This is a seaweed that’s used in some Asian cooking. It’s not the seaweed used as a wrap in sushi.
  • Don’t eat shellfish that’s labeled as unsafe due to arsenic (or other contaminants).
  • Review your local fish advisory to know which fish are the safest to eat in your area.
  • Keep eating seafood for good health.
  • Be sure to consider your total arsenic exposure from well water, other foods or other sources.

Arsenic Types Explained

Inorganic Arsenic: The most toxic form of arsenic. Inorganic arsenic occurs naturally in soils and groundwater used as drinking water in certain parts of the world. It is also found in certain foods.

Arsenobetaine: Arsenobetaine is an organic arsenic compound that is the main type of arsenic found in fish. Unlike inorganic arsenic compounds and other organic arsenic compounds, arsenobetaine is not harmful to humans.

Organic Arsenic: Other chemical forms of arsenic found in some seafood, some of which are less toxic than inorganic arsenic. Scientists are still learning more about the health effects of different organic arsenic compounds.

Why is arsenic in seafood and seaweed?

It’s complicated! Ocean plants and animals take in arsenic from seawater. Most fish and shellfish store arsenic in a harmless form called arsenobetaine. Hijiki seaweed and shellfish in some areas contain inorganic arsenic resulting in state or local fish advisories; these should be eaten rarely or avoided.

“For most people, seafood consumption is the largest source of dietary arsenic, but the arsenic is a harmless form called arsenobetaine. Hijiki seaweed and some rare types of shellfish may be high in toxic inorganic arsenic, and consumers should make an effort to limit or avoid those foods when possible. However, most seafoods, including fish, shellfish and other seaweeds, contain little inorganic arsenic, but in addition to arsenobetaine they contain other forms of organic arsenic. Scientists are studying these forms of arsenic, which are considered far less toxic than inorganic arsenic.”

Dr. Ken Reimer, Royal Military College of Canada