Last updated on 24 March 2004

Mercury in fish: your questions answered

Find out more about our latest advice about mercury in fish.

  • Mercury in fish

    Nearly all fish contain traces of mercury and in most fish this is not a problem. But certain fish contain relatively higher levels of mercury.

  • Which fish are we talking about?

    Pregnant women and women intending to become pregnant should avoid shark, marlin and swordfish. They may also need to limit the amount of tuna they eat.

  • Who could be affected by the mercury and why?

    This is mainly an issue for pregnant women and women who intend to become pregnant. This is because of the possible risks to the developing nervous system of the unborn child.

  • Are other adults affected?

    High levels of mercury can affect anyone, but while no one else over 16 years of age needs to avoid shark, marlin and swordfish, the Agency does advise that people should not eat more than one portion of any of these fish once a week.

  • Can I still eat tuna?

    Yes, everyone can eat tuna. But the mercury that it contains means that the Agency is advising that if you are pregnant or intending to become pregnant, you shouldn’t eat more than four medium-sized cans or two fresh tuna steaks per week.

  • What is the advice for children?

    Children under 16 should avoid eating shark, marlin and swordfish.

  • I’m pregnant and have been eating a lot of tuna, have I harmed my child?

    You are unlikely to have caused your unborn child any harm, as this is a limit with a safety margin built in. But to be on the safe side, you should now limit the amount of tuna you eat.

  • I’m pregnant and still want to eat fish, what should I do?

    You should not eat shark, marlin or swordfish and you may need to limit how much tuna you eat. Everyday favourites such as cod, haddock and plaice are not affected at all by this advice. And there are other oily fish with known health benefits that you can eat as an alternative to fresh tuna, such as mackerel, herring, pilchard, sardine, trout or salmon.

  • Is fish still an important part of a healthy diet?

    Yes. And most of us don’t eat enough of it. The Agency recommends that people eat at least two portions of fish a week, one of which should be oily. Oily fish provide known health benefits – for example, it contains nutrients that protect against heart disease. Although fresh tuna is an oily fish, during the canning process these fats are reduced, so canned tuna does not count as oily fish.

  • Why is this advice being updated?

    The Agency has updated its advice in the light of a new opinion from the independent Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. The COT revised its opinion following updated guidelines on mercury from the World Health Organization.