The Food Standards Agency is advising people not to eat a type of seaweed called hijiki because of the high levels of arsenic that it contains.
A survey carried out by the Agency found that hijiki contains inorganic arsenic, a form that occurs naturally in some food and can increase people's risk of developing cancer if eaten regularly.
Hijiki is a distinctive, almost black, shredded seaweed, that is used mainly as an appetiser or starter in some Japanese restaurants. It is not used in sushi or in Chinese restaurants. If you have eaten hijiki occasionally it is unlikely that you have raised your risk of developing cancer significantly.
Hijiki is also sold for use in soups and salads and some vegetarian and vegan dishes where seaweed is an ingredient. It is sometimes found in the specialist food sections of some supermarkets and department stores and in health food shops and specialist shops selling Asian and Far Eastern food.
The Agency carried out a survey of five different types of seaweed following reports from Canada that there was a problem with hijiki. They also tested arame, kombu, nori and wakame and didn't find inorganic arsenic in these types of seaweed.