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Survey of total and inorganic arsenic in seaweed

Project Code: C02042

14/05/2004

The Food Standards Agency has completed a survey of total and inorganic arsenic in five varieties of seaweed. Arsenic is present in food in different chemical forms, with inorganic forms being the most toxic. Most arsenic in the diet is present in less harmful organic forms. Results from this survey showed that one seaweed variety, hijiki (or hiziki), contains a significant level of inorganic arsenic, which is known to cause cancer, if it were regularly consumed over an extended period of time.

The key facts of this survey are:

The survey was commissioned following a report that the Canadian Food Inspection Agency was advising consumers to avoid the consumption of hijiki seaweed due to its high inorganic arsenic content.
Concentrations of total and inorganic arsenic were measured in a total of 31 samples covering five varieties of seaweed (arame, hijiki, kombu, nori and wakame) found in a range of outlets in the London area. Analysis was carried out by the Central Science Laboratory (CSL).
Seaweed is generally sold in dried form. Where preparation by soaking was recommended prior to consumption, measurements were carried out on both the initial and prepared forms and on the water collected after soaking.
Arsenic was detected in all samples. In most cases it was present in organic forms, which are not thought to represent a significant risk to health. Inorganic arsenic, a form that can cause cancer, was only detected in the nine samples of hijiki seaweed tested.
Consumption of hijiki seaweed would significantly increase daily dietary exposure to inorganic arsenic. Consumers are therefore advised not to eat hijiki seaweed.

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