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Inorganic arsenic in hijiki seaweed

Hijiki seaweed was added to New Zealand’s high risk foods list after it was found to contain levels of inorganic arsenic that were higher than the regulatory level. Exposure to low levels of organic or inorganic arsenic is not a health concern, however consumers are advised not to eat large amounts of hijiki seaweed.

The issue with hijiki seaweed

Tests were carried out on hijiki seaweed products in New Zealand after we had been alerted by some of our international counterparts that unacceptable levels of inorganic arsenic had been found in hijiki seaweed overseas.

All of the hijiki seaweed products tested in New Zealand were found to contain levels of inorganic arsenic that were higher than the regulatory level. Consequently, hijiki seaweed has been added to New Zealand’s high risk foods list.

The Canadian Food Inspection Agency and the UK’s Food Standards Agency are advising people not to consume hijiki seaweed because of survey results that show it contains high levels of inorganic arsenic. Food Standards Australia New Zealand (FSANZ) also performed a risk assessment on inorganic arsenic in hijiki seaweed in conjunction with us and provided the same advice to consumers in Australia.

How NZ is ensuring hijiki seaweed sold here is safe

Very little hijiki is imported into New Zealand (estimated at less than 300kg per year) so this does not represent a major problem for New Zealand consumers. However, we have followed similar action taken by Canada and the UK in assessing hijiki products for levels of arsenic and all hijiki products are now tested for this element before release for sale in New Zealand.

We have added hijiki seaweed to the high risk foods list. All hijiki seaweed that enters New Zealand is now tested before being released for sale. It will only be released for sale if it is shown to have arsenic levels that are within the regulatory limits. This means that hijiki seaweed for sale in New Zealand will meet the regulatory requirements for inorganic arsenic. It is only this one type of seaweed that is affected, and is not common in the diet of most New Zealanders.

How hijiki seaweed is usually consumed

Hijiki seaweed (also known as hiziki or MeHijiki (Hizikia fusiforme)) is usually sold for use in some soups, salads and vegetable dishes. It is mainly used in Japanese restaurants as an appetiser or starter. It is not the seaweed used in sushi. Hijiki seaweed can also be found in shops selling Asian or eastern food products. This type of seaweed is easy to distinguish from other seaweeds because of its distinctive black and shredded appearance.

Human health implications of hijiki seaweed

Exposure to low levels of organic or inorganic arsenic is not a health concern. Organic arsenic is commonly found in seaweed and other marine foods but has not been linked to any human illnesses.

Inorganic arsenic, formed from the combination of arsenic with oxygen, chlorine or sulphur, is more toxic and is known to add to the risk of people getting cancer if it is regularly consumed.

However it is not usually found at high levels in food. Hijiki may contain high levels of inorganic arsenic.

Though short term exposure to low levels of inorganic arsenic is unlikely to cause any health problems, we advise consumers to avoid eating large amounts of hijiki seaweed. Most people who eat hijiki seaweed consume only a small amount daily. People who have eaten large amounts of hijiki over some time and who have concerns should consult their doctor.

What is arsenic?

Arsenic is a common element occurring naturally and widespread in both living systems and geologically. It is naturally present in most soils, which may also be affected by:

• past use of pesticides containing arsenic

• proximity to smelters or coal-fired power plants

• erosion caused by intensive land use.

In addition, water often contains arsenic and extremely high levels may be found in groundwater from areas with geothermal activity and with arsenic rich rocks (Anke, 1986)¹.

Is arsenic normally found in our foods?

Arsenic occurs in food in organic and inorganic forms. Most foods contain trace levels of arsenic. Fish and seafoods can accumulate considerable amounts of organic arsenic from their environment (WHO, 1981)². The arsenic content of plants is usually determined by the arsenic content of the soil, water and air.

Arsenic and the food we eat

Page last updated: November 2007

¹ Anke M. (1986). Arsenic. In: Mertz W (Ed) Trace Elements in Human Nutrition and Animal Nutrition (fifth edition), Volume2. Orlando: Academic Press; 347-372

² WHO (1981) Arsenic. Environmental Health Criteria No 18 Geneva: World Health Organisation