Arsenic is a chemical found in soils, rocks and water, and in tiny amounts in many foods. While arsenic can be toxic to humans, exposure through food is very unlikely to make you sick. Learn more about arsenic, how it may affect your health, and how arsenic levels in food are monitored.

What is arsenic?

Arsenic is an element found naturally in the environment – in soils, rock and water. There are 2 types:

  • organic arsenic – which has a relatively low level of toxicity
  • inorganic arsenic – which is much more toxic than organic arsenic and can increase your cancer risk if you regularly eat foods that contain relatively high levels.

Environments with higher arsenic levels

All soils contain arsenic, but levels can be higher because of:

  • past use of pesticides containing arsenic
  • nearby industrial sources, like smelters or coal-fired power plants
  • volcanic activity.

Groundwater from areas that have geothermal activity or arsenic-rich rocks can contain very high levels of arsenic.

Arsenic in our food

Most foods contain trace levels of arsenic, which may be organic or inorganic. Arsenic cannot be removed from food by cooking, but exposure to low levels of either arsenic type is not a health concern.

Foods containing higher levels of arsenic

Some foods contain relatively high levels of arsenic, and should be eaten in moderation.

Plant-based foods

Most plants don't accumulate inorganic arsenic from soil, but some do. Relatively high levels have been found in:

  • watercress growing in geothermal regions and near the Waikato River. Watercress from other regions in New Zealand has very low arsenic levels
  • some rice – particularly rice products that still have their husk (such as brown rice)
  • some seaweeds and seaweed products. High levels of arsenic have been found in hijiki, a seaweed typically used in soups, salads and vegetable dishes. Hijiki is black in colour and sold in thin strips or shreds.

Information on harvesting watercress safely can be found in Te Kai Manawa Ora Marae Food Safety Guide.

Download the guide [PDF, 13 MB]

Fish and seafood

While fish and seafood can accumulate relatively high amounts of organic arsenic from the environment, this is tightly bound to a protein and does not get absorbed into your body.

How can arsenic affect health?

Long-term exposure to inorganic arsenic can cause skin lesions and some forms of cancer, and has been linked to other illnesses including diabetes and heart disease.

The greatest risk is to people living in countries with high levels of arsenic in groundwater – including Bangladesh, Chile, China and the United States – which can also affect foods grown in those areas.

Surveys show safe levels in New Zealand diet

MPI runs a survey every 5 or 6 years that tests more than 120 foods commonly eaten by New Zealanders. The New Zealand Total Diet Study then estimates New Zealanders' exposure to chemical residues, contaminants and selected nutrients.

As part of this survey, we monitor total arsenic in individual foods. To date, the survey has shown the potential arsenic content of the typical New Zealand diet remains well within safe levels.

Standards will be reviewed

The Food Standards Code sets maximum limits for arsenic in foods that are most likely to have high levels, including rice and seaweed products.

Food Standards Australia New Zealand (FSANZ) will be reviewing these standards after Codex Alimentarius (which sets international food standards for foods in trade) reassessed acceptable arsenic levels in some foods in 2015 and 2016.

Find out more

Who to contact

If you have questions about arsenic levels in food, email

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