How safe levels are set for chemical residues in food

Foods can contain residues from chemicals used during farming and in their production. Learn how we set residue limits to ensure food is safe to eat.

About chemical residues in food

Chemical residues can be natural or man-made and can enter our food in several ways. They may:

  • be found in the environment where food grows, such as lakes and seawater where fish are found
  • leach into foods from packaging, such as plastic packaging
  • be caused by food production and processing methods
  • be added illegally during production.

Chemicals are often used during farming and food production. These are known as "agricultural compounds" and include:

  • fertilisers
  • pesticides
  • antibiotics and other medicines for animals
  • growth hormones.

Rules and limits are set for how much of a chemical can be present in our food. This ensures that:

  • good farming practice is followed
  • food is safe to eat.

Find out more about agricultural compound residues in food

How safe levels are set for chemical residues in food

There are "maximum residue levels" (MRLs) for most agricultural compounds used in farming and food production. The levels determine how much of a certain chemical is allowed in our food. The labels on the agricultural compounds have instructions to ensure that the MRLs are followed.

Food that exceeds an MRL cannot legally be sold in New Zealand. We investigate and take action when food contains too much of a certain chemical.

MRLs and food safety

The MRLs are set at levels that are well below the level that would harm somebody's health.

Even if residues in food are at higher levels than the MRL allows, it isn't usually a food safety or health concern. This is because the system for setting MRLs sets them much lower than the level which could harm health. 

If you're still concerned, you can reduce your exposure by:

  • thoroughly washing all produce, especially if eating raw
  • eating undamaged produce that looks fresh
  • making sure foods are properly cooked.

Setting levels for how much of a chemical is safe to consume

MRLs determine how much of a chemical residue can be present in food. On the other hand, "acceptable daily intakes" (ADIs) determine how much of a chemical a person can safely consume over a lifetime.

ADIs are set for:

  • food additives
  • antibiotics and other medicines for animals
  • pesticides.

A "tolerable daily intake" (TDI) is set for:

  • natural toxins
  • environmental contaminants.

Setting an ADI at a safe level

The ADI is always at least 100 times lower than the highest safe dose fed to animals. If there's uncertainty, the ADI can be set at 1,000 or 10,000 times lower than the highest safe dose.

ADIs also apply to children

Chemicals in foods can potentially have a greater impact on very young children (less than 12 weeks) because:

  • their bodies are not fully developed
  • they eat more food (and any chemicals in the food) relative to their body size.

However, ADIs are set based on consumption over an entire lifetime. The large safety margins help protect children and people sensitive to specific chemicals.

NZ diets are regularly checked against ADIs

Every 5 years, the Ministry for Primary Industries surveys foods sold in New Zealand. We assess New Zealanders' exposure to chemicals. We compare New Zealanders' intakes of these chemicals with ADIs to help us identify any potential health risks.

Learn more about the New Zealand Total Diet Study

Find out more

Food additives and preservatives

Food monitoring and surveillance

Maximum residue levels (MRLs) for agricultural compounds (ACVM)

Who to contact

If you have questions about chemical residues in food, email info@mpi.govt.nz

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