With glyphosate being in the non-agricultural media over the past few months it is a good time to look at chemical residues in food and explain how acceptable levels are determined for various food types.

Chemical residues will be found in all foodstuffs. When herbicides, fungicides and insecticides are applied to a crop or pasture, they break down over time into other chemicals. The quantity and nature of these chemicals (residues) will vary between the type of chemical and the environment to which they are exposed.

Setting allowable levels of chemicals in foods
The Australian Pesticides and Veterinary Medicines Authority (APVMA) determine the maximum residue limits (MRL) for agricultural and veterinary chemicals in agricultural produce. Pesticide labels are designed to ensure that the use of those pesticides does not lead to higher than the determined MRLs in foodstuffs.
Not exceeding MRLs is extremely important to protect the environment, human health and trade.
The three main steps in assessing the safety of agricultural and veterinary chemicals in food are:

  • Toxicological – scientists review large numbers of animal feeding studies to evaluate short and long-term risk of consuming different chemicals. These studies help determine the No Observable Effect Level (NOEL) which is used to set the acceptable daily intake for a chemical. The NOEL used to set the acceptable daily intake is generally that for the most sensitive animal species in the studies.
    The Acceptable Daily Intake (ADI) – is the amount of chemical that can be consumed every day for an entire lifetime without an appreciable increase in risk to health.
    The Acute Reference Dose (ARfD) – is an estimate of the maximum amount of a chemical in food or drinking water expressed as milligrams per kilogram of body weight that can be consumed in one meal or one day without an appreciable increase in risk to consumer health.
  • Maximum residue limit (MRL) – is the highest concentration of a chemical residue that is legally permitted or accepted in a food or animal feed. Concentration is expressed in milligrams per kilogram (mg/kg) of the commodity. Australian MRL Standard (Schedule 20) can be found at the Federal Register of Legislation website . A list of global MRL databases can also be found at the Department of Agriculture website . The APVMA determines the MRL after a comprehensive analysis and calculates the minimum amount of pesticide required for effective control and that leaves minimal or no residue on the commodity. This data also helps set appropriate harvest and export withholding periods for the pesticide.
  • Dietary exposure – the APVMA uses the MRL to conduct a dietary exposure evaluation. Food Safety ANZ (FSANZ) conducts a review and undertakes public consultation before incorporating the MRL into Australian Food Standard Schedule 20.

National and state-based surveys are also carried out to monitor residue levels in food

  • National residue survey (NRS) – conducted by the Commonwealth Department of Agriculture and Water Resources to manage the risk of chemical residues and environmental contaminants in Australian animal and plant products. It aims to provide an estimate of residues in products, confirm that residues in products are below set limits and alert responsible government authorities and industry, if limits are exceeded.
  • Australian total diet study – Food Standards Australia New Zealand monitor the food supply to ensure that existing food regulatory measures provide protection of consumer health and safety. It is conducted every two years with samples collected by state and territor