Setting of Maximum Residue Limits
The maximum residue limit (MRL) is the maximum concentration of a residue, resulting from the registered use of an agricultural or veterinary chemical. MRLs set by the APVMA are referred to Food Standards Australia New Zealand (FSANZ) for incorporation into Standard 1.4.2 of the Food Standards Code entitled "Maximum Residues Limits". The Foods Standards Code is adopted by various state laws so that the MRLs become the maximum concentration of a residue, resulting from the registered use of an agricultural or veterinary chemical legally permitted or recognized as acceptable in or on a food, agricultural commodity, or animal feed.
MRLs are set for all types of raw food commodities (and some processed commodities) where the use of agricultural or veterinary chemicals is required for efficient practice. Such foods may be either of plant or animal origin and may be used for consumption by humans or animals. Residues can arise by either direct or indirect exposure to plants or animals. In animals, for example, feeding of grain or forage that has been treated with pesticide or has been grown in pesticide-treated soil may result in residues in animal tissues or in milk.
MRLs are set by the APVMA, during the evaluation of chemical products prior to registration. Evaluators consider detailed submissions on the use of the agricultural or veterinary chemical and other information including recommendations made by other governments and internationally-recognized organizations.
When MRLs are being determined, evaluators consider the most extensive permitted use of the product. They consider 'the maximum label use pattern', which defines Good Agricultural Practice (GAP) or Good Veterinary Practice (GVP) needed to control diseases or pests. The consideration takes into account such factors as:
- how accurately the chemical and/or toxicologically significant metabolites can be measured in animal tissues arid/or plant material
- how rapidly the chemical may be processed by either plant and/or animal tissues
- how rapidly the chemical may be degraded by soil and other environmental processes
- how frequently and at what intervals the chemical is used, taking into account the potential for bio-accumulation
- how close to harvesting of plants, collection of milk and eggs and/or slaughtering of livestock the chemical is used (including withholding periods)
- the acceptable dietary exposure to low levels of chemicals in food
- the effects of processing (e.g. flour from wheat; wine and dried fruit from grapes; sugar from sugar cane), and
- any differences in MRLs and residue definitions between Australia and its major trading partners and those of the Codex Alimentarius Commission of the United Nations.
Every country registers chemicals under their own regulations and according to their domestic GAP or GVP. Differences between Australia and overseas MRLs may occur for a number of reasons. These include different use patterns (presence of pests in one country but not in another, uses on the same crop but at different concentrations for control of different pests), toxicological considerations (ADIs), analytical methodology and/or residue definition.
Review and Gazetting of MRLs
Evaluations are subject to peer review. Public comment is sought, when a product containing a new active constituent is considered for registration for the first time or when a product containing an existing active constituent is first considered for registration for use on a food commodity or when there are possible trade implications arising from registration.
MRLs are gazetted by the Australian Pesticides and Veterinary Medicines Authority as amendments to the MRL Standard. For MRLs in human foods, the MRLs set by the APVMA are advanced to the Food Standards Australia New Zealand for incorporation into the Standard 1.4.2 of the Food Standards Code. In the case of MRLs in animal feeds, the entries in the MRL Standard are usually adopted into the appropriate State legislation.
Monitoring of chemical residues in food
National programs such as the Food Standards Australia New Zealand’s Australian Total Diet Survey (external site) and the Department of Agriculture, Fisheries and Forestry - Australia National Residue Survey (external site) monitor the residues found in food destined for human consumption within Australia or for export.
Various State, Territory, retailers and grower groups also monitor residue levels in food.
The commodity descriptions used throughout this document conform, where possible, with the Codex Classification of Foods and Anima/ Feeds (second edition, 1989) published by the Codex Alimentarius Commission. This international body, in collaboration with the World Health Organisation of the United Nations and other international bodies, sets standards for foodstuffs in international commerce.