This page contains background information on the establishment of maximum residue limits (MRLs).

What is an MRL?
The maximum residue limit, or MRL, is the maximum concentration of residue accepted by the European Union (EU) in a food product obtained from an animal that has received a veterinary medicine. The residues found in animal products following the administration of the medicine to the animal may be the active substances of the medicine itself, similar substances produced when the medicine is broken down in the body, or other ingredients of the medicine.

Background
The EU requires by law that foodstuffs (such as meat, milk or eggs) obtained from animals treated with veterinary medicines must not contain any residue that might represent a hazard to the health of the consumer. Before a veterinary medicine intended for food-producing animals can be authorised in the EU, the safety of its substances and their residues must first be evaluated. Food-producing animals are defined as those animals bred, raised, kept, slaughtered or harvested (e.g. aquaculture fish) specifically for the purpose of producing food for human consumption.

Once the substances have been assessed, they are listed in Annex I, II or III of Council Regulation (EEC) No 2377/90, as follows:
Annex I: Substances for which final MRLs have been established.
Annex II: Substances that do not need an MRL to protect the safety of the consumer.
Annex III: Substances with provisional MRLs. When not all aspects of the substance have been fully addressed at the time of the authorisation, provisional MRLs can be set for a defined period not exceeding five years, provided that there are no grounds for supposing that residues of the substance at the level proposed will present a hazard to the health of the consumer.
Annex IV: Substances that cannot have an MRL because residues of such substances are a risk to the safety of the consumer at whatever level. These substances cannot be used in medicines destined for use in food-producing animals.

Controls and Monitoring
Residue control programmes in the EU Member States monitor that defined MRLs are not exceeded.

To ensure that food products obtained from animals treated with veterinary medicines do not contain residues above the legally permitted MRL, withdrawal periods are set, fixing the minimum period that must be respected between the last administration of the medicine to the animal and the production of foodstuffs from the animal.

MRLs are normally set for two tissues of the animal carcass (muscle and fat), two offal tissues (liver and kidney), and milk, eggs or honey, as appropriate.