Maximum Residue Levels (MRLs)

Chemicals Safety Directorate definition

Maximum Residue Level (MRLs) are legal limits on pesticide residues in food. They are the maximum residue levels likely to be left in food after it has been treated with a pesticide. They assume that the user:

• used the pesticide according to its label conditions; and
• followed 'Good Agricultural Practice' (GAP)

MRLs provide a check that GAP is being followed and help international trade.

European Food Safety Authority (EFSA) definition

Maximum Residue Levels (MRLs) are the upper legal levels of a concentration for pesticide residues in or on food or feed based on good agricultural practices and to ensure the lowest possible consumer exposure.

Commission Regulation (EC) No. 396/2005 lists 320 defined commodities for which more than 152,000 MRLs have been set. Any commodity/pesticide combination for which there is no authorisation will automatically have a default value of 0.01 mg/kg.

For baby food, the European legislation is more restrictive than for other food categories as no more than 0.01 mg/kg of any single pesticide residue is permitted in baby food samples.

Foods derived from commodities that comply with the respective MRLs are intended to be toxicologically acceptable. If MRLs are exceeded this may indicate that GAP has not been performed. When an MRL is exceeded, comparison of consumer exposure with the Acceptable Daily Intake (ADI) and/or Acute Reference Dose (ARfD) will indicate whether, or not, there are possible chronic or acute health risks.

Acceptable Daily Intake (ADI)

The acceptable daily intake is the amount of a substance which can be ingested every day of an individual's entire lifetime, in the practical certainty, on the basis of all known facts, that no harm will result. The ADI is expressed as milligrams (mg) of chemical per kg body weight of the consumer. The ADI is derived from the most appropriate No Observed Adverse Effect Level (NOAEL) by applying an assessment factor normally 100.

Acute Reference Dose (ARfD)

This is intended to define (on the basis of all known facts at the time of the evaluation) an estimate of a chemical substance in food (or drinking water), expressed on a bodyweight basis, that can be ingested over a short period of time, usually during one meal or one day, without appreciable health risk to the consumer Joint FAO/WHO Meeting on Pesticide Residues (JMPR).

Methods of Analysis

The majority of pesticides can be analysed using multi-residue methods of analysis (MRMs) based on GC-MS and/or LC-MS instrumentation. Pesticides that are not amenable to MRMs, typically polar analytes or pesticides with multi-component complex MRLs, are analysed using more selective or single residue methods (SRMs). Details of both MRMs and SRMs are provided at the EU-RL website.

Accreditation

All official laboratories within the EU are expected to be accredited to ISO 17025. Fera is accredited for a number of MRM and SRM methods covering a large number of pesticides and their metabolites in a wide variety of foods and beverages. A copy of Fera's UKAS schedule of accreditation is available.

Method Validation and Quality Control Procedures

The latest Guidance document on analytical quality control and validation procedures for pesticide residues analysis in food and feed provides guidance to laboratories that are involved in the official control of pesticide residues in food and feed within the European Union.

The key objectives of this document are:

i) to provide a harmonised cost-effective quality assurance system in the EU
ii) to ensure the quality and comparability of analytical results
iii) to ensure that acceptable accuracy is achieved
iv) to ensure that false positive or false negative results are avoided
v) to support compliance with, and specific implementation of, ISO/IEC17025 (accreditation standard)