Pesticide Registration Toolkit

#710 Proposed residue definition and maximum residue limits

Objective of the study

1. Residue definition

Residue definitions are required to clearly establish the compound or compounds of interest to:

  • estimate dietary intake risks associated with the presence of residues in food or feed commodities; 


  • provide the basis for monitoring of compliance with maximum residue limits (MRLs).

The basic requirements for the definition of residues are different, depending on the purpose of the residue assessment.

  • The residue definition for dietary intake estimations and risk assessment should include metabolites and degradation products of toxicological concern, irrespective of their source, where present in significant concentrations.
  • The residue definition for monitoring of compliance with MRLs, on the other hand, should be:
    • based on a single compound whenever possible, which is preferably recoverable with multi-residue methods;
    • enable unambiguous identification of source of residues, to allow for effective monitoring of compliance with MRLs and enforcement of the registered Good Agricultural Practice (GAP)
    • the same for all commodities, if possible, to facilitate routine monitoring.

2. Maximum Residue Level (MRL)

The Maximum Residue Level (MRL) is the maximum concentration of a pesticide residue (expressed as mg/kg) to be legally permitted in or on food commodities and animal feeds. MRLs are based on Good Agricultural Practice (GAP) data. Foods derived from commodities that comply with the respective MRLs are intended to be toxicologically acceptable.

The objective of establishing MRLs is to provide an objective means to verify that the pesticides were used according to Good Agriculture Practice (GAP). The nationally authorized uses of pesticides are defined by the ‘use patterns’. The pesticides may be applied at different dosage rate and time before the harvest within the authorised maximum dosage and over the minimum pre-harvest intervals. The estimated maximum residue levels
should cover the residues in or on commodities harvested after the authorised minimum pre-harvest intervals following the repeated applications at the permitted minimum intervals and maximum dosage rate (the ‘critical GAP’).

Further information on residue definitions can be found in Chapter 5.12, and on estimation of MRLs in Chapter 6, of the JMPR Procedure Manual.

Worked examples on this topic are provided in Chapters 6 and 8 of the JMPR Training Manual.

Circumstances in which the information is required

1. Residue definition

A residue definition is always required if the use of the pesticide can result in residues in or on food or feed.

2. Maximum Residue Level (MRL)

A maximum residue level is always required if the use of the pesticide can result in residues in or on food or feed.

A justification of the acceptability of the proposed MRLs should also be provided, including supervised trials median residue (STMR) and highest residue (HR) values and in the case of processing of food or feed processing factors.


1. Residue definition

In general, the residue definition of a pesticide can be considered representative of its intended use if residue metabolism studies have been conducted in each type of crop category for which use is proposed.
Crops can be considered to belong to one of five group for crop metabolism studies:

  • root crops (root and tuber vegetables, bulb vegetables)
  • leafy crops (Brassica vegetables, leafy vegetables, stem vegetables, hops)
  • fruits (citrus fruit, pome fruit, stone fruit small fruits, berries, grapes, banana, tree nuts, fruiting vegetables, persimmon)
  • pulses and oilseeds (legume vegetables, pulses, oilseeds, peanuts, legume fodder crops, cacao beans, coffee beans)
  • cereals (cereals, grass and forage crops)

One crop from a group will cover the entire group for purposes of metabolism in those crops within the group.

In order to extrapolate metabolism of a pesticide to all crop groupings, metabolism studies on a minimum of three representative crops (from the five different crop categories) should be conducted. If the results of these three studies indicate a comparable metabolic route, then additional studies will not be needed on crops in the other two groups.

A residue definition for farm animals may be required whenever a pesticide is applied directly to livestock, to animal premises or housing, or where significant residues remain in crops or commodities used in animal feed, in forage crops, or in any plant parts that could be used in animal feeds. Animal groups that may have different metabolism, and thus different residue definitions, are rats, ruminants and poultry.

Further information on the procedures to establish a residue definition is provided in the Assessment Methods Module

2. Maximum Residue Level (MRL)

For reliable estimation of maximum residue levels an adequate number of independent supervised residue trials are required, reflecting the highest of national maximum GAPs and conducted according to well-designed protocols that consider geographical distribution and the inclusion of a number of different growing and management practices, and growing seasons.

The procedure of estimating MRLs can be summarized as follows:

  1. Selection of supervised trials, which correspond to the critical GAP and are suitable for estimation of maximum residue level (MRL), supervised trial median residue (STMR) and highest residue (HR) values;
  2. Estimation of STMR and HR values from the selected trials (for dietary risk assessment)
  3. Estimation of MRL values, from the selected trials, generally using an established calculator.

Further information on the procedures to establish MRLs is provided in the Assessment Methods Module

Typical endpoints of the study

A residue definition is established for the active ingredient and toxicologically relevant metabolites.

An MRL is established based on the residue definition for monitoring of compliance.

Testing guidelines

The following testing guidelines may be used for establishing residue definitions and setting MRLs: