The maximum residue limit (also maximum residue level, MRL), is the maximum amount of
pesticide residue that is expected to remain on food products when a pesticide is used according to label directions, that will not be a concern to human health.
Determination
The MRL is usually determined by repeated (on the order of 10) field trials, where the crop has been treated according to
good agricultural practice
Good agricultural practice (GAP) is a certification system for agriculture, specifying procedures (and attendant documentation) that must be implemented to create food for consumers or further processing that is safe and wholesome, using sustaina ...
(GAP) and an appropriate pre harvest interval or withholding period has elapsed. For many pesticides this is set at the
Limit of determination (LOD) – since only major pesticides have been evaluated and understanding of
acceptable daily intake (ADI) is incomplete (i.e. producers or public bodies have not submitted MRL data – often because these were not required in the past). LOD can be considered a measure of presence/absence, but certain residues may not be quantifiable at very low levels. For this reason the
limit of quantification (LOQ) is often used instead of the LOD. As a rule of thumb the LOQ is approximately two times the LOD. For substances that are not included in any of the annexes in EU regulations, a default MRL of 0.01 mg/kg normally applies.
It follows that adoption of GAP at the farm level must be a priority, and includes the withdrawal of obsolete pesticides. With increasingly sensitive detection equipment, a certain amount of pesticide residue will often be measured following field use. In the current regulatory environment, it would be wise for
cocoa
Cocoa may refer to:
Chocolate
* Chocolate
* ''Theobroma cacao'', the cocoa tree
* Cocoa bean, seed of ''Theobroma cacao''
* Chocolate liquor, or cocoa liquor, pure, liquid chocolate extracted from the cocoa bean, including both cocoa butter and ...
producers to focus only on pest control agents that are permitted for use in the EU and US. It should be stressed that MRLs are set on the basis of observations and not on ADIs.
MRL in medicinal plants
If MRL of some medicinal plant is not known it is calculated by the formula:
:
where SF is the
safety factor
*MDI is the mean daily intake
*W is the body weight
*ADI is the
acceptable daily intake
Ornamental crops
In some cases in the EU MRL's are also used for ornamental produce, and checked against MRL's for food crops. While this is a sound approach for the general environmental impact, it doesn't reflect potential exposure of people handling ornamentals. A swap test can eliminate t