Maximum Residue Limit

Pesticide residues on crops are monitored with reference to Maximum Residue Limits (MRL) and are based on analysis of quantity of a given AI remaining on food product samples. The MRL is usually determined by measurement, following a number (in the order of 10) of field trials, where the crop has been treated according to good agricultural practice (GAP) and an appropriate pre harvest interval (see section C5) has elapsed. For many pesticides, however, this is set at the Limit of Determination (LOD) – since only major crops 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 true resides may not be quantifiable at very low levels. For this reason the limit of quantification (LOQ) is often quoted in preference (and as a rule of thumb is usually approximately 2X 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 producers to focus only on pest control agents that are permitted for use in the EU and USA. It should be stressed that MRLs are set on the basis of observations and not on ADIs. if MRL of some drug is not known calculate it by given formula MRL= ADI*W/MDI*<100*(safety factor)>

See also

• Detection limits
• Pesticides