Contaminants are substances that have not been intentionally added to food. Food production processes can lead to substances entering the food at any moment: during manufacturing, handling, storage, processing or distribution. Contaminants can also enter the food from the environment. The presence of such substances in food must be monitored carefully to avoid contamination effecting the quality of the food or making the food unsafe.

Pesticides are widely used in agricultural production to prevent or control pests, diseases, weeds, and other plant pathogens in an effort to reduce or eliminate yield losses and maintain high product quality, thus contributing to food security for the country. The use of pesticides may result in residues on crop commodities. To protect the health of the consumer when consuming food crops, maximum residue limits (MRLs) are established after various considerations and these are set. MRLs are used as a standard to ensure that agricultural chemicals are used according to the approved use patterns, without harm to human health and the environment.