MRLs of Spiroxamine and Tembotrione in Foods Set in Canada

The Health Canada Pest Management Regulation Agency (PMRA) has published new MRLs for spiroxamine and tembotrione in foods. After consultation, the MRLs for both pesticides enter into force on July 22 and September 6, 2015, respectively.

Fungicides and Herbicides

Spiroxamine is a new fungicidal active substance belonging to the Spiroketalamine class, which has protective, curative, and eradicative effects against mildews. Its chemical structure is comprised of cis and trans diasteroisomers known as A and B forms, respectively. These forms have partly different biological activities, interacting with the different steps in sterol biosynthesis. Primarily, Spiroxamine is used in cereal, and recently in grape cultivation, either as a single agent, or in combination with other fungicides. For Tembotrione, it is a selective herbicide used to control a broad spectrum of broadleaf and grass weeds in maize and sweet corn. At this time, the Codex Alimentarius international standards contain no maximum residue levels (MRLs) for Spiroxamine and Tembotrione.

PMRA Risk Assessment

To ensure human health safety in Canada, the PMRA uses risk assessment to quantify the level of pesticide residues in or on foods, which, when they are employed according in accordance with label directions, will not be harmful. The resulting quantity of each residue deemed to be a safe level, is then legally specified as Canada’s MRL. Details regarding the proposed MRLs for Spiroxamine (1) and Tembotrione (2) can be found in Table 1 in the latest Safeguards bulletin. A new MRL for Spiroxamine is set for raisins, bananas, and grapes, whereas, the MRL for Tembotrione is amended by changing from 0.04 ppm to 0.01 ppm, including its metabolite in sweetcorn kernels, plus cob with husks removed for isoxadifen-ethyl. The World Trade Organization (WTO) has been notified of the updated MRLs for these pesticides to ensure compliance with the agreement on the application of sanitary and phytosanitary measures (SPS) in order to avoid a hidden trade barrier.

Due to the complexity of the food matrix, development of an efficient method to delivery high quality pesticide analysis results is quite a challenge. Nowadays, liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is recognized as one of best techniques, providing excellent sensitivity and selectivity. LC-MS/MS is the preferred instrument in many laboratories for multi-pesticide testing that complies with their regulation (mostly set to the general default MRL of 0.01 mg/kg). For more information on MRLs of Spiroxamine and Tembotrione based on Canada’s regulation please see Table 1 in the latest Safeguards bulletin.

References:

(1) Health Canada – Proposed Maximum Residue Limit PMRL2015-16, Spiroxamine – 8 May 2015

(2) Health Canada – Proposed Maximum Residue Limit PMRL2015-20, Tembotrine – 6 September 2015

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