Health Canada’s Pest Management Regulatory Agency (PMRA) has notified the WTO of proposed MRLs for dimethomorph in leaf lettuce. The MRLs were adopted on March 11, 2020.

SAFEGUARDS | FoodNO. 046/20

 SG 04620 Lettuce

Health Canada’s Pest Management Regulatory Agency (PMRA) notified the World Trade Organization (WTO) of proposed maximum residue limits (MRLs) for dimethomorph in leaf lettuce on December 17, 2019. The PMRA invited the public to submit written comments on the proposed MRLs for up to 75 days from the date of publication, and the MRLs were adopted on March 11, 2020. [1]

Pesticides are chemical substances intended for preventing, destroying, or controlling weeds, molds and pests. Dimethomorph is a systemic fungicide which is a mixture of two isomers are E-isomer and Z-isomer. It is widely used to protect plants from molds, as well as killing molds on plants and preventing their spread. However, pesticide residues can cause several human health problems, such as cancer, neurological disorders and impairment of the immune system. Therefore, the concentration of pesticide residues in food products must be monitored in order to ensure they are below the Maximum Residue Limits (MRLs).

Before registering a pesticide for food use in Canada, the PMRA must determine the quantity of residues that are likely to remain in or on the food when the pesticide is used according to label directions, and that such residues will not be a concern to human health. To comply with Canada's international trade obligations, consultation on the proposed MRLs is also being conducted internationally via the World Trade Organization, as coordinated by the Canada’s Notification Authority and Enquiry Point. [2] To avoid the issue of trade barriers, Health Canada’s PMRA has set its own MRLs for Dimethomorph in leaf lettuce at Table 1.

For pesticide analysis in various food commodities, the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) is an extraction and clean-up technique. The international methods widely used for pesticides analysis are BS EN and AOAC. They are extract by acetonitrile and analyzed by either liquid or gas chromatography coupled with tandem mass spectrometry (LC-MS/MS or GC-MS/MS) depending upon its chemical properties.

The proposed MRLs, to replace the MRLs already established for dimethomorph, are as per table 1.

Common Name Food Commodities MRLS (PPM)
Dimethomorph (CAS # 110488-70-5)
Leaf lettuce 60

Table 1: Proposed Maximum Residue Limits for Dimethomorph


This update has the potential to affect agricultural producers, food manufacturers, and pesticide manufacturers. Food products destined for Canada, if listed in Table 1, must not have residues of Dimethomorph exceeding the MRLs. Complying with food safety regulations can be a complex, time-consuming and expensive process. Food producers should seek professional advice.

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