Proposed Maximum Residue Limit PMRL2017-14, Simazine

Pest Management Regulatory Agency
11 May 2017
ISSN: 1925-0843 (PDF version)
Catalogue number: H113-24/2017-14E-PDF (PDF version)

Under the authority of the Pest Control Products Act, Health Canada’s Pest Management Regulatory Agency (PMRA) has concluded that the addition of new uses on Tree Nuts (crop group 14-11) to the product label of Princep Nine-T Herbicide, containing technical grade simazine, is acceptable. The specific uses approved in Canada are detailed on the label of Princep Nine-T Herbicide, Pest Control Products Act Registration Number 16370.

The evaluation of this simazine application indicated that the end-use product has value and the human health and environmental risks associated with the new uses are acceptable.

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. This quantity is then legally established as a maximum residue limit (MRL). An MRL applies to the identified raw agricultural food commodity as well as to any processed food product that contains it, except where separate MRLs are specified for the raw agricultural commodity and a processed product made from it.

Consultation on the proposed MRL for simazine is being conducted via this document (see Next Steps). A summary of the field trial data used to support the proposed MRL can be found in Appendix I.

To comply with Canada’s international trade obligations, consultation on the proposed MRL is also being conducted internationally by notifying the World Trade Organization, as coordinated by the Canada’s Notification Authority and Enquiry Point.

The proposed MRL is as follows:

Table 1 - Proposed Maximum Residue Limits for Simazine
Common Name Residue Definition MRL (ppm)Table 1 footnote 1 Food Commodity
Simazine 6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine 0.05 Tree nuts (crop group 14-11)
Table 1 footnote 1

ppm = parts per million


MRLs are proposed for each commodity included in the listed crop groupings in accordance with the Residue Chemistry Crop Groups webpage in the Pesticides and Pest Management section of Health Canada’s website.

MRLs established in Canada may be found using the Maximum Residue Limit Database on the Maximum Residue Limits for Pesticides webpage. The database allows users to search for established MRLs, regulated under the Pest Control Products Act, both for pesticides or for food commodities.

International Situation and Trade Implications

MRLs may vary from one country to another for a number of reasons, including differences in pesticide use patterns and the locations of the crop field trials used to generate residue chemistry data.

Table 2 compares the MRL proposed for simazine in Canada with corresponding American tolerances and Codex MRL1. American tolerances are listed inthe Electronic Code of Federal Regulations, 40 CFR Part 180, by pesticide. A listing of established Codex MRLs is available on the Codex Alimentarius Pesticide Residues in Food and Feed website, by pesticide or commodity.

Table 2 - Comparison of Canadian MRL, American Tolerances and Codex MRL (where different)
Food Commodity Canadian MRL
American Tolerance
Codex MRL

Tree Nuts (crop group 14-11)


  • 0.25 - almond, almond hulls, macadamia nut
  • 0.20 - hazelnut, pecan, walnut

Not Established

Next Steps

The PMRA invites the public to submit written comments on the proposed MRL for oxyfluorfen up to 75 days from the date of publication of this document. Please forward your comments to Publications. The PMRA will consider all comments received before making a final decision on the proposed MRL. Comments received will be addressed in a separate document linked to this PMRL. The established MRL will be legally in effect as of the date that it is entered into the Maximum Residue Limit Database.

Appendix I

Summary of Field Trial Data Used to Support the Proposed Maximum Residue Limit

Residue data for simazine in almonds and pecans were submitted to support the domestic use of Princep Nine-T Herbicide on Tree Nuts (crop group 14-11).

Maximum Residue Limits

The recommendation for maximum residue limits (MRL) for simazine was based upon the submitted field trial data, and the guidance provided in the OECD MRL Calculator. Table A1 summarizes the residue data used to calculate the proposed MRL for crop group 14-11.

Table A1 - Summary of Field Trial and Processing Data Used to Support MRL
Commodity Application Method / Total Application Rate (g a.i./ha)Table 1 footnote 1.1 Preharvest Interval (days) Lowest Average Field Trial Residues (ppm) Highest Average Field Trial Residues(ppm)
Almond nutmeat Broadcast application to the orchard floor/ 4420-4501 29-30 <0.01 0.019
Pecan nutmeat Broadcast application to the orchard floor/ 4382-4507 28-32 <0.01 0.030
Table 2 footnote 1

g a.i./ha = grams of active ingredient per hectare


Following the review of all available data, the MRL as proposed in Table 1 is recommended to cover residues of simazine in commodities in crop group 14-11. Residues of simazine in these crop commodities at the proposed MRL will not pose an unacceptable risk to any segment of the population, including infants, children, adults and seniors.

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