Proposed  Maximum Residue Limit  PMRL20 19-38 
 
 
 
 
 
 
 
Pyroxasulfone  
(publié aussi en  français)  27 November  2019  
 
This document is published by the Health Canada Pest  Management Regulatory Agency. For further 
information, please contact:  
 
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ISSN:  1925 -0835  (print)  
  1925 -0843  (online)  
 
Catalogue number:  H113 -24/2019-XXE  (print version)  
  H113 -24/2019-XXE -PDF (PDF version ) 
 
 
© Her Majesty the Queen in Right of Canada, represented by the Minister of Health Canada, 20 19 
 
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Proposed Maximum Residue Limit - PMRL201 9-38 
Page 1 Under the authority of the Pest Control Products Act , Health Canada’s Pest Management 
Regulatory Agency (PMRA) has concluded that the addition of a new use on potatoes to the 
product label of  Pyroxasulfone 85 WG, containing technical grade pyroxasulfone , is acceptable. 
The specific uses approved in Canada a re detailed on the label of Pyroxasulfone 85 WG, Pest 
Control Products Act  Registration Number 30572.  
The evaluation of this pyroxasulfone  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 residue s 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 se parate MRLs are specified for the raw agricultural commodity and a processed product 
made from it.  
Consultation on the proposed MRLs for pyroxasulfone  is being conducted via this document (see 
Next Steps). A summary of the field trial data  used to support the proposed MRLs can be found 
in Appendix  I. 
To comply with Canada’s international trade obligations, consultation on the proposed MRLs is 
also being conducted internationally by notifying the World Trade Organization , as coordinated 
by the Canada’s Notification Authority and Enquiry Point . 
The proposed MRLs, to be added  to the MRLs already established for pyroxasulfone , are as 
follows . 
Table 1  Proposed Maximum Residue Limits for Pyroxasulfone  
Common 
Name  Residue Definition  MRL 
(ppm)1 Food Commodity  
Pyroxasulfone  3-[-5-(difluoromethoxy) -1-methyl -3-
(trifluoromethyl)pyrazol -4-yl-methylsulfonyl] -
4,5-dihydro -5,5-dimethyl -1,2-oxazole including 
the metabolites (5 -difluoromethoxy -1-methyl -3-
trifluoromethyl -1H-pyrazol -4-yl)-
methanesulfonic acid, 5 -difluoromethoxyl -1-
methyl -3-trifluoromethyl -1H-pyrazole -4-
carboxylic acid, (5 -difluoromethoxy -3-
trifluoromethyl -1H-pyrazol -4-yl)-
methanesulfonic acid, and 3 -[1-carboxy -2-(5,5-
dimethyl -4,5-dihydroisoxazol -3-
ylthio)ethylamino] -3-oxopropanoic acid  
(expressed as parent equivalents)  0.2 Potato flakes , 
potato granules  
0.08  Tuberous and 
corm vegetables 
(crop subgroup 
1C) 
1 ppm = parts per million    
 
Proposed Maximum Residue Limit - PMRL201 9-38 
Page 2  
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 
the Canada.ca 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  
The MRLs proposed for pyroxasulfone  in Canada are the same  as corresponding American 
tolerances as listed in the Electronic Code of Federal Regulations , 40 CFR Part 180, by pesticide . 
Currently, there are no Codex MRLs1 listed for pyroxasulfone  in or on any commodity on the 
Codex Alimentarius Pesticide Index  webpag e. 
Next Steps  
The PMRA invites the public to submit written comments on the proposed MRLs for 
pyroxasulfone  up to 75 days from  the date of publication of this document. Please forward your 
comments to Publications (see the contact information on the cover page of this document). The 
PMRA will consider all comments received before making a final decision on the proposed 
MRLs. C omm ents received will be addressed in a separate document linked to this PMRL. The 
established MRLs will be legal ly in effect as of the date that they are entered into the Maximum 
Residue Limit Da tabase .
                                                           
1  The Codex Alimentarius Commission  is an international organization under the auspices of the United 
Nations that develops international food standards, including MRLs.  Appendix I  
  
 
Proposed Maximum Residue Limit - PMRL201 9-38 
Page 3  
Appendix  I 
Summary of Field Trial Data Used to Support the Proposed M aximum Residue Limits 
Residue data for pyroxasulfone in potatoes were submitted to support the domestic use of 
Pyroxasulfone 85 WG on potatoes. In addition, a processing study in  treated potatoes was 
reviewed to determine the potential for concentration of residues of pyroxasulfone into processed 
commodities.  
Maximum Residue Limits  
The recommendation for maximum residue limits (MRLs) for pyroxasulfone 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 MRLs  for crop subgroup 1C . 
Table A1 Summary of Field Trial and Processing Data Used to Support the MRLs  
Commodity  Application 
Method/ Total 
Application 
Rate  
(g a.i./ha)1 Preharvest 
Interval  
(days)  Lowest 
Average 
Field Trial  
Residues  
(ppm) Highest 
Average 
Field Trial 
Residues  
(ppm)  Experimental 
Processing 
Factor  
Potatoes  Pre-emergence 
/ 
250 63-117 0.05 0.05 Chips: 1.0×  
Flakes: 1.4×  
1 g a.i./ha = grams of active ingredient  per hectare  
Following the review of all available data, MRL s as proposed in Table 1 are  recommended to 
cover residues of pyroxasulfone. Residues of pyroxasulfone  in these crop commodities at the 
proposed  MRLs will not pose an unacceptable risk to any segment of the population, including 
infants, children, adults and  seniors.