UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: October 26, 2015 

Subject: Pronamide (Propyzamide). Harmonization of the Recommended Permanent 

Tolerance for Leaf Lettuce. 

From: 

Through: 

To: 

PC Code: 101701 

Decision No.: 493477 

Petition No.: 4F830 I 

Risk Assessment Type: NA 

TXRNo.: NA 

MRID No.: See Below 

Ideliz Negr6n-Encarnaci6n, Ph.D., Chemist 

Risk Assessment Branch V 

Health Effects Division (HED; 7509P) 

Michael S. Metzger, Branch Chief 

Risk Assessment Branch V (HED; 7509 

and 

DP Barcode: D429782 

Registration No.: 62719-394 

Regulatory Action: Section 3 Registration 

Case No.: NA 

CAS No.: 23950-58-5 

40 CFR: 180.3 17 

David J. Miller, Ph.D., Branch Chief 

Chemistry and Exposure Branch (HED; 7509P) 

Ray Kent, Ph.D., Toxicologist 

Immediate Office (HED; 7509P) 

and 

Reuben Baris, Risk Manager 

Registration Division (7505P) 

Page 1 of 2 
Pronamide Hannonization of Leaf Lem1ce Tolerance Barcode 0429782 

Background 

fn the residue chemistry chapter evaluating the petition to establish a U.S. registration for use of 

pronamide on leaf lettuce, HED previously recommended in favor of a tolerance at 2 ppm 

following Organisation for Economic Co-operation and Development (OECD) calculation 

procedures (I. Negron-Encarnacion, 0424598. 0 1/ 15/2015). Although the Canadian maximum 

residue limit (MRL) for lettuce is 1 ppm, at that time HED recommended in favor of 

harmonization if the use pattern was modified by increasing the pre-harvest interval (PHI) by I 0 

days. Based on feedback received from the registrant through the Registration Division 

(electronic communication from Baris Reuben on I 0/08/2015), the registrant made an argument 

that the tolerance of I ppm can be supported for the proposed use. In consideration of the 

registrant request, further analysis of the available data and MRLs in other countries was made, 

in order to determine if a tolerance of l.O ppm could be supported in the interest of 

harmonization. 

Revisions to Recommended Tolerance 

The recommended U.S. tolerance of 2 ppm was estimated following OECD calculation 

procedures using field trial data that supports the intended use pattern. The data of the 2009 

decline trials was organized in the following four sets: 0.5 lb ai/A (25 day-PHI), 1.0 lb ai/A (35-

day PHI), 1.5 lb ai/A (45-day PHI), and 2.0 lb ai/A (55-day PHI). All data sets result in a 

rounded MRL of2 ppm with the exception of the 0.5 lb ai/A which results in a rounded MRL of 

1.5 ppm. Based on these calculations, the tolerance suggested by the OECD calculation 

procedures is 2 ppm. Following Canada's MRL of l ppm for residues of pronamide on lettuce 

the registrant had proposed a tolerance of 1.0 ppm for leaf lettuce. A search in the Global MRL 

database for MR Ls that cover residues of pronamide in/on head lettuce and leaf lettuce resulted 

in a list of MRLs established or adopted in countries around the world with values ranging from 

0.2 ppm to 1 ppm (data from GlobalMRL.com obtained on 10/08/20 15). The residue definition 

is generally parent pronamide while in some countries its metabolites are included as well. 

The highest residue obtained from the crop field trial data with leaf lettuce was 1.0 ppm which is 

at the tolerance level. Because substantial data is available for pronamide on leaf lettuce (18 

crop field trials in the US; 8 of those with 4 different use patterns), residues decline significantly 

within days (e.g. mean residues observed in the 2009 decline trials decrease by a factor of 0.6 in 

comparison to those from samples harvested 10 days before), and MRLs established by most 

countries are at 1 ppm or below, HED recommends in favor of a tolerance of I ppm for leaf 

lettuce. 

Conclusion 

In order to harmonize with the Canadian MRL for lettuce, HED recommends in favor of a U.S. 

tolerance for leaf lettuce at l ppm. 

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