UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHfNGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

DATE: May 21 , 2015 

SUBJECT: Metolachlor and S-Metolachlor. Response to Comments on the HED Human Health 

Scoping Document. 

PC Code: I 08800 (S-Metolachlor); I 0880 I DP Barcode: 426906 

(Metolachlor) 

Decision No.: 50360 I 

Registration Nos.: 100-815, 11603-43, 19713-539, 

17 

Petition No.: NA 

Case No.: 0001 

TXR No.: NA 

MRID No.: NA 

FROM: 

THROUGH: 

TO: 

Regulatory Action: Registration Review 

Risk Assessment Type: NA 

CAS No.: 87392-12-9, 512 18-45-2 

40 CFR: § 180.368 

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Pesticide Re-Evaluation Division (7508P) 

Attached is HED's Response to Comment on the human health risk assessment scoping 

document for metolachlor and S-metolachlor to support Registration Review. 

60063-

The HED Metolachlor and S-metolachlor Risk Assessment team has received comments on the 

Registration Review Scoping Document (EPA Docket ID: EPA-HQ-OPP-2014-0772-0003). 

Comments relevant to HED's scoping document were provided by Syngenta. The comments all 

fall within the chemistry category. 

Page 1 of 4 
Metolachlor and S-metolachlor. Human Health Scoping Document in Support of 

Registration Review, Nov. 19, 2014. PC Code 108800 (S-metolachlor); 108801 

(Metolachlor); DP Barcode: 420468 (EPA-HQ-OPP-2014-0772-0003) 

EPA Statement 

Residue Chemistry, Page 6 The label directions for use are not all supported by residue 

data. Discrepancies were noted for S-metolachlor on bulb vegetables (shorter PHI than supported 

by data) 

Syngenta Comment: S-metolachlor bulb vegetable uses are only on Section 24c labels 

registered in multiple states. The approved directions for use allow for a single maximum 

application rate of 1.27 lb ai/A and a total maximum application rate of 2.55 lb ai/A/crop cycle 

with a pre-harvest interval (PHI) of 60 days. These directions for use are supported by MRID 

No. 46046503. In this study, bulb onions received two applications of Dual II MAGNUM (EPA 

Reg. No. 100-818), the first application applied at 590 g ai/A (1.3 lb ai/A) as an early post 

appli cation followed by a second application at 590 g ai/A (1.3 lb ai/A) made 60 days prior to the 

harvest of dry onions. Based on this information, we believe that the residue data supports the 

labeled directions for use. 

EPA Response: HED acknowledges receipt of this infonnation and agree no additional residue 

data are required for the registered bulb vegetable use. 

EPA Statement 

Residue Chemistry, Page 6 The label directions for use are not all supported by residue 

data. Discrepancies were noted for S-metolachlor on ... cotton (higher rate) 

Syngenta Comment: S-metolachlor cotton uses are on multiple product labels, the directions 

for use of which are best represented by the Dual Magnum (EPA Reg. No. l 00-816) Section 3 

label. The approved directions for use allow for a single maximum application rate of 1.6 lb ai/A 

and a total maximum application rate of2.48 lb ai/A/year. The 1.6 lb ai/A rate may only be 

applied in the fall (Sept 1 - Dec l ), which is 5-6 months prior to planting cotton. These 

directions for use are supported by MRID No. 491 8650 I. In this study, cotton received two 

applications of Dual II MAGNUM (100-818). Both applications were applied at 1.3 lb ai/A for a 

total application rate of 2.6 lb ai/A. The first application was made at planting followed by either 

a broadcast spray postemergence over the top ( 100 day PHI) or post-directed spray at lay-by (80 

day PHI). This study supports the labeled directions for use with the exception of the maximum 

fall use rate of 1.67 pt/ A ( 1.6 lb ai/ A). This use is a fall use and the label stipulates that ifsmetolachlor is used in the spring, do not exceed the 2.6 pt/A (2.48 lb ai/A) maximum total use 

rate. 

We concur that the residue study does not provide specific data representing the fa ll application 

at 1.6 lb ai/A. However, the l .33 lb ai/A preemergence application followed by 1.33 lb ai/A 

postemergence (in the same calendar year) is a worst-case scenario compared to the 1.6 lb 

ai/A Fall appli cation (long PHI) + 1.00 lb ai/A preemergence or postemergence (2.67 lb ai/A 

maximum). Therefore, we believe that data from this study would support this use as the residue 

Page 2 of 4 
study represents a worst case scenario. The residue data does support the maximum total use rate 

of 2.48 lb ai/A/year. 

EPA Response: HED acknowledges receipt of this infom1ation and agree no additional residue 

data are required for the registered cotton use. 

EPA Statement 

Residue Chemistry, Page 6 The label directions for use are not all supported by residue data. 

Discrepancies were noted for S-metolachlor on ... soybeans (higher rate) 

Syngenta Comment: S-metolachlor soybean uses are on multiple product labels, the directions 

for use of which are best represented by the Dual Magnum (EPA Reg. No. I 00-816) Section 3 

label. The approved directions for use allow for a single maximum application rate of 1.9 lb ai/A 

and a total maximum application rate of 2.48 lb ai/ A/year. These directions for use are supported 

by MRJD No. 47304702. In this study soybeans received either a single soil surface spray at 

planting at 2.0 lb ail A, or two applications consisting of a preplant spray at 1.2 lb ai/ A followed 

by a post-foliar broadcast spray at 1.3 lb ai/A for a total application rate of2.5 lb ai/A. 

This study supports both the single maximum application rate of2.0 lb ai/A and the maximum 

total application rate of 2.48 lb ai/ A, with the total application rate only being applied as a split 

application. Data from another study (MRI D No. 43928941) supports a 2.67 lb ai/ A single use 

rate of S-metolachlor as a preplant incorporated or preemergence treatment on soils having an 

organic matter content between 6% and 20%. Based on this information, we believe that the two 

residue studies support the labeled directions for use. 

EPA Response: HED acknowledges receipt of this information and agree no additional residue 

data are required for the registered soybean use. 

EPA Statement 

Residue Chemistry, Page 6 The label directions for use are not all supported by residue data. 

Discrepancies were noted for S-metolachlor on ... tomato (higher rate) 

Syngenta Comment: S-metolachlor tomato uses are on multiple product labels, the directions 

for use of which are best represented by the Dual Magnum (EPA Reg. No. l 00-816) Section 3 

label. The approved directions for use allow for a single maximum application rate of 1.9 lb ai/A. 

While the total maximum application rate is not specified, the label implies a total maximum 

application rate of 2.54 lb ail A/crop cycle. These directions for use are supported by MRID No. 

44056 l 0 I. In this study, tomatoes were treated with metolachlor at a maximum rate of 3.0 lb 

ai/A with a 90 day pre-harvest interval (PHI). In a memorandum from EPA Dated February 28, 

2002 (DP Barcode 8280219), the TRED conclusion stated that these data support the use of Smetolachlor on tomatoes at a maximum rate of I. 9 lb ai/ A, thus supporting the I. 9 lb ail A 

maximum single use rate. 

IR-4 Project PR 09668 (MRID No. 4804880 I) further supports the use of S-metolachlor, 

wherein S-metolachlor was applied two times at a rate 1.3 7 lb ai/ A per application, once at or 

around transplant followed by a banded/directed application to row middles 30 days prior to 

harvest. 

Page 3 of 4 
These two studies support two different use patterns (different application rates, methods, and 

PHls), which are explained on the label. Based on this information, we believe that the residue 

data supports the labeled directions for use. 

EPA Response: HED acknowledges receipt of this information and agree no additional residue 

data are required for the registered tomato use. 

Page 4 of 4