## UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

MEMORANDUM DATE: December 3, 2014 OFFI CE O F CHEMICAL SA FETY A ND POLLUTION PREVENTION



### SUBJECT : Metolachlor and S-Metolachlor. Recommended Environmental Degradates to Include in Drinking Water Assessment. PC Code: 108800 (S-Metolachlor); DP Barcode: 424250 1

08801 (Metolachl or) Decision No.: 491501 Registration Nos.: 100-815, 11603

- 43, 19713

- 539, 60063

- 17 Petition No.: NA Regulatory Action: Registration Review Case No.: 0001 Risk Assessment Type: NA TXRNo.: NA CAS No .: 87392-12-9,5 1 2 1 8-45-2 MRIDNo
. : NA 40 CFR: §180.368 FROM: Susan V. Hummel , Senior Chemist**~** 

# 1)**~** 

### Risk Assessmen t Branch 4 Health Effects D i vision (7509P) THROUGH: Christine Olinger, ROCKS ; / /**~** 

### / Health Effects Division (7509P} _;,c.. '

## ~**~** TO: Steven Snyderman, Chemical Review Manager Risk Management and Implementati on Branch 3 Pesticide Re

- Evaluation Division (7508P)


### I. MATE RIAL REVIEWED: The herbicides meto l achlor and S

- metolachlor are registered on a number of crops and are undergoing registrati on review
. EFED asked HED for guidance on including the meto l achl or deg radates in the drinking water assessmen t. EFED flagged four major degradates of meto l ach lor for the drinking water assessment : metolachl or oxanilic acid (metolachlor-OA; CGA

- 51202), metolachlor ethane sulfonic acid (metolachlor ESA; CGA

- 354743), CGA40172, and CGA771 02. See Table l for s tructures of meto l achlor and its degradation products.

### II. CONCLUSIONS: Four major degradates of metolachlor were identified by the EFED chemical team for the drinking water assessment: metolachlor oxanilic acid (metolachlor-OA; CGA -51202), metolachlor ethane sulfonic acid (metolachlor ESA; CGA-354 743), CGA-40 172, and CGA50720. CGA40172, and CGA-50720 were not considered as residues of concern in previous drinking water assessments. The ROCKS members recommended excluding the metolachlorESA from the drinking water assessment since the sulfonic acid is likely to be significantly less toxic than the parent compound. The ROCKS members also recomm ended including the degradates CGA-40 172 and CGA-50720, in addition to metolachlor-OA, based on the structural similarity to parent metolachlor. It 

### should be noted that the concern for CGA -40172 is diminished due to the presence of the carboxylic acid moiety, however , there is insufficient information to exclude from the drinking water assessment. Therefore, the ROCKS recommended the following degradates as residues of concern for drinking water; parent metolachlor, metolachlor-OA, CGA40172, and CGA-50720. Individuals in Attendance: 

### ROCKS: Ed Scollon, Christine Olinger, Ray Kent EFED : Chris Kop er , Edom Seifu, Meghan Radtke HED: Sue Hummel (via phone), Jessica Kidwell

Page 2 of7

### Table 1. Metolachlor /S-Metolac hlor and Its Environmental Degradates Code Name/ Chemical Name Chemica l Structure Study Type 

# I MRID 

# I Maximum Formation Synonym 

### (% Apptied) Parent Metolachlor CAS Name: 

### (CGA-24705) (R)2-Chloro-N-(2-ethyl-6- 

### CH; meth y lph enyl)-N-(2-methoxy-1- 

# I methylethyl) acetamide 

### 0 

# H ; C-< 

# l CAS Number: 051218-45

- 2 Molecular Weight: 283.80 Parent structure shown for reference g/mol 

## H; C 

# N-(_
Chemical Formula: 

### Cl CtsH22N02CI 

# Q\_- CH , SMILES: CCC! =CC = CC(= C1N(C(C)CO C)C( = O)CCI)C S

- Meto E achlor CAS Name : 

# I ! (CGA-77102) (S) -2-Chloro-N-(2

- ethyl-6- methylphenyl)-N

- (2-methoxy-1-

# :~N~~···( methylethyl) acetamide CAS Number: 087392-12-9 Molecular Weight: 283
. 80 Parent structure shown for reference g/mol Chemica l Formula:

### ~ CtsHzzNOzCI 

# I SMILES :

### ~ 

### CCC 1 =CC=CC(=C 1 N([C@ @H](C)COC)C(=O)CCI)CCode Name/ Chemica l Name C h e mical S tructure Stu d y Typ e MRID Maximum Formation Synonym (%Applied) T ransformation Prod ucts Metolachlor CAS Name: Aqueous Photolysis 40430202 3.54 Oxanilic Acid/ [(2-et hyl-6-methylph eny l) (2- 11 .3 (day 48) Metolachlor-OA methoxy-1-methylethy1) amino] Aerobi c Soi l Metabol ism 45499606 (CGA-5 1202) oxo-acetic acid 

# c; T 1l Ae robic Soil Metabolism 43928936 10.3 (day 21, met) Molecu la r We ight: 3 89 .06 10.9 (day 2 1 , S- met) g/

mol 

# r**~** 1 

# /es • al
. 0 •

### ~ Aerobic Soil Metabolism 3 1 30980 1 28.09 (day 90) A-B 

# ' Anae robic Soil 31309801 23.33 (day 29) 

# - CO • COOl M etabo li sm A-8 

# el•s T errest rial F ie ld 3.0% of appli ed SDi ss ipatio n 45848001 metolach l or at 93 day s in 0-15 em soil depth. Metolachlor CAS Nam e : ethan e sulfo ni c Not assigned 

### I fo und 2-((2- Aerobic Soi l Metabolism 4 5499606 acid/ ethyl-6 -methylphenyl)(2- 11.6 ( day 33) Metolachlor- methoxy-1-methyl ethy l)amino)- ESA 2 -o xoethanesulfonic acid 10 .7 (day 60, met) I (CGA -3 54743) http: //s item.hert s. ac.uk/aeru/ i upa A erobic Soi l Metab olism 4 392 8936 12 .4 (day 60, S-met) 

### CH 2

C

H3 c/103l.htm 

### I 2.8% of applied S- I

### oN/COC H2 SOji Molecular Weight: 329 g/mol metolachlor a t 93 day s I 

## ""- c H C H 20C H3 Terre strial Field 45848001 in 0- 15 em soil de pth Di ssipat ion 

## "'- c H3 

# JH J

I**~--**



### Page 4 of7CGA

- 41507 CAS Name: Aerobic Aquatic 41185701 3.34 (day 29) Not assigned 

## CH**~H,** . Metabolism**Mole~ular** Weight: 157 g/mol 

# o- '

1 

## CHCH,OCH, N\ Anaerobic Aquatic 41 185701 4.85 ( 1 2 months) 

## CCH, Metabolism 

## C 1 

## H 1 

## II 

## 0 Aerobic Aquatic 1.13 CGA-40172 CAS Name: 41185701 Not assigned (not reported) Metabolism

# ~ Anaerobic Aquatic 5.64 (12 months) Molecular Weight: 346.03 41185701 

### CH-CH-O-CH Metabolism g/mol 

# 'I**~** / a a 

# N'

-**~-OH** 

### II Aerobic Soi l Metabo lism 45499606 11.6 (day 19) I 

### 0 ll.3 (day 48) CGA-4 1638 CAS Name: Not assigned (not reported)

# ~ Aqueous Photolysis 40430202 3
. 63 Molecular Weight: 346.o3 

### /CH-CH 1 

## -0H Aerobic Soil Metabolism 31309801 2
. 06 (day 90) 

# 'I**~** A-B g/mol 

# N'



# - C-CH 1 

### CI Anaerobic Soil 31309801 I 

# g Metabolism A-B 8.30 (day 60)



### Page 5 of7CGA-50720 CAS Name: Aerobic Aquatic 41185701 1.17 Not assigned (not reported) Metabo l ism 

### al Mo lecu lar Weight: 346.03 

# Q-<:.=o. Aqueous Photolysis 40430202 3.20 glmo l Aerobic Soil Metabolism 3130980 1 A-B 14
. 85 (day 272) 

# el•s Anaerobic Soi l 31309801 Metabo l ism A

- B 7.34 (day 60) CGA-37913 CH**~H,** 

# o-

' / CHCH,OH Anaerobic Aquatic 41 18 570 1 

## N, Metabolism 4.28 (6 month s) H CaHs



### Page 6 of7CGA-37735 Aerobic Soil Metabo li sm 3130980 1 1.27 (day 30 ) 

# r}'H A

- B 

### I 

### H

\ 1.25 (day 29)



## CCH 1 

## 0H Anaerobic Soi l 3 1 309801 

## CIHI 

## II Metabo lis m A-B 

## 0 CGA

- 13656 31309801



# - Aerobic S oi l Metabolism 1.02 (d ay I) A-B 

# 'I

# N~



# - 'C-CHJ:I Anaerobic Soil 31309801 1.46 (day 29) 

# u Metabolism A-B 

## 0 CGA-46129



## . CH**~Hs** 

# Q-' CHCOOH I 

### N\ Aqueous Photolysis 4 0430202 3.42 

## CCH 1 

## 0H 

## C2 

## H 1 

## U 0 CGA-46127

# q:>r~~ Aerobic Aquatic Metabo lis m 41 185701 1.54 

# " Anaerobic Aquatic 41185701



## co-o-t2 -s-or3 Meta bo l ism

### ~l·J 4 .69 (12 months) 

### Note: Bold 

### values denote major 

# e 10%) 

### degradates.

L____
__ --·--·-··-·-- 

### Page 7 of7