UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, 

### D.C. 20460

MEMORANDUM
Date: August 16, 2012 OFFICE OF CHEMICAL SAFETY AND POLLUT I ON PREVENTION

SUBJECT: Acetochlor. PP #2 F7996. Request to Establish a Rotational To lerance for Inadvertent Residues In/On Rice. Request to Add Rice as a Rotational Crop to an Acetochlor ME Label. PC Code: 121601 Decision No. : 461987 Petition No.: 2F7996 Risk Assessment Type: Chemistry TXRNo.:NA MRID No.: 48720001
From: Susan V. Hummel , Senior Chemist Risk Assessment Branch 4 Health Effects Division (7509P) / DP Barcode: D401205 Registration No.: 524-591 Regulatory Acti on: Section 3 Case No.: 7230 CAS No.: 34256-82-1 40 CFR: 180.470

Through: Thurston G. Morton, Senior Chemi st

# ~ /

# .L0.~**/J~** Risk Assessment Branch 4 

# U 

# /7tlt!' """( Health Effect s Division (7509P)
To: Hope Johnson/Kable Davis , PM 25 Her bicide Branc h Registration D ivi sion (7505P) Executive Summary
Monsanto Company has submitted a pesticide petition (PP#2F7996) requesting the removal of "except rice " from th e established to lerance for inadvertent residues of acetochlor (2

- chlor-N- (ethoxymethyl)-N-(2-ethyl

- 6-methylphenyl)acetamide) in/on grain of cereal grain at 0.05 ppm and straw of cereal grain group 16 at 0.3 ppm , and a supplemental l abel to add rice as a rotational crop to MON 634 1 0 Herbicide (EPA Reg. No. 524-591 ) , a microencapsul ated formulation (ME). In support of the petition , Monsanto has cited a summary of previously submitted rotational crop data for acetochlor on grains (MRID 48720001 ), using an emulsifiable concentrate (EC) formu lation. No new residue data were submitted with thi s request. Tolerances for acetoc hlor are currently established under 40 CFR §180.470(a) and (d) and are expressed in terms of acetochlor and its metabolites, to be analyzed as acetochlor , ethyl methyl aniline (EMA), and hydroxyethyl methyl aniline (HEMA), and expressed as acetoch lor
Page I of 12equivalents. Tolerances for field corn, pop com, sweet com, cotton, sorghum, and soybean commodities are established under 180.470(a) and range from 0.05 ppm for field and pop com grain, sweet com kernels plus cob with husk removed, and sorghum grain, to 3.0 ppm for field com forage. Tolerance s for rotational crops are established under 180.470(d) and include tolerances for nongrass animal feeds, sugar beet root and tops, cereal grain commodities, peas and beans, potato, soybean forage and hay, sunflower seed, and wheat commodities. No tolerances have been established for livestock commodities. The qualitative nature of acetochlor res idues in com is adequately understood based on a com metabolism study. HED concluded that the residues of concern in com include parent and any metabolites containing th e EMA moiety or the HEMA moiety, expressed in acetochlor equivalents. The nature of the residue in rotational crops is adequately understood based on the results of confined rotational crop studies in lettuce , radis hes and wheat. HED concluded that rotational tolerance should be expressed as acetochlor and its EMA and HEMA producing metabolites , and re s idues of hydroxymeth yl ethyl aniline (HMEA) type metabolites would not be included in the tolerance expression, but should be included in the risk assessment. An adequate HPLC/oxidat ive coulometric electrochemical detector (OCED) method is available for enforcing tolerances of acetochlor and its metabolites in plant commodities. For this method, residues are solvent-ext r act ed into aqueous acetonitrile (ACN), and then base-hydrolyzed to yield EMA and HEMA. The resulting residues are steam -disti lled into dilute acid, adjusted to a basic pH, and then partitioned into dichloromethane (DCM). HEMA is methylated, then residues of EMA and methylated HEMA (MEMA) are separated, and determined via HPLC/OCED. Residues ofEMA and HEMA are expressed in acetochlor equivalents; the validated me thod limi ts of quantitation (LOQs) are 0.020 ppm for each analyte.
HED previously reviewed a confined rotational crop study submitted by Acetochlor Registration Partnership (Monsanto/Zeneca) in support ofPP# 3F2966/PP#lF4011 (08/23/93, M. Flood). The study was considered adequate. The study indicated that 14C re s idues accumulated at levels > 0.01 ppm, inion all commodities oflettuce, radish, and wheat that were planted 30, 120, and 365 days after [phenyl-14C] acetochlor was applied to sandy loam soi l at IX the proposed maximum rate. Because the three confined rotational crops all showed significant (>0.01 ppm) acetochlor residues, even at the 365 days, then HED requested that tolerances be established for inadvertent residues on rotational crops for which field rotational crop studies have been completed. Field rotatio nal crop studies for sorghum , soybean, and wheat were also reviewed in the abov e cited memo. HED recommended rotational crop tolerances for so rghum , soybean, and wheat commodities (01111/94, M. Flood). These tolerances are established under 40 CFR §180.470(d).
HED reviewed field trial data from the application of a ME formulation on field com at the same maximum rate (3.0 lb a. i ./A) as the registered use for an EC formulation (08/01194, M. Flood). At that time, HED recommended the registration of this ME formulation for use on com, providing a restriction be added against rotating crops other than sorghum, soybean, and wheat.
In addition, HED has recently reviewed several Section 3 registrations for the use of acetochlor on cotton, sorghum, and soybean. All field trial data were produced using ME formulations (11121/06, W. Drew; 06/17/09, S. Hummel). Use ofrotational crops are allowed on these ME

Page 2 of 12formu lation labels. However, HED has not reviewed rotational crop field data in which th e primary crop was treated with a ME formu l ation prior to planting any ro tational crop. Executive Summary
HED recommends for the establishment of the requested tolerances for the inadvertent residues on rice as a rotatio n a l crop (removal of"except ri ce" from the establ i shed t olerance). The fie l d trial data as a result of application of an acetochlor EC formu l ation on a primary crop are adequate to support the to l erance request, and a request to add rice as a rotational crop to an acetochlor EC label. However , there are inadequate field trial data to support rotational crops on an acetochlor ME formulation labe l. The petitioner was recently remind ed of th e need fo r rotational crop da ta using an acet o chl or ME formu l ation on the primary crop. (PP#OF7703, D387534, J. Stokes, 5/5/ 1 1, and C hemSAC meeting of 04/20111.) 

## If it is the intent of the petitioner to add peanut to the label of the ME formulation , then the petitioner must submit afull set of rotational crop data for peanut using the MEformulation (EPA Reg. No. 524-591 ) at the maximum application rate. The request to remove rice as an excep tion from the c urrent grain and straw of cerea l grain to l erances without additional data has been discussed by ChemSAC (10/5/11). ChemSAC found this proposal to be acceptab le , primarily because there were non-quantifiable residues on the other cereal grains, there were limited areas where this rotation would occur , and because rice straw had been removed as a livestock feed stuff in th e most recent Table I. There was no request from the reg i strant, nor d i scussion of allowing rice as a rotational crop on acetoch l or ME l abe ls . Although data are inadequate for rotational crops on acetoch l or ME labels, it is unlikely t h at use of the acetochl or ME formulation wi ll resu lt in finite residues on grains, so the amendment may be allowed while data are being devel oped as a condition of registration.
A revised Sect ion F is required, sta ting the proposed to lerances as fo ll ows : Grain , cereal, forage, fodder and straw, group 16 , excep t com , grain sorghum , and wheat, straw at 0.3 ppm Grain, cereal, group 1 5, except com, grain sorghum, and wheat, grain at 0.05 ppm

Note to PM: Concurrent with the establishment of the proposed tolerance for Grain, cereal, forage, fodder and straw, group 16, except corn, grain sorghum, and wheat, straw at 0.3 ppm, and Grain, cereal, group 15, except corn, grain sorghum, and wheat, grain at 0.05 ppm under 180.470(d), the tolerances for Grain, cereal, forage, fodder and straw, group 16, except corn, grain sorghum, rice and wheat, straw at 0.3 ppm 

### Grain, cereal, group 15, 

### except co r n, grain sorghum, rice, and wheat, grain at 0.05 

### ppm listed under 180.470(d) shou ld be removed.

Page 3 of 12The alachlor metabolite HEMA mu st be rep lenished prior to publication of the to lerance.
A human health risk assessment is forthcoming (dietary assessment only).


### Background The chemical structure and nomenclature of acetochlor, the EMA and HEMA moieties, and Metabolite 57 are presented in Table 1. The physiochemical properties of the technical grade of acetoc hlor are presented in Table 2.

Table 1. Acetochlor Nomenclature

. Chemical structure lLC/"-...0 0**~**

# l~cl N

H 3 C**~** CH 3 

# I //
Common name Acetochlor Company experime nta l name None IUPAC name 2-ch l oro-N-ethoxymethyl-6'-et hylacet-o-tolu idide CAS name 2-ch loro-N- (ethoxymethyl)-N-(2- ethyl-6-methylphenyl)acetamide CAS registry number 34256-82-1 End-use product (EP) 3 lb / gal Mcap formulation (MON 63410 Herbicide, EPA F ile Symbo l No

. 524

- LOR) Chemical structure of EMA NH 2 mo iety lLC -;::/ CH 3
J 

# I**~** CAS Name: 2-ethyl-6

-methylaniline Acetochlor EMA-type 0 metabolites 1 Rl-......... 

# )l N R2

H3 C**~** CH3 

# I //

Page 4 of 12Table 1. Acetochlor Nomenclature. Chemical str u cture of HEMA moie ty

Acetochlor H EMA

-type metabolites 1

Acetochlor M etabol ite 57 C AS Name: 2-(1

- hydroxyethyl)-6- meth ylani lin e 0 R3......._ RI .........._ Jl 0 N R2 

### H,C

0

HNJlCOOH

OH N-(6-ethyl-3-hydroxy-2-methylphenyl) oxamic acid For the acetochlor EMA- and HEMA-type metabolites , the Rl funct io nal group can consi st of

- H or - CH 20CH2 C H 3 and the R2 functio nal group may consi s t of many d ifferent moieties. The R3 functional group for acetochl or HEM A-type metab o lites can consist of

- H or a variety of components such as sugars.

Table 2. Physicochemical Properties of Acetocblor. Parameter Value Referenc

. e Melting point/range 163 °C at I 0 mm Hg; decompo s it ion Residue C hemistry Cha pter occurs before the bo iling po int at of the Acetochlor TRED atm ospheric pressure (calculated by ( DP# 297 06 2, 5 / 31 /05, S. extrapolation of vapor pressure at lo we r Ary) temperature) pH 4.41 , 1 % solution in acetone:water (I: 1 , v:v) Density 1 .123 g/mL at 20 °C Water so lub il ity 223 mg/ L at 25 

## o c Solvent solub ili ty Infinitely soluble in acetone , benzene, carbon tetrachloride, ethanol , chl oroform, and toluene at 25 °C Vapor pressure 0.045 11m H g (4.5 x 10" 5 mm H g) at 25 °C Dissocia tion constant , pKa Not applic able because acetochlor is neither an acid nor a bas e. Octano Vwate r partition coefficient , 970 ( Dow stu dy) or 1082 (Monsanto Log (Kow) study); differences are like ly due to experimental error

Page 5 of 12Table2. Physicochemical Properties of Acetochlor. Pa rameter Value Referenc e UV/v isible absorption spectrum Not availab le

860.1200 Directions for use Monsanto has submitted a supp lemental label to add rice as a rotational crop to MON 63410 (EPA Reg. No. 524-591) a ME formulation (3 lb a.i./gal). The fie ld treated with this product may be rotated the next season to rice. Note: The crop field trial data for rotational grains were collected using an EC formulation on the primary crop (See 860.1900, this memo). 860.1900 Field Accumulation in Rotational Crops The Acetochlor Registration Partnership (ARP), comprised of Monsanto and Dow AgroSciences, submitted a petition (PP#6 F 4 791) in 1996 supporting the direct use on sweet com of acetochlor, formulated as an EC f ormulation. In addition, under the sweet corn pet ition and a second petition (PP#IF6263) submitted in 2001, ARP requested revision to t heir current acetochlor labe ls to allow for replanting of the following rotational crops: potatoes; sugar beets; dried peas and beans (subgroup 6C); cereal grains (except rice), alfalfa, clover, and sunflowers. The submitted rotational crop field trials, were accompanied by full data sets using an acetochlor EC formulation on potatoes, sugar beets, dried peas and beans, oats, sunflowers, alfalfa and clover, were considered adequate to add these uses to the label and for the establishment of tolerances for inadvertent acetoch lor residues((§ 40 CFR 180.470a). For each rotational crop, an adequate number of field trials were conducted in the appropriate geographic regions. Ace tochl or (EC formulation only) was applied to the primar y com crop at the current maximum seasona l application rate ( 3 lb ai/A), and the rotational crops were planted the spring (9 -12 months) fo ll owing application (06/20/06, D. Davis).
Monsanto has requested a waiver from the requirement of a full set of field rotational crop trials for acetochlor on rice. Monsanto originally requested tolerances for inadvertent residues of acetochlor on the cereal grains crop group (except corn and rice). In their or i ginal petition for establishment of inadvertent (rotational crop) tolerances, they specifically reques ted that rice be excluded from t he crop group, and provided no field trials on rice. Com was originally excluded from the tolerance for inadvertent residues of acetochlor on the cereal grain crop group because corn was registered as a primary crop. Full data sets (860.1500) are available for the other representative commodities of the cereal grain crop group. Residues are non-quantifiable in the grains, but finite res idue s are found in the forages , hays, and straws.
Now Monsanto has request ed that the exclusion of rice from the crop group be deleted, but without providing field trial data for rice. Corn, sorghum, and wheat are now excluded from the crop group tolerance for inadvertent residues on cereal grains, because there are primary crop tolerances on those commodities.

Page 6 of 12ChemSAC found this proposal to be acceptabl e , primari ly beca u se there were non-quantifiabl e residues on the other cereal grain s, there were limited areas where thi s rotation would occu r, and because rice straw had been removed as a livestock feed stuff in the mo st recent Table 

### I.
Concl usion : HED has no ticed that all current rotational tolerances have b een es tablished from field crop residue data generat ed from use of EC fo rmulati o n s. The peti ti oner has requested the additi on of rice as a rotational crop to a ME formu l ation, e.g., MON 63410 (EPA Reg. No. 524-591). According to OPPTS Residue Ch emistry Test Guidelines 860.1500, the use of a s lo w - rel ease encapsulated formulatio n may lead to high er residues than conven ti onal formu lations. Thus , if the u se of a sl ow-r e lease formu latio n i s proposed, th en res idu e data reflectin g thi s ty pe will be required. It is further stated that this type of formulation will normall y require a fu ll se t of field trials to include the same number of trial s as ne eded to obtain an original to lerance regardless of th e timing and mode of app li cation and the amount of data avai labl e on other formu l at i on classes. Available extensive rotatio na l crop field tri al s conduc ted at 3.0 lb ai/A ( l x the m ax imum proposed seasonal appli cation rate) with an EC formu lation have been s ubmitted and these data support the PBi s (plantback interval s) specified on the EC product label s, and the t o lerances for indirect or inad vertent residues of acetoc hl or inion the co mmodi t ies of nongrass animal feeds ; s ugar beets; cer e al grains except corn, sorghum , ri ce, and wheat ; dri ed sh e ll ed peas and beans ; potatoes; soybean s; s unflower seed; and wheat (D193048, 11 /23/93, M. Flo od ; D2750 19 , 6/20/06, D

. Davis.). C urren tly these rotational crops are li ste d on th e ME formulation MON 63410. Note: H owever, HED has not reviewed rotational crop fiel d data i n which the primary crop was treated with a ME formula t ion prior to planting rotation al crops. There are inadeq uate field tri al data to suppo rt the request to add ri ce as a rotational crop to an acetochl or ME formulation labe l, and to supp ort the current rotational crops o n the aceto chlor ME label. Th e issue of rotational crops being adde d to a acetochlor ME form ul ation labe l has been discussed by C h e mSA C (04/2 0 / 11 ) , and th e following is needed to add a cro p as a rotational crop to a ME formu lation label : The petitioner must submit a fu ll set of rota t ional crop data fo r the crop u sing th e ME formulati on (EPA Reg. No

. 524-591) at th e maximum application rate. 860.1550 Proposed T olerances The current tolerance ex press ion for acetochlor inadverte nt to lerances i s: To lerances are esta bli shed for i nd irect or inadvertent residues of ac etochl or, including its metabolite s and d eg rada t es, in or on the raw agric ultural commodi ti es in the table to this paragraph when present therein as a result of app li cation of acetochlo r to th e growing crops in t he tab le to paragraph (a) of thi s section. Comp liance with th e to ler ance le ve l s spec ified below is to be determ in ed by measuring only acetoc hl or, 2

- chl oro - 2'- m ethy l-6- ethy l

- N

ethoxymethylacetanilide, and its metabolite s containing the ethy l methyl ani li ne (EMA) moiety and the hydroxyethyl methy l aniline (HEMA) moiety. B oth parent and the named metabolites s ha ll be determined as ethyl methy l aniline (EMA) and h ydroxye th y l methy l

Page 7 o f 12aniline (HEMA), and calculated as the stoichiometric equivalents of acetochlor, in or on the following commodities. The wording of the tolerance expression is in accord with our recent gui dance (S. Knizner, 5 /27/ 09). The petitioner has requested changing the inadvertent tolerances for grains from the current Grain, cereal, forage, fodder and straw, group 16 , except com , grain s orghum, rice and wheat, straw at 0.3 ppm Grain , cereal , group 15, except com, grain sorghum, rice, and wheat, grain at 0.05 ppm
to remove the exception for rice as follows: Grain, cereal, forage, fodder and straw, group 16 , except com, grain sorghum , and wheat, straw at 0.3 ppm Grain, cereal, group 15, except com, grain sorghum, and wheat, grain at 0.05 ppm The change in the tolerance is supported. However, in Sect ion F of the petition, the proposed tolerances still include rice as an exception. A revised Section F is required.

860 . 1650 Submittal of Analytical Refe rence Standards Analytical standards for acetochlor and its EMA and HEMA metabolites are currently available in the EPA National Pesticide Standards Repository (personal communication with Theresa Cole , ACB, 8/ 20/ 12) , with expiration dates as shown below acetochlor, expiration date 10 / 31 /2013 acetochlor E SA, (tert-sulfonic acid na salt), expiration date 4/ 30 / 2013 acetochlor metabolite (E MA) 2- ETHYL-6-METHYLANILINE , expirati o n date 5/ 31/2015 acetochlor metabol ite (HEMA) 2-( 1-hydroxyethyl)

- 6

- methylaniline , E XPIRED 7/ 3112012 acetochlor tert oxanilic acid , expiration date 4/ 30 / 2014 acetochlor tert-sulfinyl acetic acid, Na salt, expiration date 1131113 The alachlor metabolite HEMA must be replenished now. Analytical standards must be rep lenished, as requested, by the Pes ticide Repository. Analytical standards should be sen t to the attention of either Theresa Cole or Thuy Ngygen at the following address:
US EPA National Pesticide Standards Repository / Analytical Chemistry Branch!OPP 701 Mapes Road Fort George G. Meade, MD 20755-5350

Page 8 of 12Page 9 of 12International Residue Limits



### A cetoc

### hl (PC C d 121601 D t 

### fR t 

### 8/9/12) or o e ' 

### a eo eques Summary ofUS and International Tolerances and Maximum Residue Limits Res idue Definition: 

## us Canada Mexico2 Codex3 40 CFR 180.470 None None Plant & Livestock: acetoc hlo r, 2-chloro-2'- methyl-6-ethyl- N

- ethoxymethy l acetanilide, and its metabolites containing the ethyl methyl aniline (EMA) moiety an d the hydroxyethyl methyl aniline (HEMA) moiety

. Both parent and the named metabol i tes s hall be determined as ethyl methyl aniline (EMA) and hydroxyethyl methyl aniline (HEMA), and calculated as the stoichiometric equivalents of acetochlor Commodity ' Tolerance (ppm) / Maximum Residue Limit (mg /

kg) 

# us Canada Mexico.t Codex 3 Grain, cereal, group 15,except 0.05 com, grain sorghum, and wheat, grain Grain, cereal, forage, fodder 0.3 and straw, group 16, except com, grain sorghum, wheat, straw

Completed : M. Negussie; 08/20/2012



### .. Includes only commodJtJes of mterest for th1s actJOn. Tolerance values should be the H E

D recommendatiOns and not those proposed by the applicant. 2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes. 3 * = absent at the limit of quanti tation; Po = postharvest treatment, such as treatment of stored grains. PoP = proc esse d postharvest trea ted commodity, such as processing of treated stored wheat. (fat) = to be measured on the fat portion of the sample. MRLs indicated as proposed have not been finali ze d by the CCPR and the CAC.

Page 10 of 12References
DP Barcode: D189047 S ubj ect: PP#3F2966.PP#1F4011. Acetoch lor Registration Partnership. Acetochlor EC Herbicide for Use on Field Com. Confined Rotational Crop Study. Field From: Dated: MRID(s):

DP Barcode: Sub j ect: From : Dated: MRID(s): Rotational Crop Studies. M. Flood 08/ 23 / 93 42549908,42549914,42549919 , 4259150 1

D193048 Acetochlor. Rota tional Crop Tolerances for Soybeans, Wheat , and Sorghum M. Flood 01 / 11194 None

DP Barcode: D275019 Subject: Acetoch lor: Petitions for To lerances on Sweet Com and Rotational Crops of Nongrass Animal Feeds (Group 18) , Sugar Beets, Dried Shelled Beans and Peas (Subgroup 6C), S unflowers, Potatoes , Cerea l Grains (Group 15), and Forage, Fodder, and Straw of Cereal Grains (Group 16)

. Summary of Analytical
From: Dated: MRID(s): Chemistry and Residue Data. Petition Numbers: 6F4791 and 1F6263 D. Davis 06 / 20/ 06 44107101,44 1 07102,44107 1 03 , 44107104 , 44107 1 05 , 44 1 07106 , 44107107, 45322102,45322103,45322104 , 45322105,45322106,45322 1 07,45322108, 45322109 , 45322110,45322111,45322112,45483301
DP Barcode : D316496 Subject: Acetochlor. Tolerance PetitionRequesting the Establishment of Permanent

From: Dated: MRID(s):
DP Barcode: Subject: From : Dated: MRID(s): Tolerances Associated with Section 3 Registration for Food Use of the Herbicide Acetoch lor on Sorghum. Summary of Analytical Chemistry and Residue Data

. W. Drew 11121106 46507101,46507102

none Interim Guidance on Tolerance Expressions S. Knizner 5/ 27/ 09 none

Page 11 of 12DP Barcode: D359990 Subject: Acetochlor. Petition Request for New Uses on Cotton (PP#8F7443) and Soybean (PP# 8F7448). Summary of Analytical Chemistry and Residue Data. From: S. Humme l Dated: 06117/09 MRID(s): 47695701,47552201,47555601
DP Barcode: 0387534 Subject: Acetoch lor. PP#OF7703. Request to Establish a Rotational Tolerance for Inadvertent Residues In/On Peanut. Request to Add Peanut as a Rotational Crop to an Acetochlor ME Label. Request for Label Restriction on Feeding Peanut From: Dated: MRID(s): Forage to Li vestock. J. Stokes 5/5/11 41338503

RDI:SHummel:8/16/12:RAB4Chemists:8/22/12 Petition Number : 2F7996 DP Barcode: 0401205 PC Code: 121601

Page 12 of 12