UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460
OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### DP Barcode: 394887- PC Codes: 288008, 288009, 288010 Date: November3, 2011 MEMORANDUM 

### SUBJECT: Updated Drinking WaterExposure Assessmentfor Aminocyc1opyrachlor Acid and its Degradate Cyc1opropanecarboxylic Acid (IN-V0977) for Turf, and the Proposed New Use on Rangeland (Tolerance # 

### OF7817). 

### TO: Thurston Morton, Risk Assessor, RAB 4 SusanHummel, Team Leader, RAB 4 Health Effects Division (7509P)



### FROM: Kable Davis, Risk Manager (RM25) Herbicides Branch RegistrationDivision (7505P) Reuben Baris, Environmental Scientist

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# \**l/~** {Zo\\ Environmental Risk Branch VI Environmental Fate and Effects Division (7507P) Mark Corbin, Chief 

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Environmental Risk Branch VI Environmental Fate and Effects Division (7507P)
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### REVIEWED BY: Stephanie Syslo, RAPL

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### Environmental Fate and Effects Division (7507P) The Environmental Fate and Effects Division completed an updated drinking water exposure assessment for the chemical aminocylopyrachlor (ACP) in support of the proposed new use on rangeland. This memorandumtransmits the updated drinking water exposure assessmentto support the Human Health Risk Assessment and update the previous assessment which inappropriately applied a percent cropped area (PCA) to all uses of ACP. The previous drinking water exposure assessment was completedby the EFED on January 8, 2010 in support of the New Chemical registration of ACP (D368238). There is currentlyno PCA establishedfor turf, and the national default PCA of 0.87 should be applied to exposure Page 1 

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# 1II1IIIIII 2087395

### estimates for agricultural crops only; there is no PCA for non-agricultural uses. Further, since ACP is used on non-agricultural areas, turf, and isproposed for rangelanduses, the application of a PCA is inappropriate and inconsistentwith EFED divisional guidance. Therefore a PCA of 1.0 is applied to all exposure estimates; this is reflected in the EDWCs presented in Table 1. 

### Bolded EDWCs arerecommended for use in the human health risk assessmentfor the proposed new use on rangeland. The registrant is seeking aregistration for the proposed new use on rangeland which includes seven proposedproducts; two technical products and five end-useproducts (EPA Reg. No. 352- 782, EPA Reg. No. 352-783, EPA Reg. No. 352-785, EPA Reg. No. 352-786, EPA Reg. No. 352-787, EPA Reg. No. 352-ILN, EPA Reg. No. 352-ILR). The proposed products are formulated with five different active ingredients: aminocyclopyrachlor acid, aminocyclopyachlor methyl ester, aminocyclopyrachlorpotassium salt, and two coformulants chlorsulfuron and metsulfuron. Based on the submitted environmental fate data, the aminopyrachlorpotassium salt dissociates to the acid rapidly prior to application (when mixed with water as the salt formulation labels state) and the methyl ester readily hydrolyzes to the acid in the environment; therefore this assessment is based on the exposure from acid equivalents (a.e.) ofaminocyclopyrachlor. The Agency does not routinely include an evaluation of mixtures of active ingredients in its risk assessments. In the case of the productformulations of active ingredients (that is, aregistered product containing more than one active ingredient), each active ingredient is subject to an individual risk assessmentfor regulatory decision regarding the active ingredientfor aparticular use site. The maximumproposed applicationrate for rangeland is 0.17 lb a.e.zacre, 

### with a proposed maximum number ofapplications of two (2) at 30-day intervals, resulting in a total annual applicationrate of 0.34 lb a.e.lacre. This is higher than the maximum annual applicationrate assessed in the previous drinking water assessment (0.324 lb a.e.Zacre for use on turf). This assessment includes aerial applications to rangeland, and revised exposure estimates resulting from applications to turffor aminocycopyrachlor acid and the degradate cyclopropanecarboxylic acid (IN-V0977). The Residues ofConcern Knowledgebase Subcommittee (ROCKS) determinedthat aminocyclopyrachlor acid and its degradate cyclopropanecarboxylic acid (IN-V0977) are residues ofconcern in drinking water. The degradate IN-V0977 is included in this assessment because oftoxicity concerns. Additional information is described in the decision memorandum D370638 dated 15 October 2009. Due to the difference in toxicities betweenthe parent and the degradate, individual EDWCs were calculatedfor the parent aminocyclopyrachlor acid and its degradate cyclopropanecarboxylic acid (IN-V0977). EDWCs arepresentedbelow in Table 1.



### Page 2 of7

### Table 1. EstimatedDrinking Water Concentrations (EDWCs) resultingfrom applications ofaminocycIopyrachlor acid and the degradate cycIopropanecarboxylic acid (IN-V0977) 

### f h dId dt f

or t epropose range an an ur uses. Drinking Application PeakDay Annual Water Rate Adjustment (acute) Average Source Compound Use Method (interval Factor 1 Concentration (chronic) (Model) between (fJgIL) Concentration applications) (pgIL) 2app @ Rangeland Aerial 0.17 lb a.e./A 34.28 21.32 Aminocyclopyrachlor (30 days) Acid 3 app @ 0.108 Turf Granular Ib a.e./A 31.36 19.50 Surface Water (30 days) 1.0 (FIRST) 2app @ Rangeland 0.01 Ib a.e./A 2.12 1.52 Cyclopropanecarboxylic Granular 2 (30 days) Acid (IN-V0977) 3 app @ Turf 0.0061b a.e./A 2.00 1.43 (30 days)

--- 2app @



### --- Rangeland 0.171b a.e./A 42.2 <42.2 Ground Water Aminocyclopyrachlor (30 days) (SCI-GROW) Acid 3 app @ 0.108 Turf3 --- a.e./acre --- 40.2 <40.2 (30 days) Bold values denote maximumEstimated Drinking Water Concentrations (EDWCs) 1AdjustmentFactors: PCA = PercentCrop Area 2Granular method ofapplication was selected for the degradate (Drift = 0.0% and ApplicationEfficiency = 100%). All applications are liquid unless otherwisenoted. 3Model estimates obtained from D386238 

### Tier I screening models was employed for this assessment. For surface water, the FIRST CEQPA Index Reservoir ,S.creeningIool) Version1.1.1 model was used to estimate drinking water concentrations. For ground water, the SCI-GROWmodel (Screening Concentration in Ground Water Program Version 2.3 was used to predictthe maximum acute and acute concentrations present in shallow ground water. Table 2 presents the relevant inputparameters for FIRST, Table 3 presents the relevant inputparameters for SCIGROW. Relevant outputfiles for FIRST and SCIGROW are included in the attachment. The applicationrate for the degradate can be calculatedby multiplyingthe applicationrate of the parent (e.g., 0.17 lbs. a.e./acre) by the fraction of the maximum detected degradate from the submitted fate studies (0.146; MRID 47560211) then multiplied by the ratio of the molecular weights of the degradate to parent (86.09/213 .62). Followingthis equation, the maximum single application rate was 0.01 Ibs. a.e./acre for the proposedrangeland use. Soil photolysis of the parent is slow (t1l2

### = 129 days; MRID 47560213) and the primaryroute offormation of the degradate is through aqueous photolysis; therefore, exposure of the degradate is most likely to occur from spray drift in aqueous environments. There are few details on the fate and transport properties ofthe degradate IN-V0977. For modeling purposes certain fate properties were assumed to be stable where data are not available per EFED guidance. Additional detail on the Page 3 of7environmental fate and transport properties ofaminocyc1opyrachlor and its degradate IN-V0977 can be found in the previous drinking water exposure assessment D368238, dated Jan. 8,2010. 

### Table 2: FIRST InputParameters for AminocyclopyrachlorAcid and the Degradate Cyclopropanecarboxylic Acid (IN-V0977) for the Proposed Rangeland and Registered Turf Use

Parameter: Input Value: Data Source/Rationale: 1 0.17 EPA Reg. No. 352-786 (rangeland - parent) Application Rate (lbs a.e./acre) 0.108 EPA Reg. No. 352-TOT (turf

- parent) 0.01 EPA Reg. No. 352-786 (rangeland

- degradate) 2 0.006 EPA Reg. No. 352-TOT (turf

- degradate) 2 2 EPA Reg. No. 352-786 (rangeland - parent) Maximum Number of 3 EPA Reg. No. 352-TOT (turf- parent) Applications/Year 2 EPA Reg. No. 352-786 (rangeland

- degradate) 2 3 EPA Reg. No. 352-TOT (turf

- degradate) 2 30 EPA Reg. No. 352-786 (rangeland

- parent) Appl ication Interval (days) 30 EPA Reg. No. 352-TOT (turf- parent) 30 EPA Reg. No. 352-786 (rangeland

- degradate) 2 30 EPA Reg. No. 352-TOT (turf

- degradate) 2 Percent Crop Area (as decimal) 1.0 No PCA for the proposed and existing use patterns. Kllf Parent 12 Average Koc value: MRID 47560219 Degradate 2.735 Model Estimation (EPISuite v4.0, KOCWIN Version 2.0) using CAS 

### # 1759-53-1 (cyclopropanecarboxylic acid) Aerobic Soil Metabolism Half-life 373 Parent value represents the upper 90% (days) confidence limit on the mean value Parent (MRID 47560214 and 47560221). Degradate 

# o(stable) Degradate value is unavailable; entered zero as suggestedby FIRST users manual Is the pesticide wetted-in? No Chemical not known to be activated by water Method ofApplication A Aerial (rangeland

- parent) D GranularApplication (turf

- parent) D Granular App, (rangeland & turf

- degradate) 3 Incorporation Depth (inches) 0 BroadcastApplication (for D above) Solubility (ppm) Parent 2810 MRID 47559816 Degradate 149,540 Model Estimation (EPISuite v4.0, WATERNT Version 1.01) using SMILES string O=C(O)C(C1)C1 (cyclopropanecarboxylic acid) Aerobic Aquatic Metabolism Halflife (days) 

# o(stable) MRID 47560216 Parent Page 4 of7

# o(stable) Degradate value is unavailable; entered zero as Degradate suggestedby FIRST users manual Photolysis Half-life (days) Parent 7.8 MRID 47560211 Degradate 

# o(stable) Degradate value is unavailable; entered zero as suggestedby FIRST users manual I Input Parameters were selected in accordance with the Guidance for Selecting Input Parameters (Version 2.1)

dated October 22,2009 2 Application Rate of Degradate = (max. application rate of parent) x (fraction of maximum detected degradate) x

(molecular weightofdegradate/ molecular weight of parent) Non-Crop = (0.284Ibs. a.e.laere) x (0.146) x (86.091213.62) = 0.017Ibs. a.e.lacre Turf= (0.108 Ibs. a.e.lacre) x (0.146) x (86.091213.62) = 0.006 Ibs. a.e.laere 3 Granular method of application was selected for the degradate (Drift = 0.0% and App. Efficiency = 100%). NA = Not Applicable


### Table 3: SCI-GROWInput Parameters for Aminocyclopyrachlor Acid for Non-Crop and 

### TurfUse I 

### Input

Parameter: Value: Data Source/Rationale 2 Application Rate (lbs a.e./aere) 0.17 EPA Reg. No. 352-786 (rangeland0.108 parent) EPA Reg. No. 352-TOT (turf

- parent)

Maximum Number of 3 EPA Reg. No. 352-TII (non-crop

- parent) Applications/Year 3 EPA Reg. No. 352-TOT (turf

- parent) Aerobic Soil Metabolism Half-life (days) Value represents the upper 90% confidence limit on the mean value Parent 373 (MRID 47560214 and 47560221). 

# x; Parent 12 Average Koc value: MRID 47560219

1 Since the parent is not susceptible to soil photolysis (t 1/2

## =129 days; MRID 47560213), the degradate is not an issue for ground water contamination; therefore, no SCI-GROW modeling was performed. 2 Input Parameters were selected in accordance with the Guidance for Selecting Input Parameters (Version 2.1)

dated October 22, 2009

Page 

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### Attachment. Model Output Files FIRST FIRST run (comparison to DWA 2010) Aug 25, 2011
RUN No. 1 FOR ACP ON range * INPUT VALUES *

RATE (#/AC)

ONE(MULT) No.APPS & INTERVAL SOIL Koc SOLUBIL (PPM) APPL TYPE (%DRIFT) %CROPPED INCORP AREA (IN) .170( .331) 2 30 12.0 2810.0 AERIAL(16.0) 100.0 .0
FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) METABOLIC DAYS UNTIL

(FIELD) RAIN/RUNOFF HYDROLYSIS (RESERVOIR) PHOTOLYSIS (RES. -EFF) METABOLIC (RESER. ) COMBINED (RESER. ) 373.00 2 N/A 7.80- 967.20 .00 967.20
UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007 PEAK DAY (ACUTE) CONCENTRATION 34.276 ANNUAL AVERAGE (CHRONIC) CONCENTRATION 21.315
RUN No. 2 FOR acpdeg ON range 

### * INPUT VALUES 

### *

RATE (#/AC)

ONE(MULT) No.APPS & INTERVAL SOIL Koc SOLUBIL APPL TYPE (PPM) (%DRIFT) %CROPPED INCORP AREA (IN) .010( .020) 2 30 2.7******* AERIAL(16.0) 100.0 .0
FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) METABOLIC DAYS UNTIL

(FIELD) RAIN/RUNOFF HYDROLYSIS (RESERVOIR) PHOTOLYSIS (RES. -EFF) METABOLIC (RESER. ) COMBINED (RESER. ) .00 2 N/A .00- .00 .00 .00
UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007 PEAK DAY (ACUTE) CONCENTRATION 2.109 ANNUAL AVERAGE (CHRONIC) CONCENTRATION 1.509



### Page 6 of7RUN No. 3 FOR acp ON turf 

### * INPUT VALUES 

### * RATE (#/AC)

ONE (MULT) No.APPS & INTERVAL SOIL Koc SOLUBIL (PPM ) APPL TYPE (%DRIFT) %CROPPED INCORP AREA (IN) .108( .307) 3 30 12.0 2810.0 GRANUL( .0) 100.0 .0
FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) METABOLIC

(FIELD) 373.00 DAYS UNTIL RAIN/RUNOFF 2 HYDROLYSIS (RESERVOIR) N/A PHOTOLYSIS (RES.-EFF) 7.80- 967.20 METABOLIC (RESER. ) .00 COMBINED (RESER. )

967.20
UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007 PEAK DAY (ACUTE) CONCENTRATION 31. 364 

### SCIGROW (rangeland use only) ANNUAL AVERAGE (CHRONIC) CONCENTRATION 19.500

SCIGROW VERSION 2.3 ENVIRONMENTAL FATE AND EFFECTS DIVISION OFFICE OF PESTICIDE PROGRAMS U.S. ENVIRONMENTAL PROTECTION AGENCY SCREENING MODEL FOR AQUATIC PESTICIDE EXPOSURE SciGrow version 2.3 chemical:ACP time is 10/26/2011 16:28:11

Application rate (lb/acre) 0.170 Nwnber of applications 2.0 Total Use (lb/acre/yr) 0.340 Koc (ml/g) 1.20E+01 Soil Aerobic metabolism (days) 373.0 groundwater screening cond (ppb) = 4.22E+01 ************************************************************************



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