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: November 3, 2011

MEMORANDUM

SUBJECT: Updated Drinking Water Exposure Assessment for 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

Susan Hummel, Team Leader, RAB 4

Health Effects Division (7509P)

FROM:

Kable Davis, Risk Manager (RM25)

Herbicides Branch

Registration Division (7505P)

Reuben Baris, Environmental Scientist-,Z3~ \l/~ {Zo\\

Environmental Risk Branch VI

Environmental Fate and Effects Division (7507P)

Mark Corbin,

Environmental

Chief

Risk Branch VI

M U

Environmental Fate and Effects Division (7507P) .

REVIEWED

BY: Stephanie Syslo, RAPL ~~~#1.k'f ~ptv Environmental Risk Branch VI r-- cc- "/ -

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 memorandum transmits the updated drinking water exposure assessment to

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 completed by the EFED on January 8,

2010 in support of the New Chemical registration of ACP (D368238). There is currently no

PCA established for turf, and the national default PCA of 0.87 should be applied to exposure

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estimates for agricultural crops only; there is no PCA for non-agricultural uses. Further, since

ACP is used on non-agricultural areas, turf, and is proposed for rangeland uses, the application of

a PCA is inappropriate and inconsistent with 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 are recommended for use in the human health risk assessment for the proposed new use

on rangeland.

The registrant is seeking a registration for the proposed new use on rangeland which includes

seven proposed products; two technical products and five end-use products (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, aminocyclopyrachlor potassium salt, and two coformulants chlorsulfuron and

metsulfuron. Based on the submitted environmental fate data, the aminopyrachlor potassium 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.) of aminocyclopyrachlor. The

Agency does not routinely include an evaluation of mixtures of active ingredients in its risk

assessments. In the case of the product formulations of active ingredients (that is, a registered

product containing more than one active ingredient), each active ingredient is subject to an

individual risk assessment for regulatory decision regarding the active ingredient for a particular

use site.

The maximum proposed application rate for rangeland is 0.17 lb a.e.zacre, with a proposed

maximum number of applications of two (2) at 30-day intervals, resulting in a total annual

application rate of 0.34 lb a.e.lacre. This is higher than the maximum annual application rate

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 turf for aminocycopyrachlor acid and the degradate cyclopropanecarboxylic

acid (IN-V0977).

The Residues of Concern Knowledgebase Subcommittee (ROCKS) determined that

aminocyclopyrachlor acid and its degradate cyclopropanecarboxylic acid (IN-V0977) are

residues of concern in drinking water. The degradate IN-V0977 is included in this assessment

because of toxicity concerns. Additional information is described in the decision memorandum

D370638 dated 15 October 2009. Due to the difference in toxicities between the parent and the

degradate, individual EDWCs were calculated for the parent aminocyclopyrachlor acid and its

degradate cyclopropanecarboxylic acid (IN-V0977). EDWCs are presented below in Table 1.

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Table 1. Estimated Drinking Water Concentrations (EDWCs) resulting from applications

of aminocycIopyrachlor acid and the degradate cycIopropanecarboxylic acid (IN-V0977)

f h or t e proposedId range an andturf uses.

Drinking Application Peak Day 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

Turf 3 --- a.e./acre --- 40.2 <40.2

(30 days)

Bold values denote maximum Estimated Drinking Water Concentrations (EDWCs)

1 Adjustment Factors: PCA = Percent Crop Area

2 Granular method of application was selected for the degradate (Drift = 0.0% and Application Efficiency = 100%).

All applications are liquid unless otherwise noted.

3 Model estimates obtained from D386238

Tier I screening models was employed for this assessment. For surface water, the FIRST CEQPA

Index Reservoir ,S.creening Iool) Version1.1.1 model was used to estimate drinking water

concentrations. For ground water, the SCI-GROW model (Screening Concentration in Ground

Water Program Version 2.3 was used to predict the maximum acute and acute concentrations

present in shallow ground water. Table 2 presents the relevant input parameters for FIRST, Table

3 presents the relevant input parameters for SCIGROW. Relevant output files for FIRST and

SCIGROW are included in the attachment.

The application rate for the degradate can be calculated by multiplying the application rate 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). Following this equation, the maximum single

application rate was 0.01 Ibs. a.e./acre for the proposed rangeland use. Soil photolysis of the

parent is slow (t1l2 = 129 days; MRID 47560213) and the primary route of formation 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 of the 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

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environmental fate and transport properties of aminocyc1opyrachlor and its degradate IN-V0977

can be found in the previous drinking water exposure assessment D368238, dated Jan. 8,2010.

Table 2: FIRST Input Parameters for Aminocyclopyrachlor Acid 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

suggested by FIRST users manual

Is the pesticide wetted-in? No Chemical not known to be activated by water

Method of Application A Aerial (rangeland - parent)

D Granular Application (turf- parent)

D Granular App, (rangeland & turf - degradate) 3

Incorporation Depth (inches) 0 Broadcast Application (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

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o(stable) Degradate value is unavailable; entered zero as

Degradate suggested by FIRST users manual

Photolysis Half-life (days)

Parent 7.8 MRID 47560211

Degradate o(stable) Degradate value is unavailable; entered zero as

suggested by 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 weight of degradate/ 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-GROW Input Parameters for Aminocyclopyrachlor Acid for Non-Crop and

Turf Use 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

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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

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RUN 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

SCI GROW

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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