UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, DC 20460

 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

PC Code: 128974

DP Barcode: 405093

Date: September 14, 2012

MEMORANDUM

Subject: Quinclorac: Registration Review Drinking Water Assessment 

To: Elissa Reaves, Branch Chief, RAB4

Health Effects Division (7509P)

Wilhelmena Livingston, Chemical Review Manager

Risk Management and Implementation Branch IV

Pesticide Re-evaluation Division (7508P)

From: Michael B. Lowit, Ph.D., Ecologist

Nancy Andrews, Ph.D., Branch Chief

Environmental Risk Branch 1

Environmental Fate and Effects Division (7507P)

Office of Pesticide Programs

This memorandum summarizes the drinking water assessment (DWA) for the registration review 

of quinclorac. This assessment considers registered uses identified in the 2007 registration 

review problem formulation (DP 344485), subsequently assessed new uses, and proposed new 

uses on rhubarb and low growing berries except strawberry (subgroup 13-07H).
2

1. EXECUTIVE SUMMARY

Quinclorac (3,7-dichloro-8-quinolinecarboxylic acid) is a systemic herbicide used to control 

broadleaf and grass weeds. A Tier II screening-level drinking water assessment (DWA) was 

conducted for registered uses and proposed new uses. Quinclorac uses include turf grasses, rice, 

cranberry, aquatic weeds, sorghum, wheat, rangeland/pasture, rights-of-way/fencerow/hedgerow, 

grass grown for seed, fallow land, and grass forage/fodder/hay. Proposed new uses are rhubarb 

and low growing berries except strawberry (subgroup 13-07H) (see recent DWA; DP 397720). 

The low growing berries group includes cranberry, which was assessed previously at the same 

application rate.

A range of application rates and application intervals are permitted for most uses. The 

assessment is based on maximum application rates and minimum application intervals for each 

use. Ground and aerial applications are allowed for several uses. Although both ground and 

aerial applications were modeled, estimated drinking water concentrations (EDWCs) for aerial 

applications are presented when ground and aerial application are permitted by a label (EDWCs 

from aerial applications are higher than those from ground applications). Noted label 

uncertainties are listed in Section 3.2.3.

As expected, in some cases the EDWCs from the current analysis differ from those reported in 

previous analyses. There are several reasons for the difference, including but not limited to the 

following. As identified in the registration review problem formulation some previous 

assessments did not reflect the highest application rates and minimum intervals for some uses. 

Some uses were previously assessed using the Tier 1 surface-water model GENEEC while the 

current assessment is performed according to current EFED guidance1and up-to-date models2

including the Tier II surface water model (PRZM/EXAMS) for applicable uses of quinclorac.

Screening-level Tier I modeling was used to estimate surface water concentrations for use on 

cranberry (provisional cranberry model) and rice (Tier I rice model) because the current Tier II 

model is not parameterized for those uses. The Tier I SCI-GROW model was used to estimate 

groundwater concentrations.

As in past assessments, this assessment does not consider quinclorac major degradation products 

BH 514-1 and BH 514 2-OH. Although these degradates were detected in the laboratory studies, 

they seem to be intermediate degradates (DP 344485), and were not found in field dissipation 

studies at any significant levels. Furthermore, since quinclorac is persistent and mobile, it is 

expected to be the predominant residue in ground and surface waters.

Surface water EDWCs (acute = 511 μg/L and chronic = 511 μg/L) resulting from use on rice

supersede previously recommended EDWCs. The recommended groundwater EDWC has not 

changed (29 μg/L for acute and chronic exposure). Please contact us if refinements are needed.

In order to avoid repetition of material previously provided, please refer to the Registration 

Review Problem Formulation (DP 344485) for detailed information about quinclorac.

 

1 Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides, Version 

2.1, October 22, 2009

2

http://www.epa.gov/oppefed1/models/water
3

2. PROBLEM FORMULATION

This is a Tier II DWA that uses modeling to estimate the surface water concentrations of 

quinclorac in drinking water (source water, pre-treatment) resulting from use on vulnerable sites. 

While Tier I DWAs are designed to screen out chemicals with low potential risk for posing a 

drinking water concern, the Tier II assessment provides more site-specific, refined modeling 

estimates of exposure by using additional environmental fate parameters, specific soil data, 

weather information, and management practices to estimate daily concentrations for an extended 

period of time (up to 30 years). 

Screening-level Tier I modeling was used to estimate groundwater concentrations for all uses 

and surface water concentrations for use on cranberry and rice (the current Tier II model is not 

parameterized for those uses).

2.1. Mode of Action

Quinclorac is a quinoline carboxylic acid. The mechanism of action is generally similar to the 

mechanism for the phenoxy herbicides (i.e., mimicry of the plant growth hormone auxin).

2.2. Use Characteristics

The DWA is based on quinclorac uses as identified in the 2007 Problem Formulation for 

Registration Review (see DP 344485 for details) and subsequently assessed new uses. 

Quinclorac uses identified in the 2007 Problem Formulation were turf grasses, rice, aquatic 

weeds (experimental use permit), sorghum, wheat, rights-of-way/fencerow/hedgerow, grass 

grown for seed, and fallow land. Subsequently proposed uses are rangeland/pasture, 

grass/fodder/hay, low growing berry except strawberry (subgroup 13-07H), and rhubarb. Uses 

and application rates are based on the most recent label data report (label use information system 

report; LUIS) provided by BEAD (7/26/2012) plus recently proposed new uses. Maximum 

application rates, minimum application intervals, and application methods are indicated in Table 

2 (except rice and aquatic weeds). Rice is labeled for a maximum single application of 0.5 lb 

ai/A per season (aerial or ground application). Aquatic weeds are labeled for a maximum of two 

applications per year, with a water concentration of no more than 0.5 mg ai/L. Quinclorac uses 

not included in the 2012 LUIS report are reported in Table 1.

Table 1. Maximum Rates for Quinclorac Uses Not Included in the 2012 LUIS Report

Use Maximum 

Individual

Application 

Rate

(lb ai/A)

Maximum 

Annual 

Number of

Applications

Minimum

Application 

Interval 

(days)

Maximum

Annual 

Rate

(lb ai/A)

Application 

Method

Proposed New Uses

Low growing berry except 

strawberry (subgroup 13-

07H)

0.25 2 30* 0.5 Ground spray

Rhubarb 0.375 2 30* 0.75 Ground spray

* Pre-harvest interval is 60 days for low growing berry (including cranberry) and 30 days for rhubarb.
4

2.3. Monitoring Data

EFED is not aware of any surface or ground water monitoring data for quinclorac.

3. ANALYSIS

3.1. Fate and Transport Characterization

Vapor pressure (7.5 x 10-8 mm Hg at 20o C) and Henry's Law Constant (1.22 to 24.3 x 10-15

atm.m3 mol-1) indicate a low possibility of volatilization from soil and water. Laboratory data 

indicate that quinclorac is stable to hydrolysis, photolysis in soil and sterile water, aerobic soil 

metabolism, and aquatic metabolism (aerobic and anaerobic). Conversely, quinclorac undergoes 

rapid photolysis in non-sterile rice paddy water, natural river waters, and solutions containing 

activated sewage sludge (half-lives of 5-16 days uncorrected for dark controls). Based on 

available laboratory studies, two major (BH 514-1 and BH 514 2-OH; >10% applied) and one 

minor (BH 514-HMe-ester; <10% applied) metabolites of quinclorac were identified. The 

adsorption coefficients for quinclorac and its degradation products suggest that leaching could be 

a route of dissipation. Field studies indicate that quinclorac is moderately persistent to persistent 

(18-176 day half-lives) in terrestrial environments. The octanol/water partition coefficient (KOW) 

of 0.266 also suggests that quinclorac has a low potential to bioaccumulate. A detailed 

assessment of the environmental fate of quinclorac can be found in the new chemical risk 

assessment (DP 250179+).

3.2. Drinking Water Exposure Modeling

3.2.1. Surface Water Modeling

3.2.1.1 Modeling Input

All Uses Except Cranberries and Rice

Tier II surface water EDWCs were calculated using PRZM (Pesticide Root Zone Model, v3.12.3; 

June, 2006) and EXAMS (EXposure Analysis Modeling System, version 2.98.04.06, April 2005) 

models in the PE5 shell3. Standard crop scenarios were selected when available and surrogate 

scenarios (standard and non-standard) were used in the absence of a standard scenario specific to 

a given use. Table 2 lists the input parameters used for the PRZM/EXAMS modeling. A 

representative PRZM/EXAMS output file is provided in Appendix A. Table 4 presents 

EDWCs of quinclorac in surface water sources from the registered and proposed uses. 

 

3 www.epa.gov/oppefed1/models/water
5

Table 2. PRZM/EXAMS Input Parameter Values

Parameter (Units) Input Value and Unit Source/Comments

Maximum Application Rate Turf grasses

1.4 lb ai/A x 1

0.76 lb ai/A x 2

Sorghum

0.375 lb ai/A x 2

0.245 lb ai/A x 3

Wheat

0.245 lb ai/A x 3

Rangeland / Pasture

0.75 lb ai/A x 1

Rights of way/Fencerow/Hedgerows

1.5 lb ai/A x 1

0.76 lb ai/A x 2

Grass grown for seed

0.375 lb ai/A x 2

Fallow land

0.75 lb ai/A x 1

Grass forage/Fodder/Hay

0.375 lb ai/A x 2

Low growing berries subgroup 13-07H 

(except cranberry and strawberry)

0.25 lb ai/A x 2

Rhubarb

0.375 lb ai/A x 2

Labels/BEAD 2012 

information
6

Parameter (Units) Input Value and Unit Source/Comments

Minimum Reapplication Interval 14 days*

21 days (turf grasses and rights of 

way/fencerow/hedgerows at 0.7647 lb ai/A

rate)

30 days (low growing berries and rhubarb)

Labels/BEAD 2012 

information

*A minimum interval is not 

reported for all uses. It was 

assumed that the minimum 

interval was 14 days unless 

indicated otherwise, consistent 

with the Problem Formulation 

(2007) and previous 

assessments.

There is a pre-harvest interval 

of 30 days for rhubarb and 60 

days for low growing berries.

Modeling Scenarios Turf grasses

FL turf

PA turf

Sorghum

KS sorghum

Wheat

ND wheat

Rangeland / Pasture

FL turf

PA turf

CArangelandhayRLF_v2

Rights of way/Fencerow/Hedgerows

CArightofwayRLF_v2

Grass grown for seed

ORgrassseed

Fallow land

FL turf

PA turf

CArangelandhayRLF_v2

Grass forage/Fodder/Hay

FL turf

PA turf

CArangelandhayRLF_v2

Low growing berries subgroup 13-07H 

(except cranberry and strawberry)

ORberriesOP

Rhubarb

CA cole cropRLF_v2

CA lettuce

EFED standard 

PRZM/EXAMS scenarios 

unless indicated otherwise.

There is not a standard scenario

for rangeland/pasture, fallow 

land, or grass forage/ fodder/

hay. Standard turf scenarios 

and a non-standard CA range 

and hay scenario were used as 

surrogates.

In the absence of a standard 

rights-of-way scenario, a nonstandard CA scenario was used.

There is not a scenario specific 

to low growing berries 

subgroup 13-07H. 

ORberriesOP was used as a 

surrogate scenario.

There is not a scenario specific 

to rhubarb. Other leafy 

vegetable crop scenarios were 

used as surrogates (CA cole 

crop and CA lettuce).
7

Parameter (Units) Input Value and Unit Source/Comments

Initial Application Dates (dd-mm) Turf grasses

FL turf

(01-01, 01-02, 01-03, 01-04, 01-05, 01-06, 

01-07, 01-08, 01-09, 01-10, 01-11, 01-12)

PA turf

(01-03, 01-04, 01-05, 01-06, 01-07, 01-08, 

01-09, 01-10, 01-11)

Sorghum

KS sorghum 

(20-05, postplant; 09-04, preplant)

Wheat

ND wheat

(01-08, preplant winter wheat; 25-03, 

preplant spring wheat)

Rangeland / Pasture

FL turf 

(01-01, 01-02, 01-03, 01-04, 01-05, 01-06, 

01-07, 01-08, 01-09, 01-10, 01-11, 01-12)

PA turf 

(01-03, 01-04, 01-05, 01-06, 01-07, 01-08, 

01-09, 01-10, 01-11)

CArangelandhayRLF_v2 

(01-01, 01-02, 01-03, 01-04, 01-05, 01-06, 

01-07, 01-08, 01-09, 01-10, 01-11, 01-12)

Rights of way/Fencerow/Hedgerows

CArightofwayRLF_v2 

(01-01, 01-02, 01-03, 01-04, 01-05, 01-06, 

01-07, 01-08, 01-09, 01-10, 01-11, 01-12)

Grass grown for seed

ORgrassseed

(01-03, 01-04, 01-05, 01-06, 01-07, 01-08, 

01-09, 01-10, 01-11)

Fallow land

FL turf 

(01-01, 01-02, 01-03, 01-04, 01-05, 01-06, 

01-07, 01-08, 01-09, 01-10, 01-11, 01-12)

PA turf 

(01-03, 01-04, 01-05, 01-06, 01-07, 01-08, 

01-09, 01-10, 01-11)

CArangelandhayRLF_v2

(01-01, 01-02, 01-03, 01-04, 01-05, 01-06, 

01-07, 01-08, 01-09, 01-10, 01-11, 01-12)

Grass forage/Fodder/Hay

FL turf 

(01-01, 01-02, 01-03, 01-04, 01-05, 01-06, 

01-07, 01-08, 01-09, 01-10, 01-11, 01-12)

Based on labels/BEAD 2012 

information and PRZM 

scenarios.

Additional sources: Kansas 

state university research and 

extension planting guide 

(www.ksre.ksu.edu/library/crps

l2/l818.pdf), North Dakota 

State University extension 

service (www.ag.ndsu.edu)

Certain uses do not restrict 

when application may occur, in 

those cases it was assumed that 

application could occur 

throughout the year (winter 

months were excluded in 

certain scenarios depending on 

geography).
8

Parameter (Units) Input Value and Unit Source/Comments

PA turf 

(01-03, 01-04, 01-05, 01-06, 01-07, 01-08, 

01-09, 01-10, 01-11)

CArangelandhayRLF_v2 

(01-01, 01-02, 01-03, 01-04, 01-05, 01-06, 

01-07, 01-08, 01-09, 01-10, 01-11, 01-12)

Low growing berries (except cranberry 

and strawberry)

ORberriesOP

(01-05)

Rhubarb

CA cole cropRLF_v2

(01-01)

CA lettuce

(13-03)

Application Method Ground 

(turf grasses, rights-of way/ fencerow/

hedgerows, low growing berries, rhubarb)

Aerial

(sorghum, wheat, rangeland/pasture, grass 

grown for seed, fallow land, grass forage / 

fodder /hay

Foliar (CAM = 2)

(turf grasses, sorghum, rangeland/pasture, 

rights-of way/fencerow/hedgerows, grass 

grown for seed, grass forage / fodder /hay,

low growing berries, rhubarb)

Surface (CAM = 1)

(sorghum, wheat, fallow land)

Labels/BEAD 2012 

information

Aerial application method was 

used as input when aerial and 

ground applications are 

permitted at the same 

application rate. Aerial 

applications result in higher 

EDWCs.

Aerial application is permitted 

for rights-of-way/

fencerow/hedgerow but at a 

lower rate than ground 

applications. Ground 

applications resulted in higher 

EDWCs.

Application Efficiency Fraction 0.99 (ground)

0.95 (aerial)

EFED guidance1

Spray Drift Loading Fraction 0.064 (ground)

0.16 (aerial)

EFED guidance1

Incorporation depth (cm) 0

Molecular Weight (g/mole) 242 Product Chemistry

Water Solubility (mg/L) 64 Product Chemistry

Vapor Pressure (torr) 7.5 × 10-8Product Chemistry

KOC (L/kgoc) 36 Mean Value (EFED guidance)

1

MRID 41063562

Hydrolysis Half-life (days) 0 MRID 40320816

Stable

Aqueous Photolysis Half-life (days) 0 MRID 41063560

Stable
9

Parameter (Units) Input Value and Unit Source/Comments

Aerobic Soil Metabolism (days) 622 MRID 44084503 and 

41247301

90th percentile confidence 

interval on mean half-life (168 

and 391 days) (EFED 

guidance)1

Aerobic Aquatic Metabolism (days) 0 MRID 42294102 and 

42294103

Stable

Anaerobic Aquatic Metabolism (days) 0 MRID 42294104, 41063561, 

and 42786401

Stable

1

Input Parameter Guidance Manual, Pesticides (Version 2.1; Oct. 22, 2009)

Cranberries

The Provisional Cranberry Model (v2, December 8, 2010), a provisional refinement to the Tier I 

Rice Model (v1.0, May 8, 2007), was used to calculate EDWCs in surface waters for use of 

quinclorac on cranberry. Refinements include the addition of simple degradation processes in 

dry and flooded conditions and a water depth of twelve inches rather than the water depth of four 

inches used in the rice model. These modifications allow estimation of screening-level peak and 

annual mean EDWCs of quinclorac residues of concern that may occur in untreated surface 

water used as drinking water following use on cranberries.

The model assumes that degradation on dry cranberry bog soil occurs predominantly via aerobic 

microbial metabolism. Additionally, residue degradation in flooded bogs is assumed to occur via 

aerobic microbial metabolism in the water column and via anaerobic microbial metabolism in the 

sediment.

Quinclorac use on cranberries is labeled for an annual maximum of two applications of 0.25 lb 

ai/A each. The minimum interval between applications is 30 days and the preharvest interval is 

60 days. The proposed applications were first aged on dry soils because cranberry bogs are not 

typically flooded until the night before harvesting. The resulting residues (in lb ai/A) were then 

summed and used as input for the flooded component of the model to estimate peak and annual 

mean EDWCs in bog tailwater following harvest.

Model input parameters are listed in Table 3. The equations used in the Provisional Cranberry

Model are briefly described in Appendix B. Table 4 presents EDWCs of quinclorac in surface 

water sources from use on cranberry. 

Table 3. Provisional Tier 1 Cranberry Model Input Parameters

Input Parameter Value Source

Application Rate (lb ai/A) 0.25 Labels

Applications per Year 2 Labels

Organic Carbon Partition Coefficient 

(KOC) (L/kgOC)

36 MRID 41063562

Average Value (EFED guidance)
10

Input Parameter Value Source

Aerobic Soil Metabolism Half-life 

(days)

622 MRID 44084503

Upper 90th percentile confidence interval 

on the mean of two half-lives: 168 and 

391 days (EFED guidance)

Aerobic Aquatic Metabolism Half-life 

(days)

1295 MRIDs 42294102 and 42294103

Upper 90th percentile confidence interval 

on the mean of two half-lives: 1229 and 

393 days (EFED guidance)1

1 Quinclorac is considered stable to aerobic aquatic metabolism based on the available study results. Half-lives were 

extrapolated well beyond the study duration (30 days). Those values were used as the basis for representing aerobic 

aquatic metabolism in the Provisional Cranberry model because a half-life value is required for input. 

Rice

Quinclorac use on rice is labeled for a single maximum application of 0.5 lb ai/A (once per 

season). The Tier I rice model (v1.0)4 was used to estimate EDWCs for use of quinclorac on 

rice:

Cw = mai

′

/ (0.00105 + 0.0000013*Koc)

where Cw = EDWC (μg/L), mai

′

= application rate (kg/ha), and Koc = mean organic carbon 

partition coefficient (L/kgoc).

3.2.1.2 Surface Water Estimated Drinking Water Concentrations

Table 4. Estimated Drinking Water Concentrations (EDWCs) of Quinclorac in Surface 

Water Sources

Use Scenario

Estimated Drinking Water Concentrations 

from Surface Water Sources (μg/L)1,2,3

1-in-10 year 

acute

1-in-10 year 

chronic

30-year 

mean

Turf grasses

(1.4 lb ai/A x 1)

(0.76 lb ai/A x 2)

FL turf 441.3 28.5 16.8

PA turf 4,5 58.3 37.8 20.0

FL turf 443.1 32.8 16.3

PA turf 4,5 74.1 62.0 23.7

Sorghum

(0.375 lb ai/A x 2)

(0.245 lb ai/A x 3)

KS sorghum (postplant)626.3 10.5 6.9

KS sorghum

(postplant/fall)7 20.5 10.2 6.3

KS sorghum (preplant) 23.6 9.5 6.4

Wheat

ND wheat (preplant 

spring) 38.7 26.9 16.5

ND wheat (preplant 

winter) 46.6 28.6 19.3

 

4

http://www.epa.gov/oppefed1/models/water
11

Use Scenario

Estimated Drinking Water Concentrations 

from Surface Water Sources (μg/L)1,2,3

1-in-10 year 

acute

1-in-10 year 

chronic

30-year 

mean

Rangeland / Pasture

FL turf429.3 21.2 14.6

PA turf4,5 36.6 25.3 16.0

CArangelandhayRLF_v2454.0 36.9 20.5

Rights of way 

/Fencerow 

/Hedgerows

1.5 lb ai/A x 1

0.76 lb ai/A x 2

CArightofwayRLF_v2424.7 14.9 8.2

CArightofwayRLF_v24

27.7 14.3 8.4

Grass grown for 

seed4,5 ORgrassseed4,5 25.4 15.8 11.0

Fallow land

FL turf427.1 19.6 13.7

PA turf4,5 31.5 21.1 13.6

CArangelandhayRLF_v2439.3 27.2 16.4

Grass forage /Fodder 

/Hay

FL turf426.4 18.5 14.4

PA turf4,5 27.1 21.4 14.9

CArangelandhayRLF_v2446.8 31.7 20.6

Low growing berry 

(except cranberry and 

strawberry)

ORberriesOP 3.4 2.0 1.3

Rhubarb CA cole crop RLF_v2 33.8 18.0 11.4

CA lettuce 27.9 18.8 12.9

Cranberry Provisional Cranberry 

Model8 161.9 147.2 --

Rice Tier I Rice Model9

511.1 511.1 --

Aquatic Weeds10 Labeled concentration 500.0 500.0 --

1 PCA = 1 (www.epa.gov/oppefed1/models/water ) because this is a national drinking water assessment and 

quinclorac is registered for non-agricultural, non-turf uses.

2 BOLD indicates highest EDWC

3 EDWCs based on aerial applications are presented for uses that permit aerial and ground applications at the same 

application rate.

4 Highest value of twelve estimates (first application on the first day of each month) because there are no restrictions 

on when pesticide may be applied.

5 Although permitted, it was assumed that winter applications would be unlikely (December, January, February).

6 Two applications between preemergence and postemergence (up to 12 inches)

7 One application between preemergence and postemergence (up to 12 inches) and one application in the fall prior to 

the first killing frost

8Based on a one-year simulation; 1 in 10 year calculation is not applicable.

9 Based on a single, screening level concentration; 1 in10 year calculation is not applicable.

10 Registered as an experimental use permit.
12

3.2.2. Ground Water Modeling

The model SCI-GROW (v 2.3)

5 was used to calculate EDWCs in drinking water from shallow 

ground water sources. Table 5 lists model input parameters. An example output is provided in 

Appendix C. Table 6 presents EDWCs of quinclorac in groundwater sources from the 

registered and proposed uses. 

Table 5. SCI-GROW Model Input Parameters

Input Parameter Value Source

Application Rate (lb ai/A) Variable1 Labels/BEAD 2012 information

Applications per Year Variable1 Labels/BEAD 2012 information

Organic Carbon Partition Coefficient 

(KOC) (L/kgOC)

38 MRID 41063562

Median Value (EFED guidance)2

Aerobic Soil Metabolism Half-life 

(days)

280 MRID 44084503

Mean Value (EFED guidance)2

1 Modeled rates for each use are presented in Table 6.

2 www.epa.gov/oppefed1/models/water/scigrow_description.htm#instructions

Table 6. Estimated Drinking Water Concentrations (EDWCs) of Quinclorac in Ground 

Water Sources 

Use Application Rate

Estimated Drinking Water 

Concentrations from Ground 

Water Sources (μg/L)1

Acute Chronic

Turf grasses 1.4 lb ai/A x 1 27 27

0.76 lb ai/A x 2 29 29

Sorghum 0.375 lb ai/A x 2 and 0.245 lb ai/A x 3 14 14

Wheat 0.245 lb ai/A x 3 14 14

Rangeland / Pasture 0.75 lb ai/A x 1 14 14

Rights of 

way/Fencerow/Hedgerows

1.5 lb ai/A x 1 29 29

0.76 lb ai/A x 2 29 29

Grass grown for seed 0.375 lb ai/A x 2 14 14

Fallow land 0.75 lb ai/A x 1 14 14

Grass forage /Fodder /Hay 0.375 lb ai/A x 2 14 14

Low growing berry 

(except cranberry and 

strawberry)

0.25 lb ai/A x 2 10 10

Rhubarb 0.375 lb ai/A x 2 14 14

Rice2-- -- --

Cranberry2-- -- --

Aquatic Weeds2-- -- --

1 BOLD indicates highest EDWC

2 Groundwater concentrations are not estimated for aquatic uses.

 

5

http://www.epa.gov/oppefed1/models/water
13

3.2.3. Assumptions and Uncertainties

The following label uncertainties have been identified:

• All labels do not specify a minimum application interval. As in previous assessments and 

as noted in the registration review problem formulation (DP 344485), the minimum 

interval was assumed to be 14 days when an interval was not specified. A shorter 

interval may increase EDWCs.

• Most labels specify application on rice as a seasonal maximum application instead of an 

annual maximum. It was assumed that there is a limit of one crop cycle per year; that is, 

the seasonal maximum is equivalent to the annual maximum. Multiple crop seasons may

increase EDWCs given the persistence of quinclorac.

• One label (registration 279-3355) for various turf grass uses does not state a maximum 

number of applications or an annual maximum application rate per acre. EFED assumed 

that the annual maximum was 1.4 lb ai/A/year. EDWCs would be higher if the label 

intended for more than one application at this rate.

• Certain uses do not restrict when application may occur. A range of application dates

were modeled in those cases. These values may be refined if the label language is 

updated to be more restrictive in terms of timing of application.

• There are inconsistencies between and within the submitted Quinclorac 4L AG label and 

the supplemental label information sheets for proposed use on rhubarb and low growing 

berry (except strawberry) subgroup 13-07H. Specific inconsistencies include:

- The labels alternate between referring to the product as Quinstar 4L Herbicide and 

QUINCLORAC 4L AG.

- It was assumed that “Restrictions and Limitations - Cranberry” applies to all low 

growing berries in sub-group 13-07H (except strawberry). 

- The maximum annual application rate for cranberry (and other low growing berries) 

is specified as 16.8 fl oz/A on one label and as 16 fl oz/A on the other label. It was 

assumed that the maximum annual application rate is 16.8 fl oz/A (i.e., 0.5 lb ai/A) 

given that up to two applications of 8.4 fl oz/A are allowed per year.

- The maximum annual application rate for rhubarb is specified as “xx” fl oz/A on one 

label and as 25.2 fl oz/A on the other. It was assumed that the maximum annual 

application rate is 25.2 fl oz/A (i.e., 0.75 lb ai/A) given that up to two applications of 

12.6 fl oz/A are allowed per year.
14

APPENDIX A

PRZM/EXAMS Modeling Output

stored as ca lett.out

Chemical: Quinclorac

PRZM environment: CAlettuceSTD.txt modified Tueday, 26 August 2008 at 

06:16:36

EXAMS environment: ir298.exv modified Tueday, 26 August 2008 at 06:14:08

Metfile: w23273.dvf modified Tueday, 26 August 2008 at 06:15:40

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 21.06 20.96 20.45 14.35 9.946 3.265

1962 19.15 19.04 18.56 17.54 17.02 13.37

1963 28.11 27.94 27.46 26.09 25.13 18.11

1964 21.37 21.27 20.82 19.73 17.1 14.63

1965 17.84 17.74 17.32 16.42 15.99 13.92

1966 12.83 12.76 12.46 11.82 11.56 9.969

1967 13.89 13.81 13.48 12.81 12.33 9.959

1968 28.57 28.39 27.77 26.44 23.94 14.3

1969 24.46 24.32 23.89 22.82 21.95 18.96

1970 20.2 20.08 19.77 15.01 14.5 12.52

1971 21.9 21.77 21.24 20.11 19.3 16.3

1972 17.04 16.96 16.64 16.07 14.94 10.83

1973 23.49 23.4 22.86 22.18 21.39 16.33

1974 26.87 26.75 26.09 22.25 18.3 13.22

1975 24.83 24.68 24.08 22.79 22.07 16.83

1976 20.64 20.55 20.15 19.51 19.1 13.67

1977 35.75 35.61 34.78 32.89 31.55 23.09

1978 22.97 22.83 22.28 21.08 20.3 17.08

1979 16.64 16.55 16.17 15.34 15.08 13.17

1980 13.35 13.27 12.95 10.22 10.01 9.069

1981 16.95 16.87 16.47 16.14 15.6 12.76

1982 15.78 15.68 15.31 15.1 14.65 11.47

1983 11.73 11.67 11.38 10.82 10.4 8.32

1984 7.157 7.117 6.949 6.652 6.538 5.659

1985 12.17 12.09 11.88 10.8 8.786 5.804

1986 26.92 26.76 26.07 25.33 24.46 19.58

1987 21.46 21.35 20.85 19.78 19.28 15.36

1988 25.32 25.17 24.56 23.34 22.41 15.74

1989 12.52 12.46 12.18 11.57 11.33 9.403

1990 7.398 7.356 7.185 6.917 6.841 5.947

Sorted results

Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.032258064516129 35.75 35.61 34.78 32.89 31.55 23.09

0.0645161290322581 28.57 28.39 27.77 26.44 25.13 19.58

0.0967741935483871 28.11 27.94 27.46 26.09 24.46 18.96

0.129032258064516 26.92 26.76 26.09 25.33 23.94 18.11

0.161290322580645 26.87 26.75 26.07 23.34 22.41 17.08

0.193548387096774 25.32 25.17 24.56 22.82 22.07 16.83

0.225806451612903 24.83 24.68 24.08 22.79 21.95 16.33

0.258064516129032 24.46 24.32 23.89 22.25 21.39 16.3

0.290322580645161 23.49 23.4 22.86 22.18 20.3 15.74

0.32258064516129 22.97 22.83 22.28 21.08 19.3 15.36

0.354838709677419 21.9 21.77 21.24 20.11 19.28 14.63

0.387096774193548 21.46 21.35 20.85 19.78 19.1 14.3
15

0.419354838709677 21.37 21.27 20.82 19.73 18.3 13.92

0.451612903225806 21.06 20.96 20.45 19.51 17.1 13.67

0.483870967741936 20.64 20.55 20.15 17.54 17.02 13.37

0.516129032258065 20.2 20.08 19.77 16.42 15.99 13.22

0.548387096774194 19.15 19.04 18.56 16.14 15.6 13.17

0.580645161290323 17.84 17.74 17.32 16.07 15.08 12.76

0.612903225806452 17.04 16.96 16.64 15.34 14.94 12.52

0.645161290322581 16.95 16.87 16.47 15.1 14.65 11.47

0.67741935483871 16.64 16.55 16.17 15.01 14.5 10.83

0.709677419354839 15.78 15.68 15.31 14.35 12.33 9.969

0.741935483870968 13.89 13.81 13.48 12.81 11.56 9.959

0.774193548387097 13.35 13.27 12.95 11.82 11.33 9.403

0.806451612903226 12.83 12.76 12.46 11.57 10.4 9.069

0.838709677419355 12.52 12.46 12.18 10.82 10.01 8.32

0.870967741935484 12.17 12.09 11.88 10.8 9.946 5.947

0.903225806451613 11.73 11.67 11.38 10.22 8.786 5.804

0.935483870967742 7.398 7.356 7.185 6.917 6.841 5.659

0.967741935483871 7.157 7.117 6.949 6.652 6.538 3.265

0.1 27.991 27.822 27.323 26.014 24.408 18.875

Average of yearly averages: 12.9545

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: ca lett

Metfile: w23273.dvf

PRZM scenario: CAlettuceSTD.txt

EXAMS environment file: ir298.exv

Chemical Name: Quinclorac

Description Variable Name Value Units Comments

Molecular weight mwt 242 g/mol

Henry's Law Const. henry atm-m^3/mol

Vapor Pressure vapr 7.5e-8 torr

Solubility sol 64 mg/L

Kd Kd mg/L

Koc Koc 36 mg/L

Photolysis half-life kdp 0 days Half-life

Aerobic Aquatic Metabolism kbacw 0 days Halfife

Anaerobic Aquatic Metabolism kbacs 0 days Halfife

Aerobic Soil Metabolism asm 622 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI cm

Application Rate: TAPP 0.42 kg/ha

Application Efficiency: APPEFF 0.99 fraction

Spray Drift DRFT 0.064 fraction of application rate applied to pond

Application Date Date 13-03 dd/mm or dd/mmm or dd-mm or dd-mmm

Interval 1 interval 30 days Set to 0 or delete line for single app.

app. rate 1 apprate .42 kg/ha

Record 17: FILTRA

IPSCND 1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR Reservoir

Flag for runoff calc. RUNOFF total none, monthly or total(average of 

entire run)
16

Appendix B

I. Provisional Cranberry Model Equations

The Provisional Cranberry Model is a refinement of the Tier I Rice Model v1.0 (Equations 1 and 

2), which is a simple equilibrium partitioning equation that calculates a single, screening-level 

concentration in rice paddy water and released tailwater based on a compound’s application rate 

and soil mobility.

Equations 1-2: Tier I Rice Model v1.0 (USEPA, 2007b).

  w sed sed b d

ai

w

d d K

m

C

 

3

2

0

10

10 '



 

 (1)

and, if appropriate:

Kd 01KOC  0. (2)

where,

Cw0 = initial water concentration [μg/L]

mai' = mass applied per unit area [kg/ha]

Kd = water-sediment partitioning coefficient [L/kg]

KOC = organic carbon partitioning coefficient [L/kg]

dw = water column depth = 0.10 m

dsed = sediment depth = 0.01 m

θsed = porosity of sediment = 0.509

ρb = bulk density of sediment = 1300 kg/m3

First, the Tier I Rice Model was provisionally modified (Equation 3) to include as inputs 

degradation rate constants in order to estimate single, screening-level concentrations in paddy

water or tailwater at a given time after application.

Equation 3: Provisional Modified Rice Model (Jones, 2006).

     

 

t

d d K

d k d k d K k

w w

w sed sed b d

w sed sed sed b d

C C e

















 

 







 

3

3

1 2 3

10

10

0

 

 

(3)

where,

Cw = water concentration [μg/L]

t = interval since last application [d]

k1 = upper 90th percentile rate constant in water column [1/d]

k2 = upper 90th percentile rate constant in pore water [1/d]

k3 = upper 90th percentile rate constant for adsorbed residues [1/d]

Then, the Provisional Modified Rice Model water column depth was lengthened to a 

depth that is used to flood cranberry bogs (i.e., 12 inches; Cape Cod Cranberry Growers 

Association, 2001).

i.e., dw = water column depth = 0.305 m
17

In order to model degradation prior to the flood at harvest, the application rates for n 

number of pre-harvest applications were independently degraded over the interim until flooding 

and then summed (Equation 4).

Equation 4: Degradation in a Dry Bog.





 

n

k t

ai ai n

n m m e

1

4

' ' (4)

where,

mai' = mass per unit area at flood [kg/ha]

mai'n = mass applied per unit area on the nth application [kg/ha]

k4 = upper 90th percentile rate constant on dry bog [1/d]

tn = interval from the nth application to harvest [d]

n = number of pre-harvest applications

The following four equations and parameter sets constitute the Provisional Cranberry

Model (Equations 1-4).

Equations 1-4: Provisional Cranberry Model.

  w sed sed b d

ai

w

d d K

m

C

 

3

2

0

10

10 '



 

 (1)

and, if appropriate:

Kd 01KOC  0. (2)

where,

Cw0 = initial water concentration [μg/L]

Kd = water-sediment partitioning coefficient [L/kg]

KOC = organic carbon partitioning coefficient [L/kg]

dw = water column depth = 0.305 m

dsed = sediment depth = 0.01 m

θsed = porosity of sediment = 0.509

ρb = bulk density of sediment = 1300 kg/m3

and, lastly:

     

 

t

d d K

d k d k d K k

w w

w sed sed b d

w sed sed sed b d

C C e

















 

 







 

3

3

1 2 3

10

10

0

 

 

(3)

where,

Cw = water concentration [μg/L]

t = interval since flood [d]

k1 = upper 90th percentile rate constant in water column [1/d]

k2 = upper 90th percentile rate constant in pore water [1/d]

k3 = upper 90th percentile rate constant for adsorbed residues [1/d]
18

II. Output of Provisional Cranberry Model

Provisional Cranberry Model v2.0

Equation: EEC = (App rate * 100 / (dw + (dsed * (θ + (ρ * Kd / 1000))))) * exp (-day * kAAM)

*Water column depth is 12 inches (0.305 m) to 18 inches (0.457 m).

Application Inputs

App. rate (lbs/A) Days pre-flood App. rate at flood (lbs/A)

0.25 90 0.23

0.25 60 0.23

0.00

Total residues per area at flood (lbs/A): 0.46

Inputs

Parameter Value

Koc (L/kg) 36

If no Koc, enter Kd (L/kg)

AAM t1/2 (d) 1295

ASM t1/2 (d) 622

Model Parameters

Parameter Value

Water column depth (m) 0.305

Sediment depth (m) 0.01

Organic fraction of sediment 0.01

Sediment bulk density (kg/m3) 1300

Sediment porosity 0.509

Calculated Parameters

Parameter Value

Kd input (L/kg) 0.36

AAM rate constant 0.000535249

ASM rate constant 0.00111

App. rate (kg/ha) 0.515630335

DW EECs

100% PCA

Holding Time Peak Annual Mean Peak Annual Mean

3-d Tail 163.55 148.60 155.37 141.17

21-d Tail 161.98 147.18 153.88 139.82

95% PCA
19

APPENDIX C

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:quinclorac

time is 5/ 8/2012 10:49: 5

------------------------------------------------------------------------

Application Number of Total Use Koc Soil Aerobic

rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------

0.375 2.0 0.750 3.80E+01 280.0

------------------------------------------------------------------------

groundwater screening cond (ppb) = 1.43E+01

************************************************************************