Document ID: EPA-HQ-OPP-2012-0010-0006
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2012-12-21T05:00Z

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). 

   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 guidance and up-to-date models 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 ug/L and chronic = 511 ug/L) resulting from use on rice supersede previously recommended EDWCs.  The recommended groundwater EDWC has not changed (29 ug/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.
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).

   3.1. 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).

   3.2. 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.

   3.3. Monitoring Data

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

2. ANALYSIS
   
   3.1.	Fate and Transport Characterization

Vapor pressure (7.5 x 10[-8] mm Hg at 20[o] C) and Henry's Law Constant (1.22 to 24.3 x 10[-15] atm.m[3] 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+).

   2.2. 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 shell.  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.  

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
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 non-standard 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).

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)

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)
Based on labels/BEAD 2012 information and PRZM scenarios.

Additional sources: Kansas state university research and extension planting guide (www.ksre.ksu.edu/library/crpsl2/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).
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 x 10-8
Product 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
Aerobic Soil Metabolism (days)
                                      622
MRID 44084503 and 41247301
90[th] 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)
Aerobic Soil Metabolism Half-life (days)
                                      622
MRID 44084503
Upper 90[th] 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 90[th] 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) was used to estimate EDWCs for use of quinclorac on rice:
                          
                          Cw = mai[′] / (0.00105 + 0.0000013*Koc)
                          
where Cw = EDWC (ug/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 (ug/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 [4]
41.3
28.5
16.8

PA turf [4,5]
58.3
37.8
20.0

FL turf [4]
43.1
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)[6]
26.3
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
Rangeland / Pasture
FL turf[4]
29.3
21.2
14.6

PA turf[4,5]
36.6
25.3
16.0

CArangelandhayRLF_v2[4]
54.0
36.9
20.5
Rights of way /Fencerow /Hedgerows
1.5 lb ai/A x 1
0.76 lb ai/A x 2
CArightofwayRLF_v2[4]
24.7
14.9
8.2

CArightofwayRLF_v2[4]
27.7
14.3
8.4
Grass grown for seed[4,5]
ORgrassseed[4,5]
25.4
15.8
11.0
Fallow land
FL turf[4]
27.1
19.6
13.7

PA turf[4,5]
31.5
21.1
13.6

CArangelandhayRLF_v2[4]
39.3
27.2
16.4
Grass forage /Fodder /Hay
FL turf[4]
26.4
18.5
14.4

PA turf[4,5]
27.1
21.4
14.9

CArangelandhayRLF_v2[4]
46.8
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 Model[8]
161.9
147.2
--
Rice
Tier I Rice Model[9]
511.1
511.1
--
Aquatic Weeds[10]
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
[8]Based 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.

	3.2.2.	Ground Water Modeling

The model SCI-GROW (v 2.3) 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)
                                  Variable[1]
Labels/BEAD 2012 information
Applications per Year
                                  Variable[1]
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 (ug/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
Rice[2]
--
                                      --
                                      --
Cranberry[2]
--
                                      --
                                      --
Aquatic Weeds[2]
--
                                      --
                                      --
1 BOLD indicates highest EDWC
[2] Groundwater concentrations are not estimated for aquatic uses.

	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.

                                  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
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)

                                  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).
 
		(1)
                                       
      and, if appropriate:
      
		(2)

      where,
      	Cw0 = initial water concentration [ug/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/m[3]
 
 	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).
 
		(3)
    where,
    	Cw = water concentration [ug/L]
      t = interval since last application [d]
      k1 = upper 90[th] percentile rate constant in water column [1/d]
             k2 = upper 90[th] percentile rate constant in pore water [1/d]
             k3 = upper 90[th] 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

	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.
 
		(4)
    where,
      mai' = mass per unit area at flood [kg/ha]
      mai'n = mass applied per unit area on the n[th] application [kg/ha]
             k4 = upper 90[th] percentile rate constant on dry bog [1/d]
      tn = interval from the n[th] 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.
 
		(1)

      and, if appropriate:

		(2)
      
      where,
      	Cw0 = initial water concentration [ug/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/m[3]
      
      and, lastly:
      
		(3)

      where,
    	Cw = water concentration [ug/L]
      t = interval since flood [d]
      k1 = upper 90[th] percentile rate constant in water column [1/d]
             k2 = upper 90[th] percentile rate constant in pore water [1/d]
             k3 = upper 90[th] percentile rate constant for adsorbed residues [1/d]
             
II. Output of Provisional Cranberry Model
                                       
                                       
                                       

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