OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Codes: 119031

DP Barcode: D428419

Parent DP Barcode: 424558

Chemical: Penoxsulam

August 28, 2015

MEMORANDUM

SUBJECT: Penoxsulam Drinking water exposure concentrations for the proposed new uses on pome fruit 

group 11-10 (plus olive and pomegranate), stone fruit group (12-12), conversion of nut tree 

group 12 to tree nut group 14-12, and group expansion from grapes to include small fruit vine 

climbing subgroup (13-07F) and updated assessment for drinking water exposure for the 

other uses.

TO: Banza Djapao, Reviewer

Heather Garvie, PM 24

Herbicide Branch

Registration Division 7505P

 Linda Arrington, Branch Chief

 Bonnie Adler, CRM

 Jill Bloom, Team Leader

 Risk Management and Implementation Branch V

 Pesticide Re-Evaluation Branch 7508P

Christina Swartz, Branch Chief

Elizabeth Holman, Risk Assessor

Risk Assessment Branch 2

Health Effects Division (7509P)

FROM: James K. Wolf, Ph.D., Environmental Scientist

Environmental Risk Branch 3

THRU: Dana Spatz, Branch Chief

 Environmental Risk Branch 3

 Environmental Fate and Effects Division [EFED] (7507P)

PEER James A. Hetrick, Ph.D., Senior Advisor

REVIEW: Rosanna Louie-Juzwiak, RAPL

Environmental Risk Branch 3

 Environmental Fate and Effects Division [EFED] (7507P)
2

The Environmental Fate and Effects Division (EFED) has prepared a drinking water assessment for 

consideration in the tolerance for the requested new uses and crop group expansions for

Pindar® GT Herbicide which contains two active ingredients (a.i.). This assessment only considers 

penoxsulam, as oxyfluorfen would be considered in a separate assessment. This document provides 

estimated drinking water concentrations (EDWCs) for penoxsulam TTR (total toxic residues) in surface 

and ground water sources for the proposed new uses of penoxsulam. This assessment also provides an 

updated assessment for recommended EDWCs for all registered uses for human health dietary risk 

assessment.

The IR4 has requested amending the existing Pindar® GT Herbicide; (EPA Reg. # 62719-611 and 

Penoxsulam Technical EPA Reg. # 62719-499). They propose to add grapevines and a non-dormant 

application (California only), to expand the bearing and non-bearing tree nut groups for dormant and

non-dormant tree nuts, non-bearing citrus trees, and add preemergence and postemergence control of 

annual weeds on olive and pomegranate, pome fruit (crop group 11-10) and stone fruit (crop group 12-

12). The new uses and crop group expansions and application rates are summarized in Appendix A. Table 

A1. The single application rates for the new uses range from 0.010 to 0.031 lb a.i./A, and the maximum 

annual rate would be 0.047 lb a.i./A/season. Minimum reapplication (i.e., sequential) interval for the new 

uses is 30 days.

Other registered uses were re-evaluated here. The turf use has the highest single and yearly application 

rate (0.060 lb a.i./A and 0.090 lb a.i./A, respectively) and was included in the re-evaluation. Rice and 

direct treatment of water areas were considered in prior assessments for the highest registered uses (i.e., 

rice or direct aquatic applications). Reapplication intervals for existing uses ranged for 21 to 30 days. 

Recommended Drinking Water Concentrations 

 

The estimated drinking water concentrations (EDWCs) for penoxsulam residues of concern (ROCs), or 

penoxsulam TTR, are based upon model estimates using the maximum application rate and number of 

applications. 

Maximum EDWCs for the proposed new uses and crop group expansion and existing uses are summarized 

in Table 1. The EDWCs for penoxsulam TTR for all uses except direct application to water and rice were 

estimated for groundwater [with PRZM-GW or SCI-GROW] and for surface water [SWCC or FIRST] (Table 

1). The range of EDWCs for the proposed new uses for the scenarios evaluated and existing uses [e.g., 

ornamental lawns turf] are given in Table 4 (surface water) and Table 5 (groundwater). 

The recommended EDWCs (i.e., the highest value) for penoxsulam would be for the direct aquatic use 

where the exposure concentrations could be as high as the maximum treatment concentration of 150 

μg/L (penoxsulam) for as long as 60 days. While generally lower than the 150 ppb, estimates for 

groundwater are predicted to be higher compared to surface water (USEPA, 20061

, USEPA, 20082, and 

USEPA, 20103

).

 1 USEPA, 2006. Shanaman, L. Tier 1 Drinking Water Assessment for the New Use Registration on Turf and Aquatic Vegetation of 

Penoxsulam, and Six Degradation Products Identified to Be of Toxicological Concern (D325468). 2 USEPA, 2008. Wolf, J.K. Penoxsulam (New Use) Tier 1 Drinking water exposure concentrations for the proposed new uses 

almond hulls, grapes, tree nuts (crop group 14), and pistachios, and tolerance assessments. (Action Type Section, new use, 

R180 and reduce risk designation request) (D355676).

3 USEPA, 2010. Wolf, J.K. Penoxsulam (New Use) Tier 1 Drinking water exposure concentrations for the proposed new uses on 

non-bearing trees, conifers, eucalyptus, and non-cropland. (D273443). 
3

Estimated Drinking Water Concentrations 

Surface Water Exposure

The penoxsulam TTR EDWCs for the proposed new uses and crop group expansion are less than previous 

assessments for surface water. Surface water EDWCs from an earlier assessment (D325468), using the 

FIRST model for the turf use rates (D325468) were 9.4 μg/L and 0.92 μg/L for acute and chronic exposure, 

respectively, which are higher than the estimates with SWCC model (Table 1). It should be noted that the

turf use (D325468) was based upon higher application rates (0.060 to 0.090 lb a.i./A) than considered in 

this new use assessment (e.g., 0.047 lb a.i./A) (Appendix A. Table A1). The direct aquatic use results in the 

highest EDWCs, where the exposure concentrations could be as high as the maximum treatment 

concentration of 150 μg/L (penoxsulam) for as long as 60 days.

Groundwater Exposure

For groundwater, the PRZM-GW model’s NC Coastal Plain scenario resulted in highest daily and post 

breakthrough average concentrations; at the maximum rates, EDWCs for the new uses were 25.9 and 

17.5 μg/L, respectively. Ornamental lawns and turf have the highest application rates (0.06 lb a.i./A single 

application and 0.09 lb a.i./A annual rate); maximum groundwater penoxsulam TTR EDWCs estimated 

with PRZM-GW are 46.3 μg/L and 31.3 μg/L, for highest daily and post-breakthrough concentrations, 

respectively. 

Table 1. Summary of Maximum Penoxsulam TTR EDWCs for New Uses and Crop Group Expansions and Currently 

Registered Uses. 

Model Previous Assessments 

[Uses and Rates] 

New Use 

[D428419, D424558] 

All Uses 

[Updated] 

Surface Water 

μg/L

FIRST [D325468]

Peak 9.40a - -

Annual Average 0.92a - -

Long Term Average 0.92a - -

SWCC [This assessment]

1-yr in 10-yr Peak 0.95b 1.54 1.54

1-yr in 10-yr Annual Average 0.30b 0.23 0.30

30-Year Ave. 0.11b 0.11 0.11

Rice (Interim Rice Model) [D325468]

45 - 45

Water Treatmentc [D325468]

 Direct Application to Water 150 - 150 

Groundwater

PRZM-GW [This assessment]

Highest Daily Concentration 46.3d 25.9 46.3

Post-Breakthrough Average 31.3d 17.5 31.3

SCI-GROW [D325468]

23.3 - - a Turf rate with FIRST (2 apps 0.06 lb a.i./A and 0.03 lb a.i./A; 30 day interval) b Turf rate with SWCC (Table 4).
4

c Application of penoxsulam to aquatic sites can be injected under the surface of water to achieve a target concentration not to 

exceed 150 ppb, ground sprayed to exposed sediment after drawdown, or applied either aerially or by ground spray to floating or 

emerged aquatic vegetation. d Turf rate with PRZM-GW (Table 5)

 

Uses and Label Information 

Pindar GT (EPA Reg. No. 62719-611) contains two active ingredients (a.i.) penoxsulam (0.85% a.i.) and 

oxyfluorfen (40.31% a.i.). Pindar GT contains 0.083 pounds of penoxsulam per gallon. Penoxsulam is a 

systemic herbicide that can be used for postemergence burn-down and preemergence residual control of 

weeds. A single rainfall event or sprinkler irrigation of 0.5 inches or more, or flood irrigation within 21 

days after application, is necessary to activate penoxsulam. The proposed single application rate ranges 

between 0.010 to 0.031 lb a.i./A with a maximum seasonal amount of 0.047 lb a.i./A (Table 2). 

Reapplication intervals when specified on the label range from 21 to 30 days.

The current turf uses (ornamental lawns, sod farms) for products containing penoxsulam have the highest 

use rates (excluding aquatic/water uses) with a maximum single rate of about 0.060 lb a.i./A with a 

seasonal maximum rate of about 0.090 lb a.i./A. Other uses such as citrus, tree nuts, and grapes have 

lower application rates (Appendix C Table 1). Aerial application of penoxsulam (Pindar GT) is not 

permitted on the label (Pindar® GT EPA Reg. No. 62719-611 or the Supplemental Labeling (EPA Reg No. 

62719-611) MSTR/Amendment/10-17-14). However, aerial application is included on some of the other 

labels, primarily rice and aquatic uses (e.g., EPA Reg. No. 62719-546, 62719-610).

For the in-water treatment, the label specifies that the concentration of any single application or sum of 

all applications must not exceed 150 ppb per annual growth cycle. Retreat the water to maintain a 

sufficient concentration for a minimum of 60 days or until satisfactory weed control is achieved (EPA Reg. 

No. 67690-71).

Use limitations is by season (harvest to harvest) for EPA Reg. No. 62719-11, the number of seasons were 

not specified; thus, it was assumed that there is only 1 cropping season per year. Similar assumptions 

were made for the other registrations where the total maximum application rate is not given on a per 

year basis. Application rates, method and timing by rate and EPA Reg. No. are summarized from BEAD 

LUIS report (09/09/14) in Appendix C. Table 1.

 

 

Drinking Water Residues of Concern (ROC) 

 

The Health Effects Division (HED) determined that penoxsulam (synonyms DE-638, XDE-638, and XR-638) 

and six (of 11) degradation products were of toxicological concern (USEPA, 2004a) for drinking water. The 

penoxsulam degradation products identified in the fate studies are: BSTCA, 2-amino TCA, 5-OHpenoxsulam, SFA, sulfonamide, and 5,8-di OH. A combined residue, or total toxic residue (TTR), approach 

was used in the penoxsulam drinking water assessment. 

Persistence and Transformation 

Penoxsulam is expected to be moderately persistent in the aerobic terrestrial environments, and less 

persistent in anaerobic environments. The degradation products tend to be more persistent than the 

parent compound. Penoxsulam is expected to dissipate rapidly in clear shallow waters through aqueous 
5

photolysis. Thus, in turbid, shaded or acidic waters, photolysis of penoxsulam is expected to be slower, 

and other degradation mechanisms are expected to predominate. Laboratory data indicates that the four 

photolytic half-lives reported for penoxsulam in water range from 1.5 to 3.1 days between pH 7 and pH 8, 

and 14 days at pH 5.8. A reported pKa value of 5.1 suggests that pH may have an effect upon the 

photolytic half-life. In aqueous environments, penoxsulam is stable to hydrolysis at pH 5, 7 and 9. 

Eleven major degradation products were previously identified for penoxsulam (BSTCA, 2-amino-TCA, 5-

OH-penoxsulam, SFA, sulfonamide, 5,8-di-OH-penoxsulam, BSA, 2-amino-TP, TPSA, BSTCA methyl, and 5-

OH 2 amino TP). Data are not available to fully characterize these degradates and their respective 

degradation pathways. The six degradation products occurred in the [aerobic soil, aerobic and anaerobic 

aquatic] metabolism studies. Only BSTCA (soil photolysis, aqueous photolysis) and 2-Amino TCA (aqueous 

photolysis) were identified as photodegradates. The environmental fate and transport characteristics of 

penoxsulam and several degradates were described in more detail in previous assessments (D288160, 

D325783, D355671). 

Transport and Mobility 

Penoxsulam is expected to be mobile in terrestrial environments, not binding strongly to soil. Penoxsulam 

has low volatility. Submitted mobility data for three penoxsulam degradation products (BSTCA, 5-OHpenoxsulam, and BST) indicate environmental mobility roughly equivalent to or slightly greater than the 

parent compound. The soil to water partition coefficients (Kd) derived from the seventeen soils and one 

sediment studied ranged from 0.12 to 10.67 mL/g. Calculated Kocs ranged from 12 to 1,141 mL/goc. The 

Koc values for the sediment were 1118 and 1141 mL/goc (Kds = 1.38 and 1.41 mL/g). There are no data 

regarding the mobility of the remaining transformation products nor the combined parent/degradate 

residues. The lowest average Koc was 45.3 mL/goc for 5-0H-penoxsulam was used as an input for modeling 

as it is one of the ROC and it appears to be one of the more persistent degradates. A summary of the 

mobility data can be found in Appendix B, Table B2. 

The exposure from the total toxic residues (penoxsulam TTR) were estimated by using the half-life 

estimated from the decline of the penoxsulam total residues with time (D325468) and the mobility of the 

most mobile degradation product (MRID #s 45830801, 45830802). The penoxsulam TTR are more 

persistent than the parent compound. The environmental data for use as model inputs are also depicted 

in Table 3. 

Modeling Inputs

The estimated drinking water concentrations (EDWCs) for all uses (except rice and aquatic areas) were 

conducted with the PRZM-GW4 (version 1.07) model for groundwater and the SWCC5 (version 1.106) for 

surface water) model, and current guidelines for model inputs. Also, because the label (EPA Reg. No. 

62719-611) requires nozzles for “coarse” spray, the default spray drift fraction for coarse spray is used 

rather than stand default value for very fine to fine spray. The maximum number of applications, 

maximum application rates, and the minimum reapplication intervals (Table 1; e.g., 2 applications @ 

0.031 and 0.016 lb a.i./A, 30 day reapplication interval) was used.

 4http://www.epa.gov/oppefed1/models/water/index.htm#przm_gw

5 http://www.epa.gov/oppefed1/models/water/index.htm#swcc
6

A summary of the current fate and transport properties of penoxsulam appears in Table 3, below. The 

model input values [previous value] from the prior assessment is also presented in Table 3.

 

 

Table 3. Model Input parameters for Penoxsulam TTR. 

Input Variable Input Value [Previous 

Assessment]

Environmental Fate Data MRID

Molecular Weight (penoxsulam) 483.4 g/mole -- --

Solubility @ pH 7 (penoxsulam) 410 mg/L -- --

Vapor Pressure (penoxsulam) 7.16 x 10-16 torr - -

Hydrolysis (penoxsulam) Stable - 45830721

Photolysis (Aqueous) t1⁄2 (penoxsulam) (upper 

bound on mean)

2.9 day [4.3]a 40°N 1.5, 1.5, 3.1 days 45834801

TTR Aerobic Soil t1⁄26,7 (upper bound on mean) 0 days - Stable [467]a

(See Table 8)

>365 days 45830724

TTR Anaerobic Soil & Sediment - - 45830725

TTR Anaerobic Aquatic t1⁄220,21 system)

2 soils

2 soils + sediment

(upper bound on mean)

168 days

[88.3 days]a

847 days

70.8, 132 days (soil)

70.8, 132 soils; 950 days 

(sediment)

45830725

TTR Aerobic Aquatic t1⁄220,21 (system) 120.3 days

[36.6 days]a

136, 84.8, 84.9, 96 days 45830726

Kd (5-OH-penoxsulam) 0.54 mL/g 

[0.13]a

n = 16 (average)

[lowest non-sand]

45830802

Koc (5-OH-penoxsulam) 45.25 mL/goc

[13]a

n = 16 (average)

[lowest non-sand]

45830802

Spray drift Fraction

(Aerial Coarse Drop size) 0.068 [0.05]a High Boom

EFED 

Guidance

(Ground Coarse Drop size) 0.017 [0.01]a High Boom

Application Efficiency

 Aerial 

 Ground 

0.95

0.99

EFED

Guidance

t1⁄2 is the upper bound of mean total toxic residues (TTR) half-life estimated by PestDF in Appendix A, Table A1.

TTR Residues of Concern (ROC) includes penoxsulam parent plus degradation products BSTCA, 2-amino TCA, 5-OH-penoxsulam, 

SFA, sulfonamide, and 5,8-di OH. a [] value used in previous assessments.

 

 

Surface Water 

 

Eleven SWCC standard scenarios were selected to be representative of the proposed new uses and crop 

group expansions for pome fruit (NC Apple, OR Apple, PA Apple ), stone fruit (GA Peach), tree nut (CA 

Almond, GA Pecans, OR Filberts), grapes (CA grape, NY Grape), and non-bearing Citrus (FL Citrus). Two 

initial application dates were assumed, 0 and 20 days after emergence (crop emergence, scenario 

specific), with a 30 day reapplication interval.

 

Two standard turf (FL Turf and PA Turf) scenarios were selected to represent the highest use rates for

penoxsulam. The initial application selected were 230 and 20 days after crop emergence with a 28 day 

reapplication interval.

 

 6 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/NAFTA_Degradation_Kinetics_Equations.htm

7 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/archive2015/ftt_sop_using_nafta_guidance.pdf
7

The surface water EDWCs were influenced by the scenario (soil and weather differences) and the date of 

the initial application. Peak concentration for the new uses range from 0.17 to 1.54 μg/L; annual means 

ranged from 0.07 to 0.23 μg/L; 30 year means ranged from 0.029 to 0.114 μg/L. Differences in EDWCs 

between sites were more pronounced than the differences in EDWCs due to the date of the initial 

application. For turf scenarios, being the highest application rates, EDWCs range from 0.46 to 0.95 μg/L; 

annual means ranged from 0.17 to 0.30 μg/L; 30 year means ranged from 0.08 to 0.11 μg/L. As in 

previous assessments, surface water concentrations were less than those for groundwater.

Table 4. Surface Water EDWCs Penoxsulam TTR in μg/L resulting from the maximum proposed penoxsulam use ratesa 

on number of crops (scenarios) and 2 first application dates and turf (maximum registered rate) using the SWCC. 

SWCC Scenarioa

(First Applications 0 DAE)b 

Peak Annual Mean 30 Year Mean

1 yr in 10 yr (μg/L) (μg/L)

CA almond W irrigation 0.44 0.15 0.068

CA fruit W irrigation 0.42 0.18 0.051

CA grapes W irrigation 0.17 0.071 0.029

FL Citrus 1.38 0.23 0.100

GA Pecans 0.75 0.12 0.051

GA Peaches 0.28 0.080 0.035

NC apple 0.45 0.13 0.053

NY Grapes 0.43 0.15 0.101

OR apple 0.30 0.10 0.039

OR filberts 0.37 0.12 0.047

PA apple 0.43 0.14 0.054

(First Applications 20 DAE)b 

CA almond W irrigation 0.34 0.12 0.045

CA fruit W irrigation 0.30 0.12 0.039

CA grapes W irrigation 0.17 0.075 0.029

FL Citrus 1.20 0.20 0.096

GA Peach 0.23 0.072 0.027

GA Pecan 1.54 0.22 0.079

NC apple 0.51 0.13 0.063

NY Grapes 0.55 0.20 0.114

OR apple 0.31 0.11 0.039

OR filberts 0.39 0.12 0.061

PA apple 0.34 0.12 0.045

Maximum Label Rates (Ornamental Sod Farm Ornamental Lawns and Turf)c

FL Turf [230 DAE) 0.95 0.30 0.11 

PA Turf [20 DAE) 0.46 0.17 0.08

a SWCC estimated EDWCs (2 applications @ 0.031 and 0.016 lb a.i./A with 30 day reapplication interval b DAE – Day after emergence (crop) – defined by scenario c SWCC estimated EDWCs (2 application @ 0.0603 and 0.0301 lb a.i./A with 28 day reapplication interval.

The six standard PRZM-GW scenarios8 used in the groundwater simulations were developed to be 

representative of known vulnerable sites—shallow, unconfined aquifers under an agricultural field with 

leaching prone soil and adequate precipitation and/or irrigation. Output values represent pesticide 

concentrations that may be observed in private drinking water wells resulting from the use of 

groundwater vulnerable to pesticide contamination. Groundwater EDWCS estimated with PRZM-GW for 

the six scenarios are summarized in Table 5. 

 8 Florida Central Ridge, Florida Potato, Wisconsin Central Sands, Georgia Southern Coastal Plain, North Carolina 

Eastern Coastal Plain, and Delmarva Peninsula. 
8

For groundwater, the EDWCs the ranged 7.0 to 46.3 μg/L depending upon scenario and application rate. 

Post-breakthrough averages for groundwater ranged from 5.5 to 31.3 μg/L depending upon scenario and

application rate (Table 5). Example outputs are given in Appendix D.

Table 5. PRZM-GW Estimated Drinking Water Concentrations (EDWCs) in Groundwater for (Penoxsulam TTR). 

Scenarioa First Application 

[Days After Emergence] 

Highest Daily 

Value 

Post- breakthrough 

Average 

Average Breakthrough 

Time/Throughputs 

(day) μg/L Days

Maximum Rate for New use (2 applications 0.031 lb a.i./A and 0.016 lb a.i./A with 30 day reapplication interval) 

Delmarva 20 18.3 13.5 1608/6.8

FL Citrus 20 15.4 12.5 1171/9.4

FL Potato 20 12.7 9.6 1531/7.2

GA Coastal Plain 20 7.0 5.5 1962/5.6

NC Coastal Plain 20 25.9 17.5 2371/4.6

WI Central Sands 20 17.1 14.9 2977/3.7

Maximum Rate All uses (2 applications 0.0603 lb a.i./A and 0.0301 lb a.i./A with 30 day reapplication interval) 

Delmarva 20 35.2 25.9 1608/6.8

FL Citrus 20 29.7 24,0 1171/9.4

FL Potato 20 24.5 18.5 1531/7.2

GA Coastal Plain 20 13.4 10.7 1963/5.6

NC Coastal Plain 20 46.3 31.3 2371/4.6

WI Central Sands 20 33.0 28.8 2977/3/7

a SWCC Scenarios b DAE – Day after emergence (crop) – defined by scenario

The persistence of a pesticide (i.e., half-life; Appendix B Table B1) has a major influence on PRZM-GW 

estimates, the 90 percent upper bound DT50 (391.2 days) and DT90 (1,239 days) were also used with NC 

Coastal Plain scenario (highest estimated groundwater concentrations). The highest daily values were 

32.2 and 41.1 μg/L for the DT50 and DT90 half-life values, respectively. The highest concentration after 

breakthrough were 22.6 and 28.2 μg/L for the DT50 and DT90 half-life values, respectively. 

 
9

Appendix A. Proposed Application Rates and for New Uses and Crop Group Expansion for Penoxsulam. 

 

The registrant proposes to add grapevines and a non-dormant application (California only) and to expand 

the bearing and non-bearing tree nut groups for dormant9 and non-dormant10 tree nuts, non-bearing 

citrus trees11, and add supplement labeling for Pindar® GT Herbicide for preemergence and 

postemergence control of annual weeds on olive and pomegranate, pome fruit (crop group 11-10)12 and 

stone fruit (crop group 12-12).13 The proposed used rates are summarized in Appendix A. Table A1. 

 

 

Appendix A. Table A1. Proposed new uses and crop group expansion [in bold] requested by IR4 and the Registrant for 

Penoxsulam for Pindar GTa 

Summary Application Rate 

Pint/A (lb a.i./A) 

Max single 

Pint/A (lb a.i./A) 

Combined Pre and Post Emergence 

Max single seasonb 

Pint/A (lb a.i./A) 

Dormant Application: Bearing and Non-Bearing Tree Nuts and Grapevines (Small Vine Climbing Fruit 13-07F) 

Pre-emergence 1.5 – 3 (0.016-0.031) 3 (0.031) 4.5 (0.047)

1-3 months 1.5 – 2 (0.016-0.021) 2 (0.021)

1-6 months 2 – 3 (0.021-0.031) 3 (0.031)

Post-emergence 1.5 – 3 (0.016-0.031) 3 (0.031)

Non-Dormant Application Tree Nuts (For Arizona and California only) 

Pre-emergence 1.5 – 3 (0.016-0.031) 3 (0.031) 3 (0.031)

Post-emergence 1.5 – 3 (0.016-0.031) 3 (0.031)

 4-inch/4 leaf stage 0.05-1 (0.005-0.010) 1 (0.010)

 Clean-up 2 – 3 (0.021-0.031) 3 (0.031)

Grapevines Non-Dormant Application (Small Vine Climbing Fruit 13-07F) (For California Only) 

Pre-emergence 0.25 – 1 (0.003-.010) 1 (0.010) 1 non-dormant

Post-emergence 0.25 – 1 (0.003-.010) 1 (0.010)

 Per season 4 (0.042) (dormant + non-dormant)

Non-Bearing Citrus Treesc 

Pre-emergence 4.5 (0.047)

 2-3 months 1.5 (0.016) 1.5 (0.016)

4-6 months 3 (0.031) 3 (0.031)

Winter dormant- March 15 1.5 – 3 (0.016-0.031) 3 (0.031)

 Sequential appl. 1.5 (0.016) 1.5 (0.016)

Pre & Post-emergence Annual Weeds in Olive and Pomegranated 

Pre & Post-emergence Annual Weeds in Pome Fruit, 11-10d 

 9 Bearing and Non-Bearing Tree Nuts (African nut-tree; almond; beechnut; Brazil nut; Brazilian pine; bunya; bur oak; butternut; 

Cajou nut; candlenut; cashew; chestnut; chinquapin; coconut; coquito nut; dika nut; ginkgo; Guiana chestnut; hazelnut (filbert); 

heartnut; hickory nut; Japanese horse-chestnut; macadamia nut; mongongo nut; monkey-pot; monkey puzzle nut; Okari nut; 

Pachira nut; peach palm nut; pecan; pequi; Pili nut; pine nut; pistachio; Sapucaia nut; tropical almond; walnut, black; walnut, 

English; yellowhorn; cultivars, varieties, and/or hybrids of these) and Grapevines – Dormant Application. Non-bearing tree nuts 

and grapevines are those which will not bear a crop within one year.

10 Bearing and Non-Bearing Tree Nuts (African nut-tree; almond; beechnut; Brazil nut; Brazilian pine; bunya; bur oak; butternut; 

Cajou nut; candlenut; cashew; chestnut; chinquapin; coconut; coquito nut; dika nut; ginkgo; Guiana chestnut; hazelnut (filbert); 

heartnut; hickory nut; Japanese horse chestnut; macadamia nut; mongongo nut; monkey-pot; monkey puzzle nut; Okari nut; 

Pachira nut; peach palm nut; pequi; Pili nut; pine nut; Sapucaia nut; tropical almond; yellowhorn; cultivars, varieties, and/or 

hybrids of these) – Non-Dormant Application (For Use in Arizona and California Only) 11Non-Bearing Citrus Trees: Calamondin, chironja, citrus citron, grapefruit, kumquat, lemon, lime, mandarin, pummelo, satsuma

mandarin, sour orange, sweet orange, tangelo, tangerine, tangor. 

12 Pome Fruit: Apple; azarole; crabapple; loquat; mayhaw; medlar; pear; pear, Asian; quince; quince, Chinese; quince, Japanese; 

tejocote; cultivars, varieties, and/or hybrids of these. 13 Stone Fruit: Apricot; apricot, Japanese; capulin; cherry, black; cherry, Nanking; cherry, sweet; cherry, tart; Jujube, Chinese; 

nectarine; peach; plum; plum, American; plum, beach; plum, Canada; plum, cherry; plum, Chickasaw; plum, Damson; plum, 

Japanese; plum, Klamath; plum, prune; plumcot; sloe; cultivars, varieties, and/or hybrids of these.
10

Summary Application Rate 

Pint/A (lb a.i./A) 

Max single 

Pint/A (lb a.i./A) 

Combined Pre and Post Emergence 

Max single seasonb 

Pint/A (lb a.i./A) 

Pre & Post-emergence Annual Weeds in Stone Fruit, 12-12d 

Pre-emergence 1.5 – 3 (0.016-0.031) 3 (0.031) 4.5 (0.047)

Post-emergence 1.5 – 3 (0.016-0.031) 3 (0.031)

a EPA Reg. No. 62719-611 (amend 10-17-14) Pindar GT 0.85 % a.i. (Penoxsulam); 0.083 lb penoxsulam./gallon; 0.000648 lb a.i./fl oz. b Combined preemergence and postemergence for single growing season (harvest to harvest)

c Non-bearing citrus trees will not bear a crop within one year after treatment with Pindar. d Supplemental Label For use only in AZ, CA, MI, OH, OR, NC, NM, NY, PA, SC, and WA

 

 

 

 
11

Appendix B. Reassessment of Environmental Fate Data for Modeling Inputs for Drinking Water Assessments

 

No additional environmental fate studies have been considered for this assessment. However, the model 

inputs parameters in Table 3 were reevaluated to conform to current modeling input guidance.

For exposure modeling, EFED models use the simplistic approach, assuming all pesticide transformation 

processes follow the first-order exponential function even though pesticide transformation in soil and 

aquatic systems often involve multiple intertwined processes and do not follow a single exponential 

decline pattern. PestDF was developed as a tool for calculating and selecting the representative half-life 

value based on the NAFTA guidance.

14,15 The tool considers three transformation models SFO, double 

first-order in parallel (DFOP), and indeterminate order rate equation (IORE) and a set criteria for selecting 

parameters. SFO is the simplest of the three models while DFOP is the most complex.

The penoxsulam TTR “half-lives” were recalculated for modeling inputs using PestDF R software16 is a 

compatible script (PestDF version 3.1.2 and xxDeg 08.13) following NAFTA17 guidance. Several other 

practices have changed per EFED modeling input parameters guidance18 in addition to the “half-lives” [as 

determined by PestDF]. The average Kd or Koc is now recommended instead of the lowest non-sand value.

The “half-lives” calculated and chosen following the NAFTA kinetics guidances generally resulted in longer 

values (2 to 4 times) than previously used for modeling. The exception is for aerobic soil metabolism 

where half-lives were not observed in the study (e.g., penoxsulam TTR residue exceeded 50% at the end 

of the 365 day study). Half-lives estimated by PestDF (tR IORE) were in excess of 7,990 days for penoxsulam 

TTR. 

In terrestrial environments, or when sunlight is readily available to degrade penoxsulam, it is expected to 

be moderately persistent, dissipating through soil photolysis and biotic degradation. Penoxsulam has 

photolytic half-lives of 19 (flooded soil) and 109 days, on the two soils studied at pH 6. Aerobic soil 

metabolism was studied in three US soils. The resulting half-lives for parent penoxsulam calculated by 

linear regression on the log transformed data (SFO) were 62.5, 55.3, and 118 days for soils from AR, CA, 

and ND, respectively. For modeling PestDF recommended the TR IORE half-life for parent penoxsulam range 

between 17 and 142 days (Appendix A Table A1) and the 1st order model (SFO), half-lives ranged from 11 

to 64 days (Appendix B. Table B1). 

For the aerobic soil metabolism studies, PestDF recommended the tR IORE model for penoxsulam TTR for 

modeling with “half-life” values of greater than 7,900 days which far longer than 365 day study duration 

(Appendix B. Table B1), therefore, penoxsulam TTR was assumed to be stable for modeling inputs (input 

value = 0 days) . 

Aerobic aquatic metabolism was studied in six soil/water test systems (including 2 soils from Japan). The 

four total system half-lives calculated through linear regression of log transformed data ranged from 12 

to 38 days. The two Japanese soils19 were not included as they may not be representative of soils in the 

U.S. (i.e., volcanic soil). Anaerobic aquatic metabolism was studied in three soil/water test systems. The 

three total system half-lives calculated through linear regression of log transformed data were 5 days, 7 

 14 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/NAFTA_Degradation_Kinetics_Equations.htm

15 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/archive2015/ftt_sop_using_nafta_guidance.pdf 16 http://www.r-project.org/ ) R Statistical Foundation for Statistical Computing 17 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/ftt_sop_using_nafta_guidance.pdf

18 http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

19 MRID 458307-26 Aerobic Aquatic Metabolism. Japanese soils Volcanic soil (t1⁄2 = 29 days) none volcanic soil (t1⁄2 = 29.5 days)
12

days, and 11 days. Half-lives of were recalculated using PestDF the residues of concern (TTR) for model 

inputs.20,21 The resulting half-lives for penoxsulam TTR (the residues of concern) obtain by PestDF for 

modeling are summarized in Appendix B, Table B1. 

The resulting half-lives for penoxsulam TTR (the residues of concern) obtain by PESTDF for modeling are 

summarized in Appendix B, Table B1. 

 

Appendix B, Table B1. Aerobic Soil Metabolism Half-lives for Penoxsulam Parent and Penoxsulam TTR 

Estimated with PestDF 

Soil PestDF Recommendation DT50 [SFO] DT90 [SFO] MRID 

(days) 

Penoxsulam Parent 

Arkansas tR IORE = 18 11.2 37.3 45830724

California tR IORE = 17.4 11.9 39.7

North Dakota Slow t1⁄2 = 142 64 213

90% upper-bound on mean 104.24 48.07 160.01

Penoxsulam TTR 

Arkansas tR IORE = 1.54 x 107 421 1,298 45830724

California tR IORE = 7.99 x 103 178 590

North Dakota tR IORE = 4.41 x 106 341 1,131

90% upper-bound on mean 391.187 1,238.99

Note: Upon review of the DER for the aerobic soil metabolism study (MRID 45830724), it was noted that 

the half-lives calculated for the Arkansas (0 to 179 days) and California (0 to 270 days) did not include the 

final sampling date (i.e., day 365). Therefore, the half-lives presented in the DER were recalculated which 

resulted in longer half-lives. The first order linear regression half-life for Arkansas is 33.8 days (0 to 179 

days) and 62.6 days (0 to 365 days) and for California 43.4 days (0 to 270 days) and 55.3 days (0 to 365 

days). The North Dakota soil used all data (0 to 365 days).

The current model input guidance indicates that the average (Koc or Kd) be used for both groundwater and 

surface water. Previous guidance indicated that the lowest non-sand Koc or Kd be used. 

 

Appendix B, Table B2. Average Koc for penoxsulam and three degradation products in different soils and sediment. 

Soil Additional 

Information 

Penoxsulam BSTCA BST 5-0H-penoxsulam 

Location/texture/ID Koc (mL/goc) 

US NC s [M538] 76 46 34 34

US AR sil [M557] 40 156 61 34

Japan l [M558] Volcanic 22 - - -

Japan scl [M559] Non-Volcanic 40 - - -

Japan l [M560] Volcanic 305 - - -

Japan l [M561] Non-Volcanic 195 - - -

US CA cl [M562] 20 25 18 18

US ND l [M563] 21 - 21 38

 20 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/NAFTA_Degradation_Kinetics_Equations.htm 21 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/archive2015/ftt_sop_using_nafta_guidance.pdf
13

Soil Additional 

Information 

Penoxsulam BSTCA BST 5-0H-penoxsulam 

Italy sicl [M570] 253 444 85 144

France sicl [M571] 66 74 48 42

UK scl [M572] 13 5 5 18

Italy sl [M573] 46 - 71 34

Mean (all) 91.42 125.00 42.88 45.25 

Mean (US) 39.25 75.67 33.50 31.00

Sediment (U.S) 1,129.5 - - -

MRID 4580801 45830802 45830802 45830802

M558 and M559 upland soils

M560 and M561 rice

 
14

Appendix C Table 1 Penoxsulam Use Rate Summary based upon BEADa Report (09/09/14).

EPA Reg. 

No.

Use Single Max 

Appl. Rate

[lb a.i./A]

Max 

Seasonal or 

CC App

[ lb a.i./A]

Application Method Application Timing

62719-611 Agr/uncultivated 

areas

Almond

Beech Nut

Brazil Nut

Butternut

Cashew

Chestnut

Citrus

Filbert (Hazelnut)

Grape

Grape

Hickory Nut

Macadamia Nut

Pecan

Pistachio

Non Agr. 

Uncultivated/soils

Walnut (English Black 

Nut)

0.0478

0.0319

-

-

-

-

-

-

-

0.0106

0.0319

-

-

0.0319

-

0.0478

0.0319

-

0.0478

NS

0.0478

0.0106

0.0478

-

-

0.0478

-

NS

0.0478

Broadcast

Directed Spray

-

-

-

-

-

-

-

Directed Spray

Directed Spray

-

-

Directed Spray

-

Broadcast

Direct Spray

Weed pre and post 

emergence

Dormant weed pre 

and post emergence

Dormant

Dormant

Non-bearing

62719-612 Conifer (seed 

orchard)

Eucalyptus

Fruit tree (All or 

unspecified

Grapes

Grapes

Non Agr. 

Uncultivated/soils

Tree Nuts

0.0312

-

-

-

-

0.0312

0.0415

-

-

-

-

0.0415

Directed Spray

-

-

Broadcast

Directed Spray

Broadcast/Directed Spray

Weed preemergence

Dormant

Weed preemergence

Dormant

Weed preemergence

Weed preemergence

Dormant/Weed 

preemergence

62719-546 Aquatic areas/water

Aquatic areas/water

Aquatic areas/water

Ornamental 

Lawns/turf

Ornamental 

Lawns/turf

Ornamental 

Lawns/turf

Ornamental Sod Farm 

(turf)

0.0879

0.1758

0.4097

0.0603

0.0603

0.0603

0.0603

NS

-

-

0.0904

0.0904

0.0904

0.0904

Spray

Spray

Water Treatment 

(subsurface)

Broadcast

Low volume Spray 

(concentrate)

Spot Treatment

Broadcast

Low volume Spray 

(concentrate)

Spot Treatment

Weed postemergence

62719-603 Conifer (seed 

orchard)

Eucalyptus

Fruit tree (All or 

unspecified

Grapes

Non Agr. 

Uncultivated/soils

Tree Nuts

0.0314

-

0.0314

0.0314

0.0628

0.0314

0.0628

-

0.0471

0.0471

NS

0.0471

Broadcast

Directed Spray

-

Broadcast

Broadcast

Weed postemergence

Dormant/Weed 

preemergence/Weed 

postemergence

Dormant/weed pre & 

post emergence
15

EPA Reg. 

No.

Use Single Max 

Appl. Rate

[lb a.i./A]

Max 

Seasonal or 

CC App

[ lb a.i./A]

Application Method Application Timing

2217-995 Non Agr. 

Uncultivated/soils

-

Ornamental 

Lawns/turf

Ornamental Sod Farm 

(turf)

0.02

0.02

0.02

0.02

0.0401

0.0401

0.0401

0.0401

Broadcast 

Spot treatment

Broadcast/Spot 

Treatment

Weed Postemergence

2217-974 Non Agr. 

Uncultivated/soils

Ornamental 

Lawns/turf

Ornamental Sod Farm 

(turf)

0.035

0.035

0.035

0.035

0.070

0.070

0.070

0.070

Broadcast 

Spot treatment

Broadcast/Spot 

Treatment

Broadcast/Spot 

Treatment

Weed Postemergence

62719-589 Ornamental

Lawns/turf

Ornamental Sod Farm 

(turf)

Residential Lawns

0.0175

0.0175

0.035

0.035

Broadcast

Broadcast

62719-590 Ornamental 

Lawns/turf

Ornamental Sod Farm 

(turf)

Residential Lawns

0.0175

0.0175

0.035

0.035

Broadcast

Broadcast

Weed postemergence

62719-543

62719-548

62719-549

62719-550

62719-585

62719-588

62719-606

Ornamental 

Lawns/turf

Ornamental Sod Farm 

(turf)

Residential Lawns

0.063

-

-

-

-

-

-

0.091

-

-

-

-

-

-

Broadcast

-

-

-

-

-

-

Weed postemergence

62719-547 Ornamental 

Lawns/turf

Ornamental Sod Farm 

(turf)

0.0587

-

-

-

0.0899

-

-

-

Broadcast

-

Low volume Spray 

(concentrate)

Spot Treatment

Weed postemergence

62719-610

62719-500

62719-616

62719-607

Rice 0.0448

-

0.044

-

0.0415

0.042

0.0448

-

0.044

-

0.0415

0.042 

Broadcast

Flooded Treatment

Broadcast

Water Treatment 

(subsurface)

Broadcast

Broadcast

Postemergence

Weed postemergence

At permanent flood

Foliar

Foliar Postemergence

62719-501

62719503

Rice 0.0444 0.0444

Water Treatment 

(subsurface)

Weed postemergence

62719-514 Rice 0.044 0.044 Spray Weed postemergence

62719-546

67690-47

67690-71

Direct aquatic use –

aquatic weeds

Max conc. 

150 ug/L

Water application

Aerial application

Maintain for minimum 

of 60 days

a Penoxsulam (119031) Label Use Report Package in Support of Registration Review (09/11/14)
16

Appendix D. Sample Output from the SWCC and PRZM-GW Models 

 

Summary of Water Modeling of penoxsulam+degradates and the USEPA Standard Reservoir 

Estimated Environmental Concentrations for penoxsulam+degradates are presented in Table 1 for the USEPA 

standard reservoir with the GAPecansSTD field scenario. A graphical presentation of the year-to-year peaks is 

presented in Figure 1. These values were generated with the Surface Water Concentration Calculator (SWCC Version 

1.106). Critical input values for the model are summarized in Tables 2 and 3.

This model estimates that about 0.89% of penoxsulam+degradates applied to the field eventually reaches the water 

body. The main mechanism of transport from the field to the water body is by runoff (93.9% of the total transport), 

followed by spray drift (5.83%) and erosion (0.22%).

In the water body, pesticide dissipates with an effective water column half-life of 38.2 days. (This value does not 

include dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide 

from the complete system.) The main source of dissipation in the water column is washout (effective average halflife = 57.9 days) followed by metabolism (165.7 days), photolysis (351.5 days), and volatilization (5.166555E+14 

days).

In the benthic region, pesticide dissipation is negligible (1166.6 days). The main source of dissipation in the benthic 

region is metabolism (effective average half-life = 1166.6 days). Most of the pesticide in the benthic region (83%) is 

sorbed to sediment rather than in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for penoxsulam+degradates. 

Peak (1-in-10 yr) 1.54

4-day Avg (1-in-10 yr) 1.48

21-day Avg (1-in-10 yr) 1.27

60-day Avg (1-in-10 yr) 0.921

365-day Avg (1-in-10 yr) 0.224

Entire Simulation Mean 0.788E-01

 

Table 2. Summary of Model Inputs for penoxsulam+degradates. 

Scenario GAPecansSTD

Cropped Area Fraction 1.0

Koc (ml/g) 45.25

Water Half-Life (days) @ 25 °C 120.3

Benthic Half-Life (days) @ 25 °C 847

Photolysis Half-Life (days) @ 40 °Lat 2.9

Hydrolysis Half-Life (days) 0

Soil Half-Life (days) @ 25 °C 0

Foliar Half-Life (days) 0

Molecular Wt 483.4

Vapor Pressure (torr) 7.16e-16

Solubility (mg/l) 410

 
17

 

 

Table 3. Application Schedule for penoxsulam+degradates. 

Date (Days Since 

Emergence)

Type Amount (kg/ha) Eff. Drift

20 Ground 0.0347 0.99 0.017

50 Ground 0.0179 0.99 0.017

 

Figure 1. Yearly Peak Concentrations 

 

Groundwater Analysis for penoxsulam + degradates of concern (TTR) and the NC Eastern Coastal Plain - Norfolk Loamy 

Sand - Cotton Scenario

Estimated groundwater concentrations and breakthrough times for penoxsulam + degradates of concern (TTR) are 

presented in Table 1 for the NC Eastern Coastal Plain - Norfolk loamy sand - Cotton groundwater scenario. A 

graphical presentation of the daily concentrations in the aquifer is presented in Figure 1. These values were 

generated with the PRZM-GW (Version 1.07). Critical input values for the model are summarized in Tables 2 and 3.

Table 1. Groundwater Results for penoxsulam + degradates of concern (TTR) and the NC Eastern Coastal Plain - 

Norfolk loamy sand - Cotton Scenario. 

Peak Concentration (ppb) 46.3

Post-Breakthrough Mean 

Concentration (ppb)

 31.3

Entire Simulation Mean 

Concentration (ppb)

 24

Average Breakthrough Time 

(days)

2371.187
18

Throughputs 4.622157

 

Table 2. Chemical Properties for Groundwater Modeling of penoxsulam + degradates of concern (TTR). 

Koc (ml/g) 45.25

Surface Soil Half Life (days) 0

Hydrolysis Half Life (days) 0

Diffusion Coefficint Air (cm2/day) 0.0

Henry's Constant 0.0

Enthalpy (kcal/mol) 0.0

 

Table 3. Pesticide application scheme used for penoxsulam + degradates of concern (TTR). This application scheme 

was applied every year of the simulation. 

Application Days 

Relative to Emergence 

Date (05/15)

Application Method Application Rate

(kg/ha)

20 Above canopy application 0.0603

50 Above canopy application 0.0337

 

Figure 1. Aquifer Breakthrough Curve for penoxsulam + degradates of concern (TTR) and the NC Eastern Coastal Plain - 

Norfolk Loamy Sand - Cotton Scenario