1 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

Chemical: Penoxsulam

    PC Code: 119031

DP Barcode: 425158

Date: July 29, 2015

MEMORANDUM                

SUBJECT:   Registration Review Ecological Risk Assessment for Penoxsulam (PC Code

119031; DP Barcode 425158)  

TO:     Bonnie Adler, Chemical Review Manager

    Linda Arrington, Chief

    Risk Management and Implementation Branch 6

    Pesticide Reevaluation Division (7508P)

THROUGH:     Dana Spatz, Chief

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507P)

FROM:     James Wolf, Ph.D., Environmental Chemist

Rosanna Louie‐Juzwiak, Risk Assessment Process Leader

    Environmental Risk Branch 3

    Environmental Fate and Effects Division (7507P)

EXECUTIVE SUMMARY

The Environmental Fate and Effects Division (EFED) has completed the ecological risk

assessment (attached) as part of the Registration Review of the herbicide penoxsulam (PC Code

119031). Since the initial registration of penoxsulam and its use on rice in 2004, several

assessments were conducted for various non‐food uses (direct aquatic treatments and turf),

exposed sediment (including canals), non‐bearing trees, conifers (nursery and container stock),

eucalyptus, non‐cropland, and crop uses (tree nuts, grapes). Similar risks of concern (i.e., risks

to aquatic and terrestrial plants) were identified in each assessment. Based on available toxicity

data, there are no LOC exceedances for any other taxa included in those assessments.  

The Agency is unable at this time to conduct a risk assessment for pollinators (e.g., honey bees)

exposed to penoxsulam because EPA does not have a full suite of toxicity data to assess

potential risk to honey bees. EPA recently issued guidance on the framework to conduct risk
2

assessments for pollinators (e.g., honey bees). Additional data are needed in order to conduct

an assessment for pollinators. These data are:

1. Acute oral toxicity to larval honey bees (Non‐guideline, OECD TG 237)

2. Chronic oral toxicity to adult honey bees (Non‐guideline)

3. Chronic oral toxicity to larval honey bees (Non‐guideline)

4. Field trial of residues in pollen and nectar (Non‐guideline)

5. Semi‐field testing for pollinator (Non‐guideline, OECD Guidance 75)

6. Field testing for pollinators (Guideline 850.3040)

Other than the toxicity data for honey bees, no changes in use pattern, science policy, or

available data have occurred since the 2004 and subsequent assessments that would change

the risk conclusions. This document presents an overview of the chemical, its uses and usage,

summaries of the available data, and the assessments completed to date (and on which the

registration review of penoxsulam will be based).  
3

INTRODUCTION

Penoxsulam (2‐(2,2‐difluoroethoxy)‐N‐(5,8‐dimethoxy[1,2,4]triazolo[1,5‐c]pyrimidin‐2‐yl)‐6‐

(trifluoromethyl)benzenesulfonamide) is a systemic, post‐emergence herbicide belonging to the

triazolopyrimidine sulfonamides chemistry family. Penoxsulam is an acetolactate synthase (ALS)

inhibitor herbicide developed by Dow AgroSciences for the control of broadleaf weeds, aquatic

plants, and certain grasses. The mode of action for susceptible weeds is by inhibition of

acetolactate synthase (ALS), the first enzyme in the biosynthetic pathway for the amino acids

leucine, valine, and isoleucine.   

The chemical structure of penoxsulam and some of its chemical identifiers are provided in

Table 1.

Table 1. Penoxsulam Chemical Structure and Identifiers  

Chemical Name   2‐(2,2‐difluoroethoxy)‐N‐(5,8‐dimethoxy[1,2,4]triazolo[1,5‐c]

pyrimidin‐2‐yl)‐6‐(trifluoromethyl)benzenesulfonamide

Chemical Structure

Chemical Abstracts

Service (CAS) Registry

Number

219714‐96‐2  

Smiles Code C1=C(C(=C(C=C1)OCC(F)F)[S](NC2=N[N]3C(=N2)C(=CN=C3OC)OC)(=O)

=O)C(F)(F)F
4

USE CHARACTERIZATION

Penoxsulam is formulated as flowable and emulsifiable concentrate, water dispersible granules,

oil in water emulsion, granular, and soluble concentrate (liquid) with application methods

which include: broadcast, directed spray, spray, spot treatment, low volume spray

(concentrate), water treatment (subsurface), flooded area treatment. It is currently registered

for a number of agricultural use sites including dry‐ and wet‐seeded rice, grapevines, several

species of nut trees (almond, beech, Brazil, cashew, butternut, chestnut, pecan, and pistachio);

and non‐agricultural use sites including turf/sod, ornamental grasses, non‐cropland, conifers,

eucalyptus, non‐bearing fruit trees, and aquatic areas. Some labels stipulate the use of buffers

zones to reduce potential drift from the target area that may impact adjacent, sensitive crops

and/or other nontarget organisms. Some of the products labeled for use on rice includes

language restricting the raising and harvesting of fish, crawfish, shellfish, and/or other

crustaceans if penoxsulam is used in the same field/paddy.

A Screening Level Usage Analysis (SLUA) was prepared by Biological and Economical Analysis

Division (BEAD, 2014) for penoxsulam that provides an estimate of pesticide agricultural usage

data (Table 2). The use on almonds and rice accounted for the largest agricultural use during

the timeframe (2004‐2012) considered by the SLUA report. The average annual pounds of

active ingredient used on almonds was 1,000 and 6,000 lbs for almonds and rice, respectively.   

Table 2. Screening Level Estimates of Agricultural Uses of Penoxsulam (119031)

Sorted Alphabetically (Reporting Timeframe: 2004‐2012)a,b

Crop Avg. Lbs. A.I.

Applied Per Year

Percent Crop Treated

Average Maximum

1 Almonds        1,000 5 10

2 Pecans         <500 <1 <2.5

3 Pistachios         <500 5 15

4 Plums/Prunes         <500 <1 <2.5

5 Rice        6,000 5 15

6 Walnuts         <500 5 10

a

  SLUA data sources include:  

USDA‐NASS (United States Department of Agriculture's National Agricultural

Statistics Service)  

Private Pesticide Market Research

b    All numbers rounded.

<500 Less than 500 pounds of active ingredient

<2.5 Less than 2.5 percent of crop treated

<1 Less than 1 percent of crop treated

A summary of the currently registered uses and application rates for penoxsulam are in Table 3.
5 

Table 3. Registered Penoxsulam Uses and Application Rates

Crop/Site

Residential

Agricultural

Forestry Application Type Maximum Single Application Rate by Formulation (lb a.i./A)

Maximum

Application

Rates

Maximum

Application

Number

PHI (days)

MRI (days) Comm

Per Year lb a.i./A Per Year

RiceWet‐seeded anddry‐seeded

x

Foliar, granularAerialGround 0.044 0.044 1 60 ‐‐ 

Apply up to 

stage of ric

Lakes, ponds(direct aquatic,

submerged orfloating plants)

X

Foliar, granularAerial, ground

150 ppb 150 ppb

Apply tofloating/emaquatic veg

Lakes, ponds(direct aquatic,

emergentvegetation

x

FoliarBoat or ground

equipment(includinghand‐held)

0.0313 – 0.0875

Lakes, ponds,canals(exposedsediment after

draw down)

X

Spray

Boat or truck

0.0875 – 0.175 0.175 NS Hold treate

for 24 hou

Turf x x

Foliar

Aerial

Ground

0.01 ‐ 0.06 0.09 NS  ‐‐  28
6

Crop/Site

Residential

Agricultural

Forestry Application Type Maximum Single Application Rate by Formulation (lb a.i./A)

Maximum

Application

Rates

Maximum

Application

Number

PHI (days)

MRI (days) Comm

Per Year lb a.i./A Per Year

Turf x x

granular

Aerial

Ground

0.01 ‐ 0.06 0.09 NS  ‐‐  28

Grape X

Ground

Broadcast or

band

0.016 – 0.032 0.048 2 60 30

Includes apto both do

actively groplants

Tree nut (including

pistachio) X

Ground

Broadcast or

band

0.016 – 0.032 0.048 2 60 30

Includes apto both do

actively groplants

Non‐bearing tree x

Pre‐ and post‐

emergent

ground

0.0156 ‐ 0.0312 0.0625 NS

Conifer(transplants,container stocks)

x

Pre‐ and post‐

emergent

ground

0.0156 ‐ 0.0312 0.0625 NS

Eucalyptus x

Pre‐ and post‐

emergent

ground

0.0156 ‐ 0.0312 0.0625 NS
7

Crop/Site

Residential

Agricultural

Forestry Application Type Maximum Single Application Rate by Formulation (lb a.i./A)

Maximum

Application

Rates

Maximum

Application

Number

PHI (days)

MRI (days) Comm

Per Year lb a.i./A Per Year

Non‐cropland

Pre‐ and post‐

emergent

ground

0.03125 0.0625 NS
8 

SUMMARY OF RISK ASSESSMENTS

Ecological Risk Assessments  

In September 2004, EFED conducted a risk assessment to support the initial registration of

penoxsulam for use on rice (USEPA, 2004). This assessment included evaluation of ground and

air‐applied products of penoxsulam, including both foliar‐applied spray to emerged plants, as

well as a granular application to submerged plants. The results of the assessment identified

risks of concern only to aquatic and terrestrial plants. Additional analyses were conducted to

estimate distances off‐site for spray drift, as well as half‐life analyses to estimate the holding

time of the paddy water that would allow for residues to dissipate below a level that would not

pose a risk to non‐target aquatic plants.  

Since the initial registration of penoxsulam and its use on rice in 2004, several assessments

were conducted for various non‐food uses (direct aquatic treatments and turf), exposed

sediment (including canals), non‐bearing trees, conifers (nursery and container stock),

eucalyptus, non‐cropland, and crop uses (tree nuts, grapes). Similar risk conclusions (i.e., risks

to aquatic and terrestrial plants) were identified in each assessment. A summary of risk

concerns based on these previous assessments is summarized in

Table 4.

Table 4. Summary of Risk Concerns Identified for Penoxsulam

Exposure

Basis Birds Mammals

Terr.

Plants

Terr.

Inverts.

(honey

bee

hazard)

Fish Aquatic

Inverts

Aquatic

Plants

Ground‐

water

Contam‐

ination

Persistence Degradates

of Concern

Acute No No

Yes

No No No

Yes Yes No Yes

Chronic No No No No No

Drinking Water Exposure Assessments  

Drinking water assessments have been previously prepared for penoxsulam (Table 5). A Tier 1

drinking water assessment (DWA) for parent plus degradates of concern (residues of concern)

was completed for the rice use in 2004 (D298489) using the interim rice model (for surface

water) and SCI‐GROW for groundwater. In 2006, a DWA was prepared for the parent

penoxsulam [synonyms DE‐638, XDE‐638, and XR‐638] and six of 11 degradation products

identified by the Health Effects Division as residues of concern:  BSTCA, 2‐amino TCA, 5‐OH‐

penoxsulam, SFA, sulfonamide, and 5,8‐di OH. This DWA used the total toxic residue (TTR)

approach for uses on turf and aquatic vegetation (D325468) (treatment concentration of 150

ppb). Uses on almond and pistachio trees, using the Tier 1 FIRST and SCI‐GROW models, were
9

assessed in 2008 (D355676) and use on non‐bearing trees1, conifers, eucalyptus, and non‐

cropland in 2010 (D373443).

The estimated drinking water concentration (EDWCs), using the FIRST and SCI‐GROW models

from the turf use (D325468) resulted in the highest concentrations (Surface water: acute ‐ 9.4

μg/L and chronic ‐ 0.92 μg/L; groundwater: 23.3 μg/L).  

Table 5 summarizes the ecological and drinking water exposure assessments conducted to

date, as well as the pending uses, in support of penoxsulam.

Table 5. Previous Ecological Risk and Drinking Water Exposure Assessments for Penoxsulam.

Year Use/Crops Drinking Water‐

Models

Aquatic

Exposure‐

Models

DP Barcode

DWA ERA (year)

Registered Uses   

2004 Rice Interim Rice

Model/SCI‐

GROW

Interim Rice

Model

298489 288160

2006 Turf, Direct aquatic

(vegetation in lakes, ponds,

canals)

FIRST/SCI‐

GROW, Target

concentration

GENEEC2 325468 325783

(2007)

2008 Almond hull, grapes, tree

nuts, pistachio

FIRST/SCI‐

GROW

GENEEC2 355676 355671

(2009)

2010 Non‐bearing tree,

eucalyptus, conifers, non‐

cropland

FIRST/SCI‐

GROW

GENEEC2

PRZM/EXAMS

373443 373443

2011 Exposed Sediment in

Irrigation Canals (reduce

water holding period to 24

hours)

‐‐‐  ‐‐‐  ‐‐‐  395037

ENVIRONMENTAL FATE AND TRANSPORT

   

a. Persistence and Transformation  

Penoxsulam is expected to be mobile in soil, moderately persistent in the aerobic terrestrial

environments, and less persistent in anaerobic environments. Penoxsulam is expected to

dissipate rapidly in clear shallow waters through aqueous 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

 

1 Including avocado, cacao, citrus, coffee, guava, mango, olive, pomegranate, pome fruit, and stone fruit.   
10

the photolytic half‐life.  In aqueous environments, penoxsulam is stable to hydrolysis at pH 5, 7

and 9.   

In terrestrial environments, or when sunlight is not able 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 were 66, 55,

and 118 days for soils from AR, CA, and ND, respectively.  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 soils2 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 days, and 11 days. The resulting half‐lives for the residues of concern used for

modeling were recalculated using PestDF, a R software3 compatible script (PestDF version 3.1.2

and xxDeg_08.13 following NAFTA4 guidance) are summarized in Appendix A, table A3.

Eleven major degradation products have been 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 available degradates data are summarized in

Appendix A, Table A2.  Included in this table is the maximum percentage of degradation

product compared to the applied and the study type where the degradation product was

identified. The six degradation products of toxicological concern for drinking water occurred in

the aerobic soil, and 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).  

b. Transport and Mobility  

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

soil, but binding more strongly to sediments. Penoxsulam has low volatility indicating that

atmospheric transport is, at best, a very minor route of dissipation. Submitted mobility data for

three penoxsulam degradation products (BSTCA, 5‐OH‐penoxsulam, and BST) indicate

environmental mobility roughly equivalent to or slightly greater than the parent compound.  

The soil to water partitioning 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

 

2 MRID 458307‐26 Aerobic Aquatic Metabolism. Japanese soils Volcanic soil (t1⁄2 = 29 days) none volcanic soil (t1⁄2 = 29.5 days) 3 http://www.r‐project.org/ ) R Statistical Foundation for Statistical Computing 4 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/ftt_sop_using_nafta_guidance.pdf
11

mL/goc. The reported Koc values for the sediment were 1118 and 1141 mL/goc (Kds = 1.38 and

1.41 mL/g).  One of the soils was volcanic from Japanese (Kds ‐10.13 and 10.67 mL/g; Kocs = 297

and 313 mL/goc). Neither of these soils were not included in the determination of Kd or Koc

values used for model inputs, because volcanic soils are generally not present in the contiguous

United States, and therefore, not representative of the soil conditions considered in the

standard surface water and groundwater scenarios. There are no data regarding the mobility of

neither the remaining transformation products nor the combined parent/degradate residues.  

The lowest average Koc of 45.3 mL/goc for 5‐0H‐penoxsulam was used as an input for modeling

as it is one of the residues of concern identified by the Health Effects Division and it appears to

be one of the more persistent degradates. A summary of the mobility data can be found in

Appendix A, Table A4.

A summary of the current fate and transport properties of penoxsulam appears in Table 6,

below.  

Table 6. Model Input parameters for Penoxsulam (TTR)  

Input Variable Input Value   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) 0 days Stable No degradation

in study

45830721

Photolysis (Aqueous) t1⁄2 a

(penoxsulam) (upper bound on

mean)

2.9 days [4.3 days]b 1.5, 1.5, 3.1 days 45834801

TTRc Aerobic Soil t1⁄2

5,6 (upper bound

on mean)

Stable [467 days] >365 days 45830724

TTR Anaerobic Soil &  Sediment   ‐  ‐  45830725

TTR Anaerobic Aquatic t1⁄2

5,6 (system)

2 soils

2 soils + sediment

(upper bound on mean)

168 days

[88.3 days]

847 days

70.8, 132 days (soil)

70.8, 132, 950 days

(soils + sediment)

45830725

TTR Aerobic Aquatic t1⁄2

5,6 (system) 120.3 days

[36.6 days]

136, 84.8, 84.9, 96

days

45830726

Kd (5‐OH‐penoxsulam) 0.54 mL/g [0.13]   n = 16 (average)

[lowest non‐sand]

45830802

Koc (5‐OH‐penoxsulam) 45.25 mL/goc

[13]

n = 16 (average)

[lowest non‐sand]

45830802

Spray drift Fraction

(Aerial Coarse Droplet size)

0.068  

[0.05]

High Boom EFED

Guidance

 

5 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/NAFTA_Degradation_Kinetics_Equations.htm 6 http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/archive2015/ftt_sop_using_nafta_guidance.pdf
12

(Ground Coarse Drop size) 0.017

[0.01]  

High Boom EFED

Guidance a  t1⁄2 is total toxic residues (TTR) half‐life re‐estimated by PestDF in Appendix A, Table A3. b Values in [] were used in the previous assessments. c TTR Residues of Concern (ROC) includes penoxsulam parent plus some or all of the penoxsulam degradation

products BSTCA, 2‐amino TCA, 5‐OH‐penoxsulam, SFA, sulfonamide, and 5,8‐di OH.   

c. Field Dissipation Studies  

Terrestrial Field Study

Soil dissipation of penoxsulam under US field conditions was monitored in three bare plots of

loam soil in California and in three bare plots of loamy sand soil in New York. Penoxsulam was

applied once at a target rate of 0.11 kg a.i./ha (0.098 lb a.i./acre) to 39 x 7 m and 40 x 8 m

replicate plots in California and New York, respectively (MRID 467035‐01).  Penoxsulam and

transformation products were monitored in soil samples collected from Site 1 at 0 thru 327

days post application, and from Site 2 at 0 thru 150 days post treatment.  Soil samples were

collected to a depth of 0‐90 cm.  The half‐life of penoxsulam in the loam soil in California was

48.5 days (based on all replicate detections) and 18.8 days (based on 0‐92 day data).  The

calculated DT90 was 53 days and the transformation products 5‐OH penoxsulam and BSTCA

were detected.  The half‐life of penoxsulam in the loamy sand in New York was 5.9 days (based

on all replicate detections). The calculated DT90 was 12 days and the major transformation

product detected was BSTCA.

Aquatic Field Studies

In the submitted aquatic field dissipation studies, the water half‐life for penoxsulam applied by

subsurface injection to a pond in Florida to achieve a final concentration of 150 ppb in the 0.3‐

ha application zone was 24.8 days (MRID 467035‐02).  Note that 150 ppb is the maximum

penoxsulam concentration allowed in a treated water body.  5‐OH‐penoxsulam was detected in

the pond water at a maximum concentration of 6.83 ng/mL after 57 days. BSTCA was detected

in the pond water at a maximum of 13.57 ng/mL after 57 days.  TPSA was detected in the pond

water at a maximum of 2.12 ng/mL after 57 days.  The transformation products BSA, 2‐amino‐

TP, sulfonamide, and 5‐OH‐2‐amino‐TP were detected in the pond water at maximum

concentrations of 0.26 ng/mL (14 days), 0.63 ng/mL (43 days), 0.71 ng/mL (43 days), and 0.05

ng/mL (253 days), respectively.

In the same study, penoxsulam dissipated in the Florida pond sediment with a half‐life of 34.5

days based on detected concentrations following the maximum concentration at 21 days. The

transformation products 5‐OH and BSTCA were detected in the sediment at levels above the

limit of quantification [LOQ].  5‐OH was detected in the sediment at a maximum of 26.62 ng/g

by 7 days while BSTCA was detected at a maximum of 18.33 ng/g by 85 days.

In a supplemental aquatic field dissipation study (MRID 46703503), penoxsulam was applied via

subsurface injection four times at 28‐day intervals to achieve a 20 ppb concentration in the 1.2‐

ha application zone of a Florida pond.  Penoxsulam dissipated in the water with half‐lives of
13

15.4, 11.0, 12.1 and 11.7 days, respectively, following each application.  Penoxsulam dissipated

in the sediment with half‐lives of 8.2, 12.9, 7.8, and 21.7 days following each application.  

Transformation products were not monitored in this study.

ECOLOGICAL EFFECTS

Tables 7 and 8 provide a summary of the aquatic and terrestrial toxicity data, respectively, and

the most sensitive surrogate species tested to characterize the potential acute and chronic

ecological effects of penoxsulam.  

Table 7. Penoxsulam Toxicological Endpoints for Aquatic Species.

Measures of Effect   Species Toxicity Value Reference  

Freshwater fish acute

LC50, 96‐h

Rainbow trout

(Oncorhynchus mykiss)

LC50: >102 mg a.i./L

NOAEC = 102 mg a.i./L  

MRID 45834804  

Supplemental

No more than

slightly toxic

Freshwater fish Full life

cycle

Fathead Minnow

(Pimephales promelas)

NOAEC: 10.2 mg a.i./L

LOAEC: >10.2 mg a.i./L

MRID 45831027  

Supplemental

Estuarine/marine Fish,

chronic No study

Estuarine/marine Fish,

acute LC50, 96‐hour

Silverside  

(Menidia beryllina)

LC50 > 129 mg a.i./L

NOAEC = 129 mg a.i./L

MRID 45831022

Supplemental

Freshwater

invertebrate LC50,

48‐h

Waterflea

(Daphnia magna)

Static

LC50: >98.3 mg a.i./L

NOAEC:  98.3 mg a.i./L

MRID 45831012

Supplemental

No more than

slightly toxic

Freshwater

invertebrate, chronic

Waterflea

(Daphnia magna)

NOAEC = 2.95 mg a.i./L

LOAEC = 9.76 mg a.i./L

MRID 45831026

Acceptable

Estuarine/marine

Invertebrate, LC50,  

96‐hr

Saltwater mysid,

Americamysis bahia

LC50 >114 mg a.i./L

NOAEC = 114 mg a.i./L

MRID 45831024

Acceptable

Estuarine/marine

Invertebrate, 28‐day  

Saltwater mysid,

Americamysis bahia

NOAEC < 8.1 mg a.i./L

LOAEC = 8.1 mg a.i./L

MRID 45831028

Supplemental
14

Measures of Effect   Species Toxicity Value Reference  

Nonvascular aquatic

plant, 96‐hr

Green algae

Selenastrum

capricornutum

EC50 = 0.092 mg a.i/L

NOAEC = 0.005 mg a.i./L

MRID 45834805

Acceptable

Vascular aquatic

plants, 14‐day

Duckweed

Lemna gibba

EC50 = 0.003 mg a.i/L

NOAEC = 0.001 mg a.i./L

MRID 45831120

Available acute toxicity data for aquatic species indicate that penoxsulam is practically non‐

toxic to freshwater and marine/estuarine fish and to marine/estuarine invertebrates; it is

slightly toxic to freshwater invertebrates. Results of chronic studies with penoxsulam indicate

that no treatment‐related effects to growth and reproduction occurred in freshwater fish at

concentrations up to 10.2 ppm a.i. In chronic studies with daphnids, penoxsulam significantly

reduced the number of live offspring at 9.76 ppm a.i. (NOAEC = 2.95 ppm a.i.). Penoxsulam also

produced a 20% reduction in male body weights of saltwater mysids at 8.1 mg/L in chronic

studies.

Penoxsulam exhibits toxicity to aquatic vascular plants, with an EC50 of 0.003 mg/L for

duckweed (NOAEC 0.001 mg/L), based on reduction of frond number. Results of Tier II toxicity

studies with non‐vascular aquatic plants indicate that penoxsulam adversely affected cell

density with the freshwater green algae being the most sensitive species (EC50 = 0.092 mg/L;

NOAEC = 0.0046 mg/L.

Several studies were submitted on the acute toxicity of the penoxsulam degradates to D.

magna. Seven of the studies (on BSTCA; BST; 5‐OH‐penoxsulam; 2‐amino‐8‐methoxy;

2‐amino‐TP; TPSA; 5‐OH, 2‐amino‐TP; and BSA) were acceptable for risk analysis. Their 48‐hour

EC50 values for daphnids ranged from >1.0 ppm to >100 ppm. Studies with the degradates were

conducted for aquatic vascular and non‐vascular plants. The penoxsulam degradates were not

as toxic as the parent material.

Table 8. Most Sensitive Penoxsulam Toxicological Endpoints for Terrestrial Species.

Measures of Effect   Species Toxicity Value Reference / Study

classification

Avian acute oral LD50,

14‐day

Mallard

Anas platyrhynchos

LD50: >1900 mg a.i./kg‐bw

NOAEL = 1900 mg a.i./kg‐

bw

MRID 45830929  

(Acceptable)

Practically nontoxic

Avian sub‐acute

dietary LC50

8‐days

Mallard

Anas platyrhynchos

LC50: >4310 ppm  

NOAEC: <733 ppm

Reduction in body weight

gain  

MRID 45831003  

(Supplemental )

Slightly toxic
15

Measures of Effect   Species Toxicity Value Reference / Study

classification

Avian chronic Mallard duck

(Anas platyrhynchos)

NOAEC = 501 ppm‐diet

LOAEC = 958 ppm‐diet

Reduction in adult male

weight

MRID 46276401

46276402

(Acceptable)

Acute Oral Mammal Laboratory rat, Rattus

norvegicus

LD50 = >5000 mg/kg‐bw   MRID 45830812

(Acceptable)

Practically nontoxic

Chronic Mammal,

2‐gen. Reproduction

Laboratory rat, Rattus

norvegicus

NOAEL = 30 mg/kg/day

LOAEL = 100 mg/kg/day

MRID 45830920

(Likely Acceptable)

Pending final

review  

Acute Contact,

96‐hour

Honey bee

Apis mellifera

LD50 = >100 μg a.i./bee

NOEC = 100 μg a.i./bee

MRID 45831124

(Acceptable)  

Practically non‐

toxic

Acute Oral,  

48‐hour

Honey bee

Apis mellifera

LD50 = >83.5 μg a.i./bee

NOEC = 83.5 μg a.i./bee

MRID 45831125

(Acceptable)

Practically non‐

toxic

Subchronic Terrestrial

invertebrate

Earthworm LD50 > 1000 mg/kg MRID  

(Supplemental)

Seedling Emergence,

Tier II

Monocot – onion EC25 =  1.1 g/ha

NOAEC = 0.41 g/ha

MRID 45831116

(Acceptable)

Seedling Emergence,

Tier II

Dicot – sugarbeet EC25 =  3.2 g/ha

NOAEC = 1.2 g/ha

MRID 45831116

(Acceptable)

Vegetative Vigor Monocot – ryegrass EC25 =  17 g/ha

NOAEC = 0.41g/ha

MRID 45831116

(Acceptable)

Vegetative Vigor Dicot – Soybean EC25 =  3.9 g/ha

NOAEC = 1.2 g/ha

MRID 45831116

(Acceptable)

Acute toxicity data indicate that penoxsulam is practically non‐toxic to mammals (acute LD50

value of >5,000 mg/kg‐bw). In a 2‐generation reproduction study with rats exposed to

penoxsulam, preputial separation (an indicator of sexual maturation) was observed in F1 males

at 100 mg/kg/day, resulting in a reproductive/offspring toxicity NOAEL of 30 mg/kg/day (600

ppm).  
16

Acute contact and oral studies indicate that penoxsulam is practically nontoxic to the adult

honey bee. In addition, non‐guideline subchronic studies indicate that penoxsulam is practically

nontoxic to earthworms with an LD50 >1,000 mg/kg.

Terrestrial plant toxicity studies with monocots and dicots indicate that seedling emergence

and vegetative vigor are severely impacted by exposure to penoxsulam. In Tier II studies,

seedling emergence, based on shoot weight, was adversely impacted in monocots (onion) at an

EC25 of 1.1 g a.i./ha and in dicots (sugarbeet) with an EC25 of 3.2 g a.i./ha. Vegetative vigor in

monocots and dicots, based on shoot weight, was adversely impacted at an EC25 of 17 g a.i./ha

in ryegrass and an EC25 of 3.9 g a.i./ha in soybean.  

In a laboratory study, penoxsulam and 11 major metabolites were applied to seeds and saplings

(2 to 2.5 leaves) of 22 plant species including crops, weeds, grasses and flowering plants. The

parent penoxsulam caused significant injury to all exposed species when applied to pre‐

emergent seeds. However, none of the applied 11 major metabolites caused observable injury

when applied to pre‐emergent seeds. Post‐emergent treatment with penoxsulam caused

significant injury to all species with the exception of rice, wheat, and blackgrass. Two of the 11

metabolites (5‐OH penoxsulam and sulfonyl‐formamidine) caused noticeable injury to species

during the post‐emergence study at the highest concentrations (250 and 500 ppm). Oilseed

rape, chickweed, lambsquarter, redroot pigweed, velvetleaf, and wild buckwheat exhibited

minor injury when treated with these two metabolites (MRID 46758301).    

  

RISK CHARATERIZATION AND CONCLUSIONS

Since the initial registration of penoxsulam and its use on rice in 2004, several assessments

were conducted for various non‐food uses (direct aquatic treatments and turf), exposed

sediment (including canals), non‐bearing trees, conifers (nursery and container stock),

eucalyptus, non‐cropland, and crop uses (tree nuts, grapes). Similar risk conclusions (i.e., risks

to aquatic and terrestrial plants) were identified in each assessment. Based on the available

toxicity data, there are no LOC exceedances for all other taxa. EPA has recently issued guidance

on the framework to conduct risk assessments for pollinators (e.g., honey bees). Currently, EPA

does not have a full suite of toxicity data to assess potential risk to honey bees (i.e., acute and

chronic larval toxicity or chronic adult honey bee). At this time, additional toxicity data are

needed in order to conduct an assessment for pollinators (considering all registered uses).

These studies include:

1. Acute oral toxicity to larval honey bees (Non‐guideline, OECD TG 237)

2. Chronic oral toxicity to adult honey bees (Non‐guideline)

3. Chronic oral toxicity to larval honey bees (Non‐guideline)

4. Field trial of residues in pollen and nectar (Non‐guideline)

5. Semi‐field testing for pollinator (Non‐guideline, OECD Guidance 75)

6. Field testing for pollinators (Guideline 850.3040)
17

Other than the toxicity data for honey bees, no changes in use pattern, science policy, or

available data have occurred since the 2004 assessment that would change the risk conclusions.  

Clean Water Act Programs

Penoxsulam is not identified as a cause of impairment for any water bodies listed as impaired

under section 303(d) of the Clean Water Act. No Total Maximum Daily Loads (TMDLs) or water

quality criteria have been developed for penoxsulam7. Office of Pesticide Programs’ Aquatic Life

Benchmarks8 have been established for penoxsulam (refer to Table 9).  Benchmarks are

extracted from the most recent publically available OPP risk assessment for the pesticide and

are based on the most sensitive aquatic toxicity data. These values are estimates of the

concentration below which pesticides are not expected to harm aquatic life.   

Table 9. OPP Aquatic Life Benchmarks* for Penoxsulam (μg/L) (freshwater).

Year

Updated

Fish Invertebrates Nonvascular

Plants

Vascular

Plants

Office of Water

Aquatic Life Criteria

Acute1 Chronic2 Acute3 Chronic4 Acute5 Acute6

Maximum

Concentration

(CMC)

Continuous

Concentration

(CCC)

2013 > 51,000 10,200 > 49,150 2,950 92 3 ‐‐  ‐‐

1 For acute fish, toxicity value is generally the lowest 96‐hour LC50 in a standardized test, and the LOC is 0.5. 2 For chronic fish, toxicity value is usually the lowest NOEAC from a life‐cycle or early life stage test, and the

LOC is 1. 3 For acute invertebrate, toxicity value is usually the lowest 48‐ or 96‐hour EC50 or LC50 in a standardized test,

and the LOC is 0.5. 4 For chronic invertebrates, toxicity value is usually the lowest NOAEC from a life‐cycle test with

invertebrates, and the LOC is 1. 5 For nonvascular plants, toxicity value is usually a short‐term (less than 10 days) EC50, and the LOC is 1. 6 For vascular plants, toxicity value is usually a short‐term (less than 10 days) EC50 and the LOC is 1.

* Benchmark = Toxicity value x LOC

Endangered Species Assessments

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the National

Marine Fisheries Service (NMFS) (collectively, the Services), and the U.S. Department of

Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks to

listed species from pesticides. The Interim Approaches were developed jointly by the agencies

in response to the National Academy of Sciences’ (NAS) recommendations and reflect a

common approach to risk assessment shared by the agencies as a way of addressing scientific

differences between the EPA and the Services. The NAS report9 outlines recommendations on

specific scientific and technical issues related to the development of pesticide risk assessments

 

7 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885 8

 USEPA. 2014. Office of Pesticide Programs’ Aquatic Life Benchmarks. 

http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm 9

 http://www.nap.edu/catalog.php?record_id=18344 
18

that EPA and the Services must conduct in connection with their obligations under the

Endangered Species Act (ESA) and FIFRA.  

The joint Interim Approaches were released prior to a stakeholder workshop held on November

15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013

Pesticide Program Dialogue Committee (PPDC) and State‐FIFRA Issues Research and Evaluation

Group (SFIREG) meetings, and held a stakeholder workshop in April 2014, allowing additional

opportunities for stakeholders to comment on the Interim Approaches. As part of a phased,

iterative process for developing the Interim Approaches, the agencies will also consider public

comments on the Interim Approaches in connection with the development of upcoming

Registration Review decisions. The details of the joint Interim Approaches  are contained in the

white paper “Interim Approaches for National‐Level Pesticide Endangered Species Act

Assessments Based on the Recommendations of the National Academy of Sciences April 2013

Report,”10 dated November 1, 2013.    

Given that the agencies are continuing to develop and work toward implementation of the

Interim Approaches to assess the potential risks of pesticides to listed species and their

designated critical habitat, this ecological risk assessment for aquatic dyes containing

penoxsulam does not contain a complete ESA analysis that includes effects determinations for

specific listed species or designated critical habitat. Although EPA has not yet completed effects

determinations for specific species or habitats, for this preliminary assessment EPA conducted a

screening‐level assessment for all taxa of non‐target wildlife and plants that assumes for the

sake of the assessment that listed species and designated critical habitats may be present in the

vicinity of the application of penoxsulam.   This screening level assessment will allow EPA to

focus its future evaluations on the types of species where the potential for effects exists once

the scientific methods being developed by the agencies have been fully vetted. This screening‐

level risk assessment for penoxsulam indicates potential risks of direct effects to listed plants on

some of its registered use sites.  Listed species of other taxa may also be affected through

indirect effects because of the potential for direct effects on listed and non‐listed species upon

which such species may rely.  Potential direct effects on listed plants from the use of

penoxsulam may be associated with modification of Primary Constituent Elements (PCEs) of

designated critical habitats, where such designations have been made.   Once the agencies have

fully vetted the scientific methods necessary to complete risk assessments for endangered and

threatened (listed) species and their designated critical habitats, these methods will be applied

to subsequent analyses for penoxsulam as part of completing this registration review.  

Endocrine Disruptor Screening Program

Penoxsulam is not included in the first group of 67 chemicals issued an order to conduct Tier 1

EDSP testing.  For additional information on the EDSP program, visit

http://www.epa.gov/endo/.   

 

10 http://www.epa.gov/espp/2013/nas.html 
19

Review of Incident Data

Three incident databases are available: 1) the Ecological Incident Information System v. 2.1.1

(EIIS), maintained by EFED; 2) the Avian Incident Monitoring System (AIMS), maintained by the

American Bird Conservancy; and, 3) the Incident Data System (IDS) maintained by OPP.  These

databases were searched on July 13, 2015. No incidents were reported in AIMS. Overall, the

incidents consisted of plant damage to the target use area (i.e., the crop or use site).  

To date, EIIS contains three unique plant (crop) incidents that may have been attributed to

penoxsulam exposure, which were all classified as “possible.” One incident reported in April

2005 resulted in damage to ~160 acres of rice (out of 300 acres that were treated) in Arkansas

(EPA Reg. No. 62719‐500, Incident IO16962‐031). While penoxsulam is labeled for

postemergence use on rice, the report noted that there were too many uncertainties to

attribute the damage solely to the penoxsulam product. The second plant damage incident was

reported in May 2011 in California (EPA Reg. No. 62719‐611, IO23097‐009), where the product

was applied to immature almond tree orchards (labeling states that trees need to be at least 15

months old). This incident was considered a ‘misuse’ of the product (i.e., did not follow labeled

directions); ~60‐75 trees died within the 320 acre orchard. The third plant damage incident was

reported in May 2011 in California (EPA Reg. No. 62719‐611, IO23097‐011), where penoxsulam

was applied as a soil dormant application pre and post‐emergence to immature young almond

trees (<15 months old), along with other herbicide products including glyphosate and

pendimethalin. This incident was considered a ‘misuse (i.e., did not follow labeled directions) of

the product; effects included yellowing and necrotic leaves, to die‐back to terminal branches

that indicated that some trees would not recover from the exposure. These effects were

observed ~4 months post application.  

IDS returned additional aggregated incidents, all reporting plant damage. One incident

(IO23574‐38, California) consisted of damage to almond trees from an application (EPA Reg. No.

62719‐611) of a product containing penoxsulam and oxyfluorfen, tank‐mixed with a product

containing oryzalin. The application was made in December 2010 to almond trees planted in

January 2001, damaging the 100 acres that was treated; the extent of damage was not

reported. Another incident (IO 24792‐21, Texas) was reported for damage to 33 acres of

established turf (lawn) from a fertilizer containing penoxsulam (EPA Reg. No. 62719‐585)

applied in March 2012. Another incident (IO 24792‐22, California) was reported for damage

(leaf burn, yellowing, crop loss, stunting, limb die back) to 210 acres of almond trees from an

application of a product containing penoxsulam and oxyfluorfen (EPA Reg. No. 62719‐611)

during the dormant season in January 2011. The testing conducted by the registrant indicated

multiple external stressors (e.g., high nematode count, poor planting, stressed trees, poor soil)

that contributed to the damage. Another incident (IO27312‐13, Arkansas) was reported in 2013

for damage to 100 acres of rice from a product containing penoxsulam and triclopyr

triethylamine salt (EPA Reg. No. 62719‐610). There was uncertainty that this product would

have (solely) caused (although it may have contributed) the rice crop damage, as the paddy was

adjacent to an irrigation ditch shared with fields that were cropped with corn. Another incident
20

(IO27312‐50) occurred in California from an application of a product containing penoxsulam

and oxyfluorfen (EPA Reg. No. 62719‐611) to nine acres of almond trees in 2014.

References:

U.S. EPA, 2004. EFED Ecological Risk Assessment for the Section 3 Registration of the New

Chemical Penoxsulam for Uses on Rice. Environmental Fate and Effects Division. DP Barcodes

D288160, D298227, D298401, D298490, D298491, D298492. September 13, 2004

U.S. EPA, 2007. EFED Ecological Risk Assessment Section 3 New Uses on Turf and for Control of

Aquatic Vegetation in Aquatic Environments. Environmental Fate and Effects Division. DP

Barcode 325783. January 31, 2007.

U.S. EPA, 2009. EFED Ecological Risk Assessment for the Proposed New Uses of the Chemical

Penoxsulam on Tree Nuts (Crop Group 14), Grapes, and Pistachios. Environmental Fate and

Effects Division. DP Barcode 355671. February 19, 2009.
21

APPENDIX A. PHYSICAL AND CHEMICAL PROPERTIES OF PENOXSULAM AND ITS

ENVIRONMENTAL DEGRADATES.

  

Table A1. Physical and Chemical Properties of Penoxsulam

Study Type Value Study MRID

Chemical name 2‐(2,2‐difluoroethoxy)‐N‐(5,8‐dimethoxy[1,2,4]triazolo[1,5‐

c]pyrimidin‐2‐yl)‐6‐(trifluoromethyl)benzenesulfonamide ‐‐ 

CAS No. 219714‐96‐2 ‐‐ 

Molecular weight 483.4 ‐‐ 

Solubility in water 5.7  mg/L (pH 5)

410 mg/L (pH 7)

1500 mg/L (pH 9)

‐‐ 

pKa 5.1 ‐‐ 

Vapor pressure at

25C

9.55 x 10‐14 Pa or

7.16 x 10‐16 torr ‐‐ 

Octanol‐water

partition coefficient

(log Kow)

1.1  (pH 5)

  ‐0.60  (pH 7)

 ‐1.4  (pH 9)

‐‐ 

Study Type Value Test System Study MRID

Hydrolysis  ‐‐ t1/2 stable pH 5, 7, 9 buffers / natural waters 458307‐21

Photodegradation in

Water ‐‐ t1/2

1.5 days,  

1.5 days,

3.1 days,

14 days

pH 7 buffer,

pH 7.8 natural waters,

pH 7 AR pond water

pH 5.8 flooded soil  

458348‐01,

458307‐22

Photodegradation on

Soil ‐‐ t1/2

19 days,

109 days

flooded silt loam,

silty  clay  loam

458307‐23

Parent (Only)a

Aerobic Soil

Metabolism  ‐‐ t1/2

63 days,

55 days,

118 days

AR silt loam,

CA clay loam,

ND loam

1st Order Linear Regression.

(EXCELL)

458307‐24

Parent (Only)a

Anaerobic Aquatic

Metabolism  

‐‐ t1/2 (total system)

5 days,

15 days,

7 days

AR pond water / silt loam clay  

sediment,

AR pond water / silt loam soil,

distilled water / silty loam soil

(Italy)

1st Order Linear Regression.

(EXCELL)

458307‐25
22

Parent (Only)a

Aerobic Aquatic

Metabolism  

‐‐ t1/2 (total system)

29 days   

16.8 days   

12.1 days   

37.7 days   

AR pond water / silt loam clay  

sediment,

AR pond water / silt loam soil,

Italian channel water / loam

sediment,

French lake water / sand

sediment,

1st Order Linear Regression.

(EXCELL)

458307‐26

Adsorption  –  Kd

(mL/g)

Penoxsulam

U.S. Soils: 0.29 – 0.59

All Soilsb

: 0.12 – 2.56

Arkansas Sediment: 1.4

Degradates

BSTCA: 0.05 – 4.95

BST: 0.04 – 0.98

5‐OH‐penoxsulam: 0.13

– 1.44

458308‐01  

(Penoxsulam)

Degradates

458308‐02

(BSTCA, BST,  

5‐OH‐

penoxsulam)

Adsorption  –  Koc  

(mL/goc)

Penoxsulam

U.S. Soils: 16 – 80 (n =

8)

All Soilsb

: 12 – 255 (n =

30)

Arkansas Sediment:

1130  

Degradates

BSTCA: 3 – 500 (n = 12)

BST: 3 – 99 (n = 16)

5‐OH‐penoxsulam: 17 –

145 (n=16)

Bioconcentration in

Aquatic, Non‐Target

Organisms – BCF

0.02 mL/g crayfish (Procambarus clarkii), 14

days,  at 0.5 ppm under flow‐

through conditions

458311‐01

Parent (Only)

Terrestrial Field

Dissipation – t1/2  

19 day

  6 days

California sandy, loam soil

New York  loamy, sand soil

467035‐01
23

Parent (Only)

Aquatic Field

Dissipation

‐‐ t1/2 (total system)

16 days

16 days

  

5 days

10 days

  4 days

25 days

35 days

AR bare ground plot, dry seeded

(liquid)

AR cropped plot, dry seeded

(liquid)

CA bare ground plot, water

seeded (liquid)

CA cropped plot, water seeded

(liquid

CA cropped plot, water seeded

(granular)

FL pond ‐  t1/2 water column

(liquid)

FL pond – t1/2 sediment (liquid)

458308‐04,

458308‐05,

467035‐02

a Kinetics for residues of concern (ROC) or total toxic residues (TTR) used for modeling (SWCC

and PRZM‐GW) are listed in Table 6.

b Does not include volcanic soils from Japan (M558 and M560), MRID 4580801 Table 9, page

41R1.  

Table A2 – Summary of Penoxsulam Degradates and Formation in Fate Studies

Degradate Name Structure Maximum %

Applied

Study Type

BSTCA

3‐[[[2‐(2,2‐

Difluoroethoxy)‐6‐

(trifluoromethyl)phen

yl]‐sulfonyl]amino]‐

1H‐1,2,4‐triazole‐5‐

carboxylic acid

11.1% soil photolysis

7.2% aqueous photolysis

39.4%* aerobic aquatic metabolism

37.2%* aerobic soil metabolism

25.4% anaerobic aquatic metabolism

BSA

2‐(2,2‐difluoroethoxy)

‐6‐(trifluoromethyl)

benzenesulfonic acid

8.1% soil photolysis

36.1% aqueous photolysis

2‐amino‐TP

5,8‐dimethoxy

[1,2,4]triazolo[1,5‐c]

pyrimidin‐2‐amine

10.4%* soil photolysis

18.2% aqueous photolysis

O F

F

F

F

F

O S O

N N

N N H

H

OH

O

O F

F

F

F

F

O S O

OH

N N

N

N

N

H

H

OCH3

OCH3
24

Degradate Name Structure Maximum %

Applied

Study Type

TPSA

(5,8‐dimethoxy

[1,2,4]triazolo‐[1,5‐

c]pyrimidin‐2‐yl‐

sulfamic acid)

56% aqueous photolysis

5‐OH, 2‐Amino TP

8‐methoxy‐

[1,2,4]triazolo[1,5‐

c]pyrimidin‐5‐ol‐2‐

amine

32% aqueous photolysis

2‐Amino TCA

2‐amino‐1,2,4‐

triazole carboxylic

acid

85%* aqueous photolysis

BSTCA methyl

Methyl 5‐[[[2‐(2,2‐

difluoroethoxy)‐6‐

(trifluoromethyl)phen

yl]sulphony]amino],

1H‐1,2,4‐triazole‐3‐

carboxylic acid)   

12% aqueous photolysis

1.4% aerobic soil metabolism

12.8% anaerobic aquatic metabolism

Di‐FESA  

3‐(2,2‐

Difluoroethoxy) ‐2‐

hydroxybenzoic acid

7.6% aqueous photolysis

5‐OH‐penoxsulam 40.3% aerobic aquatic metabolism

62.6% aerobic soil metabolism

O O

N

N

N

N N H

OH

S

OCH3

OCH3

N N

N

N

N

H

H

OH

OCH3

N N

N O

N

H

H

OH

O F

F

F

F

F

O S O

N N

N N H

H

O

OCH3

O OH

OH

O

F

F
25

Degradate Name Structure Maximum %

Applied

Study Type

2‐(2,2‐

Difluoroethoxy) ‐N‐

(5,6‐dihydro‐8‐

methoxy‐5‐oxo[1,2,4]

triazolo[1,5‐c]

pyrimidin‐2‐yl)‐6‐

(trifluoromethyl)

benzenesulfonamide

41.6% anaerobic aquatic metabolism

BST

2‐(2,2‐

Difluoroethoxy) ‐N‐

1H‐1,2,4‐triazole‐3‐yl‐

6‐(trifluorom ethyl)

benzenesulfon amide

6.3% aerobic soil metabolism

4.8% anaerobic aquatic metabolism

SFA

2‐2,2‐

Difluoroethoxy)‐N‐

(iminomethyl‐6‐

(trifluoromethyl)‐

benzenesulfonamide

14.7%* aerobic soil metabolism

Sulfonamide

2‐(2,2‐

Difluoroethoxy) ‐6‐

(trifluoromethyl)‐

benzenesulfonamide

33.0%* aerobic soil metabolism

5,8‐diOH

2‐(2,2‐

Difluoroethoxy) ‐6‐

trifluoromethyl‐N‐

(5,8‐dihydroxy‐[1,2,4]

triazolo[1,5‐c]

pyrimidin‐2‐yl)

benzenesulfonamide

11.0%* anaerobic aquatic metabolism

14CO2    not reported aqueous photolysis

O F

F

F

F

F

O S O

N

N

N

N N H

HO

O CH3

O F

F

F

F

F

O S O

N

H

N

N N H

O F

F

F

F

F

O S O

NH

N

H

O F

F

F

F

F

O S O

NH2

O F

F

F

F

F

O S O

N

N

N

N N H

HO

OH
26

Degradate Name Structure Maximum %

Applied

Study Type

3.2%* soil photolysis

16.1%* aerobic soil metabolism

1.2%* anaerobic aquatic metabolism

2.4%* aerobic aquatic metabolism

Non‐extractable

Residues

30.1%* aqueous photolysis (over

sediment)

30.9%* soil photolysis

55.5% aerobic soil metabolism

57.9%* aerobic aquatic metabolism

55.5% anaerobic soil metabolism

Table A3.  Aerobic soil metabolism (parent and ROC), aerobic aquatic metabolism and anaerobic

aquatic metabolism “half‐lives” for the residues of concern (ROCa

) or Total Toxic Residues (TTRa) for

penoxsulam and degradates for modeling using PESTDF.

Study Type Labeled

Ring(s)

Representative half‐

life/DT50 (days)

MRID

Parent Penoxsulam Aerobic soil

metabolism

Combined Study length 365 days

Arkansas silt loam TP + PHb 18 (tR IORE)/DT50 11.2 45830724

California clay loam TP + PH 17 (tR IORE)/DT50 11.9 45830724

North Dakota loam TP + PH 142 ((slow t1⁄2)/DT50 64 45830724

TTR Aerobic Soil Metabolism   ‐  Study length 120 days   

Japanese volcanic soil TP 325 (slow t1⁄2)/DT50 165 45830724

Japanese non‐volcanic soil TP 202 (SFO)/ (238 (slow

t1⁄2))

45830724

Combined Study Length 365 days

Arkansas silt loam TP + PH 8.62E+6 (tR IORE)/DT50

409

45830724

California clay loam TP + PH 7.99E+3 (tR IORE)/DT50

178

45830724

North Dakota loam TP + PH 4.44E+3 (slow t1⁄2)/DT50

348

45830724

TTR Aerobic Aquatic Metabolism Combined Study Length 99 days

US soil‐water TP + PH 136 (SFO)/ ((slow t1⁄2)

194

45830726

Italian sediment TP + PH 84.8 (tR IORE) 45830726

French sediment TP + PH 84.9 (SFO) 45830726

US sediment TP + PH   96 (SFO) 45830726

TTR Anaerobic Soil/Sediment Metabolism

or Degradation.

Combined Study Length 365 days   

Arkansas sediment TP + PH 950 (tR IORE)/ DT50 109 45830726
27

Arkansas soil TP + PH 132 (slow t1⁄2)/DT50

76.6

45830726

    Study Length 120 days   

Italian soil TP + PH 70.8 (tR IORE)/ DT50 24 45830726 a TTR Residues of Concern (ROC) include Penoxsulam parent plus some or all of the penoxsulam degradation products BSTCA, 2‐

amino TCA, 5‐OH‐penoxsulam, SFA, sulfonamide, and 5,8‐di OH.    b TP ‐ 14C label is in triazolopyrimidine ring and PH ‐ 14C label is in the phenyl ring.

The soil to water partitioning coefficients (Kd) for BSTCA derived from the six soils studied

ranged from 0.085 to 4.4 mL/g (Kocs 5 to 444 mL/goc).  The soil to water partitioning coefficients

(Kd) for 5‐OH‐penoxsulam, derived from the eight soils studied ranged from 0.14 to 1.4 mL/g

(Kocs 18 to 144 mL/goc).  The soil to water partitioning coefficients (Kd) for BST derived from the

eight soils studied ranged from 0.075 to 0.61 mL/g (Kocs 5 to 85 mL/goc).  

Five of the thirteen identified transformation products reached peak concentrations at study

termination: 2‐amino‐TP, BSTCA, 2‐amino‐TCA, sulfonamide and 5,8‐di‐OH penoxsulam.  These

five compounds are potentially more persistent than the parent compound, and would

probably have reached even greater concentrations with increased time.  Eleven of the thirteen

penoxsulam transformation products reported in laboratory studies are considered major

degradates: BSA, 2‐amino‐TP, TPSA, BSTCA methyl, BSTCA, 2‐amino‐TCA, 5‐OH‐penoxsulam,

SFA, sulfonamide, 5,8‐di‐OH and 5‐OH 2 amino TP.  Two of the thirteen penoxsulam

transformation products are considered minor degradates: di‐FESA and BST.  

Table A4. Koc for penoxsulam and three degradation products.  

Soil Penoxsulam1 BSTCA2 BST 5‐0H‐

penoxsulam2

Soil origin/textural

class/ID

Koc (mL/goc)

Kd (mL/g)

Koc (mL/goc)

NC s [M538] 76 0.31 46 34 34

AR sil [M557] 40 0.39 156 61 34

Japan l [M558]a,b [22] [0.82]  ‐  ‐  ‐ 

Japan scl [M559]a,d 40 0.85  ‐  ‐  ‐ 

Japan l [M560]c,b [305] [10.4]  ‐  ‐  ‐ 

Japan l [M561]c,d 195 2.49  ‐  ‐  ‐ 

CA cl [M562] 20 0.48 25 18 18

ND l [M563] 21 0.57 ‐  21 38

Brazil [M564] 35 0.51      

Brazil [M565] 14 0.62      

Brazil [M566] 13 0.13      

Canada [M567] 73 1.45      

Canada [M568] 19 0.67      

Italy sicl [M570] 253 2.50 444 85 144

France sicl [M571] 66 0.64 74 48 42

UK scl [M572] 13 0.21 5 5 18
28

Soil Penoxsulam1 BSTCA2 BST 5‐0H‐

penoxsulam2

Italy sl [M573] 46 0.39  ‐  71 34

Mean (all soilse) n=30 61.3 0.81     

Mean (no Japan soils)

n=26

52.8

0.68

    

Mean (U.S. soils) n=8 39.5 0.43      

Degradates Mean

(all)

125.0 42.9 45.3

Degradates Mean

(U.S. soils)

75.7 33.5 31.0

MRID # 4580801    45830802 45830802 45830802 1 Average of 2 values (MRID 45808‐01, Table 9, page 41R1); sediment (Kd ‐ 1.4 mL/g, Koc ‐ 1,130 mL/goc not

included.

2 Degradates of Concern. a M558 and M559 upland soils b Soil parent material is volcanic. c M560 and M561 rice d Soil parent material is non‐volcanic e All soils except [M558] and [M560]  

   
29

Appendix B. Requested Data Justification Tables

Study Title: Honey Bee Acute Oral Toxicity, Adult

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticides in various use settings.   

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently

brought back to the hive.  Therefore, potential acute effects to adult honeybees and other

pollinators from oral exposure to some pesticides could exist.  Currently available toxicity studies

do not address possible effects of oral exposure on adult terrestrial insect survival.  Because of the

potential for pollen and nectar to be contaminated with pesticide residues, and subsequently

brought back to the hive, it is important to determine the acute oral toxicity of this compound to

adult honeybees and other insect pollinators.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

terrestrial invertebrates using the honeybee as a surrogate test species.  The guidance discusses

Tier I laboratory‐based acute oral toxicity studies of individual adult bees as a critical component of

the screening‐level risk assessment process for examining potential adverse effects from specific

routes of exposure.  The guidance can be found at: http://www2.epa.gov/pollinator‐

protection/pollinator‐risk‐assessment‐guidance .  Additional guidance on the honeybee oral

toxicity test design can be found in OECD Test Guideline 213 http://www.oecd‐

ilibrary.org/environment/test‐no‐213‐honeybees‐acute‐oral‐toxicity‐test_9789264070165‐en  .

Practical Utility of the Data

How will the data be used?

The Tier I acute oral toxicity data on adult bees serve as a foundation for the screening‐level

assessment of potential risk to non‐target organisms such as federally listed threatened or

endangered and non‐listed terrestrial invertebrate insects, including pollinators, from acute oral

exposures to pesticides.  The data will be used to reduce uncertainties associated with the risk

assessment for terrestrial invertebrates and will improve EPA’s understanding of the potential

direct and indirect effects on a broad range of taxa.  This study will also provide information with

which to compare whether oral toxicity estimates differ from contact toxicity estimates obtained

from other Tier I studies.  If acute oral effects data for adult honeybees and insect pollinators are

not available, risks to terrestrial insects from acute oral exposure will be assumed.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect listed threatened or endangered species and/or modify their designated

critical habitat.  Without these data, EPA may need to presume risk which will limit the flexibility of

pesticide products to comply with FIFRA and the ESA, and could result in use restrictions.   
30

Study Title: Honey Bee Acute Oral Toxicity, Larvae

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticides in various use settings.  

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently

brought back to the hive where larvae and pupae may be exposed.  Therefore, potential adverse

effects to developing bees and other insect pollinators could result from exposure to pesticide

residues.  Available toxicity studies do not address possible effects on brood (larvae and pupae)

survival/development.  Because of the potential for pollen and nectar to be contaminated with

pesticide residues, and subsequently brought back to the hive, it is important to determine the

acute oral toxicity of this compound to bee brood.   

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

terrestrial invertebrates using the honeybee as a surrogate test species.  The guidance discusses

Tier I laboratory‐based acute toxicity studies of individual honeybee larvae as a critical component

of the screening‐level risk assessment process for examining potential risks from specific routes of

exposure.  The guidance can be found at: http://www2.epa.gov/pollinator‐protection/pollinator‐

risk‐assessment‐guidance .  Additional guidance on larval honeybee toxicity test design can be

found in OECD Test Guideline 237 http://www.oecd‐ilibrary.org/environment/test‐no‐237‐honey‐

bee‐apis‐mellifera‐larval‐toxicity‐test‐single‐exposure_9789264203723‐en  .

Practical Utility of the Data

How will the data be used?

The Tier I acute oral toxicity data on honeybee larvae serve as a foundation for the screening‐level

assessment of potential risk to non‐target organisms such as federally listed threatened or

endangered and non‐listed terrestrial invertebrate insects, including pollinators, and/or modify

their designated critical habitat from acute oral exposures to pesticides.  The data will be used to

reduce uncertainties associated with the risk assessment for terrestrial invertebrates and will

improve EPA’s understanding of the potential effects on terrestrial species and whether there is a

differential sensitivity of larval bees relative to adult bees.  If acute oral effects data for larvae are

not available, risks to terrestrial insects from acute oral exposure will be assumed

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect listed threatened or endangered species and/or modify their designated

critical habitat.  Without these data, EPA may need to presume risk which will limit the flexibility of

pesticide products to comply with FIFRA and the ESA, and could result in use restrictions.   
31

Study Title:  Honey Bee Chronic Oral Toxicity, Adult

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticides in various use settings.   

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently

brought back to the hive.  Therefore, potential chronic effects to adult honeybees and other

pollinators from oral exposure to some pesticides could exist.  Currently available toxicity studies

do not address possible lethal and sublethal effects of chronic oral exposure on adult terrestrial

invertebrates and will assist in determining whether the sensitivity of adult bees differs from that

of earlier life stages.  Because of the potential for pollen and nectar to be contaminated with

pesticide residues, and subsequently brought back to the hive, it is important to determine the

chronic oral toxicity of this compound to adult honeybees and other pollinators.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance discusses Tier I laboratory‐based chronic oral

toxicity studies of individual adult honeybees as a critical component of the screening‐level risk

assessment process for examining potential risks from specific routes of exposure.  The guidance

can be found at: http://www2.epa.gov/pollinator‐protection/pollinator‐risk‐assessment‐guidance .  

Study design elements for the chronic 10‐day oral toxicity test with honeybees are similar to the

OECD Test Guideline 213 acute oral toxicity test http://www.oecd‐ilibrary.org/environment/test‐

no‐213‐honeybees‐acute‐oral‐toxicity‐test_9789264070165‐en .

Practical Utility of the Data

How will the data be used?

The Tier I chronic oral toxicity data on adult bees serve as a foundation for the screening‐level

assessment of potential risk to non‐target organisms including federally listed threatened or

endangered species and non‐listed terrestrial invertebrate insects, including pollinators, from

chronic oral exposures to pesticides.  The data will be used to reduce uncertainties associated with

the risk assessment for terrestrial invertebrates and will improve EPA’s understanding of the

potential direct and indirect lethal and sublethal effects on a broad range of terrestrial species,

particularly insect pollinators and to determine whether adult toxicity differs substantially from

other life stages evaluated in other Tier I tests.  If chronic oral effects data for adults are not

available, risks to terrestrial insects from chronic oral exposure will be assumed.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect listed threatened or endangered species and/or their designated critical

habitat.  Without these data, EPA may need to presume risk which will limit the flexibility of

pesticide products to comply with FIFRA and the ESA, and could result in use restrictions.   
32

Study Title:  Honey Bee Chronic Oral Toxicity, Larvae

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticides in various use settings.  

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently

brought back to the hive where larvae and pupae may be exposed.  Therefore, potential effects to

developing bees could result from chronic oral exposure to pesticide residues.  Available toxicity

studies do not address possible chronic effects on brood (larvae and pupae) survival.  Because of

the potential for pollen and nectar to be contaminated with pesticide residues, and subsequently

brought back to the hive, it is important to determine chronic larval/pupal toxicity and whether

adult emergence is adversely affected.  This study will provide information on whether honeybee

larvae differ in sensitivity from adult bees following chronic exposure.  

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance discusses Tier 1 laboratory‐based chronic oral

toxicity studies of individual honeybee larvae as a critical component of the screening‐level risk

assessment process for examining potential risks from specific routes of exposure.  The guidance

can be found at: http://www2.epa.gov/pollinator‐protection/pollinator‐risk‐assessment‐guidance.

Additional information on larval honeybee toxicity repeat exposure test design can be found in the

OECD draft guidance

http://www.oecd.org/env/ehs/testing/Draft_GD_honeybees_rep_exp_for_2nd_CR_25_November

_2013.pdf  .

Practical Utility of the Data

How will the data be used?

The Tier I chronic oral toxicity data on bee larvae serve as a foundation for the screening‐level

assessment of potential risk to non‐target organisms including federally listed threatened or

endangered and non‐listed terrestrial invertebrate insects, including pollinators, from chronic oral

exposures to pesticides.  The data will be used to reduce uncertainties associated with the risk

assessment for terrestrial invertebrates and will improve EPA’s understanding of the potential

direct and indirect lethal and sublethal effects on a broad range of terrestrial species, particularly

insect pollinators.  These data will also assist in determining whether early life stages of the bee

differ in their sensitivity to pesticides relative to adults.  If chronic oral effects data for larvae are

not available, risks to terrestrial insects from chronic oral exposure will be assumed.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species

or is likely to adversely affect listed threatened or endangered species and/or modify their

designated critical habitat.  Without these data, EPA may need to presume risk which will limit the

flexibility of pesticide products to comply with FIFRA and the ESA, and could result in use

restrictions.   

Study Title: Semi‐Field Toxicity Testing for Pollinators (tunnel/enclosure studies)

Rationale for Requiring the Data
33

Tier II studies are conditional on the outcome of the screening‐level assessment where acute

and/or chronic risk levels of concern have been exceeded for terrestrial invertebrates.  Terrestrial

invertebrates are likely to be impacted if exposed to pesticides in various use settings.  Pesticide

residues may be transferred to pollen and/or nectar of treated plants and subsequently brought

back to the hive and may adversely affect developing brood (egg, larvae, and pupae) and adult

bees.  Screening‐level (Tier I) studies of individual bees do not address possible effects and/or

exposure to pesticide residues at the colony‐level.  Because of the potential for pollen and nectar

to be contaminated with pesticide residues, and subsequently brought back to the hive, it is

important to determine whether bee colonies may be negatively affected under relatively

controlled exposure conditions of a semi‐field study. In addition to providing effects data, these

studies can provide data on exposure as pesticide residues in pollen/nectar of treated plants.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance describes the tiered testing process and can be

found at: http://www2.epa.gov/pollinator‐protection/pollinator‐risk‐assessment‐guidance .  

Additional information on honeybee colony studies under semi‐field conditions can be found in the

OECD Guidance 75

http://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=env/jm/mono%28 .          

Practical Utility of the Data

How will the data be used?  

Tier II colony‐level data will be used to assess potential risk to non‐target organisms including listed

and non‐listed terrestrial social invertebrate species and to determine whether effects observed in

the screening‐level (Tier I) laboratory‐based studies of individual bees are evident in colony‐level

studies under semi‐field conditions.  The Tier II semi‐field test of whole colonies is a relatively

controlled study, i.e., bees are confined to a specific area, that is designed to represent potential

field‐level exposure and account for hive dynamics, which are not achievable from other pollinator

studies.  This study will be used to determine whether adverse effects to insect pollinators at the

whole colony level, may result for the use of pesticides and will help to refine risk estimates

derived in the screening‐level risk assessment for beneficial terrestrial invertebrates.  Measured

residues in pollen/nectar can also be used to refine risk estimates derived from model‐based or

default values in the screening‐level assessment.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect federally listed threatened or endangered species or their designated

critical habitat.  Without these data, EPA may need to presume risk which will limit the flexibility of

pesticide products to comply with FIFRA and the ESA, and could result in significant use

restrictions.
34

Study Title: Semi‐Field Toxicity for Pollinator Testing (feeding studies)

Rationale for Requiring the Data

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently

brought back to the hive, and may adversely affect developing brood (egg, larvae, and pupae) and

adult bees. Tier II feeding studies are conditional on the outcome of the screening‐level

assessment where acute and/or chronic risk levels of concern have been exceeded for terrestrial

invertebrates based on Tier I studies of individual bees. Feeding studies utilize free foraging bee

colonies that are “dosed” with specific quantities of test material and represent a means of

ensuring exposure to the test material through spiked pollen and/or sugar solutions fed to the

colony while still allowing the bees to forage freely.  Since bee colonies are not confined to

enclosures, colonies can be exposed for longer duration periods without subjecting the bees to

stress that typically results from Tier II tunnel studies.  Available toxicity studies of individual bees

(Tier 1) conducted to support screening‐level assessments do not address possible effects and/or

exposure to pesticide residues at the colony‐level.  Because of the potential for pollen and nectar

to be contaminated with pesticide residues, and subsequently brought back to the hive, it is

important to determine whether bee colonies may be negatively affected where bees are free

foraging and have the option to collect/consume alternative forage items beyond the spiked food.

Since multiple dose levels can be more readily tested, feeding studies can help to define dose‐

response relationships at the whole colony level.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance describes the tiered testing process and can be

found at: http://www2.epa.gov/pollinator‐protection/pollinator‐risk‐assessment‐guidance .  

Additional information on honeybee colony feeding studies can be found in the EPPO Guidance 170

at: http://www.nationalbeeunit.com/index.cfm?pageId=187  .

Practical Utility of the Data

How will the data be used?

Tier II colony feeding data will be used to assess potential risk to non‐target organisms including

listed and non‐listed terrestrial social invertebrate species.  The colony feeding study is designed to

represent potential field‐level exposure and account for hive dynamics using longer duration

exposure periods than are possible in Tier II tunnel studies.  The study will be used to determine

whether potential adverse effects to insect pollinators at the whole colony level when bees are

able to forage naturally beyond the spiked food.  Results from the feeding study will help to refine

the screening‐level risk assessment for beneficial terrestrial invertebrates that were based on Tier I

studies on individual bees.  Since feeding studies can help to define a dose‐response relationship at

the colony level, the studies can provide a means of determining exposure thresholds below which

the likelihood of adverse effects on colonies may be low.

  

How could the data impact the Agency’s future decision‐making?

Tier II colony‐level data will be used to refine screening‐level risk estimates derived using Tier I

laboratory‐based data on individual bees.  The Tier II data will inform the determination required

under FIFRA or the ESA as to whether continued registration of a pesticide is likely to result in
35

unreasonable adverse effects to non‐target species or is likely to adversely affect federally listed

threatened or endangered species or their designated critical habitat.  Without these data, EPA

may need to presume risk which will limit the flexibility of pesticide products to comply with FIFRA

and the ESA, and could result in significant use restrictions.

Study Title:  Field Trial of Residues in Pollen and Nectar

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticide residues in various use

settings.  Pesticide residues may be transferred to pollen and/or nectar of treated plants and

subsequently brought back to hive where all life stages may be exposed.  For some pesticides, the

quantification of pollinator‐relevant residues in treated flowering plants is needed, since

pollinators will be exposed to residues from either current or prior season applications (due to the

potential for residues to accumulate in plants and trees).  Residues in edible/transportable‐to‐hive

parts of treated trees and plants, including (where appropriate), but not limited to, guttation

water, sap/resins, whole plant tissue (e.g., leaves, stems), as well as blooming, pollen‐shedding,

and nectar producing parts (i.e., flowers and, if present, extra‐floral nectaries) of plants may inform

the potential for risk.  Studies should be designed to provide residue data for crops and application

methods of concern.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance can be found at: http://www2.epa.gov/pollinator‐

protection/pollinator‐risk‐assessment‐guidance.

Practical Utility of the Data

How will the data be used?

Measured residue data will be used to refine conservative estimates of pesticide exposure and

reduce uncertainties associated with the Tier I exposure assessment by providing direct

measurements of pesticide concentrations resulting from actual use settings.  Measured residues

may provide a more realistic understanding of exposure through contact or ingestion with which to

calculate risk quotients for individual bees as well as to characterize exposure to the colony.  If

measured residue data are not available, risk estimates for terrestrial insects will be based on

model‐generated or default values used to support the screening‐level assessment.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect federally listed threatened or endangered species or their designated

critical habitat.  Without these data, EPA will have to rely on conservative estimates of exposure

which will limit the flexibility of pesticide products to comply with FIFRA and the ESA, and could

result in use restrictions.