1

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Codes: 123009

DP Barcode: 425608 

Date: August 26, 2015

MEMORANDUM

SUBJECT: Problem Formulation for the Ecological Risk and Drinking Water Exposure 

Assessments to be Conducted For the Registration Review for Topramezone

To: Kevin Costello, Chief

Jose Gayoso, Chemical Review Manager

Risk Management and Implementation Branch 2

Pesticide Re-evaluation Division (7508P)

FROM: Rochelle F. H. Bohaty, Ph.D., Chemist 

Tanja Crk, M.A., Biologist

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507P)

THROUGH: Dana Spatz, Branch Chief

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507P)

PEER REVIEW: Rosanna Louie-Juzwiak, RAPL

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507P)

This memo transmits the Problem Formulation for the ecological risk and drinking water 

exposure assessments to be conducted for the Registration Review for topramezone.
2

Contents

I. Executive Summary........................................................................................................................3

II. Introduction ..................................................................................................................................5

1. Previous Ecological Risk Assessments............................................................................................5

2. Drinking Water Exposure Assessments..........................................................................................7

3. Clean Water Act Programs.............................................................................................................8

III.Stressor Source and Distribution ....................................................................................................8

A. Description of Stressors .................................................................................................................8

B. Mechanism of Action .....................................................................................................................9

C. Overview of Pesticide Usage..........................................................................................................9

1. Label Uncertainties.......................................................................................................................10

A. Environmental Fate and Transport ..............................................................................................14

IV. Receptors..............................................................................................................................21

A. Ecological Incidents......................................................................................................................25

B. Exposure Pathways of Concern....................................................................................................26

V. Analysis Plan................................................................................................................................26

A. Ecological Risk Assessment ..........................................................................................................26

1. Stressors of Concern ....................................................................................................................26

2. Measures of Exposure..................................................................................................................27

3. Measure of Effects .......................................................................................................................27

4. Integration of Exposure and Effects.............................................................................................27

5. Endangered Species Assessments................................................................................................28

6. Endocrine Disruptor Screening Program......................................................................................28

B. Drinking Water.............................................................................................................................28

VI. Preliminary Identification of Data Gaps..................................................................................29

A. Environmental Fate......................................................................................................................29

B. Ecological Effects..........................................................................................................................30

VII. References (general) (to be completed during review)............................................................36

APPENDIX A. BIBLIOGRAPHY ............................................................................................................37

APPENDIX B. ADDITIONAL ENVIRONMENTAL FATE DATE FOR TOPRAMEZONE AND ITS 

TRANSFORMATION PRODUCTS ........................................................................................................40

APPENDIX C. SIP ANALYSIS RESULTS ................................................................................................42

APPENDIX D. STIR ANALYSIS RESULTS...............................................................................................43
3

I. EXECUTIVE SUMMARY

The Environmental Fate and Effects Division (EFED) has completed the preliminary problem formulation 

(attached) for the ecological risk and drinking water exposure assessments to be conducted as part of 

the Registration Review of the systemic herbicide topramezone (PC Code 123009). This document is 

intended to provide an overview of what is currently known regarding the environmental fate and 

ecological effects associated with topramezone and its degradation products, and outlines uncertainties 

regarding attributes of the parent compound and its transformation products. It describes the 

preliminary ecological risk hypothesis and the processes that will be used during the completion of the 

preliminary ecological risk assessment in support of Registration Review. Uncertainties unique to the 

risk assessment of topramezone are also discussed. 

A bibliography that includes the study classification for all of the studies that have been submitted to 

support the registration of topramezone is included in APPENDIX A. EFED recommends requesting the 

following additional data to better understand the environmental fate and ecological effects to support 

the current registrations of topramezone:

• The analytical soil method (LOQ = 0.001 mg/kg; 0.002 lb a.i./A) is not adequate to detect 

topramezone at concentrations equal to the level of concern (EC05 0.0000102 lb a.i./A) for 

terrestrial plants (vegetative vigor). Based on the level of concern, a soil method with a limit of 

quantification of 5.1 x 10-6 mg/kg is needed. 

• The analytical water method is adequate; however, the validations for the water methods 

(MRIDs 48600417, 48837001) were conducted under the supervision of the same study director. 

Therefore, these submissions do not have a supporting independent laboratory validation.

Guidance recommends testing on four of the most sensitive nonvascular organisms. Three are 

acceptable and the fourth (MRID 45902332) on Navicula pelliculosa was deemed invalid because it was 

not possible to differentiate whether the reduction in diatom growth was due to topramezone, or from 

a reduction in pH. Multiple incident reports have involved topramezone and plant species.

• An algal toxicity study (OCSPP 850.4500) on freshwater diatom Navicula pelliculosa using 

topramezone is needed. 

Topramezone use was previously identified as posing a risk concern to birds based on chronic exposure. 

In addition, the toxicity of topramezone on an acute basis to birds was uncertain due to lack of data 

(e.g., passerine data not used at time of risk assessment – study was deemed invalid). 

• An avian oral acute toxicity study (OCSPP 850.2100) on passerine using topramezone is needed 

to resolve this uncertainty. 

• An avian reproduction study (OCSPP 850.2300) on mallard using topramezone is needed. 

Though previous risk assessments did not identify honey bee risk concern, the conclusions are based 

solely on acute oral and contact toxicity tests for adults. The full Tier I suite of honey bee data is not 

available but is needed for parent topramezone (TGAI, unless otherwise noted below). Tier 2 testing is 

contingent on results of Tier 1 tests and screening level residues. Tier 3 testing is contingent on results 

of earlier tiers of testing.
4

• A honey bee larvae acute oral study (Non-guideline /OECD TG237, Tier 1). 

• A honey bee larvae chronic oral toxicity study (Non-guideline, Tier 1).

• A honey bee adult chronic oral toxicity study (Non-guideline, Tier 1).

• Semi-field testing for pollinators using TEP (Non-guideline / OECD 75, Tier 2)

• Field trial of residues in pollen and nectar using TEP (Non-guideline, Tier 2)

• Field testing for pollinators using TEP (OCSPP 850.3040, Tier 3)
5

II. INTRODUCTION

Conclusions of the previous assessments are summarized in Table II.1 and additional details are 

provided in the subsections below.

Table II.1. Summary of Previous Risk Concernsa Identified for Topramezone

Exposure 

Basis Birds Mammals Terrestrial Plants

Terr. 

Inverts. 

(honey 

bee 

hazard)

Fish Aquatic 

Inverts

Aquatic 

Plants Mobile Persistence Degradates of Concern

Acute Ub No

Yes Noc No NoYes Yes Yes 

M670H05, 

M670H01, 

M670H10 Chronic Yes No Yes Yes

a. At least one LOC has been exceeded in previous assessments

b. U = uncertain due to lack of data (e.g., passerine data not used at time of risk assessment – study was deemed invalid)

c. The conclusion is based on acute contact and oral adult honey bee data; the full Tier I suite of data is not available.

1. Previous Ecological Risk Assessments

Four previous ecological risk assessments have been completed for the registration of topramezone for 

use on agricultural crops and non-cropped areas. Conclusions of the previous assessments are 

summarized in Table II.2 and Table II.3. The only residue of concern identified in these assessments was 

topramezone given that limited toxicity data are available for environmental transformation products of 

topramezone. Available data (duckweed) on degradate M670H05 suggests reduced toxicity relative to 

the parent. Note that yearly application rates previously assessed do not reflect yearly application rates 

currently permitted on labels because the labels describe applications on a seasonal basis; therefore, for 

some use sites multiple crop seasons are possible and for these use sites the estimated environmental 

concentrations (EECs) may have been underestimated.

Table II.2. Summary of Previous Risk Assessments Conducted on Topramezone

Use

Reference/ 

Year 

Completed

Maximum 

Application Rate 

Assessed (lb a.i./A)

Conclusions

Corna D290065/ 

2005

0.022 (single, 

seasonal, annual

aerial and ground)

Risk was identified for aquatic plants and terrestrial 

plants. However, minimal risk was associated with 

bird, mammal, fish, reptile, amphibian, and 

invertebrate

Non-cropped 

Areasb

D352689/ 

2009

0.089c (single, 

seasonal, annual

aerial and ground)

Risk was identified for aquatic plants and terrestrial 

plants. 

Turf Grassd D397476/ 

2012

0.089 (single, 

seasonal, annual

ground and spot 

treatment)

Risk was identified for aquatic plants and terrestrial 

plants. 
6

a. See footnote 1; new chemical registration is under BAS 670 336 SC Post-Emergent Corn Herbicide end use 

product label (29.7% a.i.)

b. See footnote 2; new use registration is under end use label Topramezone 2.8 SC (29.7% a.i.) for preemergence and post-emergence weed control. 

c. In this assessment the definition of ‘season’ was unclear. The label states not to apply more than 0.089 lbs 

a.i./A of Topramezone 2.8 SC during the growing season. For the analysis, one growing season per year was 

assumed for the assessed uses.

d. See footnote 3; new use registration is under the end use label Topramezone 2.8 SC (EPA Reg No. 7969-281) 

for post-emergence weed control

Table II.3. Risk Conclusions from Aquatic Use Assessment (D400305/2013)

a,b

Application type Risk Assessment 

type Application Rate Conclusions

Foliar spray (aerial 

and ground)

Terrestrial and 

aquatic 0.35 lb a.i./A

Potential risk to birds (chronic basis), 

non-target terrestrial plants, and 

vascular aquatic plants.

Direct in-water Aquatic 0.05 mg a.i./L

Potential risk to estuarine/marine 

invertebrates (chronic basis), 

freshwater fish (chronic basis), and 

vascular aquatic plants.

Irrigation water (on 

food crops) Terrestrial plant 1.0 μg/L c Potential risk to non-target terrestrial plants. a See footnote 7; the new use registration is under end use label Oasis® Aquatic Herbicide (EPA Reg. no. 

7969-339 29.7% a.i.) for management of vegetation b The assessment was tripartite to account for multiple application rates and use areas. c The lowest labeled concentration of topramezone residues that can remain in irrigation water before 

use on hydroponic crops or ornamentals (nonfood). Other specific labeled uses permit higher residues 

in irrigation water: e.g., corn (max 25 μg/L) and turf (max 5 μg/L).

 1 grain, seed, popcorn, and sweet corn

2 Non-cropland areas include Christmas tree, conifer, and hardwood plantations; field grown ornamentals; noncropland areas such as railroad, utilities, highway, pipeline rights-of-way; highway guardrails, delineators, sign 

posts, utility substations, petroleum tank farms, pumping installations, farmyards, around farm buildings, fence 

rows, storage areas, airports, non-irrigation ditch banks, wildlife openings, and areas grazed or cut for hay. 3 Turf grass includes residential (spot spray only) and nonresidential turf grass including: airports, athletic fields, 

cemeteries, golf courses, grounds or lawns around residential and commercial establishments, houses of worship, 

military and other institutions, single/multifamily dwellings, parks, picnic grounds, roadsides, schools, and sod 

farms.
7

2. Drinking Water Exposure Assessments

Several drinking water assessments (DWA) have been completed for topramezone including for use on

corn1 (D3146424

), non-cropped areas2 (D3564975), turf grass3 (D3883686) and aquatic environments7

(D408687, D4011668

).The only residue of concern considered in these drinking water assessments was 

topramezone. The highest estimated drinking water concentrations (EDWCs) were reported for direct 

aquatic applications. According to product labels, for water bodies with functional potable water intakes 

the topramezone concentration cannot exceed 45 ppb.

Table II.4. Summary of Previous Drinking Water Assessments

Use Reference

Models 

Used

Estimated Surface Water 

Concentrations (μg/L)a

Estimated Groundwater 

Concentrationsb

(μg/L)

1-in-10 

year Peak

1-in-10 year 

Annual Mean

30 Year 

Mean Peak

Post 

Breakthrough 

Average

Corna D314642

PRZMEXAMS, 

SCI-GROW

0.77 0.14 0.07 0.0671

Noncropped 

Areasb

D356497

PRZMEXAMS, 

SCI-GROW

5.28 2.0 1.02 0.0671

Turf Grassc D388368

PRZMEXAMS, 

SCI-GROW

1.36 0.69 0.38 0.271

Terrestrial 

Sitesd D408687, 

D401166

PRZMEXAMS, 

PRZM-GW

31.2 12.5 7.2

15.4 11.4

Aquatic 

Sitese n/a 45

a. See footnote 1.

b. See footnote 2.

c. See footnote 3.

d. Terrestrial use sites were remodeled when the new use of aquatic use sites were assessed.

e. See footnote 7.

 4 Wolf, J., Termers, S., Topramezone (BAS 670H) Herbicide

CAS Name, [3-(4,5-Dihydro-3-isoxazolyl)-2-methyl-4-(methylsulfonyl)phenyl](5-hydroxy-1-methyl-1H-pyrazol-4-yl) 

methanone CAS Registry Number, 210631-68-8 Tier II Drinking Water Assessment March 18, 2005 (DP Barcode: 

388368)

5 Hetrick, J., Corbin, M. Topramezone (BAS 670H) Herbicide CAS Name, [3-(4,5-Dihydro-3-isoxazolyl)-2-methyl-4-

(methylsulfonyl)phenyl](5-hydroxy-1-methyl-1H-pyrazol-4-yl) methanone CAS Registry Number, 210631-68-8 Tier I 

and II Drinking Water Assessment September, 29, 2008 (DP Barcode: 356497) 6 Hetrick, J., Spatz, D. Drinking Water Assessment to Support Topramezone Use on Golf Courses, Sod

Farms, and Residential Lawns November, 14, 2011 (DP Barcode: 388368) 7 Vegetation in ponds, lakes, reservoirs, marshes, wetlands, bayous, drainage ditches, non-irrigation and 

dewatered irrigation canals, and slow-moving or quiescent bodies of water including vegetation control on 

shoreline and riparian areas within or adjacent to these and other aquatic sites. 8 Wolf, J., Drinking Water Exposure Assessment for a Proposed Increase of the maximum use rate of Topramezone 

Frequency Herbicide (EPA Reg. No. 7969-281) for non-cropland uses, and Proposed New Use for Direct Applications 

to Aquatic Environments (Oasis Aquatic Herbicide, EPA File Symbol No. 7969-GGO) January, 29, 2013, (DP 

Barcodes: 408687; 401166)
8

3. Clean Water Act Programs 

Topramezone has not been identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act.9 No Total Maximum Daily Load (TMDL) criteria have been 

developed for either compound.10 The EPA invites submission of water quality data for this pesticide. To 

the extent possible, data should conform to the quality standards in Appendix A of the OPP Standard 

Operating Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s 

Registration Review Risk Assessment and Management Process11 in order to ensure the data can be 

used quantitatively or qualitatively in pesticide risk assessments.

Aquatic benchmarks have been established for topramezone and are available online.12 Any data 

submitted or otherwise located as part of the registration review process may be used to update aquatic 

life benchmarks if applicable.

III. STRESSOR SOURCE AND DISTRIBUTION

A. Description of Stressors

The chemical structure of topramezone along with the chemical identification and select physicalchemical properties are provided in Table III.3. In addition to the technical grade products (5481-523 

and 7969-261), there are five topramezone registered end-use products (5481-524, 7969-327, 7969-281, 

7969-262 and 7969-339. None of these products contain other active ingredients. 

Environmental transformation products of topramezone include M670H01, M670H10, M670H11, 

M670H12 and M670H05 (additional information on these transformation products is included in the 

Environmental Fate Section of this document as well as in Appendix B; stressors of concern are 

highlighted in Table II.1.). 

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

10

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_polluta

nt_group_name=PESTICIDES

11 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm 12 http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm
9

Table III.1. Chemical Identification and Physical Chemical Properties of Topramezone

Common Chemical Name Topramezone

Company Code BASF 670H

BAS 670H

Chemical Name 3-(4,5-Dihydro-3-isoxazolyl)-2-methyl-4-(methylsulfonyl) phenyl](5-hydroxy-1-

methyl-1H-pyrazol-4-yl) methanone

CAS Registry Number 210631-68-8

Chemical Structure

S

O

O

O

N

O

N

N OH

Molecular Formula C16H17N305 S

SMILES NOTATION C1=N[N](C(=C1C(C2=CC=C(C(=C2C)C3=NOCC3)[S](=O)(=O)C)=O)O)C

Molecular Mass (g/mol) 363.39

Vapor Pressure (25 °C) 7.3 x 10-13 torr

Water Solubility (g/L; 

25 °C)

pH 5: 0.98

pH 7: 15

pH 9 23.4

Henry’s Law Constant 2.3 x 10-17

Log Kow

pH 4: -0.81

pH 7: -1.52

pH 9: -2.34

pKa 4.06

B. Mechanism of Action

Topramezone belongs to the phenyl pyrazolyl ketone chemical family of herbicides.13 Its mode of 

herbicidal action is inhibition of carotenoid biosynthesis by inhibiting the 4-hydroxyphenyl-pyruvatedioxygenase enzyme (4-HPPD) in the chlorophyll ultimately leading to breakdown of the chloroplast 

pathway. This mode of action is shared with isoxaflutole (cyclopropylisoxazole family) and mesotrione (a 

triketone belonging to the benzoylcyclohexanedione family.14

C. Overview of Pesticide Usage

Topramezone is a broad-spectrum systemic pre- and post-emergence herbicide used to control or 

suppress broadleaf and certain grass weeds. According to the Biological and Economic Analysis Division’s 

(BEAD) Chemical Profile (BCP), topramezone is the only pyrazolone herbicide in the U.S., a type of HPPD 

enzyme inhibitor. 

Topramezone was first registered in the United States in 2005. Topramezone is currently registered for 

use on corn1

, non-cropped areas2, turf grass3, and aquatic use sites7. All products are formulated as 

emulsifiable or soluble concentrate that may be applied as a liquid spray. Application types include 

broadcast (aerial and ground), shoreline treatment (aerial and ground), water treatment (subsurface 

and surface; aerial and ground), ground spot treatment, ground band treatment, and ground directed 

spray. Based on current labels, the maximum single application rate ranges from 0.022 to 0.35 pounds 

of active ingredient per acre (lb a.i./acre) and up to four applications per year for some uses. The highest 

 13 http://www.plantprotection.org/HRAC/MOA.html 14 http://www.hclrss.demon.co.uMclassqesticides.html
10

annual application rates generally are found in the non-agricultural and aquatic uses. A complete list of 

all current topramezone uses and how EFED currently understands the uses is presented in Table III.2.

Based on the BCP for Registration Review report, between 2006 -2013, the agricultural uses with the 

highest usage (in pounds a.i. applied per year) are field and sweet corn with 19,000 lb a.i. average 

pounds applied annually to 1.3 million acres. Approximately 93% of total pounds of topramezone 

applied was to field corn; 7% to sweet corn. According to the BEAD Screening Level Usage Analysis 

(SLUA) 15, between 2004-2012, the average percent crop treated (PCT) for field corn was <2.5% and 15% 

for sweet corn; the average annual pounds a.i. applied was 10,000 lb a.i. to field corn and 1,000 lb a.i. to 

sweet corn. No usage data are available for non-agricultural use sites including turf grass, non-cropped 

areas or aquatic use sites.

1. Label Uncertainties 

a) Terrestrial Uses

For some terrestrial uses, the number of applications of topramezone that can be applied per calendar 

year or the maximum annual application rate for a given use is not explicitly stated on many of the 

current labels. See Table III.2 for specifics. Assumptions that will be made in absence of label 

clarifications are provided.

b) Aquatic Uses

In addition to the uncertainties listed for terrestrial uses there are additional uncertainties associated 

with aquatic uses. These uncertainties are listed below; further details of aquatic use label uncertainties

are provided in the aquatic use assessment (D400305; USEPA 2013).

• There is no defined maximum duration of maintaining some concentration of topramezone in 

the water body. The current label language is vague and states to ‘retreat the water to maintain 

a sufficient concentration for a minimum of 60 days or until satisfactory weed control is 

achieved.

• No maximum depth is stated on the label. It is possible the water bodies may become stratified; 

therefore, the concentration of topramezone based on total volume may result in a much higher 

concentration in a given layer if thorough mixing is not observed. 

• The label indicates a maximum rate of 62 fl oz/acre-ft (1.35 lb a.i./acre-ft). This would suggest a 

potential for periods of time where concentrations may temporarily exceed the target 

concentration during an application (i.e., > 0.05 mg a.i./L) upon initial and subsequent 

applications of topramezone until dilution (i.e., achieving the desired concentration).

• The treatment of flowing water is dependent on flow rate and length of time that the 

application occurs. The label doesn’t provide information on minimum or maximum flow rates 

that can be treated. Potential Concentration Spikes: The maximum concentration permitted for 

the direct in-water uses (single or multiple applications) per year, per season, or per treatment 

period should also be clarified in the current label (Oasis® aquatic herbicide, EPA Reg. No. 7969-

GGO).

 15 LaVerne, D., Topramezone Label Use Report Package in Support of Registration Review, January 20, 2015
11

Table III.2. Topramezone Label Summary Crop/Site

Timing;

Application 

Type 

Method/

Equipment

Maximum Single 

Application Rate 

by Formulation

Maximum 

Application Rate

Maximum 

Application 

Number 

PHI (days)dMRI (days)dGeographic Restrictions

Comments

(lb/A)a

Per 

Yearb

lb/A

Per 

CCb,c

lb/A

Per 

Year

Per 

CCc

AGRICULTURAL 

FALLOW/IDLELAND / 

CONSERVATION RESERVE

NS Broadcast/ Aerial, 

Ground 0.0219 0.0219 NA 1 NA NA 14 NR None

AQUATIC AREAS/WATER Postemergence

Broadcast (floating, 

emergent, 

shoreline)/ Aerial, 

Ground

0.3501 NS NA [1] NAe NA NS NR None

Broadcast 

(surface)/ Aerial, 

Ground

0.3501 NS NA [1] NA NA 60 NR None

Single In-water 

(Pond, Lake 

Reservoir)

30-50 μg /L

(0.03-0.05 mg/L)

50 μg/Ld

0.05 

mg/L 

NS [1]c NA NA NS NR None

Split/Multiple Inwater (Pond, Lake 

Reservoir)

20-50 μg /L

(0.02-0.05 mg/L)

50 μg/Ld

0.05 

mg/L 

NS NSc NA NA NS NR None

CHRISTMAS TREE 

PLANTATIONS

PostemergenceBroadcast, Band, 

Directed/ Ground 0.0875 0.3501 NA 4 NA NS 30 NR None

Corn Postemergence

Broadcast/ Aerial, 

Ground 0.0219 [0.0657] 0.0219 [3] 1 45 NS NR None
12

Crop/Site

Timing;

Application 

Type 

Method/

Equipment

Maximum Single 

Application Rate 

by Formulation

Maximum 

Application Rate

Maximum 

Application 

Number 

PHI (days)dMRI (days)dGeographic Restrictions

Comments

(lb/A)a

Per 

Yearb

lb/A

Per 

CCb,c

lb/A

Per 

Year

Per 

CCc

FOREST TREES 

(HARDWOODS, 

BROADLEAF TREES)

Post 

transplant

Broadcast/ Aerial, 

Ground 0.0875 NS NS NS NS NA NS NR None

NONAGRICULTURAL 

UNCULTIVATED 

AREAS/SOILS

PostemergenceBroadcast/ Aerial, 

Ground 0.3501 0.3501 NS [1] NA NA NS NR None

NURSERY STOCK Pre and Post 

emergence

Direct Spray/ 

Ground 0.0875 0.3501 NA 4 NA NA NS NR None

ORNAMENTAL LAWNS 

AND TURF

PostemergenceBroadcast/ Aerial, 

Ground 0.0875 0.3501 NA 4 NA NS NS NR None

ORNAMENTAL SOD FARM 

(TURF)

Postemergence

Broadcast/ Ground 0.0438 0.0875 NA 4 NA NS NS NR None

RECREATION AREA 

LAWNS

PostemergenceSpot Treatment/ 

Ground 0.0438 0.0875 NA 4 NA NS NS NR None

RECREATION AREA 

LAWNS

PostemergenceSpot Treatment/ 

Ground 0.0438 0.0875 NA 2 NA NS NS NR None

a. Reported as per crop cycle or per season

b. PHI – Preharvest Interval; REI – Reentry Interval; MRI – Minimum Retreatment Interval

c. Per label, ‘use in compliance with Best Management Practices, which are developed to maintain and/or monitor target concentrations over large areas, 

ensure accurate applications, and maximize treatment performance, minimize resistance development, and to monitor concentrations in water used for 
13

Crop/Site

Timing;

Application 

Type 

Method/

Equipment

Maximum Single 

Application Rate 

by Formulation

Maximum 

Application Rate

Maximum 

Application 

Number 

PHI (days)dMRI (days)dGeographic Restrictions

Comments

(lb/A)a

Per 

Yearb

lb/A

Per 

CCb,c

lb/A

Per 

Year

Per 

CCc

potential irrigation.’ The label also encourages the BASF Corporation technical specialists be called upon to assist ‘applicators and resource managers to 

ensure compatibility with potential uses of the water and management objectives.

d. There is uncertainty on the maximum number of applications for these uses, which could pertain to a single treatment regimen (lasting at least 60 days 

for the split/multiple in-water use only), a growing season, or multiple times a year, but the label does not specify this point.

e. A season is only specified in the case for weed control on shoreline and riparian areas within or adjacent to aquatic sites.

No Restrictions (NR); Not Specified (NS); Not Applicable (NA)

[ ] are used to define assumptions that will be made in absences of label clarification. When information was not specified on the label the maximum 

number of applications was assumed to be 26 that corresponds to one application every two weeks.
14

A. Environmental Fate and Transport

Based on physicochemical properties (Table III.1) alone, volatility is not expected to be a major 

dissipation pathway for topramezone, and topramezone is not expected to bioconcentrate. 

Environmental fate parameters of topramezone are presented in Table III.3 and summarized below.

In summary, topramezone is persistent and mobile in terrestrial and aquatic environments. 

Topramezone is stable in sterile solutions at pH 4, 5, 7, and 9 at temperatures ranging from 25 to 50 °C

(MRID 45902416). In natural water, topramezone has a photodegradation half-life of 144 days (MRID 

45902417). Topramezone was stable to photodegradation in sterile buffered solutions.

Aerobic soil metabolism half-life values ranged from 129 to 305 days in five soils (MRID 45902421); 

however, topramezone was found to be stable in one soil (MRID 45902419). In soil, topramezone 

transforms to M670H05 at concentrations up to 15% of applied and M670H01 at concentrations up to 

10% of applied. 

Aerobic aquatic metabolism total system (sediment and water) half-life values for topramezone were 

345 and 471 days (MRID 45902423). M670H01 was the only transformation product observed but with 

concentrations that did not exceed 10% of applied. In anaerobic environments, topramezone degraded 

with total system half-life values ranging from 13 to 47 days (MRIDs 45902422, 48600413). In anaerobic 

aquatic environments, major transformation products included M670H10 (48% of applied) while 

M670H01, M67H011 and M670H12 were observed at concentrations less than 10% of the applied 

radioactivity depending on the test system. 

Based upon soil organic carbon coefficient (Kfoc 38 – 297; MRID 45902425) topramezone is considered 

mobile to moderately mobile based on FAO mobility classification16. Dissipation of topramezone in field 

studies [terrestrial (MRID 45902426) and aquatic (MRID 48600414)] was generally faster than that 

observed in the laboratory studies; however, field studies confirm persistence and mobility. No 

transformation products were observed in the field studies that were not previously identified in 

laboratory studies.

Several studies were submitted without adequate storage stability studies; however, given the 

persistence of topramezone observed in the various laboratory studies except for the anaerobic aquatic 

metabolism studies topramezone is assumed to be stable during storage.

The environmental chemistry method for soil reports the limit of quantification (LOQ) of topramezone 

and M670H05 in soil 0.001 ppm [0.001 mg/kg; 1 μg/kg; 0.002 lb/A17 (MRID 45902429)]. The 

environmental chemistry method for water and sediment reports a LOQ of 0.001 ppm [sediment: 0.001 

mg/kg; 1 μg/kg; 0.002 lb a.i./A17/water: 1.0 μg/L; 0.0002 lb a.i./A18 (MRID 48837001)]. A limit of 

 16 USEPA, 2006. Standardized Soil Mobility Classification Guidance. Memorandum: S. Bradbury, April 21, 2006. 17 LOQ = 0.001 mg/kg 

0.001 mg/kg (s) = [x] kg/ha x 106 mg/kg / [0.15 m (depth) x 104 m2

/ha x 1.5 x 103 kg(s)/m3(density)]

0.001 mg/kg(s) = [x] kg/ha x 106 mg/kg / 2.25 x 106 kg (s)/ha

= 2.25 x 10-3 kg/ha = LOQ = 0.002 lb a.i./A 18 LOQ = 1.0 μg/L

226,625 lb of water/acre x 1.0 μg/L /1,000,000,000 = 0.0002 lb /A

0.0002 lb /A = 2.54 x 10-4 kg a.e./ha
15

detection (LOD) was not established in either study; therefore, the LOD is assumed to be equal to the 

LOQ. Independent laboratory validation are not available for the water method. Based on toxicity 

information presented in Table IV.1 and Table IV.2 these methods are adequate for detecting 

topramezone at concentrations that are equal to the level of concern except for the soil method. The 

soil method is not adequate to detect topramezone at concentrations equal to the level of concern (EC05

0.0000102 lb a.i./A) for terrestrial plants (vegetative vigor MRID 49365105).

 

[x] mg/kg (s) = 1.46 x 10-5 kg a.e./ha x 106 mg/kg / [0.15 m (depth) x 104 m2/ha x 1.5 x 103 kg(s)/m3(density)]

LOQ 1.1 x 10-4 mg/kg (s)

0.00011 mg/kg (s) = [x] kg/ha x 106 mg/kg / [0.15 m (depth) x 104 m2

/ha x 1.5 x 103 kg(s)/m3(density)]

0.00011 mg/kg(s) = [x] kg/ha x 106 mg/kg / 2.25 x 106 kg (s)/ha

= 2.48 x 10-4 kg/ha = LOQ = 0.0002 lb a.i./A
16

Table III.3. Chemical Properties and Environmental Fate Parameters of Topramezone

Study/ 

Guideline

System Name/ 

Characteristics

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Half-life 

Value

--Value Used to Derive 

Model Input Values 

(days)b--

Source/ 

Classification

Comments

DT50 (days) DT90 (days)

Hydrolysis

835.2010

pH 5, 25  ̊C

stable 0

MRID

45902416

acceptable

pH 7, 25  ̊C ---

pH 9, 25  ̊C

Aqueous 

Photolysis

835.2240

0.01 M acetate, pH 5 stable

0

MRID

45902417

acceptable

---

0.01 M tris, pH 9 Stable ---

natural NC pond water, 

pH 7

72.1

144*

239

478*

*values transformation at 80% of 

natural sunlight in spring at 40  ̊N 

and reflects a 12-hour light - 12-

hour dark cycle.

Soil 

Photolysis

835.2410

sandy loam, pH 6.3 stable 0

MRID 

45902418

acceptable

There are an insufficient number of 

sampling intervals; however, the 

rate of transformation of 

topramezone in the irritated and 

dark control sample was similar. 

Therefore, soil photolysis is not 

expected to be a significant 

dissipation process in the 

environment. Therefore, despite 

the noted deficiency additional 

data are unlikely to provided 

additional information. 

Aerobic Soil 

Metabolism

835.4100

North Carolina Sandy 

Loam, pH 6.3, 2.6% OM stable 0

MRID

45902419

Reclassified to 

supplemental

The dissipation of topramezone 

was biphasic with a large amount 

(up to 65% of the applied material) 

of unextracted residues were 

observed. The extraction procedure 

was not considered exhaustive. 

Based on the profile of the 

formation of non-extracted 

residues and the apparent biphasic 
17

Study/ 

Guideline

System Name/ 

Characteristics

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Half-life 

Value

--Value Used to Derive 

Model Input Values 

(days)b--

Source/ 

Classification

Comments

DT50 (days) DT90 (days)

dissipation the unextracted 

residues may be topramezone. 

Idaho Loam, pH 6.6, 

6.3% OM 143 477 202 (DFOP)

MRID

45902421

Reclassified to 

supplemental

Not all transformation products 

detected at ≥10% of the applied 

material were identified.

Indiana Silt Loam, pH 

6.8, 1.4% OM 152 505 203 (DFOP)

Iowa Loam, pH 6.6, 

6.4% OM 305 1013 305 (SFO)

Minnesota Clay Loam, 

pH 6.0, 7.0% OM 129 429 129 (SFO)

South Dakota Silt 

Loam, pH 5.9, 4.9% OM 156 519 231 (DFOP)

Anaerobic 

Soil 

Metabolism

835.4200

No data

Aerobic 

Aquatic

Metabolism

835.4300

Ohio water-loam 

(Grand River)

pH 7.7, 0.9% OM

269 895 269 (SFO)

phenyl

MRID

45902423

47496702

Reclassified to 

supplemental

Up to 18% of the applied 

radioactivity was associated with 

unextracted residues. Application 

rate 0.033 mg/L. A relatively low 

amount of initial dissipation was 

observed (up to 25% percent of the 

applied). Kinetic analysis were 

completed for two different 

radiolabels independently and 

combined. The representative halflife value for the combined 

radiolabels is tR IORE = 3.71 x10-11

days following the NAFTA guidance; 

however, the SFO t1/2 = 345 days 

better reflect the results of the 

individual datasets.

475 1579 475 (SFO)

pyrazole
18

Study/ 

Guideline

System Name/ 

Characteristics

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Half-life 

Value

--Value Used to Derive 

Model Input Values 

(days)b--

Source/ 

Classification

Comments

DT50 (days) DT90 (days)

345 1146 345 (SFO)

combined ---

Ohio water-loam 

(Homestead Pond)

pH 4.9, 5.3% OM

471 1566 471 (SFO)

Rapid dissipation of topramezone 

was observed; however, this 

dissipation was consistent with the 

formation of unextracted residues. 

Up to 79% of the applied 

radioactivity was associated with 

unextracted residues were 

observed. The extraction procedure 

was not considered exhaustive. In 

addition, these results are not 

consistent with corresponding river 

water system. Kinetic analysis were 

completed for the combination of 

topramezone and the unextracted 

residues. The results are consistent 

with the results obtained for the 

river water system. The difference 

in unextracted residues observed 

between the two test systems may 

be a function of the higher organic 

material noted in the pond water 

test system.

Anaerobic 

Aquatic

Metabolism

834.4400

South Dakota 

water pH 8.2, organic 

carbon 15.6 mg/L; 

sediment pH 7.8, 

organic matter 8.3% 

13 43.1 13 (SFO)

MRID

45902422

Supplemental

Dissipation of topramezone was 

observed; however, there is a large 

amount of unextracted residues 

[up to 60%; half-life of 149 days 

(SFO) when unextracted residues 

are considered]. The extraction 

procedure was not considered 

exhaustive. In addition, there are 

noted study deficiencies including 
19

Study/ 

Guideline

System Name/ 

Characteristics

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Half-life 

Value

--Value Used to Derive 

Model Input Values 

(days)b--

Source/ 

Classification

Comments

DT50 (days) DT90 (days)

variability between replicate 

samples (not all samples had 

replicates) and stabilty concerns 

including sample work up and 

storage stability. 

Florida

water pH 8.6, organic 

sediment pH 7.7, 

organic matter 0.97%

47 157 47 (SFO)

MRID

48600413

supplemental

An exaggerated application rate 

(26x) was used and may have 

affected the microbial activity of 

the water:sediment systems, and 

thereby influence the rate and 

route of transformation of 

topramezone. The sediment 

extraction procedure may not have 

been adequate to remove all 

identifiable residues from the 

sediments. And, for the sand 

sediment system, transformation 

products detected at ≥10% of 

applied were not identified.

Pennsylvania

water pH 8.6, organic 

sediment pH 5.4, 

organic matter 6.7%

25 84 25 (SFO)

Terrestrial 

Field 

Dissipation

835.6100

Cambridge, Ontario 20.5 1837 912 (DFOP)

MRID

45902427

Supplemental

The results are consistent with 

laboratory data that indicate 

topramezone is persistent. Results 

indicate that topramezone may 

leach through the soil profile. 

Topramezone was detected in 

samples down to 15-30 cm (279 

and 364 days following the second 

application). Not all transformation 

products were analyzed.

Indiana, bareground, 

pH 6.3, 1.5% OM

Kinetic analyses were not 

updated 67* MRID45902426

The results are consistent with 

laboratory data that indicate 
20

Study/ 

Guideline

System Name/ 

Characteristics

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Half-life 

Value

--Value Used to Derive 

Model Input Values 

(days)b--

Source/ 

Classification

Comments

DT50 (days) DT90 (days)

South Dakota, 

bareground, pH 7.6, 

4.3% OM

185*

Supplemental topramezone is persistent. 

Topramezone was observed to 

leach through the soil profile. 

California, bareground, * values were taken from DER.

pH 8.2, 0.7% OM 158*

California, cropped 

plot, pH 8.2, 0.7% OM 29*

Aquatic 

Field 

Dissipation

835.6200

Florida, water 79.2 263 79.2 (SFO)

MRID

48600414

Supplemental

The stability of topramezone and

its transformation products in 

frozen water and sediment was not 

adequately determined. An 

insufficient number of sediment 

samples were collected per 

sampling interval and samples may 

not have been collected to a 

sufficient depth. An independent 

laboratory method validation was 

not conducted.

Florida, sediment 22.3 130 39.1 (IORE)

Indiana, water 23.7 78.6 23.7 (SFO)

Indiana, sediment 4.5 183 55 (IORE)

DT50 and DT90 values were calculated using single first-order (SFO), double first- order in parallel (DFOP), or indeterminate- order equation (IORE). For 

DFOP, the overall DT50 and DT90 are reported when available. The equations can be found in the document, Standard Operating Procedure for Using the 

NAFTA Guidance to Calculate Representative Half-life Values and Characterize Pesticide Degradation, U.S. Environmental Protection Agency, March 23, 

2012.

The value used to estimate a model input value is the calculated SFO DT50, TIORE, or the 2nd DT50 from the DFOP equation. The model chosen is consistent 

with that recommended using the, Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media, Health Canada, U.S. 

Environmental Protection Agency, December 21, 2012. The same model used to estimate the value used to derive a model input, is used to describe the 

DT50 and DT90 results.
21

IV. RECEPTORS

Table IV.1 and Table IV.2 provide a summary of the terrestrial and aquatic toxicity data, respectively, 

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

ecological effects of topramezone. Table IV.3 provides information on the non-guideline toxicity data 

available for topramezone. 

Table IV.1. Summary of the Most Sensitive Endpoints from Terrestrial Toxicity Studies for 

Topramezone

Study Type Endpoint Value Used in Risk 

Assessment

Toxicity 

Classification Study Rating MRID

Rat acute oral LD50 >2000 mg /kg-bw Practically 

nontoxic Acceptable (x3) 459021-18; -19; -20

Rat 2-

generation 

reproduction 

NOAEC/

LOAEC

Parental and offspring 

toxicity (male)a:

4 / 40 mg/kg-diet

0.4 / 4.2 mg/kg/day

Reproductive toxicity 

(male)b:

4000 />4000 mg/kg-diet

426.8 / >426.8 mg/kg/day

--- Acceptable 459022-14

Avian acute oral 

(Bobwhite) LD50

>2000 mg ai/kg-bw

No mortalities

Practically 

nontoxic Acceptable 459023-09

Avian sub-acute 

dietary

(Mallard)

LC50 >5080 mg ai/kg-diet Practically 

nontoxic Acceptable 459023-11

Avian 

reproductive 

(Mallard)

NOAEC

/LOAEC

<100 / 100 mg ai/kg 

-diet --- Supplementalc 459023-13

<66.5 / 66.5 mg 

a.i./kg-diet --- Supplementald 493651-02

Honey bee, adult

acute contact

LD50 >100 μg ai/bee Practically 

nontoxic Acceptable 459023-25

Terrestrial Plant –

Seedling 

Emergence 

IC25 / 

NOAEC

0.042 / 0.015 lb a.i. 

/acre (monocot); 

0.0039 / 0.002 lb 

a.i./acre (dicot) 

--- Acceptablee 459023-27

>0.044 / 0.044 lb 

a.i./acre (monocot) 

>0.022 / 0.022 lb 

a.i./acre (dicot)

(Deg: M670H 05)

--

Supplementalf, 

for qualitative 

use

493651-04
22

Study Type Endpoint Value Used in Risk 

Assessment

Toxicity 

Classification Study Rating MRID

Terrestrial Plant –

Vegetative Vigor

IC25 / 

NOAEC

0.01 / 0.005 lb 

a.i./acre (monocot); 

0.0001 / [0.000009]

g

lb a.i. /acre (dicot)

--- Acceptablee 459023-28

0.00204 / 0.00052 lb 

a.i./acre (monocot)

0.0000867 / 

[0.0000102]g lb 

a.i./acre (dicot)

(Parent M670 01H

mixed with adjuvant)

--

Supplementalh, 

for quantitative 

use

493651-05

*Values in bold will be used in RQ calculation. a Parental toxicity is based on decreased body weights and body weight gains in males; increased kidney and thyroid 

weights, histopathological findings in the eyes, kidney, and thyroid of both sexes. Offspring toxicity is based on 

decreased pup weight and body weight gains in the F2 generation and increased time to preputial separation in the F1 

males.

b No treatment-related effects on reproductive toxicity. c The most sensitive endpoint is non-definitive. A NOAEC is undefined given the significant treatment-related losses in 

body weight (i.e., hatchling body weight and adult female weight gain) at all treated levels relative to the control. 

d The most sensitive endpoint is non-definitive. A NOAEC is undefined given the significant, treatment-related loss in 

adult male body weight at all treated levels relative to the control.

e Toxicity of topramezone end-use product (BAS 670 00H, 31% a.i.). f Test substance is TGAI (as opposed to TEP) topramezone transformation product (BAS M670H 05).

g EC05 value. The EC05 is used in place of a NOAEC if a NOAEC value is not established in the study. h Test substance is TGAI (as opposed to TEP) topramezone mixed with an adjuvant
23

Table IV.2. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for Topramezone

Study Endpoint Toxicity Value Toxicity 

Classification Study Rating MRID

Acute freshwater 

fish (Rainbow 

Trout)

LC50

> 94.6 mg TEPa/L 

(> 28.38 mg a.i./L) ≤ Slightly toxic Acceptable 459018-13

Early life-stage 

freshwater fish 

(Rainbow Trout)

NOAEC / 

LOAEC

2.93 / 9.01 mg a.i./L

“Fo” wet weight, length, 

and survivalb

--- Acceptable 459023-21

Chronic life-cycle 

freshwater fish

(Fathead minnow)

NOAEC/ 

LOAEC

<0.248c /

0.248 mg a.i./L

F1 wet weight at 8 weeks 

post-hatch

--

Acceptable

BAS 670 H 

99.2% purity

48600406

Acute freshwater 

invertebrate 

(Waterflea)

EC50

> 99 mg TEPd

/L 

(> 29.7 mg a.i./L) ≤ Slightly toxic Acceptable 459018-20

Life-cycle 

freshwater 

invertebrate 

(Waterflea)

NOAEC 

(21-day) 

/ LOAEC

48.6 / 97.5 mg a.i./L --- Supplementale 459023-20

29 / 58 mg a.i./L -- Acceptable 493651-03

Acute 

estuarine/marine 

fish (Sheepshead 

minnow)

96-hr 

LC50/ 

NOAEC

>37 / 37 mg a.i./L

No effects

Practically nontoxic

Acceptable

BAS 670 01H TEP: 

30.2% purity

48600410†

Chronic early lifestage 

estuarine/marine 

fish (Sheepshead 

minnow)

NOAEC/

LOAEC

10 /

>10 mg a.i./L

No effects

--

Acceptable

BAS 670 H 

97.5% purity

48600404

Acute 

estuarine/marine 

invertebrate 

(Mysid)

LC50/

NOAEC

1.8/ 0.84 mg a.i./L

Mortality Moderately 

toxic

Acceptable

BAS 670 01H TEP: 

30.2% purity

48600412†

Chronic life-cycle 

estuarine/marine 

invertebrate 

(Mysid)

NOAEC/ 

LOAEC

0.036 / 0.069 mg a.i./L

Juvenile survival --

Supplementalf

BAS 670 01H TEP: 

30.2% purity

48600411†

Aquatic plant, Tier 

II – vascular 

(Duckweed)

EC50 / 

NOAEC 0.0067 / 0.001 mg a.i./L --- Acceptable 459023-29

Aquatic plant, Tier 

II – vascular 

(Duckweed)

EC50 / 

NOAEC

0.36 / 0.0067 mg 

M670H05/L --- Acceptableg 462427-04

Aquatic plant, Tier 

II – vascular 

(Duckweed)

EC50 / 

NOAEC

0.0286 / 0.0023 mg EP/L

(0.00858 / 0.00069 mg 

ai/L)

--- Acceptableh 459018-21
24

Study Endpoint Toxicity Value Toxicity 

Classification Study Rating MRID

Aquatic plant, Tier 

II – non-vascular 

(Freshwater 

Green algae; 

Marine diatom)

EC50/

NOAEC

19 / 3 mg a.i./L; 

49 / 3 mg a.i./L --- Acceptable; 

Acceptable

459023-33; -

31

10-day Spiked 

Sediment survival 

of Marine 

Arthropod 

(Leptocheirus 

plumulosus)

LC50/ 

NOAEC/

LOAEC

Mean-measured sediment: 

1.06/0.50/0.96 mg a.i./kg

OC-normalized meanmeasured sediment: 

48.2/22.7/43.6 mg a.i./kg TOC

Mean-measured pore water: 

2.65/1.23/2.49 mg a.i./kg

Mean-measured overlying 

water:

0.40/0.191/0.350 mg a.i./kg

Survival

--

Acceptable

BAS 670 H 

98.9% purity

48600407

Prolonged Spiked 

Sediment with 

Chironomus 

riparius

EC50/ 

NOAEC/

LOAEC

TWA sediment:

>55.6/55.6/>55.6 mg a.i./kg

TWA pore water: 

>23.1/23.1/>23.1 mg a.i./L

TWA overlying water:

>14.5/14.5/>14.5 mg a.i./L

No effects

--

Supplementali

BAS 670 H 

98.9% purity

48600408

*Values in bold may be used in RQ calculation. For aquatic plants, the EC50 is used to calculate the non-listed plant RQ and 

the NOAEC is used to calculate the listed plant RQ.

†The study was conducted with an end use product containing 30.2% topramezone a.i.

a TEP = Ref No. 375080 (335.6 g/L BAS 670 H; approximately 30% a.i.)

b Endpoints affected: wet weight, length, juvenile survival; abnormalities included decreased growth (reduction of body 

length) in juveniles

c Response of this endpoint was not dose-dependent, but reductions at all treatment levels ranged from 10 to 23% lower 

than weights of negative control fish. Analysis and interpretation of effects on this endpoint were limited by the low 

replicate number (n=2). Despite this low statistical power, differences from control were detected across the range of 

reduced weights. Given the magnitude of the reductions from control and the detection of a significant reduction at the 

lowest level, the possibility that the test material was affecting response of this endpoint could not be dismissed; thus, the 

NOAEC could not be defined in this study. d TEP = Ref No. 375080 (337.7 g/L BAS 670 H; 30% a.i.)

eDry weights of surviving daphnids were not measured; total length was not reported. Endpoint based on reduced number 

of live young produced.

f The number of offspring produced per female in the negative control is 4.1, which falls below the anticipated optimal 

level of 8 offspring per female.

g Toxicity of topramezone primary degradate (M670H05, 99.3 % ai)

h Toxicity of topramezone end-use product (BAS 670 00H, 30% ai) I The OECD 218 does not meet U.S. EPA guidelines for a chronic life cycle toxicity test with the midge because the test is 

run through emergence and does not include reproduction endpoints.
25

Table IV.3. Summary of the Non-Guideline Toxicity Endpoints for Topramezone

Study Endpoint Toxicity Value Toxicity 

Classification Study Rating MRID

Non-target 

Insect 

(Earthworm)

LC50 / 

NOAEC

>1000 / 296.3 mg 

ai/kg dry wt soil

Practically 

nontoxic Supplementala,b 459023-26

Non-target 

Insect

(Earthworm)

LC50

>1000 mg EP/kg dry 

wt soil

Practically 

nontoxic Supplementala,c 459018-19

Non-target 

Insect (Carabid 

beetle)

LR50d >223 mL/ha (0.07 lb 

ai/A)

Practically 

nontoxic Supplementala,c 459018-18

Non-target 

Insect

(Lacewing)

LR50d >225 mL/ha (0.07 lb 

ai/A)

Practically 

nontoxic Supplementala,c 459018-17

Non-target 

Insect (Predatory 

mite)

LR50d >675 mL/ha (0.24 lb 

ai/A)

Practically 

nontoxic Supplementala,c 459018-16

Non-target 

Insect

(Parasitic wasp)

LR50d >675 mL/ha (0.24 lb 

ai/A)

Practically 

nontoxic Supplementala,c 459018-15

 a Not an EPA guideline

 b Toxicity of topramezone (95.8 % ai)

 c Toxicity of end-use product (BAS 670 00 H, 31% ai)

 d LR50 is the application rate of compound at which 50% of test organisms die

A. Ecological Incidents

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 June 10, 2015.

The Ecological Incident Information System (EIIS) database was queried for incidents related to

topramezone use. Three incidents were reported in the EIIS database, all three with effects to plants 

(damage or mortality), specifically corn and hay. The incidents occurred in different states: Ohio, Kansas, 

and Oregon. The certainty index for the damage in all 3 incidents to plants was rated as possibly related 

to exposure to topramezone.

• Incident 1 (I022217-028): On July 1, 2010 in Warren County, Ohio 92.1% of 35 acres of corn was 

damaged from direct broadcast treatment.

• Incident 2 (I021535-001): On May 30, 2009 in Brown County, Kansas 108 acres of corn exhibited 

mortality from direct broadcast treatment.

• Incident 3 (I021950-001): On March 10, 2010 in Douglas County, Oregon 1-2 acres of hay was 

damaged from a runoff event from a right-of-way. 

A query of the aggregate Incident System (IDS) on June 10, 2015 reported no incidents.
26

The Avian Incident Monitoring System (AIMS), a database administered by the American Bird 

Conservancy, was queried for topramezone on June 10, 2015 and to date, there were no bird incidents 

reported.

The absence of documented incidents in these databases does not necessarily mean that such incidents 

did not occur. Mortality incidents must be seen, reported, investigated, and submitted to the Agency in 

order to be recorded in the incident databases. In addition, incident reports for non-target organisms 

typically provide information only on mortality events and plant damage. Sublethal effects in organisms 

such as abnormal behavior, reduced growth and/or impaired reproduction are rarely reported, except 

for phytotoxic effects in terrestrial plants.

B. Exposure Pathways of Concern

Based on the use pattern and environmental fate characteristics of this pesticide, the following exposure 

pathways are expected to be most relevant for determining exposure and potential risk to non-target 

organisms:

• Direct spray

• Spray drift

• Runoff

• Leaching to groundwater followed by irrigation 

In addition, terrestrial animals that use treated fields may be exposed to topramezone from consuming 

contaminated plants and invertebrates, dermal absorption, and drinking from contaminated puddles. 

Drinking water exposure pathways were screened using SIP (Screening Imbibition Program) and indicate 

that drinking from contaminated puddles is a pathway of potential concern for topramezone. The

potential for inhalation exposure was screened using STIR (Screening Tool for Inhalation Risk). Based on 

this analysis inhalation is a pathway of low concern (no LOC exceedances are expected).

SIP and STIR are described in detail at http://www.epa.gov/oppefed1/models/terrestrial/index.htm and 

the SIP and STIR model inputs and outputs for topramezone are available in APPENDICES C AND D, 

respectively.

While topramezone is expected to be taken up by plants and translocated, concentrations in nectar and 

pollen are unknown. Nevertheless, both oral and contact exposure to pollinators is expected to occur as 

a result of direct spray onto flowering weeds.

V. ANALYSIS PLAN

A. Ecological Risk Assessment

1. Stressors of Concern 

Both topramezone and environmental transformation products M670H05, M670H01, and M670H10 are 

considered the stressors of concern. Data on the degradate M670H05 has been submitted for only two 

sets of species, the aquatic vascular plant duckweed and the terrestrial plants (seedling emergence 

only). In both instances, the sensitivity of the plants to the transformation products appears to be orders 

of magnitude less than the sensitivity to the parent. However, little is known about the effects of the 
27

other major degradates M670H01 and M670H10. EcoSAR estimates were not informative as the

estimates for topramezone do not reasonably compare with available toxicity data. In absence of

additional data, EFED will use a total toxic residue (TTR) approach. The TTR approach is based on the 

assumption that the transformation products are of equal toxicity to the assessed organisms tested with

the parent compound. The total toxic residues (TTRs) are defined as topramezone, M670H05, M670H01, 

and M670H10 for all taxa except plants. For plants, M670H05 is excluded from the TTR because 

available data indicate that it is orders of magnitude less toxic than topramezone. In addition, the core 

structure of the parent compound is not maintained.

2. Measures of Exposure

In order to estimate risks of topramezone (and its environmental transformation products) exposure to 

aquatic and terrestrial organisms, all exposure modeling and resulting risk conclusions will be made 

based on maximum application rates, application methods, and any mitigation measures specifically 

indicated on the label. The models that will be used to predict the EECs are discussed on OPP’s model 

website.19

Available monitoring data will be evaluated and considered in an assessment conducted for Registration 

Review.

Exposure to terrestrial animals is estimated using the Terrestrial Residue Exposure (T-REX) model. 

Exposure to terrestrial plants is estimated using the TerrPlant model. For terrestrial plants, exposure is 

based on the calculated maximum application rates with assumed exposure from runoff, but not spray 

drift. A description of these models may be found at:

http://www.epa.gov/pesticides/science/models_db.htm. 

3. Measure of Effects

Ecological effects data are used as measures of direct and indirect effects to biological receptors. Data 

are typically obtained from registrant-submitted studies and from literature studies identified by 

ECOTOX (USEPA 2014). The ECOTOX database provides more ecological effects data in an attempt to 

bridge existing data gaps. ECOTOX is a source for locating single chemical toxicity data and potential 

chemical mixture toxicity data for aquatic life, terrestrial plants, and wildlife. ECOTOX was created and is 

maintained by the U.S. EPA, Office of Research and Development, and the National Health and 

Environmental Effects Research Laboratory's Mid-Continent Ecology Division. Toxicity data presented in 

Section IV of this problem formulation will be used in the quantitative risk assessment. Any additional 

toxicity data submitted by the registrant, as well as relevant toxicity information found in the open 

literature, will also be considered.

4. Integration of Exposure and Effects

Exposure and effects will be integrated in an updated risk assessment using a total toxic residue 

approach (described in the stressors of concern section of this document), incorporating new data

(described in the identification of data gaps section of this document) and analytical approaches

(current as of the time of the updated assessment), label clarifications, and any additional information 

obtained since the previous risk assessments were conducted. 

 19 http://www.epa.gov/opp00001/science/models_pg.htm
28

5. Endangered Species Assessments

Consistent with EPA’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate 

risks to federally listed threatened and endangered (listed) species from registered uses of pesticides in 

accordance with the Joint Interim Approaches developed to implement the recommendations of the 

April 2013 National Academy of Sciences (NAS) report, Assessing Risks to Endangered and Threatened 

Species from Pesticides. The NAS report outlines recommendations on specific scientific and technical 

issues related to the development of pesticide risk assessments that EPA and the Services must conduct 

in connection with their obligations under the ESA and FIFRA. EPA will address concerns specific to

topramezone in connection with the development of its final registration review decision for 

topramezone. 

In November 2013, EPA, the U.S. Fish and Wildlife Service, National Marine Fisheries (the Services), and 

USDA released a white paper containing a summary of their joint Interim Approaches for assessing risks 

to listed species from pesticides. These Interim Approaches were developed jointly by the agencies in 

response to the 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. Details of 

the joint Interim Approaches are contained in the November 1, 2013 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.

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 problem formulation supporting the Preliminary Work Plan for topramezone 

does not describe the specific ESA analysis, including effects determinations for specific listed species or 

designated critical habitat, to be conducted during registration review. While the agencies continue to 

develop a common method for ESA analysis, the planned risk assessment for the registration review of 

topramezone will describe the level of ESA analysis completed for this particular registration review 

case. This 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. Once the agencies have fully developed and implemented the scientific methods necessary to 

complete risk assessments for listed species and their designated critical habitats, these methods will be 

applied to subsequent analyses of topramezone as part of completing this registration review.

6. Endocrine Disruptor Screening Program

Topramezone was not included in the first group of 67 chemicals issued an order to conduct Tier 1 EDSP 

testing. Tier 1 screening results for List 1 chemicals are available at http://www2.epa.gov/ingredientsused-pesticide-products/endocrine-disruptor-screening-program-tier-1-assessments. For additional 

information on the EDSP, visit http://www.epa.gov/endo/.

B. Drinking Water 

Unless the residues of concern are redefined for topramezone, an updated drinking water assessment 

for registration review is not planned at this time. The most recent drinking water assessment 

conducted for aquatic uses is expected to provide conservative EDWCs and the results are expected to 

be higher than that of any other uses currently registered. 
29

VI. PRELIMINARY IDENTIFICATION OF DATA GAPS

A. Environmental Fate

Table VI.1 identifies environmental fate studies by MRID that offer data for each guideline requirement, 

as well as study classifications and whether or not further data are needed in order to support risk 

assessment.

Table VI.1. Environmental Fate Data for Topramezone and Its Environmental Transformation Products

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed? Comments

835.2120 Hydrolysis 45902416 acceptable No --

835.2240 Aqueous 

Photolysis 45902417 acceptable No --

835.2410 Soil 

Photolysis 45902418 acceptable No --

835.4100 Aerobic Soil 

Metabolism

45902419 supplemental

No

--

45902421 supplemental

45902420 acceptable Study conducted on BAS 670H Acid 

(M670H05), a major metabolite of BAS 670H

835.4200

Anaerobic 

Soil 

Metabolism

No data No --

835.4300

Aerobic 

Aquatic 

Metabolism

45902423

supplemental No

Duplicate study submission

47496702

45902424 unacceptable Semi-field study

835.4400

Anaerobic 

Aquatic 

Metabolism

45902422 supplemental

No

--

48600413 supplemental

All transformation products observed at 

concentrations greater than 10% need to be 

identified. In absence of additional 

information, these residues will be considered 

a toxicological concern.

835.1230

835.1240

Adsorption/ 

desorption 

and Leaching

45902425 acceptable

No

--

46242703 acceptable

835.6100

Terrestrial 

Field 

Dissipation

45902427 supplemental

No

45902426 supplemental

47498704 - This is a response to concerns related to the 

TFD studies 45902426 and 45902427.

47411701 -

This is a rationale document for not conducted 

a TFD for conifer and hardwood plantation 

uses. 

47496705 - This is a response to concerns related to 

storage stability studies for the TFD studies.

48739401 -

45902428 unacceptable No
30

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed? Comments

Storage 

Stability 47498705 - This is a response to concerns related to storage stability studies for the TFD studies.

835.6200 Aquatic Field 

Dissipation 48600414 supplemental No

850.6100

Analytical 

Method in 

Soil

45902429

(ECM) acceptable

Yes

Data are available for topramezone; however, 

the LOD/LOQ are not lower than the most 

sensitive terrestrial plant endpoint.

45902430

(ILV) acceptable This ILV is for the soil method presented in MRID 45902429.

Analytical 

Method in 

Water

48837001 

(ECM) acceptable

Yes

For these submission (MRIDs 48600417, 

48837001), personnel conducting the 

validation of the ECM were under supervision 

of the same study director; therefore, these 

submissions do not have a supporting 

independent laboratory validation.

48600417 

(ECM) acceptable

45902432 

(ECM) acceptable This method is not the same as the method presented in MRIDs 48837001 and 48600417.

165-4 

850.1730

Fish Bioconcentratio

n

45902322 unacceptable No

Additional data are not required at this time as 

physical-chemistry data do not suggest 

topramezone will bioconcentration. 

Environmental Chemistry Methods (ECM) 

Independent Laboratory Validation (ILV)

B. Ecological Effects

Table VI.2 and identify ecological effects studies for aquatic and terrestrial organisms, respectively, that 

provide data for each guideline requirement. These tables also identify the study classifications and 

indicate whether EFED recommends requesting additional data in order to support risk assessment and 

the rationale for the data request. 

Table VI.2. Aquatic Ecological Effects Data for Topramezone

OCSPP

Guideline

Data Requirement

Test Material

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Comments

850.1010 Freshwater 

invertebrate

acute toxicity

45901820 

(TEP) Acceptable No None

850.1025

850.1035

Estuarine/saltwater 

invertebrate

acute toxicity

48600412 

(TEP) Acceptable No None

850.1075 Freshwater fish 

acute toxicity

45901813 

(TEP)

Acceptable No None
31

OCSPP

Guideline

Data Requirement

Test Material

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Comments

850.1075 Saltwater fish acute 

toxicity

48600410 

(TEP) Acceptable No None

850.1300

Freshwater 

invertebrate

life cycle

45902320 

(TEP) Supplemental No See footnotea

.

49365103 

(TGAI) Acceptable TBD None

850.1350 Estuarine/saltwater 

invertebrates

life cycle

48600411

(TEP) Supplemental No None

850.1735 

/ OECD 

218

Benthic 

invertebrates 

(freshwater, 

prolonged)

48600408 

(TGAI)

Supplemental 

(Chironomus 

riparius)

No None

850.1740 Benthic 

invertebrates 

(marine, 10-day)

48600407 

(TGAI)

Acceptable 

(Leptocheirus 

plumulosus)

No None

850.1400 Freshwater fish

early-life stage

45902321 

(TGAI) Acceptable No None

850.1400 Estuarine/saltwater 

fish

early-life stage

48600404 

(TGAI) Acceptable No None

850.1500 Fish life cycle 

(freshwater)

48600406 

(TGAI) Acceptable No None

850.4400

Aquatic plant 

Toxicity Test Using 

Lemna spp.

45902329 

(TGAI) Acceptable No None

46242704 

(degradate: 

M670H05)

Acceptable No None

45901821 

(TEP) Acceptable No None

850.4500 Algal Toxicity

(freshwater algae: P. 

subcapitata)

45902333 

(TGAI) Acceptable

Yes

Guidance recommends 

testing on four of the most 

sensitive nonvascular 

organisms. Three are 

acceptable and the fourth 

(MRID 45902332) on 

Navicula pelliculosa was 

deemed invalidb

. Multiple 

incident reports have 

involved topramezone and 

plant species. 

Algal Toxicity

(freshwater diatom) No valid 

data No valid data

Algal Toxicity 

(marine diatom: S. 

costatum)

45902331 

(TGAI) Acceptable 
32

OCSPP

Guideline

Data Requirement

Test Material

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Comments

850.4550

Cyanobacteria 

(Anabaena flosaquae) Toxicity

45902330 

(TGAI) Acceptable No

850.1740

10-day Spiked 

Sediment survival of 

Marine Arthropod 

(Leptocheirus 

plumulosus)

48600407

(TGAI) Acceptable No

None

850.1735 

(OECD 

218)

Prolonged Spiked 

Sediment with 

(Chironomus 

riparius)

48600408

(TGAI) Supplemental No None

a The aquatic invertebrate (waterflea, Daphnia magna) life-cycle study (MRID 45902320) did not measure the dry 

weight of surviving daphnids. The EFED requested that, if available, the data on dry weight be submitted in order 

to determine growth deficiencies of daphnids. A response was provided in MRID 47496707 to address this 

request. EFED agrees that, per OPPTS 850.1300 Guideline (April 1996), either total length or dry weight (or both) 

may suffice to meet the growth assessment requirement. Presumably, only total lengths were measured. 

However, they were not reported. EFED requests that, if available, the data on total lengths be submitted in order 

to determine growth deficiencies of daphnids. The study is still considered supplemental. The endpoint (NOAEC = 

48.6 mg a.i./L) determined from this TEP-based study has been used in past assessments. A new study (MRID 

49365103) was reviewed for this problem formulation that determined greater sensitivity of the Daphnia (NOAEC 

= 29 mg a.i./L) to topramezone TGAI on the basis of reproduction endpoints (i.e., the number of live neonates per 

surviving adult and the number of immobilized neonates of surviving adults).

b The aquatic plant (freshwater diatom, Navicula pelliculosa) study (MRID 459023-32) is considered invalid 

because it was not possible to differentiate whether the reduction in diatom growth was due to topramezone, or 

from a reduction in pH. The EFED recommends a new study with N. pelliculosa. Initial pH levels at all treatment 

levels must be 7.5 ± 0.1 which should be maintained as closely as possible throughout the test. This information 

would help determine the toxicity of topramezone to freshwater diatoms. A BASF memo dated July 31, 2008 

(MRID 474967-00) states that 'BASF is requesting a time extension for one year to complete the study.'

Table VI.3. Terrestrial Ecological Effects Data for Topramezone

OCSPP 

Guideline

Data 

Requirement

Test Material

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Comments

850.2100 Avian oral toxicity 45902309 

(TGAI) Acceptable Yes Based on effects noted in the available toxicity data, 
33

OCSPP 

Guideline

Data 

Requirement

Test Material

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Comments

48600409

(TGAI)

Invalid 

(passerine)

and the potential for 

passerines to be more 

sensitive than the species 

previously tested (i.e., 

bobwhite quail), EFED 

recommends requesting a

new passerine study. See 

footnotea.

850.2200 Avian dietary 

toxicity 45902311 

(TGAI)

Acceptable 

(mallard) No

None

45902310 

(TGAI)

Acceptable 

(quail; 

upgraded from 

supplemental)

No

None

850.2300 Avian reproduction

45902313 

(TGAI)

Supplemental 

(mallard) No

See footnoteb.

49365102 

(TGAI)

Supplemental 

(mallard) Yes

See footnotec.

45902312 

(TGAI)

Acceptable 

(quail; 

upgraded from 

supplemental)

No

The study endpoints are not 

the most sensitive relative 

to the other avian 

reproduction studies and 

have not been used in 

previous risk assessments.

NonguidelineAvian inhalation

No data No

Based on STIR analysis, risks 

through inhalation pathway 

are not expected.

81-1

Acute mammalian 

oral LD50

(rat)

45902118; 

45902119; 

45902120

Acceptable (3x) No None 

83-4

Mammalian 

Reproduction

(rat)

45902214 Acceptable No

None
34

OCSPP 

Guideline

Data 

Requirement

Test Material

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Comments

850.3020 Honey bee adult 

acute contact 

toxicity

45902325

(TGAI) Acceptable

No

Tier 1 toxicity test.

45901814 

(TEP) Supplementald

850.3030 Honey bee toxicity 

of residues on 

foliage None No

This study is not triggered 

based on the reported 

endpoint in the honey bee 

adult acute contact study.

Nonguideline

OECD TG 

213

Honey bee adult 

acute oral toxicity

TGAI

45901814

(TEP) Supplementald No

Tier 1 toxicity test.

Nonguideline 

OECD TG 

237

Honey bee larvae 

acute oral toxicity

TGAI

No data Yes

Tier 1 toxicity test.

NonguidelineHoney bee larvae 

chronic oral toxicity 

TGAI

No data Yes

Tier 1 toxicity test.

NonguidelineHoney bee adult 

chronic oral toxicity

TGAI

No data Yes

Tier 1 toxicity test.

Nonguideline 

OECD 

Guidance 

75

Semi-field testing 

for pollinators

TEP

No data Yes

Tier 2 test contingent on 

results of tier 1 tests and 

screening level residues.

NonguidelineField trial of 

residues in pollen 

and nectar

TEP

No data Yes

Tier 2 test contingent on 

results of tier 1 tests and 

screening level residues.

850.3040 Field testing for 

pollinators

TEP

No data Yes

Tier 3 test contingent on 

results of earlier tiers of 

testing.
35

OCSPP 

Guideline

Data 

Requirement

Test Material

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Comments

850.4100 Terrestrial plant 

toxicity:

Tier II seedling 

emergence

45902327 

(TEP, 

parent)

Acceptable No

Data in this study is on the 

TEP with the parent 

compound. Data was 

requested for degradate in 

previous assessments.

49365104 

(TGAI, 

metabolite

BAS 

M670H 05)

Supplementale

, 

for qualitative 

use

No

Though the test was not 

conducted at 

concentrations high enough 

to detect an IC25 for either 

monocot or dicot, the study 

suggests that the tested 

metabolite is not as toxic as 

the parent compound. 

850.4150 Terrestrial plant 

toxicity:

Tier II vegetative 

vigor

45902328 

(TEP, 

parent)

Acceptable No

Data in this study is on the 

TEP without the adjuvant 

and/or surfactant. In 

previous assessments data 

was requested for the 

parent plus adjuvant and 

surfactant.

49365105 

(TGAI, 

parent 

BAS 670 

01H + 

adjuvant)

Supplementalf, 

for quantitative 

use

No

The study uses 

nomenclature for a

metabolite (BAS 670 01H) 

but chemical structure 

confirms the test compound 

was the parent.

a For the zebra finch, a fasting period prior to dosing is expected to last 2-3 hours. The fasting period in the study 

was 20-22 hours. The prolonged fasting may have stressed the birds, and also led to altered metabolic processes 

and changes in gut motility. As a result, the prolonged fasting (20-22 hours) could potentially have led to fast 

excretion of the test compound without adequate time for absorption into the test organism (evidenced by diarrhea 

noted in the control and all treatment groups within the first hour after dosing), which might have the equivalent 

effect of regurgitation in the study.

b

All three concentrations tested elicited adverse effects on hatchling body weight and adult female weight gain; 

therefore, a NOAEC could not be determined. A response was provided in MRID 47496707 to address this 

requirement but with which EFED did not agree. Without a definitive NOAEC value, EFED cannot conclusively 

determine avian chronic risk. Therefore, EFED continued to recommend that a new study be performed with 

concentrations lower than the tested concentrations in order to establish a NOAEC. A new study (MRID 

49365102) was submitted and reviewed for this problem formulation. However, see footnote (c). c All three concentrations tested elicited adverse effects on adult male body weight gain; therefore, a NOAEC 

could not be determined.

d The acute oral component of the study is not an EPA guideline study.

e Test substance is TGAI (as opposed to TEP) topramezone transformation product (BAS M670H 05). f Test substance is TGAI (as opposed to TEP) topramezone mixed with an adjuvant
36

VII. REFERENCES

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs.

January 23, 2004. Office of Pesticide Programs. Office of Prevention, Pesticides, and Toxic 

Substances. Available at: http://www.epa.gov/espp/consultation/ecorisk-overview.pdf

USEPA. 2005. Wolf, J., Termers, S., Topramezone (BAS 670H) Herbicide CAS Name, [3-(4,5-Dihydro-3-

isoxazolyl)-2-methyl-4-(methylsulfonyl)phenyl](5-hydroxy-1-methyl-1H-pyrazol-4-yl) 

methanone CAS Registry Number, 210631-68-8 Tier II Drinking Water Assessment March 18, 

2005 (DP Barcode: 388368)

USEPA. 2005. Carey, S., Termes, S., Wolf, J. New Chemical Registration: Ecological Risk Assessment of 

Proposed Use on Corn (incl. grain, seed, popcorn, and sweet corn). May 12, 2005. (DP Barcode: 

290065)

USEPA. 2008. Hetrick, J., Corbin, M. Topramezone (BAS 670H) Herbicide CAS Name, [3-(4,5-Dihydro-3-

isoxazolyl)-2-methyl-4-(methylsulfonyl)phenyl](5-hydroxy-1-methyl-1H-pyrazol-4-yl) methanone 

CAS Registry Number, 210631-68-8 Tier I and II Drinking Water Assessment September, 29, 2008

(DP Barcode: 356497)

USEPA. 2009. Crk, T., Termes, S., Hetrick. J. Ecological Risk Assessment for the Section 3 New Use 

Registration of Topramezone on non-cropland areas. March 10, 2009. (DP Barcodes: 352689, 

354091, 355501)

USEPA. 2011. Hetrick, J., Spatz, D. Drinking Water Assessment to Support Topramezone Use on Golf 

Courses, Sod Farms, and Residential Lawns November, 14, 2011 (DP Barcode: 388368)

USEPA. 2012. Wolf. J., Crk. T. Ecological Risk Assessment for the Section 3 New Use Registration of 

Topramezone on new golf courses, sod farms, and residential turfgrass uses. January 9, 2012. 

(DP Barcode: 397476).

USEPA. 2013. Wolf, J., Drinking Water Exposure Assessment for a Proposed Increase of the maximum use 

rate of Topramezone Frequency Herbicide (EPA Reg. No. 7969-281) for non-cropland uses, and 

Proposed New Use for Direct Applications to Aquatic Environments (Oasis Aquatic Herbicide, EPA 

File Symbol No. 7969-GGO) January, 29, 2013, (DP Barcodes: 408687; 401166)

USEPA. 2013. Crk. T. Wolf. J. Ecological Risk Assessment for the Proposed New Use of Topramezone for 

Aquatic Vegetation Management. May 16, 2013. (DP Barcode: 400305).

USEPA. 2014. ECOTOX User Guide: ECOTOXicology Database System. Version 4.0. Available:

http:/www.epa.gov/ecotox/

USEPA. 2015. LaVerne, D., Topramezone Label Use Report Package in Support of Registration Review,

January 20, 2015
37

APPENDIX A. BIBLIOGRAPHY

Table A.1. Environmental Fate Studies Submitted for Topramezone

Guideline MRID Classification Citation

Hydrolysis

835.2010 45902416 Acceptable

Venkatesh, K. (1999) Hydrolysis of BAS 670 H (Pyrazol-4-

(Carbon 14)) in Aqueous Media: Lab Project Number: 56797: 

99/5070: C7. Unpublished study prepared by BASF 

Corporation. 80 p.

Aqueous 

Photolysis

835.2240

45902417 Acceptable

Guirguis, A. (2000) Water Photolysis of (Carbon 14)-BAS 670 

H: Lab Project Number: 56799: 1999/5100. Unpublished 

study prepared by BASF Corporation. 65 p.

Soil Photolysis

835.2410 45902418 Acceptable

Singh, M. (2002) Photolysis of (Carbon 14)-BAS 670 H on Soil: 

Lab Project Number: 66424: 2002/5004142. Unpublished 

study prepared by BASF Corporation. 115 p.

Aerobic Soil 

Metabolism

835.4100

45902419 Supplemental

Venkatesh, K. (2002) Aerobic Soil Metabolism of (Carbon 14)-

BAS 670 H in a US Soil: Lab Project Number: 64444: 

2001/5003312. Unpublished study prepared by BASF Agro 

Research and Agvise Laboratories. 83 p.

45902421 Supplemental

Singh, M. (2002) Aerobic Degradation of (Carbon 14)-

Phenyl))-BAS 670 H in a US Soils: Lab Project Number: 58525: 

2002/5003685. Unpublished study prepared by BASF Agro 

Research and Agvise Laboratories. 216 p.

45902420 Acceptable

Venkatesh, K. (2002) Aerobic Soil Metabolism of (Carbon 14)-

BAS 670 H Acid in a US Soil: Lab Project Number: 66422: 

2002/5003792. Unpublished study prepared by BASF Agro 

Research and Agvise Laboratories. 68 p.

Anaerobic Soil 

Metabolism

835.4200

No Data

Aerobic Aquatic

Metabolism

835.4300

45902423 Supplemental

David, M. (2002) BAS 670 H: Aerobic Aquatic Metabolism: 

Lab Project Number: 56940: 2002/5003947: ENV 01-055. 

Unpublished study prepared by BASF Corporation. 165 p.

47496702 Duplicate submission as 45902423

45902424 Unacceptable

Fent, G. (2002) Degradation and Distribution of BAS 670 H in 

a Water-Sediment System Under Outdoor Conditions: Final 

Report: Lab Project Number: 2002/1007741: BAS670. 

Unpublished study prepared by Staatliche Lehr-und 

Forchungsanstalt. 43 p.

Anaerobic 

Aquatic

Metabolism

834.4400

45902422

supplemental Guirguis, A. (2002) Anaerobic Aquatic Metabolism of (Carbon 

14)-BAS 670 H: Final Report: Lab Project Number: 58523: 

2002/5003696. Unpublished study prepared by BASF 

Corporation and BASF Aktiengesellschaft. 170 p.

48600413

supplemental McGinty, K. (2012) Anaerobic Aquatic Metabolism of (Carbon 

14)-BAS 670 H. Project Number: 2011/7005338/OCR, 

402577. Unpublished study prepared by BASF Corporation. 

181p.

47496703 not classified

Paulick, R. (2008) BASF Response to EPA Conditions of 

Registration for Topramezone: Anaerobic Aquatic 

Metabolism - MRIDs 45902422. Project Number: 

2008/7012539. Unpublished study prepared by BASF Agro 

Research. 11 p.
38

Guideline MRID Classification Citation

Terrestrial Field 

Dissipation

835.6100

45902426 supplemental

Jackson, S.; Saha, M. (2002) 2000 Field Dissipation of BAS 670 

H in Terrestrial Use Patterns: Lab Project Number: 63880: 

2002/5003700: A63880. Unpublished study prepared by 

BASF Corporation, Ag Search Company, and Prairie Ag 

Research. 557 p.

45902427 supplemental

Jackson, S.; Saha, M. (2002) 2000 Field Dissipation of BAS 670 

H in Terrestrial Use Patterns for Canada: Lab Project Number: 

59933: 2002/5003699: 2002/5003700. Unpublished study 

prepared by BASF Corporation and Agvise Laboratories, Inc. 

184 p.

47411701 not classified

Lingard, S.; Zawierucha, J.; Akers, R. (2008) Rationale for a 

Terrestrial (Soil) Dissipation Study in Support of Conifer and 

Hardwood Plantation Use with BAS 670 01 H. Project 

Number: 2008/7004905, RTP/NC/27709. Unpublished study 

prepared by BASF Agro Research. 10 p.

47496704 not classified

Panek, M. (2008) BASF Response to Conditions of 

Registration for Topramezone: Terrestrial Field Dissipation -

MRIDs 45902426 and 45902427. Project Number: 

2008/7012570. Unpublished study prepared by BASF Agro 

Research. 13 p.

47496705 not classified

Panek, M. (2008) BASF Response to Conditions to 

Registration for Topramezone: Terrestrial Field Dissipation -

Storage Stability - MRID 45902468. Project Number: 

2008/7012571. Unpublished study prepared by BASF Agro 

Research. 22 p.

48739401 supplemental

Negley, T.; Warren, R.; Newcombe, A. (2012) Dissipation of 

BAS 670 H (Topramezone 2.8 SC Herbicide) in Bare Soil Plots 

at Test Sites Located in North Carolina and Texas: Final 

Report. Project Number: 2011/7002506/OCR, 201108/08/01, 

328058. Unpublished study prepared by Arcadis and ADPEN 

Laboratories, Inc. 938p.

Aquatic Field 

Dissipation

835.6200

48600414 supplemental

Petty, D.G. 2011. Aquatic Dissipation of Topramezone in 

Freshwater Systems. Unpublished study performed by NDR 

Research, Plainfield, IN; EPL-BAS, Niantic, IL; Agvise 

Laboratories Inc., Northwood, ND; Florida Pesticide 

Research, Oviedo, FL; and Paragon Research, Zionsville, IN; 

sponsored and submitted by BASF Corporation, Agricultural 

Products Division, Research Triangle Park, NC. Study ID No.: 

NDR0901. BASF Registration Doc. No.: 2011/7006384. 

Experiment initiation February 3, 2010 and completion 

October 25, 2011 (p. 3). 

Adsorption/

Desorption 

Batch 

Equilibrium 

835.1230

45902425 supplemental

Zirnstein, M. (2002) Adsorption/Desorption--Study of BAS 

670 H and M670H05 (Metabolite of BAS 670 H) on Six North 

American Soils: Final Report: Lab Project Number: PI020020: 

2002/1008895. Unpublished study prepared by BASF 

Aktiengesellschaft. 73 p. {OPPTS 835.1230}

46242703 acceptable

Zirnstein, M. (2003) Adsorption / Desorption - Study of BAS 

670 H Metabolite M670H10 (Reg. No. 4969168) on Six North 

American Soils: Final Report. Project Number: 168585, 

2003/1009251. Unpublished study prepared by BASF 

Aktiengesellschaft and BASF Aktiengesellschaft. 79 p.
39

Guideline MRID Classification Citation

Method 

Validation

850.6100

45902429 acceptable

Saha, M. (2002) Validation of BASF Method No. D0103: The 

Determination of Residues of BAS 670 H and Its Metabolites 

in Soil Using LC-MS/MS: Lab Project Number: 64266: 

2002/5002831: 64256. Unpublished study prepared by BASF 

Corporation. 67 p.

45902430 acceptable

Jackson, S.; Saha, M. (2002) 2000 Field Dissipation of BAS 670 

H in Terrestrial Use Patterns for Canada: Lab Project Number: 

59933: 2002/5003699: 2002/5003700. Unpublished study 

prepared by BASF Corporation and Agvise Laboratories, Inc. 

184 p.

45902432

Supplemental 

(not an 

independent 

validation the 

study director 

was same for 

both ECM and 

ILV)

Genari, G. (2000) Validation of Analytical Method CP 357 

"Bestimmung von BAS 670 H (Reg.-Nr. 375080) in Wasser 

Mittels HPLC": Final Report: Lab Project Number: PCP05706: 

2000/1013455. Unpublished study prepared by BASF 

Aktiengesellschaft. 14 p.

45902431 acceptable

Genari, G. (2000) Determination of BAS 670 H (Reg. No. 

375080) in Water by Means of HPLC: Lab Project Number: 

2001/1019440: 357. Unpublished study prepared by BASF 

Aktiengesellschaft. 20 p.

Bioconcentration

850.1730 45902322 unacceptable

Nietschmann, D. (2002) Uptake, Depuration, 

Bioconcentration and Metabolism of Carbon-14 Labeled BAS 

670 H in Bluegill Sunfish (Lepomis macrochirus) Under FlowThrough Conditions: Final Report: Lab Project Number: 

56754: 2002/5002984: 46811. Unpublished study prepared 

by BASF Corporation. 40 p. {OPPTS 850.1730}
40

APPENDIX B. ADDITIONAL ENVIRONMENTAL FATE DATA FOR TOPRAMEZONE AND ITS 

TRANSFORMATION PRODUCTS 

Test System Kd Koc Kf Kfoc 1/n

Topramezone

Idaho Loam

pH 6.7, 3.7% OC, 6.3% OM 1.81 48.34 1.40 38.39 0.88

South Dakota Silt Loam

pH 5.9, 2.9% OC, 4.9% OM 3.73 130.93 2.59 90.88 0.85

Iowa Loam pH 6.8, 3.7% OC, 

6.4% OM 2.59 69.72 1.98 53.12 0.86

Indiana Silt Loam pH 6.9, 

0.81% OC, 1.4% OM 0.56 68.61 0.44 53.70 0.82

Minnesota Clay Loam pH 6.1, 

4.1% OC, 7.0% OM 7.47 183.61 4.86 119.41 0.86

North Carolina Sandy Loam 

pH 5.7, 1.2% OC, 2.1% OM 6.93 48.34 3.62 296.72 0.79

M670H10

Idaho Loam

pH 6.7, 3.7% OC, 6.3% OM 13.80 376.93 10.66 291.28 0.93

South Dakota Silt Loam

pH 5.9, 2.9% OC, 4.9% OM 34.73 1218.67 23.85 836.93 0.92

Iowa Loam pH 6.8, 3.7% OC, 

6.4% OM 30.04 807.43 19.49 523.96 0.90

Indiana Silt Loam pH 6.9, 

0.81% OC, 1.4% OM 6.94 856.75 4.35 536.85 0.86

Minnesota Clay Loam pH 6.1, 

4.1% OC, 7.0% OM 81.04 1991.11 52.61 1292.61 0.92

North Carolina Sandy Loam 

pH 5.7, 1.2% OC, 2.1% OM 91.01 7459.84 69.24 5675.61 0.950

M670H05

Minnesota Clay Loam pH 6.1, 

4.1% OC, 7.0% OM 0.11 2.80 0.12 2.60 0.90

North Carolina Sandy Loam 

pH 5.7, 1.2% OC, 2.1% OM 0.20 16.29 0.18 14.34 0.88
41

Chemical Name Chemical Structure

M670H01, 

BAS 670 H cyano

[3-Cyano-4-methane-sulfonyl-2-methylphenyl](5-hydroxy-1-methyl-1H-pyrazol4-yl)methanone

SMILES: 

C1=N[N](C(=C1C(C2=CC=C(C(=C2C)C#N)[S

](=O)(=O)C)=O)O)C

S

O

O

O N

N

N OH

M670H05

BAS 670 H acid

3-(4,5-Dihydro-isoxazol-3-yl)-4-

methanesulfonyl-2-methyl-benzoic acid

SMILES:

C(C1=CC=C(C(=C1C)C2=NOCC2)[S](=O)(=

O)C)=O

S

O

O

HO

O

N

O

M670H10 6-[(5-Hydroxy-1-methyl-1H-pyrazol-4-

yl)carbonyl]-5-methyl-2,3-dihydro-4H-1-

benzothiopyran-4-one

SMILES: 

C1=N[N](C(=C1C(C2=CC=C3C(=C2)C(CCS3)

=O)=O)O)C

O

N

N OH S

O

M670H12 (tautomer)

mw 335.0940 g/mol, C15H17N3O4S

M670H11 Topramezone structural isomer

mw 363.0889 g/mol, C16H17N3O5S
42

APPENDIX C. SIP ANALYSIS RESULTS

 Table C1. SIP Inputs (using the lowest solubility value at pH 5 of 0.98 g/L)

Parameter Value

Chemical name Topramezone

Solubility (in water at 25oC; mg/L) 980

Mammalian LD50 (mg/kg-bw) 2000

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 200

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 2000

Avian test species northern bobwhite quail

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 100

Bobwhite quail NOAEC (mg/kg-diet)

NOAEC (mg/kg-diet) for other bird species

Body weight (g) of other avian species

NOAEC (mg/kg-diet) for 2nd other bird species

Body weight (g) of 2nd other avian species

Table C2. Mammalian Results taken from SIP

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 168.5600 168.5600

Adjusted toxicity value (mg/kg-bw) 1538.3211 153.8321

Ratio of exposure to toxicity 0.1096 1.0957

Conclusion*

Exposure through drinking 

water alone is a potential 

concern for mammals

Exposure through drinking 

water alone is a potential 

concern for mammals

Table C3. Avian Results taken from SIP

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 793.8000 793.8000

Adjusted toxicity value (mg/kg-bw) 1440.8590 4.9613

Ratio of exposure to acute toxicity 0.5509 159.9998

Conclusion*

Exposure through 

drinking water alone is a 

potential concern for 

birds

Exposure through 

drinking water alone is a 

potential concern for 

birds

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, 

when aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through drinking water 

may contribute to a total exposure that has potential for effects to non-target animals.
43

APPENDIX D. STIR ANALYSIS RESULTS

The Screening Tool for Inhalation Risk (STIR v.1.0, November 19, 2010) was used to calculate an upper 

bound estimate of exposure using topramezone’s vapor pressure and molecular weight for vapor phase 

exposure as well as the maximum application rate and method of application for spray drift. STIR 

incorporates results from several toxicity studies including acute oral and inhalation rat toxicity 

endpoints obtained from the “six-pack” of core studies, which are a series of six guideline studies that 

are submitted to the Registration Division of the Office of Pesticide Programs for technical and 

formulated products of a pesticide [acute oral LD50 >2,000 mg a.i./kg-bw, rat (MRID 45902118); acute 

inhalation LC50 > 5.05 mg/L, rat (MRID 45902124)] as well as the most sensitive acute oral avian toxicity 

endpoint [LD50 > 2,000 mg a.i./kg-bw, bobwhite quail (MRID 45902309)]. Based on the results of the 

STIR model, inhalation exposure alone was not determined to be a potential pathway of concern for 

avian or mammalian species on an acute basis for either ground or aerial spray types. Detailed 

information about STIR v.1.0, as well as the tool, can be found on the EPA’s website at: 

http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial. 
44

Input

Application and Chemical Information

Enter Chemical Name Topramezone

Enter Chemical Use Aquatic

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) ground

Enter Chemical Molecular Weight (g/mole) 363.39

Enter Chemical Vapor Pressure (mmHg) 7.30E-13

Enter Application Rate (lb a.i./acre) 0.35

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 2000

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 2000

Enter Lowest Rat Inhalation LC50 (mg/L) 5.05

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 1.43E-08

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.79E-09

Adjusted Inhalation LD50 2.82E+01

Ratio of Vapor Dose to Adjusted Inhalation LD50 6.37E-11

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 3.70E-02

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 1.31E-03

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 1.43E-08

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.26E-09

Adjusted Inhalation LD50 3.01E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 7.50E-12

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 4.65E-02

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 1.55E-04