UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 .. .~ 

PC Codes: 128959, 128968 

DP Barcode: 418561 

Date: September 8, 2014 

MEMORANDUM 

SUBJECT: 

FROM: 

REVIEWED 

BY: 

Problem Formulation for the Ecological Risk and Drinking Water 

Exposure Assessments to be Conducted in Support of the Registration 

Review for Fluroxypyr-MHE 

Nicholas Mastrota, Ph.D., Wildlife Biologist !Jt; a--t A ~ 'f/8/t'f 

Rochelle 

Environmental 

F. H. Bohaty, 

Risk Branch 

Ph.D., 

3 

Chemist ~~ 

Environmental Fate and Effects Division (7507P) 

Melissa Panger, Ph.D., Senior Biologist 

James Hetrick, Ph.D., Senior Advisor 

Environmental Risk Branch 3 

Environmental Fate and Effects Division (7507P) 

r/r 11'1 

THROUGH: Dana Spatz, !Jranch Chief 

Environmental Risk Branch 3,<=:::~:5~~~2~~~:­

Environmental Fate and Effects Division (7507P) 

TO: Neil Anderson, Branch Chief 

Benjamin Askin, Chemical Review Manager 

Risk Management and Implementation Branch 1 

Pesticide Re-Evaluation Division (7508P) 
2 

Contents	

I. Executive summary ................................................................................................................... 3

II. Introduction ......................................................................................................................... 4

1. Previous Ecological Risk Assessments ............................................................................. 4

2. Drinking Water Exposure Assessments ............................................................................ 5

3. Clean Water Act Programs ................................................................................................ 6

III. Stressor Source and Distribution ...................................................................................... 6

A. Description of Stressors ..................................................................................................... 6

B. Mechanism of Action ........................................................................................................ 7

C. Overview of Pesticide Usage ............................................................................................ 8

D. Environmental Fate and Transport .................................................................................. 16

IV. Receptors ........................................................................................................................... 23

1. Effects to Aquatic Organisms .......................................................................................... 23

2. Effects to Terrestrial Organisms ...................................................................................... 27

B. Ecological Incidents ........................................................................................................ 32

C. Exposure Pathways of Concern ....................................................................................... 34

V.Analysis Plan ........................................................................................................................... 34

A. Ecological Risk Assessment ............................................................................................ 34

1. Stressors of Concern ........................................................................................................ 34

2. Measures of Exposure ..................................................................................................... 35

3. Measure of Effects ........................................................................................................... 35

4. Integration of Exposure and Effects ................................................................................ 35

5. Endangered Species Assessments ................................................................................... 36

6. Endocrine Disruptor Screening Program ........................................................................ 37

B. Drinking Water ................................................................................................................ 37

VI. Preliminary Identification of Data Gaps ........................................................................ 37

A. Environmental Fate ......................................................................................................... 37

B. Ecological Effects ............................................................................................................ 39

VII. References (general) ......................................................................................................... 45

APPENDIX A. Bibliography ..................................................................................................... 47

APPENDIX B. Inputs and Outputs from the SIP and STIR Models ................................... 60
3 

I. EXECUTIVE SUMMARY 

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

formulation for the ecological risk and drinking water exposure assessments to be conducted as 

part of the registration review of the herbicide fluroxypyr-MHE (PC code: 128968). The problem 

formulation describes the methods planned to be used during the completion of drinking water 

and ecological risk assessments in support of registration review, and provides an overview of 

the environmental fate, ecological effects, and potential risks associated with the use of 

fluroxypyr-MHE. Uncertainties unique to the risk assessment of fluroxypyr-MHE are also 

discussed. 

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

submitted to support the registration of fluroxypyr-MHE 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 fluroxypyr-MHE: 

 Environmental Chemistry Methods and Associated Independent Laboratory Validation 

(Guideline 850.6100.) – Several different methods have been provided to support various 

laboratory and field studies; however, none of the soil methods are sensitive enough to 

detect fluroxypyr-MHE or fluroxypyr acid at levels of toxicological concern (0.00083 lb 

a.e./A). The lowest detection limit reported for fluroxypyr acid in soil is 3 μg/kg (0.007 

a.e. lb/A). An independent laboratory validation has not been submitted for the 

environmental chemistry method in water. 

 Compost Study (non-guideline) – a concentration based compost study (MRID 

45833601) has been submitted that examined the dissipation of fluroxypyr acid; however, 

this study has several deficiencies including: 1) no methods (including an independent lab 

validation) or control spike analysis were provided to support the analytical procedures 

used in the study, 2) recoveries were variable, 3) dilution due to sample withdrawal and 

consolidation of multiple samples was not adequately described, and 4) a comparison of 

the composting method with typical composting practices was not provided. Additional 

data are needed to address these deficiencies or a new study should be submitted to 

address the fate of fluroxypyr-MHE and fluroxypyr acid fate in composted materials.    

 Seedling Emergence, Guideline 850.4100 and Vegetative Vigor, Guideline 850.4150, 

with representative typical end-use products. 

 Tier 1 studies for assessing toxicity to bees, including a honey bee acute oral study 

(OECD 213), a honey bee chronic oral study, and a honey bee chronic larval study. These 

studies should be performed with fluroxypyr-MHE TGAI. Depending on the results of 

these studies, additional higher-tiered honey bee testing may be required. 

 
4 

II. INTRODUCTION 

1. Previous Ecological Risk Assessments 

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

fluroxypyr-MHE for use on agricultural crops. Conclusions of the previous assessments are 

summarized in Table II.1 and Table II.2. 

Table II.1. Summary of Previous Risk Assessments Conducted on Fluroxypyr-MHE 

Use Reference Application Rate Assessed 

(lbs a.i./A) 

Taxa for which risk was 

identified 

Rice D396342 0.34 (single application) 

0.56 (annual) 

Aquatic invertebrate, aquatic 

plants, terrestrial plants 

Millet D336179 0.50 (annual rate) Terrestrial plants 

Pome Fruit D336179 0.50 (annual rate) Saltwater invertebrates and 

terrestrial plants 

Onion (to control voluntary 

potatoes) D314020 0.25(single application) 

0.375 (annual) Terrestrial plants 

Wheat, Barley, and Oats D236845 

D231718 0.125 (single application) Terrestrial plants 

Uncultivated areas D236845 

D231718 0.25 (single application) Terrestrial plants 

Table II.2. Risk Concerns Identified for Fluroxypyr-MHE in Previous Assessments 

Birds Mammals Terr. 

Plants 

Terr. 

Inverts Fish BCF Aquatic Inverts 

Aquatic 

Plants 

Groundwater 

Contamination Persistence Degradates of Concern 

-- -- √ -- -- -- √ √ x x x 

√ = at least one LOC has been exceeded in previous assessments; “--“ = LOCs have not been exceeded in past assessments; x 

indicates issues raised in previous assessment that may not be directly related to an LOC exceedance. 

The most recent ecological risk assessment conducted for fluroxypyr-MHE was for a new use on 

rice (D396342). The assessment was completed in 2013 for a direct application of fluroxypyrMHE to flooded rice paddies. The maximum single application rate of 0.34 lb a.i./A and a 

maximum annual application rate of 0.56 lb a.i./A was assessed. The assessment concluded that 

acute and chronic risks were less than the EPA’s levels of concern (LOC) for fish, birds, and 

mammals. For aquatic invertebrates, the risk quotient (RQ) for acute risk was below the LOC, 

but the RQ for chronic risk exceeded the LOC. For plants, the RQs for terrestrial plants and algae 

exceeded the LOC for non-endangered species, and the RQs for all terrestrial and aquatic plants 

exceeded the LOC for endangered species. An addendum to this risk assessment (USEPA, 2014) 

estimated that water needs to be held in the paddy for between 1 and 18 days for the total toxic 

residues in water to dissipate to a concentration below the LOCs for algae and aquatic 

invertebrates. There is uncertainty in this estimate because fluroxypyr-MHE hydrolysis is 

accelerated by suspended sediment in the flood water as well as the uncertainty in the aquatic 

invertebrate chronic toxicity data for the primary transformation product, fluroxypyr acid. 
5 

A Section 3 risk assessment conducted for pome fruit and millet1

 determined that use on pome 

fruit at the maximum annual rate of 0.50 lb a.i./A poses an acute risk to saltwater invertebrates, 

whereas use on millet did not. The assessment found that use on both millet and pome fruit poses 

a risk to non-target terrestrial plants, but did not pose a risk to aquatic plants. Two Section 3 risk 

assessments were conducted for use of fluroxypyr-MHE on 1) wheat, barley, and oats,2 2) 

uncultivated areas2, and 3) onions to control voluntary potatoes3. The rates assessed for these 

uses are presented in Table II.1. In these assessments, no risk to non-target organisms were 

predicted except for risk to non-target terrestrial plants. 

2. Drinking Water Exposure Assessments 

Several drinking water assessments (DWA) have been completed for fluroxypyr-MHE including 

for use on onion4, rangeland and permanent grass pastures5, sorghum6 pome fruit and millet7, and 

rice8

. A summary of the estimated drinking water concentrations (EDWCs) reported in these 

assessments are provided in Table II.3. The highest EDWCs were reported for use on rice 

followed by rangeland. EDWCs presented for the rice use are expected to be highly conservative 

as the model used (Tier I Rice Model) to estimate the pesticide concentrations in the water 

column is an instantaneous partitioning model and does not consider transformation. Moreover, 

there are no known drinking water intakes that reside within a rice paddy or immediately 

adjacent to the paddy discharge point. Therefore, some dilution is expected to occur prior to a 

drinking water intake. 

 

 

1

 Angier, J., Jenkins, F., EFED Risk Assessment for the Proposed New Uses of Fluroxypyr on Pome Fruit, Proso 

Millet, and Pearl Millet. October 24, 2007 (DP 336179) 2

 Mastrota, F. N., Effland, W. R., Review for Section 3 Registration of Fluroxypyr Acid (128959) and Fluroxypyr –

MHE (1289685) March 31, 1998 (DPs 236845 and 231718) 3

 Jenkins, F., Abdel-Saheb, I., Ecological Risk Assessment Evaluating Fluroxypyr MHE(PC Code 128968) and 

Fluroxypyr Acid (PC Code 128959) for the Proposed New Use on Onion. May 30, 2006 (DP 314020) 4

 Abdel-saheb, I, Jenkins, F. Section 18 Emergency Exemption Request for Use of Fluroxypyr on Onions in 

Colorado April 14, 2004 (PC 128959; DP 300165) 

Abdel-saheb, I, Drinking Water Assessment for Fluroxypyr on Onion, February 15, 2006, (PC128968; DP314020) 5

 Abdel-saheeb, I, Drinking Water Assessment for Fluroxypyr on Rangeland and Permanent Grass Pasture, August 

13, 2003, (PC 128968; DP292471). 6

 Abdel-saheeb, I, Drinking Water Assessment for Fluroxypyr on Sorghum, March 5, 2003, (PC128968; DP28831) 7

 Angier, J. Drinking Water Assessment for Fluroxypyr New Uses on Pome Fruit and Millet, September 26, 2007, 

(PC 128968; DP336179) 

8

 Parker, R. Drinking Water Assessment for New Use of Fluroxypyr in Rice (Paddies), August 21, 2012, (PC 

128968; DP 396343) 
6 

Table II.3. Summary of Previous Drinking Water Assessments 

Assessment 

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 

Millet 15.4 0.2 0.07 0.03 

Pome Fruit 19.0 0.3 0.09 0.05 

Rangeland 32.9 3.3 1.8 0.05 

Onion, Sorghum 18.2 2.5 1.5 0.8 

Ricec 540 0.06 

a. PCA (0.8) Adjusted PRZM-EXAMS estimated concentrations 

b. SCI-GROW estimated concentrations 

c. Estimate was derived using the Tier I Rice Model 

3. Clean Water Act Programs 

Neither fluroxypyr-MHE (nor fluroxypyr acid) have 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 fluroxypyr acid and fluroxypyr-MHE 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 structures of fluroxypyr-MHE along with the chemical identification and select 

physical-chemical properties are provided in 

Table III.1. While fluroxypyr-MHE is the registered pesticide active ingredient, fluroxypyr acid 

(PC Code: 128959) is rapidly formed in the environment via microbial mediated deesterification 

of fluroxypyr-MHE. Fluroxypyr acid and fluroxypyr-MHE are both highly toxic to 

dicotyledonous plants (MRID 44094902). Two additional major environmental transformation 

products of fluroxypyr-MHE are known: 4-amino-3,5-dichloro-6-fluoro-2-pyridinol (fluroxypyrDCP) and 4-amino-3,5-dichloro-6-fluoro-2-methoxypyridine (fluroxypyr-MP). 

 

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_pollutant_

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 
7 

Both fluroxypyr-MHE and fluroxypyr acid were considered as residues of toxicological concern 

in prior drinking water and ecological risk assessments. Based on available data, fluroxypyr-DCP 

and fluroxypyr-MP have been shown to be much less toxic to terrestrial and aquatic plants. 

In addition to the technical grade products [fluroxypyr-MHE (35935-74, 62719-285, 35935-53 

and 35935-77), there are 68 fluroxypyr-MHE registered end-use products. All except six (Reg. 

No. 42750-204; 62719-577; 62719-586; 66330-385; 66330-387; 71368-87) products contain 

multiple active ingredients (see APPENDIX B) including other herbicides such as 2,4-D, 

dicamba, triclopyr, MCPA, picloram, and clopyralid. It should be noted that there are four 

restricted use products (see APPENDIX B). 

Table III.1. Chemical Identification and Physical Chemical Properties of Fluroxypyr-MHE

Common 

Chemical Name Fluroxypyr-MHE; Fluroxypyr 1-methylheptyl ester; Fluroxypyr-meptyl 

Company Code 128968 

Chemical Name ((4-amino-3,5-dichloro-6-fluoro-2-pyridinyl) oxy) acetic acid 1-methylheptyl ester 

2-Octanyl [(4-amino-3,5-dichloro-6-fluoro-2-pyridinyl)oxy]acetate 

CAS Registry 

Number 81406-37-3 

Chemical 

Structure 

N O

Cl

NH2

Cl

F O

O

4

Molecular 

Formula C15H21Cl2FN2O3

Smiles Notation CCCCCCC(C)OC(=O)COC1=NC(=C(C(=C1Cl)N)Cl)F 

Molecular Mass 

(g/mol) 367.24 

Vapor Pressure 

(25 °C) 1.0 x 10-8 mm Hg at 20 oC (MRID 47600903) 

Water Solubility 0.155 mg/L (pH not specified; MRID 47540703)

Henry’s Law 

Constant 5.75 X 10-7 atm m3

/mol (calculated) 

Log Kow 3.788

pKa -- 

The Agency does not routinely include in its risk assessments an evaluation of active ingredient 

(a.i.) mixtures—either mixtures of multiple active ingredients in product formulations or an 

applicator tank mix. However, if effects data are available for a formulated product containing 

more than one active ingredient, and demonstrate potentially enhanced toxicity to a non-target 

organism from exposure to the multiple active ingredients, these data may be used qualitatively 

or quantitatively for risk assessment purposes. 

B. Mechanism of Action 

Fluroxypyr-MHE is a pyridine-based herbicide with selective toxicity to broadleaf weeds. When 

applied as fluroxypyr-MHE, the molecule rapidly converts to the corresponding acid, fluroxypyr 

acid, in the environment or following plant uptake. Fluroxypyr acid is an auxin analogue that 
8 

elicits auxin-like responses in the plant. Cellular effects include alterations in cell wall elasticity 

and gene expression. Additionally, non-productive tissue growth is often induced, resulting in 

epinasty and phloem disruption, preventing the movement of photosynthates and causing death 

in days to weeks.13 

C. Overview of Pesticide Usage 

Fluroxypyr-MHE is used to control weeds on agricultural sites including barley, corn, millet, 

oats, onion, pastures, rice, sorghum, sod farms and wheat as well as non-agricultural use sites 

such as golf courses, rangeland, right-of-ways, and residential areas. The majority of products 

are formulated as emulsifiable concentrates, soluble concentrate, or water-dispersible concentrate 

that are applied as a liquid spray with aerial or ground broadcast equipment. Three products may 

be applied as a stump or basal bark treatment for control of woody weeds (Reg. No. 62719-477, 

62719-511, and 62719-637). Two products are lawn care products that are formulated as solid 

granules and are applied with a spreader (Reg. No. 961-406 and 288-426). A complete list of all 

current fluroxypyr-MHE uses and how EFED currently understands the uses, including the 

uncertainties for which reasonable conservative assumptions will be made in the absence of 

additional label clarifications, are listed in Table III.2. 

Based on pesticide usage data provided in the screening level usage analysis conducted by the 

Biological and Economic Analysis Division (BEAD), the annual total agricultural usage of 

fluroxypyr-MHE averaged just over a half million pounds. For these same years, the largest 

markets in terms of total pounds active ingredient applied are wheat (400,000 lbs.), barley 

(60,000 lbs.) and pasture (50,000 lbs.). The maximum percent cropped area treated for 

fluroxypyr-MHE are observed for barley (35% maximum percent crop treated) and wheat (25% 

maximum percent crop treated).14

No usage data are available for non-agricultural use sites including golf courses, rights-of-way or 

residential use sites. 

 

13 Thill, D. 2002. Growth regulator herbicides. In Herbicide Action. Purdue University, West Lafayette, IN. 

14 USDA-NASS 2004-2012; private pesticide market research 2004-2012; and California Department of Pesticide 

Regulation 2004-2011. 
9 

Table III.2. Fluroxypyr-MHE Label Summary 

Crop/Site Timing; Application Type Method/ Equipment 

Maximum 

Single 

Application 

Rate by 

Formulation

Maximum 

Application Rate 

Maximum 

Application 

Number 

PHI (days)d 

MRI (days)d 

Geographic Restrictions 

(a.i. lb/A)a (a.e. lb/A)b Per Yearb a.e. 

lb/A 

Per 

CCb,c 

lb a.e/A 

Per 

Year 

Per 

CCc 

Agricultural fallow/ idle land / conservation reserve 

Foliar, fallow, 

weed, 

postemergence, when needed, 

established 

plantings 

Broadcast, 

spot treatment, 

direct spray/ 

Ground 

Aerial 

0.7624 0.5295 0.5295 na ns [1] na ns na Not allowed in Arizona 

Agricultural uncultivated areas 

Weed 

postemergence 

Broadcast, 

spot treatment/ 

Ground 

Aerial 

0.1875 0.1302 ns 

na 

ns 

[26] 

na na 

ns 

[3

] NR 

0.3505 0.2434 0.2434 ns [1] na 

Agricultural/farm structures/buildings and equipment (around) 

Weed 

postemergence

, foliar 

Broadcast, 

spot treatment, 

basil 

treatment, 

stump 

treatment 

direct spray/ 

Ground 

Aerial 

0.7224 0.5017 0.5017 na ns [1] na na na NR 

Barley 

Postemergence, 

foliar 

Broadcast, 

chemigation, 

spot treatment 

spray/ 

Ground 

Aerial 

0.2307 0.1602 ns [4.2] ns [4.2] ns [26] ns [26] 

7 (forage) ns 

Not allowed 

in specific 

Counties in 

New York 

0.5633 0.3912 ns 0.3912 ns ns [1] ns Not allowed in California 
10 

Crop/Site Timing; Application Type Method/ Equipment 

Maximum 

Single 

Application 

Rate by 

Formulation

Maximum 

Application Rate 

Maximum 

Application 

Number 

PHI (days)d 

MRI (days)d 

Geographic Restrictions 

(a.i. lb/A)a (a.e. lb/A)b Per Yearb a.e. 

lb/A 

Per 

CCb,c 

lb a.e/A 

Per 

Year 

Per 

CCc 

na 0.2255 0.3834 na ns [2] na 

Not allowed 

in specific 

Counties in 

New York 

na 0.1808 ns 0.1808 ns ns [1] NR 

Commercial/industrial lawns, golf course turf, recreational area lawns, residential lawns 

Foliar, When 

needed 

Broadcast, 

spot treatment/ 

Ground 

0.4311 0.2994 ns [0.5987] na 2 na ns [0] 21 

Some labels 

do not 

permit use 

in New 

York 

Conifer and tree plantations 

Weed postemergence 

Broadcast, 

Directed Spray 

Spot 

Treatment/ 

Ground 

Aerial

0.7198 0.4999 ns [26] ns ns [26] ns na ns 

Corn 0.2003 0.1391 ns 0.2613 ns 2 ns NR 
11 

Crop/Site Timing; Application Type Method/ Equipment 

Maximum 

Single 

Application 

Rate by 

Formulation

Maximum 

Application Rate 

Maximum 

Application 

Number 

PHI (days)d 

MRI (days)d 

Geographic Restrictions 

(a.i. lb/A)a (a.e. lb/A)b Per Yearb a.e. 

lb/A 

Per 

CCb,c 

lb a.e/A 

Per 

Year 

Per 

CCc 

Preplant, Postemergence 

foliar 

Broadcast, 

Chemigation, 

Spot 

Treatment/ 

Ground 

Aerial 

- 0.1808 ns 0.1808 ns ns [1] 

31 (sweet corn) SC 

Grass forage/fodder/hay 

Weed 

postemergence 

Broadcast/ 

Ground 

Aerial 

0.199 0.1382 0.1382 ns ns [1] ns 

na 

ns 

Applications permitted in Florida only. 

0.2003 0.1391 ns 0.2434 ns ns [2] 14 NR 

Grasses Grown for Seed 

Established 

Plantings, 

Seedling stage 

Broadcast, 

Chemigation, 

Spot 

Treatment/ 

Ground 

Aerial 

- 0.1808 ns 0.1808 ns ns [1] 

na 

0.1881 0.1306 ns 0.2613 ns ns [2] 

Household/domestic dwellings outdoor premises 

weed 

postemergence 

Broadcast, 

spot treatment/ 

Ground 

Aerial 

0.7198 0.4999 ns ns ns ns na ns 

Industrial / construction areas (outdoor) 

weed 

postemergence 

Broadcast, 

spot treatment/ 

Ground 

Aerial 

0.2886 0.2004 ns [0.2004] ns 1 ns na ns NR 
12 

Crop/Site Timing; Application Type Method/ Equipment 

Maximum 

Single 

Application 

Rate by 

Formulation

Maximum 

Application Rate 

Maximum 

Application 

Number 

PHI (days)d 

MRI (days)d 

Geographic Restrictions 

(a.i. lb/A)a (a.e. lb/A)b Per Yearb a.e. 

lb/A 

Per 

CCb,c 

lb a.e/A 

Per 

Year 

Per 

CCc 

Millet spring 

Broadcast, 

spot treatment/ 

Ground 

Aerial 

0.2003 0.1391 

ns 

[see comments] 0.2434 

ns 

[see comments] 2 na 14 NR 

Nonagricultural rights-ofway/fencerows/hedgerows, 

Weed 

postemergence 

Broadcast/ 

Aerial 0.7624 0.5295 0.5295 na ns [1] na 

na 

ns 

Not allowed 

in Arizona 

When needed Broadcast/ Ground 4.3 3.0 ns [78] ns ns [26] ns ns 

Nonagricultural uncultivated areas/soils 

Weed 

postemergence 

Broadcast/ 

Ground 

Aerial 

0.7624 0.5295 0.5295 na ns [1] na na ns Not allowed in Arizona 

Oat 

Postemergence 

foliar 

Broadcast/ 

Ground 

Aerial 

0.5633 0.3912 ns [SC] 0.3912 ns [SC] ns 

7 (forage) ns NR 

0.2307 0.1602 ns ns [4.2] ns ns [26] 

Onion 

Postemergence 

foliar 

Broadcast/ 

Ground 

Aerial 

0.1753 0.1217 ns [0.7302] 0.2434 ns [6] 2 7 10 

Allowed in 

Idaho, 

Texas, Utah, 

Wisconsin 
13 

Crop/Site Timing; Application Type Method/ Equipment 

Maximum 

Single 

Application 

Rate by 

Formulation

Maximum 

Application Rate 

Maximum 

Application 

Number 

PHI (days)d 

MRI (days)d 

Geographic Restrictions 

(a.i. lb/A)a (a.e. lb/A)b Per Yearb a.e. 

lb/A 

Per 

CCb,c 

lb a.e/A 

Per 

Year 

Per 

CCc 

Ornamental lawns and turf 

Postemergence 

foliar 

Broadcast/ 

Ground 

Aerial 

0.7224 0.5017 ns [1.00] na 2 na ns NR 

Granular 

broadcast/Gro

und 

0.5394 0.3748 1.0789 0.7496 2 2 

Ornamental sod farm (turf) 

Postemergence 

foliar 

Broadcast/ 

Ground 

Aerial 

0.7198 0.4999 0.4999 na 1 na na 

ns 

S

C 

Allowed in 

Florida 

Pastures, Rangeland 

Postemergence 

foliar 

Broadcast, 

basal 

treatment, 

directed spray/ 

Ground 

Aerial 

0.7624 0.5295 0.5295 na ns [1] na na ns 

Allowed in 

Florida 

May be 

restricted in 

some other 

locations 

Paved areas (private roads/sidewalks) 

Foliar 

Broadcast, 

Spot 

treatment/ 

Ground 

0.4073 0.2829 [0.3889] ns [0.7777] 0.7777 2 ns [2] na 
14 

Crop/Site Timing; Application Type Method/ Equipment 

Maximum 

Single 

Application 

Rate by 

Formulation

Maximum 

Application Rate 

Maximum 

Application 

Number 

PHI (days)d 

MRI (days)d 

Geographic Restrictions 

(a.i. lb/A)a (a.e. lb/A)b Per Yearb a.e. 

lb/A 

Per 

CCb,c 

lb a.e/A 

Per 

Year 

Per 

CCc 

Pome fruits Weed 

postemergence 

Broadcast/ 

Ground 0.701 0.487 0.487 na 1 na 14 na NR 

Recreational areas 

Weed 

postemergence 

Broadcast/ 

Ground 

Aerial 

0.7224 0.5017 ns [13] na ns [26] na na ns NR 

Rice 

Postemergence 

foliar 

Broadcast/ 

Aerial 0.3807 0.2644 ns [0.4368] 0.4368 2 ns 60 10 

Allowed in 

Arkansas, 

Florida, 

Louisiana, 

Mississippi, 

Missouri, 

Tennessee, 

Texas 

Earthen Roofs Weed 

postemergence 

Broadcast/ 

Ground 0.7149 0.4965 ns [12.9] ns ns [26] ns na ns Allowed in Alabama 

Rye Postemergence 

Broadcast, 

spot treatment/ 

Ground 

Aerial 

0.2605 0.1809 ns [SC] ns [0.1809] ns [SC] 1 60 ns NR 

Sorghum Postemergence 

Broadcast/ 

Ground 

Aerial 

0.2003 0.1391 ns 0.2434 ns 2 45 ns 

Sudangrass Weed postemergence 

Broadcast, 

spot treatment/ 

Ground 

Aerial 

- 0.1808 ns 0.1808 ns ns [1] 45 ns NR 
15 

Crop/Site Timing; Application Type Method/ Equipment 

Maximum 

Single 

Application 

Rate by 

Formulation

Maximum 

Application Rate 

Maximum 

Application 

Number 

PHI (days)d 

MRI (days)d 

Geographic Restrictions 

(a.i. lb/A)a (a.e. lb/A)b Per Yearb a.e. 

lb/A 

Per 

CCb,c 

lb a.e/A 

Per 

Year 

Per 

CCc 

Triticale 

Postemergence 

foliar 

Broadcast/ 

Ground 

Aerial 

0.3505 0.2434 ns [SC] 0.2434 ns [SC] ns [1] 45 ns NR 

Wheat Foliar 

Broadcast/ 

Ground 

Aerial 

0.5633 0.3912 ns [24.2] ns ns [26] ns 

7 (forage) ns NR 

a. Fluroxypyr-MHE is reported in terms of active ingredient (a.i.)b. Reported in terms of fluroxypyr acid or acid equivalents (a.e.)

c. Reported as per crop cycle or per season 

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

No Restrictions (NR); See Comments (SC)[ ] are used to define assumptions that will be made in absences of label clarification. When information was not specified on the label 

applications was assumed to be 26 that corresponds to one application every two weeks.
16 

D. Environmental Fate and Transport 

Environmental fate parameters of fluroxypyr-MHE and fluroxypyr acid are presented in Table 

III.3 and Table III.4. Total toxic residues (fluroxypyr-MHE and fluroxypyr acid) residues are 

also discussed in Table III.4. Half-life values referenced are representative half-life values and 

are consistent with the NAFTA kinetics guidance15 unless otherwise specified. A discussion of 

each environmental fate parameter is provided in APPENDIX C for fluroxypyr-MHE and 

fluroxypyr acid. Kinetic analyses are also provided in APPENDIX C. The proposed fluroxypyrMHE environmental transformation scheme is presented in Figure III.1. Major transformation 

products include: fluroxypyr acid, fluroxypyr-DCP, fluroxypyr-MP, and carbon dioxide. The 

maximum observed concentrations of each of the environmental transformation products are 

provided in APPENDIX C as well as a full list of chemical code names and synonyms. 

In summary, laboratory data suggest that fluroxypyr-MHE, a methylheptyl ester, undergoes rapid 

deesterification to fluroxypyr acid following application. Aerobic soil half-life values are less 

than one day (MRID 42137317) for fluroxypyr-MHE while the aerobic aquatic half-life is 

approximately one day (MRID 44080345) under basic conditions (pH 8.2). Hydrolysis of 

fluroxypyr-MHE is pH dependent. Under basic conditions (pH 9) hydrolysis is rapid with a halflife of approximately 3 days while under acid conditions fluroxypyr-MHE is stable (half-life 454 

days). Increased hydrolysis of the ester in aquatic soil systems as compared to sterile aqueous 

solutions is thought to be due to microbial mediation (i.e., enzymatic catalysis). This hypothesis 

is supported in the open literature.16 Mobility data for fluroxypyr-MHE are not considered 

reliable due to short incubation period (MRID 42137319); however, it is not expected to be 

mobile. Fluroxypyr-MHE is not expected to be volatile (MRID 47600903) and is not expected to 

bioconcentrate. BCF values for fluroxypyr-MHE and total 14C activity were 42 (uncorrected; 26 

corrected value) and 167 for whole fish, respectively [MRIDs 44080348 and 44605403 (response 

to review of MRID 44080348)]. 

While fluroxypyr-MHE is subject to both abiotic (aqueous photolysis and alkaline hydrolysis) 

and biotic (metabolism) degradation, the corresponding acid, fluroxypyr acid, is expected to be 

more persistent and is mobile, as are some of the other structurally similar transformation 

products (fluroxypyr-DCP and fluroxypyr-MP). In the environment, fluroxypyr acid is expected 

to be present as the anion (estimated pKa 2.94). Aerobic soil metabolism half-life values for 

fluroxypyr acid range from 8.2 to 30 days while the aerobic aquatic half-life is approximately 3 

days. Koc values range from 51 to 81 mL/goc for fluroxypyr acid (MRID 42137319). 

Field data (MRIDs 44896702, 45204201, 45204202, and 44080347) indicate that combined 

residues (summation of fluroxypyr-MHE and fluroxypyr acid) half-life values range from 5 to 55 

days. The terrestrial field dissipation studies also indicate that fluroxypyr-MHE residues (i.e. 

fluroxypyr acid), may leach through the soil profile. 

 

15 Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media Health Canada, U.S. 

Environmental Protection Agency, December 21, 2012. 16 Lehmann, R. G., Miller, J. R., Weed Research, 1989, 29, 385-389. 
17 

Table III.3. Chemical Properties and Environmental Fate Parameters of Fluroxypyr-MHE 

Study 

System Name/ 

Characteristics 

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Halflife Value 

--Value Used to Derive 

Model Input Values 

(days)b-- 

Guideline/ 

Source/ 

Classification 

DT50 (days) DT90 (days) 

Hydrolysis 

pH 5 Not observed Stable 835.2010 

MRID 

40244539 

Acceptable 

pH 7 454 1510 t1/2=454 pH 9 3.1 10.3 t1/2=3.1 

Aqueous 

Photolysis 

natural water Not Determinable Assumed Stable 835.2240 

MRID 

44080342 

Acceptable 

Due to the rapi(faster than irrphototransformcould not be apdissipation. 

0.01 M sodium phosphate 

pH 5 128 424 Stable 

Definitive deteproducts was nindividual prodapplied radioac

Soil 

Photolysis Clay loam Not Determinable Assumed Stable 

835.2410 

MRID 

44080343 

Acceptable 

Due to the rapi(equal to the irtransformation not be approprdissipation. 

Aerobic Soil 

Metabolism 

“M172” Illinois Catlin Silt loam (2.2% OC, pH 5.9, 26 ± 1 oC) 

0.3 (SFO) 1.0 (SFO) t1/2=0.3 835.4100 

MRID 

42137317 

Acceptable 

42730001 

(response 

from 

registrant) 

Deesterificatiofluroxypyr-MHseparate storag44080355) wanot specified) characterizatiodays for fluroxup to a year at 

“M174” California Hanford Sandy loam (0.2% OC, pH 7.5, 26 ± 1 oC) 

0.3 (SFO) 0.9 (SFO) t1/2=0.3 

“M177” North Dakota Barnes Loam (3.1% OC, pH 6.8, 26 ± 1 oC 

0.1 (IORE) 1.5 (IORE) TIORE=0.4

“M192” Mississippi Mhoon Silty clay (1.3% OC, pH 7.0, 26 ± 1 oC) 

0.3 (IORE) 3.7 (IORE) TIORE=1.1

Anaerobic 

Soil 

Metabolism 

No data are available 835.4200 
18 

Study 

System Name/ 

Characteristics 

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Halflife Value 

--Value Used to Derive 

Model Input Values 

(days)b-- 

Guideline/ 

Source/ 

Classification 

DT50 (days) DT90 (days) 

Aerobic 

Aquatic 

Metabolism 

North Dakota silt loam 

sediment with natural water 

(25 oC, pH 8.2) 

1.0 (SFO) 3.4 (SFO) t1/2=1.0 

835.4300 

MRID 

44080345 

Acceptable 

Unextracted rethe applied radmonths posttreData are only athe pH of the twas shown to rconditions (pH the applied rad

Anaerobic 

Aquatic 

Metabolism 

North Dakota silt loam 

sediment flooded with 

natural water 

(25 oC, pH 8.2) 

1.3 (SFO) 4.2 (SFO) t1/2=1.3

834.4400 

MRID 

44080344 

reclassified to 

supplemental 

Sample frequeassess the tranunder anaerobiMHE was only radioactivity aweek). Data arand the pH of tMHE was showbasic conditionwere 28.2% of months posttredeficiencies, thMHE rapidly dconditions test

Terrestrial 

Field 

Dissipation 

Missouri, Putnam silty clay 

loam, pH 7.5 Not determinable t1/2=24.8 

835.6100 

MRID 

44080347 

Supplemental 

Data for fluroxtabular form in application ratverified. Storagfor the soils uswere stored froup to 693 days(MRID 440803(temperature n(soil characteri422 days for fldemonstrated tsoil frozen up remained and aConcurrent ana

North Dakota, gardena 

sandy clay loam, pH 6.2 Not determinable t1/2=36.3

Washington, quincy loamy 

sand, pH 6.8 Not determinable t1/2=13.2
19 

Study 

System Name/ 

Characteristics 

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Halflife Value 

--Value Used to Derive 

Model Input Values 

(days)b-- 

Guideline/ 

Source/ 

Classification 

DT50 (days) DT90 (days) 

fluroxypyr-MHseparately werReported half-half-life values residues of fluracid. Because report for flurocould not be ve

Aquatic Field 

Dissipation 

Texas, cropped plot; 

pH 6.4, 0.7% OM 

Values not calculated 

MRID 

48581303 

Scientifically 

valid; 

however, 

study is under 

review 

Kinetic evaluafluroxypyr-MHrapid hydrolysfluroxypyr acidbe conducted freview. 

Texas, non-cropped plot; 

pH 6.1, 0.9% OM 

California, cropped plot; pH 

7.9, 1.2% OM 

California, non-cropped 

plot; pH 7.8, 1.6% OM 

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

overall DT50 and DT90 are reported when available. The equations can be found in the document, Standard Operating Procedure for Calculate Representative Half-life Values and Characterize Pesticide Degradation, U.S. Environmental Protection Agency, November 

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

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

Agency, December 21, 2012. The same model used to estimate the value used to derive a model input, is used to describe the DT50 an

c. Reported value is an extrapolated value determined by the study author and is based on the assumption that continuation of the apparen

beyond the scope of the observed data. Due to the stability of fluroxypyr-MHE to aquatic photolysis and the minimal impact of aquatic the environment updated kinetic analysis were not completed. 
20 

Table III.4. Chemical Properties and Environmental Fate Parameters of Fluroxypyr 

Study 

System Name/ 

Characteristics 

Kinetic Model Fitteda Value 

and Unit (Fitting Equation)

Representative Halflife Value 

--Value Used to 

Derive Model Input 

Values (days)b-- 

Guideline/ 

Source/ 

Classification 

DT50 (days) DT90 (days) 

Hydrolysis 

pH 5 

Not observed Stable 

835.2010 

MRID 

40244539 

Acceptable 

Total toxic residhydrolysis. 

pH 7 pH 9 

Aqueous 

Photolysis 

natural water Not determinable 

Stable 

835.2240 

MRID 

44080342 

Acceptable 

0.01 M sodium phosphate 

pH 5 558 1853 

Definitive deterproducts was noproducts made uradioactivity. Total toxic residaquatic photoly

Soil Photolysis Clay loam Not determinable Stable 

835.2410 

MRID 

44080343 

Acceptable 

Due to the rapid (equal to the irrphototransformcould not be appdissipation unde

Aerobic Soil 

Metabolism 

“M172” Illinois Catlin Silt 

loam (2.2% OC, pH 5.9) 13.5 (SFO) 44.9 (SFO) t1/2=13.5 

835.4100 

MRID 

42137317 

Acceptable 

Within one dayhydrolyzed to fldone using data Total residues (values ranged fr

“M174” California 

Hanford Sandy loam 

(0.2% OC, pH 7.5) 

30 (SFO) 99.7 (SFO) t1/2=30 

“M177” North Dakota 

Barnes Loam (3.1% OC, 

pH 6.8) 

15.7 (SFO) 52.3 (SFO) t1/2=15.7

“M192” Mississippi 

Mhoon Silty clay (1.3% 

OC, pH 7.0) 

8.2 (SFO) 27.3 (SFO) t1/2=8.2

Anaerobic Soil 

Metabolism No data are available 835.4200 
21 

Aerobic 

Aquatic 

Metabolism 

North Dakota silt loam 

sediment with natural 

water 

(25 oC, pH 8.2) 

3.2 (SFO) 10.5 (SFO) t1/2=3.2

835.4300 

MRID 

44080345 

Supplemental 

Half-life value cweek 2 - 12 moone test system and fluroxypyr hydrolysis unde

Anaerobic 

Aquatic 

Metabolism 

North Dakota silt loam 

sediment flooded with 

natural water 

(25 oC, pH 8.2) 

2.7 9.1 t1/2=2.7

834.4400 

MRID 

44080344 

reclassified to 

supplemental 

Half-life value cweek 2 - 12 mo12.1% and 27.8weeks and 12 mData are only avpH of the test syshown to be staconditions (pH A total residues life value of 4.9 

Terrestrial 

Field 

Dissipation 

See Table III.4 Reported half-li

residues of fluro

Aquatic Field 

Dissipation 

Texas, cropped plot; 

pH 6.4, 0.7% OM t1/2=14.7 (study author reported value) MRID 48581303 

Scientifically 

valid; 

however, 

study is under 

review

Reported half-lirecoveries from reported by the updated if needthese results the pH. 

Texas, non-cropped plot; 

pH 6.1, 0.9% OM t1/2=16.7 (study author reported value)

California, cropped plot; 

pH 7.9, 1.2% OM t1/2=4.0 (study author reported value)

California, non-cropped 

plot; pH 7.8, 1.6% OM t1/2=4.6 (study author reported value)

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

overall DT50 and DT90 are reported when available. The equations can be found in the document, Standard Operating Procedure for Calculate Representative Half-life Values and Characterize Pesticide Degradation, U.S. Environmental Protection Agency, November 

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

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

Agency, December 21, 2012. The same model used to estimate the value used to derive a model input, is used to describe the DT50 an

c. Registrant-calculated half-life as the sum of the fluroxypyr-MHE plus fluroxypyr (acid). 
22 

N O

Cl

NH2

Cl

F O

O

4 N O

Cl

NH2

Cl

F OH

O

N OH

Cl

NH2

Cl

F

N OH

NH2

Cl

F N OH

Cl

NH2

F

N OCH3

Cl

NH2

Cl

F

Fluroxypyr-MHE Fluroxypyr

Fluroxypyr-DCP Fluroxypyr-MP

Figure III.1. Fluroxypyr-MHE Environmental Transformation Scheme 

Environmental chemistry methods along with an independent laboratory validation study report 

the limit of quantification (LOQ) of fluroxypyr acid, fluroxypyr-DCP and fluroxypyr-MP in soil 

[0.01 ppm (0.01 mg/kg; 10 μg/kg; 0.02 lb/A17) (MRIDs 44080346 (ECM; GRM 93.03), 

44896703 (ECM; GRM 98.04 superseding GRM 93.03) and 45084601 (ILV; GRM 98.04))]. A 

limit of detection (LOD) was not established in these studies; therefore, the LOD is assumed to 

be equal to the LOQ. 

A recently submitted aquatic field dissipation study (MRID 48581303; GRM 08.06) reported a 

LOQ of 10 μg/kg and an LOD of 3 μg/kg (0.007 lb/A) for fluroxypyr-MHE, fluroxypyr acid, 

fluroxypyr-DCP and fluroxypyr-MP in soil. No independent laboratory validation is available for 

this method (GRM 08.06). The analytical method available for fluroxypyr-MHE, fluroxypyr 

acid, fluroxypyr-DCP and fluroxypyr-MP in water reports a LOQ of 0.05 μg/L with an LOD of 

0.015 μg/L (MRID 48581303); however, an independent laboratory validation has not been 

submitted for this method. An alternative method (MRID 45824101; GRM 00.21) is available 

that reports a LOQ of 5 μg/L. This method has also not been independently verified. 

A non-guideline study was submitted to assess the fate of fluroxypyr-MHE and fluroxypyr acid 

in compost (MRID 45833601). This study suggests that fluroxypyr acid residues should not pose 

 

17 LOQ = 0.01 mg/kg 

0.02 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)] 

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

 mg/kg / 2.25 x 106 kg (s)/ha 

= 2.25 x 10-2 kg/ha = LOQ = 0.02 lb/A
23 

a compost concern (fluroxypyr acid half-life is approximately 5 days); however, some major 

study deficiencies were identified. Without additional information to support the methods used 

and how the study was conducted, another compost study is warranted (additional discussion 

provided in APPENDIX C).

IV. RECEPTORS

This section describes the aquatic and terrestrial taxonomic groups that represent receptors in the 

ecological risk assessment for the use of fluroxypyr-MHE, and the toxicological endpoints 

selected to characterize acute and chronic effects to these taxonomic groups. In general, the 

endpoints selected are the most sensitive (i.e., lowest) value measured among all test species in 

the taxa obtained from acceptable studies. In cases when an acceptable study is not available or 

indicates less sensitivity than does a supplemental study, results from a supplemental study may 

be used. A complete listing of all toxicological results from submitted ecotoxicological studies 

and relevant open literature studies is provided in APPENDIX D. 

Because fluroxypyr-MHE rapidly transforms into fluroxypyr acid, toxicity endpoints for both 

fluroxypyr-MHE and fluroxypyr acid are provided and will be considered in future risk 

assessments. When available, ecotoxicity data for the environmental transformation products of 

fluroxypyr acid, fluroxypyr-DCP and fluroxypyr-MP, are also provided. 

1. Effects to Aquatic Organisms 

Table IV.1 and Table IV.2 summarizes the toxicity endpoints for the most sensitive species, by 

taxa, for fluroxypyr-MHE and fluroxypyr acid, respectively. The data for fluroxypyr-MHE are 

presented as both active ingredient (a.i.) and the acid equivalent (a.e.). 

Based on acute toxicity, the aquatic animal species most sensitive to fluroxypyr-MHE was the 

Eastern oyster (Crassostrea virginica). In a 96-hr shell deposition study (MRID 44080310), a 

significant decrease in shell deposition was observed at concentrations of 50 μg a.i./L and 

greater. The EC50 was 68 μg a.i./L, which classifies fluroxypyr-MHE as highly toxic to the 

oyster on an acute exposure basis. 

In all other taxa of aquatic animals, the acute toxicity classification could not be determined 

because of the limited solubility of fluroxypyr-MHE and lack of mortality observed at the 

solubility limit of the compound. When tested at a concentration near the solubility limit, no 

mortality or sublethal effects were observed in the bluegill sunfish (Lepomis macrochirus, MRID 

44080307), rainbow trout (Oncorhynchus mykiss, MRIDs 40244522 and 42137307), the golden 

orfe (Leucescus idus, MRID 40244523), the Atlantic silverside (Menidia menidia, MRID 

42137309), the sheepshead minnow (Cyprinodon variegatus, MRID 44080308), or the grass 

shrimp (Palaemonetes pugio, MRID 44080313). Tests with the water flea (Daphnia magna) also 

found no mortality when tested at the solubility limit (MRIDs 40244520 and 42137308). The 

sublethal effect of occasional immobility was observed in one of these two studies (MRID 

42137308); however, this effect appears to be from physical impairment of movement by large 

clumps of undissolved test material, and therefore were not indicative of toxicity of fluroxypyrMHE. While the toxicity endpoint could not be determined, these tests nevertheless indicate that 
24 

fluroxypyr-MHE is not acutely toxic to the test organism at concentrations up to the solubility 

limit. 

Therefore, prior to transformation to fluroxypyr acid, residues of fluroxypyr-MHE that may be 

present in natural water are expected to have minimal toxicity on an acute exposure basis to 

aquatic animals except for mollusks, to which fluroxypyr-MHE is highly toxic. Information on 

the chronic toxicity of fluroxypyr-MHE is limited, but based on the results of a supplemental 

life-cycle study with Daphnia magna, chronic toxicity appears to be greater than acute toxicity. 

Adverse effects on the reproduction of Daphnia magna were observed at concentrations as low 

as 0.109 mg a.i./L (MRID 44080314). 

Testing with aquatic plants and algae found that the freshwater diatom (Navicula pelliculosa) is 

the most sensitive species, with an EC50 of 56 μg/L and toxic effects observed at test 

concentrations as low as 15 μg/L (the lowest concentration tested) (MRIDs 44080339 and 

44527201). For assessing risk to vascular aquatic plants, reliance on results from testing with 

duckweed would not be appropriate since duckweed is a monocotyledonous plant, and the 

toxicity of auxin growth regulators like fluroxypyr-MHE is selective to dicotyledonous plants 

(Mohr et al., 2013, Maltby et al., 2010). Mohr et al (2013) report results of tests of the effects of 

fluroxypyr-MHE on water milfoil (Myriophyllum spicatum), an aquatic dicotyledonous 

macrophyte that has been shown to be more sensitive to fluroxypyr-MHE than is duckweed. The 

paper reports results for a 14-day laboratory study without sediment, which is similar to the draft 

OECD guideline ENV/JM/TG(2014)5, as well as a 16-day and a 30-d microcosm studies. A 

review of this paper will be conducted to determine which of these results (if any) are suitable 

for quantitative or qualitative use in risk assessment. A preliminary review of this paper indicates 

that all three of the studies are scientifically sound and are suitable for at least qualitative use in 

risk assessment. 

Table IV.1. Most Sensitive Endpoints from Aquatic Toxicity Studies for Fluroxypyr-MHE 

Taxonomic 

Group 

Study 

Type 

Surrogate 

Species Toxicity Value 

Acute 

Toxicity 

Classification 

Source (Study 

Classification) 

Freshwater fish1

Acute 

Bluegill Sunfish 

(Lepomis 

macrochirus) 

LC50 

> 0.63 mg a.i./L2

(> 0.44 mg a.e./L) 

Not 

determined 

44080307 

(Acceptable) 

Chronic -- Not Available -- -- 

Freshwater 

invertebrates 

Acute Water Flea 

(Daphnia magna) 

EC50 

> 0.6 mg a.i./L2 

(>0.4 mg a.e./L) 

Not 

determined 

40244520 

(Acceptable) 

Chronic Water Flea 

NOAEC = 

60.5 μg a.i./L 

(42.0 μg a.e./L) 

LOAEC = 

109 μg a.i./L 

(75.7 μg a.e./L) 

Endpoint: Number of 

young per female 

-- 44080314 

(Supplemental)3 
25 

Taxonomic 

Group 

Study 

Type 

Surrogate 

Species Toxicity Value 

Acute 

Toxicity 

Classification 

Source (Study 

Classification) 

Estuarine/marine 

fish 

Acute 

Sheepshead 

Minnow 

(Cyprinodon 

variegatus) 

LC50 

> 0.087 mg a.i./L 

(> 0.060 mg a.e./L) 

Not 

determined 

44080308 

(Acceptable) 

Chronic -- Not Available -- -- 

Estuarine/marine 

crustaceans Acute 

Grass shrimp 

(Palaemonetes 

pugio)

EC50 

> 0.13 mg a.i./L 

(> 0.090 mg a.e./L) 

Not 

determined 

44080313 

(Acceptable) 

Estuarine/marine 

mollusks 

Acute 

Shell 

Deposition 

Eastern oyster, 

(Crassostrea 

virginica) 

EC50 = 

0.068 mg a.i./L 

(0.047 mg a.e./L) 

Highly toxic 44080310 

(Supplemental)4 

Aquatic plants 

and algae 

Vascular 

Duckweed 

(Lemna gibba) 

NOAEC = 

0.44 mg a.i./L 

(0.31 mg a.e./L) 

IC50 = 

1.4 mg a.i./L 

(0.97 mg a.e./L) 

-- 44744001 

(Supplemental)5 

Water milfoil 

(Myriophyllum 

spicatum) 

14-day IC50

(laboratory study): 

0.42 mg a.i./L 

(0.29 mg a.e./L) 

16-day IC50

(Microcosm study): 

0.12 mg a.i./L 

(0.083 mg a.e./L) 

30-day IC50

(Microcosm study): 

0.09 mg a.i./L 

(0.06 mg a.e./L) 

-- 

Mohr et al., 

2013 

(in review) 

Nonvascular 

Freshwater 

Diatom 

(Navicula 

pelliculosa) 

NOAEC 

< 15 μg a.i./L 

< 10 μg a.e./L 

IC50 = 

56 μg a.i./L 

(39 μg a.e./L) 

-- 

44080339 

44527201 

(Supplemental)6 

1 Freshwater fish may be surrogates for aquatic-phase amphibians. 2 The LC50 is greater than the solubility limit of fluroxypyr MHE. 3 This study is supplemental because insoluble test material was present in the test solution. 4 This study is supplemental because it was conducted at nominal concentrations which far exceeded the solubility of fluroxypyr MHE, 

and the three highest test solutions were cloudy throughout the test. The oysters apparently were exposed to suspended undissolved test 

material as well as test material within solution, and this exposure to undissolved test material may have contributed to the toxicity observed 

in this study.

5 This study is supplemental because test conditions (temperature, light intensity, and pH) were slightly outside the ranges 

recommended by the test guideline. 

6 This study is supplemental because the solvent control solutions were contaminated with the test solution and the failed to 

establish an NOAEC.
26 

Table IV.2 summarizes the toxicity endpoints used to assess the risk of fluroxypyr acid to aquatic 

organisms. The data indicate that fluroxypyr acid is much less toxic to aquatic animals than 

fluroxypyr-MHE. The most sensitive species to fluroxypyr acid is the bluegill sunfish, for which 

the acute toxicity is classified as slightly toxic (LC50 = 14.3 mg/L). Fluroxypyr acid is classified 

as slightly toxic to saltwater fish, practically nontoxic to freshwater invertebrates, and slightly 

toxic to saltwater mollusks. Chronic toxicity data are only available for a freshwater fish (the 

fathead minnow). The NOAEC for freshwater fish is 5.9 mg a.i./L based on reductions in length 

and wet weight. 

For fluroxypyr acid, valid toxicity data are available for one species of nonvascular plant, the 

freshwater algal Scenedesmus pannonicus. The acute 96-hr toxicity was greater than 100 mg 

a.i./L, indicating that the species is relatively insensitive to fluroxypyr acid. However, little 

information on toxicity to nonvascular plants can be drawn from this one study because it is 

supplemental and used a non-preferred species. Based on the results of this study conducted with 

fluroxypyr-MHE it is assumed that algae is relatively insensitive to fluroxypyr (either ester or 

acid) compared to freshwater and saltwater diatoms. 

Table IV.2. Most Sensitive Endpoints from Aquatic Toxicity Studies for Fluroxypyr Acid 

Taxonomic 

Group 

Study 

Type Surrogate Species 

Toxicity Value 

(in terms of measured 

active ingredient) 

Acute 

Toxicity 

Classification 

Source (Study 

Classification) 

Freshwater fish1

Acute Bluegill Sunfish LC50 = 14.3 mg a.i./L Slightly toxic 42137306 

(Acceptable) 

Chronic 

(Early Life 

Stage) 

Fathead minnow 

(Pimephales 

promelas) 

NOAEC = 3.0 mg a.i./L 

LOAEC = 5.9 mg a.i./L 

Endpoints: Length and 

wet weight 

-- 48559401 

(Acceptable) 

Saltwater fish 

Acute Atlantic Silverside LC50 = 40 mg a.i./L Slightly toxic 44080309 

(Acceptable) 

Chronic -- Not available -- -- 

Freshwater 

invertebrates 

Acute Water Flea EC50 > 100 mg a.i./L Practically 

nontoxic 

40244521 

40244524 

(Acceptable) 

Chronic Water Flea Not available -- 

Saltwater 

invertebrates 

Acute 

Shell 

Deposition 

Eastern oyster 

(Crassostrea 

virginica) LC50 = 51 mg a.i./L Slightly toxic 44080311 

(Acceptable) 

Chronic -- Not available -- -- 
27 

Taxonomic 

Group 

Study 

Type Surrogate Species 

Toxicity Value 

(in terms of measured 

active ingredient) 

Acute 

Toxicity 

Classification 

Source (Study 

Classification) 

Aquatic plants 

and algae2

Vascular -- Not available -- -- 

Nonvascular 

Freshwater Algae 

(Scenedesmus 

pannonicus) 

NOAEC = 100 mg a.i./L 

EC50 > 100 mg a.i./L -- 40244526 

(Supplemental)3 

1 Freshwater fish may be surrogates for aquatic-phase amphibians. 2 Toxicity endpoints presented, i.e., NOAEC or EC50, are the only ones available from the study. 3 The test species is not an acceptable in US guidelines, and cell counts were not determined.

2. Effects to Terrestrial Organisms 

The LOD of fluroxypyr-MHE and fluroxypyr acid residues in soil (3 μg/kg) are not sufficient for 

identifying the presence or absence of fluroxypyr-MHE at levels equal to the toxicological 

endpoints for terrestrial plants. Therefore, it is possible that effects could occur following the 

application of fluroxypyr-MHE without being able to detect the presence of the chemical. The 

LOD of fluroxypyr-MHE residues in water (0.05 μg/L) is sufficient based on data currently 

available. If more sensitive aquatic species are identified a new method may be needed in order 

to insure residues of levels of toxicological concern can be detected. 

Table IV.3 summarizes the toxicity endpoints used to assess the risk of fluroxypyr-MHE to 

terrestrial organisms. The data indicates that fluroxypyr-MHE has low toxicity to terrestrial 

animals. Acute and sub-acute toxicity data categorizes fluroxypyr-MHE as practically nontoxic 

to birds and mammals. A honey bee contact toxicity study shows that fluroxypyr-MHE is 

practically nontoxic to bees (MRID 421373-14). A honey bee acute oral toxicity study has not 

been submitted to EPA, but the PPDB database of the University of Herfordshire18, as well as 

material safety data sheets for products containing fluroxypyr-MHE19, suggest low toxicity to the 

honey bee via oral exposure (LD50 > 100 μg/bee). An avian reproduction study with the mallard 

found that fluroxypyr-MHE reduces egg production at dietary concentrations as low as 500 mg 

a.i./kg-diet, establishing the NOAEL at 250 mg a.i./kg-diet. The selected NOAEC for chronic 

toxicity to mammals based on frank sublethal effects is 300 mg a.i./kg-bw based on mortality, 

decreased body weight, and decreased food consumption (MRID 44094901). 

Phytotoxicity testing with fluroxypyr-MHE showed that the most sensitive species were cotton 

and cucumber. The IC25 was 0.075 lb a.i./A for effects to cucumber in the seedling emergence 

study, and 0.0012 lb a.i./A for effects to cotton in the vegetative vigor study. The lowest NOAEC 

was 0.0010 lb a.i./A for effects to cotton in the vegetative vigor study. 

The LOD of fluroxypyr-MHE and fluroxypyr acid residues in soil (3 μg/kg) are not sufficient for 

identifying the presence or absence of fluroxypyr-MHE at levels equal to the toxicological 

 

18 Pesticide Property Database (PPDB). University of Herfordshire. Developed by the 

Agriculture & Environment Research Unit (AERU), University of Hertfordshire, 2006-2013. 

, available at http://sitem.herts.ac.uk/aeru/ppdb/en/index.htm. 19 Acute oral toxicity data for the honey bee is provided in the Material Safety Data Sheet for several formulated 

products, for example Widematch®, available at http://ws.greenbook.net/Docs/Msds/M75292.pdf. 
28 

endpoints for terrestrial plants. Therefore, it is possible that effects could occur following the 

application of fluroxypyr-MHE without being able to detect the presence of the chemical. The 

LOD of fluroxypyr-MHE residues in water (0.05 μg/L) is sufficient based on data currently 

available. If more sensitive aquatic species are identified a new method may be needed in order 

to insure residues of levels of toxicological concern can be detected. 

Table IV.3. Most Sensitive Endpoints from Terrestrial Toxicity Studies for FluroxypyrMHE 

Taxonomic 

Group Study Type Surrogate Species 

Toxicity Value 

(units in terms of 

active ingredient and 

acid equivalence) 

Acute 

Toxicity 

Classification 

Source (Study 

Classification) 

Birds1

Acute 

Bobwhite 

(Colinus virginianus) 

and Mallard 

(Anas platyrhynchos) 

LD50 

>2000 mg a.i./kg-bw 

(>1389 mg a.e./kg-bw) 

No mortality or signs of 

toxicity were observed. 

Practically 

nontoxic 

40244546 

40244516 

(Acceptable) 

Sub-acute 

dietary Bobwhite 

LC50 

>5000 mg a.i./kg-diet 

(>3470 mg a.i./kg-diet) 

No mortality or signs of 

toxicity were observed. 

Practically 

nontoxic 

40244517 

(Acceptable) 

Chronic Mallard 

NOAEC 

250 mg a.i./kg-diet 

(174 mg a.e./kg-diet) 

LOAEC 

500 mg a.i./kg-diet 

(347 mg a.e./kg-diet) 

Endpoint: egg 

production 

-- 42137304 

(Acceptable) 

Mammals 

Acute Oral Laboratory rat 

(Rattus norvegicus) 

LD50 

3160 mg product/kgbw 

(809 mg a.i./kg-bw or 

562 mg a.e./kg-bw) 

Practically 

nontoxic 44080329 

Acute 

Dermal Laboratory rat 

LD50 

>5000 mg a.i./kg-bw 

(>3470 mg a.e./kg-bw) 

Toxicity 

Category IV 47934606 

Acute 

Inhalation Laboratory rat 

LC50 

>2.09 mg a.i./L 

(>1.45 mg a.e./L) 

Toxicity 

Category IV 47888703 
29 

Taxonomic 

Group Study Type Surrogate Species 

Toxicity Value 

(units in terms of 

active ingredient and 

acid equivalence) 

Acute 

Toxicity 

Classification 

Source (Study 

Classification) 

Chronic Laboratory rat 

NOAEL 

300 mg a.i./kg-bw/day 

(6000 mg a.i./kg-diet or 

4170 mg a.e./kg-diet) 

LOAEL 

600 mg a.i./kg-bw/day 

(12,000 mg a.e./kg-diet 

or 

8330 mg a.e./kg-diet) 

Endpoint: Pup survival 

and weight gain 

-- 44094901 

Insects Acute 

contact 

Honey bee 

(Apis mellifera L.) 

LD50 

>25 μg a.i./bee 

(>17 μg a.e./bee) 

(mortality < 10% in all 

treatment groups) 

Practically 

nontoxic 42137314 

Terrestrial 

plants 

Seedling 

Emergence2 

Dicots: 

Cucumber 

NOAEC 

0.031 lb a.i./A 

(0.022 lb a.e./A) 

EC25 

0.075 lb a.i./A 

(0.052 lb a.e./A) 

Endpoint affected: 

Visual signs of 

phytotoxicity 

-- 44080335 

(Acceptable) 

Monocots: 

Ryegrass 

NOAEC 

0.124 lb a.i./A 

(0.0861 lb a.e./A) 

EC25 

>0.25 lb a.i./A 

(>0.17 lb a.e./A) 

Endpoint affected: 

Visual signs of 

phytotoxicity 

-- 44080335 

(Acceptable) 

Terrestrial 

plants 

Vegetative 

Vigor2

Dicots:

Cotton 

NOAEC 

0.0010 lb a.i./A 

0.00069 lb a.e./A 

EC25 

0.0012 lb a.i./A 

0.00083 lb a.e./A 

Endpoint affected: 

Visual signs of 

phytotoxicity 

-- 44080335 

(Acceptable) 
30 

Taxonomic 

Group Study Type Surrogate Species 

Toxicity Value 

(units in terms of 

active ingredient and 

acid equivalence) 

Acute 

Toxicity 

Classification 

Source (Study 

Classification) 

Monocots:

Onion 

NOAEC 

0.062 lb a.i./A 

0.043 lb a.e./A 

EC25 

0.124 lb a.i./A 

0.0861 lb a.e./A 

Endpoint affected: 

Visual signs of 

phytotoxicity 

-- 44080335 

(Acceptable) 

1 Birds represent surrogates for terrestrial-phase amphibians and reptiles. 2 The test was conducted with an unidentified end-use product containing 26.9% fluroxypyr-MHE.

Table IV.4 summarizes the toxicity endpoints used to assess the risk of fluroxypyr acid to 

terrestrial animals and plants. As for fluroxypyr-MHE, acute toxicity testing classifies fluroxypyr 

acid as practically nontoxic to birds, mammals, and bees. No chronic avian toxicity data are 

available for fluroxypyr acid. A supplemental vegetative vigor study indicates that fluroxypyr 

acid shows similar or greater toxicity to dicotyledonous plants than that of fluroxypyr-MHE, 

while having relatively low toxicity to monocotyledonous plants. Due to numerous guideline 

deviations, the EC25 results obtained from this study are uncertain and should not be used for risk 

assessment (see DERs for MRID 44094902). 

The vegetative vigor study for fluroxypyr acid also provides limited data on the phytotoxicity of 

fluroxypyr-MP and fluroxypyr-DCP (MRID 44094902). Seedling emergence and vegetative 

vigor using four dicots (cotton, radish, soybean, and sunflower) and three monocots (corn, wheat, 

and bentgrass) were tested for these transformation products. These studies are classified as 

invalid as tier 2 studies but supplemental for tier 1. These studies demonstrate that exposure to 

fluroxypyr-MP and fluroxypyr-DCP at rates up to 0.50 lb a.i./A are not toxic to non-target plants 

(NOAEL = 0.50 lb a.i./A for all test species). 

Table IV.4. Most Sensitive Endpoints from Terrestrial Toxicity Studies for Fluroxypyr 

Acid 

Taxonomic 

Group Study Type Surrogate Species Toxicity Value 

Acute 

Toxicity 

Classification 

Source 

(MRID) 

Birds 

Acute Bobwhite and 

mallard 

LD50 > 2000 mg a.e./kgbw 

Practically 

nontoxic 

40244514 

40244515 

(Acceptable) 

Sub-acute 

dietary Bobwhite LC50 > 5000 mg a.e./kgdiet 

Practically 

nontoxic 

40244547 

(Acceptable) 

Chronic Not available 
31 

Taxonomic 

Group Study Type Surrogate Species Toxicity Value 

Acute 

Toxicity 

Classification 

Source 

(MRID) 

Mammals 

Acute Laboratory Rat 

LD50 = 2408 mg a.e./kgbw 

(males) 

LD50 > 3000 mg a.e./kgbw 

(males) 

Practically 

nontoxic 

Chronic Laboratory Rat 

Frank effects 

LOAEL > 10,000 mg 

a.e./kg-diet 

NOAEL = 10,000 mg 

a.e./kg-diet 

(No effects observed) 

-- 40244509 

(Acceptable) 

Insects Acute contact 

Honey bee 

(Apis mellifera 

L.) 

LD50 > 25 μg a.e./bee Practically 

nontoxic 421373134 

Terrestrial 

plants 

Seedling 

Emergence 

Monocots:

wheat 

EC25 = 0.074 lb a.e./A 

(NOAEC not determined) -- 44094902 (Supplemental1

) 

Dicots: 

sunflower 

EC25 = 0.024 lb a.e./A 

(NOAEC not determined) -- 44094902 (Supplemental1

) 

Vegetative 

Vigor 

Monocots:

Corn and wheat 

EC25 > 0.50 lb a.e./A 

(NOAEC not determined) -- 44094902 (Supplemental1

) 

Dicots: 

Soybean 

EC25 = 0.00067 lb a.e./A 

(NOAEC not determined) -- 44094902 (Supplemental1

) 

1 This study was classified as invalid as a tier 2 study but supplemental as a tier 1 study. The study tested only 6 species (corn, 

wheat, sunflower, cotton, soybean, and radish), did not determine NOAECs, and had other guideline deviations. The EC25 values 

obtained from this study are approximate, should not be used for quantitative risk assessment, and should not be compared with 

results from acceptable phytotoxicity studies.

Table IV.5. Mammalian Toxicity Studies for Formulated Products Containing 

Fluroxypyr-MHE 

Formulation Study Type Surrogate 

Species 

Toxicity Value 

(all units in terms of 

active ingredient) 

Acute 

Toxicity 

Classification 

Source 

(MRID) 

Dicamba 

(8.47%) and 

FluroxypyrMHE (11.1%) 

EC 

Acute Oral Laboratory Rat 

LD50 > 5000 mg 

a.i./kg-bw 

(females) 

Practically 

nontoxic, 

Toxicity 

Category IV 

47619803 

(Acceptable) 

Acute 

Dermal Laboratory Rat 

LD50 > 5000 mg 

a.i./kg-bw 

(males) 

LD50 > 5000 mg 

a.i./kg-bw 

(females) 

Toxicity 

Category IV 

47619804 

(Acceptable) 

Acute 

Dermal Laboratory Rat 

LD50 > 2.52 mg a.i./L 

(males) 

LD50 > 2.52 mg a.i./L 

(females) 

Toxicity 

Category IV 

47619805 

(Acceptable) 

1 The study does not provide sufficient information to convert the toxicity values to lb a.i./A.
32 

B. Ecological Incidents 

A preliminary review of the Ecological Incident Information System (EIIS, version 2.1.1) in June 

2014 identified 12 ecological incidents of adverse field effects to non-target organisms which 

were attributed to use fluroxypyr-MHE. All of the incidents involved damage to plants. A search 

of the Avian Monitoring Information System (AIMS), which is maintained by the American Bird 

Conservancy, did not identify any avian incident associated with the use fluroxypyr-MHE 

Of the plant damage incidents, nine incidents were associated with application of an herbicide 

product containing fluroxypyr-MHE directly to the crop that was damaged. The other three 

incidents involved damage allegedly caused by spray drift of a product applied to an adjacent 

crop. These incidents indicate that off-site movement of herbicide products containing 

fluroxypyr-MHE are capable of damaging dicotyledonous plants. Since these products all 

contain multiple herbicidal active ingredients, the contribution of fluroxypyr-MHE (or the 

corresponding acid) to the observed phytotoxicity is uncertain and the observed damage may be 

the result of other active ingredients or additive toxicity. 

Two carryover incidents reported for Goldsky Herbicide suggest that this product may persist 

enough in soil to cause damage to crops planted the next growing season. However, the 

carryover toxicity may have been caused by two sulfonylurea active ingredients, pyroxsulam and 

florasulam. 

Table IV.6. Incidents Associated with Off-Site Movement of Fluroxypyr-MHE Residues 

Incident 

# Date Location Use Site Crop Damaged Certainty Active Ingredients Comments 

I020627-

003 

June 1, 

2001 

Grant 

County, 

WA 

Timothy hay Wine grapes Possible Fluroxypyr1

2,4-D 

The applicators were in 

violation for applying 

restricted-use pesticides 

without a license. 

I014266-

002 

July 3, 

2003 

Manitoba, 

Canada 

Unidentified Strawberries Possible fluroxypyrMHE, 

2,4-D, 

clodinafoppropargyl 

A temperature inversion 

was believed to have 

caused spray drift from 

an adjacent field. 

I015748-

017 

June 6, 

2004 

Richland 

County, 

MT 

Wheat Sugar beets Probable MCPA, 2-

ethylexyl 

ester, 

fluroxypyrMHE, and 

clopyralid 

The wheat field had 

been sprayed with the 

herbicide product 

Widematch M (Reg. 

No. 62719-513). Plants 

exhibited symptoms 

associated with growth 

regulator herbicides. 

I024789-

001 

June 16, 

2011 

Versailles, 

KY 

Pasture Black locust 

trees 

Probable FluroxypyrMHE, 

triclopyr-BEE 

Black locust trees along 

a fence lines were 

severely damaged 

following application of 

Pasturegard Herbicide 

(Reg. No. 62719-477) 

to an adjacent pasture. 

I024792-

004 

March 

26, 

2011 

Moses 

Lake, WA 

Not reported Mustard Possible FluroxypyrMHE, A farmer alleged that 

mustard plants were 

injured by carryover of 
33 

pyroxsulam, 

florasulam 

an application of 

Goldsky Herbicide 

(62719-582)10 months 

earlier. 

I024792-

025 

April 

20, 

2011 

Scobey, 

MT 

Not reported Lentil Possible FluroxypyrMHE, 

pyroxsulam, 

florasulam 

A farmer alleged that 

lentils were injured by 

carryover of an 

application of Goldsky 

Herbicide (62719-

582)11 months earlier. 1

 The report did not specify if fluroxypyr was applied fluroxypyr acid or fluroxypyr-MHE. 

In addition to the incidents recorded in EIIS and AIMS, the Agency maintains a database which 

stores counts of minor incidents that pesticide registrants record in quarterly aggregated incident 

reports. Ecological incidents recorded in these aggregated reports include those categorized as 

‘minor fish and wildlife’ (W-B), ‘minor plant’ (P-B), and ‘other non-target’ (ONT) incidents. A 

review of this database in June 2014 identified a total of 59 incidents of minor plant damage 

attributed to use of a product containing fluroxypyr-MHE (Table IV.7). Most of the herbicide 

products associated with the incidents contained one or more active ingredients in addition to 

fluroxypyr-MHE, although there were three that contained only fluroxypyr-MHE. 

Table IV.7. Incidents Reported by Pesticide Registrants for Products Containing 

Fluroxypyr-MHE 

Product Name Reg. # Date Range Incident 

Number Active Ingredients Number of 

From To Incidents 

Attain 

(Canadian) 12/1/2010 11/30/2011 024333 - 00043 

Fluroxypyr-MHE 

2,4-D, 2-ethylhexyl ester 2 

Attain XC 

(Canadian) 12/1/2010 11/30/2011 024333 - 

00045 

Fluroxypyr-MHE 1 

Cleanwave 62719-

525 8/1/2009 8/31/2009 023787 - 

00522 

Fluroxypyr-MHE 

Aminopyralid, 1 

Goldsky 

Herbicide 

62719-

582 12/1/2011 11/30/2012 024791 - 00007 

Fluroxypyr-MHE 

Pyroxsulam 

Florasulam 

3 

Momentum 

FX2 Herbicide 228-447 4/1/2011 6/30/2011 023050 - 00006 

Fluroxypyr-MHE 

Triclopyr, triethylamine salt 

2,4-D, triisopropanolamine salt 

1 

Octtain XL 

Herbicide 

(Canadian) 

 12/1/2012 11/30/2013 025992 - 

00007 

Fluroxypyr-MHE 

2,4-D, 2-ethylhexyl ester 1 

Pasturegard 62719-

477 12/1/2010 11/30/2011 024333 - 

00061 

Fluroxypyr-MHE 

Triclopyr, butoxyethyl ester 1 

Prestige 

Herbicide 

(Canadian) 

 12/1/2010 11/30/2011 024333 - 

00048 

Fluroxypyr-MHE 

Clopyralid 

MCPA, 2-ethylhexyl ester 

29 

Spotlight 

Herbicide 

62719-

308 12/1/2004 11/30/2005 016962 - 

00061 

Fluroxypyr-MHE 1 

Starane F 62719-

285 4/1/2000 6/30/2000 010424 - 

00013 

Fluroxypyr-MHE 1 

Stellar 

Herbicide 

(Canadian) 

12/1/2010 11/30/2011 024333 - 

00050 

Fluroxypyr-MHE 

Florasulam 

MCPA, 2-ethylhexyl ester 

1 

12/1/2012 11/30/2013 025992 - 

00011 1 

Tandem 

Herbicide 12/1/2010 11/30/2011 024333 - 

00051 

Fluroxypyr-MHE 

Pyroxsulam 6 
34 

(Canadian) 12/1/2012 11/30/2013 025992 - 

00013 2 

4/1/2013 6/30/2013 025643 - 

00074 1 

Unknown 4/1/2004 6/30/2004 015419 - 

00604 

Fluroxypyr-MHE 

MCPA 

Clopyralid 

1 

Widematch 

Herbicide 

062719-

00512 

12/1/2004 11/30/2005 016962 - 

00064 

Fluroxypyr-MHE 

Clopyralid, monoethanolamine 

salt 

3 

12/1/2012 11/30/2013 025992 - 

00014 2 

Widemtch 

Herbicide 

062719-

00512 12/1/2009 11/30/2010 023787 - 00536 

Fluroxypyr MHE,Clopyralid, 

monoethanolamine salt, 1 

TOTAL 59 

C. 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 (primarily acid) 

 Leaching to groundwater followed by irrigation (primarily acid) 

In addition, terrestrial animals that use treated fields may be exposed to fluroxypyr acid from 

consuming contaminated plants and invertebrates, dermal absorption, and drinking from 

contaminated puddles. With use of granular products, terrestrial animals also may be exposed by 

consumption of granules that are on the soil surface or on vegetation. 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 fluroxypyr-MHE and 

fluroxypyr acid residues. 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) for both fluroxypyr acid and fluroxypyr-MHE. 

Input parameters and outputs from SIP and STIR are provided in APPENDIX E. SIP and STIR 

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

While fluroxypyr-MHE and fluroxypyr acid are expected to be taken up by plants and 

translocated as fluroxypyr acid, concentrations in nectar and pollen are unknown. However, 

contact exposure to pollinators is expected to be primary as a result of direct spray onto 

flowering weeds. 

V. ANALYSIS PLAN 

A. Ecological Risk Assessment 

1. Stressors of Concern 

Both fluroxypyr-MHE and fluroxypyr acid are considered the stressors of concern; together 

using a total toxic residue approach for plants and individually for all other taxa. 
35 

2. Measures of Exposure

In order to estimate risks of fluroxypyr-MHE and fluroxypyr acid residues 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 estimated 

environmental concentrations (EECs) are discussed on OPP’s model website.20 These models 

include: PRZM (Pesticide Root Zone Model) and VVWM (Variable Volume Water Model), 

PRZM-groundwater (GW), PFAM (Pesticides in Flooded Application Model), AgDrift, AgDisp, 

T-REX, TerrPlant, SIP (Screening Imbibition Program), and STIR (Screening Tool for 

Inhalation Risk). 

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

Toxicity data presented in Section 4.C.2 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, incorporating new data 

and information obtained since the previous risk assessments were conducted. Since previous 

risk assessments have consistently identified nontarget plants as being at greatest risk, a risk 

assessment will be conducted for aquatic and terrestrial plants using the EPA’s updated risk 

assessment methods. For terrestrial plants, the risk assessment will incorporate new TEP data on 

phytotoxicity and may utilize improved methods for modeling exposure and risk to terrestrial 

plants. In addition, a new study on the persistence of fluroxypyr residues in compost will allow 

the EPA to assess with improved certainty the potential for persistent fluroxypyr residues in 

compost to harm crops and garden plants. 

For aquatic plants, the risk assessment will utilize data from a new study on toxicity to the most 

sensitive aquatic test species, the freshwater diatom Navicula pelliculosa. The results from the 

current supplemental study with this species (MRID 44527201) are considered unreliable 

because the solvent control solutions were contaminated with the test material. Furthermore, the 

response of the diatoms in the medium control was much stronger than those in solvent control 

and the lower treatment levels, an unexpected result that suggests the study was affected by the 

solvent contamination or some other extraneous factor. Therefore, a repeat of this study may 

 

20 http://www.epa.gov/opp00001/science/models_pg.htm 
36 

result in a different toxicity endpoint, which may result in different RQ values for nonvascular 

aquatic plants. 

Another source of new information that may affect the aquatic plant risk assessment is a recent 

published paper reporting the toxicity of fluroxypyr-MHE to the aquatic macrophage, 

Myriophyllum spicatum (Mohr et al., 2013). This species is considered a more preferred test 

species than duckweed (Lemna gibba) for testing herbicides that are auxin analogs, like 

fluroxypyr-MHE, because these herbicides are known to have toxicity that is specific to dicots, 

and M. spicatum is a dicot whereas duckweed is a monocot (Mohr et al., 2013). As expected, the 

studies with M. spicatum exhibited greater toxicity than the duckweed study used in the previous 

assessment. Depending on which M. spicatum study is considered, the IC50 was 3.3 to 15.6 times 

lower than the duckweed IC50. This would result in RQs that would be higher by the same 

factors. 

Some previous risk assessments have identified risk to aquatic invertebrates that exceed the LOC 

for listed species. An aquatic risk assessment will be conducted for these species using the most 

current use information for fluroxypyr-MHE, and its environmental fate data and toxicity, to 

better define and characterize potential adverse effects to listed aquatic invertebrates. 

Additional data on toxicity of fluroxypyr-MHE to the honeybee will allow for a more complete 

assessment of potential risk to insect pollinators. Currently, data are only available for acute 

toxicity from acute contact exposure. Additional data on acute oral exposure will allow assessing 

potential risk to bees from ingestion of nectar and/or pollen contaminated with fluroxypyr. [In 

addition, data will be obtained from tier-1 honeybee studies with chronic exposure to adult bees 

and larval bees. These studies will allow evaluation of acute and chronic effects on bee larvae 

and chronic effects on adult bees.] 

Finally, a review of the open literature may provide additional information on the environmental 

fate and ecotoxicity of fluroxypyr-MHE and fluroxypyr acid. Any new information from 

published literature may be used to refine the quantitative risk assessment or to expand upon the 

qualitative characterization of risk. 

5. Endangered Species Assessments 

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

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

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

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

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

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

differences between the EPA and the Services. The NAS report21 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 

Endangered Species Act (ESA) and FIFRA. The joint Interim Approaches were released prior to 

a stakeholder workshop held on November 15, 2013. In addition, the EPA presented the joint 

 

21 http://www.nap.edu/catalog.php?record_id=18344 
37 

Interim Approaches at the December 2013 Pesticide Program Dialogue Committee (PPDC) and 

State-FIFRA Issues Research and Evaluation Group (SFIREG) meetings, and held a stakeholder 

workshop in April 2014, allowing additional opportunities for stakeholders to comment on the 

Interim Approaches. As part of a phased, iterative process for developing the Interim 

Approaches, the agencies will also consider public comments on the Interim Approaches in 

connection with the development of upcoming Registration Review decisions. The details of the 

joint Interim Approaches are contained in the white paper “Interim Approaches for NationalLevel Pesticide Endangered Species Act Assessments Based on the Recommendations of the 

National Academy of Sciences April 2013 Report,”22 dated November 1, 2013. 

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

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

designated critical habitat, the ecological risk assessment supporting the proposed interim 

registration review decision for fluroxypyr-MHE is not expected to contain a complete ESA 

analysis. Once the agencies have fully vetted the scientific methods necessary to complete risk 

assessments for endangered and threatened (listed) species and their designated critical habitats, 

these methods will be applied to subsequent analyses for fluroxypyr-MHE as part of completing 

this registration review. 

6. Endocrine Disruptor Screening Program 

Fluroxypyr-MHE was not included in the first group of 67 chemicals that were issued an order to 

conduct Tier 1 EDSP testing, nor in the second revised list of 109 chemicals issued for the next 

phase of Tier 1 testing. For additional information the EDSP program, visit 

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

B. Drinking Water 

Although there are number of uses for which a drinking water assessment has not been 

completed as well as uses that have a number of uncertainties associated with the label language 

(e.g., unknown number of yearly applications) an updated drinking water assessment for 

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

conducted on rice is expected to provide very conservative EDWCs and the results are expected 

to be much higher than that of any other uses current registered, even if these uncertainties were 

taken into account. 

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. 

 

22 http://www.epa.gov/espp/2013/nas.html 
38 

Table VI.1. Environmental Fate Data for Fluroxypyr-MHE and Fluroxypyr Acid 

OCSPP 

Guideline 

Data 

Requirement 

Submitted 

Studies 

(MRID) 

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Comments 

835.2120 Hydrolysis 40244539 Acceptable No -- 

835.2240 Aqueous 

Photolysis 44080342 Acceptable No -- 

835.2410 Soil Photolysis 44080343 Acceptable No -- 

835.4100 Aerobic Soil 

Metabolism 42137317 Acceptable No -- 

835.4200 Anaerobic Soil 

Metabolism No data are available No -- 

835.4300 

Aerobic 

Aquatic 

Metabolism 

44080345 Acceptable No -- 

835.4400 

Anaerobic 

Aquatic 

Metabolism 

44080344 supplemental No -- 

835.1230 

835.1240 

Adsorption/ 

desorption and 

Leaching 

42137319 acceptable No -- 

835.1410 Volatility – 

Laboratory No data are available No 

Fluroxypyr-MHE and fluroxypyr are not expected to be 

volatile based on vapor pressure and Henry’s Law 

Constant. 

835.6100 Terrestrial Field 

Dissipation 

44080347 Supplemental 

No -- 44896702 Acceptable 

45204201 Acceptable 

45204202 Acceptable 

835.6200 Aquatic Field 

Dissipation 48581303 

Scientifically 

valid; study is 

currently under 

review 

No

850.6100 

Analytical 

Method in Soil 

44080346 

(ECM 

Acceptable Yes 

Data are available for fluroxypyr acid, fluroxypyr-DCP 

and fluroxypyr-MP; however, the LOD/LOQ are not 

lower than the most sensitive terrestrial plant endpoint. No 

data are available for fluroxypyr-MHE. 

44896703 

(ECM) 

45084601 

(ILV) 

Analytical 

Method in 

Water 

48581303 

(ECM) Acceptable Yes No ILV has been provided for this method. 

ILV No data Yes 

165-4 

(850.1730) 

Fish Bioconcentration 

44080348 supplemental No -- 

44605403 
39 

OCSPP 

Guideline 

Data 

Requirement 

Submitted 

Studies 

(MRID) 

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Comments 

Nonguideline Compost 45833601 Upgradeable Yes 

Several deficiencies were identified in the submitted study 

including: 1) There are no methods including an 

independent lab validation or control spikes to support the 

analytical methods used in the study; 2) A discussion of 

how sampling withdrawal (material reduction), etc. 

followed by sample consolidation impacted the results is 

needed; 3) While analytical replicate samples were 

conducted, replicate experiment samples (multiple 

compost piles) were not provided to assess the 

experimental variability; 4) The representation of the 

composting method used in the study was not provided; 

and 5) The study only looked for fluroxypyr acid. If these 

deficiencies cannot be addressed a new study is needed to 

assess the fate of fluroxypyr-MHE and fluroxypyr acid in 

compost materials. 

B. Ecological Effects 

Table VI.2 and 

Table VI.3 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. Rationale for requests for the additional data is presented below the 

tables.

EFED recommends requesting the following additional data for assessing ecological risk: 

 (GLN 850.4500) Algal toxicity test with a freshwater diatom 

 GLN 850.4100) Seedling emergence test with 10 plant species using a TEP containing 

fluroxypyr-MHE 

 (GLN 850.4150) Vegetative vigor test with 10 plant species using a TEP containing 

fluroxypyr-MHE 

Table VI.2. Aquatic Ecological Effects Data for Fluroxypyr-MHE and Fluroxypyr Acid 

OCSPP 

Guideline 

Data 

Requirement 

Submitted 

Studies 

(MRID) 

Test Species Study 

Classifications

Are data 

needed to 

conduct risk 

assessment? 

Comments 

FLUROXYPYR-MHE 

850.1010 

850.1020 

Freshwater 

invertebrate 

acute toxicity 

40244520 Water flea Acceptable No -- 

42137308 Water flea Acceptable 

850.1035 

850.1045 

Saltwater 

crustacean 

acute toxicity 

44080313 Grass shrimp Acceptable No -- 

42137311 Pink shrimp Supplementary

850.1025 45725801 Eastern oyster Acceptable No 
40 

OCSPP 

Guideline 

Data 

Requirement 

Submitted 

Studies 

(MRID) 

Test Species Study 

Classifications

Are data 

needed to 

conduct risk 

assessment? 

Comments 

850.1055 Saltwater 

mollusk 

acute toxicity 

44080310 Eastern oyster Supplemental -- 

 850.1075 Freshwater 

fish acute 

toxicity 

44080307 Bluegill 

sunfish 

Acceptable No 

-- 

40244522 Rainbow trout Acceptable 

40244523 Golden orfe Supplemental 

40244525 Rainbow trout Supplemental 

 850.1075 Saltwater fish 

acute toxicity 

44080308 Sheepshead 

minnow 

Acceptable No 

-- 

42137309 Atlantic 

silverside 

Supplemental 

 850.1300 Freshwater 

invertebrate 

life cycle 

44080314 Water flea Supplemental No -- 

 850.1350 Saltwater 

invertebrates 

life cycle 

(None) (N/A) (N/A) No -- 

 850.1400 Freshwater 

fish 

early-life stage 

(None) (N/A) (N/A) No The fish early life-stage 

study conducted with 

fluroxypyr acid (MRID 

48559401) provides 

sufficient information 

for this guideline. 

 850.1400 Saltwater fish 

early-life stage 

(None) (N/A) (N/A) No -- 

 850.1500 Fish life cycle (None) (N/A) (N/A) No -- 

850.4400 Aquatic plant 

toxicity test 

with duckweed 

(Lemna spp.) 

45011602 Lemna gibba Acceptable No -- 

44080338 Lemna gibba Acceptable 

44744001 Lemna gibba Supplemental 

850.4500 Algal toxicity 

with green 

algae 

45011603 Kirchneria 

subcapitata 

Acceptable No -- 

44080340 Kirchneria 

subcapitata 

Acceptable 

42137312 Kirchneria 

subcapitata 

Supplemental 
41 

OCSPP 

Guideline 

Data 

Requirement 

Submitted 

Studies 

(MRID) 

Test Species Study 

Classifications

Are data 

needed to 

conduct risk 

assessment? 

Comments 

850.4500 Algal toxicity 

with 

freshwater 

diatom 

44080339 

44527201 

Navicula 

pelliculosa 

Supplemental Yes This test is needed to 

replace the inadequate 

supplemental studies 

and to provide reliable 

EC50 and NOAEC for 

Navicula pelliculosa, 

which is the most 

sensitive test species of 

nonvascular plants. 

850.4500 Algal toxicity 

with saltwater 

diatom 

44080337 Skeletonema 

costatum 

Acceptable No -- 

850.4550 Cyanobacteria 44080336 Anabaena 

flos-aquae 

Acceptable No -- 

FLUROXYPYR ACID

850.1010 

850.1020 

Freshwater 

invertebrate 

acute toxicity 

40244521 Water flea Acceptable No -- 

40244524 Water flea Acceptable 

850.1035 

850.1045 

Saltwater 

crustacean 

acute toxicity 

44080312 Grass shrimp Acceptable No -- 

850.1025 

850.1055 

Saltwater 

mollusk 

acute toxicity 

44080311 Eastern oyster Acceptable No -- 

42137310 Eastern oyster Invalid 

 850.1075 Freshwater 

fish acute 

toxicity 

42137306 Bluegill 

sunfish 

Acceptable No -- 

42137307 Rainbow trout Acceptable 

40244518 Rainbow trout Acceptable 

44080309 Inland 

silverside 

Acceptable 

40244519 Golden orfe Acceptable 

 850.1075 Saltwater fish 

acute toxicity 

44080309 Atlantic 

silverside 

Acceptable No -- 

 850.1300 Freshwater 

invertebrate 

life cycle 

(None) (N/A) (N/A) No 

-- 

 850.1350 Saltwater 

invertebrates 

life cycle 

(None) (N/A) (N/A) No 

-- 

 850.1400 Freshwater 

fish 

early-life stage 

48559401 Fathead 

minnow 

Acceptable No -- 

 850.1400 Saltwater fish 

early-life stage 

(None) (N/A) (N/A) No -- 
42 

OCSPP 

Guideline 

Data 

Requirement 

Submitted 

Studies 

(MRID) 

Test Species Study 

Classifications

Are data 

needed to 

conduct risk 

assessment? 

Comments 

 850.1500 Fish life cycle (None) (N/A) (N/A) No 

850.4400 Aquatic plant 

toxicity test 

with duckweed 

(Lemna spp.) 

44094902 Lemna gibba Invalid No Testing done with the 

fluroxypyr-MHE is 

adequate for assessing 

risk. 

850.4500 Algal toxicity 

with green 

algae 

40244526 Chorella 

vulgaris 

Supplemental 

No -- 

 42164501 Kirchneria 

subcaitatum 

Invalid 

850.4500 Algal toxicity 

with 

freshwater 

diatom 

(None) (N/A) (N/A) No 

-- 

850.4500 Algal toxicity 

with saltwater 

diatom 

(None) (N/A) (N/A) No -- 

850.4550 Cyanobacteria (None) (N/A) (N/A) No -- 

Table VI.3. Terrestrial Ecological Effects Data for Fluroxypyr-MHE and Fluroxypyr Acid

OCSPP 

Guideline 

Data 

Requirement 

Submitted 

Studies 

(MRID) 

Test Species Study 

Classifications 

Are data 

needed for 

risk 

assessment? 

Current Additional Data 

Need 

FLUROXYPYR-MHE 

 850.2100 Avian oral toxicity 

with quail or duck 

40244546 Bobwhite Acceptable No -- 

40244516 Mallard Acceptable 

 850.2100 Avian oral toxicity 

with passerine 

(None) (N/A) (N/A) No 

Because fluroxypyr-MHE 

has been shown to have very 

low acute toxicity to birds 

and mammals, acute testing 

with a passerine bird is not 

needed. 

 850.2200 Avian dietary 

toxicity 

40244517 Bobwhite Acceptable No -- 

42137301 Mallard Acceptable 

 850.2300 Avian 

reproduction 

42137303 Bobwhite Acceptable No -- 

42137304 Mallard Acceptable 

Nonguideline Avian inhalation (None) (N/A) (N/A) No -- 

 850.3020 Honey bee acute 

contact toxicity 

42137313 Honey bee Acceptable No -- 

40244527 Honey bee Supplemental 
43 

OCSPP 

Guideline 

Data 

Requirement 

Submitted 

Studies 

(MRID) 

Test Species Study 

Classifications 

Are data 

needed for 

risk 

assessment? 

Current Additional Data 

Need 

Nonguideline Honey bee acute 

oral study 

(None) Honey bee (N/A) Yes This study appears to have 

already been conducted and 

submitted to EU countries. 

The submittal of this study to 

the EPA would be helpful for 

assessing risk to insect 

pollinators. 

Nonguideline Honey bee, 

chronic oral 

toxicity to adults 

(None) Honey bee (N/A) Yes This study is now needed for 

assessing pesticide risk to 

bees. 

Nonguideline Honey bee, 

chronic oral 

toxicity to larvae 

(None) Honey bee (N/A) Yes This study is now needed for 

assessing pesticide risk to 

bees. 

850.3030 Honey bee residue 

on foliage 

(None) (N/A) (N/A) Reserved 

pending 

results of 

tier I studies

-- 

 850.3040 Field testing for 

pollinators 

(None) (N/A) (N/A) Reserved 

pending 

results of 

tier I studies

-- 

850.4100 Seedling 

Emergence and 

Seedling Growth 

44080335 10 species Acceptable Yes The TEP used in this study 

was not reported. Additional 

testing may be needed to 

assess risk of TEPs to 

terrestrial plants. 

850.4150 Vegetative Vigor 44080335 10 species Acceptable Yes The TEP used in this study 

was not reported. Additional 

testing may be needed to 

assess risk of TEPs to 

terrestrial plants. 

 
44 

FLUROXYPYR ACID

 850.2100 Avian oral toxicity 

with quail or duck 

40244515 Bobwhite Acceptable No -- 

40244514 Mallard Acceptable 

850.2100 Avian oral toxicity 

with passerine 

(None) (N/A) (N/A) No 

Because fluroxypyr acid has 

been shown to have very low 

acute toxicity to birds and 

mammals, acute testing with a 

passerine bird is not needed. 

 850.2200 Avian dietary 

toxicity 

40244547 Bobwhite Acceptable No -- 

42137302 Mallard Acceptable 

 850.2300 Avian 

reproduction 

(None) (N/A) (N/A) No -- 

(None) (N/A) (N/A) 

Nonguideline Avian inhalation (None) (N/A) (N/A) No -- 

 850.3020 Honey bee acute 

contact toxicity 

42137314 Honey bee Acceptable No -- 

850.3030 Honey bee residue 

on foliage 

(None) (N/A) (N/A) No -- 

 850.3040 Field testing for 

pollinators 

(None) (N/A) (N/A) No -- 

850.4100 Seedling 

Emergence and 

Seedling Growth 

44094902 Corn, wheat, 

sunflower, 

cotton, 

soybean, and 

radish 

Invalid for Tier 

2, Supplemental 

for Tier 1 

No 

-- 850.4150 Vegetative Vigor 44094902 Corn, wheat, 

sunflower, 

cotton, 

soybean, and 

radish 

Invalid for Tier 

2, Supplemental 

for Tier 1 

No 

Limited ecological effects data are available on the toxicity of two major degradation products of 

fluroxypyr-MHE, fluroxypyr-pyridinol (4-amino-3-5,5-dichloro-6-fluoro-2-pyridinol) and 

fluroxypyr-methylpyridine (4-amino-3,5-dichloro-6-fluoro-2-methylpyridine) (Table VI.4). 

Results of these studies are presented in Appendix D. The studies submitted provide sufficient 

information on the toxicity of these degradation products to terrestrial and aquatic plants for the 

registration review risk assessment. Since the parent compound has low toxicity to terrestrial and 

aquatic animals, toxicity data with these degradates for terrestrial or aquatic animals are not 

needed. 
45 

Table VI.4. Aquatic Ecological Effects Data for Degradation Products of Fluroxypyr-MHE 

and Fluroxypyr (acid)

OCSPP 

Guideline Data Requirement 

Submitted 

Studies 

(MRID) 

Test Species Study 

Classifications 

Are data 

needed for 

risk 

assessment? 

Current 

Additional Data 

Need 

4-AMINO-3-5,5-DICHLORO-6-FLUORO-2-PYRIDINOL

850.4400 Aquatic plant Toxicity 

Test with Duckweed 

(Lemna spp.) 

45011602 Lemna gibba Acceptable No -- 

850.4500 Algal toxicity with 

green algae 

45011603 Pseudokirchner

ia subcapitata 

Acceptable No -- 

850.4500 Algal toxicity with 

freshwater diatom 

45011601 Navicula 

pelliculosa 

Acceptable No -- 

850.4500 Algal toxicity with 

saltwater diatom 

45011605 Skeletonema 

costatum

Acceptable No -- 

850.4550 Cyanobacteria 45011604 Anabaena 

flos-aquae 

Acceptable No -- 

850.4100 Seedling Emergence 

and Seedling Growth 

44094902 Corn, wheat, 

sunflower, 

cotton, soybean, 

and radish 

Acceptable as 

tier 1 study 

No -- 

850.4150 Vegetative Vigor Acceptable as 

tier 1 study 

No -- 

4-AMINO-3,5-DICHLORO-6-FLUORO-2-METHYLPYRIDINE

850.4400 Aquatic plant Toxicity 

Test with Duckweed 

(Lemna spp.) 

45011607 Lemna gibba Acceptable No -- 

850.4500 Algal toxicity with 

green algae 

44080341 Pseudokirchner

ia subcapitata 

Supplemental No -- 

850.4500 Algal toxicity with 

freshwater diatom 

45011606 Navicula 

pelliculosa 

Acceptable No -- 

850.4500 Algal toxicity with 

saltwater diatom 

45011609 Skeletonema 

costatum 

Acceptable No -- 

850.4550 Cyanobacteria 45011608 Anabaena 

flos-aquae 

Acceptable No -- 

850.4100 Seedling Emergence 

and Seedling Growth 

44094902 Corn, wheat, 

sunflower, 

cotton, soybean, 

and radish

Acceptable as 

tier 1 study 

No -- 

850.4150 Vegetative Vigor Acceptable as 

tier 1 study 

No -- 

VII. REFERENCES (GENERAL) 

Mohr, S. J. Schott, D. Maletzki, and A. Hünken. 2013. Effects of toxicants with different modes 

of action on Myriophyllum spicatum in a test system with varying complexity.

Ecotox.Environ. Saf. 97:32-39. 
46 

Maltby, L., Arts, G., Heimbach, F., Davies, J., Poulsen, V., Pickl, C., Poulsen, V. 2010. Aquatic 

Macrophyte Risk Assessment for Pesticides. SETAC Europe Workshop AMRAP, 

Wageningen Netherlands. CRC Press, USA p. 135. 

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. 2013. EFED Risk Assessment for the Proposed New Use of Fluroxypyr 1-

methylheptylester on Rice. Office of Pesticide Program. Memorandum from the 

Environmental Fate and Effects Division to the Registration Division. January 11, 2013. 

D396342. 

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

Available: http:/www.epa.gov/ecotox/ 
47 

BLIOGRAPHY 

ental Fate Studies Submitted for Fluroxypyr-MHE and Fluroxypyr

e MRID Test Material Citation Remarks 

40244539 fluroxypyr- MHE Lehmann, R. (1987) The Hydrolysis of Fluroxypyr-MHE in Dilute Aqueous Solution: Laboratory Project ID: GH-C 1910. Unpublished study prepared by Dow Chemical U.S.A. 40 p. 42137318 2-Octanol 

Lehmann, R. (1991) A Review of 2-Octanol, Hydrolysis Product of Fluroxypyr-1-Methyl-Heptyl Ester: Lab Project Number: GH-C 2607. Unpublished study prepared by DowElanco. 14 p. 

lysis 44080342 fluroxypyr- MHE 

Cleveland, C.; Holbrook, D. (1992) The Aqueous Photolysis of Fluroxypyr Methylheptyl Ester and Fluroxypyr (Acid) in Natural Sunlight: Lab Project Number: ENV91079. Unpublished study prepared by DowElanco. 95 p. 

sis 44080343 fluroxypyr- MHE 

Batzer, F.; Lubinski, R. (1996) Soil Photolysis of Fluroxypyr 1-Methylheptyl Ester in Natural Sunlight: Amended Report: Lab Project Number: ENV91080. Unpublished study prepared by DowElanco. 79 p. 

l 

m

42137317 fluroxypyr- MHE Lehmann, R.; Miller, J. (1989) Aerobic Soil Metabolism of Fluroxypyr-MHE: Lab Project Number: GH-C 2149. Unpublished study pre- pared by Dow Chemical U.S.A. 63 p. 

42137316 fluroxypyr- MHE 

Lehmann, R. (1988) Formation of Fluroxypyr from Fluroxypyr-MHE by Soil Catalysis: Lab Project Number: GH-C 2068. Unpublished study prepared by Dow Chemical U.S.A. 26 p. 

oil 

m 40244540 

Hawkins, D.; Kirkpatrick, D.; Conway, B.; et al. (1982) The Metabolism of [Carbon 14]-Dowco 433 MHE in Laboratorystored Soil: Laboratory Project ID: DWC 312/341 8240. Unpublished study pre- pared by Huntingdon Research Centre. 144 p. 

atic 

m 44080345 fluroxypyr- MHE 

Cleveland, C.; Miller, J. (1993) Aerobic Aquatic Metabolism of Fluroxypyr Methylheptyl Ester: Lab Project Number: ENV91075: Unpublished study prepared by DowElanco, North American Environmental Chemistry Lab. 125 p. 

uatic 44080344 fluroxypyr- MHE Cleveland, C.; Miller, J. (1993) Anaerobic Aquatic M t b li f Fl M th lh t l E t L b P j t
48 

Guideline MRID Test Material Citation 

834.4400 Number: ENV91075: ENV91075.1. Unpublished study 

prepared by DowElanco, North American Environmental Chemistry Lab. 108 p. 

Terrestrial Field 

Dissipation 

835.6100 

44080347 

Formulated 

product 

(XRM-5316; 

26.6%) 

Poletika, N.; Roberts, D.; Phillips, A.; et al. (1996) Terrestrial Field Dissipation of Fluroxypyr: Lab Project Number: ENV92023. Unpublished study prepared by A & L Great Lakes Labs., Inc.; Agvise; and DowElanco. 393 p. 

40244544 

 Freeman, J. (1985) The Degradation and Leaching of 

Fluroxypyr in Soil--U.K. 1984: Laboratory Project ID: GHEP-1303R. Unpublish- ed study prepared by Dow Chemical Co. 159 p. 

44080346 

Fluroxypyr, 

fluroxypyrDCP, 

fluroxypyr-MP 

Moore, M. (1996) Determination of Residues of Fluroxypyr ((4-Amino-3,5-dichloro-6-fluoro-2-oxy Acetic Acid) Pyridine), Methoxypyridine ((4-Amino-3,5-dichloro-6-fluoro2-methoxy) Pyridine) and 3,5-Dichloropyridinol ((4-Amino3,5-dichloro- 6-fluoro-2-hydroxy) Pyridine) in Soil by Capillary Gas Chromatography Using Mass Selective Detection: Lab Project Number: GH-C 4170. Unpublished study prepared by DowElanco, Global Environmental Chemistry Lab. 63 p. 

44896702 

Attain A: 

FluroxypyrMHE (27.1 % 

by weight), 

fluroxypyr 

(18.8% a.e.) 

Roberts, D.; Phillips, A.; Rutherford, L. (1999) Field Dissipation of Fluroxypyr in North Carolina: Lab Project Number: RES98073. Unpublished study prepared by Dow AgroSciences LLC. and Stone Environmental Inc. 225 p. 

45204201 Product containing 

27.1% 

fluroxypyrMHE and 

18.8% 

fluroxypyr 

Roberts, D.; Robb, C. (2000) Terrestrial Dissipation of Fluroxypyr in Oklahoma Sorghum Agriculture: Lab Project Number: 990024. Unpublished study prepared by Dow AgroSciences LLC, Crop Guard Research, Inc. & A&L Great Lakes Laboratories, Inc. 225 p. 

45204202 

Roberts, D.; Rutherford, L. (2000) Terrestrial Dissipation of Fluroxypyr in Missouri Sorghum Agriculture: Lab Project Number: 990037. Unpublished study prepared by Dow AgroSciences LLC, Stewart Agricultural Research Service, Inc., & A&L Great Lakes Laboratories, Inc. 299 p. 
49 

Guideline MRID Test Material Citation 

Aquatic Field 

Dissipation 

835.6200 

48581303 

Formulated 

product GF1784 

(fluroxypyrMHE) 

Newcombe, A.; Negley, T.; van Wesenbeeck, I. (2011) Aquatic Dissipation of Fluroxypyr under Dry-Seeded (Texas) and Water-Seeded (California) Rice Production Conditions after Two Foliar Spray Applications: Final Report. Project Number: 101622, 101622/OCR. Unpublished study prepared by Pyxant Labs Inc., Agvise Laboratories, Inc. and Arcadis. 1292 p. 

Adsorption/ 

Desorption Batch 

Equilibrium 

835.1230 

42137319 fluroxypyr 

Lehmann, R.; Miller, J.; Olberding, E. (1988) An Adsorption/ Desorption Study of Fluroxypyr: Lab Project Number: GH-C 2124. Unpublished study prepared by Dow Chemical U.S.A. 74 p. 

40244541 fluroxypyr 

Taylor, D. (1985) Study of the Leaching Characteristics of Dowco 433 (Fluroxypyr) as Determined in an Aged Leaching 

Study: Laboratory Report No.: 4536-295/11. Unpublished study prepared by Hazleton Laboratories Europe Ltd. 120 p. 

40244542 fluroxypyr 

Taylor, D. (1985) Study of the Leaching Characteristics of Dowco 433 Acid (Fluroxypyr) in Soil: Laboratory Report No.: 4537-295/ 12. Unpublished study prepared by Hazleton Laboratories Europe Ltd. 112 p. 

44094903 

fluroxypyrDCP, 

fluroxypyr-MP 

Cleveland, C.; Ostrander, J. (1996) Adsorption/Desorption Batch Equilibrium Partitioning of Methoxypyridine and Dichloropyridinol Metabolites of Fluroxypyr: Lab Project Number: ENV95072: GHE-P-4500R: 4V. Unpublished study prepared by DowElanco North American Environmental Chemistry Lab. 150 p. 

44605401 -- 

Cleveland, C. (1998) Response to the U.S. EPA Data Evaluation Report on: Adsorption/Desorption Batch Equilibrium Partitioning of Methoxypyridine and Dichloropyridinol Metabolites of Fluroxypyr: Lab Project Number: GH-C 3854R. Unpublished study prepared by Dow AgroSciences LLC 18 p. 

40244543 Fluroxypyr- MHE 

Yon, D. (1986) Determination of the Adsorption of Fluroxypyr 1 Methylheptyl Ester (MHE) onto Ditch Bottom Sludge: (Holland, 1985): Laboratory Project ID: GHE-P 1517. Unpublished compilation prepared by Dow Chemical Co. 15 p. 
50 

Guideline MRID Test Material Citation 

40244544 fluroxypyr 

Freeman, J. "The Degradation and Leaching of Flumxypyr in Soil- U.K. 1984". Performed by Dow Chemical Co., England. Submitted by Ikw CXlanical U.S.A. 

Method Validation 

850.6100 

44080346 

fluroxypyr, 

fluroxypyrDCP, 

fluroxypyr-MP 

Moore, M. (1996) Determination of Residues of Fluroxypyr ((4-Amino-3,5-dichloro-6-fluoro-2-oxy Acetic Acid) Pyridine), Methoxypyridine ((4-Amino-3,5-dichloro-6-fluoro2-methoxy) Pyridine) and 3,5-Dichloropyridinol ((4-Amino3,5-dichloro- 6-fluoro-2-hydroxy) Pyridine) in Soil by Capillary Gas Chromatography Using Mass Selective Detection: Lab Project Number: GH-C 4170. Unpublished study prepared by DowElanco, Global Environmental Chemistry Lab. 63 p. 

45824101 

FluroxypyrMHE, 

fluroxypyr, 

fluroxypyrDCP, 

fluroxypyr-MP 

Shackelford, D. (2000) Validation Report for the Determination of Residues of Fluroxypyr 1-methylheptyl ester, Fluroxypyr-acid, Fluroxypyr-2-pyridinol, and Fluroxypyr-2-methoxypryidine in Surface Water by Capillary Gas Chromatography with Mass Spectrometric Detection: Lab Project Number: 001016: GRM 00.21. Unpublished study prepared by Dow AgroSciences LLC. 

44896703 

 ECM Method Review ENVIRONMENTAL CHEM STRY 

Method REVIEW REPORT NUMBER ECM0205Sl-S3 Determination of Residues of Fluroxypyr, Fluroxypyr-DCP, and Fluroxypyr-MP in Soil 

45084601 

Bioconcentration 

850.1730 44605403 fluroxypyr- MHE 

Woodburn, K. (1998) Response to the U.S. EPA Data Evaluation Report on: The Bioconcentration and Metabolism of Fluroxypyr 1-Methylheptyl Ester by the Rainbow Trout, Ocorhynchus mykiss Walbaum: Lab Project Number: ES-
51 

Guideline MRID Test Material Citation 

2679S. Unpublished study prepared by The Dow Chemical Company. 40 p. 

44080348 fluroxypyr- MHE 

Rick, D.; Kirk, H.; Fontaine, D.; et al. (1996) The Bioconcentration and Metabolism of Fluroxypyr 1-Methylheptyl Ester by the Rainbow Trout, Oncorhynchus mykiss Walbaum: Lab Project Number: DECO-ES-2679. Unpublished study prepared by The Toxicology Research Lab., The Dow Chemical Co. 90 p. 

Storage Stability 

40244540 fluroxypyr- MHE 

Hawkins, D.; Kirkpatrick, D.; Conway, B.; et al. (1982) The Metabolism of [Carbon 14]-Dowco 433 MHE in Laboratorystored Soil: Laboratory Project ID: DWC 312/341 8240. Unpublished study pre- pared by Huntingdon Research Centre. 144 p 

44080355 fluroxypyr- MHE 

Phillips, A.; Blakeslee, B. (1996) Frozen Storage Stability Study of Fluroxypyr 1-Methylheptyl Ester, Fluroxypyr, 4-Amino-3,5-dichloro-6-fluoro-Pyridinol and 4-Amino-3,5- dichloro- 6-fluoro-Methoxypyridine in Soil: Lab Project Number: RES93010/RES93051. Unpublished study prepared by Dow Elanco. 112 p. 

Non-guideline; 

Compost Study 45833601 fluroxypyr- MHE 

Brinton, W.; Evans, E. (2002) Herbicide Content Changes in Bench-Scale Compost Made with Fluroxypyr and Dicamba Treated Grass Clippings: Lab Project Number: PROJECT 633. Unpublished study prepared by Woods End Research Laboratory. 13 p. 
52 

Table A.2. Ecotoxicology Studies Submitted for Fluroxypyr-MHE and Fluroxypyr Acid

Guideline MRID Test Material Citation 

Avian Acute Oral 

Toxicity 

850.2100 40244546 Fluroxypyr-MHE 

Roberts, N.; Phillips, C. (1984) The Acute Oral Toxicity (LD50) of Dowco 433 Ester to the Bobwhite Quail: Laboratory Project ID: DWC 398a/84178. Unpublished study prepared by Huntingdon Research Centre. 16 p. 

40244516 Fluroxypyr-MHE 

Roberts, N.L and C.N.K. Phillips. 198b. The acute oral toxicity (LD50) of DOWCO 433 to the mallard buck. Conducted by 

Huntingdon Research Centre plc, Huntingdon, Cambridgeshire, England. Submitted by Dow Chemical Europe, Research and Development, Bachtobelstrasse 3, 8810 Horgen, Switzerland. 

40244514 Fluroxypyr acid 

Roberts, N.; Phillips, C. (1984) The Acute Oral Toxicity (LD50) of Dowco 433 Acid to the Mallard Duck: Laboratory Project ID: DWC 397/84158. Unpublished study prepared by Huntingdon Research Centre. 15 p. 

40244515 Fluroxypyr acid 

Roberts, N.; Phillips, C. (1984) The Acute Oral Toxicity (LD50) of Dowco 433 Acid to the Bobwhite Quail: Laboratory Project ID: DWC 398b/84233. Unpublished study prepared by Huntingdon Research Centre. 17 p. 

Avian Dietary 

Toxicity 

850.2200 40244517 Fluroxypyr-MHE 

Roberts, N.; Phillips, C. (1983) The Subacute Dietary Toxicity (LC 

50) of Dowco 433 Ester to the Bobwhite Quail: Laboratory Project ID: DWC 393B/83903. Unpublished study prepared by Huntingdon Research Centre. 20 p. 

42137301 Fluroxypyr-MHE 

Grimes, J., and M. Jaber. 1988. Fluroxypyr, 1-methyheptyl ester: A Dietary LC50 Study with the Mallard. Project No. 103-286. Performed by Wildlife International, Ltd., Easton, MD. Submitted by Dow Chemical Company, Midland, MI. 

40244547 Fluroxypyr acid 

Roberts, N.; Phillips, C. (1983) The Subacute Dietary Toxicity 

(LC50) of Dowco 433 Acid to the Bobwhite Quail: Laboratory Project ID: DWC 393A/83902. Unpublished study prepared by Huntingdon Research Centre. 20 p. 

42137302 Fluroxypyr acid 

Grimes, J.; Lynn, S.; Smith, G. (1991) Fluroxypyr: A Dietary LC50 Study with the Mallard: Lab Project Number: ES/DR/0170/8550/5. Unpublished study prepared by Wildlife International Ltd. 21 p. 

Avian Reproduction 

Test 

850.2300 40244517 Fluroxypyr-MHE 

Roberts, N.; Phillips, C. (1983) The Subacute Dietary Toxicity (LC 50) of Dowco 433 Ester to the Bobwhite Quail: Laboratory Project ID: DWC 393B/83903. Unpublished study prepared by Huntingdon Research Centre. 20 p. 
53 

Guideline MRID Test Material Citation 

42137301 Fluroxypyr-MHE 

Grimes, J., and M. Jaber. 1988. Fluroxypyr, 1-methyheptyl ester: A Dietary LC50 Study with the Mallard. Project No. 103-286. Performed by Wildlife International, Ltd., Easton, MD. Submitted by Dow Chemical Company, Midland, MI. 

42137303 Fluroxypyr acid 

Beavers, J.; Hawrot, R.; Jaber, M. (1989) Fluroxypyr 1-Methylheptyl Ester Herbicide: A One-Generation Study with the Bobwhite (Colinus virginianus): Lab Project Number: ES-DR0186-1887-14: 103-295. Unpublished study prepared by Wildlife International Ltd. 116 p. 

42137304 Fluroxypyr acid 

Beavers, J.; Hoxter, K.; Nichols, L.; et al. (1989) Fluroxypyr 1- Methylheptyl Ester Herbicide: A One-Generation Reproduction Study with the Mallard (Anas platyrhynchos): Lab Project Number: ES-DR-0186-1887-15: 103/296. Unpublished study prepared by Wildlife International Ltd. 118 p. 

Fish Acute Toxicity 

(Freshwater) 

850.1075 

40244519 Fluroxypyr-MHE 

Willis, C. (1984) The Acute Toxicity of Dowco 433 Acid to Golden Orfe: Amended Report: LSR/Aquatox Schedule No. AFT/84/012. Un- published study prepared by Aquatox Limited. 24 p. 

40244522 Fluroxypyr-MHE 

Willis, C. (1984) The Acute Toxicity of Dowco 433 Ester to Rainbow Trout: LSR/Aquatox Schedule No. AFT/84/013. Unpublished study prepared by Aquatox Limited. 33 p. 

40244523 Fluroxypyr-MHE 

Willis, C. (1984) The Acute Toxicity of Dowco 433 Ester to Golden Orfe: LSR/Aquatox Schedule No. AFT/84/015. Unpublished study prepared by Aquatox Limited. 41 p. 

44080307 Fluroxypyr-MHE 

Rick, D.; Landre, A.; Kirk, H. (1996) Evaluation of the Acute Toxicity of Fluroxypyr 1-Methylheptyl Ester to the Bluegill, Lepomis macrochirus Rafinesque: Lab Project Number: DECO-ES3020. Unpublished study prepared by The Environmental Toxicology Research Lab., the Dow Chemical Co. 53 p. 

44080307 Fluroxypyr-MHE 

Boeri, R.; Kowalski, P.; Ward, T. (1996) Fluroxypyr 1-Methylheptyl Ester: Acute Toxicity to the Sheepshead Minnow, Cyprinodon variegatus: Lab Project Number: DECO-ES-2961: 707-DO. Unpublished study prepared by T. R. Wilbury Labs., Inc. 24 p. 

40244525 Fluroxypyr-MHE 

Hill, R.W. 1984. EF689: Determination of the Acute Toxicity to Rainbow Trout (Salmo gairdneri). Laboratory Study Number M083/A. Prepared by Imperial Chemical Industries PLC , Brixham, 

Devon, England. Submitted by Agricultural Products Department, Dow Chemical U. S .A. MRID Number 402443 -25. 
54 

Guideline MRID Test Material Citation 

42137305 Fluroxypyr-MHE 

Dill, D.C. and E.A. Bartlett. 1989. Fluroxypyr 1-Methylheptyl 

Ester: Evaluation of the Toxicity to the Bluegill, Lepomis macrochirus Rafinesque. Laboratory project Study ID. ES-DR0186-1887-3. Prepared by Mammalian & Environmental Toxicology Research Laboratory, The Dow Chemical Company, Midland, MI. Submitted by Dow Elanco. EPA MRID No. 421373-05. 

42137307 Fluroxypyr-MHE 

Weinberg, J.; Richardson, C.; Rick, D.; et al. (1991) Fluroxypyr, 1-Methylheptyl Ester: Evaluation of the Acute Toxicity to the Rainbow Trout, Oncorhynchus mykiss Walbaum: Lab Project Number: ES-DR-0186-1887-18. Unpublished study prepared by Dow Chemical Co., Environ. Tox. & Chem. Research Lab. 25 p. 

40244518 Fluroxypyr acid 

Willis, C. (1984) The Acute Toxicity of Dowco 433 Acid to Rainbow Trout: LSR/Aquatox Schedule No. AFT/84/008. Unpublished study prepared by Aquatox Limited. 19 p. 

40244519 Fluroxypyr acid 

Willis, C.A. 1984. The Acute Toxicity of DOWCO 433 Acid to Golden Orfe. Laboratory Project ID: LSR/~tox Schedule No. AFT/84/012. Prepared by Aquatox Limited, Suffolk, England. 

Submitted by Agricultural Products Department, Dow Chemical U. S .A. Accession 402445-19. 

42137306 Fluroxypyr acid 

Weinberg, J.; Richardson, C.; Rick, D.; et al. (1991) Fluroxypyr: Evaluation of the Acute Toxicity to the Bluegill, Lepomis macroochirus Rafinesque: Lab Project Number: ES-DR-0170-8550-7. Un- published study prepared by Dow Chemical Co., Environ. Tox. and Chem. Research Lab. 26 p. 

Fish Acute Toxicity 

(Saltwater) 

850.1075 44080308 Fluroxypyr-MHE 

Boeri, R.; Kowalski, P.; Ward, T. (1996) Fluroxypyr 1-Methylheptyl Ester: Acute Toxicity to the Sheepshead Minnow, Cyprinodon variegatus: Lab Project Number: DECO-ES-2961: 707-DO. Unpublished study prepared by T. R. Wilbury Labs., Inc. 24 p. 

42137309 Fluroxypyr-MHE 

Manning, C. (1988) Fluroxypyr 1-MHE: Acute Toxicity to Atlantic Silversides (Menidia menidia) Under Flow-through Conditions: Lab Project Number: 87388-0200-2130: ES-DR-0186-1887-6. Unpublished study prepared by Environmental Science and Engineering, Inc. 30 p. 

Aquatic Invertebrate 

Acute Toxicity, 

Daphnids 

40244520 Fluroxypyr-MHE 

Jones, N. 1984. The Acute Toxicity of DOWCO433 Ester to 

Daphnia magna. Laboratory Project ID: LSR/Aquatox Schedule No. AFT/84/014. Prepared by Aquatox Limited, Suffolk, England. 
55 

Guideline MRID Test Material Citation 

850.1010 Submitted by Agricultural Products Department, Dow Chemical,

U.S.A. Accession Number 402445-20. 

42137308 Fluroxypyr-MHE 

Weinberg, J.; Milazzo, D.; Servinski, M.; et al. (1991) Fluroxypyr, 1-Methylheptyl Ester: Evaluation of the Acute Toxicity to the Water Flea, Daphnia magna Straus: Lab Project Number: ES-DR01- 86-1887-19. Unpublished study prepared by Dow Chemical Co., Environ. Tox. & Chem. Research Lab. 26 p. 

40244524 Fluroxypyr acid 

Jones, N. (1984) The Acute Toxicity of Dowco 433 Acid to Daphnia magna: LSR/Aquatox Schedule No. AFT/84/009. Unpublished study prepared by Aquatox Limited. 22 p. 

Prolong Toxicity 

with Daphnia magna 

(nonguideline) 

40244521 Fluroxypyr acid 

Jones, N. (1984) Prolonged Toxicity of Dowco 433 Acid to Daphnia magna: LSR/Aquatox Schedule No. AFT/84/010. Unpublished study prepared by Aquatox Limited. 38 p. 

Penaeid (Shrimp) 

Acute Toxicity 

850.1045 44080313 Fluroxypyr-MHE 

Boeri, R.; Kowalski, P.; Ward, T. (1996) Fluroxypyr 1-Methylheptyl Ester: Acute Toxicity to the Grass Shrimp, Palaemonetes pugio: Lab Project Number: 706-DO: DECO-ES2962: Unpublished study prepared by T. R. Wilbury Labs., Inc. 24 p. 

42137311 Fluroxypyr-MHE 

Manning, C. (1988) Fluroxypyr 1-MHE: Acute Toxicity to Pink Shrimp (Penaeus duorarum) Under Flow-through Conditions: Lab Project No: 87388-0300-2130. Unpublished study prepared by Environmental Science and Engineering, Inc. 31 p. 

42137312 Fluroxypyr acid 

Boeri, R.; Kowalski, P.; Ward, T. (1994) Fluroxypyr: Acute Toxicity to the Grass Shrimp, Palaemonetes pugio: Lab Project Number: 197-DO: ES-2643. Unpublished study prepared by T. R. Wilbury Labs., Inc. 24 p. 

Oyster Acute 

Toxicity 

(Shell Deposition) 

850.1025 

44080310 Fluroxypyr-MHE 

Boeri, R.; Kowalski, P.; Ward, T. (1996) Fluroxypyr 1-Methylheptyl Ester: Acute Flow-Through Mollusc Shell Deposition Test: Lab Project Number: 646-DO: DECO-ES-2925. Unpublished study prepared by T. R. Wilbury Labs., Inc. 28 p. 

45725801 Fluroxypyr-MHE 

Dionne, E. (2002) Fluroxypyr 1-Methylheptyl ester--Acute Toxicity to Eastern Oysters (Crassostrea virginica) Under FlowThrough Conditions: Lab Project Number: 12550.6202: 021015. 

Unpublished study prepared by Springborn Smithers Laboratories. 60 p. 

42137310 Fluroxypyr-MHE Manning, C. (1988) Fluroxypyr 1-MHE: Shell Growth of the Eastern Oyster (Crassostrea virginica): Lab Project No: 87388-
56 

Guideline MRID Test Material Citation 

0400-2130. Unpublished study prepared by Environmental Science and Engineering, Inc. 31 p. 

42137311 Fluroxypyr acid 

Boeri, R.; Kowalski, P.; Ward, T. (1994) Fluroxypyr: Acute FlowThrough Mollusc Shell Deposition Test: Lab Project Number: 198-DO: ES-2645. Unpublished study prepared by T. R. Wilbury Labs., Inc. 25 p. 

Daphnid Life Cycle 

Toxicity 

850.1300 44080314 Fluroxypyr-MHE 

Kirk, H.; Miller, J.; Hugo, J.; et al. (1996) Evaluation of the Chronic Toxicity of Fluroxypyr 1-Methylheptyl Ester to the Daphnid, Daphnia magna Straus: Lab Project Number: DECO-ES3079: 19023. Unpublished study prepared by The Dow Chemical Co. 78 p. 

Fish Early-Life 

Stage Toxicity 

850.1400 48559401 Fluroxypyr acid 

Gallagher, S.; Kendall, T.; Krueger, H. (2011) Fluroxypyr: An Early Life-Stage Toxicity Test with the Fathead Minnow (Pimephales promelas): Final Report. Project Number: 101728 379A/147A. Unpublished study prepared by Wildlife International, Ltd. 97p. 

Honey Bee Acute 

Contact Toxicity 

850.3020 40244527 Fluroxypyr-MHE 

Cole, J. (1983) The Acute Contact and Oral Toxicity to Honey Bees of Technical Dowco 433--MH Ester: Laboratory Project ID: DWC 387/83717/2. Unpublished study prepared by Huntingdon Research Centre. 9 p. 

42137313 Fluroxypyr-MHE 

Lynn, S.; Hoxter, K. (1991) Fluroxypyr, 1-MHE: An Acute Contact Toxicity Study with the Honey Bee: Lab Project No: ES-DR-0186- 1887-17. Unpublished study prepared by Wildlife International Lab. 18 p. 

42137314 Fluroxypyr acid 

Lynn, S.; Hoxter, K. (1991) Fluroxypyr: An Acute Contact Toxicity Study with the Honey Bee: Lab Project Number: ES-DR-0170-

8550-4: 103-358. Unpublished study prepared by Wildlife International Ltd. 18 p. 

Seedling Emergence 

850.4100 44080335 Fluroxypyr-MHE 

Schwab, D. (1996) Evaluating the Effects of Fluroxypyr-MHE on the Seedling Emergence and Vegetative Vigor of Non-Target Terrestrial Plants: Lab Project Number: 42838: RES95175. Unpublished study prepared by ABC Labs., Inc. 168 p. 

44094902 Fluroxypyr-MHE 

Wright, J.; Rowland, L. (1996) Phytotoxicity of Fluroxypyr MHE and Its Metabolites Fluroxypyr, Methoxypyridine, and Pyridinol to Non-Target Terrestrial Plants: Amended Report: Lab Project Number: GH-C 3859. Unpublished study prepared by DowElanco Global Environmental Chemistry Lab. 201 p. 
57 

Guideline MRID Test Material Citation 

Vegetative Vigor 

850.4150 44080335 Fluroxypyr-MHE 

Schwab, D. (1996) Evaluating the Effects of Fluroxypyr-MHE on the Seedling Emergence and Vegetative Vigor of Non-Target Terrestrial Plants: Lab Project Number: 42838: RES95175. Unpublished study prepared by ABC Labs., Inc. 168 p. 

44094902 Fluroxypyr-MHE 

Wright, J.; Rowland, L. (1996) Phytotoxicity of Fluroxypyr MHE and Its Metabolites Fluroxypyr, Methoxypyridine, and Pyridinol to Non-Target Terrestrial Plants: Amended Report: Lab Project Number: GH-C 3859. Unpublished study prepared by DowElanco Global Environmental Chemistry Lab. 201 p. 

Aquatic Plant 

Toxicity Using 

Lemna sp. 

850.4400 

44080338 Fluroxypyr-MHE 

Kirk, H.; Milazzo, D.; Hugo, J.; et al. (1996) Fluroxypyr 1-Methylheptyl Ester: The Toxicity to the Aquatic Plant, Duckweed, Lemna gibba L. G-3: Lab Project Number: DECO-ES-3074: 19023. Unpublished study prepared by The Dow Chemical Co. 61 p. 

44744001 Fluroxypyr-MHE (as Starane 180) 

Kirk, H.; Gilles, M.; Rick, D. et al. (1998) Phytotoxicological Evaluation of Starane 180 Emulsifiable Herbicide Concentrate (Formulation EF-1463) Exposed Aquatic Plant, Duckweed, Lemna gibba L. G-3: Lab Project Number: 981132. Unpublished study prepared by Dow Chemical Company. 75 p. 

Algal Toxicity 

850.5400 44080337 Fluroxypyr-MHE 

Hughes, J.; Alexander, M.; Conder, L. (1996) Fluroxypyr 1-Methylheptyl Ester: The Toxicity to Skeletonema costatum: Lab Project Number: 10-04-1. Unpublished study prepared by Carolina Ecotox, Inc. 86 p. 

44080339 Fluroxypyr-MHE 

Milazzo, D.; Landre, A.; Hugo, J.; et al. (1996) Fluroxypyr 1-Methylheptyl Ester: The Toxicity to the Freshwater Diatom, Navicula pelliculosa: Lab Project Number: ES-3075: 19023: DECO-ES-3075. Unpublished study prepared by The Dow Chemical Co. 56 p. 

44527201 Fluroxypyr-MHE 

Kirk, H.; Landre, A.; Hugo, J. et al. (1998) Supplemental Report for: Fluroxypyr 1-Methylheptyl Ester: The Toxicity to the Freshwater Diatom, Navicula pelliculosa: Lab Project Number: ES3075. Unpublished study prepared by The Dow Chemical Co. 44 p. 

44527201 Fluroxypyr-MHE 

Milazzo, D.; Hugo, J.; Martin, M. (1996) Fluroxypyr 1-Methylheptyl Ester: The Toxicity to the Freshwater Green Alga, Selenastrum capricornutum Printz: Lab Project Number: ES-3076: 19023: DECO-ES-3076. Unpublished study prepared by The Dow Chemical Co. 53 p. 

45820801 Fluroxypyr-MHE Hoberg, J. (2002) Fluroxypyr 1-Methylheptyl Ester Technical-- Acute Toxicity to the Freshwater Diatom (Navicula pelliculosa): 
58 

Guideline MRID Test Material Citation 

Lab Project Number: 12550.6203: 021014. Unpublished study prepared by Springborn Smithers Laboratories. 68 p. 

42137312 Fluroxypyr-MHE 

Hughes, J.; Alexander, M. (1991) The Toxicity of Fluroxypyr 1- Methylheptyl Ester to Selenastrum capricornutum: Lab Project No: B460-12-1: ES-DR-0186-1887-16. Unpublished study prepared by Malcolm Pirnie, Inc. 37 p. 

42164501 Fluroxypyr-MHE 

Cowgill, U.; Milazzo, D.; Murphy, P. (1988) The Five-Day Toxicity Of Fluoroxypyr (Dowco 433) to Selenastrum Capricornutum Printz, a Freshwater Green Alga: Lab Project Number: ES-DR-0170-8550-3: ES-1016. Unpublished study prepared by The Dow Chemical Co. 19 p. 

40244526 Fluroxypyr acid 

Jones, N. (1984) Toxicity of Dowco 433 Acid to Chlorella vulgaris, CCAP 211/11b: LSR/Aquatox Schedule No. AFT/84/011. Unpublished study prepared by Aquatox Limited. 31 p. 

44080341 

4-Amino-3,5-

Dichloro-6-Fluoro-2-

Methoxypyridine 

Kirk, H.; Landre, A. (1995) Evaluation of the Phytotoxicity of 4-Amino-3,5-Dichloro-6-Fluoro-2-Methoxypyridine to the Green Algae, Selenastrum capricornutum Printz: Lab Project Number: DECO-ES-3029. Unpublished study prepared by The Dow Chemical Co. 15 p. 

45011601 

4-Amino-3,5-

dichloro-6-fluoro-2-

pyridinol 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-pyridinol (A Metabolite of Fluroxypyr): Toxicity to the Freshwater Diatom, Navicula pelliculosa: Lab Project Number: 990032: 1728-DO. Unpublished study prepared by T.R. Wilbury Labs., Inc. 26 p. 

45011602 

4-Amino-3,5-

dichloro-6-fluoro-2-

pyridinol 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-pyridinol (A Metabolite of Fluroxypyr): Toxicity to the Duckweed, Lemna gibba: Lab Project Number: 990033: 1731-DO. Unpublished study prepared by T.R. Wilbury Labs., Inc. 26 p. 

45011603 

4-Amino-3,5-

dichloro-6-fluoro-2-

pyridinol 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-pyridinol (A Metabolite of Fluroxypyr): Toxicity to the Green Alga, Selenastrum capricornutum: Lab Project Number: 990034: 1732-DO. Unpublished study prepared by T.R. Wilbury Labs., Inc. 26 p. 

45011604 

4-Amino-3,5-

dichloro-6-fluoro-2-

pyridinol 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-pyridinol (A Metabolite of Fluroxypyr): Toxicity to the Freshwater Bluegreen Alga, Anabaena flos-aquae: Lab Project Number: 990035: 1729-DO. Unpublished study prepared by T.R. Wilbury Labs., Inc. 26 p. 
59 

Guideline MRID Test Material Citation 

45011605 

4-Amino-3,5-

dichloro-6-fluoro-2-

pyridinol 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-pyridinol (A Metabolite of Fluroxypyr): Toxicity to the Saltwater Diatom, Skeletonema costatum: Lab Project Number: 990036: 1730-D0. Unpublished study prepared by T.R. Wilbury Labs., Inc. 26 p. 

45011606 

4-Amino-3,5-

dichloro-6-fluoro-2-

methoxypyridine 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-methoxypyridine (A Metabolite of Fluroxypyr): Toxicity to the Freshwater Diatom, Navicula pelliculosa: Lab Project Number: 990037: 1733-DO. Unpublished study prepared by T.R. Wilbury Labs., Inc. 36 p. 

45011607 

4-Amino-3,5-

dichloro-6-fluoro-2-

methoxypyridine 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-methoxypyridine (A Metabolite of Fluroxypyr): Toxicity to the Duckweed, Lemna gibba: Lab Project Number: 990038: 1736-DO. Unpublished study prepared by T.R. Wilbury Labs., Inc. 36 p. 

45011608 

4-Amino-3,5-

dichloro-6-fluoro-2-

methoxypyridine 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-methoxypyridine (A Metabolite of Fluroxypyr): Toxicity to the Freshwater Bluegreen Alga, Anabaena flos-aquae: Lab Project Number: 90039: 1734-DO. Unpublished study prepared by T.R. Wilbury Labs., Inc. 26 p. 

45011609 

4-Amino-3,5-

dichloro-6-fluoro-2-

methoxypyridine 

Ward, T.; Magazu, J.; Boeri, R. (1999) 4-Amino-3,5-dichloro-6-fluoro-2-methoxypyridine (A Metabolite of Fluroxypyr): Toxicity to the Saltwater Diatom, Skeletonema costatum: Lab Project Number: 990040: 1735-DO. Unpublished study prepared by T.R. Wilbury Labs., Inc. 26 p. 

Cyanobacteria 

Toxicity 

850.4550 44080336 Fluroxypyr-MHE 

Milazzo, D.; Miller, J.; Hugo, J.; et al. (1996) Fluroxypyr 1-Methylheptyl Ester: The Toxicity to the Blue-Green Alga, Anabaena flos-aquae: Lab Project Number: ES-3073: 19023: DECO-ES-3073. Unpublished study prepared by The Dow Chemical Co. 55 p. 
60 

APPENDIX B. INPUTS AND OUTPUTS FROM THE SIP AND STIR MODELS 

I. Screening Imbibition Program (SIP), Version 1.0 

A. Fluroxypyr 

Table 1. Inputs 

Parameter Value 

Chemical name Fluroxypyr 

Solubility (in water at 25oC; mg/L) 255.03 

 

Mammalian LD50 (mg/kg-bw) 2408 

Mammalian test species laboratory rat 

Body weight (g) of "other" mammalian 

species 

 

Mammalian NOAEL (mg/kg-bw) 500 

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) 

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 

 
61 

Table 2. Mammalian Results 

Parameter Acute Chronic 

Upper bound exposure (mg/kg-bw) 43.8652 43.8652 

Adjusted toxicity value (mg/kg-bw) 1852.1386 384.5803 

Ratio of exposure to toxicity 0.0237 0.1141 

Conclusion* 

Drinking water exposure 

alone is NOT a potential 

concern for mammals 

Drinking water exposure 

alone is NOT a potential 

concern for mammals 

Table 3. Avian Results 

Parameter Acute Chronic 

Upper bound exposure (mg/kg-bw) 206.5743 206.5743 

Adjusted toxicity value (mg/kg-bw) 1440.8590 0.0000 

Ratio of exposure to acute toxicity 0.1434 0.0000 

Conclusion* 

Exposure through 

drinking water alone is a 

potential concern for 

birds 

Due to insufficient data, 

risk cannot be precluded 

*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. 

B. Fluroxypyr-MHE 

Table 1. Inputs 

Parameter Value 

Chemical name Fluroxypyr-MHE 

Solubility (in water at 25oC; mg/L) 0.9 

 

Mammalian LD50 (mg/kg-bw) 809 

Mammalian test species laboratory rat 

Body weight (g) of "other" mammalian 

species 

 

Mammalian NOAEL (mg/kg-bw) 300 

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) 250 

Bobwhite quail NOAEC (mg/kg-diet) 1000 

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

Body weight (g) of other avian species 
62 

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

species 

Body weight (g) of 2nd other avian species 

Table 2. Mammalian Results 

Parameter Acute Chronic 

Upper bound exposure (mg/kg-bw) 0.1548 0.1548 

Adjusted toxicity value (mg/kg-bw) 622.2509 230.7482 

Ratio of exposure to toxicity 0.0002 0.0007 

Conclusion* 

Drinking water exposure 

alone is NOT a potential 

concern for mammals 

Drinking water exposure 

alone is NOT a potential 

concern for mammals 

Table 3. Avian Results 

Parameter Acute Chronic 

Upper bound exposure (mg/kg-bw) 0.7290 0.7290 

Adjusted toxicity value (mg/kg-bw) 1440.8590 12.4031 

Ratio of exposure to acute toxicity 0.0005 0.0588 

Conclusion* 

Drinking water exposure 

alone is NOT a potential 

concern for birds 

Drinking water exposure 

alone is NOT 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. 

II. Screening Tool for Inhalation Risk (STIR), Version 1.0 

A. Fluroxypyr 

Input 

Application and Chemical Information 

Enter Chemical Name Fluroxypyr

Enter Chemical Use grains

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

If Spray What Type (enter ground or air) air

Enter Chemical Molecular Weight (g/mole) 255.03

Enter Chemical Vapor Pressure (mmHg) 9.50E-11

Enter Application Rate (lb a.i./acre) 0.225

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) 2408

Enter Lowest Rat Inhalation LC50 (mg/L) 2.09

Duration of Rat Inhalation Study (hrs) 4
63 

Enter Rat Weight (kg) 0.35

Output 

Results Avian (0.020 kg ) 

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 1.30E-06 

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.64E-07 

Adjusted Inhalation LD50 9.68E+00 

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.69E-08

Exposure not Likely 

Significant 

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 2.16E-02 

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 2.23E-03

Exposure not Likely 

Significant 

Results Mammalian (0.015 kg ) 

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 1.30E-06 

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.06E-07 

Adjusted Inhalation LD50 1.24E+02 

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.66E-09

Exposure not Likely 

Significant 

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 2.72E-02 

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 2.18E-04

Exposure not Likely 

Significant 

 
64 

B. Fluroxypyr-MHE 

Input 

Application and Chemical Information 

Enter Chemical Name Fluroxypyr-MHE

Enter Chemical Use Pastures

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

If Spray What Type (enter ground or air) air

Enter Chemical Molecular Weight (g/mole) 367.24

Enter Chemical Vapor Pressure (mmHg) 1.07E-07

Enter Application Rate (lb a.i./acre) 0.76

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) 809

Enter Lowest Rat Inhalation LC50 (mg/L) 2.09

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) 2.11E-03 

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.66E-04 

Adjusted Inhalation LD50 2.88E+01 

Ratio of Vapor Dose to Adjusted Inhalation LD50 9.23E-06

Exposure not Likely 

Significant 

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 7.30E-02 

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 2.53E-03

Exposure not Likely 

Significant 

Results Mammalian (0.015 kg ) 

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 2.11E-03 

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 3.34E-04 

Adjusted Inhalation LD50 1.24E+02 

Ratio of Vapor Dose to Adjusted Inhalation LD50 2.69E-06

Exposure not Likely 

Significant 

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 9.18E-02 

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 7.38E-04

Exposure not Likely 

Significant