UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON. D.C. 20460 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

PC Code: 030090 

DP Barcode: 417685 

Date: June 3rd, 2014 

SUBJECT: EFED Registration Review Problem Formulation for Pyraflufen-ethyl 

FROM: 

Mohammed 

Justin Housenger, 

Ruhman, 

B~ologist Ph.D., Senior fJ/ Agronom~j!!_t~Jf!!~~~:::::--~7.~-~· :~OJ~ Environmental Risk Branch 5 . Ot jo~f Jt 

Environmental Fate and Effects Division (7507P) 

TO: Steven Snyderman, Chemical Review Manager 

Tracy Perry, Risk Manager 

Risk Management and Implementation Branch 3 

Pesticide Re-Evaluation Division (7508P) 

REVIEWED Hannah Yingling, Biologist 

BY: Michael Barrett, Senior Chemist 

Environmental Risk Branch 5 

Environmental Fate and Effects Division (7507P) 

THROUGH: Mah Shamim, Branch Chief 

Environmental Risk Branch 5 

Environmental Fate and Effects Division (7507P) 

1 
2

Table of Contents

1. Executive summary................................................................................................................. 3

2. Introduction............................................................................................................................. 5

3. Use Characterization............................................................................................................... 6

4. Conclusions from Previous Risk Assessments....................................................................... 8

5. Environmental Fate and Transport........................................................................................ 11

6. Receptors............................................................................................................................... 17

7. Exposure Pathways of Concern ............................................................................................ 25

8. Analysis Plan ........................................................................................................................ 27

9. Endangered Species Assessments......................................................................................... 29

10. Endocrine Disruptor Screening Program........................................................................... 29

11. Preliminary Identification of Data Gaps............................................................................ 29

12. References.......................................................................................................................... 34
3

1. Executive summary

The Environmental Fate and Effects Division (EFED) have completed the attached preliminary 

problem formulation for the ecological risk, environmental fate, endangered species, and drinking 

water assessments to be conducted as part of the registration review pyraflufen-ethyl. 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 

pyraflufen-ethyl as well as uncertainties unique to risk assessment of pyraflufen-ethyl. This 

document also identifies additional studies that may be included in a data call-in (DCI) to address 

uncertainties surrounding the environmental fate and potential ecological effects. 

Although pyraflufen-ethyl is relatively insoluble in water, the low application rate makes the 

amount applied readily soluble. The major degradates of the chemical are much more soluble 

which makes it readily available for leaching. Pyraflufen-ethyl is not likely to volatilize 

significantly from wet or dry surfaces (very low vapor pressure and Henry’s Law Constant). The 

octanol/water partition coefficients (KOWs) of pyraflufen-ethyl and its degradate E-3 are relatively 

high suggesting possible bio-concentration in aquatic organisms such as fish. In contrast, the other 

two major transformation products (E-1 and E-2) show much lower octanol/water partition 

coefficient suggesting low tendency to bio-concentrate. Pyraflufen-ethyl shows a high potential to 

hydrolyze under alkaline conditions. The major transformation product is E-1, which resists 

further hydrolysis at all pH levels tested. Pyraflufen-ethyl also undergoes photolysis quickly in 

water and on soil (half-lives of about 2.5 and 2 days, respectively). The major transformation 

products were PD-1 (not found in other fate studies) and E-1 in water and on loamy sand, 

respectively. Please see Appendix 2 for more information on the chemical names and structures 

for each degradate. 

Based on laboratory and field studies, parent pyraflufen-ethyl was found to be short-lived in 

aerobic and aquatic systems (half-lives <2 days and in hours, respectively). The major 

transformation pathways are hydrolysis, photolysis and metabolism forming transformation 

products E-1, E-2 and E-3. The E-1 and E-2 transformation products show different persistence 

patterns in different soils/aquatic systems depending on soil type, temperature and aerobicity

(refer to Section 5) but E-3, which is the terminal degradate, is expected to be highly persistent in 

the environment. A notable exception to this degradation pattern was the aqueous photolysis

dissipation pathway, where PD-1 was a major transformation product although PD-1 did not 

appear to be persistent under photolytic conditions. For pyraflufen-ethyl, E-1, E-2, and E-3, 

mobility was classified as slightly mobile, moderately mobile to mobile, slightly mobile, and 

slightly mobile, respectively (FAO, http://www.fao.org/docrep/003/x2570e/x2570e06.htm). 

Terrestrial field dissipation studies conducted in CA and WA confirm that the major 

transformation products found in the field are E-1 and E-3. They were not present at significant 

amounts below the 6-inch level. Due to the fact that parent is short-lived in the soil it is not 

expected to be leached and/or transported into aquatic systems by run-off.
4

The combined parent pyraflufen-ethyl and degradates E1, E-2 and E-3 are considered to be the 

main stressor in this risk assessment for both drinking and surface waters noting that short-term 

exposure will be mainly associated with E-1 because parent is expected to degrade rather quickly 

(half-life <1 day). In contrast, chronic or long-term exposure is expected to be, in most cases, 

associate with E-3 as it is the most persistent degradate (the terminal degradate). A different 

approach may be used, by calculating exposure EECs for individual species in the stressor 

depending on toxicity data that may be submitted by the registrant and how it compares to parent 

toxicity.

The main driver of potential risk for pyraflufen-ethyl is terrestrial and aquatic plants (which is 

anticipated for a chemical with a known herbicidal mode of action). Parent pyraflufen-ethyl did 

not cause mortality in acute aquatic toxicity studies (fish and invertebrates) at concentrations up 

to and including the solubility limit (82 μg a.i/L). Definitive endpoints were established in 

chronic aquatic toxicity studies but previous assessments show that parent pyraflufen-ethyl 

degrades to the degradate E-1 in 1-2 days. Available toxicity data for E-1 (acute and chronic) 

shows that E-1 is 2-3 orders of magnitude less toxic than parent pyraflufen-ethyl (depending on 

the taxa). There is currently no ecotoxicity data available for E-2 and E-3.

For terrestrial organisms, pyraflufen-ethyl caused no treatment related mortality in one acute oral 

and two sub-acute dietary studies that are available. The acute oral and sub-acute dietary studies 

tested up to concentrations of 2000 mg a.i/kg-bw and 4836 mg a.i/kg-diet, respectively. While 

two chronic avian reproduction studies were submitted, one was determined to be unacceptable 

due to several deviations which included instability of the test substance in the treated feed, onset 

of egg laying during the test, and humidity and temperature conditions of the adult birds and 

stored eggs. In another study determined to be suitable for quantitative risk assessment, there 

were no effects observed up to and including the highest treatment concentration (500 mg a.i/kgdiet). Available acute and chronic toxicity data for mammals indicate no mortalities or treatment 

related effect on any reproductive parameter.

There are a couple of sources of uncertainty for the ecological risk assessment for pyraflufenethyl:

- Lack of E-2, E-3 data, ECOSAR estimates:

As stated previously, parent pyraflufen-ethyl is expected to undergo degradation to E-1 within 1-2 

days, and subsequently transforms to E-2 and then to E-3. Currently, there are toxicity data 

available only for E-1, that indicate the degradate is 2-3 orders of magnitude less toxic than 

pyraflufen-ethyl. As no data are available for E-2 and E-3, the quantitative structure activity 

relationship (QSAR) tool ECOSAR was used to estimate toxicity to various taxa (Section 6). 

While the estimates are subject to uncertainty based on the lack of data points that inform the 

estimates, the analysis showed that E-2 and E-3 are generally more toxic than E-1 but still less 

toxic than parent pyraflufen-ethyl. Additionally, application rates of parent pyraflufen-ethyl are 

quite low (maximum seasonal rate on currently registered labels is 0.018 lbs a./A). The degradate 

E-3 can reach aquatic systems either by drift (maximum percentage expected to be 10%) or by 

run-off in soils where E-3 formation can be up to 50% of the applied pyraflufen-ethyl application 

rate. Therefore, while it is an uncertainty on the toxicity of E-2 and E-3 without registrant 
5

submitted toxicity data, the contribution to ecological risk posed by these degradates is expected 

to be low.

- Toxicity of ET-751 2.5% formulation:

While available acute aquatic toxicity data indicate that pyraflufen-ethyl TGAI did not cause 

mortalities up to and including the solubility limit, there are three acute toxicity studies conducted 

with formulated pyraflufen ethyl (as ET-751 2.5%) that did show mortality effects. There are two 

studies available for freshwater fish, and one study for freshwater invertebrates. In one study with 

the bluegill sunfish, formulated pyraflufen ethyl was tested at concentrations up to 6.3 mg a.i/L 

(mean measured). There was 100% mortality observed in the top two concentrations with the 

first 24 hours. Total mortality occurred at the third highest treatment concentration by test 

termination and by 48 hours in the formulation blank. In a second freshwater fish study with the 

rainbow trout, 100% mortality occurred in the top treatment concentration (mean measured 3.5 

mg a.i/L) and 95% in the second highest concentration by test termination. Additionally, 95% 

mortality occurred in the formulation blank by test termination. Finally, in a freshwater 

invertebrate toxicity study with formulated product, percent immobilization was observed to be 

70 and 80% for the 1.8 and 3.0 mg a.i/L mean measured concentration (top two concentrations). 

There was also 55% immobilization in the formulation blank. This data indicate that a 

component of the formulation ET-751 2.5% is highly toxic on an acute exposure basis to 

freshwater fish and invertebrates based on significant mortality effects in the formulation blank 

group. It is not known at present the extent of use of this formulation as its use would be 

expected to impact aquatic systems to a greater extent than TGAI pyraflufen-ethyl.

It was determined that there are no major data needs for ecological effects. At this time no major 

need for environmental fate data. However, a clarification is needed on the environmental 

chemistry methods (ECMs) and associated independent laboratory validations (ILVs). Needed 

clarification is noted in Table 11, below.

2. Introduction

For this Problem Formulation (PF), EFED evaluated the most recent ecological risk assessments 

for pyraflufen-ethyl association with any updated toxicity, exposure, and use and usage 

information to determine if sufficient data are available and if further updates are needed to 

support registration review. Pyraflufen-methyl was registered on September, 27, 2002 with an 

ecological risk assessment conducted for Section 3 registration on Corn (grain, stover and forage); 

Cotton; Potatoes; and Soybeans (grain, hay and forage)1. The registration was followed, in 2008, 

2011 and 2012; by new use registrations on many other use patterns (refer to use characterization 

section for these use patterns). It is noted that the ecological risk assessment conducted in 2002 

was used to support the new use registrations of 2008, 2011 and 2012. EFED considered this 

referenced assessment in addition to the latest Agency science policies and risk assessment 

 

1 EFED Section 3 Registration Chapter for Pyraflufen-Ethyl (DP Barcodes: D283754, D279383, and D278170; Dated 

August 2002)
6

methodologies. The structures of pyraflufen-ethyl and major degradate as well as the chemical 

names and other identifiers can be found elsewhere in this document.

Pyraflufen-ethyl is a contact herbicide and, according to the label, the product is rain-fast 

(efficacious if no rain occurs). The chemical belongs to the phenyl pyrazole class of chemicals 

called protox inhibitors. Protox is also known as protoporphyrinogen oxidase whose inhibition 

leads to the buildup of the compound protoporphyrin IX. This buildup causes protoporphyrin IX 

to move from the reaction center in the chloroplast into the cytoplasm where interactions with 

oxygen and light results in formation of oxygen free radicals that cause lipid peroxidation. This 

eventually causes plant death by disrupting the cell membrane. As the process is dependent on 

light, chemicals in this group of compounds inhibiting protox are called light-dependent 

peroxidizing herbicides (LDPH). This class of herbicide is known to have a photo-toxic mode of 

action in plants and possibly in fish. LDPHs may be more toxic when exposed to natural sunlight, 

such as exposure conditions in the field. 

3. Use Characterization

Labeled Use

Pyraflufen-ethyl is herbicide with 17 active registrations including one Section 24(c) – Special 

Local Needs (SLN) for Arizona and no pending new uses. The chemical is currently labeled for:

 Pre-plant burn-down, post-emergence weed control in corn, pastureland, peanuts, rangeland 

and soybeans;

 Pre-plant burn-down, post-emergence and layby weed control and as a defoliation agent in 

Cotton;

 Weed control in turf (turf area, golf courses and sod farms), crop areas (pre-plant fallow beds 

and crop stubble) and non-crop and uncultivated areas;

 Weed control in certain bearing & non-bearing tree crops as dormant, pre-bloom, in season, 

and postharvest applications in pome/stone fruits (CGs= Crop Groups 11/12), nut trees (CG 

14), olives, pomegranates, hops, and vines “grapes”;

 Crop desiccation in potatoes; and

 Pre-plant burn-down weed control in cereal grains (CG15), cole crops (CG5), cucurbits 

(CG9), fruiting veg. (CG8), leafy veg. (CG4), legumes (CG6), oil seed crops (CG20), root & 

tuber vegetables (CG1) and sugarcane

Pyraflufen-ethyl is formulated in two products: 2% SC and 2.5% EC ET Herbicide/Defoliant. It 

can be applied by ground and/or aerial equipment depending on the use pattern.

Recently, labeled uses were examined and a summary of the main uses/application parameters 

were summarized and are presented in Appendix 1. It is noted that EFED will use this referenced 
7

data in future exposure modeling. Therefore, the registrant is requested to review data presented 

in Appendix 1 for accuracy and completeness noting that EFED exposure modeling is largely 

based on the following:

 The highest single application rate and the highest number of applications/crop/year to arrive 

at the maximum lbs a.i/A/year. The maximum annual rate allowed per acre not crop should be 

stated in the label. This rate should take in consideration all a.i applied to one acre of land 

throughout the year.

 The shortest application intervals (days);

 The type of application and equipment (foliar, soil, incorporation with stated depth, aerial, 

ground or other);

 Timing of the first application (should be clearly defined in the label); and

 Any other information and restrictions that should be considered in exposure modeling.

Missing information will result in conservative assumptions in modeling exposure that will result 

in conservative risk estimation.

Usage

Screening level of agricultural usage data for pyraflufen-ethyl is summarized in Table 1. This 

pesticide usage data is compiled by the Biological and Economic Analysis Division (BEAD) from 

various sources for pyraflufen-ethyl as a single active that is used on agricultural crops.

Table 1 Screening Level Usage Analysis (SLUA): Screening Level Estimates of Agricultural 

Uses of Pyraflufen-ethyl (2004-2011 reporting years; dated April 15, 2013)

Crop (s)

Lbs a.i 

Used

Percent Crop Treated

Average Maximum

Cotton 2,000 5% 10%

Tomatoes 10 10% 20%

Peaches, Pistachios, Plums/Prunes, Each <500 <2.5% <2.5%

Alfalfa, Almonds, Apples, Cherries, Corn, Dry beans/Peas, Fallow, 

Grapes, Onions, Pasture, Peanuts, Pecans, Potatoes, Sorghum, Soybeans, 

Squash, Sunflower, Walnuts and Wheat, Each <500 <1% <2.5%

Apricots*, Kiwi*, Nectarines*, Olives*, and Pomegranates*, Each <500 NC NC

* Based on California department of pesticide regulations (CA DPR) data only; noting that California represents 

>80% of the USA acreage for these crops; and NC= Not calculated; only pounds a.i are available.

Data in Table 1 suggest that the highest usage was reported for cotton (mostly as defoliant) and 

tomatoes. Reported usage on other crops appears to limit to <500 lbs a.i/each crop with a 

maximum of <2.5% of the acres treated for crops other than cotton and tomatoes.
8

An overview of Pyraflufen-ethyl and its use and usage information were prepared by the 

Biological and Economic Analysis Division (BEAD). This report is included in the docket 

(Screening Level Usage Analysis (SLUA) Date: April 15, 2013”)

4. Conclusions from Previous Risk Assessments

The ecological risk assessments that were conducted for pyraflufen-ethyl were:

(1) The 2002 Section 3 new chemical registration on Corn (grain, stover and forage); Cotton; 

Potatoes; and Soybeans (grain, hay and forage)2;

(2) The Section 3 new use registrations on:

a. Non-crop areas; Nurseries, Ornamental plantings; and Pastures; and Ground Pre-plant burndown for Vegetables “Tuber & Root, Fruiting, and Cucurbits”, Cole crops, Legumes, and 

Small grains; Sod farms; and Christmas Trees in 20083;

b. Aerial Pre-plant burn-down uses in 20094;

c. Tree Nuts, Stone Fruits, Pome Fruits, Hops, Grapes, Olives, and Pomegranates in 20115; and

d. Hops and Peanuts in 20126

a. Ecological Risk Assessment 

The ecological risk assessment conducted in 2002 (EFED Section 3 Registration Chapter for

Pyraflufen-Ethyl; DP Barcodes: D283754, D279383, and D278170; Dated August 2002) was 

used to support the initial registration as well as the new use registrations of 2008, 2011 and 2012. 

This is because rates for the new uses were similar to uses in the initial registration. The 2002 

 

2 EFED Section 3 Registration Chapter for Pyraflufen-Ethyl (DP Barcodes: D283754, D279383, and D278170; Dated 

August 2002)

3 EFED Registration for Pyraflufen-ethyl to be used on Pastures, Wheat, Soybean, Corn, Pastures, Sod farms, 

Christmas Trees, Nurseries, Ornamental plantings and for Non-Crop Weed Control. Also for Use as a Pre-Plant 

Burn down on Root and Tuber Vegetables, Cole Crops, Legumes, Fruiting Vegetables, Cucurbits and Small Grains

(DP Barcodes: D337845, D342902, D343458, D343461 and D343914; Dated Jan, 2008)

4 EFED Registration of Pyraflufen-ethyl for Aerial Pre-Plant Burn down Uses (DP Barcodes: D364054 and 

D364057; dated August, 2009)

5 Section 3 New Use for Pyraflufen-ethyl for the Uses on Tree Nuts, Stone Fruits, Pome Fruits, Hops, Grapes, Olives, 

and Pomegranates as the End Use Products ET® 2% Herbicide/Defoliant and ET® Herbicide/Defoliant (DP Barcodes: 

D377362, D377366; Dated 01/24/2011)

6 Section 3 New Use for Pyraflufen-ethyl for the Uses on Hops and Peanuts as the End Use Product ET® 2% 

Herbicide/Defoliant and ET® 2.5% Herbicide/Defoliant on Peanuts (DP Barcode: 397880; Dated 10/09/2012)
9

ecological risk assessment along with additional information presented in the 2008, 2011 and 

2012 documents served as the basis for this scoping document covering pyraflufen-ethyl. The risk 

assessment identified risk to endangered and non-endangered terrestrial and aquatic plant species 

but predicted risk below the level of concern for other terrestrial and aquatic species tested. Other 

ecological risk conclusions are described below.

 It was in identified in the new chemical assessment (August 2002) that for dicot terrestrial 

plants adjacent to treatment areas and in semi aquatic areas, risk quotients (RQs) exceeded 

the levels of concern (LOCs) for potatoes (ground application) and for cotton (aerial and 

ground applications). It was stated in this assessment that EFED is concerned about the 

toxicity of the formulation used in the typical end use product (TEP). ET-751 2.5% EC 

contains a solvent in the formulation that is believed to be very toxic to aquatic organisms.

The formulation produced mortality (26% on day 1 and 75% by day 14) and reductions in 

reproduction (# eggs and larvae per female) in a study using predacious mites. It appears 

that the formulation may pose similar toxicity and risk to honeybees. Furthermore, while 

the data set is limited, there are three acute toxicity studies available with this formulation 

that indicate the ET-751 2.5% EC is in the range of a factor of 2.5 to 4 times more toxic 

than TGAI pyraflufen-ethyl. There was no risk identified for other aquatic or terrestrial 

species for the proposed uses.

 All subsequent new use assessments relied on the risk findings of the initial new chemical 

assessment as application rates were similar to those previously assessed.

Table 2. Summary of Risk Concerns Identified for Pyraflufen-ethyl in Previous Assessments

Birds Mammals Terr.

Plants

Terr.

Inverts Fish BCF Aquatic Inverts

Aquatic 

Plants

Groundwater 

Contamination Persistence Degradates of Concern

No No Yes N/A Noa No Noa Yes Nob Noc E-1, E-2, E3

a Studies with parent pyraflufen-ethyl were tested up to solubility limit (82 μg/L) with no definitive LC50 being 

established due to lack of mortality. However, in three acute toxicity studies with formulated pyraflufen-ethyl (ET571 2.5%), there were significant levels of mortality in multiple treatment concentrations as well as the formulation 

blank concentration.

bParent pyraflufen-ethyl is not expected to leach due to non-persistence, however its major degradates are expected to 

leach in variable amounts depending on persistence mobility that appear to change with soil type and temperature.

c Parent pyraflufen-ethyl is expected to degrade rapidly in the soil and aquatic media to the transient degradates E-1 

and E-2. Eventually E-2 degrades to E-3 which is shown by environmental fate data to be persistent.

Yes = at least one LOC has been exceeded in previous assessments; “No“ = LOCs have not been exceeded in 

previous assessments; NA = RQs have not been calculated previously.

b. Drinking Water Exposure Assessments

The first drinking water exposure assessment was conducted in 2002 based on estimated drinking 

water concentrations EDWCs for use on potatoes (highest application rate)

7

. Tier 1 FIRST

model was used for surface water and SCIGROW model for ground water. EDWCs for the 

 

7 Tier I Estimated Environmental Concentrations of Pyraflufen for the Use in the Human Health Risk Assessment 

(DP Barcode: D274672; dated July 18, 2002). This is the DW assessment associated with the chemical first 

registration: Section 3 registration on Corn (grain, stover and forage); Cotton; Potatoes; and Soybeans (grain, hay 

and forage)
10

stressor (parent with E-1, E-2, and E-3) were estimated to be 1.25 ppb for acute exposure (peak 

value) and 0.28 ppb for chronic exposure (annual average value). The groundwater screening 

concentration from SCIGROW was 0.002 ppb for acute/chronic exposures. The same EDWCs 

were used as exposure estimated for new use assessments conducted later in 2009 and 20088. In

this assessment, two modeling runs were executed: the 1st run was for E-1 giving the 1st acute and 

1

st chronic values and the 2nd run was for E-3 giving the 2nd acute and 2nd chronic values. The 

total of the 1st and 2nd acute values was taken to represent the acute EDWC for the total stressor 

while the total of the 1st and 2nd chronic values was taken to represent the chronic EDWC for the 

total stressor. This was based on two assumptions: parent degrades very quickly to E-1 and that E2 is a transient degradate. It is noted, however, that this estimate is conservative because, even 

though it is reasonable to assume that at time zero (i.e., at application) approximately 100% of the 

pyraflufen-ethyl transforms very quickly to E-1, not all the E-3 would be available at time zero as 

it forms much later in time (E-3 may be considered as a terminal degradate).

In 2011, all of the labeled uses, including previously assessed use patterns, were considered and 

modeled using Tier 2 PRZM-EXAMS resulting in revised EDWCs of: 0.425 ppb for acute 

exposure, 0.295 ppb (annual average) and 0.268 ppb (30-year average) for non-cancer/cancer 

chronic exposures. The groundwater screening concentration did not change from the 0.002 ppb

for acute/chronic exposures. Again, the same EDWCs were used as exposure estimated for the 

new use assessment conducted later in 20129. In this assessment, four different modeling 

approaches were used: one modeling run for the combined parent with E-1 to arrive at the 0.425 

ppb acute exposure; a modeling run for parent with E-1, E-2, and E-3 to arrive at 0.295 ppb

(annual average) and 0.268 ppb (30-year average) for non-cancer/cancer chronic exposures; a 

modeling run for parent with E-1, E-2, and E-3 using the lowest average partitioning rate (Koc) of 

the four components to arrive at an upper bound for the chronic exposure; and a modeling run 

using the formation and decline procedure assuming that parent with E-1 (as one parent) that 

degrades into E-2 with E-3 (as one degradate). The last approach gives two separate EDWCs: one 

for parent pyraflufen-ethyl with E-1 and the other for E-2 with E-3 using a feature in PRZMEXAMS that is currently in the experimental stage. EDWC values were reported for the four 

approaches but the first two approaches were used in the assessment.

Stressor for the drinking water assessments of 2002 (Tier 1) and 2011 (tier 2) consisted of parent, 

E-1, E-2, and E-3. This was based on the 2002 decision of the Metabolism Assessment Review 

 

82008: Tier I Estimated Environmental Concentrations of Pyraflufen for the Use in the Human Health Risk 

Assessment (DP Barcodes: D337845, D342902, D343458, D343461 and D343914; dated February 29, 2008. This 

was an updated drinking water assessment that incorporated use site and/or rate and pattern data for Pyraflufenethyl for pastures, wheat, soybean, corn, pastures, sod farms, Christmas trees, nurseries, ornamental plantings, noncrop weed control; and for pre-plant burn-down on root and tuber vegetables, Cole crops, legumes, fruiting 

vegetables, cucurbits and small grains

2009: Tier I Drinking Water Assessment, for the Registration of the New Non-Food Uses of Pyraflufen-ethyl on 

Established Ornamental Turf Lawns (Residential, Industrial, and Institutional), Parks, Cemeteries, Athletic Fields, 

Golf Courses (Fairways, Aprons, Tees, and Roughs), Sod Farms, and Similar Turf Areas (DP Barcodes: D361815, 

D361816; dated August 7, 2009)

9 2011: Drinking Water Assessment, for the Registration of new uses of pyraflufen-ethyl on tree nuts, stone fruit, 

pome fruit, hops, grapes, olives and pomegranates (DP Barcode:D377360; dated March 23, 2011)

2012: Drinking Water Assessment, for the Registration of New uses of Pyraflufen-ethyl on Peanuts and Additional 

Registration on Hops (DP Barcode: 402766; dated October 4, 2012)
11

Committee (MARC)10. In absence of toxicity data, the decision was based on structural similarity 

of E-1, E-2, and E-3 to the parent (i.e., E-1, E-2, and E-3 were considered of similar toxicity to 

parent). In this MARC decision, degradates U-1 (a major soil photolysis degradate) and PD-1 (a 

major aqueous photolysis degradate) were not considered as residues of concern in drinking 

water. This is because U-1 results from soil photolysis (not a major route of environmental 

degradation) and PD-1 appeared to be relatively unstable in water.

If necessary, a tier 2 drinking water assessment (from surface water) which will be similar to that 

conducted in 2011 for the total toxic residue of parent with E-1, E-2, E-3. The new assessment 

will consider any new uses and any changes in the characteristics of the chemicals in the residue

of concern that might results from submittal of new studies. Additionally, previously estimated 

EDWCs for the ground water will be conducted using EFED new model PRZM-GW11 which may 

give different values compared to the previously used SCIGROW model.

c. Clean Water Act Programs

Pyraflufen-ethyl is not identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act12. In addition, no Total Maximum Daily Loads 

(TMDL) have been developed for [insert pesticide]13. More information on impaired water 

bodies and TMDLs can be found at the Agency’s website14. The Agency invites submission of 

water quality data for this pesticide. To the extent possible, submissions should include the key 

data elements noted in the OPP Guidance for Submission of State and Tribal Water Quality 

Monitoring Data15 in order to ensure they can be used quantitatively or qualitatively in pesticide 

risk assessments.

5. Environmental Fate and Transport

Pyraflufen-ethyl is relatively insoluble in water although it is expected to be in soluble form due 

to the low application rate (EECs to a depth of 15 cm resulting from the maximum labeled single 

application of 0.00895 lb. a.i/A= 0.0044 ppm compared to a solubility of 0.082 ppm). The 

solubility of the chemical major degradates vary: E-1 six orders of magnitude higher; E-2 nearly 

two orders of magnitude higher and E-3 one order of magnitude higher. Pyraflufen-ethyl is 

determined to have a very low vapor pressure and Henry’s Law Constant indicating that it is not 

likely to volatilize significantly from wet or dry surfaces. The octanol/water partition coefficients

(KOWs) of pyraflufen-ethyl and its degradate E-3 are relatively high (3,090 “Log Kow= 3.49” and 

4,750 “Log Kow= 3.66”) suggesting possible bio-concentration in aquatic organisms such as fish. 

However, the other two major transformation products (E-1 and E-2) show much lower 

octanol/water partition coefficient (794 and 759 suggesting low tendency to bio-concentrate.

 

10 PP#1F06248. Pyraflufen ethyl on Cotton and Potato. Outcome of Health Effects Division (HED) Metabolism 

Assessment Review Committee (MARC) Meeting Held July, 2002. PC Code 030090, DP Barcode: D284438.

11 URL: http://www.epa.gov/oppefed1/models/water/przm_gw/wqtt_przm_gw_guidance.htm

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

13 http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_group_name=PESTICIDES

14 http://www.epa.gov/owow/tmdl/

15 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
12

Pyraflufen-ethyl shows a high potential to hydrolyze under alkaline conditions. The major 

transformation product is E-1, which resists further hydrolysis at all pH levels tested. Pyraflufenethyl also undergoes photolysis quickly in water and on soil (half-lives of about 2.5 and 2 days, 

respectively). The major transformation products were PD-1 and E-1 in water and on loamy sand, 

respectively.

Based on laboratory and field studies, parent pyraflufen-ethyl was found to be short-lived under 

most environmental conditions (half-lives generally <2 days). The major transformation 

pathways are hydrolysis, photolysis and metabolism forming transformation products E-1, E-2 

and E-3. The E-1 and E-2 transformation products show different persistence patterns in different 

soils/aquatic systems depending on soil type, temperature and aerobicity (refer to section 5) but E3, which is the terminal degradate, is expected to be highly persistent in the environment. A 

notable exception to this degradation pattern was the aqueous photolysis dissipation pathway, 

where PD-1 was a major transformation product. PD-1 did not appear to be persistent under 

photolytic conditions. For pyraflufen-ethyl, E-1, E-2, and E-3, mobility was classified as slightly 

mobile, moderately mobile to mobile, slightly mobile, and slightly mobile, respectively (FAO 

Mobility Classification, FAO 200016). Terrestrial field dissipation studies conducted in CA and 

WA confirm that the major transformation products found in the field are E-1 and E-3. They 

were not present at significant amounts below the 6-inch level. Half-lives of E-1 in the field were 

11 days in CA and 161 days in WA. No field half-lives were established for E-3. 

In the soil system, parent pyraflufen-ethyl is expected to be short lived and therefore would not 

have ample time to leach. In contrast, the moderately mobile to mobile E-1 and the slightly 

mobile E-2 are expected to reside longer in the soil suggesting possibility for leaching. Finally, 

the persistent/slightly mobile/low concentration degradate E-3 is not expected to leach in 

appreciable amounts. Therefore, the potential is for degradate E-1 and E-2 only to leach to ground 

water in vulnerable aquifers, such as those with coarse-textured soils low in organic matter.

A summary of the physical/chemical and Environmental Fate and transport properties of parent 

pyraflufen ethyl is presented in Table 3.

Table 3 Chemical Properties and Environmental Fate Parameters of Pyraflufen ethyl

Parameter Value MRID No.

Chemical Name ethyl 2-[2-chloro-5-[4-chloro-5-(difluoromethoxy)-1-methylpyrazol-3-yl]-4-

fluorophenoxy] acetate

Chemical Structure Refer to Appendix 2

Molecular Weight (parent) 413.18 g mol-1

Solubility of parent (20oC) 0.082 ppm (MRID 452828-05)

Vapor Pressure of parent (25oC) 1.6 x 10-8torr

 

16 Food and Agriculture Organization of the United Nations. FAO PESTICIDE DISPOSAL SERIES 8. Assessing

Soil Contamination: A Reference Manual. Appendix 2. Parameters of pesticides that influence processes in the soil. 

Editorial Group, FAO Information Division: Rome, 2000.

URL: http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm
13

Parameter Value MRID No.

Henry’s Law constant

1.06 x 10-7atm m3 mol-1

(Estimated from vapor pressure and water solubility)

Octanol-Water Partition 

Coefficient

(KOW, at 20oC)

3,090 (log KOW = 3.49)

 Hydrolysis Half-life 

 [pH 5, 7, 9 and 25oC]

Relatively stable (267 d) at pH 5, 10.8 days at pH 7, 6.2 hrs

at pH 8. 

Major and only hydrolysis product: E-1, which increased 

to up to 6% at pH5, 83% at pH 7 and up to 100.0% at 30 d 

(study termination)

452830-17

(Acceptable=A)

Aqueous Photolysis (predicted)

environmental photo 

degradation Half-life at pH 5 

and 20 oC

2.5 days

Major and only photoproduct: PD-1 (max. 32% at 36 

hours, then declined to 19% after 48 hours)

453276-28 and 

461627-02 

(Supplemental=S)

Soil Photolysis (predicted)

environmental photo 

degradation Half-life at 25oC

Cannot be determined (t 1⁄2 = 2 days for irradiated samples 

compared to <1 day for the dark control)

Major photoproduct: E-1 (max. 53-68% at 5 days declining 

to 17-19% at 30 days), U-1 (max. 5-21% at 30 days) and CO2 

(max. 6-25% at 30 days)

Minor photoproduct: E-2 (max. 7%) and E-9 (max. 2%)

452830-19 (S)

Aerobic Soil Metabolism Halflife

<0.25 days (LS, Fresno, CA; pH 6.7; OM 0.6%); <7 days

(SSiL, UK; pH 5.3; OM 2.4%); <1 day (SL, UK; pH 4; OM 

1.9%); <0.25 days (CL, UK; pH 6.9; OM 5.9%) @ 20 and 25

oC

~1-1.7 days (SSiL, UK @ 10 oC)

Major degradates: E-1, E-2 and E-3 in addition to E-11 and 

U-1 (in CA soil)

Minor degradates:E-9, E-8, U-1 and U-2

452830-20, 452830-

21, 452830-22 (S)

Anaerobic Aquatic Metabolism 

Half-life

<4 hours (clay sediment system from CA)

Major degradates: E-1 (92.3% at 1 day) and E-2 (93.0% at 

62 days)

453276-29 (A)

Aerobic Aquatic Metabolism 

Half-life

<6 hours (Two water/clay loam, and a water/sand sediment 

systems from UK)

Major degradates: E-1 (99-100% at 2 days) and E-2

(increased throughout the study to a max. of 21-51% at 100 

days – last test interval). 

Minor degradates: E-3 (max. 9.91% at 100 days). 

E-1 was associated with the water and sediment layers; E-2

and E-3 was mostly associated with the sediment layer

452830-25 (A)

Mobility of Parent and 

Degradates in Soil Columns

Two SL, SSiL and CL soil columns: 83-94% in the 0-5 cm 

soil depth. Leachates contained variable amounts of 

pyraflufen-ethyl, E-1, and E-2, with varying ratios, but the 

major component was E-1 in all cases. Other minor 

components were E-3, and E-9

452830-26 (S)
14

Parameter Value MRID No.

Mobility of Aged Parent and 

Degradates in one Soil Column

SL from UK – 30 day aging period: 68, 30, 4 and <0.3% in 

the 0-5, 5-10, 10-15 and 15-30 cm soil depths, respectively. 

0.5% was found in the leachate. Following the aging period, 

pyraflufen-ethyl was on the average 4%, E-1 was 51 % and 

E-3 was 13% of the applied. E-2 was not detected, but 

following the leaching period, it was present at up to 26% of 

the applied in the 0-5 cm soil depth

452830-28 (A)

Organic Carbon Partition 

Coefficient (KOC)

In a batch equilibrium study Pyraflufen-ethyl was unstable 

when shaken for 2-4 hours in a SL from the UK 452830-29 (A)

Organic Carbon Partition 

Coefficient (KOC)

The log KOC for pyraflufen-ethyl as determined using HPLC 

methodology is 3.3 (KOC.~ 2000)

MRID: 452830-30 

(S)

Terrestrial Field Dissipation 

Half-life

Two studies conducted with radiolabeled material in Madera, 

CA and Ephrata, WA at a rate of 30 g/ha. DT50 in both sites 

were short (<6 hours), with near quantitative formation of E1. In CA, the half-life for E-1 was 10.5 days and in WA, it 

was 161 days. Major degradates were E-1 and E-3. The 

residues of pyraflufen-ethyl and its transformation products 

were almost exclusively detected in the 0-15 cm soil layer. 

A significant fraction of the applied radioactivity was not 

extracted at later sampling intervals and increased to over 23-

30% of the applied by the end of the study period.

452830-34, 452830-

35 (A)

It is noted that important fate studies, such as aqueous photolysis and aerobic soil studies (only 

one soil from the USA) are classified as supplemental due to various deficiencies that are stated in 

their respective data evaluation records (DERs). Also, the aerobic aquatic study used only one 

water/sediment system instead of the required two systems. Giving the fact that this chemical is 

applied at a relatively low rate, no new studies are required at this time. This may change if new 

registrations are requested with significantly higher application rates.

Finally, a summary of the available physical/chemical and environmental fate and transport 

properties is presented in Table 4 for degradates E-1, E-2 and E-3. Detailed description of each 

degradation pathway are included in the “transformation products section” below. 

Table 4 Chemical Properties and Environmental Fate Parameters of E-1, E-2 and E-3; Pyraflufenethyl Degradates

Parameter Value(s) MRID No(s).

 Chemical Names and 

Structures Refer to Appendix 2

 Molecular Weight (parent) 413.18 g mol-1

 Molecular Weight (g mole1

)

E-1= 385; E-2= 327 and E-3= 341

 Solubility of E-1 (20oC) E-1= 1,020 ppm @pH 5; and 11,800 ppm @pH 9; E-2= 7.60 ppm and E-3= 0.53 ppm 

(MRIDs: 453276-09, 452828-07)

Octanol-Water Partition 

Coefficient KOW (log KOW) at 

20 oC

E-1= 794 (2.90); E-2= 759 (2.88) and E-3= 4,570 (3.66)
15

Parameter Value(s) MRID No(s).

Hydrolysis Half-life of E-1 

(pH 4, 7, 9; and 50o C) E-1= Stable 452830-18 (Acceptable= A)

Aerobic Soil Metabolism for 

E-1 Half-life from parent 

studies@ 20 and 25 oC

8.4 days (LS, Fresno, CA, pH=); 15 days (SSiL, UK); 11 

days (SL, UK); 22 days (CL, UK) 

452830-20, 452830-21, 

452830-22 

(Supplemental= S)

Aerobic Soil Metabolism for 

E-2 Half-life @ 20 oC

9 days (SiL soil; pH 6; OM 3.6%); 10 days (SL soil; pH 4; 

OM 2.1%); and 8 days (CL soil; pH 7; OM 6.4%)

Major transformation product: E-3 (max. 30% at 

termination; No decline)

Minor transformation product: U-1 and 

un-extractable residues (max. 39% at termination)

452830-23 (S)

Aerobic Soil Metabolism for 

E-3 Half-life @ 10 oC

330 days (SiL soil; pH 6; OM 3.6%); 495 days (SL soil; pH 

4; OM 2.1%); and 154 days (CL soil; pH 7; OM 6.4%)

Major transformation product: U-1

Minor transformation product: U-2, U-3 and U-4

452830-24 (S)

Mobility Batch Equilibrium 

of Degradate E-1 – Batch 

Equilibrium Study (KOC in 

Lkg-1)

197 (SL soil); 100 (SL soil) and 82 (CL soil); Moderately 

mobile to mobile (FAO mobility classification) 452830-31 (S)

Mobility Batch Equilibrium 

of Degradate E-2 – Batch 

Equilibrium Study (KOC in 

Lkg-1)

2,197 (SL soil); 2,145 (SL soil) and 1,424 (CL soil); Slightly 

mobile (FAO mobility classification) 452830-32 (S)

Mobility Batch Equilibrium 

of Degradate E-3 – Batch 

Equilibrium Study (KOC in 

Lkg-1)

4,354 (SL soil); 4,173 (SL soil) and 3,098 (CL soil); 

Slightly mobile (FAO mobility classification) 452830-33 (S)

 Bio-concentration in Fish 

for E-1

E-1 (also known as pyraflufen) residues did not accumulate 

appreciably in rainbow trout (Oncorhynchus mykiss). The 

max. BCFs were as follows: whole body 2.4X, flesh 18.0X, 

carcass 3.3X. The exposure period was 7 days.

452828-03 (A)

a. Transformation Products

Upon application of pyraflufen-ethyl most of parent pyraflufen-ethyl will eventually reach the 

aerobic soil system earlier from direct soil application and later from plant wash-off. Lower 

amounts of the chemical will reach aquatic systems by drift. The parent chemical reaching both 

the soil and aquatic system is expected to degrade rather quickly (within one to two days) giving 

different suites of degradation products with varied physical/chemical and fate and transport 

properties.

Parent reaching the soil system is expected to degrade into multiple degradation products 

including E-1, E-2, E-3, E-8, E-9, E-11, U-1, U-2 (refer to Appendix 2 for chemical names and 

structures) in addition to CO2 and un-extracted residues (not always measured) and unknown 
16

minor degradates. In most of the soils tested the major degradates were E-1, E-2 and E-3 (refer to 

Table 3). Almost complete transformation of parent into the first degradate, E-1 was observed in 

all aerobic soils tested in the short-term (Maximum reached 75 to 95% within 1-7 days) noting 

that it reached the maximum of 89% at 28 days when one of these soils (soil 2) was incubated at 

low temperature (10oC compared to 20-25oC). This first degradate, E-1 is expected to be 

moderately persistent in most aerobic soils at temperatures between 20-25oC and appears to be 

highly persistent at lower temperatures such as 10oC (Table 5). 

Table 5 Major degradation products of pyraflufen-ethyl in four aerobic soils

Item/Soil Soil 1 (CA, USA) Soil 2 (UK) Soil 3 (UK) Soil 4 (UK) Soil 2 (UK)

Parent Label Both Labels * pyrazole-5-

14C]

Temperature oC 25 20 20 20 10

Texture Sandy Loam

Sand Silt 

Loam Sandy Loam Clay Loam Sand Silt Loam

pH (I M KCl) 6.7 5.3 4 6.9 5.3

Organic Matter 0.6 2.4 1.9 5.9 2.4

Study Duration 366 d 179 d 179 d 179 d 178 d

Parent t 1⁄2 <1 d <1 d <1 d <1 d 1-2 d

E-1 t 1⁄2 60 53 22 25 328

Degradate E-1

% Max Reached (time) ** 95% (3 d) 84% (7 d) 75% (3 d) 84% (1 d) 89% (28 d)

Declined to% (time)** 1% (366 d) 8% (179 d) 3% (179 d) 3% (179 d) 56% (179 d)

Degradate E-2

% Max. Reached (time) 15% (21 d) 39% (100 d) 36% (28 d) 7-8% (28-179 d) 23% (178 d)

Declined to% (time) 2% (366 d) 24% (179 d) 31% (179 d) No decline No decline

Degradate E-3

% Max. Reached (time) 37-44% (238-366 d) 38% (179 d) 21-24% (28-179 d) 52-55% (66-179 d) 5-6% (63-179 d)

Declined to% (time) No decline No decline No decline No decline No decline

* Note: The two labels [pyrazole-5-

14C] and [phenyl-U14C] labels was used in the study. However, data presented in this Table 

are the [pyrazole-5-

14C] label due to inappropriate sampling frequency used in the [phenyl-U14C] label

** For example degradate E-1 reached a maximum of 93% of the applied at day 3 then declined afterwards to 1% of the applied at 

366 days.

The second major aerobic soil degradate is E-2 with observed maximums/timing and persistence 

that vary by incubation temperature and soil characteristic (maximums of 7-39% occurring at 21 

to 179 days). E-2 shows slight decline (low persistence) in three soils (reached 2-31%) and no 

decline (high persistence) in two soils (soil 4 and soil 2 at 10oC, Table 5). When E-2 was used as 

a test material and incubated at 20

oC, much lower persistence was observed in three soils (t 1⁄2 

ranged from 8 to 10 days (Table 4) transforming into the third major degradate of pyraflufenethyl E-3 (maximum of E-3 forming from E-2= 30% at study termination with no decline). Based 

on this data it is clear that E-3 forms from E-2 and that its concentration and timing of presence in 

the soil system can be at the mid-term or the long-term depending on soil type and temperature.

The third major aerobic soil degradate is E-3 with observed maximums of 5-55% occurring at the 

termination of the experiment in all soils tested (Table 5). E-3 is expected to be highly persistent 
17

in all soils but forming at variable quantities. The same high persistence was observed in three 

soils when E-3 was used as a test material (t 1⁄2 ranged from 154-495 days (Table 4) transforming 

into multiple unknowns.

Based on data presented in Table 5 above, parent is expected to degrade very quickly and almost 

completely into E-1 with a maximum observed transformation of 95% of the applied parent. 

Therefore, acute or short-term exposure is expected to be associated with parent and E-1. E-1 

transforms into E-2 and E-2 resident time, in the soil system, varies from soil to soil (medium to 

long term) with a maximum observed transformation of 39% of the applied parent. Therefore, 

medium-term exposure is expected to be mainly associated with E1 and E-2. E-3 is expected to 

be the terminal/persistent degradate and associated with the long-term chronic exposure with a 

maximum transformation of 55% of the applied parent. In some soils, E-2 may also be present at 

the long-term exposure.

The lower amounts of applied parent reaching aquatic systems by drift are expected to transform 

very quickly (within hours) into E-1 degradate with a maximum observed transformation of 100% 

and 92% of the applied parent in aerobic and anaerobic systems, respectively. Therefore, acute or 

short-term exposure is expected to be mainly associated with E-1. E-1 transforms into E-2 and E2 concentration level, in the aquatic system, varies depending on the aerobicity of the system with 

a maximum observed transformation of 51% and 93% of the applied parent in aerobic and 

anaerobic systems, respectively. Therefore, medium-term exposure is expected to be mainly 

associated with E-2. E-3 is expected to be the terminal/persistent degradate and associated with 

the long-term chronic exposure with a maximum transformation of 10% of the applied parent in 

only aerobic systems. E-3 was not observed in anaerobic systems where E-2 appears to be 

extremely persistent and therefore would be the major component of chronic risk (unless 

additional transformation had already occurred prior to the system becoming anaerobic).

6. Receptors

As described in the Agency's Overview Document (U.S EPA, 2004), the most sensitive endpoint 

for each taxonomic group will be used to calculate risk quotients (RQs). Assessment endpoints 

include direct toxic effects on the survival, reproduction, and growth of terrestrial and aquatic life 

as well as indirect effects such as reduction in prey base and/or modification of habitat. Acute 

and chronic toxicity data from studies submitted by pesticide registrants along with the available 

open literature are used to evaluate the potential direct effects of pyraflufen-ethyl to the aquatic 

and terrestrial receptors identified in this section. This includes toxicity data on the technical 

grade active ingredient, degradates, and when available, formulated products. The open literature 

studies are identified through EPA's ECOTOX database (http://cfuub.epa.gov/ecoto20, which 

employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial 

plants, and wildlife. 

A summary of the available ecotoxicity information and the incident information for pyraflufenethyl are provided below. Table 9 provides a summary of the taxonomic groups and the surrogate 

species tested to help understand potential acute and chronic ecological effects of pyraflufenethyl. In addition, the table provides a preliminary overview of the potential acute toxicity of 

pyraflufen-ethyl by providing the acute toxicity classifications. 
18

Pyraflufen-ethyl generally did not elicit a 50% mortality response in all aquatic acute toxicity 

tests that are available nearing and up to the limit of solubility (0.082 mg/L). For the three 

species for which they are available, formulated pyraflufen-ethyl showed a mixed response in 

terms of being equal or greater toxicity than parent pyraflufen-ethyl. Chronic toxicity studies 

with daphnia magna show no effects up to the solubility limit of pyraflufen-ethyl. Two chronic 

early life stage studies with fathead minnow (one with standard and one with enhanced light 

conditions) showed about a 3.5 fold increase in toxicity of enhanced light over standard light 

(both had most sensitive endpoint as weight). Aquatic vascular and non-vascular plant studies 

showed effects on frond and cell density; respectively well below the limit of solubility. 

Additionally, available studies for the degradate E-1 indicate that it is at least two orders of 

magnitude less toxic than parent, depending on the taxa.

Terrestrial studies indicated a general lack of toxicity for birds (acute oral and sub-acute dietary 

based) and mammals (acute and chronic). In one avian reproduction study with the northern 

bobwhite quail, pyraflufen-ethyl did not exhibit any adverse effects on any reproductive 

parameter up to and including the highest treatment concentration (4836 ppm). In the companion 

mallard duck study, several effects were observed (including eggs laid, eggs set, viable embryos, 

viable embryos/eggs set, live- 3 week embryos, number hatched, number hatched/eggs laid, 

number hatched/eggs set, number hatched/live 3-week embryos, hatchling survival, hatchling 

survival/eggs set, hatchling weight, survivor weight, food consumption, and female weight gain). 

This study was determined to be invalid due to the stability of the test substance in the treated 

feed. However, given the deficiencies in the study where effects were seen, a lack of effects in 

the other avian reproduction study, an absence of effects in acute and chronic studies for 

mammals, and the known herbicidal mode of action of pyraflufen-ethyl, further avian 

reproduction studies would not provide an added benefit to the risk assessment. Furthermore, the 

highest pyraflufen-ethyl application rates are currently 0.00894 lbs a.i/A (2 applications at a 7-day 

interval), which means that n additional avian reproduction study would have to exhibit effects at 

three orders of magnitude below where the effects were observed in the original mallard study. 

a. Effects to Aquatic Organisms

Table 7. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for 

Pyraflufen-ethyl

Taxonomic 

Group Study Type Surrogate Species

Toxicity Value

(all units in 

terms of 

measured 

active 

ingredient)

2

Acute Toxicity 

Classification Source

(Classification)

Freshwater fish1

Acute

Bluegill Sunfish 

(Lepomis 

macrochirus)

LC50 = >85 

μg/L (N/A; 

N/A)

Very highly 

toxic

45327604 

(Acceptable)

Acute

(formulation)

Rainbow Trout

(Oncorhynchus 

mykiss)

LC50 = 0.42

μg/L (37-47; 

12.9)

Very highly 

toxic

45282723

(Acceptable)
19

Taxonomic 

Group Study Type Surrogate Species

Toxicity Value

(all units in 

terms of 

measured 

active 

ingredient)

2

Acute Toxicity 

Classification Source

(Classification)

Chronic 

(Early LifeStage)

Fathead minnow

(Pimephales 

promelas)

NOAEC = 3.4 

μg/L

LOAEC = 7.2 

μg/L

Endpoint: 35-

day length, 

weight

--

45389205

(Supplemental)

Chronic 

(Early LifeStage –

enhanced light 

conditions)

NOAEC = 0.89 

μg/L

LOAEC = 1.6

μg/L

Endpoint: 32-

day weight

--

48409701

(Supplemental)

Freshwater 

invertebrates

Acute Water Flea 

(Daphnia magna)

EC50 = >82 

μg/L (N/A; 

N/A)

Very highly 

toxic

45282713

(Supplemental)

Acute 

(formulation)

Water Flea 

(Daphnia magna)

EC50 = 0.02 

mg/L (N/A; 

N/A)

Very highly 

toxic

45282724

(Acceptable)

Chronic Water Flea 

NOAEC = 81

μg/L

LOAEC = >81

μg/L

Endpoint: None 

affected

--

45389201

(Acceptable)

Estuarine/marine 

fish Acute

Sheepshead Minnow 

(Cyprinodon 

variegatus)

LC50 = >56 

μg/L (N/A; 

N/A)

Very highly 

toxic

45389204

(Supplemental)

Estuarine/marine 

invertebrates Acute

Mysid Shrimp

(Americamysis bahia)

LC50 = >60

μg/L (N/A; 

N/A)

Very highly 

toxic

45389203

(Supplemental)

Eastern oyster

(Crassostrea virginica

LC50 = >43

μg/L (N/A; 

N/A)

Very highly 

toxic

45389202 

(Supplemental)

Aquatic plants 

and algae

Vascular Duckweed 

(Lemna gibba)

NOAEC = 2.4

μg/L

EC50 = 16 μg/L 

(31-36; N/A)

Endpoint: 

Frond density

--

45282728

(Acceptable)

Non-vascular

Freshwater diatom

(Navicula 

pelliculosa)

NOAEC = 

0.05μg /L

EC50 = 1.5 

μg/L

Endpoint: Cell 

density

--

45282729

(Acceptable)

1 Freshwater fish may be surrogates for aquatic-phase amphibians.

2Numbers in parenthesis following ECx estimates are 95% confidence intervals; slope (when applicable)
20

Table 8. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for E-1

Taxonomic

Group

Study 

Type Surrogate Species

Toxicity Value

(all units in terms 

of measured active 

ingredient)

Acute

Toxicity 

Classification

Source

(Classification)

Freshwater fish1

Acute

Bluegill Sunfish 

(Lepomis 

macrochirus)

LC50 = 90 mg/L Slightly toxic 45282712

(Supplemental)

Chronic 

(Early Life 

Stage)

Fathead minnow 

(Pimephales 

promelas)

NOAEC = 10 mg/L

LOAEC = >10

mg/L

Endpoints: None 

affected

--

45282719

(Supplemental)

Freshwater 

invertebrates

Acute

Water Flea 

(Daphnia magna)

EC50 = >121 mg/L

(N/A; N/A)

Practically nontoxic45282715 

(Acceptable)

Chronic

NOAEC = 99 mg/L

LOAEC = 120 mg/L

Endpoints: 

Reproduction

--

45282720

(Supplemental)

Estuarine/marine 

fish Acute

Sheepshead 

Minnow 

(Cyprinodon 

variegatus)

LC50 = >99 mg/L Slightly toxic 45282718

(Supplemental)

Estuarine/marine 

invertebrates Acute

Mysid Shrimp

(Americamysis 

bahia)

LC50 = 9.4 mg/L 

(6.1 – 13)

Moderately 

toxic

45282717

(Acceptable)

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.

3Numbers in parenthesis following ECx estimates are 95% confidence intervals; slope (when applicable)

b. Effects to Terrestrial Organisms

Table 9. Summary of the Most Sensitive Endpoints from Terrestrial Toxicity Studies for 

Pyraflufen-ethyl

Taxonomic 

Group Study Type Surrogate Species

Toxicity Value

(all units in terms of 

measured active 

ingredient)

Acute 

Toxicity 

Classification

Source

(Classification)

Birds1

Acute

Bobwhite quail

(Colinus 

virginianus)

LD50 = > 2000 mg/kgbw (N/A; N/A)Practically 

non- toxic

45282704

(Acceptable)

Sub-acute 

dietary Bobwhite quail

LC50 = > 5000 

mg/kg-diet (N/A; 

N/A) 

Practically 

non- toxic

45282707

(Acceptable)

Chronic Bobwhite quail

NOAEC = 4836 ppm

LOAEC = >4836

ppm

--

45327603

(Supplemental)
21

Taxonomic 

Group Study Type Surrogate Species

Toxicity Value

(all units in terms of 

measured active 

ingredient)

Acute 

Toxicity 

Classification

Source

(Classification)

Mammals

Acute Oral

Laboratory rat 

(Rattus 

norvegicus)

LD50 = >5000 mg/kgbwPractically 

non-toxic 45327615

Acute 

Inhalation Laboratory rat LC50 = 5.03 mg/L Toxicity Category IV

45282821

Chronic Laboratory rat 

NOAEL = 10000

ppm

LOAEL = >10000 

mg/kg/day

Endpoint: None

-- 45282922

Insects

Acute 

contact/oral 

combination 

study

Honey bee 

(Apis mellifera 

L.)

Contact LD50 = >112

μg/bee (N/A; N/A)

Oral LD50 = >100 

μg/bee (N/A; N/A)

Practically 

non-toxic

45282732

(Acceptable)

Terrestrial plants

Seedling 

Emergence

Dicot – lettuce

(Lactuca sativa)

EC05 = 0.0001 lb/A

EC25 = 0.001 lb/A

(0.00002 – 0.07; 

N/A)

Endpoint: shoot dry 

weight --

45282725

(Acceptable)

Monocot – None

NOAEC = 0.009 

lbs/A

EC25 = >0.009 

lbs/AA

Endpoint: N/A

Vegetative 

Vigor

Dicot – Turnip

(Brassica rapa)

NOAEC = 0.000007 

lb/A

EC25 = 0.0001 lb/A

(0.000002 – 0003; 

N/A)

Endpoint: shoot dry 

weight --

45282727

(Acceptable)

Monocot – Onion

(Allium cepa)

NOAEC = 0.0005 

lb/A

EC25 = 0.001 lb/A

(0.0004 – .002; N/A)

Endpoint: shoot dry 

weight

Determination 

of Multiple 

Applications 

on Early 

Seedling 

Growth (Non 

guideline)

Dicot – lettuce

(Lactuca sativa)

NOAEC = 0.026 lb/A

EC25 = 0.096 lb/A

(0.038 – 0.22; N/A)

Endpoint: root dry 

weight

--

45282727

(Supplemental)

Monocot –

Ryegrass

(Lolium perenne)

NOAEC = <0.096 

lb/A

EC25 = <0.096 lb/A

(N/A; N/A)

Endpoint: root dry 

weight

1 Birds represent surrogates for terrestrial-phase amphibians and reptiles.
22

In addition to the studies listed above, there is also a 21-day freshwater midge sediment study 

(MRID 46641601), a subchronic earthworm toxicity study (MRID 45282733), and an acute 

contact toxicity study with the predacious mite (Typhlodromus pyri) (MRID 45282801). In the 

freshwater midge study (conducted with Chironomus riparius), pyraflufen-ethyl was spiked into 

the overlying water at 5 concentrations in a static system. Emergence rate and development rate 

was examined with the 21-day NOAEC determined as the highest mean measured concentration 

tested (54 μg a.i/L). While the study was determined to be scientifically sound, EPA recommends 

spiked sediment studies rather than spiked water. The study also failed to measure concentrations 

in the pore water and it was uncertain from this study whether the water column concentrations 

that were achieved are reflective of the maximum concentrations that may occur from the labeled 

use of pyraflufen-ethyl.

In a subchronic earthworm toxicity study, pyraflufen-ethyl caused no mortality or significant 

changes to body weight after 14-days of exposure at nominal concentrations of up 1000 mg/kg. 

In an acute contact toxicity study with the predacious mite, formulated pyraflufen-ethyl (ET-751 

2.5% EC) was applied at a single dose of 1.6 L/ha for 14 days. At test termination, the number of 

eggs and larvae per female in the control group were 1.64 and 0.28, respectively. In the treatment 

group, the number of eggs and larvae per female were 0.64 and 0, respectively. The LC50 could 

not be estimated, because there was only one treatment level; however, it was empirically 

determined to be 4.6 L/ha, based on mortality and reproduction (# of eggs and larvae/female). The 

NOEC was determined to be <1.6 L/ha, based on significant reductions in mite mortality and 

reproduction at the single treatment level. 

Although there are only three studies for which data are available, it is indicated by these studies 

that formulated pyraflufen-ethyl (as the TEP ET-751 2.5% EC) may have greater toxicity than

TGAI pyraflufen-ethyl. Two acute freshwater fish studies (one conducted with rainbow trout and 

ne with the bluegill sunfish) and one acute freshwater invertebrate study each are available to 

TGAI and formulated pyraflufen-ethyl. Results of these studies show a more sensitive endpoint 

by about a factor of 2 for the rainbow trout (TGAI LC50 = >101μg a.i/L vs. TEP LC50 = 42 μg 

a.i/L). Although the rainbow trout TGAI is non-definitive, the study showed no mortality effects 

up to the solubility limit of parent pyraflufen-ethyl (82 μg a.i/L). A similar trend is seen when 

comparing results of the acute freshwater invertebrate studies (TGAI LC50 = >82 μg a.i/L vs. TEP 

LC50 = 20 μg a.i/L). Again, the TGAI study showed no effect on mortality up to the solubility 

limit. These results contrast with those of the bluegill sunfish studies (TGAI LC50 = >85 μg a.i/L 

vs. TEP LC50 = 86 μg a.i/L). It is an uncertainty about whether there exists a marked increase of 

toxicity for formulated pyraflufen-ethyl vs. that of TGAI.

ECOSAR Analysis of the Degradates of Pyraflufen-ethyl

As described in Section 5a, pyraflufen-ethyl degrades by various routes in the environment up to 

three different degradation products that are considered to be major, depending on the route of 

degradation (Tables 5 and 6). The ECOSAR (v1.0) module of EPISUITE (v.4.0) was employed 

to estimate the toxicity of these degradates as compared to registrant submitted data of parent 

pyraflufen-ethyl. ECOSAR uses structure activity relationships to predict the toxicity of 

compounds that share similar structural moieties. In cases where multiple estimates of toxicity 
23

for a particular taxa are predicted for adegradate, the most sensitive estimate was tabulated. 

Table 10 shows the ECOSAR classes for each degradate for which toxicity estimates were 

predicted. These results are compared alongside registrant submitted data that is available for 

pyraflufen-ethyl as well as the degradate E-1.

For each ECOSAR class, varying numbers of data points are associated in building the structure 

activity relationship that informs the estimate of toxicity for a given ECOSAR class. While 

estimates of toxicity provided by ECOSAR are less reliable than those of actual laboratory 

studies, ECOSAR class estimates that are associated with several endpoints generally have less 

uncertainty associated with them than those ECOSAR classes that only have a few.

Table 10. ECOSAR predicted toxicity (μg a.i./L) of the degradates of pyraflufen-ethyl3

Compound 

(Chemical class)

Toxicity Endpoint (μg a.i/L)

Acute 

FW 

Fish 

LC50

Acute FW 

Invertebrate 

EC50

Chronic 

FW Fish 

NOAEC

Chronic FW 

Invertebrate 

NOAEC

Acute 

E/M 

Fish 

LC50

Acute E/M 

Invertebrate 

LC50

Green 

Algae 

EC50

Parent pyraflufen-ethyl

Pyraflufen-ethyl 

(registrant submitted 

studies) – TGAI4

>85 >82 

3.4 (TGAI

– normal 

light 

conditions); 

0.89 (TGAI 

- high light 

conditions)

81 >56 >60 1.5

Pyraflufen-ethyl 

(registrant submitted 

studies) – TEP4

0.42 0.02

Pyraflufen-ethyl 

(Esters)5 11701 17921 48 537 14951 358 484

Pyraflufen-ethyl 

(Pyrazoles/pyrroles)5 815 14571 312 552 77

Degradate E-1

E-1 

(registrant submitted 

studies) – TGAI

90000 >121000 10000 99000 >99000 9400 --

E-1

(pyrazoles/pyrrolesacid)214081 352311 9602 15502 2453

Degradate E-2

E-2 (phenols) 1057 881 158 167 195 3251

E-2 

(pyrazoles/pyrroles) 1422 2386 612 1012 156

Degradate E-3

E-3 

(pyrazoles/pyrroles) 702 1250 272 472 67

Degradate PD-1 

PD-1

(Esters) 80081 142851 446 64781 111611 54311 48491

PD-1

(Vinyl/allyl ethers) 1839 53151 442 14322 61041

PD-1

(Vinyl/allyl 

alcohols)

48401 759 382 172 89511

PD-1

(pyrazoles/pyrroles) 54741 84011 2792 4222 735
24

1

Indicates that chemical may not be soluble enough to measure this predicted effect

2

Indicates that this value was estimated using an acute-to-chronic ratio (ACR)

3The lowest toxicity estimate for a given taxa was used when estimates for more than one ECOSAR class were 

yielded for a given degradate.

4Data in this column refer to registrant submitted studies for pyraflufen-ethyl deemed suitable for risk estimation. 

These values are included in the table for comparison purposes against the ECOSAR predicted endpoints.

5Data in this column refer to ECOSAR estimates of toxicity for parent pyraflufen-ethyl

Table 10 shows that when comparing registrant submitted data for the taxa that are available, 

degradate E-1 is at least two orders of magnitude less toxic than parent pyraflufen-ethyl and some 

cases three orders of magnitude less toxic. This finding is significant given the previous 

discussion in the assessment that parent pyraflufen-ethyl is short lived in the aquatic media, 

rapidly transforming to E-1 in one to two days. The toxicity profile beyond E-1 is uncertain 

however, as there are currently no registrant submitted toxicity data available for either E-2 or E3. 

With E-2, ECOSAR returned estimates of two classes, phenols and pyrazoles/pyrroles. For the 

phenol class of E-2, there were several data points that comprised the estimate of each taxa and

results indicated that E-2 is generally at least one order of magnitude less toxic than parent 

pyraflufen-ethyl. The second ECOSAR class associated with E-2, pyrazoles/pyrroles in contrast 

had very low numbers of data points with each estimate (in some cases, less than 3 data points). 

While the estimates from this class show generally less toxicity than parent pyraflufen-ethyl, 

these results should be viewed as highly uncertain. The ECOSAR results of E-2 indicate 

generally less toxicity than parent pyraflufen-ethyl, but greater toxicity than that of E-1, from 

which E-2 is formed. Based on the previous discussion however, E-2 itself is a transient 

degradate, giving way to E-3.

The ECOSAR results of E-3 are also highly uncertain given that the only ECOSAR class 

informing estimates of toxicity for this degradate are the pyrazoles/pyrroles class that have the 

same uncertainties associated with it as they did for E-2. The results of E-3 indicate generally 

less toxicity than parent pyraflufen-ethyl but greater toxicity than E-1 and generally greater 

toxicity than E-2, from which it is formed.

Finally, ECOSAR results for the aqueous photolysis degradate PD-1 was supported by 4 

ECOSAR classes; esters, vinyl allyl ethers, vinyl allyl alcohols, and pyrazoles/pyrroles. The 

results from the ECOSAR classes of pyrazoles/pyrroles and the high uncertainty with those 

estimates based on a small number of data points has been previously discussed with regards to 

the E-2 and E-3 degradates. Similarly, the vinyl allyl/ethers and vinyl allyl/alcohols classes are 

also associated with a very small number of data points that make comparisons to these classes 

highly uncertain. The esters class is associated with a higher number of data points for each taxa 

and indicates that PD-1 is 2-4 orders of magnitude less toxic than parent pyraflufen-ethyl. 

Given these results that indicate E-1 is orders of magnitude less toxic than parent pyraflufen-ethyl 

but give way to potentially more toxic E-2 and E-3, it is important to establish the concentrations 

at which E-2 and E-3 will ultimately be present. Parent pyraflufen-ethyl has very low (less than 

0.018 lbs a.i/A) application rates associated with it and therefore the concentrations that will 

eventually be available to transform to E-2 and E-3 are important to consider when weighing the 

need for additional toxicity data on these degradates. See Section 11 for more information.
25

c. Ecological Incidents

The ecological incident information system (EIIS) is an OPP database that houses ecological 

incidents that have been reported to the Agency. When available, EIIS includes date and location 

of an incident, type and magnitude of effects observed in various species, use(s) of pesticides 

known or suspected of contributing to the incident, and results of any chemical residue analysis or 

other analyses conducted during incident investigation. EIIS incidents are categorized according 

to the certainty that the incident resulted from pesticide exposure. The Avian Monitoring System 

(AIMS) is a database administered by the American Bird Conservancy that contains publicly 

available data on reported avian incidents involving pesticides. Many of the incidents listed in 

this database are also in the EIIS. 

EIIS returned one terrestrial plant incidents in California attributed to pyraflufen-ethyl use with 

“possible” certainty (USEPA, 2007b). Incident #I023587-006 occurred in October 2011. An 

unidentified farmer filed a claim reporting $250,000 worth of economic loss to 25 acres of 

Chinese leafy vegetables had been damaged by suspected aerial application of paraquat to cotton 

on a nearby field. Further investigation by county officials determined that ET 

Defoliant/Herbicide (Pyraflufen-ethyl) had been applied to a cotton site across the road to the 

farm from the southwest corner of the vegetable site. Seven foliage samples were taken and 

submitted to the Center for Analytical Chemistry for Analysis. 

As of February 24, 2014, the ITRMD maintained Incident Database System (IDS) and the 

Aggregate Incident System identified no ecological incidents involving pyraflufen-ethyl. 

Additionally, the Avian Incident Monitoring System, maintained by the American Bird 

Conservancy, did not identify any ecological incident to birds resulting from the use of 

pyraflufen-ethyl.

7. Exposure Pathways of Concern

The environmental fate properties and use patterns of pyraflufen-ethyl indicate that direct spray, 

spray drift, leaching to ground water and runoff represent potential transport mechanisms of 

pyraflufen-ethyl residues to aquatic and terrestrial organisms. 

For aquatic systems, parent pyraflufen-ethyl should not be available for runoff but may reach the 

aquatic systems by drift. Parent reaching the aquatic system by drift is very short-lived and would 

not be the main species present in aquatic systems. E-1 is moderately persistent in the soil, 

making it available for runoff during rain events occurring after application and it also forms from 

parent reaching these systems by drift (almost 100% transformation). Formed E-2 (from E-1) and 

E-3 (from E-2) are more persistent in the soil and are expected to reach aquatic systems by runoff. E-3 is a highly persistent degradate (terminal degradate) and is expected to reach aquatic 

systems by run-off in eroded soil because of its affinity to soil (Koc range from 3,098 to 4,354 L 

Kg-1).

For ground water, parent is not expected to be leached due to its short half-life in the soil system. 

However, E-1 is expected to leach into ground water (moderately persistent and moderately 
26

mobile to mobile). E-2 and to a lower extent E-3 may leach (both are persistent but E-2 is at the 

low limit of the slight mobility class and E-3 at the high limit of the slight mobility class).

For terrestrial systems, the exposure pathways include direct spray and spray drift to adjacent 

areas to treated fields. Exposure is expected to be associated with parent residues unless the 

chemical is transformed into PD-1 by photolysis on wet foliage. It not likely that this photolysis 

degradate will persist for a long time on the foliage because it appeared to decline in the lab study 

and because it will be subject to wash-off.

Other exposure pathways to terrestrial species

Potential for Risk to Terrestrial Organisms from Drinking Water Exposure

The Screening Imbibition Program (SIP v.l.0), Released June 15, 2010) was used to calculate an 

upper bound estimate of exposure using pyraflufen-ethyl’s solubility (0.082 mg/L), the most 

sensitive acute and chronic avian toxicity endpoints (northern bobwhite quail duck LD50 of >2000 

mg a.i/kg-bw and northern bobwhite quail NOAEC of 4836 ppm, respectively) and the most 

sensitive acute and chronic mammalian toxicity endpoints (Norway rat LD50 of >5000 mg a.i/kgbw and Norway rat NOAEL of 10000 ppm, respectively). Drinking water exposure alone was not 

determined to be a potential pathway of concern for both avian and mammalian species on both 

an acute and chronic basis.

Although drinking water exposure alone does not appear to be of concern, this does not take into 

account that when aggregated with other exposure pathways (dietary food sources, dermal,

inhalation) drinking water may contribute to a total exposure that has a potential for effects on 

non-target animals and should be explored further. Because there is a high degree of conservatism 

in the SIP 1.0 exposure estimate, there is a limited expectation that use scenarios not triggering a 

SIP 2.0 concern would contribute significantly to aggregate risks from water plus diet when a 

refined water exposure model is incorporated in the actual quantitative risk assessment. Detailed 

information about SIP v.l.0 as well as he tool can be found on the EPA's website at

http://www.epa.gov/pesticides/science/models/pg.htm#terrestrial

Potential for Risk to Terrestrial Organism from Inhalation Exposure

The Screening Tool for Inhalation Risk (STIR v.l.0, November 19, 2010) was used to calculate an 

upper bound estimate of exposure using pyraflufen-ethyl’s vapor pressure and molecular weight 

for vapor phase exposure as well as the maximum application rate and method of application for 

spray drift. STIR incorporates results from several toxicity studies including acute oral and 

inhalation rat toxicity endpoints obtained from the "six pack," of core studies, which are a series 

of six guideline studies that are submitted to the Registration Division of the Office of Pesticide 

Programs for technical and formulated products of a pesticide (oral LD50 = >5000 mg a.i/kg-bw 

and inhalation LC50 = >5.03 mg/L) as well as the most sensitive acute oral avian toxicity endpoint 

(mallard duck oral LD50 = >500 mg a.i/kg-bw). Based on the results of the STIR model, 

inhalation exposure alone was not determined to be a potential pathway of concern for avian and 

mammalian species on an acute basis.
27

Inhalation exposure via spray drift and/or vapor-phase of pyraflufen-ethyl alone does not appear 

to be of concern. The analysis of the inhalation route in STIR does not consider that aggregation 

with other exposure pathways such as dietary, dermal, or drinking water may contribute to a total 

exposure that has a potential for effects to non-target animals. However, the Agency does 

consider the relative importance of other routes of exposure may be potentially significant 

contributors to wildlife risk (US EPA, 2004). Detailed information about STIR v.l.0, as well as 

the tool, can be found on the EPA's website at:

http://www.epa.gov/pesticides/science/models/pg.htm#terrestrial

Dermal exposure

Potential exists for pyraflufen-ethyl dermal exposure to terrestrial wildlife. At the present time,

the Agency does not have a method to quantify levels of dermal exposure from chemical

applications, but is actively working on a screening tool to account for this route of exposure.

8. Analysis Plan

The ecological and drinking water risk assessments will focus on pyraflufen-ethyl and its major 

degradates (E-1, E-2 and E-3) as the main stressor of concern for important exposure pathways 

specified above in Section 7. Exposure EECs will be modeled for affected environmental 

compartments using various environmental fate and transport models. The EECs will be 

compared with toxicological endpoints from various aquatic and terrestrial taxa to quantitatively 

compute risk quotients (RQs). The RQs will be compared to the Agency’s levels of concern 

(LOC) to determine the risk to organisms resulting from exposure pyraflufen-ethyl and its 

residues following applications.

a. Stressors of Concern

i. Ecological Risk Assessment

The stressor of ecological concern for terrestrial organisms is parent pyraflufen-ethyl and its 

major degradates E-1, E-2, and E-3. It is noted that the photolysis degradate PD-1 may form

upon contact with foliage . However, PD-1 showed decline with continued light exposure and any 

that may form is expected to be less than or of equal toxicity to the parent (PD-1 is structurally 

similar to parent with OH substitution to Cl). As indicated in Section 6, PD-1 is shown by 

ECOSAR analysis to be at least 2 orders of magnitude less toxic than parent pyraflufen-ethyl. 

Please see the section “ECOSAR Analysis of the Degradates of Pyraflufen-ethyl,” in Section 6 for 

information on the EOCSAR estimates of the other degradates.

The stressor of concern for aquatic organisms is the combined parent pyraflufen-ethyl and 

degradates E1, E-2 and E-3 and surface water exposure EEC averages will be obtained by 

modeling the total toxic residue of parent+ E-1+ E-2+ E-3 assuming similar toxicity. In this 

respect, it is noted that major acute exposure is expected from E1 and chronic exposure from E-3 

and possibly E-2+ E-3 when run-off is originated from soils in which E-2 is persistent (refer to 

transformation products section for more information). A different approach may be used, by 

calculating exposure EECs for individual species in the stressor depending on degradates toxicity 
28

data that may become available. Due to the fact that some toxicity data are available for E-1 

degradate, risk quotas (RQs) will be calculated using acute total toxic residues EECs divided by 

available acute toxicity of E-1. When acute toxicity are not available for E-1 parent data will be

used (assumption of similar toxicity to parent).

ii. Drinking Water 

For drinking water, acute EDWC exposure will be determined by modeling the total toxic reside 

of parent with E-1 noting that this short-term exposure will be mainly associated with E-1 because 

parent is expected to degrade rather quickly (half-life <1 day). In contrast, chronic EDWC 

exposure will be determined by modeling the total toxic reside of parent with E-1, E-2, and E-3 

noting that this long-term exposure will be mainly associated with E-3 as it is the most persistent 

degradate (the terminal degradate). It is noted that the total toxic residue approach can only be 

used if parent, E-1, E-2, and E-3 are of similar toxicity. Similarity in toxicity of E-1, E-2, and E-3 

were assumed by the Metabolism Assessment Review Committee (MARC)17.

b. Measures of Exposure 

Measures of exposure of pyraflufen-ethyl to the aquatic and terrestrial organisms are derived from 

the utilization of environmental fate and transport models. 

For aquatic exposure EECs (surface water EECs) will be obtained by modeling using the total 

toxic residue approach and the Pesticide Root Zone Model coupled with the Exposure Analysis 

Model System PRZM/EXAMS (PRZM v.3.12.2, May 2005 and EXAMS v.2.98.4.6, April2005

models coupled with the input shell PE5.pl, August, 2007). The same models will be used to 

estimate surface water EDWCs in addition to the PRZM-GW model for ground water EDWCs. 

All of these models are available at EPA web site: http://www.epa.gov/oppefed1/models/water/

Exposures to aquatic and terrestrial organisms will be estimated based on maximum application 

rates and all application methods cited in Section 3 . 

The model used to predict terrestrial EECs on food items is T-REX. The model to derive EECs 

relevant to terrestrial and wetland plants is TerrPlant. These models are parameterized using 

relevant reviewed registrant submitted environmental fate data. Exposure estimates for terrestrial 

animals assumed to be in the target area or in an area exposed to spray drift are derived using the 

T-REX model (version 1.5.2, 06/20/2013). EECs for terrestrial plants inhabiting dry and wetland 

areas are derived using TerrPlant (version 1.2.2, 12/26/2006). This model uses estimates of 

pesticides in runoff and in spray drift to calculate EECs. EECs are based upon solubility, 

application rate and minimum incorporation depth. Additional information regarding these 

models can be found at: http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial

 

17 PP#1F06248. Pyraflufen ethyl on Cotton and Potato. Outcome of Health Effects Division (HED) Metabolism 

Assessment Review Committee (MARC) Meeting Held July, 2002. PC Code 030090, DP Barcode: D284438.
29

i. Available Monitoring Data

The Agency is not aware of monitoring conducted by federal and state agencies for this chemical 

as it is short-lived in the environment. However, this route of exposure will be considered in the 

assessment to the extent that data on pyraflufen or any of its degradation products are available.

c. Measures of Effect 

Toxicity data presented in Section 3 of this problem formulation will be used to calculate risk 

quotients. Any additional information submitted by the registrant or found in the open literature 

prior to conduct of the risk assessment will also be considered. The open literature studies are 

identified using EPA’s ECOTOXicology database (ECOTOX) (USEPA, 2007c), which employs 

a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and 

wildlife. The evaluation of both sources of data can also provide insight into the direct and 

indirect effects of pesticides on biotic communities from loss of species that are sensitive to the 

chemicals and from changes in structure and functional characteristics of the affected 

communities.

9. Endangered Species Assessments

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

Agency will evaluate risks to federally listed threatened and/or endangered (listed) species from 

registered uses of pesticides in registration review. The process for evaluating potential risks to 

listed species is further described at 

http://www.epa.gov/oppfead1/endanger/litstatus/riskasses.htm.

10. Endocrine Disruptor Screening Program

Pyraflufen-ethyl was not included in the first group of 67 chemicals issued an order to conduct 

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

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

11. Preliminary Identification of Data Gaps 

a. Environmental Fate

Table 11 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.
30

Table 11 Submitted Environmental Fate and Transport Data for Pyraflufen-ethyl; noting that

studies submitted for degradates are identified by the name of the degradate: E-1, E-2 or E-3

OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications

835.2120 Hydrolysis 452830-17 Acceptable

835.2120 Hydrolysis for E-1 452830-18 Acceptable

835.2240 Aqueous photolysis 453276-28 & 461627-02 Supplemental

835.2410 Soil photolysis 452830-19 Supplemental

835.4100 Aerobic soil metabolism 452830-20/21/22 Supplemental

835.4100 Aerobic soil metabolism for E-2 452830-23 Supplemental

835.4100 Aerobic soil metabolism for E-3 452830-24 Supplemental

835.4300 Aerobic aquatic metabolism 452830-25 Acceptable

835.4400 Anaerobic aquatic metabolism 453276-29 Acceptable

835.1230

835.1240 Adsorption/ desorption & leaching 452830-29 & 452830-26/28 Supplemental

835.1230 Adsorption/ desorption for E-1 452830-31 Supplemental

835.1230 Adsorption/ desorption for E-2 452830-32 Supplemental

835.1230 Adsorption/ desorption for E-3 452830-33 Supplemental

835.6100 Terrestrial field dissipation 452830-34/35 Acceptable

850-1730 Bio-concentration in Fish for E-1 452828-03 Acceptable

850.6100

ECM & ILV* 

for soil

850.6100

ECM & ILV* 

for sediment

850.6100

ECM & ILV* 

for water

A cursory review of the methods (MRIDs: 452830-08, 452830-07, 473687-02, 483812-02, and 

452828-02) indicated that it is necessary to verify the following:

(1) Which ECM is associated with which ILV;

(2) What are the verified LODs and LOQs for each procedure; Noting that the chemical is 

expected to be at low concentrations in the environment and that LOQs for the residues of concern 

(parent, E-1, E-2 and E-3) are lower than the relevant toxicological levels of concern;

(3) That there are ECMs/ILVs for water, soil and/or sediment (should specify/test if the method 

works for soil and sediment if that is the case;

(4) )The method is not affected by the fact that parent and E-3 elute at almost the same time (6.5 

and 6.6 min); and 

Finally, ECMs and ILVs should be for parent + E-1 + E-2 + E-3 for water and soil/sediment alone 

or in combination.

*ECMs= Environmental Chemistry Methods & Associated ILVs= Independent Laboratory Validations (ILVs)

With the exception of ECMs and ILVs, at this time no data gaps are identified noting that many of 

the studies are supplemental studies and reasons for such classification were clearly defined in the 

data evaluation reports (DERs). It might be possible to ask for additional data if new uses are 

requested with higher application rates.

b. Effects

Table 12 and Table 13 identify ecological effects studies by MRID that offer data for each 

guideline requirement for parent pyraflufen-ethyl and the E-1 degradate in the aquatic medium, 

respectively, as well as study classifications and whether or not further data are needed in order to 
31

support risk assessment. Table 14 provides the previously mentioned information for parent 

pyraflufen-ethyl studies conducted on terrestrial organisms. 

With respect to the submitted studies, there are a couple points to be made. First, 40 CFR Part 

158 requires one waterfowl or one upland game species for an acute oral study and an acute oral 

study to passerines. Currently, there is only one acute oral study available for pyraflufen-ethyl 

which is conducted on the mallard duck. The study was tested up to concentrations of 2000 mg 

a.i/kg-bw with no mortalities or clinical signs of toxicity observed in the study. Similarly, in two 

available acute dietary studies with the mallard duck and northern bobwhite quail, birds were 

exposed to concentrations of pyraflufen-ethyl in the diet up to 5000 mg a.i/kg-diet. As in the 

acute oral study, there were no treatment related mortalities or clinical signs of toxicity observed. 

As discussed earlier in this assessment, pyraflufen-ethyl has a generally herbicidal mode of action 

in and is applied at very low application rates (max seasonal rates do not exceed 0.018 lbs a.i/A). 

An additional acute oral study with a passerine species would have to show increased toxicity by 

three orders of magnitude over the submitted study for the mallard duck to trigger an acute dosebased risk concern. Therefore, an additional avian acute oral study with a passerine species is not 

determined to have a substantial added value to the overall risk assessment of pyraflufen-ethyl.

Currently, only one chronic avian reproduction study is available for pyraflufen-ethyl. One study 

with the northern bobwhite quail was submitted and found to be supplemental with no treatment 

related effects up to and including the highest concentration tested (4836 mg a.i/kg-diet). Based 

on currently registered labels of pyraflufen-ethyl, an additional chronic avian reproduction study 

would have to show effects at levels of approximately 4 mg a.i/kg-diet, more than 3 orders of 

magnitude lower from where the northern bobwhite study showed no effects. Due to the 

generally herbicidal mode of action of pyraflufen-ethyl, the very low application rates of 

pyraflufen-ethyl, and the results of the current avian reproduction study indicating no treatment 

related effects, an additional chronic avian reproduction study would not have a substantial added 

value to the overall risk assessment.

The second point relates to the various degradates of pyraflufen-ethyl in the aquatic media. 

Currently, data are available for parent pyraflufen-ethyl and the degradate E-1, which forms 

within 1-2 days in the aquatic systems. Available data indicate that parent pyraflufen-ethyl is 2-3 

orders of magnitude more toxic than E-1, depending on the taxa. As discussed previously in this 

assessment, E-1 further transforms to E-2, which itself along with E-1, is a transient degradate. 

E-2 ultimately transforms to E-3, for which, along with E-2, there are currently no toxicity data 

available for. An analysis of the estimated toxicity of thedegradates was presented in Section 6 

using the quantitative structure activity relationship (QSAR) tool ECOSAR (v.1.0). That 

analysis, while subject to the uncertainty inherent in estimating toxicity from a few data points, 

suggests that E-2, and E-3, while more toxic than E-1, are at least an order of magnitude less toxic 

than parent pyraflufen-ethyl. 

It’s also important to note from the discussion on transformation products earlier in the document 

that E-3 will ultimately form at concentrations that are substantially less than that of the total 

amount of pyraflufen-ethyl applied. Concentrations of E-3 in aquatic systems can arise from two 

sources; from drift of the parent and from run-off from soil. Residues of E-3 forming due to drift 

of the parent are expected to reach a maximum of 10% while formation of E-3 on soils reached a 

maximum of 50% (depending on the soil) that is available for runoff. To further characterize this, 
32

PRZM/EXAMS was run for a scenario that represents the highest labeled rate of pyraflufen-ethyl 

(0.00894 lbs a.i/A, 2 applications, 7-day interval, ground application, potatoes). In modeling, 

parent, E-1, E-2, and E-3 were considered as one chemical and the most conservative parameters 

were chosen from among the three chemicals. The results of this exercise gave a chronic value of 

0.77 ppb which is considered to be related to the terminal degradate E-3. In another words, the 

overall average of 0.77 ppb represents estimated E-3 concentrations in aquatic systems following 

the highest currently registered use of pyraflufen-ethyl. While there is uncertainty in the 

ECOSAR estimates, the analysis presented earlier indicates toxicity anywhere from 2-4 orders of 

magnitude less toxic than this threshold.

Based on all of these lines of evidence, further toxicity data on the degradation products of 

pyraflufen-ethyl are not determined to have substantial added value to the overall risk assessment. 

Table 12. Submitted Aquatic Ecological Effects Data for Pyraflufen-ethyl

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Assumptions EPA will Make in 

Absence of Data

850.1010

Freshwater 

invertebrate 

acute toxicity

45282724 Acceptable

No

45282713 Supplemental

850.1025

850.1035

850.1045

850.1055

Saltwater 

invertebrate

acute toxicity

45389203 Supplemental

No

45389202 Supplemental

850.1075 Freshwater fish 

acute toxicity

45282722 Acceptable

No

45282723 Acceptable

45327604 Supplemental

45282710 Supplemental

46641602 Supplemental

850.1075 Saltwater fish 

acute toxicity 45389204 Supplemental No

850.1300

Freshwater 

invertebrate

life cycle

45389201 Acceptable No

850.1400 Freshwater fish

early-life stage 45389205 Supplemental No

850.1400 

(modified)

Freshwater fish 

early-life stage 

under high 

light 

conditions

48409701 Supplemental No
33

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Assumptions EPA will Make in 

Absence of Data

Non-guideline 

(OECD 219)

Spiked water 

sediment test 

with 

freshwater 

midge

46641601 Supplemental No

850.4400

Aquatic plant 

Toxicity Test 

using Lemna 

spp.

45282728 Acceptable No

850.4500 Algal toxicity

45327606 Acceptable

45282730 Supplemental No

45282729 Acceptable

850.4550 Cyanobacteria 45282731 Acceptable No

Table 13. Aquatic Ecological Effects Data for the Pyraflufen-ethyl Degradate, E-1

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Current Additional Data Need

850.1075 Freshwater fish 

acute toxicity

45282712 Supplemental No

45282711 Supplemental No

45282718 Supplemental No

850.1010

Freshwater 

invertebrate 

acute toxicity

45282715 Supplemental No

850.1300

Freshwater 

invertebrate

life cycle

45282720 Supplemental No

850.1400 Freshwater fish 

early-life stage 45282719 Supplemental No

850.1025

850.1035

850.1045

850.1055

Saltwater 

invertebrate

acute toxicity

45282717 Acceptable No
34

Table 14. Submitted Terrestrial Ecological Effects Data for Pyraflufen-ethyl

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Assumptions EPA will Make in 

Absence of Data

850.2100 Avian oral 

toxicity 45282704 Acceptable No

850.2200 Avian dietary 

toxicity

45282706 Acceptable

No

45282707 Acceptable

850.2300 Avian 

reproduction 45327603 Supplemental No

850.3020

Honey bee 

acute contact 

toxicity

45282732 Acceptable No

Nonguideline

Contact study 

with 

Predacious 

Mite

45282801 Supplemental No

850.6200

Earthworm 

subchronic 

toxicity test

45282733 Supplemental No

850.4100 Seedling 

Emergence 45282725 Acceptable No

850.4150 Vegetative 

Vigor 45282726 Acceptable No

Nonguideline

Effect of 

multiple 

applications on 

seedling 

growth

45282727 Supplemental No

12. References 

Jones, R.D. et al., 2000. Guidance for use of the Index Reservoir and Percent Crop Area Factor in 

Drinking Water Assessments (March 21, 2000). Office of Pesticide Programs, 

Environmental Fate and Effects Division, U.S. Environmental Protection Agency. 

Arlington, VA.
35

USEPA. 1999. Guidance for Use of the Index Reservoir in Drinking Water Exposure 

Assessments. Arlington, VA.

USEPA. 2000. Drinking Water Screening Level Assessment. Part A: Applying a Percent Crop 

Area Adjustment to Tier II Surface Water Model Estimates for Pesticide Drinking Water 

Exposure Assessments. FQPA Science Policy Document .Public Comment Draft 

September 1, 2000. Federal Register: October 11, 2000 (volume 65, number 197). 

Electronic copy available at http://www.epa.gov/pesticides/trac/science/ .

USEPA. 2002a. Guidance for Selecting Input Parameters in Modeling the Environmental Fate 

and Transport of Pesticides, Version II (February 28, 2002). Office of Pesticide 

Programs, Environmental Fate and Effects Division, U.S. Environmental Protection 

Agency. Arlington, VA.

U.S. EPA. 2002b. Pesticide Root Zone Model (PRZM) Field and Orchard Crop Scenarios: 

Standard Procedures for Conducting Quality Control and Quality Assurance. Office of 

Pesticide Programs, Environmental Fate and Effects Division, U.S. Environmental 

Protection Agency. Arlington, VA. 

U.S. EPA. 2003b. Use of Regional Percent Crop Area Factors in Refined Drinking Water 

Assessments. US EPA Office of Pesticide Programs (OPP), Environmental Fate and 

Effects Division (EFED), Water Quality Technical Team (WQTT). Arlington, VA

USEPA, 2003c. SCI-GROW 2.3: Windows Version of SCI-GROW. September 30, 2003. Office 

of Pesticide Programs, Environmental Fate and Effects Division, U.S. Environmental 

Protection Agency. Arlington, VA. 

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

Programs. United States Environmental Protection Agency (USEPA). Environmental 

Fate and Effects Division. Office of Pesticide Programs. Available at 

http://www.epa.gov/espp/consultation/ecorisk-overview.pdf.
36

Environmental Fate Studies

Hydrolysis 835.2120 (previously 161-1)

MRID Citation Reference

45283017 2010868 McKemie, T. (1999) Hydrolysis of (carbon 14) ET-751 at pH 5, 7, 9: Lab Project 

Number: 802W-1: 802W: E-5034. Unpublished study prepared by PTRL West, 

Inc. 107 p. 

45283018 2010869 Lewis, C. (1997) (Carbon 14)-E-1 Hydrolytic Stability: Lab Project Number: 

CHE 608/49: E-5024. Unpublished study prepared by Corning Hazleton 

(Europe). 60 p. 

Photodegradation in Water 835. 2240 (previously 161-2)

MRID Citation Reference

45327628 2010870

2048725-

revision

Ikemoto, Y.; Shigemura, M.; Takahashi, Y. (1997) Aqueous Photolysis Study of 

ET-751: Lab Project Number: LSRC-E96-066A: E-5025. Unpublished study 

prepared by Nihon Nohyaku Co., Ltd., Research Center. 83 p. 

46162702 2048724

2048725=-

revision

Maks, M. (2003) Supplement 1: Aqueous Photolysis Study of ET/751. Project 

Number: LSRC/E96/066A, E/5025, GC/03/96/0037. Unpublished study prepared 

by Nihon Nohyaku Co., Ltd. 14 p.

Photodegradation in Soil Guideline 835.2410 (previously 161-3)

MRID Citation Reference

45283019 2010871 Concha, M. (2000) Photodegradation of (carbon 14)ET-751 in/on Soil by 

Artificial Sunlight: Lab Project Number: 783W-1: 783W: E-5038. Unpublished 

study prepared by PTRL West, Inc. 211 p. 

Aerobic Soil Metabolism Guideline 835.4100 (previously 162-1)

MRID Citation Reference

45283020 2010872 Shepler, K. (2000) Aerobic Soil Metabolism of (Carbon 14)ET-751: Lab Project 

Number: E-5036: 745W. Unpublished study prepared by PTRL West, Inc. 196 p. 
37

45283021 2010873 Purser, D. (1995) (Carbon 14)ET-751: Soil Degradation at 20 (degrees)C: Lab 

Project Number: E-5001: 608/8-1015. Unpublished study prepared by Corning 

Hazleton (Europe). 112 p.

45283022 2010874 Purser, D. (1995) (Carbon 14)ET-751: Soil Degradation at 10 (degrees)C: Lab 

Project Number: E-5003: 608/9-1015. Unpublished study prepared by Corning 

Hazleton (Europe). 97 p. 

45283023 2010876 Yeomans, P. (1996) (Carbon 14)-E-2 (ET-751 Metabolite): Soil Degradation at 

20 (degrees)C: Lab Project Number: E-5013: 608/12-1015. Unpublished study 

prepared by Corning Hazleton (Europe). 110 p. 

45283024 2010877 Yeomans, P. (1996) (Carbon 14)-E-3 (ET-751 Metabolite): Soil Degradation at 

20 (degrees)C: Final Report: Lab Project Number: E-5014: 608/13-1015. 

Unpublished study prepared by Corning Hazleton (Europe). 107 p. 

Anaerobic Aquatic Metabolism Guideline 835.4400(previously 161-4)

MRID Citation Reference

45327629 2010878 Concha, M. (2000) Anaerobic Aquatic Metabolism of (carbon-14)ET-751: Lab 

Project Number: 781W-1: 781W: E-5037. Unpublished study prepared by PTRL 

West, Inc. 189 p. 

Aerobic Aquatic Metabolism Guideline 835.4300 (previously 161-3)

MRID Citation Reference

45283025 2010879 Lewis, C. (1996) (Carbon 14)ET-751: Degradation and Retention in WaterSediment Systems: Lab Project Number: E-5011: 608/23-1015. Unpublished 

study prepared by Corning Hazleton (Europe). 166 p. 

Adsorption/Desorption (Batch Equilibrium) 835.1230 (old 163-1)

MRID Citation Reference

45283026 2010881 Kimura, Y. (1996) Soil Column Leaching of (Pyrazole-5(Carbon 14))ET-751: 

Lab Project Number: LSRC-M96-007A: GC-04: 95-0047. Unpublished study 

prepared by Nihon Nohyaku Co., Ltd. 31 p. 

45283027 2011135

Amend.

Pg.6

Chisholm, K. (2000) E-5009: Addendum 1 to Report E-5009: Soil Column 

Leaching of (Pyrazole-5(carbon 14))ET-751: Lab Project Number: E-5009. 

Unpublished study prepared by Nihon Nohyaku Co., Ltd. 12 p. 

45283028 2011135 Kimura, Y. (1996) Soil Column Leaching of (Pyrazole-5(carbon 14))ET-751: Lab 

Project Number: LSRC-M96-008A: GC-04: 95-0100. Unpublished study 

prepared by Nihon Nohyaku Co., Ltd. 30 p. 

45283029 2011134 Yeomans, P. (1996) (Carbon 14)ET-751: Adsorption/Desorption in Four Soils: 
38

Final Report: Lab Project Number: 608/29-1015: E-5015. Unpublished study 

prepared by Corning Hazleton (Europe). 79 p. 

45283030 2010880 Bates, M. (1996) ET-751: Determination of Adsorption Coefficient on Soil (Koc) 

HPLC Simulation: Final Report: Lab Project Number: 608/34-1014: E-5005. 

Unpublished study prepared by Corning Hazleton (Europe). 20 p. 

45283031 2010882 Yeomans, P. (1996) (Carbon 14)-E-1 (ET-751 Metabolite): 

Adsorption/Desorption in Three Soils: Final Report: Lab Project Number: E5016: 608/14-1015. Unpublished study prepared by Corning Hazleton (Europe). 

91 p. 

45283032 2010883 Yeomans, P. (1996) (Carbon 14)-E-2 (ET-751 Metabolite): 

Adsorption/Desorption in Three Soils: Final Report: Lab Project Number: E5017: 608/15-1015. Unpublished study prepared by Corning Hazleton (Europe). 

91 p. 

45283033 2011136 Yeomans, P. (1996) (Carbon 14)-E-3 (ET-751 Metabolite): 

Adsorption/Desorption in Three Soils: Lab Project Number: E-5017: 608/15-

1015. Unpublished study prepared by Corning Hazleton (Europe). 91 p. 

Terrestrial Field Dissipation 835.6100 (previously 164-1)

MRID Citation Reference

45283008 2083970

Pg. 3

Benwell, L.; Burden, A. (1995) Analytical Procedure (CHE 608/26-02R) ET-751 

and Its Metabolite E1,E2,E3: The Determination of Residues in Soil: Lab Project 

Number: 608/26-1016A: A-5025. Unpublished study prepared by Covance 

Laboratories. 26 p. 

45283034 2010884 Baker, F.; Estigoy, L.; Kimmel, E. (1996) Field Soil Dissipation of (Pyrazole-5 

(carbon 14))ET-751 in Bare Ground in California: Lab Project Number: E-5035: 

737W. Unpublished study prepared by PTRL West, Inc. 92 p. 

45283035 2010885 Baker, F.; Bautista, A.; Kimmel, E. (2000) Field Soil Dissipation of (Pyrazole-5-

(carbon 14))ET-751 in Bare Ground in Washington: Lab Project Number: 854W: 

854W-1: E-5039. Unpublished study prepared by PTRL West, Inc. and Qualls 

Agricultural Laboratory. 318 p. 

Confined rotational crop

MRID Citation Reference

45327627 Check with 

HED

Clarke, D. (1998) (Carbon-14)-ET-751: A Confined Rotational Crop Study Using 

Radishes, Lettuces and Barley: Lab Project Number: 12170: R-5049: 201603. 

Unpublished study prepared by Rhone-Poulenc Agriculture Limited. 192 p. 

{OPPTS 860.1850} 

Fish Bioaccumulation 850.1730 (previously 72-6 and 165-4)

MRID Citation Reference
39

45282803 2010886 Grinell, A.; Croudace, C.; Caunter, J. et al. (1996) E-1: Determination of the 

Accumulation and Elimination of (carbon-14)E-1 in Rainbow Trout 

(Oncorhynchus mykiss): Lab Project Number: AB0831/H: W-5030: BL5605/B. 

Unpublished study prepared by Zeneca Ltd. 42 p. 

Non-Guideline Study

MRID Citation Reference

45282703 Registrant 

modeling

Habig, C. (2000) Pyraflufen-Ethyl: AgDrift Modeling to Assess Risk to 

Aquatic and Terrestrial Plants from Spray Drift: Lab Project Number: ETGEN-04. Unpublished study prepared by Nihon Nohyaku America, Inc. 18 p. 

45283007

2083970

Pg 3

Anding, C. (1997) Analytical Method Validation of ET-751 and Its Metabolite 

E-1 Water: Lab Project Number: RPA/96-061: AR 133-95: A-5027. 

Unpublished study prepared by Defitraces. 34 p. 

45327601

Registrant 

assessment

Esterly, D. (2000) Comparison of Estimated Environmental Exposures for 

Pyraflufen-Ethyl with Alternative Chemicals: Lab Project Number: ET-GEN03. Unpublished study prepared by Environmental Focus, Inc. 42 p. 

47368702

Not located O'Connor, B.; Atwal, S.; Woolley, S. (2008) NNH-950-4: Analytical Method 

Validation . Project Number: 0199/0324. Unpublished study prepared by 

Safepharm Laboratories, Ltd. 64 p.

48381202

Not located Jones, S. (2008) To Conduct a Validation of the Analytical Method Pyraflufen 

E1/Water/SJ/08/1 for the Analysis of Pyraflufen E1 in Water: Final Report. 

Project Number: A/5062. Unpublished study prepared by Eurofins-Agrisearch 

Americas, Inc. 65 p. 

45282802

2010875 Dengler, D. 1997. Assessment of the side effects of ET-75 1 technical on the

activity of the soil microflora. Unpublished study performed by 

Arbeitsgemeinschail, GAB Biotechnologie GmbH & IFU Umweltanalytik 

GmbH, Hiefern-0scheo Germany and submitted by Nihon Nohyaku Co. Ltd., 

Tokyo, Japan. Study code and Report No.: 95 1 80/0 1 - ABMF. Study initiated 

(experimental phase) February 3, 1997 and final report issued April 2,1997.

Request for 

review

Analytical Procedure (CHE 608/26-02R) ET-751 and Its Metabolites El,

E2, E3: The Determination of Residues in Soil

Ecological Effects Studies

Avian Acute Oral Toxicity Test Guideline 850.2100 (previously 71-1)

MRID Citation Reference

45282704 2011161 van Dreumel, I.; Leopold, M. (1995) Acute Oral Toxicity Data on Bobwhite 

Quail(Pyraflufen-Ethyl): Lab Project Number: 144945: 50427: W-5010. 
40

Unpublished study prepared by NOTOX B.V. 39 p. 

Avian Dietary Toxicity Guideline 850.2200 (previously 71-2)

MRID Citation Reference

45282706 2011160 van Druemel, I.; Leopold, M. (1995) 5-Day Dietary Toxicity Study in Mallard 

Duck with ET-751 Technical: Lab Project Number: 153045: 50427: W-5011. 

Unpublished study prepared by NOTOX B.V. 82 p. 

45282707 2011159 van Druemel, I.; Reijnders, J (1996) 5-Day Dietary Toxicity Study in Bobwhite 

Quail with ET-751 Technical: Lab Project Number: 146824: 50427: W-5019. 

Unpublished study prepared by NOTOX B.V. 76 p.

Avian Reproduction Guideline 850.2300 (previously 71-4)

MRID Citation Reference

45282709 2011148 Stadens-Peek, W.; Leopold, M. (1997) Reproduction Study in Mallard Duck 

with ET-751 Technical: Lab Project Number: 157242: 50427: W-5032. 

Unpublished study prepared by NOTOX B.V. 157 p. 

45327602 2052183 

pilot study

Leopold, M. (1997) 6-Weeks Dietary Study in Mallard Duck with ET-751 

Techn. (Pilot Dietary Study for Reproduction Study): Lab Project Number: 

157253: 50427: W-5033. Unpublished study prepared by NOTOX B.V. 27 p. 

45327603 2011141 Frieling, W. (2000) Reproduction Study in Bobwhite Quail with PyraflufenEthyl Technical (By Dietary Admixture): Lab Project Number: 265062: 89397: 

W-5052. Unpublished study prepared by NOTOX B.V. 196 p. {OPPTS 

850.2300} 

46447901 Supplement 

1 to MRID 

# 45282709

Maks, M. (2004) Supplement 1 to: Reproduction Study in Mallard Duck with 

ET-751 Technical. Project Number: 157242, 50427, W/5032. Unpublished study 

prepared by Notox B.V. 39 p.

Acute Toxicity to Freshwater Fish Guideline 850-1075 (previously 72-1)

MRID Citation Reference

45282710 2011167 Caunter, J.; Magor, S.; Croudace, C. (1995) ET-751: Acute Toxicity to Rainbow 

Trout: Lab Project Number: BL5511: W-5003. Unpublished study prepared by 

Zeneca Limited. 18 p. 

45282711 2011151 Caunter, J.; Johnson, P.; Croudace, C. (1995) E-1: Acute Toxicity to Rainbow 

Trout: Lab Project Number: W-5017: BL5601. Unpublished study prepared by 

Zeneca Limited. 19 p. 

45282712 2011144 Caunter, J.; Cornish, S.; Croudace, C. (1995) E-1: Acute Toxicity to Bluegill 

Sunfish: Lab Project Number: W-5018: BL5602. Unpublished study prepared by 

Zeneca Limited. 19 p. 
41

45282715 2011173 Croudace, C.; Banner, A.; Johnson, P. (1995) E-1: Acute Toxicity to Daphnia 

magna: Lab Project Number: BL5600: W-5016: AB0831/C. Unpublished study 

prepared by Pharmaco LSR Ltd. 18 p.

45282722 2011145 Sousa, J. (2000) ET-751 2.5% EC(N) Acute Toxicity to Bluegill Sunfish 

(Lepomis macrochirus) Under Flow-Through Conditions: Lab Project Number: 

13657.6125: W-5046. Unpublished study prepared by Springborn Laboratories, 

Inc. 78 p. {OPPTS 850.1075} 

45282723 2011146 Sousa, J. (2000) ET-751 2.5% EC(N) Acute Toxicity to Rainbow Trout 

(Oncorhynchus mykiss) Under Flow-Through Conditions: Lab Project Number: 

13657.6124: W-5050. Unpublished study prepared by Springborn Laboratories, 

Inc. 78 p. {OPPTS 850.1075} 

45327604 2011166 Moore, K.; Caunter, J.; Shearing, J. (1999) ET-751: Determination of Acute 

Toxicity to Bluegill Sunfish (Lepomis macrochirus): Lab Project Number: 

BL6592/B: AG0225/A: W-5042. Unpublished study prepared by Zeneca Ltd. 19 

p. 

46641602 2052183

Contractor 

Draft

Palmer, S.; Kendall, T.; Krueger, H. (2004) A 96-Hour Flow-Through Acute 

Toxicity Test with the Rainbow Trout (Onchorhynchus mykiss): Final Report. 

Project Number: 397A/102. Unpublished study prepared by Wildlife 

International, Ltd. 41 p. with 2% active ingredient

Acute Toxicity to Freshwater Invertebrates Guideline 850-1010 or 850-1020 

(previously 72-2)

MRID Citation Reference

45282713 2011163 Banner, A.; Johnson, P.; Croudace, C. (1995) ET-751: Acute Toxicity to Daphnia 

magna: Lab Project Number: BL5510: W-5020. Unpublished study prepared by 

Zeneca Limited. 20 p. 

45282715 2011173 Croudace, C.; Banner, A.; Johnson, P. (1995) E-1: Acute Toxicity to Daphnia 

magna: Lab Project Number: BL5600: W-5016: AB0831/C. Unpublished study 

prepared by Pharmaco LSR Ltd. 18 p.

45282724 2011143 Cafarella, M. (2000) ET-751 2.5% EC(N) Acute Toxicity to Water Fleas, 

(Daphnia magna) Under Flow-Through Conditions: Lab Project Number: W-5047: 

13657.6123. Unpublished study prepared by Springborn Laboratories, Inc. 78 p. 

{OPPTS 850.1010} 

Acute Toxicity to Estuarine/Marine Crustacean Guidelines 850-1035 or 850.1045 

(previously 72-3)

MRID Citation Reference

45282717 2011155 Cafarella, M. (2000) E-1 Acute Toxicity to Mysids (Mysidopsis bahia) Under 

Static Conditions: Lab Project Number: 13657. 6129: W-5048. Unpublished study 

prepared by Springborn Laboratories, Inc. 56 p. 

45389203 2011174 Putt, A. (2001) ET-751--Acute Toxicity to Mysids (Americamysis bahia) Under 

Flow-Through Conditions: Lab Project Number: 13657.6147: W-5053. 
42

Unpublished study prepared by Springborn Labs., Inc. 69 p. {OPPTS 850.1035} 

Acute Toxicity to Marine Estuarine Fish Guideline 850-1075 (previously 72-3)

MRID Citation Reference

45282718 2011154

Cafarella, M. (2000) E-1 Acute Toxicity to Sheepshead Minnow (Cyprinodon 

variegatus) Under Static Conditions: Lab Project Number: 13657.6127: W-5049. 

Unpublished study prepared by Springborn Laboratories, Inc. 51 p. 

45389204

2011162

Sousa, J. (2001) ET-751--Acute Toxicity to Sheepshead Minnow (Cyprinodon 

variegatus) Under Flow-Through Conditions: Lab Project Number: 13657.6145: 

W-5054. Unpublished study prepared by Springborn Labs., Inc. 69 p. {OPPTS 

850.1075} 

Acute Toxicity to Estuarine/Marine Mollusc Shell Deposition Guideline 850.1025 

(previously 72-3)

MRID Citation Reference

45327605 2011153

Dionne, E. (2000) E-1-Acute Toxicity to Eastern Oysters (Crassostrea virginica) 

Under Static (Recirculated) Conditions: Lab Project Number: 13657.6128: W5051. Unpublished study prepared by Springborn Laboratories. 57 p. {OPPTS 

850.1025} 

45389202

2011175

Dionne, E. (2000) ET-751--Acute Toxicity to Eastern Oysters (Crassostrea 

virginica) Under Flow-Through Conditions: Lab Project Number: 13657.6146: W5055. Unpublished study prepared by Springborn Labs., Inc. 72 p. {OPPTS 

850.1025} 

Fish Early Life Stage (Freshwater or Marine) Guideline 850.1400 (previously 72-4)

MRID Citation Reference

45282719 2011156 Croudace, C.; Caunter, J.; Wallace, S. (1996) E-1 Chronic Toxicity to Fathead 

Minnow (Pimephales promelas) Embryos and Larvae: Lab Project Number: W5029: BL5604: AB0831/G. Unpublished study prepared by Zeneca Limited. 61 p. 

45389205 2011164 Sousa, J. (2001) ET-751--The Toxicity to Fathead Minnow (Pimephales promelas) 

During an Early Life-Stage Exposure: Lab Project Number: W-5059: 13657.6148. 

Unpublished study prepared by Springborn Labs., Inc. 91 p. 

48409701 2086483 York, D. (2011) Pyraflufen-Ethyl - Early Life-Stage Toxicity Test with Fathead 

Minnow (Pimephales promelas) Under High Light Conditions: Final Report. 

Project Number: 13971/6101, TK0001570. Unpublished study prepared by 

Smithers Viscient Laboratories. 93 p.

48409701 Delete York, D. (2011) Pyraflufen-Ethyl - Early Life-Stage Toxicity Test with Fathead 
43

duplicate Minnow (Pimephales promelas) Under High Light Conditions: Final Report. 

Project Number: 13971/6101, TK0001570. Unpublished study prepared by 

Smithers Viscient Laboratories. 93 p.

Freshwater Aquatic Invertebrate Life Cycle Study Guideline 850.1500 (previously 

72-4)

MRID Citation Reference

45282720

2011152 Croudace, C.; Williams, N.; Shearing, J. (1996) E-1 Chronic Toxicity to Daphnia 

magna: Lab Project Number: W-5026: BL5603/B: AB0831/F. Unpublished study

prepared by Zeneca Limited. 27 p. 

45389201

2011165

Cafarella, M. (2000) ET-751--Full Life Cycle Toxicity Test with Water Fleas, 

Daphnia magna Under Flow-Through Conditions: Lab Project Number: W-5058: 

13657.6149. Unpublished study prepared by Springborn Labs., Inc. 101 p. 

{OPPTS 850.1300} 

Tier I Seedling Emergence (single dosage test) Guideline 850.4100 (previously 122-

1)

MRID Citation Reference

45282725 2011149 Teixeira, D. (2000) ET-751 2.5%-EC Determination of Effects on Seedling 

Emergence of Ten Plant Species: Lab Project Number: 13657.6119: N-5021. 

Unpublished study prepared by Springborn Laboratories, Inc. 176 p. {OPPTS 

850.4100 and 850.4225} 

Tier I Vegetative Vigor (single dosage test) Guideline 850.4150 (previously 122-1)

MRID Citation Reference

45282726 2011150 Teixeira, D. (2000) ET-751 2.5% EC(N) Determination of Effects on Vegetative 

Vigor of Ten Plant Species: Lab Project Number: 13657.6120: N-5014. 

Unpublished study prepared by Springborn Laboratories, Inc. 162 p. {OPPTS 

850.4150, 850.4250} 

Algal Plant Toxicity Test Tiers I and/or II Guideline 850.5400 (previously 123-2)

MRID Citation Reference

45282729 2011172 Hoberg, J. (2000) ET-751 2.5% EC(N) Acute Toxicity to the Freshwater Diatom 

(Navicula pelliculosa): Lab Project Number: N-5025: 13657.6117. Unpublished 
44

study prepared by Springborn Laboratories, Inc. 70 p. {OPPTS 850.5400} 

45282730 2011171 Hoberg, J. (2000) ET-751 2.5% EC(N) Acute Toxicity to the Marine Diatom, 

Skeletonema costatum: Lab Project Number: 13657.6118: N-5023. Unpublished 

study prepared by Springborn Laboratories, Inc. 69 p. {OPPTS 850.5400} 

45282731 2011168 Hoberg, J. (2000) ET-751 2.5% EC(N) Acute Toxicity to the Freshwater BlueGreen Alga (Anabaena flos-aquae): Lab Project Number: 13657.6115: N-5022. 

Unpublished study prepared by Springborn Laboratories, Inc. 69 p. {OPPTS 

850.5400} 

45327606 2011170 Hoberg, J. (2000) ET-751 2.5% EC(N) - Acute Toxicity to the Freshwater Green 

Alga (Pseudokirchneriella subcapitata): Lab Project Number: 13657.6116: N5024. Unpublished study prepared by Springborn Laboratories, Inc. 69 p. 

Aquatic Plant Toxicity Test using Lemna spp. Tiers I and II Guideline 

850.4400 (previously 123-2)

MRID Citation Reference

45282728

2011169 Hoberg, J. (2000) ET-751 2.5% EC Toxicity to Duckweed, Lemna gibba: Lab 

Project Number: 13657.6114: N-5026. Unpublished study prepared by Springborn 

Laboratories, Inc. 77 p. {OPPTS 850.4400} 

Tier II Seedling emergence Guideline 850.4150 (previously 123-1)

MRID Citation Reference

45282725 2011149

Teixeira, D. (2000) ET-751 2.5%-EC Determination of Effects on Seedling 

Emergence of Ten Plant Species: Lab Project Number: 13657.6119: N-5021. 

Unpublished study prepared by Springborn Laboratories, Inc. 176 p. {OPPTS 

850.4100 and 850.4225} 

45282727

2011142 Teixeira, D. (2000) ET-751 2.5% EC(N) Determination of Effects on Multiple 

Applications on Early Seedling Growth of Ten Plant Species: Lab Project 

Number: 13657.6121: N-5013. Unpublished study prepared by Springborn 

Laboratories, Inc. 335 p. {OPPTS 850.4230} 

Tier II Vegetative vigor Guideline 850.4250 (previously 123-1)

MRID Citation Reference

45282726 2011150 Teixeira, D. (2000) ET-751 2.5% EC(N) Determination of Effects on Vegetative 

Vigor of Ten Plant Species: Lab Project Number: 13657.6120: N-5014. 

Unpublished study prepared by Springborn Laboratories, Inc. 162 p. {OPPTS 

850.4150, 850.4250} 
45

Honey bee acute contact Guideline 850.3020 (previously 141-1)

MRID Citation Reference

45282732 2011157 Nengel, S. (1996) Assessment of Side Effects of ET-751 Technical to the Honey 

Bee, Apis mellifera L. in the Laboratory Following the EPPO Guideline No.170: 

Lab Project Number: 95180/01-BLEU: N-5010. Unpublished study prepared by 

GAB Biotechnologie GmbH & IFU Umweltanalytik GmbH. 23 p. 

Chironomid Sediment Toxicity Test Guideline 850.1790 (no previous FIFRA 

guideline)

MRID Citation Reference

46641601 2052184 Odin-Feurtet, M. (1998) ET-751 Toxicity to the Sediment Dwelling Chronomid 

Larvae = 28 Days-(Chiromus riparius). Project Number: SA/97497, W/5037. 

Unpublished study prepared by Rhone-Poulenc Agrochemie. 89 p.

47635001 2052184 

supplemental

Brooks, M. (2008) Supplement 1: ET-751 Toxicity to the Sediment Dwelling 

Chironomid Larvae-28 Days (Chironomus riparius). Project Number: SA/97497, 

W/5037, T/5064SUPPLEMENT/1. Unpublished study prepared by Rhone-Poulenc 

- Secteur Agro. 24 p.

Beneficial Insects 850.3000 Series 143-1 Toxicity to Predator and Parasite Insects

MRID Citation Reference

45282801 2011147 Nienstedt, K. (2000) ET-751 2.5% EC(N): Laboratory Contact Toxicity Test with 

the Predacious Mite, Typhlodromus pyri Scheuten (Acari: Phytoseiidae): Final 

Report: Lab Project Number: N-5015: 1012.002.268. Unpublished study prepared 

by Springborn Labs., (Europe) AG. 25 p. 

Earthworm Toxicity

MRID Citation Reference

45282733 2011158 Wachter, S. (1996) Acute Toxicity ET-751 Technical on Earthworms, Eisenia 

foetida Using an Artificial Soil Test: Lab Project Number: 95180/01-NLEF. 

Unpublished study prepared by GAB Biotechnologie GmbH & IFU 

Umweltanalytik GmbH. 21 p. 
46

Appendix 1: Labeled use patterns for pyraflufen-ethyl

Use Pattern

Application Parameters

Single 

(lb. a.i./A)

No. of 

Applications

Yearly

(lb. a.i./A)

Min Intervals 

(days) Method*

Turf lawns (residential, industrial, and institutional), parks, 

cemeteries, athletic fields, golf courses (fairways, aprons, tees, 

and roughs), sod farms, and similar turf areas 0.00463 ? ? ? G

Cotton (pre-plant burn-down) 0.00325 1 0.00325 N/A G, A

Cotton (post-emergence weed control) 0.00325 1 0.00325 30 G

Cotton (post-emergence layby) 0.00163 1 0.00163 30 G

Cotton (cotton defoliation) 0.00447 2 0.00894 7 G, A

Cotton, combined uses (do not exceed this overall rate) ca. 5 0.01381 7 to 30 G & A

Corn (pre-plant burn-down) 0.00325 1 0.00325 30 G, A

Corn (post-emergence, except sweet corn) 0.00122 2 0.00163 30 G, A

Corn, combined uses (do not exceed this overall rate) ? ? 30 G & A

Deciduous fruit and nut trees and vines (dormant, pre-bloom, in 

season, and postharvest applications) (including pome fruits, 

stone fruits, and tree nuts) 0.00325 3 0.00894 30 B&BD

Tree Nut Crop Group 14 (bearing & non-bearing: post-harvest, 

dormant, pre-bloom, or in-season application) 0.00528 3 or 2 ** 0.00894 30 G

Non-bearing tree fruit, nut and vine crops 0.00325 3 0.00894 30 NS

Grapes – bearing and non-bearing (postharvest, dormant, prebloom, & in-season) 0.00528 3 or 2 1 0.00894 30 G

Stone Fruit Crop Group 12 – bearing & non-bearing trees 

(postharvest, dormant, pre-bloom, & in-season) 0.00528 3 or 2 ** 0.00894 30 G

Pome Fruit Crop Group 11 – bearing & non-bearing trees 

(postharvest, dormant, pre-bloom, & in-season) 0.00528 3 or 2 ** 0.00894 30 G

Olives – bearing & non-bearing trees (postharvest, dormant, prebloom, & in-season) 0.00528 3 or 2 ** 0.00894 30 G

Pomegranates – bearing& non-bearing (postharvest, dormant, prebloom, & in-season) 0.00528 3 or 2 ** 0.00894 30 G

Hops – bearing& non-bearing (postharvest, dormant, & inseason) – Old ET 2.5% formulation registration 0.00528 3 0.00894 30 G

Hops – bearing& non-bearing (postharvest, dormant, & inseason) - New ET 2% SC formulation registration 0.00531 3 0.00903 40 G

Pre-plant fallow beds and crop stubble 0.00325 3 0.00894 30 NS

Non-crop land and uncultivated areas, Conservation Reserve 

Programs (CRP) and set-aside acreage 0.00325 3 0.00894 30 G, A

Non-crop weed control (airports, commercial plants, storage and 

lumber yards, barrier strips and firebreaks, equipment areas, 

nurseries and ornamental plantings, sod farms) 0.00447 3 0.01594 NS G

Peanuts (pre-plant burn-down) 0.00325 NS 0.00325 NS G
47

Use Pattern

Application Parameters

Single 

(lb. a.i./A)

No. of 

Applications

Yearly

(lb. a.i./A)

Min Intervals 

(days) Method*

Peanuts (after planting before crop emergence) 0.00325 NS 0.00325 NS G

Peanuts (post-emergence) 0.00325 ? 0.00625 30 G

Peanuts, combined uses (do not exceed this overall rate) 0.00325 2 0.00625 30 G

Pasture and rangeland 0.00366 2 0.00894 14 G, A

Potato desiccation 0.00894 2 0.01789 7 G

Root and tuber veg. (CG1), leafy veg. (CG4), cole crops (CG5), 

legumes (CG6), fruiting veg. (CG8), cucurbits (CG9), oil seed 

crops (CG20), sugarcane, and cereal grains (CG15) – All limited 

to pre-plant burn-down 0.00325 3 0.00894 30 G

Soybeans (pre-plant burn-down) 0.00325 1 0.00325 30 G, A

Soybeans (post-emergence) 0.00122 2 0.00163 30 G, A

Soybeans, combined uses (do not exceed this overall rate)

Wheat (pre-plant burn-down) 0.00163 2 0.00325 30 G, A

Wheat (post-emergence) 0.00163 1 0.00163 30 G, A

Wheat, combined uses (do not exceed this overall rate) 0.00163 ? ? 30

* G= Ground, A= Aerial and B&BD= Broadcast & band directed application

** 2 applications per season allowed for “in-season” application, 3 applications are allowed for other types of applications.

NS= Not specified; ?= unknown (Need registrant to clarify by providing the correct information in the label); In previous 

modeling a value was assumed. For example: in turf, it was assumed that the number of applications= 2 and the interval between 

7-14 days. The registrant is requested to clarify the label language and give the correct values.
48

Appendix 2: Parent, Major and Minor Degradates of Pyraflufen-ethyl

(1) Parent

Common name: Pyraflufen-ethyl.

IUPAC Chemical name: ethyl 2-[2-chloro-5-[4-chloro-5-(difluoromethoxy)-1-methylpyrazol3-yl]-4-fluorophenoxy] acetate

CAS No: 129630-19-9.

SMILES string (Canonical SMILES): 

CCOC(=O)COC1=C(C=C(C(=C1)C2=NN(C(=C2Cl)OC(F)F)C)F)Cl

Molecular Weight: 413.2 g/mol

(2) Major Degradates

E-1

Common name: E-1 (transformation product of pyraflufen-ethyl) Or Pyraflufen 

IUPAC Chemical name: 2-[2-chloro-5-[4-chloro-5-(difluoromethoxy)-1-methylpyrazol-3-yl]-4-

fluorophenoxy]acetic acid

CAS No: 129630-17-7

SMILES string: CN1C(=C(C(=N1)C2=CC(=C(C=C2F)Cl)OCC(=O)O)Cl)OC(F)F

Molecular Weight: 385 g/mol

 
49

E-2

Common name: E-2

Chemical name: 

IUPAC Chemical name: 2-chloro-5-[4-chloro-5-(difluoromethoxy)-1-methylpyrazol-3-yl]-4-

fluorophenol

CAS No: Not reported

SMILES string: CN1C(=C(C(=N1)C2=CC(=C(C=C2F)Cl)O)Cl)OC(F)F

Molecular Weight: 327.1 g/mol

E-3

Common name: E-3

IUPAC Chemical name: 4-chloro-3-(4-chloro-2-fluoro-5-methoxyphenyl)-5-

(difluoromethoxy)-1-methylpyrazole

CAS No: Not reported

SMILES string: CN1C(=C(C(=N1)C2=CC(=C(C=C2F)Cl)OC)Cl)OC(F)F

Molecular Weight: 341 g/mol
50

PD-1

PD-1 (A major photolysis degradate)

C1(=CCC(=C(C=C1F)O[H])OCC(=O)OCC)C2=N[N](C(=C2Cl)OC(F)F)C

Major degradates Forms as follows:

CH3 OH

= E1 degradate

All OH

= E-2 Degradate

OR 

If All Cleaves Away

E-3 Degradate

All Cleaves Away E-3 Degradate
51

(3) Minor Degradates of pyraflufen-ethyl

Name IUPAC Name Structure

E-8

Ethyl 2-chloro-5-(4-chloro-5-difluoromethoxy-1Hpyrazol-3-yl)-4-fluorophenoxyacetate

N

N

Cl

H

OCHF2

Cl

F

OCH2COOCH2CH3

E-9

2-Chloro-5-(4-chloro-5-difluoromethoxy-1-H-pyrazol-3-

yl)-4-fluorophenoxyacetic acid

N

N

Cl

H

OCHF2

Cl

F

OCH2COOH

E-10

2-Chloro-5-[4-chloro-5-difluoromethoxy-1H-pyrazol-3-

yl]-4-fluorophenol

N

N

Cl

H

OCHF2

Cl

F

OH

E-11 4-Chloro-3-(4-chloro-2-fluro-5-methoxyphenyl)-5-

difluoro-methoxy-1H-pyrazole

N

N

Cl

H

OCHF2

Cl

F

OCH3

U-1

2-Fluoro-5-hydroxy-5-(N-methylcarbamoyl)-4-oxo-pent2-enoic acid

O O

OH

NHCH3

CF CH

HOOC

U-1 A

2-Fluoro-5-hydroxy-5-(N-carbamoyl)-4-oxo-pent-2-enoic 

acid)

NH2

OH

O

C

H

O

CF

HOOC