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UNITED STATES ENVIRONMENTAL PROTECTION A(aENCY 

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$ < WASHINGTON, D.C. 20460 

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OFFICE OF CHEMICAL SAFETY 

ANO POLLUTION PREVENTION 

September 10, 2014 

PC Code: 082583 

MEMORANDUM DP Bareode: 418273 

SUBJECT: Preliminary Ecological Risk Assessment for Registration Review of cyhalofop-butyl 

FROM: Kristina Garber, Senior Biologist 

Richard Shamblen, Chemist 

ER132/EFED (7507P) RICHARDSHAMBLEN 

2014.09.11 09:09:58 

- 4'00' 

THROUGH: Brian Anderson, Branch Chief 

ERB2/EFED (7507P) 

TO: Jolene Trujillo, Chemical Review Manager 

Linda Arrington, Branch Chief 

RMIBV/PRD (7508P) 

This memorandum transmits the problem formulation and preliminary ecological risk assessment 

for the registration review of the herbicide cyhalofop-butyl. A preliminary risk assessment was 

conducted at the problem formulation stage because the current database was sufficient to support 

an ecological risk assessment. Based on currently registered uses and labeled rates, this 

preliminary assessment identifies potential risks to non-target organisms. This assessment is 

focused on species that are not federally listed as threatened or endangered (referred to as 

"listed"); however, some general discussion of taxa of listed species for which "no effect" 

determinations are expected is included in this assessment. For taxa where there may be risk, 

specific determinations for listed species are considered uncertain at this time. Currently labeled 

rates of cyhalofop-butyl have the potential to cause adverse effects, i.e., pose risk, to non-target 

grasses (located adjacent to rice paddies). There is also potential for chronic effects to mammals 

feeding within treated fields as well as potential mortality to fish and invertebrates located within 

a rice paddy on the day of the application. The distance from treated areas potentially affected 

may be reduced by use of larger droplet spectrum or other spray drift reduction technology. 

Section 2.3 addresses ambiguous label language - that could be revised to reduce conservative 

assumptions used in assessing potential risks. Respective risk and degree of risk certainty for each 

major taxonomic group assessed are illustrated below. Placement was based on risk calculations, 

fate characteristics, incident reports, completeness of data set and other factors considered and 

detailed in the following ecological risk assessment. 

Page 1 of 48 
Taxa at Risk From Registered Cyhalophop Uses 

Aquatic plants Terrestrial plants 

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Page 2 of 48 
Ecological Risk Assessment for the Registration Review of 

Cyhalofop-butyl 

IUPAC name : Butyl-(R)-2-[4(4-cyano-2-fluorophenoxy) phenoxy]propionate 

CAS Number: 122008-85-9 

USEPA PC CODE: 082583 

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Prepared by: 

Kristina Garber, MS, Senior Science Advisor 

Richard Shamblen, Chemist 

Reviewed by: 

Melanie Biscoe, MEM, Physical Scientist (Review Panel) 

Nick Federoff, Ph.D., Wildlife Biologist 

Jean Holmes, DVM, MPH, Risk Assessment Process Leader 

James Lin, Ph.D., Environmental Engineer 

Keith Sappington, MS, Senior Science Advisor (Review Panel) 

Approved by: 

Brian Anderson, MEM, Branch Chief, Environmental Risk Branch 11 

Environmental Fate and Effects Division 

Office of Pesticide Programs 

U.S. Environmental Protection Agency 

1200 Pennsylvania Avenue, NW 

Washington, D.C. 20460 

September 10, 2014 

Page 3 of 48 
Table of Contents 

l . Executive Summary ..............................................................................................................5 

2. Problem Formulation ............................................................................................................8 

2.1. Mode of Action ......................................................................................................... 8 

2.2. Use Characterization .................................................................................................8 

2.3. Label Uncertainties .................................................................................................11 

2.4. Previous Risk Assessments .....................................................................................12 

2.5. Water Quality ..........................................................................................................12 

2.6. Stressors of Concern ...............................................................................................13 

2.7. Analysis plan ........................................................................................................... 14 

3. Exposure Analysis ..............................................................................................................18 

3.1. Environmental Fate and Transport Summary .........................................................18 

3.2. Estimated exposure .................................................................................................20 

3.2.1. Direct Deposition onto terrestrial Food Items (located on treated paddies) ...........20 

3.2.3. Spray Drift Transport ..............................................................................................23 

4. Effects Analysis ..................................................................................................................25 

4.1. Toxicity data ...........................................................................................................25 

4.2. Reported Ecological Incidents ................................................................................29 

4.3. Endocrine Disruptor Screening Program ................................................................29 

5. Risk Estimation and Characterization .................................................................................30 

5.1. TerrestrialOrganisms ..............................................................................................30 

5.1.1. Animals .......................................................................................................30 

5.1.2. Plants .............................................................................................................32 

5.2. Aquatic Organisms ..................................................................................................33 

5.3. Listed Species .........................................................................................................33 

5.4. Risk Conclusions ....................................................................................................34 

6. Literature Cited ...................................................................................................................35 

Page 4 of 48 
1. Executive Summary 

Initially registered in the United States in 2002, cyhatofop-butyl is a post-emergent herbicide for 

the selective control of grass weeds in the production of rice. Cyhalofop-butyl is registered for use 

in nine states, including Arkansas, California, Florida, Louisiana, Mississippi, Missouri, 

Tennessee, and Texas. Currently, there are 14 registrations for liquid and granular formulated 

products, including two Special Local Needs supplemental labels. The herbicide may be applied 

via ground or aerial broadcast to dry and wet seeded rice paddies. With maximum application 

rates of up to 0.29 lb a.i./A, sequential applications may be made with total seasonal rates of 0.47 

lb a.i./A. Two granular formulated supplemental labels allow for only a single application at a 

maximum rate of 0.361b a.i./A/ season. 

For this ecological risk assessment, degradates of cyhalofop-butyl were determined to not be of 

concern to aquatic organisms and terrestrial vertebrates. However, cyhalofop-acid appears to be of 

comparable toxicity to the parent to terrestrial plants. Cyhalofop-butyl is slightly mobile, with an 

organic carbon partition coefficient (K oc) of 2892 — 7960 1/kg, and is slightly soluble at 0.44 mg/L. 

With a calculated Henry's law constant of 9.4 x 10' 9atm-m3/mole, the herbicide is not likely to 

volatilize. Although it has a log Kow of 3.3, a fish bioconcentration study indicates that cyhalofopbutyl does not significantly bioconcentrate. 

Cyhalofop-butyl degrades by b io logical ly-med iated hydrolysis to cyhalofop-acid in less than a day. 

Further degradation leads to cyhalofop-amide and to cyhalofop-diacid. Abiotic hydrolysis and 

photolysis are much slower compared to biological degradation at neutral to acidic pH. The major 

degradates (acid, amide, diacid) are generally water-soluble and acidic. The K oefor cyhalofop-acid 

is about 60 mL/g. Field study results indicated that residues in rice paddy water dissipated to below 

detectable levels after 28 days. 

The modified Tier 1 Rice Model was used to model various registered product application scenarios 

to estimate environmental concentrations (EECs). Results indicate that California's Special Local 

Need supplemental labels for Clincher®GR and Clincher®Granule yield the highest peak 

concentration of 363 ,ug/L. Both supplemental labels allow for a single maximum application rate 

of 0.36 lbs a.i./A per event annually. These supplemental labels will expire in August 2015. 

Available toxicity data indicate that cyhalofop-butyl is practically non-toxic to mammals, birds, 

and bees on an acute exposure basis. Available chronic toxicity data with mammals and birds 

indicate no effects to reproduction or offspring at 100 mg/kg-food for rats and 736 mg/kg-food for 

bobwhite quail. Cyhalofop-butyl is highly toxic to aquatic animals on an acute exposure basis. 

Toxicity data are available for several different test species. Available chronic toxicity data 

indicate effects to survival at concentrations >_287 μg a.i./L (NOEC = I 34) to fish and to 

reproduction at >_77.9 ,ug a.i./L (NOEC = 47.4) to invertebrates. In terrestrial plant studies, 

barnyard grass was the most sensitive species tested, with NOAEC and EC25 values of 0.007 and 

0.017 Ib a.i./A, which are 2.4 and 5.9% of the maximum application rate for foliar sprays. 

Available test data for six species of dicots indicated no effects at the highest application rate. The 

Page 5 of 48 
freshwater diatom was the most sensitive aquatic plant species, with NOAEC and ECso values of 

530 and 890 μg a.i./L, respectively. Based on the available evidence, the primary risk concerns 

for applications of this chemical are to non-target plants located in adjacent areas (receiving spray 

drift exposure). 

Conclusions of this ecological risk assessment for the cyhalofop rice use are summarized in Table 

1. This table identifies taxa that are and are not at risk (evidence of risk and negligible risk, 

respectively) due to cyhalofop-butyl applications. This table also takes into account the certainty 

associated with the risk conclusions for a taxa. Appendix E includes general criteria for 

distinguishing between the different risk conclusions and certainty levels. 

Page 6 of 48 
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2. Probleni Formulatioti 

2.1. Mode of Action 

Cyhalofop-butyl is a member of the aryloxyphenoxy-propionate (APP) chemical class. These 

chemicals are selective inhibitors of de novo fatty acid biosynthesis. Specifically, they inhibit the 

first step in fatty acids biosynthesis, f.e., the carboxylation of acetyl-CoA to malonyl-CoA. This 

carboxylation process is catalyzed by the enzyme Acetyl-Coenzyme A Carboxylase (ACC'ase). 

There are two forms of ACC'ase: prokaryotic and eukaryotic, the latter of which is the form that is 

susceptible to cyhalofop-butyl. Since grasses only have the eukaryotic form, whereas broadleaf 

plants have both forms of ACC'ase, grasses are more susceptible to cyhalofop-butyl. Therefore, the 

target pests of this chemical are grasses (e.g., barnyard grass, crab grass, Johnson grass). Available 

toxicity data also suggest that the acid degradate of cyhalofop-butyl may also be herbicidal. 

2.2. Use Characterization 

Cyhalofop-butyl is applied as a post-emergent herbicide for the selective control of grass weeds in 

the production of rice'. It has no pre-emergence or soil residual activity. Only actively growing 

grass weeds from the 1-2 leaf stage to 60 days before harvest are controlled at the time of 

herbicide application. Formulations include both liquid (emulsifiable concentrate, soluble 

concentrate, and ready to use solution) and granular forms. Cyhalofop-butyl can be applied either 

ground or aerial broadcast to wet and dry (drill) seeded rice fields. 

Cyhalofop-butyl is registered for use in eight states in two geographic regions of the United 

States: California and southern states. The seven southern states include: Arkansas, Florida, 

Louisiana, Mississippi, Missouri, Tennessee and Texas. For 2011, Figure 1 illustrates the use 

density (lbs/ mi 2) of cyhalofop-butyl applied among the two geographic regions in the U.S. The 

figure also includes the estimated amount of the herbicide used in both regions for rice production 

for the period 2001 to 2011 (USGS, 2011). 

California rice producers seed primarily by air directly into flooded fields. Except for parts of 

southwest Louisiana and the Texas Gulf Coast, most producers in the South drill seed (i.e. planted 

in dry land prior to permanent flood). Planting typically begins in early March in Texas and 

southwest Louisiana. Rice farmers in the Mississippi Delta region plant the majority of the rice 

crop in April, whereas, farmers in California plant from late April through mid-May. Harvest 

begins in early or mid-July in Texas and southwest Louisiana. Peak harvest in the South is in 

September and early October, when the southern states harvests the most of their crop. Some 

producers in Texas and southwest Louisiana are able to re-flood their fields after harvest and 

achieve a partial second or "ratoon" crop from the initial crop's stubble. California typically 

begins harvest at the end of September and finishes by early November (USDA, 2012). 

' Wild rice is not included in this assessment because on July 11, 2014, at the Office of Pesticide Program (OPP) 

facilitated Focus meeting, Dow Agrosciences verbally indicated that they intend remove wild rice from cyhalofopbutyl containing labels. 

Page 8 of 48 
Estimated Agricultural Use for Cyhalofop , 2011 

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201 1. (;raph c9epicts estiinated uSe (in i»iili0n rOiIMds) on rice in the U.S. fior the heriod 

?(.)(.) i throtigh 20 1 1( t..:S(;S, 2()1 1). 

Page 9 of 48 
Currently, there are ten registered formulated products containing cyhalofop-butyl. Both Clincher 

GR (62719-613) and Granule (62719-647) are registered in both California and southern states. 

One registration, Clincher GR (62719-613) has an alternate name Clincher DR in the southern 

states. Appendix A contains two tables that itemize the registered products by region: California 

and southern states. Each table lists the registered products by formulation (liquid or granular), 

and then summarizes the rice seeding method, general application period, maximum single 

application rate, sequential application scenario and rate, total annual application rates, holding 

time and comments. Most formulated products containing cyhalofop-butyl allow a maximum 

single application of 0.288 pounds active ingredient per acre (Ibs a.i./A), with sequential 

applications at least 10 days later, for a total of 0.471b a.i./A per season; including ratoon crops. 

In California, two granular formulated registrations (Clincher GR and Clincher Granule) include 

Special Local Need supplemental labels that allow for a single maximum application rate of 0.36 

lb a.i./A per year. Both supplemental labels are currently set to expire in August 2015. 2 

Common among all cyhalofop-butyl labels are the following agronomic use restrictions: 

• Do not apply within 60 days of harvest; 

• Do not fish or commercially grow fish, shellfish, or crustaceans on treated acres during the 

year of treatment; 

• Do not rotate treated land to crops other than rice for 3 months following application; 

• Do not apply where runoff or irrigation water may flow directly onto agricultural land 

other than rice fields; 

• Do not apply if crop and weeds are under drought stress or reduced weed control may 

result; and, 

• Do not apply cyhalofop-butyl through any type of irrigation system. 

To help avoid injury to non-target terrestrial plants, all registered product labels have buffer zone 

application restrictions. Appendix B contains two tables that summarize the buffer zone 

distances for each registered product label by region. Non-target peaches and nectarines have the 

greatest buffer distances in California of up to 4 miles when cyhalofop-butyl is aerially applied. 

Only RebelEx and Rebelsx CA contain buffer zone distance to protect endangered species. This is 

attributed to the co-formulated herbicides in each product, and not cyhalofop-butyl. Example 

language of the use of buffer zones on the product labels include: 

• The pesticide should only be applied when the potential is minimal for drift to adjacent 

sensitive areas that include: residential areas, bodies of water, known habitat for 

threatened or endangered species, and non-target crops. 

• Buffer zones are defirred as the distarrce between the application site and the sensitive 

agrricultural production crop. 

• Sensitive agricultural production crops include: 

■ Commercial production ofnon-tar-aetcereal and grass crops such as corn, 

sugar cane, sudangrass, sorghum, grass grown for seed, millet, and sod 

farms. 

2On July 11, 2014, at the Office of Pesticide Program (OPP) facilitated Focus meeting, Dow Agrosciences verbally 

indicated that they intend apply to extend both Supplemental labels beyond August, 2015. 

Page 10 of 48 
■ Commercial peaches and nectarines (for liquid formulations buffer 

restrictions are 2-4 mfles for aerial applications and 600 feet for ground 

applfcations). 

• If endangered plant species occur in the proximity of the application site, the following 

mitigation measure is required to avoid adverse effects. Leave untreated buffer zones of 

85 feet from ground applications or 470 feet for aerial applicators. (Only on the 

RebelExT"t CA3and RebelExT"' labels) 

2.3. Label Uncertainties 

This draft risk assessment is based on the current product registration labels. During development 

of this draft risk assessment, several issues and uncertainties were identified with the product 

labels. These issues have been communicated with the registrant, and the registrant has agreed to 

address the following identified label issues: 

l. There is ambiguity on some labels that allow users to apply both granule and liquid 

formulated cyhalofop-butyl containing products in a single season. In particular, it is 

unclear how the sequential application rate is determined for granulated formulated 

products; especially when the sequential application is liquid formulation. In some 

cases, the sequential product application rate is specified (e.g. 10 oz of Clincher CA), 

in other cases it is undefined. Therefore, the product user will be required to calculate 

not only the active ingredient rate, but also the product application rate. 

2. Clincher GR 

• This label specifies the amount of the granular formulation for the initial 

application at 16 Ibs product/ acre. However, the label does not specify the 

maximum product application rate for the sequential application (e.g. 9.8 

product oz. / acre). Here, the user must calculate the difference between the 

active ingredient maximum annual application rate of 0.47 lbs a.i./ acre and the 

initial application rate of 0.288 lbs a.i./acre; this difference is 0.182 lbs a.i./ 

acre from Clincher CA. Thus, the calculated maximum sequential product 

application rate would be 9.8 oz of Clincher CA. By rounding this to 10 oz, 

(not an improbable occurrence) the total annual application rate could reach 

0.53 lbs a.i./ acre, or 11 % more active ingredient than currently registered. 

• Contains language indicating the product could be used on wild rice but wild 

rice is not a registered use. 

• Contains language recommending to use Clincher®EZ on sequential 

applications where Clincher ®EZ is not registered for use in Southern States, 

but is only registered for use in California. 

• Contains language which includes Clincher ®DR; an alternate brand name for 

southern states (September 30, 2010). 

Clincher®5G 

• Contains language indicating the produet eould be used on wild rice but wild rice 

3 Rebelex" CA is currently not being marketed in California; verbal communications from Dow Agrosciences 7/11/14. 

Page 11 of 48 
is not a registered use. 

• For California, maximum seasonal application rates exceed 0.47 lbs ai/ A at 0.495 

Ibs ai/ A. This is based on (page 9 of the Clincher O5G label) the sequential 

Clinchero5G application rate of 3.83 lbs product / acre, in addition to the initial 

application rate of 5.33 lbs a.i./ A. 

• Contains language recommending to use Clincher ®EZ on sequential applications 

where Clincher®EZ is not registered for use in southei -n states, but is only 

registered for use in California. 

• For southern states, maximum seasonal application rates exceed 0.47 Ibs ai/ A at 

0.495 Ibs ai/ A. This is based on (page 19 of the Clincher O5G label) the sequential 

Clincher®5G application rate of 3.83 !bs product / acre, in addition to the initial 

application rate of 5.33 ibs a.i./ A. 

4. GF-2764 

• Minimum sequential application interval has a range of 7 to 14 days. A11 other 

registered product labels have a minimum sequential application interval of 10 

days. 

5. ClincheroGranule 

• Contains language recommending to use Clincher eEZ on sequential applications 

where Clincher®EZ is not registered for use in southern states, but is only 

registered for use in California. 

2.4. Previous Risk Assessments 

A number of ecological and drinkiilg water risk assessments have been completed for cyhalofopbutyl between the time of registration (2002) to present day. The general use patterns assessed 

have been similar to the currently labeled use patterns; however, the aquatic models used for risk 

assessment have evolved and the residues of concern have been refined over time. Nonetheless, 

identified risks have been siinilar with potential risks to aquatic and terrestrial plants and aquatic 

animals in rice paddies being the primary risk concerns. The primary differences between the 

current assessment and previous assessments incltide: 

(1) the current aquatic risk assessment is limited only to exposure from parent cyhalofopbutyl (previous assessments included some degradates of concern) and 

(2) the mammalian toxicity endpoint was changed. 

2.5. Water Quality 

Cyhalofop-butyl is not identified as a cause of impairment for any water bodies under section 

303(d) of the Clean Water Act (based on information provided at 

http://iaspub.epa.gov/tmdl watersl0/attains natlon cv.cause detail 303d?p cause group id=88 

5, accessed September 10, 2014). In addition, no Total Maximum Daily Loads (TMDLs) have 

been developed for cyhalofop-butyl (based on information provided at 

httn://iaspub.epa.gov/tmcil watersl0/attains nation.tmdl pollutant detail?p pollutant 91-OLIn id= 

885K1) pollutant group name=l'ES"T'ICIDES , accessed September 10, 2014) and there are no 

Page 12 of 48 
aquatic life criteria for cyhalofop-butyl (based on information provided at 

httn://www.epa.gov/waterscience/criteria/aglife/index.hti -ni). 

2.6. Stressors of Concern 

Available toxicity data (Table 2) indicate that the degradates of cyhalofop-butyl are less toxic 

than the parent to aquatic organisms. In cases where toxicity was observed in organisms exposed 

to the parent (i.e., bluegill sunfish LC50 = 760 μg a.i./L), no mortality was observed in the same 

test species exposed to concentrations of degradates that were two orders of magnitude greater 

than the LCso of the parent. In studies conducted with terrestrial plants, only the acid degradate 

showed toxicity, with EC25 values for decreased shoot weight in vegetative vigor studies that were 

similar to those of the parent for corn and barnyard grass. This suggests that the acid degradate 

has herbicidal active. For this assessment, only cyhalofop-butyl is of toxicological concern for 

aquatic organisms. For terrestrial plants, cyhalofop-butyl and cyhalofop-acid are of concern. For 

modeling purposes, the parent only will be considered in water. For terrestrial animals, estimated 

exposures are related to the application rate. For terrestrial plants, since both exposure and effects 

are linked to the application rate and since cyhalofop-acid is of similar toxicity, RQs will be 

derived using application rates of the parent. If cyhalofop-acid is formed in the terrestrial plant 

toxicity studies conducted with the parent, it is indirectly accounted for in the assessment. 

Page 13 of 48 
Table 2: '1'oxicity clat.t avail:able for cyhalofop-butvl and dcgradates 

Test Endpoint Cyhalofop Cyhalofop ('} halofop Cyhalofop 

s ecies units -butvl -acid -amide -diacid FHPBA HPP;e MRIDs 

Rainbow LCso 45000217, 

trout (μg a.i./L) 

>490 >100,000 1~ A >95,400 ti:~ ~1;1 45000213, 

45000212 

Bluegill LCso 45000216, 

sunfsh (μg a.i./L) 760 >99,200 88,400 >98,700 '\':1 NA 45000215, 

45000214 

45000226, 

45000221, 

ECso 

(Etg a.i./L) >2700 > 100,000 = 100,000 >95900 >400 >400 45000222, 45000220, Daphnia 45000224, 

magna 45000225 

21 d 45000230, NOAEC 47.4 NA NA 98 300 NA NA 45000232 (jig a.i./L) 

45000432, 

45000435, 

Green ECso >1000 >78200 50000 >96400 >400 >400 45000436, 

algae (μg a.i./L) 45000434, 

45000437, 

45000438 

EC2s 

Barnyard (g a' t'

/ha' 45000430, 

grass 

shoot 19 >580 >580 >350 >350 45000431 weight in 

VV stud ) 

Corn ECZS 9 ~ ?.8 =~ 580 =>580 -3 5 0 > ;50 45000430, 

a.i./ha) 45000431 

NA = not available 

2.7. Analysis plan 

2.7.1. Ecosystems of Concern 

Given that cyhalofop-butyl applications are only allowed for rice, ecosystems of concern are those 

that are in proximity to rice paddies. Terrestrial habitats adjacent to the paddies may receive spray 

drift deposition from applications of liquid based formulations of cyhalofop-butyl. Non-target 

aquatic organisms (e.g., fish, aquatic invertebrates, plants) inhabiting rice paddies may also be 

exposed for direct applications. Aquatic ecosystems that occur down stream of rice paddies are 

also of concern, potentially being exposed to cyhalofop-butyl when water is released from the rice 

paddy into those down-stream habitats. Because the spatial extent of eyhalofop-butyl registrations 

is limited, i.e., Arkansas, California, Florida, Louisiana, Mississippi, Missouri, Tennessee and 

Texas, ecosystems of concern exist within those states. 

Page 14 of 48 
2.7.2. Risk Hypotheses 

For cyhalofop-butyl, the following ecological risk hypotheses are being employed for this risk 

assessment: 

Terrestria! Environment 

Exposure to cyhalofop-butyl residues on seeds, insects, and foliage due to direct spray 

drift from labeled use of the pesticide will cause reduced survival, growth and 

reproduction to terrestrial vertebrates (birds, mammals, reptiles, terrestrial-phase 

amphibians) and terrestrial invertebrates. 

Exposure to cyhalofop-butyl residues on foliage due to spray drift resulting from labeled 

use of the pesticide will result in reduced survival and biomass to upland plants and 

riparian/wetland plants in areas adjacent to a treated rice paddy. 

Aquatic Environment 

• Exposure to cyhalofop-butyl residues in paddy water due to direct applications according 

to labeled uses of cyhalofop-butyl will cause reduced survival, growth and reproduction to 

aquatic animals and non-target plants located within the rice paddy. 

• Exposure to cyhalofop-butyl residues in water released from treated rice paddies will 

cause reduced survival, growth and reproduction to aquatic animals and non-target plants 

located within the aquatic habitats downstream of the treated rice paddy. 

2.7.3. Conceptual Diagram 

Figure 2 depicts the conceptual model of the fate and potential effects associated with 

applications of cyhalofop-butyl to rice. In the figure, dashed lines represent pathways of exposure 

that are unlikely to occur because of physical or chemical properties of the chemical. For 

example, cyhalofop-butyl is not expected to volatilize or significantly bioaccumulate. Major nontarget organism exposure routes of concern for this assessment include ingestion of food items 

that have received direct deposition (i.e., on the treated field) or spray drift to non-target areas, 

contact with treated water within the paddy or ecosystems receiving released water. 

Page 15 of 48 
Cyhalofop-butyl applied to rice paddy 

Stressor 

,-----1 v--- ~ ~ ~ ~----'- --- _ ' __ Source/ ; Volatilization , Direct Spray Runoff/ Release of ; Lea hing ; Transport; of degradatesi ; Deposition Drift Erosion paddy water ;(Inflltration/ ; , Wind ~ ' Percolation ' Pathwa s, -~~~----' ~ y Sus ension• ; _ ~ ~ ~ -----r------ ~--p ------ 

' ' --~----n Source/ TerrestrialFood Upland ^ Riparian/ Receiving ;Groun~Jwater~ 

----- Exposure Residues (foliage, Foliage/Soil Wetland Water Body/ _ _ _ _ _ _ _ _ 

Media fruit, insects Foliaqe/Soil Sediment 

Attribute Individual Animals 

Changes Reduced survival 

Reduced growth 

Reduced 

Direct contacU Direct contact/ Uptake/ 

Root Uptake Root Uptake Adsorption 

Terrestrial Wetland/ Aquatic 

Upland Riparian Plants 

Plants, Inverts Plants 

IS 21a.LlI 

Seedling emergence p.o.RulaliQn 

Vegetative vigor Reduced 

population 

growth 

Gill/ _ _ Ingestion 

Integument ~ — ♦ up the 

Uptake Food Chain 

Aquatic Piscivourous 

Invertebrates Vertebrates 

Aquatic Birds, 

Vertebrates Mammals 

lLlljlvttdudl 1L1iGll1dLl81 

vertebrates and Apit]aIS 

invertebrates Reduced 

Reduced survival 

survival Reduced 

Reduced growth 

growth Reduced 

Reduced reproduction 

Exposure Ingestion 

Route 

Terrestrial I nvertebrates 

Receptors Birds, Mammals, 

Reptiles, Terrestrial 

Phase Amphibians 

F i-urc 2: 9:coItst,'ica9 C'nttcrptu:tl N'I.xlei f'or eyhitlrtfot.a-hutyl a pplic:ttitrns to rice itacldie ,,. 

Assessment endpoints are intended to relate to ecosystems at risk. If risks are expected for a given 

species/taxa based on the risk assessment, then risks might be expected to translate to higher 

levels of biological organization (e.g., ecosystems). Assessment endpoints are represented by 

measurement endpoints, which are the most sensitive toxicity endpoints from a surrogate test 

species, used to estimate treatment-related direct effects following acute and chronic exposure. 

Measurement endpoints are standardized so that acute toxicity is represented by levels that result 

in mortality to 50% of tested individuals (i.e., LCso, LDSo and ECso) and chronic toxicity is 

represented as a no observed adverse effect concentration or dose (i.e., NOAEC or NOAEL). 

Table 3 includes the most sensitive toxicity endpoints available for cyhalofop-butyl that will be 

used as measurement endpoints to assess risks to terrestrial and aquatic organisms. These values 

are used to derive risk quotients. 

Page 16 of 48 
'Table 3: iNIcasurcnient endpoints to derive ltisit Ouotients (ItQs) t'or cvlialofon-butvl. 

Taxa Species Toxicity Value* Citation Study 

Re resented MRID ClassiCcation 

Birds, terrestrial- LDso > 2250 mg/kg-bw 45000207 Acceptable 

phase Anas platyrhynchos LCso > 5620 mg/kg 45000209 Acce table amphibians and (Mallard Duck) 

re tiles NOAEC = 736 mg/kg 45152501 Acceptable 

Rattus norvegfcus LDso>5000mg/kg 45000240 Acceptable 

NOAEC = 100 mg/kg 

45000419 Acceptable 

Mammals laborato ( rY rat ) 

Apfs mellifera 48 h NOEL = 100 μg 45000502 Acceptable "I'crrestrial (hone bee) a.i./bee 

Invertebrates Eiseniafoetida 14 d NOAEC = 1120 45000504 Supplemental earthworm) m 

Terrestrial and Echinochloa crus- NOAEC = 0.007 Ib a.i./A 

wetland plants ga!!i (Barnyard 

r~s EC25 = 0.017 Ib a.i./A 45000431 Acceptable 

Lepomis 

Fish and aquatic- macrochrrus 96 h LCso = 760 45000219 Acceptable 

phasc Blue ill 

pimephales aniphibians promelas (Fathead 31 d NOAEC = 134 45000231 Acceptable 

minnow 

Crassostrea 

virginica (Eastern 96 h ECso = 520 45014704 Acceptable 

Aquatic o ster 

invertebrates Daphnfa magna 21 d NOAEC = 47.4 45000230 Supplemental 

Chfronomus 28 d NOAEC = 661 (pore 45000508 Supplemental ri arius (mid e) water 

Aquatic Plants Navicula 5 d NOAEC = 530 (unicellular and pelliculosa 5 d ECso = 890 45000429 Acceptable 

vascular) (freshwater diatom 

2.7.4. Modeling Approach 

Measures of exposure are based on aquatic and terrestrial models that predict estimated environmental 

concentrations (EECs) of cyhalofop-butyl using maximum -labeled application rates and methods. For 

this assessment, pesticide residues on the food items of terrestrial animals (birds, mammals, 

amphibians and reptiles) are assessed using the T-REX model (v. 1.5.2). The AgDRIFT model 

(version 2.01) is used to estimate the deposition of cyhalofop-butyl in areas that are adjacent to the 

treated field. In this assessment, it is assumed that granules do not drifft, therefore, AgDRIFT is only 

used to simulate deposition of liquid formulations. The modified Tier I Rice Model is used to estimate 

concentrations of cyhalofop-butyl in the flooded rice paddy over time. More information on the TREX and AgDRIFT models is available at: http://v.,%v4v.epa. ~ov/pesticides/science/models db.htm . 

Appendix B contains an explanation of the modified Tier I rice model. 

Page 17 of 48 
3. Exposure Analysis 

3.1. Environmental Fate and Transport Summary 

Table 4 summarizes the physicochemical properties of cyhalofop-butyl. A more comprehensive 

and detailed physicochemical properties and environmental fate characteristics of cyhalofop-butyl 

and its degradates have been well documented in previous risk assessments (USEPA, 2008: DP 

Barcode 357419), and are briefly summarized herein. 

Cyhalofop-butyl is slightly mobile, 2892 — 7960 1/kg, and slightly soluble at 0.44 mg/L. With a 

calculated Henry's law constant of 9.4 x 10 -9atm-m3/mole, the herbicide is not likely to volatilize 

substantially at environmental temperatures. It has a log Kow of 3.3, indicating that it has a 

higher affinity for organics than for water and has the potential to accumulate in organisms. 

However, a fish bioconcentration study indicates that cyhalofop-butyl does not significantly 

bioconcentrate. 

Cyhalofop-butyl degrades to cyhalofop-acid by biologically-mediated hydrolysis in less than a 

day. Further degradation leads to cyhalofop-amide and to cyhalofop-diacid. Hydrolysis and 

photolysis are much slower compared to biological degradation at neutral to acidic pH. Abiotie 

hydrolysis is more rapid at pH 9. Appendix D provides a table that summarizes the major and 

minor degradates of cyhalofop-butyl, their structures, and the range of maximum percent of 

applied equivalents in degradation studies. These properties indicate that cyhalofop-butyl's 

degradates will have little tendency to volatilize or to sorb to soil. The degradates will be mobile 

due to the low Ko, values. Cyhalofop-butyl residues will likely degrade in the water column 

rapidly and predominantly mineralize to carbon dioxide. Residues in paddy water from 

California and Arkansas field studies dissipated to below detectable levels after 28 days. 

Tahle 4: 1'hvsicochentic..;l 0'rooc.rtics cff t.:t'It<jlo9'nu-htitN - l. 

Parameter Value Description Source 

(M R[ D) 

Selected Physical/Chemical Parameters 

Molecular Formula C2o HZo FNOa - 45000201 

Molecular Mass 357.4 g/mol 45000201 

Vapor pressure (25°C) <1.0 x 10'' torr -- 43193203 

Aqueous solubility 0.44 - 45000203 

(20°C) mg/L 

Henry's Law Constant 9.4 x 10' 9 

(20°C) (calculated) Not likely to volatilize 45000203 

atm-tn'/mole 

Log octanol-to-water partition 3.3 -- 45000203 coefficient (Kow) (25°C) 

Acid dissociation constant (pKa) Not Measurable -- 43000203 (23±1°C) 

Page 18 of 48 
Pa ra meter Value Description Sou rce 

(MRID) 

Persistence 

Hydrolysis: Half-life 

(25f 1°C) 0.5 to Stable --- 

45000510 

days 45000511 

Aqueous Photolysis: Half-life 41.5 (alpha)' ) 45014712 (25±1'C) 

days 36.7 (beta) Supplemental 

Soil Photolysis: Half life Not a major degradation (25f 1°C) pH 5.8: Stable pathway 45000514 

days 

9 Silt Loam (AR) 45000515 8 Clay Loam (CA) 

2.32 Silt Loam (AR) 45000516 

Aerobic Soil Metabolism: DTso 

(25f 1 -C) 28 Sandy loams (Italy) 

28 Clay loam (ltaly) days 

45014?IS 

29 Loamy Sand (Germany) 

44 Sandy clay loam (UK) 

0.1 Flooded 45000518 Silt Loam Sediment (AR) 

Flooded 

Aerobic Aquatic Metabolism: DTso 0.18 Silt Loam Sediment 

days (Spain) 45000526 Flooded 

0.22 Silt Loam Sediment 

(France) 

Anaerobic Aquatic Metabolism: 

DStI 0.5 Silt loa n (A/)Rl water ond 45000517 0C) 

days 

Mobility 

Soil-water partition coefficients 

(Kd) 17.8 — 75.0 1/kg 

Sl ghtly Mobile 45000519 

Organic carbon-normalized 2892 - 7960 1/kg 

coefficients (Koc) 

Field Dissipation 

Aquatic Field Dissipation: Silt loam soil (AR) flooded 

DTso 0.04 Residues measured in 45000520 

days water 

Page 19 of 48 
Parameter Value Description Source 

(MRID) 

Clay loam soil (CA) 

flooded 

0.01 45000520 

Residues measured in 

water 

Fish Bioconcentration 

Fish Bioaccumulation Factors Edible: 27 Does not signifcantly 45000233 Whole Body: 507-672 bioconcentrate 

Abbreviations: °C - degrees Celsius; d= day; DT - disappearance tinie; hrs. = hours; in. = inch; 1= liters; kg = 

kilograms; I.OQ = level of quantitation; <= less than 

1) alpha and beta represent radiolabeled ring. 

3.2. Estimated exposure 

3.2.1. Direct Deposition onto terrestrial Food Items (located on treated paddies) 

Cyhalofop-butyl concentrations on terrestrial animal food items were estimated using the T-REX 

model (Table 5). These EECs are based on direct applications of the chemical to the paddy. The 

rnodel was parameterized with two applications (at rates of 0.29 and 0.18 ib a.i./A) spaced 10 

days apart. These values diffei• from the aquatic assessment because they correspond to liquid 

formulation applications whereas the maximttm rate simulated in the aquatic exposure assessment 

applied to granular formulations. The default half-life of 35 days was used because no chemicalspecific data were available to refine the default assumption. Given the available half-life data 

from laboratory fate studies, this half-life is likely an overestimation. 

TabEe 5: E stinaated c-«neentrations on different fooc.i itt•m, Iocatecl in tre<ttetl ric:c natldies. 

Food item Concentration 

(nig a.i./k 

Short Grass 100 

Tall Grass 46 

Broadleaf plants 56 

Fruits/ ods/seeds 6.3 

Arthro ods 39 

3.2.2. Estimated concentrations in water 

The Tier 1 Rice Model was used to estimate environmental concentration (EECs) in the rice 

paddy under flooded conditions. The post permanent flood scenario was modeled because 

dryland applications of cyhalofop-butyl must begin flooding within three hours of application. 

Table 6 sutnmarizes the model input parameters selected pursuant to the model input guidance 

document (USEPA, 2007). 

Page 20 of 48 
Table 6: 7`ier I Rice Model Anplfcation ScenQrios ancl Innut Pararneters 

Southern California Califo •nia California 

States & (Special Local Need (Special Local leed 

Soutl ee•n States Supplemental) Suppleniental) 

Clincher®DR Clincher' 5G; $ 

Registered + Clincher®GR; or Clincher GR ® Clinchcr x Granulc Product(s) 

Clincher®DR Clincher®Granule 

Seeding Type Wet 

Application 

Per od Post I'ermanernt Floo(i 

Application Sequential' Single Events 

Maximum 

Applioation Single:0.288 Single:0.288 Single:0.36 Single:0.36 

Rates;) followed by 0.207 followed by 0.18611 Annual: Annual: 

(Ibs a.i. /A) Annual: 0.495 Annual: 0.474 0.36 0.36 

Water Depth 10.0 (cm) 

Soil-Water 

Distribution 0.463 Coefficient, 

Kd (Ukg) 

Aerobic 

Aquatic 0.2 Metabolism 

ttn (da s) 

Aerobic 

Aquatic 

Metabolism 0.0165 

rate constant, 

k da '' 

Abbreviations: A= acre; a.i. = active ingredient; kg = kilogram; Ibs = pounds; ha = hectare 

1 Sequential refers to the splitting of product applications into two events separated by at least 10 days. 

2 The second application is a liquid formulation such as Clincher ®CA and Clincher® SF. 

3 Application rates were rounded to 3 significant digits, except for the existing label for Clincher ®GR and 

Clincher® Granule single event applications. 

Assumptions. Data Gaps and Uncertainties 

Assumptions, uncertainties and limitations of the modified Tier I Rice model were fully explored 

in the model's guidance document (USEPA, 2007). To account for known and unknown data 

gaps and model uncertainties, several conservative assumptions were incorporated into the model 

analysis and includes the following: 

Page 21 of 48 
1. To account for the discrepancy identified on the ClincheroDR product label's total annual 

application limit for sequential applications, a total annual application rate of 0.495 ibs a.i. 

/A was used instead of 0.47 Ibs a.i./A; 

2. The highest total annual single application rate of 0.36 lbs a.i./A was used for the 

California Special Local Need supplemental product labels; 

3. A 10-cm (4-inch) flood was assumed to be representative of the average depth of the rice 

paddy. Rice paddies have a slight slope for drainage purposes. The label recommends 

flood depths of 2-5 inches. Exposure estimates are more or less conservative when paddy 

water depths are shallower or deeper, respectively, than 10 cm; and, 

4. The modified Tier I Rice model does not account for all the routes of dissipation for the 

pesticide, such as all types of pesticide degradation, mass transfer, volatilization, or other 

dissipation pi-ocesses. 

"ratale 7: `('ies i 12ire Mocicl Igcstilts: l;stimated I:nvironrncntal Cortcentralic ns ( EI:C;) by 33 rc,duct 

ApplicatEon Sci'oltrio. 

California California 

California (Special Local (Special Local 

Southern & Need Need 

States Southern States Su lemental) Su lemental 

Clinchcr" DR Clincher® 5G; 

Registered + Clincher® GR; or Clinchery GR Clincher' Ciranule Product(s) 

Clincher" DR Clincher®Granule 

Peak 290.6 290.6 363 363 (ug/L) 

21-day A4ean 24.6 23.5 17.8 17.8 (ug/L) 

60-day \4ean 8.6 8.2 6.2 6.2 (ug/L) 

Results 

Table 7 summarizes the Tier I Rice Model results. Both Clincher GR and Granule have Special 

Local Need suppletnental registration labels, and are applicable only to the state of California. 

Both labels provide single naximum application rates of 0.36 lbs a.i./ acre per event and annually. 

Although the total annual application rate is lower than other cyhalofop-butyl containing labels of 

0.47 Ibs a.i./ acre, the single higher application rate produces the peak highest ecological 

estimated environmental concentration (EEC) of 363 ppb. Figure 3 depicts the concentrations of 

cyhalofop-butyl in paddy water for up to 14 days following application; the required minimum 

retention period of flooded rice paddies treated with granular formulations. Because of the very 

short half-life of cyhalofop-butyl in water (e.g. DT5o = 2.4 to 5.3 hours), the residues decrease by 

orders of magnitude below the initial peak concentration the day aftec -application. As shown in 

the figure, when multiple applications yield two peaks, one on the first day, and the second 10 

days later when the second application occurs. 

Page 22 of 48 
400 

mliil 

— 300 

an 

~ 250 

_ 0 

L 200 

~ 

c 

a~ 

~ 150 

0 

: 

a 100 

0 a~ 

a 50 Q 

7 

Rice Paddy EECs vs Time 

3 Maximum Sequential r 

..... . .. ...... . ..... . . ................... 

Application Rates i 

; ♦ Maximum Single ~ 

Application Rate ! 

,~.,w.. ....,,.,~

,,,. _.. .................. ~ .,,~.,,~,,,..T-~. ~ 

.....~..._ ■ - -- -------_.. 

0 5 10 15 

Days After Application 

Figure 3: Estimatec! eiaiiy cc ~ nce ~itrations of ryhhlofop-l ~utyl nfter apl ~ lic:atiura o.felthet• Clinclier (;K 

or t;r ~~ ni~ lc sulyl ~ lemcntai labels at the sinl;lc applic ~ation r.ate of 4.36 Ebs aa.i./ A. 

3.2.3. Spray Drift Transport 

The spray deposition curves for aerial and ground applications as calculated by AgDRIFT are 

provided in Figures 4 and 5, respectively. Note that these figut•es represent point estimates of 

spray drift deposition at distances from the edge of the field. Values are expressed as the percent 

of the applied rate. These curves are used to determine the distance from the edge of the field 

where risk extends to non-target plants. 

Page 23 of 48 
50.0% 

45.0% 

40.0% 

35.0% 

-0 30.0% 

a~ 

Q25.0% 

cm 

0 20.0% 

a 

15.0% 

10.0% 

5.0% 

0.0% 

..nr.. 4nn !n ffne .ia..Js.s 

> 

ilets 

0 200 400 600 800 1000 

Distance from edge of field (feet) 

Figure 4. Percent of applied pesticide at different distances from the 

edge of the field treated by aerial methods (calculated using AgDRIFT 

v2.01; 10 foot release height). 

50% 

45% 

40% 

35% 

-o 30% 

a-25% 

ca 

~ 

° 20% 

0 

15% 

10% 

5% 

0% 

0 

Hinh hnnm ACAG vPrv finP tn fino 

100 200 300 400 500 

Distance from edge of field (feet) 

Figure S. Percent of applied pesticide at different distances from the 

edge of the field treated by ground methods (calculated using AgDRIFT 

v2.01). 

Page 24 of 48 
4. Effects Analvsis 

4.1.Toxicity data 

Available toxicity data indicate that cyhalofop-butyl is practically non-toxic to mammals, birds and 

bees on an acute oral exposure basis. It is also practically non-toxic to birds on a sub-acute dietary 

basis and bees on an acute contact basis. In sub-chronic exposures involving earthworms, no effects 

were observed at 1120 mg/kg-soil. Available chronic toxicity data with mammals and birds indicate 

no effects to reproduction or offspring at 100 mg/kg-food for rats and 736 mg/kg-food for bobwhite 

quail (Table 8). 

Cyhalofop-butyl is highly toxic to aquatic animals on an acute exposure basis. Toxicity data are 

available for several different test species. Available chronic toxicity data indicate effects to 

survival at concentrations >_287 ,ug a.i./L (NOEC = 134) to fish and to reproduction at >_77.9 ,ug 

a.i./L (NOEC = 47.4) to invertebrates. (Table 9). 

Based on a seedling emergence and a vegetative vigor study for non-target terrestrial plants (Table 

10), barnyard grass (a monocot) was the most sensitive species tested. The lowest parent cyhalofopbutyl EC25 for barnyard grass is a vegetative vigor endpoint of 0.0017 lb a.i./A (corresponding 

NOAEC = 0.007). Available test data for six species of dicots indicated no effects at the highest 

application rate. The freshwater diatom was the most sensitive aquatic plant species, with NOAEC 

and EC50 values of 530 and 890 μg a.i./L, respectively. 

Page 25 of 48 
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4.2.Reported Ecological Incidents 

Four incident reports are included in EIIS. Two involved incidents associated with direct effects 

to treated rice. Two involved incidents with non-target plants exposed through spray drift. The 

incident reports are summarized here. 

Incident number I014266-003: An aerial application of Clincher was made to rice field near a 

milo sorghum field in June, 2003 in MO. The milo field suffered plant damage from spray drift. 

The legality of the use was classified as a"misuse". The certainty was identified as "probable". 

Incident number I015360-003: In May, 2004 in CA, aerial application was made to a rice 

field. The spray drift resulted in damage to 120 peach trees less than 2 miles from the site of 

application. There was red spotting on the leaves and some defoliation of the leaves. Lab 

analysis confirmed the presence of Clincher on the peach leaves. Since this incident occurred 

inside the 2 mile buffer zone, it is considered an accidental misuse. The certainty was identified 

as "probable." 

Incident number I014266-003: An application of Clincher was made to rice field in June, 2003 

in WI. Damage to the treated rice was observed. The incident was associated with a registered 

use. The certainty category was identified as "possible". 

Incident number I013636-007: An application of Clincher was made to rice field in January, 

2003 in CA. Decrease in yield of rice was reported. The incident was associated with a 

registered use. The certainty category was identified as "possible". 

4.3.Endocrine Disruptor Screening Program 

As required by FIFR.A and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As required by FFDCA section 408(p), cyhaolfop-butyl is subject to the 

endocrine screening part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a"naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate." The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier I consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

Page 29 of 48 
systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicais. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list 

of chemicals identified for EDSP screening was published on June 14, 2013 4and includes some 

pesticides scheduled for registration review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors. 

Cyhaolfop-butyl is not on the first or second list. The second list represents the next set of 

chemicals for which EPA intends to issue test orders/data call-ins in the near future. For further 

information on the status of the EDSP, the policies and procedures, the lists of chemicals, future 

lists, the test guidelines and the Tier 1 screening battery, please visit our website. 5 

5. Risk Estimation and Characterization 

For this preliminary assessment of cyhalofop-butyl, the deterministic RQ method was used to 

provide a metric of potential risks. The RQ is a comparison of exposure estimates to toxicity 

endpoints (i.e., RQ = EEC/toxicity endpoint). The resulting RQs are compared to the Agency's 

risk levels of concern (LOC), which are the Agency's interpretive policy such that when acute or 

chronic risk LOCs are exceeded, the need for regulatory action may be considered. These 

criteria are used to indicate when the use of a pesticide, as directed on the label, has the potential 

to cause adverse effects to non-target organisms. For acute and chronic risks to animals, the 

LOCs are 0.5 and 1.0, respectively, and for plants, the LOC is 1.0. For each taxa, RQs are 

generated and risks are discussed. This discussion includes consideration of additional data and 

lines of evidence. 

5.1. Terresta-ialOrganisnis 

5.1.1. Anianals 

Acute RQs generated using the T-REX model do not exceed acute LOCs for terrestrial animals, 

including birds (and terrestrial-phase amphibians and reptiles) and mammals (Tables 11 and 12). 

This applies to both non-listed and listed species (LOCs = 0.5 and 0.1, respectively). Chronic 

RQs do not exceed the LOC for birds, indicating that reproductive effects are not expected for 

non-listed and listed species (LOC = 1 for both). Chronic RQs for mammals consuming grass 

^ Seehttp://www.reaulations.gov/#!docinnentDetail;D=EPA-HO-OPPT-2009-0477-0074 for the final second list of 

chemicals. 

5http://www.epa.gov/endo/ 

Page 30 of 48 
and broadleaf plants located on the treated field exceed the LOC (1.0), indicating potential risk to 

offspring of mammals. There is uncertainty associated with the conclusion that exposures to 

cyhalofop-butyl will impact mammals because, 1) cyhalofop-butyl is not particularly persistent 

in the environment b , therefore, mammals feeding on the treated field may not consume 

cyhalofop-butyl residues for a sufficient amount of time to represent a chronic exposure; 2) the 

magnitude of the effect to mammals was only 5-7% decrease in body weight of the F 1 

generation; although this was a statistically significant effect; the biological relevance of this 

effect is uncertain and 3) there is uncertainty associated with the NOAEC due to a 10-fold dose 

spacing between test concentrations. 

i abEe 1 1: I3tiv for liirds (and terrestrial-phase antphdbians and reptiles) 1'ee<linl; c rt thc trcateci 

iicfc6. 

Dietary I:tem 

Acute, dose-based RQs * 

Acute, 

dietary Based 

RQs * 

Chronic, 

dietary Based 

RQs* * 

20 g bird 100 g bird 1000 g bird AII sizes All sizes 

Short Grass <0.10 <0.04 <0.01 <0.02 0.14 

Tall Grass <0.04 <0.02 <0.01 <0.01 0.06 

Broadleaf plants <0.05 <0.02 <0.01 <0.01 0.08 

Fruits/ ods <0.01 <0.01 <0.01 <O.OI 0.01 

Arthro ods <0.04 <0.02 <0.01 <0.01 0.05 

Seeds <0.01 <0.01 <0.01 <0.01 O.OI 

*Non-listed species LOC = 0.5, Listed species LOC = 0.1. 

**Non-listed and listed species LOCs = 1.0. 

l:ibie 12: F2Os lot-mamnlals feedin<r on the treated fielti. 13o1<i values exceed I.10C. 

` 

Dietary Item 

Acute, dose-based RQsK Chronic, dose-based RQs** 

15 g 

mammal 100 g mammal 1000 g mammal 15 g 

mammal 

100 g 

mammal 

1000 g 

mammal 

Short Grass <0.01 <0.01 <0.01 8,7 7.4 4.0 

Tall Grass <0.01 <0.01 <0.01 4.0 3.4 1.8 

Broadleaf plants <0.01 <0.01 <0.01 4.9 4.2 2.2 

Fruits/ ods <0.01 <0.01 <0.01 0.54 0.46 0.25 

Arthro ods <0.01 <0.01 <0.01 3.4 2.9 1.6 

Seeds <0.01 <0.01 <0.01 0.12 0.10 0.06 

*Non-listed species LOC = 0.5, Listed species LOC = 0.1. 

**Non-listed and listed species LOCs = 1.0. 

6 Although soil metabolism half-lives range 2.3-44 days, after cyhalofop-butyl is applied to the rice paddy as a foliar 

spray, the paddy is flooded. Once the paddy is flooded, cyhalofop-butyl is expected to go through several half-lives 

within a day (aerobic aquatic half-life: 0.1-0.22 days). 

Page 31 of 48 
Available honey bee data include acute NOAEL values of 100 μg a.i./bee for both contact and 

oral exposures routes (Table 9). According to EFED's risk assessment method for honey bees, 

the contact value can be converted to Ib a.i./A by dividing by 2.7 (μg a.i./bee per 1 lb a.i./A). The 

result is an NOAEL of 37 lb a.i./A. Similarly, the oral NOAEL can be converted by dividing by 

32 (μg a.i./bee per l Ib a.i./A), with a NOAEL value of 3.1 lb a.i./A. Since both values are at 

least an order of magnitude below the maximum allowed application rate for cyhalofop-butyl, 

acute effects to adult bees are not expected. It should be noted that there is uncertainty associated 

with the risks of cyhalofop-butyl to bees due to a lack of chronic toxicity data for adults as well 

as acute and chronic toxicity data to larvae. No data are available to assess the chronic toxicity of 

cyhalofop-butyl to adult honey bees. Data are not available to assess the acute or chronic toxicity 

of cyhalofop-butyl to honey bee larvae. Despite this lack of data, the risk of cyhalofop-butyl to 

bees is considered negligible because exposure is expected to be minimal. This is because 1) rice 

is not a pollinator attractive crop and 2) cyhalofop-butyl degrades rapidly in the environment. 

5.1.2. Plants 

Spray drift from aerial and ground spray applications of cyhalofop-butyl are expected to pose a 

risk of growth effects to non-target grass species. Given that no effects were observed in dicots 

exposed to cyhalofop-butyl at rates exceeding the maximum application rates allowed on labels, 

effects to dicot species are not expected. 

The most sensitive endpoints for terrestrial plants correspond to effects to shoot weight of 

barnyard grass from a vegetative vigor study. These endpoints, i.e., NOAEC = 0.007 lb a.i./A 

and EC25 = 0.0017 lb a.i./A equate to 2.4% and 5.9% of the maximum single application rate 

(0.291b a.i./A) allowed for liquid formulations containing cyhalofop-butyl. When considering 

the spray drift deposition predicted by AgDRIFT (Figures 4 and 5), cyhalofop-butyl exposures 

may cause effects to grasses that are located well beyond the edge of the treated field. Table 13 

presents the farthest distances from the edge of the treated field where spray drift deposition is of 

concern based on NOAEC and EC25 values for barnyard grass. For aerial applications, risks 

extend beyond the predictive abilities of the Tier I AgDRIFT model (i.e., >997 feet). For aerial 

applications, risks extend as far as 100 feet from the edge of the field. If nozzles are used that 

limit the droplet spectra to medium or coarse, the distances from the edge of the field where risk 

extends are lowered. 

T'able 13: .approximate distance froiu ed re nf field to i-each NOA) ~;C aud I?C25 ~~ alues for barnyard 

g r.i; s. 

Application description (method, droplet 

spectra, release height) 

Distance from edge 

of field (ft) to 

NOAEC 

llistancc from edge 

of field (ft) to F;C25 

Aerial, very fine to fine >997 600 

Aerial, fine to medium 1400 175 

Aerial, medium to coarse 1200 100 

Ground, ver fine to fine, hi h boom 100 50 

Ground, fine to medium/eoarse, hi h boom d 25 10 

Page 32 of 48 
~

roun ver fine to fine, low boom 25 40 

 fine to medium/coarse, low boom 15 5 

5.2. Aquatic Organisms 

Acute and chronic RQs were derived using the maximum estimated concentrations of cyhalofopbutyl in rice paddies along with the most conservative endpoints for fish, invertebrates and 

aquatic plants (Table 14). The acute RQ for fish exceeds the listed species LOC. The acute RQ 

for invertebrates exceeds the non-listed as well as the listed species LOC. These LOC 

exceedances indicate potential risk of cyhalofop-butyl to fish and invertebrates inhabiting a rice 

paddy on the day that it is treated with cyhalofop-butyl. Because of the rapid degradation of 

cyhalofop-butyl, estimated exposures on the day after the exposure (11.4 μg a.i./L; Figure 3) are 

insufficient to cause a risk concern especially if paddy water is held before release into 

downstream habitats. Therefore, effects to non-target organisms outside of the rice paddy are not 

expected. RQs for plants and chronic RQs for animals are below the LOC (1.0), indicating low 

risk of effects to plants or chronic effects to animals. 

'1`ablc 14: 12(}s f'or Atitiatic ()manisms. 

Parameter Fish Invertebrates Plants 

Acute EEC a.i./L) 363 363 363 

Acute End oint a.i./L 760 520 530 

Acute RQ 0.48* 0.70** 0.68 

Chronic EEC a.i./L 6.2 17.8 Not applicable 

Chronic End oint a.i./L) 134 47.4 

Chronic RQ 0.04 0.38 _ 

*Exceeds listed species LOC of 0.05. 

**Exceeds non-listed species LOC of 0.5 and listed species LOC. 

5.3. Listed Species 

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

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

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

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

agencies in response to the National Academy of Sciences' (NAS) recommendations and reflect 

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

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

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

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

Endangered Species Act (ESA) and FIFRA. 

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

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

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

Evaluation Group (SFIREG) meetings, and held a stakeholder workshop in Apri12014, allowing 

Page 33 of 48 
additional opportunities for stakeholders to comment on the Interim Approaches. As part of a 

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

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

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

white paper "Interim Approaches for National-Level Pesticide Endangered Species Act 

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

Report," dated November l, 2013. 

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

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

designated critical habitat, this preliminary risk assessment for cyhalofop-butyl does not contain 

a complete ESA analysis that includes effects determinations for specific listed species or 

designated critical habitat. Although EPA has not yet completed effects determinations for 

specific species or habitats, for this preliminary assessment EPA conducted a screening-level 

assessment for all taxa of non-target wildlife and plants that assumes for the sake of the 

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

the application of cyhalofop-butyl. This screening level assessment will allow EPA to focus its 

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

methods being developed by the agencies have been fully vetted. This screening-level risk 

assessment for cyhalofop-butyl indicates potential risks of direct effects to listed mammals, 

birds, terrestrial invertebrates, fish, and aquatic invertebrates on all of its registered use sites. 

Listed species of aquatic and terrestrial plants may also be affected through indirect effects 

because of the potential for direct effects on listed and non-listed species upon which such 

species may rely. Potential direct effects on listed mammals, birds, terrestrial invertebrates, fish, 

and aquatic invertebrates from the use of cyhalofop-butyl may be associated with modification of 

Primary Constituent Elements (PCEs) of designated critical habitats, where such designations 

have been made. Once the agencies have fully developed and implemented the scientific 

methods necessary to complete risk assessments for endangered and threatened (listed) species 

and their designated critical habitats, these methods will be applied to subsequent analyses for 

cyhalofop-butyl as part of completing this registration review. 

5.4. Risk Conclusions 

Risk conclusions are summarized as follows: 

- The primary risk concern for cyhalofop-butyl is to non-target plant species located in areas 

that receive spray drift (i.e., those that are adjacent to treated rice paddies). 

• Risks of concern for plants resulting from spray drift of aerial and ground 

applications may extend > 1000 feet and 600 feet, respectively, from the edge of the 

treated field. 

• If applications are made using nozzles that generate medium or coarse droplets, risks 

would not extend as far from the edge of the field (based on AgDRIFT model runs 

with alternate droplet spectra). 

• It is assumed that granular formulations do not drift from the treated field and 

therefore do not pose a risk to non-target plants. 

Page 34 of 48 
o Although seedling emergence and vegetative vigor toxicity data do not suggest that 

cyhalofop-butyl or cyhalofop-acid will impact dicots, available incident reports and 

spray drift buffer restrictions for peaches and nectarines (24 miles for aerial 

applications, 600 feet for ground) suggest that there may be impacts to non-grass 

species of plants (e.g., other monocots, dicots). 

o Risks to specific listed species of terrestrial and wetland plants are uncertain at this 

time. 

Cyhalofop-butyl residues on mammalian food items located on the treated field (f.e., grass, 

broadleaf plants and invertebrates) may pose a chronic risk to mammals consuming those 

food items. 

o There is uncertainty associated with the conclusion that exposures to cyhalofop-butyl 

will impact mammals because: 1) cyhalofop-butyl is not particularly persistent in the 

environment; therefore, mammals feeding on the treated field may not consume 

cyhalofop-butyl residues for a sufficient amount of time to represent a chronic 

exposure; 2) the magnitude of the effect to mammals was only 5-7% decrease in body 

weight of the F1 generation; although this was a statistically significant effect; the 

biological relevance of this effect is uncertain and 3) there is uncertainty associated 

with the NOAEC due to a 10-fold spacing between the NOAEC and the LOAEC. 

o Risks to listed mammals are uncertain at this time. 

On the day of the application, concentrations of cyhalofop-butyl in the rice paddy water may 

be sufficient to pose a risk of mortality to fish and aquatic invertebrates located within the 

rice paddy. 

o This would only apply to situations where cyhalofop-butyl is applied to rice paddies 

that contain water inhabited by aquatic life. 

This assessment indicates that cyhalofop butyl does not pose a risk of concern to: 

o Birds, terrestrial-phase amphibians and reptiles; 

o Terrestrial invertebrates; 

o Fish and invertebrates in non-target areas; and 

o Aquatic plants. 

No Effect determinations may be made for listed species of birds, amphibians, reptiles, 

invertebrates, fish and aquatic plants that do not depend upon plants or mammals (e.g., for 

food, habitat). Given that many species depend upon terrestrial, wetland and riparian 

vegetation for food or shelter, No Effect determinations will be limited to a only a small 

proportion of all of the currently listed species (e.g., cave-dwelling species of animals). 

6. Literature Cited 

United State Department of Agriculture (USDA). 2012. Rice: Background, U.S. Rice 

Production. htti2://www.ers.tisda.gov/tol2ics/crops/rice/backp-rouiid.aspx (Date Accessed: 

July 30, 2014). Economic Research Service. Washington, DC. 

United States Environmental Protection Agency (USEPA). 2007. Guidance for Tier 1 Estimation 

of Aqueous Pesticide Concentrations in Rice Paddies. Memo from S. Bradbury to 

Environmental Fate and Effects Division; May 8, 2007. U.S. Environmental Protection 

Page 35 of 48 
Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide 

Programs, Environmental Fate and Effects Division, Washington, DC. Available at 

littp://www.el2a. ~i, ov/ol2l2efed l/models/water/#rice (accessed July 30, 2014). 

USEPA. 2008. Drinking Water Assessment for the Section 3 Registration of Cyhalofop-butyl for 

Use of Wild Rice in California. Memo from Katrina White to Daniel Rosenblatt; DP 

Barcode 357419; October 17, 2008. U.S. Environmental Protection Agency, Office of 

Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, 

Environmental Fate and Effects Division, Washington, DC. 

USEPA, 2014. BEAD Chemical Profile (BCP) for Registration Review: Cyhalofop-butyl 

(082583). Memo from Biological and Economic Analysis Division (7503P) to 

Environmental Fate and Effects Division; May 7, 2014. U.S. Environmental Protection 

Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide 

Programs, Biological and Economic Analysis Division, Washington, DC. 

United States Geological Survey (USGS), 2011. Pesticide Use Maps: Estimated Agricultural 

Use for Cyhalofop, 2011. 

littp://water.usgs.gov/nawqa/pnsp/usa: .>e/maps/sthow map.php?veat=201I&map=CYHAL 

OFOP&hilo=L&disp=Cyhalofop (Date Accessed: July 30, 2014). U.S. Department of the 

Interior. Washington, DC. 

Page 36 of 48 
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Appendix C. llescription of niodified Tier I I2ice model 

The Environmental Fate and Effects Division (EFED) developed the screening level Tier I Rice 

model (i.e. an equation) to estimate pesticide concentration residues in surface waters of floodcd 

rice fields (USEPA, 2007). The Tier I Rice Model is expressed in the following equation: 

Equation 1: C,- = mei' /(0.00105 + 0.00013 x Kd) 

where; 

CW = the paddy water concentration (μg/L) 

m8i' = the application rate (kg/hectare) 

Kd = the soil-water distribution coefficient in L/kg 

Tier I Rice Model Modifred with Aerobic Aquatic Degradation 

The Tier I Rice Model was provisionally modified to estimate pesticide residues in surface water 

discharged from rice fields (e.g. tail water) following a retention period and allowing aerobic 

aquatic degradation. Incorporating the aerobic aquatic degradation pathway into the Tier I Rice 

model was used to identify: 

1) acute (peak) concentrations following single, or sequential-applications; 

2) acute concentrations after the label "recommended" pesticide retention periods (for either 

single or sequential application scenarios); and, 

3) chronic (annual mean) exposure. 

The moditied Tier I Rice Model includes the additional equation: 

Lquation 2: C,,,, c= CW, o e("kt) 

where; 

Cw, t= the concentration in water at time, t(μg/L) 

Cw, 0= the concentration in water at application or time of zero 

(μg/L) (calculated using the Tier I Rice Model) 

k= the aerobic aquatic metabolism rate constant (d' 1 ) 

t = days after application (d) 

Page 45 of 48 
Appendix D: Summary of Major and Minor llegradates 

'I'abte 15: Sun;ltnary c 3'rnajur ancl miuor de[;radates cat'cyt alofr. p-lyutyf and the range of nlaximurrl 

percent ofa p iied ec ui'valents in def*rr cfation stucties" (US EPA, 2008; Dl' C3.zreo(fe 3 ~~ 7-419). 

Degradate Names Maximum % 

SMILES String applied 

Structure e uivalertts 

Ma'or Dc radates Made u>10%, of a>>lied parent e uivalents 

Cyhalofop-acid (CAS No. 122008-78-0); 1.2 — 98.7 

(R-(+)-2-[4-(2-fluoro-4-cyanophenoxy)phenoxy]propanoic acid); 

XRD-537 acid; 

(2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid 

SMILES String: CC(OC1=CC=C(OC2=C(F)C(=CC=C2)C#N)C=C1)C(0)=0 

O 

~C\ F / O O H I ~ 

I ~` CH3 \ H 

O 

Cyhalofop—amide (CAS No. Unavailable); 1.9 - 44.5 

(2-[4-(4-aminocarboxyl-2-fluorophenoxy)phenoxy]propanoic acid); 

XRD-537 a nide; 

2-[p-(4-carbamoyl-2-fluorophenoxy)phenoxy]propionic acid; 

2-[4-[4-(aminocarbonyl)-2-fluorophenoxy]phenoxyl]propanoic acid; 

SMILES String: CC(OC1=CC=C(OC2=C(F)C=C(C=C2)C(N)=0)C=C1)C(0)=O 

O 

O 

F 

Ni 2 O 

OH 

~ 

CH 3 

Cyhalofop-diacid (CAS No. Unavailable); 11.9 — 86.5 

(R-(+)-2-[4-(4-carboxy-2-fluorophenoxy)phenoxy]propanoic acid); 

XRD-537 diacid; 

4-[p-(1-carboxyethoxy) phenoxy]-3-fluorobenzoic acid;4-[4-(I-carboxyethoxy)phenoxy]-3- 

fluorobenzoic acid 

SMILES String: CC(OC1=CC=C(OC2=C(F)C=C(C=C2)C(0)=0)C=C1)C(0)=0 

O 

O 

F 

HO O I ~ ` OH 

I ~ CH3 ~ \ H 

O 

Page 46 of 48 
Degradate Names Maximum % 

SMILES String applied 

Structure e uivalents 

FHPBA (CAS No. Unavailable); 0.2 — 20.3 

3-fluoro-4-(4-hydroxyphenoxy)benzoic acid O 

F 

HO ~ / OH 

I I 

/ O \ 

DP or FCPP; 0.4 -12.0 

(4-(2-fl uoro-4-eyanophenoxy)phenol); 

XRD-537 DP; 

3-fluoro-4-(4-hydroxyphenoxy)benzonitrile 

NoC ~ F / OH 

I I 

O 

Minor De radates made u<10% of applied parent e uivalents 

HPPA; 0.14 - 7.7 

(R-(+)-2-(4-hydroxyphenoxy)propanoic acid); 

(2R)-2-(4-hydroxyphenoxy)propanoic acid O 

~ O 

I

OH 

OH / 

FHB; 0.19 — 0.37 

(3-fluoro-4-hydroxybenzonitrile); 

XRD-537 HBN / \ F 

N I 

~ 

OH 

Page 47 of 48 
Appendix E. Example lines of evidence for deriving risk conclusions and their certainty 

Conclusion: No Risks of Concern Conclusion: Risks of Concern Identified 

Certain in : Hi h Certaintv: Hi h 

• High magnitude and/or long duration 

• More than one line of evidence predicts effects will 

occur 

• No LOC exceedance with relatively complete data • LOC exceedances, fate, and toxicity profile should 

set or risks have been mitigated; be considered 

• High confidence in data • Exposure is expected to occur based on fate profile 

• Fate and toxicity profiles clearly support low risk and uses 

• Probable cause of incident(s). 

• Examples: High toxicity, high persistence, 

incident(s), little exposure needed to cause effects 

Conclusion: No Risks of Concern Conclusion: Risks of Concern Identiried 

Certaint : Low Certaintv: Low 

• Chronic risk called for non-persistent chemical 

• No LOCs exceeded but other non-compelling • Risk to taxonomic group called based on complete 

circumstances suggest that there may be issues lack of submitted data 

• Missing endpoints, poorly spaced test • Risk calls based on lack of data without other lines 

concentrations, low confidence in data showing of evidence available 

low toxicity • Risk calls based on uncertain extrapolation 

• Lack of LOC exceedances based on extrapolation methods or conflicting data 

and additional information is being requested to • Missing endpoints, poorly spaced test 

corroborate low risk concentrations, low confidence in data showing 

• Examples: high persistence and bioaccumulation, high toxicity 

but low risk calls • Examples: Risk calls based on total residues, but 

not parent only (sometimes) 

Page 48 of 48