1 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

Date: November 3, 2014

PC Code: 111601

DP Barcode: 419419

MEMORANDUM 

SUBJECT: Registration Review Problem Formulation for Oxyfluorfen 

FROM: Robin Sternberg, Ph.D., Wildlife Biologist 

 He Zhong, Ph.D., Biologist 

 Environmental Risk Branch 1 

Environmental Fate and Effects Division (7507P) 

THROUGH: Sujatha Sankula, Ph.D., Branch Chief 

 Meghan Radtke, Ph.D., Acting RAPL 

Environmental Risk Branch 1 

 Environmental Fate and Effects Division (7507P) 

 

TO: Benjamin Askin, Risk Review Manager 

 Tom Moriarty, Team Leader 

Neil Anderson, Branch Chief 

 Risk Management and Implementation Branch 1 

Pesticide Re-Evaluation Division (7508P) 

Attached is the Registration Review problem formulation for the herbicide oxyfluorfen. 

 
2 

REGISTRATION REVIEW 

PROBLEM FORMULATION ______________________________________________________________________________ 

Oxyfluorfen 

CAS Number 

US EPA PC CODE 111601 

Prepared by: 

Robin Sternberg, Ph.D., Wildlife Biologist 

He Zhong, Ph.D., Biologist 

Edom Seifu, Intern 

Environmental Risk Branch 1 

Reviewed by: 

Edward Odenkirchen, Ph.D., Senior Science Advisor 

Faruque Khan, Ph.D., Senior Fate Scientist 

Environmental Risk Branch 1 

U.S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division 

Environmental Risk Branch I 

1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington, DC 20460 
3 

1 Executive Summary 

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

formulation (attached) for the ecological risk, environmental fate, endangered species, and 

drinking water assessments to be conducted as part of the Registration Review of oxyfluorfen, a 

light-dependent peroxidizing herbicide (LDPH). The problem formulation describes the 

methods 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 oxyfluorfen as well as uncertainties unique 

to risk assessment of oxyfluorfen. This document also identifies additional studies that would be 

beneficial to conducting an ecological risk assessment. Major findings include the following 

data needs and the uncertainties described below: 

All studies should be conducted with parent oxyfluorfen. 

 OCSPP 835.2240: Aqueous photolysis (TGAI) 

 OCSPP 835.4300: Aerobic aquatic metabolism (TGAI) 

 OCSPP 835.4400: Anaerobic aquatic metabolism (TGAI) 

 OCSPP 850.6100: ECM/ILV for soil and water 

 OCSPP 850.2100: Avian acute oral toxicity test, passerine species 

 OCSPP 850.1075: Fish acute toxicity test, estuarine/marine fish or fathead minnow 

 OCSPP 850.1350: Fish early life stage toxicity test, estuarine/marine species 

 Special study (OECD 213): Acute oral toxicity to adult honey bees 

 Special study: Chronic oral toxicity to adult honey bees 

 Special study: Chronic and acute toxicity to larval honey bees 

 Special study: Pollinator feeding/semi-field/pollen and nectar residue studies – The need 

for these studies is contingent upon the results of lower tier bee studies. 

 OCSPP 850.3040: Field testing for pollinators – The need for field testing is contingent 

upon the results of lower tier bee studies. 

Justifications for these data needs as well as assumptions that will be made in the absence of 

these data are provided in Section 11. 

 The potential for phototoxic effects is a serious concern for oxyfluorfen. With the 

exception of a fish early life stage toxicity test, all of the toxicity tests were conducted 

under standard laboratory lighting conditions which may result in an underestimation of 

the toxicity of oxyfluorfen to some taxa under natural sunlight conditions. No further UV 

enhanced ecotoxicity studies are being requested, but the uncertainties associated with 

data generated under standard laboratory lighting conditions will be characterized in the 

risk assessment. 

 The stressors of ecological concern for aquatic organisms are oxyfluorfen and any major 

degradates identified in the requested aquatic fate studies. As a conservative estimate, 

the unknown percentage(s) of the major degradate(s) will be treated as parent unless the 

amount(s) of maximum formation are identified as a result of the data call-in. Degradate 

MW-332, which formed at >10% in the aquatic photolysis study (MRID 42129101), is 
4 

estimated to be 3-4 times less toxic than the parent. Additional information for the 

maximum formation of MW-332 is needed to determine if it will be included or excluded 

in the Registration Review ecological risk assessment. 

 Most labels do not specify a minimum application interval. In addition, the maximum 

yearly application rate is not identified for many of the labels. In the absence of this 

information, conservative assumptions will be made. 

2 Introduction 

Oxyfluorfen is a light-dependent peroxidizing herbicide (LDPH) in the diphenyl ether chemical 

class. It is used for pre- and post-emergence control of monocotyledonous and broad leaf weeds 

in agricultural crops (including fallow fields prior to planting), ornamental nurseries, and 

residential areas. LDPHs target a specific enzyme, protoporphyrinogen oxidase, in the heme and 

chlorophyll biosynthetic pathway. Inhibiting protoporphyringen oxidase in plants leads to an 

accumulation of phototoxic heme and chlorophyll precursors that, in the presence of light, 

produce activated oxygen species which rapidly disrupt cell membrane integrity. 

EFED evaluated the most recent ecological risk assessments for oxyfluorfen in association with 

updated toxicity, exposure, and usage information to determine if sufficient data are available 

and if further updates are needed to support Registration Review. Recent ecological risk 

assessments for oxyfluorfen include the 2002 EFED chapter for the Reregistration Eligibility 

Decision (RED) document (original, DP 250187, August 31, 2001; revised, DP 279498, 

December 11, 2001; revised, DP 282182, May 2, 2002) and a 2008 litigation assessment for the 

California red-legged frog (Rana aurora draytonni) (USEPA, 2008)1

. In addition, EFED 

considered the latest Agency science policies and risk assessment methodologies. 

3 Use Characterization 

Oxyfluorfen is a pre- and post-emergent diphenyl ether herbicide used to control 

monocotyledonous and broad leaf weeds. Registered use sites of oxyfluorfen are provided in 

Table 3-1. Oxyfluorfen is formulated as an emulsifiable concentrate, flowable concentrate, 

granule, ready-to-use liquid, and soluble concentrate/liquid. Treatment equipment includes 

aircraft, low pressure ground sprayer, sprinkler irrigation, spreader, and ready-to-use spray 

container. EFED will use application scenarios that result in maximum exposure scenarios for a 

given use for the risk assessment (see Appendix A). The Label Data Report produced by 

BEAD, located in the docket, identifies legitimate gaps in label information by EPA Reg. No. 

Specifically, many labels identify a seasonal maximum application rate or maximum application 

rate per crop cycle. They do not identify a maximum yearly rate (lbs a.i./year), which is 

necessary for ecological risk assessment. Most labels do not specify an application interval 

either. The absence of a maximum single application rate, an application interval, a maximum 

rate (lbs a.i./year), and/or application method on labels may result in conservative assumptions. 

 

 

1

 http://epa.gov/espp/litstatus/effects/redleg-frog/index.html
5 

Table 3-1. Registered Uses of Oxyfluorfen by Use Group 

Terrestrial Food Terrestrial Non-Food Terrestrial Food + Feed 

Apricot 

Artichoke 

Agricultural fallow/idleland/ 

conservation reserve 

Agricultural fallow/idleland/ 

conservation reserve 

Avocado Agricultural uncultivated areas Almond 

Blackberry Christmas tree plantations Corn (unspecified) 

Broccoli Citrus Corn, field 

Cabbage Cocoa Cotton (unspecified) 

Cauliflower Coffee Garbanzos (including chick peas) 

Cocoa Conifers (plantations/nurseries) Grapes 

Coffee Deciduous trees Mint/peppermint/spearmint 

Date Eucalyptus Peppermint 

Feijoa (pineapple guava) Grapes Pome fruits 

Fig Grasses grown for seed Soybeans (unspecified) 

Garlic Guava Stone fruits 

Guava Jojoba Tree nuts 

Horseradish Lesquerella 

Kiwi fruit Nonagricultural uncultivated areas/soils Forestry 

Nectarine Nursery stock Cottonwood (forest/shelterbelt) 

Olive Onion Forest trees (softwoods, conifers) 

Onion Ornamental and/or shade trees Shelterbelt plantings 

Papaya Ornamental woody shrubs and vines 

Peach 

Persimmon 

Ornamentals (unspecified) 

Pineapple 

Terrestrial Non-Food + Outdoor 

Residential 

Pistachio Rose Rose 

Plum Sweet peas (ornamental) 

Pomegranate Tree nuts 

Prune 

Raspberry (black, red) 

Sage, clary 

Taro 

Walnut (English/black) 

4 Conclusions from Previous Risk Assessments 

4.1 Ecological Risk Assessments 

EFED has conducted ecological risk assessments on oxyfluorfen that serve as a basis for this 

problem formulation, including the 2002 EFED chapter for the RED document (original, DP 

250187, August 31, 2001; revised, DP 279498, December 11, 2001; revised, DP 282182, May 2, 

2002) and a 2008 litigation assessment for the California red-legged frog (Rana aurora 

draytonii) (USEPA, 2008)2

. EFED’s RED chapter stated that oxyfluorfen presents the greatest 

risks to: 

 terrestrial plants through spray drift of liquid formulations and 

 aquatic organisms through spray drift of liquid formulations and runoff of dissolved and 

soil-entrained oxyfluorfen. 

Risk concerns were also identified for birds and mammals from chronic exposures. The RED 

also indicated that oxyfluorfen may be more toxic in the presence of intense light (i.e., UV), 

which may result in enhanced toxicological effects that were not observed in tests conducted 

 

2

 http://epa.gov/espp/litstatus/effects/redleg-frog/index.html
6 

under laboratory lighting. Ecological effects studies called in as a result of the RED are provided 

in Table 4-1. 

Table 4-1. Status of Studies Requested as a Result of the RED 

Data Requirement Study 

submitted? 

MRID Classification 

OPPTS 850.1400: Estuarine/marine fish 

early-life stage 

Yes 46794501 Invalid 

(due to low hatching success in 

the controls and high variability 

in measured test concentrations) 

OPPTS 850.1735: Whole sediment acute 

toxicity invertebrates, fresh water 

Yes 46585102 Supplemental 

(due to lower than recommended 

light intensity) 

OPPTS 850.1740: Whole sediment acute 

toxicity invertebrates, estuarine/marine 

Yes 46585103 Supplemental 

(due to uncertain exposure 

concentrations and not using 

continuous lighting per guideline) 

OPPTS 850.1300: Daphnid chronic 

toxicity 

Yesa 42142305 

45550201 

92136106 

Acceptable 

OPPTS 850.2300: Avian reproduction 

studies, quail 

Yes 46070102 Acceptable 

OPPTS 850.2300: Avian reproduction 

studies, duck 

Yes 46070101 Acceptable 

OPPTS 850.4225: Seed 

germination/seedling emergence (TEP) 

Yes 45861101 Acceptable 

OPPTS 850.4250: Vegetative vigor (TEP) Yes 45861102 Acceptable 

OPPTS 850.4400: Aquatic plant growth Yes 45861103 

(Lemna gibba) 

Supplemental 

(due to uncertain exposure 

concentrations) 

45861104 

(Anabaena 

flos-aquae) 

Supplemental 

(due to uncertain exposure 

concentrations) 

45861105 

(Navicula 

pelliculosa) 

Supplemental 

(due to uncertain exposure 

concentrations) 

45861106 

(Skeletonema 

costatum) 

Supplemental 

(due to uncertain exposure 

concentrations) 

Non-guideline: Fish phototoxicity study Yes 46585104 Acceptable a

 raw data for existing study submitted 

The RED included several risk mitigations to reduce environmental risk concerns for 

oxyfluorfen: 

 Lowering the maximum rate to 1.5 lbs ai/broadcast acre/season for food crops and 2 

lbs ai/acre/season for conifer seedlings. 

 For liquid or granular formulations applied to field-grown ornamentals, lowering the 

seasonal maximum rate to 4.5 lbs ai/A (1.5 lbs ai/A/application). For granulars 

applied to containerized ornamentals, lowering the rate to a seasonal maximum of 6 

lbs ai/A (2 lbs ai/A/application). 
7 

 The addition of a 25 foot, no-spray, vegetative buffer zones around surface water 

bodies such as rivers, lakes, streams, and ponds. 

 Requiring the use of a coarse, very coarse, or extremely coarse spray [ASAE 572 

definitions for standard nozzles, or a volume median diameter (VMD) of 385 microns 

or larger for spinning atomizer nozzles]. 

For the litigation assessment, the Agency made a Likely to Adversely Affect (LAA) 

determination for the CRLF from the use of oxyfluorfen. Additionally, the Agency determined 

that there is the potential for modification of CRLF designated critical habitat from the use of 

oxyfluorfen. 

4.2 Drinking Water Exposure Assessments 

A drinking water exposure assessment was conducted for oxyfluorfen in 2001 (USEPA 2001, DP 

277546) to support the RED (USEPA DP 279498). Exposure estimates of oxyfluorfen from 

currently labeled uses that produced maximum exposure via drinking water from surface water 

were: 

 23.4 g /L for the 1 in 10 year annual peak concentration (acute); 

 7.1 g /L for the 1 in 10 year annual mean concentration (chronic); and 

 5.7 g /L for the 36 year annual mean concentration. 

These concentrations were derived from modeling oxyfluorfen use on Oregon apples with an 

application rate of 2 lb a.i./A. 

The SCI-GROW model concentration estimate of oxyfluorfen in drinking water from shallow 

groundwater sources was 0.08 g /L. 

4.3 Clean Water Act Programs 

Oxyfluorfen was identified as a cause of impairment for two water bodies (Gilsizer Slough and 

Live Oak Slough in California) listed as impaired under section 303(d) of the Clean Water Act 

http://iaspub.epa.gov/tmdl_waters10/attains_impaired_waters.control?p_cause_name=OXYFLU

ORFEN. No Total Maximum Daily Load (TMDL) criteria have been developed for oxyfluorfen. 

Aquatic benchmarks have been established for chemical oxyfluorfen and are available at 

http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm. Any data submitted or 

otherwise located as part of the Registration Review process will be used to update aquatic life 

benchmarks, if applicable. 

5 Environmental Fate and Transport 

The major route of oxyfluorfen dissipation is aqueous photolysis. The compound, when 

dissolved in water, is readily degraded by sunlight (half-lives = 4-5 days, MRIDs 42142307 and 

42142308) and by artificial light with 330-800 nm wavelength (half-lives = 6-8 days, MRID 

42129101). Oxyfluorfen moderately degraded by sunlight when on soil surfaces (half-life = 28 

days, a minor route of dissipation), and is stable to hydrolysis (> 97% parent after 30 days at pH 

4, 7, and 10). Its soil microbial degradation was slow with aerobic soil metabolism half-lives 

ranging from 69 to 596 days [t1/2 = 77 days in a sandy loam soil, t1/2 = 68 days in a loamy 
8 

sand/sandy loam soil, and t1/2 = 69 days in a clay loam soil from France (MRID 46373103); t1/2 ≈

290 days in a clay loam soil and t1/2 = 575 days in a sandy loam soil (MRID 42142309)]. 

Anaerobic soil metabolism half-lives ranged between 554 and 603 days. The aerobic soil halflives demonstrated a broad range, which could be attributed to decreased microbial population 

observed in one study (MRID 42142309). Open literature data suggest that the rate of 

oxyfluorfen dissipation in soil depends on both temperature and soil moisture content; half-lives 

ranged from 72 to 160 days (Yen et al., 2003). In the water column, oxyfluorfen dissipated with 

half-lives of 4 and 5 days, in sediment with half-lives of 30 to 51 days (MRID 46373104). Once 

the soil-bound oxyfluorfen reaches deep or turbid surface water, it will persist since it is stable to 

hydrolysis and light penetration would be limited. 

Adsorption/desorption studies suggest oxyfluorfen is slightly mobile, in sandy soils, sandy loam, 

and clay loam (Koc = 2,891 L/kg, 8,076 L/kg, and 5,585 L/kg, respectively), and hardly mobile in 

silty clay loam soils (Koc = 32,381 L/kg) (MRID 42142311). However, in coarse texture sandy 

soils of low organic matter content, oxyfluorfen has the potential to leach into shallow 

groundwater less than three meters deep (Yen et al. 2003). 

Oxyfluorfen dissipated from bare ground loamy sand and clay loam soil plots in California with 

half-lives of 53 and 58 days, respectively. The half-lives for degradates RH-4672, RH-0671, and 

RH-2382 varied from 37 to 61 days. These half-lives were estimated based on the formation and 

decline curves from the field dissipation study (MRID 43840101). The dissipation half-lives for 

oxyfluorfen ranged from 30 to 103 days in Canadian muck soil (Frank et al. 1991). In another 

study conducted in Australian vineyards during a cool and damp season, the half-life was 119 

days (Ying and Williams 2000). 

Volatilization loss of oxyfluorfen from soil and water systems is expected to be insignificant 

based on oxyfluorfen low vapor pressure (3.54 x 10-7 torr at 25o

C) and Henry's Law Constant 

(8.21 x 10-7 atm·m3

/mol). Considering this low volatility along with high sensitivity to photolytic 

degradation, oxyfluorfen is not expected to have long-range atmospheric transport in appreciable 

quantities. 

Oxyfluorfen is expected to bioconcentrate in fish, which is in concurrence with its high Kow

value of 29,400 (log Kow = 4.46). The bioconcentration factors observed in a bluegill sunfish 

study were 450 and 605X in muscle, 3265 and 4360X in viscera, and 1075 and 2200X in whole 

fish (MRID 00096883). Elimination of accumulated residues by day fourteen of depuration was 

82% in viscera and 91% in whole fish. 

In summary, oxyfluorfen is expected to reach surface water via transport during runoff events 

and via spray drift during application events. The chemical is unlikely to leach into 

groundwater, although limited vertical movement through soils may be possible in sandy soils of 

low organic matter. Tables 5-1 list the environmental fate properties of oxyfluorfen, along with 

the major and minor degradates detected in the submitted environmental fate and transport 

studies. 

 
9 

Table 5-1. Physical, Chemical and Environmental Fate Properties of Oxyfluorfen 

Property Value Source & Study 

Classification 

PC Code 111601 

Common name Oxyfluorfen MRID 44828902 

Acceptable 

Product chemistry 

CAS Registry No. 42874-03-3 MRID 44828902 

Chemical name (CAS) 2-Chloro-1-(3-ethoxy-4-nitrophenoxy)-4-

(trifluoromethyl)benzene 

MRID 44828902 

IUPAC name 2-chloro-alpha, alpha, alpha-trifluoro-p-tolyl 3-

ethoxy-4-nitrophenyl ether 

MRID 47303701 

Acceptable 

Product chemistry 

Synonyms RH-32915 

RH-2915 (alternate) 

RH-915 (alternate) 

MRID 44828902 

SMILES CCOC1=C(C=CC(=C1)OC2=C(C=C(C=C2)C(F)(

F)F)Cl)[N+](=O)[O-] 

EPI Suite, v4.1 

Structure Toxnet 

Molecular formula C15H11ClF3NO4 MRID 44828902 

Physical and Chemical Properties 

Molecular weight (g/mole) 361.7 MRID 44828902 

Color Brown MRID 44828902 

Physical state (24 oC) Crystalline solid MRID 44828902 

Vapor pressure (25 oC) 3.54 x 10-7 torr @ 25oC 

9.78 x 10-7 torr @ 32oC 

2.80 x 10-6 torr @ 44oC 

MRID 44828902 

Henry’s Law constant 

(Exper Database) 

8.2 x 10-7 atm x m3/mol EPI Suite, v4.1 

pH (1% aqueous dispersion of 

GOAL® HIGH PURITY) 

9.35 @ 20oC MRID 44828902 
10 

Property Value Source & Study 

Classification 

Relative density 1.53 g/cm3 @ 20oC MRID 44828902 

Solubility in water (25oC) 0.116 mg/L MRID 44828902 

Partition coefficient 2.94 x 104 or 

log Kow = 4.47 

MRID 44828902 

Bioconcentration in Fish (bluegill 

sunfish) 

Muscle: 450 & 605X 

Viscera (non-edible tissues): 32265 & 4360X 

Whole fish: 1075 & 2200X 

By day 14 of depuration, elimination of residues 

was 82% in viscera and 91% in whole tissue. 

MRID 00096883 

Supplemental 

Environmental Fate Properties 

Hydrolysis half-life 

 pH = 4 

 pH = 7 

 pH = 10 

Stable 

Minor Degradate 

1.2-1.7% RH-34670 

MRID 00134454 

Acceptable 

Photodegradation in Water (t 1⁄2 ) 3.7 to 5.4 days (nature light, 3.4 – 4.4 W/cm2) 

6.27 and 7.56 days (330 – 800 nm @ 150 W/m2

) 

Identified degradates with unknown amount 

(MRID 42129101) 

RH -34800, RH-34670, RH-45469, RH-34860, 

MW 180, MW 327 and MW 332 

(MRID 42142307&08) 

RH-4800, 3-chloro-4-hydroxy benzoic acid, RH4670, RH-5298, and RH-5451 

Unidentified degradates (MRID 42142307&08)

15.3-16.8% nonpolar residues at day 8 

37.2-41.3% polar residues at day 15-20 

MRID 42142307 

MRID 42142308 

MRID 42129101 

Supplemental 

Photodegradation on Soil (t 1⁄2 ) 28 days 

Minor Degradates: 

6.5% methyl ester of 3-Cl,4-OH benzoic acid, 

6.5% 3-Cl,4-OH benzoic acid 

18.5% composed of 4 unidentified degradates 

7.5% unidentified in acidified methanol extracts 

8.1% CO2 collected in NaOH trap 

MRID 41999901 

Acceptable 

Aerobic Soil Metabolism (t 1⁄2 ) 556-596 days (sandy loam soil) 

291-294 days (clay loam soil) 

Minor degradate, 2.9% RH-34800 

Nonextractable residue, up to 43% 

European soils: 

 77 days-sandy loam, 

MRID 42142309 

Acceptable 

MRID 46373103 

Supplemental 
11 

Property Value Source & Study 

Classification 

 68 days-loamy sand/sandy loam, 

 69 days-clay loam 

Eight unidentified minor degradate: 5.5% M1, and 

≤ 2.1% for M3, M4, M5, M6, M7, M8, and M9) 

Nonextractable residue, 37.3-45.4% at 120 days 

Anaerobic Soil Metabolism (t 1⁄2 ) 554 and 603 days 

Degradates: None 

MRID 42142310 

Supplemental 

Aerobic Aquatic Metabolism t 1⁄2 in 

Total System (t 1⁄2 in water/sediment 

system) 

River water/sandy loam sediment 

Water: 4.7 days 

Sediment 50.6 days 

Total system 39.6 days 

Pond water/silt loam sediment 

Water 3.9 days 

Sediment 31.5 days 

Total system 29.6 days 

Eight unidentified minor degradates with 9.6% 

M5 and the rest M1 to M9 ≤ 4.9% 

Nonextractable residue, 42.6-43.3% at 100 days 

MRID 46373104 

Supplemental 

Anaerobic aquatic metabolism half-life No data 

Leaching & Adsorption (ADS) 

Koc (L/kg) 

Sand: 2891 

Sandy loam: 8076 

Clay loam: 5585 

Silty clay loam: 32381 

MRID 42142311 

Supplemental 

Terrestrial Field Dissipation (t 1⁄2 ) 

(CA bare ground loamy sand and clay 

loam soil plots) 

Parent: 53 and 58 days 

Degradates (RH-4672, RH-0671 and RH-2382): 

37 to 62 days. 

RH-4672 was max of 0.379 ppm, RH-0671 was 

0.044 ppm, and RH-2382 was 0.095 ppm 

immediately post treatment 

MRID 43840101 

Supplemental 

 

Drift Field Evaluation 

(using lettuce as bioassay) 

Visible symptoms: 800 m downwind 

Quantifiable symptoms up to 100 

MRID 43840101 

Supplemental 

5.1 Transformation Products 

Several degradates have been reported for oxyfluorfen but only a few have been identified and 

quantified. The major degradate found in the environmental fate studies was MW-332 [2-chloro1-(3-ethoxy-4-hydroxyphenol)-4-(trifluoromethyl) benzene], which was identified in the aqueous 

photolysis study (MRID 42129101) to be > 10 % of the applied radioactivity. Other degradates 

identified in the aqueous photolysis study but not quantified include RH-34670, RH-34860, RH34800, RH-45469, MW-327, and MW-180. In the hydrolysis study (MRID 134454), RH-34670 
12 

[(2-chloro-1-(3-hydroxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] was identified at a 

maximum concentration of 1.2-1.7% of the applied radioactivity. In the soil photodegradation 

study, isolated volatile material was composed of two degradates, RH-34800 and RH-36329, the 

methyl ester of 3-Cl,4-OH benzoic acid. RH-34800 was the only degradate identified in the 

aerobic soil metabolism study (MRID 42142309) at a maximum concentration of 2.9 % of the 

applied radioactivity. Another aerobic soil study showed that oxyfluorfen mineralized to CO2 (≤

21% of the applied) with the formation of multiple unidentified minor transformation products, 

each ≤ 2.1%, but one at 5.8%, and of ≤ 45% bound residues (MRID 46373103). Oxyfluorfen 

applied to water dissipated by mineralization to ≤ 9.4% CO2 and unidentified minor 

transformation products, each ≤ 4.9%, but one at 9.6% of the applied, and by incorporation into 

the organic matter of the sediment (extractable residues ≤ 71% at 7 days; nonextractable residues 

≤ 59% of the applied at 100 days; MRID 46373104). There were no degradates isolated and 

identified in the anaerobic soil metabolism, aerobic aquatic metabolism, and leaching studies. 

Presently no fate and ecotoxicological data are available for oxyfluorfen degradates. Chemical 

structure examples of selected oxyfluorfen degradates are provided in Figure 5-1. 

 

2-chloro-1-(3-hydroxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (RH-34670) 

 

Acyl-670 (RH-45469) 

 

 

2-chloro-1-(3-ethoxy-4-hydroxy-phenoxy)-4-(trifluoromethyl) benzene (MW-332) 

Figure 5-1. Degradate Structures 

 

O

Cl

CF3 NO2

OH

O

Cl

CF3 NHCOCH 3

OCH2CH3

O

Cl

CF3 OH

OCH2CH3
13 

6 Receptors 

Summaries of the most sensitive endpoints used to characterize the toxicity of oxyfluorfen to 

aquatic and aquatic organisms are provided in Table 6-1. Summaries of all submitted 

oxyfluorfen toxicity data can be found in Appendix B. No toxicity data are available for any of 

the degradates of oxyfluorfen. 

For oxyfluorfen, no data are available for the following: 

 chronic toxicity to estuarine/marine fish; 

 acute oral toxicity to a passerine species; and 

 acute and chronic oral toxicity to adult and larval honey bees. 

Oxyfluorfen is classified as: up to highly toxic to fish on an acute basis; up to very highly toxic 

to aquatic invertebrates; practically non-toxic to birds on an acute oral basis (based solely on data 

for bobwhite quail); practically non-toxic to birds on a sub-acute dietary basis; practically nontoxic to mammals on an acute oral basis; and practically non-toxic to adult honey bees on an 

acute contact basis. 

More recently submitted toxicity studies were conducted using a technical grade of oxyfluorfen 

with purity ranging from 95 to 99% whereas older studies were conducted using a technical 

grade of oxyfluorfen with purity ranging from 71 to 85%. The newer technical material has a 

similar profile of impurities when compared to the older material, but in reduced concentrations 

(USEPA, 2002). In the 2002 RED (USEPA, 2002), the human health effects assessment noted 

reduced toxicity in older studies with a 98% product and used newer studies with the 98% 

product to identify toxicological endpoints when studies with newer and older technical material 

were available. Based on this, it is possible that the newer, higher purity technical material will 

have a reduced toxic effect on species evaluated in the ecological risk assessment; however, no 

data have been submitted to the Agency to confirm the extrapolation. Within the suite of 

ecological effects studies, limited comparisons can be made due to lack of data for both the 

newer, higher purity and older, lower purity technical material. When available, toxicity data for 

the newer, higher purity technical will be used in the assessment as such data would better 

represent the material currently used in the environment. 

As previously noted in the CRLF litigation assessment (USEPA, 2008) and EFED RED chapter 

(original, DP 250187, August 31, 2001; revised, DP 279498, December 11, 2001; revised, DP 

282182, May 2, 2002), the potential for phototoxic effects is a serious concern for oxyfluorfen. 

LDPHs are a class of weed control chemicals that act in plants by inhibiting the enzyme 

protoporphyrinogen oxidase (protox), which is the last common enzyme in the heme and 

chlorophyll biosynthetic pathways. Protox exists in both plants and animals and the enzyme 

from both sources has been shown to be highly sensitive to many LDPHs. Several studies have 

documented enhanced toxicity of LDPHs to fish in the presence of uV light compared to toxicity 

observed under standard laboratory lighting. Given that aquatic organisms are likely to be 

exposed simultaneously to LDPH and uV light in natural settings, concerns have been raised that 

guideline chronic exposure laboratory tests may underestimate the toxicity of LDPH in the field. 

With the exception of a fish early life stage toxicity test (MRID 46585104), all of the toxicity 

tests were conducted under standard laboratory lighting conditions which may result in an 
14 

underestimation of the toxicity of oxyfluorfen to some taxa under natural sunlight conditions. 

The NOAEC of 1.3 μg/L for the fish early life stage study conducted under enhanced UV 

lighting simulating summer light intensity for the Florida or California latitudes (MRID 

46585104) is over an order of magnitude lower than the NOAEC of 38 μg/L for a fish early life 

stage study conducted with standard laboratory lighting (MRIDs 00099270, 00030249, and 

92136057). In the study with enhanced UV lighting, the larval fish appeared to hatch 

prematurely compared to the control and then die. Based on the mode of action, it is possible 

that disruption of the egg cell membrane caused the premature hatch. 

The extent to which UV light enhances the toxicity of oxyfluorfen to other taxa or other life 

stages is unknown and could be observed in other taxa such as aquatic invertebrates, birds, and 

mammals (Birchfield and Casida, 1997). Anemia and other hematologic consequences have 

been observed in developmental studies with mammals (USEPA, 2002). In wild mammal 

populations, hematologic effects have the potential to magnify since the lack of natural sunlight 

in the laboratory reduces the likelihood of activating the phototoxic effects of oxyfluorfen. 

It should be noted that the classification of an acute study with sheepshead minnow (MRID 

41698801) has been downgraded from “acceptable” to “supplemental” due to considerable 

uncertainty regarding the exposure concentrations. There was a large discrepancy between 

nominal (13, 22, 36, 60, and 100 mg/L) and mean-measured (0.07, 0.06, 0.13, 0.11, and 0.17 

mg/L, respectively) concentrations because the range of nominal concentrations greatly exceeds 

the solubility of oxyfluorfen (0.116 mg/L). Most of the chemical precipitated out of solution and 

accumulated on the surface of water in the test vessels. The samples for quantification were not 

centrifuged and/or filtered before being analyzed. In addition, the concentrations of the nominal 

60 and 100 mg/L treatment levels were not stable throughout the test; measured test 

concentrations for these treatment levels declined from 0.16 and 0.28 mg/L at 0 hours to 0.06 

and 0.06 mg/L at 96 hours, respectively. Although there was no mortality in the study and the 

test organisms appeared normal, surfacing was observed at nominal concentrations ≥36 mg/L. 

This observation was attributed to low dissolved oxygen. The study author proposed that the 

drop in dissolved oxygen could have been due to the accumulation of precipitated chemical on 

the surface of the water. 

 
15 

Table 6-1. Summary of Most Sensitive Endpoints from Toxicity Studies with Oxyfluorfen 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Avian acute oral: single dose, 21-day observation (instead of usual 14-day observation) 

Oxyfluorfen technical (70.2) 

Bobwhite quail (Colinus virginianus) 

LD50 > 2150 mg/kg-bw (nom) 

NOAEL < 1470 mg a.i./kg-bw (nom) (1 mortality at 2150 mg /kg-bw ; sublethal effects: weaknessanorexia, piloerection, and abnormal cage droppings at 1470 2150 mg/kg-bw, recovery by day 7; food consumption severdepressed at 1470 and 2150 mg/kg-bw during first 2 and 7 drespectively; weight loss at 1470 and 2150 mg/kg-bw during 3 days) Practically non-toxic 

Avian acute oral NA Passerine species No data Avian sub-acute dietary: 5-day exposure; 3-day post-exposure observation 

Oxyfluorfen technical (70.2) 

Mallard duck (Anas platyrhynchos)

LC50 > 5000 mg a.i./kg-diet (nom) 

NOAEC = 312 mg a.i./kg-diet (nom) LOAEC = 625 mg a.i./kg-diet (nom) (10% [1/10] mortality at 5000 mg/kg-diet; sublethal effects: anorexia at 5000 mg/kg-diet on days 2-3; concentrationdependent reduction in food consumption at ≥ 625 mg/kg-di

during exposure period; reduction in food consumption at alreatment levels on days 6-8; NOAEC based on reduction in consumption) Practically non-toxic 

Oxyfluorfen technical (70.2) 

Bobwhite quail (Colinus virginianus) 

LC50 > 5000 mg a.i./kg-diet (nom) 

NOAEC = 625 mg a.i./kg-diet (nom) LOAEC = 1250 mg a.i./kg-diet (nom) (no mortality; sublethal effects: reduction in body weight gaat 1250 and 2500 mg/kg-diet during days 0-5; body wieght l5000 mg/kg-diet by day 5; food avoidance during days 3-5 areduction in food consumption durings days 0-5 at 2500 and 5000 mg/kg-diet; NOAEC based on reduction in body weighgain) Practically non-toxic 

Avian reproduction: 20 weeks (chronic) 

Oxyfluorfen technical, purified (99.3) 

Bobwhite quail (Colinus virginianus) 

NOAEC = 124 mg a.i./kg-diet (mm) LOAEC = 256 mg a.i./kg-diet (mm) 
16 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

 (based on most sensitive parameter of survivor weight; ratio 

hatchling survival to number of hatchlings, viable embryos, embryos, number of hatchlings, ratio of eggs set to eggs laidratio of number of hatchlings to eggs laid, ratio of hatchling survival to eggs set also affected) 

Oxyfluorfen technical, purified (99.3) 

Mallard duck (Anas platyrhynchos) 

NOAEC = 506 mg a.i./kg-diet (mm) LOAEC = 751 mg a.i./kg-diet (mm) (based on eggs laid, eggs set, viable embryos, the ratio of viaembryos to eggs set, live embryos, number of hatchlings, the ratios of normal hatchlings to eggs laid and to eggs set, and hatchling survival) 

Mammalian acute oral, limit: single dose; 14-day observation 

Oxyfluorfen (96) 

Rat (Rattus norvegicus) 

LD50 > 5,000 mg a.i./kg-bw 

(no effects) Practically non-toxic 

Oxyfluorfen technical 95 (97.1) 

Rat (Rattus norvegicus) 

LD50 > 5,000 mg a.i./kg-bw 

(no effects) Practically non-toxic 

Mammalian acute inhalation 

Oxyfluorfen (96) 

Rat (Rattus norvegicus) 

LC50 > 3.71 mg/L 

Mammalian 2- generation reproduction (chronic) 

Oxyfluorfen Rat 

(Rattus norvegicus) 

Parental 

NOAEC = 400 mg a.i./kg-diet LOAEC = 1600 mg a.i./kg-diet (based on parental effects including mortality, decreased bodweight, liver and kidney histopathology) Reproductive NOAEC = 400 mg a.i./kg-diet LOAEC = 1600 mg a.i./kg-diet (based on decreased body weight and decreased live pups/lit

Acute contact with adult honey bees: single dose, 96-hour observation 

Oxyfluorfen technical (71.4) 

Adult honey bee (Apis mellifera)

LD50 > 100 μg a.i./bee (nom) 

NOAEL: Not specified (4-5% mortality across control and 3 treatment concentrationPractically non-toxic 

Acute oral with honey bee adults 

NA Adult honey bee No data 
17 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Acute oral with honey bee larvae 

NA Larval honey bee No data 

Chronic oral with honey bee adults 

NA Adult honey bee No data 

Chronic oral with honey bee larvae 

NA Larval honey bee No data 

Terrestrial plant seedling emergence: minimum of 14 days after 50% of the control plants had emerged 

Goal 2XL (23.1) 

Most sensitive monocot: Ryegrass 

EC25 = 0.0063 lb a.i./A (nom) 

EC05 = 0.00065 lb a.i./A (nom) NOAEC = 0.030 lb a.i./A (nom) Note: Since the NOAEC > EC25, the EC05 will be used for 

assessing risk to listed species. (based on dry weight) 

Most sensitive dicot: Lettuce 

EC25 = 0.0072 lb a.i./A (nom) 

EC05 = 0.0024 lb a.i./A (nom) NOAEC = 0.0080 lb a.i./A (nom) Note: Since the NOAEC > EC25, the EC05 will be used for 

assessing risk to listed species. (based on dry weight) 

Terrestrial plant vegetative vigor: 22-23 days 

Goal 2XL (23.1) 

Most sensitive monocot: Oat 

EC25 = 0.27 lb a.i./A (nom) 

EC05 = 0.08 lb a.i./A (nom) NOAEC = 0.22 lb a.i./A (nom) (based on dry weight) 

Most sensitive dicot: Lettuce 

EC25 = 0.0078 lb a.i./A (nom) 

EC05 = 0.00032 lb a.i./A (nom) NOAEC = 0.000035 lb a.i./A (nom) (based on dry weight) 

Freshwater fish acute: 96 hours, flow-through, standard laboratory lighting 

Oxyfluorfen (94) 

Bluegill sunfish (Lepomis macrochirus) 

LC50 (95% C.I.) = 200 (130-310) μg/L (nom) 

NOAEC: Not specified (no mortality at lowest test concentration, 56 μg/L; sublethaeffects: darkening, lethargy, and loss of equilibrium) Highly toxic 

Freshwater fish acute: 96 hours, static 

Oxyfluorfen technical (71.4) 

Rainbow trout (Oncorhynchus mykiss) 

LC50 (95% C.I.) = 253 (186-355) μg a.i./L (mm) 

Probit slope (95% C.I.) = 2.4 (1.6-3.1) NOAEC = 37 μg a.i./L (mm) LOAEC = 83 μg a.i./L (mm) 
18 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) (NOAEC based on mortality and sublethal effects at ≥83 μg

no mortality or sublethal effects at 37 μg/L; sublethal effectslethargy in surviving fish at 398 and 1090 μg/L) Highly toxic 

Freshwater fish early life stage: 30 days, flow through, standard laboratory lighting 

Oxyfluorfen technical (71) 

Fathead minnow (Pimephales promelas) 

NOAEC = 38 μg/L (mm) LOAEC = 74 μg/L (mm) Note: This study was conducted under standard laboratory lighting. (based on reduction in fry survival, total length, and weigh) 

Freshwater fish early life stage: 33 days, flow through, enhanced UV lighting (chronic) 

Oxyfluorfen technical (99.3) 

Fathead minnow (Pimephales promelas) 

NOAEC = 1.3 μg a.i./L (TWA) LOAEC = 2.4 μg a.i./L (TWA) Note: This study was conducted under UV lighting simulatinsummer light intensity for the Florida or California latitudes

(based on most sensitive endpoint of post-hatch survival; hatching success, post-hatch physical/behavioral abnormalitand growth [length, wet weight, and dry weight] also affecte

Estuarine/marine fish acute: 96 hours, static 

Oxyfluorfen technical (71.4) 

Sheepshead Minnow (Cyprinodon variegatus) 

LC50 > 116 μg a.i./L (mm) 

NOAEC = 60 μg a.i./L (mm) (no mortality; sublethal effect of surfacinga at ≥130 μg a.i./L

Practically non-toxic up to the limit of solubility 

Estuarine/marine fish early life stage (chronic) 

Oxyfluorfen Estuarine/marine 

species 

No data Note: A chronic toxicity endpoint for estuarine/marine fish cannot be estimated using an acute-to-chronic ratio (ACR) ffreshwater fish because the available freshwater fish chronic toxicity endpoints were generated for fathead minnow, a spefor which we do not have an acute toxicity endpoint. 

Freshwater invertebrate: 48 hours, static 

Oxyfluorfen (82.2) 

Water flea (Daphnia magna) 

LC50 (95% C.I.) = 1.5 (0.75-2.9) mg/L (nom) 

Moderately toxic 

Freshwater invertebrate acute: 48 hours, flow through 

Goal 2XL (P) (23.2) 

Water flea (Daphnia magna) 

EC50 (95% C.I.) = 80 (60-150) μg a.i./L (mm) 

NOAEC = 20 μg a.i./L (mm) (NOAEC based on mortality and sublethal effects) Very highly toxic 
19 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Freshwater invertebrate life cycle: 21 days, flow through (chronic) 

Oxyfluorfen technical (71.8) 

Water flea(Daphnia magna) 

NOAEC = 13 μg a.i./L (mm) LOAEC = 28 μg a.i./L (mm) (NOAEC based reductions in adult survival, growth [length]and reproductive output) 

Estuarine/marine invertebrate: 96 hours, static 

Oxyfluorfen technical (74) 

Grass shrimp (Palaemonetes pugio) 

LC50 (95% C.I.) = 32 (18-56) μg/L (nom) 

NOAEC = 18 μg/L (nom) Very highly toxic 

Estuarine/marine mollusc: 96 hours, flow through, shell deposition 

Oxyfluorfen technical (71.4) 

Eastern oyster (Crassostrea virginica) 

EC50 (95% C.I.) = 69.3 (62.2-98.5) μg a.i./L (mm)b

NOAEC = 37.5 μg a.i./L (mm)c

Very highly toxic 

Estuarine/marine invertebrate life cycle: 30 days, flow through (chronic) 

Oxyfluorfen technical (99.3) 

Mysid shrimp(Mysidopsis bahia)

NOAEC = 8.1 μg a.i./L (TWA) LOAEC = 16 μg a.i./L (TWA) (NOAEC based on most sensitive endpoint of reproduction; survival, and growth [length and dry weight] also affected)) 

Benthic freshwater invertebrate: 10 days, flow through, spiked sediment 

Oxyfluorfen technical (99.3) 

Midge (Chironomus tentans) 

Based on pore water concentrations (mm) LC50 > 498.5 μg a.i./L 

NOAEC = 484.5 μg a.i./L Based on sediment concentrations (dry weight, mm) LC50 > 97.6 mg a.i./kg-dw NOAEC = 55.7 mg a.i./kg-dw Based on sediment concentrations (organic carbon [OC], mmLC50 > 4880 mg a.i./kg-OC NOAEC = 2750 mg a.i./kg-OC (NOAEC based on mortality) 

Benthic estuarine/marine invertebrate: 10 days, static, spiked sediment 

Oxyfluorfen technical (99.3) 

Amphipod (Leptocheirus plumulosus) 

Based on pore water concentrations (mm) LC50 (95% C.I.) = 130 (81-200) μg a.i./L 

Probit slope = 2.73±0.833 NOAEC = 27.9 μg a.i./L Based on sediment concentrations (mm) LC50 (95% C.I.) = 37 (26-53) mg a.i./kg-dw Probit slope = 2.54±0.44 NOAEC = 16.0 mg a.i./kg-dw 
20 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) Based on overlying water concentrations (mm) LC50 (95% C.I.) = 42 (22-82) μg a.i./L 

Probit slope = 1.79±0.44 NOAEC = 12.6 μg a.i./L (NOAEC based on mortality) 

Aquatic vascular plant: 14 days, staticrenewal 

Oxyfluorfen technical (99.1) 

Duckweed (Lemna gibba) 

EC50 (95% C.I.) = 0.33 (0.20-0.38-27) μg a.i./L (m) 

NOAEC/EC05: Could not be determined 

(based on most sensitive endpoint of frond number) 

Aquatic nonvascular plant: 96 hours, static 

Goal 2XL (P) (23.2) 

Green alga (Selenastrum capricornutum) 

EC50 (95% C.I.) = 0.29 (0.27-30) μg a.i./L (mm) 

NOAEC = 0.10 μg a.i./L (mm) LOAEC = 0.26 μg a.i./L (mm) (NOAEC based on reduction in cell density) 

Aquatic nonvascular plant: 96-240 hours, static, sediment 

Oxyfluorfen technical (99.1) 

Green alga (Pseudokirchneriella subcapitata) 

96-hr EC50 > 2.9 μg a.i./L (im) 

96-hr NOAEC = 1.4 μg a.i./L (im) 96-hr LOAEC = 2.9 μg a.i./L (im) 240-hr EC50 > 2.9 μg a.i./L (im) 

240-hr NOAEC = 2.9 μg a.i./L (im) 240-hr LOAEC > 2.9 μg a.i./L (im) (NOAEC based on reductions in cell density, growth rate, anbiomass) 

Aquatic nonvascular plant: 120 hours, static 

Oxyfluorfen technical (99.1) 

Cyanobacterium (Anabaena flos-aquae) 

EC50 > 100 μg a.i./L (mm) 

NOAEC = 20.1 μg a.i./L (mm) LOAEC = 47.2 μg a.i./L (mm) (NOAEC based on most sensitive endpoint of biomass [area under the growth curve; cell density and growth rates also affected) 

Aquatic nonvascular plant: 120 hours, static 

Oxyfluorfen technical (99.1) 

Freshwater diatom (Navicula pelliculosa) 

EC50 = 29 μg a.i./L (mm) 

NOAEC = 19.2 μg a.i./L (mm) LOAEC = 49.7 μg a.i./L (mm) (based on most sensitive endpoint of cell density for EC50; 

growth rate and biomass also affected with same NOAEC anLOAEC) 
21 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Aquatic nonvascular plant: 96 hours, static 

Oxyfluorfen technical (99.1) 

Marine diatom (Skeletonema costatum) 

EC50 = 1.10 μg a.i./L (mm) 

NOAEC = 0.65 μg a.i./L (mm) LOAEC = 1.20 μg a.i./L (mm) (based on most sensitive endpoint of biomass [area under thcurve]; cell density and growth rate also affected) 

Abbreviations: C.I. = confidence interval; ELS = early life stage; im = initial measured; mm = mean measured; nom = nominal; NA = n

specified; TEP = typical end-use product; TWA = time-weighted average 

a This observation was attributed to low dissolved oxygen. The study author proposed that the drop in dissolved oxygen could have bee

of precipitated chemical on the surface of the water. b based on pooled control data 

c based on comparison to solvent control; NOAEC may be lower when using a comparison to the negative control 
22 

6.1 Ecological Incidents 

A preliminary review on June, 23, 2014, of the Ecological Incident Information System (EIIS, 

version 2.1), which is maintained by the Agency’s Office of Pesticide Programs, and the Avian 

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

Conservancy, indicates a total of 25 reported ecological incidents associated with the use of 

oxyfluorfen (see Appendix C). These incidents involved terrestrial, plant and aquatic taxonomic 

groups. This total excludes incidents classified as ‘unlikely’ or ‘unrelated’ and only includes 

those incidents with certainty categories of ‘possible’, ‘probable’, and ‘highly probable’ (for 

EIIS) and ‘possible’, ‘probable’, ‘likely’, ‘highly likely’ and ‘certain’ (for AIMS). Incidents 

classified as ‘unlikely’ the result of or ‘unrelated’ to oxyfluorfen will not be included in this 

Problem Formulation or the ecological risk assessment conducted for Registration Review. 

All of the oxyfluorfen incidents, excluding those classified as ‘unlikely’ or ‘unrelated’, occurred 

between 1996 and 2002. One of the oxyfluorfen incidents involved aquatic animals, 7 involved 

terrestrial animals, and 17 involved plants. The certainty categories regarding the likelihood that 

the use of oxyfluorfen caused the 25 incidents ranged from ‘possible’ (15 incidents) to ‘probable’ 

(10 incidents). Eight of the incidents were considered registered uses at the time of the incident, 

12 involved misuses, and the legality of use was undetermined in 5 incidents. Eighteen of the 

incidents involved additional chemicals besides oxyfluorfen. Oxyfluorfen residues were 

reported in one of the incident reports involving aquatic organisms. The reported incidents for 

oxyfluorfen involved 21 uses that are currently registered, and 4 in which the use site was not 

specified. The reported incidents associated with the 21 currently registered uses had certainty 

categories of ‘possible’ and ‘probable’. 

In the risk assessment, the incidents will be further evaluated to determine if the reported 

incidents represent current patterns of use for oxyfluorfen. Examples of additional 

considerations are mitigation (e.g., reduced application rates), product cancellations, and changes 

in use patterns that have occurred since the date of the reported incidents. 

In addition to the incidents recorded in EIIS and AIMS, additional incidents have been reported 

to the Agency in aggregated incident reports. Pesticide registrants report certain types of 

incidents to the Agency as aggregate counts of incidents occurring per product per quarter. 

Ecological incidents reported in aggregate reports include those categorized as ‘minor fish and 

wildlife’, ‘minor plant’, and ‘other non-target’ incidents. ‘Other non-target’ incidents include 

reports of adverse effects to insects and other terrestrial invertebrates. For oxyfluorfen, 

registrants have reported no minor fish and wildlife incidents, 42 minor plant incidents, and no 

other non-target incidents. Unless additional information on these aggregated incidents become 

available, they will be assumed to be representative of registered uses of oxyfluorfen in the risk 

assessment. 

7 Exposure Pathways of Concern 

The environmental fate properties and use patterns of oxyfluorfen indicate that direct spray, 

spray drift, and runoff represent potential transport mechanisms of oxyfluorfen to aquatic and 

terrestrial organisms. Drinking water and inhalation exposure pathways were screened using the 
23 

SIP (Screening Imbibition Program) and STIR (Screening Tool for Inhalation Risk) screening 

methods and were found to be exposure pathways of low concern (no LOC exceedances are 

expected; see Appendix D). SIP and STIR are described in detail at: 

http://www.epa.gov/oppefed1/models/terrestrial/index.htm. Oxyfluorfen is expected to 

bioaccumulate in aquatic organisms, thus, the exposure pathway is complete for organisms that 

feed on fish and other aquatic animals. 

8 Analysis Plan 

8.1 Stressors of Concern 

8.1.1 Ecological Risk Assessment 

The stressors of ecological concern for aquatic organisms are oxyfluorfen and any major 

degradates identified in the requested aquatic fate studies. As a conservative estimate, the 

unknown percentage(s) of the major degradate(s) will be treated as parent unless the amount(s) 

of maximum formation are identified as a result of the data call-in. Degradate MW-332, which 

formed at >10% in the aquatic photolysis study (MRID 42129101), is estimated to be 3-4 times 

less toxic than the parent (Appendix E). Additional information for the maximum formation of 

MW-332 is needed to determine if it will be included or excluded in the Registration Review 

ecological risk assessment. 

The stressor of ecological concern for terrestrial organisms is oxyfluorfen. 

 

8.1.2 Drinking Water Exposure Assessment 

An EFED drinking water assessment was conducted for Oregon apples to establish tolerances of 

oxyfluorfen for human health risk assessment (USEPA 2001; DP277546). Recommended 

Estimated Drinking Water Concentrations (EDWCs) were modeled for parent oxyfluorfen only. 

The oxyfluorfen residues of concern may be reevaluated pending receipt and review of 

additional environmental fate and toxicity data for oxyfluorfen and its potential degradates. The 

drinking water assessment will be performed based on EFED’s current guidance using 

appropriate surface and groundwater models. Descriptions of all executable versions of current 

models for drinking water exposure can be obtained from URL link: 

http://www.epa.gov/oppefed1/models/water/. 

8.2 Measures of Exposure 

EFED will use standard available models to evaluate potential exposures to aquatic and 

terrestrial organisms, including bioconcentration, as described at 

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

8.2.1 Available Monitoring Data 

The Agency is aware of monitoring conducted by federal and state agencies such as U.S. 

Geological Survey (USGS) National Water Quality Assessment (NAWQA) Data Warehouse and 
24 

California Environmental Data Exchange Network (CEDEN). This route of exposure will be 

considered in the assessment to the extent that data on oxyfluorfen are available. 

8.3 Measures of Effect 

Toxicity data presented in Section 6 of this problem formulation will be used to calculate risk 

quotients. The toxicity of oxyfluorfen is known to increase in the presence of UV light and will 

be characterized in the risk assessment. According to the Agency’s website 

http://www.epa.gov/sunwise/doc/uvradiation.html, factors to consider regarding the amount of 

UV light are time of day, time of year, stratospheric ozone and weather (cloud cover). In 

addition, for aquatic organisms, water depth and turbidity may also affect UV penetration. An 

LDPH adjustment factor (29x) will be applied to chronic fish endpoints, as support by submitted 

data. Consistent with other LDPH chemical assessments, risks to other taxa will be 

characterized. 

Any additional information submitted by the registrant or found in the open literature prior to 

conducting the risk assessment will also be considered. The open literature studies are identified 

using EPA’s ECOTOXicology database (ECOTOX)3

, 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. 

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. 

9 Endocrine Disruptors Screening Program 

Oxyfluorfen 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/. 

10 Preliminary Identification of Data Gaps 

10.1 Environmental Fate 

Table 11-1 identifies environmental fate studies by MRID that offer data for each guideline 

requirement, as well as study classifications and whether or not further data are needed to 

support the risk assessment. 

 

3 http://cfpub.epa.gov/ecotox/
25 

Table 10-1. Environmental Fate Data for Oxyfluorfen 

OCSPP 

Guideline 

Data 

Requirement 

Submitte

d Studies 

(MRID) 

Study 

Classification 

Data 

needed to 

conduct 

risk 

assessment

Justification 

835.2120 Hydrolysis 00134454 Acceptable No -- 

835.2240 Aqueous 

photolysis 

(TGAI) 

42142307 

42142308 

42129101 

Supplemental Yes An aqueous photolysis study is 

required under the 40 CFR Part 158. 

Since this is a major degradation 

pathway, a clarification is needed for 

the % formation of degradates. 

In absence of the complete degradate 

data, a conservative approach will be 

used by assuming the parent for those 

degradates. 

835.2410 Soil photolysis 41999901 Acceptable No -- 

835.4100 Aerobic soil 

metabolism 

42142309 

46373103 

Acceptable 

Supplemental 

No -- 

835.4200 Anaerobic soil 

metabolism 

42142310 Supplemental No -- 

835.4300 Aerobic aquatic 

metabolism 

(TGAI) 

46373104 Supplemental Yes An aerobic aquatic metabolism study 

is required under the 40 CFR Part 

158. The excessive nonextractable 

residues (45.5 – 59.3%) needed to be 

clarified 

Unless registrant can characterize the 

nonextractable residues, a 

conservative approach will be used to 

revisit the DT50 by including 

nonextractable residue. 

835.4400 Anaerobic 

aquatic 

metabolism 

(TGAI) 

No Data --- Yes Anaerobic soil metabolism data are 

available 

Data are required under 40 CFR Part 

158. OCSPP guidance recommends 

that these tests be performed with two 

sediments. The assumption of 

compound stability will be made in 

the absence of acceptable data. 

835.1230 

835.1240 

Adsorption/ 

desorption and 

leaching 

42142311 Supplemental No -- 

835.1410 Volatility – 

laboratory 

No Data --- No Oxyfluorfen is not expected to be 

volatile under normal use conditions 

based on low vapor pressure and 

Henry’s Law Constant 

835.6100 Terrestrial field 

dissipation 

43840101 Supplemental No --- 
26 

OCSPP 

Guideline 

Data 

Requirement 

Submitte

d Studies 

(MRID) 

Study 

Classification 

Data 

needed to 

conduct 

risk 

assessment

Justification 

850-6100 ECM/ILV in soil 

and water 

No data --- Yes Environmental chemistry method 

(ECM) and independent laboratory 

validation (ILV) are required under 

the 40 CFR Part 158. 

165-4 

(850.1730) 

Fish 

bioconcentration 

00096883 Supplemental No --- 

Ecological Effects 

Table 11-3 identifies ecological effects studies (by MRID) that offer data for each guideline 

requirement, as well as study classifications and whether or not further data are needed to 

support the risk assessment. 

10.1.1 Justification for 10-day Adult Chronic Toxicity Study

Bees can be exposed to pesticides through multiple pathways including contact with sprays and 

dusts and through ingestion of residues in food/water (e.g., pollen/nectar and water used to 

maintain colony temperature). Worker bees foraging on flowers for pollen and nectar can be 

repeatedly exposed to residues in pollen and nectar through direct contamination of these 

matrices by foliar sprays. Residues can in turn be brought back to bee colonies where in-hive 

bees including young adult and developing brood (i.e., eggs, larvae and pupae) may be exposed. 

EPA guidance (USEPA 2014) on assessing the risk of pesticides to bees identifies a suite of 

laboratory-based studies intended to serve as the foundation for screening chemicals for potential 

acute and chronic exposure effects to individual adult and larval bees. The 10-day toxicity study 

with young adult bees provides no-observed adverse effect level (NOAEL) and lowest-observed 

adverse effect level (LOAEL) for assessing chronic effects. Data obtained from this study will be 

used in estimating chronic risk to individual adult bees. This is a non-guideline study; an OECD 

protocol is expected to be available in October 2014. A protocol should be submitted to the 

Agency for review before commencing the study and should include provisions for measuring 

the concentration of oxyfluorfen in the actual diet of the honeybee. 

10.1.2 Justification for 21-day Larval Toxicity Study

Developing bee brood (i.e., larvae and pupae) can be exposed to pesticides through residues 

brought back to the colony by worker bees foraging in areas where the pesticide has been 

applied. While larvae are typically fed royal or brood jelly during their early stages of 

development, worker bee (females) and drone (males) larvae are also fed pollen/honey (bee 

bread) directly by in-hive nurse bees. EPA guidance (USEPA 2014) on assessing the risk of 

pesticides to bees identifies a suite of laboratory-based studies intended to serve as the 

foundation for screening chemicals for potential acute and chronic effects to individual adult and 

larval bees. The 21-day larval toxicity study under development by OECD provides both acute 

and chronic toxicity data on developing bee brood and will yield a median lethal dose (LD50) for 

assessing acute toxicity during the early part of the study as well as a 21-day no-observed 

adverse effect level (NOAEL) and lowest-observed adverse effect level (LOAEL) for assessing 
27 

chronic effects. Alternatively, registrants may submit a separate acute (single dose) larval 

toxicity study following OECD Guideline 237 as well as the 21-day repeat dose chronic toxicity 

study to address both acute and chronic larval endpoints. Effects on survival and development 

(adult bee emergence) from repeat exposures to the active ingredient will be used in estimating 

chronic risk to individual brood. A protocol for the 21-day larval toxicity test should be 

submitted to the Agency for review before commencing the study and should include provisions 

for measuring the concentration of oxyfluorfen in the actual diet of the honeybee. 

________________________________________________ 

Draft guidance for the 21-day larval toxicity study is available at: 

http://www.oecd.org/env/ehs/testing/Draft_GD_honeybees_rep_exp_for_2nd_CR_25_November_2013.pdf

OECD Guideline 237 is available at: http://www.oecdilibrary.org/docserver/download/9713171e.pdf?expires=1407449911&id=id&accname=guest&checksum=E67BED

EB01DB12D815E858CB45A989FB
28 

Table 11-3. Ecological Effects Data for Oxyfluorfen 

OCSPP Guideline 

Data Requirement 

Submitted Study (MRID) 

Classification Are data 

needed to conduct the risk assessment? 

Justification and Assumptions EAbsence of Data 

Avian Testing 850.2100 Avian oral 

toxicity 

92136102 (upland game) Acceptable Yes Acute oral toxicity data for a passe

under the new 40 CFR Part 158. A submitted for this data requiremenA guideline-compliant passerine aneeded. Acute oral toxicity data aavian species (i.e., bobwhite quail

utilize metabolic pathways that are and therefore be more sensitive to passerines exhibit behavioral respothat are potential indicators of redu(e.g., regurgitation of contaminatebiochemically-mediated lethal toxIn the absence of these data, passesurrogate pesticides – starting with pesticides (e.g., diphenyl ethers) aless related pesticides – may be ustoxicity of oxyfluorfen to passerin

No data (passerine species) NA 

850.2200 Avian dietary 

toxicity 

92136104 (waterfowl) Acceptable No -- 

92136103 (upland game) Acceptable 

850.2300 Avian 

reproduction 

46070102 (upland game) Acceptable No -- 

46070101 (waterfowl) Acceptable 

Insect Pollinator Testing 850.3020 Honey bee acute 

contact toxicity 

42368101 Acceptable No -- 

Special study (OECD 213) 

Acute oral toxicity to adult honey bees 

No data NA Yes Guidance for assessing pesticide r

recommends requesting the follow

 Acute oral toxicity to adu
29 

OCSPP Guideline 

Data Requirement 

Submitted Study (MRID) 

Classification Are data 

needed to conduct the risk assessment? 

Justification and Assumptions EAbsence of Data 

Special study 

Chronic oral toxicity to adult honey bees 

No data NA Yes  Acute oral toxicity to larv

 Chronic oral toxicity to a

 Chronic oral toxicity to la

In the absence of these data, honey surrogate pesticides – starting with pesticides (e.g., diphenyl ethers) aless related pesticides – may be ustoxicity of oxyfluorfen to larval anTier II (feeding/semi-field/pollen aIII (full field) studies may be needresults of lower tier studies. 

Special study 

Acute and chronic oral toxicity to larval honey bees 

No data NA Yes 

Special study 

Pollinator feeding/semifield/pollen and nectar residue studies 

No data NA Need for data 

contingent upon results of Tier I bee studies 

850.3040 Field testing for 

pollinators 

No data NA Need for data 

contingent upon results of Tier I bee studies 

Aquatic Organisms Testing850.1010 Freshwater 

invertebrate acute toxicity 

00134449 Acceptable No -- 

45217301 Supplemental 

850.1025 850.1035 850.1045 850.1055 

Saltwater invertebrate acute toxicity 

00134451 and 30971107 (shrimp) 

Supplemental No Although the submitted study with 

classified as Supplemental due to deemed sufficient for quantitative assessment. 

42378901 (mollusc) Acceptable No -- 

850.1075 Freshwater fish 

acute toxicity 

00081856 (warm water) Acceptable Yes The submitted acute test with shee

41698801) was downgraded from “supplemental” due to considerablexposure concentrations. Measurethe nominal 60 and 100 mg/L trea0.16 and 0.28 mg/L at 0 hours to 0hours, respectively. The most sen

fish is 0.200 mg/L. This suggests concentrations over the test period 

42129801 (warm water) Acceptable 00134448 (warm water) Acceptable 42129802 (cold water) Acceptable 00081856 (cold water) Acceptable 

850.1075 Saltwater fish 

acute toxicity 

41698801 Supplemental
30 

OCSPP Guideline 

Data Requirement 

Submitted Study (MRID) 

Classification Are data 

needed to conduct the risk assessment? 

Justification and Assumptions EAbsence of Data underestimation of toxicity. Furthexceedances for freshwater fish in It should be noted that an acute toxestuarine/marine fish cannot be eschronic ratio (ACR) for freshwateendpoint generated from the requeearly life stage test [OCSPP 850.1for quantitative use in the ecologicthe available freshwater fish chrongenerated for fathead minnow, a shave an acute toxicity endpoint. Therefore, an acute test with fatheacute test with an estuarine/marine In the absence of these data, estuartoxicity data for surrogate pesticidclosely related pesticides (e.g., dipproceeding to data for less related characterize the acute toxicity of oestuarine/marine fish. 

850.1300 Freshwater 

invertebrate life cycle 

45550201, 92136106, and 42142305 

Acceptable No -- 

850.1350 Saltwater 

invertebrates life cycle 

46597701 Supplemental No Although the submitted study with 

as Supplemental due to guideline 

for quantitative use in the ecologic

850.1400 Freshwater fish 

early life stage 

00099270, 00030249, and 92136057 (standard lighting) 

Acceptable No -- 

46585104 (UV lighting) Acceptable 

850.1400 Saltwater fish 

early life stage 

No data NA Yes This study was identified as a data 

subsequent DCI for this study was submitted in response to the DCI (classified as Invalid due to low hacontrols and high variability in me
31 

OCSPP Guideline 

Data Requirement 

Submitted Study (MRID) 

Classification Are data 

needed to conduct the risk assessment? 

Justification and Assumptions EAbsence of Data A guideline-compliant early life stestuarine/marine species is neededIn the absence of these data, estuartoxicity data for surrogate pesticidclosely related pesticides (e.g., dipproceeding to data for less related characterize the chronic toxicity oestuarine/marine fish. 

850.1735 Whole sediment: 

acute freshwater invertebrates 

46585102 Supplemental No Although the submitted study with 

Supplemental due to lower than rintensity, it is sufficient for quantirisk assessment. 

850.1470 Whole sediment: 

acute marine invertebrates 

46585103 Supplemental No Although the submitted study with 

as Supplemental due to uncertain 

and not using continuous lighting sufficient for quantitative use in thassessment. 

Nontarget area phytotoxicity testing 850.4100 Seedling 

emergence and seedling growth 

45861101 Acceptable No -- 

850.4150 Vegetative vigor 45861102 Acceptable No -- 850.4400 Aquatic plant 

test using Lemna

spp. 

45861103 Supplemental No Although the submitted study with 

Supplemental due to uncertain exsufficient for quantitative use in th

850.4500 Algal toxicity 45271302 (green alga) Acceptable No Although the submitted studies wi

diatoms, N. pelliculosa and S. cost

classified as Supplemental due to concentrations, they are sufficient ecological risk assessment. 

45861105 (freshwater diatom) Supplemental 45861106 (marine diatom) Supplemental 

850.4550 Cyanobacteria 

toxicity 

45861104 Supplemental No Although the submitted studies wi

classified as Supplemental due to 

concentrations, it is sufficient for qecological risk assessment. 

Abbreviations: NA = not applicable
32 

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35 

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42142302 

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42255901 

92136102 

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42368101 Atkins, E. (1992) Bee Adult Toxicity Dusting Test Evaluating the 

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45271302 Sutherland, C.; Kendall, T.; Krueger, H. (2000) Goal 2XL (P) Herbicide: A 

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45271303 Milligan, D. (2000) Goal 4F (AKA Goal 480 SC) Herbicide: Laboratory 

Contact Toxicity Test with the Predacious Mite, Typhlodromus pyri Scheuten 

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42378901 Graves, W. (1992) Goal Technical Herbicide: A 96-Hour Shell Deposition 

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45581601 Hoberg, J. (1999) Goal Technical Purified Herbicide--Toxicity to the 

Freshwater Green Alga, Pseudokirchneriella subcapitata in a Naturalized 

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45861101 Aufderheide, J. (2002) Effects of Oxyfluorfen on Seedling Emergence and 

Growth of Selected Non-Target Terrestrial Plants (Tiers 1 and II): Lab Project 

Number: 47453: 021306. Unpublished study prepared by ABC Laboratories, 

Inc. 124 p. 
37 

45861102 Aufderheide, J. (2002) Effects of Oxyfluorfen on the Vegetative Vigor of 

Non-Target Terrestrial Plants (Tiers 1 & II): Lab Project Number: 47454: 

021307. Unpublished study prepared by ABC Laboratories, Inc. 111 p. 

45861103 Roshon, R. (2002) Oxyfluorfen (Goal): Growth Inhibition Test with the 

Freshwater Aquatic Plant, Lemna gibba L.G3: Final Study: Lab Project 

Number: S2310-04: 4686: 021022. Unpublished study prepared by ESG 

International Inc. 132 p. {OPPTS 850.4400} 

45861104 Roshon, R. (2002) Oxyfluorfen (Goal): Growth Inhibition Test with the 

Freshwater Bluegreen Alga, Anabaena flos-aquae: Final Study Report: Lab 

Project Number: S2310-01: 4686: 021019. Unpublished study prepared by 

ESG International Inc. 125 p. {OPPTS 850.5400} 

45861105 Roshon, R. (2002) Oxyfluorfen (Goal): Growth Inhibition Test with the 

Freshwater Diatom, Navicula pelliculosa: Final Study Report: Lab Project 

Number: S2310-02: 4686: 021020. Unpublished study prepared by ESG 

International Inc. 126 p. {OPPTS 850.5400} 

45861106 Roshon, R. (2002) Oxyfluorfen (Goal): Growth Inhibition Test with the 

Marine Diatom Skeletonema costatum: Final Study Report: Lab Project 

Number: S2310-03: 4686: 021021. Unpublished study prepared by ESG 

International Inc. 105 p. {OPPTS 850.5400} 

45906008 Sutherland, C.; Kendall, T.; Krueger, H. (2000) MON 78095: A 96-Hour 

Toxicity Test with the Freshwater Alga (Selenastrum capricornutum): Final 

Report: Lab Project Number: 129A-179: 00RC-0045: 00P-045. Unpublished 

study prepared by Wildlife International, Ltd. 98 p. {OPPTS 850.5400} 

45906003 Nienstedt, K. (1999) Goal 2XL (P): Laboratory Acute Toxicity Test with the 

Parasitic Wasp, Aphidius rhopalosiphi (Hymenoptera: Aphididae): Final 

Report: Lab Project Number: 98RC-0086: 98-086-1007: 1007.039.270. 

Unpublished study prepared by Springborn Laboratories (Europe) Ag. 52 p. 

45906004 Nienstedt, K. (1999) Goal 2XL (P): Laboratory Acute Toxicity Test with the 

Ground Beetle Poecilus cupreus L. (Coleoptera: Carabidae): Final Report: 

Lab Project Number: 98-088-1007: 98RC-0084: 1007.039.267. Unpublished 

study prepared by Springborn Laboratories (Europe) Ag. 59 p. 

45906005 Nienstedt, K. (1999) Goal 2XL (P): Laboratory Toxicity Test with Spiders, 

Pardosa sp. (Araneae: Lycosidae): Final Report: Lab Project Number: 98-

087-1007: 98RC-0083: 1007.039.272. Unpublished study prepared by 

Springborn Laboratories (Europe) Ag. 58 p. 

45906006 Nienstedt, K. (1999) Goal 2XL (P): Laboratory Contact Toxicity Test with the 

Predacious Mite, Typhlodromus pyri Scheuten (Acari: Phytoseiidae): Final 

Report: Lab Project Number: 98-085-1007: 98RC-0085: 1007.039.268. 

Unpublished study prepared by Springborn Laboratories (Europe) Ag. 63 p. 
38 

45906007 Nienstedt, K. (1999) Goal 2XL (P): A 14-Day Acute Toxicity Test with the 

Earthworm (Eisenia foetida): Final Report: Lab Project Number: 98-089-

1007: 98RC-0087: 1007.039.630. Unpublished study prepared by Springborn 

Laboratories (Europe) Ag. 75 p. 

46070101 Frey, L.; Martin, K.; Beavers, J.; et. al. (2003) Oxyfluorfen: A Reproduction 

Study with the Mallard: Final Report. Project Number: 379/128. Unpublished 

study prepared by Wildlife International, Ltd. 188 p. 

46070102 Frey, L.; Martin, K.; Beavers, J.; et. al. (2003) Oxyfluorfen: A Reproduction 

Study with the Northern Bobwhite: Final Report. Project Number: 379/127, 

021017. Unpublished study prepared by Wildlife International, Ltd. 189 p. 

46585102 Palmer, S.; Thomas, S.; Kendall, T.; et. al. (2005) Oxyfluorfen: A Survival 

and Growth Sediment Toxicity Test with Chironomus tentans Using Spiked 

Sediment. Project Number: 040438, 379A/112. Unpublished study prepared 

by Wildlife International, Ltd. 89 p..

46585103 Palmer, S.; Thomas, S.; Kendall, T.; et. al. (2005) Oxyfluorfen: A 10-Day 

Sediment Toxicity Test with Leptocheirus plumulosus Using Spiked 

Sediment. Project Number: 379A/113A, 040439. Unpublished study prepared 

by Wildlife International, Ltd. 84 p. 

46585104 Palmer, S.; Kendall, T.; Krueger, H. (2005) Oxyfluorfen: An Early Life-Stage 

Toxicity Test with the Fathead Minnow (Pimephales promelas) Under 

Ultraviolet Light Conditions. Project Number: 379A/114, 040442. 

Unpublished study prepared by Wildlife International, Ltd. 127 p. 

46597701 Blankinship, A.; Kendall, T.; Krueger, H. (2005) Oxyfluorfen: A FlowThrough Life-Cycle Toxicity Test with the Saltwater Mysid (Mysidopsis 

bahia). Project Number: 379A/110A, 040441. Unpublished study prepared by 

Wildlife International, Ltd. 91 p. 
39 

Appendix A: Application Information by Use for Oxyfluorfen 

Use Method of Application Maximum Application Rate (Minimum 

Application Interval)1

Terrestrial Food

Apricot Broadcast 62

 apps at 0.2436 lb ai/A –yearly max not specified

Chemigation, direct spray 62 apps at 0.2539 lb ai/A –yearly max not specified

Artichoke Direct spray 12 app of 1.522 lb ai/A –yearly max not specified 

Avocado Band treatment 12

 app of 2.040 lb ai/A –yearly max not specified 

Chemigation, direct spray 12,3 app of 1.530 lb ai/A 

Blackberry Band treatment, broadcast 2 apps at 1.015 lb ai/A 

Broccoli, Cabbage, Cauliflower Broadcast 12

 app at 0.5099 lb ai/A –yearly max not specified

Direct spray 12 app at 0.5078 lb ai/A –yearly max not specified

Cocoa Broadcast 63

 apps at 1.020 lb ai/A 

Direct spray 33 apps at 2.040 lb ai/A 

Coffee Broadcast, direct spray 33 apps at 2.040 lb ai/A 

Date, Feijoa (pineapple guava), 

Fig, Kiwi fruit, Olive, 

Persimmon, Pistachio, 

pomegranate, Walnut 

(English/black) 

Band Treatment 12

 app at 2.040 lb ai/A –yearly max not specified 

Chemigation, direct spray 12,3 app at 1.530 lb ai/A 

Garlic Broadcast 12

 app at 0.5099 lb ai/A –yearly max not specified

Chemigation, direct spray 22 apps at 0.2550 lb ai/A –yearly max not specified

Guava Direct spray 22 apps at 2.040 lb ai/A –yearly max not specified 

Horseradish Broadcast, direct spray 12 app at 0.5099 lb ai/A –yearly max not specified

Nectarine, Peach, Plum, Prune Broadcast, chemigation, direct 

spray 

62

 apps at 0.2436 lb ai/A –yearly max not specified

Olive Broadcast 62 apps at 0.2436 lb ai/A –yearly max not specified

Onion 

Band treatment, broadcast 12

 app at 0.5099 lb ai/A –yearly max not specified

Chemigation 22 apps at 0.2550 lb ai/A –yearly max not specified

Direct spray 22 apps at 0.1912 lb ai/A –yearly max not specified

Papaya Direct spray 33 apps at 1.020 lb ai/A 

Raspberry (black, red) Band treatment, broadcast 12 app at 0.7610 lb ai/A –yearly max not specified

Sage, clary Broadcast 63 apps at 0.2550 lb ai/A 

Taro Band treatment, direct spray 63

 apps at 0.2550 lb ai/A 

Broadcast 22 apps at 0.5099 lb ai/A –yearly max not specified

Terrestrial Non-Food

Agricultural fallow/idleland/ 

conservation reserve Broadcast 12

 app at 0.5099 lbs ai/A –yearly max not specified

Agricultural uncultivated areas Broadcast NS apps at 2.040 lbs ai/A 4

Christmas tree plantations Broadcast 2 apps at 2 lbs ai/A (2 months) 

Direct spray 23 apps at 2.031 lb ai/A 

Citrus Direct spray 12 app at 1.530 lbs ai/A –yearly max not specified 

Clover Broadcast 12 app at 0.0951 lbs ai/A –yearly max not specified

Cocoa Broadcast 63

 apps at 1.020 lb ai/A 

Direct spray 33 apps at 2.040 lb ai/A 

Coffee Broadcast, direct spray 33 apps at 2.040 lb ai/A 

Conifers (plantations/nurseries) Broadcast 2 apps at 2 lbs ai/A (2 months) 

 Chemigation NS apps at 1.001 lb ai/A 4

Deciduous trees 

Broadcast 12

 app at 2.029 lb ai/A –yearly max not specified 

Direct spray, spot soil treatment 13 app at 1.530 lb ai/A 

Spray 33 apps at 1.570 lb ai/A 
40 

Use Method of Application Maximum Application Rate (Minimum 

Application Interval)1

Eucalyptus Broadcast, direct spray 33 apps at 1.530 lb ai/A 

Grapes Broadcast, direct spray 12 app of 2.031 lb ai/A –yearly max not specified 

Grasses grown for seed Broadcast 12 app of 0.3808 lb ai/A –yearly max not specified

Guava Direct spray 22 apps at 2.040 lb ai/A –yearly max not specified 

Jojoba Direct spray 13 app at 1.530 lb ai/A 

Lesquerella Broadcast NS apps at 0.5233 lb ai/A 4

Nonagricultural uncultivated 

areas/soils 

Broadcast NS apps at 2.040 lb ai/A 4 

Spray, sprinkle NS apps at 4.530 lb ai/A 4 

Nursery stock Broadcast NS apps at 2.003 lb ai/A (60 days) 

Soil broadcast treatment 32 apps at 2 lb ai/A –yearly max not specified 

Onion Broadcast, chemigation 42 apps at 0.1275 lb ai/A –yearly max not specified

Ornamental and/or shade trees Spray, sprinkle NS apps at 4.530 lb ai/A 4

Ornamental woody shrubs and 

vines Spray, sprinkle NS apps at 4.530 lb ai/A 4

Ornamentals (unspecified) 

Broadcast, soil broadcast 

treatment 

32

 apps at 2.003 lb ai/A (60 days) –yearly max not 

specified 

Spray 2 apps at 1.921 lb ai/A (3 months) 

Pineapple Band Treatment, broadcast, 

direct spray NS apps at 2.040 lb ai/A 

Rose Direct spray 22 apps at 1.016 lb ai/A –yearly max not specified 

Sweet peas (ornamental) Broadcast NS apps at 0.2537 lb ai/A 4

Tree nuts Band Treatment 12

 app at 2.040 lb ai/A –yearly max not specified 

Chemigation, direct spray 12,3 app at 1.530 lb ai/A 

Terrestrial Food + Feed

Agricultural fallow/idleland/ 

conservation reserve 

Band treatment, broadcast 12

 app at 0.5099 lbs ai/A –yearly max not specified

Spray 12 app at 0.5073 lbs ai/A –yearly max not specified

Almond, Stone fruits Band Treatment 12

 app at 2.040 lbs ai/A –yearly max not specified

Chemigation, direct spray 12 app at 1.530 lbs ai/A –yearly max not specified 

Corn (unspecified) Broadcast 12

 app at 0.5233 lbs ai/A –yearly max not specified

Direct spray 12 app at 0.7850 lbs ai/A –yearly max not specified

Corn, field Broadcast 12

 app at 0.5078 lbs ai/A –yearly max not specified

Direct spray 12 app at 0.7649 lbs ai/A –yearly max not specified

Cotton (unspecified) 

Band treatment 22

 apps at 0.5099 lbs ai/A –yearly max not 

specified 

Direct spray 22

 apps at 0.5100 lbs ai/A –yearly max not 

specified 

Garbanzos (including chick peas) Broadcast 63 apps at 0.2539 lbs ai/A 

Grapes, Pome fruits Band treatment 12

 app at 2.040 lbs ai/A –yearly max not specified 

Chemigation, direct spray 12,3 app at 1.530 lbs ai/A 

Mint/peppermint/spearmint, 

Peppermint Broadcast 1 app at 1.530 lbs ai/A 

Soybeans (unspecified) 

Broadcast 2 apps at 0.5099 lbs ai/A 

Conservation tillage 2 apps at 0.7649 lbs ai/A 

Direct spray 12 - 33 apps at 0.5078 lbs ai/A 

Tree nuts 

Band treatment 12

 app at 2.031 lbs ai/A –yearly max not specified 

Chemigation, direct spray 12 app at 1.523 lbs ai/A –yearly max not specified 
41 

Use Method of Application Maximum Application Rate (Minimum 

Application Interval)1

Forestry

Cottonwood (Forest/Shelterbelt) Direct spray 32 apps at 1.53 lbs ai/A –yearly max not specified 

Forest Trees (Softwoods Conifers)

Direct spray 22 apps at 2.04 lbs ai/A –yearly max not specified 

Chemigation 22 apps at 1.02 lbs ai/A –yearly max not specified 

Shelterbelt Plantings Band treatment, broadcast, direct 

spray 

32

 apps at 1.53 lbs ai/A –yearly max not specified 

Terrestrial Non-Food + Outdoor Residential

Rose Direct spray 22 apps at 1.01 lbs ai/A –yearly max not specified 

NS – not specified on the label 

1

 Minimum application interval was not specified unless otherwise noted. 

2

 Number of applications assumed, based on the crop cycle maximum application rate. 3

 Number of applications assumed, based on the yearly maximum application rate. 

4

 Identified as a gap in label information by BEAD. 
42 

Appendix B: Summary of Endpoints from Oxyfluorfen Toxicity Stud

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Avian acute oral: single dose, 21-day observation (instead of usual 14-day observation) 

Oxyfluorfen technical (70.2) 

Bobwhite quail (Colinus virginianus) 

LD50 > 2150 mg/kg-bw (nom) 

NOAEL < 1470 mg a.i./kg-bw (nom) (1 mortality at 2150 mg /kg-bw ; sublethal effects: weaknessanorexia, piloerection, and abnormal cage droppings at 1470 2150 mg/kg-bw, recovery by day 7; food consumption severdepressed at 1470 and 2150 mg/kg-bw during first 2 and 7 drespectively; weight loss at 1470 and 2150 mg/kg-bw during 3 days) Practically non-toxic 

Avian acute oral NA Passerine species No data Avian sub-acute dietary: 5-day exposure; 3-day post-exposure observation 

Oxyfluorfen technical (70.2) 

Mallard duck (Anas platyrhynchos)

LC50 > 5000 mg a.i./kg-diet (nom) 

NOAEC = 312 mg a.i./kg-diet (nom) LOAEC = 625 mg a.i./kg-diet (nom) (10% [1/10] mortality at 5000 mg/kg-diet; sublethal effects: anorexia at 5000 mg/kg-diet on days 2-3; concentrationdependent reduction in food consumption at ≥ 625 mg/kg-di

during exposure period; reduction in food consumption at alreatment levels on days 6-8; NOAEC based on reduction in consumption) Practically non-toxic 

Oxyfluorfen technical (70.2) 

Bobwhite quail (Colinus virginianus) 

LC50 > 5000 mg a.i./kg-diet (nom) 

NOAEC = 625 mg a.i./kg-diet (nom) LOAEC = 1250 mg a.i./kg-diet (nom) (no mortality; sublethal effects: reduction in body weight gaat 1250 and 2500 mg/kg-diet during days 0-5; body wieght l5000 mg/kg-diet by day 5; food avoidance during days 3-5 areduction in food consumption durings days 0-5 at 2500 and 5000 mg/kg-diet; NOAEC based on reduction in body weighgain) Practically non-toxic 

Avian reproduction: 21 weeks (chronic) 

Oxyfluorfen (72.5) Mallard duck 

(Anas platyrhynchos) 

NOAEC = 100 mg/kg-diet (nom) LOAEC > 100 mg/kg-diet (nom) 
43 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Avian reproduction: 22 weeks (chronic) 

Oxyfluorfen (72.5) Bobwhite quail 

(Colinus virginianus) 

NOAEC < 50 mg/kg-diet (nom) LOAEC = 50 mg/kg-diet (nom) (based on reduced body weights of 14-day chicks) 

Avian reproduction: 20 weeks (chronic) 

Oxyfluorfen technical, purified (99.3) 

Bobwhite quail (Colinus virginianus) 

NOAEC = 124 mg a.i./kg-diet (mm) LOAEC = 256 mg a.i./kg-diet (mm) (based on most sensitive parameter of survivor weight; ratio hatchling survival to number of hatchlings, viable embryos, embryos, number of hatchlings, ratio of eggs set to eggs laidratio of number of hatchlings to eggs laid, ratio of hatchling survival to eggs set also affected) 

Avian reproduction: 20 weeks (chronic) 

Oxyfluorfen technical, purified (99.3) 

Mallard duck (Anas platyrhynchos) 

NOAEC = 506 mg a.i./kg-diet (mm) LOAEC = 751 mg a.i./kg-diet (mm) (based on eggs laid, eggs set, viable embryos, the ratio of viaembryos to eggs set, live embryos, number of hatchlings, the ratios of normal hatchlings to eggs laid and to eggs set, and hatchling survival) 

Mammalian acute oral, limit: single dose; 14-day observation 

Oxyfluorfen (96) 

Rat (Rattus norvegicus) 

LD50 > 5,000 mg a.i./kg-bw 

(no effects) Practically non-toxic 

Mammalian acute oral, limit: single dose; 14-day observation 

Oxyfluorfen technical 95 (97.1) 

Rat (Rattus norvegicus) 

LD50 > 5,000 mg a.i./kg-bw 

(no effects) Practically non-toxic 

Mammalian acute inhalation 

Oxyfluorfen (96) 

Rat (Rattus norvegicus) 

LC50 > 3.71 mg/L 

Mammalian 2- generation reproduction (chronic) 

Oxyfluorfen Rat 

(Rattus norvegicus) 

Parental 

NOAEC = 400 mg a.i./kg-diet LOAEC = 1600 mg a.i./kg-diet (based on parental effects including mortality, decreased bodweight, liver and kidney histopathology) Reproductive NOAEC = 400 mg a.i./kg-diet 
44 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) LOAEC = 1600 mg a.i./kg-diet (based on decreased body weight and decreased live pups/lit

Acute contact with adult honey bees: single dose, 96-hour observation 

Oxyfluorfen technical (71.4) 

Adult honey bee (Apis mellifera)

LD50 > 100 μg a.i./bee (nom) 

NOAEL: Not specified (4-5% mortality across control and 3 treatment concentrationPractically non-toxic 

Acute oral with honey bee adults 

NA Adult honey bee No data 

Acute oral with honey bee larvae 

NA Larval honey bee No data 

Chronic oral with honey bee adults 

NA Adult honey bee No data 

Chronic oral with honey bee larvae 

NA Larval honey bee No data 

Terrestrial invertebrate 

Goal 4F Herbicide (aka Goal 480 SC) (42.09) 

Predacious mite (Typhlodromus pyri)

7-day mortality = 98% at 1.28 lb a.i./A compared to control mortality of 5% 

Goal 2XL (22.26) 

Parasitic wasp (Aphidus rhopalosiphi) 

24-hour mortality = 100% at 1.29 lb a.i./A (5.80 lb Goal 2-XL/A) compared to no control mortality 

Goal 2XL (22.26) 

Ground beetle (Poecilus cupreus L.) 

No effects after 21 days at 1.29 lb a.i./A (5.80 lb Goal 2-XL/

Goal 2XL (22.26) 

Spider (Paradosa sp.) 

24-hour mortality = 100% at 1.08 lb a.i./A (4.86 lb Goal 2-XL/A) compared to no control mortality 

Goal 2XL (22.26) 

Predacious mite (Typhlodromus pyri)

7-day mortality = 100% at 1.29 lb a.i./A (5.80 lb Goal 2-XLcompared to control mortality of 2% 

Goal 2XL (P) (22.26) 

Earthworm (Eisenia foetida) 

14-day LC50 (95% C.I.) = 89 (79-100) mg a.i./kg-dry soil (4

[356.6-447.6] mg Goal 2-XL/kg-dry soil) (nom) 
45 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) Probit slope (95% C.I.) = 7.20 (5.03-9.36) 14-day NOAEC = 29 mg a.i./kg-dry soil (125 mg Goal 2-XLdry soil) (nom) 14-day LOAEC = 56 mg a.i./kg-dry soil (250 mg Goal 2-XLdry soil) (nom) (NOAEC based on reductions in growth) 

Terrestrial plant seedling emergence: 14 days 

Oxyfluorfen technical (71.5) 

Most sensitive monocot: Ryegrass 

EC25 = 0.0058 lb a.i./A 

NOAEC = 0.0024 lb a.i./A (based on length) 

Most sensitive dicot: Cabbage 

EC25 = 0.0026 lb a.i./A 

NOAEC = 0.0024 lb a.i./A (based on length) 

Terrestrial plant vegetative vigor: 14 days 

Oxyfluorfen technical (71.5) 

Most sensitive monocot: Onion 

EC25 = 0.0062 lb a.i./A 

NOAEC = 0.0071 lb a.i./A (based on weight) 

Most sensitive dicot: Tomato 

EC25 = 0.00043 lb a.i./A 

NOAEC = 0.00066 lb a.i./A (based on weight) 

Terrestrial plant seedling emergence: minimum of 14 days after 50% of the control plants had emerged 

Goal 2XL (23.1) 

Most sensitive monocot: Ryegrass 

EC25 = 0.0063 lb a.i./A (nom) 

EC05 = 0.00065 lb a.i./A (nom) NOAEC = 0.030 lb a.i./A (nom) Note: Since the NOAEC > EC25, the EC05 will be used for 

assessing risk to listed species. (based on dry weight) 

Most sensitive dicot: Lettuce 

EC25 = 0.0072 lb a.i./A (nom) 

EC05 = 0.0024 lb a.i./A (nom) NOAEC = 0.0080 lb a.i./A (nom) Note: Since the NOAEC > EC25, the EC05 will be used for 

assessing risk to listed species. (based on dry weight) 
46 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Terrestrial plant vegetative vigor: 22-23 days 

Goal 2XL (23.1) 

Most sensitive monocot: Oat 

EC25 = 0.27 lb a.i./A (nom) 

EC05 = 0.08 lb a.i./A (nom) NOAEC = 0.22 lb a.i./A (nom) (based on dry weight) 

Most sensitive dicot: Lettuce 

EC25 = 0.0078 lb a.i./A (nom) 

EC05 = 0.00032 lb a.i./A (nom) NOAEC = 0.000035 lb a.i./A (nom) (based on dry weight) 

Freshwater fish acute: 96 hours, flow-through, standard laboratory lighting 

Oxyfluorfen (94) 

Bluegill sunfish (Lepomis macrochirus) 

LC50 (95% C.I.) = 200 (130-310) μg/L (nom) 

NOAEC: Not specified (no mortality at lowest test concentration, 56 μg/L; sublethaeffects: darkening, lethargy, and loss of equilibrium) Highly toxic 

Freshwater fish acute: enhanced UV lighting 

Oxyfluorfen Bluegill sunfish 

(Lepomis macrochirus) 

Estimated LC50= LC50(bluegill sunfish)/Ratio(standard lighting: enhanced UV lighting) 

= 200 μg/L/29.2 = 7 μg/L Where: Ratio(standard lighting: enhanced UV lighting) = NOAEC(fathead minnow ELS, standard lighting)/NOAEC(fathead minnow EL

enhanced UV lighting)

= 38 μg/L/1.3 μg/L = 29.2 

Freshwater fish acute: 96 hours, static 

Oxyfluorfen technical (71.4) 

Bluegill sunfish (Lepomis macrochirus) 

LC50 (95% C.I.) = 210 (175-346) μg a.i./L (mm) 

NOAEC = 93 μg a.i./L (mm) LOAEC = 175 μg a.i./L (mm) (NOAEC based on mortality and sublethal effects at ≥175 μ

no mortality or sublethal effects at 29-93 μg/L; sublethal effhyperexcitability in surviving fish at 175 μg/L) Highly toxic 

Freshwater fish acute: 96 hours, static 

Oxyfluorfen technical (71.4) 

Rainbow trout (Oncorhynchus mykiss) 

LC50 (95% C.I.) = 253 (186-355) μg a.i./L (mm) 

Probit slope (95% C.I.) = 2.4 (1.6-3.1) NOAEC = 37 μg a.i./L (mm) LOAEC = 83 μg a.i./L (mm) 
47 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) (NOAEC based on mortality and sublethal effects at ≥83 μg

no mortality or sublethal effects at 37 μg/L; sublethal effectslethargy in surviving fish at 398 and 1090 μg/L) Highly toxic 

Freshwater fish acute: 96 hours, static 

Oxyfluorfen (74) Channel catfish 

(Ictalurus punctatus) 

LC50 (95% C.I.) = 400 (360-450) μg/L (nom) 

NOAEC: Not specified (sublethal effects: erratic swimming behavior and mucous shedding at ≥320 μg/L) 

Highly toxic 

Freshwater fish acute: 96 hours, flow-through 

Oxyfluorfen (94) 

Rainbow trout (Oncorhynchus mykiss) 

LC50 (95% C.I.) = 410 (310-560) μg/L 

NOAEC: Not specified (no mortality at 2 lowest test concentration, 140 and 180 μg/sublethal effects: darkening, lethargy, and loss of equilibriumHighly toxic 

Freshwater fish early life stage: 30 days, flow through, standard laboratory lighting 

Oxyfluorfen technical (71) 

Fathead minnow (Pimephales promelas) 

NOAEC = 38 μg/L (mm) LOAEC = 74 μg/L (mm) Note: This study was conducted under standard laboratory lighting. (based on reduction in fry survival, total length, and weigh) 

Freshwater fish early life stage: 33 days, flow through, enhanced UV lighting (chronic) 

Oxyfluorfen technical (99.3) 

Fathead minnow (Pimephales promelas) 

NOAEC = 1.3 μg a.i./L (TWA) LOAEC = 2.4 μg a.i./L (TWA) Note: This study was conducted under UV lighting simulatinsummer light intensity for the Florida or California latitudes

(based on most sensitive endpoint of post-hatch survival; hatching success, post-hatch physical/behavioral abnormalitand growth [length, wet weight, and dry weight] also affecte

Estuarine/marine fish acute: 96 hours, static 

Oxyfluorfen technical (71.4) 

Sheepshead Minnow (Cyprinodon variegatus) 

LC50 > 116 μg a.i./L (mm) 

NOAEC = 60 μg a.i./L (mm) (no mortality; sublethal effect of surfacinga at ≥130 μg a.i./L

Practically non-toxic up to the limit of solubility 

Estuarine/marine fish early life stage (chronic) 

Oxyfluorfen Estuarine/marine 

species 

No data Note: A chronic toxicity endpoint for estuarine/marine fish cannot be estimated using an acute-to-chronic ratio (ACR) f
48 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) freshwater fish because the available freshwater fish chronic toxicity endpoints were generated for fathead minnow, a spefor which we do not have an acute toxicity endpoint. 

Freshwater invertebrate: 48 hours, static 

Oxyfluorfen (82.2) Water flea 

(Daphnia magna) 

LC50 (95% C.I.) = 1.5 (0.75-2.9) mg/L (nom) 

Moderately toxic 

Freshwater invertebrate acute: 48 hours, flow through 

Goal 2XL (P) (23.2) 

Water flea (Daphnia magna) 

EC50 (95% C.I.) = 80 (60-150) μg a.i./L (mm) 

NOAEC = 20 μg a.i./L (mm) (NOAEC based on mortality and sublethal effects) Very highly toxic 

Freshwater mollusc: 96 hours 

Oxyfluorfen Technical (74) 

Freshwater clam (Elliptio complanata) 

LC50 (95% C.I.) = 9.57 (6.67-13.73) mg/L 

Freshwater invertebrate life cycle: 21 days, flow through (chronic) 

Oxyfluorfen technical (71.8) 

Water flea(Daphnia magna) 

NOAEC = 13 μg a.i./L (mm) LOAEC = 28 μg a.i./L (mm) (NOAEC based reductions in adult survival, growth [length]and reproductive output) 

Estuarine/marine invertebrate: 96 hours, static 

Oxyfluorfen technical (74) 

Grass shrimp (Palaemonetes pugio) 

LC50 (95% C.I.) = 32 (18-56) μg/L (nom) 

NOAEC = 18 μg/L (nom) Very highly toxic 

Estuarine/marine mollusc: 96 hours, flow through, shell deposition 

Oxyfluorfen technical (71.4) 

Eastern oyster (Crassostrea virginica) 

EC50 (95% C.I.) = 69.3 (62.2-98.5) μg a.i./L (mm)b

NOAEC = 37.5 μg a.i./L (mm)c

Very highly toxic 

Estuarine/marine invertebrate: 96 hours, static 

Oxyfluorfen technical (74) 

Fiddler crab (Uca pugilator) 

Mortality = 30 and 20% at 560 and 1000 mg/L (nom), respectively 

Estuarine/marine invertebrate life 

Oxyfluorfen technical (99.3) 

Mysid shrimp(Mysidopsis bahia)

NOAEC = 8.1 μg a.i./L (TWA) LOAEC = 16 μg a.i./L (TWA) 
49 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

cycle: 30 days, flow through (chronic) 

(NOAEC based on most sensitive endpoint of reproduction; survival, and growth [length and dry weight] also affected)) 

Benthic freshwater invertebrate: 10 days, flow through, spiked sediment 

Oxyfluorfen technical (99.3) 

Midge (Chironomus tentans) 

Based on pore water concentrations (mm) LC50 > 498.5 μg a.i./L 

NOAEC = 484.5 μg a.i./L Based on sediment concentrations (dry weight, mm) LC50 > 97.6 mg a.i./kg-dw NOAEC = 55.7 mg a.i./kg-dw Based on sediment concentrations (organic carbon [OC], mmLC50 > 4880 mg a.i./kg-OC NOAEC = 2750 mg a.i./kg-OC (NOAEC based on mortality) 

Benthic estuarine/marine invertebrate: 10 days, static, spiked sediment 

Oxyfluorfen technical (99.3) 

Amphipod (Leptocheirus plumulosus) 

Based on pore water concentrations (mm) LC50 (95% C.I.) = 130 (81-200) μg a.i./L 

Probit slope = 2.73±0.833 NOAEC = 27.9 μg a.i./L Based on sediment concentrations (mm) LC50 (95% C.I.) = 37 (26-53) mg a.i./kg-dw Probit slope = 2.54±0.44 NOAEC = 16.0 mg a.i./kg-dw Based on overlying water concentrations (mm) LC50 (95% C.I.) = 42 (22-82) μg a.i./L Probit slope = 1.79±0.44 NOAEC = 12.6 μg a.i./L (NOAEC based on mortality) 

Benthic invertebrate: 96 hours, static, spiked sediment 

Goal 1.6E (19.5) 

14C-Goal 1.6E 

(99) 

Midge (Chironomus tentans) 

EC50 > 5.1 mg Goal 1.6E/kg-dry soil 

EC50 > 0.029 mg Goal 1.6E /L overlying water 
50 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Aquatic vascular plant: 14 days, staticrenewal 

Oxyfluorfen technical (99.1) 

Duckweed (Lemna gibba) 

EC50 (95% C.I.) = 0.33 (0.20-0.38-27) μg a.i./L (m) 

NOAEC/EC05: Could not be determined 

(based on most sensitive endpoint of frond number) 

Aquatic nonvascular plant: 96 hours, static 

Goal 2XL (P) (23.2) 

Green alga (Selenastrum capricornutum) 

EC50 (95% C.I.) = 0.29 (0.27-30) μg a.i./L (mm) 

NOAEC = 0.10 μg a.i./L (mm) LOAEC = 0.26 μg a.i./L (mm) (NOAEC based on reduction in cell density) 

Aquatic nonvascular plant: 96-240 hours, static, sediment 

Oxyfluorfen technical (99.1) 

Green alga (Pseudokirchneriella subcapitata) 

96-hr EC50 > 2.9 μg a.i./L (im) 

96-hr NOAEC = 1.4 μg a.i./L (im) 96-hr LOAEC = 2.9 μg a.i./L (im) 240-hr EC50 > 2.9 μg a.i./L (im) 

240-hr NOAEC = 2.9 μg a.i./L (im) 240-hr LOAEC > 2.9 μg a.i./L (im) (NOAEC based on reductions in cell density, growth rate, anbiomass) 

Aquatic nonvascular plant: 120 hours, static 

Oxyfluorfen technical (99.1) 

Cyanobacterium (Anabaena flos-aquae) 

EC50 > 100 μg a.i./L (mm) 

NOAEC = 20.1 μg a.i./L (mm) LOAEC = 47.2 μg a.i./L (mm) (NOAEC based on most sensitive endpoint of biomass [area under the growth curve; cell density and growth rates also affected) 

Aquatic nonvascular plant: 120 hours, static 

Oxyfluorfen technical (99.1) 

Freshwater diatom (Navicula pelliculosa) 

EC50 = 29 μg a.i./L (mm) 

NOAEC = 19.2 μg a.i./L (mm) LOAEC = 49.7 μg a.i./L (mm) (based on most sensitive endpoint of cell density for EC50; 

growth rate and biomass also affected with same NOAEC anLOAEC) 

Aquatic nonvascular plant: 96 hours, static 

Oxyfluorfen technical (99.1) 

Marine diatom (Skeletonema costatum) 

EC50 = 1.10 μg a.i./L (mm) 

NOAEC = 0.65 μg a.i./L (mm) LOAEC = 1.20 μg a.i./L (mm) (based on most sensitive endpoint of biomass [area under thcurve]; cell density and growth rate also affected) 
51 

Study Type Test Substance 

 (% a.i.) 

Species Toxicity Endpoints and 

Acute Toxicity Classification (If Applicable) 

Aquatic nonvascular plant: 96 hours, static 

TEP: MON 78095 2.50% oxyfluorfen + 30.27% glyphosate acid-equivalent 

Green alga (Selenastrum capricornutum) 

EC50 = 0.213 μg oxyfluorfen/L (mm) 

NOAEC = 0.039 μg oxyfluorfen/L (mm) LOAEC = 0.088 μg oxyfluorfen/L (mm) EC50 = 8.5 μg MON 78095/L (mm) NOAEC = 1.5 μg MON 78095/L (mm) NOAEC = 3.5 μg MON 78095/L (mm) (based on most sensitive endpoint of biomass [area under thcurve]; cell density and growth rate also affected) 

Abbreviations: C.I. = confidence interval; ELS = early life stage; im = initial measured; mm = mean measured; nom = nominal; NA = n

specified; TEP = typical end-use product; TWA = time-weighted average 

a This observation was attributed to low dissolved oxygen. The study author proposed that the drop in dissolved oxygen could have bee

of precipitated chemical on the surface of the water. b based on pooled control data 

c based on comparison to solvent control; NOAEC may be lower when using a comparison to the negative control 

1 
52 

Appendix C: Ecological Incidents Associated with Oxyfluorfena

Incident Number 

Taxa Involved 

Effects Route of 

Exposure 

Magnitude Year State Use Legality of 

Use 

Certainty Category

I023931-055 Terrestrial Plant 

damage 

Treated directly 

1 bush 2012 TX Ornamental Undetermined Possible 

I023097-009 Terrestrial Mortality Treated 

directly 

60-75 trees 2011 CA Orchard 

(almond) 

Misuse (accidental) 

Possible 

I023097-010 Terrestrial Plant 

damage 

Treated directly 

60 acres 2011 CA Orchard 

(almond) 

Undetermined Possible 

I023097-010b

Terrestrial Plant 

damage 

Treated directly 

60 acres 2011 CA Orchard 

(almond) 

Misuse (accidental) 

Possible 

I023097-011 Terrestrial Plant 

damage 

Treated directly 

Unknown 2011 CA Orchard 

(almond) 

Undetermined Possible 

I024499-001 Terrestrial Mortality Not 

reported 

60-75 trees 2011 CA Orchard 

(almond) 

Misuse (accidental) 

Possible 

I023044-006 Terrestrial Plant 

damage (wheat) 

Drift, spray 

30% of 40 acre 

2010 CA Cotton Misuse Probable 

I023574-001 Plants Plant 

damage 

Not reported 

66 acres 2010 CA Strawberry Undetermined Possible 

I020180-019 Plants Plant 

damage (wheat) 

Drift, spray 

40 acres 2008 CA Cotton Undetermined Possible 

I016962-027 Plants Plant 

damage 

Treated directly 

38 acres 2004 OR Ryegrass Misuse 

(accidental) 

Probable 

I021276-015 Plants Plant 

damage 

Drift Not 

reported 

2004 WA Agricultural 

area 

Misuse Possible 

I012366-049 Plants Plant 

Damage (onion) 

Treated directly 

33 acres 2001 CA N/r Misuse 

(accidental) 

Probable 

I013563-006 Plants Plant 

damage 

Treated directly 

110 acres 2001 CA Beans Registered use Possible 

I010844-001 Aquatic Mortality Spill Chinook 

salmon (1336) 

2000 OR Spill Misuse 

(accidental) 

Probable 
53 

Incident Number 

Taxa Involved 

Effects Route of 

Exposure 

Magnitude Year State Use Legality of 

Use 

Certainty Category

Steelhead (850) 

I013563-005 Plants Plant 

damage 

Treated directly 

332 acres 2000 CA Almonds Registered use Possible 

I013563-009 Plants Plant 

damage 

Treated directly 

20 acres 2000 CA Grape Registered use Probable 

I016102-001 Plants Plant 

damage 

(blueberry)

Drift 20 acres 2000 MI Tree farm/ 

plantation 

Registered use Possible 

I013563-003 Plants Plant 

damage 

Treated directly 

Unknown 1999 CA Onion Misuse 

(accidental) 

Possible 

I013563-004 Plants Plant 

damage 

Treated directly 

10 acres 1999 CA Grapes Registered use Probable 

I013563-001 Plants Plant 

damage 

Treated directly 

Unknown 1998 CA Onions Registered use Possible 

I013563-008 Plants Plant 

damage 

Treated directly 

Unknown 1998 CA Grapes Registered use Probable 

I013563-002 Plants Plant 

damage 

Treated directly 

78 acres 1997 CA Bean Misuse 

(accidental) 

Probable 

I013563-007 Plants Plant 

damage (lettuce) 

Treated directly 

50 acres 1997 CA Field Misuse 

(accidental) 

Probable 

I003377-003 Plants Plant 

damage (plum, almond) 

Drift Thousands 1996 CA N/r Misuse 

(accidental) 

Probable 

I013636-029 Plants Plant 

damage (peppermint) 

Treated directly 

181 acres 1996 OR N/r Registered use Possible 

a ‘Minor’ incidents aggregately reported by the registrant(s) are not included in this table. b Same incident as that listed above record, but second involves an additional application of an oxyfluorfen product which led to an exc

recommendation for total amount of oxyfluorfen to be used on a single crop. 
54 

Appendix D: SIP and STIR Outputs 

SIP (v. 1.0) 

 Table 1. Inputs 

 Parameter Value 

 Chemical name oxyfluorfen 

 Solubility (in water at 25oC; mg/L) 0.116 

 

 Mammalian LD50 (mg/kg-bw) 5000 

 Mammalian test species laboratory rat 

 Body weight (g) of "other" mammalian species 

 

 Mammalian NOAEL (mg/kg-bw) 20 

 Mammalian test species laboratory rat 

 Body weight (g) of "other" mammalian species 

 

 Avian LD50 (mg/kg-bw) 2150 

 Avian test species mallard duck 

 Body weight (g) of "other" avian species 

 Mineau scaling factor 1.15 

 

 Mallard NOAEC (mg/kg-diet) 124 

 Bobwhite quail NOAEC (mg/kg-diet) 124 

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

 Body weight (g) of other avian species 

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

 Body weight (g) of 2nd other avian species 

 

 Table 2. Mammalian Results 

 Parameter Acute Chronic 

 Upper bound exposure (mg/kg-bw) 0.0200 0.0200 

 Adjusted toxicity value (mg/kg-bw) 3845.8028 15.3832 

 Ratio of exposure to toxicity 0.0000 0.0013 

 

Conclusion* 

Drinking water 

exposure alone is 

NOT a potential 

concern for mammals 

Drinking water exposure 

alone is NOT a potential 

concern for mammals 

 

 Table 3. Avian Results 

 Parameter Acute Chronic 

 Upper bound exposure (mg/kg-bw) 0.0940 0.0940 

 Adjusted toxicity value (mg/kg-bw) 1116.3346 6.1520 

 Ratio of exposure to acute toxicity 0.0001 0.0153 

 

Conclusion* 

Drinking water 

exposure alone is 

NOT a potential 

concern for birds 

Drinking water exposure 

alone is NOT a potential 

concern for birds 
55 

 

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

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

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

STIR (v. 1.0) 

Welcome to the EFED 

Screening Tool for Inhalation Risk 

This tool is designed to provide the risk assessor with a rapid method for determining 

the potential 

significance of the inhalation exposure route to birds and mammals in a risk 

assessment. 

 

Input 

Application and Chemical Information 

Enter Chemical Name oxyfluorfen 

Enter Chemical Use multiple 

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

If Spray What Type (enter ground or air) ground 

Enter Chemical Molecular Weight (g/mole) 361.72 

Enter Chemical Vapor Pressure (mmHg) 2.50E-07 

Enter Application Rate (lb a.i./acre) 2 

 

Toxicity Properties 

Bird 

Enter Lowest Bird Oral LD50 (mg/kg bw) 2150 

Enter Mineau Scaling Factor 

Enter Tested Bird Weight (kg) 0.178 

Mammal 

Enter Lowest Rat Oral LD50 (mg/kg bw) 5000 

Enter Lowest Rat Inhalation LC50 (mg/L) 3.71 

Duration of Rat Inhalation Study (hrs) 4 

Enter Rat Weight (kg) 0.35 

 

Output 

Results Avian (0.020 kg ) 

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 4.87E-03 

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 6.12E-04 

Adjusted Inhalation LD50 1.10E+02 

Ratio of Vapor Dose to Adjusted Inhalation LD50 5.57E-06

Exposure not Likely 

Significant 

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 2.11E-01 
56 

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 1.92E-03

Exposure not Likely 

Significant 

 

Results Mammalian (0.015 kg ) 

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 4.87E-03 

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 7.69E-04 

Adjusted Inhalation LD50 2.21E+02 

Ratio of Vapor Dose to Adjusted Inhalation LD50 3.48E-06

Exposure not Likely 

Significant 

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 2.66E-01 

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 1.20E-03

Exposure not Likely 

Significant 

Welcome to the EFED 

Screening Tool for Inhalation Risk 

This tool is designed to provide the risk assessor with a rapid method for determining 

the potential 

significance of the inhalation exposure route to birds and mammals in a risk 

assessment. 

 

Input 

Application and Chemical Information 

Enter Chemical Name oxyfluorfen 

Enter Chemical Use multiple 

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

If Spray What Type (enter ground or air) air 

Enter Chemical Molecular Weight (g/mole) 361.72 

Enter Chemical Vapor Pressure (mmHg) 2.50E-07 

Enter Application Rate (lb a.i./acre) 0.5 

 

Toxicity Properties 

Bird 

Enter Lowest Bird Oral LD50 (mg/kg bw) 2150 

Enter Mineau Scaling Factor 

Enter Tested Bird Weight (kg) 0.178 

Mammal 

Enter Lowest Rat Oral LD50 (mg/kg bw) 5000 

Enter Lowest Rat Inhalation LC50 (mg/L) 3.71 

Duration of Rat Inhalation Study (hrs) 4 

Enter Rat Weight (kg) 0.35 

 

Output 
57 

Results Avian (0.020 kg ) 

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 4.87E-03 

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 6.12E-04 

Adjusted Inhalation LD50 1.10E+02 

Ratio of Vapor Dose to Adjusted Inhalation LD50 5.57E-06

Exposure not Likely 

Significant 

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 4.80E-02 

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 4.37E-04

Exposure not Likely 

Significant 

 

Results Mammalian (0.015 kg ) 

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 4.87E-03 

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 7.69E-04 

Adjusted Inhalation LD50 2.21E+02 

Ratio of Vapor Dose to Adjusted Inhalation LD50 3.48E-06

Exposure not Likely 

Significant 

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 6.04E-02 

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 2.73E-04

Exposure not Likely 

Significant 

 
58 

Appendix E: Results of ECOSAR Modeling 

 

ECOSAR is a screening-level tool based on chemical structures developed by the USEPA’s 

Office of Chemical Safety and Pollution Prevention for rapid screening of chemicals for 

ecotoxicity hazards. The modeling results show that MW-332, a degradate of oxyfluorfen, is 

about 3-4 times less toxic than parent oxyfluorfen. With the exception of green algae, the 

ECOSAR estimated toxicity values for oxyfluorfen are similar to observed toxicity values. 

Taxon Endpoint (mg/L) 

Oxyfluorfen 

ECOSAR Class: 

Neutral Organic SAR 

Oxyfluorfen 

 Observed 

MW-332 

ECOSAR Class: 

Neutral Organic SAR 

Acute Chronic Acute Chronic Acute Chronic 

Fish 0.392 0.054 0.200 0.038/0.0013* 1.132 0.148 

Daphnid 0.299 0.066 0.080 0.013 0.821 0.158 

Green algae 0.758 0.384 0.00029 - 1.685 0.761 

Saltwater fish 0.503 0.387 >0.170 - - - 

Saltwater mysid 0.043 0.0014 0.032 0.008 - - 

* Standard laboratory lighting/UV lighting