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Revised Problem Formulation for the 

Environmental Fate, Ecological Risk, and Endangered 

Species Assessments 

in Support of the Registration Review of Fluridone

Fluridone 

CAS Number 59756-60-4 

PC Code 112900 

Prepared by:

Katrina White, Ph.D., Biologist (Effects Scientist) 

Ibrahim Abdel-Saheb, Ph.D, Environmental Scientist

Tiffany Mason, Environmental Engineer 

Reviewed by: 

Jean Holmes, Senior Biologist 

William Eckel, Senior Fate Scientist 

Tom Bailey, Branch Chief

U. S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division 

Environmental Risk Branch II 

1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington, DC 20460

February 24, 2010 
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Table of Contents 

1. Purpose.................................................................................................................................... 4 

2. Problem Formulation .............................................................................................................. 4 

2.1. Nature of Regulatory Action........................................................................................... 4 

2.2. Previous Risk Assessments............................................................................................. 4 

3. Stressor Source and Distribution ............................................................................................ 5 

3.1. Mechanism of Action in Plants....................................................................................... 5 

3.2. Overview of Pesticide Usage.......................................................................................... 5 

3.3. Environmental Fate and Transport.................................................................................. 7 

4. Receptors............................................................................................................................... 13 

4.1. Effects to Aquatic Organisms ....................................................................................... 14 

4.2. Effects to Terrestrial Organisms ................................................................................... 16 

4.3. Incident Database Review............................................................................................. 18 

4.4. Ecosystems Potentially at Risk ..................................................................................... 20 

5. Assessment Endpoints .......................................................................................................... 20 

6. Conceptual Model................................................................................................................. 21 

6.1. Risk Hypothesis ............................................................................................................ 21 

6.2. Conceptual Diagram ..................................................................................................... 22 

7. Analysis Plan ........................................................................................................................ 24 

7.1. Stressors of Concern ..................................................................................................... 25 

7.2. Measures of Exposure................................................................................................... 25 

7.2.1 Aquatic Organisms................................................................................................ 26 

7.2.2 Terrestrial Organisms............................................................................................ 26 

7.3. Measures of Effect ........................................................................................................ 27 

7.4. Integration of Exposure and Effects ............................................................................. 28 

7.5. Deterministic and Probabilistic Assessment Methods.................................................. 29 

7.6. Endangered Species Assessments................................................................................. 29 

7.7. Drinking Water Assessment ......................................................................................... 29 

7.8. Preliminary Identification of Data Gaps....................................................................... 30 

7.8.1 Fate........................................................................................................................ 30 

7.8.2 Effects ................................................................................................................... 31 

7.9. Other Information Needed for the Risk Assessment .................................................... 40 

8. References............................................................................................................................. 40 

8.1. Open Literature ............................................................................................................. 40 

8.2. Submitted Fate Studies ................................................................................................. 43 

8.3. Submitted Effects Studies............................................................................................. 47 
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List of Tables 

Table 3-1. Summary of Section 3 Products, Formulations, and Maximum Application Rates for 

Products Containing Fluridone* ..................................................................................................... 7 

Table 3-2. General chemical and environmental fate properties of fluridone ............................... 8 

Table 3-3. Maximum Reported Amounts of Fluridone Degradation Products 1 .......................... 10 

Table 4-1. Summary of Sensitive Endpoints for Aquatic Organisms Under Consideration for 

Use in the Risk Assessment for Fluridonea

................................................................................... 15 

Table 4-2. Summary of Sensitive Toxicity Endpoints for Terrestrial Organisms Under 

Consideration for Use in Risk Assessment*................................................................................. 17 

Table 4-3. Summary of Incidents Reported in the Ecological Incident Information System (EIIS) 

for Fluridone ................................................................................................................................. 19 

Table 7-1. Summary of Environmental Fate Studies................................................................... 30 

Table 7-2. Available Ecological Effects Data for Terrestrial Animals Exposed to Fluridone .... 32 

Table 7-3. Available Ecological Effects Data for Aquatic Animals Exposed to Fluridone ....... 33 

List of Figures 

Figure 3-1. Structure of fluridone and its degradation products.................................................. 11 

Figure 3-2. Other degradates isolated during fluridone lab photolysis study in amounts up to 

6.8% of the applied radioactivity.................................................................................................. 12 

Figure 6-1. Conceptual Model Depicting Exposure Pathways and Potential Risks to Aquatic 

Organisms from the Use of Fluridone to Control Aquatic Vegetation. Dashed lines indicate 

routes of exposure considered of lower importance for fluridone................................................ 23 

Figure 6-2. Conceptual Model Depicting Exposure Pathways and Potential Risks to Terrestrial 

Organisms from the Use of Fluridone to Control Aquatic Vegetation. Dashed lines indicate 

routes of exposure considered of lower importance for fluridone................................................ 24 

Appendices 

Appendix A: Data Call In Tables................................................................................................. 53 

Appendix B: Summary of Toxicity Data..................................................................................... 64 

Appendix C: Preliminary TREX Output for NMF ...................................................................... 77 

Appendix D: ECOSAR (version 1.0) Results for 3-trifluoromethyl benzoic acid ...................... 79 
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1. Purpose 

The purpose of this problem formulation is to provide an understanding of what is known about 

the environmental fate and ecological effects of the registered uses of fluridone. Fluridone is a 

systemic aquatic herbicide. This document will provide a plan for analyzing data relevant to 

fluridone and for conducting environmental fate, ecological risk, and endangered species 

assessments for its registered uses. Additionally, this problem formulation is intended to identify 

data gaps, uncertainties, and potential assumptions used to address those uncertainties relative to 

characterizing the ecological risk associated with the registered uses of fluridone. 

2. Problem Formulation 

2.1. Nature of Regulatory Action 

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides distributed 

or sold in the United States generally must be registered by the United States Environmental 

Protection Agency (USEPA). To determine whether a pesticide can be registered, the USEPA 

evaluates its safety to non-target species based on a wide range of environmental and health 

effects studies. In 1996, FIFRA was amended by the Food Quality Protection Act, and EPA was 

mandated to implement a new program for the periodic review of pesticides, i.e., registration 

review (http://www.epa.gov/oppsrrd1/registration_review/). The registration review program is 

intended to ensure that, as the ability to assess risk evolves and as policies and practices change, 

all registered pesticides continue to meet the statutory standard of no unreasonable adverse 

effects to human health and the environment. Changes in science, public policy, and pesticide 

use practices will occur over time. Through the new registration review program, the Agency 

periodically reevaluates pesticides to make sure that as change occurs, products in the 

marketplace can be used safely. 

As part of the implementation of the new Registration Review program pursuant to Section 3(g) 

of FIFRA, the Agency is beginning its evaluation of fluridone to determine whether it continues 

to meet the FIFRA standard for registration. This problem formulation for the environmental fate 

and ecological risk assessment chapter in support of the registration review will be posted in the 

initial docket opening the public phase of the review process. 

2.2. Previous Risk Assessments 

In 2004, a human health risk assessment for fluridone and a drinking water assessment were 

completed to support the tolerance decision in the Tolerance Reregistration Eligibility Decision 

document (USEPA 2004a; USEPA 2004b). A corresponding ecological risk assessment was not 

completed. The most recent ecological risk assessment was completed in 1991 (USEPA 1991). 

The review included reference to a biological opinion written by the U.S. Fish and Wildlife 

Service which found, "the registration of this product as proposed is likely to jeopardize the 

continued existence of all listed U.S. freshwater aquatic species including plants, fishes, reptile, 

amphibians, and invertebrates (principally mussels) and is likely to destroy or adversely modify 

all aquatic designated critical habitat" (USEPA 1991). The review predicted direct and indirect 

risk to reproduction of aquatic organisms and risk to aquatic vegetation. The review requested 

the following studies: 
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• 123-2 Tier II Aquatic Plant Growth, 

• 72-1 Acute Toxicity Test for Freshwater Fish, 

• 72-4 Freshwater Invertebrate Lifecycle, and 

• 72-3 Testing for Estuarine and Marine Organisms. 

The review concluded that a risk assessment on revisions for increased application rates could 

not be completed until data were submitted. The review stated that the label requires that the 

State Fish and Game Agency of the U.S. Fish and Wildlife Service should be contacted prior to 

making applications to avoid impact on threatened or endangered species. Current labels have a 

statement that state and local water authorities should be consulted prior to use of the product; 

however, it is not a restricted use pesticide. Additionally, the label does not mention the 

protection of threatened or endangered species. The models, procedures, and data requirements 

for the ecological risk assessment process have all been modified since the previous ecological 

risk assessment was completed. 

3. Stressor Source and Distribution 

3.1. Mechanism of Action in Plants 

Fluridone is a systemic aquatic herbicide that is used to manage aquatic weeds in ponds and 

lakes. It does not belong to a specific chemical class of pesticides (Wood 2009). The mode of 

action is inhibition of carotenoid biosynthesis at the phytoene desaturase step of the isoterpenoid 

pathway (Popova 1996; Schmitz 1986). The lack of carotenoid pigments in leaves results in 

chlorophyll bleaching by sunlight and prevents plants from synthesizing food (Doong et al.

1993). This mode of action is also seen with pyridazinones and pyridinecarboxamides (HRAC 

2005). Fluridone has also been shown to inhibit the production of abscisic acid (MacDonald et 

al. 2008). 

3.2. Overview of Pesticide Usage 

Fluridone was originally registered for use in the United States in 1960. There are currently 18 

registered products, with 12 national labels (Section 3), ten special local need labels (Section 

24c), and three experimental use permits. Table 3-1 lists the Section 3 labels currently 

registered. Formulations of fluridone include emulsifiable concentrate, liquid, pelleted/tablet, 

and soluble concentrate/solid. It may be applied directly to water as a broadcast spray through 

both aerial and ground dispersal methods (Fox et al. 1996; BLM 2005) or to the subsurface of 

water.1

 The water bodies where it may be applied include ponds, lakes, reservoirs, potable water 

sources, drainage canals, and irrigation canals. Application equipment includes a metering 

pump, sprayers, trailing hose, and weighted trailing hose. It is particularly useful for the control 

of hydrilla in the southern states and Eurasian milfoil in the northern states (USEPA 2004b). 

The labels permit treatments of up to 90 parts per billion (ppb) for ponds and up to 150 ppb for 

lakes and reservoirs, with a maximum cumulative application of 150 ppb per growth cycle. The 

reported maximum application rate in lbs active ingredient per acre (lbs ai/acre) is 4.9 pounds 

 

1

 Labels do not have specific instructions for application of fluridone by air; however, the labels do not prohibit 

application by air. Therefore, it is assumed that aerial application of fluridone is approved on the label. 
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active ingredient per acre (lbs ai/A) for aquatic areas, lakes, ponds, and reservoirs, 2 lbs ai/A for 

drainage systems and streams, rivers, or channeled water, and 0.865 lbs ai/A in human drinking 

water systems (USEPA 2009a). The maximum application rate in human drinking water systems 

is 20 ppb (USEPA 2009a). It is prohibited from application in tidewater or brackish water; 

however, as it may be applied in freshwater streams and rivers it could easily enter the 

estuarine/marine environment. Concentrations must be maintained over a long period of time 

(30-90 days) in order for fluridone to be effective. Repeated applications may be needed to keep 

the concentration high enough for weed control. Some labels instruct the user to use an enzymelinked immunoassay (ELISA) test to monitor the concentration of fluridone in water and repeat 

applications as needed. Due to the mode of action of fluridone, it is important that it be applied 

to plants that are actively growing. For this reason, many applications are made in the spring 

(MacDonald et al. 2008). Typically, the number of applications is 1-3 with a minimum of 2-3 

weeks between treatments (USEPA 2003). Some precautionary statements are summarized 

below. 

Example Precautionary Statements on Labels 

• Permits: Consult with appropriate state or local water authorities before applying since 

state or local agencies may require permits to use product. 

• Chemigation: Do not apply through any type of irrigation system. 

• Hydroponic Farming: Do not use treated water for hydroponic farming. 

• Greenhouse and Nursery Plants: Do not use water which has been treated to irrigate 

greenhouse or nursery plants unless chemical assays of the water indicate fluridone 

residues are less than one parts per billion (ppb). 

• Maximum Use Rates: Do not apply more than a total of 90 ppb in ponds and 150 ppb in 

lakes and reservoirs per annual growth cycle. These maximum concentrations are the 

amounts of fluridone calculated as the target application rate, NOT the concentration 

determined by analysis of fluridone in the treated water. 

• Waiting Periods: If application rates are 150 ppb or less, treated water may be used 

immediately with no waiting period for drinking (potable) water (including watering 

livestock and pets), fishing or swimming. See specific restrictions below for Potable 

Water Intakes and Irrigation. 

• Potable Water Intakes: In lakes and reservoirs or other sources of potable water, DO 

NOT APPLY at application rates greater than 20 ppb within 1/4 mile (1320 feet) of any 

functioning potable water intake. If rates are between 6 and 20 ppb, the product MAY BE 

APPLIED where functioning potable water intakes are present. 

• Note: Existing potable water intakes which are no longer in use, such as those replaced 

by potable water wells or connections to a municipal water system, are not considered to 

be functioning potable water. 

• Irrigation: Irrigation using water treated may injure the irrigated vegetation. Instruct those 

who use product-treated water to follow the recommended waiting periods listed in the 

table below and to assay the water for fluridone residues. For crops grown on low organic 

and sandy soils and irrigated with product-treated water, the potential for crop injury is 

greater than for crops grown on heavier soils. 
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Table 3-1. Summary of Section 3 Products, Formulations, and Maximum Application 

Rates for Products Containing Fluridone* 

Product Name 

EPA Reg. Num. 

Percent ai 

Formulation 

Pounds ai/amount 

product 

Maximum Application Rate 

WhiteCap SC 

61842-11 

41.7% ai 

Liquid 

4 lbs ai/ gallon 

product 

90 ppb in ponds and 150 ppb in lakes, reservoirs, and static canals 

per annual growth cycle 

4.88 lbs ai/A1

Sonar*SRP 

67690-3 

5.0% ai 

Pellet/tablet 

0.05 lbs ai / pound 

product 

90 ppb in ponds and 150 ppb in lakes, reservoirs, and static canals 

per annual growth cycle 

2.0 lbs ai/A2

Sonar*A.S. 

67690-4 

41.7% 

Emulsifiable Conc. 

4 lbs ai/gallon 

product 

90 ppb in ponds and 150 ppb in lakes, reservoirs, and static canals 

per annual growth cycle 

4.88 lbs ai/A1

Sonar*X 

67690-12 

5.0% ai 

Pellet/tablet 

0.05 lbs ai / pound 

product 

90 ppb in ponds and 150 ppb in lakes and reservoirs per annual 

growth cycle 

4.9 lbs ai/A3

Sonar Q Quick 

Release 

676901-21 

5.0% ai 

Pellet/tablet 

2 lbs ai/40-pounds 

product 

90 ppb in ponds and 150 ppb in lakes and reservoirs per annual 

growth cycle 

4.9 lbs ai/A3

Fluridone SC 

67690-30 

41.7% ai 

Liquid 

4lbs ai/gallon 

product 

90 ppb in ponds and 150 ppb in lakes, reservoirs, and static canals 

per annual growth cycle 

4.88 lbs ai/A1

Fluridone SRP 

67690-32 

5.0% ai 

Pellet/tablet 

2 lbs ai/40-pounds 

product 

90 ppb in ponds and 150 ppb in lakes and reservoirs per annual 

growth cycle 

4.9 lbs ai/A3

SonarOne* 

67690-45 

5.0 % ai 

Pellet/tablet 

0.05 pound ai/pound 

product 

90 ppb in ponds and 150 ppb in lakes and reservoirs per annual 

growth cycle 

4.9 lbs ai/A3

Sonar*Extra 

67690-48 

3.79% ai 

Liquid 

0.08 lbs ai/quart 

product 

0.48 lbs ai/A followed by 2 applications at 0.24 lbs ai/A with a 20 

day interval 

Fluridone Technical 

83504-2 

99.3% ai 

Not applicable 

Fluridone Technical 

67690-31 

99.2% ai 

Not applicable 

ai = active ingredient 

*The list of currently registered products was obtained from OPPIN in April 2009. The maximum application rates 

were obtained from USEPA 2009a. 

1 Calculated from 156.2 oz product/acre x 1gallon/128 oz conversion factor x 4 lbs ai/gallon = 4.88 lbs ai./Acre. 

2 Calculated from 40 pounds/acre x 0.05 lbs ai/pound = 2 lbs ai/Acre 

3 Calculated from 98 pounds Sonar X per treated surface Acre x 0.05 lbs ai/pound Sonar X = 4.9 lbs ai/A 

4 Calculated from 6 quarts/acre x 0.08 lbs ai/quart = 0.48 lbs ai/A. and 3 quarts /acre x 0.05 lbs ai/quart = 0.24 lbs 

ai/A.

3.3. Environmental Fate and Transport 

Registrant-submitted data defining the physical, chemical, fate, and transport characteristics 

associated with fluridone (1-methyl-3-phenyl-5-(α,α,α-trifluoro-m-tolyl)-4-pyridone) are 

summarized in Table 3-2. As part of registration review, available fate studies for fluridone have 
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been reevaluated. The fate and transport of fluridone in the environment is briefly discussed 

below. 

Under field conditions, photolysis and soil adsorption are the major routes for fluridone 

dissipation. 

The results of two fish bioaccumulation studies along with low n-octanol/water partition 

coefficient (1.87) tend to indicate that fluridone has a low potential to bioaccumulate in fish. 

Table 3-2. General chemical and environmental fate properties of fluridone

Chemical/Fate 

parameter 

Value Source (MRID) 

Molecular Weight (g/mol) 329.3 Footprint @ 

http://sitem.herts.ac.uk/aeru/footprint/en/, 

accessed on April 28, 2009 

Vapor Pressure (mm Hg at 

25 o C) 

9.77 x 10-8

<1 x 10-7

USEPA 2007c 

Weed Science, 4th Ed. 2002 

Henry's law constant at 25oC 

(Pa m3

 mol-1) 

3.57 x 10-04 Footprint @ 

http://sitem.herts.ac.uk/aeru/footprint/en/, 

accessed on April 28, 2009 

Octanol-water Partition 

Coefficient (Log KOW) 

1.87 Footprint @ 

http://sitem.herts.ac.uk/aeru/footprint/en/, 

accessed on April 28, 2009 

Water Solubility (mg/L; at 25 

°C) 

12.3 Footprint @ 

http://sitem.herts.ac.uk/aeru/footprint/en/, 

accessed on April 28, 2009 

Hydrolysis half lives (days) 

 

Stable MRID# 30257 

Aqueous photolysis half-life 

(d) 

0.9 – 2.3 MRID# 103326 

Aerobic Soil Metabolism 

half-life (y) 

Stable MRID# 135217 

Anaerobic Soil Metabolism 

half-life (days) 

Stable Acc. No. 070937 

Anaerobic Aquatic 

Metabolism half-life (days) 

Stable MRID# 103327 

Aerobic Aquatic Metabolism 

half-life (days) 

117 MRID# 44154801 

Organic carbon normalized 

partition coefficients (KOC)

260 – 740 L/kg MRID# 44138501 

Fish Bioconcentration Factor 

(BCF) 

3.97x (whole fish) 

4.32x (non-edible tissues) 

1.46x (edible tissues) 

MRID# 162775 
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3.3.1.a Degradation 

Fluridone is stable to hydrolysis (MRID 0030257). Fluridone photodegrades in distilled water 

rapidly with a half - lives of 55 hours (pH 6), and 34 hours in natural pond water. Photoproducts 

include volatile and non-volatile compounds (MRID 00103326). Volatile photoproducts were 

formed through destruction of the pyridinone ring. Degradation in water is attributed to 

photolysis and adsorption by aquatic plants and hydrosoil (October 1978 Trip Report Document, 

Sonar Aquatic Tour P000071). 

Fluridone in water/methanol solution and exposed to sunlight for 53 days produced volatile 

photoproducts: 3-trifluoromethyl-benzoic acid (the chemical identity information and structures 

for these compounds are shown in below), benzoic acid (IV, CAS Number 65-85-0), 3-

trifluoromethyl-benzaldehyde (V, CAS Number 454-89-7), benzaldehyde (VI, CAS Number 

100-52-7), and N-methyl formamide (NMF, VII). These products suggest that fluridone 

photolysis occurs through degradation of the pyridinone ring. Benzaldehydes rapidly degraded to 

benzoic acid. Both benzoic acids slowly degraded in distilled water but 3-trifluoromethyl 

benzoic acid was stable in lake water. NMF did not degrade in lake or distilled water exposed to 

sunlight. NMF did completely degrade in lake water held as dark control (suggesting microbial 

activity involved). 

In distilled water, N-methyl Formamide (NMF) and 3-trifluoromethyl benzoic acid (CAS 

Number 454-92-2) were the major photoproducts that were observed after 27 days exposure (3:1 

ratio) (Acc. No. 070937). In lake water, NMF, 3-trifluoromethyl-benzoic acid, and benzoic acid 

(1:1:1 ratio) were the major photoproducts present. 

Under aerobic aquatic and anaerobic aquatic conditions, fluridone will decline at a very slow rate 

with half- lives of 117 days (MRID 44154801), and >365 (MRID 103327), respectively. The 

degradation of fluridone in soil (under aerobic and anaerobic soil conditions) was highly 

variable. Fluridone is very persistent in soils with an apparent half-life of approximately 6 

months although some studies indicate that its half life may be as long as 2 to 5 years. 

Degradation products also persist in the soil but are as yet uncharacterized. 

Figure 3-1 and Figure 3-2 list all degradates identified in laboratory studies and their amounts, 

followed by chemical structures for each degradate. 
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Table 3-3. Maximum Reported Amounts of Fluridone Degradation Products 1

Degradate Maximum % of 

Applied (time of maximum) 

Study Duration (day) 

% of Applied at Study Termination 

Study Type MRID 

[Parent compound] 

Not applicable 27 

365 30 2 365 

N/A (stable) 36-65 N/A (stable) 46 (water), 38.6 (sediment) 27.6 – 75.9 (in solution) 

Hydrolysis Aqueous photolysis Anaerobic aquatic metabolism Aerobic aquatic metabolism Adsorption/Desorption/Leaching Aquatic field dissipation 

MRIDMRIDMRIDMRIDMRIDMRID

NMF 74 (day 27) 27 74 Aqueous photolysis MRIDFluridone acid 2.6 30 0.6 Aerobic aquatic metabolism MRID1,4-dihydro-1-methyl-4-oxo-5-(3-triflouromethyl)- phenyl ) - 3 - pyr idinecarboxylic acid 

Not measured 365 N/A 

Anaerobic aquatic metabolism MRID

Benzaldehyde 2 (day 7) 27 0.5 Aqueous photolysis MRID3CF3-

benzaldehyde 

0.6 (day 7) 27 0.3 Aqueous photolysis MRID

Benzoic acid 40 (day 21) 27 0.7 Aqueous photolysis MRID3CF3- Benzoic 

acid 

33 (day 21) 27 24 Aqueous photolysis MRID

1 Degradates with >10% of applied parent equivalents are in bold. Refer to chemical names and structures in Figure 3-1. 
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Fluridone (Parent Compound) 

3-trifluoromethyl benzoic acid 3-trifluoromethyl benzaldahyde (V) 

Benzoic Acid (IV) Benzaldehyde (VI) 

N-methyl Formamide (VII) 1,4-dihydro-1-methyl-4-oxo-5-(3-

triflouromethyl)- 

phenyl ) - 3 - pyridinecarboxylic 

acid 

Figure 3-1. Structure of fluridone and its degradation products 
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Figure 3-2. Other degradates isolated during fluridone lab photolysis study in amounts up 

to 6.8% of the applied radioactivity 

3.3.1.b Transport 

Fluridone has relatively high potential for sorption to hydrosoil or sediment. Laboratory studies 

show that fluridone residues are adsorbed strongly to soils. Fluridone was sorbed to soils with 

Freundlich Kads values ranging from 2.16 to 28.0 L/kg; and Koc values range from 260 to 740 

L/kg (MRID 44138501). Based on its Koc values and according to the mobility classification 

presented by the Food and Agricultural Organization of the United Nations (FAO); fluridone is 

considered as moderately mobile. Open literature studies reported KOC values ranging from 270 

to 6400 L/kg (BLM 2005). These studies will be evaluated to determine whether the reported 

values are reliable for use in the environmental fate characterization. 

3.3.1.c Aquatic Field Dissipation 

Under field conditions, fluridone apparently dissipates from hydrosoil by gradual desorption into 

the water where it photodegrades. However, the degree of photodegradation in the aquatic field 

environment will be influenced by several variables, namely, degree of weed infestation, depth of 

water, cloud cover, etc. 

Liquid fluridone decreased in concentration logarithmically with time when applied in two North 

Carolina ponds at 1.0 lb ai/A and 2.0 lb ai/A. Estimated time to reach a concentration of zero 

was 64 and 69 days respectively. No observed decrease in a treated Virginia pond was seen over 

a 53 day period when a pellet formulation at 1.0 ai/A was used. It is speculated that the reduced 

loss due to photolysis was because of shading in the Virginia pond (Langeland and Warner 

1986). Half-lives ranging from 4-7 days were reported for fluridone in Canadian fish ponds 

applied at 70, 700, and 5000 μg ai/L (Muir et al. 1980). In 12 ponds located across the United 

States and one in Canada treated with liquid fluridone, the half-lives ranged from 5-60 days 

(average 20 days). Lake half-lives less than 1 week have been attributed to dispersion, dilution, 

and degradation and/or adsorption (West et al. 1983). Ponds treated with pelleted fluridone had 

reached the maximum concentration approximately 14 days following treatment. Then fluridone 

levels began to decline at a similar rate as seen with the liquid fluridone. 

Hydrosoil degradation has only been observed in laboratory experiments. Degradation has not 

been observed in aquatic systems. It is believed that desorption followed by photolysis is 
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responsible for the loss from sediments. In ponds treated with liquid fluridone, hydrosoil 

concentrations reached maximum within approximately 14 days after treatment. The average 

half-life was found to be 3 months. No fluridone was found in treated lake sediments (West et 

al. 1983). 

Fluridone was found to have a half-life in surface water of 21 days (Mackay et al. 1997), an 

anaerobic aquatic half-life of 9 months and an aerobic half-life of 20 days (Tomlin 1994, USEPA 

1982). When basing the fluridone half-life on its estimated photolysis in water, the surface water 

half-life was 12-36 days, and the ground water half-life based on estimated unacclimated 

aqueous aerobic biodegradation was found to be 88-383 days (Howard et al. 1991). 

3.3.1.d Bioaccumulation 

In a bioconcentration study with crayfish, fluridone residues concentrated in fish tissues at a 

factor of 3.97X for whole fish, 4.32 for non edible tissues, and 1.46X for edible tissues (MRID # 

162775). 

Fluridone has a relatively low octanol/water partition coefficient. Based on the Kow of 1.87, 

fluridone would have a low potential for bioaccumulation in fish (Acc. No. 070937). 

3.3.1.e Impaired Water Bodies 

Fluridone is not identified as a cause of impairment for any water bodies listed as impaired under 

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

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=88

5. In addition, no Total Maximum Daily Loads (TMDL) have been developed for fluridone, 

based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id

=885&p_pollutant_group_name=PESTICIDES. More information on impaired water bodies and 

TMDLs can be found at http://www.epa.gov/owow/tmdl/. The Agency invites submission of 

water quality data for this pesticide. To the extent possible, data should conform to the quality 

standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired 

Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and 

Management Process (see: http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-

sop.pdf), in order to ensure they can be used quantitatively or qualitatively in pesticide risk 

assessments.

4. Receptors 

The receptor is the biological entity that is exposed to the stressor (USEPA 1998). Consistent 

with the process described in the Overview Document (USEPA 2004d), the risk assessment for 

fluridone relies on a surrogate species approach. Toxicological data generated from surrogate 

test species, which are intended to be representative of broad taxonomic groups, are used to 

extrapolate to potential effects on a variety of species (receptors) included under these taxonomic 

groupings. 

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

available open literature are used to evaluate the potential direct and indirect effects of fluridone 

to aquatic and terrestrial receptors. This includes toxicity on the technical grade active 
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ingredient, degradates, and when available, formulated products (e.g., “Six-Pack” studies). The 

open literature studies are identified through EPA’s ECOTOXicology (ECOTOX) database 

(USEPA 2009b), 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 may also 

provide insight into the direct and indirect effects of fluridone on biotic communities from loss 

of species that are sensitive to the chemical and from changes in structure and functional 

characteristics of the affected communities. Open literature data from ECOTOX on fluridone 

was searched on January 31, 2009. The data is being evaluated for possible quantitative and/or 

qualitative inclusion in the risk assessment. 

A summary of the aquatic and terrestrial toxicity data used to derive a preliminary evaluation of 

risk for fluridone is provided in Sections 4.1 and 4.2, respectively. In addition, a summary of 

ecological incidents associated with fluridone and a description of ecosystems potentially at risk 

are provided in Sections 4.3 and 4.4, respectively. 

4.1. Effects to Aquatic Organisms 

A summary of sensitive aquatic toxicity data from registrant-submitted studies and data available 

from the ECOTOX database is provided in Table 4-1. Appendix B includes a table summarizing 

toxicity data submitted to the Agency. Fluridone is classified as slightly toxic to moderately 

toxic to aquatic organisms based on data for aquatic vertebrates and invertebrates. Sublethal 

effects such as hyperactivity, irregular swimming, loss of equilibrium, immobilization, 

discoloration, and prostration were observed in both vertebrate and invertebrate studies and in 

some studies at all treatment levels. Jumping, surfacing, and change in percent hematocrit were 

observed in acute freshwater fish studies. Chronic effects observed in aquatic studies include 

mortality, survival of fry, and hatching success. Toxicity data for aquatic plants have not been 

submitted for fluridone. Several studies are available in the open literature. The open literature 

studies will be evaluated for possible use in the risk assessment. 

Most of the submitted studies were completed in the late 1970s and early 1980s. These studies 

are currently under review to determine if the studies still meet guideline requirements. Special 

attention will be given to whether an accurate estimate of exposure can be established. In many 

of the studies, precipitate was present and treatment levels exceeded the level of solubility. The 

concentration was measured in most of the studies; however, in some studies the water was not 

centrifuged or filtered to remove any pesticide that would be bound to organic matter or present 

as a precipitate. Therefore, the measured concentration likely exceeded the exposure 

concentration. These studies will be used as supplemental information as they do provide some 

information on whether toxicity may occur; however, due to the uncertainty in the exposure 

concentration, the studies cannot be used to fulfill guideline requirements. Steep slopes were 

observed with much of the mortality occurring near the level of solubility (12.3 mg/L). The 

steep slopes indicate that a small change in concentration may have a large impact on mortality. 

N-methyl formamide (NMF) is a compound of toxicological concern to mammals and the only 

degradate identified by the Health Effects Division (HED) to be of toxicological concern 

(USEPA 2004b). It was found at a maximum of 74% of applied fluridone equivalents in a study 

examining photolysis in distilled water and a maximum of 36% applied fluridone equivalents in 

a study examining photolysis in lake water (MRID 00103326). Concentrations of NMF in 
15 of 80

photolysis studies increased over time, indicating that NMF could be stable to hydrolysis and 

photolysis (MRID 00103326). No toxicity data were submitted on the toxicity of NMF to 

aquatic species; however, open literature acute toxicity data for the fathead minnows and 

daphnia indicates that NMF is less toxic than fluridone to these species.2

 Little information on 

the quality of these data is available and these data cannot be used to discount risk. Therefore, 

toxicity data for NMF are needed to assess potential risk to aquatic organisms due to exposure to 

NMF. Toxicity studies will be requested for fish and invertebrates. No aquatic toxicity data 

were available in the public ECOTOX database when searched on April 21, 2009 (USEPA 

2009b). 

No aquatic toxicity data were available for 3-trifluoromethyl benzoic acid in the public 

ECOTOX database when searched on April 22, 2009 (USEPA 2009b). Data based on ECOSAR 

version 1.0 indicates that the toxicity endpoints for aquatic organisms would range from 9-2706 

mg/L, using the neutral organic acid chemical class (Appendix D). This suggests that the 

toxicity of this degradate is similar to the toxicity of the parent. 

Table 4-1. Summary of Sensitive Endpoints for Aquatic Organisms Under Consideration 

for Use in the Risk Assessment for Fluridonea

Common Name 

(Species) 

TGAI /TEP 

Duration End-point 

(effect) 

 Mean 

concentration in 

mg a.i./L (effect) 

Citation or 

MRID/status or 

review 

Acute Toxicity 

Classification 

Freshwater Vertebrates and Aquatic-phase amphibians 

Rainbow Trout 

(Salmo gairneri) 

TGAI 

96 hours LC50 

5.1 

(mortality) 

00103297 

Acceptable Moderately Toxic 

Rainbow Trout 

(Salmo gairneri) 

EP 

96 hours LC50

4.3 

(mortality) 00103297 Moderately Toxic 

Fathead Minnow 

(Pimephales promelas) 

EP 

96 hours LC50

8.3 

(mortality) 

103297 

Acceptable Moderately Toxic 

Walleye 

(Sander vitreus) 

TEP 

96 hours LC50

Near 1.8b

(mortality) 

Paul et al. 1994 

Preliminary 

Supplementalc

Moderately Toxic 

Fathead Minnow 

(Pimephales promelas) 

TGAI 

Full 

Lifecycle NOAEC 

0.48 

(Survival of 30 

day fry) 

00103309 

Acceptable NA 

Chinook Salmon 

(Oncorhyncus tshawytscha) 

TGAI 

Early Life 

Stage NOAEC 0.43 

(length) 

45915601 

Supplemental NA 

Estuarine Marine Vertebrates 

Sheepshead Minnow 

(Cyprinodon variegates) 

TGAI 

96 hours LC50

near 10.7b

(mortality) 

00108837 

Supplemental Slightly Toxic 

Freshwater Invertebrates 

 

2

 The 96-hr LC50 was > 10,000 mg/L for the fathead minnow based on nominal concentration and the 48-hr LC50

was >500 mg/L for Daphnia magna based on nominal concentrations (E.I. du Pont de Nemours and Company, LP., 

2005). 
16 of 80

Common Name 

(Species) 

TGAI /TEP 

Duration End-point 

(effect) 

 Mean 

concentration in 

mg a.i./L (effect) 

Citation or 

MRID/status or 

review 

Acute Toxicity 

Classification 

Midge 

(Chironmous plumosus) 

TGAI 

48 hours LC50

1.3 

(immobility) 

00103297 

Preliminary 

Supplementalc

Moderately Toxic 

Waterflea 

(Daphnia magna)

TGAI 

48 hours LC50

5.2 

(immobility) 

00103297 

Acceptable Moderately Toxic 

Waterflea 

(Daphnia magna)

EP 

48 hours LC50

3.0 

(immobility) 

00103297 

Acceptable Moderately Toxic 

Waterflea 

(Daphnia magna)

TGAI 

21 day life 

cycle NOAEL Near 0.2b

(mortality) 

00103297 

Preliminary 

Supplementalc

NA 

Estuarine Marine Invertebrates 

Pink Shrimp 

(Panaeus duorarum) 

TGAI 

96 hours LC50

4.6 

(mortality) 

00112789 

Acceptable Moderately Toxic 

Pink Shrimp 

(Panaeus duorarum) 

TEP 43.6% a.i.

96 hours LC50

 Near 2.4b

(morality) 

00103312 

Supplemental Moderately Toxic 

TGAI=technical grade active ingredient; TEP=typical end use product; LC50 = median lethal concentration; 

NOAEL=no observable adverse effect level; a.i. active ingredient 

a Data in this table may be used in the risk assessment, but it will not necessarily be used to calculate risk 

quotients. 

b This endpoint may only be used qualitatively in the assessment. For submitted studies, see the comments in 

Appendix B on why the quality of the data is not acceptable to use quantitatively. For open literature studies, 

not enough information on the study procedures was available to determine if the study was conducted and 

data analyzed in a way that is consistent with current guideline requirements. 

c Preliminary classification of studies indicates the studies have not been fully reviewed. 

4.2. Effects to Terrestrial Organisms 

A summary of sensitive terrestrial toxicity data from registrant-submitted studies and data 

available from the ECOTOX database is provided in Table 4-2. Appendix B includes a table 

summarizing toxicity data submitted to the Agency. Based on the available data, fluridone is 

classified as practically nontoxic to birds, mammals, and terrestrial invertebrates. 

Acute, subchronic, and chronic toxicity studies are available for mammals. These results are 

fully discussed in USEPA 2004c. In acute studies, fluridone was shown to cause slight to 

moderate corneal dullness, iritis, and conjunctivitis. Subchronic studies resulted in increased 

incidence of hepatic centrilobular hypertrophy, increased relative liver weights, and increased 

relative kidney weights in rats. In developmental studies, increased incidence of abortions, 

decreased body weights, decreased food consumption, increased incidence of rudimentary ribs, 

and delayed ossification of sternebrae and pelvic girdle were observed. Chronic effects observed 

include small testes, ocular karatitis, and pale and granular kidneys. In metabolism studies, 

fluridone was rapidly and almost completely absorbed into systemic circulation within 3 days 

and 78-97% radioactivity was recovered in the urine and feces, with the majority of elimination 
17 of 80

in the feces. The primary components in feces were fluridone and fluridone metabolites 

resulting from ring hydroxylation and N-demethylation. 

No mortality was observed in acute avian studies. Submitted chronic avian studies are 

considered invalid. 

No terrestrial plant toxicity data were submitted. One open literature study was listed in 

ECOTOX for tomatoes and it will be evaluated for possible use in the risk assessment. 

N-methyl formamide (NMF, CAS Number 123-39-7) is a fluridone metabolite formed by the 

photolysis of fluridone (MRID 00103326). It is the only degradate identified by the health 

effects division (HED) as a degradate of toxicological concern (USEPA 2004b). One 

developmental toxicity study was reportedly available examining toxicity in mammals when the 

TRED was completed. NMF caused skeletal malformations in both rats and rabbits with a 

NOAEL of 10 mg/kg/day (USEPA 2004b). NMF is an investigational anticancer drug that has 

undergone clinical trials (HSDB 2002). Data are available on the toxicity of NMF in the open 

literature (HSDB 2002). These data suggest that NMF is more acutely toxic than fluridone.3

 

The quality of these data are unknown; however, the information does support the need for more 

information on the toxicity of NMF if potential exposure is likely at high enough levels from the 

use of fluridone. Based on the preliminary TREX run and the 10 mg/kg/day endpoint available 

for mammals, exposure to NMF may be high enough to elicit toxicity (Appendix C). No toxicity 

data were available to evaluate potential toxicity to birds. Therefore, avian toxicity data will be 

requested for NMF. No toxicity data were available for NMF in the public ECOTOX database 

when searched on May 9, 2009 (USEPA 2009b). 

No terrestrial toxicity data were available for 3-trifluoromethyl benzoic acid in the public 

ECOTOX database when searched on April 22, 2009 (USEPA 2009b). Avian toxicity data will 

be requested so that risk to birds due to exposure to 3-trifluoromethyl benzoic acid may be 

evaluated. 

Table 4-2. Summary of Sensitive Toxicity Endpoints for Terrestrial Organisms Under 

Consideration for Use in Risk Assessment* 

Common 

Name 

(Species) 

TGAI /TEP

End-point Mean Concentration and Effect 

Citation or 

MRID / 

Status 

Acute Toxicity 

Classification 

Mammals

Rat 

(Rattus 

norvegicus) 

TGAI 

LD50

10,000 mg/kg-body weight (mortality) USEPA 2004b Practically 

Nontoxic 

Rabbit 

TGAI 

Gestation 

day 6-18 

NOAEL/ 

LOAEL 

125/300 mg/kg/day 

(Increased incidence of abortions in parent, 4/14 

aborted between days 20 and 25 of gestation, 

decreased body weight) 

00103302/ 

USEPA 2004c NA 

 

3

 Reported oral acute LD50 values for mice were 2600 mg/kg and 4000 mg/kg in rats (HSDB 2002). These data have 

not been reviewed and the quality of the data is unknown. 
18 of 80

Common 

Name 

(Species) 

TGAI /TEP

End-point Mean Concentration and Effect 

Citation or 

MRID / 

Status 

Acute Toxicity 

Classification 

Rat 

(Rattus 

norvegicus) 

TGAI 

3 generation 

reproduction 

NOAEL/ 

LOAEL 

36/112 mg/kg/day (decreased offspring body 

weight, 90% of control) 

00103304/ 

USEPA 2004c NA 

Rat 

(Rattus 

norvegicus) 

TGAI 

2 year 

NOAEL/ 

LOAEL 

7.65/25.15 mg/kg/day (body weight 92% of 

control) 

25.15/80.8 mg/kg/day (Body weight was 59-

89% of control, and increased incidence of small 

testes, enlarged and granular kidneys, opaque, 

cloudy ulcerated eyes, and skin nodules and 

masses observed. The effects were dose 

related.) 

00103305/ 

USEPA 2004c NA 

Birds**

Bobwhite 

Quail (Colinus 

virginianus) 

TGAI 

Highest 

Dose Tested 2000 mg/kg-bw (no mortality) 00121686/ Acceptable 

Practically 

Nontoxic 

Bobwhite 

Quail (Colinus 

virginianus) 

TGAI 

8-day 

Highest 

Conc. Tested 

4390 mg/kg-diet (no mortality) 

00121687/ 

Acceptable NA 

Terrestrial Invertebrates 

Honey Bee 

(Apis 

mellifera)

TEP 33.3 

Highest 

Dose Tested 

362.58 μg/bee 

(no mortality) 

00103295/ 

Acceptable 

Practically 

Nontoxic 

Earthworm 

(Eisenia fetida) 

TGAI 

14-day 

Highest 

Dose Tested 

102.6 mg/kg (no mortality attributed to 

treatment) 

00121692/ 

Supplemental NA 

TGAI=technical grade active ingredient; TEP=typical end use product; LD50 = median lethal dose; NOAEL=no 

observable adverse effect level; a.i. active ingredient; NA = not applicable 

* Data in this table may be used in the risk assessment, but it will not necessarily be used to calculate risk quotients. 

**Birds represent surrogates for terrestrial-phase amphibians and reptiles.

4.3. Incident Database Review 

A preliminary review of the Ecological Incident Information System (EIIS) maintained by the 

Agency’s Office of Pesticide Programs (OPP) indicates a total of 12 reported ecological 

incidents associated with the use of fluridone occurred. Nine incidents were reported for aquatic 

animals and three are reported for plants. All incidents were reported between 2000 and 2005. 

Seven of the incidents were associated with registered uses of fluridone, three were associated 

with uses where it was undetermined if the use was a registered use, and one incident was 

associated with a misuse. The certainty that the incidents were associated with fluridone 

exposure was considered possible for two incidents and probable for nine incidents. One 

incident was reported where fluridone was a contaminant in another pesticide formulation 

(I020064-001). This incident was not included in the table. The incident data that are available 
19 of 80

indicate that exposure pathways are complete and that exposure levels are sufficient to result in 

field-observable effects in fish, especially when a liquid formulation is used. The maximum use 

rate (0.150 mg/L) is approximately 10-100 times lower than the acute toxicity values observed in 

aquatic toxicity studies on fish (1.8 - >12.3 mg/L). We speculate that the incidents could be 

explained by the following. 

• The submitted studies on acute toxicity to fish are supplemental due to the inability to 

identify the exposure concentration. It is possible the true exposure concentration is less than 

that reported in the studies. 

• Variation in the sensitivity of fish to fluridone is expected in the natural environment due to a 

number of factors including interspecies and intraspecies variation. 

• Many of the incidents were observed for liquid formulations. The concentration of fluridone 

is higher in a localized area when it is first applied and before it is distributed throughout the 

water body. This higher concentration may be more pronounced for liquid applications than 

for the slow release pellet formulations. The observed incidents could be due to fish being 

exposed to fluridone before it is evenly distributed throughout the water column. 

Table 4-3. Summary of Incidents Reported in the Ecological Incident Information System 

(EIIS) for Fluridone 

Incident ID 

Source 

Formulation/ 

Application 

Method 

Use 

Site 

Legality/ 

Certainty 

Month/

Year 

State Total Magnitude 

I014700-001/ 

CA Dept. of 

Fish & Game 

Sonar/ 

EC/ 

NR 

Lake Registered Use/ 

Possible 

09/ 

2003 

CA Over 6 threadfin shad were found dead 

near the time of fluridone use to control 

hydrilla. Fluridone was measured in the 

gill of fish. 

I0013560-

001/ 

SePRO 

Sonar AS/ 

FC/ 

NR 

NR Misuse 

1qt/acre/ 

Probable 

09/ 

2002 

IN 50-100 bluegill sunfish and one bass were 

found dead 5 days after fluridone 

application. 

I016555-002/ 

SePRO 

Sonar/ 

NR/ 

Spray 

Pond Undetermined/ 

Probable 

05/ 

2005 

TX Applied to pond by homeowner using 

hand pump sprayer. Fish died 3 weeks 

later. 10 catfish, 8-10 bass, and 1 grass 

carp died. 

I016555-009/ 

SePRO 

Sonar/ 

NR/ 

NR 

Pond Undetermined/ 

Probable 

06/ 

2005 

OH Over 500 fish died two days after 

fluridone treatment 

I016555-010/ 

SePRO 

Sonar/ 

NR/ 

NR 

Pond Registered Use/ 

Probable 

06/ 

2005 

NC 2 carp and bass died 16 days after 

fluridone treatment 

I016846-004/ 

SePRO 

Sonar/ 

EC/ 

Direct App. 

Pond Registered Use/ 

Probable 

07/ 

2005 

 300 sunfish, 30 catfish, and 50 largemouth 

bass died 2 days after fluridone 

application 

I016846-006/ 

SePRO 

Avast/ 

SC/ 

Injection 

Pond Registered Use/ 

Probable 

08/ 

2005 

TX 350 tilapia died one day after fluridone 

treatment at a target concentration of 50 

ppb. Bass, catfish, and other species were 

not affected. 

I017148-002/ 

SePRO 

Sonar AS/ 

FC/ 

Hand sprayer 

Pond Registered Use/ 

Probable 

10/ 

2005 

KY 100 catfish, 50 bass, and 50 bluegill 

sunfish died after treatment of pond at a 

target concentration of 60 ppb. 
20 of 80

Incident ID 

Source 

Formulation/ 

Application 

Method 

Use 

Site 

Legality/ 

Certainty 

Month/

Year 

State Total Magnitude 

I017148-003/ 

SePRO 

Sonar AS/ 

FC/ 

Spray 

Pond Registered Use/ 

Probable 

10/ 

2005 

WV 100 bluegill, 40 bass, 25 catfish, and 6 

grass carp died 3-5 days after treatment 

with fluridone. 

I011930-001/ 

SePRO 

Sonar AS/ 

NR/ 

NR 

Pond Undetermined/ 

Probable 

10/ 

2000 

NC A one acre pond was treated with 

fluridone in October 2000. The following 

March pond water was used to irrigate 

strawberries with no adverse effects 

observed. In June, pond water was used to 

irrigate 2 acres of tomatoes and damage 

was reported. 

I016846-002/ 

SePRO 

Sonar/ 

Liquid & 

Pellet/ 

NR 

Pond Registered Use/ 

Possible 

07/ 

2005 

OH Damage to a willow tree was reported by 

homeowner who treated pond every year 

with SONAR for many years. 

NR=not reported, Dept.=Department; App.= application; EC=emulsifiable concentrate; SC=soluble concentrate; FC 

= flowable concentrate 

4.4. Ecosystems Potentially at Risk 

The ecosystems at risk are often extensive in scope; therefore, it may not be possible to identify 

specific ecosystems during the development of a nation-wide ecological risk assessment. 

However, in general terms, terrestrial ecosystems potentially at risk could include the areas that 

are immediately adjacent to treated water that may receive drift or runoff during flooding. Areas 

adjacent to the treated water could include cultivated fields, fencerows and hedgerows, 

meadows, fallow fields or grasslands, woodlands, riparian habitats and other uncultivated areas. 

Also, areas that are irrigated with treated water may also be at risk. 

Aquatic ecosystems potentially at risk include treated water bodies and water bodies adjacent to 

or down stream from, the treated water and could include impounded bodies such as ponds, lakes 

and reservoirs, or flowing waterways such as streams or rivers. For uses in coastal areas, aquatic 

habitat also includes marine ecosystems, including estuaries. 

5. Assessment Endpoints 

Assessment endpoints are defined as “explicit expressions of the actual environmental value that 

is to be protected” (USEPA 1998). Selection of the assessment endpoints is based on valued 

entities (e.g., fish, birds), the ecosystems potentially at risk (e.g., waterbodies, riparian 

vegetation, and upland habitats), the migration pathways of fluridone (e.g., runoff, spray drift, 

etc.), and the routes by which ecological receptors are exposed to fluridone (e.g., direct contact, 

etc.). 

Assessment endpoints for fluridone include direct toxic effects on the survival, reproduction, and 

growth of the receptors, as well as indirect effects, such as reduction of the prey base or 

modification of habitat. Each assessment endpoint requires one or more “measures of ecological 

effect,” defined as changes in the attributes of an assessment endpoint or changes in a surrogate 

entity or attribute in response to exposure to a pesticide. Specific measures of ecological effect 
21 of 80

are generally evaluated based on acute and chronic toxicity information from registrantsubmitted guideline tests that are performed on a limited number of organisms. Additional 

ecological effects data from the open literature will also be considered.

6. Conceptual Model 

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically 

significant concentrations. An exposure pathway is the means by which a pesticide moves in the 

environment from a source to an ecological receptor. For an ecological pathway to be complete, 

it must have a source, a release mechanism, an environmental transport medium, a point of 

exposure for ecological receptors, and a feasible route of exposure. 

The conceptual model for fluridone provides a written description and visual representation of 

the predicted relationships between fluridone, potential routes of exposure, and the predicted 

effects for the assessment endpoint. A conceptual model consists of two major components: risk 

hypothesis and a conceptual diagram (USEPA 1998). 

6.1. Risk Hypothesis 

A risk hypothesis describes the predicted relationship among the stressor, exposure, and 

assessment endpoint response along with the rationale for their selection. For fluridone, the 

following overall ecological risk hypothesis is being employed for this ecological risk 

assessment: 

Based on the application methods, mode of action, fate and transport, and the sensitivity 

of non-target aquatic and terrestrial species, fluridone and its degradates, NMF and 3-

trifluoromethyl benzoic acid, have the potential to reduce survival, reproduction, and/or 

growth in non-target terrestrial and aquatic organisms when used in accordance with the 

current label. These non-target organisms include federally listed threatened and 

endangered species as well as non-listed species. 

The specific exposure routes quantitatively evaluated include, water concentrations, spray drift, 

drinking water, and irrigation water. The following hypotheses reflect these exposure pathways. 

• Fluridone, NMF, and 3-trifluoromethyl benzoic acid concentrations in water have the 

potential to reduce survival, reproduction, and/or growth of aquatic vertebrates, 

invertebrates, and plants. 

• Fluridone, NMF, and 3-trifluormethyl benzoic acid residues on plants and other 

dietary surfaces deposited with spray drift have the potential to reduce survival, 

reproduction, and/or growth of terrestrial organisms such as birds, mammals, 

invertebrates, and plants. 

• When water treated with fluridone is used as irrigation water, residues of fluridone, 

NMF, and 3-trifluoromethyl benzoic acid have the potential to reduce survival, 

reproduction, and/or growth of terrestrial organisms such as birds, mammals, 

invertebrates, and plants. 
22 of 80

• Survival, reproduction, and/or growth may be reduced in birds, mammals, and 

amphibians exposed to fluridone, NMF, and 3-trifluoromethyl benzoic acid in 

drinking water. 

6.2. Conceptual Diagram 

The environmental fate properties of fluridone indicate that runoff, spray drift, volatilization and 

direct spray represent potential transport mechanisms of fluridone to aquatic and terrestrial 

habitats where non-target organism may be exposed. These transport mechanisms (i.e., sources) 

are depicted in the conceptual models below (Figure 6-1 and Figure 6-2) along with the receptors 

of concern and the potential attribute changes in the receptors due to exposures of fluridone. 

Fluridone will enter the aquatic environment via direct application. Aquatic organisms in water 

will be exposed to fluridone in both the water column and in sediment. The open literature KOC

values indicate that fluridone concentrations in sediment could be a relevant exposure pathway 

(BLM 2005). Terrestrial organisms that drink treated water will also be exposed. Treated water 

used as irrigation water may result on residues on plants and dietary items for other terrestrial 

organisms. Finally, spray drift that may occur during treatment of water may result in residues 

on plants and on dietary items for birds and mammals. 

Aquatic and terrestrial exposure to NMF and 3-trifluormethyl benzoic acid may occur with the 

degradation of fluridone over time. The concentration may be prolonged as fluridone 

concentrations will be maintained and will provide a continuous source of degradates. 
23 of 80

 

Figure 6-1. Conceptual Model Depicting Exposure Pathways and Potential Risks to 

Aquatic Organisms from the Use of Fluridone to Control Aquatic Vegetation. Dashed lines 

indicate routes of exposure considered of lower importance for fluridone.

Fluridone, NMF, and 3-trifluoromethyl benzoic 

acid 

Fluridone 

Applied to Water 

as liquid or pellet 

Sediment/ 

Suspended 

Solids 

Plant Matter Water Column 

Aquatic Vertebrates 

and Invertebrates 

Nonvascular Plants 

Vascular Plants 

Aquatic Vertebrates 

and Invertebrates 

Source/Transport 

Pathways 

Source/Exposure 

Media 

Exposure 

Receptors 

Reduced Survival, 

Growth, or 

Reproduction 

Reduced Survival, 

Growth, or 

Reproduction

Attribute 

Stressors 

Reduced Survival, 

Growth, or 

Reproduction 

Uptake/Gills or 

integument 

Uptake/Gills or 

Integument

Uptake/cell, 

roots, leaves Ingestion
24 of 80

Figure 6-2. Conceptual Model Depicting Exposure Pathways and Potential Risks to 

Terrestrial Organisms from the Use of Fluridone to Control Aquatic Vegetation. Dashed 

lines indicate routes of exposure considered of lower importance for fluridone.

7. Analysis Plan 

In order to address the risk hypothesis, the potential for adverse effects on the environment is 

estimated. The use, environmental fate, and ecological effects of fluridone are characterized and 

integrated to assess the risks. This is accomplished using a risk quotient (ratio of exposure 

concentration to effects concentration) approach. Although risk is often defined as the likelihood 

and magnitude of adverse ecological effects, the risk quotient-based approach does not provide a 

quantitative estimate of likelihood and/or magnitude of an adverse effect. However, as outlined 

in the Overview Document (USEPA 2004d), the likelihood of effects to individual organisms 

from particular uses of fluridone is estimated using the probit dose-response slope and either the 

level of concern (discussed below) or the actual calculated risk quotient value. 

Residues in Water 

Terrestrial Vertebrates 

and Invertebrates 

Terrestrial Plants 

Source/Transport 

Pathways

Source/Exposure 

Media

Exposure 

Receptors 

Attribute 

Direct Application of 

Fluridone as Liquid or Pellet 

Stressors 

Ingestion Direct Contact/Root 

Uptake Ingestion on 

dietary items 

Individual organisms 

Reduced survival 

Reduced growth 

Reduced reproduction

Food chain

Reduction in primary 

productivity 

Reduction in prey 

Shift in community composition 

Volatization and 

Redeposition 

Leaching/ 

Percolation Groundwater 

Habitat integrity 

Reduction in primary productivity 

Reduced cover 

Community change 

Modification of PCEs related to 

habitat 

Residues in Irrigation Water or Spray Drift To 

Terrestrial Environment 

Fluridone, NMF, 3-trifluoremethyl benzoic acid 
25 of 80

This analysis plan will be revisited and may be revised depending upon the data available in the 

open literature and the information submitted by the public in response to the opening of the 

Registration Review docket. 

7.1. Stressors of Concern 

As discussed above, fluridone degradates measured in photolysis studies at greater than 10% 

applied equivalents include NMF, 3-trifluoromethyl benzoic acid, and benzoic acid. Benzoic 

acid will degrade rapidly in the environment and the toxicity is less than that of the parent 

(HSDB 2005). Based on previous assessments (e.g., USEPA 2004b), NMF is a degradate of 

toxicological concern. Additionally, ECOSAR data indicates that 3-trifluromethyl benzoic acid 

has a similar toxicity to fluridone to aquatic organisms (Appendix D). Therefore, the focus of 

the assessment is expected to be the parent, fluridone, NMF, and 3-trifluoromethyl benzoic acid. 

However, the Agency will review all available current degradate ecotoxicity data to identify any 

additional stressors of concern for the assessment. 

In its ecological risk assessments, the Agency does not routinely include an evaluation of 

mixtures of active ingredients, either those mixtures of multiple active ingredients in product 

formulations or those in the applicator’s tank. In the case of the product formulations of active 

ingredients (that is, a registered product containing more than one active ingredient), each active 

ingredient is subject to an individual risk assessment for regulatory decision regarding the active 

ingredient on a particular use site. If effects data are available for a formulated product 

containing more than one active ingredient, the data may be used qualitatively or quantitatively 

in accordance with the Agency’s Overview Document and the Services’ Evaluation 

Memorandum (USEPA 2004d; U.S. FWS/NMFS 2004). 

Available toxicity data for environmental mixtures of fluridone with other pesticides will be 

presented as part of the ecological risk assessment.4

 It is expected that the toxic effect of 

fluridone, in combination with other pesticides used in the environment, is likely to be a function 

of many factors including but not necessarily limited to: (1) the exposed species, (2) the cocontaminants in the mixture, (3) the ratio of fluridone and co-contaminant concentrations, (4) 

differences in the pattern and duration of exposure among contaminants, and (5) the differential 

effects of other physical/chemical characteristics of the receiving waters (e.g. organic matter 

present in sediment and suspended water). Quantitatively predicting the combined effects of all 

these variables on mixture toxicity to any given taxa with confidence is beyond the capabilities 

of the available data and methodologies. However, a qualitative discussion of implications of the 

available pesticide mixture effects data on the confidence of risk assessment conclusions will be 

addressed as part of the uncertainty analysis. 

7.2. Measures of Exposure 

In order to estimate risks of fluridone exposures in aquatic and terrestrial environments, all 

exposure modeling and resulting risk conclusions will be made based on maximum application 

rates for fluridone. Measures of exposure are based on aquatic and terrestrial models that predict 

estimated environmental concentrations of fluridone using maximum labeled application rates 

 

4

 No data on mixtures with fluridone, other than testing on formulations, have been found. 
26 of 80

and methods, as well as any mitigation measures specifically indicated on the label (e.g. spray 

drift buffers). Aquatic exposures will be estimated using data from the aquatic dissipation 

studies and other environmental fate studies. The model used to predict terrestrial EECs on food 

items is T-REX. The model used to derive EECs relevant to terrestrial and wetland plants is 

TerrPlant. A standard model is not available to estimate exposure to birds and mammals to 

residues in drinking water or to terrestrial organisms due to exposure to residues of fluridone in 

irrigation water; however, a preliminary method was used in a recent ecological risk assessment 

(USEPA 2008a). 

7.2.1 Aquatic Organisms 

A standard model is not available to estimate residues of fluridone applied directly to water over 

time. Exposure will be estimated using data from the aquatic dissipation studies. The values 

estimated using the dissipation studies may be bracketed using aerobic aquatic degradation rates 

and photolysis degradation rates. As the instructions indicate that concentrations in water must 

be maintained over time and there is no limit on the application interval, the target application 

rate will be used as a starting point for exposure estimates. Total toxic residues of fluridone and 

3-trifluoromethyl benzoic acid will be estimated. Additionally, data on NMF will be evaluated 

to determine whether it is appropriate to estimate exposure to total toxic residues or to NMF 

alone. Although NMF is believed to be toxic, is not expected to hydrolyze since amides 

hydrolyze very slowly at environmental conditions. Since NMF’s vapor pressure is 0.25 mm 

Hg, it appears that volatility may be a dissipation route. 

7.2.2 Terrestrial Organisms 

Terrestrial wildlife may be exposed to fluridone via the following pathways: 1) ingestion of 

pellets from aerial application to water; 2) drinking treated water; and 3) consumption of 

fluridone on food items via spray drift applications. Terrestrial exposure to NMF and 3-

trifluoromethyl benzoic acid may also be estimated. 

7.2.2.a Residues on Terrestrial Invertebrates and Dietary Items of Terrestrial 

Organisms 

Exposure estimates for terrestrial animals assumed to be in the target area or in an area exposed 

to spray drift are derived using the (Terrestrial Residue EXposure model) T-REX model. This 

model incorporates the Kenaga nomograph, as modified by Fletcher et al. (1994), which is based 

on a large set of actual field residue data. The upper limit values from the nomograph represent 

the 95th percentile of residue values from actual field measurements (Hoerger and Kenaga 1972). 

The Fletcher et al. (1994) modifications to the Kenaga nomograph are based on measured field 

residues from 249 published research papers, including information on 118 species of plants, 121 

pesticides, and 17 chemical classes. For aerial applications of pellet or granular formulations, an 

estimation of loadings of pesticide per unit area is calculated using the T-REX model. No drift is 

assumed for ground applications of pellet and granular formulations. For broadcast spray 

applications, the T-REX model is also used to predict dietary exposure of birds and mammals to 

fluridone residues on foliar surfaces and insects using the Kenaga nomogram as modified by 

Fletcher (Hoerger and Kenaga 1972; Fletcher et al. 1994). The residues estimates on insects are 

also used to estimate terrestrial exposure to insects. 
27 of 80

7.2.2.b Drinking Water Exposure of Birds and Mammals 

A model to estimate exposure of birds and mammals to residues in drinking water is not 

currently available. A preliminary method to estimate exposure to residues in drinking water has 

been used in previous risk assessments and is based on body weight-specific consumption rates 

and the concentration of fluridone in water bodies (USEPA 1993; USEPA 1998; USEPA 2008b). 

This preliminary approach may be used to estimate exposure of terrestrial birds and mammals to 

fluridone, NMF, and 3-trifluoromethyl benzoic acid in drinking water. Drinking water 

concentrations will be based on those predicted for aquatic exposure. 

7.2.2.c Spray Drift Residues on Terrestrial Plants 

Estimated Environmental Concentrations (EECs) for terrestrial plants inhabiting dry and wetland 

areas are derived using TerrPlant. This model uses estimates of pesticides in runoff and in spray 

drift to calculate EECs. EECs are based upon solubility, application rate, and minimum 

incorporation depth. 

7.2.2.d Residues in Water Used for Irrigation 

A model to estimate exposure of terrestrial organisms to residues of fluridone in irrigation water 

is not currently available; however, a preliminary method was used in a recent ecological risk 

assessment (USEPA 2008a). This method will be evaluated to determine if it is appropriate to 

assess risk of residues of fluridone in irrigation water to terrestrial organisms. 

7.2.2.e Terrestrial Exposure to NMF and 3-trifluoromethyl benzoic acid 

Terrestrial exposure to NMF and 3-trifluoromethyl benzoic acid will be estimated if exposure is 

likely to be high enough to elicit toxicity. Terrestrial exposure to degradates will be estimated 

using the same models used to estimate exposure to the parent compound; however, the amount 

of degradates will be estimated based on the amount observed in the environmental fate studies. 

7.3. Measures of Effect 

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

Data are obtained from registrant-submitted studies or from literature studies identified by 

ECOTOX. The ECOTOX database (USEPA 2009b) provides more ecological effects data in an 

attempt to bridge existing data gaps. ECOTOX is a source for locating single chemical toxicity 

data and potential chemical mixture toxicity data for aquatic life, terrestrial plants, and wildlife. 

ECOTOX was created and is maintained by the USEPA, Office of Research and Development, 

and the National Health and Environmental Effects Research Laboratory's Mid-Continent 

Ecology Division. 

Information on the potential effects of fluridone on non-target animals is also collected from the 

Ecological Incident Information System (EIIS).5

 The EIIS is a database containing adverse 

effect (typically mortality) reports on non-target organisms where such effects have been 

associated with the use of pesticides. 

 

5

 http://www.epa.gov/oppefed1/general/databasesdescription.htm#eiis 
28 of 80

Where available, sublethal effects observed in both registrant-submitted and open literature 

studies will be evaluated qualitatively. Such effects may include behavioral changes (e.g., 

lethargy and changes in coloration). Quantitative assessments of risks, though, are limited to 

those endpoints that can be directly linked to the Agency’s assessment endpoints of impaired 

survival, growth, and reproduction. 

The acute measures of effect used for animals in this assessment are the LD50, LC50 and EC50. 

LD stands for "Lethal Dose", and LD50 is the amount of a material, given all at once, that is 

estimated to cause the death of 50% of the test organisms. LC stands for “Lethal Concentration” 

and LC50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. 

EC stands for “Effective Concentration” and the EC50 is the concentration of a chemical that is 

estimated to produce a specific effect in 50% of the test organisms. Endpoints for chronic 

measures of exposure for listed and non-listed animals are the NOAEL/NOAEC and NOEC. 

NOAEL stands for “No Observed-Adverse-Effect-Level” and refers to the highest tested dose of 

a substance that has been reported to have no harmful (adverse) effects on test organisms. The 

NOAEC (i.e., “No-Observed-Adverse-Effect-Concentration”) is the highest test concentration at 

which none of the observed effects were statistically different from the control. The NOEC is 

the No-Observed-Effects-Concentration. For non-listed plants, only acute exposures are 

assessed (i.e., EC25 for terrestrial plants and EC50 for aquatic plants); for listed plants either the 

NOAEC or EC05 is used. 

In the absence of taxon-specific data, the assessment of risk for direct effects to non-target 

organisms makes the assumption that toxicity of fluridone to birds is similar to terrestrial-phase 

amphibians and reptiles. The same assumption is made for fish and aquatic-phase amphibians. 

In the absence of data for either acute or chronic effects, the conservative assumption will be to 

presume that fluridone is toxic. 

Fluridone can form NMF and 3-trifluormethyl benzoic acid with exposure to light (MRID 

00103326). NMF may be more toxic to receptors than parent fluridone (USEPA 2004b, HSDB 

2002) and 3-trifluormethyl benzoic acid may have a similar toxicity to fluridone (Appendix D). 

Open literature data for NMF and 3-trifluormethyl benzoic acid will be evaluated for possible 

use in the risk assessment. If no data are available specific to NMF and 3-trifluoromethyl 

benzoic acid, data on chemicals with a similar structure may be used to evaluate risk. 

7.4. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects characterization to 

determine the potential ecological risk from the use of fluridone as an aquatic herbicide and the 

likelihood of direct and indirect effects to non-target organisms in aquatic and terrestrial habitats. 

The exposure and toxicity effects data are integrated in order to evaluate the risks of adverse 

ecological effects on non-target species. For the assessment of fluridone risks, the risk quotient 

(RQ) method is used to compare exposure and measured toxicity values. EECs are divided by 

acute and chronic toxicity values. The resulting RQs are then compared to the Agency’s Levels 

of Concern (LOCs) (USEPA 2004d). These criteria are used to indicate when fluridone’s uses, 

as directed on the label, have the potential to cause adverse direct or indirect effects to non-target 

organisms. In addition, incident data from the EIIS will be considered as part of the risk 

characterization. 
29 of 80

7.5. Deterministic and Probabilistic Assessment Methods 

The quantitative assessment of risk will primarily depend on the deterministic point-estimate 

based approach described in the risk assessment. An effort will be made to further qualitatively 

describe risk using probabilistic tools that the Agency has developed. These tools have been 

reviewed by FIFRA Scientific Advisory Panels (http://www.epa.gov/scipoly/sap/index.htm) and 

have been deemed as appropriate means of refining assessments where deterministic approaches 

have identified risks.

7.6. Endangered Species Assessments 

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

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

registered uses of fluridone. This assessment will be conducted in accordance with the Overview 

Document (USEPA 2004d), provisions of the ESA, and the Services’ Endangered Species 

Consultation Handbook (U.S. FWS/NMFS 1998). 

The assessment of effects associated with the registration of fluridone is based on an action area. 

The action area is considered to be the area directly or indirectly affected by the federal action, as 

indicated by the exceedance of Agency Levels of Concern (LOCs) used to evaluate direct or 

indirect effects. The Agency’s approach to defining the action area under the provisions of the 

Overview Document (USEPA 2004d) considers the results of the risk assessment process to 

establish boundaries for that action area with the understanding that exposures below the 

Agency’s defined LOCs constitute a no-effect threshold. For the purposes of this assessment, 

attention will be focused on the footprint of the action (i.e., the area where fluridone application 

occurs), plus all areas where offsite transport (i.e., spray drift, runoff, etc.) may result in potential 

exposure that exceeds the Agency’s LOCs. Specific measures of ecological effect that define the 

action area for listed species include any direct and indirect effects and/or potential modification 

of its critical habitat, including reduction in survival, growth, and reproduction as well as the full 

suite of sublethal effects available in the effects literature. Therefore, the action area extends to a 

point where environmental exposures are below any measured lethal or sublethal effect threshold 

for any biological entity at the whole organism, organ, tissue, and cellular level of organization. 

In situations where it is not possible to determine the threshold for an observed effect, the action 

area is not spatially limited and is assumed to be the entire United States. 

7.7. Drinking Water Assessment 

A drinking water assessment will be conducted to support future human health risk assessments 

of fluridone. The drinking water assessment will incorporate model estimates of fluridone in 

surface water. Since no PRZM scenario is available for aquatic pesticides, and in order to assess 

potential exposures for aquatic herbicides, a first approximation of a drinking water EEC was 

modeled assuming direct application to the index reservoir. EFED developed an approach using 

a simple spreadsheet model that incorporates degradation based on an acceptable aerobic aquatic 

metabolism, photolysis, hydrolysis studies, and flow through the Index Reservoir. 

This scenario includes the assumption that fluridone or NMF is uniformly applied to the index 

reservoir with a surface area of 5.3 hectares and a volume of 144,000,000 liters. In this model, 
30 of 80

the 90 day average and annual mean concentrations were calculated assuming first-order 

dissipation from aerobic aquatic degradation, aquatic photolysis, hydrolysis, and reservoir flowthrough. A conservative approach will be used that accounts for possible reapplication of 

fluridone to the water body. The label indicates that fluridone should be reapplied if 

concentrations fall below an effective level but does not provide a minimum application interval.

The scenario evaluated with the simple spreadsheet model approach will rely on an interpretation 

of the label for aquatic weed control requiring a target rate for fluridone use based on target 

concentration and not application rate. In order to account for this interpretation it will be 

assumed that fluridone will be applied at a rate to meet the target concentration. This assumption 

is applicable across all water bodies since the target rate is based on a rate shown in the Master 

Label and is independent of water body geometry/volume. This scenario will include the 

assumption of uniform application across the entire water body without any setbacks from 

drinking water intakes. 

7.8. Preliminary Identification of Data Gaps 

7.8.1 Fate 

All environmental fate data requirements have been satisfied for the use of fluridone as an 

aquatic herbicide in lakes and ponds. Table 7-1 summarizes the submitted environmental fate 

studies and the submitted environmental chemistry methods are discussed below. 

Table 7-1. Summary of Environmental Fate Studies 

Guideline Description MRID Classification Data Gap? 

835.2120 Hydrolysis MRID# 

30257 

Acceptable No 

835.2240 Photodegradation in water MRID# 

103326 

Acceptable No 

835.4100 Aerobic soil metabolism MRID# 

135217 

Acceptable No 

835.4200 Anaerobic soil metabolism MRID# 

135217 

Acceptable No 

835.4300 Aerobic Aquatic Metabolism MRID# 

44154801 

Acceptable No 

835.4400 Anaerobic Aquatic 

Metabolism 

MRID# 

1033327 

Acceptable No 

835.1230 

835.1240 

 Leaching and adsorption/ 

desorption 

MRID# 

44138501 

Acceptable No 

835.6200 Aquatic (Sediment) Field 

Dissipation 

MRID# 

162339 

Acceptable No 

165-4 Bioaccumulation in Fish MRID# 

162775 

Acceptable No 
31 of 80

There are four possible environmental chemistry methods available for fluridone and NMF. The 

paper “Determination of Fluridone in Soil and Hydrosoil by High Pressure Liquid 

Chromatography” prepared by Lilly Research Laboratories (MRID 159966 – No independent lab 

verification), “Residues of Fluridone and Its Major Metabolites in Crayfish from Ponds Treated 

with the Aquatic Herbicide Sonar” prepared by Lully Research laboratories (MRID 162775 – No 

independent lab verification), “Determination of Fluridone in Water by High –performance 

Liquid Chromatography Following Extraction with Sep-Pak C18 Cartridges” prepared by Lilly 

Research Laboratories (MRID 40485901- Independent Lab Verification done by Elanco 

Products Co. Lab # 591416), and “Gas Chromatography Determination of Residue Levels of Nmethylformamide in Water” prepared by Lilly Research Laboratories (MRID 40485902- 

Independent Lab Verification done by Elanco Products Co. Lab # 591416). 

 

The MRIDs 159966 and 162775 need to be validated. EFED does not recommend a validated 

soil method be requested at this time; however, if a state requests a validated method or a risk 

concern arises due to potential exposure to residues in soil or sediment, a validated method may 

be requested at that time. The other two methods, MRIDs 40485901 and 40485902, have yet to 

be reviewed. Therefore, they may be acceptable ECMs for water. 

7.8.2 Effects 

Although many submissions have been made to provide data on the effects of fluridone to 

aquatic and terrestrial organisms, several data gaps still exist. Table 7-2 and Table 7-3 

summarize the data submitted and data needed to assess the ecological risk of the use of 

fluridone to control aquatic vegetation. All studies should be conducted at high enough 

concentrations to predict toxicity at predicted exposure levels. Data gaps are listed below. 

Terrestrial Organisms 

• avian acute oral toxicity (Guideline 850.2100) study with a passerine species 

• avian reproduction studies (Guideline 850.2300) with an upland game bird and waterfowl 

with the technical grade active ingredient (TGAI) 

• honeybee acute contact toxicity (Guideline 850.3020) test using the TGAI 

• terrestrial plants seedling emergence and vegetative vigor studies (Guideline 850.4100 

and 850.4150) using EPs representative if current TEPs 

Aquatic Organisms 

• acute toxicity to freshwater fish (Guideline 850.1075) for one coldwater and one 

warmwater species using EPs representative if current TEPs 

• estuarine/marine acute toxicity to fish (Guideline 850.1075) using the TGAI and EP 

representative of current TEPs, 

• freshwater invertebrate acute toxicity (Guideline 850.1010) using EPs representative if 

current TEPs 

• estuarine/marine invertebrate acute toxicity (Guideline 850.1025) examining oyster shell 

deposition with TGAI and using EPs representative if current TEPs 

• freshwater invertebrate full lifecycle study (850.1300) with the TGAI 
32 of 80

• estuarine/marine fish full life cycle (Guideline 850.1500) 

• whole sediment chronic invertebrate freshwater 

• aquatic plant growth studies (Guideline 850.4400 and 850.5400) using EPs representative 

if current TEPs 

Studies for the Degradate, NMF 

• avian acute oral toxicity (Guideline 850.2100) 

• avian reproduction study (Guideline 850.2300) 

• acute toxicity to freshwater fish (Guideline 850.1075) for one coldwater and one 

warmwater species 

• freshwater invertebrate acute toxicity (Guideline 850.1010) 

• Freshwater invertebrate life cycle: Daphnid (Guideline 850.1075) 

• Freshwater Fish Early-Life Stage and Estuarine/Marine Early-Life Stage (Guideline 

850.1400) 

Studies for the Degradate, 3-trifluromethyl benzoic acid 

• avian acute oral toxicity (Guideline 850.2100) 

• avian reproduction study (Guideline 850.2300) 

An estuarine marine invertebrate lifecycle study (Guideline 850.1300) may be needed if the 

acute LC50 < 1 mg/L or the EEC is ≥0.01 of acute LC50 (USEPA 2007b). 

Data gaps for the parent compound are discussed below and summarized in Table 7-2 and Table 

7-3. Data gaps for the degradate, NMF and 3-trifluoromethyl benzoic acid, are not included in 

Table 7-2 and Table 7-3.

Table 7-2. Available Ecological Effects Data for Terrestrial Animals Exposed to Fluridone 

Guideline 

Description 

Species TGAI 

or TEP 

MRID/ 

Accession 

Classification Data 

Gap? 

Comments 

850.2100 

Avian oral 

toxicity1

Bobwhite 

Quail 

TGAI 00121686 Acceptable Yes* 

Bobwhite 

Quail 

850.2200 TGAI 00121687 Acceptable 

Avian dietary 

toxicity2

Mallard Duck TGAI 00121687 Acceptable 

No 

*Avian acute oral toxicity data 

are not available for 

passerines, which are required 

under the new 40 CFR Part 

158. An acute oral toxicity 

study using passerines must be 

submitted to fulfill this data 

requirement. 
33 of 80

Guideline 

Description 

Species TGAI 

or TEP 

MRID/ 

Accession 

Classification Data 

Gap? 

Comments 

Bobwhite 

Quail 

850.2300 TGAI 00103293 Invalid 

Avian 

reproduction2

Mallard Duck TGAI 00103294 Invalid 

Yes** 

850.3020 

Honeybee 

acute contact 

toxicity3

Honeybee TEP 00103295 Acceptable Yes*** 

1 Data are required on one passerine species and either one waterfowl species or one upland game bird species 

2 Data are required on waterfowl and upland game bird species. 

3 Data using the TGAI are required to support all outdoor end-use product uses 

Table 7-3. Available Ecological Effects Data for Aquatic Animals Exposed to Fluridone 

Guideline Number 

Description 

Species TGAI/ 

TEP 

MRID/ 

Accession 

Classification Data 

Gap? 

Comments 

Rainbow 

Trout 

TGAI 00103297 Acceptable 

(6 studies) 

Supplemental 

(3 studies) 

Rainbow 

Trout 

EP 00103297 Acceptable 

Channel 

Catfish 

TGAI 00103297 Acceptable 

(1 study) 

Supplemental 

(9 studies) 

Channel 

Catfish 

EP 00103297 Supplemental 

Bluegill 

Sunfish 

TGAI 00103308 Supplemental 

Bluegill 

Sunfish 

EP 00103306 Supplemental 

Bluegill 

Sunfish 

EP 00103297 Acceptable 

Bluegill 

Sunfish 

TGAI 00121689 Invalid 

Bluegill 

Sunfish 

TGAI 00103297 Supplemental 

Rainbow 

Trout 

TGAI 00121690 Supplemental 

Rainbow 

Trout 

EP 00103307 Supplemental 

850.1075 

Freshwater fish – 

Acute toxicity 

Data needed for 1 

coldwaterspecies and 1 

warmwater species. Data 

needed for TEP if applied 

directly to water, 

maximum EEC≥0.5 LC50, 

or end product enhances 

toxicity 

Fathead 

Minnow 

TGAI 00103297 Supplementalqualitative1

Yes Data are needed on EPs that are 

representative of current TEPs. 

The registrant should provide 

information indicating whether 

studies examining toxicity to EPs 

are applicable to current products 

or submit studies examining 

exposure EPs that are 

representative of current TEPs for 

a coldwater and warmwater 

species. The tests should be 

conducted with a species that also 

have TGAI data available. 

 
34 of 80

Guideline Number 

Description 

Species TGAI/ 

TEP 

MRID/ 

Accession 

Classification Data 

Gap? 

Comments 

Fathead 

Minnow 

EP 00103297 Acceptable 

Chinook 

Salmon 

TGAI 46112001 Supplemental 

Sheepshead 

Minnow 

850.1075 TGAI 00108837 Supplemental 

Estuarine/Marine 

fish – 

Acute toxicity

Data needed for 1 

species. Data needed for 

TEP if applied directly to 

water, maximum 

EEC≥0.5 LC50, or end 

product enhances 

toxicity.

Sheepshead 

Minnow 

EP 00103316 Supplemental 

Yes Based on variability in the 

measured concentrations compared 

to nominal concentrations, the 

presence of precipitate and the test 

concentrations exceeding 

solubility, the true exposure 

concentration is not known in 

submitted tests. Studies examining 

the toxicity of the TGAI and TEP 

to E/M fish are needed. 

Waterflea TGAI 00103297 Acceptable1

Waterflea EP 00010329

7 

Acceptable 

Waterflea EP 00103296 Supplemental 

850.1010 

Freshwater 

invertebrates – 

Acute toxicity3

Crayfish TGAI 00162774 Supplemental 

No Data are needed on EPs that are 

representative of current TEPs. 

The registrant should provide 

information indicating whether 

studies examining toxicity to EPs 

are applicable to current TEPs or 

submit studies examining exposure 

to EPs that are representative of 

current TEPs. 

Midge TGAI 00103297 Supplemental1

Eastern 

oyster (shell 

deposition) 

TGAI 00103310 Supplemental 

Eastern 

oyster 

TGAI 00103311 Supplemental 

Eastern 

oyster (shell 

deposition) 

EP 00103314 Supplemental 

Eastern 

oyster 

EP 00103315 Supplemental 

Pink Shrimp TGAI 00112789 Acceptable2

Pink Shrimp EP 00103312 Supplemental2

Blue Crab TGAI 00108836 Supplemental 

850.1025, 850.1035, Yes 

850.1045, 850.1055 

Estuarine/Marine 

invertebrates – 

Acute toxicity4

Blue Crab EP 00103313 Supplemental 

Data are needed on oyster shell 

deposition for the TGAI and TEP 

because of variable results and due 

to variability in measured 

concentrations or the presence of 

precipitate in tests. 
35 of 80

Guideline Number 

Description 

Species TGAI/ 

TEP 

MRID/ 

Accession 

Classification Data 

Gap? 

Comments 

Waterflea TGAI 00103297 Supplemental1

Waterflea TGAI 00103297 Supplemental1

Waterflea EP 00103297 Supplemental1

850.1300 

Freshwater 

invertebrate – 

 life cycle test 

Data required for 1 

species. 

Midge EP 00103297 Supplemental1

Yes A full lifecycle study for one 

freshwater invertebrate study is 

needed. The exposure 

concentration of the submitted 

studies is not known because the 

concentration was not measured. 

Measured concentrations in studies 

conducted with these studies were 

sometimes very different from 

nominal concentrations. 

850.1350 

E/M invertebrate – 

Life Cycle5

No data submitted Pending May be needed if the acute LC50 < 

1 mg/L or the EEC is ≥0.01 of 

acute LC50.

850.1400 

Freshwater fish – 

early life stage test6

Chinnok 

Salmon 

TGAI 45915601 Acceptable No An ACR can be calculated using 

the acute value for an EP for the 

Fathead minnow and the full lifecycle study. 

850.1400 

E/M – 

early life stage test7

No data submitted 

Yes 

Data are needed because chronic 

exposure to E/M species may 

occur; however, these data will be 

available from the fish full life 

cycle study. 

850.1500 

Freshwater Fish – 

life cycle test8

Fathead 

Minnow 

TGAI 00103309 Acceptable No An ACR can be calculated using 

the acute value for an EP for the 

Fathead minnow and the full lifecycle study. 

850.1500 

E/M Fish – 

life cycle test9

No data submitted Yes Data are needed because chronic 

exposure to E/M species may 

occur and a reduced egg 

production was observed at the 

highest test concentration in the 

freshwater fish full lifecycle test 

(MRID 00103309). 

850.1735 

Whole sediment 

acute freshwater 

invertebrate10

No data submitted No The aerobic aquatic degradation 

half-life was greater than 10 days 

(MRID 44154801). No data are 

needed.

850.1740 

Whole sediment 

acute marine 

invertebrates11

No data submitted No No data are needed because direct 

application to the E/M 

environment is prohibited on the 

labels.
36 of 80

Guideline Number 

Description 

Species TGAI/ 

TEP 

MRID/ 

Accession 

Classification Data 

Gap? 

Comments 

Whole sediment 

chronic 

invertebrate 

freshwater and 

marine12

No data submitted Yes Data are needed for freshwater 

invertebrates because aerobic 

aquatic half-lives of fluridone 

(MRID 44154801) are greater than 

10 days and some KOC values are ≥

1000 L/kg (BLM 2005). Most 

reported KOC values ranged from 

270-6400 (BLM 2005). 

Abbreviations: E/M = estuarine/marine; TEP=typical end use product; EP= end use product; TGAI=technical grade 

active ingredient; 

1- The test was conducted by the U.S. Fish and Wildlife Service and a complete review has not been completed. 

2- Concentrations in solution were measured after filtering and showed reasonable recovery. 

3- Data needed for one species. Data needed for TEP if applied directly to water, maximum EEC≥0.5 LC50, or 

end product enhances toxicity 

4- Data required for one mollusk and invertebrate. Data needed for TEP if applied directly to water, maximum 

EEC≥0.5 LC50, or end product enhances toxicity. 

5- Data are required for one species when the chemical is applied directly to the E/M environment, acute LC50 < 1 

mg/L, or the EEC is ≥0.01 of acute LC50. 

6- Data on one species are needed on a species with acute data. 

7- Data are required for one species when the chemical is applied directly to the E/M environment, acute LC50 < 1 

mg/L, or the EEC is ≥0.01 of acute LC50. 

8- Data are required for one species when applied directly to water or if EEC is ≥0.1 of NOEL in fish early life 

stage, or if studies suggest reproduction physiology may be affected. 

9- Data are required for one species when applied directly to water or if EEC is ≥0.1 of NOEL in fish early life 

stage or if studies suggest reproduction physiology may be affected. 

10- Data are required when half-life of pesticide in sediment ≤ 10 days and 1) the Kd is ≥50 L/kg, 2) the KOC

≥1000 L/kg, or the KOW ≥1000. 

11- Data are required for one species for uses with direct application to E/M water. Data are required when halflife of pesticide in sediment ≤ 10 days and 1) the Kd is ≥50 L/kg, 2) the KOC ≥1000 L/kg, or the KOW ≥1000 

L/kg. 

12- Data required if EEC> 0.1 of acute LC50 and the half-life > 10 days and if any of the following exist: the log 

KOW ≥3 or the KOC≥1000 L/kg. Data required for E/M when applied directly to E/M environment. 

Avian Acute Oral Toxicity (Guideline 850.2100): Passerine Species and Upland Game Bird or 

Waterfowl 

Acceptable acute avian oral toxicity data were submitted for exposures of bobwhite quail to 

fluridone; however, data are not available for passerines, which are required under the new 40 

CFR Part 158 data requirements for conventional pesticides (72 FR 60934; USEPA 2007b). The 

new Part 158 data requirements specify that acute avian oral toxicity data be submitted for either 

a mallard duck or bobwhite quail AND a passerine species. EFED suggests that the Special 

Review and Reregistration Division (SRRD) request submission of a passerine study protocol for 

review by the Agency prior to initiation of this study. If oral acute toxicity data are not 

submitted for passerines, EFED will assume acute risk for passerine species. The highest dose 

tested should be high enough to evaluate risk at the predicted exposure. 

Additionally, estimated exposure using TREX (version 1.4.1, 10/9/2008) and the highest 

application rate (4.9 lbs a.i./A) with one application predicts a maximum exposure of 1339 

mg/kg-body weight (bw). The ratio of the EEC/LD50 of 2000 mg/kg-bw results in a ratio of 
37 of 80

0.93. As multiple applications may take place, predicted exposure may exceed the highest dose 

tested for birds. Without data to predict effects at the predicted exposure level, we may not be 

able to preclude risk for birds. 

Avian Reproduction Studies (Guideline 850.2300): Upland Game Bird and Waterfowl 

No acceptable avian reproduction studies are available to evaluate the reproductive and chronic 

toxicity of fluridone to birds. Birds may be exposed to fluridone via drinking water and on 

residues on food items. Without toxicity data for fluridone available to preclude chronic risk to 

birds, it is assumed that risk to birds may occur. 

Honeybee Acute Contact Toxicity (Guideline 850.3020) with TGAI 

The honeybee acute contact toxicity test was completed using the TEP and a dust carrier. The 

use of the dust could result in lower exposure to the bee than for a liquid because the dust 

particles may not be in dermal contact if the dust is caught in hairs. Fluridone does have 

registered products with liquid formulations and the available test could underestimate toxicity of 

a liquid formulation. Therefore, an acute contact toxicity study using the TGAI is needed to 

assess risk to bees. Without data to preclude risk to terrestrial invertebrates, risk will be 

presumed. 

Terrestrial Plants (Guideline 850.4100 and 850.4150) 

Toxicity data for terrestrial plants are not available. Based on the 40 CFR Part 158 data 

requirements, Tier II level non-target terrestrial plant data are required for all herbicides. In 

addition, the label indicates that irrigation of terrestrial plants with water containing fluridone 

could injure the irrigated vegetation at 10 ppb or 5 ppb (EPA Registration Number 61842-11). 

Therefore, this data gap must be filled, and non-target terrestrial plant data are required. In the 

absence of Tier II data, EFED will assume risk to terrestrial monocots and dicots.

Acute Toxicity to Freshwater Fish (Guideline 850.1075): Coldwater and Warmwater species 

using the TEP; 

Estuarine/marine Acute Toxicity to Fish (Guideline 850.1075) using the TGAI and TEP; and 

Freshwater Invertebrate Acute Toxicity (Guideline 850.1010) with the TEP; and 

Estuarine/marine Invertebrate Acute Toxicity (Guideline 850.1025) examining Oyster Shell 

Deposition with TGAI and TEP 

Quantitative data examining acute toxicity to freshwater fish and freshwater invertebrates 

exposed to an EP are available; however, it is not known if the studes were conducted on 

products that are representative of products currently registered. EFED recommends the 

registrant provide information on whether the available data are applicable to current products or 

conduct studies with EPs that are representative of current TEPs. Quantitative estuarine/marine 

fish, and estuarine/marine invertebrates shell deposition are not available for the TGAI or TEP. 

Quantitative acute toxicity to estuarine/marine invertebrate shell deposition is not available for 

the TEP. Based on the 40 CFR Part 158 data requirements, these data are required for all 

pesticides applied directly to water. In addition, available qualitative data and incident data 
38 of 80

indicate that direct effects are likely with use of fluridone as recommended on labels. Therefore, 

these data gaps must be filled. In the absence of data, EFED will assume risk to both freshwater 

and estuarine/marine fish and invertebrates.

Estuarine/marine Fish Full Life Cycle (Guideline 850.1500) with TGAI 

40 CFR Part 158 requires an estuarine/marine fish full lifecycle study for one species when the 

pesticide is applied directly to water or if EEC is ≥0.1 of NOEL in fish early life stage or if 

studies suggest reproduction physiology may be affected. Data are needed because fluridone 

will be applied directly to water, chronic exposure to estuarine/marine species may occur, and a 

reduced egg production was observed at the highest test concentration in the freshwater fish full 

lifecycle test (MRID 00103309). Given that fecundity endpoints are highly variable, the lab that 

conducts the test should ensure that an appropriate number of replicates be used. Usually for 

nonparametric tests, four replicates are required. 

Freshwater Fish Full Lifecycle (Guideline 850.1500) for One Species with Acute Data 

Chronic toxicity data are available for the fathead minnow. Quantitative acute data with the 

TGAI are not available for the fathead minnow6

. Based on the 40 CFR Part 158 data 

requirements, these data are required for all pesticides applied directly to water. These data are 

needed to evaluate risk to more sensitive species using an acute-to-chronic ratio (ACR). An 

acute endpoint for the fathead minnow is available for an EP. Based on the data available for 

Rainbow trout and Channel catfish, the toxicity endpoints of the EP and TGAI are similar 

(MRID 00103297). Therefore, an ACR may be calculated for Fathead minnow using the EP 

endpoint of 8.3 mg a.i./L. EFED does not recommend requesting additional data for this 

requirement at this time.

Whole Sediment Chronic Freshwater Invertebrate 

No chronic toxicity data for freshwater invertebrates are available. 40 CFR 158 requires whole 

sediment chronic toxicity data for freshwater invertebrates if the EEC > 0.1 of acute LC50 and the 

half-life > 10 days and if any of the following exist: the log KOW ≥3 or the KOC≥1000 L/kg. 

Data are needed for freshwater invertebrates because: 

• the maximum applied concentration per growing season of 0.150 mg/L is > 0.1 of the 

preliminary supplemental acute 48-hr EC50 of 1.3 mg/L for the midge (MRID 00103297); 

• aerobic aquatic half-lives of fluridone (MRID 44154801) are greater than 10 days; 

• and some KOC values are ≥ 1000 L/kg (BLM 2005).7

 

 

6

 The acute toxicity test submitted for the fathead minnow resulted in an LC50 value that is greater than the solubility 

(MRID 00103297). As exposure is not likely to occur at a concentration much greater than the solubility in distilled 

water, the true exposure concentration resulting in mortality is not known. 

7

 Most reported KOC values ranged from 270-6400 L/kg (BLM 2005). Open literature values have not been formally 

reviewed. The values will be reviewed for possible use in the environmental fate characterization. In the interim, 

sediment toxicity data is requested. The need to evaluate potential sediment toxicity as an exposure pathway in the 

future risk assessment will be determined based on the review of the open literature KOC values. 
39 of 80

In the absence of data, toxicity will be estimated using the lowest chronic toxicity endpoint for 

freshwater invertebrates in freshwater and the estimated pore water concentrations in sediment. 

Aquatic Plant Studies (850.4400 and 850.5400)

Toxicity data for vascular and non-vascular aquatic plants were not submitted to the Agency. 

Based on the 40 CFR Part 158 data requirements, Tier II level non-target aquatic plant data are 

required for all herbicides. In addition, available open literature data for non-target aquatic 

plants show impacts to many aquatic species at a concentration less than the maximum single 

application rate for fluridone (MacDonald et al. 2008; Doong et al. 1993) and it is used to 

control aquatic vegetation. Therefore, this data gap must be filled, and non-target aquatic plant 

data for algae and vascular plants are required. In the absence of Tier II data, EFED will assume 

risk to both vascular and non-vascular aquatic plants. 

Toxicity of NMF 

The potential toxicity of NMF is a source of uncertainty for the assessment. Although potential 

exposure of receptors to NMF is uncertain, NMF can form in the environment; however, the 

toxicity threshold for receptors is not known. During Registration Review, toxicity data will be 

evaluated for compounds with a similar structure to NMF. NMF has been detected in some 

submitted fate studies and concentrations increased throughout the study (MRID 00103326), 

therefore acute and chronic toxicity data on NMF to fish, aquatic invertebrates, and birds are 

necessary for the Registration Review risk assessment. If data are not submitted and exposure is 

likely to occur, the Agency will evaluate potential toxicity using data for chemicals with a 

similar structure. A preliminary estimate of exposure, assuming only one application indicates 

that exposure to NMF may occur at high enough levels to elicit toxicity (Appendix C). 

Toxicity of 3-trifluoromethyl benzoic acid 

No aquatic toxicity data were available for 3-trifluoromethyl benzoic acid in the public 

ECOTOX database when searched on April 22, 2009 (USEPA 2009b). Data based on ECOSAR 

version 1.0 indicates that the toxicity endpoints for aquatic organisms would range from 9 - 2706 

mg/L, using the neutral organic acid chemical class (Appendix D). This suggests that the 

toxicity of 3-trifluoromethyl benzoic acid is similar to the toxicity of fluridone. 3-

trifluoromethyl benzoic acid was detected in some submitted fate studies and concentrations 

increased throughout the study, indicating that exposure to 3-trifluoromethyl benzoic acid may 

occur (MRID 00103326). During Registration Review, toxicity data will be evaluated for 

compounds with a similar structure to 3-trifluoromethyl benzoic acid. Based on the submitted 

ECOSAR data, the toxicity of this degradate will be assumed to be similar to the parent for 

aquatic organisms. Acute and chronic toxicity data on 3-trifluoromethyl benzoic acid to birds 

are necessary for the Registration Review risk assessment. If data are not submitted, the Agency 

will evaluate potential toxicity using data for chemicals with a similar structure. 
40 of 80

Testing on Typical end-use products (TEP) 

A Typical End-Use Product is defined in the Pesticide Assessment Guidelines Subdivision J 

Hazard Evaluation: Nontarget plants on Part 120-2(1) on Page 18 as “a pesticide product that is 

representative of a major formulation category (e.g., emulsifiable concentrate, granular product, 

wettable powder) and pesticide group (e.g., herbicide, fungicide, insecticide etc.) and contains 

the active ingredient of the applicant’s product.” (Holst and Ellwanger, 1982) 

Page 5 of the Pesticide Assessment Guidelines Subdivision J Hazard Evaluation: Nontarget 

plants provides additional information on what TEP data should be tested for toxicity testing in 

the following excerpt. 

“The Agency seeks to avoid imposing a burden of duplicative testing on applicants for 

registration. Therefore, where 40 CFR Part 158 specifies that the test substance should 

be a representative end-use product, testing may be performed using the formulation in 

question (end-use product being registered) or similar, yet representative, end-use 

product. It is not necessary to repeat the test using other similar products.” (Holst and 

Ellwanger, 1982) 

When TEP data are requested data should be submitted for the different formulations, 

e.g., wettable powder, emulsifiable concentrate, granular, along with a rationale as to why 

the TEP is representative of other similar end-use products.” 

 

7.9. Other Information Needed for the Risk Assessment 

Current labels do not have a maximum number of applications or minimum application interval. 

In order to estimate exposure, a maximum number of applications and minimum application 

interval will be assumed based on a conservative estimate. Adding a maximum number of 

applications and a minimum application interval to labels would significantly reduce uncertainty 

in exposure estimates. Additionally, information on typical number of applications and 

application intervals would be useful. 

In order to assess the risk to terrestrial organisms exposed to fluridone pellets the weight of one 

pellet for each pelleted formulation is needed. 

8. References 

8.1. Open Literature 

BLM (Bureau of Land Management). 2005. Fluridone Ecological Risk Assessment. Final 

Report. BLM Contract Number NAD010156. ENSR Document Number 09090-020-

650. Reno, Nevada. 

CFR 40. 2007. Code of Federal Regulations 40 Parts 150 to 189. Protection of the 

Environment. U.S. Government Printing Office. 
41 of 80

Doong, R.L.; G.E. Macdonald; and D.G. Shilling. 1993. Effect of fluridone on chlorophyll, 

carotenoid, and anthocyanin content of Hydrilla. J. Aquat. Plant Manage 31: 55-59. 

E.I. du Pont de Nemours and Company, LP. 2005. Overall summary for N-methyl formamide. 

Robust Summaries and Test Plans. November 5, 2005. 

http://www.epa.gov/HPV/pubs/summaries/monomthf/c15159rt2.pdf (accessed April 13, 

2009). 

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the 

EPA food-chain (Kenaga) nomogram, an instrument for estimating pesticide residues on 

plants. Environ. Tox. Chem. 13:1383-1391. 

Fox, A.M.; W.T. Haller; D.G. Shilling. 1996. Hydrilla control with split treatments of fluridone 

in Lake Harris, Florida. Hydrobiologia 340: 235-239. 

HSDB (Hazardous Substances Data Bank). 2002. N-Methylformamide. Complete update on 

04/19/2002. Available at: http://toxnet.nlm.nih.gov/cgi-bin/sis/search (accessed 

05/03/2009). 

HSDB. 2005. Benzoic acid. Updated 11/14/2005. Available at: http://toxnet.nlm.nih.gov/cgibin/sis/search (accessed 05/21/2009). 

Herbicide Resistance Action Committee (HRAC). 2005. Classification of Herbicides According 

to Mode of Action. January 2005. Available at: 

http://www.hracglobal.com/Publications/ClassificationofHerbicideModeofAction/tabid/2

22/Default.aspx (accessed April 17, 2009). 

Hoerger, F. and E. E. Kenaga, 1972. Pesticide Residues on Plants: Correlation of Representative 

Data as a Basis for Estimation of their Magnitude in the Environment. In F. Coulston and 

F. Korte, eds., Environmental Quality and Safety: Chemistry, Toxicology, and 

Technology, Georg Thieme Publ., Stuttgart, West Germany, pp. 9-28. 

Holst, R. W., & Ellwanger, T. C. 1982. Pesticide Assessment Guidelines. Subdivision J. Hazard 

Evaluation: Nontarget Plants. EPA-540/09-82-020. October 1982. Office of Pesticide 

Programs. Office of Pesticides and Toxic Substances. United States Environmental 

Protection Agency. 

MacDonald, G. E.; A. Puri; and D.G. Shilling. 2008. Interactive effect of photoperiod and 

fluridone on growth, reproduction, and biochemistry of Dioecious Hydrilla (Hydrilla 

verticiliata). Weed Science 56: 189-195. 

Paul, E. A., Simonin, H. A., Symula, J., & Bauer, R. W. 1994. The toxicity of diquat, endothall, 

and fluridone to the early life stages of fish. J. Freshwater, Ecol., 9(3), 229-239. 

Popova, L. 1996. Effect of fluridone on plant development, leaf anatomy and plastid 

ultrastructure of barley plants. Bulg. J. Plant Physiology 22(1-2): 3-12. 
42 of 80

Schmitz, D.C. 1986. The Aquatic Herbicide Sonar (Fluridone): A Review of the Scientific 

Literature. TSS-86-100. June 1986. Florida Department of Natural Resources. Bureau 

of Aquatic Plant Research and Control. Tallahassee, FL. 

USEPA (U.S. Environmental Protection Agency). 1991. Ecological Effects Branch Review. 

Sonar as herbicide. Case Number 031626. Office of Pesticide Programs. Washington, 

D.C. 

USEPA. 1993. Wildlife Exposure Factors Handbook. EPA/600/R-13/187a, Office of Research 

and Development, Washington, D.C. 

USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office of 

Research and Development, Washington, D.C. EPA/630/R-95/002F. April 1998. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=30759 

USEPA. 2002. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides, Version II. US Environmental Protection Agency, Washington 

DC. Online at: http://www.epa.gov/oppefed1/models water/input_guidance2_28_02.htm. 

USEPA. 2003. Fluridone Use Closure Memo (PC Code 112900). Memo From R. McNally, to 

M. Stasikowski. Special Review Branch, Office of Pesticide Programs. Washington, 

D.C. 

USEPA. 2004a. Fluridone and its major degradate, N-methyl formamide - Drinking Water 

Assessment for the Health Effects Division (HED) Reregistration Eligibility Decision 

Document. PC Code 112900. DP Barcode D300012. April 1, 2004. Environmental 

Fate and Effects Division. Office of Pesticide Programs. Washington, D.C. 

USEPA. 2004b. Human Health Risk Assessment for Fluridone TRED. PC Code 112900. DP 

Barcode D306456. August 17, 2004. Registration Branch, Office of Pesticide Programs. 

Washington, D.C. 

USEPA 2004c. Fluridone: Toxicology Chapter for RED and Updating Executive Summaries 

for 11 studies. DP Barcode D291522. August 30, 2004. Health Effects Division, Office 

of Pesticide Programs. Washington, D.C. 

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

Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Washington DC. January 23, 2004. 

USEPA. 2007a. Ecological Incident Information System. 

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

USEPA. 2007b. 40 CFR Part 158. Pesticides; Data Requirements for Conventional Chemicals: 

Final Rule. 72 FR 60934. October 26, 2007. 
43 of 80

USEPA 2007c. Product Chemistry Review on Fluridone Technical. August 6, 2007. D338136. 

Registration Division. Office of Pesticide Programs. Washington, DC. 

USEPA. 2008a. Environmental Fate, Ecological Risk and Endangered Species Assessment in 

Support of the Registration Review of Fomesafen Sodium (PC123802). December 2008. 

Environmental Fate and Effects Division. Office of Pesticide Programs. Washington, 

DC. 

USEPA. 2008b. Environmental Fate and Ecological Risk Assessment for Etofenprox New Uses 

on Rice and for Vector Control. June 30, 2008. Environmental Fate and Effects 

Division. Office of Pesticide Programs. Washington, DC. 

USEPA. 2009a. Usage/Use Report Package in Support of Registration Review for Fluridone. 

January 29, 2009. Biological and Economic Analysis Division. Office of Pesticide 

Programs. Washington, DC. 

USEPA 2009b. ECOTOXicology Database. Office of Research and Development National 

Health and Environmental Effects Research Laboratory’s (NHEERL’s) Mid-Continent 

Ecology Division (MED). http://cfpub.epa.gov/ecotox/

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. 

Endangered Species Consultation Handbook: Procedures for Conducting Consultation 

and Conference Activities Under Section 7 of the Endangered Species Act. Final Draft. 

March 1998. 

U.S. FWS/NMFS. 2004. Letter providing an evaluation by the U.S. Fish and Wildlife Service 

and National Marine Fisheries Service of an approach to assessing the ecological risks of 

pesticide products. From Steve Williams and William Hogarth to Susan Hazen. January 

26, 2004. 

Ware, G. W.; D. M. Whitacre. 2004. An Introduction to Herbicides. In The Pesticide Book, 6th

ed; Radcliffe, E. B, Hutchison, W. D. Eds.; MeisterPro Information Resources: 

Willoughby, OH, 2004. Available at http://ipmworld.umn.edu/chapters/whitacreherb.htm

(accessed March 26, 2008). 

Wood, A. 2009. Compendium of Pesticide Common Names. Last updated on January 8, 2009. 

Online at: http://www.alanwood.net/pesticides/index.html

8.2. Submitted Fate Studies 

MRID Citation Reference 
44 of 80

MRID Citation Reference 

28724 Berard, D.F.; Rainey, D.P.; Shuey, E.W. (1980) Dissipation of 14C Fluridone 

from Water of Artificial Ponds. (Unpublished study received Feb 7, 1980 under 

1471-EX-67; submitted by Elanco Prod- ucts Co., Div. of Eli Lilly and Co., 

Indianapolis, Ind.; CDL: 099227-A) 

28725 West, S.D. (1980) An Interim Report of Fluridone Residues in Water and Fish. 

(Unpublished study received Feb 7, 1980 under 1471- EX-67; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; CDL:099227-

B) 

30255 Berard, D.F.; Rainey, D.P. (1980) Dissipation of 14C Fluridone from Water of 

Artificial Ponds. (Unpublished study received Apr 3, 1980 under 1471-EX-67; 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; 

CDL:099338-A) 

30256 Rainey, D.P. (1978) Uptake and Metabolism of 14C Fluridone by Blue- gills. 

(Unpublished study received Apr 3, 1980 under 1471-EX- 67; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; CDL:099338-

C) 

30257 West, S.D.; Day, E.W., Jr.; Burger, R.O. (1979) Dissipation of the experimental 

aquatic herbicide Fluridone from lakes and ponds. Journal of Agricultural and 

Food Chemistry 27(5):1067-1072. (Also~In~unpublished submission received 

Apr 3, 1980 under 1471- EX-67; submitted by Elanco Products Co., Div. of Eli 

Lilly and Co., Indianapolis, Ind.; CDL:099338-D) 

30257 West, S.D.; Day, E.W., Jr.; Burger, R.O. (1979) Dissipation of the experimental 

aquatic herbicide Fluridone from lakes and ponds. Journal of Agricultural and 

Food Chemistry 27(5):1067-1072. (Also~In~unpublished submission received 

Apr 3, 1980 under 1471- EX-67; submitted by Elanco Products Co., Div. of Eli 

Lilly and Co., Indianapolis, Ind.; CDL:099338-D) 

51379 Eli Lilly and Company (1979) EL-171 (Fluridone) Aquatic Weed Management. 

(Reports by various sources; received May 21, 1980 under 1471-EX-67; 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; 

CDL:242489-A) 

103318 Meyerhoff, R.; Parka, S.; Brannon, D.; et al. (1982) Some Physical, Chemical, 

and Biological Characteristics of a Lake and Ponds Treated with Sonar AS and 

Sonar 5P Aqueous and Pellet Formula- tions of Fluridone (EL-171, Compound 

112371). (Unpublished study received Jun 10, 1982 under 1471-126; submitted 

by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL: 

070935-G) 

103320 Berard, D.; Rainey, D.; Shuey, E. (1980) Dissipation of 14C Fluridone from 

Water of Artificial Ponds. (Unpublished study received Jun 10, 1982 under 

1471-126; submitted by Elanco Prod- ucts Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL: 070936-B) 

103321 Rainey, D.; Shuey, E. (1978) Uptake and Metabolism of 14C Fluridone by 

Bluegills. (Unpublished study received Jun 10, 1982 under 1471-126; submitted 

by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL:070936-C) 
45 of 80

MRID Citation Reference 

103326 Mosier, J.; Saunders, D.; Sieck, R.; et al. (1982) Photolysis of Fluridone in 

Aqueous Solution: S-AAC-79-10. (Unpublished study received Jun 10, 1982 

under 1471-126; submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL: 070937-B) 

103327 Rainey, D.; Shuey, E. (1982) Anaerobic Aquatic Metabolism of 14C Fluridone. 

(Unpublished study received Jun 10, 1982 under 1471-126; submitted by Elanco 

Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:070937-C) 

103333 West, S.; Burger, R.; Poole, G.; et al. (1982) Field Dissipation and Residue 

Trials with the Aquatic Herbicide Sonar in Lakes and Ponds. (Unpublished study 

received Jun 10, 1982 under 1471-126; submitted by Elanco Products Co., Div. 

of Eli Lilly and Co., Indianapolis, IN; CDL:070937-I) 

103334 West, S.; Burger, R.; Hamelink, J. (1980) Determination of Residues of 

Fluridone and its Major Metabolite in Fathead Minnows during a Full Life Cycle 

Study. (Unpublished study received Jun 10, 1982 under 1471-126; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:070937-J) 

121695 Rainey, D.; Shuey, E. (1978) Uptake and Metabolism of 14C Fluridone by 

Bluegills. (Unpublished study received Dec 14, 1978 under 1471-EX-66; 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL:236621-N) 

121696 Arnold, W. (1978) Fluridone--a New Aquatic Herbicide. (Unpublished study 

received Dec 14, 1978 under 1471-EX-66; submitted by Elanco Products Co., 

Div. of Eli Lilly and Co., Indianapolis, IN; CDL:236621-O) 

121697 McCowen, M.; Young, C.; West, S.; et al. (1978) Fluridone, a New Herbicide 

for Aquatic Plant Management. (Unpublished study received Dec 14, 1978 under 

1471-EX-66; prepared by Aquatic Plant Management Society, Inc., submitted by 

Elanco Products Co., Div of Eli Lilly and Co., Indianapolis, IN; CDL:236621-P) 

125742 West, S.; Burger, R.; Schmalz, C.; et al. (1983) Residues in Crops and Soils 

Irrigated with Water Containing the Aquatic Herbicide Fluridone: S-AAC-81-20. 

(Unpublished study received Feb 17, 1983 under 1471-126; submitted by Elanco 

Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:071406-B) 

125743 Mosier, J.; Saunders, D.; Sieck, R.; et al. (1982) Photolysis of Fluridone in 

Aqueous Solution: S-AAC-79-10. (Unpublished study received Feb 17, 1983 

under 1471-126; submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:071406-C) 

135213 Day, E.; West, S. (1975) EL-171 for Weed Control in Cotton Soil Residues. 

(Unpublished study received Aug 21, 1978 under 1471- EX-64; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:097341-

H) 

135214 West, S.; Amundson, M. (1978) Fluridone Residues in Soil. (Unpub- lished 

study received Aug 21, 1978 under 1471-EX-64; submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:097341-I) 

135215 West, S.; Burger, R.; Cleary, D.; et al. (1978) Fluridone and Trifluralin Residues 

in Soil. (Unpublished study received Aug 21, 1978 under 1471-EX-64; 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL:097341-J) 
46 of 80

MRID Citation Reference 

135216 Rainey, D.; Magnussen, J. (1977) 14C Fluridone Soil Degradation Studies. 

(Unpublished study received Aug 21, 1978 under 1471- EX-64; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:097341-

K) 

135217 Berard, D.; Amundson, M. (1978) 14C Fluridone Degradation Study in Aerobic 

and Anaerobic Soil. (Unpublished study received Aug 21, 1978 under 1471-EX64; submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, 

IN; CDL:097341-L) 

135218 Loh, A.; Buchanan, G.; Amundson, M. (1978) Soil Adsorption Coeffi- cient of 

Fluridone. (Unpublished study received Aug 21, 1978 under 1471-EX-64; 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL:097341-M) 

135219 Decker, O.; Amundson, M. (1978) Fluridone Soil Leaching Study. (Unpublished 

study received Aug 21, 1978 under 1471-EX-64; submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:097341-N) 

135220 Decker, O. (1975) Hydrolysis Study of Compound EL-171. (Unpub- lished study 

received Aug 21, 1978 under 1471-EX-64; submitted by Elanco Products Co., 

Div. of Eli Lilly and Co., Indianapolis, IN; CDL:097341-O) 

135221 Day, E.; Sherman, W. (1975) Photochemical Rate Studies with EL-171 in 

Aqueous Solution. (Unpublished study received Aug 21, 1978 under 1471-EX64; submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, 

IN; CDL:097341-P) 

135369 Elanco Products Co. (1978) EL-171 as for Aquatic Plant Manage- ment Systems: 

Fish and Wildlife ?and Microscopic Organisms|. (Unpublished study received 

Dec 14, 1978 under 1471-EX-67; CDL:097725-C) 

135371 Elanco Products Co. (1978) EL-171 as for Aquatic Plant Manage- ment Systems: 

Environmental Chemistry. (Unpublished study received Dec 14, 1978 under 

1471-EX-67; CDL:097725-L) 

135372 Rainey, D. (1978) Uptake and Metabolism of 14C Fluridone by Blue- gills. 

(Unpublished study received Dec 14, 1978 under 1471- EX-67; prepared by 

Lilly Research Laboratories, submitted by Elanco Products Co., Div. of Eli Lilly 

and Co., Indianapolis, IN; CDL:097725-N) 

159966 West, S. (1982) Determination of Fluridone in Soil and Hydrosoil by High 

Pressure Liquid Chromatography: AM-AA-CA-R017-AC-755. Un- published 

study prepared by Lilly Research Laboratories. 10 p. 

162339 West, S.; Weston, J. (1985) Fluridone Concentration in Water from Drainage 

Canals Receiving Split Applications of Sonar 5P: Study No. EWD8501. 

Unpublished study prepared by Lilly Research Lab- oratories. 27 p. 

162340 West, S. (1984) Projected Residues of Fluridone in Water, Hydro-soil, and 

Edible Fish Tissue upon Retreatment of Lakes with Sonar: Study No. EWD8426. 

Unpublished study prepared by Lilly Research Laboratories. 11 p. 

162341 West, S. (1986) Data To Support a Seven-day Retreatment Interval for Sonar in 

Lakes, Reservoirs, Canals, and Rivers: Study No. EWD8621. Unpublished study 

prepared by Lilly Research Labora- tories. 6 p. 
47 of 80

MRID Citation Reference 

162775 West, S.; Weston, J. (1985) Residues of Fluridone and Its Major Metabolites in 

Crayfish from Ponds Treated with the Aquatic Herbicide Sonar: EWD8436. 

Unpublished study prepared by Lilly Research Laboratories. 76 p. 

162775 West, S.; Weston, J. (1985) Residues of Fluridone and Its Major Metabolites in 

Crayfish from Ponds Treated with the Aquatic Herbicide Sonar: EWD8436. 

Unpublished study prepared by Lilly Research Laboratories. 76 p. 

40485901 West, S.; Turner, L. (1987) Determination of Fluridone in Water by Highperformance Liquid Chromatography Following Extraction with Sep-Pak C18 

Cartridges. Unpublished validation study prepared by Lilly Research 

Laboratories. 13 p. 

40485902 West, S.; Turner, L. (1987) Gas Chromatographic Determination of Residue 

Levels of N-methylformamide in Water. Unpublished Validation study prepared 

by Lilly Research Laboratories. 16 p. 

41424101 Decker, O. (1988) Hydrolysis Study of Fluridone: Lab Project I.D.: ODD8803. 

Unpublished study prepared by Lilly Research Laboratories. 8 p. 

44138501 Heim, L. (1996) Adsorption-Desorption of (carbon 14)-Fluridone in Soil and 

Sediment: (Final Report): Lab Project Number: 43187: 

T3E/ /ESADSB/US/** **/162. Unpublished study prepared by Analytical 

Bio-Chemistry Labs., Inc. 103 p. 

44154801 Serak, K. (1996) Aerobic Aquatic Metabolism of (carbon 14)-Fluridone: Lab 

Project Number: 43186: T3E/ /EWMETB/US/** **/3. Unpublished study 

prepared by Analytical Bio-Chemistry Labs, Inc. 91 p. 

46866401 Heilman, M.; Koschnick, T.; Tarver, D.; et. al. (2006) Depuration of Fluridone 

Residues From Dry-Treated Sediments Following Seasonal Flooding of 

Irrigation Canals in Idaho. Unpublished study prepared by SePRO Corp. 16 p. 

47139001 West, S. (1986) Data To Support a Seven-Day Retreatment Interval for Sonar in 

Lakes, Reservoirs, Canals, and Rivers. Project Number: EWD8621, YAQUAT. 

Unpublished study prepared by Lilly Research Laboratories. 6 p. 

47139002 West, S. (1982) Determination of Fluridone in Water by High Pressure Liquid 

Chromatography with U.V. Detection. Project Number: 

AM/AA/CA/R011/AC/755. Unpublished study prepared by Lilly Research 

Laboratories. 4 p. 

47139007 West, S. (1984) Projected Residues of Fluridone in Water, Hydrosoil, and Edible 

Fish Tissue Upon Retreatment of Lakes with Sonar. Project Number: EWD8426. 

Unpublished study prepared by Lilly Research Laboratories. 11 p. 

 

8.3. Submitted Effects Studies 

MRID Citation Reference 

00121686 Kehr, C.; West, H.; Hamelink, J.; et al. (1978) The Toxicity of Compound 112371 

(EL-171) to Bobwhite Quail in a 14-day Acute Oral Study: Study No. 7005-78. 

(Unpublished study received Dec 14, 1978 under 1471-EX-66; submitted by 
48 of 80

MRID Citation Reference 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:236621-E) 

00121687 Kehr, C.; Hamelink, J.; Probst, G.; et al. (1978) The Toxicity of Compound 112371 

(EL-171) to Bobwhite Quail in an Eight-day Dietary Study: Study No. 7008-78. 

(Unpublished study received Dec 14, 1978 under 1417-EX-66; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:236621-F) 

00121688 Kehr, C.; Hamelink, J.; Probst, G.; et al. (1978) The Toxicity of Compound 112371 

(EL-171) to Mallard Ducks in an Eight-day Die- tary Study: Study No. 7009-78. 

(Unpublished study received Dec 14, 1978 under 1471-EX-66; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:236621-G) 

00135211 Kehr, C.; Hamelink, J.; Probst, G.; et al. (1978) The Toxicity of Compound 112371 

(EL-171) to Mallard Ducks in an Eight-day Dietary Study: Study No. 7009-78. 

(Unpublished study received Aug 21, 1978 under 1471-EX-64; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:097341-C) 

00135370 Kehr, C.; Hamelink, J.; Probst, G.; et al. (1978) The Toxicity of Compound 112371 

(EL-171) to Mallard Ducks in an Eight-day Dietary Study: Study No. 7009-78. 

(Unpublished study received Dec 14, 1978 under 1471-EX-67; prepared by Lilly 

Research Laboratories, submitted by Elanco Products Co., Div. of Eli Lilly and 

Co., Indianapolis, IN; CDL:097725-G) 

00103293 Ringer, R.; Breslin, W.; Flaga, C.; et al. (1981) The Toxicity of Fluridone (EL-171, 

Compound 112371) in a One-generation Re- production Study with Bobwhite: 

Study A018-79. (Unpublished study received Jun 10, 1982 under 1471-126; 

prepared in coopera- tion with Michigan State Univ., submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:070932-B) 

00103294 Ringer, R.; Breslin, W.; Flaga, C.; et al. (1981) The Toxicity of Fluridone (EL-171, 

Compound 112371) in a One-generation Re- production Study with Mallards: 

Study A019-79. (Unpublished Study received Jun 10, 1982 under 1471-126 

prepared in coopera- tion with Michigan State Univ., submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:070932-C) 

00103297 Probst, G.; Hamelink, J.; Mayerhoff, R.; et al. (1982) The Toxicity of Fluridone 

(El-171, Compound 112371) and of Sonar AS, an Aqueous Suspension 

Formulation of Fluridone, to Aquatic In- vertebrates and Fish in Acute and Chronic 

Studies. (Unpublished study received Jun 10, 1982 under 1471-126; prepared in 

cooperation with U.S. Fish and Wildlife Service, Columbia National Fisheries 

Research Laboratory, submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:070932-F) 

00103306 Negilski, D.; Probst, G. (1981) The Toxicity of Sonar AS, an Aqueous Suspension 

Formulation of Fluridone (EL-171, Compound 112371), to Bluegills in a 96-hour 

Static Test: Study F053-80. (Unpublished study received Jun 10, 1982 under 1471-

126; sub- mitted by Elanco Products Co., Div. of Eli Lilly and Co., In- dianapolis, 

IN; CDL:070934-A) 
49 of 80

MRID Citation Reference 

00103307 Negilski, D.; Probst, G. (1981) The Toxicity of Sonar AS, an Aqueous Suspension 

Formulation of Fluridone (EL-171, Compound 112371), to Rainbow Trout in a 96-

hour Static Test: Study F056- 80. (Unpublished study received Jun 10, 1982 under 

1471-126; submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:070934-B) 

00103308 Negilski, D.; Probst, G. (1981) The Toxicity of Fluridone (EL-171, Compound 

112371) to Bluegills in a 96-hour Static Test: Study 2023-79. (Unpublished study 

received Jun 10, 1982 under 1471- 126; submitted by Elanco Products Co., Div. of 

Eli Lilly and Co., Indianapolis, IN; CDL:070934-C) 

00121689 Karnak, R.; Kehr, C.; Hamelink, J.; et al. (1978) The Toxicity of Compound 

112371 (EL-171) to Bluegills in a 96 Hour Static Test: Study No. 2075-78. 

(Unpublished study received Dec 14, 1978 under 1471-EX-66; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:236621-H) 

00121690 Kehr, C.; Karnak, R.; Hamelink, J.; et al. (1978) The Toxicity of Compound 

112371 (EL-171) to Rainbow Trout in a 96 Hour Static Test: Study No. 2019-78. 

(Unpublished study received Dec 14, 1978 under 1471-EX-66; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:236621-I) 

00135212 Karnak, R.; Kehr, C.; Hamelink, J.; et al. (1978) The Toxicity of Compound 

112371 (EL-171) to Bluegills in a 96 Hour Static Test: Study No. 2075-78. 

(Unpublished study received Aug 21, 1978 under 1471-EX-64; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:097341-D) 

00103296 Negilski, D.; Probst, G. (1981) The Toxicity of Sonar AS, an Aqueous Suspension 

Formulation of Fluridone (EL-171, Compound 112371) to Daphnia magna in a 48-

hour Static Test: Study C001- 80. (Unpublished study received Jun 10, 1982 under 

1471-126, submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:070932-E) 

00103297 Probst, G.; Hamelink, J.; Mayerhoff, R.; et al. (1982) The Toxicity of Fluridone 

(El-171, Compound 112371) and of Sonar AS, an Aqueous Suspension 

Formulation of Fluridone, to Aquatic In- vertebrates and Fish in Acute and Chronic 

Studies. (Unpublished study received Jun 10, 1982 under 1471-126; prepared in 

cooperation with U.S. Fish and Wildlife Service, Columbia National Fisheries 

Research Laboratory, submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:070932-F) 

00121691 Kehr, C.; Karnak, R.; Hamelink, J.; et al. (1978) The Toxicity of Compound 

112371 (EL-171) to Daphnia magna in a 48-hour Static Test: Study No. 5004-78. 

(Unpublished study received Dec 14, 1978 under 1471-EX-66; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:236621-J) 

00162774 Meyerhoff, R. (1984) The Toxicity of Fluridone (EL-171, Compound 112371) to 

Crayfish (Orconectes immunis) in a 14-day Flow- through Test: Study C03083. 

Unpublished study prepared by Lilly Research Laboratories. 32 p. 
50 of 80

MRID Citation Reference 

00103310 Heitmuller, T. (1981) Acute Toxicity of Compound 112371 to Eastern Oysters 

(Crassostrea virginica): Report No. BP-80-8-136; Lilly Study No. S001-80. 

(Unpublished study received Jun 10, 1982 under 1471-126; prepared by EG & G 

Bionomics, submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:070934-G) 

00103311 Hollister, T. (1981) Acute Toxicity of Compound 112371, to Embryos- larvae of 

Eastern Oysters (Crassostrea virginica): Report No. BP-80-7-125; Lilly Study No. 

S005-80. (Unpublished study received Jun 10, 1982 under 1471-126; prepared by 

EG & G Bionomics, submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:070934-H) 

00103312 Heitmuller, T. (1981) Acute Toxicity of Sonar AS, a Formulation of Lilly 

Compound 112371 to Pink Shrimp (Penaeus duorarum): Report No. BP-80-8-137; 

Lilly Study No. C005-80. (Unpublished study received Jun 10, 1982 under 1471-

126; prepared by EG & G Bio- nomics, submitted by Elanco Products Co., Div. of 

Eli Lilly and Co., Indianapolis, IN; CDL:070935-A) 

00103313 Heitmuller, T. (1981) Acute Toxicity of Sonar AS, a Formulation of Lilly 

Compound 112371 to Blue Crabs (Callinectes sapidus): Report No. BP-80-10-172; 

Lilly Study No. C008-80. (Unpublished study received Jun 10, 1982 under 1471-

126; prepared by EG & G Bionomics, submitted by Elanco Products Co., Div. of 

Eli Lilly and Co., Indianapolis, IN; CDL:070935-B) 

00103314 Heitmuller, T. (1981) Acute Toxicity of Sonar AS, a Formulation of Lilly 

Compound 112371 to Eastern Oysters (Crassostrea virgin- ica): Report No. BP-80-

10-193; Lilly Study No. S002-80. (Unpub- lished study received Jun 10, 1982 

under 1471-126; prepared by EG & G Bionomics, submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:070935-C) 

00103315 Hollister, T. (1981) Acute Toxicity of Sonar AS, a Formulation of Lilly Compound 

112371 to Embryos-larvae of Eastern Oysters (Crassostrea virginica): Report No. 

BP-80-7-126; Lilly Study No. S006-80. (Unpublished study received Jun 10, 1982 

under 1471-126; prepared by EG & G Bionomics, submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL: 070935-D) 

00103316 Heitmuller, T. (1981) Acute Toxicity of Sonar AS, a Formulation of Lilly 

Compound 112371 to Sheepshead Minnows (Cyprinodon vari- egatus): Report No. 

BP-80-7-130; Lilly Study No. F13480. (Un- published study received Jun 10, 1982 

under 1471-126; prepared by EG & G Bionomics, submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:070935-E) 

00108836 Heitmuller, T. (1981) Acute Toxicity of Compound 112371 to Blue Crabs 

(Callinectes sapidus): Report No. BP-80-10-168; Lilly Study No. C007-80. 

(Unpublished study received Jun 10, 1982 under 1471-126; prepared by EG & G 

Bionomics, submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:070934-F) 
51 of 80

MRID Citation Reference 

00108837 Heitmuller, T. (1981) Acute Toxicity of Compound 112371 to Sheeps- head 

Minnows (Cyprinodon variegatus): Report No. BP-80-7-131; Lilly Study No. 

F13180. (Unpublished study received Jun 10, 1982 under 1471-126; prepared by 

EG & G Bionomics, submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL:070934-I) 

00112789 Heitmuller, T. (1981) Acute Toxicity of Compound 112371 to Pink Shrimp 

(Penaeus duorarum): Report No. BP-80-8-135; Lilly Study No. C004-80. 

(Unpublished study received Jun 10, 1982 under 1471-126; prepared by EG & G 

Bionomics, submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL: 070934-E) 

46112001 Rhodes, J. (2003) Seawater Challenge Test to Measure Seawater Adaptability of 

Juvenile Chinook Salmon Oncorhynchus tshawytscha, Exposed to Fluridone. 

Project Number: 48163. Unpublished study prepared by Analytical Bio-Chemistry 

Labs, Inc. 47 p. 

45915601 Madsen, T. (2003) Early Life Stage Toxicity of Fluridone to the Chinook Salmon, 

Oncorhynchus tshawytscha, Under Flow-Through Conditions: Lab Project 

Number: 47895: AM-AA-CA-R031-AC-755. Unpublished study prepared by ABC 

Laboratories, Inc. 106 p. {OPPTS 850.1400} 

00103309 Hamelink, J.; Sauter, S.; Probst, G.; et al. (1981) The Toxicity of Compound 

112371 (EL-171, Fluridone) to Fathead Minnow, in a Full Life Cycle Study: Study 

2019-79. (Unpublished study received Jun 10, 1982 under 1471-126, prepared in 

cooperation with E.G. and G. Bionomics, submitted by Elanco Products Co., Div. 

of Eli Lilly and Co., Indianapolis, IN; CDL:070934-D) 

00103317 Meyerhoff, R.; Probst, G.; Hamelink, J.; et al. (1982) Performance of Fish 

Populations in Ponds Treated with Sonar 4AS, an Aqueous Formulation of 

Fluridone (EL-171, Compound 112371): Study F14880. Interim rept., year one. 

(Unpublished study received Jun 10, 1982 under 1471-126; prepared in 

cooperation with Aquatic Control, Inc., submitted by Elanco Products Co., Div. of 

Eli Lilly and Co., Indianapolis, IN; CDL:070935-F) 

00103334 West, S.; Burger, R.; Hamelink, J. (1980) Determination of Residues of Fluridone 

and its Major Metabolite in Fathead Minnows during a Full Life Cycle Study. 

(Unpublished study received Jun 10, 1982 under 1471-126; submitted by Elanco 

Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:070937-J) 

00103295 Atkins, E. (1982) Letter sent to R. Willemsen dated Mar 17, 1982: Laboratory 

honey bee toxicity tests on fluridone. (Unpublished study received Jun 10, 1982 

under 1471-126; prepared by Univ. of California--Riverside, Dept. of Entomology, 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL: 070932-D) 

00121685 Lembi, C.; Leva, S. (1977) Effects of Fluridone on Benthic Inverte- brates: Report 

#1. (Unpublished study received Dec 14, 1978 under 1471-EX-66; prepared by 
52 of 80

MRID Citation Reference 

Purdue Univ., Dept. of Botany and Plant Pathology., submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:236621-D) 

00121692 Karnak, R.; Kehr, C.; Hamelink, J.; et al. (1978) The Toxicity of Compound 

112371 (EL-171) to Earthworms in a 14-day Soil Incorporated Study: Study No. 

6002-78. (Unpublished study received 

00121698 Hiltibran, R. (1978) Letter sent to G. Shoop dated Jun 1, 1978 ?Effects of EL 171 

on Pond Life|: Report #2. (Unpublished study received Dec 14, 1978 under 1471-

EX-66; prepared by Illi- nois Natural History Survey, Aquatic Biology Section, 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL:236621-Q) 
53 of 80

Appendix A: Data Call In Tables 

Fluridone: Acute Oral Toxicity to Passerine Species

Guideline Number: 850.2100

Study Title: Avian Oral Toxicity (Passerine Species with TGAI) 

Rationale for Requiring the Data

No data for passerine species are available. Although the submitted avian acute data suggest that 

fluridone is practically nontoxic to the bobwhite quail, toxicity data for game birds may not 

reflect risks to passerine birds which have been identified to be more sensitive to pesticides in 

some cases than the Bobwhite Quail or Mallard Duck. Therefore, additional data are needed to 

accurately assess risks to these species. Specifically, data are required on one passerine species 

in addition to either one waterfowl species or one upland game bird species for terrestrial, 

aquatic, forestry, and residential outdoor uses. 

 

Practical Utility of the Data

How will the data be used? 

The passerine acute toxicity data are needed for future regulatory decisions, and for endangered 

species assessments. The data will allow the Agency to better assess the risks to these 

organisms, including the likelihood of potential risks to endangered species, either by direct 

effects or by indirect effects such as reducing food sources to listed predators and scavengers. 

Results of this study would be used to calculate acute risks to passerine species from exposure to 

fluridone and to identify whether current labeling is appropriate and whether further mitigation is 

necessary. 

 

How could the data impact the Agency’s future decision-making?

If the data indicate that fluridone poses a significant acute risk to upland game or passerine birds, 

the Agency may explore additional decision options to minimize the risk of fluridone to these 

species. If future endangered species risk assessments are performed without these data, the 

Agency would have to assume that fluridone "may affect" passerine birds directly and other 

endangered species indirectly through loss of prey. The lack of these data will limit the 

flexibility the Agency and registrants have in complying with the Endangered Species Act and 

could result in unnecessary use restrictions, and the use of fluridone may need to be restricted in 

areas where endangered species occur unless these data are provided. 

Fluridone: Chronic Toxicity for Avian Species

Guideline Number: 850.2300 

Study Title: Avian Reproduction Study (Upland Game Bird and Waterfowl with TGAI) 

Rationale for Requiring the Data 

No data on reproductive toxicity to birds is available. A chronic risk assessment for birds is 

needed based on fluridone's use patterns and potential impact on birds. The avian reproduction 

toxicity study is justified for fluridone because 1) the avian reproduction studies for waterfowl 

and upland game bird species are standard data requirements for all outdoor terrestrial and 

aquatic use patterns, 2) evidence of chronic toxicity to mammals indicates possible chronic 

toxicity in birds, and 3) fluridone's use pattern indicates that chronic exposure is likely. 

Practical Utility of the Data 
54 of 80

How did the Agency make its re-registration decision without this data? 

An ecological risk assessment was not conducted for the re-registration decision for fluridone. 

How will the data be used? 

The avian reproduction studies are needed for future regulatory decisions and for an endangered 

species assessment in particular. The data would allow the Agency to quantify the potential for 

chronic risk, as measured by effects on reproduction and hatchling survival, from the use of 

fluridone. Results of this study would be used to calculate risks to avian reproduction from 

dietary exposure to fluridone at labeled use rates and to identify what, if any, label language is 

needed to mitigate identified risks. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency 

would have to assume that fluridone "may affect" birds directly (and endangered species from 

other taxa indirectly), and use of fluridone might need to be restricted in areas where endangered 

species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in 

use restrictions for fluridone which are unnecessarily severe. 

Fluridone: Honeybee Acute Contact Toxicity

Guideline Number: 850.3020

Study Title: Honeybee Acute Contact Toxicity with TGAI 

Rationale for Requiring the Data

The honeybee acute contact toxicity test submitted was completed using the TEP using a dust 

carrier. The use of the dust could result in lower exposure to the bee if the dust is caught in 

hairs. Fluridone does have registered products with liquid formulations and the available test 

could underestimate toxicity of a liquid formulation. Additionally, 40 CFR 158 requires the 

Honeybee Acute Contact Toxicity study to be completed using the TGAI. Therefore, an acute 

contact toxicity study is needed to assess risk to bees. Without data to preclude risk to terrestrial 

invertebrates, risk will be presumed. 

Practical Utility of the Data

How did the Agency make its re-registration decision without this data? 

An ecological risk assessment was not conducted for the re-registration decision for fluridone. 

How will the data be used? 

The honeybee acute contact toxicity data are needed for future regulatory decisions, and for 

endangered species assessments. The data will allow the Agency to better assess the risks to 

these organisms, including the likelihood of potential risks to endangered species, either by 

direct effects or by indirect effects such as reducing food sources to listed predators and 

scavengers. Results of this study would be used to calculate risks to insects and endangered 

species from exposure to fluridone and to identify whether current labeling is appropriate and 

whether further mitigation is necessary. 

 

How could the data impact the Agency’s future decision-making?

If the data indicate that fluridone poses a significant risk to terrestrial invertebrates, the Agency 

may explore additional decision options to minimize the risk of fluridone to these species. If 
55 of 80

future endangered species risk assessments are performed without these data, the Agency would 

have to assume that fluridone "may affect" terrestrial invertebrates directly and other endangered 

species indirectly through loss of prey. The lack of these data will limit the flexibility the 

Agency and registrants have in complying with the Endangered Species Act and could result in 

unnecessary use restrictions, and the use of fluridone may need to be restricted in areas where 

endangered species occur unless these data are provided. 

Fluridone: Acute and Chronic Toxicity to Freshwater Fish

Guideline Number: 850.1075 

Study Title: Acute Toxicity Freshwater Fish (Coldwater and Warmwater Fish with TEP)

Rationale for Requiring the Data 

It is likely that aquatic organisms may be acutely exposed to the entire formulation because it is 

applied directly to water. 40 CFR 158 requires data for both the TGAI and TEP for products 

applied directly to water. It is not known if acute data available on end products are applicable 

to current products of fluridone on the market. Information on whether the available data on 

end-products are applicable to current products or new toxicity testing (OPPTS Guideline 

850.1075) on using EPs that are representative of current TEPs are needed to assess risk from 

exposure to the formulation. 

The requested data would allow EPA to estimate acute risks to freshwater fish, including 

defining an action area for endangered species. Risk mitigation strategies (e.g., determining the 

maximum fluridone application rate that results in an RQ below the LOC) cannot be evaluated 

without these data. 

Practical Utility of the Data 

How did the Agency make a re-registration decision without these data? 

An ecological risk assessment was not completed with the reregistration decision for fluridone. 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. These data would allow the Agency 

to determine acute and chronic risk to freshwater fish from exposure to fluridone formulations. 

The effects data would be used to determine the likelihood that the acute risks can potentially 

impact aquatic communities, either by direct effects or by indirect effects on other organisms by 

reducing their food sources. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be evaluated 

without these data. If future endangered species risk assessments are performed without these 

data, the Agency would have to assume that fluridone “may affect” endangered freshwater fish 

directly (and endangered species from other taxa indirectly), and use of fluridone might need to 

be restricted in areas where endangered species could be exposed. The lack of these data will 

limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act and could result in use restrictions for fluridone which are unnecessarily 

severe. 
56 of 80

Fluridone: Acute Estuarine/Marine Organism Toxicity

Guideline Number: 850.1025 

Study Title: Acute Toxicity Estuarine/Marine Mollusk Toxicity Study (Shell Deposition, 

TGAI and TEP) 

Guideline Number: 850.1075 

Study Title: Estuarine/Marine Fish Acute Toxicity Study (TGAI and TEP) 

Rationale for Requiring the Data 

40 CFR Part 158 requires acute toxicity data on one estuarine/marine mollusk and one 

estuarine/marine fish species. When a pesticide enters the aquatic environment estuarine/marine 

organisms may be exposed. When the pesticide is added directly to the aquatic environment a 

study examining the toxicity of the formulation is also required. Acute toxicity data for the 

Sheepshead minnow have been submitted; however the exposure concentration in the studies is 

not known and more data are needed for use quantitatively in the assessment. Data are also 

available on oyster shell deposition; however, data are still needed on oyster shell deposition for 

the TGAI and TEP because of variable results and due to variability in measured concentrations 

or the presence of precipitate in submitted tests. 

There is insufficient data available to assess the potential mortality risk of fluridone to 

marine/estuarine organisms. Fluridone is added directly to freshwater aquatic environments 

which may flow into estuarine/marine waters. Additionally, fluridone concentrations in treated 

water must be maintained for prolonged periods in order for fluridone to be effective for some 

species. Therefore, exposure to fluridone is likely. 

The requested data would allow EPA to estimate acute risks to estuarine/marine mollusks and 

fish, including defining an action area for endangered species. Risk mitigation strategies (e.g., 

determining the maximum fluridone application rate that results in an RQ below the LOC) 

cannot be evaluated without these data. 

Practical Utility of the Data 

How did the Agency make a re-registration decision without these data? 

An ecological risk assessment was not completed with the reregistration decision for fluridone. 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. The data would allow the Agency 

to determine acute risk to estuarine/marine organisms from water exposure to fluridone. The 

effects data would be used to determine the likelihood that the acute risks can potentially impact 

aquatic communities, either by direct effects or by indirect effects on other organisms by 

reducing their food sources. Additionally, endpoints may be used to estimate chronic toxicity to 

estuarine/marine organisms using an acute-to-chronic ratio from data on freshwater species. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be evaluated 

without these data. If future endangered species risk assessments are performed without these 
57 of 80

data, the Agency would have to assume that fluridone “may affect” endangered saltwater 

mollusks and fish directly (and endangered species from other taxa indirectly), and use of 

fluridone might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in use restrictions for fluridone 

which are unnecessarily severe. 

Fluridone: Acute and Chronic Toxicity and Sediment Toxicity to Freshwater 

Invertebrates

Guideline Number: 850.1010 

Study Title: Freshwater Invertebrate Acute Toxicity (TEP) 

Guideline Number: 850.1300 

Study Title: Daphnid chronic life-cycle 

Guideline Number: Not Available 

Study Title: Whole Sediment Chronic Freshwater Invertebrate 

Rationale for Requiring the Data 

Fluridone is applied directly to the aquatic environment and concentrations are maintained for 

several weeks. It is likely that aquatic organisms may be acutely exposed to the entire 

formulation because it is applied directly to water. 40 CFR 158 requires data for both the TGAI 

and TEP for products applied directly to water. It is not known if acute data available on end 

products are applicable to current products of fluridone on the market. Information on whether 

the available data on end-products are applicable to current products or new toxicity testing 

(OPPTS Guideline 850.1010) on EPs that are representative of current TEPs are needed to 

assess risk from exposure to the formulation. 

No data that can be used quantitatively were available to the Agency for chronic toxicity to 

freshwater invertebrates. Data on OPPTS Guideline 850.1300 will be used to evaluate chronic 

risk of freshwater invertebrates exposed to fluridone. 

No chronic whole sediment toxicity data for freshwater invertebrates are available. 40 CFR 158 

requires whole sediment chronic toxicity data for freshwater invertebrates if the EEC > 0.1 of 

acute LC50 and the half-life > 10 days and if any of the following exist: the log KOW ≥3 or the 

KOC≥1000 L/kg. Data are needed for freshwater invertebrates because: 

• the maximum applied concentration per growing season of 0.150 mg/L is > 0.1 of the 

preliminary supplemental acute 48-hr EC50 of 1.3 mg/L for the midge (MRID 

00103297); 

• aerobic aquatic half-lives of fluridone (MRID 44154801) are greater than 10 days; 

• and some KOC values are ≥ 1000 L/kg (BLM 2005).8 

In the absence of data, toxicity will be estimated using the lowest chronic toxicity endpoint for 

freshwater invertebrates in freshwater and the estimated porewater concentrations in sediment. 

This does not consider possible exposure via ingestion and could underestimate risk for some 

 

8

 Most reported KOC values ranged from 270-6400 L/kg (BLM 2005). 
58 of 80

invertebrates where ingestion is an important exposure pathway. 

The requested data would allow EPA to estimate acute and chronic risks to freshwater 

invertebrates, including defining an action area for endangered species. Risk mitigation 

strategies (e.g., determining the maximum fluridone application rate that results in an RQ below 

the LOC) cannot be evaluated without these data. 

Practical Utility of the Data 

How did the Agency make a re-registration decision without these data? 

An ecological risk assessment was not completed with the reregistration decision for fluridone. 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. The data would allow the Agency 

to determine acute and chronic risk to freshwater invertebrates from fluridone in water and 

sediment. The effects data would be used to determine the likelihood that the acute risks can 

potentially impact aquatic communities, either by direct effects or by indirect effects on other 

organisms by reducing their food sources. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be 

evaluated without these data. If future endangered species risk assessments are performed 

without these data, the Agency would have to assume that fluridone “may affect” endangered 

freshwater invertebrates directly (and endangered species from other taxa indirectly), and use of 

fluridone might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in use restrictions for fluridone 

which are unnecessarily severe. 

Fluridone: Toxicity to Terrestrial Plants

Guideline Number: 850.4100 

Study Title: Seedling emergence (Tier II) 

Guideline Number: 850.4150 

Study Title: Vegetative vigor (Tier II) 

Rationale for Requiring the Data 

The only data on the toxicity of fluridone to terrestrial plants is found in the ECOTOX database 

(a collection of reports from the open literature). Because the fluridone studies in this database 

differ significantly from OPP standards or are in other ways not reliable, they are not sufficient 

for a quantitative assessment of risks to terrestrial plants. Terrestrial plants may be exposed to 

fluridone with spray drift or when water treated with fluridone is used with irrigation. As 

fluridone is an herbicide it is expected to result in toxicity to plants. Possible risks to terrestrial 

plants cannot be evaluated without these data. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

An ecological risk assessment was not completed with the reregistration decision for fluridone. 
59 of 80

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. The data would allow the Agency 

to determine acute and chronic risk to freshwater invertebrates from water exposure to 

fluridone. The effects data would be used to determine the likelihood that terrestrial plants may 

be injured with use of fluridone, either by direct effects or by indirect effects on other 

organisms. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be 

evaluated without these data. If future endangered species risk assessments are performed 

without these data, the Agency would have to assume that fluridone “may affect” endangered 

terrestrial plants directly (and endangered species from other taxa indirectly), and use of 

fluridone might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in use restrictions for fluridone 

which are unnecessarily severe. 

Fluridone: Toxicity to Aquatic Plants

Guideline Number: 850.4400 

Study Title: Aquatic plant toxicity (Tier II) 

Guideline Number: 850.5400 

Study Title: Algal Toxicity (Tier II)

Rationale for Requiring the Data 

The only data on the toxicity of fluridone to aquatic plants is found in the ECOTOX database (a 

collection of reports from the open literature). Because the fluridone studies in this database 

differ significantly from OPP standards or are in other ways not reliable, they are not sufficient 

for a quantitative assessment of risks to aquatic plants. Aquatic plants may be exposed to 

fluridone as it is applied directly to water. As fluridone is an herbicide it is expected to result in 

toxicity to plants. Possible risks to aquatic plants cannot be evaluated without these data. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

An ecological risk assessment was not completed with the re-registration decision for fluridone. 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. Effects data would be used to 

determine the likelihood that aquatic plants may be injured with use of fluridone. The data 

would allow the Agency to evaluate potential risk to aquatic plants and indirect risk to other 

taxa due to reduction in food and/or habitat. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 
60 of 80

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be 

evaluated without these data. If future endangered species risk assessments are performed 

without these data, the Agency would have to assume that fluridone “may affect” endangered 

plants (and endangered species from other taxa indirectly), and use of fluridone might need to 

be restricted in areas where endangered species could be exposed. The lack of these data will 

limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act and could result in use restrictions for fluridone which are 

unnecessarily severe. 

Fluridone: Chronic Toxicity to Estuarine/marine Fish

Guideline Number: 850.1500 

Study Title: Estuarine/marine Fish Full Lifecycle with TGAI

Rationale for Requiring the Data 

40 CFR Part 158 requires an estuarine/marine fish full lifecycle study for one species when the 

pesticide is applied directly to water or if EEC is ≥0.1 of NOEL in fish early life stage or if 

studies suggest reproduction physiology may be affected. Data are needed because fluridone 

will be applied directly to water, chronic exposure to estuarine/marine species may occur, and a 

reduced egg production was observed at the highest test concentration in the freshwater fish full 

lifecycle test (MRID 00103309). Given that fecundity endpoints are highly variable, the lab that 

conducts the test should ensure that an appropriate number of replicates be used. Usually for 

nonparametric tests, four replicates are required. A fish early life cycle test was not requested 

because these data will be available from the full lifecycle test. 

The requested data would allow EPA to estimate chronic risks to estuarine/marine vertebrates, 

including defining an action area for endangered species. 

Practical Utility of the Data 

How did the Agency make a re-registration decision without these data? 

An ecological risk assessment was not completed with the reregistration decision for fluridone. 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. The data would allow the Agency 

to determine chronic risk to estuarine/marine fish. The effects data would be used to determine 

the likelihood that the chronic risks can potentially impact aquatic communities, either by direct 

effects or by indirect effects on other organisms by reducing their food sources. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be evaluated 

without these data. If future endangered species risk assessments are performed without these 

data, the Agency would have to assume that fluridone “may affect” endangered estuarine/marine 

fish directly, and use of fluridone might need to be restricted in areas where endangered species 

could be exposed. The lack of these data will limit the flexibility the Agency and registrants 

have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for fluridone which are unnecessarily severe. 
61 of 80

Degradate: N-Methyl Formamide (NMF)

Guideline 850.2100: avian acute oral toxicity 

Guideline 850.2300: avian reproduction study 

Guideline 850.1075: acute toxicity to freshwater fish for one coldwater and one warmwater 

species 

Guideline 850.1010: freshwater invertebrate acute toxicity 

Guideline 850.1400: freshwater fish early life stage and estuarine/marine early life stage 

Guideline 850.1300: freshwater invertebrate life cycle 

Rationale for Requiring the Data 

There is insufficient data available to assess the potential mortality risk of the degradate Nmethyl formamide to aquatic and terrestrial organisms. N-methyl formamide was identified by 

the Health Effects Division in the Human Health Risk assessment used to support the tolerance 

re-registration decision (TRED) for fluridone. It was found at a maximum of 74% of applied 

fluridone equivalents in a study examining photolysis in distilled water and a maximum of 36% 

applied fluridone equivalents in a study examining photolysis in lake water (MRID 00103326). 

Concentrations of NMF in photolysis studies increased over time, indicating that NMF could be 

stable to hydrolysis and photolysis (MRID 00103326). As fluridone may be applied with slowrelease pellets or with repeated applications, exposure to NMF is likely. The limited data on 

NMF submitted to the Agency showed developmental toxicity in mammals (see the human 

health risk assessment used to support the TRED). This indicates that chronic toxicity may occur 

with exposure to NMF. 

If data are not submitted, toxicity data for chemicals with a similar structure to NMF will be used 

to predict potential toxicity of NMF to aquatic and terrestrial organisms. 

The requested data would allow EPA to estimate risk to aquatic and terrestrial organisms to 

exposure to N-methyl formamide, including defining an action area for endangered species. 

Risk mitigation strategies (e.g., determining the maximum fluridone application rate that results 

in an RQ below the LOC) cannot be evaluated without these data. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

An ecological risk assessment was not completed with the re-registration decision for fluridone. 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. The data would allow the Agency 

to determine risk to aquatic and terrestrial organisms exposed to NMF as a result of the use of 

fluridone. The effects data would be used to determine the likelihood that the acute risks can 

potentially impact aquatic and terrestrial communities, either by direct effects or by indirect 

effects on other organisms by reducing their food sources. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be evaluated 

without these data. If future endangered species risk assessments are performed without these 
62 of 80

data, the Agency would have to assume that fluridone “may affect” endangered aquatic and 

terrestrial organisms directly (and endangered species from other taxa indirectly), and use of 

fluridone might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in use restrictions for fluridone 

which are unnecessarily severe. 

Degradate: 3-trifluoromethyl benzoic acid

Guideline 850.2100: avian acute oral toxicity 

Guideline 850.2300: avian reproduction study 

Rationale for Requiring the Data 

There is insufficient data available to assess the potential mortality risk of the degradate 3-

trilfluormethyl benzoic acid to terrestrial organisms. It was found at a maximum of 24% of 

applied fluridone equivalents in a study examining photolysis in distilled water and a maximum 

of 33% applied fluridone equivalents in a study examining photolysis in lake water (MRID 

00103326). As fluridone may be applied with slow-release pellets or with repeated applications, 

exposure to 3-trifluoromethyl benzoic acid is likely. 

If data are not submitted, toxicity data for chemicals with a similar structure to 3-trifluoromethyl 

benzoic acid will be used to predict potential toxicity of 3-trifluoromethyl benzoic acid to aquatic 

and terrestrial organisms. 

The requested data would allow EPA to estimate risk to aquatic and terrestrial organisms to 

exposure to 3-trifluoromethyl benzoic acid, including defining an action area for endangered 

species. Risk mitigation strategies (e.g., determining the maximum fluridone application rate 

that results in an RQ below the LOC) cannot be evaluated without these data. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

An ecological risk assessment was not completed with the re-registration decision for fluridone. 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. The data would allow the Agency 

to determine risk to aquatic and terrestrial organisms exposed to 3-trifluoromethyl benzoic acid 

as a result of the use of fluridone. The effects data would be used to determine the likelihood 

that the acute risks can potentially impact aquatic and terrestrial communities, either by direct 

effects or by indirect effects on other organisms by reducing their food sources. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be evaluated 

without these data. If future endangered species risk assessments are performed without these 

data, the Agency would have to assume that fluridone “may affect” endangered aquatic and 

terrestrial organisms directly (and endangered species from other taxa indirectly), and use of 
63 of 80

fluridone might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in use restrictions for fluridone 

which are unnecessarily severe. 

Fluridone and Degradate N-methylformamide

ECM and ILV Request 

Rationale for Requiring the Data 

Independent lab verification is being requested for MRID 162775. In order to support 

registration actions and registration review, relevant ECMs and associated ILV reports regarding 

fluridone and metabolites of concern should be submitted, reviewed, and found acceptable for 

the residues of concern. Acceptable ECMs for the residues of concern should have levels of 

quantitation that are adequate to address risk concerns or that are at levels below the 

toxicological endpoints for the relevant aquatic or terrestrial organisms. 

The requested data would allow EPA to estimate risk to aquatic and terrestrial organisms and to 

aid in validating dissipation studies. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

An ecological risk assessment was not completed with the re-registration decision for fluridone. 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. The data would allow the Agency 

to determine risk to aquatic and terrestrial organisms exposed to NMF as a result of the use of 

fluridone. The effects data would be used to determine the likelihood that the acute risks can 

potentially impact aquatic and terrestrial communities, either by direct effects or by indirect 

effects on other organisms by reducing their food sources. 

How could the data impact the Agency’s future decision-making? 

Risk assessment and mitigation strategies (e.g., determining the maximum fluridone application 

rate that results in Risk Quotients (RQs) below the Level of Concern (LOC)) cannot be evaluated 

without these data. If future endangered species risk assessments are performed without these 

data, the Agency would have to assume that fluridone “may affect” endangered aquatic and 

terrestrial organisms directly (and endangered species from other taxa indirectly), and use of 

fluridone might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in use restrictions for fluridone 

which are unnecessarily severe. 
64 of 80

Appendix B: Summary of Toxicity Data Table B1. Summary of Submitted Aquatic Toxicity Data for Fluridone. The Solubility of fluridone is 12.3 mranged from 240-6400 mg/kg (BLM 2005).* 

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

Freshwater Vertebrates

Acute 

850.1075 

Bluegill Sunfish 

(Lepomis 

macrochirus)/ 

Static 

TGAI 

99.4 

96-hr LC50= 12.1 mg/L 

(measured) 

 LOAEL = 10.6 mg/L 

NOAEL = 9.45 mg/L 

Mortality 00103308 

(1981) 

Supplemental 

DER 

Addendum 

09/01/2009) 

Water was not centr

measuring concentr

reported. Test concent

Acetone solvent w

concentrations of 

concentrations cannot 

effects included hyp

swimming. No subleth

2 mg/L and below

significantly with a slig

around the solub

concentrations ranged 

and mortality occurre

Acute 

850.1075 

Bluegill Sunfish 

(Lepomis 

macrochirus)/ 

Static 

EP 

44.5 

96-hr LC50 > 7.4 mg/L 

NOAEL < 5.9 mg/L 

(measured) 

No NOEL for sublethal 

effects 

No mortality, 

sublethal effects at 

all treatment levels 

00103306 

(1982) 

Supplemental 

DER 7/14/82 

Water was filter

concentrations. Total o

not reported. The hi

exceeded solubility. M

79% of measured value

cannot be determined. 

concentrations. Assaye

groups ranged from 

concentrations decrea

dose related effects 

hyperactivity, irregula

of equilibrium, immob
65 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

Acute 

850.1075 

Bluegill Sunfish 

(Lepomis 

macrochirus)/ 

Static 

TGAI 

NR 

 00121689 

(1978) 

Invalid 

Acute 

850.1075 

Bluegill Sunfish 

(Lepomis 

macrochirus)/ 

Static 

TGAI 96-hr LC50 = 11 mg 

a.i./L (total) 

(95% C.I. = 9.0 – 14 

(total)) 

Nominal, Moving 

Average Method 

Mortality 00103297 

Supplemental

-qualitative 

DER 

02/24/2010 

Mortality occurred at a

fluridone concentratio

>79% nominal, expos

above solubility are 

concentrations near n

values that were rep

Without actual repor

results are qualified he

were filtered prior to a

an effects endpoint 

treatment levels betw

Acute 

850.1075 

Bluegill Sunfish 

(Lepomis 

macrochirus)/ 

Static 

EP 96-hr LC50 = 6.5 (95% 

C.I.= 5.5-7.7; 

Litchfield-Wilcoxon) 

 (measured) 

Mortality 00103297 

Acceptable 

DER 

02/24/2010 

Samples were filte

concentration. TEP t

less than 79%. Measur

provided but the 96-h

concentrations was rep

stud

Acute 

850.1075 

Rainbow Trout 

(Salmo gairneri)/ 

Static 

TGAI 96-hr LC50 = 11.7±1.2 

mg/L (nominal) 

NOAEL = 5 mg/L 

No NOEL for sublethal 

effects 

Mortality 00121690 

(1978) 

Supplemental 

DER 

Addendum 

09/01/2009 

The highest nominal tesolubility (14 mg/L). 

80 was used due to t

7.5mL of solvent was 

The exposure concentr

because test concentr

Sublethal effects were 

Hyperactivity occurred 

within 24 hours. Pro

higher test 

Acute 

850.1075 

Rainbow Trout 

(Salmo 

gairdneri)/ Static 

EP 

44.5 

96-hr LC50 = 8.1 mg/L 

(measured) 

No NOEL for sublethal 

Mortality, sublethal 

effects at all 

treatment levels. 

00103307 

(1981) 

Supplemental 

DER 7/14/82 

Water was filtere

concentration. All no

exceeded solubility (1

test vessels displayed ir
66 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

effects or were prostrate on the 

Surviving fish, 96-hr 

stressed. Poo

Acute 

850.1075 

Rainbow Trout 

(Salmo gairneri)/ 

Static 

TGAI 6 studies 

96-hr LC50 = 

5.1 mg/L (95% C.I.= 

4.1-6.4; binomial) 

(measured) 

5.7 mg/L (95% C.I.= 

4.5-7.4, probit) 

Slope = 6.7 (3.0-10.3) 

(nominal) 

5.6 (95% C.I.=3.2-10.0; 

binomial) 

(nominal) 

7.0 mg/L (95% C.I. = 

5.6-10.0; binomial) 

(nominal) 

6.7 mg/L (95% C.I. = 

5.3-8.5; probit) 

(nominal) 

8.0 mg/L (95% 

C.I.=5.6-10.0, 

binomial) 

(nominal) 

Immobility and loss of 

equilibrium occurred at 

3.2 mg/L. Surfacing 

occurred at 5.6 mg/L. 

Mortality 00103297 

Acceptable 

DER 

02/24/2010 

Analytical results for 

actual fluridone conce

nominal concentration

pH or hard
67 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

Acute 

850.1075 

Rainbow Trout 

(Salmo gairneri)/ 

Static 

TGAI 3 studies 

96-hr LC50 ranged from 

4.5-8.0 mg/L, binomial, 

nominal 

Mortality 00103297 

Supplemental

-qualitative 

DER 

02/24/2010 

Analytical results for 

actual fluridone conce

nominal concentrations 

long. No trend with 

ob

Acute 

850.1075 

Rainbow Trout 

(Salmo gairneri)/ 

Static 

EP 96-hr LC50=4.3 (95% 

C.I.= 2.9-6.3, binomial) 

(nominal) 

Mortality 00103297 

Acceptable 

DER 

02/24/2010 

Only 4 treatment levels

averaged <

Acute 

850.1075 

Channel Catfish 

(Ictalurus 

punctatus)/ 

Static 

TGAI 96-hr LC50 = 7.5 mg/L 

(95% C.I.=6.1-9.2; 

probit) 

Slope=10.2 (4.3-16.1) 

(nominal) 

Immobility occurred at 

5.6 mg/L. Loss of 

equilibrium occurred at 

10 mg/L and surfacing 

at 7.5 mg/L. 

Mortality 00103297 

Acceptable 

DER 

02/24/2010 

Analytical results for 

actual fluridone conce

nominal concentration

concentrations bel

Acute 

850.1075 

Channel Catfish 

(Ictalurus 

punctatus)/ 

Static 

TGAI 9 studies 

96-hr LC50 = 8.7-13 

mg/L (nominal) 

Could not be 

determined in some 

studies due to no or low 

mortality at highest 

treatment level below 

solutiliby. 

Mortality 00103297 

Supplemental

-qualitative 

DER 

02/24/2010 

Measured concentrati

samples were lost o

occurred to determine 

above solubility were i

LC50 values as total co

values likely overestim

Acute 

850.1075 

Channel Catfish 

(Ictalurus 

punctatus)/ 

Static 

EP 96-hr LC50 = 13 (total) 

(95% C.I.= 10 -18, 

binomial) 

Nominal 

Mortality 00103297 

Supplemental

-qualitative 

DER 

02/24/2010 

Water samples wer

confirmation of solubl

can be made. No m

nominal treatment 

Exposure concentrat
68 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

unlikely to have solu

nominal (as eviden

reported for obs 13, 1

solubility were includ

values as total concentr

likely overestimate 

Acute 

850.1075 

Fathead Minnow 

(Pimephales 

promelas)/ Static 

TGAI 96-hr LC50>10 

(nominal) 

Mortality 00103297 

Supplemental

-qualitative 

DER 

02/24/2010 

No mortality at any 

solubility, all mortality 

While fluridone con

reported as >79% 

concentrations at and a

to have soluble conce

evidenced by values th

14, 24). Without actua

the results are quali

Acute 

850.1075 

Fathead Minnow 

(Pimephales 

promelas)/ Static 

EP 96-hr LC50 = 8.3 mg/L 

(measured, binomial) 

Mortality 00103297 

Acceptable 

DER 

02/24/2010 

Full Life 

Cycle 

850.1500 

Fathead Minnow 

(Pimephales 

promelas)/ Flow 

Through 

TGAI 

99.2 

LOAEL = 0.96 mg/L 

NOAEL = 0.48 mg/L 

(measured) 

Hatching success 

(80-85% versus 95-

98%) and survival 

of 30 day fry (0-5% 

versus 100%) 

00103309 

(1981) 

Acceptable 

DER 7/15/82 

Water samples were 

BCF = 3.23±1.65. E

highest test concentra

exposed to 0.96 mg/L 

when compared to wa

control 30 days after h

after hatching. The num

the number of eggs pe

substantially betwee

treatments and contr

(0.12 mg/L) treatment g

tank ov

Chronic Channel Catfish 

(Ictalurus 

punctatus) 

EP 60-day NOAEL = 0.5 

mg/L (nominal) 

Growth 00103297 

Preliminary 

supplemental 

Analytical results for 

actual fluridone conce

nominal concentration

and 2.0 mg/L after 15 
69 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

was not statistically 

control but was much lo

(68-70% versus 91%)

attributed to a diluter m

resulted 2.5 fold 

conc

Seawater 

adaptability 

test and 

Acute 

Toxicity 

850.1075 

Chinook Salmon 

(Oncorhynchus 

tshawytscha)/ 

Static 

TGAI 

99.4 

96-hr LC50 >5.76 mg/L 

96-hr LC22 = 5.76 mg/L 

(measured) 

Mortality 46112001 

(2003) 

Supplemental 

DER 

02/24/2010 

Some fish jumped out 

fish jumped out of cont

observed in 1.53, 3.06

dark discolorations, l

swimming patter, fish 

surfacing, and jump

saltwater was also exa

reported. Mean length 

fish. Test fish were ne

test and 22 g for the sa

acute toxicity test, fish 

and be juveniles. The 

juv

Early life 

stage 

850.1400 

Chinook Salmon 

(Oncorhynchus 

tshawytscha)/ 

Flow Through 

TGAI 

99.4 

NOAEC = 0.430 mg/L NOAEC = 0.222 mg/L 

(measured) 

Length 

Gill histopathology 

(hypertrophy of gill 

lamellar epithelium) 

45915601 

(2003) 

Supplemental 

DER 

02/24/2010 

Study initiated with 3

hour old embryos are t

A 34 day salmon embr

Raw data on daily num

and daily swim up 

develo

Estuarine/Marine Vertebrates 

Acute 

850.1075 

Sheepshead 

Minnow 

(Cyprinodon 

variegatus)/ 

Static 

TGAI 

98.1 

96-hr LC50 = 10.7 mg/L 

(measured) 

NOAEC = 3.1 mg/L 

Mortality 00108837 

(1981) 

Supplemental 

DER 

Addendum 

09/01/2009 

Fish were exposed to 

solubility (3.1, 5.8, 

measured). Probit w

Treatments were no

collected at the beginni

of the test, combine

measured. The wate

filtered pr

Acute Sheepshead EP 96-hr LC50 = 18.1 mg/L Mortality 00103316 Based on the varia
70 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

850.1075 Minnow 

(Cyprinodon 

variegatus)/ 

Static 

43.16 (measured) (1981) 

Supplemental 

DER 8/16/82 

concentrations c

concentrations, the pre

test concentrations ex

exposure concentratio

concentrations ranged 

observed at 12 mg/L 

filtered prior to analysis

ranged from 44-93% o

in controls. Data n

mo

Freshwater Invertebrates

Acute 

850.1010 

Waterflea 

(Daphnia 

magna)/ Static 

EP 

44.5 

48-hr EC50 = 3.6 mg/L 

(measured) 

NOAEL = 2.0 mg/L 

No NOAEL for 

sublethal effects. 

Mortality 00103296 

(1981) 

Supplemental 

DER 7/13/82 

Water samples were 

Vessel did have aera

material was observed

ranged from 65-111

quality parameters m

mortality was observe

observed at the next hig

mg/L. Data were not a

Sublethal effect

concentrations include 

and p

Acute Crayfish 

(Orconectes 

immunis)/ Flow 

through 

TGAI 

99.7 

14 day LC50 > 16.9 

mg/L (measured) 

Mortality 00162774 

(1984) 

Supplemental 

DER 11/6/86 

Water samples were f

water concentrations. 2

all treatment levels but 

No mortality or behav

observed for crayfish 

level. Sublethal effe

highest tr

Acute 

850.1010 

Waterflea 

(Daphnia 

magna) 

TGAI 

and 

EP 

48-hr EC50 = 5.2 mg/L 

in 2 TGAI studies 

 (nominal) 

48-hr EC50 = 3.0 and 

4.0 mg/L in 2 EP 

Mortality 00103297 

Acceptable 

DER 

02/24/2010 

Water samples were f

not specified) prior 

concentration in water

were ≥ 79% of nom

concentrations wer

Technical and formul
71 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

studies 

 (nominal) 

48-Hr EC50 of studies 

mg/L hardne

Acute Midge 

(Chironomous 

plumosus) 

TGAI 48-hr EC50 = 1.3 mg/L 

(nominal, results from 2 

tests) 

Mortality 00103297 

Preliminary 

Supplemental 

Water samples were f

not specified) prior 

concentration in water

were ≥ 79

Acute Amphipod 

(Gammarus 

pseudolimnaeus) 

TGAI 96-hr LC50 =2.1 -4.1 

mg/L (nominal; 2 

studies) 

Mortality 00103297 

Preliminary 

Supplemental 

Water samples were f

not specified) prior 

concentration in water

were ≥ 79

Chronic 

850.1300 

Waterflea 

(Daphnia 

magna) 

TGAI 21 day NOAEL = 0.2 

mg/L (nominal) 

Mortality 00103297 

Preliminary 

Supplemental 

Samples were stored 

shipment was received 

concentrations 

Chronic Amphipod 

(Gammarus 

pseudolimnaeus) 

EP 60-day NOAEL = 0.6 

mg/L (nominal) 

Mortality 00103297 

Preliminary 

Supplemental 

Samples were stored 

shipment was received 

concentrations 

Chronic Midge 

(Chironomous 

plumosus) 

EP 30-day NOEL = 0.6 

mg/L (nominal) 

Mortality 00103297 

Preliminary 

Supplemental 

Samples were stored 

shipment was received 

concentrations 

Estuarine/Marine Invertebrates

Acute 

850.1025 

Eastern Oyster 

(Crassostrea 

virginica)/ Flow 

Through 

TGAI 

98.1 

25% reduction in shell 

growth observed for 

solvent control and at 

0.25 mg/L, a mid dose 

level. 

Shell Growth 00103310 

(1981) 

Supplemental 

DER 7/27/82 

Water samples were f

fluridone concentration

were 70-102% of nom

Precipitation observed 

guideline recommend

level and for controls. 

than 2 mm 

Acute 

(EmbryoLarval) 

850.1055 

Eastern Oyster 

(Crassostrea 

virginica)/ Static 

Age=embryo 

TGAI 

98.1 

48-hr EC50 = 16.8 mg/L 

(measured) 

NOAEC = 9.2 mg/L 

Reduction in normal 

larvae 

00103311 

(1981) 

Supplemental 

DER 

Addendum 

09/02/2009 

Water samples were f

fluridone concentratio

much lower than n

concentrations excee

concentrations rang

Acute Eastern Oyster EP LOAEC = 0.08-0.62 Increased shell 00103314 Water samples were 
72 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

(EmbryoLarval) 

850.1055 

(Crassostrea 

virginica)/ Flow 

Through 

Age=embryo 

43.16 mg/L (measured) 

NOAEC not 

determined. 

deposition (1981) 

Supplemental 

DER 8/6/82 

Precipitate was presen

measured concentrati

final measured conce

New shell growth in al

to or greater than that o

measured concentration 

true exposure conc

Acute 

(EmbryoLarval) 

850.1055 

Eastern Oyster 

(Crassostrea 

virginica)/ Static 

Age=embryo 

EP 43.16 

48-hr EC50 = 6.8 mg/L 

(measured) 

Normal larvae 00103315 

(1981) 

Supplemental 

DER 8/6/82 

Water samples were fi

significant reduction in 

in concentrations ≥ 10 m

3 mg/L of the measur

provided a significant i

Probit was not a

Acute 

850.1045 

Pink Shrimp 

(Panaeus 

duorarum)/ 

Static 

Age = Juvenile 

TGAI 98.1 

LC50 = 4.6 mg/L 

(measured) 

Mortality 00112789 

(1981) 

Acceptable 

DER 7/23/82 

Water was filter

concentrations of flurid

a sample was collected 

and at the end of the te

then the concentratio

concentrations exceede

tre

Acute 

850.1045 

Pink Shrimp 

(Panaeus 

duorarum)/ 

Static 

Age = Juvenile 

EP 43.16 

96-hr LC50 = 2.4 mg/L 

(measured) 

NOAEC = 0.6 mg/L 

Mortality 00103312 

(1981) 

Supplemental 

DER 8/4/82 

Water was filter

concentrations of flurid

a sample was collected 

and at the end of the te

then the concentration 

concentrations were 

concentrations were b

per treatment. Aerated

paper used to filter wa

filter paper was “A

Schleicher and Schuel

enough information is 

exposure c

Acute Blue Crab 

(Callinectes 

TGAI 

98.1 

96-hr LC50 = 27.04 

mg/L (measured) 

Mortality 00108836 

(1981) 

Water samples were fil

fluridone concentration
73 of 80

Study 

Type 

Test Species 

(Genus 

Species)/ Flowthrough/ 

Static 

% 

a.i. 

Toxicity Endpoint 

(Measured/ 

Nominal) 

Effect 

MRID (Year) 

Classification 

or Source 

Com

sapidus)/ Static 

Age = Juvenile 

Supplemental 

DER 7/26/82 

at concentration > 

concentrations were hig

on average concentrati

and e

Acute Blue Crab 

(Callinectes 

sapidus)/ Static 

Age = Juvenile 

EP 43.6 

96 hr LC50 = 34.0 mg/L 

(measured) 

Mortality 00103313 

(1982) 

Supplemental 

DER 

8/4/1982 

Water samples were fil

fluridone concentration

Aerated. 50% moralit

10% mortality at 77

concentrations exceed 

measured. The ex

unc

Other Studies

Field Study Benthic 

Community 

 00121685 

(1978) 

Not reviewed 

Benthic organisms wer

treatment of po

Abbreviations: TGAI = technical grade active ingredient; EP=end use product; conc.=concentration *Data submitted under MRID 103297 are data collected by the United States Fish and Wildlife Service. When toxicity data were avail

concentrations ≥79% of nominal the results from those tests were reported and the endpoints where the analytical chemistry was missin

were not reported. When data were only available without measured concentrations or with low recoveries, than the nominal value is r

Table B2. Summary of terrestrial toxicity data submitted for fluridone. 

Study Type Test Species TGAI or EP 

Toxicity 

Endpoint 

(95% C.I.) 

(Measured/ 

Nominal)/ 

Slope 

Effect 

MRID (Year) 

Classification, 

DER date or 

source 

Com

Acute Oral Rat TGAI LD50 = 10,000 

mg/kg 

Mortality USEPA 2004c 

Subchronic Oral 

(90 day oral) 

Mice TGAI NOAEL =15 

mg/kg/day 

LOAEL=25 

mg/kg/day 

Hepatic 

centrilobular 

hypertrophy 

00082342 

Acceptable 

USEPA 2004c 
74 of 80

Study Type Test Species TGAI or EP 

Toxicity 

Endpoint 

(95% C.I.) 

(Measured/ 

Nominal)/ 

Slope 

Effect 

MRID (Year) 

Classification, 

DER date or 

source 

Com

Subchronic Oral 

(90 day oral) 

Rat TGAI NOAEL =25 

mg/kg/day 

LOAEL=44 

mg/kg/day 

Increased absolute 

and relative liver 

weights and 

relative kidney 

weights 

00135209 

Acceptable 

USEPA 2004c 

Chronic Toxicity Rat TGAI 2 year NOAEL/LOAEL 

7.65/25.15 mg/kg/day (body weight 

92% of control) 

25.15/80.8 mg/kg/day (Body weight 

was 59-89% of control, and increased 

incidence of small testes, enlarged and 

granular kidneys, opaque, cloudy 

ulcerated eyes, and skin nodules and 

masses observed. The effects were 

dose related.) 

00103305 

Acceptable 

(U.E. EPA 

2004b 

Reproduction and 

Fertility Effects 

Rat (wistar) TGAI 3 generation 

reproduction 

study 

NOAEL=36 

mg/kg/day 

LOAEL=112 

mg/kg/day 

Decrease in pup 

weight on lactation 

day 21 00103304 

Acceptable 

(USEPA 2004c) 

Acute dietary Rabbit TGAI LOAEL = 300 

mg/kg/day 

NOAEL = 125 

mg/kg/day 

Increased incidence 

of abortions 

00103302 

Acceptable 

(USEPA 2004c) 

Exposed days 6-1

aborted between 

gestation, decreas

obse

Chronic Dietary ICR Mice TGAI 2 year dietary 

LOAEL = 50 

mg/kg/day 

NOAEL = 15 

mg/kg/day 

Increased alkaline 

phosphatase and 

hepatocelluar 

hyperplasia 

00103335 

Acceptable 

(USEPA 2004c) 

USEPA 

Avian

Acute Oral Bobwhite Quail TGAI LD50 > 2000 None observed 00121686 MRID and DE
75 of 80

Study Type Test Species TGAI or EP 

Toxicity 

Endpoint 

(95% C.I.) 

(Measured/ 

Nominal)/ 

Slope 

Effect 

MRID (Year) 

Classification, 

DER date or 

source 

Com

(Colinus 

virginianus) 

Age=8 mos. 

bw=198.1±5.6 

g 

95-97 mg/kg-bw 

(nominal) 

(1978) 

Acceptable, DER 

09/18/1978 

whether the 2000 

weight or diet. As

Acute Dietary Bobwhite Quail 

(Colinus 

virginianus) 

Age = 10 days 

bw = 15.9 ±0.4 

g 

TGAI 

95-97 

8-day LC50 > 

4390 mg/kg-diet 

LOAEL = 2500 

mg/kg-diet (body 

weight) 

(measured) 

No mortality 

observed 

00121687 

(1978) 

Acceptable, DER 

9/16/78 

10 birds per tr

A statistically sign

weight was observ

mg/kg-diet. 

consumpti

Acute Dietary Mallard Duck 

(Anas 

platyrhynchos) 

Age = 16 day 

bw=280.2±6.4g 

TGAI 

95-97 

8-day LC50 > 

4540 mg/kg-diet, 

LOAEL = 1580 

mg/kg-diet (body 

weight) 

No mortality 

observed 

00135211 

(1978) 

Acceptable DER 

9/16/78 

Only 8 birds in 

recommends a m

per replicate. Foo

reduced, possibly 

statistically signi

body weight wa

treatment levels. 

00121688, and 00

study with DER l

Reproductive Bobwhite Quail 

(Colinus 

virginianus) 

Age = 17 wks 

TGAI 

99.7 

 00103293 

(1982) 

Invalid 

DER Addendum 

09/01/2009 

A statistically sig

the number of eggs 

were larger in the 

group when compa

birds showed very 

and a high percent

especially for the 

could indicate tha

husbandry pra

hatchability decre

only significant

controls at lowe
76 of 80

Study Type Test Species TGAI or EP 

Toxicity 

Endpoint 

(95% C.I.) 

(Measured/ 

Nominal)/ 

Slope 

Effect 

MRID (Year) 

Classification, 

DER date or 

source 

Com

because the con

lowest ha

Reproductive Mallard Duck 

(Anas 

platyrhynchos) 

Age = 13 wks 

Male bw = 

1114±14 g 

Female bw = 

976±9g 

TGAI 

99.7 

 00103294 

(1981) 

Invalid 

DER Addendum 

09/01/2009 

4 pens each wi

females. Sixteen 

observed 3-4 bird

and control gro

indications of st

housing conditions 

and bacterial i

percentages of c

higher than norma

lowest treatment 

10% mortality 

con

Terrestrial Invertebrates

Acute Contact Honey Bee 

(Apis mellifera 

L.) 

EP 

33.3 

Highest test 

concentration = 

362.58 

μg/bee 

No mortality 00103295 

(1982) 

Acceptable 

DER 7/16/82 

Bees were exposed 

of fluridone in com

toxic du

Earthworm 

Acute/subchronic Earthworm 

(Eisenia fetida) 

TGAI 

95-97 

102.6 ppm was 

the highest tested 

concentration 

No mortality 

observed 

00121692 

(1978) 

Supplemental 

DER 9/18/1978 

Earthworms expos

ppm of fluridone 

mortality. A few 

slight changes 

Abbreviations: TGAI = technical grade active ingredient; EP=end use product; conc.=concentration 
77 of 80

Appendix C: Preliminary TREX Output for NMF 

The application rate was estimated using the following equation: 

Parent application rate (lbs ai/A) x Maximum Percent NMF parent equivalents in photolysis 

study x Molecular weight of NMF ÷ molecular weight of parent = 4.9 lbs ai/A x 0.74 x 59.07 

g/mole ÷ 329.30 g/mole = 0.65 lbs NMF /A 
78 of 80
79 of 80

Appendix D: ECOSAR (version 1.0) Results for 3-trifluoromethyl benzoic acid 

SMILES : OC(=O)c1cccc(c1)C(F)(F)F 

CHEM : 

CAS Num: 

ChemID1: 

ChemID2: 

ChemID3: 

MOL FOR: C8 H5 F3 O2 

MOL WT : 190.12 

Log Kow: 2.84 (KowWin estimate) 

Melt Pt: 

Wat Sol: 148.5 mg/L (WskowWin estimate) 

ECOSAR v1.00 Class(es) Found 

------------------------------ 

Neutral Organics-acid 

 Predicted 

ECOSAR Class Organism Duration End Pt mg/L (ppm) 

=========================== ================== ======== ====== 

========== 

--> Acid moeity found: Predicted values multiplied by 10 

Neutral Organics-acid : Fish 96-hr LC50 268.600 * 

Neutral Organics-acid : Fish 14-day LC50 275.276 * 

Neutral Organics-acid : Daphnid 48-hr LC50 171.422 * 

Neutral Organics-acid : Green Algae 96-hr EC50 117.058 

Neutral Organics-acid : Fish 30-day ChV 29.599 

Neutral Organics-acid : Daphnid ChV 22.692 

Neutral Organics-acid : Green Algae ChV 51.431 

Neutral Organics-acid : Fish (SW) 96-hr LC50 350.406 * 

Neutral Organics-acid : Mysid Shrimp 96-hr LC50 147.394 

Neutral Organics-acid : Fish (SW) ChV 63.303 

Neutral Organics-acid : Mysid Shrimp (SW) ChV 9.940 

Neutral Organics-acid : Earthworm 14-day LC50 2706.424 * 

 Note: * = asterisk designates: Chemical may not be soluble 

 enough to measure this predicted effect. 

 

Neutral Organics: 

---------------- 

 For Fish LC50 (96-h), Daphnid LC50, Mysid: If the log Kow is greater 

than 5.0, or if the compound is solid and the LC50 exceeds the water 

solubility by 10X, no effects at saturation are predicted. 

 
80 of 80

 For Fish LC50 (14-day) and Earthworm LC50: If the log Kow is greater 

than 6.0, or if the compound is solid and the LC50 exceeds the water 

solubility by 10X, no effects at saturation are predicted. 

 

 For Green Algae Acute Toxicity Values: If the log Kow of the chemical is 

greater than 6.4, or if the compound is solid and the EC50 exceeds the water 

solubility by 10X, no effects at saturation are predicted for these endpoints. 

 

 For All Chronic Toxicity Values: If the log Kow of the chemical is greater 

than 8.0, or if the compound is solid and the ChV exceeds the water solubility 

by 10X, no effects at saturation are predicted for these endpoints. 

 

ECOSAR v1.00 SAR Limitations: 

---------------------------- 

Maximum LogKow: 5.0 (Fish 96-hr LC50; Daphnid LC50, Mysid LC50) 

Maximum LogKow: 6.0 (Fish 14-day LC50; Earthworm LC50) 

Maximum LogKow: 6.4 (Green Algae EC50) 

Maximum LogKow: 8.0 (ChV) 

Maximum Mol Wt: 1000