MEMORANDUM 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

• OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

PC Code : 125701 

DP Barcode: 424764 

Date: June 4, 2015 

Subject: Ecological Risk Assessment for Registration Review of Flurprimidol. 

To: Kelly Ballard, Chemical Review Manager 

Neil Anderson, Branch Chief 

Risk Management and Implementation Branch 

Pesticide Re-evaluation Division 

Through: 

Environmental 

Environmental 

Dana Spatz, Branch 

Fate 

Risk Branc

Chief

and Effects 

~~ 

~ 

Division 

From: James K. Wolf, Ph .D. , Environmental Scientist % Katherine Stebbins, Biologist 

Environmental Risk Branch Ill 

Environmental Fate and Effects Division 

Peer Review: Melissa Panger, Ph.D., Senior Advisor 

James Hetrick Ph.D., Senior Advisor _J~ (A . 

Rosanna Louie-Juzwiak, RAPL 

Environmental Risk Branch Ill 

Environmental Fate and Effects Division 

This memorandum transmits the Environmental Fate and Effects Division's {EFED) ecological risk 

assessment for flurprimidol. As the ecological risk assessment for uses other than the tree 

injection/implant use is current, the focus of this assessment is the tree injection/implant use. 

The results of the screening level analysis conducted for the tree injection use pattern, which 

assumes the total mass of chemical applied reaches the terrestrial and aquatic environments, as 

well as distribution of concentrations in tree trunks and leaves, suggest that translocation of 
2 

flurprimidol from the site of injection to edible portions of a tree may result in potential effects

to birds, mammals, and terrestrial invertebrates. There are no risk concerns identified for aquatic

animals and non‐vascular plants. For listed and non‐listed vascular plants, there is a potential risk

identified for plants in aquatic areas where contaminated tree parts may contact the waterbody.

The exposure pathway for non‐target terrestrial plants is incomplete/negligible for the tree

injection use pattern. In general, despite the differences in the exposure pathways, the primary

risk conclusions for the tree injection uses are similar to the turf and ornamental uses previously

assessed.  

At this time, additional toxicity data are needed in order to conduct an assessment for

pollinators (considering all registered uses). These studies include:

1. Acute oral toxicity to adult honey bees (Non‐guideline, OECD TG 213)

2. Acute oral toxicity to larval honey bees (Non‐guideline, OECD TG 237)

3. Chronic oral toxicity to adult honey bees (Non‐guideline)

4. Chronic oral toxicity to larval honey bees (Non‐guideline)

5. Field trial of residues in pollen and nectar (Non‐guideline)

6. Semi‐field testing for pollinator (Non‐guideline, OECD Guidance 75)

7. Field testing for pollinators (Guideline 850.3040)

 
3 

Ecological Risk Assessment for the Registration Review of Flurprimidol 

α‐(1‐methylethyl)‐α‐[4‐(trifluoromethoxy) phenyl]‐5‐pyrimidinemethanol

C15H15F3N2O2

(CAS Reg. No. 56425‐91‐3; PC Code 125701)

  

Prepared by: 

 

Katherine Stebbins, Biologist

James Wolf, Ph.D., Environmental Scientist

 

Reviewed by: 

 

James A. Hetrick, Ph.D., Senior Advisor

Melissa Panger, Ph.D., Senior Scientist

Rosanna Louie‐Juzwiak, Risk Assessment Process Leader

 

Approved by: 

Dana S. Spatz, Branch Chief

Environmental Risk Branch III

Environmental Fate and Effects Division

Office of Pesticide Programs

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, NW

Washington, D.C.  20460

March 4, 2015
4 

I. EXECUTIVE SUMMARY 

 

Nature of the Stressor 

Flurprimidol (RS)‐2‐methyl‐1‐pyrimidin‐5‐yl‐1‐(4‐trifluromethoxyphenyl)propan‐1‐o1, is a

systemic plant growth regulator that reduces internode elongation of plants through the

inhibition of gibberellic acid biosynthesis (paclobutrazol and uniconazole are also in this class).

Flurprimidol reduces leaf blade length and stem internode elongation in grasses and suppresses

terminal growth and biomass in established woody ornamental and perennial ground covers.

Tree injections/implant uses are also registered for non‐crop ornamental trees. 

There are 14 end use products that are registered for use on: golf course turf (perennial cool and

warm season), athletic fields, commercial, municipal, and residential turf, container grown

ornamental plants and perennial landscapes (including shrubs and trees). Previous assessments

have evaluated the risks for the turf and ornamental uses. The focus of this assessment is to

determine the risk to terrestrial and aquatic organisms from the tree injection/implant uses.  

The dominant dissipation pathways for flurprimidol are expected to be via leaching through soil,

plant uptake, and photolysis in water. For the tree injection use, it is assumed that flurprimidol

will be translocated to the leaves, which will degrade, releasing flurprimidol, after falling to the

ground (Premachandra et al., 19971). Flurprimidol is stable to hydrolysis and resistant to

degradation in both aerobic and anaerobic terrestrial systems. Field dissipation data for cropped

turf plots suggest that much more rapid dissipation was found than might be expected from the

laboratory studies. The registrant postulates that this could be due to a number of factors not

tracked in the study, including plant uptake and volatilization, although vapor pressure and

Henry’s law constant would suggest that volatilization would not be an important dissipation

process. Field dissipation data on bare ground sites yields much longer dissipation times that are

comparable to laboratory estimates, suggesting that plant uptake via transpiration or absorption

through plant or root surfaces is influencing the dissipation in the field.

  

Summary of Effects and Risk Conclusions

 

Laboratory toxicity data suggest that flurprimidol is slightly toxic on an acute basis to freshwater

animals, with fish and invertebrate LC50s ranging from 12‐18 milligrams of active ingredient per

liter (mg a.i./L). There are no acute toxicity data available to characterize acute effects to their

estuarine/marine counterparts; however, based on data for freshwater animals, flurprimidol is

assumed to be, at most, slightly toxic to estuarine/marine organisms. Chronic toxicity data

indicate reductions in fry survival, length, and weight of freshwater fish and reductions in days of

first brood, young per adult, and adult length of invertebrates, with fish and invertebrate

NOAECs ranging from 0.939 to 2.95 mg a.i./L. Toxicity data for aquatic vascular and non‐vascular

 

1 Premachandra, G.S., W.R. Chaney, and H.A. Holt. 1997. Effects of mulch made from flurprimidol treated zinnia, silver maple,

and white ash on growth of zinnia. J. Environ. Hort. 15:215‐221.
5 

plants identified EC50s of less than 1 mg a.i./L. For vascular aquatic plants, the EC50 was 0.0085

mg a.i./L with a NOAEC of 0.00089 mg a.i./L  based on a reduction in the number of fronds.  

Acute oral and subacute dietary toxicity tests suggest that flurprimidol is practically nontoxic to

birds. Flurprimidol is slightly toxic to mammals on an acute oral basis, with an LD50 of 709 mg

a.i./kg‐bw. Chronic toxicity data with birds indicate reductions in egg production, embryo

survival, and hatchability with a NOAEC of 309 mg a.i./kg‐diet. A two‐generation chronic

mammalian (rat) toxicity study demonstrated decreased mating, fertility, and fetal survival

(stillbirths) in both generations at flurprimidol levels of 1000 mg a.i./kg‐diet (equivalent to 74 mg

a.i./kg‐bw/day) resulting in a reproductive NOAEL of 100 mg a.i./kg‐diet (equivalent to 7.3 mg

a.i./kg‐bw/day).

Overall, the screening level analysis conducted for the tree injection use pattern, which assumes

total mass of chemical applied reaches the terrestrial and aquatic environments, as well as

distribution of concentrations in tree trunks and leaves, suggests that translocation of

flurprimidol from the site of injection to edible portions of a tree may result in potential effects

to birds, mammals, and terrestrial invertebrates. There are no risk concerns identified for aquatic

animals and non‐vascular plants. For listed and non‐listed vascular plants, there is a potential risk

identified for plants in aquatic areas where contaminated tree parts may contact the waterbody.

The exposure pathway for non‐target terrestrial plants is incomplete/negligible for the tree

injection use pattern.  

In general, despite the differences in the exposure pathways, the risk conclusions for the tree

injection uses are similar to the turf and ornamental uses previously assessed (except for

terrestrial plants).  

II.  Problem Formulation

This document generally follows the process and assessment methods as outlined in the

preliminary Problem Formulation for the Ecological Risk and Drinking Water Exposure

Assessments for Flurprimidol (USEPA, 20092

). However, since the 2009 document was prepared,

several new uses were assessed or updated (USEPA, 20103). Additional uses, additional data, and

current methods and exposure models not included in the Problem Formulation are considered

in this document.  

   

 

2 USEPA, 2009. Carey, S. and S. Syslo. Registration Review ‐ Preliminary Problem Formulation for the Ecological Risk and Drinking

Water Exposure Assessments for Flurprimidol (PC Code 125701; DP Barcodes 362451, 362452, 366858; July 8, 2009) 3 USEPA, 2010. Carey, S. and J.K. Wolf. Revised Section 3 Environmental Fate and Ecological Risk Assessment of Flurprimidol

proposed for New Uses on Turf grasses and Ornamentals (DP Barcode 374783, June 9, 2010).
6 

A. Pesticide Type, Class, and Mode of Action  

Flurprimidol (RS)‐2‐methyl‐1‐pyrimidin‐5‐yl‐1‐(4‐trifluromethoxyphenyl)propan‐1‐o1, is a

systemic plant growth regulator that reduces internode elongation of plants through the

inhibition of gibberellic acid biosynthesis. Flurprimidol reduces leaf blade length and stem

internode elongation in grasses and suppresses terminal growth and biomass in established

woody ornamental and perennial ground covers. Tree injections/implant uses are also registered

for non‐crop/ornamental trees.   

Overall, the dominant dissipation mechanism for flurprimidol is expected to be via leaching due

to its mobile nature, plant uptake (via transpiration or absorption through plant leaves or root

surfaces) because the compound is a plant growth regulator, and by photolysis in aqueous

systems. Flurprimidol is stable to hydrolysis and resistant to degradation in both aerobic and

anaerobic terrestrial systems. Field dissipation data for cropped turf plots suggest that much

more rapid dissipation was found than might be expected from the laboratory studies. The

registrant postulates that this could be due to a number of factors not tracked in the study

including plant uptake and volatilization. Field dissipation data on bare ground sites yields much

longer dissipation times that are comparable to laboratory estimates, suggesting that the

presence of plant material is influencing the dissipation in the field. No data were available to

suggest how available flurprimidol is in plant residues. Finally, flurprimidol is not expected to be

volatile (based upon a vapor pressure of 3.7 x 10‐7 mm Hg and Henry’s Law constant of 3.97 x 10‐

9 atm∙m3/mol), or to bioaccumulate, as demonstrated by its relatively low Kow and low BCF

factors in bluegill sunfish.  The chemical structure of flurprimidol is shown in Figure 1.  

Figure 1.   Flurprimidol Structure 

A summary of selected physical and physiochemical properties of flurprimidol is presented in

Table 1.
7 

Table 1.  Summary of Physiochemical Properties of Flurprimidol.

Parameter Value MRID # 

CAS Reg. No. 56425‐91‐3  ‐ 

Chemical Name  IUPAC: (RS)‐2‐methyl‐1‐pyrimidin‐5‐yl‐1‐(4‐

trifluoromethoxyphenyl)propan‐1‐ol

‐ 

CAS: α‐(1‐methylethyl)‐α‐[4‐(trifluoromethoxy)phenyl]‐5‐

pyrimidinemethanol

‐ 

Smiles Code  CC(C)C(C1=CC=C(C=C1)OC(F)(F)F)(C2=CN=CN=C2)O Pub Chem, 2014a

Molecular Weight 312.30 g/mole   

Molecular Formula C15H15F3N2O2 Pub Chem, 2014a

Vapor pressure   3.64 x 10‐7 mm Hg [torr] @ 25Cb

   00162772  

Solubility in Water 130 mg/L 40981703 a http://pubchem.ncbi.nlm.nih.gov/compound/Flurprimidol#section=MeSH‐Synonyms b Vapor pressure at 25 C calculated from measured values at 20C and 39.7C.

It should be noted that the carbon in the 1‐position in the propane moiety (the carbinol C) is a

chiral molecule. Technical flurprimidol is a racemic mixture. 

 

B. Overview of Pesticide Use and Usage 

Flurprimidol is used to regulate growth in plants requiring routine mowing, pruning or edging.

It is used on perennial turfgrass (cool and warm season), a number of ornamental ground

cover species, herbaceous and ornamental plants, and deciduous tree species (via

injection/implant). Turfgrass uses include golf courses, athletic fields, commercial, municipal,

and residential turf, including edging/banding applications for landscape beds, sidewalks,

perimeter of lawns, curbs, parking lots, driveways, posts, mailboxes, building structures,

gravestones, fences, and other similar areas. Ornamental plant uses include: bedding,

flowering, and perennial, and woody landscape plants in nurseries, greenhouses, and shade

houses. The tree injection/implant uses are for treating non‐crop ornamental trees in

commercial/residential/municipal settings (e.g., near houses, rights of way/power lines,

streetlights, signs, etc.) and in areas such as airports or parks where vista control is desired.  

There are 14 end use products that are registered for flurprimidol (Table 2). Formulations

include:  wettable powder (10% ‐ 50% active ingredient), soluble/solid concentrate (99.3%

a.i.), liquid (0.38% ‐ 13.26% a.i.), liquid – ready to use (48.1% a.i.), granule (0.17% ‐ 0.5% a.i.),

and impregnated (93.6% a.i.) on granular fertilizer producing granular formulation products.

Application equipment includes spreader, backpack sprayer, low‐pressure hand wand, ground

boom sprayer, injection equipment, by hand, drencher, drip irrigation, tank‐type sprayer or

sprinkler irrigation. Application is via foliar treatment, spot treatment, chemigation, tree

injection or implant treatment, drench, edging treatment, or band treatment. Single

application rates for treatment range from 0.26 to 1.5 pounds active ingredient/acre (lb a.i./A)

and seasonal application rates are up to 3.00 lb a.i./A. A more comprehensive listing of the

individual uses/use patterns is provided in Appendix A.  
8 

Table 2. Flurprimidol Registrations 

EPA Reg. No.  Formulation  Product Name

67690‐15 Liquid  Cutless 50W TGR

67690‐46a Liquid  SP5075 TGR

67690‐51 Liquid  SP5100 TGR

67690‐13 Granular  Cutless 0.33G LGR

67690‐20 Liquid  Topflor PGR

67690‐44 Granular  Turf Fertilizer 0.17% Cutless

67690‐19 Turf‐Fertilizer Turf Fertilizer 0.5% Cutless

67690‐14   Water sol. pack Cutless 10W PGR

67690‐57a Liquid SP5411 TGR

67690‐62b Liquid Edgeless Conc. TGR

67690‐68 Granular Cutless 0.67G

67690‐34 Trunk Injection impregnated material Cutless Solution

67690‐17 Trunk injection Liquid (EC) Cutless TP

67690‐18 Trunk implant impregnated material Cutless Tree Implants

Previous assessments have evaluated the risks for the turf and ornamental uses. The focus of

this assessment is to determine the risk to terrestrial and aquatic organisms from the tree

injection/implant uses. There are three tree injection/implant products that are formulated

specifically to reduce vegetative growth and reduce the volume of biomass that must be

removed when trimming occurs. In general, the directions for application are to apply just

prior to or during the most rapid period of water uptake when trees are actively transpiring

(from 1 month prior to bud swell to just before color change in the fall). The active ingredient

from the implant/injection sites is translocated through the xylem to growing leaves and stems

to provide long term growth suppression. More details on the specific application instructions

are discussed in the Analysis Sections.  

C. Previous Ecological Risk Assessments and Evaluations 

The most recent ecological risk assessment was conducted in 2010. The 2010 assessment

(USEPA, 20104) considered the proposed new uses for residential, commercial, municipal and

industrial areas including golf resorts and athletic fields to control growth of turf grasses,

ornamentals, and a variety of bedding, flowering, bulb crop, perennial, and woody landscape

plants. This risk assessment was later revised to update the terrestrial exposure analysis for

banded application to ground surfaces.  

The risk conclusions were that there was a potential chronic risk identified for mammals

(RQ=<0.1‐30) and birds (RQ=<0.1‐1.6) based on reproductive effects. Acute risks to mammals

were identified (RQs <0.1‐1.3) and for birds the risk was presumed to be minimal based on the

non‐definitive endpoint. The potential for risks to aquatic non‐vascular plants was determined to

be minimal; however, there were risks identified for aquatic vascular plants (RQs up to 8.4 for

 

4 USEPA, 2010. Carey, S. and J.K. Wolf. Revised Section 3 Environmental Fate and Ecological Risk Assessment of Flurprimidol

proposed for New Uses on Turf grasses and Ornamentals (DP Barcode 374783, June 9, 2010).
9 

listed species) and terrestrial plants (RQs up to 40 and 341, for listed monocots and dicots,

respectively). There were no LOC exceedances for acute or chronic risks to aquatic organisms.   

 

Table 3. Summary of Risks Identified in Previous Assessment (2010)  

Flurprimidol RQs and Use Patterns 

Species  Broadcast Spray  Banded Spray  Broadcast 

Granular 

Banded Granular 

Aquatic Organisms and Plants 1

Fish All Acute RQs: <0.01

Chronic RQs: <0.1 – 0.13

Invertebrates All Acute RQs: <0.01

All Chronic RQs: <0.1

Aquatic Non‐

Vascular Plants

All Non‐Listed Plant RQs: 0.14 – 0.16

All Listed Plant RQs: 0.42 – 0.49

Aquatic Vascular

Plants

Non‐Listed Plant RQs: 0.18 – 0.48

Listed Plant RQs: 1.76 – 4.59

Non‐Listed Plant RQs: 0.34 – 0.88

Listed Plant RQs: 4.65 – 8.42

Terrestrial Animals2 and Plants3

Birds

Acute RQs: NC

Chronic RQs: <0.1–

1.6 

Acute RQs: NC

Acute RQs: NC

Chronic RQs:

<0.1

Acute RQs: NC

Mammals

Acute RQs:

<0.1‐0.3

Chronic RQs:

<0.1‐30

Acute RQs:

0.01 – 0.31 

Acute RQs:

0.06 – 1.3

Chronic RQs:

<0.1

Acute RQs:

0.03 – 0.67 

Terrestrial

Monocots

Non‐Listed Plant RQs: <0.1 – 2.7

Listed Plant RQs: <0.1 – 10

Non‐Listed Plant RQs: <0.1 ‐ 11

Listed Plant RQs: <0.1 ‐ 40

Terrestrial Dicots Non‐Listed Plant RQs: 0.24 ‐ 32

Listed Plant RQs: <0.1 ‐ 125

Non‐Listed Plant RQs: 0.57 ‐ 87

Listed Plant RQs: <0.1 ‐ 341

* Bold entries indicate LOC exceedance

NC – RQs not calculated since toxicity was greater than the highest doses tested; potential risk is presumed

minimal

1 For aquatic organisms, peak values are from 3.0 lb a.i. single granular app (Note: this rate was reduced to

1.5 lb a.i./A as the single application rate for the ornamentals). 2 For birds and mammals, the spray applications were assessed at 0.75 lbs a.i./A  with 4 applications every

14 days (this rate is reduced to 0.75 twice a year) and also 0.26 lbs a.i./A 12 times per year every 14 days.      3 For terrestrial plants, the assessed rates were 0.26‐ 0.75 lb a.i./A spray. Granular rates ranged from 0.75‐

3.0.(Note: the 3 lb rate was reduced to 1.5lb a.i./A.  

The aquatic environmental exposure concentrations (EEC) for the 2010 assessment were based

upon PRZM/EXAMS5 . However, since that assessment, a second aerobic soil metabolism (MRID

48555801) study was submitted and reviewed by the Agency. Additionally, the use of the surface

water concentration calculator (SWCC) has been implemented by EFED. Although the model

inputs were essentially the same as the previous assessment, the SWCC EECs were generally

lower than those simulated by PRZM/EXAMS (Appendix B provides the input and EECs from

SWCC). Because the EECs are less than the values used in the 2010 assessment, the aquatic risk

 

5 Pesticide Root Zone Model (PRZM, version 3.12.3, June 2006) and Exposure Analysis Modeling System (EXAMS; version

2.98.04.06, April 2005), linked with the PE5.pl input shell (November 2006).
10 

conclusions are the same as those from the previous assessment and, thus, are not revisited in

this assessment.  

D. Environmental Fate and Ecological Effects Characterization 

 

Environmental Fate Characterization

The dominant dissipation mechanism for flurprimidol is expected to be via leaching with

Freundlich sorption coefficients (Kd) ranging from 0.12 to 4.9 mL/g (Kocs values ranged between

140 and 535 mL/goc) and by photolysis in aqueous systems (half‐life = 1.4 days). Flurprimidol is

stable to hydrolysis and resistant to degradation in soil with aerobic soil metabolism half‐life of

470 days or more. Field dissipation data for cropped turf plots suggest that much more rapid

(soil) dissipation was found than might be expected from the laboratory studies. The registrant

postulates that this could be due to a number of factors not tracked in the study including plant

uptake via transpiration or sorption through plant surfaces and volatilization. Field dissipation

data on bare ground sites yields much longer dissipation times that are comparable to laboratory

estimates, suggesting that the presence of actively growing plants (i.e., uptake) is influencing the

dissipation in the field. No data were available to suggest how available flurprimidol is in plant

residues. Finally, flurprimidol is not expected to be volatile (based upon a vapor pressure of 3.7 x

10‐7 mm Hg and Henry’s Law constant of 3.97 x 10‐9 atm∙m3/mol), or to bioaccumulate, as

demonstrated by its relatively low Kow (2.97) and low BCF factors in bluegill sunfish.   

The environmental chemistry and fate properties of flurprimidol are summarized in Table 4.

Table 4.  Summary of Environmental Chemistry and Fate Properties of Flurprimidol

Parameter Value MRID # 

Persistence and Dissipation

Hydrolysis t1/2 Stable @ pH 5,7, and 9 00117921

Henry’s Law Constant 3.97 x 10‐9 atm∙m3

/mol

1.15 x10‐9 atm∙m3

/mol  @ 25°C

USEPA, 2009a

Calculated

Photolysis t1/2 in water 1.4 days 41228001

Photolysis t1/2 on soil No data   

Soil metabolism aerobic t1/2

@25°C

Linear Regression: 482 days [24–25 C]

DFOPb,c (slow): 475 days

00117918

48555801

Soil metabolism anaerobic t1/2 Stable 40858504

Aquatic metabolism aerobic t1/2 No data (assume stable)  ‐ 

Aquatic metabolism anaerobic t1/2 No data (assume stable)  ‐ 

Mobility/Adsorption‐Desorption

Batch equilibrium – unaged Soil Textural

Classification

Kd

(mL/g)

Koc

(mL/goc)

00142919

00117919

00117920

sand 3.09 535   
11 

Parameter Value MRID # 

sandy loam 1.86 268   

loam 3.11 283   

clay loam 4.77 266   

loam 4.9 212   

sandy loam 0.89 140   

sand 0.12 208   

sandy loam 3.46 333   

Laboratory volatility NA NA

Field Dissipation

Terrestrial field dissipation 5 to 23 days–cropped

560 days –bare soil

40184403

40401007

Aquatic field dissipation NA NA

Bioaccumulation

BCF  

[Accumulation in fish, maximum]  

19.3x ‐ edible tissues

52.3x ‐ nonedible tissues

6.2x ‐ whole fish

Kow = 933 (log Kow = 2.97)

40401001

Octanol/Water Partition Coefficient log Kow 2.96 00117923

a Ibid. USEPA, 2009; USEPA, 2010. b Ibid. USEPA, 2012. http://www.epa.gov/oppefed1/ecorisk_ders/degradation_kinetics/ftt_sop_using_nafta_guidance.pdf   c Double First‐Order in Parallel (slow half‐life)

Ecological Effects Characterization 

 

An ecological effects characterization for flurprimidol was previously conducted by EFED. A more

robust discussion of toxicity to aquatic and terrestrial organisms is presented in previous risk

assessments (D292874, D310484, D315363, D315836 and D3747836). The most sensitive toxicity

endpoints for available studies are summarized in Tables 5‐6 below.  

 

Table 5.   Most Sensitive Toxicity Endpoints Used to Estimate Risk to Aquatic Organisms 

 

6 Ibid, USEPA, 2010. 

 

Taxon 

Exposure 

Duration 

Most Sensitive 

Species Tested  Toxicity Value  Toxicity 

Category 

MRID / 

Classification  

Freshwater

Fish

Acute

Bluegill Sunfish

Lepomis 

macrochirus

LC50 = 17.2 mg a.i./L Slightly toxic 00117925

(acceptable)

Chronic

Fathead minnow

Pimephales 

promelas

NOAEC = 0.939 mg

a.i./L

LOAEC = 1.75 mg a.i./L

Reductions in fry

survival, length, and

weight.

Not applicable 47459602

(acceptable)
12 

 

Table 6.  Most Sensitive Toxicity Endpoints Used to Estimate Risk to Terrestrial Organisms 

Taxon  Exposure 

Duration 

Most Sensitive 

Species Tested  Toxicity Value  Toxicity Category 

MRID 

Reference 

Mammals

Acute

Rat

Rattus 

norvegicus

LD50 = 709 mg a.i./kg bw Slightly

toxic

00117932

(acceptable)

Chronic

Rat

Rattus 

norvegicus

NOAEL = 100 mg a.i./kg

diet

(7.3 mg a.i./kg‐bw/day)

LOAEL = 1000 mg a.i./kg

diet

Decreased mating,

fertility, and fetal survival

(stillbirths) in both

generations and

increased incidence of

persistent vaginal estrous

and no corpora lutea.

Not

applicable 00162770

Non‐passerine

Birds

Acute

Oral

Bobwhite quail

Colinus 

virginianus

LD50 >2000 mg a.i./kg bw

NOAEC= 125 mg a.i./kg

1 mortality at 2000 mg

a.i./kg bw  

Sublethal effects: signs of

toxicity, loose feces, body

weight gain, food

consumption

Practically

nontoxic

00117928

(acceptable)

Freshwater

Invertebrates

Acute

Water Flea

Daphnia magna  EC50 = 11.8 mg a.i./L Slightly toxic 00117927

(acceptable)

Chronic

Water Flea

Daphnia magna

NOAEC = 2.95 mg a.i./L

LOAEC = 5.70 mg a.i./L

Reductions of young

per adult and adult

length, as well as

significant difference in

day of first brood when

compared to control

Not applicable 47459601

(acceptable)

Vascular plant Acute Duckweed

Lemna gibba 

EC50 = 8.5 μg a.i./L

NOAEC = 0.89 μg a.i./L

Reduction in # of fronds

Not applicable 47472101

(supplemental)

Non‐vascular

plant Acute

Green algae

Selenastrum 

capricornutum

EC50 = 0.84 mg a.i./L

NOAEC = 0.28 mg a.i./L

Reduced biomass

Not applicable 40401011

(acceptable)
13 

Taxon  Exposure 

Duration 

Most Sensitive 

Species Tested  Toxicity Value  Toxicity Category 

MRID 

Reference 

Acute

Dietary

Bobwhite quail

Colinus 

virginianus

LC50 >4310 mg a.i./kg diet

No mortality.  

Sublethal effects: signs of

toxicity, reduced weight

gain and feed

consumption.

Practically

nontoxic

00117929

(supplemental‐

did not

determine

stability

/homogeneity

of test material

in diet)

Chronic

Mallard duck

Anas 

platyrhynchos 

NOAEC = 309 mg a.i./kg

diet

LOAEC = 642 mg a.i./kg

diet

Reductions in egg

production, embryo

survival, and hatchability

Not

applicable

47459603

(acceptable)

Terrestrial

Invertebrates

Acute

Contact

Honey Bee

Apis mellifera LD50 >100 μg a.i./bee Relatively

nontoxic1

40401004

(acceptable)

Terrestrial

Invertebrates Acute

Earthworm

Lumbricus 

terrestris 

LD50 >100 mg a.i./kg Practically

nontoxic

00117931

(supplemental)

Terrestrial

Plants ‐

Seedling

Emergence

Survival

and

growth

Ryegrass

(monocot)

Lolium perenne 

EC25 = 0.14 lb a.i./A

NOAEC = 0.038 lb a.i./A

Reduced shoot length   Not

applicable

47459606

Cucumber (acceptable)

(dicot)

Cucumis sativa 

EC25 = 0.012 lb a.i./A

NOAEC = 0.0044 lb a.i./A

Reduced shoot length

Terrestrial

Plants ‐

Vegetative

Vigor

Ryegrass

(monocot)

Lolium perenne 

EC25 = 0.42 lb a.i./A

NOAEC = 0.11 lb a.i./A

Reduced shoot length Not

applicable

47459607

(acceptable) Lettuce (dicot)

Lactuca sativa 

EC25 = 0.011 lb a.i./A

NOAEC = 0.046 lb a.i./A

Reduced shoot length

1 http://bees.ucr.edu/tox.html  

III.  Analysis Plan 

A. Measures to Evaluate Risk Hypotheses 

All use patterns except for the tree trunk injection applications have been addressed in previous

risk assessments. The risk conclusions for those use patterns can be found in the cited

assessments (USEPA, 2010). The primary focus of this assessment, therefore, is on the tree

injection/implant use pattern.  

Detailed information about the models, selection of input parameters and scenarios can be

obtained from http://www.epa.gov/oppefed1/models/water/index.htm.
14 

Measures of effect are obtained from a suite of studies conducted with a limited number of

surrogate species. The lowest toxicity endpoints for the most sensitive surrogate test species are

used to estimate treatment‐related effects on growth, reproduction and/or survival.

B.   Risk Hypothesis

For this assessment, the risk to non‐target organisms is based on potential effects from the

application of flurprimidol to the environment. The Agency presumes the following risk

hypothesis for this screening level assessment:

Based on mode of action, the use patterns, and the sensitivity of non‐target aquatic and 

terrestrial species, flurprimidol has the potential to reduce survival, reproduction, and/or 

growth in terrestrial and aquatic animals and plants through direct application or runoff. 

C.         Conceptual Model  

For the tree injection use, the potential route of exposure to terrestrial organisms is expected to

be primarily through consumption of various parts of the tree after flurprimidol has been

translocated throughout the tree after injection. It is assumed that the pesticide may enter

foliage, fruit, seeds, and pollen, which can in turn be used as food items by other organisms. In

addition, secondary exposure may occur for animals that consume invertebrates that have been

exposed to the chemical. There are no data on the rate of translocation or decay of flurprimidol

in trees or in fallen leaves, nor has the presence of transformation products in trees been

evaluated.  

Given the specificity of the tree injection use pattern, the predominant transport mechanism

consists of translocation/uptake to foliage, fruit, seeds, and pollen in treated trees. The transport

mechanism (i.e., source) is depicted in the conceptual model below (Figure 2) along with the

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

flurprimidol. The conceptual model also depicts the potential for flurprimidol residues in leaves,

fruits, and seeds to enter adjacent water bodies.
15 

Figure 2.  Conceptual Model for Flurprimidol Application via Tree Injection 

D.  Measures of Exposure 

There is no currently approved model for estimating potential exposure to organisms from tree

injection methods. Evaluating exposure for this use pattern requires information on

concentrations of the pesticide in animal food items after the chemical is translocated

throughout the tree from the application site. This information is not available for flurprimidol.  

Therefore, exposure estimates used in this assessment are screening level estimates. Additional

data, if available in the future, may allow for a refinement of the screening level estimates. The

screen is based on the following assumptions:  

(1) Total mass of chemical applied (Terrestrial and Aquatic Assessments) 

a. Terrestrial Assessment: The total mass of chemical applied to the tree was

compared to toxicity values of terrestrial animals; EEC = total mass of chemical 

applied

b. Aquatic Assessment: The total mass of chemical applied to a given number of

trees per acre assumed to enter a 20,000,000 L water body directly; EEC = total 

mass of chemical applied to trees on one acre/ 20,000,000 L 

Stressor 

Source

Receptors 

Attribute 

Change 

Flurprimidol  

applied to use site (tree injection)

Direct 

application 

Individual organisms 

Reduced survival 

Reduced growth 

Reduced reproduction 

Terrestrial food items (fruit, 

seeds, foliage, and pollen) 

Mammals 

Exposure 

Media 

Direct Contact/ 

Ingestion Ingestion

Translocation/uptake 

Terrestrial Birds 

insects 

Aquatic 

Animals 

Shedding 

leaves 
16 

(2) Tree trunk concentration (Terrestrial Assessment, cont.) 

a. Concentrations in the tree trunk were estimated by assuming that the chemical

was evenly distributed within the tree trunk. Estimates of tree mass were based

on information published by the University of Arkansas Cooperative Extension

Service; EEC = total mass of chemical applied / mass of stem or trunk of tree. These 

dietary based EECs were converted to a dose‐basis by assuming that 20g birds 

consume 114% and 15g herbivorous mammals consume 95% of their body weight 

daily. These assumptions are based on feeding rates provided in the Wildlife 

Exposure Factors Handbook (USEPA 1993)7 and are consistent with T‐REX. 

(3) Concentration of chemical in leaves (Terrestrial Assessment, cont.) 

a. Leaf concentration was estimated by assuming that 100% of the chemical was

translocated to the leaves only. Leaf mass was estimated using allometric

equations developed for blue oak trees presented by the USDA Forest Service

(Karlik and McKay 2002). EEC = total mass of chemical applied / leaf mass on tree.

These dietary based EECs were converted to a dose‐basis by assuming that 20g 

birds consume 114% and 15g herbivorous mammals consume 95% of their body 

weight daily. These assumptions are based on feeding rates provided in the 

Wildlife Exposure Factors Handbook (USEPA 1993) and are consistent with T‐REX. 

   

 

7 USEPA 1993. Wildlife Exposure Factors Handbook. Volume I of II. EPA/600/R-93/187a. Office of Research and 

Development, Washington, DC 20460. 
17 

IV. Exposure Analysis 

Three approaches were used to estimate exposures: (1) total mass of flurprimidol applied to

various sizes of trees (terrestrial and aquatic EECs), (2) estimated concentration in leaves

assuming 100% of the chemical translocates to the leaves (terrestrial EECs), and (3) estimated

whole tree concentrations (terrestrial EECs). In order to refine these exposure estimates, data

that evaluate uptake, translocation, and degradation of flurprimidol in situ are needed.   

A. Estimates based on total mass of Flurprimidol applied (Terrestrial and Aquatic EECs) 

Terrestrial EECs 

There are three tree injection/implant products for flurprimidol. The Cutless Tree Implant (Reg

No. 67690‐18) is formulated as an implant containing 1 gram of flurprimidol. The directions for

application state to install just prior to or during the most rapid period of water uptake when

trees are actively transpiring (from 1 month prior to bud swell to just before color change in the

fall). The number of implants required should be determined by measuring the tree diameter

~4.5 feet above the ground to accurately determine the dosage in grams a.i. per inch of

diameter. The holes for implants are spaced evenly around the tree and are seated firmly into

the tree trunk one inch below the bark. After installation the holes may be covered with bark

dressing or colored latex caulk. The rates are provided for two different groups of trees. The

Group 1 trees (e.g., ash, elm, maple, oak) are treated at rates of 0.5‐0.75 g a.i./inch diameter and

the Group 2 trees (e.g., aspen, sycamore, willow) are treated at rates of 1‐1.5 g a.i./inch

diameter.

A second product, CutlessTP (Reg. No. 67690‐18), is also applied at rates of 0.5‐1.5 g a.i./inch

and is, thus, covered with the Cutless Implant analysis. A range of the total mass of flurprimidol

that may be applied to trees via the Cutless implant/injection products are summarized in Table 

7. 

 

Table 7. Exposure Screen for Flurprimidol Cutless Tree Implant/Injection Products

Cutless Tree Implant (Reg. No 67690‐18) 

Diameter 

of tree 4 

ft above 

ground 

Group 1 Trees 

(Number of 

implants/tree) 

0.75  g a.i.rate 

Group 2 Trees 

(Number of 

implants/tree) 

1.5  g a.i.rate 

Total Grams 

Flurprimidol 

/Group 1 trees 

Total Grams 

Flurprimidol 

/Group 2 trees 

 

Range of a.i./tree 

(mg a.i. /tree) 

6 4 9 4 9 4,000‐9000

12 9 18 9 18 9,000‐18,000

30 22 45 22 45 22,000‐45,000

The third product, Flurprimidol Solution (Reg. 67690‐34), is formulated for direct injection so

drilling is not required prior to application. Each injection pack contains 65.6 grams a.i. per 120 ml

(0.546 g a.i./ml). A range of the total mass of flurprimidol that may be applied via Flurprimidol

Solution is summarized in Table 8.  
18 

Table 8. Exposure Screen for Flurprimidol Solution‐Tree Injection

Flurprimidol Solution‐Direct Inject (Reg. No. 67690‐34) 

Tree 

diameter 

Number of 

injection holes 

Volume of 

Product per 

injection site (ml) 

Total Volume 

of Product per 

Tree (ml) 

Flurprimidol (mg 

a.i.) per Tree1

 

6 5 1 5 2,730

12 9 2 18 9,282

30 23 2 46 25,116 1

Total grams a.i. per tree= total volume (ml) per tree *a.i. concentration [65.6 gram

a.i./120 ml product= 0.546 g a.i. /ml]

Do not apply more than once every 2 years.

These values were compared with terrestrial animal toxicity values to determine if there is a

potential for LOC exceedances.    

 

Aquatic EECs 

Direct contamination with tree parts 

 

There is also the potential for aquatic systems to be exposed to flurprimidol either directly from

contaminated tree parts (e.g., leaves, sticks, flowers, pollen) entering the water or from tree

parts falling onto land and subsequent runoff into aquatic systems. As a screen, the total amount

of chemical applied to a tree was added to a 20,000,000 liter pond. The resulting water

concentration would result in a conservative screen, but could be used to preclude risks to

taxonomic groups if no LOCs are exceeded. Using the product with the highest rate/tree (the

implant) for the screen, the resulting pesticide concentrations range from 0.2 μg a.i./L to 2.25 μg

a.i./L (4,000 mg a.i. to 45,000 mg a.i./ 20,000,000 L / 0.001 mg *μg‐1 ) depending on the amount

of pesticide applied to the tree. Table 9 provides the estimated EECs for the tree implant use.

Table 9.   Exposure Screen for Flurprimidol for Tree Implant

 

Tree Size  

diameter at breast

height (dbh), in 

Concentrations expected in a 20,000,000 L pond

in μg a.i./L

6 in. 0.20‐0.45

12 in. 0.45‐0.9

30 in. 1.1‐2.25

At this time, the label is lacking language on the number of trees that may be treated in a given

area. In order to get a better understanding of the risk, the number of treated trees that would

be needed to contribute to an EEC that would reach an LOC was calculated. For fish and

invertebrates, the mass from approximately 1000 treated trees would need to enter the pond to

reach an LOC. For non‐vascular plants, approximately 125 treated trees would be required.  

Given that the nature of the labelled use is generally for reduced pruning of ornamental trees in
19 

settings such as around utility lines or in residential areas, an analysis of tree densities in urban

forests prepared by the Biological and Economic Analysis Division (BEAD)8

, was consulted. The

BEAD analysis provided the median value of 36 trees/A (range 9‐119) as an estimate of tree

densities in urban forests.   

Altogether, given the conservative nature of the EECs (total mass per tree is available), the

toxicity of flurprimidol, and also considering the likely number of treated trees contributing to

the aquatic exposures, the risk to aquatic nonvascular plants and animals is considered to be low

for the tree injection use. For listed vascular plants, some of the EECs exceeded the LOC of 1 with

RQs from 0.05‐2.5, and for non‐listed species, depending on the tree size, there would need to

be approximately 4‐20 trees contributing to the 20,000,000 liter pond to reach an exceedance.

Therefore, there is a potential risk identified for listed and non‐listed vascular plants.  

Estimates Based on Tree Trunk Concentrations‐(Terrestrial EECs) 

 

The tree injection formula of flurprimidol is designed to be distributed throughout the tree, but

the fate of the chemical within a tree after injection is uncertain. Therefore, potential exposures

to terrestrial organisms that feed on treated trees were estimated using estimated tree trunk

concentrations and leaf concentrations. These estimates were used to design a screening‐level

analysis of risk and to determine if a magnitude of residues study that measures potential

exposures to organisms that may feed on treated trees would be useful.   

Tree trunk concentration estimates assume that the chemical is evenly distributed throughout

the tree trunk. Submission of a magnitude of residues study would reduce uncertainty in these

estimates. Pesticide mass applied to trees was obtained from the proposed label. Tree weight

estimates were obtained from the Cooperative Extension Service of the University of Arkansas9

,

and they represent estimates for standing hardwood trees. The estimate was based on the

merchantable portion of the tree (stem or trunk of the tree). The estimate does not include tops,

foliage, or limbs and, therefore, provides a conservative measure of whole‐tree concentration.

However, the estimates were comparable to the values calculated for above ground biomass for

similar size trees (esp. 12 in DBH or 30 cm DBH size class) reported by Tritton and Hornbeck

(1982, USDA Forest Service)10. Therefore, the estimate was not further refined for this

assessment.  

 

8 Becker, J. (2011). Per Acre Application Rates for Ornamental Trees in Urban Forests, Seed Treatment and

Container‐Grown Ornamental Uses of Paclobutrazol. U.S. EPA. November 30, 2011.   9 University of Arkansas Division of Agriculture (David W. Patterson).  Undated.    Landowner’s guide to determining weight of

standing hardwood trees.  University of Arkansas Division of Agriculture, Cooperative Extension Service.  FSA 5021‐PD‐

5‐08N.  http://www.uaex.edu/Other_Areas/publications/PDF/FSA‐5021.pdf  

10 Tritton L.M. and J. W. Hornbeck.  1982.  Biomass Equations for Major Tree Species of the Northeast.  USDA ‐ Forest Service,

Northeastern Forest Experiment Station. General Technical Report NE‐69.  

http://www.fs.fed.us/ne/newtown_square/publications/technical_reports/pdfs/scanned/gtr69.pdf
20 

The largest tree included in the U. of Arkansas publication was a 36 inch DBH tree.  For this

assessment trees that range from 12 to 30 inch DBH were selected for analysis because 30 in

DBH is the maximum tree size for which rates are supplied on the implant label. The resulting

tree trunk concentrations were compared with toxicity values to characterize potential risks to

terrestrial organisms by converting the concentrations in the trunk to a dose value (used as a

proxy for the concentration found in edible portions of the tree). Tree trunk pesticide

concentration was converted to dose by assuming that 20g birds consume 114% and 15g

herbivorous mammals consume 95% of their body weight daily using the following equation:

 

Body weight adjusted EEC for residues in tree trunk mg/kg bw

= X mg/kg tree x 1.14 or 0.95 kg tree/kg‐bw

Table 10 provides the estimated dietary and dose based EECs for Flurprimidol based on dilution

of the pesticide within the tree.

Table 10.  Range of Tree Trunk Concentration Estimates of Flurprimidol

DBH (inches) Tree Weight (kg)

Mass of pesticide injected

in tree (mg a.i./tree)

Pesticide concentration mg a.i./kg

Dietary

based

mg a.i./kg‐

tree

Dose based mg a.i./kg‐bw

birds mammals

Flurprimidol Solution‐Direct Inject (Reg. No. 67690‐34)

12 750 9,282 12.38 14.11 11.76

30 5650 25,116 4.45 5.07 4.22

Cutless Tree Implant (Reg. No 67690‐18)

12 750 18,000 24 27.36 22.8

30 5650 45,000 7.96 9.07 7.56

Estimates Based on Leaf Concentrations‐(Terrestrial EECs) 

 

Flurprimidol concentration was also estimated in leaves of treated trees.  Estimated leaf

concentrations resulting from tree injection assume that 100% of the chemical was translocated

to the leaves and that the chemical was evenly distributed across the leaf mass. Submission of a

magnitude of residues study would reduce uncertainty in these assumptions.   

Pesticide mass applied to trees was obtained from the proposed label (Tables 7 and 8). Estimated

leaf mass was based on an allometric equation for oak trees published by the USDA Forest

Service that relates tree size to estimated leaf mass (Karlik and McKay 2002)11:   

   

 

11 Karlik, J.F. and A.H. McKay.  2002.  Leaf area index, leaf mass density, and allometric relationships derived from harvest of blue

oaks in California oak Savanna.  USDA Forest Service Gen. Tech. Rep.  PSW‐GTR‐184.2002.

http://www.fs.fed.us/psw/publications/documents/psw_gtr184/061_Karlik.pdf  
21 

Leaf mass (g) = 1.78x2 – 12.4x – 108.5   

x = tree circumference at breast height (cm), where

dbh (cm) = tree circumference at breast height (cm)/ 

Resulting estimates of leaf concentrations are summarized in Table 11. The resulting leaf

concentration estimates were compared to toxicity values from terrestrial organisms to

characterize potential risks by converting the concentrations in leaves to a dose value. Pesticide

concentration on leaves was converted to dose by assuming that 20g birds consume 114% and

15g herbivorous mammals consume 95% of their body weight daily using the following equation:

 

Body weight adjusted EEC for residues on leaves mg/kg bw

= X mg/kg leaf x 1.14 or 0.95 kg leaf/kg‐bw

Table 11. Range of Estimated Concentrations of Flurprimidol in Leaves 

DBH (in.)  Leaf mass (kg)  Pesticide mass 

(mg a.i./tree)a 

Pesticide concentration mg a.i./kg 

Dietary based  Dose based 

mg a.i./kg‐leaf  mg a.i./kg‐bw 

birds  mammals 

Flurprimidol Solution‐Direct Inject (Reg. No. 67690‐34) 

6 3.4 2730 809 922 769

12 15.0 9282 618 705 588

30 98.8 25116 254 290 241

Cutless Tree Implant (Reg. No 67690‐18) 

6 3.4 9,000 2,667 3,041 2,534

12 15.0 18,000 1,199 1,367 1,139

30 98.8 45,000 455 519 433

a Calculated as dbh * a.i./inch of dbh

 

V.     Risk Characterization 

Risk Estimation ‐ Integration of Exposure and Effects Data 

This screening level risk assessment identified potential risks to birds and mammals that forage

on treated trees. Risk to bees is uncertain based on the available data. There were no risks

identified for fish and aquatic invertebrates exposed via treated plant parts that end up in water

bodies. However, there was a risk identified for vascular aquatic plants.

 

Risk estimates were based on (1) the total mass of flurprimidol applied to a tree is available‐a

highly conservative first screen (2) estimated concentration of flurprimidol in the tree trunk

assuming that the pesticide is evenly distributed throughout the tree trunk (thus, diluted), and

 
22 

(3) estimated concentrations of flurprimidol in leaves assuming 100% translocation of the

applied pesticide to the leaves. The total mass assumption and translocation to leaves resulted in

acute and chronic risk concerns for birds and mammals.

For aquatic exposure estimation, a conservative approach assuming that all of the mass per tree

is applied to a 20,000,000 L pond. The resulting EECs were 0.2‐2.25 ug/L.  To gain a better

understanding of the risk, the number of treated trees needed to reach the aquatic LOCs for

aquatic organisms was considered. For fish and invertebrates, the a.i. mass from approximately

1000 treated trees would need to enter the pond to reach an LOC, and for non‐vascular plants,

approximately 125 treated trees would be required. For listed vascular plants, some of the EECs

exceeded the LOC of 1 with RQs from 0.05‐2.5 and for non‐listed species, depending on the tree

size, there would need to be approximately 4‐20 trees contributing to the 20,000,000 liter pond

to reach an exceedance. Altogether, the risk to aquatic animals (acute and chronic) and non‐

vascular plants is low, however, there is a potential risk identified to listed and non‐listed

vascular plants based on this screen.  

A.  Potential Risk to Terrestrial Organisms 

Birds and Mammals 

Screen by total mass available 

For birds, the LD50 was non‐definitive (i.e., a greater than value), although, there was one

mortality at the highest dose tested (2,000 mg a.i./kg bw) and sublethal effects started at 250

mg a.i./kg‐bw. Using the assumption that the acute avian endpoint is definitive, the adjusted LD50

is 1441 mg/kg‐bw for a 20 g bird, which corresponds to 28.8 mg (1441 mg/kg‐bw *0.02 kg) for a

20g bird. Therefore, consumption of ≥2.9 mg a.i. for birds would result in exceedance of the

endangered terrestrial animal species level of concern (LOC) of 0.1. Likewise, consumption of

≥14.5 mg a.i. would result in exceedance of the acute non‐listed species terrestrial animal LOC of

0.5.

There is a definite endpoint for mammals, given by an acute oral study on the rat. The adjusted

LD50 = 1,736 mg/kg‐bw for a 15 g mammal, which corresponds to 26.04 mg (=1,736 mg/kg‐bw *

0.015 kg) for a 15 g mammal. Therefore, consumption of 2.6 mg a.i. for mammals or more would

result in exceedance of the endangered terrestrial animal species level of concern (LOC) of 0.1.

Likewise, consumption of 13.0 mg a.i. or more would result in exceedance of the acute terrestrial

animal LOC of 0.5.

Given there is up to 45,000 mg a.i. available per tree from the tree injection, the next tier of

exposure estimates was conducted based on the dilution of flurprimidol within the tree.
23 

Concentration based estimates  

 

Exposures based on concentrations in the tree trunk  

 

The acute avian LD50 endpoint is 1441 mg/kg‐bw for a 20g bird (assuming non‐definitive is the

endpoint) and the mammalian endpoint is the adjusted LD50 of 1736 mg/kg‐bw for a 15 g

mammal. Therefore, exposure to doses of 144.1 mg a.i./kg‐bw (for birds) and 173.6 mg a.i./kg‐

bw (for mammals) or greater from tree parts would result in exceedance of the endangered

terrestrial animal species LOC of 0.1. Likewise, exposure of 720.5 mg a.i./kg‐bw (for birds) 867.5

mg a.i./kg‐bw (for mammals) or more from tree parts would result in exceedance of the acute

non‐listed species terrestrial animal LOC of 0.5. Body weight adjusted (dose based) EECs for

residues in the whole tree ranged from 5.07 to 27.36 mg a.i./kg‐bw  (birds) and from 4.2‐22.8 mg

a.i./kg‐bw  (mammals), and therefore, do not lead to an LOC exceedance for birds or mammals.  

Exposures based on Concentration in Leaves 

On an acute exposure basis, based on the analysis of the residue concentration in the leaves of

the tree, the body weight adjusted (dose based) EECs for residues in leaves ranged from 241‐

2534 mg/kg‐bw for mammals and resulted in acute and ES LOC exceedances (RQs ranging from 

0.14‐1.46). For birds, RQs are not calculated because the toxicity threshold was non‐definitive,

therefore, in order to gain a better understanding of how the EECs relate to the toxicity data

currently available for birds, the EEC was compared to the endpoint using the conservative

assumption that the highest level tested is the endpoint value (LD50 = 2,000 mg a.i./kg‐bw which

adjusts to 1,441 for the 20g bird).  In this exercise the EECs ranged from 290‐3041 mg/kg‐bw and

were greater than 1/10 and 1/2 of the LD50 (current basis of the acute and listed species LOCs),

thus, based on the current estimates of the tree injection EECs, the highest test concentrations

were not high enough to be protective for birds. In summary, on an acute exposure basis, there

is a risk identified for mammals and the risk to birds cannot be precluded based on the available

data.

For terrestrial invertebrates, there was not sufficient information to assess the risk because the

non‐definitive contact study was not tested at high enough concentrations to preclude risk.

Additional data are needed to assess the risk to pollinators (see Uncertainties and Data gaps).  

 

On a chronic exposure basis, the 20‐week NOAEC for mallard duck is 309 mg a.i./kg‐diet (based

on reductions in egg production, embryo survival and hatchability) and for mammals, the NOAEC

is 100 mg a.i./kg diet [based on decreased mating, fertility, and fetal survival (stillbirths) in both

generations and increased incidence of persistent vaginal estrous and no corpora lutea]. When

compared to the dietary based EECs ranging from 254‐2667 mg a.i./kg diet, the resulting RQ 

values ranged from  0.8‐8.6 for birds and 2.5‐26.7 for mammals, thus, there are risks identified

based on reproductive effects.  

The exceedances predicted from single tree exposures are complicated by several factors

including feeding/foraging behavior of the given organism, visitation of multiple contaminated
24 

tree parts, and availability of the pesticide residues in edible portions of the tree and, thus, there

is uncertainty in this analysis.  

As shown in Table 12, screening level EECs exceeded levels that may result in potential risk to

terrestrial organisms.  

Table 12.  Risk Summary for Terrestrial Animals

Screening EEC  Toxicity Value Risk Summary

Assumption  EEC  Birds (20g) Mammals (15g) Inverts. 

Total Mass 

Available 

6 in. DBH 2730 mg a.i.

(inject)/

9000 mg

a.i.(implant)

>29 mg a.i. 26 mg a.i. >100  ug

a.i./bee

Sufficient mass is

available to

potentially affect

mammals. Risks to

birds and terrestrial

invertebrates cannot

be precluded.  

12 in. DBH 9282 mg a.i.

(inject)/

18,000 mg a.i.

(implant)

30 in. DBH 25,116 mg a.i.

(inject)/

45,000 mg a.i.

(implant)

 

 

Concentration 

Based –[Tree 

trunk]  

12  and 30

in dbh

Birds: 5‐27 mg

a.i./kg‐bwa

  

Mammals: 4‐23

mg a.i./kg‐bwa

Dietary Based :

4.5‐24 mg /kg

*Ranges are across

the injection and

implant products

Adj. LD50

>1441 mg

a.i./kg‐bw

Adj. LD50 1736

mg a.i./kg‐bw

>100  μg

a.i./bee

[100 μg

/bee*1

bee/0.128

g=781 μg/g

bee, thus, an

EEC of 312

μg/g would

exceed the

LOC of 0.4.]

Estimated

concentrations of

flurprimidol are not

sufficient to result in

potential risks to

birds, mammals, or

terrestrial

invertebrates.  

 

Concentration 

Based 

[Concentrated 

in Leaf] 

6‐30 in

dbh

Birds: 290‐922 mg

a.i./kg‐bw

(inject)/519‐3041

(implant)

Mammal:241‐769

mg a.i./kg‐bw

(inject)/433‐2534

(implant)

Dietary Based: 

254—2667 mg/kg 

*Ranges are across

the injection and

implant products

Adj. LD50

>1441 mg

a.i./kg‐bw

   

Adj. LD50 =1736

mg a.i./kg‐bw

>100  ug

a.i./bee

[100 ug

/bee*1

bee/0.128

g=781ug/g

bee, thus, an

EEC of

312ug/g

would

exceed the

LOC of 0.4.]

Estimated

concentrations of

flurprimidol are

sufficient to result in

potential risks to

mammals.  For birds

and terrestrial

invertebrates, risk

cannot be precluded

based on the available

data.

a  Pesticide concentrations in whole tree and on leaves were converted to dose by assuming that birds and mammals consume,

respectively, 114% and 95% of their body weight daily.     
25 

Conclusions 

Potential Risk to Terrestrial Organisms 

The analysis based on the total mass of flurprimidol applied to a treated tree ranges from 9,000

mg a.i. to 45,000 mg a.i./tree (considering the highest rates), therefore, there is sufficient mass

applied to trees to potentially affect terrestrial organisms, thus, a more refined analysis

considering the dilution of flurprimidol within the treated tree was used.  

When considering the dilution of flurprimidol within the tree, the estimates of whole‐tree

pesticide concentrations (assuming that the chemical is evenly distributed throughout the above

ground biomass), were not sufficient to result in risk concerns for terrestrial organisms.  

However, when considering the estimated concentrations in the leaves, the EECs  were sufficient

to result in acute risk concerns for organisms that may eat leaves of treated trees (with leaves

being a surrogate for other edible parts of the tree).  This evaluation assumed that 100% of the

injected chemical was translocated to the leaves and 100% of the organisms diet was treated

leaves.  

There is also potential for repeated or prolonged exposures to terrestrial animals because

flurprimidol is not expected to rapidly dissipate from trees after it is injected and translocated.

On a chronic exposure basis, based on the types of effects observed in the bird and mammal

chronic toxicity studies at levels within the exposure estimates, there is also potential risk to

reproduction from the proposed tree injection use. Although sublethal (i.e., reproductive,

growth) effects are more subtle than acute mortality events, they can have profound ecological

consequences. Depending on the magnitude of the effect, impacts on higher levels of biological

organization are possible. In the case of flurprimidol, a two‐generation rat study revealed a

reproductive LOAEL of 1000 ppm (equivalent to 74 mg/kg/day) based on decreased mating,

fertility, and fetal survival (stillbirths) in both generations. Fertility was decreased by up to 46%,

the precoital interval was 2‐3 times longer, and mating was decreased by up to 60% for treated

rats. Furthermore, treated rats produced only about half of the number of live offspring as their

control counterparts, and gestation survival and litter size were significantly affected.

Therefore, the results of this screening level analysis suggest that there are potential risks to

non‐target terrestrial organisms as a result of the tree injection use. Submission of a magnitude

of residues study that quantifies potential exposure levels after tree injection would be of high

value to this risk assessment. Exposures may be further quantified and refined if a magnitude of

residues study in treated trees is submitted that evaluates concentrations of flurprimidol in

edible parts of treated trees, including leaves, fruit, seeds, as well as blooming, pollen‐shedding,

and nectar producing parts of plants.

Potential Risk to Aquatic Organisms

 

There is also potential for aquatic systems to be exposed to flurprimidol either directly from

contaminated tree parts (e.g., leaves, sticks, flowers, pollen) entering the water or from tree

parts falling onto land and subsequent runoff into aquatic systems. As a conservative screen, the

total amount of chemical applied to a tree was added to a 20,000,000 liter pond. EECs and
26 

toxicity values are summarized in Table 13. At this time the label is lacking language on the

number of trees that may be treated in a given area. For fish and invertebrates, the mass from

approximately 1000 treated trees would need to enter the pond to reach an LOC, and for non‐

vascular plants, approximately 125 treated trees would be required. Altogether, given the

conservative nature of the EECs (total mass per tree is available), the toxicity of flurprimidol, and

also considering the likely number of treated trees contributing to the aquatic exposures (see

earlier discussion in the exposure analysis section), the risk to aquatic nonvascular plants and

animals is considered to be low for the tree injection use. For listed vascular plants, some of the

EECs exceeded the LOC of 1 with RQs from 0.05‐2.5 and for non‐listed species, depending on the

tree size, there would need to be approximately 4‐20 trees contributing to the 20,000,000 liter

pond to reach an exceedance. Therefore, there is a potential risk identified for listed and non‐

listed vascular plants.  

Table 13.   Risk Summary for Aquatic Animals

Screening EEC (μg a.i./L)  Toxicity Value (μg a.i./L) Risk Quotients: Acute/Chronic (animals) 

and Non‐Listed/Listed (plants) 

(based on highest rates in range) 

Assumption/Tree 

Size (inches) 

EEC FW Fish  FW 

Inverts. 

Non‐

vasc. 

Plant 

Vascular 

Plants 

FW Fish FW 

Inverts. 

Non‐

vasc. 

Plant 

Vascular 

Plants  

Direct

Deposition

with tree

parts

6   0.2‐

0.45

LD50=  

17200  

NOAEC=

939

LD50=

11800

NOAEC=

2950

EC50=

840

NOAEC=

280

EC50= 8.5

NOAEC=

0.89  

0.00003 0.00004 0.00054 0.053

0.00048 0.00015 0.00161 0.506

12 0.45-

0.9

0.00005 0.00008 0.00107 0.106

0.00096 0.00031 0.00321 1.011

30 1.1-

2.25

0.00013 0.00019 0.00268 0.265

0.00240 0.00076 0.00804 2.528

Uncertainties and Data Gaps 

 

There is currently no standard methodology for evaluating potential ecological risks from

application of pesticides via tree injection. This assessment was based on conservative estimates

of exposure. A primary uncertainty in this assessment is that the screening level exposure

estimates cannot be refined based on the currently available data. In addition, there is no limit

indicated on the label on the maximum number of trees that may be treated on an area basis.  

Screening level exposure values were used in this assessment that identified potential risks to

non‐target terrestrial animals. However, the exceedances predicted from single tree exposures

are complicated by several factors including feeding/foraging behavior of the given organism,

visitation of multiple contaminated tree parts, and availability of the pesticide residues in edible

portions of the tree. Submission of a magnitude of residues study that evaluates pesticide

concentrations in various parts of the tree that may serve as food for birds, mammals, and

invertebrates would be needed to allow for refinements of potential risks.  
27 

Estimates of exposure included estimations of pesticide concentrations in leaves and in the tree

trunk. Estimated pesticide concentrations in leaves were determined by assuming that 100% of

the chemical is translocated to leaves.  Leaf mass was estimated using the following allometric

equation developed for blue oak trees presented by the USDA Forest Service (Karlik and McKay

2002):

  

Leaf mass (g) = 1.78x2 – 12.4x – 108.5   

x = tree circumference at breast height (cm)

The regression was developed based on a study of 14 blue oak trees harvested in the Sierra

Nevada foothills with an r2 value of 0.98. The extent to which the equation estimates leaf mass

for other types of trees or for blue oak trees in other locations has not been evaluated for this

assessment.  

Estimates of pesticide concentration in the tree trunk assumed that the chemical was evenly

distributed within the tree and required an estimate of tree mass. Estimates of tree mass were

based on information published by the University of Arkansas Cooperative Extension Service and

included only the merchantable portion of the tree (stem or trunk of the tree). The estimate did

not include tops, foliage, or limbs and it, therefore, provides a conservative measure of whole‐

tree concentration. However, the estimates were comparable to the values calculated for above

ground biomass for similar size trees (esp. 12 in dbh or 30 cm dbh size class) reported by Tritton

and Hornbeck (1982, USDA Forest Service). Therefore, the estimate was not further refined for

this assessment. However, use of a tree trunk concentration may not be conservative because

the estimate assumes that the pesticide is evenly distributed throughout the tree trunk, which

could lead to an underestimation of exposure and risk if the chemical concentrates in an edible

portion of the tree. It is also possible that when a tree is not growing rapidly that the pesticide

within it may not be diluted via the generated biomass.

Data Gaps 

No additional environmental fate data are needed. There are insufficient data to conduct a Tier 1

assessment for risk to pollinators.  While there is currently only the honeybee acute contact

study available and it is non‐definitive with the highest test concentration below the estimated

EEC’s, the risk to pollinators cannot be precluded or fully assessed at this time.  The additional

data that are needed for pollinator assessments are summarized in Table 14; refer to Appendix C

for the data justification rationales.  
28 

Table 14. Recommendations for Bee Exposure and Effects Testing* 

Number  Study Type  Test Material 

Tier 1  (Non‐guideline, OECD TG 213)    Honey bee adult acute oral toxicity TGAI

Tier 1  (Non‐guideline, OECD TG 237) Honey bee larvae acute oral toxicity TGAI

Tier 1  (Non‐guideline) Honey bee adult chronic oral toxicity TGAI

Tier 1  (Non‐guideline) Honey bee larvae chronic oral toxicity TGAI

Tier 2 (Non‐guideline) Field trial of residues in pollen and

nectar

TEP

Tier 21 (Non‐guideline, OECD

Guidance 75)

Semi‐field testing for pollinators

(tunnel or colony feeding studies) TEP

Tier 2 and 31 (Guideline 850.3040) Field testing for pollinators TEP

1Higher tierstudies (Tier 2 and Tier 3) may be required pending the results and evaluation of Tier 1 studies.  Higher tierstudies

may be required if the ratio of the EEC and larval or adult bee acute LD50 >0.4 or the ratio of the EEC and chronic NOAEC

>1.  Incident data and/or compelling open literature studies can also serve as rationale for requiring Tier 2 and Tier 3 studies.

* The “Honey bee toxicity of residues on foliage” study (OCSPP Guideline 850.3030) is not triggered because the results for

the acute adult contact honey bee study is > 11 ug a.i./bee (i.e., >100 ug a.i./bee).

Review of Incident Data 

Reviews of the Ecological Incident Information System (EIIS) and the Avian Incident Monitoring

System (AIMS)12 were conducted on12/17/14. There are no reported incidents for flurprimidol in

the EIIS or AIMS databases. In addition to the incidents recorded in EIIS and AIMS, additional

pesticide incidents are reported to the Agency in aggregated incident reports. Ecological

incidents reported in aggregate reports include those categorized as ‘minor fish and wildlife’ (W‐

B), ‘minor plant’ (P‐B), and ‘other non‐target’ (ONT) incidents. ‘Other non‐target’ incidents

include reports of adverse effects to insects and other terrestrial invertebrates. A query of the

aggregate incident report on 12/17/14 also reported no incidents.  

Federally Threatened and Endangered (Listed) Species Concerns 

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

evaluate risks to federally listed threatened and endangered (listed) species from registered

uses of pesticides in accordance with the Joint Interim Approaches developed to implement the

recommendations of the April 2013 National Academy of Sciences (NAS) report, Assessing Risks

to Endangered and Threatened Species from Pesticides.  The NAS report outlines

recommendations on specific scientific and technical issues related to the development of

pesticide risk assessments that EPA and the Services must conduct in connection with their

 

12 http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm 
29 

obligations under the ESA and FIFRA.  EPA will address concerns specific to flurprimidol in

connection with the development of its final registration review decision for flurprimidol.

In November 2013, EPA, the U.S. Fish and Wildlife Service, National Marine Fisheries (the

Services), and USDA released a white paper containing a summary of their joint Interim

Approaches for assessing risks to listed species from pesticides.  These Interim Approaches

were developed jointly by the agencies in response to the NAS recommendations, and reflect a

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

differences between the EPA and the Services.  Details of the joint Interim Approaches are

contained in the November 1, 2013 white paper, Interim Approaches for National‐Level

Pesticide Endangered Species Act Assessments Based on the Recommendations of the National

Academy of Sciences April 2013 Report.

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

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

designated critical habitat, this ecological problem formulation supporting the Preliminary

Work Plan for flurprimidol does not describe the specific ESA analysis, including effects

determinations for specific listed species or designated critical habitat, to be conducted during

registration review.  While the agencies continue to develop a common method for ESA

analysis, the planned risk assessment for the registration review of flurprimidol will describe

the level of ESA analysis completed for this particular registration review case. This assessment

will allow EPA to focus its future evaluations on the types of species where the potential for

effects exists, once the scientific methods being developed by the agencies have been fully

vetted. Once the agencies have fully developed and implemented the scientific methods

necessary to complete risk assessments for listed species and their designated critical habitats,

these methods will be applied to subsequent analyses of flurprimidol as part of completing this

registration review.

Clean Water Act  

Flurprimidol 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=885.

In addition, no Total Maximum Daily Loads (TMDL) have been developed for limonene, based on

information provided at

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutan

t_group_name=PESTICIDES.

More information on impaired water bodies and TMDLs can be found at

http://www.epa.gov/owow/tmdl/.
30 

Endocrine Disruptor Screening Program  

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse

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

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

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

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

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

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

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

taxonomic groups. As part of registration review for flurprimidol, EPA reviewed these data and

selected the most sensitive endpoints for relevant risk assessment scenarios from the existing

hazard database. However, as required by FFDCA section 408(p), flurprimidol is subject to the

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

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

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

a “naturally occurring estrogen, or other such endocrine effects as the Administrator may

designate.” The EDSP employs a two‐tiered approach to making the statutorily required

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a

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

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

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

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

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

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

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

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

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

identified for EDSP screening was published on June 14, 201313 and includes some pesticides

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

construed as a list of known or likely endocrine disruptors.  Flurprimidol is not among the group

of pesticide active ingredients on the initial lists to be screened under the EDSP.  Accordingly, as

part of registration review, EPA will issue future EDSP orders/data call‐ins, requiring the

submission of EDSP screening assays for flurprimidol.  For further information on the status of

the EDSP, please visit our website:  http://www.epa.gov/endo/.

 

13 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 
31 

Appendix 1. Summary of Labeled Uses  

Use Site  Application  Method 

Maximum 

Single 

Application 

Rate 

(lb a.i./A) 

Maximum 

Number of  

Applications 

per Crop 

Cycle 14 

Maximum 

Cumulative 

Application  

Rate per Crop 

Cycle  (lb a.i./A) 

# of 

Crop 

Cycles 

Per Year 

Maximum 

Number of 

Applications 

per Year1 

Maximum 

Application  

Rate per Year 

(lb a.i./A)  MRI

 (days) 

REI (hours) 

Golf Course Turf 

Broadcast

application

[Groundboom or

handgun]

0.75

[L/WP] 2

3.0

*

Broadcast

application

[Groundboom or

handgun]

0.26

[L] 111 14

Broadcast

application

[Drop/rotary‐

type spreader]

0.75 [G] 41 21

Broadcast 

application 

[Drop/rotary‐

type spreader] 

1.0[G] 31 21

Edging/banding

[backpack

sprayer]

1.5

[L/WP] 21 56

Edging/banding

[backpack

sprayer]

0.69 [L] 41 56

Turfgrass (commercial ,

Edging/banding

[backpack

sprayer and

1.5

[L/WP/G] 21 3.0 56

14 In cases where the maximum number of applications were not specified on the label the values were derived by dividing the maximu

the maximum single application rate 
32 

Use Site  Application  Method 

Maximum 

Single 

Application 

Rate 

(lb a.i./A) 

Maximum 

Number of  

Applications 

per Crop 

Cycle 14 

Maximum 

Cumulative 

Application  

Rate per Crop 

Cycle  (lb a.i./A) 

# of 

Crop 

Cycles 

Per Year 

Maximum 

Number of 

Applications 

per Year1 

Maximum 

Application  

Rate per Year 

(lb a.i./A)  MRI

 (days) 

REI (hours) 

municipal,athletic fields)

granular

spreader]

Edging/banding

[backpack

sprayer]

0.69 [L] 41 3.0 56

Residential Turf 

Edging/banding

[backpack

sprayer, granular

spreader and

homeowner

“shaker”]

1.5

[L/WP/G] 21 3.0 56

Landscape ornamentals(non‐woodyground covers

andherbaceousornamentals& woodyground covers

and shrubsand hedges)

Rotary type,

gravity, or air

flow spreader

1.5* [G] 21 3.0 60

Plant‐directed 

spray 

1.08 [L] NS 1 year for woody plants 1.08** NS
33 

Use Site  Application  Method 

Maximum 

Single 

Application 

Rate 

(lb a.i./A) 

Maximum 

Number of  

Applications 

per Crop 

Cycle 14 

Maximum 

Cumulative 

Application  

Rate per Crop 

Cycle  (lb a.i./A) 

# of 

Crop 

Cycles 

Per Year 

Maximum 

Number of 

Applications 

per Year1 

Maximum 

Application  

Rate per Year 

(lb a.i./A)  MRI

 (days) 

REI (hours) 

Container grown ornamentals(perennial,herbaceous,woody)

Hand held 

delivery device/ 

topical hand 

application 

1.5 lbs (G) 21 3.0 NS*

Spray/Drench/

chemigation

[Backpack

sprayer, low

pressure

handwand;

drencher,

sprinkler, drip]

0.36 (L) 81 3.0 5 

Trunk/ Ornamental trees(In urbanareas, utilityrights of way,residentialareas andinteriorlandscapes)

Trunk injection  1.1 g a.i./ 4” trunk circ. NS 730

Trunk implant 

0.0033 lb

a.i./inch

trunk

diameter

(1.5 g

a.i./inch

diameter)

NS NS*
34 

Appendix B. SWCC calculations to compare with the Previous Assessment 

Environmental fate and other data needed for the SWCC (or PRZM/EXAMS) are summarized in 

Appendix B Table 1 

 

Table 1. Selected input parameters for SWCC values for surface water concentrations of Flurprimidol.   

PARAMETER (units) VALUE(S) SOURCE  COMMENT

Foliar/Broadcast/Banded

Applications:

Max. Rate; # of App  

        (lb a.i./A; #)

3.0;1  

1.5; 2

0.69; 5   

Labels Rates assessed in Section 3

(D374783)

Organic Carbon Partition

Coefficient (Koc; mL/g)

280.6 MRIDs:

00142919, 00117919,

00117920

Represents the mean of the

following values 8 values, Table 

4) or the parent compound.   

Aerobic Soil Metabolism Half‐

life (days)

489.3b MRIDs:

00117918, 48555801

Represents the upper 90th

percentile of the following 2

values (Table 4) 482 and 475

days.   

Solubility limit (ppm) 130 MRID:

40981703

Upper Limit on concentration

value

Aerobic aquatic metabolic half‐

life (days)

Assume

Stable

‐‐ No data

Aqueous Photolysis half‐ life

(days)

1.4 MRID:

41228001

Single Available Value

Molecular Weight (g/mol) 312.3 ‐‐

Vapor Pressure [mm Hg]   3.64 x 10‐7 MRID:

00162772

@25C

Application Efficiency 0.99

1.0

Ground Application

Granular

Spray Drift  

ground spray %

Granular Application

6.2

1.0

Aquatic Exp. Eco.

DW and Eco

EFED Guidance (White et al.,

201315)

Date of Initial Application

(relative date) 30 days after

emergence

Defined by Scenario

[Except where noted as 08/08

for the Florida Nursery]. a Rate which result in the highest concentrations in previous assessment. Also 5 applications at 0.69 lb a.i./A per applications

slightly exceeds the 3.0 lb a.i./A/year rate. b A second aerobic soil metabolism study (MRID 48555801) was submitted since the previous assessment. Therefore, the upper

bound of the mean (489.3 days) was used instead of three times the single value (MRID 00117918; 482 days * 3 = 1444 days with

GENEEC2) and 482 days (PRZM/EXAMS‐deviated from guidance did not multiply single value x 3) used in the previous assessment

(USEPA, 2010).

 

 

 

15 White et al., 2013. Guidance on Modeling Offsite Deposition of Pesticides via Spray Drift for Ecological and Drinking Water

Assessments. USEPA. OPP. OPPTS, EFED (December 20, 2013)
35 

The surface water EECs for aquatic exposure estimates obtain with the SWCC16 are summarized

in Appendix B Table 2. Although the model inputs (Appendix B Table 1 are essentially the same as

the previous assessment (USEPA, 2010; D374783), the SWCC EECs are somewhat less than those

simulated by PRZM/EXAMS. The maximum peak (acute), 21‐day and 60‐day average flurprimidol

concentrations from PRZM/EXAMS for the FL nursery scenario were 74.9, 72.7, and 68.0 μg/L,

respectively (USEPA, 2010). The flurprimidol concentration estimated with the SWCC (Appendix

B Table 2) (using same input values) were 51.6, 47.2, and 41. 5 μg/L for the maximum peak

(acute), 21‐day and 60‐day average, respectively.  

Appendix B Table 2.  SWCC Estimated Environmental Concentrations (EECS) for Flurprimidol. 

SWCC Scenario      #app/rate/interval Peak 21‐day

Ave

60‐day

Ave

Yearly

Ave

Overall

Ave

(#/lb a.i./A/days) μg/L

CA nursery        2/1.5/56 days 11.5 10.6 9.33 6 5.4

FL nursery          36.7 33.5 29.1 15.6 11.5

FL turf               14 12.9 11.4 6.76 5.83

MI nursery          34.3 32.2 30 20.5 17.6

NJ nursery          31.8 30.2 29 17.7 13.8

TN nursery          31 29.5 27.1 17.1 12.6

PA turf               17.9 16.5 14.9 11 8.43

OR nursery          23.7 21.9 19.6 12.5 10

OR grass seed          27.7 27 22.6 14.6 11.2

CA nursery        1/3.0/‐days 15.5 14.1 12.3 6.68 5.59

FL nursery          33.2 30.1 26.8 14.1 10.3

FL turf               15.5 14.1 12.4 6.87 5.8

MI nursery          33 31.8 30 20 16.9

NJ nursery          48.4 46.4 41.6 23.5 14.2

OR grass seed          23.8 22.5 20.5 11.9 10.1

OR nursery          29.4 27.1 24.7 14.6 10.7

PA turf               19.1 17.7 15.7 9.71 7.9

TN nursery          41.7 38 33.7 18.5 12.6

CA nursery        5/0.60/56 days 18.9 17.3 15.3 9.58 7.26

FL nursery          42.3 24.6 16.1 10.4 8.42

FL turf               13.7 12 13 8.49 6.57

MI nursery          28.1 23.9 20.4 16.4 14.8

NJ nursery          40.3 27.5 21.7 14.3 12.1

OR grass seed          21.3 17.2 15.2 12.5 10.1

OR nursery          19 16.8 15 12.1 10.3

PA turf               20.4 16.9 15.2 11.3 9.34

 

16 http://www.epa.gov/oppefed1/models/water/index.htm#swcc
36 

SWCC Scenario      #app/rate/interval Peak 21‐day

Ave

60‐day

Ave

Yearly

Ave

Overall

Ave

TN nursery          32.3 26.9 20.3 13.8 9.89

FL nurserya   1:3.0:‐days: granular 51.6 47.2 41.5 18.1 12.2

TN nursery          30.5 27.8 24.5 13.2 7.27

NJ nursery    35.9 34.3 30.7 16.8 7.77 a For comparison purposes the application rate, spray drift and application efficiency, and date of application (mn/day: 08/08) are

the same value that resulted in the highest EECs in the previous assessment (USEPA, 2010).  

   
37 

Appendix C. Requested Data Justification Tables 

Study Title: Honey Bee Acute Oral Toxicity, Adult

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticides in various use settings.   

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently

brought back to the hive.  Therefore, potential acute effects to adult honeybees and other

pollinators from oral exposure to some pesticides could exist.  Currently available toxicity studies

do not address possible effects of oral exposure on adult terrestrial insect survival.  Because of the

potential for pollen and nectar to be contaminated with pesticide residues, and subsequently

brought back to the hive, it is important to determine the acute oral toxicity of this compound to

adult honeybees and other insect pollinators.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

terrestrial invertebrates using the honeybee as a surrogate test species.  The guidance discusses

Tier I laboratory‐based acute oral toxicity studies of individual adult bees as a critical component of

the screening‐level risk assessment process for examining potential adverse effects from specific

routes of exposure.  The guidance can be found at: http://www2.epa.gov/pollinator‐

protection/pollinator‐risk‐assessment‐guidance .  Additional guidance on the honeybee oral

toxicity test design can be found in OECD Test Guideline 213 http://www.oecd‐

ilibrary.org/environment/test‐no‐213‐honeybees‐acute‐oral‐toxicity‐test_9789264070165‐en  .

Practical Utility of the Data

How will the data be used?

The Tier I acute oral toxicity data on adult bees serve as a foundation for the screening‐level

assessment of potential risk to non‐target organisms such as federally listed threatened or

endangered and non‐listed terrestrial invertebrate insects, including pollinators, from acute oral

exposures to pesticides.  The data will be used to reduce uncertainties associated with the risk

assessment for terrestrial invertebrates and will improve EPA’s understanding of the potential

direct and indirect effects on a broad range of taxa.  This study will also provide information with

which to compare whether oral toxicity estimates differ from contact toxicity estimates obtained

from other Tier I studies.  If acute oral effects data for adult honeybees and insect pollinators are

not available, risks to terrestrial insects from acute oral exposure will be assumed.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect listed threatened or endangered species and/or modify their designated

critical habitat.  Without these data, EPA may need to presume risk which will limit the flexibility of

pesticide products to comply with FIFRA and the ESA, and could result in use restrictions.   

Study Title: Honey Bee Acute Oral Toxicity, Larvae
38 

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticides in various use settings.  

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently

brought back to the hive where larvae and pupae may be exposed.  Therefore, potential adverse

effects to developing bees and other insect pollinators could result from exposure to pesticide

residues.  Available toxicity studies do not address possible effects on brood (larvae and pupae)

survival/development.  Because of the potential for pollen and nectar to be contaminated with

pesticide residues, and subsequently brought back to the hive, it is important to determine the

acute oral toxicity of this compound to bee brood.   

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

terrestrial invertebrates using the honeybee as a surrogate test species.  The guidance discusses

Tier I laboratory‐based acute toxicity studies of individual honeybee larvae as a critical component

of the screening‐level risk assessment process for examining potential risks from specific routes of

exposure.  The guidance can be found at: http://www2.epa.gov/pollinator‐protection/pollinator‐

risk‐assessment‐guidance .  Additional guidance on larval honeybee toxicity test design can be

found in OECD Test Guideline 237 http://www.oecd‐ilibrary.org/environment/test‐no‐237‐honey‐

bee‐apis‐mellifera‐larval‐toxicity‐test‐single‐exposure_9789264203723‐en  .

Practical Utility of the Data

How will the data be used?

The Tier I acute oral toxicity data on honeybee larvae serve as a foundation for the screening‐level

assessment of potential risk to non‐target organisms such as federally listed threatened or

endangered and non‐listed terrestrial invertebrate insects, including pollinators, and/or modify

their designated critical habitat from acute oral exposures to pesticides.  The data will be used to

reduce uncertainties associated with the risk assessment for terrestrial invertebrates and will

improve EPA’s understanding of the potential effects on terrestrial species and whether there is a

differential sensitivity of larval bees relative to adult bees.  If acute oral effects data for larvae are

not available, risks to terrestrial insects from acute oral exposure will be assumed

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect listed threatened or endangered species and/or modify their designated

critical habitat.  Without these data, EPA may need to presume risk which will limit the flexibility of

pesticide products to comply with FIFRA and the ESA, and could result in use restrictions.   

Study Title:  Honey Bee Chronic Oral Toxicity, Adult

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticides in various use settings.   

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently
39 

brought back to the hive.  Therefore, potential chronic effects to adult honeybees and other

pollinators from oral exposure to some pesticides could exist.  Currently available toxicity studies

do not address possible lethal and sublethal effects of chronic oral exposure on adult terrestrial

invertebrates and will assist in determining whether the sensitivity of adult bees differs from that

of earlier life stages.  Because of the potential for pollen and nectar to be contaminated with

pesticide residues, and subsequently brought back to the hive, it is important to determine the

chronic oral toxicity of this compound to adult honeybees and other pollinators.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance discusses Tier I laboratory‐based chronic oral

toxicity studies of individual adult honeybees as a critical component of the screening‐level risk

assessment process for examining potential risks from specific routes of exposure.  The guidance

can be found at: http://www2.epa.gov/pollinator‐protection/pollinator‐risk‐assessment‐guidance .  

Study design elements for the chronic 10‐day oral toxicity test with honeybees are similar to the

OECD Test Guideline 213 acute oral toxicity test http://www.oecd‐ilibrary.org/environment/test‐

no‐213‐honeybees‐acute‐oral‐toxicity‐test_9789264070165‐en  .

Practical Utility of the Data

How will the data be used?

The Tier I chronic oral toxicity data on adult bees serve as a foundation for the screening‐level

assessment of potential risk to non‐target organisms including federally listed threatened or

endangered species and non‐listed terrestrial invertebrate insects, including pollinators, from

chronic oral exposures to pesticides.  The data will be used to reduce uncertainties associated with

the risk assessment for terrestrial invertebrates and will improve EPA’s understanding of the

potential direct and indirect lethal and sublethal effects on a broad range of terrestrial species,

particularly insect pollinators and to determine whether adult toxicity differs substantially from

other life stages evaluated in other Tier I tests.  If chronic oral effects data for adults are not

available, risks to terrestrial insects from chronic oral exposure will be assumed.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect listed threatened or endangered species and/or their designated critical

habitat.  Without these data, EPA may need to presume risk which will limit the flexibility of

pesticide products to comply with FIFRA and the ESA, and could result in use restrictions.   

Study Title:  Honey Bee Chronic Oral Toxicity, Larvae

Rationale for Requiring the Data

Terrestrial invertebrates are likely to be impacted if exposed to pesticides in various use settings.  Pesticide

residues may be transferred to pollen and/or nectar of treated plants and subsequently brought back to the

hive where larvae and pupae may be exposed.  Therefore, potential effects to developing bees could result

from chronic oral exposure to pesticide residues.  Available toxicity studies do not address possible chronic

effects on brood (larvae and pupae) survival.  Because of the potential for pollen and nectar to be

contaminated with pesticide residues, and subsequently brought back to the hive, it is important to
40 

determine chronic larval/pupal toxicity and whether adult emergence is adversely affected.  This study will

provide information on whether honeybee larvae differ in sensitivity from adult bees following chronic

exposure.  

The Office of Pesticide Programs has made available a guidance regarding ecological testing for invertebrates

with the honeybee.  The guidance discusses Tier 1 laboratory‐based chronic oral toxicity studies of individual

honeybee larvae as a critical component of the screening‐level risk assessment process for examining

potential risks from specific routes of exposure.  The guidance can be found at:

http://www2.epa.gov/pollinator‐protection/pollinator‐risk‐assessment‐guidance.

Additional information on larval honeybee toxicity repeat exposure test design can be found in the oECD

draft guidance

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

.

Practical Utility of the Data

How will the data be used?

The Tier I chronic oral toxicity data on bee larvae serve as a foundation for the screening‐level assessment of

potential risk to non‐target organisms including federally listed threatened or endangered and non‐listed

terrestrial invertebrate insects, including pollinators, from chronic oral exposures to pesticides.  The data will

be used to reduce uncertainties associated with the risk assessment for terrestrial invertebrates and will

improve EPA’s understanding of the potential direct and indirect lethal and sublethal effects on a broad

range of terrestrial species, particularly insect pollinators.  These data will also assist in determining whether

early life stages of the bee differ in their sensitivity to pesticides relative to adults.  If chronic oral effects

data for larvae are not available, risks to terrestrial insects from chronic oral exposure will be assumed.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued registration

of a pesticide is likely to result in unreasonable adverse effects to non‐target species or is likely to adversely

affect listed threatened or endangered species and/or modify their designated critical habitat.  Without

these data, EPA may need to presume risk which will limit the flexibility of pesticide products to comply with

FIFRA and the ESA, and could result in use restrictions.   

Study Title: Semi‐Field Toxicity Testing for Pollinators (tunnel/enclosure studies)

Rationale for Requiring the Data

Tier II studies are conditional on the outcome of the screening‐level assessment where acute

and/or chronic risk levels of concern have been exceeded for terrestrial invertebrates.  Terrestrial

invertebrates are likely to be impacted if exposed to pesticides in various use settings.  Pesticide

residues may be transferred to pollen and/or nectar of treated plants and subsequently brought

back to the hive and may adversely affect developing brood (egg, larvae, and pupae) and adult

bees.  Screening‐level (Tier I) studies of individual bees do not address possible effects and/or

exposure to pesticide residues at the colony‐level.  Because of the potential for pollen and nectar

to be contaminated with pesticide residues, and subsequently brought back to the hive, it is

important to determine whether bee colonies may be negatively affected under relatively

controlled exposure conditions of a semi‐field study. In addition to providing effects data, these

studies can provide data on exposure as pesticide residues in pollen/nectar of treated plants.
41 

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance describes the tiered testing process and can be

found at: http://www2.epa.gov/pollinator‐protection/pollinator‐risk‐assessment‐guidance .  

Additional information on honeybee colony studies under semi‐field conditions can be found in the

OECD Guidance 75

http://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=env/jm/mono%28 .          

Practical Utility of the Data

How will the data be used?  

Tier II colony‐level data will be used to assess potential risk to non‐target organisms including listed

and non‐listed terrestrial social invertebrate species and to determine whether effects observed in

the screening‐level (Tier I) laboratory‐based studies of individual bees are evident in colony‐level

studies under semi‐field conditions.  The Tier II semi‐field test of whole colonies is a relatively

controlled study, i.e., bees are confined to a specific area, that is designed to represent potential

field‐level exposure and account for hive dynamics, which are not achievable from other pollinator

studies.  This study will be used to determine whether adverse effects to insect pollinators at the

whole colony level, may result for the use of pesticides and will help to refine risk estimates

derived in the screening‐level risk assessment for beneficial terrestrial invertebrates.  Measured

residues in pollen/nectar can also be used to refine risk estimates derived from model‐based or

default values in the screening‐level assessment.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect federally listed threatened or endangered species or their designated

critical habitat.  Without these data, EPA may need to presume risk which will limit the flexibility of

pesticide products to comply with FIFRA and the ESA, and could result in significant use

restrictions.

Study Title: Semi‐Field Toxicity for Pollinator Testing (feeding studies)

Rationale for Requiring the Data

Pesticide residues may be transferred to pollen and/or nectar of treated plants and subsequently

brought back to the hive, and may adversely affect developing brood (egg, larvae, and pupae) and

adult bees. Tier II feeding studies are conditional on the outcome of the screening‐level

assessment where acute and/or chronic risk levels of concern have been exceeded for terrestrial

invertebrates based on Tier I studies of individual bees. Feeding studies utilize free foraging bee

colonies that are “dosed” with specific quantities of test material and represent a means of

ensuring exposure to the test material through spiked pollen and/or sugar solutions fed to the

colony while still allowing the bees to forage freely.  Since bee colonies are not confined to

enclosures, colonies can be exposed for longer duration periods without subjecting the bees to

stress that typically results from Tier II tunnel studies.  Available toxicity studies of individual bees

(Tier 1) conducted to support screening‐level assessments do not address possible effects and/or
42 

exposure to pesticide residues at the colony‐level.  Because of the potential for pollen and nectar

to be contaminated with pesticide residues, and subsequently brought back to the hive, it is

important to determine whether bee colonies may be negatively affected where bees are free

foraging and have the option to collect/consume alternative forage items beyond the spiked food.

Since multiple dose levels can be more readily tested, feeding studies can help to define dose‐

response relationships at the whole colony level.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance describes the tiered testing process and can be

found at: http://www2.epa.gov/pollinator‐protection/pollinator‐risk‐assessment‐guidance .  

Additional information on honeybee colony feeding studies can be found in the EPPO Guidance 170

at: http://www.nationalbeeunit.com/index.cfm?pageId=187  .

Practical Utility of the Data

How will the data be used?

Tier II colony feeding data will be used to assess potential risk to non‐target organisms including

listed and non‐listed terrestrial social invertebrate species.  The colony feeding study is designed to

represent potential field‐level exposure and account for hive dynamics using longer duration

exposure periods than are possible in Tier II tunnel studies.  The study will be used to determine

whether potential adverse effects to insect pollinators at the whole colony level when bees are

able to forage naturally beyond the spiked food.  Results from the feeding study will help to refine

the screening‐level risk assessment for beneficial terrestrial invertebrates that were based on Tier I

studies on individual bees.  Since feeding studies can help to define a dose‐response relationship at

the colony level, the studies can provide a means of determining exposure thresholds below which

the likelihood of adverse effects on colonies may be low.

  

How could the data impact the Agency’s future decision‐making?

Tier II colony‐level data will be used to refine screening‐level risk estimates derived using Tier I

laboratory‐based data on individual bees.  The Tier II data will inform the determination required

under FIFRA or the ESA as to whether continued registration of a pesticide is likely to result in

unreasonable adverse effects to non‐target species or is likely to adversely affect federally listed

threatened or endangered species or their designated critical habitat.  Without these data, EPA

may need to presume risk which will limit the flexibility of pesticide products to comply with FIFRA

and the ESA, and could result in significant use restrictions.

Study Title:  Field Trial of Residues in Pollen and Nectar

Rationale for Requiring the Data
43 

Terrestrial invertebrates are likely to be impacted if exposed to pesticide residues in various use

settings.  Pesticide residues may be transferred to pollen and/or nectar of treated plants and

subsequently brought back to hive where all life stages may be exposed.  For some pesticides, the

quantification of pollinator‐relevant residues in treated flowering plants is needed, since

pollinators will be exposed to residues from either current or prior season applications (due to the

potential for residues to accumulate in plants and trees).  Residues in edible/transportable‐to‐hive

parts of treated trees and plants, including (where appropriate), but not limited to, guttation

water, sap/resins, whole plant tissue (e.g., leaves, stems), as well as blooming, pollen‐shedding,

and nectar producing parts (i.e., flowers and, if present, extra‐floral nectaries) of plants may inform

the potential for risk.  Studies should be designed to provide residue data for crops and application

methods of concern.

The Office of Pesticide Programs has made available a guidance regarding ecological testing for

invertebrates with the honeybee.  The guidance can be found at: http://www2.epa.gov/pollinator‐

protection/pollinator‐risk‐assessment‐guidance  .

Practical Utility of the Data

How will the data be used?

Measured residue data will be used to refine conservative estimates of pesticide exposure and

reduce uncertainties associated with the Tier I exposure assessment by providing direct

measurements of pesticide concentrations resulting from actual use settings.  Measured residues

may provide a more realistic understanding of exposure through contact or ingestion with which to

calculate risk quotients for individual bees as well as to characterize exposure to the colony.  If

measured residue data are not available, risk estimates for terrestrial insects will be based on

model‐generated or default values used to support the screening‐level assessment.

How could the data impact the Agency’s future decision‐making?

The data will inform the determination required under FIFRA or the ESA as to whether continued

registration of a pesticide is likely to result in unreasonable adverse effects to non‐target species or

is likely to adversely affect federally listed threatened or endangered species or their designated

critical habitat.  Without these data, EPA will have to rely on conservative estimates of exposure

which will limit the flexibility of pesticide products to comply with FIFRA and the ESA, and could

result in use restrictions.