Page 2 of 38

be conducted as part of the registration review of the fungicide, imazalil and imazalil 

sulfate. The revisions update the preliminary problem formulation (DP 411863). They

reflect additional data submitted to the Agency for review and a more detailed description 

of the requested chronic sediment toxicity data request. 

The problem formulation draws on information from both open literature and studies 

submitted by the technical registrants in response to data requirements. This document is 

intended to provide an overview of what is currently known regarding the environmental 

fate and ecological effects associated with imazalil and imazalil sulfate and their degradates 

and outlines uncertainties regarding attributes of the parent compound and its 

transformation products. It describes the preliminary ecological risk hypothesis and the 

processes that will be used during the completion of drinking water and ecological risk 

assessments in support of reregistration. This document also recommends studies that 

should be included in a data call-in (DCI) to address uncertainties surrounding the 

environmental fate and potential ecological effects of imazalil and imazalil sulfate.
Page 3 of 38

Revised Problem Formulation for the Environmental 

Fate and Ecological Risk, Endangered Species, and

Drinking Water Assessments in Support of the 

Registration Review of Imazalil and Imazalil Sulfate

 

1-[2-(2,4-dichlorophenyl)-2-(2-propen-1-yloxy)ethyl]-1H-imidazole

1-[2-(2, 4-dichlorophenyl)-2-(2-propen-1-yTileloxy)ethyl]-1H-imidazolium hydrogen sulfate

(CAS 3555-44-0 and 58594-72-2)

Environmental Fate and Effects Division Team:

Environmental Risk Branch II

Christine Hartless, Ph.D., Wildlife Biologist

R. David Jones, Ph.D. Senior Agronomist

Reviewed by:

James Lin, Ph.D. Chemist

Jean Holmes, DVM, RAPL

Brian Anderson, Branch Chief

U. S. Environmental Protection Agency

Office of Pesticide Programs

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Antimicrobials Division Team:

Laura Parsons, Acting Associate Branch Chief

Bill Erickson, Biologist

Cl

Cl

O

NH+

N

S O

OOH

O

Cl

Cl

O

N

N
Page 4 of 38

Table of Contents

1. Executive summary........................................................................................................ 5

2. Introduction.................................................................................................................... 6

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

4. Conclusions from Previous Risk Assessments.............................................................. 9

5. Environmental Fate and Transport................................................................................ 10

6. Receptors...................................................................................................................... 14

7. Exposure Pathways of Concern ................................................................................... 16

8. Analysis Plan ................................................................................................................ 16

8.1 Stressors of Concern........................................................................................... 16

8.2 Measures of Exposure ........................................................................................ 17

8.3 Measures of Effect ............................................................................................. 18

9. Endangered Species Assessment ................................................................................. 18

10. Endocrine Disruptor Screening Program ................................................................... 18

11. Preliminary Identification of Data Gaps.................................................................... 18

11.1. Fate...................................................................................................................... 18

11.2. Effects................................................................................................................. 21

12. References.................................................................................................................. 26

Appendix A. Screening Ground Water Exposure Assessment Using PRZM GW....... 31

Appendix B. Screening Level Models to Evaluate Potential Importance of Drinking 

Water and Inhalation Exposure Pathways .................................................................... 33

Appendix C. Data Justification Tables for Chronic Sediment Toxicity Studies ......... 35
Page 5 of 38

1. Executive summary

The Environmental Fate and Effects Division (EFED) and Antimicrobials Division (AD) 

have completed the preliminary problem formulation for the ecological risk, environmental 

fate, endangered species, and drinking water assessments to be conducted as part of the 

registration review of imazalil and imazalil sulfate. The problem formulation describes the 

methods planned to be used during the completion of drinking water and ecological risk 

assessments in support of registration review and provides an overview of the 

environmental fate, ecological effects, and potential risks associated with the use of 

imazalil and imazalil sulfate as well as uncertainties unique to risk assessment of imazalil 

and imazalil sulfate. This document also identifies additional studies that would be 

beneficial to the conduct of an ecological risk assessment. 

Data needs for ecological effects are:

 Freshwater fish early-life stage (850.1400)

1

 Estuarine/marine acute fish toxicity (850.1075)

 Whole Sediment Chronic Invertebrate Toxicity (Freshwater, two species, nonguideline)

2

 Whole Sediment Chronic Invertebrate Toxicity (Estuarine/marine, non-guideline)

3

 Acute passerine toxicity (850.2100)

 Earthworm Subchronic Toxicity Test (850.3100)4

 Honey bee acute contact toxicity (850.3020)5

 Honey bee acute oral toxicity (non-guideline)6

Data needed for fate and exposure assessment are:

 Aerobic soil metabolism (835.4100) for three additional soils

 Aqueous photolysis (835.2240)

 Laboratory Volatility (835.1410)[to be conducted in a basic environment]

 Terrestrial Field Dissipation Study (835.6100)

 Bioaccumulation in Fish (850.1730)

 Environmental chemistry method for soil (850.6100)

 

1 A study has been submitted to the Agency and is currently under review (MRID 49106401). 

2 Requested freshwater studies are a 42-day study with Hyallela azteca and a 56-day study with 

Chironomus dilutus or C. tentans. Both are found in Second Edition EPA/600/R-99/064, Duluth, MN. A 

chronic C. riparius study has been submitted to the Agency and is currently under review (MRID

49215906).

3 Requested estuarine/marine study is a 28-day study conducted with the Amphipod Leptocheirus 

plumulosa found in First Edition, EPA Report 600/R-01/020, March 2001.

4 A study has been submitted to the Agency and is currently under review (MRID 49215905). 

5 A study has been submitted to the Agency and is currently under review (MRID 49215902).

6 A study has been submitted to the Agency and is currently under review (MRID 49215903).
Page 6 of 38

2. Introduction

Imazalil and imazalil sulfate are imidazole systemic fungicides. They are specifically 

effective in controlling seed- and soil-borne pathogens, such as Pyrenophora, Fusarium, 

and Septoria fungi. Imazalil and imazalil sulfate are imidazole fungicides which are sterol 

demethylation inhibitors (SDI). The fungicidal action interferes with ergosterol synthesis 

of fungi by inhibiting the sterol C14 demethylation process. Physiologically, imazalil 

inhibits gibberellic acid biosynthesis and production of demethyl sterol in seedlings. In 

the demethylation process, the 14-α-methyl group in a sterol is removed by three 

NADPH-dependent oxygenase's oxidative reactions which are catalyzed by a 

cytochrome-P450 enzyme. Imazalil, as an SDI, inhibits spore germination, activates 

uncoordinated chitin syntheses (which affects budding fungi), and accumulates free fatty 

acids (which is toxic to fungal cells).

The uses in the profile to be evaluated by EFED include 1) terrestrial feed crop (barley, 

wheat, and triticale seed treatment), 2) indoor food (post-harvest citrus fruit treatment), and

3) greenhouse fogger (bedding plants, cut flowers, flowering plants (baskets and hanging), 

foliage, ornamentals, and perennials). Note the only outdoor uses are seed treatments.

The use in the profile to be evaluated by AD includes indoor non-food (egg hatching 

facilities and equipment disinfection). Treatment of egg hatching facilities and equipment 

disinfection is considered to be an agricultural premise use for purposes of risk assessment. 

As labeled, this use is not expected to result in environmental exposures because the spray 

is allowed to dry prior to introduction of eggs. AD is not requesting any additional 

environmental fate or ecotoxicology data to evaluate this use.

EFED evaluated the most recent ecological risk assessments for imazalil and imazalil 

sulfate in association with the updated toxicity, exposure, and usage information to 

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

registration review. In addition, EFED considered the latest Agency science policies and 

risk assessment methodologies. The structures of imazalil and imazalil sulfate, as well as 

the chemical names and other identifiers can be found in the chemical identity table in 

Section 5 of this document. 

3. Use Characterization

The chemical profile produced by Biological and Economic Analysis Division (BEAD), 

located in the docket, lists the use patterns of maximum exposures for the current uses of 

imazalil and imazalil sulfate. The chemical profile includes both a summary of labeled 

uses and rates as well as a summary of available reported usage data. EFED will use 

application scenarios that result in maximum exposure scenarios for a given use for the risk 

assessment. Any absence of information on the labels that specifies the maximum single 

application rate, the application interval, the annual maximum rate allowed (lbs a.i./year), 

or application method may result in conservative assumptions.
Page 7 of 38

The use profile to be utilized in the ecological risk assessment include 1) terrestrial feed 

crop (barley, wheat, and triticale seed treatment), 2) indoor food (post-harvest citrus fruit 

treatment), and 3) greenhouse fogger (bedding plants, cut flowers, flowering plants 

(baskets and hanging), foliage, ornamentals, and perennials), and 4) indoor non-food (egg 

hatching facilities and equipment disinfection). Maximum application rates, application 

methods, and affiliated labels are outlined below for field uses (Table 1) and non-field uses 

(Table 2).

Table 1. Methods and rates of application of currently registered used of imazalil 

(field uses).

Crop Max. Single App. 

Rate

Annual 

Max. No. 

of Apps.

Application 

Intervals 

(days)

Application 

Method

End-use 

Product 

Labels

Wheat 0.0001 lb a.i./ lb seed 1 NA seed treatment

264-976

264-977

83991-1*

83991-2*

Barley 0.0001 lb a.i./ lb seed 1 NA seed treatment

264-976

264-977

83991-1*

83991-2*

Triticale 0.00003523 lb a.i. / 

lb seed 1 NA seed treatment 264-976*264-977

*label with the highest rate
Page 8 of 38

Table 2. Methods and rates of application of currently registered used of imazalil and imazalil 

sulfate (indoor and greenhouse uses).

Active Ingredient/

Commodity 

Max. Single App. 

Rate

Annual 

Max. No. of 

Apps.

Application 

Intervals 

(days)

Application 

Method

End-use 

Product 

Labels

Imazalil

Citrus**

0.6265 lb a.i./100 

gal.

1 NA

Dip treatment

Drench

Wash

43813-6

66222-20

2792-51

66222-100*

Imazalil

Citrus

0.8353 lb a.i./100 

gal. 1 NA Spray

43813-6

66222-20

2792-51

66222-100*

Imazalil

Citrus

3.3 lb a.i./100 gal. 1 NA Wax treatment

43813-6*

66222-20*

2792-51

66222-100*

Imazalil

Citrus

3.3 lb a.i./100 gal. 1 NA Foam

66222-100*

Imazalil sulfate

Citrus

0.8348 lb a.i./100 

gal. 1 NA

Dip treatment

Drench

Wash

43813-26*

43813-38*

Imazalil sulfate

Citrus

1.1 lb a.i./

100 gal.

1 NA Spray

43813-26*

43813-38*

Imazalil sulfate

Citrus

2.2 lb a.i./

100 gal.

1 NA Wax treatment

43813-38*

Imazalil

Ornamental 

herbaceous plants, 

Ornamental nonflowering plants, 

Ornamental woody 

shrubs and vines

0.704 lb a.i./acre 8 7 days Aerosol, fog, or 

fumigation.

499-508*

Imazalil

Poultry and turkey 

hatchery 

equipment.

1 mL 0.15% 

solution per 10 ft3 NS NS Aerosol, fog, or fumigation.

773-55*

773-56*

53883-327*

*label with the highest rate

** All imazalil and imazalil sulfate citrus labels contain the following statement: “Do not discharge effluent 

containing this product into lakes, streams, ponds, estuaries, oceans, or other waters unless in accordance with the 

requirements of a National Pollutant Discharge Elimination System (NPDES) permit and the permitting authority 

has been notified in writing prior to discharge. Do not discharge effluent containing this product to sewer systems 

without previously notifying the sewage treatment plant authority. For guidance, contact your State Water Board 

or Regional Office of the Environmental Protection Agency.”

NA = not applicable

NS =not specified
Page 9 of 38

4. Conclusions from Previous Risk Assessments

The Agency has conducted previous ecological risk assessments on imazalil that serve as 

a basis for this problem formulation. These are briefly summarized below. No ecological 

risk assessments have been conducted by the Agency for imazalil sulfate. No endangered 

species assessments have been conducted for either imazalil or imazalil sulfate.

At the time the EFED Reregistration Eligibility Decision (RED) Chapter was signed (April 

18, 2001), imazalil was registered as a fungicide for seed treatment of small grains (wheat 

and barley), for post-harvest use on citrus fruits by water and wax application, and as a 

disinfectant in chicken hatching equipment. The EFED risk assessment did not result in 

any RQs that exceeded levels of concern for either terrestrial or aquatic non-target 

organisms, and, therefore, imazalil was not expected to represent a risk to the environment. 

No previous ecological risk assessment has been located for the triticale seed treatment 

use. The use rate for triticale is approximately 1/3 that of wheat and barley; therefore, the 

risks from triticale would be expected to be less than those for wheat or barley. In the RED, 

EFED expressed concerns regarding the endocrine disrupting potential of imazalil based 

on the chemical's mode of action as a sterol inhibitor and on reproductive effects (eggshell 

thinning) observed in chronic toxicity studies of mallard ducks.

Environmental fate data were complete at the time the RED was completed, and no 

additional data were required. Ecological effect data were relatively complete at the time 

the RED was finalized. Based on the data requirements for seed treatment chemicals, the 

registrant was required to submit aquatic plant acute toxicity studies for two species. 

Additionally, because of concerns regarding the endocrine disrupting potential of imazalil, 

EFED requested that additional tests be conducted to better characterize these potential 

effects once the appropriate methodology has been developed. Imazalil toxicity studies for 

Lemna gibba and Selenastrum capricornutum were submitted, reviewed, and classified as 

Supplemental (MRIDs 46818201 and 46818202, respectively). A short-term reproduction

zebrafish (Danio rerio) assay with imazalil following OECD 229 was submitted to the 

Agency and is currently under review (MRID 49106401).

A drinking water exposure assessment for use in the human dietary risk assessment was 

completed for the RED. This assessment found that an upper-bound concentration in 

surface water from the use of imazalil as a seed treatment was 0.072 μg∙L-1and that the 

concentration is ground water was ‘negligible’. An assessment of ground using PRZMGW performed for this assessment showed upper bound concentrations in ground water 

were no higher than 5 x 10-3 μg∙L-1. (See Appendix A)

In 2006, EFED reviewed a Section 3 request to use imazalil as a greenhouse fogger 

(bedding plants, cut flowers, flowering plants (baskets and hanging), foliage, ornamentals, 

and perennials) (DP Barcode: 326607). EFED concluded that no environmental exposure

was anticipated and that the product, when label directions were followed, will have no 

effect on non-target organisms as the product was a total release aerosol formulation 

intended strictly for non-food, indoor greenhouse use. 
Page 10 of 38

5. Environmental Fate and Transport 

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

associated with imazalil are summarized in Table 3. EFED is not aware of any monitoring 

data for imazalil or imazalil sulfate.

Table 3. General physico-chemical and environmental fate properties of imazalil.

Parameter Value Reference

Selected Physical/Chemical Parameters

Molecular Mass

imazalil: 297.18 g∙mol-1

imazalil sulfate: 395.26 g∙mol-1 calculated

Water Solubility

imazalil: 0.3 mg∙L-1(temperature unspecified)

imazalil sulfate: 500 mg∙L-1(temperature 

unspecified)

Goodwine (1987)

Vapor pressure 1.52 x 10-6torr at 25o C MRID 44107218

Density 1.40 kg∙L-1 @ 20o C MRID 44107208

Henry's Law Constant 1.98 x 10-6atm∙m3∙mol-1calculated

Octanol/Water Partition Coefficient 

(Kow)

pH 5: 18,600

pH 7: 10,000

pH 9: 15,800

MRID 44107211

pKa 6.48 MRID 44107210

Hydrolysis t1/2 pH 5

 pH 7

 pH 9

no evidence of degradation at all pHs MRID 00115272

Aqueous Photolysis 1.5 d

MRID 40926701

MRID 41350801

MRID 92072015

Aerobic Soil metabolism t1⁄2

Watervliet loam: 157 days (parent) @ 25oC

468 d (parent + unextracted residues) @ 25oC

MRID 00148314

MRID 00158160

Batch Equilibrium

Kf =28.9 L∙kg-1 – Kessel sand

 80 L∙kg-1- Groostrees loamy sandt

 137.6 L∙kg-1- Ekeren-Laar sandy loam

187.8 L∙kg-1 – Watervliet loam

187.9 L∙kg-1 – Haacht silt loam

195.3 L∙kg-1- Ekeren silt loam

110 - L∙kg-1 Tongeren silt loam

111.8 L∙kg-1 Dronten silty clay loam

1/n values ranged from 0.71-0.98

van Leemput, 1986

MRID 00158160

Column Leaching

no detected movement in columns (30-cm length) 

of sandy loam, silty clay loam, silt loam, and 

loamy sand soils

MRID 00148072

MRID 00158160

MRID 91072017
Page 11 of 38

The dominant route of dissipation of imazalil is expected to be aerobic metabolism in 

terrestrial environments (T1⁄2 = 157 d). Partition coefficients vary with pH, and are not 

correlated with soil organic carbon content. The magnitude of the adsorption coefficients 

indicates that imazalil is not prone to leaching. There is some uncertainty associated with 

the environmental fate of imazalil because the pKa of 6.48, (the acid equilibrium constant) 

is in the middle of the range of pHs commonly found in the environment, so the form of 

imazalil, the protonated acid form or the neutral basic form will vary with pH. At a soil or 

water pH of 6.48, there will be equal amounts of both species present. At lower pHs, the 

cationic form will predominate and at higher pHs, there will be more of the neutral 

conjugate base form. Since these two forms will have different properties, the 

environmental fate profile is likely different for the two forms and there is currently 

insufficient data to evaluate how imazalil behavior changes as a function of pH. Note that 

the active ingredient imazalil (PC code: 111901) is the basic form while imazalil hydrogen 

sulfate is the salt of the acid form (PC Code: 111902). The form of imazalil which is applied 

is not important in determining the fate and transport properties as the acid-base buffering 

capacity in the environment is quite large and the form of imazalil which will be present in 

the environment is determined by the local pH and not by form applied. There are currently 

no acceptable field dissipation studies so the fate assessment based on laboratory data 

cannot be evaluated against field results. No monitoring data has been identified for 

imazalil.

Physical and Chemical Properties

The reported solubility of imazalil is 0.3 mg∙L-1(Goodwine 1987). However, details 

describing the measurement, such as the temperature and the pH, were not provided so 

there is some uncertainty regarding this value. The same source reported the solubility of 

imazalil sulfate as 500 mg∙L-1. Because imazalil is a Lowery-Bronsted base, its solubility 

would be expected to vary with pH. In addition, the solubility of the conjugate acid depends 

somewhat on the counter anion. For example imazalil nitrate solubility is 24 mg∙L-1. 

Imazalil is not expected to volatilize with a vapor pressure of 1.52 x 10-6torr at 25o C. The 

octanol-water partition coefficient varies with pH from 10,000 at pH 7 to 18,000 at pH 5. 

These values suggest that imazalil may bioconcentrate, but no bioconcentration data are 

available.

Abiotic Degradation.

There is no evidence that imazalil degrades by hydrolysis at any pH. Some imazalil may 

be removed by runoff and be susceptible to photolysis in aquatic systems, so aqueous 

photolysis may be an important route of degradation. Imazalil degrades moderately rapidly 

in aqueous systems with a 1.5 d half-life. There were two major degradates, only one of 

which was identified: N-([2-(2,4-dichloropheny1)-2-(2-propenyloxy) ethyl] formamide

which was at 17.8% of the applied amount at 6 d after initiation the experiment (Figure 

1.1 and Table 4). The other major (unidentified) degradate, labeled ‘F-I’ by the registrant 

was at 72% of the applied at 6 d. This may have consisted of more than one compound as 

it was in a peak at the start of the chromatogram. This peak did not appear until 1.5 d after 
Page 12 of 38

the start of the experiment indicating that it is a secondary or tertiary degradate. Imazalil is 

not expected to degrade by photolysis in terrestrial systems as the seed treatment use results 

in the imazalil being below the surface and not exposed to light. 

Figure 1. Imazalil environmental degradates: 

F2: N-[2-(2,4-dichlorophenyl)-2-hydroxyethyl]formamide; F-IV: 1-[2-(2,4-dichlorophenyl)-2-

hydroxyethyl-IH-imidazole; FV-A: N-[[[2-(2,4-dichlorophenyl)-2-(Z-propenyoxy~ethyl]imino]methyl]-

2,4-dichloro-beta-(2-propeny1oxy) benzenethamine; F-VII: N-([2-(2,4-dichloropheny1)-2-(2-

propenyloxy)ethyl]formamide.

Cl

Cl

O

F-V-A

N

H

N

O

Cl

Cl

Cl

Cl

OH

N

N

F-IV

Cl

Cl

OH

HN

O

F2

Cl

Cl

O

HN

O

F-VII
Page 13 of 38

Metabolic Degradation. 

A single aerobic soil metabolism study is available to describe the degradation of imazalil 

in aerobic soils. No acceptable aquatic metabolism data is available and no anaerobic soil 

metabolism study has been conducted. This study was performed on a Watervliet silt loam 

from Belgium and found the imazalil degraded with a half-life of 157 d. However, there 

were substantial unextracted, unidentified residues (31%) present at the end of the study at 

366 d, and these residues present a significant uncertainty in the degradation rate of the 

imazalil in aerobic soil. If these residues are assumed to be the parent or degradates which 

are of similar toxicity to the parent, the estimated half-life is 487 d. Since these residues 

were not identified their nature is unknown. A significant fraction of the total degradate 

formed during the study was carbon dioxide (20.8%). This suggests that these residues may 

be intermediate breakdown products of imazalil. An additional uncertainty results from 

having only a single study conducted at a single pH as the acid and base forms of imazalil 

may have different degradation profiles.

Other than CO2, there were two minor degradates formed during the aerobic soil 

metabolism (Table 4). Both of these compounds were measured as a single fraction which

peaked at a maximum level of 7% of the applied at 70 days after application, Component 

I was confirmed (by GC/MS) to be 1-[2-(2, 4-dichlorophenyl)-2-hydroxyethyl-IHimidazole. The structure of component II was not known.

Table 4. The Maximum Amount of Degradates Formed in Laboratory Degradation 

Studies by Imazalil and the Time When the Maximum Occurred.

Degradate Hydrolysis Photolysis

Aerobic Soil 

Metabolism

CO2 -- 1.5% @ 6 d* 20.8%

1-[2-(2,4-dichlorophenyl)-2-hydroxyethyl-IH-imidazole -- <7% @ 70 d

N-([2-(2,4-dichloropheny1)-2-

(2-propenyloxy)ethyl]formamide

-- 17.8% @ 6 d*

N-[2-(2,4-dichlorophenyl)-2-hydroxyethyl]formamide -- 8.8% @ 6 d*

N-[[[2-(2,4-dichlorophenyl)-2-(Zpropenyoxy~ethyl]imino]methyl]-2,4-

dichloro-beta-(2-propeny1oxy) benzenethamine

-- 5.8% @ 2 d

Unidentified major photolysis degradate F1 -- 72.2% @ 6 d*

Unidentified minor metabolism degradate -- <7% @ 70 d

Unidentified minor photolysis degradate F3 -- 5.2% @ 6 d*

Unidentified minor photolysis degradate F3 -- 6.7%@ 6 d*

Unextracted residues 31% @ 366 d*

* The time of maximum occurrence of the degradate was at the termination of the study.
Page 14 of 38

Mobility

A soil column leaching study for imazalil showed no movement of residues through soil 

and no residues in the leachate in four different soil columns. A batch equilibrium study 

evaluated adsorption in eight Belgian soils (Table 3). Kf values ranged from 28.9 to 187.9 

L·kg-1. No correlation with organic carbon content was found across the soils. However, 

Kf was significantly correlated with pH with a regression equation of Kf = 48.1(pH)-182.

This is expected as the conjugate acid and base forms would be expected to have difference 

propensities for adsorption. The acid form likely binds to the cation exchange complex, as 

it has a positive charge and the basic form likely binds to the soil organic matter. However, 

there is insufficient data available to establish the nature of the binding of the two forms 

separate from the pH effect with the amount of data available.

6. Receptors

Table 5 provides a summary of the taxonomic groups and the surrogate species tested to 

characterize the potential acute and chronic ecological effects of imazalil. In addition, the 

table provides a preliminary overview of the potential acute toxicity of imazalil by 

providing the acute toxicity classifications. No ecotoxicity data are available for imazalil 

sulfate or any degradates of imazalil.

Technical grade imazalil is classified as moderately toxic to freshwater fish and aquatic 

invertebrates on an acute exposure basis. Chronic exposure effect data to imazalil for 

freshwater fish are still under review. No data were available for estuarine/marine 

organisms. Toxic effects were observed in both freshwater vascular and non-vascular 

aquatic plants. EPA does not currently classify toxicity to aquatic plants.

Imazalil is slightly toxic to birds on an acute oral basis, practically non-toxic to birds on a 

subacute dietary exposure basis, and moderately toxic to mammals on an acute oral 

exposure basis. For bobwhite quail, chronic exposure to imazalil resulted in reduced adult 

body weights, and for mallard ducks, chronic exposure to imazalil resulted in reduced 

second generation viability, hatchability, and survival as well as reduction in eggshell 

thickness and egg production. Chronic exposure to laboratory rats resulted in reductions 

in body weight, litter size and gestation length. Data on toxicity of imazalil to honeybees 

and terrestrial plants have not been submitted to the Agency. 

A review of the Ecological Incident Information System (EIIS, version 2.1) and the Avian 

Monitoring Information System (AIMS) was completed on November 15, 2013, and no 

ecological incidents involving imazalil or imazalil sulfate were identified. Incident 

databases will be reviewed again at the time of the risk assessment. 
Page 15 of 38

Table 5. Test Species Evaluated for Assessing Potential Ecological Effects of Imazalil.

Taxonomic 

Group

Study 

Type Tested Species Toxicity Endpoint

Acute Toxicity 

Classification/

NOAEC most sensitive 

endpoint(s)

Source 

MRID

Birds1

Acute oral

Ring-necked 

Pheasant

Phasianus colchicus

LD50 = 1912 mg a.i./kg-bw Slightly toxic 163243

Dietary

Mallard duck

(Anas 

platyrhynchos)

LC50 >5620 mg a.i./kg-diet Practically non-toxic 30542

Northern bobwhite 

quail (Colinus 

virginianus)

LC50 >5620 mg a.i./kg-diet Practically non-toxic 30543

Chronic

Mallard duck NOAEC = 250 mg a.i./kg-diet

LOAEC = 500 mg a.i./kg-diet

Second generation 

viability, hatchability, 

and survival. Reduction 

in eggshell thickness 

and egg production. 

42039801

Northern bobwhite 

quail

NOAEC = 250 mg a.i./kg-diet

LOAEC = 500 mg a.i./kg-diet

Adult body weight 

change

41663801

Mammals

Acute Laboratory rat 

(Rattus norvegicus)

LD50 = 343 mg a.i./kg-bw Moderately toxic 00031596

Chronic Laboratory rat 

NOAEC = 300 mg a.i./kg-diet

LOAEC = 1,200 mg a.i./kgdiet

Body weight; litter size; 

duration of gestation 42570701

Insects No data

Freshwater 

fish2

Acute

Rainbow trout

Oncorhynchus 

mykiss

LC50 = 1.48 mg a.i./L moderately toxic 41606102

Chronic Zebrafish 

Danio rerio Under review 49106401

Freshwater 

invertebrates Acute Waterflea

Daphnia magna EC50 = 3.54 mg a.i./L moderately toxic 41606103

Chronic No data

Estuarine/

marine fish

Acute and 

Chronic No data

Estuarine/

marine 

invertebrates

Acute and 

Chronic No data

Terrestrial 

plants

Seedling 

emergence/ 

vegetative 

vigor

No data

Aquatic 

plants and 

algae

Vascular Duckweed,

Lemna gibba

IC50 = 0.35 mg 

a.i./L 95% C.I.: 

0.17-0.70 mg ai/L

NOAEC = 0.0954 mg a.i./L

Frond Number and Area 

Under the Growth 

Curve

46818201

Nonvascular

Green alga 

Selenastrum 

capricornutum

IC50 = 0.73 mg 

a.i./L 95% C.I.: 

0.58-0.91 mg ai/L

NOAEC = 0.5 mg a.i./L

Cell density 46818202

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

2 Freshwater fish may be surrogates for aquatic-phase amphibians.
Page 16 of 38

7. Exposure Pathways of Concern

The environmental fate properties and use patterns of imazalil and imazalil sulfate indicate 

that discharge of treated water from use on post-harvest citrus, leaching to ground water, 

and runoff and movement of imazalil from treated seeds to the growing plant represent 

potential transport mechanisms of imazalil and imazalil sulfate to aquatic and terrestrial 

organisms. 

Drinking water and inhalation exposure pathways were screened using the SIP (Screening 

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

SIP and STIR are described in detail at: 

http://www.epa.gov/oppefed1/models/terrestrial/index.htm. The inhalation exposure 

pathway was found to be an exposure pathway of low concern (no LOC exceedances are 

expected). Because of the high water solubility of imazalil, the drinking water pathway 

was found to be an exposure pathway of potential concern. SIP and STIR results are 

presented in Appendix B.

8. Analysis Plan 

8.1 Stressors of Concern

i. Ecological Risk 

The stressors of ecological concern for terrestrial and aquatic organisms are imazalil and 

imazalil sulfate. As discussed above in the fate assessment, once these two compounds are 

released into the environment, they will rapidly interconvert to one of the two forms 

according to the local environmental pH. While the environmental fate and toxicity data 

for imazalil do not distinguish between these two forms, it is likely that the environmental 

fate and toxicology properties differ for the two forms. Consequently, this assessment will 

assume that the properties of both forms are the same. An exception will be if Tier 2 aquatic 

modeling in necessary. In that case the assessment will consider changes in soil-water 

partitioning as a function of pH.

Because there is considerable uncertainty in the nature of unextracted uncharacterized 

residues in the aerobic soil metabolism study, a total toxic residues approach is being used 

to estimate the soil metabolism half-life which considers the unextracted residues to be of 

equivalent toxicity as the parent. If risk thresholds are exceeded in assessments using this 

assumption, additional simulations will be performed using parent only half-lives in order 

assess the amount of uncertainty in the risk assessment due to lack of characterization of 

unextracted residues in this study.

ii. Drinking Water 

If a new assessment is conducted, it will consider imazalil, imazalil sulfate, the 
Page 17 of 38

unidentified, unextracted residues in metabolism study, and the single identified degradate, 

1-[2-(2,4-dichlorophenyl)-2-hydroxyethyl-IH-imidazole in the drinking water exposure 

assessment.

8.2 Measures of Exposure 

i. Ecological Exposure

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

terrestrial organisms as described at 

http://www.epa.gov/pesticides/science/models_db.htm. E-FAST and additional available 

exposure models may be used to assess use and discharge from post-harvest citrus 

treatment. E-FAST is described in detail at 

http://www.epa.gov/oppt/exposure/pubs/efast.htm. As imazalil is a systemic chemical, 

exposure to terrestrial organisms may occur when feeding on plants growing from the 

treated seed. Magnitude of residue data reviewed by HED will be used as screening level 

estimates of imazalil concentrations in various plant components. 

Screening level calculations suggested that drinking water pathway may be significant for 

terrestrial organisms. This exposure pathway may be further considered at the time of the 

risk assessment (Appendix B). 

The Agency is aware of monitoring conducted by federal and state agencies and this 

route of exposure will be considered in the assessment to the extent that data on imazalil

are available.

ii. Drinking Water in Human Dietary Risk Assessment

Because the estimates of fate and transport properties have changed since the RED (Lee, 

Liu, and Breithaupt, 2001), drinking water exposure will be re-evaluated to support 

registration review. The Health Effects Division is currently reconsidering the cancer 

human health endpoint for imazalil. Changes in cancer classification may obviate the 

need for a drinking water exposure assessment, in which case not new assessment will be 

performed. The assessment will use the screening model FIRST for assessing exposure in 

surface water source drinking water and will use the models SCI-GROW and PRZM-GW 

for assessment exposure through ground water as according to current OPP guidance. 

PRZM-GW is currently in a one year evaluation period. Guidance for its use may be 

adjusted to better characterize exposure following that evaluation period.
Page 18 of 38

8.3 Measures of Effect 

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

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

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

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

(USEPA, 2007c), which employs a literature search engine for locating chemical toxicity 

data for aquatic life, terrestrial plants, and wildlife. The evaluation of both sources of data 

can also provide insight into the direct and indirect effects of pesticides on biotic 

communities from loss of species that are sensitive to the chemicals and from changes in 

structure and functional characteristics of the affected communities.

9. Endangered Species Assessment

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

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

from registered uses of pesticides in registration review. The process for evaluating 

potential risks to listed species is further described at 

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

10. Endocrine Disruptor Screening Program

Imazalil and imazalil sulfate were not included in the first group of 67 chemicals issued 

an order to conduct Tier 1 EDSP testing. For additional information the EDSP program, 

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

11. Preliminary Identification of Data Gaps 

11.1. Fate

The environmental fate database for imazalil is not complete (Table 6). Additional data is 

required to replace several studies which have been found to be invalid and to better 

describe the differential fate properties of imazalil’s conjugate acid and base forms. A new 

aqueous photolysis study is required since the study used to support reregistration has since 

been found to be invalid due to the use of a photosensitizer, acetone, in the test system. 

Additional aerobic soil metabolism studies in three soils are required to better describe how 

imazalil’s degradation rate and products may change due to differences in environmental 

pH. The additional test systems should be conducted in soils with a range of pH from acid 

to basic. A laboratory volatility study (835.1410) is needed to support the greenhouses so 

the exposure from imazalil in air can be assessed. This study is not required to support the 

indoor citrus use, or the seed treatment uses, where the pesticide would be expected to be 

buried beneath the soil surface. Because the octanol-water partition coefficient is greater 

than 10,000, a BCF study is required (835.1730).
Page 19 of 38

An assessment of the potential for exposure through ground-water source drinking water 

was assessed to determine if additional data was needed to support this assessment (See 

Appendix A). However, the concentrations estimated using PRZM-GW were found to be 

well below thresholds of concern for human health from dietary routes and additional data 

are not required to support this assessment.
Page 20 of 38

Table 6. Available environmental fate data for imazalil and remaining data gaps.

158

Guideline

(OPPTS)

Description MRID Classification Data Gap? Comments

835.1230

(163-1)

Leaching MRID 00096425

MRID 00096426

MRID 00148072

MRID 00158560

unacceptable

unacceptable

acceptable

acceptable

no data requirement satisfied

835.1240

(163-1)

Adsorption/Desorption van Leemput, 1986

MRID 92072016

MRID 92072017

acceptable

acceptable

acceptable

no data requirement satisfied

835.1410

(163-2)

Laboratory Volatility none NA yes required as Henry’ Law Constant 

> 10-6atm∙m3∙mol-1and to support 

greenhouse use.

835.2120

(161-1)

Hydrolysis MRID 00088226

MRID 00055360

MRID 00115272

unacceptable

unacceptable

acceptable

no data requirement satisfied

835.2240

(161-2)

Photodegradation in water MRID 00096422

MRID 40926701

MRID 41350801

MRID 92072015

unacceptable

supplemental

supplemental

supplemental

yes Originally submitted study was 

found to be invalid due to the use 

of a photosensitizer, acetone, in 

the test system.

835.2370

(161-4)

Photodegradation in air none NA no not required

835.2410 

(161-3)

Photodegradation on soil none NA no not required to support current use 

pattern

835.4100

(162-1)

Aerobic soil metabolism MRID 00096423

MRID 00148314

MRID 00158560

MRID 92072034

unacceptable

supplemental

supplemental

supplemental

yes 3 additional soils are required to 

satisfy current guideline 

requirement 

835.4200

(162-2)

Anaerobic soil metabolism none NR no not required to support current use 

patterns

835.4300

(162-4)

Aerobic aquatic metabolism none no risks below LOC with current data

835.4400

(162-3)

Anaerobic Aquatic 

Metabolism

MRID 42012004 unacceptable no risks below LOC with current data

835.6100

(164-1)

Terrestrial Field Dissipation MRID 00096427 unacceptable yes

835.6200

(164-2)

Aquatic Field Dissipation none NA no not required for current uses

835-6300

(164-3)

Forestry Field Dissipation none NA no not required for current uses

850.1730

(165-4)

Fish Bioconcentration Factor none NA yes Koc >10,000

850.6100 Environmental Chemistry 

Method: Soil

none NA yes supports terrestrial field 

dissipation study

850.6100 Environmental Chemistry 

Method: Water

none NA no no aquatic uses & and no aquatic 

risk exceedances

NGS Drinking Water Treatment none NA no risks from drinking water are 

currently expected to be below 

levels of concern
Page 21 of 38

11.2. Effects

Tables 7 and 8 identify ecological effects studies by MRID that offer data for each 

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

needed in order to support risk assessment. 

Freshwater fish early-life stage (850.1400)

In the RED, EFED requested that additional tests be conducted to better characterize 

potential endocrine effects once the appropriate methodology was developed because of 

concerns regarding the endocrine disrupting potential of imazalil. A study following 

OECD 229 conducted with zebrafish (Danio rerio) was submitted to the Agency (MRID 

49106401). As the review by the Agency has not been completed, the data requirement is 

still considered unmet. The review will be completed prior to risk assessment.

Whole Sediment Chronic Invertebrate Toxicity (Freshwater and Estuarine/marine, 

Special Non-guideline Study)

There is a reasonable expectation of residue in freshwater and marine water sediments 

bodies as a result of effluent discharge from harvested citrus treatment. Presence and 

persistence in sediment is expected based on a Kow >10,000 and on an aerobic soil 

metabolism half-life of 157 days. Requested freshwater studies are a 42-day study with 

Hyallela azteca and a 56-day study with Chironomus dilutus or C. tentans. Both are 

found in Second Edition EPA/600/R-99/064, Duluth, MN. Requested estuarine/marine 

study is a 28-day study conducted with the Amphipod Leptocheirus plumulosa found in 

First Edition, EPA Report 600/R-01/020, March 2001. A detailed data justification is 

provided in Appendix C.

Acute passerine toxicity (850.2100)

The revised Part 158 data requirements specify that acute avian oral toxicity data be 

submitted for either one waterfowl or one upland game species and one passerine species. 

The available acute oral toxicity data, when compared to estimated environmental 

concentrations, indicate that levels of concern are exceeded for birds on an acute basis. 

Because passerine species have higher metabolic rates due to their smaller sizes than 

either waterfowl or upland game bird species and because they may utilize different 

metabolic pathways, they may be more or less sensitive to imazalil. In order to properly 

characterize risk to passerines, an avian oral toxicity test is required for passerine birds. A 

passerine study protocol must be submitted for review by the Agency prior to initiation of 

the study. These data will be used to refine the screening-level risk assessment by 

determining whether there are differences in avian species sensitivity to imazalil between 

currently tested passerine and upland game and/or waterfowl species that are beyond the 

simple allometric predictions currently employed in the absence of such passerine data. 

The current extrapolation method may be under- or over-estimating risks to passerines. If 

data are not submitted, than risk to passerines from acute exposure to imazalil will be 

assumed.
Page 22 of 38

Honey bee acute contact toxicity (850.3020) and Honey bee acute oral toxicity (nonguideline)

At this time, no reviewed data are available to define the toxicity of imazalil to honey 

bees on an acute exposure basis. Given that the chemical is a systemic compound, it will 

be available to bees through contact and consumption of the growing plant and pollen. 

Although the oral toxicity study is not an EPA guideline, guidelines are available (e.g., 

OECD 213). The data will reduce uncertainties associated with the current risk 

assessment for terrestrial insects and will improve the Agency’s understanding of the 

potential effects of imazalil on terrestrial species. Honey bee acute contact and oral 

toxicity studies were submitted to the Agency (MRIDs 49215902 and 49215903). As the 

reviews by the Agency have not been completed, the data requirements are still 

considered unmet. The reviews will be completed prior to risk assessment.

Earthworm Subchronic Toxicity Test (850.3100)

At this time, no data are available have been submitted to the Agency to evaluate the 

toxicity of imazalil to earthworms or terrestrial invertebrates. Given that the chemical is 

applied as treated seed, it will be available not only through consumption of and contact 

with the seed and growing plant, as well as consumption of and contact with the 

surrounding soil. An earthworm toxicity study was submitted to the Agency (MRID 

49215904). The review will be completed prior to risk assessment.

Table 7. Available ecological effects data for aquatic organisms exposed to imazalil

and remaining data gaps. 

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct 

risk 

assessment?

Justification and Assumptions 

EPA will Make in Absence of 

Data

850.1010 Freshwater 

invertebrate 

acute toxicity

41606103 Acceptable No --

850.1025

850.1035

850.1045

850.1055 

Saltwater 

invertebrate 

acute toxicity 

(None) (N/A) No Data have not been submitted to 

fulfill this guideline. A data gap was 

not identified as these data are not 

necessary for risk assessment at this 

time.

850.1075 Freshwater fish 

acute toxicity 

41606101 Acceptable No --

41606102 Acceptable

850.1075 Saltwater fish 

acute toxicity 

(None) (N/A) Yes

850.1300 Freshwater 

invertebrate 

life cycle 

(None) (N/A) No Data have not been submitted to 

fulfill this guideline. A data gap was 

not identified as these data are not 

necessary for risk assessment at this 

time.
Page 23 of 38

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct 

risk 

assessment?

Justification and Assumptions 

EPA will Make in Absence of 

Data

850.1350 Saltwater 

invertebrates 

life cycle 

(None) (N/A) No Data have not been submitted to 

fulfill this guideline. A data gap was 

not identified as these data are not 

necessary for risk assessment at this 

time.

850.1400 Freshwater fish 

early-life stage

49106401 Under review Yes Data requirement may be satisfied 

pending completion of review 

(MRID 49106401).

850.1400 Saltwater fish 

early-life stage 

(None) (N/A) No Data have not been submitted to 

fulfill this guideline. A data gap was 

not identified as these data are not 

necessary for risk assessment at this 

time.

850.1500 Fish life cycle (None) (N/A) No Data have not been submitted to 

fulfill this guideline. A data gap was 

not identified as these data are not 

necessary for risk assessment at this 

time.

Special 

Study

Toxicity and 

Bioaccumulation 

of Sedimentassociated 

Contaminants 

with Freshwater 

Invertebrates. 1

(None) (N/A) Yes There is a reasonable expectation of 

residue in freshwater and marine 

water sediments bodies as a result of 

effluent discharge from harvested 

citrus treatment. Presence and 

persistence in sediment is expected 

based on a Kow >10,000 and an 

aerobic soil metabolism half-life of 

157 days. Special 

Study

Whole Sediment 

Lifecycle 

Toxicity Test 

with Estuarine 

Invertebrates. 2

(None) (N/A) Yes

850.4400 Aquatic plant 

Toxicity Test 

using Lemna 

spp.

46818201 Supplemental No --

850.4500 Algal toxicity 46818202 Supplemental No

850.4550 Cyanobacteria (None) (N/A) No Data have not been submitted to 

fulfill this guideline. A data gap was 

not identified as these data are not 

necessary for risk assessment at this 

time.

1 This is a 42-day study with Hyallela azteca and a 56-day study with Chironomus dilutus or C. tentans. Both are found 

in Second Edition EPA/600/R-99/064, Duluth, MN.

2 This is a 28-day study conducted with the Amphipod Leptocheirus plumulosa found in First Edition, EPA Report 

600/R-01/020, March 2001.
Page 24 of 38

Table 8. Available ecological effects data for terrestrial organisms exposed to 

imazalil and remaining data gaps. 

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Current Additional Data 

Need

850.2100 Avian oral 

toxicity

163243 Acceptable Yes Requesting acute oral for 

passerine species

850.2200 Avian dietary 

toxicity 

30542 Acceptable No --

30543 Acceptable

850.2300 Avian 

reproduction

41663801 Acceptable No

42039801 Acceptable

NonguidelineAvian inhalation (None) (N/A) No Data have not been 

submitted to fulfill this 

guideline. A data gap was 

not identified as these data 

are not necessary for risk 

assessment at this time.

850.3020 Honey bee acute 

contact toxicity

(None) (N/A) Yes Given that the chemical is 

a systemic compound, it 

will be available to bees 

through contact and 

consumption of the 

growing plant and pollen.

Data requirement may be 

satisfied pending 

completion of review 

(MRID 49215902).

850.3030 Honey bee residue 

on foliage

(None) (N/A) No Data have not been 

submitted to fulfill this 

guideline. A data gap was 

not identified as these data 

are not necessary for risk 

assessment at this time.

850.3040 Field testing for 

pollinators

(None) (N/A) No Data have not been 

submitted to fulfill this 

guideline. A data gap was 

not identified as these data 

are not necessary for risk 

assessment at this time.

850.3100 Earthworm 

Subchronic 

Toxicity Test 

(None) (N/A) Yes Given that the chemical is 

applied as treated seed, it 

will be available not only 

through consumption of 

and contact with the seed 

and growing plant, as well 

as consumption of and 

contact with the 

surrounding soil. Data 

requirement may be 

satisfied pending 

completion of review 

(MRID 49215905).
Page 25 of 38

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Current Additional Data 

Need

850.4100 Seedling 

Emergence and 

Seedling Growth

(None) (N/A) No Data have not been 

submitted to fulfill this 

guideline. A data gap was 

not identified as these data 

are not necessary for risk 

assessment at this time.

850.4150 Vegetative Vigor (None) (N/A) No Data have not been 

submitted to fulfill this 

guideline. A data gap was 

not identified as these data 

are not necessary for risk 

assessment at this time.

NonguidelineHoney bee acute 

oral toxicity

(None) (N/A) Yes Given that the chemical is 

a systemic compound, it 

will be available to bees 

through contact and 

consumption of the 

growing plant and pollen.

Data requirement may be 

satisfied pending 

completion of review 

(MRID 49215903).
Page 26 of 38

12. References 

Internal Office of Pesticide Program Documents

D266173. Lee, Richard Larry Liu, and James Breithaupt. 2001. Revised Environmental 

Risk Assessment for the Reregistration of Imazalil. Internal EPA Memorandum to 

Mark Howaed, dated April 18, 2001.

D174917. Belew, Carol. 1992. Proposed Section 18 for Use on Barley in Utah. Internal 

EPA document dated April 9, 1992. EFED # 2067901.

Environmental Fate Data Submitted To Support Registration

Goodwine, W. R. 1987. On the Equivalence in Environmental Behaviour of Imazalil and 

Its Salts. Letter from W. R. Goodwine, Jansen Pharmaceutica to Herbert Manning, 

date March 26, 1987.

MRID 00055360. Peeters, J. 1980. R 23979: Hydrolysis Study in Acid, Neutral and 

Alkaline Medium: F.C. 79-85 Addendum. Unpublished study received Jan 8, 1981. 

Submitted by Janssen R&D, Inc., New Brunswick, N.J.

MRID 00088226. Meuldermans, W., F. Knaops, E. Swysen, J. Hendrickx, and J. Heykants. 

1981. Stability of the tritium-label of imazalil-3 in acidic, a1kaline, neutral and 

bio1ogical medium. Janssen Pharmaceutica, N.V., Belgium.

MRID 00096422. Torfs, F., and J. Peeters.1980. R 23979: Light Stability in Aqueous 

Solution: FC 80-86. Unpublished study received Feb 24, 1982. Prepared by Janssen 

Pharmaceutica, Belgium. Sub-mitted by Janssen R & D, Inc., New Brunswick, N.J.

MRID 00096423. Scherpenisse, P.M.; K. D. Joustra, A. J. M. Borst, et al., 1979. An 

Attempt To Identify the Main Metabolite of Imazalil in Soil: Report Nr. 

56635/49/1979. Unpublished study received Feb 24, 1982. Prepared by PhilipsDuphar B.V., The Netherlands, Submitted by Janssen R & D, Inc., New Brunswick, 

N.J.

MRID 00096425. Balk, W., and A. G. M. Willems. 1979. Leaching of Imazalil and Its 

Metabolites: Report Nr. 56635/58/1979/WB/ybz. Unpublished study received Feb 

24, 1982. Prepared by Philips- Duphar B.V., The Netherlands. Submitted by 

Janssen R & D, Inc., New Brunswick, N.J.

MRID 00022923. Hill, E.F.; Heath, R.G.; Spann, J.W.; et al. 1975. Lethal Dietary 

Toxicities of Environmental Pollutants to Birds: Special Scientific Report--Wildlife 

No. 191. U.S. Dept. of the Interior, Fish and Wildlife Service, Patuxent Wildlife 

Research Center; unpublished report).
Page 27 of 38

MRID 00096427. Organisch Chemisch Instituut TNO. 1977. Degradation of Imazalil in

Soil under Field Conditions (Including Residue Data of Harvested Barley Grains): 

Report of Project 5, Part 3. Unpublished study received Feb 24, 1982.Submitted 

by Janssen R & D, Inc., New Brunswick, N.J.

MRID 00148072. Van Leemput, L. E. Swysen, W. Meuldermans, et al. 1985. On the Leaching of Imazalil and Its Transformation Products in Soil. Unpublished study 

prepared by Janssen Pharmaceutica. 20 p.

MRID 00148314. Van Leemput, L. 1984. The Transformation of [Carbon-14]-imazalil in 

Watervliet Loam, Incubated at 25 [degrees] C in Flow-through Soil Metabolism 

Systems: Serial No. R 23 979/L8. Unpublished study prepared by Janssen 

Pharmaceutica. 33 p.

MRID 00115272. Van Leemput, L., and J. Heykants. 1982. Hydrolysis as a Possible 

Mechanism of Dissipation of Imazalil from Aqueous Environments: R 23 979/LI.

Unpublished study received Oct 8, 1982. Submitted by Janssen R & D Inc., New 

Brunswick, NJ.

MRID 00158560. Janssen Pharmaceutica. 1986. Janssen Response [to EPA Deficiency 

Letters in re Environmental Fate of Fecundal]. Unpublished study. 55 p.

MRID 40926701. Van Leemput, L., E. Swysen, J. Hendrickx, et al. 1988. On the 

Photolysis of Imazalil (R23979) in the Aquatic Environment. Artificial Sunlight 

Experiments: Project ID. A8 1988. Unpublished study prepared by Janssen 

Pharmaceutica. 87 p.

MRID 41350801. Van Leemput, L., E. Swysen, J. Hendrickx, et al. 1988. On the 

Photolysis of Imazalil (R23979) in the Aquatic Environment. Artificial Sunlight 

Experiments: Project ID. A8 1988. Unpublished study prepared by Janssen 

Pharmaceutica. 87 p. (same as MRID 40926701).

MRID 42012004. Sterkins, P. 1991. Anaerobic Aquatic Transformation of Imazalil: Lab 

Project Number: R 23979/ENV76. Unpublished study prepared by Janssen 

Research Foundation. 146 p.

MRID 92072015. Goodwine, W. 1990. Janssen Pharmaceutica Phase 3 Summary of 

MRID 40926701 and Related MRIDs 41350801. On the Photolysis of Imazalil 

(R23979) in the Aquatic Environment: Artificial Sunlight Experiments: Report No. 

R23979/L25, Rec #317. Prepared by Janssen Pharmaceutica. 29 p.

MRID 92072016. Van Leemput, L. 1990. Janssen Pharmaceutic Phase 3 Summary of 

MRID 00148072. On the Leaching of Imazalil (R23979) and Its Transformation 

Products in Soil: Report No. R23979/L11, Rec #138. Prepared by Janssen 

Pharmaceutica. 19 p.
Page 28 of 38

MRID 92072017. Goodwine, W. 1990. Janssen Pharmaceutic Phase 3 Summary of MRID 

00158160. Adsorption of Imazalil (R23979) on Soil: Report No. R23979/L18,

February, 1986. Prepared by Janssen Pharmaceutica. 27 p.

MRID 92072034. Goodwine, W. 1990. Janssen Pharmaceutica Phase 3 Summary of 

MRID 00148314 and Related MRIDs 00148314, 00158160. The Transformation of 

[Carbon-14| Imazalil in Watervliet Loam, Incubated at 25 Degrees C in Flowthrough Soil Metabolism Systems: Report No. R23979/L8, Rec #133. Prepared by 

Janssen Pharmaceutica. 32 p.

49215907 Schafers, C. (2011) Simulation Test - Aerobic Sewage Treatment 

Biodegradability of Imazalil in Activated Sludge Units. Project Number: 

GAB/031/3/40 ENI/10/PREC/02. Unpublished study prepared by Fraunhofer 

Institute for Molecular Biology & Applied Ecology. 190p.

Ecological Toxicity Data Submitted To Support Registration:

MRID 00030542. Beavers, J.B.; Fink, R.; Brown, R.; et al. (1979) Final Report: EightDay Dietary LC50--Mallard Duck: Project No. 168-102. (Un- published study 

received Mar 7, 1980 under 43813-1; prepared by Wildlife International, Ltd. in 

cooperation with Washington College, submitted by Janssen R & D, Inc., New 

Brunswick, N.J.; CDL:099290-E) 

MRID 00030543. Beavers, J.B.; Fink, R.; Brown, R.; et al. (1979) Final Report: EightDay Dietary LC50--Bobwhite Quail: Project No. 168-101. (Unpublished study 

received Mar 7, 1980 under 43813-1; prepared by Wildlife International, Ltd. in 

cooperation with Washington College, submitted by Janssen R & D, Inc., New 

Brunswick, N.J.; CDL:099290-F) 

MRID 00163243. Van Ravestyn, C.; Marsboom, R. (1985) Acute Oral Toxicity Study in 

Ring-necked Pheasants: Imazalil--R 23979: Experiment No. 1601 (86.03.10). 

Unpublished study prepared by Janssen Pharmaceutica N.V., Dept. of 

Toxicology. 18 p. 

MRID 41606101. Weytjens, D.; Boonen, P.; Leemput, L. et al. (1988) The Acute 

Toxicity of Imazalil (R 23979) for the Bluegill (Lepomis macrochirus): Lab 

Project Number: R23979/AF/LM/6. Unpublished study prepared by Janssen 

Pharmaceutica. 88 p. 

MRID 41606102. Weytjens, D.; Boonen, P.; Callens, V. et al. (1989) The Acute Toxicity 

of Imazalil (R 23979) for the Rainbow Trout (Salmo gairdneri): Lab Project 

Number: R23979/AF/SG. Unpublished study pre- pared by Janseen 

Pharmaceutica. 52 p. 
Page 29 of 38

MRID 41606103. Weytjens, D.; Wils, R. (1990) The Acute Toxicity of Imazalil (R 239 

79) in the Water-flea (Daphnia magna): Lab Project Number: 23979/AD/K6. 

Unpublished study prepared by Janssen Pharmaceu- tica. 89 p. 

MRID 41663801. VanCauteren, H.; Coussement, W.; Teuns, G.; et al. (1988) 

Reproduction Study in Bobwhite Quails: Imazalil: Nonclinical Laboratory Study: 

Lab Project Number: 1822. Unpublished study prepared by Jassen Pharmaceutica 

N. V. 147 p. 

MRID 42039801. Teuns, G.; Lampo, A.; Coussement, W.; et al. (1991) R 23979-

Imazalil: Reproduction Study in Mallard Ducks: Report No. 2288: Rec No. 498. 

Unpublished study prepared by Janssen Research Foundation. 321 p. 

MRID 46818201. Vinken, R.; Wydra, V. (2006) Toxicity of ZR023979 Technical to the 

Aquatic Plant Lemna gibba in a Semi-Static Growth Inhibition Test. Project 

Number: AGR/1267, 27021240. Unpublished study prepared by Institut fuer 

Biologische Analytik und Consulting IBACON. 93 p.

MRID 46818202. Van Ginneken, I. (1996) The Effect of Imazalil (R023979) on the 

Growth of the Unicellular Green Alga Selenastrum capricornutum: Final Report. 

Project Number: AASC/0034, ENV419, ENV/AR/002. Unpublished study 

prepared by Janssen Pharmaceutica. 90 p.

MRID 49215902 Hamon, N.; Lacy, J.; Twinn, C. (1986) Imazalil: Laboratory 

Determination of Direct Contract Toxicity to Adult Honeybees, Apis Mellifera L. 

by Potter Tower Application. Project Number: AGR/NH/JL/DCT/213/1. 

Unpublished study prepared by May & Baker, Ltd. 8p. 

MRID 49106401. Teigeler, M. (2012) Imazalil: A Short term reproduction assay with the 

Zebrafish (Danio rerio) under flow through conditions. Project Number: CER001/4-68/A. Unpublished study prepared by Fraunhofer Institute for Molecular 

Biology and Applied Ecology (IME). 131 p.

MRID 49215903 Lacy, J.; Hamon, N.; Twinn, C. (1986) Imazalil: Laboratory 

Determination of Ingestion Toxicity to Adult Honeybees, Apis mellifera L. 

Project Number: AGR/JL/NH/DCT/207/1. Unpublished study prepared by May & 

Baker, Ltd. 11p. 

MRID 49215904 Leemput, L.;Swysen, E.;Meuldermans, W.;et al. (1986) The Toxicity of 

Imazalil ot Earthworms. Toxicity of Imazalil Sulphate to Eisenia foetida in an 

Artificial Soil Toxicity Test. Project Number: R/23/979/L20. Unpublished study 

prepared by Janssen Pharmaceutica. 15p

MRID 49215905 Leemput, L.;Swysen, E.;Meuldermans, W.;et al. (1986) The Toxicity of 

Imazalil to Earthworms. Toxicity of Imazalil Sulphate to Eisenia foetida in an 
Page 30 of 38

Artificial Soil Toxicity Test. Project Number: R/23/979/L19. Unpublished study 

prepared by Janssen Pharmaceutica. 16p. 

MRID 49215906 Wyness, L. (1996) Imazalil: Chronic Sediment Toxicity Test Using and 

Infaunal Insect Chironomus riparius: Final Report. Project Number: 1073/2/1018. 

Unpublished study prepared by Corning Hazleton (Europe). 108p.
Page 31 of 38

Appendix A. Screening Ground Water Exposure Assessment 

Using PRZM GW

This assessment was conducted as a screen to determine whether additional data was 

needed for assessing exposure from ground-water source drinking water as estimated using 

PRZM-GW. Estimates of concentrations in ground water were estimated for all 6 PRZMGW scenarios using the application rate for wheat. The scenarios were used as is rather 

than adjusted to represent wheat culture as these calculations were not meant to be used for 

exposure assessment but only as a guide to additional data needs. The six scenarios 

simulated and their characteristics are listed in Table A-1. 

Table A-1. Scenarios used for PRZM-GW Simulations.

Location Scenario Date Soil Weather Station (ID)

Delmarva Delmarva_STD 12/27/2012 Evesboro loamy 

sand

Wilmington, DE 

(13781)

FL citrus FLCitrus_STD 12/18/2012 Candler, Tavares 

& Astatulas soils

Tampa, FL (12842)

Fl potato FLPotato_STD 12/20/2012 Pomona fine sand Jacksonville, FL 

(13889)

Coastal Georgia GACoastal_STD Tifton loamy sand Tallahassee, FL 

(93805)

Coastal North 

Carolina

NC 

Coastal_STD

12/20/2012 Norfolk loamy 

sand

Raleigh/Durham, NC 

(13722)

Central Sands, 

Wisconsin

WISands_STD 12/20/2012 Coloma loamy 

sand

La Crosse, WI 

(W14920)

All simulations assessed the seed treatment uses of imazalil. Since the label application 

rate is the amount applied to a pound of seed, the amount of imazalil applied to a field 

depends on the seeding rate. The maximum seeding rate amongst the three registered crops 

is for wheat which can be seeded at 156 lb∙acre-1. With an application rate to seed of 0.0001 

pounds ai of imazalil per pound of seed, the resulting field application rate of imazalil of 

0.0156 lb ai∙acre-1or 0.0175 kg∙ha-1. The application date was set to the planting date, 

which is typically 14 days before the emergence date for wheat. The application was made 

using assuming a surface application as only surface and foliar applications are allowed in 

the PRZM-GW shell. Generally, applications made with seed treatments would be made 

below the surface with the planted seed. 
Page 32 of 38

Table A-2. Pesticide management practices import parameters for PRZM-GW used for 

each simulation of imazalil use on wheat.

Location App. Rate

kg∙ha-1

Number of 

Apps

Application 

Interval (days)

First App 

Date

Application 

method

Delmarva 0.0175 1 NA 3/28 surface

FL citrus 0.0175 1 NA 3/15 surface

Fl potato 0.0175 1 NA 3/15 surface

Coastal GA 0.0175 1 NA surface

Coastal NC 0.0175 1 NA surface

Central Sands, 

WI

0.0175 1 NA 4/15 surface

The lowest measured Kd for imazalil was used for this assessment as it is conservative. 

For exposure assessments, the partition coefficient would likely be estimated as a 

function of pH. The hydrolysis rate was assumed to 0 as there is no observable 

degradation in the hydrolysis study. The aerobic soil metabolism rate was set to 3x the 

value for parent plus unidentified residues from the single measured rate for this 

compound. The factor of 3 is intended to represent an upper 90% confidence bound on 

the mean when only a single value is available and a standard deviation cannot be 

calculated.

Table A-3. Chemistry Input Parameters for PRZM –GW for Imazalil.

Input Parameter Value Comment

hydrolysis half-life 0 d no measureable degradation

aerobic soil metabolism 1401d 3x single value, parent plus 

unidentified residues

soil water partition 

coefficient (Kd)

28 L∙kg-1lowest Kd

The results of the simulations are in Table A-4. Since all the estimated values are well 

below previously estimate concentrations in drinking water (7.2 x 10-2 μg∙L-1in surface 

waters, these levels are not expected to generate risk concerns for human health and 

additional data will not be required to support ground water exposure assessments for 

imazalil.

Table A-4. Peak GW EECs for different ground water scenarios.

Location Peak EEC Mean EEC Breakthrough Time

Delmarva 1.58 x 10-6 μg∙L

-1

1.45x 10-7 μg∙L-111 y

FL citrus 5.65 x 10-3μg∙L-19.18 x 10-3 μg∙L-12 y 9 mo

FL potato 2.37 x 10-2 μg∙L-13.71 x 10-4 μg∙L-13 y 0 mo

Coastal GA 6.93 x 10-10 μg∙L-13.81 x 10-11 μg∙L-127 y 6 mo

Coastal NC 1.03 x 10-7 μg∙L-19.01 x 10 -10 μg∙L-113 y 6 mo

WI sands 1.36 x 10-19 μg∙L-15.3 x 10-21 μg∙L-187 y 7 mo
Page 33 of 38

Appendix B. Screening Level Models to Evaluate Potential 

Importance of Drinking Water and Inhalation Exposure Pathways

SIP (Screening Imbibition Program, v1.0) Inputs and Conclusions

Table 1. Inputs

Parameter Value

Chemical name imazalil

Solubility (in water at 25oC; mg/L) 180

Mammalian LD50 (mg/kg-bw) 343

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 15

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 1912

Avian test species other

Body weight (g) of "other" avian species 1000

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 250

Bobwhite quail NOAEC (mg/kg-diet) 250

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 30.9600 30.9600

Adjusted toxicity value (mg/kg-bw) 263.8221 11.5374

Ratio of exposure to toxicity 0.1174 2.6834

Conclusion*

Exposure through drinking water 

alone is a potential concern for 

mammals

Exposure through drinking water 

alone is a potential concern for 

mammals

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 145.8000 145.8000

Adjusted toxicity value (mg/kg-bw) 1063.2671 12.4031

Ratio of exposure to acute toxicity 0.1371 11.7551

Conclusion*

Exposure through drinking water 

alone is a potential concern for 

birds

Exposure through drinking water 

alone is a potential concern for 

birds

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

with other routes (i.e., diet, inhalation, dermal), pesticide exposure through drinking water may contribute to a total exposure 

that has potential for effects to non-target animals.
Page 34 of 38

STIR (Screening Tool for Inhalation Risk, v1.0) Inputs and Conclusions

Input Value Conclusion

Application and Chemical Information

Enter Chemical Name imazalil

Enter Chemical Use seed treatment

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

If Spray What Type (enter ground or air) ground

Enter Chemical Molecular Weight (g/mole) 297.2

Enter Chemical Vapor Pressure (mmHg) 1.20E-06

Enter Application Rate (lb a.i./acre) 0.0156

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 1912

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 1

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 343

Enter Lowest Rat Inhalation LC50 (mg/L) 2.43

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 1.92E-02

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.41E-03

Adjusted Inhalation LD50 5.83E+01

Ratio of Vapor Dose to Adjusted Inhalation LD50 4.14E-05 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) not applicable

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 not applicable not applicable

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 1.92E-02

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 3.03E-03

Adjusted Inhalation LD50 1.45E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 2.10E-05 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) not applicable

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 not applicable not applicable
Page 35 of 38

Appendix C. Data Justification Tables for Chronic Sediment 

Toxicity Studies

No chronic whole sediment toxicity data for freshwater or saltwater invertebrates are available. 40 CFR 

158 conditionally requires whole sediment chronic toxicity data for freshwater and estuarine/marine 

invertebrates. Whole sediment chronic toxicity data would be useful to risk assessment because the log 

KOW of imazalil is ≥3. Current EFED recommendations for freshwater sediment testing follow Agencywide guidance stated in Test Method 100.4: 

“Hyalella azteca 42-d Test for Measuring the Effects of Sediment Associated Contaminants on 

Survival, Growth, and Reproduction” contained in USEPA 2000 Methods for Measuring the 

Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater 

Invertebrates EPA 600/R-99/064 (OCSPP 850.1770). 

A protocol should be submitted for approval prior to testing. Based on test variability for the endpoints of 

concern and the need to establish a NOAEC/LOAEC the following number of replicates and test animals 

are recommended for the freshwater amphipod H. azteca: 

 12 replicates per treatment (4 for 28-d survival and growth and 8 for the remainder of the test) 

with 10 neonates per replicate.

In the absence of data, toxicity will be estimated using the lowest chronic toxicity endpoint for freshwater 

invertebrates and the estimated pore water concentrations in sediment. This does not consider possible 

exposure via ingestion and could underestimate risk for some invertebrates where ingestion is an important 

exposure pathway; therefore, there will be considerable uncertainty in risk conclusions.

The requested data would allow EPA to estimate chronic risks to benthic invertebrates, including defining 

an effect area for endangered species. Risk mitigation strategies (e.g., determining the maximum imazalil 

application rate that results in a Risk Quotient (RQ) below the Level of Concern (LOC) cannot be 

evaluated without these data.

Imazalil is likely to partition to soil and sediment and may enter water via soil erosion and via waste water 

from citrus packing plants. Given the lack of chronic aquatic data, the high Kow of imazalil and an aerobic 

soil metabolism half-life of 157 days, these data would be useful to the risk assessment.

Practical Utility of the Data

How will the data be used? 

The data would allow the Agency to determine chronic risk to benthic freshwater invertebrates from 

imazalil in water and sediment. The effects data would be used to determine the likelihood that the 

chronic risks can potentially impact aquatic communities, either by direct effects or by indirect effects on 

other organisms by reducing their food sources. 

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

Risk assessment and mitigation strategies (e.g., determining the maximum imazalil application rate that 

results in RQs below the LOC) cannot be evaluated without these data. If future endangered species risk 

assessments are performed without these data, the Agency would have to assume that imazalil “may 

Guideline Number: Non-Guideline study (850 Method not yet available) Use Test Method 100.4 

(citation included in text).

Study Title: Whole Sediment: Chronic Toxicity to Freshwater Invertebrate - Examining Survival, 

Growth, and Reproduction for Hyaella azteca.

Test Chemical: Imazalil

Rationale for Requiring the Data
Page 36 of 38

affect” endangered freshwater invertebrates directly (and endangered species from other taxa indirectly), 

and use of imazalil might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into compliance with 

the Endangered Species Act and could result in use restrictions for imazalil which are unnecessarily 

severe.

No chronic whole sediment toxicity data for freshwater or saltwater invertebrates are available. 40 CFR 

158 conditionally requires whole sediment chronic toxicity data for freshwater and estuarine/marine 

invertebrates. Whole sediment chronic toxicity data would be useful to risk assessment because the log 

KOW of imazalil is ≥3. Current EFED recommendations for freshwater sediment testing follow Agencywide guidance stated in Test Method 100.5: 

“Life-cycle Test for Measuring the Effects of Sediment-associated Contaminants on Chironomus 

dilutus or C. tentans” contained in USEPA 2000 Methods for Measuring the Toxicity and 

Bioaccumulation of Sediment-associated Contaminants with Freshwater Invertebrates EPA 600/R99/064 (OCSPP 850.1760). 

A protocol should be submitted for approval prior to testing. Based on test variability for the endpoints of 

concern and the need to establish a NOAEC/LOAEC the following number of replicates and test animals 

are recommended for the midge test with C. dilutus or C. tentans: 

 16 replicates per treatment containing 12 test organisms each (12 replicates at test initiation; 4 

added at 10 days for auxiliary males).

In the absence of data, toxicity will be estimated using the lowest chronic toxicity endpoint for freshwater 

invertebrates and the estimated pore water concentrations in sediment. This does not consider possible 

exposure via ingestion and could underestimate risk for some invertebrates where ingestion is an important 

exposure pathway; therefore, there will be considerable uncertainty in risk conclusions.

The requested data would allow EPA to estimate chronic risks to benthic invertebrates, including defining 

an effect area for endangered species. Risk mitigation strategies (e.g., determining the maximum imazalil 

application rate that results in a Risk Quotient (RQ) below the Level of Concern (LOC) cannot be 

evaluated without these data.

Imazalil is likely to partition to soil and sediment and may enter water via soil erosion and via waste water 

from citrus packing plants. Given the lack of chronic aquatic data, the high Kow of imazalil and an aerobic 

soil metabolism half-life of 157 days, these data would be useful to the risk assessment.

Practical Utility of the Data

How will the data be used? 

The data would allow the Agency to determine chronic risk to benthic freshwater and estuarine/marine 

invertebrates from imazalil in water and sediment. The effects data would be used to determine the 

likelihood that the chronic risks can potentially impact aquatic communities, either by direct effects or by 

indirect effects on other organisms by reducing their food sources. 

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

Guideline Number: Non-Guideline study (850 Method not yet available) Use Test Method 100.5 

(citation included in text).

Study Title: Whole Sediment: Chronic Toxicity to Freshwater Invertebrates - Examining Survival, 

Growth, and Reproduction for Chironomus dilutus or C. tentans.

Test Chemical: Imazalil.

Rationale for Requiring the Data
Page 37 of 38

Risk assessment and mitigation strategies (e.g., determining the maximum imazalil application rate that 

results in RQs below the LOC) cannot be evaluated without these data. If future endangered species risk 

assessments are performed without these data, the Agency would have to assume that imazalil “may 

affect” endangered freshwater invertebrates directly (and endangered species from other taxa indirectly), 

and use of imazalil might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into compliance with 

the Endangered Species Act and could result in use restrictions for imazalil which are unnecessarily 

severe.

No chronic whole sediment toxicity data for saltwater invertebrates are available. 40 CFR 158 

conditionally requires whole sediment chronic toxicity data for freshwater and estuarine/marine 

invertebrates. Whole sediment chronic toxicity data for saltwater invertebrates would be useful to risk 

assessment because the log KOW of imazalil is ≥3. Current EFED recommendations for freshwater 

sediment testing follow Agency-wide guidance stated in:

“Method for Assessing the Chronic Toxicity of Marine and Estuarine Sediment-associated 

Contaminants with the Amphipod Leptocheirus plumulosus EPA 600/R-01/020 (OCSPP 

850.1780). 

A protocol should be submitted for approval prior to testing. In the absence of data, toxicity will be 

estimated using the lowest chronic toxicity endpoint for saltwater invertebrates and the estimated pore 

water concentrations in sediment. This does not consider possible exposure via ingestion and could 

underestimate risk for some invertebrates where ingestion is an important exposure pathway; therefore, 

there will be considerable uncertainty in risk conclusions.

The requested data would allow EPA to estimate chronic risks to benthic invertebrates, including defining 

an effect area for endangered species. Risk mitigation strategies (e.g., determining the maximum imazalil 

application rate that results in a Risk Quotient (RQ) below the Level of Concern (LOC) cannot be 

evaluated without these data.

Imazalil is likely to partition to soil and sediment and may enter water via soil erosion and via waste water 

from citrus packing plants. Given the lack of chronic aquatic data, the high Kow of imazalil and an aerobic 

soil metabolism half-life of 157 days, these data would be useful to the risk assessment.

Practical Utility of the Data

How will the data be used? 

The data would allow the Agency to determine chronic risk to benthic estuarine/marine invertebrates from 

imazalil in water and sediment. The effects data would be used to determine the likelihood that the 

chronic risks can potentially impact aquatic communities, either by direct effects or by indirect effects on 

other organisms by reducing their food sources. 

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

Risk assessment and mitigation strategies (e.g., determining the maximum imazalil application rate that 

results in RQs below the LOC) cannot be evaluated without these data. If future endangered species risk 

Guideline Number: Non-Guideline study (850 Method not yet available) Use Citation included in 

text.

Study Title: Whole Sediment: Chronic Toxicity to Saltwater Invertebrates - Examining Survival, 

Growth, and Reproduction for Leptocheirus plumulosus.

Test Chemical: Imazalil

Rationale for Requiring the Data
Page 38 of 38

assessments are performed without these data, the Agency would have to assume that imazalil “may 

affect” endangered saltwater invertebrates directly (and endangered species from other taxa indirectly), 

and use of imazalil might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into compliance with 

the Endangered Species Act and could result in use restrictions for imazalil which are unnecessarily 

severe.