OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 041101

DP Barcode : D410027

MEMORANDUM 

September 18, 2015

Subject: Environmental Fate and Ecological Risk Assessment for the Registration

Review of Ethoprop

To: Eric Miederhoff, Chemical Review Manager

Tracy Perry, Team Leader

Kelly Sherman, Branch Chief

Risk Management and Implementation Branch III

Pesticide Re-Evaluation Division (7508P)

From: Geoffrey Sinclair, Ph.D., Biologist 

Michael Barrett, Chemist

Environmental Risk Branch V

Environmental Fate and Effects Division (7507P)

Reviewed By: Justin Housenger, Biologist

Jose Melendez, Chemist

Environmental Risk Branch V

Environmental Fate and Effects Division (7507P)

 

Through: Mah Shamim, Ph.D., Branch Chief 

Environmental Risk Branch V

Environmental Fate and Effects Division (7507P)

This memorandum transmits the Environmental Fate and Effects Division’s (EFED) registration

review ecological risk assessment for the organophosphate nematicide/insecticide ethoprop (PC 

Code 041101, also known as ethoprophos; chemical name O-ethyl-S,S-dipropyl 

phosphorodithioate). The end use products include water dispersible granule and emulsified 

concentration formulations for ground application to soil and immediate incorporation. 

Application rates range from 1.95 to 12 pounds active ingredient per acre (lbs a.i./A) on uses 

such as cucurbits, hops, nursery stock, sugar beets, sweet potato, sugarcane, cabbage, corn, mint, 
2

tobacco, succulent (lima) beans, potatoes east of the Mississippi, and potatoes west of the 

Mississippi. The conclusions of this assessment remain largely unchanged from previous 

assessments. When estimates of ethoprop exposure in terrestrial and aquatic environments are 

compared to the available ecotoxicity data, the results of the screening-level assessment indicate 

a potential for acute and chronic risk above the level of concern (LOC) to both aquatic and 

terrestrial taxa. 

Ethoprop can persist in the environment for months after application and is highly to very highly 

toxic to aquatic invertebrates and fish and birds and mammals and moderately toxic to honey 

bees. Environmental fate modeling and risk quotient determination indicate potential adverse 

effects on aquatic animal taxa. Acute and chronic risk to freshwater fish, estuarine/marine fish, 

freshwater invertebrates, and estuarine/marine invertebrates, and both freshwater and 

estuarine/marine sediment invertebrates was identified. Risk was not identified for aquatic 

plants based on one available diatom study. LD50/ft2 analysis indicated that there is acute risk to 

both birds and mammals from granular formulations. There was also acute dose based and subacute dietary based risk as well as chronic dietary risk to birds associated from all emulsifiable 

concentrate (EC) applications. Similarly, there was acute and chronic dose based risk as well as 

chronic dietary based risk to mammals from all EC applications. Other indirect routes of 

exposure may include consumption of contaminated earthworms in treated fields. Based on 

estimated EECs of ethoprop in earthworm tissues and acute and chronic endpoints for both bird

species tested, there is potential for avian risk from dietary exposure to earthworms. Ethoprop is 

moderately volatile (vapor pressure: 3.5 x 10-4 mm to 8.3 x 10-4 mm Hg at 25-26o C; Henry’s law 

constant value about 1.3 E-8 atm.m3/mole) but modeling suggests that inhalation is not a risk to 

either birds or mammals. While ethoprop is applied by boom sprayer the coarse droplet size 

specified on current labels reduce risk to terrestrial taxa through spray drift. Consistent with 

ethoprop’s mode of action as an insecticide, Bee-REX modeling predicted risk to bees if exposed 

to residues of ethoprop. Results of past assessments and current application practices are 

designed to limit exposure but exposure from residues on plants remaining in the field or from 

spray drift is possible and would present a risk to pollinators and other beneficial insects.

Data gaps for this chemical include acute and chronic toxicity studies for larval bees and chronic 

feeding studies for adult bees, as well as sediment chronic toxicity tests. In the absence of this 

data, risk is presumed in these compartments as well. Data are also limited in terms of the 

aerobic soil and anaerobic aquatic metabolism of ethoprop (OCSPP guideline 835.4100 and 

835.4400 studies): the 835.4100 study is available in only one test soil (current guidance now 

generally requires at least 4 test soils) and no study is available to meet the 835.4400 guideline

(previously waived, but the lack of which appears now to be a significant source of uncertainty 

regarding the environmental fate of ethoprop).
3

`

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

Preliminary Environmental Fate and Ecological Risk

Assessment for the Registration Review of Ethoprop (Ethoprophos)

O

P

O S

S

CH2

CH3

CH2

H2C CH3

H2

C

H3C

H2C

CAS 13194-48-4

PC Code 041101

DP Barcode 410027

July 7, 2015

Prepared by

Michael R. Barrett, Chemist

Geoffrey Sinclair, Ph.D., Biologist

U.S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch V

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by

Justin Housenger, Biologist

Jose Melendez, Chemist

Mah T. Shamim, Ph.D., Branch Chief
4

Table of Contents

Executive Summary.....................................................................................................................................................7

Purpose of Assessment............................................................................................................................................7

Summary of Relevant Environmental Fate, Transport, and Exposure Pathways............................................7

Summary of Effects and Risk Conclusions...........................................................................................................7

Introduction .................................................................................................................................................................9

Pesticide Use Characterization.................................................................................................................................10

Drift / Exposure Reduction Label Language......................................................................................................11

Method and Rates of Application:.......................................................................................................................11

Specific Label Directions by Crop.......................................................................................................................12

Fate and Exposure Characterization .......................................................................................................................20

Physical and Chemical Properties and Environmental Fate.............................................................................20

Updated Information on Environmental Fate Studies ......................................................................................23

Hydrolysis.........................................................................................................................................................23

Soil Metabolism................................................................................................................................................27

Field Dissipation...............................................................................................................................................29

Adsorption / Desorption Studies.....................................................................................................................30

Volatility 31

Measures of Exposure ..........................................................................................................................................31

Measures of Aquatic Exposure and Exposure Estimates .............................................................................31

Comparison of Aquatic Exposure Estimates with Monitoring Data ...........................................................33

Measures of Terrestrial Exposure ..................................................................................................................34

Effects Characterization ...........................................................................................................................................40

Aquatic Toxicity....................................................................................................................................................40

Terrestrial Toxicity...............................................................................................................................................45

Terrestrial Toxicity Assessment ..........................................................................................................................45

Review of Incident Data .......................................................................................................................................48

Risk Characterization and Description ...................................................................................................................50

Risk Estimation and Description.........................................................................................................................50

Non-target Aquatic Animals and Plants ........................................................................................................50

Non-target Terrestrial Animals and Plants ...................................................................................................54

Risk Characterization and Description from exposure to pollinators.........................................................61

Terrestrial Plants .............................................................................................................................................61

Risk description associated with consumption of earthworms ....................................................................61

Risk description through inhalation...............................................................................................................63

Risk from Drift to Aquatic Ecosystems..........................................................................................................63

Endocrine Disruptor Screening Program (EDSP)..................................................................................................64

Federally Threatened and Endangered (Listed) Species of Concern....................................................................66

Conclusions ................................................................................................................................................................67

Uncertainties, Limitations, and Identification of Data Gaps.................................................................................72

Data Gaps and Uncertainties ..........................................................................................................................72

Environmental Fate ..............................................................................................................................................72

Ecological Effects..................................................................................................................................................72

Terrestrial Exposure Assessment ...................................................................................................................72

Reference Citations....................................................................................................................................................76

Bibliography of Ecological Effect and Environmental Fate Guideline Studies....................................................79

MRID/Accession Studies for Ecological Data: ...................................................................................................79

MRID/Accession Studies for Environmental Fate Data:...................................................................................82
5

165-4 Bioaccumulation in fish ...................................................................................................................86

APPENDICES............................................................................................................................................................89

Appendix A: Chemical Structures of Ethoprop and Degradates .....................................................................89

Appendix B: Risk Quotients and Levels of Concern for Exposed Organisms.................................................93

Appendix C: Aquatic Exposure Modeling selected Input and Output ............................................................93

FL Sugarcane Scenario Input file ...................................................................................................................94

FL Sugarcane Scenario Output Summary.....................................................................................................95

Maine Potato Scenario SWCC Model input and Output Summary............................................................99

Groundwater Modeling Example Input – Output Summary.....................................................................100

Appendix D. T-REX Model Input and Output ...............................................................................................103

Appendix E. STIR Model Example ..................................................................................................................108
6

List of Tables

Table 1. Summary of current uses of ethoprop.......................................................................................................17

Table 2. Screening Level Estimates of Agricultural Uses of Ethoprop based upon 2004 – 2011 usage reports.

.....................................................................................................................................................................................19

Table 3. SWCC model inputs for estimated environmental concentrations for aquatic exposure.2 ..................21

Table 4. Observed and calculated hydrolysis rates of ethoprop at different temperatures and pH conditions.

.....................................................................................................................................................................................26

Table 5. Summary of ethoprop field dissipation studies. .......................................................................................29

Table 6. Estimated aquatic environmental concentrations for ethoprop for current uses (in ppb) using EFED 

standard pond and 1/10 year return frequency. .....................................................................................................32

Table 7. Representative hydrologic characteristics, estimated ethoprop usage intensity, and ethoprop 

detection rates in monitored community water systems (CWS)............................................................................33

Table 8. Raw water ethoprop and SME detection rates and maximum observed concentrations for the five 

monitored CWS. ........................................................................................................................................................34

Table 9. Input parameters for the T-REX model for different uses for ethoprop. ..............................................35

Table 10. Avian dose-based ethoprop EECs (mg/kg-bw) for three size classes of birds......................................36

Table 11. Mammalian dose-based ethoprop EECs (mg/kg-bw) for three size classes of mammals. ..................36

Table 12. Dietary based EECs (ppm) for application rates of ethoprop...............................................................38

Table 13. Acute and chronic Toxicity endpoints for ethoprop. .............................................................................40

Table 14. Terrestrial toxicity endpoints for ethoprop. ..........................................................................................45

Table 15. Summary of EIIS incidents as of June 2014. .........................................................................................48

Table 16. Acute and chronic risk quotients for freshwater and estuarine/marine fish. ......................................51

Table 17. Acute and chronic risk quotients for freshwater and estuarine/marine invertebrates. ........................52

Table 18. Acute and chronic risk quotients for freshwater and estuarine/marine sediment dwelling 

invertebrates estimated from water column EC50/NOAEC and pore water concentrations (peak and 21-day).

.....................................................................................................................................................................................53

Table 19 LD50 ft-2 risk quotients from granular and incorporated applications of ethoprop. ...........................54

Table 20. Avian dose-based acute RQs....................................................................................................................57

Table 21. Avian dietary-based acute and chronic RQs. ........................................................................................57

Table 22. Mammalian dose-based acute and chronic RQs. ..................................................................................59

Table 23. Mammalian dietary-based chronic RQs................................................................................................61

Table 24. Soil EECs generated from uses of ethoprop from the earthworm fugacity model..............................62

Table 25. Endpoints compared to EECs in earthworms generated by the earthworm fugacity model. ...........62

Table 26. Aquatic Effects Distance in feet from low boom applications.................................................................64
7

Executive Summary

Purpose of Assessment

This screening-level risk assessment examines the potential ecological risks associated with the 

uses of the pesticide ethoprop (O-ethyl-S,S-dipropyl phosphorodithioate; alternate common 

name ethoprophos (interchangeable with ethoprop). This risk assessment utilizes the best 

available scientific information and current labels to evaluate the environmental fate and 

transport, and effects on non-target organisms. The end use products are emulsifiable 

concentrate and water dispersible granule formulations for ground application for various 

agricultural crops with maximum single annual application rate ranging from 1.95 to 12 lb a.i./A. 

Ethoprop is currently used on cucurbits, hops, nursery stock, sugar beets, sweet potato, 

sugarcane, cabbage, corn, mint, tobacco, succulent (Lima) beans, and potatoes.

Summary of Relevant Environmental Fate, Transport, and Exposure 

Pathways

Ethoprop is moderately to strongly persistent in the environment (degradation half-lives of 1 to 5 

months by most pathways; but there is high uncertainty since field studies imply that persistence 

may vary significantly from site to site and possibly also may depend on previous use history). 

Ethoprop is highly mobile according to the McCall (1980) classification1. Ethoprop is semivolatile2

. Exposure off-site may occur via drift (however, as discussed below application 

methods are restricted to minimize drift), runoff, and potentially via leaching to groundwater that 

interacts with surface waters or is used for irrigation.

Summary of Effects and Risk Conclusions

The conclusions of this assessment remain largely unchanged from previous assessments. 

Additional routes of exposure that were not modeled in previous assessments and are areas of 

concern include consumption of contaminated fish and earthworms. When estimates of ethoprop 

exposure in terrestrial and aquatic environments are compared to the available ecotoxicity data, 

the results of the screening-level assessment indicate a potential for risk to both aquatic and 

terrestrial taxa. 

Ethoprop is highly toxic to aquatic invertebrates and fish. Based on current uses and potential 

aquatic exposure levels, acute and chronic risk above the established levels of concern was 

identified for all aquatic taxa except for plants in both freshwater and estuarine/marine 

 1 McCall, P. J., Swann, R. L., Laskowski, D. A., Unger, S. M., Vrona, S. A. and Dishburger, H. J. 1980. Estimation of chemical mobility in soil from liquid chromatographic 

retention times, Bull. Environ. Contam. Toxicol., 24, 190–195.

2 A vapor pressure of ≥ 3.90 x 10-5 is considered to be predictive of “Intermediate to high volatility under field conditions”. See: “Guidance for Reporting on the Environmental 

Fate and Transport of the Stressors of Concern in Problem Formulations” EFED / OPP Memorandum dated January 25, 2010; available at: 

http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_species_reregistration_workgroup/esa_reporting_fate.htm .
8

environments. Environmental fate modeling and risk quotient determination indicate potential 

adverse effects on aquatic animal taxa. Acute and chronic risk to freshwater fish, 

estuarine/marine fish, freshwater invertebrates, and estuarine/marine invertebrates, and both 

freshwater and estuarine sediment invertebrates was identified. Risk above the level of concern 

was not identified for aquatic plants based on one available diatom study. 

Ethoprop is also highly toxic to terrestrial taxa. LD50 per square foot analysis indicated that there 

is acute risk to both birds and mammals from granular formulations. There was also acute dose 

based and acute dietary based risk as well as chronic dietary risk to birds associated from EC 

applications. Similarly, there was acute and chronic dose based risk as well as chronic dietary 

based risk to mammals from EC applications. Both bird and mammals are predicted to be 

adversely affected by consumption of fish contaminated with ethoprop. Modeling predicted risk 

to birds from acute dose based, acute dietary based and chronic dietary based exposure to 

contaminated fish. Mammals are also predicted to be at risk from acute dose based as well as 

chronic dose based and dietary based exposure to contaminated fish. Other indirect routes of 

exposure may include consumption of contaminated earthworms in treated fields. Modeling 

indicated acute avian risk from both dose-based and dietary exposure as well as chronic risk 

from dietary exposure. Risk was not identified for mammals consuming contaminated 

earthworms. Ethoprop is slightly to moderately volatile but modeling suggests that inhalation is 

not a risk to either birds or mammals. While ethoprop is applied by boom sprayer, the coarse 

droplet size and maximum nozzle height of 4 feet specified on current labels eliminates most risk 

to terrestrial taxa through spray drift. Risk to terrestrial invertebrates is predicted from Bee-REX 

modeling if exposure occurs to pollinators foraging on fields during the time of application. 

Results of past assessments and current application practices are designed to limit exposure. As 

an insecticide, ethoprop would pose a risk to pollinators and other beneficial insects only if they 

are exposed.
9

Introduction

The risk assessment is conducted as part of the Agency’s Registration Review process for 

pesticide active ingredients that was established under the Food Quality Protection Act (FQPA 

1996). In an attempt to streamline documents produced by EFED, this risk assessment will 

rely, when appropriate, on information/data presented in the previously prepared problem 

formulation and in the latest EFED Reregistration Eligibility Decision (RED) document entitled

Environmental Risk Assessment for Ethoprop (DP dated October 5, 1998 The majority of 

information, included in the referenced two documents, will not be repeated here. Instead new 

data and/or information and any changes will be indicated. These changes are related to the 

following:

1. Description of new uses

2. Description of new fate data

- Additional hydrolysis studies characterized for new model input

- Other fate data limitations with respect to parameterization of current models. 

3. Description of new effects data 

– Two additional avian reproductions studies

– Reevaluation and reclassification of the fish full life cycle study from invalid to 

supplemental.

4. Description and use of new and updated models.

As part of the Registration Review process, a detailed Problem Formulation (DP Barcode 

D353378) for this risk assessment was published to the docket [Docket ID: EPA-HQ-OPP-2008-

0560] in September 2009. This problem formulation provided the foundation for the 

environmental fate and ecological risk assessment being conducted for the labeled uses of 

ethoprop, based on the seven approved labels for this chemical at the time (there are currently 

three Section 3 end-use product labels).. The problem formulation sets the objectives for the risk 

assessment and provides a plan for analyzing the data and characterizing the risk (USEPA 

1998a). The Ecological Risk Assessment (DP Barcode D368753, 4/15/2010), includes 

information on previous risk assessments; chemical mode of action; overview of the labeled use; 

environmental fate and transport characteristics; receptors (aquatic and terrestrial effects, 

incidents and ecosystems potentially at risk); assessment endpoints; risk hypothesis and a 

conceptual diagram; along with the analysis plan specifying the stressor of concern, measures of 

exposure/effects, integration of exposure and effects, assessment method (deterministic and 

probabilistic) and endangered species and drinking water assessments.

Ethoprop (Ethoprophos, CAS Name: O-ethyl-S,S-dipropylphosphorodithioate, and IUPAC 

Name: 1-(ethoxy-propylsulfanylphosphoryl)sulfanylpropane), has a CAS Number of 13194-48-4

and a PC Code of 041101. It is an organophosphate (OP) nematicide/insecticide with contact 

and stomach action poison and long residual effects. Ethoprop shares a common mechanism of 

toxicity with other OP’s, such as the toxicity expressed through a common biochemical 

interaction with the cholinesterase enzyme. Although some degradates of ethoprop are 

cholinesterase inhibitors (the major route of toxicological effect for ethoprop and other 
10

organophosphate insecticides), none of these were found in major amounts in the environmental 

fate studies. Results from various aquatic and soil metabolism studies indicated that none of the 

individual environmental degradates were ever present at greater than about 4% of the applied 

ethoprop concentration. However the results of the submitted studies indicate that S-ME 

exposure may be significant in some surface waters (see Appendix A for chemical names and 

structures of ethoprop and its degradates). The S-ME and O-ME ethoprop degradates have been 

determined by the Health Effects Division to be ChE inhibitors and are included in the residues 

of concern for drinking water (DP Barcode D342754 and D342793, HED Memorandum dated 

7/10/1998) While these compounds might be considered of concern for ecological effects as 

well, given the fate parameters for parent ethoprop (e.g., degradation half-lives of months by 

most pathways), it is highly unlikely that SME residues alone or even total residues would be 

significantly higher than estimated with the current modeling. Therefore, all exposure 

assessments in this review are expressed in terms of parent ethoprop and are also expected to 

conservatively represent the total toxic residues (TTR) of ethoprop. 

The stressor is expected to reach terrestrial and aquatic receptors mostly from application runoff 

rather than drift, since labels require applications to be incorporated (some applications are 

incorporated by a wetting in process rather than mechanically). EFED evaluated the possibility 

of drift from applications that are not incorporated deeply enough or rapidly enough to eliminate 

drift potential. Based on laboratory data, ethoprop appears to be fairly persistent in soil and 

water. However, in the field, dissipation has generally been more rapid than expected from the 

laboratory studies – some of the difference could potentially be due to enhanced degradation 

rather than dissipation processes such as volatilization and leaching. Previous work with the 

organophosphate insecticides has also shown that volatilization and microbial degradation 

increases as soil moisture content and temperature increases. Note also that, while this is not 

supposed to be a factor for the guideline field dissipation studies, at least in general there is a 

possibility of enhanced microbial transformation at sites with a history of organophosphate

pesticide use, including for ethoprop (Arbeli and Fuentes, 2007; Karpouzas et al., 1999; Racke 

and Coats, 1988; Singh et al., 2005; and Smelt et al., 1987)3

.

Pesticide Use Characterization

Ethoprop is a restricted use organophosphate pesticide developed for control of soil insects and

 3 Arbeli. Z. and C.L. Fuenes. 2007. Accelerated biodegradation of pesticides: An overview of the phenomenon, its basis and possible solutions; and a discussion on 

the tropical dimension. Crop Protection 26(2007)1733-1746.

Karpouzas, D.G., ,A. Walker, R.J Froud-Williams, and ,D.S.H Drennan. 1999. Evidence for the enhanced biodegradation of ethoprophos and carbofuran in soils from 

Greece and the UK. Pesticide Science 55: 301–311,

Racke, K.D. and J.R. Coas. 1988. Comparative Degradation of Organophosphorus Insecticides in Soil: Specificity of Enhanced Microbial Degradation. J. Agric. Food 

Chem. 1988:, 193-199.

Singh, B.K.,, A. Walker and D.J. Wright. 2005. Cross-enhancement of accelerated biodegradation of organophosphorus compounds in soils: Dependence on structural 

similarity of compounds. Soil Biology and Biochemistry 37: 1675-1682.

Smelt, J. H., Crum, S. J. H., Teunissen, W. and Leistra, M., 1987. Accelerated transformation of aldicarb, oxamyl and ethoprophos after repeated soil treatments, Crop 

Protection, 6: 295-303.
11

includes granular (G) and emulsifiable concentrate (EC) formulations. All applications must be 

incorporated either physically or by wetting in. Ethoprop has been registered since the late 

1960s for use on a variety of crops and turf grasses and may be formulated with other pesticides 

and fertilizers. The pesticide may be applied by ground application methods only and one 

application per season is permitted.

Drift / Exposure Reduction Label Language

Product labels have the following language to minimize the potential for drift and/or applicator 

exposure from ground spray applications:

For ground boom applications, apply with nozzle height no more than 4 feet above the 

ground and only when wind speed is 10 mph or less at the application site as measured by 

an anemometer. Use medium or coarser spray as described according to ASAE 572 

definition for standard nozzles or VMD for spinning atomizer nozzles.

For application only by motorized ground boom equipment and through irrigation

systems if specified in crop-specific use directions. Do not apply with liquid backpack 

sprayers, low-pressure hand-wand liquid equipment, sprinkler cans or hand-held 

measuring containers, or by hand-dipping of seedlings.

For use on ornamentals: only preplant broadcast application to soil for field nursery 

stock, which may only be mechanically transplanted into the treated area, and not until 72 

hours after treatment.

This product is to be soil incorporated to a depth of at least 2 to 4 inches, during or 

immediately following application by mechanical means, including by rotary tiller, rotary 

hoe, springtooth harrow, or by double-disking.

Method and Rates of Application:

Equipment –

The current labels for ethoprop indicate that the products may be applied by chemigation (i.e., 

drip irrigation and sprinkler irrigation), granule applicator [i.e., tractor-drawn mechanical 

spreader, push-type spreader, and backpack (for banana only)], and ground sprayer equipment.

Method –

The insecticidal / nematicidal activity of ethoprop is highly dependent upon incorporating the 

product into the soil (mechanically or with water) soon after application to be effective, 

especially for those nematodes and insects which live deep in the soil. All labels specify 

immediate soil incorporation by mechanical equipment for all products as they are being applied 

by ground equipment, or that watering-in is to be conducted immediately following applications 

(for chemigation methods, which are permitted on bananas and plantains only). No aerial 

applications of any type or hand-held application methods are permitted. For some crops only 
12

banded (not broadcast) applications are permitted (this restriction applies to the EC label for 

cabbage and the EC and granular formulations for sweet potatoes).

Ethoprop is applied to most crops pre-plant or pre-emergent, but it can also be applied as 

follows: banana and plantain plants as soil-directed liquid spray or granular broadcast (backpack 

spreader) around the stems of the plants up to 2 times per year; and corn at cultivation after plant 

emergence until layby (i.e., the last time the corn plants are cultivated). In addition, potatoes may 

be treated prior to crop emergence.

Rate –

For soil treatments of field crops, the maximum label rates range from 2 lb active ingredient per 

acre (ai/acre) on cucumbers to 12 lb ai/A on potatoes (reduced to 9 lb ai /A for potatoes east of 

the Mississippi River) for agricultural crops. Close to a majority of the ethoprop total amount 

applied in the United States annually is to potatoes in the Pacific Northwest (PNW), where 

growers apply either granular or EC formulation at two application rates: up to 12 lb ai/A for 

control of nematodes, and up to 6 lb ai/A for control of wireworms. For bananas, the EC label 

states “apply 8 mL of MOCAP EC in a radius of 3/4 meter around each producing stem,” and the 

10G and 15G granular labels similarly list rates to be applied per producing stem (at product 

rates which are equivalent to 6 grams or 0.2 ounces of and gel labels specify that multiple 

applications are permitted, but not more than 8 gallons of MOCAP® per acre per year for plant 

crops, or not more than 5 gallons of MOCAP® per acre per year for ratoon crops.

Timing –

For field crops, applications must be pre-plant or at-plant and usually occur in the spring, before 

the growing season, with only one application per crop; only the banana / plantain labels permit 

more than one application per year. For some ratoon row crops, such as sugar cane, applications 

may occur only at the time of planting, and the crop grows for 3 to 5 years before a new crop is 

replanted. Applications to banana plants may be up to two times per year. 

Specific Label Directions by Crop

There are specifically three different formulation types (the associated crop or other use sites for 

each product are listed in Table 1):

1. An emulsifiable concentrate (EC) formulation. (EPA Reg. No. 5481-9041). Includes uses 

on cabbage, hops, mint, potatoes, sweet potatoes, and ornamentals. 

2. A 15% Granular formulation (EPA Reg. No. 5481-9040). Includes uses for bananas and 

plantains, cabbage, hops, snap and lima beans, field and sweet corn, cucumber, potatoes, 

sugarcane, and tobacco. 

3. A 20% Granular formulation (EPA Reg. No. 5481-9042) (for sugarcane only). 

Additional details on the application specifications for each use site (except nursery stock are 
13

provided below (refer to the original labels for exact language; the label language can very 

slightly for different marketing companies).

Reg. no. 5481-9041 (formerly 264-458), EC formulation:

• Cabbage:

o For at-planting application to seeded crops, apply in 12 to 15 inch band on the 

row (36-inch row spacing) and incorporate 2 to 4 inches deep with mechanical 

equipment during or immediately following treatment.

• Hops:

o [Post plant, pre-emergence, Pre-plant broadcast and incorporated application 

method options below.] 

 [Method 1.] Mix MOCAP EC Nematicide-Insecticide with sufficient 

water and broadcast apply immediately ahead of equipment such as a 

double disc or rotary cultivator to thoroughly incorporate MOCAP EC 

Nematicide-Insecticide solution into the top 2 to 4 inches of soil.

 [Method 2.] Mix MOCAP EC Nematicide-Insecticide with sufficient 

water and broadcast or band apply solution. Immediately apply 1 to 2 

inches of overhead irrigation water to incorporate MOCAP EC 

Nematicide-Insecticide into soil. If band applying, apply in band at least 2 

feet wide over row.

 [Method 3.] Mix MOCAP EC Nematicide-Insecticide with sufficient 

water and broadcast apply immediately ahead of equipment such as a 

double disc or rotary cultivator to thoroughly incorporate MOCAP EC 

Nematicide-Insecticide solution into the top 2 to 4 inches of soil. Wait a 

minimum of 3 days before planting the baby hops.

o [Producing hops]. Apply in the spring after pruning, but before stringing or after 

Harvest.

 Method 1. See above.

 Method 2. See above.

 [Method 4.] Chemigation Method: Apply Mocap EC NematicideInsecticide to prewetted hop yards through subsurface drip irrigation (SDI) 

systems with pressure compensating emitters only. The Emission 

Uniformity (EU) of the drip irrigation system must be at 85 percent or 

greater (refer to USDA-NRCS Practice Standard Code 441). Do not apply 

through any other type of irrigation system. Follow chemigation with 

enough irrigation to move MOCAP EC Nematicide- Insecticide into the 

top 2-4 inches of soil.

• Mint: 

o Apply preplant or after last harvest of the growing season. Spray with ground 

equipment, broadcast, over the field. Do not apply by air or through any type of 

irrigation equipment. This product is to be soil incorporated to a depth of at least 2 

to 4 inches, during or immediately following application by mechanical means, 

including by rotary tiller, rotary hoe, springtooth harrow, or by double discing, or 
14

by immediate application of 1 to 2 inches of overhead irrigation. Repeat irrigation

before soil dries.

• Potatoes (West of the Mississippi River):

o Apply prior to planting, at planting or prior to crop emergence.

o BAND (Insect control; maximum rate is 6 lb ai/Acre): Uniformly distribute spray 

in a 12 inch band over the row (36-inch row spacing), either behind the planter 

shoe next to the closing disk or immediately in front of the planter shoe. Mix with 

the top 2 to 4 inches of soil during or immediately following treatment.

o BROADCAST (Nematode control; maximum rate is 12 lb ai/Acre): Apply 

uniformly and immediately incorporate 2 to 4 inches deep using suitable tillage 

equipment. For some pests in Pacific Northwest: Apply uniformly and 

immediately incorporate 4 to 8 inches deep using suitable tillage equipment. Best 

results are obtained with deep (6-8 inches), even incorporation.

• Potatoes (East of the Mississippi River):

o Apply prior to planting, at planting or prior to crop emergence.

o BAND (Insect control; maximum rate is 6 lb ai/Acre): Uniformly distribute spray 

in a 12 inch band over the row (36-inch row spacing), either behind the planter 

shoe next to the closing disk or immediately in front of the planter shoe. Mix with 

the top 2 to 4 inches of soil during or immediately following treatment.

o BROADCAST (Nematode control; maximum rate is 9 lb ai/Acre): Apply 

uniformly and immediately incorporate 2 to 4 inches deep using suitable tillage 

equipment / mechanical equipment. Apply within 2 weeks before planting until 

prior to crop emergence.

• Sweet Potatoes

o [2 to 3 weeks before planting.] 

o BAND: Apply in a band 12 to 15 inches wide on the row (minimum 42-inch row 

spacing) and incorporate 2 to 4 inches deep during or immediately following 

treatment. Good results have been obtained by opening the row, applying in a 12 

to 15 inch band on the row, bedding over and dragging

Reg. no. 5481-9042 (20% Granular):

• Sugarcane:

o For application by ground equipment only. This product must be soil incorporated 

or covered with soil to a depth of at least 2 to 4 inches, during or immediately 

following application by mechanical means, including by disc hiller, rotary tiller, 

rotary hoe or springtooth harrow.
15

Reg. no. 5481-9040 (15% Granular):

• Banana and Plantain:

o Apply 40 grams of product in a radius of 3/4 meter around each producing stem 

or 1.3 ounces of product in a radius of 30 inches around each producing stem. 

Before application, remove ground litter from area to be treated, and apply 

granules evenly. Incorporate into the soil immediately following application by 

hand-raking to a depth of at least 1 inch. For best results, apply just before 

irrigation or a rainy period. Repeat application in 6 months.

• Beans (snap and lima only):

o BROADCAST: Apply from 3 days before planting to at planting time. Mix with 

the top 2 to 4 inches of soil with mechanical equipment right after application. 

Use the higher rates in fields where nematode infestations have been especially 

severe.

• Cabbage:

o BAND: Apply 13 pounds per acre (36 inch row spacing) or 0.9 pounds per 1,000 

linear feet of row in a band 15 inches wide on the row at planting. Mix with the 

top 2 to 4 inches of soil with mechanical equipment during or immediately 

following application. DO NOT use as a seed furrow treatment or allow granules 

to contact the seed.

o BROADCAST: Apply from 1 week before planting to at planting time. Mix with 

the top 2 to 4 inches of soil with mechanical equipment right after application.

• Corn (field and sweet):

o BAND (Insect control; equivalent maximum rate is 3 lb ai/Acre): Apply the 

granules in a 6 to 7 inch band on the row over a closed seed furrow at-planting.

Mix the granules with the top 1/2 inch of soil with mechanical equipment during 

or immediately following application4

.

o BAND (Nematode control; equivalent maximum rate is 6 lb ai/Acre): Mix with 

the top 2 to 4 inches of soil with mechanical equipment right after application.

o BROADCAST (Insect control; maximum rate is 3 lb ai/Acre): Apply 3 days 

before planting to at planting time. Mix with the top 2 inches of soil with 

mechanical equipment right after application.

o BROADCAST (Nematode control; maximum rate is 6 lb ai/Acre): Apply 3 days 

before planting to at-planting time. Mix with the top 2 to 4 inches of soil with 

mechanical equipment right after application.

• Cucumber:

o BAND: Apply 13 pounds per acre (7-foot row spacing) or 2.1 pounds per 1,000 

linear feet of row in a band 12 to 15 inches wide on the row at planting. Prepare 

bed and knock off top to provide a level area for treatment. Mix with the top 2 to 

4 inches of soil with mechanical equipment right after application.

• Sugarcane:

 4 The 0.5 inch incorporation depth specified appears to be inconsistent with the requirements for a 2-inch or more incorporation depth for other types of application on 

corn and for other crops.
16

o BAND: Apply evenly in a band 12 to 15 inches wide to the seed pieces in open 

furrows or beds and immediately cover with soil. Mix with the soil using a disc 

hiller or other suitable equipment as the cane is covered. Use the higher rates in 

fields where nematode and/or wireworm infestations are severe. Minimum 6-foot 

row spacing.

o (Similar directions on EPA Reg. no. 264-469 label)

• Sweet Potato:

o BAND: Apply 20 to 26 pounds per acre or 1.6 to 2.1 pounds per 1,000 linear feet 

of row in a band 12 to 15 inches wide on the row (minimum 42-inch row 

spacing). Mix with the top 2 to 4 inches of soil with mechanical equipment right 

after application. Good results have been obtained by opening the row, applying 

product in a 12 to 15 inch band on the row, bedding over and dragging

• Tobacco:

o BAND: Apply in a band 18 to 24 inches wide on the row (42-inch row spacing) 

after the fertilizer has been listed or bedded. Mix with the top 2 to 4 inches of soil 

with mechanical equipment right after application.

o BROADCAST: Mix with the top 2 to 4 inches of soil with mechanical equipment 

right after application. Use a disc harrow or other cultivating equipment that will 

do a good job of mixing the MOCAP® 15% Granular with the soil.

• Sugarbeets [SLN-24(c) for Oregon]-EC Formulation:

o SHANKING AND INJECTING After seedling emergence or after 

transplanting seedling. Shank or inject solution 1 to 2 inches from plants and to 

a depth of 2 to 4 inches on both sides of seedlings or transplants. Mix with 

sufficient water and inject product to side of plants close to but not in contact with 

the roots. Follow with irrigation. 

o BROADCAST: Prior to seeding or transplanting. Apply immediately ahead of 

equipment such as a double disc or rotary cultivator to thoroughly incorporate 

MOCAP EC solution into the top 2 to 4 inches of soil. 

There are no registered homeowner uses. Current uses are further discussed in the Problem 

Formulation (DP Barcode: D353378) and the section 3 new use drinking water assessment 

(D342755). 
17

Table 1. Summary of current uses of ethoprop.

Use Site Max. Rate

per App

Max. Rate

as lb ai/ Acre 

or 1000 linear 

feet

Form Max 

#

Apps/

yr 

Max. 

App.

Rate/

cc & 

yr 

Application Equipment

//Type

NON-FOOD/NON-FEED USES

hops 3~ lb ai /A EC 1 NS Boom sprayer/ Ground/ Soil 

incorporation equipment 

//Soil band treatment/ Soil 

broadcast treatment 

Nursery stock 3 (SLN = 

65)

lb ai /A EC 1 NS Soil incorporation equipment 

//Broadcast

sugar beet 

(Special local 

need supplemental 24(c) 

Labeling

only.)

3~ lb ai /A EC NS NS Shank/ Soil incorporation 

equipment/ Soil injector 

equipment 

//Soil broadcast treatment/ 

Soil injection treatment/ 

Soil treatment

Tobacco 6 lb ai /A G 1 NS Granule applicator 

//Soil broadcast treatment 

.4800 linear ft G 1 NS Granule applicator 

//Soil band treatment

FOOD/FEED USES

Banana .0132 lb/ plant

 

G 2/1 yr NS Spreader 

//Soil broadcast treatment 

beans, 

succulent 

(lima) 

8.1 lb ai /A G 1 NS Granule applicator 

//Soil broadcast treatment (a)

.1828~ linear ft

 

EC 1 NS Shank/ Soil incorporation 

equipment/ Soil injector 

equipment 

//Soil band treatment/ Soil 

injection treatment/ Soil 

shanking treatment 

beans, 

succulent 

(snap) 

8.1 lb ai /A G 1 NS Granule applicator 

//Soil broadcast treatment 

.1828~ linear ft EC 1 NS Shank/ Soil incorporation 

 5 See: CA120009 expires in November 30, 2017.

OR090003 expires on December 31, 2014.

The higher 6.05 lb ai/acre rate is only allowed on the SLN label for Easter lilies grown for commercial bulbs in California and Oregon. Use in Oregon at this rate is 

limited to Curry County. For the bulk of ornamentals in the U.S. the maximum rate is 3.0 lbs a.i./acre. 
18

Use Site Max. Rate

per App

Max. Rate

as lb ai/ Acre 

or 1000 linear 

feet

Form Max 

#

Apps/

yr 

Max. 

App.

Rate/

cc & 

yr 

Application Equipment

//Type

equipment/ Soil injector 

equipment 

//Soil band treatment/ Soil 

injection treatment/ Soil 

shanking treatment

cabbage 5.1 lb ai /A G 1 NS Granule applicator 

//Soil broadcast treatment 

.1125 linear ft

 

EC 1 NS Soil incorporation 

equipment 

//Soil band treatment

corn, field 6 lb ai /A G 1 NS Granule applicator 

//Soil broadcast treatment 

.1500 linear ft

 

G 1 NS Granule applicator 

//Soil band treatment

corn, sweet 6 lb ai /A G 1 NS Granule applicator 

//Soil broadcast treatment 

.1500 linear ft

 

G 1 NS Granule applicator 

//Soil band treatment 

cucumber 1.95 lb ai /A G 1 NS Granule applicator 

//Soil band treatment 

mint/

peppermint/

spearmint 

3~ lb ai /A EC 1 NS Soil incorporation equipment 

//Soil broadcast treatment/ 

Soil incorporated treatment

Application may be preplant or after last 

harvest of the growing season (mint is the 

only crop with postharvest applic. 

allowed.) There is a minimum 225-day 

preharvest interval required.

plantain .0132 lb / plant G 2/1 yr NS Spreader 

//Soil broadcast treatment 

potato, 

white/irish 

12 W of 

Miss. River

or

9 E of the

Miss. River

lb ai /A G 1 NS Granule applicator 

//Soil broadcast treatment 

Apply within 2 weeks before planting 

until prior to crop emergence.

12 

(9 E of 

Miss. 

lb ai /A EC 1 NS Soil incorporation 

equipment 

//Soil broadcast treatment 
19

Use Site Max. Rate

per App

Max. Rate

as lb ai/ Acre 

or 1000 linear 

feet

Form Max 

#

Apps/

yr 

Max. 

App.

Rate/

cc & 

yr 

Application Equipment

//Type

River)

.2100 linear ft

 

G 1 NS Granule applicator 

//Soil band treatment 

.2063 linear ft

 

EC 1 NS Soil incorporation 

equipment 

//Soil band treatment 

sugarcane 4 lb ai/A G 1 NS Soil incorporation 

equipment 

//Soil band trmt. 

“Apply to seed pieces in 

opened furrow or beds and 

immediately cover with 2-4 

inches of soil. Mix the soil 

with a disc hiller or other 

suitable equipment as the cane 

is covered.”

.5600 linear ft G 1 NS 

sweet potato 3.9 lb ai /A G 1 NS Granule applicator 

//Soil band treatment 

.3` 

234 

linear ft

 

EC 1 NS Soil incorporation 

equipment 

//Soil band treatment 

Cc = Crop cycle.

Yr = Year.

~ = In this table indicates a use rate that can be interpreted slightly differently depending on how it is calculated. The 

variation is not significant for the risk assessment.

NS = Not specified.

For all crop use sites only one application is allowed per growing season. For bananas and plantains there is a minimum 

interval of 180 days.

All applications are from a few days before planting or at planting unless otherwise specified.

A summary of ethoprop usage rates by crop in recent years is provided in Table 2. Only the 

green bean, cucumber, potato, and sugarcane crop sites are estimated to have annual percent crop 

treated (PCT) rates above 5% and only potatoes and sugarcane reach as much as 10% PCT. The 

PCTs have been consistently low in evaluations by OPP- Biological and Economic Analysis 

Division (BEAD) in recent years (see also: Screening Level Usage Analysis (SLUA).

February 14, 2008: OPP-BEAD). Field corn usage was apparently too low to even be estimated 

and the rate of usage on sweet corn was very low with only 10,000 acres estimated to be treated 

with ethoprop annually.

Table 2. Screening Level Estimates of Agricultural Uses of Ethoprop based upon 2004 – 2011 
20

usage reports.

Crop Average Percent Crop Treated

Lbs. A.I. Average Maximum

1 Beans, Green 40,000 5 10

2 Cabbage 3,000 <2.5 <2.5

3 Cucumbers 4,000 <2.5 5

4 Dry Beans++/Peas 7,000 <1 <2.5

5 Peanuts++ 2,000 <1 <2.5

6 Potatoes 100,000 5 10

7 Sugarcane 100,000 5 10

8 Sweet Corn 7,000 <1 <2.5

9 Tobacco 8,000 <1 <2.5

Prepared August 14, 2013.

All numbers are rounded.

 <2.5: indicates less than 2.5 percent of crop is treated.

 <1: indicates less than 1 percent of crop is treated.

++ There are no current active registrations listing these uses. Cancellations were issued for dry beans and 

peanuts in 2008. Usage in this report may reflect usage occurring before cancellation or as a result of using 

existing stocks after cancellation.

Site Name Cancelled Date

Dry Beans 10-Apr-08

Peanuts 10-Apr-08

Fate and Exposure Characterization

Physical and Chemical Properties and Environmental Fate

The environmental fate of ethoprop has previously been summarized in the EFED Problem 

Formulation for registration review (DP Barcode D353378, 10/30/2008), the Ecological Risk 

Assessment (DP Barcode D368753, 4/15/2010), and a Drinking Water Exposure Assessment 

(DP Barcode D375927, 4/15/2010); the Drinking Water Assessment has been recently updated 

for the registration review (DP Barcode D428028). Some limited additional information has been 

reviewed for this risk assessment and is discussed below. Emphasis is on the fate of the parent 

since no metabolites appear to form at greater than 10 % of applied. 

Ethoprop degrades primarily by microbial metabolism as well as the abiotic process of 

hydrolysis. The aerobic soil metabolism half-life is 100 days in the guideline study (these data 

are more limited than would be required under current regulatory guidance recommending that 

metabolism rates be examined in at least four test soils for OCSPP 835.4100 aerobic soil 

metabolism studies). Field dissipation half-lives are 3 to 60 days at approximately 24 different 
21

sites. There are no acceptable anaerobic aquatic metabolism studies available but a 100 day halflife was observed in an anaerobic soil metabolism study. Degradation due to hydrolysis varies 

with pH, with estimated half-lives at 25 °C estimated of 205 days for acidic (pH 5) waters, 150-

155 days for waters with neutral pH (pH 7), and 39 days for alkaline waters (pH 9). Ethoprop is 

not subject to photolysis. Ethoprop is classified as highly mobile with a median Koc of 109 in 

five test soils6.

Ethoprop is a soluble (aqueous solubility: 843 ppm), somewhat volatile (vapor pressure: 3.5 x 10-

4 mm to 8.3 x 10-4 mm Hg at 25-26oC) insecticide/nematicide. Based only on laboratory data

from previously reviewed and accepted studies, ethoprop is fairly persistent (most degradation 

pathways with first order kinetic half-lives of a few months). In field studies, dissipation was

generally more rapid than would be predicted on the basis of degradation alone (from rates 

measured in the laboratory studies), especially under warm, moist conditions. The range in field 

dissipation rates was quite wide between sites / studies, however, and furthermore, the mass 

leaching captured in deeper depth increments of soil was significant enough at some sites to 

result in much slower dissipation rates when calculated from the total soil profile. The field data 

are not adequate to develop estimates of actual degradation rates for ethoprop in soil and are 

therefore only used for characterization of uncertainties in the current risk assessment. 

Some new models have been incorporated into the ecological exposure assessment (discussed 

further below) and additional data not used in the most recent ecological risk assessments has 

been incorporated into the current assessment. A new hydrolysis rate was calculated, and other 

minor changes in the fate modeling are noted in Table 3.

Some published sources (including studies submitted to regulatory agencies in other countries)

indicate that it is possible that aerobic soil, aerobic aquatic, and hydrolysis rates may be faster 

than estimated from guideline studies. This information has been used for further 

characterization of ethoprop environmental fate; however, these data have not been submitted to 

the Agency and have not been reviewed in detail by EPA.

The environmental fate of ethoprop is further summarized in DP Barcodes D368753 (4/15/2010 

EFED New Use Assessment for Chemigation on Hops). Additional details on hydrolysis, field 

dissipation, and published soil metabolism studies are provided below as they are relevant to 

refinements used in the current risk assessment.

Table 3. SWCC model inputs for estimated environmental concentrations for aquatic 

exposure.2

Chemical name Model Input Value /

Additional Notes

MRID Reference / Comment

Molecular Weight 242.3 (parent, used for Product chemistry Although some degradates in the TTR have a much 

 6 McCall, P. J., Swann, R. L., Laskowski, D. A., Unger, S. M., Vrona, S. A. and Dishburger, H. J. 1980. Estimation of chemical mobility in soil from liquid 

chromatographic retention times, Bull. Environ. Contam. Toxicol., 24, 190–195.
22

Chemical name Model Input Value /

Additional Notes

MRID Reference / Comment

TTR) data lower MW, parent is the most persistent moiety and 

is expected to dominate exposure.

Solubility 843 mg L-1 Product chemistry 

data

Vapor pressure

(mm Hg) 0.000827

Product chemistry 

data

Other reported values:

3.5 x 10-4 mm Hg

4.6 x 10-2 Pa @ 26o C (California Environ. 

Monitoring & Pest Mgmt., 1990). Reports similarly 

high VP for other organophosphates.

79 mPa @ 20o C (OPPTS 830.7950)

123 mPa @ 25o C(92/69/EC A8)

Henry’s Law Constant Calculated by model Product chemistry 

data

Reported to be 1.32 E-08 atm.m3/mo – may also be 

calc. value.

pH 7 Hydrolysis half-life

(days)

150 41270703 

00067321

00160166 

Previous value was “stable”, derived as a default 

value from MRID 41270703 (not enough data to 

calculate a hydrolysis rate over the 30 day study).

Data from MRID 00067321 and MRID 00160166 

at other temperature and pH levels were used to 

interpolate a new estimate for the hydrolysis rate at 

pH 7 and 25o C.

Soil Photolysis half-life

(days) 

Stable (not used) 41270704

41568102

43833501

Aquatic photolysis halflife (days)

Stable 41270702

41568101

43833502

Aerobic soil metabolism 

half-life (days)

300 days (3 x single 

study value)

00160171 When compared to published values in the 

literature and field studies it appears this value 

might be high. Studies on additional soils would 

reduce the uncertainty regarding model input 

values.

Aerobic aquatic (water 

column) metabolism 

half-life (days)

TTR = 0

(insufficient data to 

accurately calculate 

TTR persistence)

Supplemental data:

Parent DT50 = 71 (low 

organic matter, pH = 

8.5)

Parent DT50 = 95 (high 

O.M., pH = 8)

Parent t1/2: 162 days 

44989502 This value set to a zero rate and a hydrolysis rate 

was used instead to account for the transformation 

rate in the pond.
23

Chemical name Model Input Value /

Additional Notes

MRID Reference / Comment

(upper 90% confidence 

interval of registrant 

study) (supplemental)

Anaerobic soil 

metabolism half-life

(days)

100 days (ultimately not 

used in modeling)

0016071

Anaerobic aquatic 

(benthic) metabolism 

half-life (days)

0 None In previous assessments was 50 days (no study 

conducted; 0.5 x anaerobic soil metabolism) 1

For this assessment the newly calculated hydrolysis 

rate was used to account for the transformation rate 

in the pond.

Koc / Kd / Kf 109

Kd: 2.1 L/kg in silt loam 

soil; Kads: 1.08-3.78

43778601 New value (previous modeling used a Kd) was 

determined to be appropriate for environmental fate 

modeling. Median Koc value used to account for 

one apparent outlier: Koc values of 43 (loamy sand, 

2.1% OC), 50 (Pond sediment, 4.3% OC), 109 

(sandy loam, 0.8% OC), 129 (silt loam, 0.7% OC), 

and 1652 (clay, 0.4% OC).

Application Rates 3 to 12 lb ai/ acre NA Rate determined by the maximum application rate 

allowed on the modeled crop site.

Application Efficiency 0.99 NA

Number of Applications 1 NA

Application Method Soil incorporated, 

broadcast (except hops)

NA

Incorporation Depth 

(cm) – except 

application to hops was 

not incorp.

5 NA 7 cm used for PRZM-GW modeling, which is only 

used for characterization purposes of potential 

contributions from groundwater when it impacts 

surface waters through lateral flow or use in 

irrigation.

IPSCND (post-harvest 

foliar pesticide 

disposition)

1

(Surface applied)

NA

Foliar degradation halflife (days)

0

(no data)

NA

1 Per EFED guidance document when no hydrolysis is assumed (version 2, 2/28/2002), the method used in previous EFED 

assessments). In the current assessment a hydrolysis rate was instead calculated\\

2 Data was selected per... (Add the guidance for selection of input parameters, current version is 2.1 an

Updated Information on Environmental Fate Studies

Hydrolysis

In an effort to provide more precise data for modeling (modeling of pesticide leaching to 

groundwater was particularly sensitive to this parameter) EFED utilized additional data sources 
24

for more precise calculation of modeling inputs for hydrolysis. 

A two-step process was used to estimate an ethoprop hydrolysis rate at pH 7 and 25 C, a standard 

input value generally used for EFED models. These calculations were based upon an earlier 

study submitted to the Agency (MRID 160166) with hydrolysis rates calculated in pH 3, 6, and 9 

buffered solutions incubated at 20o C and 35o C.

The first step was to calculate a Q10 value (the factor by which the rate of a 

reaction increases for every 10‐degree rise in the temperature) for pH 7 waters based upon the 

measured values at pH 3, 6, aqnd 9 at the two temperatures - the results of which are shown in 

Figure 1. The Q10 values for each pH were used to calculate an interpolated Q10 value for pH 7 

using the equation shown in Figure 1. 

The second step was to convert the measured hydrolysis rates / half-lives (assuming first-order kinetics) to 25o

C, these calculated values are plotted in Figure 2; a polynomial equation was used to interpolate an estimate 

for the hydrolysis half-life at pH 7 and 25o C (Figure 2). Observed and calculated values are summarized in 
25

Figure 1. Variance of ethoprop Q10 values with solution pH (from MRID 00160166).

y = 1.1511e0.0743x

R2 = 0.9999

0

0.5

1

1.5

2

2.5

0 2 4 6 8 10

Q10 Value

pH of Test System

Q10 Coefficient Calculation
26

Figure 2. Measured ethoprop hydrolys half-lives adjusted to 25o C and a fitted equation.

 

pH 7 Hydrolysis half-life 

(days)

150 41270703 

00067321

00160166 

Previous value was “stable”, derived as a default 

value from MRID 41270703 (not enough data to 

calculate a hydrolysis rate over the 30 day study).

Data from MRID 00067321 and MRID 00160166 

at other temperature and pH levels were used to 

interpolate a new estimate for the hydrolysis rate at 

pH 7 and 25o C.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/30/038/30038768.pdf

Table 4. Observed and calculated hydrolysis rates of ethoprop at different temperatures 

and pH conditions.

Source pH temp.

Measured 

T1/2, days k TC, days-1 T Kelvin

Q10 

calc.

Target 

Temp. 

C

Estimted

T 1/2, 

days 

@25 C

Degrad. 

Rate 

Adj. 

Factor

1.) 3 20 196 0.0035 293 1.44 25 163 0.8338

y = -8.4145x2 + 76.34x + 33.236

R2 = 0.9233

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10

Half-life, days

Test pH

Ethoprop Hydrolysis T 1/2 Values adjusted to 25 Celsius 
27

1.) 3 20 252 0.0028 293 1.44 25 210 0.8338

1.) 3 35 112 0.0062 308 1.44 25 161 1.4385

1.) 3 35 147 0.0047 308 1.44 25 211 1.4385

1.) 6 20 231 0.0030 293 1.80 25 172 0.7458

1.) 6 20 273 0.0025 293 1.80 25 204 0.7458

1.) 6 35 98 0.0071 308 1.80 25 176 1.7977

1.) 6 35 112 0.0062 308 1.80 25 201 1.7977

1.) 9 20 44.1 0.0157 293 2.25 25 29 0.6672

1.) 9 20 39.2 0.0177 293 2.25 25 26 0.6672

1.) 9 35 10.5 0.0660 308 2.25 25 24 2.2466

1.) 9 35 14 0.0495 308 2.25 25 31 2.2466

2.) 9 25 83 0.0084 298 2.25 25 83 1.0000

Calculated Half-lives Using Interpolated Q10 Value for 25 C

3.) 5 25 >>30 0.0034 298 1.67 25 205 1

3.) 7 25 >>30 0.0045 298 1.94 25 150 1

3.) 9 25 83 0.0178 298 2.25 25 39 1

Key:

1.) MRID 00160166.

2.) MRID 41270703.

3.) Temperature-adjusted hydrolysis values and predictions for pH 5, 7, and 9 at 

Soil Metabolism

Guideline data.

The results from the available aerobic soil metabolism study established a half-life of 100 days. 

At 252 days post-treatment, 24.8% of the applied radioactivity was not degraded ethoprop. The 

major degradate was CO2 (accounting for 53.9% of the applied radioactivity by the end of the 

study); the major nonvolatile degradates were identified as O-ethyl-S-methyl-Spropylphosphorodithioate (SME), O-ethyl-O-methyl-S-propylphosphorodithioate (OME), and Oethyl-S-propylphosphorothioate (OHE or M1), with the measured amount of each accounting for 

less than 4% of the applied, at every sampling interval. In addition, an anaerobic soil 

metabolism study showed a similar rate of degradation, with the half-life of approximately 100 

days. During the 56-day anaerobic incubation test, a total of 2.25% of the radioactivity had been 

volatilized, and 10.5% was remaining in the soil in an unextractable form. The degradates OME 

and OHE (M1) each accounted for less than 1% of the applied radiolabeled parent ethoprop.

An aerobic aquatic metabolism laboratory study was conducted with sediment/water systems. 
28

The reported data indicated a half-life value 75 days in the sand sediment/water system and a 

half-life of 90 days in the silt loam sediment/water system. Nonextractable residue amounts 

were reported, and in addition, specific degradates were analyzed. The degradates, OHE (M1) 

was identified as the degradate reported to be present at the greatest concentration, but it was 

never reported at greater than about 1% at any of the time intervals of analysis. 

Ancillary data.

Additional soil metabolism studies have been reported in the literature but these studies are not 

available for a full review as with the environmental fate studies submitted to fulfill Agency 

guidelines. A summary review of laboratory metabolism and field dissipation studies (include 

studies submitted to EPA and other published studies) by staff members of the ethoprop

registrant (Jones and Norris, 1998) covers most of the available data. Additional studies are 

referred to in some European regulatory documents. The following points are particularly 

relevant for comparison to the data available through the US regulatory process:

1. One European Food Safety Agency (EFSA) document7 reports the use of a 22.8-day halflife (normalized to 10kPa soil moisture and 20 C with a Q10 of 2.2 from fate data for 

modeling of ethoprop degradation when used to calculate regulatory endpoints for 

groundwater (page 58 of 72 in the report). This converts to a value of approximately 19

days at 25 C (EFED does not currently routinely calculate variations in degradation with 

the soil moisture level). There were a total of six aerobic soil metabolism studies with 

half-lives of 10 to 113 days (3 studies conducted at 20 C, 2 at 22 C, and 1 at 25 C – which 

was also the soil incubated at 25 C); see page 53 of the report. No information about the 

characteristics of the test soils was reported nor were study references provided. 

2. The recommended input for sorption modeling was a calculated mean Kfoc of 111 mL/g 

and a Freundlich 1/n exponent value of 0.89 (page 54).

Some European regulatory agency reviews are available online but the publicly available

documentation is limited. From these it has been determined that aerobic soil metabolism studies 

for 3 test soils have been submitted and reviewed by the Netherlands National Institute of Public 

Health and the Environment (RIVM)8

The studies used for calculation of the European regulatory agency environmental fate values 

 7

 EFSA Scientific Report (2006) 66, 1-72, Conclusion on the peer review of ethoprophos. Available at: 

http://www.efsa.europa.eu/en/efsajournal/doc/3089.pdf ; also available at: Also available at: 

http://www.fytoweb.fgov.be/NL/doc/EthoprophosEFSA.pdf

8 A “First Draft” review by Trijntje van der Velde-Koerts and Bernadette C. Ossendorp,

National Institute of Public Health and the Environment (RIVM), Bilthoven, The Netherlands is available at: 

http://www.fao.org/fileadmin/templates/agphome/documents/Pests_Pesticides/JMPR/Evaluation04/Ethopropos.pdf

An evaluation of ethoprop metabolism in three test soils is cited and reviewed:

Greenslade D, Ward J and Hopkins R. 1984. (14C)-Ethoprop: aerobic soil metabolism and rate of degradation. Hazleton Laboratories Europe, Ltd. Harrogate, North 

Yorkshire, UK. Report no. 3594-68/33. Provided by Bayer Crop Science AG, Monheim, Germany (Document No: R009121). Non-GLP. Unpublished.
29

have not been reviewed by the Agency. Nonetheless, these secondary sources do suggest that an 

additional conservative factor for the aerobic soil metabolism rate may not be needed in 

environmental fate modeling for ecological risk. Further refinement of the ecological risk 

assessment may be possible if additional laboratory metabolism studies are made available for 

Agency review.

Field Dissipation

A number of field dissipation studies have been conducted and submitted to support the 

registration of ethoprop. The reported half-lives are between 3 and 60 days (Table 5). These halflives were generally calculated for only the top soil layer sampled which was generally about 0 

to 6 inches. The difference in half-lives between laboratory and field studies may be partially due 

to leaching/runoff, as well as to the increased soil moisture and temperature in the field soils, 

which might result in increased microbial degradation and volatilization. These data suggest that 

ethoprop degradation may frequently be more rapid under field conditions than reported in the 

guideline laboratory soil metabolism studies but it is not possible to separate out the portion of 

dissipation attributable to degradation processes. 

Table 5. Summary of ethoprop field dissipation studies.

Study 

location

Soil Type 

or Series

Depth of 

Sample, 

ft.

Formulation Rate,

Lb ai / A or 

other

Reported 

dissipation 

half-life, 

days

Authors MRID

Hanover 

Co., VA

Sandy loam 0.5 Uk. 5 – 25 ppm <8 Boyd 

and 

Duval

00092040

NE Silt loam 0.25 EC 12 lb ai /A <3a Guyton 00160174

NJ Loamy sand 0.25 EC 12 lb ai /A <30a Guyton 00160174

MO Clay 0.25 EC 12 lb ai /A <30a Guyton 00160174

IL Silt loam 0.25 EC 12 lb ai /A <30a Guyton 00160174

IL Silty clay 

loam

0.25 EC 12 lb ai /A <30a Guyton 00160174

Madison, 

WI

? 0.5? G 1 lb ai/A <9 Davis 

and 

Boyd

00092033

York, NE ? 0.5? G 1 lb ai/A 7 - 30 Davis 

and 

Boyd

00092033

WI, NE, 

and MO

? 0.5? G 2 lb ai/A 7 – 36 b Davis 

and 

Boyd

00092033

Hanover 

Co., VA

Sandy loam 0.5? G 1 - 5 lb ai/A <21 Davis 

and 

Boyd

00092033

Hanover 

Co., VA

Sandy loam 0.5? G 10 - 50 lb 

ai/A

28 - 42 Davis 

and 

Boyd

00092033

FL Near 

Bradenton

0.5 G 12 lb ai/A 40 Norris 

(1987)

40470601

FL Near Lake 0.5 EC 12 lb ai/A 13 Norris 40470601
30

Study 

location

Soil Type 

or Series

Depth of 

Sample, 

ft.

Formulation Rate,

Lb ai / A or 

other

Reported 

dissipation 

half-life, 

days

Authors MRID

Hamilton (1987)

Suffolk 

Co., NY

(multiple 

sites)

Various 0.5? G 9 ai / A 17 - 60 Norris 

(1987)

40519901

NC Sand 

(Norfolk 

series; pH 

6.3, 1.4% 

OM)

0.5? EC, G 12 lb ai/A

(pre to 

potatoes)

8 - 10 Norris 

(1990)

41712401

WA Loamy sand 

(Timmerman 

series; pH 

6.3, 2%OM)

0.5? EC, G 11.8 lb ai/A

(pre to 

potatoes)

36 – 48 Norris 

(1990)

41712401

NC Sandy loam

(Norfolk 

series; 2.0% 

OM)

(turfed)

0.5 G 20 lb ai/A 18 Norris 

(1997)

44398001

NC Sandy loam

(Norfolk; 

2.2% OM)

(bare soil)

0.5 G 20 lb ai/A 13 Norris 

(1997)

44398001

FL Sand

(Fuquay 

series; 1.8% 

OM)

(turfed)

0.5 G 20 lb ai/A 10 Norris 

(1997)

44398001

FL Loamy sand

(Fuquay; 

1.2% OM)

(bare soil)

0.5 G 20 lb ai/A 12 Norris 

(1997)

44398001

a Significant leaching of residues occurred at these sites (up to 1.71 ppm detected at depths of up to 12 

inches.

b Although specific field dissipation half-lives were not calculated it is notable that residues in the top soil 

layer at 59 – 60 days were 1.3 to 1.4 ppm at NE, 0.2 – 0.7 ppm at MO, and 0.00 to 0.01 ppm at WI.

Adsorption / Desorption Studies

Ethoprop was determined to have Kf values of of 0.53 (loamy sand, 2.1% OC), 1.24 (Pond 

sediment, 4.3% OC), 0.51 (sandy loam, 0.8% OC), 0.53 (silt loam, 0.7% OC), and 4.12 (clay, 

0.4% OC) (MRID 43778601). The corresponding Koc values were: 43 (loamy sand, 2.1% OC), 

50 (Pond sediment, 4.3% OC), 109 (sandy loam, 0.8% OC), 129 (silt loam, 0.7% OC), and 1652 

(clay, 0.4% OC). Ethoprop is considered to be highly mobile in soil (see classification system of 

McCall, 1980). The low Kf values (except for the one clay, low organic carbon test soil)
31

determined from a batch equilibrium study (<1.3 in the other 4 test soils), suggests a limited 

potential for sorption to soil. Mobility information on OHE (M1) indicates that it also is highly 

mobile; however, the mobility of the other degradates (OME, SME, and S,Sdipropyl

phosphorodithioate [SSDP or M2]) is not known; however, the similarities in structure of these 

compared with parent ethoprop and OHE (M1) suggest that these other three degradates will all 

have similar, moderately low soil sorption values.

For ecological exposure modeling the median Koc value of 109 was used (taking the median 

rather than the mean of these values reduces an overwhelming dominance of a single high value 

which would occur in this case with the very high and possibly outlier Koc value for the clay 

soil). This is consistent with values used for representative modeling elsewhere (e.g., Koc = 111 

was used in EFSA, 2006 available at: http://www.efsa.europa.eu/en/efsajournal/doc/3089.pdf ).

Volatility

In a laboratory volatility study, the resulting volatiles comprised only a small amount of the 

applied dose, with parent ethoprop being about one quarter to one-half of the volatile 

components on day 7, the last day of sampling. The vapor pressure of ethoprop is moderate to 

high, depending on the classification scheme used (the vapor pressure is 3.5 x 10-4 mm to 8.3 x 

10-4 mm Hg at 25-26oC mm Hg; between 1 x 10-8 and 1 x 10-3 mm Hg is generally considered to 

be in the moderate range for pesticides), and it has a Henry’s Law Constant which is moderately 

low (1.5 x 10-7 atm m3/mol)9.

Measures of Exposure

Measures of Aquatic Exposure and Exposure Estimates

Screening-level EECs of ethoprop in surface water, pore water and sediment were generated 

based on maximum labeled use rates (Table 1). Simulations were conducted using the tier II 

surface water concentration calculator (SWCC). For agricultural and certain non-agricultural 

uses, exposure concentrations for surface ecological assessments are estimated based on EFED’s 

Tier II aquatic model PRZM/VVWM. A graphical user interface Surface Water Concentration 

Calculator (SWCC v.1.106, May 6, 2014), developed by the EPA, was used to facilitate inputting 

chemical and use specific parameters into the appropriate input files and chemical files, replacing 

the older PE5 shell (November 2006), which used PRZM3 and EXAMS. The SWCC estimates 

pesticide concentrations in water bodies that result from pesticide applications to land. The 

calculator was designed for regulatory applications as applied in the Office of Pesticide 

Programs, USEPA, as well as PMRA, Health Canada. The calculator uses the Pesticide Root 

Zone Model (PRZM v5.0+, May 6, 2014) and the Varying Volume Water Body Model (VVWM, 

May 6, 2014, a replacement for the older EXAMS model). The PRZM crop / use site scenario is 

the basic file which describes the local or regional climatological information, soil hydrology, 

soil characteristics, crop characteristics, and the pesticide properties necessary to determine 

 9 A vapor pressure of > 10-5 Torr is considered predictive of “intermediate to high volatility under field conditions”. See: 
32

pesticide loadings to surface water. This basic file constitutes the first part of the “exposure 

scenario.” It simulates the processes in the agricultural field, such as runoff and erosion, on a 

daily time step. The runoff and erosion flux output data from PRZM are used as chemical 

loadings to the VVWM, which simulates surface water, in order to predict the EECs. The 

VVWM is conceptually similar to the current EXAMS-based model in that both are 2-

compartment models driven by first-order processes. It simulates the USEPA standard water 

bodies (i.e., farm pond and/or index reservoir) but with greater efficiency and flexibility for 

incorporation into a user interface. The VVWM also allows for variations in water body volume 

on a daily basis due to runoff, precipitation, and evaporation. Temperature, wind speeds, and 

pesticide dissipation processes are also allowed to vary daily. EECs were determined using the 

standard pond scenario which describes a vulnerable surface waters scenario for the VVWM 

component of the modeling exercise (Table 6). 

Table 6. Estimated aquatic environmental concentrations for ethoprop for current uses (in 

ppb) using EFED standard pond and 1/10 year return frequency.

Crop Scenario

State

Rate; 

lb 

ai/A

Peak 4-

day

21-

day

60-

day

90-

day Yr overall PW_pk PW_21

corn MS 6.0 141.0 138.0 130.0 116.0 107.0 56.3 25.6 85.3 85.5

Sugarcane FL 4.0 58.1 57.2 53.7 49.6 47.6 27.2 8.9 36.7 36.6

Corn IL 6.0 47.1 46.4 44.2 39.8 37.4 18.1 11.5 37.9 39.6

Sugarcane LA 4.0 47.0 46.2 44.8 40.8 37.9 21.2 7.9 28.3 28.2

Corn OH 6.0 42.3 42.0 40.9 36.7 33.7 17.1 7.2 26.0 26.1

Cabbage FL 5.1 42.2 41.6 39.5 36.1 33.0 14.4 7.3 26.1 25.9

Corn NC 6.0 33.5 33.0 31.1 27.7 25.6 15.2 6.4 21.1 21.0

Potato ME 9.0 32.6 32.1 30.8 28.4 26.4 15.2 9.8 27.0 27.9

Snap 

beans OR 8.1 32.1 31.7 30.1 26.9 25.2 14.9 8.9 21.5 21.5

Cucumber FL 2.0 28.0 27.5 25.8 25.0 24.7 10.5 6.2 21.8 21.9

Corn PA 6.0 24.5 24.2 23.1 21.7 22.0 11.4 6.3 20.9 20.8

Tobacco NC 6.0 20.5 20.2 19.0 17.0 15.8 10.0 3.6 14.0 14.6

Sweet 

potato NC 3.9 17.7 17.5 16.5 14.7 13.5 7.2 4.7 10.9 10.9

Potato ID 12.0 13.2 13.0 12.2 10.8 10.0 5.4 3.9 7.8 7.8

Mint OR 6.0 6.0 5.9 5.6 4.9 4.6 2.6 2.0 3.7 3.7

Hop OR 3.0 4.9 4.8 4.5 4.1 3.8 2.4 1.3 3.3 3.3

Values are those estimated to be exceeded on average once every 10 years for the specified exposure designation 

PW_pk = Pore water peak exposure estimate.

PW_21 = Pore water 21-day exposure estimate.

SWCC model inputs for ethoprop follow those listed in Table 3, more information on model 

inputs and outputs is provided in “Appendix C: Aquatic Exposure Modeling selected Input and 

Output”. Note that the EECs provided reflect standard assumptions for drift from ground 
33

application for low-boom application (except for the sugarcane scenarios)10; sugarcane 

applications are all buried at a specified depth for the 20% granular formulation (EPA 

Registration # 5481-9042), which is a specific label for the sugarcane use only. All scenarios 

were run with both assumptions of no drift and the EFED default assumption of 1% drift for the 

standard farm pond from ground applications (potentially applicable to the uses of ethoprop EC 

formulations). Adding a drift assumption increased the EECs for each scenario by less than 5%. 

For all crops a single application at the maximum label rate was assumed to be applied one day 

before emergence. 

Comparison of Aquatic Exposure Estimates with Monitoring Data

Targeted retrospective ground and surface water monitoring studies have been submitted by the 

registrant and have been previously reviewed (see ethoprop (DP Barcodes 323344; 335734; 

295045; 295035; Memorandum dated 12/18/2007). The focus of both of the groundwater and 

surface water surveys was vulnerable drinking water supplies so the sampled water does not 

represent the most vulnerable waters for ecological exposure to many organisms. The highest 

surface water supply acute concentration was 0.22 ppb and the highest chronic (in terms of 

annual mean concentrations) was 0.018 ppb. The surface water results are further summarized in 

Table 7 and Table 8; see DP Barcode 323344 for additional details. Since these monitoring data 

do not represent the most vulnerable streams for ecological risk assessment, they were not used 

in the risk assessment. In the USGS National Water Quality assessment (NAWQA) monitoring 

program, ethoprop has been detected at up to 5.8 ppb (from Zollner Creek in the Willamette 

Basin of Oregon). 

Table 7. Representative hydrologic characteristics, estimated ethoprop usage intensity, and ethoprop

detection rates in monitored community water systems (CWS).

Watershed 

ID

Watershed 

Area

(acres)

% C & D 

hydrologic

Runoff 

Depth, 

in.

% 

Ethp.-

Crops

Ethoprop

lb / ws*

Acre

% 

Parent 

> 3 

ppt

% SME 

Detects > 

4 ppt

Jefferson, 

OR

1,141,478 49.3 0.10 0.5 0.0059 0.00 2.90

Ontario, OR 37,686,339 59.4 0.05 1.3 0.0032 0.00 1.45

Lodi, CA 1,320,278 59.8 0.33 0.3 0.0009 0.00 0.00

Franklin, LA 1,304,097 66.3 2.18 3.1 0.0097 0.81 57.26

Wilson, NC 150,166 27.1 0.54 5.8 0.0077 2.90 5.80

* ws = watershed

Source: MRID 48983801. 2006. Surface Water Monitoring for Residues of Ethoprophos in High Use 

Areas in the United States, Amended Report.

 10 Currently, the SWCC User Manual (USEPA/OPP 734F14001; 7/1/2014) states that a drift fraction of 0.01 is typical for ground spray applications. A more detailed 

guidance document now approved in EFED (see Memorandum “Guidance on Modeling Offsite Deposition of Pesticides via Spray Drift for Ecological and Drinking 

Water Assessments” 12/20/2014). In the December 2013 guidance a 0.011 spray drift fraction is recommended for low boom applications with a fine to medium 

/coarse drop size distribution from the nozzles. Given the nature of the restrictions on the ethoprop EC labels, a 1% drift assumption is still considered to be 

conservative for ethoprop aquatic exposure modeling.
34

Table 8. Raw water ethoprop and SME detection rates and maximum observed 

concentrations for the five monitored CWS.

Watershed Ethoprop

detection rate

SME Degradate 

Detection Rate

Ethoprop

Maximum , ppt

SME 

Maximum, ppt

Jefferson, OR 0.00% 0.00% 0.0 2.9

Ontario, OR 0.00% 1.45% 0.0 6.7

Lodi, CA 0.00% 0.00% 0.0 0.0

Franklin, LA 0.81% 57.26% 14.4 202.0

Wilson, NC 2.90% 5.80% 12.4 11.8

Concentrations are ng/L or parts per trillion.

SME = O-ethyl-S-methyl-S-propylphosphorodithioate; See table of parent and degradate 

structures in Appendix A.

Source: MRID 48983801. 2006. Surface Water Monitoring for Residues of Ethoprophos in High 

Use Areas in the United States, Amended Report.

Measures of Terrestrial Exposure

Terrestrial Residue Exposure Model (T-REX)

Terrestrial wildlife exposure estimates are typically calculated for birds and mammals by 

emphasizing the dietary exposure route of uptake of pesticide active ingredients. These 

exposures for birds are considered to be surrogates for exposures to terrestrial-phase amphibians 

and reptiles. For exposures to terrestrial organisms, such as birds and mammals, pesticide 

residues on food items are estimated based on the assumption that organisms are exposed to 

pesticide residues as a function of the pesticide use pattern. Ethoprop is predominantly applied

with ground incorporation methods reducing exposure to terrestrial taxa relative to foliar 

application. In order to estimate risk for granular or ground incorporated formulations, T-REX 

(v. 1.5.2; 03/22/2012) is able to calculate the LD50 ft-2 risk index values for the labeled uses. The 

assumed incorporation of these methods of application is 85%. Thus 15% of the chemical is

assumed to be available for consumption by both avian and mammalian taxa. The LD50 ft-2 value 

is calculated using a toxicity value (adjusted LD50) and the EEC (mg a.i. ft-2

) and is directly 

compared with the Agency’s levels-of-concern (LOCs). Consideration is given to different types 

of feeding strategies for mammals, including herbivores, insectivores and granivores. Dosebased exposures are estimated for three weight classes of birds (20 g, 100 g, and 1000 g) and 

three weight classes of mammals (15 g, 35 g, and 1000 g). The input parameters for the model 

are given in Table 9 and calculated EECs are given in Table 10, Table 11, and Table 12.
35

Table 9. Input parameters for the T-REX model for different uses for ethoprop.

Input Parameters Value Source

Single Application Rate (lb a.i./A)

Cucurbits (cucumbers) 1.95

Product 

labels

hops, nursery stock, sugar beets 3

sweet potato 3.9

sugarcane 4

sugarcane 4

cabbage 5.1

corn (field or sweet) 6

mint 6

tobacco 6

succulent (lima) beans 8.1

potatoes (East of the Mississippi) 9

potatoes (West of the Mississippi) 12

All Uses: 1 Product 

Number of Applications (Interval between labels

Applications, days)

Avian Oral LD50 4.21 mg/kg-bw (red winged blackbird, 63.6 g)

Avian Dietary LC50 33 mg/kg-diet (bobwhite)

Avian Repro NOEAC 0.95 ppm (bobwhite)

Mammal LD50 32.8 mg/kg-bw (rat)

Mammal NOAEC 2.3 mg/kg-diet (rat)

1 The foliar half-life did not influence the prediction of the terrestrial EECs for ethoprop because only one 

application of ethoprop is allowed per season, and thus the peak concentration occurs immediately after this 

single application before any dissipation occurs.

Bolded values indicate labels allow application of EC formulations
36

Table 10. Avian dose-based ethoprop EECs (mg/kg-bw) for three size classes of birds.

20 g "Small" Bird 100 gram "Medium" Bird 1000 gram "Large" Bird

Use 

(application 

rate lbs 

a.i./A)

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Hops, 

Nursery 

Stock, Sugar 

Beets (3)

1066 489 600 67 418 15 608 279 342 38 238 8 272 125 153 17 107 4

Sweet 

Potato (3.9) 1093 501 615 68 428 15 623 286 351 39 244 9 279 128 157 17 109 4

Mint (6) 1640 752 923 103 642 23 935 429 526 58 366 13 419 192 236 26 164 6

Potatoes 

(East of the 

Mississippi) 

(9)

2460 1128 1384 154 964 34 1403 643 789 88 549 19 628 288 353 39 246 9

Potatoes 

(West of 

Mississippi) 

(12)

3280 1503 1845 205 1285 46 1870 857 1052 117 733 26 837 384 471 52 328 12

Table 11. Mammalian dose-based ethoprop EECs (mg/kg-bw) for three size classes of mammals.
37

15 gram "Small" Mammal 35 gram "Medium" Mammal 1000 gram "Large" Mammal

Use 

(application 

rate lbs 

a.i./A)

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Hops, 

Nursery 

Stock, Sugar 

Beets (3)

892 409 502 56 350 12 617 283 347 39 242 9 143 66 80 9 56 2

Sweet 

Potato (3.9) 915 420 515 57 358 13 633 290 356 40 248 9 147 67 83 9 57 2

Mint (6) 1373 629 772 86 538 19 949 435 534 59 372 13 220 101 124 14 86 3

Potatoes 

(East of the 

Mississippi) 

(9)

2059 944 1158 129 807 29 1423 652 801 89 557 20 330 151 186 21 129 5

Potatoes 

(West of 

Mississippi) 

(12)

2746 1259 1545 172 1075 38 1898 870 1067 119 743 26 440 202 248 28 172 6
38

Table 12. Dietary based EECs (ppm) for application rates of ethoprop.

Use 

(application 

rate lbs 

a.i./A)

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Hops, 

Nursery 

Stock, 

Sugar Beets 

(3)

936 429 527 59 367

Sweet 

Potato (3.9) 960 440 540 60 376

Mint (6) 1440 660 810 90 564

Potatoes 

(East of the 

Mississippi) 

(9)

2160 990 1215 135 846

Potatoes 

(West of 

Mississippi) 

(12)

2880 1320 1620 180 1128
39

Runoff and Spray Drift to Terrestrial and Semi-Aquatic Plants

Exposure of non-target terrestrial and semi-aquatic (wetland) plant species is estimated using the 

TerrPlant (v. 1.2.2) model (release date: December 26, 2006). There were not any data available 

for terrestrial plants so TerrPlant was not used in this assessment.

Screening Tool for Inhalation Risk (STIR v. 1.0)

The Screening Tool for Inhalation Risk (STIR v.1.0, November 19, 2010) was used to calculate 

an upper bound estimate of exposure using ethoprop’s vapor pressure and molecular weight for 

vapor phase exposure as well as the maximum application rate and method of application for 

spray drift. STIR incorporates results from several toxicity studies including acute oral and 

inhalation rat toxicity endpoints obtained from the “six-pack” of core studies, which are a series 

of six guideline studies (including acute oral, acute inhalation, acute dermal contact, and others)

that are submitted to the Registration Division of the Office of Pesticide Programs for technical 

and formulated products of a pesticide (rat oral LD50 = 32.8 mg/kg bw, MRID 00078035 ; and

rat inhalation LC50 0.123 mg/L, MRID 00070060, respectively) as well as the most sensitive 

acute oral avian toxicity endpoint (house sparrow, Red winged blackbird, or the ring-necked 

pheasant (all LD50 4.21 mg/kg bw), MRID 40378401, 40378401 respectively). Based on the 

results of the STIR model (Appendix E), exposure through inhalation of spray drift or the vapor 

phase of ethoprop was not determined to be a potential pathway of concern for either avian or 

mammalian species on an acute exposure basis. The analysis of the inhalation route in STIR 

does not include aggregation with other exposure pathways, such as dietary, dermal, or drinking 

water, which may contribute to a total exposure that has a potential for effects to non-target 

animals. However, the Agency does consider the relative importance of other routes of exposure 

in situations where data indicate that pesticide exposures through other routes may be potentially 

significant contributors to wildlife risk (USEPA 2004). The risk characterization section (Section 

4.3), includes a discussion of the impact of consideration of other routes of exposure that have 

been identified as potentially important and the degree of certainty associated with screeninglevel risk assessment conclusions. Detailed information about STIR v.1.0, as well as the tool, can 

be found on EPA’s website (http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial).
40

Effects Characterization

Measures of effect are obtained from a suite of registrant-submitted guideline studies which were 

conducted with a limited number of surrogate test species described in previous assessments. 

The test species are not intended to be representative of the most sensitive species but rather 

were selected based on their ability to thrive under laboratory conditions. Toxicity testing 

reported in this risk assessment utilizes surrogate species to represent all freshwater fish (2000+) 

and bird (680+) species in the U.S. The ECOTOXicology database (ECOTOX), was searched in 

March 2013 to identify whether additional, more sensitive ecological effects data were available 

for ethoprop; however, no more useful data were identified (USEPA 2013).

The end points for acute and measures of effect used in this screening-level assessment are 

described in Appendix B. There was one new study submitted for avian reproduction that 

yielded a No Observable Effects Concentration that was not included in the previous assessments 

and risk characterizations. 

Aquatic Toxicity

Table 13 represents aquatic toxicity endpoints for ethoprop (EFED RED Chapter for Ethoprop, 

1998). For more information on the submitted studies please reference the previous EFED 

RED chapter (EPA 1998).

The only change since that assessment was the fish full life cycle test with sheepshead minnow 

(MRID 46315401) was upgraded from invalid to supplemental and is used as a toxicity 

endpoint in determining chronic risk quotients in this assessment. In this study, fertilized eggs 

(>24 to <48 hours old) were exposed to the test material at mean-measured concentrations were 

<0.22 (control), 1.2, 2.0, 3.7, 7.4, and 15 ppb a.i., respectively. The endpoints affected were 

weight of 4 week old F1 minnows with a 32 % reduction in weight at 3.7 μg a.i/L.

There were no sediment studies submitted for ethoprop for either freshwater or 

estuarine/marine environments. 

Table 13. Acute and chronic Toxicity endpoints for ethoprop.

Acute Freshwater Fish Tests

Species Study 

Type

Test 

Substance 

(Purity)

LC50

Toxicity Classification 

(MRID)

(μg 

a.i/L)1,2,3

(95% CL; 

slope)

Bluegill sunfish 

(Lepomis 

macrochirus)

96-hr, 

flowthrough

TGAI 

(99.7%) 300 Highly toxic (00160187), 

Acceptable
41

(230-400; 

N/A)

Goldfish 

(Carassius 

aruratus)

96-hr, 

flowthroughTechnical

13600

Slightly toxic 00780427)

(N/A; N/A)

Rainbow trout 

(Salmo 

gairdneri)

96-hr, 

flowthrough

TGAI 

(92%)

1020

Moderately toxic 

(GS0106001), 

Supplemental (N/A; N/A)

Rainbow trout 

(Salmo 

gairdneri)

96-hr, 

flowthrough

TGAI 

(92%)

1850

Moderately toxic 

(ZUOETHO1)

(N/A; N/A)

Rainbow trout 

(Salmo 

gairdneri)

96-hr, 

flowthroughTechnical

13800

Slightly toxic (0072042) (N/A; N/A)

Bluegill sunfish 

(Lepomis 

macrochirus)

96-hr, 

flowthroughTechnical

2070

Moderately toxic 

(0078042) (N/A; N/A)

Rainbow trout 

(Salmo 

gairdneri)

96-hr, 

flowthrough

TGAI 

(92%)

1150

Highly to moderately toxic 

(40378201) (425-3000; 

N/A)

Chronic Freshwater Fish Tests

Species Study 

Type

Test 

Substance 

(Purity)

NOAEC; Endpoints

LOAEC (MRID)

(μg a.i/L) 1,2

Fathead minnow 

Pimephales 

promelas

32-d 

Early 

Life 

Stage

Not 

specified 24; 54

Growth

40650102, Supplemental

Acute Freshwater Invertebrate Tests

EC50
42

Study 

Type

Test 

Substance 

(Purity)

(μg a.i/L)1,2

Toxicity Classification 

(MRID) (95% CL; 

slope)

Water flea 

(Daphnia 

magna)

48-hr, 

static

TGAI 

(99.7%)

93 Very Highly toxic 

(00160188), Acceptable (56-180)

48-hr, 

flowthrough

TGAI 

(96.8%)

42.3 Very highly toxic

(31.1-51.7; 

4.9) (00068325), Acceptable

Chronic Freshwater Invertebrate Tests

Species Study 

Type

Test 

Substance 

(Purity)

NOAEC; 

LOAEC Endpoints

(μg a.i/L) 1,2 (MRID)

Water flea

21-day 

Life 

Cycle 

TGAI 

(96.8%) 0.8; 2.4 Length (438774-01), 

Acceptable

(Daphnia 

magna)

Water flea

21-day 

Life 

Cycle 

TGAI 

(96.8%) 2.4; 5.4 Supplemental/Reproduction 

(406501-01) (Daphnia 

magna)

Acute Estuarine/Marine Fish Tests

Species Study 

Type

Test 

Substance 

(Purity)

EC50

Toxicity Classification 

(MRID) (μg 

a.i/L)1,2,3

(95% CL; 

slope)

Sheepshead 

minnow 

(Cyprinodon 

variegatus)

96-hour, 

flowthrough

TGAI 

(96.8%)

958

Highly toxic, survival 

(436863-01), Acceptable (761– 1145; 

0.34)

Sheepshead 

minnow 

(Cyprinodon 

variegatus)

96-hour, 

flowthrough

TGAI 

(95%)

180

Highly toxic, survival 

00066341) Supplemental (85-390; 

NA)

Pinfish 

(Lagodon 

rhomboides)

96-hour, 

flowthrough

TGAI 

(95%)

6.3

Very highly toxic, survival 

(40228401), Acceptable (4.8-8.4; 

NA)

740
43

Sheepshead 

minnow 

(Cyprinodon 

variegatus)

96-hour, 

flowthrough

TGAI 

(96.8%)

(505-1070; 

NA)

Highly toxic, survival 

(00066341), Supplemental

Spot 

(Leiostomus 

xanthurus)

96-hour, 

flowthrough

TGAI 

(95%)

33

Very highly toxic, survival 

(40228401), Supplemental (0-48; NA)

Chronic Estuarine/Marine Fish Tests

Species Study 

Type

Test 

Substance 

(Purity)

NOAEC; 

LOAEC Endpoints

(μg a.i/L)1,2 (MRID)

Sheepshead 

minnow 

(Cyprinodon 

variegatus)

29-d 

Early 

Life 

Stage

TGAI 

(96.8%) 5.9; 11 Length, Wet Weight 

(444721-01), Acceptable

Sheepshead 

minnow 

(Cyprinodon 

variegatus)

29-d 

Early 

Life 

Stage

TGAI 

(95%) 12;21

Mortality of embryos and 

juveniles (00066341), 

Supplemental

Sheepshead 

minnow 

(Cyprinodon 

variegatus)

Full life 

cycle

TGAI 

(94.8%) 2;3.7 Growth (46315401), Supplemental

Acute Estuarine/Marine Invertebrate Tests

Species Study 

Type

Test 

Substance 

(Purity)

EC50

Toxicity Classification 

(MRID)

(μg 

a.i/L)1,2,3

(95% CL; 

slope)

Eastern oyster 96-hour, 

flowthrough

TGAI 

(98.7%)

3700

Moderately toxic (436863-

02) Acceptable Crassostrea 

virginica

(1100 –

1900; 5.44)

Eastern oyster 96-hour, 

flowthrough

TGAI 

(95%)

14900

Slightly toxic (00066341) 

Acceptable Crassostrea 

virginica (N/A;N/A)

Saltwater mysid 96-hour, 

flowthrough

TGAI 

(96.7%)

18.78

Very highly toxic (436863-

03) Acceptable Americamysis 

bahia

(15-22– 45; 

16.13)

Saltwater mysid 96-hour, 

flowthrough

TGAI 

(95%)

7.5

Very highly toxic 

(40228401) Supplemental Americamysis 

bahia (N/A;N/A)

Grass Shrimp 96-hour, 

flowthroughTechnical

56.4

Very highly toxic 

(40048779) Supplemental Palaemonetes 

vulgaris (N/A;N/A)
44

Fiddler Crab 96-hour, 

flowthroughTechnical

1600 Moderately toxic 

Uce pugilator (40048779) Supplemental (N/A;N/A)

White Shrimp 96-hour, 

flowthrough

TGAI 

(95%)

6.4

Very highly toxic 

(40228401) supplemental Penaeus 

stylirostris (N/A;N/A)

Sand Shrimp 96-hour, 

flowthrough

TGAI 

(98.9%)

<1000

Highly toxic (00092111) 

supplemental Crangon 

septemspinosa (N/A;N/A)

Pink shrimp 96-hour, 

flowthrough

TGAI 

(95%)

13

Very highly toxic 

(40228401) supplemental Panaeus 

duorarum

(1100 –

1900; 5.44)

Blue crab 96-hour, 

flowthrough

TGAI 

(98.9%)

<1000

Highly toxic (00092111) 

supplemental Callinectes 

sapidus (N/A;N/A)

Saltwater mysid 96-hour, 

flowthrough

TGAI (95 

%)

23

Very highly toxic 

(00066341) Americamysis 

bahia (19 -27)

Chronic Estuarine/Marine Invertebrate Tests

Species Study 

Type

Test 

Substance 

(Purity)

NOAEC; 

LOAEC Endpoints

(μg a.i/L)1,2 (MRID)

Saltwater mysid 28-d 

Life 

Cycle 

TGAI 

(96.8%) 1.4 ; 2.7

Growth (Male length, Dry 

weight) (444575-01), 

Acceptable

Americamysis 

bahia

Saltwater mysid 28-d 

Life 

Cycle 

TGAI 95.0 

'%) 0.36 Growth, survival 

(00066341), Supplemental Americamysis 

bahia

Aquatic Plant Tests

Species Study 

Type

Test 

Substance 

(Purity)

EC50

Effect (MRID) (ug a.i./L)

(95% 

CL)1,2

Marine diatom

96-hr, 

static

TGAI 

(99.3%)

8400 (7600-

9000)

Cell density (402284-01)

Supplemental (Skeletonema 

costatum)
45

Terrestrial Toxicity

Table 14 represents terrestrial toxicity endpoints for ethoprop (EFED RED Chapter for 

Ethoprop, 1998). For more information on the submitted studies please reference the previous 

EFED RED chapter (EPA 1998).

At the time of the previous assessment, there were no chronic avian reproduction studies 

available for risk assessment. Since then there were two chronic reproduction tests submitted for 

ethoprop for bobwhite quail (MRID 47679601) and mallard duck (MRID 48956401). In the 

study with bobwhite quail, birds were exposed to mean measured treatment concentrations of 

0.952, 2.88, 5.67, and 11.1 mg ai/kg diet. There were no treatment-related effects on mortality, 

clinical signs of toxicity, or treatment-related abnormalities observed at necropsy. The most 

sensitive endpoints were eggs set, live 3-week embryos, hatchling survivors, and eggshell 

thickness, which showed adverse effects at all but the lowest treatment level during the exposure 

period. Only effects on eggshell thickness persisted during the withdrawal period, while this 

endpoint and the proportion of eggs set to eggs laid were impacted when the exposure and 

withdrawal periods were combined for analysis. While eggshell thickness was the most 

sensitive reproductive endpoint, numerous other reproductive endpoints were adversely affected 

at the highest treatment level before and after treatment, including eggs laid, eggs set, viable 

embryos, live 3-week embryos, number hatched, hatchling survivors, and the ratios of eggs set to 

eggs laid, live embryos to viable embryos, and number hatched to eggs laid. Reductions from 

control during treatment ranged from 26 to 35% at treatment levels of 2.88, 5.67, and 11.1 mg 

ai/kg diet levels. Statistically significant reductions in eggshell thickness ranged from 3% at the 

2.88 mg a.i/kg-diet treatment level to 6% at the highest treatment level.

The study with mallard duck assessed five month old mallard ducks over 22 weeks and 

administered a diet with mean measured concentrations of 0.96, 2.8, 9.5, and 37 mg ai/kg diet.

There was no treatment-related mortality during this test. The NOAEC was 9.5 mg ai/kg diet 

(mean-measured concentration) based on treatment-related effects on adult male and female 

weight gain, egg shell thickness, and percentage of eggs undamaged of eggs laid. Male and 

female weight decreased 6% and 5% respectively at the highest treatment level. There was an 

8% decrease in egg shell thickness at the highest treatment concentration and the percentage of 

eggs damaged per eggs laid increased by 70% over the controls. 

There are no terrestrial plant studies available for ethoprop. Ethoprop is an organophosphate 

nematicide/insecticide that inhibits the activity of the enzyme acetylocholinesterase causing 

toxicity in invertebrates and vertebrates and is not presumed to be toxic to plants. 

Terrestrial Toxicity Assessment

Table 14. Terrestrial toxicity endpoints for ethoprop.
46

Acute and Sub-acute Toxicity in Birds

Species Study Type

Test 

Substance 

(Purity)

LD50

(mg/kg bw) 

or

LC50

(mg/kg diet); 

(95% CI; 

slope)1,2

Toxicity 

Classification 

(MRID)

Acceptability

Coturnix quail

(Colinus 

virginianus)

Acute oral 

toxicity

TGAI 

(95.8%) 7.5 Highly toxic

(40378401) Supplemental

Rock dove 

(Columba 

livia)

Acute oral 

toxicity

TGAI 

(95.8%) 13.3

Highly toxic Supplemental

(40378401)

Mallard duck

(Anas 

platyrhynchos)

Acute oral 

toxicity

TGAI 

(95.8%)

12.6 Highly toxic 

(50083963) Acceptable

12.6 (10.6-15) Highly toxic

(05008363) Supplemental

61 (47-79) Highly toxic

(05008363) Acceptable

House 

Sparrow

(Passer 

domesticus)

Acute oral 

toxicity

TGAI 

(95.8%) 4.21

Very Highly 

Toxic

(40378401)

Supplemental

Red-Winged 

blackbird

(Agelaius 

phoeniceus)

Acute oral 

toxicity

TGAI 

(95.3%) 4.21

Very Highly 

Toxic

(40378401)

Supplemental

Starling

(Sturnus 

vulgaris)

Acute oral 

toxicity

TGAI 

(95.3%) 7.5

Very Highly 

Toxic

(40378401)

Supplemental

Ring-necked 

Pheasant 

(Phaianus 

colchicus)

Acute oral 

toxicity

TGAI 

(95.8%) 4.21

Very Highly 

Toxic

(00160000)

Supplemental

Domestic hen 

(Gallus 

domesticus)

Acute oral 

toxicity technical 5.62

Very Highly 

Toxic

000780838

Supplemental

Grackle

(Quiscalus 

quiscula)

Acute oral 

toxicity

TGAI 

(95.3%)

10.0 (5.62-

17.8)

Very Highly 

Toxic

(40378401)

Supplemental

Mallard duck 

(Anas 

platyrhynchos)

Subacute 

dietary 

toxicity

TGAI 

(95.3%) 10-d: = 550

Moderately 

toxic

(00022923)

Supplemental
47

Ringnecked 

pheasant

(Phasianus 

colchicus)

Subacute 

dietary 

toxicity

TGAI 

(95.8%)

118 (103-

134) 

Highly toxic

(00022923) Acceptable

Bobwhite quail 

(Colinus 

virginianus)

Subacute 

dietary 

toxicity

TGAI 

(95.8%) 33(27-40)

Very Highly 

Toxic

(00022923)

Acceptable

Mallard duck 

(Anas 

platyrhynchos)

Subacute 

dietary 

toxicity

TGAI 

(95.8%)

5-d LC50 = 

287 (215-382)

Highly Toxic

(00022923) Acceptable

Japanese Quail

Subacute 

dietary 

toxicity

TGAI 

(95.8%) 100 (85-117) Highly toxic

(00022923) Supplemental

Chronic Bird Toxicity Tests

Species Study Type

Test 

Substance 

(Purity)

NOAEC; 

LOAEC

(mg/kg diet)

Endpoints

(MRID) Classification

Northern 

bobwhite quail

Colinus 

virginianus

Chronic 

reproduction 

TGAI 

(96.2%) 0.95 ; 2.9

eggs set, live 

3-week 

embryos, 

hatchling 

survivors, and 

eggshell 

thickness 

(47679601)

Acceptable

Mallard duck 

(Anas 

platyrhynchos)

Chronic 

reproduction

TGAI 

(96.6%) 9.5 ; 37

14-d adult 

survivor 

weight gain, 

egg shell 

thickness, 

percentage 

undamaged 

eggs laid 

(48956401)

Acceptable

Acute and Chronic Mammal Toxicity Tests

Species Study Type

Acute Chronic

LD50

(mg/kg bw) Toxicity 

Classification 

(MRID)

NOAEC

(mg/kg diet)

NOAEL

(mg/kg 

bw/day)

Endpoints (MRID)

Norway rat 

(Rattus 

norvegicus)

Acute oral 

toxicity

14-d LD50 = 

32.8 mg a.i/kg 

bw

Highly toxic

(0078035)

NOAEC= 30 

ppm (2.3 

mg/kg/day)

LOAEL =

150 ppm (13 

mg/kg/day)

Reproduction and Growth

(419212-01) Supplemental
48

Acute Terrestrial Invertebrate Toxicity Tests

Species

Study Type

(TGAI or 

EP)

Test 

Substance 

(Purity)

LD50 (μg 

a.i./bee)

Toxicity 

Classification 

(MRID)

Acceptability

Honey bee 

(Apis 

mellifera)

Acute oral 

and contact 

toxicity

(TGAI) 2.58 (contact)

Moderately 

toxic Acceptable

00066220

Acute 

contact 

toxicity

(EP) 5.56 (contact) Moderately 

toxic 

(00043714)

Acceptable

Bolded values represent the lowest definitive toxicity endpoint and are used in risk estimation

Review of Incident Data 

The Ecological Incident Information System (EIIS), which is maintained by the Agency’s Office 

of Pesticide Programs, was searched to determine if ecological incidents have been reported for 

ethoprop. Incidents have been reported from the use of ethoprop and are in the EPA incident 

database, which was searched in June 2014. There are eight reported incidents with one incident 

reported as unlikely (Table 15). Reported incidents involved fish, birds and plants. EFED has 

not received any ecological effects data to corroborate possible impacts of ethoprop on plants. 

Two incidents of the 8 reported on ethoprop in the EIIS database involve effects on plants 

(potato). One incident with MOCAP EC and an application rate of 2 quarts/acre was an infurrow application that affected 3535 acres of potatoes. The other application was as a granular 

formulation with an application rate of 25 lbs / Acre that affected 15.6 acres. Other plant 

incidents involving organophosphates have likely been caused by joint application of other 

herbicides. For the OP terbufos, flumetsulam, an ALS-herbicide, was one of two herbicides 

applied along with terbufos. Terbufos and other OP insecticides increase the risk of plant injury 

in corn plants due to toxic effects of ALS-herbicides. Similar effects may occur in other crops. 

Terbufos labels provide warnings about the timing of application of terbufos and ALS-herbicides 

and similar recommendations may be needed for ethoprop. This interaction occurs because 

terbufos and ALS-herbicides are degraded by the same enzyme system; thus, the presence of 

terbufos may reduce the rate of degradation of the herbicide and allow it to accumulate in the 

plant to toxic levels.

Table 15. Summary of EIIS incidents as of June 2014.

Type 

(Quantity) Use Site Date Legality Certainty State Route of Exposure Year

American 

Robin (1) N/R 1-Jan81 Undetermined Probable FL Ingestion 1981
49

Fish (400) Tobacco

9-

May89

Registered 

Use Possible NC Runoff 1989

Eel, Bass, 

Mullet

Turf, 

golf 

course

3-

Aug92

Registered 

Use Probable SC Runoff 1992

Unknown 

fish

Turf, 

golf 

course

12-

Apr94Undetermined Probable LA Runoff 1994

Shad (200)

Turf, 

golf 

course

3-

Aug94

Registered 

use

Probable LA Runoff 1994

Canada 

goose (3) N/R

9-

Sep96Undetermined Highly 

Probable GA Ingestion 1996

Potato 

(3535 

acres)

Potato

19-

Jun03

Registered 

use

Probable NE Holt 2003

Potato 

(15.8 

acres)

Potato

17-

Aug03

Misuse 

(accidental) Probable ME Aroostook 2003

Four of the incidents involved registered uses, two incidents resulted from misuse of ethoprop 

and two incidents were of undetermined uses. Three of the eight incidents also correlated with 

excess rainfall promoting runoff of both granular and EC formulations. Unfortunately the 

database does not indicate how soon the fish were killed after ethoprop was applied. It is 

reasonable to assume that the concentrations of ethoprop that caused the kills were higher than 

those eventually measured at the sites. Fish kills at golf course sites are generally easier to 

document than in flowing open water systems which are typical of estuaries, due to the ease of 

close, oftentimes daily, monitoring. Recurring fish kills, even though these kills may not 

significantly reduce fish populations as a whole or even locally, may still, in themselves, be 

considered an adverse effect. There have not been any incidents reported other than with plants 

since the last assessment.

The American Bird Conservancy (ABC) Avian Incident Monitoring System (AIMS) was 

searched in June 2014 and returned three records of incidents associated with ethoprop totaling 

510 bird mortalities (ABC, 2014). The AIMS incidents seem to confirm claims that other 

incidents have occurred involving waterfowl, upland game birds, and songbirds (Stone, 1980).

A June 2014 search of the Incident Database System (IDS), maintained by OPP’s Information 

Technology and Resource Management Division (ITRMD), yielded one incident for ethoprop 

involving wildlife. This incident was associated with Chipco Mocap Brand 10G granular 

formulation (no longer registered) and was classified as minor.

A lack of reported incidents does not necessarily mean that such incidents have not occurred. In 

addition, incident reports for non-target plants and animals typically provide information on 

mortality events only. Reports for other adverse effects, such as reduced growth or impaired 

reproduction, are rarely received.
50

Risk Characterization and Description

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

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

(RQ) method is used to compare estimated exposure and measured toxicity values. The RQ 

method involves dividing EECs by point estimates of the most sensitive acute and chronic 

toxicity values. The resulting RQs are then compared to the Agency’s Levels of Concern (LOC) 

(USEPA 2004). These criteria are used to indicate when applications of ethoprop, as directed on 

the label, have the potential to cause adverse effects to non-target organisms.

Risk Estimation and Description

Non-target Aquatic Animals and Plants

Freshwater and Estuarine/Marine Fish

Ethoprop was classified as highly toxic to freshwater fish with a LC50 of 300 ug a.i./L (MRID 

00160187) and very highly toxic to estuarine/marine fish with and LC50 of 6.3 ug a.i./L (MRID 

R2043487). Both freshwater and estuarine/marine fish demonstrated sensitivity to ethoprop on a 

chronic basis as well with a NOAEC of 24 (MRID 40650102) and 2 ug a.i. /L (MRID 

46305401), respectively. For freshwater fish, the acute RQs for freshwater fish exceeded the 

acute listed species LOC in 9 of 16 scenarios and the chronic RQs exceeded the chronic LOC in 

10 of the 16 scenarios (Table 16). The acute RQs for freshwater fish ranged from 0.02 to 0.47

and the chronic RQs ranged from 0.17 to 4.83. For estuarine/marine fish both the acute and 

chronic RQs exceeded the LOCs in all 16 scenarios modeled. Estuarine/marine fish were 

markedly more sensitive to ethoprop than freshwater fish as indicated by acute RQs that ranged 

from 0.77 (greater than the non-listed species LOC of 0.5) to 22.38. The chronic RQs for ranged 

from 2.05 to 58 (Table 16). Both the acute and chronic RQs of freshwater and estuarine/marine 

fish suggest there is both acute and chronic risk concern over a broad range of uses of ethoprop. 

While the models have changed to generate environmental exposure since the last assessment, 

the conclusions of acute and chronic risk to freshwater and estuarine/marine fish remain largely 

the same. Risk to aquatic fish is also reflected in the 5 fish kill incidents involving ethoprop. 

The likelihood that ethoprop was responsible for the remaining three incidents, two from 

registered uses and a third incident that where the use was unspecified, were listed as probable in 

the EIIS report. 

The likelihood of adverse effects on aquatic organisms is increased by the fact that ethoprop can 

contaminate surface water via runoff for up to several months after application. Ethoprop will 

enter surface waters in both the dissolved form as well as bound to suspended and eroding 

materials as suggested by its water solubility and its partitioning, respectively. It appears that 

ethoprop can be persistent in surface water especially in water with low to moderate microbial 

activity and moderate acidity (less hydrolysis, see Figure 2) or where abundant alternative energy 
51

(carbon) sources are not available. In waters with short hydrological residence times (streams 

and rivers), its persistence is limited by the flow out of the system more so than by metabolism.

Table 16. Acute and chronic risk quotients for freshwater and estuarine/marine fish.

Peak 

EECs 

(ppb)

60-day 

Chronic 

EECs 

(ppb)

FW Fish 60day SW Fish 60day

State Crop Acute 

RQ

Chronic 

RQ

Acute 

RQ Chronic RQ

MS corn 141 116 0.5 4.8 22.4 58.0

FL Sugarcane 58.1 49.6 0.2 2.1 9.2 24.8

IL Corn 47.1 39.8 0.2 1.7 7.5 19.9

LA Sugarcane 47 40.8 0.2 1.7 7.5 20.4

OH Corn 42.3 36.7 0.1 1.5 6.7 18.4

FL Cabbage 42.16 36.125 0.1 1.5 6.7 18.1

NC Corn 33.5 27.7 0.1 1.2 5.3 13.9

ME Potato 32.55 28.35 0.1 1.2 5.2 14.2

OR Snap 

beans 32.13 26.865 0.1 1.1 5.1 13.4

FL Cucumber 27.95 24.96 0.1 1.0 4.4 12.5

PA Corn 24.5 21.7 0.1 0.9 3.9 10.9

NC Tobacco 20.5 17 0.1 0.7 3.3 8.5

NC Sweet 

potato

17.745 14.69 0.1 0.6 2.8 7.3

ID Potato 13.18 10.84 0.04 0.5 2.1 5.4

OR Mint 6.02 4.94 0.02 0.2 1.0 2.5

OR Hop 4.86 4.095 0.02 0.2 0.8 2.0

Bolded values represent LOC exceedances.

Freshwater and Estuarine/Marine Invertebrates

Ethoprop was classified as very highly toxic to freshwater invertebrates with a LC50 of 42.3 ug 

a.i./L (MRID 00068325) and very highly toxic to estuarine/marine invertebrates with and LC50

of 18.78 ug a.i./L (MRID 43686303). Both freshwater and estuarine/marine invertebrates 

demonstrated sensitivity to ethoprop on a chronic basis as well with a NOAEC of 0.8 (MRID 

443877401) and 0.36 ug a.i. /L (MRID 00066341), respectively. For freshwater invertebrates, 

the acute RQs exceeded the acute listed species LOC in all 16 scenarios and acute non-listed 

LOC (0.5) in 12 of 16 scenarios (Table 17). The acute RQs ranged from 0.1 to 3.3. The 

freshwater invertebrates chronic RQs also exceeded the LOC in all 16 scenarios ranging from 34
52

to 361. For estuarine/marine invertebrates both the acute and chronic RQs exceeded the LOCs in 

all 16 scenarios modeled. Estuarine/marine invertebrates acute RQs that ranged from 0.3 to 7.5

with 14 of 16 scenarios exceeding the non-listed species LOC and all scenarios exceeding the 

listed species LOC. The chronic RQs for estuarine/marine invertebrates for ranged from 5.7 to 

163 (Table 17). Both the acute and chronic RQs of freshwater and estuarine/marine

invertebrates suggest there is both acute and chronic risk concern over a broad range of uses of 

ethoprop. While the modeling has been refined since the last assessment, the conclusions of

acute and chronic risk to freshwater and estuarine/marine invertebrates remain largely the same. 

Environments that promote higher EECs, such as in water bodies with high residence times like 

those coastal regions with low tidal cycles (i.e. estuarine ecosystems where ethoprop is 

frequently used like Florida) will be particularly at risk.

Table 17. Acute and chronic risk quotients for freshwater and estuarine/marine invertebrates.

Peak 

EECs 

(ppb)

21-day 

Chronic 

EECs 

(ppb)

FW 

Invert 21 day SW 

Invert 21 day

State Crop Acute 

RQ

Chronic 

RQ

Acute 

RQ

Chronic 

RQ

MS corn 141 130 3.3 361.1 7.5 162.5

FL Sugarcane 58.1 53.7 1.4 149.2 3.1 67.1

IL Corn 47.1 44.2 1.1 122.8 2.5 55.3

LA Sugarcane 47 44.8 1.1 124.4 2.5 56.0

OH Corn 42.3 40.9 1.0 113.6 2.3 51.1

FL Cabbage 42.16 39.525 1.0 109.8 2.2 49.4

NC Corn 33.5 31.1 0.8 86.4 1.8 38.9

ME Potato 32.55 30.75 0.8 85.4 1.7 38.4

OR Snap 

beans 32.13 30.105 0.8 83.6 1.7 37.6

FL Cucumber 27.95 25.7725 0.7 71.6 1.5 32.2

PA Corn 24.5 23.1 0.6 64.2 1.3 28.9

NC Tobacco 20.5 19 0.5 52.8 1.1 23.8

NC Sweet 

potato

17.745 16.51 0.4 45.9 0.9 20.6

ID Potato 13.18 12.24 0.3 34.0 0.7 15.3

OR Mint 6.02 5.59 0.1 15.5 0.3 7.0

OR Hop 4.86 4.53 0.1 12.6 0.3 5.7

Bolded values represent LOC exceedances.

Benthic Invertebrates

Ethoprop is highly persistent in water and is capable of reaching water bodies. Modeled pore

water values were between 62% and 73% the modeled surface water values and water column 
53

exchange with pore waters suggest that benthic invertebrates would be exposed to ethoprop even 

if the chemical does not partition strongly to the sediment. 

Per the recent sediment toxicity guidance, acute and chronic risk to benthic invertebrates can be 

estimated in several ways depending on the availability of data. Due to lack of sediment data for 

ethoprop, acute RQs were based on the peak pore water concentration compared to the most 

sensitive water column EC or LC50 presented in the water column invertebrate section above.

Chronic RQs were estimated by comparing the 21-day pore water EEC to the most sensitive 

water column NOAEC presented in the water column invertebrate section above. 

Acute RQs ranged from 0.1 to 2.0 for freshwater sediment invertebrates and 0.2 to 4.5 for 

estuarine/marine sediment invertebrates and exceeded the acute listed species LOC (0.05) in all 

scenarios for both (Table 18). Chronic RQs exceeded the chronic LOCs as well and ranged from 

9.3 to 238 for freshwater invertebrates and from 4.6 to 107 (Table 18). Both the acute and 

chronic RQs of freshwater and estuarine/marine sediment dwelling invertebrates suggest there is 

both acute and chronic risk concern over a broad range of uses of ethoprop. While there is 

uncertainty in these estimates due to lack of data, it highlights the risk to multiple compartments 

within the water column should ethoprop enter water ways.

Table 18. Acute and chronic risk quotients for freshwater and estuarine/marine sediment dwelling 

invertebrates estimated from water column EC50/NOAEC and pore water concentrations (peak and 21-day).

4-day 

Sediment 

Peak 

EECs 

(ppb)

21-day 

Chronic 

Sediment 

EECs 

(ppb)

FW Sed Invert SW Invert

State Crop Acute 

RQ

Chronic 

RQ

Acute 

RQ

Chronic 

RQ

MS corn 85.3 85.5 2 237.5 4.5 106.9

FL Sugarcane 36.7 36.6 0.9 101.7 2 45.8

IL Corn 37.9 39.6 0.9 110 2 49.5

LA Sugarcane 28.3 28.2 0.7 78.3 1.5 35.3

OH Corn 26 26.1 0.6 72.5 1.4 32.6

FL Cabbage 26.1 25.9 0.6 72 1.4 32.4

NC Corn 21.1 21 0.5 58.3 1.1 26.3

ME Potato 27 27.9 0.6 77.5 1.4 34.9

OR Snap 

beans 21.5 21.5 0.5 59.6 1.1 26.8

FL Cucumber 21.8 21.9 0.5 60.9 1.2 27.4

PA Corn 20.9 20.8 0.5 57.8 1.1 26
54

NC Tobacco 14 14.6 0.3 40.6 0.7 18.3

NC Sweet 

potato

10.9 10.9 0.3 30.3 0.6 13.7

ID Potato 7.8 7.8 0.2 21.7 0.4 9.8

OR Mint 3.7 3.7 0.1 10.2 0.2 4.6

OR Hop 3.3 3.3 0.1 9.3 0.2 4.2

Bolded values represent LOC exceedances.

Aquatic Plants

There were not any LOC exceedances for aquatic plants based on the one study that was 

available for the saltwater diatom. There was not any data available for additional non-vascular 

plants or vascular plants. While there is uncertainty due to lack of additional data, the lack of 

exceedances is consistent with the mode of action of ethoprop that is not anticipated to affect 

plants. 

Non-target Terrestrial Animals and Plants

Ethoprop has granular applications. The LD50/ft2 value is used to estimate risk for granular 

formulations and row, banded, and in-furrow applications. Conceptually, an LD50 ft-2 is the 

amount of a pesticide estimated to kill 50% of exposed animals in each square foot of applied 

area. Although a square foot does not have defined ecological relevance, and any unit area could 

be used, risk presumably increases as the LD50/ft2 value increases. The LD50 ft-2 value is 

calculated using a toxicity value (adjusted LD50) and the EEC (mg ai. ft-2) and is directly

compared with the Agency’s levels-of-concern (LOCs). The LD50/ft2 was calculated assuming 

85 percent incorporation since labels specify that ethoprop granules need to be incorporated. 

LOCs were exceeded for every proposed use of ethoprop for both birds and mammals. For birds, 

the LD50/ft2 exceeded the acute non-listed LOC and ranged from 0.5 for large birds (1000 g) at 

the lowest application rate to 264.8 for small birds (20g) at the highest application rate. For 

mammals, the LD50/ft2 ranged from 0.1 for large mammals (1000g) at the lowest application rate 

to 17.3 for small mammals (15g) at the highest application rate. Despite an 85% incorporation, 

current uses of ethoprop result in risk to both birds and mammals for all proposed granular uses. 

The results are consistent with the conclusions from previous risk assessments for ethoprop

(Table 19).

Table 19 LD50 ft-2 risk quotients from granular and incorporated applications of ethoprop.

LD50 ft2 Analysis (85% incorporation)

Use (application rate lbs a.i./A)

Avian Mammal

20 g 100 g 1000 g 15 g 35 g 1000 g

Cucurbits (1.95) 43.0 6.8 0.5 2.8 1.5 0.1
55

Hops, Nursery Stock, Sugar 

Beets (3) 66.2 10.4 0.7 4.3 2.3 0.2

Sweet Potato (3.9) 86.1 13.5 1.0 5.6 3.0 0.2

Sugarcane (4) 88.3 13.9 1.0 5.8 3.1 0.2

Cabbage (5.1) 112.5 17.7 1.3 7.4 3.9 0.3

Corn, Tobacco (6) 132.4 20.8 1.5 8.7 4.6 0.4

Succulent (lima) beans (8.1) 178.7 28.1 2.0 11.7 6.2 0.5

Potatoes (East of the 

Mississippi) (9) 198.6 31.2 2.2 13.0 6.9 0.6

Potatoes (West of Mississippi) 

(12) 264.8 41.6 2.9 17.3 9.2 0.7
56

EC formulations with application from boom sprayers include 3 lb a.i./A application rates on 

hops, sugar beets and nursery stock, 3.9/4 lbs a.i./A on sweet potatoes, and 9 and 12 lbs a.i./A on 

potato. This application method may expose residual in-field weeds and flowering plants to 

residues of ethoprop that may be used as forage by birds and mammals. The lowest application 

rate of ethoprop resulted in LOC exceedances in almost every size class of birds and mammals 

from both acute and chronic exposure. There was one dietary item for chronic dietary exposure 

for mammals that did not exceed the LOC at the lowest application rate (3.0 lbs a.i./A). The RQ

for mammalian chronic exposure to seeds in the largest bird size class was 0.9 (Table 22). At the 

next lowest application rate (3.9 lbs a.i./A), all exposures for birds and mammals exceeded the 

acute and chronic LOCs. 

For the lowest application rate avian dose-based acute RQs ranged from 0.5 for seeds in the 

largest avian size class to 231.7 for short grass in the smallest avian size class. For the highest 

application rate, avian dose-based acute RQs ranged from 1.8 for seeds in the largest avian size 

class to 926.7 for short grass in the smallest avian size class. All exposure routes at every 

application rate exceeded the non-listed species acute LOC (Table 20). RQs for acute dietary 

exposures ranged from 1.4 to 21.8 for the lowest application rates and from 5.5 to 87.3 for the 

highest application rate. The RQs exceeded the non-listed species LOC for all exposure routes at 

every application rate (Table 21). RQs for avian chronic dietary exposure exceeded the LOC 

ranging from 47.3 for fruits/pods to 756.3 for short grass from the lowest application rates and 

from 189.1 to 3025.1 for the highest application rates. For the lowest application rate,

mammalian dose-based acute RQs ranged from 0.1 for seeds in the largest avian size class to 9.5 

for short grass in the smallest avian size class. All exposure routes exceeded the listed species 

acute LOC for the lowest application rate. Mammalian dose-based chronic RQs ranged from 0.9

to 135.8 and exceeded the chronic LOCs for all exposure routes except one (seeds for large 

mammals; Table 22) at the lowest application rate. At the highest application rate RQs ranged 

from 0.2 to 38.1 for dose-based acute exposure. Mammalian RQs for chronic dietary exposures 

varied from 1.0 to 15.7 for the lowest application rates and 24.5 to 62.6 at the highest application 

rates and exceeded the non-listed species LOC for all exposure routes (Table 23). Analysis of 

terrestrial application residues indicate that residues on all dietary items would remain in 

concentrations that exceed the chronic toxicity endpoints for birds longer than the 105 days 

that is model in T-REX at the lowest application rates. The same is true for mammals with 

the exception of the fruits/pods/seeds dietary item that has residues persisting for 

approximately 60 days before the concentration is lower than the mammalian chronic 

toxicity endpoints.

LOC exceedances from EC formulations are also well documented in the previous 

assessment (EPA 1998). If residues of ethoprop exist on dietary items they pose significant

acute and chronic risk concern for both birds and mammals at all current application rates

due to ethoprop’s high toxicity, high solubility in water and resistance to hydrolytic, 

photolyic and metabolic degradation in water and soil. All EC uses that have higher 

application rates would have higher RQs.
57

Table 20. Avian dose-based acute RQs

Small Medium Large

Use 

(applicat

ion rate 

lbs 

a.i./A)

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Hops, 

Nursery 

Stock, 

Sugar 

Beets 

(3)

231

.7

106

.2

130

.3

14.

5

90.

7 3.2 103

.8

47.

6

58.

4 6.5 40.

6

1.

4

32.

9

15.

1

18.

5

2.

1

12.

9

0.

5

Sweet 

potatoes 

(3.9)

308

.9

141

.6

173

.8

19.

3

121

.0 4.3 138

.4

63.

4

77.

8 8.6 54.

2

1.

9

43.

9

20.

1

24.

7

2.

7

17.

2

0.

6

Potatoes 

(12)

926

.7

424

.8

521

.3

57.

9

363

.0

12.

9

415

.1

190

.3

233

.5

25.

9

162

.6

5.

8

131

.6

60.

3

74.

0

8.

2

51.

5

1.

8

Acute listed species LOC = 0.1; Acute Restricted Use LOC = 0.2; Non-listed animals acute LOC = 0.5

Table 21. Avian dietary-based acute and chronic RQs.

Use (application rate lbs a.i./A)

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Acute

Hops, Nursery Stock, Sugar 

Beets (3) 21.8 10.0 12.3 1.4 8.5

Sweet potatoes (3.9) 29.1 13.3 16.4 1.8 11.4

Potatoes (12) 87.3 40.0 49.1 5.5 34.2

Chronic

Hops, Nursery Stock, Sugar 

Beets (3) 756.3 346.6 425.4 47.3 296.2

Sweet potatoes (3.9) 1008.4 462.2 567.2 63.0 395.0

Potatoes (12) 3025.2 1386.6 1701.7 189.1 1184.9

Chronic LOC = 1.0

Acute LOC = 0.5
58
59

Table 22. Mammalian dose-based acute and chronic RQs.

Small Medium Large

Use 

(application 

rate lbs 

a.i./A)

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Seeds

Acute

Hops, 

Nursery 

Stock, 

Sugar Beets 

(3)

9.5 4.4 5.4 0.6 3.7 0.1 8.1 3.7 4.6 0.5 3.2 0.1 4.4 2.0 2.5 0.3 1.7 0.1

Sweet 

potatoes 

(3.9)

12.7 5.8 7.1 0.8 5.0 0.2 10.8 5.0 6.1 0.7 4.2 0.2 5.8 2.7 3.3 0.4 2.3 0.1

Potatoes 

(12) 38.1 17.5 21.4 2.4 14.9 0.5 32.5 14.9 18.3 2.0 12.7 0.5 17.4 8.0 9.8 1.1 6.8 0.2

Chronic

Hops, 

Nursery 

Stock, 

Sugar Beets 

(3)

135.8 62.2 76.4 8.5 53.2 1.9 116.0 53.2 65.2 7.2 45.4 1.6 62.2 28.5 35.0 3.9 24.4 0.9

Sweet 

potatoes 

(3.9)

181.1 83.0 101.8 11.3 70.9 2.5 154.7 70.9 87.0 9.7 60.6 2.1 82.9 38.0 46.6 5.2 32.5 1.2

Potatoes 

(12) 543.2 249.0 305.5 33.9 212.8 7.5 464.0 212.7 261.0 29.0 181.7 6.4 248.7 114.0 139.9 15.5 97.4 3.5

Chronic LOC = 1.0

Acute listed species LOC = 0.1; Acute Restricted Use LOC = 0.2; Non-listed animals acute LOC = 0.5
60
61

Table 23. Mammalian dietary-based chronic RQs

Use (application rate lbs 

a.i./A)

Short Grass

Tall Grass

Broadleaf Plants

Fruits/pods

Arthropods

Hops, Nursery Stock, Sugar Beets 

(3) 15.7 7.2 8.8 1.0 6.1

Sweet potatoes (3.9) 20.9 9.6 11.7 1.3 8.2

Potatoes (12) 62.6 28.7 35.2 3.9 24.5

Chronic LOC = 1.0

Risk Characterization and Description from exposure to pollinators

Contact exposure to bees is expected to be very low from granular applications. There is 

uncertainty however about exposure to ground dwelling bees that may be exposed to ground 

applications. The EC formulation is registered with application from boom sprayers. Drift from 

the boom sprayers or residues that are not incorporated into the soil would pose high risk to 

pollinators that may come into direct contact or contact with residues. Using calculations 

(2.7*Application Rate÷Toxicity = Contact RQ) from Bee-Rex modeling within the pollinator 

guidance, the RQs for contact exposure are 2.0 and 12.5 for the lowest (1.95 lbs a.i./A) and 

highest (12 lbs a.i./A) application rates respectively, both significantly exceeding the established 

LOC of 0.4. There were not any acute oral studies for adult honey bees. Ethoprop is not a 

systemic pesticide so exposure through this route is presumed to be low. There were also not 

any acute or chronic toxicity studies submitted for larval bees or chronic oral studies for adult 

bees. Therefore, risks to terrestrial invertebrates is presumed, consistent with ethoprop’s mode of 

action and the demonstrated toxicity in the adult bee contact studies.

Terrestrial Plants

There is not any data on terrestrial plants so risk quotients could not be determined.

Risk description associated with consumption of earthworms

Ethoprop is incorporated into the soil whether it is applied as a granular or emulsified 

concentrate formulation. The physical and chemical characteristics of ethoprop suggest that it 

may partition to earthworms that may be consumed by either mammals or birds. In order to 

assess this possibility of pesticide exposure to terrestrial animals resulting from consumption of 

earthworms contaminated with pesticide mass present in the soil of the application site the EPA 

developed an earthworm fugacity model. A simple fugacity approach has been used to estimate 

concentrations of the pesticide in earthworms (Table 24). This model assumes the pesticide 
62

partitions between the soil, porewater and air within the soil and that worms are exposed to the 

pesticide through ingestion of the soil and birds and mammals are exposed through the ingestion 

of worms. The input parameters and example of the model can be found in Appendix F. 

Comparison of the EECs that are generated can be compared to toxicological endpoints to 

provide an estimate if there is potential risk. The endpoints used in the model are presented in 

Table 24.

Table 24. Soil EECs generated from uses of ethoprop from the earthworm fugacity model.

Earthworm EECs (g/Kg) in earthworm tissue consumed by either mammals or birds.

Use (application rate lbs a.i./A)

Mammal Avian

Acute 

dosebased

Chronic 

dosebased

Chronic 

dietary 

based

Acute 

dosebased

Acute 

dietary 

based

Chronic 

dietary 

based

Cucurbits (1.95) 0.05 0.05 1.16 0.42 1.16 1.16

Hops, Nursery Stock, Sugar 

Beets (3) 0.07 0.07 1.78 0.64 1.78 1.78

Sweet Potato (3.9) 0.09 0.09 2.31 0.84 2.31 2.31

Sugarcane (4) 0.09 0.09 2.37 0.86 2.37 2.37

Cabbage (5.1) 0.12 0.12 3.03 1.09 3.03 3.03

Corn, Mint, Tobacco (6) 0.14 0.14 3.56 1.29 3.56 3.56

Succulent (lima) beans (8.1) 0.19 0.19 4.81 1.74 4.81 4.81

Potatoes (East of the 

Mississippi) (9) 0.21 0.21 5.34 1.93 5.34 5.34

Potatoes (West of Mississippi) 

(12) 0.28 0.28 7.12 2.57 7.12 7.12

Table 25. Endpoints compared to EECs in earthworms generated by the earthworm 

fugacity model.

Endpoint

Toxicity 

Value 

Mammalian, acute 

dose-based

14.9 mg/kgbw

Mammalian, chronic 

dose-based

1.0 mg/kg-bw
63

Endpoint

Toxicity 

Value 

Mammalian, chronic 

dietary-based 46 mg/kg-diet

Avian, acute, dosebased

4.21 mg/kgbw

Avian, acute, dietarybased

33 mg/kg-diet

Avian, chronic, dietarybased

0.95 mg/kgdiet

Based on the EECs generated and the mammalian endpoints used in the T-REX model, risk to 

mammals consuming earthworms appears to be low for any of the uses and application rates of 

ethoprop to mammals either on an acute or chronic basis. The comparison of avian toxicity 

endpoints with EECs for birds does suggest that birds may be at risk from both acute dose and 

dietary based exposure as well as chronic dietary exposure. The toxicity of ethoprop to avian 

species and the propensity of ethoprop to partition to earthworm tissues suggest that this pathway 

is of both acute and chronic concern for those avian taxa consuming worms in fields treated with 

ethoprop at all nine application rates that ethoprop is registered under. 

Risk description through inhalation

Previous work with the organophosphate insecticides has shown that volatilization and microbial 

degradation increases as soil moisture content and temperature increases. The field dissipation 

rates are likely a result of microbial degradation, leaching, runoff, plus volatilization. STIR 

models with ethoprop indicate that risk through inhalation is not likely a concern when 

comparing the ratio of droplet inhalation dose to the adjusted inhalation dose (LD50) in the STIR 

model. The ratio for birds and mammals was predicted to be 3.8X 10-2 and 6.7X10-4 respectively 

indicating exposure is not likely significant. The majority of ethoprop labels additionally require 

immediate incorporation in the soil either by mechanical means or through immediate watering 

in of the chemical further reducing the risk through inhalation. Output of the STIR model is 

presented in Appendix E.

Risk from Drift to Aquatic Ecosystems

The current EC formulation label specifies that ethoprop should be used from a low boom with 

coarse droplet sizes. Table 26 presents the results of AgDrift modeling with finer droplet sizes 

on the distance from the edge of the treated field whereby effects to aquatic environments would 

not be expected (effects distance) using the most sensitive aquatic acute endpoint (6 ug a.i./L; 

MRID 00066341). As an example, very fine to fine droplet sizes results in an effects distance

from 3 to 33 feet from aquatic waterways and ponds, whereas coarse droplet sizes largely reduce
64

the risk of drift and the effects distance in all but the highest application rates. Under current 

restrictions, coarse droplet sizes from a low boom should minimize risk due to drift on 

neighboring aquatic ecosystems in all but the highest application rates.. It is important to note 

that risk would still be present in aquatic systems from runoff as reviewed in the aquatic RQs. 

The previous ecological risk assessment (EPA 1998) presents a more detailed discussion of the 

importance of reducing risk by reducing drift.

Table 26. Aquatic Effects Distance in feet from low boom applications.

Application Rate (lbs a.i/A)

Distance (in feet) from edge of field according to droplet size from low boom

Very fine to fine Fine to medium/coarse

1.95 0 0

3 0 0

6 3.28 0

8 9.84 0

9 16.4 0

12 32.81 3.28

Endocrine Disruptor Screening Program (EDSP)

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 cycles, sexual maturation, fertility, pregnancy rates, reproductive loss, and 

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

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

groups. As required by FFDCA section 408(p), ethoprop 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. 
65

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, 201311 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. 

Ethoprop is on List 1 for which EPA has received all of the required Tier 1 assay data. The 

Agency has reviewed all of the assay data received for the appropriate List 1 chemicals and the 

conclusions of those reviews are available in the chemical-specific public dockets (see EPA-HQOPP-2008-0560 for ethoprop).. For further information on the status of the EDSP, the policies 

and procedures, the lists of chemicals, future lists, the test guidelines and the Tier 1 screening 

battery, please visit our website.12

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

12 http://www.epa.gov/endo/
66

Federally Threatened and Endangered (Listed) Species of Concern

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

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

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

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

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

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

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

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

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

Endangered Species Act (ESA) and FIFRA. 

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

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

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

Evaluation Group (SFIREG) meetings, and held stakeholder workshops in April and October 

2014, allowing additional opportunities for stakeholders to comment on the Interim Approaches. 

As part of a phased, iterative process for developing the Interim Approaches, the agencies will 

also consider public comments on the Interim Approaches in connection with the development of 

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

contained in the white paper “Interim Approaches for National-Level Pesticide Endangered 

Species Act Assessments Based on the Recommendations of the National Academy of Sciences 

April 2013 Report,” dated November 1, 2013. 

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

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

designated critical habitat, this preliminary risk assessment for ethoprop does not contain a 

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

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

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

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

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

the application of ethoprop. This screening level assessment will allow EPA to focus its future 

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

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

assessment for ethoprop indicates potential risks of direct effects to listed mammals, birds, 

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

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

the potential for direct effects on listed and non-listed species upon which such species may rely. 

Potential direct effects on listed mammals, birds, terrestrial invertebrates, fish, and aquatic 

invertebrates from the use of ethoprop may be associated with modification of Primary 

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

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

necessary to complete risk assessments for endangered and threatened (listed) species and their 
67

designated critical habitats, these methods will be applied to subsequent analyses for ethoprop as 

part of completing this registration review. 

Conclusions

After reviewing the most recent environmental fate and effects data for ethoprop, the screeninglevel assessment concludes that registered uses of the pesticide may result in risk to both listed 

and non-listed species of aquatic and terrestrial animals and wildlife over a wide range of uses 

and through multiple exposure pathways. 

Acute and chronic risk to freshwater fish, estuarine/marine fish, freshwater invertebrates, and 

estuarine/marine invertebrates, and both freshwater and estuarine sediment invertebrates was

identified. Risk was not identified for aquatic plants based on one available diatom study and is 

consistent with the insecticidal mode of action of ethoprop. Some uncertainty exists in the 

impacts on aquatic plants, however, due to lack of a complete data set. LD50 analysis indicated 

that there is acute risk to both birds and mammals from granular formulations. Additional 

information from the registrants on mass of a.i. per granule and weight of one granule would 

help in defining how many granules would have to be consumed to be of concern for both birds 

and mammals. There was also acute dose based and acute dietary based risk as well as chronic 

dietary risk to birds associated with EC applications. Similarly, there was acute and chronic dose 

based risk as well as chronic dietary based risk to mammals from EC applications. Indirect routes 

of exposure may include consumption of contaminated earthworms in treated fields. Modeling 

indicated that there may be potential for acute avian risk from both dose-based and dietary 

exposure as well as chronic risk from dietary exposure through the consumption of earthworms. 

There was low potential for risk for mammals consuming contaminated earthworms. Ethoprop is 

slightly to moderately volatile but modeling suggests that inhalation is not a risk to either birds or 

mammals. While ethoprop is applied by boom sprayer, the coarse droplet size specified on 

current labels reduces risk to terrestrial and aquatic taxa through spray drift. 

As a pesticide, risk to terrestrial invertebrates is predicted. Bee-REX modeling confirmed if 

exposure occurs, pollinators foraging on fields during the time of application would also be at 

risk. Results of past assessments and current application practices are designed to limit exposure 

but exposure from residues on residual flowering plants or from spray drift is possible and would 

present a risk to pollinators and other beneficial insects. The overall risk conclusions for aquatic 

and terrestrial taxa broken down by each registered use of ethoprop are presented below in Table 

27 and Table 28 respectively. 

Collectively, for all registered uses of ethoprop, no risks to listed terrestrial plant species are 

anticipated but uncertainty exists due to lack of submitted data and the existence of two incidents 

in the EIIS database involving mortality to potato crops since the time of the last assessment. 

The conclusions of this assessment remain largely unchanged from previous assessments. 

Additional discussion of the risk is also presented in the 1998 assessment.
68

Table 27. Summary of adverse impacts for aquatic organisms expected from the registered uses of ethoprop.

Use 

(Application 

rate lbs a.i./A

Adverse Impacts Expected for Aquatic Organisms? (No/Yes: A = Acute, C=Chronic)

Freshwater 

Fish

Estuarine/Marine 

Fish

Freshwater 

Invertebrates

(Water 

Column)

Estuarine/

Marine 

Invertebrates

(Water 

Column)

Freshwater and 

Saltwater 

Benthic 

Invertebrates 

(Sediment)

Freshwater 

Benthic 

Invertebrates 

(Pore water)

Saltwater 

Benthic 

Invertebrates 

(Pore water)

Aquatic 

Plants

Cucurbits 

(1.95) YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No

Hops, Nursery 

Stock, Sugar 

Beets (3)

YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No

Sweet Potato 

(3.9) YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No

Sugarcane (4) YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No

Cabbage (5.1) YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No

Corn, Mint, 

Tobacco (6) YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No

Succulent 

(lima) beans YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No

Potatoes (East 

of the 

Mississippi (9)

YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No
69

Potatoes (West 

of the 

Mississippi (12)

YesA,C YesA,C YesA,C YesA,C No Data YesA,C YesA,C No
70

Table 28. Summary of adverse impacts for terrestrial organisms expected from the registered uses of ethoprop.

Use 

(Application 

rate lbs 

a.i./A

Adverse Impacts Expected for Terrestrial Organisms? (No/Yes: A = Acute, C=Chronic)

Birds Mammals Birds consuming 

earthworms

Mammals 

consuming 

earthworms

Terrestrial Plants Terrestrial

Invertebrates1

Birds and 

mammals 

through 

inhalation

Cucurbits 

(1.95) YesA,C YesA,C YesA No No data YesA,C No

Hops, 

Nursery 

Stock, Sugar 

Beets (3)

YesA,C YesA,C YesA No No data YesA,C No

Sweet Potato 

(3.9) YesA,C YesA,C YesA No No data YesA,C No

Sugarcane 

(4) YesA,C YesA,C YesA No No data YesA,C No

Cabbage 

(5.1) YesA,C YesA,C YesA, No No data YesA,C No

Corn, Mint, 

Tobacco (6) YesA,C YesA,C YesA No No data YesA,C No

Succulent 

(lima) beans YesA,C YesA,C YesA No No data YesA,C No
71

Use 

(Application 

rate lbs 

a.i./A

Adverse Impacts Expected for Terrestrial Organisms? (No/Yes: A = Acute, C=Chronic)

Birds Mammals Birds consuming 

earthworms

Mammals 

consuming 

earthworms

Terrestrial Plants Terrestrial

Invertebrates1

Birds and 

mammals 

through 

inhalation

Potatoes 

(East of the 

Mississippi 

(9)

YesA,C YesA,C YesA No No data YesA,C No

Potatoes 

(West of the 

Mississippi 

(12)

YesA,C YesA,C YesA No No data YesA,C No
72

Uncertainties, Limitations, and Identification of Data Gaps

Data Gaps and Uncertainties

Environmental Fate

The environmental fate database for ethoprop is complete enough to conduct a risk assessment 

but there are limitations in the database such that additional data might reduce uncertainties. 

Although a valid aerobic soil metabolism study (OCSPP Guideline no. 835.4100) has been 

submitted and previously accepted to fulfill data requirements, EFED currently requires four 

such studies for pesticides with significant outdoor uses and believes that submission of 

additional studies would reduce the uncertainty regarding the persistence of ethoprop in aerobic 

soil. For other environmental fate guideline studies additional data, while not required at this 

time, could reduce uncertainties in the risk assessment: (1.) An extended hydrolysis study (EFED 

has relied on an early study at elevated temperatures to extrapolate a value for modeling input 

since the study accepted under Guideline no. 835.2120 did show enough hydrolysis to calculate a 

rate in the standard 30-day study). Results of the hydrolysis studies are significant for aquatic 

exposure modeling, especially for groundwater that could impact surface waters during interflow 

periods or affect terrestrial organisms when used for irrigation. (2.) An anaerobic aquatic study 

(Guideline no. 835.4400) has been waived, but submission of such a study could potentially 

reduce uncertainty in aquatic exposure assessments. 

Ecological Effects

There are a number of areas of uncertainty in the aquatic and terrestrial risk assessments. The 

toxicity assessment for terrestrial and aquatic plants and animals is limited by the number of 

species tested in the available toxicity studies. Use of toxicity data on representative species 

does not provide information on the potential variability in susceptibility to acute and chronic 

exposures. 

For each registered use, the risk assessment is based on the maximum application rate on the 

registered label. The frequency at which actual uses approach these maximum scenarios is 

dependent on the resistance to the pesticide, the timing of applications, and market forces. 

Exposure and risks could be overestimated if the actual application rates, frequency of 

application, or number of applications are lower than the input parameters used for the 

conservative exposure scenario that was modeled. However, if there are conditions under which 

there is more than one growing season for a crop within a single year, exposure estimates and 

risk to aquatic and terrestrial organisms could be significantly underestimated. 

Terrestrial Exposure Assessment

The exposure assessment for terrestrial organisms in this risk assessment relies on the best 

available estimates of environmental fate and physicochemical properties, maximum application 
73

rate of ethoprop, maximum number of applications, and the shortest interval between 

applications. However, several uncertainties and model limitations are noted and should be 

considered in interpreting the results of this terrestrial risk assessment.

When effects data are available, dose-based and dietary-based acute RQs should be provided to 

risk managers. The dose-based approach assumes that the uptake and absorption kinetics of a 

gavage toxicity study approximate the absorption associated with uptake from a dietary matrix. 

Toxic response is a function of duration and intensity of exposure. Absorption kinetics across the 

gut and enzymatic activation/deactivation of a toxicant may be important and are likely variable 

across chemicals and species. For many compounds, a gavage dose represents a very short-term, 

high intensity exposure, whereas dietary exposure may involve a more prolonged exposure period. 

The dietary-based approach assumes that animals in the field are consuming food at a rate similar 

to that of confined laboratory animals. Energy content in food items differs between the field and 

the laboratory as do the energy requirements of wild and captive animals. The Wildlife Exposure 

Factors Handbook can provide insights into energy requirements of animals in the wild as well as 

energy content of their diets (USEPA, 1993).

The typical 21-week avian reproduction study does not define the true exposure duration needed 

to elicit the observed responses. The study protocol was designed to establish a steady-state tissue 

concentration for bioaccumulative compounds. For other pesticides, it is entirely possible that 

steady-state tissue concentrations are achieved earlier than the 21-week exposure period. 

Moreover, pesticides may exert effects at critical periods of the reproduction cycle; therefore, longterm exposure may not be necessary to elicit the effect observed in the 21-week protocol. The 

EFED screening-level risk assessment uses the single-day maximum estimated EEC as a 

conservative approach. The degree to which this exposure is conservative cannot be determined 

by the existing reproduction study.

In the risk assessment, RQs were only calculated for the most sensitive dietary class relevant to 

the organisms assessed. For most organisms, not enough data is available to conclude that birds 

or mammals may not exclusively feed on a dietary class for at least some time period. However, 

most birds and mammals consume a variety of dietary items and thus the RQ will overestimate 

risk to those organisms. Additionally, some organisms will not feed on all of the dietary classes. 

For example, many amphibians would only consume insects and not any plant material.

• Other General Uncertainties for Screening Risk Assessments

Routes of Exposure

The screening assessment does not consider ethoprop dermal exposure to terrestrial organisms. 

The Agency is actively pursuing modeling techniques to account for dermal exposure via direct 

application of spray and by incidental contact with contaminated vegetation, soil and water.

Age Class and Sensitivity of Effects Thresholds 
74

It is generally recognized that test organism age may have a significant impact on the observed 

sensitivity to a toxicant. The screening risk assessment acute toxicity data for fish are collected 

on juvenile fish and aquatic invertebrate acute testing is performed on recommended immature 

age classes. Similarly, acute dietary testing with birds is also performed on juveniles, with 

mallard being 5-10 days old and quail at 10-14 days of age. 

Testing of juveniles may overestimate the toxicity of direct acting pesticides in adults. As 

juvenile organisms do not have fully developed metabolic systems, they may not possess the 

ability to transform and detoxify xenobiotics equivalent to the older/adult organism. The 

screening risk assessment has no current provisions for a generally applied method that accounts 

for this uncertainty. In so far as the available toxicity data may provide ranges of sensitivity 

information with respect to age class, the risk assessment uses the most sensitive life-stage 

information as the conservative screening endpoint.

Lack of Effects Data for Amphibians and Reptiles 

Currently, toxicity studies on amphibians and reptiles are not required for pesticide registration. 

Since these data are lacking, the Agency uses fish as surrogates for aquatic phase amphibians and 

birds as surrogates for terrestrial phase amphibians and reptiles. If other species are more or less 

sensitive to ethoprop than the surrogates, risks may be under- or overestimated, respectively. The 

Agency is not limited to a base set of surrogate toxicity information in establishing risk 

assessment conclusions. The Agency also considers toxicity data on non-standard test species 

when available. Further research is needed to determine whether, in general, reptiles and 

terrestrial-phase amphibians are suitably represented by bird species in assessing risks for 

ethoprop and fish are an appropriate surrogate for aquatic-phase amphibians. 

Use of the Most Sensitive Species Tested 

Although the screening risk assessment relies on a selected toxicity endpoint from the most 

sensitive species tested, it does not necessarily mean that the selected toxicity endpoints reflect 

sensitivity of the most sensitive species existing in a given environment. The relative position of 

the most sensitive species tested in the distribution of all possible species is a function of the 

overall variability among species to a particular chemical. The relationship between the 

sensitivity of the most sensitive tested species versus wild species (including listed species) is 

unknown and a source of significant uncertainty. In addition, in the case of listed species, there is 

uncertainty regarding the relationship of the listed species' sensitivity and the most sensitive 

species tested. 

Sublethal Effects

When assessing acute risk, the screening risk assessment relies on the acute mortality endpoint as 

well as a suite of sublethal responses to the pesticide, as determined by the testing of species 

response to chronic exposure conditions and subsequent chronic risk assessment. Consideration 

of additional sublethal data in the effects determination is exercised on a case-by-case basis and 

only after careful consideration of the nature of the sublethal effect measured and the extent and 
75

quality of available data to support establishing a plausible relationship between the measure of 

effect (sublethal endpoint) and the assessment endpoints. However, the full suite of sublethal 

effects from valid open literature studies is considered for the characterization purposes.

To the extent to which sublethal effects are not considered in this assessment, the potential direct 

and indirect effects of ethoprop on listed species may be underestimated.

Ecological Effects Data Gaps

The ecological effects data profile for ethoprop is essentially complete as indicated by the 

problem formulation and the last assessment. For this assessment, an avian reproduction study 

was received and incorporated into the assessment. There is not any terrestrial plant data for 

ethoprop. Other assessments with organophosphates have required aquatic and terrestrial plant 

studies (e.g. chlorethoxyfos) but the mode of action of organophosphates is not anticipated to 

impact plants. However, two adverse incidents to plants have been reported for ethoprop, so 

plant data on vegetative vigor and seedling emergence would be informative to examine if future 

incidents would be anticipated. There are also not any sediment invertebrate toxicity tests. 

Given the mode of action of ethoprop and its very high toxicity to other aquatic taxa, both fish 

and invertebrates, risk to sediment fauna is presumed. Additional data on sediment invertebrates 

would likely not change any risk conclusions or provide any additional insights as to the risk 

posed to aquatic ecosystems. Similarly there are also not any larval honey bee or chronic adult 

honey bee toxicity tests. As an insecticide, risk to insects is presumed from use of ethoprop and 

risk can only be minimized by eliminating exposure to the insecticide (e.g. current ground 

incorporation requirements.)
76

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 Bibliography of Ecological Effect and Environmental Fate Guideline Studies

MRID/Accession Studies for Ecological Data:

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) 

00048779 Vilkas, A.G. (1977) Acute Toxicity of Mocap to the Grass Shrimp, 

Palaemonetes pugio, and Fiddler Crab, Uca pugilator: UCES Project # 11506-05-04. 

(Unpublished study received Jul 15, 1977 under 2224-43; prepared by Union Carbide 

Corp., submitted by Mobil Chemical Co., Industrial Chemicals Div., Richmond, Va.; 

CDL:230885-H) 

00068325 Vilkas, A.G. (1977) Acute Toxicity of Ethoprop to the Water Flea, Daphnia magna 

Straus: UCES Proj. #1506-05-03. (Unpublished study received Aug 16, 1977 under 2224-44; 

prepared by Union Carbide Corp., submitted by Mobil Chemical Co., Industrial Chemicals 

Div., Richmond, Va.; CDL:231370-B) 

00066220 Atkins, E.; Anderson, L.; Kellum, D.; et al. (1977) Protecting Honey Bees from 

Pesticides. Riverside, CA: Univ. of California. (Leaflet 2883; also In unpublished submission 

received Nov 2, 1983 under 239-2507; submitted by Chevron Chemical Co., Richmond, CA; 

CDL:251760-B) (Study is duplicate of MRID# 00132710) 

00078038 Weir, R.J.; Clark, O. (1966) Acute Oral LD50 -- Hens: Project No. 230-108. 

(Unpublished study received Nov 25, 1968 under 9F0750; prepared by Hazleton Laboratories, 

Inc., submitted by Mobil Chemical Co., Macedon, N.Y.; CDL:091295-F) 

00078042 Weir, R.J. (1967) Final Report: Acute Aqueous Exposure--Goldfish, Bluegill, and 

Rainbow Trout: Project No. 230-111. (Unpublished study received Nov 25, 1968 under 

9F0750; prepared by Hazleton Laboratories, Inc., submitted by Mobil Chemical Co., Macedon, 

N.Y.; CDL:091295-J) 

00092147 Fink, R.; Beavers, J.B.; Brown, R. (1978) Final Report: Acute Oral LD50 -Mallard 

Duck: Ethoprop Technical: Project No. 155-104. (Unpublished study received Jan 4, 1979 under 

2224-54; prepared by Wildlife International, Ltd., submitted by Mobil Chemical Co., Industrial 

Chemicals Div., Richmond, Va.; CDL:236710-C) 

00160000 Hudson, R.; Tucker, R.; Haegele, M. (1984) Handbook of toxicity of 

pesticides to wildlife: Second edition. US Fish and Wildlife Service: Resource 

Publication 153. 91 p. 
80

60187 Swigert, J.; Bowman, J. (1986) Acute Toxicity of Ethoprop to Blue-gill Sunfish 

(Lepomis macrochirus): Static Acute Toxicity Report #34319. Unpublished study 

prepared by Analytical Bio-Chemistry Laboratories, Inc. 53p 

00160188 Forbis, A.; Frazier, S.; Schoen, L. (1986) Acute Toxicity of Ethoprop 

Technical to Daphnia magna: Static Acute Toxicity Report #34320. Unpublished study 

prepared by Analytical Bio-Chemistry Laboratories, Inc. 38 p. 

05008363 Hudson, R.H.; Haegele, M.A.; Tucker, R.K. (1979) Acute oral and 

percutaneous toxicity of pesticides to mallards: correlations with mammalian toxicity 

data. Toxicology and Applied Pharmacology 47(3):451-460. 

40228401 Mayer, F.; Ellersieck, M. (1986) Manual of Acute Toxicity: Interpretation 

and Data Base for 410 Chemicals and 66 Species of Freshwater Animals. US Fish & 

Wildlife Service, Resource Publication 160. 579 p. (Study is duplicate of MRID# 

40098001) 

40378401 Schafer, E.W.; Brunton, R.B. 1979. Indicator bird species for toxicity 

determinations: Is the technique usable in test method development? Vertebrate Pest 

Control and Management Materials, ASTM STP 680, J.R. Beck, Ed., American Society 

for Testing and Materials, 1979, pp. 157-168. (cited in the EFED Environmental Risk 

Assessment as reference GS0106004) 

40650101 Surprenant, D. (1988) The Chronic Toxicity of Ethoprop Technical to 

Daphnia magna under Flow-through Conditions: Report #87-10-2512: Study #10566-

0986-6105-130. Unpublished study prepared by Springborn Life Sciences, Inc. 44 p. 

40650102 Surprenant, D. (1987) The Toxicity of Ethoprop Technical to Fathead 

Minnow (Pimephales promelas) Embryos and Larvae: SLS Report #: BW-87-6-2408; 

SLS Study # 10566.0986.6105.120. Unpublished study prepared by Springborn Life 

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43686301 Machado, M. (1995) Ethoprop Technical--Acute Toxicity to Sheepshead 

Minnow (Cyprinodon variegatus) Under Flow-Through Conditions: Final Report: Lab 

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81

43686302 Dionne, E. (1995) Ethoprop Technical--Acute Toxicity to Eastern Oyster 

(Crassostrea virginica) Under Flow-Through Conditions: Final Report: Lab Project 

Number: 95-5-5839: 10566.1294.6350.504. Unpublished study prepared by Springborn 

Labs, Inc. 71 p. 

43686303 Machado, M. (1995) Ethoprop Technical--Acute Toxicity to Mysids 

(Mysidopsis bahia) Under Flow-Through Conditions: Final Report: Lab Project 

Number: 95-4-5802:10566.1294.6349.515. Unpublished study prepared by Springborn 

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43877401 Putt, A. (1995) Ethoprop Technical--The Chronic Toxicity to Daphnia magna 

Under Flow-Through Conditions: Final Report: Lab Project Number: 95-5-5857: 

10566.1294.6351.130. Unpublished study prepared by Springborn Labs, Inc. 115 p. 

44114001 Klonne, D. (1996) Summary of Acute Toxicity and Cholinesterase-Inhibiting 

Potential for Several Possible Ethoprop Plant Metabolites: 1) O-Ethyl-Spropylphosphorothioate ("M1" Metabolite), 2) Ethyl Phosphate, 3) O-Ethyl-O-methylS-propylphosphorothioate, 4) O-Ethyl-S-methyl-Spropylphosphorodithioate: Lab 

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by Rhone-Poulenc Ag Co. 70 p. 

4312701 Taliaferro, M.; Miller, V. (1997) Reproduction Study with Ethoprop in the 

Northern Bobwhite (Colinus virginianus): Lab Project Number: 029516: EBA-029516. 

Unpublished study prepared by EBA, Inc. 319 p. 

44312702 Taliaferro, M.; Miller, V. (1997) Reproduction Study with Ethoprop in the 

Mallard Duck (Anas platyrhynchos): Lab Project Number: 029515: EBA-029515. 

Unpublished study prepared by EBA, Inc. 313 p. 

44457501 Sousa, J. (1997) Ethoprop Technical: Chronic Toxicity to Mysids 

(Mysidopsis bahia) under Flow-Through Conditions: Lab Project Number: 97-10-7128: 

10566.0497.6418.530. Unpublished study prepared by Springborn Laboratories, Inc. 98 

p. 

44472101 Sousa, J. (1997) Ethoprop Technical--Early Life-Stage Toxicity Test with 

Sheepshead Minnow (Cyprinodon variegatus): Final Report: Lab Project Number: 97-

10-7127: 10566.0497.6419.520: 021797/FIFRA/520. Unpublished study prepared by 

Springborn Labs., Inc. 91 p. 
82

MRID/Accession Studies for Environmental Fate Data:

161-1 Hydrolysis

MRID Citation Reference

67321 Boyd, G.R.; Gaskill, D.R. (1971) Hydrolysis of Prophos in Aqueous Solutions: 

Report No. A-61587-C. (Unpublished study received Aug 16, 1977 under 

2224-44; submitted by Mobil Chemical Co., In- dustrial Chemicals Div., 

Richmond, Va.; CDL:231371-D) 

160165 Norris, F.; Guyton, C. (1986) Executive Summaries: Ethoprop. Un- published 

summaries prepared by Rhone-Poulenc Inc. 19 p. 

160166 Norris, F. (1983) The Hydrolysis of Ethoprop in Aqueous Solution at 

Environmental pH's and Temperatures: ASD No. 83/059. Unpublished study 

prepared by Rhone-Poulenc Inc. 57 p. 

41270703 Das, Y. (1989) Hydrolysis of ?1-Ethyl-?carbon 14||Ethoprop in Aqueous 

Solutions Buffered at pH 5, 7, and 9: Project No. ISSI No. 89140. Unpublished 

study prepared by Innovative Scientific Services, Inc., (ISSI). 76 p. 

161-2 Photodegradation-water

MRID Citation Reference

160167 Norris, K. (1985) Ethoprop (...) Absorption Characteristics in the Ultraviolet 

Region: ASD No. 85/122. Unpublished study prepared by Rhone-Poulenc Inc. 

9 p. 

160168 Norris, F. (1983) The Photodegradation of Ethoprop in Aqueous Solution 

Using Simulated Sunlight: ASD No. 83/064. Unpublished study prepared by 

Rhone-Poulenc Inc. 33 p. 

160169 Cresswell, D.; Hopkins, R. (1986) ([Carbon 14])-Ethoprop: Photodegradation 

Studies in in [sic] Water: Rept. No. 4728-68/36. Un- published study prepared 

by Hazleton Laboratories Europe Ltd. 108 p. 

41270702 Carpenter, M. (1989) "Photodegradation of ?Carbon 14|-Ethoprop in pH 7 

Buffered Solution": Project ID: ABC Final Report No. 38139. Unpublished 

study prepared by Analytical Bio-Chemistry Laboratories, Inc. 45 p. 

41568101 Carpenter, M. (1989) Photodegradation of ?carbon 14|-Ethoprop in pH 7 

Buffered Solution: Lab Project Number: 38139. Unpublished study prepared by 

Analytical Bio-chemistry Laboratories, Inc. 745 p. 

43833502 Gorman, M. (1995) Photodegradation of (carbon 14)-Ethoprop in pH 7 

Buffered Solution--Supplemental Study: Final Report: Lab Project Number: 

38139-1: EC-95-316: 38139. Unpublished study prepared by ABC Labs, Inc. 

137 p. 
83

161-3 Photodegradation-soil

MRID Citation Reference

160170 Cresswell, D.; Hopkins, R. (1986) ([Carbon 14])-Ethoprop: Photodegradation 

Studies in Soil: Rept. No. 3845-68/36. Unpublished study prepared by Hazleton 

Laboratories Europe Ltd. 111 p. 

41270704 Carpenter, M. (1989) "Determination of the Photolysis Rate of ?carbon 14|-

Ethoprop on the Surface of Soil": ABC Final Report No. 38140. Unpublished 

study prepared by Analytical Bio-Chemistry Laboratories, Inc. 47 p. 

41568102 Carpenter, M. (1989) Determination of the Photolysis Rate of ?carbon 14|-

Ethoprop on the Surface of Soil: Lab Project Number: 38140. Unpublished 

study prepared by Analytical Bio-chemistry Laboratories, Inc. 747 p. 

43833501 Gorman, M. (1995) Determination of the Photolysis Rate of (carbon 14)-

Ethoprop on the Surface of Soil--Supplemental Study: Amended Final Report: 

Lab Project Number: 38140-1: EC-95-316: 38140. Unpublished study prepared 

by ABC Labs, Inc. 117 p. 

161-4 Photodegradation-air

MRID Citation Reference

41388701 Carpenter, M.; Gorman, M. (1990) Photodegradation Study of Ethoprop in Air: 

Lab Project Number: 38216. Unpublished study prepared by Analytical BioChemistry Laboratories. 37 p. 

41596401 Carpenter, M.; Gorman, M. (1990) Photodegradation Study of Ethoprop in Air: 

Lab Project Number: 38216. Unpublished study prepared by Analytical BioChemistry Laboratories. 483 p. 

162-1 Aerobic soil metabolism

MRID Citation Reference

160171 Jordan, E. (1986) Metabolism of Ethoprop (...) in Soil under Aerobic and 

Anaerobic Conditions: ASD No. 86/199. Unpublished study prepared by 

Rhone-Poulenc Inc. in cooperation with Mobil Environmental and Science Lab. 

147 p. 

162-2 Anaerobic soil metabolism

MRID Citation Reference

160171 Jordan, E. (1986) Metabolism of Ethoprop (...) in Soil under Aerobic and 

Anaerobic Conditions: ASD No. 86/199. Unpublished study prepared by 

Rhone-Poulenc Inc. in cooperation with Mobil Environmental and Science Lab. 

147 p. 
84

163-1 Leaching /adsorption /desorption

MRID Citation Reference

40384 Huvar, A.J.; DuVal, A. (1970) Loss of Prophos from Dry and Wet 10% Mocap 

Granules: Project No. 253. (Unpublished study received Sep 2, 1971 under 

2F1204; submitted by Mobil Chemical Co., Richmond, Va.; CDL:094057-H) 

57209 Boyd, G.R.; DuVal, A. (1966) The Disappearance of V-C 9-104 from Treated 

Soil: Report No. RN 66-2. (Unpublished study received Feb 28, 1966 under 

unknown admin. no.; submitted by Mobil Chemical Co., Industrial Chemicals 

Div., Richmond, Va.; CDL:105954-D) 

76721 Norris, F.A. (1979) Letter sent to D.D. Phillips dated Jun 12, 1979: Soil 

dissipation studies, ethoprop alone and in combination with trifluralin: Project 

No. 15915. (Unpublished study received Mar 19, 1981 under 2224-44; 

submitted by Mobil Chemical Co., Industrial Chemicals Div., Richmond, Va.; 

CDL:244801-A) 

92040 DuVal, A.F.; Boyd, G.R. (1966) The Disappearance of V-C 9-104 from 

Treated Soil: RN 66-2. (Unpublished study received Feb 28, 1966 under 2224-

37; submitted by Mobil Chemical Co., Industrial Chemicals Div., Richmond, 

Va.; CDL:006815-G) 

92103 Mobil Chemical Company (1968) The Fate of Mocap in Soil and Plants. 

(Unpublished study received on unknown date under 9F0750; CDL: 098645-D) 

160172 Jordan, E. (1985) Adsorption-desorption of Ethoprop-O-ethyl-1-[car- bon 14] 

by Four Agricultural Soils: ASD No. 85/128. Unpublished study prepared by 

Rhone-Poulenc Inc. 53 p. 

160173 Perrette, T. (1986) Mobility of O-Ethyl-S,S-di-n-propyl Phosphoro- dithioate 

(Ethoprop) in Four Soil Types: ASD No. 86/170. Un- published revision of 

ASD No. 84/103, prepared by Rhone-Poulenc Inc. 35 p. 

41340501 Cameron, B.; Hall, B.; Jamieson, J. (1989) [Carbon 14]-Ethoprop: Aged Soil 

Leaching: Lab Project Number: 140951 : 7045. Unpublished study prepared by 

Inveresk Research International. 77 p. 

41547701 Cameron, B.; Hall, B.; Jamieson, J. (1989) ?Carbon 14|-Ethoprop: Aged Soil 

Leaching: Addendum: Lab Project Number: 140951: 7045A. Unpublished 

study prepared by Inveresk Research International. 25 p. 

43778601 Feung, C.; Stillwell, D. (1995) O-Ethyl-S-Propyl Phosphorothioic Acid 

(Ethoprop Metabolite) Adsorption/Desorption Study: Lab Project Number: EC94-291. Unpublished study prepared by Rhone-Poulenc Ag Co. and A & L 

Great Lakes Lab., Inc. 126 p. 

163-2 Volatility - lab

MRID Citation Reference
85

41211201 Carpenter, M. (1989) Laboratory Volatility from Soil of Ethoprop: ABC 

Laboratory Project ID 38001. Unpublished study prepared by Analytical BioChemistry Laboratories, Inc. 784 p. 

164-1 Terrestrial field dissipation

MRID Citation Reference

40382 Huvar, A.J.; Bolinskey, B.; Boyd, G.R.; et al. (1969) Percolation of Prophos 

(Mocap) through the Soil: Project No. 253. (Unpublished study received Sep 2, 

1971 under 2F1204; submitted by Mobil Chemical Co., Richmond, Va.; 

CDL:094057-F) 

57209 Boyd, G.R.; DuVal, A. (1966) The Disappearance of V-C 9-104 from Treated 

Soil: Report No. RN 66-2. (Unpublished study received Feb 28, 1966 under 

unknown admin. no.; submitted by Mobil Chemical Co., Industrial Chemicals 

Div., Richmond, Va.; CDL:105954-D) 

75252 DuVal, A.F.; Boyd, G.R. (1967) The Persistence of Mocap in Treated Soil: RN 

67-3. (Unpublished study received Nov 25, 1968 under 9F0750; submitted by 

Mobil Chemical Co., Industrial Chemicals Div., Richmond, Va.; CDL:091296-

Q) 

92033 Duval, A.F.; Boyd, G.R. (1967) The Persistence of Mocap in Treated Soil: 

Project 532. (Unpublished study received Jan 26, 1967 under unknown admin. 

no.; submitted by Mobil Chemical Co., In- dustrial Chemicals Div., Richmond, 

Va.; CDL:006786-A) 

92034 Wilson, J.H., Jr.; Downing, C.R. (1966) The Soil Persistence and Effect on 

Nematode Population of Mocap Soil Incorporation Treatments in the Field: 

Project 789. (Unpublished study received Jan 26, 1967 under unknown admin. 

no.; submitted by Mobil Chemical Co., Industrial Chemicals Div., Richmond, 

Va.; CDL: 006786-B) 

92040 DuVal, A.F.; Boyd, G.R. (1966) The Disappearance of V-C 9-104 from 

Treated Soil: RN 66-2. (Unpublished study received Feb 28, 1966 under 2224-

37; submitted by Mobil Chemical Co., Industrial Chemicals Div., Richmond, 

Va.; CDL:006815-G) 

92082 Mobil Chemical Company (19??) ?Recovery of Mocap-equivalents from Beans 

and Soil|. (Compilation; unpublished study received Aug 19, 1969 under 

0F0872; CDL:093170-C) 

160174 Guyton, C. (1986) The Dissipation of Ethoprop in Soil under Field Conditions: 

1984 Field Program F-21: ASD No. 86/195. Unpublished study prepared by 

Rhone-Poulenc Inc. and Morse Laboratories, Inc. 168 p. 

40470601 Norris, F. (1987) Measurement of Ethoprop Movement and Degradation in 

Florida Soils. Unpublished study prepared by Rhone-Poulenc Ag Co. 29 p. 
86

40519901 Norris, F. (1987) Field Report: Field Dissipation and Groundwater Monitoring 

Study. Unpublished study prepared by Rhone-Poulenc AG Company. 21 p. 

41712401 Norris, F. (1990) A Terrestrial Field Soil Dissipation Study with Ethoprop in 

Washington and North Carolina: Final Report. Lab Project numbers 40641; 

EC/P-89-0012: R109-082/087;R122-009/011: ML 89-0095-RHP. Unpublished 

study prepared by Rhone-Poulenc Ag Co. in coop with A & L Eastern Ag Labs, 

Inc. and Morse Labs, Inc. 164 p. 

41767201 Norris, F. (1990) A Terrestrial Field Soil Dissipation Study with Ethoprop in a 

California Soil: Lab Project No: 40863: EC-89-082: R102-076. Unpublished 

study prepared by Rhone-Poulenc Ag Co., in cooperation with A & L Eastern 

Agric., Labs., Inc. and others. 150 p. 

44398001 Norris, F. (1997) Ethoprop: Terrestrial Soil Dissipation after Application to 

Turf: Final Report: Lab Project Number: 96M08726: 45369: 10159. 

Unpublished study prepared by American Agricultural Services, Inc. 923 p. 

45304901 Norris, F.; Noling, J.; Jones, R. et al. (1988) Measurement of Ethoprop 

Movement and Degradation in Florida Soils. Unpublished study prepared by 

Rhone-Poulenc Ag Company. 37 p. 

162-4 Aerobic aquatic metabolism

MRID Citation Reference

44989502 Lewis, C. (1993) (14-carbon)-Ethoprophos: Degradation and Retention in 

Water/Sediment Systems: Final Report: Lab Project Number: 68/135-1015: 

P6875D. Unpublished study prepared by Hazleton UK. 172 p. 

165-0 Accumulation Studies -- General

MRID Citation Reference

66341 U.S. Environmental Protection Agency, Environmental Research Laboratory 

(1981) Acephate, Aldicarb, Carbophenothion, DEF, EPN, Ethoprop, Methyl 

Parathion, and Phorate: Their Acute and Chronic Toxicity, Bioconcentration 

Potential, and Persistence as Related to Marine Environments: EPA-600/4-81-

023. (Unpublished study) 

165-4 Bioaccumulation in fish

MRID Citation Reference

160176 McAllister, W.; Cohle, P.; Burnett, J.; et al. (1986) Bioconcentration and 
87

Depuration of [Carbon 14]-Ethoprop by Bluegill Sun- fish (Lepomis 

macrochirus) under Flow-through Conditions: Final Report: Report No. 33068. 

Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 46 

p. 

160177 Bunch, B. (1986) Metabolite Characterization of [Carbon 14]-Ethoprop in 

Bluegill Sunfish (Lepomis macrochirus): ABC Final Rept. #33991. 

Unpublished study prepared by Analytical Bio-Chemistry Laboratories. 45 p. 

41425601 Burgess, D. (1990) Uptake, Depuration and Bioconcentration of ?Carbon 14|-

Ethoprop by Bluegill Sunfish (Lepomis macrochirus) Project Number: 38161. 

Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 41 

p. 

41425602 Heitkamp, J. (1990) Characterization of ?Carbon 14|-Ethoprop Residues in 

Bluegill (Lepomis macrochirus) Water and Tissues: Lab Project Number: 

38162. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, 

Inc. 61 p. 

43038401 Heintzelman, R. (1993) Selected Raw Data Submission Pertaining to Uptake, 

Depuration and Bioconcentration of (carbon 14)-Ethoprop by Bluegill Sunfish 

(Lepomis macrochirus): Lab Project Number: 38161. Unpublished study 

prepared by Analytical Bio-Chemistry Labs., Inc. 136 p. 

43038402 Heintzelman, R. (1993) Selected Raw Data Submission Pertaining to 

Characterization of (carbon 14)-Ethoprop Residues in Bluegill Sunfish 

(Lepomis macrochirus) Water and Tissues: Lab Project Number: 38162. 

Unpublished study prepared by Analytical Bio-Chemistry Labs., Inc. 181 p. 

166-3 Ground water Large-scale retrospective

MRID Citation Reference

45729701 Van Kretschmar, J.; Daussin, S. (2002) Surface Water Monitoring for Residues 

of Ethoprop in High-Use Areas in the United States: Lab Project Number: 

00M19458: 19458-01: 19458-02. Unpublished study prepared by Bayer 

CropScience, Stone Environmental, Inc. and Agvise Laboratories. 61 p. 

46674601 Lee, Robert. (2005) A Retrospective Groundwater Monitoring Study for 

Ethoprophos and Metabolites in Five Regions of the USA. Bayer CropScience

Study Number RAERX008. Unpublished study prepared by Bayer CropScience

and Stone Environmental, Inc. 338 p.

47417301 Jones. R.: Ramanaravanan, T.: Desmarteau, D. (2008) Response to EPA’s 

Revised Ethoprophos Drinking water assessment. Bayer CropScience Project 

Number: G201876, 00M1945, M/240244/02/1. Unpublished study prepared by 

Bayer Cropscience. 13 p.

[No Guideline #] Surface water Large-scale retrospective
88

46983601 Braun, David C. and Robert J. Seymour. (2006) Surface Water Monitoring for 

Residues of Ethoprophos in High Use Areas in the United States, Amended 

Report. Bayer CropScience PSI Project No. RAERX004, Study Number 

00M19458. Unpublished study prepared by Bayer CropScience, Stone 

Environmental, Inc., and Agvise Laboratories. 755 p.

47417301 Jones. R.: Ramanaravanan, T.: Desmarteau, D. (2008) Response to EPA’s 

Revised Ethoprophos Drinking water assessment. Bayer CropScience Project 

Number: G201876, 00M1945, M/240244/02/1. Unpublished study prepared by 

Bayer Cropscience. 13 p.
89

APPENDICES

Appendix A: Chemical Structures of Ethoprop and Degradates

Residues of concern include:

Ethoprop (O-ethyl-S,S-dipropyl phosphorodithioate), ethoprop SME, and ethoprop OME.

Table 3. Nomenclature of Ethoprop and its Metabolites of Concern.

Structure

Molecular formula [C8H19O2PS2]

Molecular weight 242,33

Common name Ethoprop

Company experimental 

name

Ethoprop or ethoprophos

IUPAC and CAS name O-ethyl-S,S-dipropyl phosphorodithioate

Chemical class Organophosphate

CAS registry number 13194-48-4

End-use product (EP) 6 lb./gal EC (MOCAP® EC Nematicide-Insecticide, EPA Reg. No. 264-

458)

15% G (MOCAP® 15% Granular Nematicide-Insecticide, EPA Reg. No. 

264-457)

Structure

Molecular formula C6H15O2PS2

Molecular weight 214.29

Chemical name O-ethyl-S-methyl-S-propylphosphorodithioate 

Structure

Molecular formula C6H15O2PS2

Molecular weight 214.29

P

O

O S

CH3

S

CH3

H3C

H3C

P

O

O S

CH3

S

CH3
90

Table 3. Nomenclature of Ethoprop and its Metabolites of Concern.

Common name Ethoprop SME or

Metabolite II or

S-methyl degradateChemical name O-ethyl-S-methyl-S-propylphosphorodithioate 

More Information: Degradate of concern for human health; may be toxic to non-target 

animals but no significant environmental exposure expected

Structure

Molecular formula C6H15O2PS

Molecular weight 182.22

Common name Metabolite III (ethoprop O-Me)

Chemical name O-ethyl-O-methyl-S-propyl phosphorodithioate

Structure

Molecular formula C5H13O3PS

Molecular weight 184.19

Common name Metabolite IV (M-1)

Chemical name O-ethyl-S-propyl phosphorodithioate

H3C

P

O

O S

CH3

O

CH3

H3C

P

O

O S

CH3

OH
91

Figure 3. Proposed pathway for ethoprop in soil (from registrant documents).

Figure taken from: R.L. Jones and F.A. Norris. 1998. Authors were involved in the generation 

of many of the environmental fate studies submitted to EPA to support the registration of 

ethoprop. Factors affecting degradation of aldicarb and ethoprop. Journal of Nematology

30:45-55. Similar proposed pathways are provided in registrant submisssions such as MRID 

00160171.
92
93

Appendix B: Risk Quotients and Levels of Concern for Exposed Organisms

Agency Risk Quotient (RQ) Metrics and Levels of Concern (LOC) Per Risk Class.

Risk Class Risk Description RQ LOC

Aquatic Animals (fish and invertebrates)

Acute Potential for effects to non-listed animals from acute 

exposures

Peak EEC/LC501 0.5

Acute 

Restricted Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use classification Peak EEC/LC501 0.1

Acute Listed 

Species

Listed species may be potentially affected by acute 

exposures

Peak EEC/LC501 0.05

Chronic Potential for effects to non-listed and listed animals from 

chronic exposures

60-day EEC/NOAEC 

(fish) 1

21-day EEC/NOAEC 

(invertebrates)

Aquatic Plants

Non-Listed Potential for effects to non-listed plants from exposures Peak EEC/LC501 1

Listed Potential for effects to listed plants from exposures Peak EEC/NOAEC 1

Terrestrial Animals (mammals and birds)2

Acute Potential for effects to non-listed animals from acute 

exposures

EEC/LC50 (Dietary) 0.5

EEC/LD50 (Dose)

Acute 

Restricted Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use classification

EEC/LC50 (Dietary) 0.2

EEC/LD50 (Dose)

Acute Listed 

Species

Listed species may be potentially affected by acute 

exposures

EEC/LC50 (Dietary) 0.1

EEC/LD50 (Dose)

Chronic Potential for effects to non-listed and listed animals from 

chronic exposures EEC/NOAEC 1

Terrestrial and Semi-Aquatic Plants

Non-Listed Potential for effects to non-target, non-listed plants from 

exposures

EEC/ EC25 1

Listed Plant Potential for effects to non-target, listed plants from 

exposures

EEC/ NOAEC

1

EEC/ EC05

1 LC50 or EC50. 2 EEC based on upper bound Kenaga nomogram values for foliar exposure.

Appendix C: Aquatic Exposure Modeling selected Input and Output
94

Surface Water Concentration Calculator (SWI) Representative Input and out Output Files

FL Sugarcane Scenario Input file 

Input highlights: Application at Depth no drift, applications every two years, 300-day 

aerobic soil half-life assumed.

Ethoprop TTR CAM4 wDrft4Rt

1

True

109,,,

0,,,

25,,,

0,,,

0,,,

0,,,

40,,,

150,,,

300,,,

25,

0,,,

242.3,,,

.000827,,,

843,,,

0,0,

0,0,

0,0,

0,0,

0,0,

0,0,

2

1

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,

4.48,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,,,,

False

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,

3,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,

.99,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,,,

0,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,

.99,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,,,

.00,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,,,

.99,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,,,

.0,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,,

5,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,

-

1,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,

False

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,

FLsugarcaneSTD

C:\Models\Inputs\Metfiles\W12844.dvf

True,True,False,False,False

False,30

False

10000

12

4.2

4.8

1E-08

0.5

0.05

0.5

1.35

0.04

5

0.006

1.19

30

0.005

0.04

5

0.4

False

1.0,1.0

1

1

2

1

31

12

100,300

100

0.1

1

0.78

0

32.5

0

0.1
95

0.2

1

4

1

600

2

10,95,

1.45,1.75,

0.066,0.178,

0.036,0.078,

2.32,0.29,

100,19,

,,

,,

False

25

1,16,1,16,1,16,1,16,25,1,16,1,16,1,16,1,16,1,1

6,1,16,1,16,1,16,,,,,,,,,,,,,,,,,,,,,,,,,,,,

1,1,2,2,3,3,4,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11

,11,12,12,,,,,,,,,,,,,,,,,,,,,,,,,,,,

91,91,91,91,91,91,91,91,91,91,91,91,91,91,91,9

1,91,91,91,91,91,91,91,91,91,,,,,,,,,,,,,,,,,,

,,,,,,,,,,

.194,.215,.240,.268,.300,.334,.358,.584,.638,.

673,.675,.666,.662,.650,.631,.636,.659,.680,.6

99,.717,.699,.669,.624,.551,.468,,,,,,,,,,,,,,

,,,,,,,,,,,,,,

.014,.014,.014,.014,.014,.014,.014,.014,.014,.

014,.014,.014,.014,.014,.014,.014,.014,.014,.0

14,.014,.014,.014,.014,.014,.014,,,,,,,,,,,,,,

,,,,,,,,,,,,,,

2.0,1.55,0.266,

0.1,0,

False

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

,,,,,,

FL Sugarcane Scenario Output Summary 

Estimated Environmental Concentrations for Ethoprop TTR are presented in Table 1 for the USEPA 

standard pond with the LAsugarcaneSTD field scenario. A graphical presentation of the year-to-year 

peaks is presented in Figure 1. These values were generated with the Surface Water Concentration 

Calculator (SWCC Version 1.106). Critical input values for the model are summarized in Tables 2 and 3.

This model estimates that about 1.5% of Ethoprop TTR applied to the field eventually reaches the water 

body. The main mechanism of transport from the field to the water body is by runoff (99.1% of the total 

transport) followed by erosion (0.86%).

In the water body, pesticide dissipates with an effective water column half-life of 125.1 days. (This value 

does not include dissipation by transport to the benthic region; it includes only processes that result in 

removal of pesticide from the complete system.) The main source of dissipation in the water column is 

hydrolysis (effective average half-life = 150 days) followed by volatilization (750.9 days).

In the benthic region, pesticide dissipation is negligible (1915.9 days). The main source of dissipation in 

the benthic region is hydrolysis (effective average half-life = 1915.9 days). The vast majority of the 

pesticide in the benthic region (92.17%) is sorbed to sediment rather than in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for Ethoprop TTR.

Peak (1-in-10 yr) 47.0

4-day Avg (1-in-10 yr) 46.2

21-day Avg (1-in-10 yr) 44.8

60-day Avg (1-in-10 yr) 40.8

365-day Avg (1-in-10 yr) 21.2

Entire Simulation Mean 7.87
96

Table 2. Summary of Model Inputs for Ethoprop.

Scenario LAsugarcaneSTD

Cropped Area Fraction 1

Koc (ml/g) 109

Water Half-Life (days) @ 25 °C 0

Benthic Half-Life (days) @ 0 °C 0

Photolysis Half-Life (days) @ 40 °Lat 0

Hydrolysis Half-Life (days) 150

Soil Half-Life (days) @ 25 °C 300

Foliar Half-Life (days) 0

Molecular Wt 242.3

Vapor Pressure (torr) .000827

Solubility (mg/l) 843

Table 3. Application Schedule for Ethoprop TTR.

Date (Days Since 

Emergence)

Type Amount (kg/ha) Eff. Drift

-1 Incorporated to 5 

cm

4.48 .99 .0

Figure 1. Yearly Peak Concentrations
97

Variable Volume Water Model, SWCC Compatible Version

*******************************************

Performed on: 9/16/2014 at 17:53

Peak 1-in-10 = 58.1 ppb

Chronic 1-in-10 = 27.2 ppb

Simulation Avg = 8.87 ppb

4-day avg 1-in-10 = 57.2 ppb

21-day avg 1-in-10 = 53.7 ppb

60-day avg 1-in-10 = 49.6 ppb

90-day avg 1-in-10 = 47.6 ppb

Benthic Pore Water Peak 1-in-10 = 36.7 ppb

Benthic Pore Water 21-day avg 1-in-10 = 36.6 ppb

Benthic Conversion Factor = 4.73 -Pore water (ug/L) to 

(total mass, ug)/(dry sed mass,kg)

Benthic Mass Fraction in Pore Water = 0.783E-01

YEAR Peak 4-day 21-day 60-day 90-day Yearly Avg Benthic Pk Benthic 21-day

 1 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00

 2 1.58E+01 1.56E+01 1.47E+01 1.31E+01 1.21E+01 7.82E+00 1.03E+01 1.03E+01

 3 5.35E+01 1.38E+01 3.74E+00 4.13E+00 4.47E+00 1.95E+00 4.77E+00 4.98E+00

 4 5.79E+01 5.70E+01 5.37E+01 4.98E+01 4.79E+01 2.76E+01 3.71E+01 3.71E+01

 5 9.80E+00 9.85E+00 1.03E+01 1.13E+01 1.23E+01 4.57E+00 1.32E+01 1.39E+01

 6 3.86E+01 3.80E+01 3.69E+01 3.35E+01 3.08E+01 1.69E+01 2.29E+01 2.29E+01

 7 5.95E+00 5.97E+00 6.22E+00 6.88E+00 7.45E+00 2.77E+00 7.99E+00 8.36E+00

 8 1.29E+01 1.27E+01 1.19E+01 1.06E+01 9.75E+00 5.50E+00 7.60E+00 7.58E+00

 9 2.43E+00 2.44E+00 2.55E+00 2.81E+00 3.04E+00 1.12E+00 3.25E+00 3.40E+00

10 4.11E+01 4.05E+01 3.84E+01 3.51E+01 3.24E+01 1.77E+01 2.39E+01 2.39E+01

11 6.70E+00 6.74E+00 7.01E+00 7.72E+00 8.34E+00 3.13E+00 8.96E+00 9.38E+00

12 1.88E+01 1.85E+01 1.79E+01 1.73E+01 1.65E+01 9.60E+00 1.28E+01 1.28E+01

13 3.46E+00 3.48E+00 3.63E+00 4.01E+00 4.33E+00 1.62E+00 4.65E+00 4.87E+00

14 7.42E+01 7.30E+01 6.97E+01 6.15E+01 5.63E+01 3.04E+01 4.10E+01 4.09E+01

15 1.11E+01 1.12E+01 1.17E+01 1.28E+01 1.39E+01 5.25E+00 1.50E+01 1.57E+01

16 1.79E+01 1.77E+01 1.71E+01 1.52E+01 1.40E+01 7.85E+00 1.09E+01 1.09E+01

17 3.51E+00 3.53E+00 3.68E+00 4.07E+00 4.41E+00 1.62E+00 4.72E+00 4.94E+00

18 3.99E+01 3.92E+01 3.67E+01 3.36E+01 3.10E+01 1.68E+01 2.27E+01 2.27E+01

19 6.40E+00 6.44E+00 6.74E+00 7.45E+00 8.08E+00 2.90E+00 8.66E+00 9.07E+00

20 5.82E+01 5.72E+01 5.34E+01 4.83E+01 4.44E+01 2.38E+01 3.26E+01 3.26E+01

21 9.47E+00 9.51E+00 9.92E+00 1.10E+01 1.19E+01 4.37E+00 1.27E+01 1.33E+01

22 1.77E+01 1.75E+01 1.68E+01 1.55E+01 1.51E+01 9.63E+00 1.28E+01 1.28E+01

23 2.01E+01 5.52E+00 3.98E+00 4.41E+00 4.78E+00 1.88E+00 5.12E+00 5.36E+00

24 2.36E+01 2.33E+01 2.20E+01 1.96E+01 1.90E+01 1.16E+01 1.55E+01 1.54E+01

25 4.30E+00 4.32E+00 4.52E+00 4.98E+00 5.39E+00 2.03E+00 5.80E+00 6.07E+00

26 7.24E+01 7.14E+01 6.70E+01 5.92E+01 5.44E+01 2.98E+01 3.97E+01 3.97E+01

27 1.07E+01 1.07E+01 1.12E+01 1.23E+01 1.34E+01 4.88E+00 1.44E+01 1.50E+01

28 1.37E+01 1.35E+01 1.28E+01 1.18E+01 1.10E+01 6.30E+00 8.75E+00 8.73E+00

29 2.23E+00 2.24E+00 2.34E+00 2.59E+00 2.81E+00 1.03E+00 3.02E+00 3.16E+00

30 1.18E+01 1.16E+01 1.11E+01 9.96E+00 9.27E+00 5.70E+00 7.56E+00 7.55E+00

*************************************************************************************************

***

Effective compartment halflives averaged over simulation duration:

zero washout 0

zero metabolic 0

hydrolysis halflife (days) = 150.040126616221 

zero photolysis 0

volatile halflife (days) = 587.713320830168 

total water col halflife (days) = 119.525813639529 
98

zero burial 0

zero benthic metab 0

benthic hydrolysis halflife (days) = 1915.86477013956 

total benthic halflife (days) = 1915.86477013956 

***********************************************************************

Fractional Contribution of Transport Processes to Waterbody & Total Mass 

(kg):

Due to Runoff = 0.9987 11.45 

Due to Erosion = 0.0013 0.1467E-01

Due to Drift = 0.0000 0.000 

***********************************************************************

Flow in/out Characteristics of Waterbody:

Average Daily Runoff Into Waterbody (m3/s) = 1.983254077242644E-003

Baseflow Into Waterbody (m3/s) = 0.000000000000000E+000

Average Daily Flow Out of Waterbody (m3/s) = 1.983254077242588E-003

***********************************************************************

Inputs:

 109.0 = oc partitioning coefficient

 0.000 = water column half Life

 25.00 = reference temp for water column degradation

 0.000 = benthic Half Life

 0.000 = Reference temp for benthic degradation

 2.000 = Q ten value

 0.000 = photolysis half life

 40.00 = reference latitude for photolysis study

 150.0 = hydrolysis half life

 242.3 = molecular wt

 0.8270E-03 = vapor pressure

 843.0 = solubility

 0.1000E+06 = field area

 0.1000E+05 = water body area

 2.000 = initial depth

 2.000 = maximum depth

 2 1=vvwm, 2=usepa pond, 3 = usepa reservoir, 4 = const vol no 

flow, 5 = const vol w/flow 

F T = burial, else no burial

 0.1000E-07 = mass transfer coefficient 

 0.5000 = PRBEN

 0.5000E-01 = benthic compartment depth

 0.5000 = benthic porosity

 1.350 = benthic bulk density

 0.4000E-01 = OC frcation in benthic sediment

 5.000 = DOC in benthic compartment

 0.6000E-02 = benthic biomass

 1.190 = DFAC

 30.00 = SS

 0.5000E-02 = chlorophyll

 0.4000E-01 = OC frcation in water column SS

 5.000 = DOC in water column

 0.4000 = biomass in water column

FRACTION AREA CROPPED = 1.00000000000000 
99

Maine Potato Scenario SWCC Model input and Output Summary

Summary of Water Modeling of Ethoprop and the USEPA 

Standard Pond

Estimated Environmental Concentrations for Ethoprop are presented in Table 1 for the USEPA standard 

pond with the MEpotatoSTD field scenario. A graphical presentation of the year-to-year peaks is 

presented in Figure 1. These values were generated with the Surface Water Concentration Calculator 

(SWCC Version 1.106). Critical input values for the model are summarized in Tables 2 and 3.

This model estimates that about 0.4% of Ethoprop applied to the field eventually reaches the water body. 

The main mechanism of transport from the field to the water body is by runoff (65.5% of the total 

transport), followed by spray drift (24.9%) and erosion (9.61%).

In the water body, pesticide dissipates with an effective water column half-life of 129.2 days. (This value 

does not include dissipation by transport to the benthic region; it includes only processes that result in 

removal of pesticide from the complete system.) The main source of dissipation in the water column is 

hydrolysis (effective average half-life = 150 days) followed by volatilization (928.8 days).

In the benthic region, pesticide dissipation is negligible (1915.9 days). The main source of dissipation in 

the benthic region is hydrolysis (effective average half-life = 1915.9 days). The vast majority of the 

pesticide in the benthic region (92.17%) is sorbed to sediment rather than in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for Ethoprop.

Peak (1-in-10 yr) 32.5

4-day Avg (1-in-10 yr) 32.1

21-day Avg (1-in-10 yr) 30.8

60-day Avg (1-in-10 yr) 28.4

365-day Avg (1-in-10 yr) 15.2

Entire Simulation Mean 9.82

Table 2. Summary of Model Inputs for Ethoprop t.

Scenario MEpotatoSTD

Cropped Area Fraction 1

Koc (ml/g) 109

Water Half-Life (days) @ 25 °C 0

Benthic Half-Life (days) @ 0 °C 0

Photolysis Half-Life (days) @ 40 °Lat 0

Hydrolysis Half-Life (days) 150

Soil Half-Life (days) @ 25 °C 300

Foliar Half-Life (days) 0

Molecular Wt 242.3
100

Vapor Pressure (torr) .000827

Solubility (mg/l) 843

Table 3. Application Schedule for Ethoprop TTR CAM4 wDrft9Rt.

Date (Days Since 

Emergence)

Type Amount (kg/ha) Eff. Drift

-1 Incorporated to 5 

cm

10.1 .99 .01

Figure 1. Yearly Peak Concentrations

Groundwater Modeling Example Input – Output Summary

(Used for characterization of potential irrigation hazard)

Groundwater Analysis for Ethoprop and the FLORIDA - Potato - Met File (13889.Dvf) 

Jacksonville Scenario - Estimated groundwater concentrations and breakthrough times for Ethoprop 

are presented in Table 1 for the FLORIDA - potato - Met File (13889.dvf) Jacksonville groundwater 

scenario. A graphical presentation of the daily concentrations in the aquifer is presented in Figure 1. 

These values were generated with the PRZM-GW (Version 1.07). Critical input values for the model are 

summarized in Tables 2 and 3.

Table 1. Groundwater Results for Ethoprop and the FLORIDA - potato - Met File (13889.dvf) 

Jacksonville Scenario.
101

Peak Concentration (ppb) 197

Post-Breakthrough Mean 

Concentration (ppb)

 91.5

Entire Simulation Mean 

Concentration (ppb)

 76.8

Average Breakthrough Time 

(days)

2931.985

Throughputs 3.738082

Table 2. Chemical Properties for Groundwater Modeling of Ethoprop .

Koc (ml/g) 109

Surface Soil Half Life (days) 300

Hydrolysis Half Life (days) 150

Diffusion Coefficint Air (cm2/day) 4300

Henry's Constant 2E-6

Enthalpy (kcal/mol) 21.7

Table 3. Pesticide application scheme used for Ethoprop . This application scheme was applied 

every year of the simulation.

Application Days 

Relative to 

Emergence Date 

(02/15)

Application Method Application Rate

(kg/ha)

-1 Ground application with mass 

uniformly distributed to 7 cm

13.5

Figure 1. Aquifer Breakthrough Curve for Ethoprop and the FLORIDA - Potato - Met File 

(13889.Dvf) Jacksonville Scenario
102
103

Appendix D. T-REX Model Input and Output

Chemical Name: Ethoprop

Seed Treatment? (Check if yes)

FALSE

 Use: 118

Product name and form: MOCAP 15% Granular

% A.I. (leading zero must be entered 

for formulations <1% a.i.): 100.00%

Application Rate (lb ai/acre) 12

Half-life (days): 35

Application Interval (days):

Number of Applications: 1

Are you assessing applications with 

variable rates or intervals? no

Endpoint Toxicity value

LD50 (mg/kg-bw) 4.21

LC50 (mg/kg-diet) 33.00

NOAEL (mg/kg-bw)

NOAEC (mg/kg-diet) 0.95

Endpoint Toxicity value

LD50 (mg/kg-bw) 32.80

LC50 (mg/kg-diet)

Reported Chronic 

Endpoint 2.30

Is dietary concentration 

(mg/kg-diet) reported from 

the available chronic 

mammal study? (yes or no)

no

Enter dietary concentration 

(mg/kg-diet)
104

Estimated Chronic Diet 

Concentration Equivalent 

to Reported Chronic Daily 

Dose

46

Dietary-based EECs 

(ppm)

Kenaga

Values

Short Grass 2880.00

Tall Grass 1320.00

Broadleaf plants 1620.00

Fruits/pods/seeds 180.00

Arthropods 1128.00

Avian Body 

Ingestion 

(Fdry)

Ingestion 

(Fwet) % body wgt FI

Class Weight (g) (g bw/day) (g/day) consumed (kg-diet/day)

Small 20 5 23 114 2.28E-02

Mid 100 13 65 65 6.49E-02

Large 1000 58 291 29 2.91E-01

20 5 5 25 5.06E-03

Granivores 100 13 14 14 1.44E-02

1000 58 65 6 6.46E-02

Avian Body Adjusted LD50

Weight (g) (mg/kg-bw)

20 3.54

100 4.51

1000 6.36

Dose-based EECs (mg/kg-bw)

Avian Classes and Body Weights (grams)

small mid large

20 100 1000

Short Grass 3280.03 1870.41 837.41

Tall Grass 1503.35 857.27 383.81

Broadleaf plants 1845.02 1052.11 471.04

Fruits/pods 205.00 116.90 52.34

Arthropods 1284.68 732.58 327.99

Seeds 45.56 25.98 11.63

Dose-based RQs 

(Dose-based EEC/adjusted LD50)

Avian Acute RQs

Size Class (grams)

20 100 1000

Short Grass 926.74 415.12 131.58

Tall Grass 424.76 190.26 60.31
105

Broadleaf plants 521.29 233.51 74.01

Fruits/pods 57.92 25.95 8.22

Arthropods 362.97 162.59 51.53

Seeds 12.87 5.77 1.83

Dietary-based RQs 

(Dietary-based EEC/LC50 or 

NOAEC)

RQs

Acute Chronic

Short Grass 87.27 3025.21

Tall Grass 40.00 1386.55

Broadleaf plants 49.09 1701.68

Fruits/pods/seeds 5.45 189.08

Arthropods 34.18 1184.87

Mammalian Body 

Ingestion 

(Fdry)

Ingestion 

(Fwet) % body wgt FI

Class Weight (g bwt/day) (g/day) consumed (kg-diet/day)

15 3 14 95 1.43E-02

Herbivores/ 35 5 23 66 2.31E-02

insectivores 1000 31 153 15 1.53E-01

15 3 3 21 3.18E-03

Grainvores 35 5 5 15 5.13E-03

1000 31 34 3 3.40E-02

Mammalian Body Adjusted Adjusted

Class Weight LD50 NOAEL

15 72.09 5.06

Herbivores/ 35 58.33 4.09

insectivores 1000 25.23 1.77

15 72.09 5.06

Granivores 35 58.33 4.09

1000 25.23 1.77

Dose-Based EECs 

(mg/kg-bw)

Mammalian Classes and Body weight

(grams)

15 35 1000

Short Grass 2745.86 1897.76 440.00

Tall Grass 1258.52 869.80 201.67

Broadleaf plants 1544.55 1067.49 247.50

Fruits/pods 171.62 118.61 27.50

Arthropods 1075.46 743.29 172.33
106

Seeds 38.14 26.36 6.11

Dose-based RQs 

(Dose-based EEC/LD50 or 

NOAEL)

Small mammal Medium mammal

15 grams 35 grams

Acute Chronic Acute Chroni 

Short Grass 38.09 543.20 32.54 463.99

Tall Grass 17.46 248.96 14.91 212.66

Broadleaf plants 21.43 305.55 18.30 261.00

Fruits/pods 2.38 33.95 2.03 29.00

Arthropods 14.92 212.75 12.74 181.73

Seeds 0.53 7.54 0.45 6.44

Dietary-based RQs 

(Dietary-based EEC/LC50 or 

NOAEC)

Mammal RQs

Acute Chronic

Short Grass #DIV/0! 62.61

Tall Grass #DIV/0! 28.70

Broadleaf plants #DIV/0! 35.22

Fruits/pods/seeds #DIV/0! 3.91

Arthropods #DIV/0! 24.52

LD50 ft-2

INPUTS

Do not overwrite these 

numbers.

Application Rate: 12 lbs / acre

% A.I.: 100.00%

Avian LD50 (20g): 3.54 mg/kg bw

(100g) 4.51

(1000g) 6.36

Mammalian LD50 (15g): 72.09 mg/kg bw

(35g) 58.33

(1000g) 25.23

Row Spacing: 0 inches

Bandwidth: 0 inches

Unincorporation: 15%

Broadcast applications

Granular
107

Intermediate Calculations

mg ai/ft2: 18.74

LD50 ft2

wgt class 

(grams)

Avian 20 264.79

100 41.60

1000 2.94

Mammal 15 17.33

35 9.18

1000 0.74
108

Appendix E. STIR Model Example

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) #VALUE!

Maximum 1-hour Vapor Inhalation Dose (mg/kg) #VALUE!

Adjusted Inhalation LD50 3.33E+01

Ratio of Vapor Dose to Adjusted Inhalation LD50 #VALUE!

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.27E+00

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 3.81E-02

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) #VALUE!

Maximum 1-hour Vapor Inhalation Dose (mg/kg) #VALUE!

Adjusted Inhalation LD50 2.37E+03

Ratio of Vapor Dose to Adjusted Inhalation LD50 #VALUE!

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.59E+00

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 6.72E-04

Appendix F. Earthworm Fugacity Model

Table 2. Characteristics of Ethoprop.

Parameter (symbol) Value Units

Pesticide Name Ethoprop none

Molecular weight (MW) 164.38 g/mol

Octanol-water Partition Coefficient (Kow) 38905 none

Soil partition coefficient (Kd) 0.3 cm3/g

Table 3. Soil parameters.

Parameter (symbol) Value Units

Bulk density of soil (ρs)* 2.45 g/cm3

Concentration of pesticide in soil (estimated using PRZM) do 

not enter value for this cell calculated automatically 0.009078839 g/m3

Concentration of Ethoprop in soil (Cs) 5.52E-05 mol/m3

Table 4. Earthworm parameters.

Parameter (symbol) Value Units

Lipid fraction of earthworm (L) 0.01 none

Water fraction of earthworm (W) 0.84 none

Density of earthworm (ρE) 1000 kg/m3
109

Concentration of Ethoprop in earthworm (CE) 2.92E-02 mol/m3

Concentration of Ethoprop in earthworm (CE') 0.004806 g/kg*

*equivalent to mg/g

Table 5. Mammalian toxicity data for Ethoprop.

Endpoint/Parameter (symbol) Value Units

Acute oral LD50 32.8 mg/kg-bw

Body weight of acute test animal* (TW) 350 g

Chronic NOAEL 2.3 mg/kg-bw

Chronic NOAEC 46 mg/kg-diet

Body weight of chronic test animal* (TW) 350 g

Body weight of assessed animal (AW) 350 g

Food intake of assessed animal (F) 14.0 g/day

Body weight normalized food intake of assessed animal (FN) 40 g/kg-bw-day

*For rats, the default body weight is 350 g, if no other data are available.

Table 6. Avian toxicity data for Ethoprop.

Endpoint/Parameter (symbol) Value Units

Acute oral LD50 4.21 mg/kg-bw

Body weight of test animal for LD50* (TW) 63.6 g

Subacute dietary LC50 33 mg/kg-diet

Chronic NOAEC 0.95 mg/kg-diet

Mineau Scaling Factor** 1.15 none

Body weight of assessed animal (AW) 63.6 g

Food intake of assessed animal (F) 23.00 g/day

Body weight normalized food intake of assessed animal (FN) 362 g/kg-bw-day

*Unless study specific data are available: For bobwhite quail, assume 178 g. For mallard duck, 

assume 1580 g.

**Default value is 1.15. Consult Mineau et al. (1996) to obtain pesticide specific values.

Table 7. Mammalian and avian risk quotients for Ethoprop.

Endpoint EEC Toxicity Value RQ

Mammalian, acute dose-based 0.19 32.8 0.01

Mammalian, chronic dose-based 0.19 2.3 0.08

Mammalian, chronic dietary-based 4.81 46.0 0.10

Avian, acute, dose-based 1.74 4.2 0.41

Avian, acute, dietary-based 4.81 33.0 0.15

Avian, chronic, dietary-based 4.81 1.0 5.06
110
111