UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

PC Code: 09980 J 

DP Barcode: D423166 

Date: October 29, 2015 

MEMORANDUM 

SUBJECT: Transmitta l of the Preliminary Environmental Fate and Ecological Risk 

Assessment fo r the Registration Review of Ethephon 

TO: 

FROM: 

Marquea King, Chemical Review Manager 

Jill Bloom, Team Leader 

Linda Arrington, Branch Chief 

Risk Management and Implementation Branch 5 

Pestic ide Re-Evaluation Division (7508P) 

Nathan Mi ller, Biologist Ilk~ /{J - 2 9 - 2 015 

Ibrahim Abdel-Saheb, Ph.D., Environmental Scientist '' 

Environmental Risk Branch VI 

Environmental Fate and Effects Division (7507P) 

REVIEWED (), y(;;? I (} c . ..-- BY: Amy Blankinship, Senior Biologist ~ /<'§. ~ ~- / -2 7 I ) 

Andrew Shelby, Physical Sc nti ~ ~ /b. 2 tj - 15 

Monica Wait, Risk Assessment Process Leader U 

Environmental Risk Branch VI 

Environmental Fate and Effects Division (7507P) 

THROUGH: Mark Corbin, Branch Chief ~ UJ 'I q, ~ Environmental Risk Branch IV \ (J· l- f ' \ J 

Environmental Fate and Effects Division (7507 

This memorandum transmits the preliminary ecological risk assessment for the registration 

review of ethephon (2-chloroethylphosphonic acid; CAS No.: 16672-87-0; PC Code 099801). 

After reviewing the most recent environmental fate and effects data fo r ethephon, the assessment 

concludes that registered uses of the plant growth regulator ethephon may result in risks that 

exceed both listed and non-listed species LOCs for birds, mammals, and terrestrial plants, and 

listed species LOCs for aquati c vascular plants. 
-Page 2 of 87-

Environmental Fate and Ecological Risk Assessment 

for the Registration Review of Ethephon

 

O

Cl

C

H2

C

H2

P

OH

OH

2-chloroethylphosphonic acid

CAS Registry Number: 16672-87-0

PC Code: 099801

Prepared by:

Nathan Miller, Biologist

Ibrahim Abdel-Saheb, Ph.D., Environmental Scientist

U.S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division 

(EFED)

Environmental Risk Branch VI

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by:

Amy Blankinship, Senior Biologist

Andrew Shelby, Physical Scientist

Monica Wait, Risk Assessment Process Leader

Mark Corbin, Branch Chief

October 29, 2015
-Page 3 of 87-

Table of Contents

1. Executive Summary .............................................................................................................. 4

2. Problem Formulation ........................................................................................................... 6

2.1. Nature of Regulatory Action........................................................................................ 6

2.2. Stressor Source and Distribution ................................................................................ 7

2.2.1. Nature of the Stressor..........................................................................................................................7

2.2.2. Overview of Pesticide Use ..................................................................................................................8

2.3. Receptors ....................................................................................................................... 8

2.3.1. Aquatic and Terrestrial Effects............................................................................................................8

2.3.2. Ecosystems Potentially at Risk............................................................................................................9

2.4. Assessment Endpoints .................................................................................................. 9

2.5. Conceptual Model ........................................................................................................... 9

2.5.1. Risk Hypotheses................................................................................................................................10

2.5.2. Conceptual Pathways Table ..............................................................................................................10

2.6. Analysis Plan ................................................................................................................. 12

2.6.1. Residues of Concern..........................................................................................................................12

2.6.2. Measures of Exposure .......................................................................................................................12

2.6.3. Measures of Effect.............................................................................................................................15

2.6.4. Integration of Exposure and Effects..................................................................................................16

3. Analysis............................................................................................................................. 18

3.1. Use Characterization .................................................................................................. 18

3.2. 3.2. Exposure Characterization ................................................................................. 21

3.2.1. Environmental Fate and Transport Characterization .........................................................................21

3.2.2. Measures of Aquatic Exposure..........................................................................................................25

3.2.3. Measures of Terrestrial Exposure............................................................................. 28

3.3. Ecological Effects Characterization .......................................................................... 35

4. Risk Characterization......................................................................................................... 43

4.1. Risk Estimation ................................................................................................................... 43

4.2. Incident Database Review .................................................................................................. 52

4.3. Risk Description.................................................................................................................. 54

4.3.1 Risk to Aquatic Organisms................................................................................................................54

4.3.2. Risk to Terrestrial Organisms............................................................................................................55

4.4. Uncertainties and Data Gaps..................................................................................... 60

4.4.1. Fate and Transport.............................................................................................................................60

4.4.2. Effects................................................................................................................................................61

5. Endocrine Disruptor Screening Program (EDSP)........................................................... 61

6. Federally Threatened and Endangered (Listed) Species Concerns............................... 61

7. Conclusions.......................................................................................................................... 63

8. References............................................................................................................................ 64

8.1 Submitted Product Chemistry and Environmental Fate Studies................................... 66

8.2. Submitted Ecotoxicity Studies........................................................................................... 70
-Page 4 of 87-

Appendices

Appendix A. Selected SWCC Output Files................................................................................. 77

Appendix B. Toxicity Categories and Levels of Concern ........................................................... 79

Appendix C. Example T-REX (v. 1.5.2) Input and Output for Ethephon ................................... 80

Appendix D. STIR Results .......................................................................................................... 82

Appendix E. Screening Imbibition Program (SIP) Version 1.0 Inputs and Results.................... 83

Appendix F. Accepted ECOTOX Data Table (2009 Report) ...................................................... 84

1. Executive Summary

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

risk assessment for the Registration Review of ethephon (2-chloroethylphosphonic acid; CAS 

No.: 16672-87-0; PC Code 099801) and its end-use products. Ethephon is an 

organophosphonate plant growth regulator intended to promote fruit ripening, abscission, flower 

induction, breaking of apical dominance (inhibition of the growth of lateral buds by the terminal 

bud of a shoot), and other plant responses through the release of ethylene gas, a natural plant 

hormone. It has been registered in the United States for more than 40 years for use on a number 

of terrestrial food, feed and nonfood crops, greenhouse food crops and outdoor residential plants. 

Ethephon is applied as a broadcast foliar spray via ground, aerial, or backpack sprayer 

equipment. Application rates range from 0.25 pounds of active ingredient per acre (lb a.i./A) for 

a niche use on cucurbit crops for hybrid seed production (applied up to six times at a minimum

of three day interval) to 4 lbs a.i./A for turf (applied up to five times at a minimum of 14 day 

interval). The highest registered ethephon use rate for a food crop is a single application at 2 lbs 

a.i./A on apples, berries, pineapples, and tobacco.

Ethephon is characterized as nonvolatile, soluble compound that is slightly to moderately mobile 

in soil. Ethephon dissipates in the environment through both biotic and abiotic degradation and 

by leaching in soils that are low in organic carbon. Therefore, there is slight potential for 

ethephon to accumulate in soil with repeated applications. Ethephon is not expected to

bioaccumulate due to its low Kow (≤6.3 x 10-3).

Potential Risks to Non-target Organisms

Summary of the Major Risk Conclusions for Aquatic Taxa

Fish and Aquatic Invertebrates. The estimated environmental concentration are well below 

ecotoxicity study-defined toxic thresholds, such that neither acute nor chronic effects to fish or 

aquatic invertebrates are expected. There were no levels of concern (LOC) exceedances of listed 

and non-listed species of fish or aquatic invertebrates for the registered uses of ethephon.
-Page 5 of 87-

Aquatic Plants. Risk Quotients (RQs) do not exceed the LOC for non-listed aquatic vascular 

plants or listed or non-listed species of aquatic non-vascular plants. For ethephon used on turf, 

ornamentals, and cotton, risk exceeds the LOC for listed species of aquatic vascular plants. The 

LOC exceedances for these three use patterns may be overestimated by the absence of a 

definitive no-adverse effect concentration (NOAEC) in the available study.

Summary of the Major Risk Conclusions for Terrestrial Plants and Animals 

Terrestrial Plants. There is potential for adverse effects to non-target plants based on 

ethephon’s plant growth regulator mode of action. The available terrestrial plant studies 

demonstrate that effects to non-target plants occur at rates well below the maximum labeled 

application rates. RQs exceed the LOC for listed and non-listed terrestrial plants, and the extent 

of adverse effects from spray drift in terms of distance away from the treated field exceed the 

AgDRIFT model range (>997 feet) for multiple use sites. Additionally, there are seven 

terrestrial plant incidents associated with ethephon use which reinforce the certainty of adverse 

effects.

Birds and Surrogates (Reptiles and Terrestrial Amphibians). There is a potential for adverse 

chronic effects (e.g., reduced number of hatchling, reduced survival of hatchlings) and acute 

effects for birds consuming short grass, tall grass, broadleaf plants/small insects, and arthropods 

(RQs exceed acute listed, acute non-listed, and chronic risk LOCs for multiple use patterns). 

Mammals. There is a potential for adverse chronic effects (e.g., reduced offspring bodyweight) 

and acute effects for mammals consuming short grass, tall grass, broadleaf plants/small insects, 

and arthropods (RQs exceed acute listed, acute non-listed [turf use pattern only], and chronic risk 

LOCs for multiple use patterns). 

Honey Bees and Terrestrial Invertebrates. Acute oral and contact honey bee (Apis mellifera) 

toxicity data indicate that the likelihood of adverse effects from exposure to ethephon is 

considered low (RQ<LOC) for all use patterns. However, chronic oral toxicity data for young 

adult bees and acute and chronic larval honey bee data are not available to fully evaluate the 

potential for effects to individual adult honey bees or their brood (eggs, larvae, and pupae), and 

risk is uncertain.

Data Gaps and Uncertainties 

Fate and ecotoxicity data gaps discussed in Section 4.4. There are no significant data gaps in the 

environmental fate database submitted by the registrant. Fate data submitted with the RR DCI –

aerobic soil metabolism studies MRIDs 48202001 (MRIDs 48202002 was classified as 

unacceptable) and aerobic aquatic metabolism MRID 48202003 were considered in this 

assessment. Submitted independent laboratory validation (ILV) studies for these ECMs (MRIDs 

49305601, 49305603) are in review.

The main ecotoxicity uncertainties in the risk assessment concern terrestrial plants and terrestrial 

invertebrates, because the available toxicity data are not comprehensive. For terrestrial plants, a 
-Page 6 of 87-

no effect concentration could not be established for the most sensitive dicot species tested in the 

vegetative vigor study design. In lieu of a NOAEC, the EC05 is used to estimate risk to listed 

terrestrial dicots, consistent with EFED policy. Concerning terrestrial invertebrates, chronic 

dietary risk to adult honeybees and acute and chronic dietary risk to larval honeybees is uncertain 

due to a lack of data. Honey bee risk assessment guidance has recently been finalized and 

recommends the following honey bee data for a Tier I screening-level risk assessment for bees:

 acute oral toxicity to adult honey bees;

 acute oral toxicity to larval honey bees;

 chronic oral toxicity to adult honey bees; and,

 chronic oral toxicity to larval honey bees.

Acute oral toxicity data for adult honey bees are available, and no effects were seen at an 

acceptable limit dose. However, if the other Tier I studies identify the potential for a risk 

concern, additional studies may be requested (i.e., semi-field testing for pollinators [special 

study, Tier II], field testing for pollinators [OCSPP 850.3040, Tier III], and field trial of residues 

in pollen and nectar [special study, Tier III]). Since these data are currently unavailable for 

ethephon, the potential for adverse effects to individual honey bees and their brood is uncertain.

2. Problem Formulation

The purpose of problem formulation is to provide the foundation for the environmental fate and 

ecological risk assessment for the Registration Review of the organophosphonate plant growth 

regulator ethephon (2-chloroethylphosphonic acid; CAS No.: 16672-87-0; PC Code 099801) and 

its end-use products. The problem formulation sets the objectives for the risk assessment, 

establishes a risk hypothesis and conceptual model depicting potential routes of exposure, 

biological receptors and their measurement endpoints, and it provides a plan for analyzing the 

data and characterizing the risk associated with the use of ethephon (USEPA, 1998). 

2.1. Nature of Regulatory Action

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

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

Agency (EPA). To determine whether a pesticide can be registered, the EPA evaluates its safety 

to non-target species based on a wide range of environmental and health effects studies. In 1996, 

FIFRA was amended by the Food Quality Protection Act (FQPA), and EPA was mandated to 

implement a new program for the periodic review of pesticides, i.e., Registration Review1. The 

Registration Review program is intended to ensure that as the ability to assess risk evolves and as 

policies and practices change, all registered pesticides continue to meet the statutory standard of 

no unreasonable adverse effects to human health and the environment. Changes in science, 

public policy, and pesticide use practices will occur over time. Through the registration review 

program, the Agency periodically reevaluates pesticides to make sure that as changes occur, 

products in the marketplace can be used safely.

 

1 http://www.epa.gov/oppsrrd1/registration_review/
-Page 7 of 87-

2.2. Stressor Source and Distribution

2.2.1. Nature of the Stressor

Ethephon is an organophosphonate plant growth regulator intended to promote fruit ripening, 

abscission, flower induction, breaking of apical dominance (inhibition of the growth of lateral 

buds by the terminal bud of a shoot), and other plant responses. Ethephon is not a plant hormone

per se; however, its principal degradation product, ethylene, is a natural plant hormone that is 

distributed systemically in plants (Archer et al., 1973), and exerts effects on plant physiology. A 

Reregistration Eligibility Decision (RED) for ethephon was published in 1995 (USEPA, 1995). 

In 2006, an ecological risk assessment was conducted for proposed new uses of ethephon on 

filbert and coffee to aid in harvesting (DP 324040). In 2010, a Preliminary Problem Formulation 

for Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure 

Assessments for Ethephon was conducted (DP 371952).

An organophosphonate pesticide, ethephon demonstrates inhibition of plasma 

butyrylcholinesterase (EPA R.E.D. Facts Ethephon, 1995) in mice. However, its single 

degradate retains the phosphate moiety, 2-hydroxyethylphosphonic acid (HEPA), and does not 

inhibit plasma butyrylcholinesterase (see chemical structures in Table 8). The Health Effects 

Division (HED) completed a screening level review of comparative toxicity studies of ethephon 

and HEPA that were submitted. This review concluded that the HEPA metabolite does not pose a 

concern for risk assessment (USEPA, 2002). 

Ethylene does not contain the organophosphonate moiety of the ethephon molecule. Therefore, 

although ethephon may inhibit cholinesterase in animals, no degradates of ethephon are expected 

to do so. The 1992 RED for ethylene (PC 041901) confirms that ethylene is not a cholinesterase 

inhibitor (USEPA, 1992). Ethephon alone is the residue of concern for animals in this 

assessment.

The biologically active degradate of ethephon, ethylene, is a degradate of concern for plants in 

this risk assessment, as it demonstrates a phytohormonal mode of action that could have adverse 

effects on plant growth. Therefore, ethephon and ethylene are the residues of concern for plants 

in this assessment. Table 1 summaries the chemical profile of ethephon.
-Page 8 of 87-

Table 1. Chemical Profile of Ethephon.

Common name Ethephon

Chemical name

Chemical formula

[(2-chloroethyl) phosphonic acid]

C2H6ClO3P

Structure 

SMILES Notation C(CCl)P(=O)(O)O

Pesticide type plant growth regulator

Chemical class Organophosphonate

CAS number 16672-87-0

Molecular Weight 144.5 g/mol

2.2.2. Overview of Pesticide Use 

Ethephon was first registered in the United States in 1973 to promote fruit ripening, abscission, 

flower induction, breaking of apical dominance and other plant responses. Ethephon currently has 

43 active registered products for use on terrestrial food, feed and nonfood crops, greenhouse food 

crops and outdoor residential plants. Ethephon end use products are formulated as flowable liquids 

and soluble concentrates. Broadcast applications to plant foliage are made by either ground or 

aerial equipment. Ethephon may also be applied by hand sprayer to select home garden 

vegetables. The turf use represents the highest application rate: 3.4 lb a.i/A, 6 applications, 28-day 

interval. This assessment evaluates risk based on currently labeled maximum application rates. 

2.3. Receptors

2.3.1. Aquatic and Terrestrial Effects

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

with the process described in the Overview Document (USEPA, 2004a), this risk assessment uses 

a surrogate species approach. Toxicity data generated from surrogate test species, which are 

intended to be representative of broad taxonomic groups, are used to extrapolate potential effects 

on a variety of species (receptors) included under these taxonomic groupings. 

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

available open literature are used to evaluate potential direct effects to aquatic and terrestrial 

receptors. The open literature studies are located through EPA’s ECOTOXicity database 

(ECOTOX; http://cfpub.epa.gov/ecotox/), which provides a source for locating single chemical 

toxicity data for aquatic life, terrestrial plants, and wildlife. 
-Page 9 of 87-

2.3.2. Ecosystems Potentially at Risk

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

to identify specific ecosystems during the development of a nation-wide ecological risk 

assessment. However, in general terms, terrestrial ecosystems potentially at risk could include 

the treated field or tree(s) and immediately adjacent areas that may receive spray drift or runoff. 

Areas adjacent to the treated field or tree(s) could include cultivated fields, fencerows and 

hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats, and other 

uncultivated areas. 

Aquatic ecosystems potentially at risk include water bodies adjacent to or downstream from use 

sites, and might include natural or impounded lentic water bodies such as ponds, lakes and 

reservoirs, or flowing waterways such as streams or rivers including all adjacent off-channel 

habitats that are permanently or intermittently connected to flowing waters. For uses in coastal 

areas, aquatic habitat also includes marine ecosystems, including estuaries, embayments, and 

near-shore environments such as tidal marshes.

2.4. Assessment Endpoints

Assessment endpoints represent the actual environmental value that is to be protected, defined by 

an ecological entity (species, community, or other entity) and its attribute or characteristics 

(USEPA, 1998). For ethephon, ecological entities of potential concern include the following: 

birds, terrestrial- and aquatic-phase amphibians, reptiles, mammals, freshwater fish and 

invertebrates, estuarine/marine fish and invertebrates, non-target terrestrial plants, terrestrial 

invertebrates, and aquatic vascular and non-vascular plants. The attributes for each of these 

entities include growth, survival, and reproduction.

The assessment endpoints are intended to reflect population sustainability and community 

structure within ecosystems and hence relate back to ecosystems at risk. If risks are expected for 

given species/taxa based on the screening-level assessment, then risks might be expected to 

translate to higher levels of biological organization.

2.5. Conceptual Model

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

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

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

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

exposure for ecological receptors, and a feasible route of exposure. The conceptual model is 

intended to provide a written description and visual representation of the predicted relationships 

between ethephon, potential routes of exposure, and the predicted effects for the assessment 

endpoint. The conceptual model consists of two major components: the risk hypotheses and a 

conceptual model (USEPA, 1998).

The conceptual model used to depict the potential ecological risk associated with the existing 

uses of ethephon relies on previous assessments and the Agency’s current understanding of the 
-Page 10 of 87-

environmental fate and ecological effects of the chemical. Consistent with the intended use of 

ethephon as a plant growth regulator, risk to non-target terrestrial and aquatic plants is expected. 

Effects on plants, which represent the primary producers in an ecosystem, may result in 

secondary effects on consumers which may include a broad range of taxa.

2.5.1. Risk Hypotheses

For ethephon, the following generic ecological risk hypotheses are being employed for this risk 

assessment:

Given the currently labeled uses of ethephon and its environmental fate properties, there 

is a likelihood of exposure to non-target terrestrial and aquatic organisms. 

When used in accordance with the label, ethephon may result in potential adverse effects 

upon the survival, growth, and reproduction of non-target terrestrial and aquatic 

organisms. 

 2.5.2. Conceptual Pathways Table

The environmental fate properties of ethephon indicate that for foliar applications, spray drift and

runoff (including of eroded sediment) are potential transport mechanisms to aquatic habitats 

where non-target organisms may be exposed. It is expected that non-target terrestrial organisms 

can be exposed via foliar applications of ethephon through consumption of exposed plants and 

invertebrates on treated fields. Additionally, ethephon may reach terrestrial environments off the 

field via spray drift. A summary of the transport pathways and the models used for those 

pathways in the assessment are provided in Table 2. 

Ethephon is not persistent in the environment. The major routes of dissipation appear to be 

chemical hydrolysis under neutral and alkaline conditions and microbial degradation. Although 

ethephon does degrade fairly rapidly in somewhat acidic soils (pH 6.1) under aerobic and 

anaerobic conditions, it does not hydrolyze in sterile, acidic water (pH 5). The major degradates 

of ethephon are ethylene gas and 2-hydroxy ethyl phosphonic acid (HEPA), the latter formed by 

microbially mediated hydrolytic dehalogenation. Ethephon can be characterized as having 

moderate to low mobility in soil. The mobility of the soil degradate 2-hydroxy ethyl phosphonic

acid is slightly to hardly mobile (Kfoc range of 1460–12100 L/kg). Ethephon is reported to have 

a very low octanol/water partition coefficient (Kow <0.00626), therefore, it is not expected to 

accumulate in fish. 

Additionally, the Screening Tool for Inhalation Risk (STIR) version 1.0 (November 23, 2010) 

indicates that ethephon exposure via inhalation is not likely to be a risk concern for birds and 

mammals (Appendix D). Another screening tool, the Screening Imbibition Program (SIP v.1.0, 

released June 15, 2010) was used to calculate an upper-bound estimate of wildlife drinking water 

exposure. The SIP screening tool indicates that drinking water exposure alone is considered a 

potential pathway of concern for birds or mammals on either an acute or chronic exposure basis

based on solubility and available toxicity data (
-Page 11 of 87-

Appendix E). 

The exposure pathways may result in exposure to various aquatic and terrestrial organisms. 

With exposure, the following attribute changes have the potential to occur: 

 effects to individual organisms;

 effects to the food chain (reduction in prey and food, modification of primary constituent 

elements (PCE) related to prey availability); and,

 effects to habitat integrity (reduction in primary productivity, reduced cover, community 

change, and modification of PCE related to habitat).

Table 2. List of the Various Models and the Related Taxa for which the Models will be 

Used to Assess Risk.

Environment Taxa of Concern Exposure

Media

Exposure 

Pathway

Model(s) or 

Pathway Attribute Change

Aquatic

Vertebrates/ 

Invertebrates

(including 

sediment 

dwelling)

Surface water and 

sediment

Runoff and spray 

drift to water and 

sediment

SWCC

Individual Organisms

Food Chain

Habitat Integrity

Aquatic Plants 

(vascular and 

nonvascular)

Food Chain

Habitat Integrity

Riparian plants See terrestrial exposure pathways Habitat Integrity

Terrestrial

Vertebrate

Dietary items

Ingestion of 

residues in/on 

dietary items as a 

result of direct 

application

T-REX

Individual Organisms

Food Chain

Habitat Integrity

Consumption of 

aquatic organisms

Residues taken up 

by aquatic 

organisms

KABAM

Individual Organisms

Food Chain

Habitat Integrity

Plants

Spray drift/runoff Runoff and spray 

drift to plants TERRPLANT

Food Chain

Habitat Integrity Surface water

Residues in 

irrigation water Not a major 

transport pathway

Groundwater

Bees and other 

terrestrial 

invertebrates1

Contact

Dietary items

Spray contact and 

ingestion of 

residues in/on 

dietary items as a 

result of direct 

application

See honey bee risk 

assessment 

guidance (USEPA 

et al., 2014)

Individual Organisms

Colony/Population 

Integrity

All 

Environments All

Movement through 

air to aquatic and 

terrestrial media

Spray drift AgDRIFT (Spray 

drift) Individual Organisms

Food Chain

Atmospheric Habitat Integrity

transport2

Not a major 

transport pathway

Text in italics represent transport pathways that are not of concern.

1 See pollinator SAP white paper for full list of modelling approaches for evaluating exposure used in this 

assessment (USEPA, 2012b).

2 Ethephon is non-volatile. Gaseous ethylene will be degraded in the atmosphere by reaction with photochemically-
-Page 12 of 87-

produced hydroxyl radicals with DT50 of 24 hours; therefore, it is not likely to disperse via atmospheric transport.

2.6. Analysis Plan

2.6.1. Residues of Concern

Ethephon alone is the stressor of concern for animals in the risk assessment. Ethephon’s single 

organophosphate degradate, HEPA, does not inhibit plasma butyrylcholinesterase (Morton, 

2002). Therefore, the degradates of ethephon are not expected to be cholinesterase inhibitors and 

are not of toxicological concern for animals.

The biologically active degradate of ethephon, ethylene gas, is a stressor of concern for plants in 

the risk assessments, as it demonstrates a phytohormonal mode of action that could have adverse 

effects on plant physiology. Therefore, the stressors of concern for plants in the risk assessment 

include ethephon and ethylene.

2.6.2. Measures of Exposure

Using EFED’s standard suite of models, surface water estimated environmental concentrations 

(EECs) were generated for ethephon for the registered uses. The Surface Water Concentration 

Calculator (SWCC, v 1.106, May, 2014) is used to generate estimated environmental 

concentrations (EEC)s that may occur in surface water. The SWCC simulates pesticide transport 

via runoff from an agricultural field (in addition to loadings from spray drift), following 

applications to crops. The model then simulates resulting concentrations in an adjacent surface 

water body (i.e., the standard pond). The measure of exposure for aquatic species in surface 

water bodies receiving runoff and/or spray drift is a return frequency of 1-in-10 years of the 

EEC, based on 30-year simulations. The maximum 1-in-10 year return frequency concentration 

is used for estimating acute exposures to aquatic organisms (plants and animals); the 1-in-10 year 

21-day mean concentration is used for assessing aquatic invertebrate chronic exposure; and the 

1-in-10 year 60-day mean concentration is used for assessing chronic exposure for fish (and 

aquatic-phase amphibians for which freshwater fish serve as surrogates). EECs for ethephon 

include only the parent compound as the single residue of concern. Additional details on the 

model can be found at http://www.epa.gov/oppefed1/models/water/.

Terrestrial wildlife are potentially exposed to ethephon via consumption of residues on food 

items from spray applications on various use sites. For spray applications, the T-REX model 

(Terrestrial Residue EXposure model; v. 1.5.2; June 6, 2013) is used to predict dietary exposure 

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

Fletcher (Fletcher et al., 1994; Hoerger and Kenaga, 1972). In this assessment, the default foliar 

dissipation half-life of 35 days was used for terrestrial modeling purposes. Additionally, the 

influence of lower foliar dissipation half-live values on risk was explored. Estimated exposures 

of terrestrial insects to ethephon are evaluated. Additional details on the model may be found at 

http://www.epa.gov/oppefed1/models/terrestrial/trex/trex_v1_5_webversion.xlsm.

The TERRPLANT (v. 1.2.2; October 29, 2009) model is used to derive EECs relevant to 

terrestrial and wetland plants for the registered uses of ethephon. The model assumes that 
-Page 13 of 87-

default fractions of the intended application will be transported to an adjacent field through 

runoff and spray drift. Measures of exposure to terrestrial plants are expressed as a fraction of 

the mass of the ethephon applied to a treated field. Additional details on the model may be 

found at http://www.epa.gov/oppefed1/models/terrestrial/index.htm#terrplant.

To characterize potential non-target animal and plant exposure from spray drift alone, Tier 1 

modules in AgDRIFT (v. 2.1.1, December 2011) were used to estimate how far off-site spray 

drift exposure might occur at a level known to cause adverse effects based on aquatic and 

terrestrial toxicity endpoints. Additional details on the model may be found at 

http://www.agdrift.com/AgDRIFt2/DownloadAgDrift2_0.htm.

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

an upper-bound estimate of wildlife inhalation exposure using ethephon’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 is a series of six guideline studies that are submitted to the Registration Division of the 

Office of Pesticide Programs for technical and formulated products of a pesticide (LD50 = 1205

mg/kg-bw/day, MRID 00029509; and inhalation LC50 >2.13 mg/L, MRID 43849403, 

respectively) as well as the most sensitive acute oral avian toxicity endpoint (Bobwhite quail; 

Colinus virginianus; LD50 =596 mg/kg-bw, MRID 00027493). Based on the results of the STIR 

model (
-Page 14 of 87-

Appendix D), exposure through inhalation of spray drift or the vapor phase of ethephon is not 

considered a primary pathway of concern for either avian or mammalian species on an acute 

inhalation exposure basis. Additional details on the model may be found at 

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

 

The analysis of the inhalation route in STIR does not consider that aggregation with other 

exposure pathways such as dietary, dermal, or drinking water 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, 2004a). The risk characterization section (Section 4.3), discusses the impact of 

consideration of other routes of exposure that have been identified as potentially important and 

the degree of certainty associated with screening-level 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).

The Screening Imbibition Program (SIP v.1.0, released June 15, 2010) was used to calculate an 

upper-bound estimate of wildlife drinking water exposure using ethephon’s solubility (i.e., 1.24 x 

106 mg/L at 23oC, MRID 41154506), and compared to the most sensitive acute and chronic avian 

and mammalian toxicity endpoints (see Table 117). Based on this analysis, drinking water 

exposure alone is considered a potential pathway of concern for birds or mammals on either an 

acute or chronic exposure basis. For a sample of the output generated by SIP v.1.0, please see 
-Page 15 of 87-

Appendix E. Additional details on the model may be found at

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

Ethephon is reported to have a very low octanol/water partition coefficient (Kow <0.00626;

MRID 41743501), therefore, it is not expected to accumulate in fish.

2.6.3. Measures of Effect 

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

conducted with a limited number of surrogate test species (Table 3). 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. In addition, the ECOTOX database was searched twice; once in 2009 by USEPA’s Office 

of Research and Development Mid-Continent Ecology Division (ORD-MED), and once in 2015 

using the ECOTOX website; to provide more ecological effects data for ethephon. The 2009 

ECOTOX run was reviewed in 2010 for the ethephon Problem Formulation. Data were further 

examined if endpoints were more sensitive (lower) than endpoints available from submitted 

studies or were available for amphibians, freshwater molluscs, or reptiles (USEPA, 2011). Data 

meeting the OPP’s standard for inclusion in risk assessment 

(http://www.epa.gov/pesticides/science/literature-studies.html) were available at the time of the 

2009 ECOTOX run that showed greater sensitivity than results from submitted studies for 

aquatic nonvascular plants (Ma et al, 2004, ECOTOX Number E095681).

The acute measures of effect used in this screening-level assessment are the LD50 (Lethal Dose), 

LC50 (Lethal Concentration), EC50 (Effects Concentration), and IC50 (Inhibition Concentration). 

These are measures of acute toxicity which result in 50% of the respective effect in tested 

organisms. The endpoints for chronic measures of exposure are the NOAEC (No Observed 

Adverse Effects Concentration) and the NOAEL (No Observed Adverse Effects Level). 

Toxicity studies were submitted for freshwater fish and invertebrates, estuarine/marine fish and 

invertebrates, aquatic and terrestrial plants, birds, mammals, and honey bees. The endpoints 

used for risk characterization were derived from studies which underwent review and were 

classified as “acceptable” (conducted under guideline conditions and considered to be 

scientifically valid) or “supplemental” (conditions deviated from guidelines but the results are 

considered to be scientifically valid). 

Table 3 lists the measures of environmental exposure and ecological effects used to assess the 

potential risks of ethephon to non-target organisms. The methods used to assess the risk are 

consistent with those outlined in the document “Overview of the Ecological Risk Assessment 

Process in the Office of Pesticide Programs” (USEPA, 2004a).
-Page 16 of 87-

Table 3. Measures of Exposure and Effect Used in Assessing Potential Risks Associated with 

the Proposed Uses of Ethephon.

Assessment Endpoint Surrogate Species and Measures of 

Ecological Effect1 Measures of Exposure

Birds2

Survival

Lowest acute LD50 (single oral dose test) 

and LC50 (subacute dietary test)

Upper-bound residues on 

food items

Reproduction 

and Growth

Lowest NOAEC

(21-week reproduction test)

Mammals

Survival Lowest acute LD50 (single oral dose test)

and LC50 (subacute dietary test)

Reproduction 

and Growth

Lowest NOAEC

(2-generation reproduction test)

Aquatic Animals (Fish and 

invertebrates)3

Survival Lowest tested LC50 or EC50

(acute toxicity test)

Peak EECs4

Reproduction 

and Growth

Lowest NOAEC (early life-stage, full 

life-cycle tests, 10-day sediment tests, 

or chronic sediment tests)

21-day EECs for invertebrates 

and 60-day EECs for fish4

Terrestrial plants5 Survival and 

growth

Lowest EC25 (for non-listed plants) and 

corresponding NOAEC (for listed 

plants)

(endpoints derived for monocots and 

dicots from seedling emergence and 

vegetative vigor studies)

Estimates of runoff and spray 

drift to non-target areas

Insects6

Survival Lowest honey bee LD50 (acute contact 

test)

Upper-bound residues on tall 

grass7

Aquatic plants (vascular 

and non-vascular)

Survival and 

growth

Lowest EC50 (for non-listed plants) and 

corresponding NOAEC or EC05 (for 

listed plants)

Peak EECs4

1 The most sensitive species tested within taxonomic groups is used for screening-level risk assessments.

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

3 Freshwater fish represent surrogates for aquatic-phase amphibians.

4 Aquatic EECs are based on modeling described in Section 3.2.2.1.

5 Four species of two families of monocots - one is corn, six species of at least four dicot families, of which one is 

soybeans. 

6 Risk to terrestrial invertebrates from ethephon use is quantitatively evaluated against the acute listed terrestrial 

invertebrate LOC of 0.4.

7 The tall grass residue value from the T‐REX model (v. 1.5.2) is used as a surrogate for pesticide concentrations in 

nectar and pollen.

2.6.4. Integration of Exposure and Effects

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 ethephon, the risk quotient 

(RQ) method is used to compare estimated exposure and measured toxicity values. The RQ 

method involves dividing estimated environmental concentrations (EEC) by acute and chronic 

toxicity values. The resulting RQs are then compared to the Agency’s Levels of Concern (LOC) 

(USEPA, 2004a) (Table 4). The LOCs are used to indicate when applications of ethephon, as 
-Page 17 of 87-

directed on the label, have the potential to cause adverse effects to non-target organisms from 

exposure to ethephon.

Table 4. 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/LC50

1 0.5

Acute 

Restricted Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use 

classification

Peak EEC/LC50

1 0.1

Acute Listed 

Species

Listed species may be potentially affected by acute 

exposures

Peak EEC/LC50

1 0.05

Chronic Potential for effects to non-listed and listed animals 

from chronic exposures

60-day EEC/NOAEC (fish)

21-day EEC/NOAEC 1

(invertebrates)

Aquatic Plants

Non-Listed Potential for effects to non-listed plants from 

exposures

Peak EEC/LC50

1 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

Honey bees

Acute Potential for effects to individual bees or brood due 

to contact and dietary exposure.

Contact EEC/acute contact 

LD50

Diet EEC/ acute oral LD50

Diet EEC/ Larval LD50

0.4

Chronic Potential for effects to individual bees or brood due 

to contact and dietary exposure.

Diet EEC/ adult NOAEL

Diet EEC/ larval NOAEL 1.0

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.
-Page 18 of 87-

3. Analysis

3.1. Use Characterization

Use patterns 

Ethephon was first registered in the United States in 1973. Ethephon is a plant growth regulator 

used on field crops (e.g., blueberries, cotton, cucumbers, and wheat), fruit and nut orchards, 

vineyards, ornamentals and turf (e.g., golf courses and residential lawns). Currently, there are 43

active product registrations for ethephon. These formulations are flowable liquids or emulsifiable 

concentrates.

Applications are made by ground or air spray. Maximum single application rates for ethephon, 

numbers of applications per year, application intervals and application methods for all registered 

uses are provided in Table 5.

Table 5. Ethephon Application Rates for the Various Uses. 

Use

Single max 

application 

rate (lb a.i./A)

Number of 

app. per year

Application 

interval (d)

max annual 

application 

rate

(lb a.i./A)

Application method(s)

Barley 0.5 1 Not stated 0.5 Ground, aerial

Blackberry 2 1 Not stated 2 Ground, aerial

Blueberry 2 1 Not stated 2 Ground, aerial

Blueberry (SLN) 0.43 2 21 Not stated Ground, aerial

Cantaloupe 0.75 1 Not stated 0.75 Ground, aerial

Coffee (SLN) * 0.5 Not stated Not stated Not stated Not stated

Cotton 2 1 Not stated 2 Ground, aerial

Cucumber (CA) 0.25 6 3 Not stated Ground, aerial

Cucumber (outside 

CA) 0.083 Not stated 7

Not stated Ground, aerial

Grass for seed 1 1 Not stated Not stated Ground, aerial

Pepper 1 1 Not stated 1 Ground, aerial

Pineapple 2 2 ** Not stated 3 Ground, aerial

Pumpkin 0.25 6 3 1.5 Ground, aerial

Squash 0.25 6 3 1.5 Ground, aerial

Sugarcane 0.5 1 Not stated 0.5 Aerial

Tobacco 2 1 Not stated 2 Ground, aerial

Tomato 1.63 1 Not stated 1.63 Ground, aerial

Tomato (large-fruited 

greenhouse variety; 

SLN) 

1.25 Not stated Not stated Not stated Ground

Wheat 0.5 1 Not stated 0.5 Ground, aerial

Apples 2 1 Not stated 2 Ground, aerial

Pears (SLN) 1 1 Not stated Ground

Cherries 1 1 Not stated 1 Ground, aerial

Douglas firs (seed 

orchards; SLN) 3.3 Not stated Not stated Not stated

Ground, aerial
-Page 19 of 87-

Grapes 0.5 1 Not stated 0.5 Ground, aerial

Macadamia nut (SLN) 1.44 1 Not stated Not stated Ground, aerial

Walnut 1.25 1 Not stated 1.25 Ground, aerial

Ornamental conifers 0.5 Not stated Not stated Not stated Ground, aerial

Ornamental deciduous 

fruit trees 1 Not stated Not stated Not stated Ground, aerial

Ornamental Douglas 

fir 0.25 Not stated Not stated Not stated Ground, aerial

Ornamental 

herbaceous plants 5.28 Not stated 14 Not stated Ground

Ornamental trees 0.19 per 20 

gallon 1 Not stated 0.19 per 20 gallon Ground, aerial

Plumeria (SLN) 0.013 (lbs 

a.i./tree) 1 Not stated Not stated Ground

Commercial lawns 

and golf courses† 4.1 Not stated 28 Not stated Ground

Recreational lawns 3.4 6 28 Not stated Ground

 Bold text indicates the use with the highest annual application rate

 *: Allowed in Puerto Rico only 

 **: Plus an additional application of 1 lb a.i./A

 †:

 Max application rate

According to the 2014 Screening Level Usage Analysis (SLUA) prepared by the Biological and 

Economic Analysis Division (BEAD) using data from 2004-2012, the average percent crop 

treated for cotton is estimated to be 55% nationally, with a maximum estimate of 70% (USEPA, 

2012). The average annual pounds applied for cotton estimated in the SLUA was 8,400,000 

pounds per year. Use sites with the next highest usage after cotton are apples, tomatoes, and 

grapes, but the overall pounds applied to those use sites is much lower (30,000; 30,000; and 

20,000 pounds annually respectively).

As shown in Figure 1, based on USGS National Water Quality Assessment Program (NAWQA) 

from 2012, ethephon agricultural usage appears to be predominately on cotton. NAWQA does 

not consider non-agricultural uses of ethephon in its data collection. Neither does BEAD include 

non-agricultural uses in the SLUA.
-Page 20 of 87-

Figure 1 . Reported Ethephon Use from USGS NAWQA Database

http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2011&map=ETHEPHON&hilo=L&disp=Ethephon

(accessed July 14, 2015).
-Page 21 of 87-

3.2. 3.2. Exposure Characterization

3.2.1. Environmental Fate and Transport Characterization

The general physical/chemical properties of ethephon are summarized in Table 6. Environmental 

fate and transport-related properties of ethephon are characterized in further detail in the 

following sections. 

Table 6. General Physical and Chemical Properties of Ethephon.

Parameter Value Reference

Physical/Chemical Parameters

Molecular mass 144.5 g/mol USEPA, 1995

Vapor pressure (25°C) <1.0 x 10-7torr MRID 41154506

Water solubility (23°C, pH not reported) 1.24 x 106 mg/L MRID 41154506

Dissociation constants (25°C) 2.5 (pKa1); 7.2 (pKa2) MRID 41154506

Octanol-water partition coefficient (KOW) 

(25°C, pH not reported)

<6.3 x 10-3 MRID 41743501

Table 7 contains the submitted environmental fate data for the pesticide.

Table 7. Environmental Fate Data Summary for Ethephon.

Mobility

Freundlich adsorption Coefficient (kd) 30 L/kg (5 soils; range:

2.37-57.3 L/kg)

MRID 

42126001

Persistence in Water

Hydrolysis half-life (25°C) 74 d (pH 5)

2.4 d (pH 7)

1.0 d (pH 9)

MRID 

41545701

Aqueous photolysis half-life (25°C) 139 d MRID 

41545601

Aerobic aquatic metabolism half-life (25°C) 2.6 d MRID 

48202003

Anaerobic aquatic metabolism half-life (25°C) 5.3 d MRID 

41757702

Persistence in Soil

Soil photolysis half-life (25°C) 12 d (sandy loam, pH 6.1, OM 1.1%) MRID 

41681401

Aerobic soil metabolism half-life (25°C) 9.1 d (sandy loam, pH 6.1, OM 1.1%)

11 d (clay loam soil, pH 7.6, OM 4.8%)

MRID 

41757701, 

48202001 

Field Dissipation

Terrestrial field dissipation half-life; maximum 

leaching depth

6.8 d; 15 cm (NC; pH 6.6)

12 d; 45 cm (CA; pH 7.8)

25 d; 60 cm (WA; pH 7.1)

MRID 

42011501
-Page 22 of 87-

3.2.1.1. Transport and Mobility

Ethephon (2-chloroethylphosphonic acid) is a white, waxy solid (MRID 41154506) and will not 

likely volatized as indicated by a low partial vapor pressure of <1 x 10-7torr (25°C; MRID 

41154506). The compound is an anion (pKa1 = 2.5) in acidic and neutral environments and a 

double anion in alkaline environments (pKa2 = 7.2). Ethephon is present as an anion in most 

environmentally relevant conditions. As an anion, ethephon is soluble in water up to 1.24 x 106

mg/L at 23°C (pH not reported; MRID 41154506). Also, ethephon will not bioaccumulate in 

aquatic or terrestrial food chains, which is supported by its low octanol-to-water partitioning 

coefficient (KOW) of ≤6.3 x 10-3(MRID 41743501).

Ethephon showed high variability in adsorption to five studied acidic soils (initial soil pH values 

of 4.6-6.0), ranging from moderately to slightly mobile in soil (KFOC range of 386–3070 L/kgOC; 

1/n range of 0.98–1.02; MRID 42126001), according to the FAO soil mobility classification 

scheme (USEPA, 2006d). The mechanisms behind this variability are not well understood; 

however, adsorption to organic matter appears to account for some of the variability, as the 

coefficient of variation for the Freundlich organic carbon-normalized soil partition coefficients 

(KFOC; CV = 58%) is less than that for the Freundlich soil-water partition coefficients (KF; CV = 

85%). However, regression of percents organic carbon in soil versus Freundlich soil-water 

partition coefficients is characterized by a correlation coefficient of 0.75 and a probability value 

>0.05 (0.057), which indicates uncertainty in correlating the data. Adsorption/desorption are not 

pH dependent. Regression of soil pH versus Freundlich soil-water partition coefficients is 

characterized by a correlation coefficient of 0.1444.

3.2.1.2. Degradation

Ethephon is relatively stable to photodegradation in water, with a half-life of 139 days (MRID 

41545601); however, the compound more readily photodegrades in soil, with a half-life of 12 

days (MRID 41681401). Ethephon is also relatively stable to hydrolysis in acidic conditions, 

with a half-life of 74 days (MRID 41545701). However, ethephon hydrolyzes readily in neutral 

and alkaline conditions, with half-lives of 2.4 and 1.0 days, respectively. 

Ethephon is susceptible to microbial degradation in aerobic soil, with a half-lives that range from 

9.1 – 11 days (MRID 41757701, 48202001). Ethephon moderately persistent in soil according to 

Goring et al., 1975 scale for pesticide degradation in soil. Susceptibility to biodegradation in 

acidic, aerobic soil indicates that ethephon will degrade in acidic, aerobic water bodies; however, 

if ethephon biodegradation in aerobic aquatic systems is similar to that of anaerobic aquatic 

systems, ethephon may persist in acidic, aerobic water bodies.

Major degradates of ethephon identified in environmental fate studies include ethylene, 

phosphoric acid, and 2-hydroxyethylphosphonic acid (HEPA), the latter of which is less mobile 

than the parent compound. Minor identified degradates include methylated phosphoric acid and 

carbon dioxide. Ethylene was quantified in submitted studies based on its conversion to carbon 

dioxide. While ethephon is not expected to degrade into volatile compounds other than ethylene 
-Page 23 of 87-

and carbon dioxide, data were not provided to confirm that ethylene and carbon dioxide were the 

only volatilized degradates present in the test vessels’ headspace. 

3.2.1.3. Field Studies

Ethephon dissipated with half-lives of 7 to 25 days and showed moderate to low mobility under 

actual field conditions (MRID 42011501), which is relatively consistent with the submitted 

laboratory data. Although ethephon was detected at depths of 45 and 60 cm in the loam soil in 

California and the loamy sand soil in Washington, respectively, these detections were likely the 

result of sample contamination through the use of the bucket auger sampling apparatus, given 

that these detects were first encountered within 1 week after application. In North Carolina sand 

soil, ethephon did not move below the 15-cm depth.

In California, ethephon dissipated with a calculated half-life of 12 days in the 0- to 45-cm depth 

of loam soil after spraying with Ethrel (2 lbs a.i./gallon SC/L) at a nominal concentration of 1.6 

lbs a.i./A (maximum label rate). At the time of application (May 1990), the field plot contained 

tomato plants that were 10-30 cm in height. At 0- to15-cm soil depth, ethephon concentrations 

ranged from 0.62-0.87 ppm immediately post treatment, 0.31-0.39 ppm at 4 days, 0.13-0.19 ppm 

at 15 days, 0.06-0.08 ppm at 29 days, and 0.02 ppm at 98 days. In the 15- to 30-cm soil depth, 

ethephon averaged 0.026 ppm at 4 and 9 days post treatment and ≤0.01 ppm at 15 through 98 

days. Ethephon was detected in the 30- to 45-cm depth only at 4 and 9 days post treatment, at 

0.010-0.020 ppm. Ethephon was not detected below a depth of 45 cm.

In North Carolina, ethephon dissipated with a calculated half-life of 6.8 days in the 0- to 15-cm 

depth of sand soil that was sprayed with Prep (6 lbs a.i./gallon SC/L) at a nominal concentration 

of 2.0 lbs a.i./A (maximum label rate). At the time of application (August 1990), the field plot 

contained cotton plants trimmed to 0.2 m in height. In the 0- to 15-cm soil depth, ethephon was 

detected at 0.72-1.29 ppm immediately post treatment, 0.35-0.41 ppm at 4 days, 0.06-0.11 ppm 

at 16 days, and 0.03-0.05 ppm at 31 days. Ethephon was not detected below a depth of 15 cm.

In Washington State, ethephon dissipated with a calculated half-life of 25 days in the 0- to 60-cm 

depth of loamy sand soil that was sprayed with Cerone (4 lbs a.i./gallon SC/L) at a nominal 

concentration of 1.66 lbs a.i./A (>3x maximum label rate). At the time of application (April 

1990), the field plot contained wheat plants that were 0.5-0.7 cm in height. In the 0- to15-cm 

soil depth, ethephon was detected at 1.18-1.34 ppm immediately post treatment, 0.14-0.31 ppm 

at 7 days, 0.10-0.21 ppm at 30 days, and 0.01-0.04 ppm at 58 through 128 days. In the 15- to 30-

cm soil depth, ethephon averaged 0.30 ppm at 7 days post treatment and steadily decreased to 

0.01 ppm at 128 days. Ethephon averaged a maximum of 0.205 ppm in the 30- to 45-cm depth 

and 0.06 ppm in the 45- to 60-cm depth, both at 7 days post treatment.

3.2.1.4. Monitoring Data

Monitoring studies of ethephon and/or its major degradates were not found in a literature search. 

The U.S. Geological Service National Water Quality Assessment (NAWQA) and

National Stream Quality Accounting Network (NASQAN) databases do not show instances of

ethephon or its degradates monitored in water bodies. The California Department of Pesticide
-Page 24 of 87-

Regulation Surface Water Database does not contain instances of ethephon or its degradates.

Ethephon is not a regulated chemical under the Safe Water Drinking Act or related statutes.

Therefore, it is not listed in the EPA Safe Drinking Water Information System database nor is it

found in the EPA Unregulated Contaminants Monitoring Regulation chemical monitoring

database. Groundwater monitoring studies from 1971 to 1991 listed in the EPA Pesticides in

Ground Water Database (Environmental Protection Agency, 1992) did not test for ethephon.

3.2.1.5. Bioconcentration Data

Fish bioconcentration data are not necessary for compounds with low Kow, but data have been 

submitted for ethephon (MRID 00136290; in review).

3.2.1.5. Environmental Degradates

Table 8 lists the maximum degradate amounts measured in degradation studies.

Table 8. Ethephon and its Major Radiolabeled Degradates (amounts >10% in bold).

Common 

Name Chemical Name Chemical Structure Study Type Maximum %AR A (day)

Parent

Ethephon 2-chloroethylphosphonic 

acid

O

Cl

C

H2

C

H2

P OH

OH

-- --

Major Radiolabeled (>10%) Degradates

Ethylene ethene

H2C CH2

Hydrolysis (pH 5) 23 (30 d)

Hydrolysis (pH 7) 81 (7 d)

Hydrolysis (pH 9) 71 (2 d)

Soil Photolysis 53 (30 d)

Aerobic Soil Metabolism 15 (21 d)

Anaerobic Aquatic Metabolism 52 (14-30 d)

HEPA 2-hydroxyethylphosphonic 

acid

O

HO

C

H2

C

H2

P OH

OH

Hydrolysis (pH 5) Not detected

Hydrolysis (pH 7) Not detected

Hydrolysis (pH 9) Not detected

Soil Photolysis 20 (10-30 d)

Aerobic Soil Metabolism 64 (30 d)

Anaerobic Aquatic Metabolism 43 (30 d)

Unextracted 

residue -- --

Hydrolysis (pH 5) Not detected

Hydrolysis (pH 7) Not detected

Hydrolysis (pH 9) Not detected

Soil Photolysis 23 (30 d)

Aerobic Soil Metabolism 15 (30 d)

Anaerobic Aquatic Metabolism 7.7 (30 d)

A. %AR means “percent of applied radioactivity”.
-Page 25 of 87-

Ethylene (as a gas; CAS No. 74-85-1) was the primary degradate in both the photolysis and 

hydrolysis studies. The SRC PhysProp database (accessed Mar. 3, 2010) reports the 

experimentally-derived physical-chemical properties of ethylene listed in Table 9.

TABLE 9. General Chemical Properties of Ethylene.

Parameter Value Reference

Molecular mass 28.05 g/mol (Calculated)

Vapor pressure (25°C) 5.21 x 104torr Daubert & Danner, 1985

Water solubility (25°C) 131 mg/L McAuliffe, 1966

Henry’s law constant (25°C) 0.228 atm-m3/mol Wasik and Tsang, 1970

Octanol-water partition coefficient (KOW) 

(temperature not reported)

13 Hansch et al., 1995

The experimental Henry’s law constant of 0.228 atm-m3/mol at 25°C is two orders of magnitude 

less than the value calculated from vapor pressure and solubility in water at the same temperature 

(i.e., 14.7 atm-m3/mol). Even with the lower Henry’s law constant, and with a vapor pressure of 

5.2 x 104torr at 25°C, most ethylene produced from ethephon in terrestrial or aquatic 

environments will partition into the air. The Level III fugacity model in EpiSUITE (v4.0) 

estimates a half-life in air of 25 hours, which is driven by reaction with hydroxyl radicals.

The major degradate in the aerobic soil metabolism study, HEPA, was soil-bound, not easily 

extracted, and possibly persistent, as the concentration of HEPA increased across the length of 

the 30-day study. The mobility of HEPA was confirmed in a batch equilibrium study as slightly 

to hardly mobile (KfOC range of 1460–12100 L/kgOC; 1/n range of 0.89–0.98; MRID 43991301), 

according to the FAO soil mobility classification scheme (USEPA, 2006d). Data from

supplemental aerobic soil studies (MRID # 48202001-2) and soil photolysis study (MRID#

41681401) showed unextracted residues represented >10% of applied radioactivity was likely to 

be ethephon parent or HEPA. The anaerobic aquatic metabolism study’s major degradates 

included both ethylene gas and HEPA. Ethylene gas is the biologically active degradate of 

ethephon. 

3.2.2. Measures of Aquatic Exposure

3.2.2.1. Surface Water Exposure to Ethephon

Using EFED’s standard suite of models, surface water EECs were generated for ethephon for the 

registered uses on various crops. The Surface Water Concentration Calculator (SWCC, v 1.106, 

May, 2014), which incorporates the Pesticide Root Zone Model (PRZM) and the Exposure 

Analysis Model System (EXAMS), is used to generate EECs that may occur in surface water. 

The SWCC simulates pesticide transformation on and runoff from an agricultural field (in 

addition to loadings from spray drift), following applications to crops. The model then simulates 

resulting concentrations in an adjacent surface water body. The EXAMS model simulates 
-Page 26 of 87-

pesticide concentrations in water due to loading via runoff, erosion, and spray drift, assuming a 

standard 1-ha pond, 2-m deep (20,000 m3) with no outlet that borders a 10-ha treated field. 

Simulations are for 30 years, from which the Agency estimates peak values that are expected to 

recur on average once every ten years, based on time series of daily estimated concentrations. 

The coupled PRZM and EXAMS models and user’s manuals are available from the U.S. 

Environmental Protection Agency Water Models web-page 

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

Exposure estimates generated using the standard pond are intended as surrogates for potential 

concentrations in a wide variety of vulnerable water bodies, including prairie potholes, playa 

lakes, vernal pools, other wetlands, man-made and natural ponds, and ephemeral and first-order 

streams. Multiple site-specific factors will tend to make such water bodies more or less 

vulnerable than the standard pond. Static water bodies that have larger ratios of pesticide-treated 

drainage area to water body volume are generally expected to have higher peak concentrations 

than the standard pond’s EECs. Such water bodies may be smaller in size, and/or have larger 

drainage areas. However such water bodies may be more likely to overflow and discharge 

pesticide in their effluent, whereas the EFED standard pond has no discharge. As watershed size 

increases, it becomes increasingly unlikely that the entire watershed is planted with a single crop 

that is all treated simultaneously with a pesticide. Headwater streams may have peak 

concentrations that are higher than those predicted for the standard pond, but such concentrations 

will likely persist for only short periods of time or distance, as they are carried downstream and 

diluted with water originating elsewhere.

The general chemical and environmental fate data for ethephon listed in Table 7 & Table 7 were 

used for generating model input parameter values for SWCC (Table 11). Chemical specific and 

model input values were chosen in accordance with current divisional guidance (USEPA, 2009). 

Modeling was conducted to generate EECs in surface water of ethephon using SWCC. 

Modeling results are reported in Table 12.

Table 10. Registered Uses Modeled for Ethephon

Crop

Application

method Registration (application timing)

Max single 

application 

rate (lb 

a.i./A)

Max

seasonal 

application 

rate (lb 

a.i./A)

Minimum 

retreatment 

interval (days)

Cotton Ground, 

Aerial

At mature "cut-out" stage 2 2 NA

Tobacco Ground Mature leaves, not overly rank green 2 2 NA

Apples Ground, 

Aerial

2-4 weeks after full bloom 2 2 NA

Berries Ground, 

Aerial

Apply when barren berries are between 

90% and 100% petal fall

2 2 NA

Cherries Ground Varies with plant variety 1 1 NA

Grapes Ground, 

Aerial

5-30% berry showing color 0.5 0.5 NA

Peppers Ground, 

Aerial

10-30% red and chocolate fruit 1 1 NA

Pineapple Ground, "bearing age", 12 months after planting 2 2 NA
-Page 27 of 87-

Aerial and 6 months prior to harvest

Sugar cane Aerial Just prior to flower formation 1 1 NA

Tomatoes Ground, 

Aerial

5-30% of fruit are pink 1.63 1.63 NA

Tomatoes (Processing) Ground 5-30% of fruit are pink 1.63 1.63 NA

Tomatoes -Fresh 

Market (CA only)

Ground 3-6 days prior to harvest 1.25 1.25 NA

Walnuts Ground, 

Aerial

95-100% of nuts are mature size 1.25 1.25 NA

Wheat and Barley Ground, 

Aerial

Growth stage Feekes 8 to 10 and 

Zadok’s Code 37-45

0.5 0.5 NA

Ornamentals Ground Varies with plant variety 2.8 2.8 7-14

Turf** Ground Actively growing turf; Prior to seed head 

formation (poa annua)

4 20 14

Pumpkin (Hybrid seed 

production only) 

(IL only

Ground 2-4 Leaf stage 0.25 1.5 7

Cantaloupes (TX only) Ground, 

Aerial

2-5 days prior to harvest 0.75 0.75 NA

Cucumber, Pumpkins, 

and squash (Hybrid 

seed production only) 

(CA only)

Ground First true leaf stage 0.25 1.5 3

NA: Not Available.

*: Maximum application rate registered.

Table 11. SWCC Chemical Specific Input Parameter Values for Modeling Ethephon Use.

Input Parameter Value Source Comment

Application Rate in lbs a.i./A See Table 10

Application Method See Table 10

Molecular Mass (g/mol) 144.5 MRID 46255403

Spray Drift Fraction 12.5 (aerial 

default)

6.2 (Ground 

default)

Guidance on Modeling Offsite 

Deposition of Pesticides via Spray Drift 

for Ecological and Drinking Water 

Assessments. 2013

Application Efficiency 0.99 (ground)

0.95 (aerial)

Vapor Pressure (Torr) 1.00E-7 MRID 41154506

Solubility in Water at 25°C(mg/L) 1.2E+6

(essentially 

completely 

miscible with 

water)

MRID 41154506

Freundlich adsorption Coefficient (Kd)

(L/kg)

30 MRID 42126001 Represents the mean KD, of five soils. 

Binding is not correlated with organic 

carbon content.

Aerobic Soil Metabolism Half-life 

(days)

13 MRID 41757701, 

48202001

The 90th percentile confidence bound on 

the mean half-life value (9.11, and 11 

days). The input guidance (2009).

Aerobic Aquatic Metabolism Half-life 

(days)

2.6 MRID 48202003 The 90th percentile confidence bound on 

the mean half-life value (2.5, and 2.4
-Page 28 of 87-

days). The input guidance (2009).

Anaerobic Aquatic Metabolism Halflife (days)16 MRID 41757702 Represents 3x the non-linear half-life of 

5.3 days.

Hydrolysis Half- life (days) 2.4 (pH 7) MRID 41545701

Aqueous Photolysis -Half-life (days) 139 MRID 41545601

Table 12. Surface Water Modeling Results for Ethephon on Various Crops.

Aquatic Surface Water Modeling Results

Crop Group SWCC Model

Scenario

1-in-10 year Surface Water (μg/L)

peak daily peak 21-day 

average

peak 60-day 

average

Berries OR berries 14.0 1.49 0.53

Cucurbits FL cucumber 4.28 0.96 0.41

Field crops & 

Tropical fruit

MS cotton

FL sugarcane

NC tobacco

14.3

3.59

7.25

2.25

0.58

1.14

0.92

0.26

0.45

Fruiting vegetables FL tomato

PA tomato

CA tomato

23.0*

13.2

11.5

3.07

2.20

1.79

1.08

0.80

0.63

Grasses FL turf

ND wheat

17.7

3.49

4.00*

0.58

3.00*

0.21

Grapes NY grape 4.01 0.70 0.26

Nuts OR filbert

GA Pecans

CA Almond

8.73

11.0

9.40

0.94

1.70

0.93

0.33

0.60

0.33

Ornamentals FL nursery

NJ nursery

CA nursery

16.0

14.2

9.72

2.13

2.11

0.95

0.84

0.86

0.34

Pome fruit NC apples 14.0 2.22 0.83

Stone fruit MI cherries 4.14 0.74 0.30

Bold text and asterisk(*) denote the highest EEC

Selected model input and output files supporting these values are presented in Appendix A. 

3.2.3. Measures of Terrestrial Exposure

3.2.3.1. Ingestion of Surface Residues by Birds and Mammals

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

emphasizing a dietary exposure route for uptake of pesticide active ingredients. Avian exposures 

are considered surrogates for exposures to terrestrial-phase amphibians and reptiles. For 

exposure 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 in a 

given exposure use pattern. For ethephon, application methods for the registered uses include 
-Page 29 of 87-

foliar spray. For terrestrial animals, the T-REX model (Version 1.5.2)2is used to calculate 

dietary- and dose-based EECs of ethephon for mammals and birds feeding on the site of 

application. Input values for T-REX include the maximum single application rates, number of 

applications, and retreatment interval for a given use and are located in Table 10. In this 

assessment, EFED uses a default foliar dissipation half-life of 35 days as an input for terrestrial 

exposure modeling in T-REX. Additionally, foliar dissipation half-life values between 1 and 35 

days were explored as inputs for terrestrial exposure modeling in T-REX.

Upper-bound Kenaga nomogram values based on Hoerger and Kenaga (1972) as modified by 

Fletcher et al. (1994) are used to derive EECs for ethephon exposures to terrestrial mammals and 

birds based on dietary- and dose-based exposures from foliar applications of ethephon (Table 

13). A one-year time period is simulated. Consideration is given to different types of feeding 

strategies for mammals and birds, including herbivores, insectivores and granivores. For dosebased exposures, three weight classes of mammals (15, 35, and 1000 g) and birds (20, 100, and 

1000 g) are considered. For more information on estimating exposure to terrestrial organisms, 

see the T-REX User’s Guide3. EECs derived based on mean Kenaga nomogram values were 

also selectively evaluated.

 

2 http://www.epa.gov/oppefed1/models/terrestrial/

3 http://www.epa.gov/oppefed1/models/terrestrial/trex/t_rex_user_guide.htm
-Page 30 of 87-

Table 13. T-REX Calculated EECs as Food Residues for Terrestrial Animals from Ethephon Uses.

Food Type

Dietary-Based

EEC (mg/kgdiet)Dose-Based EEC (mg/kg-body weight)

Mammals and 

Birds Birds Mammals

All Sizes 

Classes Small (20 g) Medium (100 g) Large(1000 g)

Small

(15 g)

Medium

(35 g)

Large

(1000 g)

Max Label Rate for Cotton, Tobacco, Apples, Berries, and Pineapple: 2 lbs a.i./A, 1 application

Short grass 480 547 312 140 458 316 73.3

Tall grass 220 251 143 64 210 145 33.6

Broadleaf plants/small insects 270 308 175 78.5 257 178 41.3

Fruits/pods/(seeds, dietary only) 30 34.2 19.5 8.72 28.6 19.8 4.58

Arthropods 188 214 122 54.7 179 124 28.7

Seeds (granivore) N/A 7.59 4.33 1.94 6.36 4.39 1.02

Max Label Rate for Tomatoes (including tomatoes for processing): 1.63 lbs a.i./A, 1 application

Short grass 391.20 446 254 114 373 258 59.8

Tall grass 179.30 204 117 52.1 171 118 27.4

Broadleaf plants/small insects 220.05 251 143 64 210 145 33.6

Fruits/pods/(seeds, dietary only) 24.45 27.9 15.9 7.11 23.3 16.1 3.74

Arthropods 153.22 175 99.5 44.5 146 101 23.4

Seeds (granivore) N/A 6.19 3.53 1.58 5.18 3.58 0.83

Max Label Rate Used on Tomatoes -Fresh Market (CA only) and Walnuts: 1.25 lbs a.i./A, 1 application

Short grass 300 342 195 87.2 286 198 45.8

Tall grass 137 157 89.3 40.0 131 90.6 21

Broadleaf plants/small insects 169 192 110 49.1 161 111 25.8

Fruits/pods/(seeds, dietary only) 18.8 21.4 12.2 5.45 17.9 12.4 2.86

Arthropods 118 134 76.3 34.2 112 77.4 18

Seeds (granivore) N/A 4.75 2.71 1.21 3.97 2.75 0.64

Max Label Rate for Peppers, Cherries, and Sugarcane: 1 lb a.i./A, 1 application

Short grass 240 273 156 69.8 229 158 36.7

Tall grass 110 125 71.4 32 105 72.5 16.8

Broadleaf plants/small insects 135 154 87.7 39 129 89 20.6

Fruits/pods/(seeds, dietary only) 15 17.1 9.74 4.36 14.3 9.88 2.29

Arthropods 94 107 61.1 27.3 89.6 61.9 14.4

Seeds (granivore) N/A 3.80 2.16 0.97 3.18 2.20 0.51

Max Label Rate for Cantaloupes (TX only): 0.75 lb a.i./A, 1 application

Short grass 180 205 117 52.3 172 119 27.5

Tall grass 82.5 94 53.6 24 78.7 54.4 12.6
-Page 31 of 87-

Food Type

Dietary-Based

EEC (mg/kgdiet)Dose-Based EEC (mg/kg-body weight)

Mammals and 

Birds Birds Mammals

All Sizes 

Classes Small (20 g) Medium (100 g) Large(1000 g)

Small

(15 g)

Medium

(35 g)

Large

(1000 g)

Broadleaf plants/small insects 101 115 65.8 29.4 96.5 66.7 15.5

Fruits/pods/(seeds, dietary only) 11.3 12.8 7.31 3.27 10.7 7.41 1.72

Arthropods 70.5 80.3 45.8 20.5 67.2 46.4 10.8

Seeds (granivore) N/A 2.85 1.62 0.73 2.38 1.65 0.38

Max Label Rate for Wheat, Barley, and Grapes: 0.5 lb a.i./A, 1 application

Short grass 120 137 77.9 34.9 114 79.1 18.3

Tall grass 55 62.6 35.7 16 52.4 36.2 8.40

Broadleaf plants/small insects 67.5 76.9 43.8 19.6 64.4 44.5 10.3

Fruits/pods/(seeds, dietary only) 7.5 8.54 4.87 2.18 7.15 4.94 1.15

Arthropods 47 53.5 30.5 13.7 44.8 31 7.18

Seeds (granivore) N/A 1.90 1.08 0.48 1.59 1.10 0.25

Max Label Rate for Ornamentals: 2.8 lbs a.i./A, 1 application

Short grass 672 765 436 195 641 443 103

Tall grass 308 351 200 89.6 294 203 47.1

Broadleaf plants/small insects 378 431 246 110 360 249 57.8

Fruits/pods/(seeds, dietary only) 42 47.8 27.3 12.2 40 27.7 6.42

Arthropods 263 300 171 76.5 251 173 40.2

Seeds (granivore) N/A 10.6 6.06 2.71 8.90 6.15 1.43

Max Label Rate for Turf: 4 lbs a.i./A, 5 applications, 14-day interval

Short grass 2973 3387 1931 865 2835 1959 454

Tall grass 1363 1552 885 396 1299 898 208

Broadleaf plants/small insects 1673 1905 1086 486 1595 1102 256

Fruits/pods/(seeds, dietary only) 186 212 121 54 177 122 28.4

Arthropods 1165 1326 756 339 1110 767 178

Seeds (granivore) N/A 47.0 26.8 12.0 39.4 27.2 6.31

Max Label Rate for Pumpkin (Hybrid seed production in IL only): 0.25 lb a.i./A, 6 applications, 7-day interval

Short grass 261.75 298.11 169.99 76.11 249.56 172.48 39.99

Tall grass 119.97 136.63 77.91 34.88 114.38 79.05 18.33

Broadleaf plants/small insects 147.23 167.69 95.62 42.81 140.38 97.02 22.49

Fruits/pods/(seeds, dietary only) 16.36 18.63 10.62 4.76 15.60 10.78 2.50

Arthropods 102.52 116.76 66.58 29.81 97.74 67.55 15.66
-Page 32 of 87-

Food Type

Dietary-Based

EEC (mg/kgdiet)Dose-Based EEC (mg/kg-body weight)

Mammals and 

Birds Birds Mammals

All Sizes 

Classes Small (20 g) Medium (100 g) Large(1000 g)

Small

(15 g)

Medium

(35 g)

Large

(1000 g)

Seeds (granivore) N/A 4.14 2.36 1.06 3.47 2.40 0.56

Max Label Rate for Cucumber, Pumpkins, and Squash (Hybrid seed production in CA only): 0.25 lb a.i./A, 6 applications, 3-day interval

Short grass 311.91 355.23 202.57 90.69 297.38 205.53 47.65

Tall grass 142.96 162.82 92.84 41.57 136.30 94.20 21.84

Broadleaf plants/small insects 175.45 199.82 113.95 51.01 167.28 115.61 26.80

Fruits/pods/(seeds, dietary only) 19.49 22.20 12.66 5.67 18.59 12.85 2.98

Arthropods 122.16 139.13 79.34 35.52 116.47 80.50 18.66

Seeds (granivore) N/A 4.93 2.81 1.26 4.13 2.85 0.66
33

3.2.3.4. Exposure to Honey bees

Potential risk to bees is assessed in this document according to the tiering process described in 

the Guidance for Assessing Pesticide Risks to Bees (USEPA et al., 2014). As part of the Tier I 

risk assessment, screening-level exposures are estimated in pollen and nectar using generic 

residue data generated from other chemicals as well as other plant parts as described Table 84. 

For dietary exposures resulting from foliar applications, it is assumed that pesticide residues on 

tall grass (from the Kenaga nomogram of T-REX) are a suitable surrogate for residues in pollen 

and nectar of flowers that are directly sprayed during application. For contact exposure, 

exposure estimates are based on the work of Koch and Weisser4(Koch and Weißer, 1997). For 

soil applications, pesticide concentrations in pollen and nectar are assumed to be consistent with 

chemical concentrations in the xylem of barley (calculated using the Briggs’ model). For seed 

treatments, pesticide concentrations in pollen and nectar are based on concentrations in leaves 

and stems of treated plants (based on the European and Mediterranean Plant Protection 

Organization (EPPO) default value discussed in the White Paper), assumed to be 1 milligram per 

kilogram (mg/kg) or 1 part per million (ppm). More details on these methods are available in the 

in the T-REX User’s Guide5. 

The Tier I method is intended to generate “reasonably conservative” estimates of pesticide 

exposure to honey bees which are then refined using available empirical residue data from a 

variety of crops; however, these data are not available for ethephon. The Tier I exposure method 

is intended to account for the major routes of pesticide exposure that are relevant to bees (i.e., 

through diet and contact). Exposure routes for bees differ based on application type. Under the 

approach used in this assessment, bees foraging in a field treated with a pesticide through foliar 

spray could potentially be exposed to the pesticide through direct spray, i.e., contact, as well 

through consuming ethephon residues in pollen and nectar. Table 84 summarizes exposure 

estimates for honey bees for the Tier I assessment.

 Table 84. Screening-level EECs for honey bees based on foliar applications.

Use Exposure 

Route Exposure Estimate Calculation1 Lifestage

EEC

(μg 

a.i./bee/day)

Max Label Rate for Turf: 4 lbs 

a.i./A, 5 applications, 14-day 

interval

Contact APP*(2.7 μg a.i./bee) Adults 10.8

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 128

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 55

Max Label Rate for 

Ornamentals: 2.8 lbs a.i./A, 1 

application

Contact APP*(2.7 μg a.i./bee) Adults 7.56

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 89.9

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 38.2

Max Label Rate for Cotton, 

Tobacco, Apples, Berries, and 

Pineapple: 2 lbs a.i./A, 1 

application

Contact APP*(2.7 μg a.i./bee) Adults 5.4

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 64.2

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 27.3

Max Label Rate for Tomatoes 

(including tomatoes for 

Contact APP*(2.7 a.i./bee) Adults 4.4

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 52.4

 

4 Koch, H. and P. Weißer. 1997. Exposure of honey bees during pesticide application under field conditions. 

Apidologie, 28: 439-447.

5 http://www.epa.gov/oppefed1/models/terrestrial/trex/t_rex_user_guide.htm
34

processing): 1.63 lbs a.i./A, 1 

application Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 22.2

Max Label Rate Used on 

Tomatoes -Fresh Market (CA 

only) and Walnuts: 1.25 lbs 

a.i./A, 1 application

Contact APP*(2.7 a.i./bee) Adults 3.4

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 40.2

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 17.1

Max Label Rate for Peppers, 

Cherries, and Sugarcane: 1 lb 

a.i./A, 1 application

Contact APP*(2.7 a.i./bee) Adults 2.7

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 32.1

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 13.6

Max Label Rate for 

Cantaloupes (TX only): 0.75 

lb a.i./A, 1 application

Contact APP*(2.7 a.i./bee) Adults 2.03

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 24.1

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 10.2

Max Label Rate for Wheat, 

Barley, and Grapes: 0.5 lb 

a.i./A, 1 application

Contact APP*(2.7 a.i./bee) Adults 1.35

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 16.1

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 6.82

Max Label Rate for Pumpkin 

(Hybrid seed production in IL 

only): 0.25 lb a.i./A, 6 

applications, 7-day interval

Contact APP*(2.7 a.i./bee) Adults 0.68

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 8.03

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 3.41

Max Label Rate for 

Cucumber, Pumpkins, and 

Squash (Hybrid seed 

production in CA only): 0.25 

lb a.i./A, 6 applications, 3-day 

interval

Contact APP*(2.7 a.i./bee) Adults 0.68

Diet APP*(110 μg a.i /g)*(0.292 g/day) Adults 8.03

Diet APP*(110 μg a.i /g)*(0.124 g/day) Brood 3.41

APP = application rate in lbs ai/A

*The label maximum single application rate was modeled

1Based on food consumption rates for larvae (0.124 g/day) and adult (0.292 g/day) worker bees and concentration in 

pollen and nectar.

 

3.2.3.2. Runoff and Spray Drift to Terrestrial and Semi-Aquatic Plants

TERRPLANT (Version 1.2.2)6is used to calculate EECs for non-target plants that inhabit dry 

and semi-aquatic areas. In this assessment, exposure to non-target plants is calculated based on 

the potential runoff and spray drift of foliar applications of ethephon and potential runoff after 

soil and seed treatment applications (Table 95). TERRPLANT does not account for particulate 

drift.

Table 95. EECs for Non-target Terrestrial and Semi-aquatic Plants for Ethephon (based on 

TERRPLANT).

Uses App

Technique

Single Max. 

App. Rate

(lbs a.i./A)

EECs (lbs a.i./A)

Semi-Aquatic 

Areas (Total)

Dry Areas 

(Total)

Max Label Rate for Turf: 4 lbs a.i./A* Foliar 4 2.04 0.24

Max Label Rate for Ornamentals Foliar 2.8 1.43 0.17

Max Label Rate for Cotton, Tobacco, 

Apples, Berries, and Pineapple Foliar 2.0 1.1 0.2

 

6 http://www.epa.gov/oppefed1/models/terrestrial/
35

Max Label Rate for Tomatoes (including 

tomatoes for processing) Foliar 1.63 0.90 0.16

Max Label Rate Used on Tomatoes -Fresh 

Market (CA only) and Walnuts

Foliar 1.25 0.70 0.13

Max Label Rate for Peppers, Cherries, and 

Sugarcane

Foliar 1.0 0.55 0.1

Max Label Rate for Cantaloupes (TX only) Foliar 0.75 0.41 0.08

Max Label Rate for Wheat, Barley, and 

Grapes

Foliar 0.5 0.28 0.05

Max Label Rate for Pumpkin (Hybrid seed 

production in IL only) and Cucumber, 

Pumpkins, and Squash (Hybrid seed 

production in CA only)*

Foliar

0.25 0.13 0.02

App = Application

*A single application was modeled, consistent with the model input parameter guidance

The spray drift model AgDrift version 2.1.1 is also used to provide bounds defining the spatial 

extent of risk concern resulting from off-field drift at currently registered ethephon application 

rates. 

3.3. Ecological Effects Characterization 

The ecological effects characterization for ethephon is based upon registrant-submitted toxicity 

data for the technical grade active ingredient (TGAI) and for formulations. The ecotoxicity data 

for ethephon and its associated products have been reviewed previously in multiple ecological 

risk assessments (USEPA, 2013) (USEPA, 2006) and in a Preliminary Problem Formulation for 

Registration Review (USEPA, 2010, DP Barcode 371952). These data are summarized briefly in 

Sections 3.3.1 and 3.3.2. Various studies with terrestrial and aquatic plants, birds, and aquatic 

animals exposed to TGAI ethephon have been received since the Problem Formulation was 

issued in 2010; the results of these studies are described briefly in this section. 

The results of a 2015 review of the Ecological Incident Information System (EIIS) are described 

in Section 3.3.3 (USEPA, 2012a). In addition, the ECOTOX open literature report prepared in 

2009 was reviewed in 2010 for the ethephon Problem Formulation. Data were further examined 

if endpoints were more sensitive (lower) than endpoints available from submitted studies or were 

available for amphibians, freshwater molluscs, or reptiles (USEPA, 2011). Data meeting the 

OPP’s standard for inclusion in risk assessment 

(http://www.epa.gov/pesticides/science/literature-studies.html) were available in ECOTOX that 

showed greater sensitivity than results from submitted studies for aquatic nonvascular plants (Ma 

et al, 2004, ECOTOX Number E095681). An ECOTOX refresh report was not available for 

ethephon at the time of the writing of this preliminary risk assessment. The endpoints from the 

ECOTOX-catalogued open literature studies are provided in Appendix F, for reference. 
36

3.3.1. Aquatic Toxicity Assessment

A summary of the most sensitive toxicity endpoints for aquatic organisms is shown in Table 

106. These endpoints will be used to calculate risk quotients.

The available data indicate that ethephon TGAI is slightly toxic to freshwater fish and freshwater

and estuarine/marine invertebrates on an acute exposure basis. No chronic estuarine/marine fish 

studies are available. Effects on fry hatching success were observed in the available chronic 

freshwater fish study at 86 mg a.i./L. Adult length was significantly reduced at 38 mg a.i./L in 

the available chronic daphnid study. Effects on survival were observed in the vascular aquatic 

plant duckweed (Lemna gibba; EC50= 2.49 mg a.i./L, EC05=0.017 mg a.i./L) and inhibited 

growth was observed when nonvascular freshwater green alga (Chlorella pyrenoidosa; EC50= 

23.5 mg a.i./L, NOAEC= 2 mg a.i./L) was exposed to ethephon at 5 mg a.i./L. 

Table 106. Summary of Most Sensitive Toxicity Data for Aquatic Organisms Exposed to 

Ethephon (TGAI).

Common Name

(Species)

Study Type

and

(Duration of 

Exposure)

Test 

Substance 

(% a.i.)

Endpoint

(Effect Observed 

at Endpoint)

Toxicity Value

(95% CI)

mg a.i./L

(Acute Toxicity 

Category)

MRID

Study 

Classification1

Freshwater Fish (Surrogate for Aquatic-phase Amphibians)

Fathead minnow

(Pimephales promelas)

Static

(96-hour)

TGAI

(Not 

specified)

LC50

(Survival)

88 (73.2-106)

(slightly toxic)

00027496

Supplemental

Fathead minnow

(Pimephales promelas)

Flow-through

(34-day)

TGAI

(71.4%)

NOAEC/LOAEC

(survival at hatch) 43/86 48202004Acceptable

Estuarine/Marine Fish

Sheepshead minnow

(Cyprinodon 

variegatus)

Acute TGAI

(73.8%)

LC50

(Survival)

>102

(Practically 

nontoxic)

49040501

Acceptable

Sheepshead minnow

(Cyprinodon 

variegatus)

Chronic -- NOAEC >502 ACR

Freshwater Aquatic Invertebrates

Water flea

(Daphnia magna)

Static

(48-hour)

TGAI

(88.3%)

EC50

(Immobility)

31.7

(slightly toxic)

00054013

Supplemental

Water flea

(Daphnia magna)

Flow-through

(21-days)

TGAI

(71.2%)

NOAEC/LOAEC

(length)

17/38 42294501

Acceptable

Estuarine/marine Aquatic Invertebrates

Eastern oyster

(Crassostrea virginica) 

Flow-through

(96-hour)

TGAI 

(72.2%)

Growth

(reduced shell 

deposition)

60 (25-93)

(slightly toxic)

41296202

Acceptable

Grass shrimp 

(Palaemonetes spp.)

Chronic -- NOAEC >1983 ACR

Aquatic Plants

Duckweed 

(Lemna gibba)

Static Renewal

14-day

TGAI 

(71.9%)

EC50

(Survival)

2.5 (Slope: 0.65; 

CI:1.34-9.48)

41509001

Acceptable EC05 0.017
37

Common Name

(Species)

Study Type

and

(Duration of 

Exposure)

Test 

Substance 

(% a.i.)

Endpoint

(Effect Observed 

at Endpoint)

Toxicity Value

(95% CI)

mg a.i./L

(Acute Toxicity 

Category)

MRID

Study 

Classification1

Freshwater green alga

(Chlorella pyrenoidosa)

96-hr TGAI 

(85%)

EC50

(growth inhibition) 23.5 Acceptable

E095681

NOAEC/LOAEC 2/5 Acceptable

E095681

TGAI=technical grade active ingredient:

1 Supplemental studies may or may not be suitable to calculate RQs. Quantitative values are suitable for calculation 

of RQ. Qualitative values are not considered suitable for calculation of RQs but may be useful in understanding the 

weight of evidence for evaluating the likelihood of risk.

2 This NOAEC is based on the acute-to-chronic ratio using fathead minnow endpoints [88/43=2.1 (ACR)] and the 

96-hour LC50 of the sheepshead minnow.

3 This NOAEC is based on the acute-to-chronic ratio using water flea endpoints [31.7/17=1.9 (ACR)] and the grass 

shrimp 96-hour LC50 (>370 mg a.i./L).

3.3.1.1. Toxicity to Aquatic Vertebrates

On an acute exposure basis, ethephon TGAI is slightly toxic to practically nontoxic to freshwater 

fish, with 96-hour LC50 values ranging from 88 mg a.i./L for the fathead minnow (Pimephales 

promelas; MRID 27496) to 357 mg a.i./L for the rainbow trout (Oncorhynchus mykiss; MRID 

252943). On an acute exposure basis, ethephon TGAI is practically nontoxic to estuarine/marine 

fish, with a 96-hour nondefinitive LC50 value of >102 mg a.i./L for sheepshead minnow 

(Cyprinodon variegatus; MRID 49040501). 

One freshwater fish early-life stage study was submitted (Pimephales promelas; MRID 

48202004) where survival of organisms at hatch averaged 73% for the control level, compared to 

72, 71, 66, 72, and 0% for the mean-measured 5.0, 10, 21, 43, and 86 mg a.i./L levels, 

respectively. The survival at the 86 mg ai/L level was statistically significant compared to the 

control. The study NOAEC and LOAEC were 43 mg a.i./L and 86 mg a.i./L, respectively, based 

on survival at hatch. No chronic estuarine/marine fish studies are available; however, an acuteto-chronic ratio (ACR) was determined from fathead minnow endpoints [88/43=2.1] and applied 

to the 96-hour LC50 of the sheepshead minnow to estimate the chronic toxicity of ethephon to 

estuarine/marine fish. Since the acute sheepshead minnow endpoint is non definitive (>102 mg 

a.i./L), the estimated chronic sheepshead minnow endpoint is also non definitive (>50 mg a.i./L).

3.3.1.2. Toxicity to Aquatic Invertebrates

On an acute exposure basis, ethephon is slightly toxic to practically nontoxic to freshwater 

invertebrates, with water-column 48-hour EC50 values ranging from 31.7 mg a.i./L for the water 

flea (Daphnia magna; MRID 00054013) to 165 mg a.i./L for the midge (Chironomus tentans; 

MRID 00054013). Ethephon is also slightly toxic to practically nontoxic to estuarine/marine 

invertebrates, with 96-hour IC50 values ranging from 60 mg a.i./L for the eastern oyster 

(Crassostrea virginica; MRID 41296202) based on inhibition of shell growth to a 96-hour LC50
38

of >370 mg a.i./L for the grass shrimp (Palaemonetes spp.; MRID 00054013).

Chronic toxicity data are available for freshwater but not estuarine/marine invertebrates. For the 

water flea (Daphnia magna), the 21-day NOAEC/ LOAEC was 17/38 mg a.i./L (MRID 

42294501) based on a statistically significant (p<0.05) 3.5% reduction of adult body length in 

the 38 mg a.i./L treatment compared to the control. The estuarine/marine invertebrate NOAEC 

is based on the ACR derived from water flea endpoints [31.7/17=1.9] which was subsequently 

applied to the 96-hour LC50 of the grass shrimp (>370 mg a.i./L), resulting in an estimated

chronic toxicity of >198 mg a.i./L for grass shrimp. The ACR was not applied to the most 

sensitive acute toxicity value (i.e., the endpoint used for RQ determination) because it is of 

questionable validity to compare the mollusc shell growth inhibition test sublethal effects 

endpoint to the lethality endpoint from a test with non-molluscs.

3.3.1.3. Toxicity to Aquatic Plants

Tier I toxicity testing with duckweed (Lemna gibba) exposed to 1.5 mg a.i./L ethephon TGAI 

resulted in a 56.1% decrease in frond production compared to controls. In a Tier II test, exposure 

to the highest test concentration (1.6 mg a.i./L) resulted in growth inhibition of 46.1%, compared 

to controls. The estimated EC50 for the Tier II test was 2.5 mg a.i./L. Statistically significant 

effects were observed at all test concentrations (19, 23, 27, 39, and 46% growth reductions were 

recorded in the 0.10, 0.17, 0.44, 0.81, and 1.6 mg a.i./L treatment compared to the control); 

therefore, the NOAEC was not established. The EC05 was estimated as 0.017 mg a.i./L (MRID 

41509001). 

Data from Tier 1 studies are available for 4 species of non-vascular plants (Skeletonema 

cosatum, Navicula pelliculosa, Anabaena flos-aquae and Pseudokirchneriella subcapitata 

formerly Selenastrum capricornutum) exposed to ≥1.4 mg a.i./L ethephon for 120 hours. In 

these studies, cell densities of treatment groups were not significantly different when compared 

to controls (MRIDs 41403301, -02, -03 and -04).

In a study located in the scientific literature (Ma et al., 2004; ECOTOX #095681), 4 species of 

non-vascular aquatic plants were exposed to 85% ethephon. The study authors reported EC50

values (based on growth inhibition) ranging 23.5-174 mg/L, with NOECs ranging from 2-50 

mg/L.

3.3.2. Terrestrial Effects Characterization

A summary of the most sensitive terrestrial animal toxicity data for ethephon, based on a current 

EPA review of all submitted data, is provided in Table 117 and is discussed further in Sections 

3.3.2.1 to 3.3.2.3. The available data indicate that ethephon TGAI ranges from practically nontoxic to slightly toxic to birds, including passerines, and is slightly toxic to mammals on an acute 

oral exposure basis and highly toxic to mammals on an subacute-dietary exposure basis. 

Ethephon is practically non-toxic to young adult honey bees on an acute oral and contact 

exposure basis.
39

Mallard duck (Anas platyrhynchos) fed diets containing ethephon for 20-weeks were found to 

have significantly fewer hatchlings per eggs set and surviving hatchlings per eggs set relative to 

controls at 300 mg a.i./kg-diet; however, there were no effects to any parameter evaluated at the 

955 mg a.i./kg diet treatment compared to the control. Laboratory rats fed diets containing 

ethephon (3000 mg a.i./kg-diet) had significant bodyweight and food consumption reductions 

relative to controls.

The available data for terrestrial plants exposed to technical ethephon for formulation into enduse products (71.9-73.8% a.i.) described in Section 3.3.2.4, indicate that ethephon exposure to 

seeds and/or emerging plants (i.e., seedling emergence) resulted in significantly reduced plant 

height at application rates equivalent to 0.22 lb a.i./A compared to the control (significant effects 

to emergence and survival were recorded for a dicot species tested at 0.32 lb a.i./A). Ethephon 

exposure to foliage (i.e., vegetative vigor) resulted in significantly reduced plant height at 

application rates equivalent to 0.008 lb a.i./A compared to the control. 

Table 117. Summary of the Most Sensitive Toxicity Data for Terrestrial Animals Exposed 

to Ethephon.

Common Name

(Species)

Study Type

(Duration of 

Exposure)

Test 

Substance 

(% a.i.)

Endpoint

(Effect at 

endpoint)

Toxicity Value

(95% CI)

(Acute Toxicity 

Category)

MRID

Study 

Classification

Birds

Canary 

(Serinus canaria)

Acute Oral 

(capsule with 14-

day observation)

TGAI 

(73.8%)

LD50

(Mortality)

1640 mg a.i./kg-bw 

(1230-2480)

Slope = 6.1 (1.9-10.3)

(slightly toxic)

49160601

Acceptable

Bobwhite quail

(Colinus 

virginianus)

Acute Oral (Oral 

gavage with 14-

day observation)

TGAI 

(75%)

LD50

(Mortality)

596 mg a.i./kg-bw

(521-681)*

(slightly toxic)

00027493

Acceptable

Bobwhite quail

(Colinus 

virginianus)

Subacute Dietary

(8-day)

TGAI

(71.3%)

LC50

(Mortality)

>5000 mg a.i./kg-diet

(practically nontoxic)

41080201

Acceptable

Mallard duck

(Anas 

platyrhynchos)

Reproduction

(20 week) TGAI

(73.8%)

NOAEC/

LOAEC 

(hatchlings per 

eggs set)

106/300 mg a.i./kg-diet*

49305605

SupplementalQuantitative

Mammals1

Laboratory rat

(Rattus 

norvegicus)

Acute Oral TGAI

(75%)

LD50

(Mortality)

1205 mg a.i./kg-bw 

(slightly toxic)

00029509

Laboratory rat

(Rattus 

norvegicus)

Two-generation 

Reproduction TGAI

NOAEL/

LOAEL

(bodyweight 

and food 

consumption 

reductions)

NOAEL: 300 mg a.i./kgdiet* or

24 mg a.i./kg/day/

LOAEL: 3000 mg a.i./kgdiet or

245 mg a.i./kg/day

41508701

Honey bees
40

Common Name

(Species)

Study Type

(Duration of 

Exposure)

Test 

Substance 

(% a.i.)

Endpoint

(Effect at 

endpoint)

Toxicity Value

(95% CI)

(Acute Toxicity 

Category)

MRID

Study 

Classification

Honey Bee

(Apis mellifera)

Acute contact

(48-hour) 71.6% LC50

(Mortality)

>0.100 mg a.i./bee

(practically nontoxic)

48202006

Acceptable

Acute oral

(48-hour) 71.6% LD50

(Mortality)

>0.117 mg a.i./bee

(practically nontoxic)

48202006

Acceptable

* Most sensitive endpoint; will be used in RQ calculations.

1 Mammalian toxicity endpoints were provided and reviewed by EPA/OCSPP/OPP Health Effects Division

3.3.2.1. Toxicity to Animals

Ethephon is classified slightly toxic to birds on an acute oral exposure basis. Two acute oral 

toxicity studies have been submitted for northern bobwhite quail (Colinus virginianus) exposed 

to technical ethephon. In these studies, LD50 values were 596 (521-681) mg/kg (MIRD 

00027493) and 1072 (907-1267) mg/kg (MRID 00026041). In an acute oral study with the 

mallard duck (Anas platyrhyncos) exposed to technical ethephon, the LD50 was 1998 (1748-

2283) mg/kg (MRID 00026040). 

On a subacute dietary basis, ethephon is classified practically non-toxic. Data are available from 

two registrant submitted studies where 8-d LC50 values were >5000 mg/kg-diet for bobwhite 

quail (MRID 41080201) and mallard duck (MRID 00056480).

Since the time of the Problem Formulation, three avian reproduction studies (MRIDs 48202005, 

49305605, and 49325701) and one passerine acute oral toxicity study (MRID 49160601) have 

been submitted and reviewed. MRID 48202005 is a Japanese quail (Couturnix japonica) avian 

reproduction test that was classified as supplemental because NOAECs could not be established 

for the most sensitive endpoints (number of hatchlings and hatchling survival) and because of 

test species selection (the Japanese quail is not a preferred test species). Studies with mallard 

and bobwhite quail were conducted and submitted between 2012 and 2014 (MRIDs 49305605 

and 49325701). Both mallard and bobwhite avian reproduction studies included dietary 

exposure concentrations greater than environmental exposures estimated to result from the 

highest registered single application rate of ethephon; however, environmental exposures 

estimated to result from multiple applications of ethephon to turf exceed the highest dietary 

exposure concentration of these studies. Since the avian reproduction NOAEC has been 

established below the highest concentration tested, this uncertainty does not affect chronic avian 

risk estimation.

The mallard avian reproduction study (MRID 49305605) is the source of the lowest avian 

chronic endpoint which is used to calculate RQs. 15 pairs per level of 20-week old mallard duck 

(Anas platyrhynchos) were exposed to technical ethephon at mean-measured concentrations of

<20 (<LOQ, negative control), 106, 300 and 955 mg ai/kg diet, over ca. 20 weeks. The number 

of hatchlings per eggs set and hatchling survival per eggs set were significantly reduced in the 

300 mg a.i./kg diet treatment compared to the control; however, there were no significant effects 

to these parameters at the highest test concentration (955 mg a.i./kg diet). Since more than a 

quarter of the pens at the 300 mg a.i./kg diet treatment had a strikingly low number of viable 
41

embryos it is uncertain whether the effects on the number of hatchlings per eggs set and the 

number of hatchlings surviving at 14 days post hatch per eggs set were toxicant mediated, the 

result of a greater proportion of sensitive birds in the 300 mg ai/kg diet treatment, or related to 

husbandry; however, the effects at the 300 mg ai/kg diet treatment are conservatively considered 

to be a direct result of ethephon exposure. Therefore, the mallard avian reproduction NOAEC 

and LOAEC are conservatively established at 106 and 300 mg ai/kg diet, respectively.

In acute oral toxicity testing with the passerine canary (Serinus canaria; MRID 49160601), no 

regurgitation was observed following dosing with two gelatin capsules per bird. Observations 

continued for 14-days during which 70% mortality was recorded at the highest treatment and the 

LD50 was 1640 mg ai/kg bw.

Ethephon is slightly toxic to mammals on an acute oral exposure basis. The acute oral LD50 was 

1205 mg a.i./kg-bw (corrected for 75% a.i.; MRID 00029509). Additional data were available to 

describe the acute oral toxicity of ethephon to rats. The LD50 values for males, females and 

combined sexes, when corrected for percent a.i., were 2641, 1565, and 2145 mg a.i./kg-bw, 

respectively (MRID 41154501).

In a 2-generation reproduction study, the LOAEL for ethephon parental toxicity was 3,000 ppm 

(245 mg a.i./kg/day) based on decrements in adult female pre-mating body weight, reduced food 

consumption and relative food utilization. The LOAEL for offspring toxicity was 3000 ppm 

(245 mg a.i./kg/day) based on body weight decrease (4.5% relative to controls). The resulting 

NOAEL for the study was 300 ppm (24 mg a.i. mg/kg/day) (MRID 41508701). 

As of September 15, 2009, no additional acute or chronic toxicity data for animals exposed to 

ethephon were identified in the scientific literature (based on a search of ECOTOX).

Additional honey bee toxicity data have also been received since the time of the Problem 

Formulation. The honey bee, Apis mellifera L., was exposed to ethephon (71.4% a.i.) for 48

hours in oral and contact toxicity tests (MRID 48202006). The oral and contact nominal 

concentrations were 0 (solvent control), 6.3, 12.5, 25, 50, and 100 μg ai/bee. The measured

concentrations of ethephon in the oral toxicity test were 7.3, 14.2, 28.5, 58.5, and 116.5 μg 

ai/bee. By 48 hours in the oral test, mortality was 0, 3, 0, 7, and 0%. One bee in the 58.5 μg 

ai/bee test level had coordination problems at 4 hours, which did not persist. By 48 hours in the 

contact test, there was no mortality in the controls or treatment groups. There were no sub-lethal 

effects. The LC50 value for the oral test was >116.5 μg ai/bee. The LD50 value for the contact 

test was >100 μg ai/bee. As a result, ethephon is categorized as practically nontoxic to honey 

bees on an acute oral and contact basis. The NOAELs for the oral and contact tests were 116.5 

and 100 μg ai/bee, respectively.

3.3.2.4. Toxicity to Terrestrial Plants

Terrestrial plant toxicity studies are required for pesticides that have terrestrial use patterns or 

may move off of the application site. The NOAEL and IC25 (concentration that causes an 
42

inhibitory effect in 25% of the population for the monitored endpoint) values are established for

markers of seedling emergence and vegetative vigor. 

Seedling emergence and vegetative vigor data are available for 6 species of dicots and 4 species 

of monocots (MRIDs 41403305, 41659401, 49037901, 49037902) (Table 18). These studies 

were conducted with 71.3-73.8% active ingredient ethephon formulations. While the tested 

formulations were not typical end use products (TEPs) as required by 40 CFR §158.660, the 

tested products are understood to approximate ethephon TEPs compositionally (i.e., the ethephon 

TEPs do not contain additional surfactants, wetting agents, or other inert ingredients compared to 

the tested formulations of higher active ingredient percentage) when diluted with water.

The lowest available IC25 values for monocots are 0.24 lb a.i./A for seedling emergence of 

ryegrass and 2.1 lbs a.i./A for vegetative vigor of corn (MRIDs 41659401 and 49037902, 

respectively). The corresponding NOAEC value for seedling emergence of ryegrass is 0.11 lbs 

a.i./A. The corresponding NOAEC value for vegetative vigor of corn is 0.127 lb a.i./A. 

The lowest available IC25 values for dicots are 0.318 lb a.i./A for seedling emergence of cabbage 

and 0.0106 lb a.i./A for vegetative vigor of cucumber. The corresponding NOAEC value for 

seedling emergence of cabbage is 0.127 lb a.i./A. Because there were significant effects at all 

treatment concentrations for cucumber shoot length, a NOAEC could not be established. 

According to EFED policy, in the absence of a suitable NOAEC, the IC05 is used as a surrogate. 

The corresponding IC05 value for vegetative vigor of cucumber is 0.000418 lb a.i./A. 

Table 128. Summary of Terrestrial Plants Toxicity Data for Ethephon Formulations.

Crop Formulation 

(% a.i.) Species IC25(lbs a.i./A)

NOAEC

or IC05/ 

LOAEC

(lbs a.i./A)

Most Sensitive 

Endpoint 

Affected

MRID

Study Classification

Seedling Emergence

Monocots

Ethephon 

[for 

formulation 

into end-use 

products] 

(73.8%)

Ryegrass 

(Lolium 

perenne)

0.24* 0.11*/

0.22 Shoot length

49037901

Supplementalquantitative Dicots

Cabbage 

(Brassica 

oleracea)

0.318* 0.127*/

0.318

Emergence, 

survival

Vegetative Vigor

Monocots Ethephon 

[for 

formulation 

into end-use 

products] 

(73.8%)

Corn (Zea 

mays)

2.1*

0.127*/

0.318 Shoot length

49037902

SupplementalDicots quantitative

Cucumber

(Cucumis 

sativus)

0.0106*

0.000418*†/

0.00799 Shoot length

* Most sensitive endpoint used for risk estimation (i.e., RQ calculations) or risk description (for non-definitive 

endpoints).

†The IC05 is reported because there were significant effects at all treatment concentrations
43

4. Risk Characterization

4.1. Risk Estimation

This assessment of the labeled uses of ethephon relies on the deterministic RQ method to provide 

a metric of potential risks. The RQ provides a comparison of exposure estimates to toxicity 

endpoints (i.e., estimated exposures divided by acute and/or chronic toxicity endpoints expressed 

in the same units as exposures, respectively). The resulting unitless RQ values, calculated in the 

Risk Estimation Section) are compared to the Agency’s LOCs (see Table 4). The LOCs are 

used by the Agency to indicate when the use of a pesticide, as directed by the label, has the 

potential to result in exposure levels sufficient to cause adverse effects to non-target organisms. 

For endangered species, LOC exceedances require an additional in-depth listed species 

evaluation to characterize risks for the potential co-occurrence of listed species and areas in 

which crops are grown. In this approach, RQs that exceed non-listed species LOCs necessarily 

also exceed the corresponding listed species LOCs. Acute risk LOCs are different for listed and 

non-listed taxa; however, the chronic LOC is 1.0 across all animals. For plants, unlike for 

animals, RQ values are not presented for acute versus chronic risk; instead, RQ values are 

presented for listed and non-listed species based on a comparison of a given EEC to NOAEL and 

EC25 values (for terrestrial plants) and EC50 values (for aquatic plants), respectively. The LOC 

for all plants is 1.0. A discussion of the RQ values for ethephon and of other information that 

provides context for the interpretation of potential risk to various taxa is presented in the Risk 

Description in Section 4.2. Risk quotients were estimated for maximum labeled rates.

 

4.1.1. RQ Values for Aquatic Organisms

The SWCC was used to calculate water-column 1-in-10-year peak, 21-day average, and 60-day 

average EECs for aquatic organisms. Toxicity endpoints used to calculate risk quotients are the 

most sensitive acute and chronic endpoints for each taxon and are specified in the table showing 

the RQ value.

Freshwater fish serve as surrogates for aquatic-phase amphibians. RQ values based on both 

maximum application rates for freshwater and estuarine/marine fish exposed to ethephon are less 

than 0.01, below the LOC (0.05) for acute risk for listed species for all registered uses (Table19). 

Similarly, chronic RQ values for freshwater and estuarine/marine fish are less than the chronic 

risk LOC (1.0) for maximum label rates for all uses.

Table 19. RQs for Direct Effects to Fish from Ethephon Use

Model scenario

App. 

Rate

(lbs 

a.i./A)

Peak

EECs

(mg 

a.i./L)

60-day 

average

EECs

Risk Quotients

Freshwater Fish Estuarine/Marine Fish

Acute

LC50 = 88 mg 

a.i./L

Chronic

NOAEC = 

43 mg 

a.i./L

Acute

EC50 = 

>102 mg 

a.i./L

Chronic

NOAEC = >50 

mg a.i./L1

Maximum Label Rates – Runoff and Spray Drift Simulated

OR berries 2.0 0.014 0.0005 < 0.01 < 0.01 < 0.01 < 0.01

FL cucumber 0.25 0.004 0.0004 < 0.01 < 0.01 < 0.01 < 0.01

MS cotton 2.0 0.014 0.0009 < 0.01 < 0.01 < 0.01 < 0.01

FL sugarcane 1.0 0.004 0.0002 < 0.01 < 0.01 < 0.01 < 0.01
44

NC tobacco 2.0 0.007 0.0005 < 0.01 < 0.01 < 0.01 < 0.01

FL tomato 1.63 0.023 0.0010 < 0.01 < 0.01 < 0.01 < 0.01

PA tomato 1.63 0.013 0.0008 < 0.01 < 0.01 < 0.01 < 0.01

CA tomato 1.63 0.012 0.0006 < 0.01 < 0.01 < 0.01 < 0.01

FL turf 4 0.017 0.0030 < 0.01 < 0.01 < 0.01 < 0.01

ND wheat 0.5 0.003 0.0002 < 0.01 < 0.01 < 0.01 < 0.01

NY grape 0.5 0.004 0.0003 < 0.01 < 0.01 < 0.01 < 0.01

OR filbert 1.25 0.009 0.0003 < 0.01 < 0.01 < 0.01 < 0.01

GA pecan 1.25 0.011 0.0006 < 0.01 < 0.01 < 0.01 < 0.01

CA almond 1.25 0.009 0.0003 < 0.01 < 0.01 < 0.01 < 0.01

FL nursery 2.8 0.016 0.0008 < 0.01 < 0.01 < 0.01 < 0.01

NJ nursery 2.8 0.014 0.0008 < 0.01 < 0.01 < 0.01 < 0.01

CA nursery 2.8 0.010 0.0003 < 0.01 < 0.01 < 0.01 < 0.01

NC apples 2.0 0.014 0.0008 < 0.01 < 0.01 < 0.01 < 0.01

MI cherries 1.0 0.004 0.0003 < 0.01 < 0.01 < 0.01 < 0.01

Abbreviations: App.= Application

1 Estimated using the estuarine/marine fish 96-hr LC50 of >102 mg a.i./L and an ACR from freshwater fish

RQ values based on maximum application rates for freshwater and estuarine/marine 

invertebrates exposed to ethephon on an acute exposure basis are well below the LOCs for risk to

listed (LOC=0.05) and non-listed (LOC=0.5) species (Table 21). RQ values for freshwater and 

estuarine/marine invertebrates, based on chronic exposure to ethephon, likewise do not exceed 

LOCs for chronic risk (Table 20). 

Table 20. RQs for Direct Effects to Aquatic Invertebrates from Ethephon Use

Model scenario

App. 

Rate

(lbs 

a.i./A)

Peak

EECs

(mg 

a.i./L)

21-day 

average

EECs

(mg 

a.i./L)

Risk Quotients

Freshwater 

Invertebrates E/M Invertebrates

Acute

EC50 = 

31.7 mg 

a.i./L

Chronic

NOAEC =

17 mg 

a.i./L

Acute

EC50 = 

60 mg 

a.i./L

Chronic

NOAEC = 

>198 mg 

a.i./L1

Maximum Label Rates – Runoff and Spray Drift Simulated

OR berries 2.0 0.014 0.001 < 0.01 < 0.01 < 0.01 < 0.01

FL cucumber 0.25 0.004 0.001 < 0.01 < 0.01 < 0.01 < 0.01

MS cotton 2.0 0.014 0.002 < 0.01 < 0.01 < 0.01 < 0.01

FL sugarcane 1.0 0.004 0.0006 < 0.01 < 0.01 < 0.01 < 0.01

NC tobacco 2.0 0.007 0.001 < 0.01 < 0.01 < 0.01 < 0.01

FL tomato 1.63 0.023 0.003 < 0.01 < 0.01 < 0.01 < 0.01

PA tomato 1.63 0.013 0.002 < 0.01 < 0.01 < 0.01 < 0.01

CA tomato 1.63 0.012 0.002 < 0.01 < 0.01 < 0.01 < 0.01

FL turf 4 0.017 0.004 < 0.01 < 0.01 < 0.01 < 0.01

ND wheat 0.5 0.003 0.0006 < 0.01 < 0.01 < 0.01 < 0.01

NY grape 0.5 0.004 0.0007 < 0.01 < 0.01 < 0.01 < 0.01

OR filbert 1.25 0.009 0.0009 < 0.01 < 0.01 < 0.01 < 0.01

GA pecan 1.25 0.011 0.002 < 0.01 < 0.01 < 0.01 < 0.01

CA almond 1.25 0.009 0.0009 < 0.01 < 0.01 < 0.01 < 0.01

FL nursery 2.8 0.016 0.002 < 0.01 < 0.01 < 0.01 < 0.01

NJ nursery 2.8 0.014 0.002 < 0.01 < 0.01 < 0.01 < 0.01

CA nursery 2.8 0.010 0.001 < 0.01 < 0.01 < 0.01 < 0.01

NC apples 2.0 0.014 0.002 < 0.01 < 0.01 < 0.01 < 0.01
45

MI cherries 1.0 0.004 0.0007 < 0.01 < 0.01 < 0.01 < 0.01

Abbreviations: App.= Application.; E/M=estuarine/marine

1 Estimated using the estuarine/marine invertebrate (grass shrimp) 96-hr LC50 of >370 mg a.i./L and an ACR from 

freshwater invertebrates. 

For aquatic vascular and non-vascular plants exposed to ethephon, RQ values based on 

maximum application rates equaled or exceeded the LOC (1.0) for risk to listed aquatic vascular

plants associated with use on tomato and turf; however RQs were considerably less than the 

LOC for listed and non-listed aquatic non-vascular plants and non-listed aquatic vascular plants 

for the same use patterns (Table 21).

Table 21. RQ Values for Direct Effects to Aquatic Vascular and Nonvascular Plants from

Ethephon Use

Model scenario

App. 

Rate

(lbs 

a.i./A)

Peak water

EEC

(mg a.i./L)

Risk Quotients

Aquatic Vascular Plants Aquatic Non-vascular Plants

Listed

EC05 =

0.017 mg 

a.i./L

Non-listed

EC50=

2.5 mg a.i./L

Listed

NOAEC =

2 mg a.i./L

Non-listed

EC50 =

23.5 mg a.i./L

Maximum Label Rates – Runoff and Spray Drift Simulated

OR berries 2.0 0.014 0.82 < 0.01 < 0.01 < 0.01

FL cucumber 0.25 0.004 0.24 < 0.01 < 0.01 < 0.01

MS cotton 2.0 0.014 0.82 < 0.01 < 0.01 < 0.01

FL sugarcane 1.0 0.004 0.24 < 0.01 < 0.01 < 0.01

NC tobacco 2.0 0.007 0.41 < 0.01 < 0.01 < 0.01

FL tomato 1.63 0.023 1.35 < 0.01 0.01 < 0.01

PA tomato 1.63 0.013 0.76 < 0.01 < 0.01 < 0.01

CA tomato 1.63 0.012 0.71 < 0.01 < 0.01 < 0.01

FL turf 4 0.017 1.00 < 0.01 < 0.01 < 0.01

ND wheat 0.5 0.003 0.18 < 0.01 < 0.01 < 0.01

NY grape 0.5 0.004 0.24 < 0.01 < 0.01 < 0.01

OR filbert 1.25 0.009 0.53 < 0.01 < 0.01 < 0.01

GA pecan 1.25 0.011 0.65 < 0.01 < 0.01 < 0.01

CA almond 1.25 0.009 0.53 < 0.01 < 0.01 < 0.01

FL nursery 2.8 0.016 0.94 < 0.01 < 0.01 < 0.01

NJ nursery 2.8 0.014 0.82 < 0.01 < 0.01 < 0.01

CA nursery 2.8 0.010 0.59 < 0.01 < 0.01 < 0.01

NC apples 2.0 0.014 0.82 < 0.01 < 0.01 < 0.01

MI cherries 1.0 0.004 0.24 < 0.01 < 0.01 < 0.01

Abbreviations: App.= Application

RQs exceeding the aquatic plant risk LOC of 1.0 shown in bold font

4.1.2. RQ Values for Terrestrial Organisms

Exposure estimated for birds and mammals were calculated using upper-bound Kenaga values 

calculated using T-Rex version 1.5.2. As noted previously, birds are the surrogate species for 

reptiles and terrestrial-phase amphibians. Toxicity endpoints used to calculate risk quotients are 

the most sensitive for the taxa evaluated and are described in the tables showing the RQ values.

For ethephon applied at maximum applications rates on turf and ornamentals, the acute dosebased RQ values for birds exceed the LOC for acute risk to listed (RQ≥0.1) species for four or 
46

more dietary items for all size classes (Table 22). In addition, for turf, the acute dose-based RQ 

values for birds exceed the LOC for acute risk to non-listed (RQ≥0.5) species for all size classes 

of birds feeding on three types of dietary items; no other registered uses have acute non-listed 

LOC exceedances for all size classes of birds for any dietary items. The chronic risk LOC 

(RQ≥1) is exceeded for birds consuming short grass, tall grass, broadleaf plants/small insects, or 

arthropods at the maximum label rate for all registered uses with the exception of peppers, 

cherries, sugarcane, cantaloupes (TX only), pumpkin (hybrid seed production in IL only), wheat, 

barley, and grapes. For use on turf, the chronic risk LOC is exceeded for birds consuming every 

dietary item, with RQs ranging from 1.75 for fruits and pods to 28 for short grass.

Table 22. Acute and Chronic RQ for Birds Exposed to Ethephon as a Result of Registered 

Uses

Food Type

Acute Dose-Based RQs1

Subacute Dietary 

RQs2

Chronic

Dietary-Based RQs Small 3

(20 g)

Medium 

(100 g)

Large

(1000 g)

National Maximum Label Rate for

Ornamentals: 2.8 lbs a.i./A, 1 application, Foliar

Short grass 1.78* 0.80* 0.25 0.13 6.34

Tall grass 0.82* 0.37 0.12 0.06 2.91

Broadleaf plants/small 

insects 1.00* 0.45 0.14 0.08 3.57

Fruits/pods/(seeds, 

dietary only) 0.11 0.05 0.02 0.01 0.40

Arthropods 0.70* 0.31 0.10 0.05 2.48

Seeds (granivore) 0.02 0.01 <0.01 N/A N/A

National Maximum Label Rate for

Cotton, Tobacco, Apples, Berries, and Pineapple: 

2 lbs a.i./A, 1 application, Foliar

Short grass 1.27* 0.57* 0.18 0.10 4.53

Tall grass 0.58* 0.26 0.08 0.04 2.08

Broadleaf plants/small 

insects 0.72* 0.32 0.10 0.05 2.55

Fruits/pods/(seeds, 

dietary only) 0.08 0.04 0.01 0.01 0.28

Arthropods 0.50* 0.22 0.07 0.04 1.77

Seeds (granivore) 0.02 0.01 <0.01 N/A N/A

National Maximum Label Rate

for Tomatoes (including tomatoes for processing): 

1.63 lbs a.i./A, 1 application, Foliar

Short grass 1.04* 0.46 0.15 0.08 3.69

Tall grass 0.48 0.21 0.07 0.04 1.69

Broadleaf plants/small 

insects 0.58* 0.26 0.08 0.04 2.08

Fruits/pods/(seeds, 

dietary only) 0.06 0.03 0.01 <0.01 0.23

Arthropods 0.41 0.18 0.06 0.03 1.45

Seeds (granivore) 0.01 0.01 <0.01 N/A N/A

National Maximum Label Rate

for Tomatoes -Fresh Market (CA only) and Walnuts:

 1.25 lbs a.i./A, 1 application, Foliar

Short grass 0.80* 0.36 0.11 0.06 2.83

Tall grass 0.36 0.16 0.05 0.03 1.30
47

Food Type

Acute Dose-Based RQs1

Subacute Dietary 

RQs2

Chronic

Dietary-Based RQs Small 3

(20 g)

Medium 

(100 g)

Large

(1000 g)

Broadleaf plants/small 

insects 0.45 0.20 0.06 0.03 1.59

Fruits/pods/(seeds, 

dietary only) 0.05 0.02 0.01 <0.01 0.18

Arthropods 0.31 0.14 0.04 0.02 1.11

Seeds (granivore) 0.01 <0.01 <0.01 N/A N/A

National Maximum Label Rate for

Peppers, Cherries, and Sugarcane: 

1 lb a.i./A, 1 application, Foliar

Short grass 0.64* 0.29 0.09 0.05 2.26

Tall grass 0.29 0.13 0.04 0.02 1.04

Broadleaf plants/small 

insects 0.36 0.16 0.05 0.03 1.27

Fruits/pods/(seeds, 

dietary only) 0.04 0.02 0.01 <0.01 0.14

Arthropods 0.25 0.11 0.04 0.02 0.89

Seeds (granivore) 0.01 <0.01 <0.01 N/A N/A

National Maximum Label Rate for

Cantaloupes (TX only):

0.75 lb a.i./A, 1 application, Foliar

Short grass 0.48 0.21 0.07 0.04 1.70

Tall grass 0.22 0.10 0.03 0.02 0.78

Broadleaf plants/small 

insects 0.27 0.12 0.04 0.02 0.96

Fruits/pods/(seeds, 

dietary only) 0.03 0.01 <0.01 <0.01 0.11

Arthropods 0.19 0.08 0.03 0.01 0.67

Seeds (granivore) 0.01 <0.01 <0.01 N/A N/A

National Maximum Label Rate for

Wheat, Barley, and Grapes: 

0.5 lb a.i./A, 1 application, Foliar

Short grass 0.32 0.14 0.05 0.02 1.13

Tall grass 0.15 0.07 0.02 0.01 0.52

Broadleaf plants/small 

insects 0.18 0.08 0.03 0.01 0.64

Fruits/pods/(seeds, 

dietary only) 0.02 0.01 <0.01 <0.01 0.07

Arthropods 0.12 0.06 0.02 0.01 0.44

Seeds (granivore) <0.01 <0.01 <0.01 N/A N/A

National Maximum Label Rate for

Turf: 

4 lbs a.i./A, 5 applications, 14-day interval, Foliar

Short grass 7.89* 3.53* 1.12* 0.59* 28.05

Tall grass 3.61* 1.62* 0.51* 0.27 12.86

Broadleaf plants/small 

insects 4.44* 1.99* 0.63* 0.33 15.78

Fruits/pods/(seeds, 

dietary only) 0.49 0.22 0.07 0.04 1.75

Arthropods 3.09* 1.38* 0.44 0.23 10.99

Seeds (granivore) 0.11 0.05 0.02 N/A N/A

Pumpkin (Hybrid seed production in IL only): 

0.25 lb a.i./A, 6 applications, 7-day interval, Foliar

Short grass 0.69* 0.31 0.10 0.05 2.47
48

Food Type

Acute Dose-Based RQs1

Subacute Dietary 

RQs2

Chronic

Dietary-Based RQs Small 3

(20 g)

Medium 

(100 g)

Large

(1000 g)

Tall grass 0.32 0.14 0.05 0.02 1.13

Broadleaf plants/small 

insects 0.39 0.17 0.06 0.03 1.39

Fruits/pods/(seeds, 

dietary only) 0.04 0.02 0.01 <0.01 0.15

Arthropods 0.27 0.12 0.04 0.02 0.97

Seeds (granivore) 0.01 <0.01 <0.01 N/A N/A

Cucumber, Pumpkins, and Squash (Hybrid seed production in CA only): 

0.25 lb a.i./A, 6 applications, 3-day interval, Foliar

Short grass 0.83* 0.37 0.12 0.06 2.94

Tall grass 0.38 0.17 0.05 0.03 1.35

Broadleaf plants/small 

insects 0.47 0.21 0.07 0.04 1.66

Fruits/pods/(seeds, 

dietary only) 0.05 0.02 0.01 <0.01 0.18

Arthropods 0.32 0.15 0.05 0.02 1.15

Seeds (granivore) 0.01 0.01 <0.01 N/A N/A

N/A=not applicable

Bolded values meet or exceed the Level of Concern (LOC) for acute risk to listed (RQ > 0.1) birds or chronic risk to 

birds (RQ > 1).

*Bolded values with an asterisk meet or exceed the Level of Concern (LOC) for acute risk to non-listed (RQ > 0.5) 

birds

1 Acute dose-based RQ values are based on the bobwhite quail LD50 value of 596 mg ai/kg-bw (MRID 00027493). 

2 Acute dietary RQ values are based on the bobwhite quail 8-day LC50 value of >5,000 mg a.i./kg diet (MRID 

41080201).

3 Chronic RQ values are based on the mallard NOAEC value of 106 mg a.i./kg diet (MRID 49305605).

For maximum applications rates for use of ethephon on turf, the acute dose-based RQ values for 

all size classes of mammals exceed the LOC for acute risk to listed (RQ≥0.1) species for short 

grass, tall grass, broadleaf plants/small insects, or arthropods (Table 23). For maximum 

applications rates for use of ethephon on ornamentals, the acute dose-based RQ values for all 

size classes of mammals exceed the LOC for acute risk to listed (RQ≥0.1) species for short grass 

only. There are no acute dose-based LOC exceedances for peppers, cherries, sugarcane, 

cantaloupes (TX only), pumpkin (hybrid seed production in IL only), wheat, barley, or grapes at

maximum application rates for these uses. No subacute dietary studies were available for 

ethephon so no subacute dietary RQs were calculated. Chronic dietary RQs exceed the chronic 

risk LOC of 1.0 for turf and ornamentals for at least three dietary classes. There are no chronic 

dietary LOC exceedances for peppers, cherries, sugarcane, cantaloupes (TX only), pumpkin 

(hybrid seed production in IL only), wheat, barley, or grapes at maximum application rates for 

these uses.

Table 23. Acute and Chronic RQ for Mammals Exposed to Ethephon as a Result of 

Registered Use

Food Type

Acute Dose-Based RQs1

Chronic

Dietary-Based RQs Small 2

(15 g)

Medium 

(35 g)

Large

(1000 g)

National Maximum Label Rate for

Ornamentals: 2.8 lbs a.i./A, 1 application, Foliar

Short grass 0.24 0.21 0.11 2.24
49

Food Type

Acute Dose-Based RQs1

Chronic

Dietary-Based RQs Small 2

(15 g)

Medium 

(35 g)

Large

(1000 g)

Tall grass 0.11 0.09 0.05 1.03

Broadleaf plants/small 

insects 0.14 0.12 0.06 1.26

Fruits/pods/(seeds, dietary 

only) 0.02 0.01 0.01 0.14

Arthropods 0.09 0.08 0.04 0.88

Seeds (granivore) <0.01 <0.01 <0.01 N/A

National Maximum Label Rate for

Cotton, Tobacco, Apples, Berries, and Pineapple: 

2 lbs a.i./A, 1 application, Foliar

Short grass 0.17 0.15 0.08 1.60

Tall grass 0.08 0.07 0.04 0.73

Broadleaf plants/small 

insects 0.10 0.08 0.04 0.90

Fruits/pods/(seeds, dietary 

only) 0.01 0.01 <0.01 0.10

Arthropods 0.07 0.06 0.03 0.63

Seeds (granivore) <0.01 <0.01 <0.01 N/A

National Maximum Label Rate

for Tomatoes (including tomatoes for processing): 

1.63 lbs a.i./A, 1 application, Foliar

Short grass 0.14 0.12 0.06 1.30

Tall grass 0.06 0.06 0.03 0.60

Broadleaf plants/small 

insects 0.08 0.07 0.04 0.73

Fruits/pods/(seeds, dietary 

only) 0.01 0.01 <0.01 0.08

Arthropods 0.06 0.05 0.03 0.51

Seeds (granivore) <0.01 <0.01 <0.01 N/A

National Maximum Label Rate

for Tomatoes -Fresh Market (CA only) and Walnuts:

 1.25 lbs a.i./A, 1 application, Foliar

Short grass 0.11 0.09 0.05 1.00

Tall grass 0.05 0.04 0.02 0.46

Broadleaf plants/small 

insects 0.06 0.05 0.03 0.56

Fruits/pods/(seeds, dietary 

only) 0.01 0.01 <0.01 0.06

Arthropods 0.04 0.04 0.02 0.39

Seeds (granivore) <0.01 <0.01 <0.01 N/A

National Maximum Label Rate for

Peppers, Cherries, and Sugarcane: 

1 lb a.i./A, 1 application, Foliar

Short grass 0.09 0.07 0.04 0.80

Tall grass 0.04 0.03 0.02 0.37

Broadleaf plants/small 

insects 0.05 0.04 0.02 0.45

Fruits/pods/(seeds, dietary 

only) 0.01 <0.01 <0.01 0.05

Arthropods 0.03 0.03 0.02 0.31

Seeds (granivore) <0.01 <0.01 <0.01 N/A
50

Food Type

Acute Dose-Based RQs1

Chronic

Dietary-Based RQs Small 2

(15 g)

Medium 

(35 g)

Large

(1000 g)

National Maximum Label Rate for

Cantaloupes (TX only):

0.75 lb a.i./A, 1 application, Foliar

Short grass 0.06 0.06 0.03 0.60

Tall grass 0.03 0.03 0.01 0.28

Broadleaf plants/small 

insects 0.04 0.03 0.02 0.34

Fruits/pods/(seeds, dietary 

only)

<0.01 <0.01 <0.01

0.04

Arthropods 0.03 0.02 0.01 0.24

Seeds (granivore) <0.01 <0.01 <0.01 N/A

National Maximum Label Rate for

Wheat, Barley, and Grapes: 

0.5 lb a.i./A, 1 application, Foliar

Short grass 0.04 0.04 0.02 0.40

Tall grass 0.02 0.02 0.01 0.18

Broadleaf plants/small 

insects 0.02 0.02 0.01 0.23

Fruits/pods/(seeds, dietary 

only)

<0.01 <0.01 <0.01

0.03

Arthropods 0.02 0.01 0.01 0.16

Seeds (granivore) <0.01 <0.01 <0.01 N/A

National Maximum Label Rate for

Turf: 

4 lbs a.i./A, 5 applications, 14-day interval, Foliar

Short grass 1.07* 0.91* 0.49 9.91

Tall grass 0.49 0.42 0.22 4.54

Broadleaf plants/small 

insects 0.60* 0.51* 0.28 5.58

Fruits/pods/(seeds, dietary 

only) 0.07 0.06 0.03 0.62

Arthropods 0.42 0.36 0.19 3.88

Seeds (granivore) 0.01 0.01 0.01 N/A

Pumpkin (Hybrid seed production in IL only): 

0.25 lb a.i./A, 6 applications, 7-day interval, Foliar

Short grass 0.09 0.08 0.04 0.87

Tall grass 0.04 0.04 0.02 0.40

Broadleaf plants/small 

insects 0.05 0.05 0.02 0.49

Fruits/pods/(seeds, dietary 

only) 0.01 0.01 <0.01 0.05

Arthropods 0.04 0.03 0.02 0.34

Seeds (granivore) <0.01 <0.01 <0.01 N/A

Cucumber, Pumpkins, and Squash (Hybrid seed production in CA only): 

0.25 lb a.i./A, 6 applications, 3-day interval, Foliar

Short grass 0.11 0.10 0.05 1.04

Tall grass 0.05 0.04 0.02 0.48

Broadleaf plants/small 

insects 0.06 0.05 0.03 0.58

Fruits/pods/(seeds, dietary 

only) 0.01 0.01 <0.01 0.06

Arthropods 0.04 0.04 0.02 0.41

Seeds (granivore) <0.01 <0.01 <0.01 N/A
51

N/A=not applicable

Bolded values meet or exceed the Level of Concern (LOC) for acute risk to listed (RQ > 0.1) mammals or chronic 

risk to mammals (RQ > 1).

*Bolded values with an asterisk meet or exceed the Level of Concern (LOC) for acute risk to non-listed (RQ > 0.5) 

mammals

1 Acute dose-based RQ values are based on the laboratory rat LD50 value of 1205 mg a.i./kg-bw (MRID 00029509). 

2 Chronic RQ values are based on the laboratory rat NOAEC value of 300 mg a.i./kg-diet (MRID 41508701).

4.1.2.3. Terrestrial Invertebrates 

EECs for terrestrial invertebrates were calculated using the equations described in Section

3.2.3.4. Ethephon is classified as practically nontoxic to honey bees on an acute contact and oral 

exposure basis. Since the acute oral and contact toxicity studies for honey bees exposed to 

ethephon were non-definitive (i.e., LD50s greater than highest concentration tested), RQs are not 

calculated. The risk to insect pollinators is discussed in greater detail in the Risk Description 

(Section 4.2).

4.1.2.4. Non-target Terrestrial Plants

EECs for terrestrial plants were calculated using TERRPLANT (Version 1.2.2). RQ values for 

terrestrial plants are calculated using the most sensitive endpoints for monocot and dicot species 

in vegetative vigor and seedling emergence tests with ethephon technical grade active ingredient

(TGAI) (Table 134). For all label uses of ethephon (except for use on pumpkin, cucumber, and 

squash), RQ values for monocot and dicot plants exposed to runoff exceed the risk to non-listed 

and listed species LOC (LOC =1). 

The potential for adverse effects to listed and non-listed species of terrestrial and semi-aquatic 

plants from exposure to ethephon is discussed in greater detail in the Risk Description (Section 

4.2). In the risk description, the distance from the edge of the field where effects may occur due 

to exposure to spray drift is described. 

Table 134. RQs for Non-target Terrestrial Plants Adjacent to Ethephon Use Sites.

Use Plant Type Listed Status

Risk Quotients

Dry Semi-Aquatic

Turf (modeled application: 4 lbs a.i./A)

Monocot non-listed 1.00 8.50

Monocot listed 2.18 18.55

Dicot non-listed 0.75 6.42

Dicot listed 1.89 16.06

Ornamentals (modeled application: 2.8 lbs a.i./A)

Monocot non-listed 0.70 5.95

Monocot listed 1.53 12.98

Dicot non-listed 0.53 4.49

Dicot listed 1.32 11.24

Cotton, Tobacco, Apples, Berries, and Pineapple (modeled application: 2 lbs a.i./A)

Monocot non-listed 0.83 4.58

Monocot listed 1.82 10.00

Dicot non-listed 0.63 3.46
52

Use Plant Type Listed Status

Risk Quotients

Dry Semi-Aquatic

Dicot listed 1.57 8.66

Tomatoes (including tomatoes for processing) (modeled application: 1.63 lbs a.i./A)

Monocot non-listed 0.68 3.74

Monocot listed 1.48 8.15

Dicot non-listed 0.51 2.82

Dicot listed 1.28 7.06

Tomatoes -Fresh Market (CA only) and Walnuts (modeled application: 1.25 lbs a.i./A)

Monocot non-listed 0.52 2.86

Monocot listed 1.14 6.25

Dicot non-listed 0.39 2.16

Dicot listed 0.98 5.41

Peppers, Cherries, and Sugarcane (modeled application: 1 lb a.i./A)

Monocot non-listed 0.42 2.29

Monocot listed 0.91 5.00

Dicot non-listed 0.31 1.73

Dicot listed 0.79 4.33

Cantaloupes (TX only) (modeled application: 0.75 lb a.i./A)

Monocot non-listed 0.31 1.72

Monocot listed 0.68 3.75

Dicot non-listed 0.24 1.30

Dicot listed 0.59 3.25

Wheat, Barley, and Grapes (modeled application: 0.5 lb a.i./A)

Monocot non-listed 0.21 1.15

Monocot listed 0.45 2.50

Dicot non-listed 0.16 0.86

Dicot listed 0.39 2.17

Pumpkin (Hybrid seed production in IL only) and Cucumber, Pumpkins, and Squash 

(Hybrid seed production in CA only) (modeled application: 0.25 lb a.i./A)

Monocot non-listed <0.1 0.53

Monocot listed 0.14 1.16

Dicot non-listed <0.1 0.40

Dicot listed 0.12 1.00

Bold values indicate LOC (1.0) exceedence

*Runoff RQ values for nontarget plants are based on the seedling emergence NOAEC of 0.11 lb a.i./A for monocots 

and 0.127 lb a.i./A for dicots. Corresponding IC25 values were estimated to be 0.24 lb a.i./A for monocots and 0.32 

lb a.i./A for dicots. The most sensitive NOAEC for vegetative vigor is 0.13 lb a.i./A for monocots and 0.00042 lb 

a.i./A for dicots. 

4.2. Incident Database Review

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 

ethephon. Based on a search of EIIS conducted in July 2015, there are eight incidents in the EIIS 

database associated with ethephon. Of the eight incidents, six allege crop damage following 

application. Three incidents are associated with barley crop damage (I010934-010; I016662-

029; I017865-030); one is associated with grape crop damage (I014426-010); one is associated 
53

with rye crop damage (I021411-019); and one is associated with spring wheat crop damage 

(I016912-018). Of the two remaining incidents, one (B0000-500-14) is a farm pond fish kill that 

occurred following application of ethephon, malathion, and merphos to nearby cotton, and the

other involved horses that became ill after entering a treated pasture (I024576-001). 

 Incident# B0000-500-14 occurred in Brooks County, GA in October 1989. Malathion (PC 

code 057701), merphos (PC code 074901) and ethephon were aerially applied adjacent to a

pond at rates of 1, 1 and 1.5 pt/A, respectively. Water sampling approximately two weeks 

after the applications detected malathion at 0.18 ppb. Malathion had been sprayed as part of 

the program to eradicate the boll weevils on cotton and the certainty index for this incident 

indicated that it was probable that malathion was most likely responsible for the fish kill. 

The certainty of ethephon contributing to this incident was designated possible.

 Incident# I010934-010 occurred in 2000 in Teton, ID. This incident reported plant damage 

in 360 A of barley fields directly sprayed with ethephon contained in Cerone (39.9% a.i.). 

Cerone was broadcast at 0.66 pt/A as a registered use. It was assumed that the product was 

responsible for the damage and the certainty index of the incident was reported as probable.

 Incident# I014426-010 occurred in 2003 in Kern County, CA. This incident reported crop 

drop and loss in 78 A of grape crops (vineyard) treated directly with 1 pint/A of Ethrel

(21.7% a.i.). Effects were observed in 100% of the plants, but the entire crop was not lost. 

The application was made with high temperatures and improper timing. The registrant, 

Bayer CropScience, reported that the symptoms were related to Ethrel; the certainty index 

was possible.

 Incident# I016662-029 occurred in 2005 in Burleigh County, ND. This incident reported leaf 

burn and leaf loss in 65 A of barley fields directly treated with ethephon. Cerone (39.9% 

a.i.; Registration #264-377) was applied aerially at 8 oz/A. At the time of application, 

temperatures were very high, which was against the directions of that label and was thus, a 

misuse of this product. The certainty index of this incident was probable.

 Incident# I016912-018 occurred in 2005 in Henry County, ID. This incident reported 

stunting of 60 A of spring wheat treated directly with Cerone (39.9% a.i.). Cerone plant 

regulator was applied at 0.66 pint/A by ground spray under registered use. The certainty 

index was classified as possible, but it was unclear why the effects occurred.

 Incident# I017865-030 occurred in 2006 in Montana. This incident reported yellowing of 

540 acres of barley treated directly with Cerone at 7 oz/A. The certainty index was 

classified as probable.

 Incident# I021411-019 occurred in October 2009 in Halifax County, NC. This incident 

reported a phototoxic reaction from an application of the products Dropp SC (1.5 pint/acre; 

a.i. thiadiazuron) and Finish Pro (2.4 oz/acre; a.i. cyclanilide and ethephon) onto 75 acres of 

rye in Halifax County, NC. The rye was allegedly desiccated by the application throughout 

100% of the field. The certainty index was classified as possible.
54

 Incident# I024576-001 occurred in October 2012 in Parker County, TX. It was reported that 

ethephon was applied to a field by an aerial applicator several days before several horses 

became ill after going into the pasture. The certainty of this incident was classified as 

possible.

Based on a search of the U.S. EPA Office of Pesticide Programs Incident Data System (IDS), 

which compiles aggregate incidents, only one incident involving ethephon was found. This 

incident (016573-00081) was for minor plant damage associated with Ethrel® soluble 

concentrate occurring between April and June of 2005.

A lack of reported incidents does not necessarily mean that incidents have not occurred. In 

addition, incident reports for non-target plants and animals typically provide information on 

acute mortality events only. Reports for other adverse effects, such as reduced growth or 

impaired reproduction, are rarely received. Available incident information indicates that 

registered uses of ethephon have the potential to result in adverse effects to terrestrial plants and 

animals.

4.3. Risk Description

 

This preliminary risk assessment of the labeled uses of ethephon relies on the deterministic RQ 

method to provide a metric of potential risks. RQs for some registered ethephon uses exceed 

LOC values for:

 birds (acute listed, acute non-listed, and chronic risk LOCs);

 mammals (acute listed, acute non-listed, and chronic LOCs); 

 listed aquatic vascular plants; and,

 terrestrial plants (listed and non-listed)

Toxicity data available for adult honey bees suggest that LOCs would not be exceeded on an 

acute oral or contact basis.

4.3.1 Risk to Aquatic Organisms

Aquatic Exposure

Surface water EECs resulting from applications of ethephon are estimates of exposure for the use 

of ethephon as a plant growth regulator. Application practices were modeled using the 

maximum annual application rates. Environmental fate data were conservatively represented in 

keeping with EFED’s Input Parameter Guidance 

(http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm) by using an 

uncertainty factor of 3X applied to the single soil and sediment metabolism half-life estimates. 

Finally, scenario selection was conservatively performed by modeling runoff prone soils that 

drain to a small pond without an outlet. 

Aquatic Animals

Risk to freshwater and estuarine/marine fish and invertebrates is well below the established acute 

and chronic levels of concern and adverse effects to aquatic animals are not anticipated to result 

from registered uses of ethephon. Although there is one aquatic animal incident associated with 
55

ethephon in the EIIS database, this incident was more likely caused by the malathion rather than

ethephon applied.

Aquatic Plants

Based on available data, the likelihood for adverse effects to listed and non-listed vascular and 

nonvascular aquatic plants is considered low. RQ values for non-listed vascular and listed and 

non-listed nonvascular aquatic plants range from <0.01 to 0.01. RQ values for listed vascular 

aquatic plants range from 0.24 to 1.23. The aquatic modelling scenarios having exposures higher 

than the vascular aquatic plant toxicity endpoint— thereby resulting in risk exceeding the LOC 

of 1.0— are FL tomato (RQ=1.35) and FL turf (RQ=1.00). There is some uncertainty with this 

conclusion of adverse effects to listed vascular aquatic plants because the toxicity endpoint is an 

EC05 rather than a NOAEC, since statistically significant effects were observed at all 

concentrations tested (19% growth reduction compared to the control in the lowest treatment).

The lowest concentration tested was 0.10 mg a.i./L, but the EC05 was determined to be 

approximately an order of magnitude smaller than this concentration (0.017 mg a.i./L).

Therefore, since a NOAEC of 0.024 mg a.i./L would eliminate risk exceeding the LOC for 

aquatic vascular plants, additional data establishing a NOAEC only 0.007 mg a.i./L higher than 

the current EC05 would change risk conclusions.

4.3.2. Risk to Terrestrial Organisms

Terrestrial Exposure

To evaluate the potential for terrestrial exposure from the multiple registered uses of ethephon, 

application practices were modeled by using maximum application rates. Exposure was 

estimated using upper-bound Kenaga values from T-REX version 1.5.2. The spray drift model 

AgDrift version 2.1.1 provides helpful bounds which define the spatial extent of risk concern 

resulting from off-field drift at currently registered ethephon application rates. 

Birds and Mammals

Ethephon is categorized as slightly toxic to birds on an acute oral exposure basis. On a subacute 

dietary basis, ethephon is categorized as practically non-toxic. Ethephon is categorized as 

slightly toxic to mammals on an acute oral exposure basis. 

In this assessment, RQs based on acute oral exposure to birds exceed the acute risk to listed

species LOC of 0.1 and acute risk to non-listed species LOC of 0.5 for at least four of the dietary 

classes for small birds at maximum application rates. Risk to non-listed species LOCs are 

exceeded for small birds foraging on short grass at maximum labeled rates for all uses except 

cantaloupes, wheat, barley, and grapes. Risk to non-listed species LOCs are exceeded for three

dietary classes for small, medium, and large-sized birds for turf at maximum labeled rates. RQs 

calculated based on a subacute dietary exposure to birds exceed LOCs for risk to listed birds 

foraging on short grass at the maximum label rates for ornamentals, cotton, tobacco, apples, 

berries, and pineapple. RQs calculated based on a subacute dietary exposure to birds exceed 

LOCs for risk to listed birds foraging on tall grass, broadleaf plants/small insects, and 

arthropods, and listed and non-listed birds foraging on short grass at the maximum label rate for 

turf. 
56

RQs for birds based on chronic dietary exposure exceed the chronic risk LOC for birds 

consuming short grass, tall grass, broadleaf plants/small insects, and arthropods at the maximum 

label rate for all registered uses with the exception of peppers, cherries, sugarcane, cantaloupes

(TX only), pumpkin (hybrid seed production in IL only), wheat, barley, and grapes (RQs for 

these uses, at application rates ranging from 0.25 lb a.i./A to 1 lb a.i./A, exceed the avian chronic 

risk LOC for one to three dietary categories. For use on turf, the chronic risk LOC is exceeded 

for birds consuming every dietary item, with RQs as high as 28 for foragers consuming short 

grass. Avian reproduction testing with mallard found a significant reduction in hatchlings (24% 

reduction compared to the control) and hatchling survival per eggs set (25% reduction compared 

to the control) at the 300 mg a.i./kg diet treatment level compared to the control; however, no 

significant reductions for the parameters of number of hatchlings and hatchling survival per eggs 

set (2% reduction compared to the control for both number of hatchlings and hatchling survival)

were seen in the 955 mg a.i./kg diet treatment. Therefore, the NOAEC used to estimate avian 

chronic RQs is conservatively established at 106 mg a.i./kg diet, since it is uncertain whether the 

reductions were toxicant mediated, the result of a greater proportion of sensitive birds in the 300 

mg a.i./kg diet treatment, or related to husbandry.

For maximum applications rates for use of ethephon on turf, the acute dose-based RQ values for 

all size classes of mammals exceed the LOC for acute risk to listed (RQ≥0.1) species for short 

grass, tall grass, broadleaf plants/small insects, or arthropods. For maximum applications rates 

for use of ethephon on ornamentals, the acute dose-based RQ values for all size classes of 

mammals exceed the LOC for acute risk to listed (RQ≥0.1) species for short grass only. There 

are no acute dose-based LOC exceedances for peppers, cherries, sugarcane, cantaloupes (TX 

only), pumpkin (hybrid seed production in IL only), wheat, barley, or grapes at maximum 

application rates for these uses. No subacute dietary studies were available for ethephon so no 

subacute dietary RQs were calculated. Chronic dietary RQs exceed the chronic risk LOC of 1.0 

for turf and ornamentals for at least three dietary classes. There are no chronic dietary LOC 

exceedances for peppers, cherries, sugarcane, cantaloupes (TX only), pumpkin (hybrid seed 

production in IL only), wheat, barley, or grapes at maximum application rates for these uses

(ranging from 0.25 lb a.i./A to 1 lb a.i./A).

Laboratory rats fed diets containing ethephon (3000 mg a.i./kg-diet) had significant bodyweight 

and food consumption reductions relative to controls. Dietary EECs range from 1,362 to 2,973

mg/kg-diet for maximum label rates and are lower than the LOAEC. Standard RQs are 

calculated based on upper-bound Kenaga values. When considering EECs based on mean 

Kenaga exposure estimates and the maximum application rate for turf, chronic dietary RQs for 

mammals are approximately 66% less than RQs associated with the upper-bound Kenaga values. 

Chronic LOC exceedances remain for mean Kenaga exposure estimates for the turf use pattern; 

however, the magnitude of the exceedances is lesser.

The potential for risk to birds and mammals from proposed foliar uses were evaluated in this 

assessment using the default foliar dissipation half-life of 35 days, since no additional data were

available to determine the decline in ethephon residues in dietary items. However, since LOCs 

for acute risk to listed (RQ≥0.05) and non-listed (RQ≥0.1) birds and chronic risk (RQ≥1) to 

mammals are exceeded in this assessment, the impact of different half-lives on RQs was 

examined for purposes of characterization (Table 145). Based on this analysis, at maximum 
57

labeled application rates, both acute and chronic risk LOCs are exceeded even when a half-life of 

1 day is considered. Additionally, at maximum label rates and assuming the default 35 day foliar 

dissipation rates, LOCs are exceeded for 7 to more than 56 days. Therefore, potential risks of 

concern to birds and mammals from labeled uses of ethephon would not be precluded based on 

refinements to the default foliar dissipation half-life.

Table 145. Impact of Different Foliar Dissipation Half-lives on the Number of Days RQs 

Based on Dietary Exposure Exceed LOCs.

Application Rate 

(lbs a.i./A)

Number of Days There is a Dietary LOC exceedance1

Avian Mammalian

Acute Chronic Acute Chronic

35 day foliar dissipation rate

4 (5 applications, 14-

d interval)

56 56 56 56

1 56 42 0 56

0.5 56 7 0 40

0.25 (6 applications,

7-d interval)

56 45 0 54

0.25 (6 applications,

3-d interval)

56 53 6 56

1 day foliar dissipation rate

4 (5 applications, 14-

d interval)

20 16 8 20

1 3 2 0 3

0.5 2 1 0 2

0.25 (6 applications,

7-d interval)

6 0 0 6

0.25 (6 applications,

3-d interval)

6 0 0 6

1 The analysis is only carried out to a maximum of 56 days based on limitations in T-REX.

The STIR model output indicates that inhalation of ethephon is not likely to be a significant 

exposure pathway of concern for avian and mammalian species. 

The SIP model output indicates that drinking water exposure alone is considered a potential 

pathway of concern for birds or mammals on an acute and chronic exposure basis. However, the 

model employs a number of conservative assumptions to derive upper bound exposure estimates, 

the most important of which being how it equates the concentration of chemical in drinking 

water to the solubility of the chemical in water. Since ethephon is highly soluble (1.24 x 106

mg/L), the drinking water concentrations estimated by SIP are far higher than would conceivably

be found in a puddle following application.

Terrestrial Invertebrates

In a 48-hour acute oral and contact toxicity test in which young adult honey bees were exposed 

to ethephon, there was 7% mortality observed at 58.5 μg a.i./bee in the oral toxicity assay, and 

no mortality in the contact toxicity assay. The NOAELs for the oral and contact tests were 116.5 

and 100 μg ai/bee, respectively. The LC50 value for the oral test was >116.5 μg ai/bee. The 

LD50 value for the contact test was >100 μg ai/bee. Based on these limited data, ethephon is 

categorized as practically nontoxic to honey bees on an acute oral and contact basis. The acute 
58

dietary exposure EECs for tall grass range from 0.68 to 10.8 μg a.i./bee/day, the highest ratio of 

the EEC to the highest level tested in the contact toxicity assay (10.8/100 = 0.11) is less than the

acute risk LOC (0.4) for individual bees. 

Since ethephon is used on cotton and and other insect pollinator-attractive crops used by some 

beekeepers to produce honey, the proximity of bee colonies to ethephon use areas may be high. 

Cotton specifically is an indeterminate blooming crop, i.e., blooms over a protracted period of 

time, which increases the potential timeframe for exposure. Ethephon is taken up into plants; 

however, it is unknown whether it is transported in the xylem and phloem and whether bees may 

be exposed to ethephon taken up into plant materials such as pollen, nectar, etc. 

There are no reported incidents of bee kills for ethephon. However, the absence of bee kill 

incident data cannot be construed as the absence of incidents. 

Based on the acute oral and contact toxicity studies, risk to individual adult honey bees would be 

considered low; however, a full dataset is not available to fully evaluate risk to honey bees (i.e., 

chronic oral toxicity to adults and acute and chronic toxicity to larvae). Pollinator risk 

assessment guidance has recently been finalized and recommends the following honey bee data 

be available for a Tier I screening level

risk assessment for honey bees:

 acute oral toxicity to adult honey bees;

 acute oral toxicity to larval honey bees;

 chronic oral toxicity to adult honey bees; and,

 chronic oral toxicity to larval honey bees.

Acute oral toxicity data for adult honey bees are available and no effects were seen at an 

acceptable limit dose; however, if the other Tier I studies identify the potential for a risk concern, 

additional studies may be requested. 

Until these data are available, the risk to honey bees cannot be fully evaluated. Risk to 

individual adult honey bees exposed in their diet to ethephon could not be evaluated. 

Additionally, data are not available to evaluate potential effects to brood. 

Non-target terrestrial plants

Based on the available registrant-submitted toxicity data, RQs exceed the Agency’s LOC for risk

to terrestrial plants (Table 134). Application of technical grade ethephon at rates of up to 2.1 lb 

a.i./acre resulted in statistically significant (p<0.05) reductions in shoot length for cucumber 

(Cucumis sativus) in vegetative vigor testing at treatment rates as low as 0.008 lb a.i./acre (EC05

= 0.000418 lb a.i./A) and shoot length for corn (Zea mays) in vegetative vigor testing at 

treatment rates as low as 2.1 lbs a.i./acre (NOAEC = 0.127 lb a.i./A). This indicates that there is

potential for effects to non-target plants at the maximum labeled rates. Assuming an aerial 

application, ASAE fine to medium drop size distribution, and 0.5 lb a.i./A application rate, 

exposure at 0.0106 lb a.i./A (the vegetative vigor dicot IC25) would occur up to 433 feet from the 

edge of the field. Aerial application rates greater than or equal to 1 lb a.i./A would require a 

spray drift buffer greater than 997 feet to protect sensitive non-target plants. Based on available

data, a 719-foot spray drift buffer for aerial applications of ethephon at 0.75 lb a.i./A, and a 435-
59

foot spray drift buffer for aerial applications of ethephon at 0.5 lb a.i./A would be protective of 

sensitive non-target plants. 

Six terrestrial plant incidents in the EIIS database are associated with ethephon: Three incidents 

are associated with barley crop damage (I010934-010; I016662-029; I017865-030); one is 

associated with grape crop damage (I014426-010); one is associated with rye crop damage 

(I021411-019); and one is associated with spring wheat crop damage (I016912-018). The 

certainty of each terrestrial plant incident in EIIS was categorized as either possible or probable. 

A search of the U.S. EPA Office of Pesticide Programs Incident Data System (IDS) identified 

one additional aggregate incident involving ethephon. This incident (016573-00081) was for 

minor plant damage associated with Ethrel® soluble concentrate occurring between April and 

June of 2005. Based on the fact that ethephon is a known plant growth regulator having a 

mechanism of action that could result in effects to plants, the EIIS and IDS incidents corroborate 

the potential for ethephon to directly affect terrestrial plants.

Terrestrial Spray Drift Distance

It is useful to know how far from the edge of the field spray drift exposure alone could result in 

risk to terrestrial organisms. Spray drift exposure to ethephon was determined using AgDRIFT 

version 2.1.1 (USEPA, 2013). The terrestrial spray drift distance was determined using Tier I 

Ground and Tier I Aerial terrestrial point deposition estimates using a fraction of applied based 

on the acute-dose based RQ for birds and the acute listed and acute non-listed LOC. The default 

ASAE Fine to Medium droplet size distribution was assumed for aerial applications. For ground 

applications, a high boom, ASAE very fine to fine drop size distribution, and the 90th data

percentile was assumed. These are the default spray drift inputs recommended for modeling 

spray drift (USEPA, 2013).

The acute-dose based RQ value combined with the acute risk to listed and acute risk to non-listed

species LOCs, results in the greatest spray drift distance for terrestrial organisms. The terrestrial

spray drift distance (i.e., the distance from the edge of the field where spray drift exposure could 

result in RQs that exceed LOCs) for acute and chronic risk to listed and non-listed birds was

explored for the turf use pattern (the highest registered application rate for ethephon) and for 

cotton, tobacco, apples, berries, and pineapple (the highest registered aerial application rate for 

ethephon) and other select application rates (Table 27). For ground applications to turf, the 

spray drift buffer distances range from three feet to 190 feet from the edge of the field for listed 

birds. On a chronic basis, the spray drift distances range from seven to 72 feet for the turf use 

pattern for birds. For listed species, the buffer distance for aerial applications to cotton, tobacco, 

apples, berries, and pineapple range from zero to 121 feet for birds. On a chronic basis, the spray 

drift distances range from zero to 26 feet for the cotton/tobacco/apples/berries/pineapple use 

pattern for birds. The terrestrial spray drift distance estimated for birds is protective of other 

terrestrial organisms (e.g., mammals, reptiles, terrestrial phase amphibians) from effects due to 

exposure to spray drift since avian toxicity endpoints are the lowest of tested terrestrial animals. 

The use of drift reduction technology (DRT) could reduce the distance necessary to prevent 

exceedances of the LOC but DRT is not currently required on ethephon labels. 

Table 27. Spray Drift Distance Where Avian RQs do not Exceed Acute and Chronic LOCs
60

Application Rate (lbs a.i./A)

Distance to no LOC exceedance (feet)*

Avian

Acute Chronic

20 (ground application) Listed: 190

Non-listed: 43

72

2.8 (ground application) Listed: 45

Non-listed: 10

20

2 (aerial application) 121 26

1 (ground application) Listed: 20

Non-listed: 3

7

0.5 (ground application) Listed: 10

Non-listed: 0

3

*Results generated by AgDRIFT

The terrestrial spray drift distance (i.e., the distance from the edge of the field where spray drift 

exposure could result in RQs that exceed LOCs) for risk to non-listed terrestrial plants was

explored for the turf use pattern (the highest registered application rate for ethephon) and for 

cotton, tobacco, apples, berries, and pineapple (the highest registered aerial application rate for 

ethephon) (Table 28). 

Table 28. Spray Drift Distance Where Terrestrial Plant RQs do not Exceed LOCs

Application Rate (lb a.i./A)

Distance to no LOC exceedance (feet)*

Terrestrial Plant

Monocot Vegetative Vigor

Zea mays IC25 = 2.1 lb a.i./A

Dicot Vegetative Vigor

Cucumis sativus IC25=0.0106 lb a.i./A

Ground application

4 7 659

2.8 3 515

2 3 400

1 --** 226

0.75 --** 174

0.5 --** 118

0.25 --** 59

Aerial application

2 --** >997

1 --** >997

0.75 --** 719

0.5 --** 433

*Results generated by AgDRIFT

**Off-site exposure resulting from spray drift is less than toxicity threshold for this comparison

4.4. Uncertainties and Data Gaps

4.4.1. Fate and Transport

The studies submitted to fulfill environmental fate data requirements for ethephon are sufficient 

to conduct an exposure assessment.
61

T-REX EECs are based on residues on surfaces of dietary items. Ethephon is taken up into 

leaves and it is uncertain whether ethephon is taken up by roots and/or distributed in xylem 

and/or phloem. Exposure based on this exposure route was not assessed.

4.4.2. Effects 

Pollinator risk assessment guidance has recently been finalized and recommends a suite of 

laboratory-based studies extending beyond the acute contact study with adult bees.

As these data are currently unavailable for ethephon, the potential risk to individual honey bees 

and brood success could not be fully assessed.

5. Endocrine Disruptor Screening Program (EDSP)

Ethephon was not included in the first group of 67 chemicals issued an order to conduct Tier 1 

EDSP testing. For additional information on the EDSP, visit http://www.epa.gov/endo/.

6. Federally Threatened and Endangered (Listed) Species Concerns

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 a stakeholder workshop in April 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 ethephon does not contain a 
62

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 ethephon. This preliminary risk 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 ethephon indicates potential risks of direct effects to listed dicot terrestrial plants, 

monocot terrestrial plants, aquatic vascular plants, mammals, birds, and terrestrial invertebrates

for registered ethephon use sites. Listed species of semi-aquatic 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 dicot terrestrial plants, 

monocot terrestrial plants, aquatic vascular plants, mammals, birds, and terrestrial invertebrates

from the use of ethephon 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 designated critical 

habitats, these methods will be applied to subsequent analyses for ethephon as part of completing 

this registration review. 

Table 159. Preliminary Conclusions for Potential Direct Effects to Federally Listed Taxa 

Associated with the Registered Uses of Ethephon.

Listed Plant Taxon Potential Direct Effects

Terrestrial and semi-aquatic plants –

monocots and dicots Yes

Aquatic vascular plants Yes

Aquatic non-vascular plants No

Listed Animal Taxon Potential Direct Effects

Acute Chronic

Terrestrial invertebrates Uncertain: No toxicity data for

larval bees

Uncertain: No chronic toxicity

data for adult or larval honey 

bees

Mammals Yes Yes

Birds

Reptiles Yes Yes

Amphibians

Freshwater fish No No

Freshwater invertebrates No No

Mollusks No No data

Estuarine/marine fish No No

Estuarine/marine invertebrates No No
63

7. Conclusions

The risk hypothesis identified in the problem formulation stated, 

Given the currently labeled uses of ethephon and its environmental fate properties, there 

is a likelihood of exposure to non-target terrestrial and aquatic organisms. 

When used in accordance with the label, ethephon may result in potential adverse effects 

upon the survival, growth, and reproduction of non-target terrestrial and aquatic 

organisms. 

After reviewing the most recent environmental fate and effects data for ethephon, the preliminary 

risk assessment concludes that registered uses of the plant growth regulator ethephon may result 

in risks to both listed and non-listed species of birds, mammals, and terrestrial plants and listed 

aquatic vascular plants. 

With respect to exposure, ethephon is characterized as nonvolatile, soluble compound that is

slightly to moderately mobile in soil. Ethephon dissipates in the environment through both biotic 

and abiotic degradation and by leaching in soils that are low in organic carbon. Therefore, there 

is slight potential for ethephon to accumulate in soil with repeated applications. Surface water 

contamination may also occur due to spray drift and/or transport of residues sorbed to sediment 

in runoff (i.e, erosion). In either aquatic or terrestrial environments, ethephon is not expected to

bioaccumulate due to its low Kow.

The available data indicate that ethephon is slightly toxic to freshwater fish and freshwater and 

estuarine/marine invertebrates on an acute exposure basis. Effects on fry hatching success were 

observed in the available chronic freshwater fish study. Chronic effects to adult length were 

observed in the available chronic freshwater invertebrate testing. Effects on survival were 

observed in testing with vascular aquatic plants, and inhibited growth was observed when 

nonvascular aquatic plants were exposed to ethephon. 

The available data indicate that ethephon ranges from practically non-toxic to slightly toxic to 

birds, including passerines, and is slightly toxic to mammals on an acute oral exposure basis and 

highly toxic to mammals on an subacute-dietary exposure basis. Ethephon is practically nontoxic to young adult honey bees on an acute oral and contact exposure basis.

The available data for terrestrial plants exposed to technical ethephon for formulation into enduse products (71.9-73.8% a.i.) indicate that ethephon exposure to seeds and/or emerging plants 

(i.e., seedling emergence) can effect significantly reduced plant height at application rates 

equivalent to 0.22 lb a.i./A compared to the control while exposure to foliage (i.e., vegetative 

vigor) can effect significantly reduced plant height at application rates equivalent to 0.008 lb

a.i./A compared to the control. 

There is a potential for direct adverse effects to the following taxa based on LOC exceedances:

 Mammals (acute listed, acute non-listed, and chronic risk LOCs exceeded)

 Birds, terrestrial-phase amphibians, and reptiles (acute listed, acute non-listed, and 
64

chronic risk LOCs exceeded)

 Aquatic vascular plants (listed species LOC exceeded for three ethephon use patterns)

 Terrestrial plants

Limited available toxicity data for honey bees suggest that acute risk LOCs are not exceeded on 

an acute contact or oral basis; however, data are not available to evaluate potential for effects to 

individual bees and their brood exposed via the diet.

8. References

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USEPA. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Risk 

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USEPA. 2004a. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

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(USEPA). Available at http://cfpub.epa.gov/ecotox/

USEPA. 2010. Registration Review: Preliminary Problem Formulation for Ecological Risk, 

Endangered Species, and Drinking Water Exposure Assessments for Ethephon. DP 

Barcode 371952. April 19, 2010. Environmental Fate and Effects Division. Office of 

Pesticide Programs. U.S. Environmental Protection Agency. 

USEPA. 2011. Evaluation for Ecological Toxicity Data in Open Literature. May 9, 2011. 

Environmental Fate and Effects Division. Office of Pesticide Programs. Office of 

Chemical Safety and Pollution Prevention. U.S. Environmental Protection Agency. 

Available at 

http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_s

pecies_reregistration_workgroup/esa_evaluation_open_literature.htm (Accessed April 3, 

2015).

USEPA. 2012. Screening Level Usage Analysis (SLUA) of Ethephon (099801). U.S. 

Environmental Protection Agency, Office of Prevention, Pesticides and Toxic 

Substances, Biological and Economic Analysis Division. May 14, 2012.

USEPA. 2012a. Ecological Incident Information System. Environmental Fate and Effects 

Division. United States Environmental Protection Agency. 

USEPA. 2012b. White Paper in Support of the Proposed Risk Assessment Process for Bees. 

September 11-14, 2012. September 11, 2012. U.S. Environmental Protection Agency. 

Pest Management Regulatory Agency. California Department of Pesticide Regulation. 

Available at http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2012-

0543-0004 (Accessed June 22, 2014).

USEPA. 2013. Guidance on Modeling Offsite Deposition of Pesticides Via Spray Drift for 

Ecological and Drinking Water Assessment. Environmental Fate and Effects Division. 

Office of Pesticide Programs. Office of Chemical Safety and Pollution Prevention. U.S. 

Environmental Protection Agency. Available at 

http://www.regulations.gov/#!docketDetail;D=EPA-HQ-OPP-2013-0676 (Accessed 

April 11, 2014).

USEPA. 2013. Ethephon: Incremental Ecological Risk Assessment for New Use on Greenhouse 

Tomatoes (PP# 2E7993; IR-4). DP Barcode no. 402283. January 2, 2013.

USEPA, Health Canada PMRA, & California Department of Pesticide Regulation. 2014. 

Guidance for Assessing Pesticide Risks to Bees. June 23, 2014. U.S. Environmental 

Protection Agency. Health Canada Pest Management Regulatory Agency. California 

Department of Pesticide Regulation. Available at http://www2.epa.gov/pollinatorprotection/pollinator-risk-assessment-guidance (Accessed April 10, 2015).
66

8.1 Submitted Product Chemistry and Environmental Fate Studies

161-1 Hydrolysis

40270 Raman, H.P. (1969) The Effect of pH, Time and Temperature on the Degradation of Ethrel. (Unpublished 

study received Aug 27, 1971 under 2G1195; submitted by Union Carbide Agricultural Products Co., Ambler, Pa.; 

CDL:095928-C)

54003 Amchem Products, Incorporated (1972) (2-Chloroethyl)phosphonic acid (Ethephon): Photodecomposition 

Study. (Unpublished study re- ceived Dec 5, 1974 under 264-292; submitted by Union Carbide Ag- ricultural 

Products Co., Inc., Ambler, Pa.; CDL:230425- E)

54004 Biddle, E.; Russell, K.E. (1969?) The Decomposition of 2-Chloro- ethylphosphonic acid in Aqueous 

Solution under Controlled Condi- tions of pH. (Unpublished study received Dec 5, 1974 under 264- 292; prepared 

by Queen's Univ., Dept. of Chemistry, Canada, sub- mitted by Union Carbide Agricultural Products Co., Inc., 

Ambler, Pa.; CDL:230425-G)

54007 Harrison, S. (1973) Letter sent to R.J. Otten dated Jan 26, 1973: Photodecomposition of (2-

Chloroethyl)phosphonic acid in dilute aqueous solution. (Unpublished study received Dec 5, 1974 under 264-292; 

submitted by Union Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:230425-K)

122420 Harrison, S. (1973) Letter sent to R. Otten dated Jan 26, 1973: Photodecomposition of (2- chloroethyl) 

phosphonic acid in dilute aqueous solution. (Unpublished study received 1973 under 2F1275; submitted by Union 

Carbide Agricultural Products Co., Inc., Research Triangle Park, NC; CDL:095926-B)

123944 Harrison, S. (1973) Letter sent to R. Otten dated Jan 26, 1973: Photodecomposition of (2- chloroethyl) 

phosphonic acid in dilute aqueous solution. (Unpublished study received 1973 under 3F1325; submitted by Union 

Carbide Agricultural Products Co., Inc., Research Triangle Park, NC; CDL:093556-C)

124862 Chib, J.; Heintzelman, R. (1983) Ethephon ... Photolytic Degrada- tion Study: File No. 29241. (Unpublished 

study received Jan 18, 1983 under 264-257; submitted by Union Carbide Agricultural Products Co., Inc., Research 

Triangle Park, NC; CDL:249295-B)

136289 Biddle, E.; Russell, K. (1969) The Decomposition of 2-chloroethyl- phosphonic Acid in Aqueous Solution 

under Controlled Conditions of pH. (Unpublished study received Oct 3, 1972 under 3F1321; prepared by Queen's 

Univ., Dept. of Chemistry, Ontario, sub- mitted by Troy Janitorial Supply Co., Inc., Troy, MI; CDL: 092129-I)

41545701 Das, Y. (1990) Hydrolysis of ?Ethyl(U)-?carbon 14|Ethephon in Aqueous Solutions Buffered at pH 5, 7 

and 9: Lab Project Number: 89150. Unpublished study prepared by Innovative Scientific Services, Inc. 113 p.

161-2 Photodegradation-water

41545601 Das, Y. (1990) Photodegradation of ?Ethyl(U)-?carbon 14||Ethephon in Aqueous Solution Buffered at pH 

5 under Sunlight: Lab Project Number: 89151. Unpublished study prepared by Innovative Scien- tific Services, Inc. 

95 p.
67

161-3 Photodegradation-soil

124861 Chib, J.; Heintzelman, R. (1981) Ethephon ... Hydrolytic Degrada- tion Study: File No. 29242. 

(Unpublished study received Jan 18, 1983 under 264-257; submitted by Union Carbide Agricultural Products Co., 

Inc., Research Triangle Park, NC; CDL:249295-A)

157624 Smith, B.; Huhtanen, K. (1986) Ethrel: Photolysis of Ethephon (2- Chloroethyl Phosphonic Acid) on a Soil 

Surface: Project No. 866R10: File No. 34393. Unpublished study prepared by Union Carbide Agricultural Products 

Co., Inc. 26 p.

41681401 Das, Y. (1990) Photodegradation of [Ethyl(U)-(carbon 14)]| Ethephon on Soil under Artificial Sunlight: 

Lab Project Number: 90032. Unpublished study prepared by Innovative Scientific, Inc. 106 p.

162-1 Aerobic soil metabolism

124863 Chib, J.; Heintzelman, R. (1983) Ethephon ... Aerobic Soil Metabo- lism Study on Sand: File No. 31181. 

(Unpublished study re- ceived Jan 18, 1983 under 264-257; submitted by Union Carbide Agricultural Products Co., 

Inc., Research Triangle Park, NC; CDL:249295- C)

41757701 Das, Y. (1991) Metabolism of [Ethyl(U)-[carbon 14]Ethephon Under Aerobic Soil Conditions: Lab 

Project Number: EC-90-111: 90031. Unpublished study prepared by Innovative Scientific Services, Inc. 82 p.

162-3 Anaerobic aquatic metab.

157158 Huhtanen, K. (1986) Anaerobic Aquatic Metabolism Study [Using Ethrel]: Project No.

866R10. Unpublished study prepared by Union Carbide Agricultural Products Co., Inc. 13 p.

41757702 Das, Y. (1991) Metabolism of [Ethyl(U)-[carbon 14]Ethephon Under Anaerobic Aquatic Soil Conditions: 

Lab Project No: EC-90-112. Unpublished study prepared by Innovative Scientific Services, Inc. 92 p.

163-1 Leach/adsorp/desorption

27015 McManus, J. (1972) Soil Mobility Study of A-820. (Unpublished study received Sep 26, 1973 under 264-

265; prepared by Amchem Products, Inc., submitted by Union Carbide Agricultural Products Co., Ambler, Pa.; 

CDL:120461-F)

30177 Amchem Products, Incorporated (1976) Mobility of 2-(3-Chlorophen- oxy)-propionamide and 2-(3-

Chlorophenoxy)-propionic acid on Two Hawaiian Soils. (Unpublished study received Dec 10, 1979 under 264-338; 

submitted by Union Carbide Agricultural Products Co., Ambler, Pa.; CDL:099174-C)

33327 Union Carbide Agricultural Products Company (1972) Soil Mobility Study of A-820. (Unpublished study 

received Dec 19, 1974 under 2G1285; CDL:093814-J)

33334 McManus, J. (1972) Soil Mobility Study of A-820: Amchem Analytical Report. (Appendix; unpublished 

study received Dec 19, 1974 under 2G1285; submitted by Union Carbide Agricultural Products Co., Ambler, Pa.; 

CDL:093814-U)

42974 Union Carbide Agricultural Products Company (1969) Effect of 2-Chloroethylphosphonic acid on 

Witchweed and Crops. (Unpub- lished study received Dec 23, 1969 under 264-257; CDL:100700-A)

54002 Amchem Products, Incorporated (1972) Studies of the Behavior of (2- Chloroethyl) phosphonic acid 

(Ethephon) in Soils. (Unpublished study received Dec 5, 1974 under 264- 292; submitted by Union Carbide 

Agricultural Products Co., Inc., Ambler, Pa.; CDL: 230425-D)
68

71012 Chib, J.S.; North, S.P.; Harrison, S.L. (1980) Ethephon ?(2-Chloro- ethyl)phosphonic Acid| Leaching 

Studies: Project No. 10221/580B. (Unpublished study received Feb 23, 1981 under 264-257; submit- ted by Union 

Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:244607-A)

122405 U.S. Agricultural Research Service (1969) Evaluation of Experi- mental Chemical for Activity on 

Witchweed: ?Ethrel|. (Unpub- lished study received Dec 23, 1969 under 264- 257; submitted by Union Carbide 

Agricultural Products Co., Inc., Research Triangle Park, NC; CDL:002225-B)

125332 Heintzelman, R. (1983) Letter sent to W. Davis dated Jan 27, 1983: Ethephon leaching study. (Unpublished 

study received Feb 1, 1983 under 264-376; submitted by Union Carbide Agricultural Products Co., Inc., Research 

Triangle Park, NC; CDL:249424-A)

129395 Union Carbide Agricultural Products Co., Inc. (1972) Studies of the Behavior of (2-

Chloroethyl)phosphonicacid (Ethephon) in Soils. (Unpublished study received Jun 27, 1983 under 264-257; CDL: 

250644-K)

41263801 Dykes, J. (1989) Soil Adsorption/Desorption with ?Carbon 14|-Ethe- phon: Rept. No.

37275. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 32 p.

42126001 Das, Y. (1991) Soil Adsorption and Desorption of ?carbon 14| Ethephon: Lab Project Number: ISSI 

91020: EC-91-166. Unpub- lished study prepared by Innovative Scientific Services, Inc. 182 p .

43991301 Miller, N.; Liu, A. (1996) 2-Hydroxyethylphosphonic Acid (Ethephon Metabolite): 

Adsorption/Desorption Study: Lab Project Number: EC-95-314: F95332-129: 1095 RP SOIL. Unpublished study 

prepared by Rhone-Poulenc Ag Co. 232 p.

44526801 Mislankar, S.; Estes, T. (1994) Adsorption/Desorption of (carbon 14)-RPA 090946: Amended Final 

Report: Lab Project Number: EC-94-259. Unpublished study prepared by Rhone-Poulenc Ag Co. 98 p.

164-1 Terrestrial field dissipation

42974 Union Carbide Agricultural Products Company (1969) Effect of 2-Chloroethylphosphonic acid on 

Witchweed and Crops. (Unpub- lished study received Dec 23, 1969 under 264-257; CDL:100700-A)

54000 Fritz, C.D. (1971) Letter sent to Anson R. Cooke dated Mar 19, 1971: Ethrel rate of disappearance in soil. 

(Unpublished study received Dec 5, 1974 under 264-292; submitted by Union Carbide Agricultural Products Co., 

Inc., Ambler, Pa.; CDL:230425-B)

54001 Cantliffe, D.J.; Robinson, R.W. (1971) Response of cucumber to soil application of (2-

Chloroethyl)phosphonic acid. Horticultural Science 6(4):336-337. (Also~In~unpublished submission received Dec 

5, 1974 under 264-292; submitted by Union Carbide Agricul- tural Products Co., Inc., Ambler, Pa.; CDL:230425-C)

116123 Amchem Products, Inc. (1970) Residue and Metabolism: Ethephon in Pineapples. (Compilation; 

unpublished study received Jul 30, 1970 under 1F1016; CDL:091065-A)

122405 U.S. Agricultural Research Service (1969) Evaluation of Experi- mental Chemical for Activity on 

Witchweed: ?Ethrel|. (Unpub- lished study received Dec 23, 1969 under 264- 257; submitted by Union Carbide 

Agricultural Products Co., Inc., Research Triangle Park, NC; CDL:002225-B)

125588 Union Carbide Agricultural Products Co., Inc. (1971) ?Ethrel Resi- dues in Various Subjects|. 

(Compilation; unpublished study re- ceived Sep 1, 1971 under 1F1016; CDL:093325-A)
69

42011501 Norris, F. (1991) A Terrestrial Field Soil Dissipation Study with Ethephon: Lab Project Number: EC-89-

070: R092-079: R094-052. Unpublished study prepared by Rhone-Poulenc Ag Co., A & L East- ern Agriculteral 

Labs and A & L Western Agriculteral Labs. 250 p.

49305601 Chen, C. (2014) Independent Laboratory Validation of Bayer Method ET 001 S13;01: An Analytical 

Method for the Determination of Residues of Ethephon and its Metabolite 2- HEPA in Soil and Sediment Using 

LC/MS/MS - Final Report. Project Number: 13/CPS/029, RAETL041. Unpublished study prepared by Critical Path 

Services, LLC (CPS). 107p.

49305603 Sears, K. (2014) Independent Laboratory Validation of "An Analytical Method for the Determination of 

Residues of Ethephon and its Metabolite 2-HEPA in Water Using LC/MS/MS - Final Report. Project Number: 

RAETL042 80907. Unpublished study prepared by Pyxant Labs, Inc. 88p.

165-4 Bioaccumulation in fish

136290 Sleight, B. (1972) Exposure of Fish to 14C-labeled Ethephon: Accumulation, Distribution and Elimination

of Residues. (Unpub- lished study received Oct 3, 1972 under 3F1321; prepared by Bionomics, Inc., submitted by

Troy Janitorial Supply Co., Inc., Troy, MI; CDL:092129-J)

164666 Kuo, W. (1981) [Carbon 14]-Ethrel: Channel Catfish, Ictalurus punctatus (Rafinesque): Bioconcentration 

Study: UCCES Project No. 11507-80. Unpublished study prepared by Union Carbide Corp. Environmental Services. 

195 p.
70

8.2. Submitted Ecotoxicity Studies

Avian Single Dose Oral Toxicity

MRID Citation Reference

26040 Beavers, J.B.; Fink, R.; Brown, R. (1979) Final Report: Acute Oral LD50--Mallard Duck: Project No. 113-146.

(Unpublished study re- ceived Dec 19, 1979 under 264-267; prepared by Wildlife Interna- tional, Ltd. in cooperation with

Washington College, submitted by Union Carbide Agricultural Products Co., Ambler, Pa.; CDL: 099158-A)

26041 Beavers, J.B.; Fink, R.; Brown, R. (1979) Final Report: Acute Oral LD50--Bobwhite Quail: Project No. 113-145.

(Unpublished study received Dec 19, 1979 under 264-267; prepared by Wildlife Inter- national, Ltd. in cooperation with

Washington College, submitted by Union Carbide Agricultural Products Co., Ambler, Pa.; CDL: 099158-B)

27493 Beavers, J.B.; Fink, R.; Brown, R. (1978) Final Report: Acute Oral LD50--Bobwhite Quail: Project No. 164-104.

(Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Wildlife In- ternational, Ltd. in cooperation with

Washington College, sub- mitted by GAF Corp., Chemical Div., New York, N.Y.; CDL: 099355-A)

27497 Hinkle, S.; Twigg, C.J. (1980) Final Report: Acute Oral LD50 Study in Bobwhite Quail: Project No. 257-111.

(Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Hazleton Laboratories America, Inc., submitted by

GAF Corp., Chemical Div., New York, N.Y.; CDL:099355-F)

27502 Moore, S.C.; Reno, F.E. (1979) Final Report: Acute Oral LD50 in Bobwhite Quail: Project No. 257-104. Rev.

(Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Hazleton Labo- ratories America, Inc., submitted by

GAF Corp., Chemical Div., New York, N.Y.; CDL:099355-L)

54012 Gabriel, K.L. (1969) Acute Oral Toxicity--Bob White Quail. (Unpub- lished study received Dec 5, 1974 under 264-

292; prepared by Biosearch, Inc., submitted by Union Carbide Agricultural Prod- ucts Co., Inc., Ambler, Pa.; CDL:230425-Q)

57812 Gabriel, K.L. (1969) Acute Oral Toxicity--Bob White Quail. (Unpub- lished study received Sep 4, 1975 under 264-290;

prepared by Biosearch, Inc., submitted by Union Carbide Agricultural Prod- ucts Co., Inc., Ambler, Pa.; CDL:225086-C)

69674 Gabriel, K.L. (1969) Acute Oral Toxicity--Bob White Quail. (Unpub- lished study received Feb 27, 1970 under

1F1016; prepared by Biosearch, Inc., submitted by Amchem Products,

Inc., Ambler, Pa.; CDL:091064-J)

Avian Dietary Toxicity

MRID Citation Reference

27494 Hinkle, S.; Cameron, J.T. (1979) Final Report: Avian Dietary Toxic- ity (LC50) Study in Bobwhite Quail: Project No.

257-108. (Un- published study received Apr 3, 1980 under 1529-EX-2; prepared by Hazleton Laboratories America, Inc.,

submitted by GAF Corp., Chemical Div., New York, N.Y.; CDL:099355-B)

27498 Hinkle, S.; Cameron, J.T. (1979) Final Report: Avian Dietary Toxic- ity (LC50) Study in Bobwhite Quail: Project No.

257-110. (Un- published study received Apr 3, 1980 under 1529-EX-2; prepared by Hazleton Laboratories America, Inc.,

submitted by GAF Corp., Chemical Div., New York, N.Y.; CDL:099355-G)

27503 Moore, S.C.; Reno, F.E. (1979) Final Report: Subacute Dietary LC50 in Bobwhite Quail: Project No. 257-106. Rev.

(Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Hazleton Laboratories America, Inc., submitted by

GAF Corp., Chemical Div., New York, N.Y.; CDL:099355-M)

27504 Moore, S.C.; Reno, F.E. (1979) Final Report: Subacute Dietary LC50 in Mallard Ducks: Project No. 257-105. Rev.

(Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Hazleton Labo- ratories America, Inc., submitted by
71

GAF Corp., Chemical Div., New York, N.Y.; CDL:099355-N)

56480 Hinkle, S.; Cameron, J.T. (1979) Final Report: Avian Dietary Toxic- ity (LC50) Study in Mallard Ducks: Project No.

257-107. (Un- published study received Apr 3, 1980 under 1529-EX-2; prepared by Hazleton Laboratories America, Inc.,

submitted by GAF Corp., Chemical Div., New York, N.Y.; CDL:099355-C)

72983 Fink, R. (1972) Final Report: Eight-Day Dietary LCI50^--Mallard Ducks: Project No. 141-

246. (Unpublished study received Dec 5, 1974 under 264-292; prepared by Environmental Sciences Corp., submitted by Union

Carbide Agricultural Products Co., Inc., Am- bler, Pa.; CDL:230425-P)

73622 Fink, R. (1972) Final Report: Eight-Day Dietary LCI50^--Mallard Ducks: Project No. 141-

246. (Unpublished study received Sep 4, 1975 under 264-290; prepared by Environmental Sciences Corp., submitted by Union

Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:225086-B)

85446 Fink, R.; Beavers, J.B.; Brown, R. (1977) Final Report: Eight-day Dietary LCI50^-- Bobwhite Quail: Project No. 113-

139. (Unpub- lished study received Mar 2, 1979 under 264-267; prepared by Wildlife International, Ltd. and Washington

College, submitted by Union Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:097830-F)

104086 Fink, R.; Reno, F. (1976) Final Report: Eight-day Dietary LC50-- Bobwhite Quail: ?

CPGR/2|: Project No. 257-203. (Unpublished study received Feb 9, 1976 under 1529-20; prepared by Truslow Farms, Inc. and

Hazleton Laboratories America, Inc., submitted by GAF Corp., Chemical Div., New York, NY; CDL:239732-A)

107428 Fink, R.; Reno, F. (1974) Final Report: Eight-day Dietary LC50-- Mallard Ducks: ?CPGR|: Project No. 257-102.

(Unpublished study received Mar 15, 1974 under 1529-20; preparedby Truslow Farms, Inc., and Environmental Sciences Corp.,

submitted by GAF Corp., Chemical Div., New York, NY; CDL:132053-A)

122414 Fink, R. (1972) Eight-day Dietary LC50--Mallard Ducks: Ethephon: Project No. 141-246. Final rept. (Unpublished

study received Dec 5, 1974 under 264-292; prepared by Hazleton Laboratories, Inc., submitted by Union Carbide Agricultural

Products Co., Inc., Research Triangle Park, NC; CDL:028299-D)

123801 Fink, R.; Reno, F. (1974) Eight-day Dietary LC50--Mallard Ducks: CPGR: Project No.

257-102. Final rept. (Unpublished study received Mar 15, 1974 under unknown admin. no.; prepared by Hazleton Laboratories,

Inc., submitted by GAF Corp., Chemical Div., New York, NY; CDL:131715-A)

40874301 Fletcher, D. (1988) 8-Day Dietary LC50 Study with Base 250 in Bob- white Quail: Project No. BLALA Study No.

86 QC 75. Unpublished study prepared by Bio-Life Associates, Ltd. 73 p.

41080201 Fletcher, D. (1988) 8-Day Dietary LC50 Study with Base 250 in Bob- white Quail: Project No. BLAL Study No. 86

QC 75. Unpublished study prepared by Bio-Life Associates, Ltd. 73 p.

Acute Toxicity to Freshwater Fish

MRID Citation Reference

122412 Sleight, B. (1971) The Acute Toxicity of Ethrel to Bluegill ... and ... Salmo gairdneri. (Unpublished study received Dec

5, 1974 under 264-292; prepared by Bionomics, Inc., submitted by Union Carbide Agricultural Products Co., Inc., Research

Triangle Park, NC; CDL:028299-B)

122443 Pitcher, F. (1974) (Cepha--Bluegill): Test No. 665. (Unpublished study received Mar 13, 1974 under 1529-20; prepared

by Pesticides Regulation Div., Animal Biology Laboratory, submitted by U.S. Environmental Protection Agency, Beltsville,

MD; CDL: 128204-A)

44389903 Dionne, E. (1997) Finish--Acute Toxicity to Channel Catfish (Ictalurus punctatus) Under Flow-Through Conditions:

Final Report: Lab Project Number: 97-2-6870: 10566.1096.6407.107: 100296/FIFRA/107/FIN. Unpublished study prepared by

Springborn Labs, Inc. 90 p. (Relates to L0000183)

Acute Toxicity to Freshwater Invertebrates
72

MRID Citation Reference

122448 Pitcher, F. (1974) (Cepha--Daphnia magna): Test No. 672. (Unpublished study received Mar 13, 1974 under 1529-20;

prepared by Pesticides Regulation Div., Animal Biology Laboratory, submitted by U.S. Environmental Protection Agency,

Beltsville, MD; CDL: 132055-A)

Acute Toxicity to Estuarine/Marine Organisms

MRID Citation Reference

41296202 Dionne, E. (1989) Ethephon--Acute Toxicity to Eastern Oyster (Crassostrea virginica) under Flow-through

Conditions: Final: SLI Report No. 89-10-3121; SLI Study 10566.1288.6123.504. Unpublished study prepared by Springborn

Laboratories, Inc., Environmental Sciences Div. 37 p.

Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

MRID Citation Reference

27495 Bentley, R.E. (1974) Acute Toxicity of CPGR Formulation and CPGR 100% to Bluegill (?

~Lepomis macrochirus~?) and Rainbow Trout (?~Salmo gairdneri~?). (Unpublished study received Apr 3, 1980 under 1529-EX2; prepared by Bionomics, EG&G Environmental Con- sultants, submitted by GAF Corp., Chemical Div., New York, N.Y.;

CDL:099355-D)

27496 Foote, K.C. (1978) Toxicity Test of GAF's Corporation: Teceth 75 ?8065-20|: Contract No.

L1362-05. (Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Syracuse Research Corp., submitted by GAF

Corp., Chemical Div., New York, N.Y.; CDL:099355-E)

27499 Foote, K.C. (1979) Toxicity Test of GAF Corporation's NMP with ?~Lepomis macrochirus~(Bluegill): Contract No.

L1393-05. (Un- published study received Apr 3, 1980 under 1529-EX-2; prepared by Syracuse Research Corp., submitted by

GAF Corp., Chemical Div., New York, N.Y.; CDL:099355-I)

27501 Posner, S. (1969) The Effect of Methyl pyrrolidone on Fingerling Fish: Laboratory No. 90458. (Unpublished study

received Apr 3, 1980 under 1529-EX-2; prepared by Food and Drug Research Labo- ratories, Inc., submitted by GAF Corp.,

Chemical Div., New York, N.Y.; CDL:099355-K)

27505 Buccafusco, R.J. (1978) Acute Toxicity of Sample 7767-141AF to Bluegill (?~Lepomis macrochirus~?) and Rainbow

Trout (?~Salmo ?~gairdneri~?): Report # BW-78-4-115. (Unpublished study re- ceived Apr 3, 1980 under 1529-EX-2; prepared

by Bionomics, EG&G, submitted by GAF Corp., Chemical Div., New York, N.Y.; CDL: 099355-O)

27506 Foote, K.C. (1979) Toxicity Test of GAF Corporation's 7767-141: Contract No. L1393-05. (Unpublished study

received Apr 3, 1980 under 1529-EX-2; prepared by Syracuse Research Corp., submitted by GAF Corp., Chemical Div., New

York, N.Y.; CDL:099355- P)

54010 Sleight, B.H., III (1971) Bioassay Report: The Acute Toxicity of Ethrel to Bluegill (?

~Lepomis macrochirus~?) and Rainbow Trout (?~Salmo gairdneri~?). (Unpublished study received Dec 5, 1974 under 264-292;

prepared by Bionomics, Inc., submitted by Union Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL: 230425-N)

42294501 Putt, A. (1992) Ethephon Technical--The Chronic Toxicity to Daphnia magna Under Flow- through Conditions:

Final Report: Lab Project Number: 92-1-4074: 10566.0891.6210.130. Unpublished study prepared by Springborn Labs., Inc. 98

p.

81-1 Acute oral toxicity in rats

MRID Citation Reference

28615 Griffiths, J.T.; Babish, J.G. (1978) Approximate Acute Oral Toxic- ity (LD50) in Rats: Laboratory No. 5659b.

(Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Food and Drug Research Laboratories, Inc., submitted

by GAF Corp., Chemical Div., New York, N.Y.; CDL:099359-D)
73

28620 Griffiths, J.T.; Babish, J.G. (1978) Approximate Acute Oral Toxic- ity (LDI50^) in Rats: Laboratory No. 5659a.

(Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Food and Drug Research Laboratories, Inc., submitted

by GAF Corp., Chemical Div., New York, N.Y.; CDL:099359-I)

29509 Griffiths, J.T.; Parent, R.A. (1979) The Approximate Acute Oral Toxicity (LDI50^) of GAF CPD 71921/L9 in Male

Sprague-Dawley Rats: Laboratory No. 2-6153. (Unpublished study received Apr 3, 1980 under 1529-EX-2; prepared by Food

and Drug Research Labora- tories, Inc., submitted by GAF Corp., Chemical Div., New York, N.Y.; CDL:099356-A)

55315 Holsing, G.C. (1968) Final Report: Acute Oral Administration-- Rats: Project No. 141-169. (Unpublished study

received Mar 6, 1969 under 264-263; prepared by TRW, Inc., submitted by Union Carbide Agricultural Products Co., Inc.,

Ambler, Pa.; CDL: 002234-D)

57166 Moldovan, M. (1974) Determination of the Acute Oral LDI50^: OE No. 4199-1670. (Unpublished study received Jul

16, 1974 under 1529-20; prepared by Food and Drug Research Laboratories, Inc., submitted by GAF Corp., Chemical Div., New

York, N.Y.; CDL: 119822-A)

81317 Field, W.E.; Carter, W. (1978) Oral LDI50^ In Rats: Study No. CDC- AM-014-78. (Unpublished study received Mar

2, 1979 under 264- 267; prepared by CDC Research, Inc., submitted by Union Carbide Agricultural Products Co., Inc., Ambler,

Pa.; CDL:097830-A)

85754 Weatherholtz, W.M.; Twigg, C.J.; Wolfe, G.W. (1980) Acute Oral Toxicicity Study in Rabbits: Project No. 400-630.

Final rept. (Unpublished study received Oct 19, 1981 under 264-267; pre- pared by Hazleton Laboratories America, Inc.,

submitted by Union Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:246064-A)

89757 Bach, K.J. (1974) Acute Oral Toxicity in Rats: ?Amchem 73-A191|. Final rept. (Unpublished study received Mar 18,

1974 under 264- 290; prepared by Affiliated Medical Research, Inc., submitted by Union Carbide Agricultural Products, Co.,

Inc., Ambler, Pa.; CDL:023033-E)

116549 DeProspo, J. (1972) Effective Dose for Vomiting: ?Tech. Ethrel|: Contract No. 121-1498-

52. Final rept. (Unpublished study re- ceived Oct 8, 1972 under 2F1275; prepared by Affiliated Medical Enterprises, Inc.,

submitted by Amchem Products, Inc., Ambler, PA; CDL:091812-C)

116670 Myers, R.; Coleman, J.; Bellich, N.; et al. (1982) Ethephon AXF- 1209: Acute Toxicity and Irritancy Study: Project

Report 45-172. (Unpublished study received Oct 15, 1982 under 264-380; sub- mitted by Union Carbide Agricultural Products

Co., Inc., Re- search Triangle Park, NC; CDL:248658-A)

116931 Holsing, G. (1968) Acute Oral Administration--Rats: Amchem 68-250 (Ethrel) 39.5% Active Ingredient by Weight:

Project No. 141-169. Final rept. (Unpublished study received Jul 29, 1970 under 1F1016; prepared by Hazleton Laboratories,

Inc., submitted by Amchem Products, Inc., Ambler, PA; CDL:092124-B)

122446 Hazleton Laboratories, Inc. (1968) Acute Oral Administration--Rats: Amchem 68-250 (Ethrel) 39.5% Active Ingredient

by Weight: Project No. 141-169. Final rept. (Unpublished study received Sep 1, 1969 under 264-263; submitted by Union

Carbide Agricul- tural Products Co., Inc., Research Triangle Park, NC; CDL: 129923-C)

128627 Myers, R.; Christopher, S.; Coleman, J.; et al. (1983) Cerone 4 Liquid Plant Growth Regulator--Peroral and

Percutaneous Toxicity Study: Project Report 46-37. (Unpublished study received May 11, 1983 under 264-257; submitted by

Union Carbide Agricultural Products Co., Inc., Research Triangle Park, NC; CDL:250387-A)

41154501 Myers, R. (1989) Acute Peroral Toxicity Study: Ethephon Base 250: Project ID 47-49 (Revised). Unpublished study

prepared by Bushy Run Research Center. 11 p.

43123904 Kuhn, J. (1993) Flordimex-Konzentrat (sic) 65 (Ethephon 65%): Acute Oral Toxicity Study in Rats: Lab Project

Number: 0421-93. Unpublished study prepared by Stillmeadow, Inc 23 p.

43368423 Douds, D. (1993) An Acute Oral Toxicity Study in Rats with EXP 31039B: Final Report: Lab Project Number:

3147.185. Unpublished study prepared by Springborn Labs, Inc. 69 p.

43837102 Wnorowski, G. (1995) ETK-2201: Acute Oral Toxicity Test (in Rats): Lab Project Number: 3936. Unpublished
74

study prepared by Product Safety Labs. 22 p.

43849401 Kuhn, J. (1994) Ethephon 6#: Acute Oral Toxicity Study in Rats: Lab Project Number: 0610-93. Unpublished study

prepared by Stillmeadow, Inc. 23 p.

43920501 Varsho, B. (1996) Acute Oral Toxicity of Florel Plant Growth Regulator in Albino Rats: Final Report: Lab Project

Number: WIL-21068. Unpublished study prepared by WIL Research Labs, Inc. 25 p.

43920502 Varsho, B. (1996) Acute Oral Toxicity Study of Ethrel Plant Regulator in Albino Rats: Final Report: Lab Project

Number: WIL-21069. Unpublished study prepared by WIL Research Labs, Inc. 51 p.

44652501 Douds, G. (1998) An Acute Oral Toxicity Study in Rats with EXP 31648A: Final Report: Lab Project Number:

3147.258. Unpublished study prepared by Springborn Laboratories, Inc. 34 p.

45568104 Rodabaugh, D. (2001) An Acute Oral Toxicity Study in Rats with Finish Extra: Final Report: Lab Project Number:

3522.41. Unpublished study prepared by Springborn Laboratories, Inc. 26 p. {OPPTS 870.1100}

2-generation repro.-rat

MRID Citation Reference

36508 Weatherholtz, W.M.; Ferrell, J.F. (1972) Final Report: Three-Gener- ation Reproduction Study--Rats: Project No. 141-

214. (Unpub- lished study received on unknown date under 4F1490; prepared by Hazleton Laboratories, Inc., submitted by

Union Carbide Agricul- tural Products Co., Ambler, Pa.; CDL:093946-B)

80405 Weatherholtz, W.M. (1972) Final Report: Three-generation Reproduc- tion Study--Rats: Project No. 141-214.

(Unpublished study re- ceived Oct 6, 1972 under 2F1275; prepared

by Environmental Sci- ences Corp., submitted by Union Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:091810-A)

80985 Weatherholtz, W.M. (1972) Final Report: Three-generation Reproduc- tion Study--Rats: Project No. 141-214.

(Unpublished study re- ceived Dec 5, 1974 under 264-292; prepared by Environmental Sciences Corp., submitted by Union

Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:028298-B)

81076 Weatherholtz, W.M. (1972) Final Report: Three-generation Reproduc- tion Study--Rats: Project No. 141-214.

(Unpublished study re- ceived Dec 5, 1974 under 264-292; prepared by Environmental Sci- ences Corp., submitted by Union

Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:050583-B)

81781 Union Carbide Agricultural Products Company, Incorporated (1970) Three-generation Reproduction Study--Rats.

(Unpublished study received May 7, 1971 under 1G1172; CDL:090971-B)

83627 Weatherholtz, W.M. (1972) Final Report: Three-generation Reproduc- tion Study--Rats: Project No. 141-214.

(Unpublished study re- ceived Jun 1, 1974 under 5F1524; prepared by Environmental Sciences Corp., submitted by Union

Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL:094482-B)

41508701 Neeper-Bradley, T.; Tyl, R. (1990) Two-generation Reproduction Study in CD Albino Rats exposed to Ethephon by

Dietary Inclu- sion: Lab Project I.D.: 51-539. Unpublished study prepared by Union Carbide Bushy Run Research Center. 760 p.

Seed Germination/Seedline Emergence and Vegetable Vigor

MRID Citation Reference

41403305 Hoberg, J. (1990) Ethephon--Determination of Effects on Seedling Germination, Shoot Emergence and Seedling

Vigor of Ten Plant Species: Lab Project Number: 90-2-3220: 10566-1288-6124-610. Unpublished study prepared by Springborn

Laboratories, Inc. 311 p.

44518602 Teixeira, D. (1998) EXP-31039C--Determination of Effects on Seedling Emergence of Two Plant Species and

Vegetative Vigor of Ten Plant Species: Lab Project Number: 97-12- 7199: 10566.0797.6431.610. Unpublished study prepared

by Springborn Laboratories, Inc. 263 p.

Aquatic plant growth

MRID Citation Reference
75

41403301 Giddings, J. (1990) Ethephon--Toxicity to the Marine Diatom Skele- tonema costatum: Lab Project Number: 90-1-

3207: 10566-0389-6131- 450. Unpublished study prepared by Springborn Laboratories, Inc. 36 p.

41403302 Giddings, J. (1990) Ethephon--Toxicity to the Freshwater Diatom Navicula pelliculosa: Lab Project Number: 90-2-

3234: 10566-0389- 6131-440. Unpublished study prepared by Springborn Laboratories Inc. 36 p.

41403303 Giddings, J. (1990) Ethephon--Toxicity to the Freshwater Bluegreen Alga Anabaena flos- aquae: Lab Project

Number: 90-1-3206: 10566- 0389-6131-420. Unpublished study prepared by Springborn Labora- tories, Inc. 35 p.

41403304 Giddings, J. (1990) Ethephon--Toxicity to the Freshwater Green Alga Selenastrum capricornutum: Lab Project

Number: 90-1-3197: 10566- 0389-6131-430. Unpublished study prepared by Springborn Labora- tories, Inc. 36 p.

41509001 Giddings, J. (1990) Ethephon--Toxicity to the Freshwater Plant Lemna gibba G3: Final Report: SLI Report No.: 90-

04-3302; SLI Study No.: 10566.0389.6131.410. Unpublished study prepared by Springborn Laboratories, Inc., Environmental

Sciences Div. 42 p.

Seed germination/seedling emergence and vegetative vigor

MRID Citation Reference

43868323 Hoberg, J. (1995) EXP-31039B--Determination of Effects on Seedling Emergence and Vegetative Vigor of Ten

Plants Species: Lab Project Number: 95-5-5867: 10566.0495.6364.610. Unpublished study prepared by Springborn Labs, Inc.

343 p.

44518602 Teixeira, D. (1998) EXP-31039C--Determination of Effects on Seedling Emergence of Two Plant Species and

Vegetative Vigor of Ten Plant Species: Lab Project Number: 97-12- 7199: 10566.0797.6431.610. Unpublished study prepared

by Springborn Laboratories, Inc. 263 p.

Aquatic plant growth

MRID Citation Reference

41509001 Giddings, J. (1990) Ethephon--Toxicity to the Freshwater Plant Lemna gibba G3: Final Report: SLI Report No.: 90-

04-3302; SLI Study No.: 10566.0389.6131.410. Unpublished study prepared by Springborn Laboratories, Inc., Environmental

Sciences Div. 42 p.

850.2100 Avian acute oral toxicity test

MRID Citation Reference

49160601 Christ, M. ; Shepherd, J. (2013) Toxicity of Ethephon Technical During an Acute Oral LD50 with the Canary

(Serinus canaria). Project Number: 07SRLS13C3. Unpublished study prepared by SynTech Research Laboratory Services, LLC.

51p.

850.2300 Avian reproduction test

MRID Citation Reference
76

48202005 Mitchell, L.; Martin, K.; Beavers, J.; et al. (2001) Ethephon: A Reproduction Study with the Japanese

Quail: Final Report. Project Number: 171/159, C012884. Unpublished study prepared by Wildlife International, Ltd.

158 p.

49305605 Christ, M.; Shepherd, J.; Moore, S. (2014) Toxicity of Ethephon (Base 250) on the Reproduction of the

Mallard Duck (Anas platyrhynchos). Project Number: 07SRLS13C4. Unpublished study prepared by SynTech

Research Laboratory Services, LLC. 73p.

49325701 Stafford, J. (2014) Ethephon: Reproductive Toxicity Test with the Northern Bobwhite (Colinus

virginianus): Final Report. Project Number: 13798/4138, XY4711. Unpublished study prepared by Smithers Viscient.

439p.

850.3020 Honey bee acute contact toxicity

MRID Citation Reference

48202006 Schmitzer, S.; Sterk, N. (1999) Laboratory Testing for Toxicity (Acute Contact and Oral LD50) of

Ethephon on Honey Bees (Apis mellifera L.) (Hymenoptera, Apidae): Final Report. Project Number: R006341,

6291036. Unpublished study prepared by Institut fuer Biologische Analytik und Consulting IBACON. 28 p.

850.4225 Seedling emergence, Tier II

MRID Citation Reference

49037901 Kohler, P. (2012) Ethephon 71.3: Effects on the Seedling Emergence and Growth of Three Species of

Non-Target Terrestrial Plants (Tier 2). Project Number: VV12/038, EBETL017, M/443312/01/1. Unpublished study

prepared by Bayer CropScience GmbH. 116p.

850.4250 Vegetative vigor, Tier II

MRID Citation Reference

48976901 Kohler, P. (2012) Ethephon 71.3: Effects on the Vegetative Vigour of Six Species of Non- Target

Terrestrial Plants(Tier 2): Final Report. Project Number: M/443312/01/1/OCR, VV12/038, EBETL017. Unpublished

study prepared by Bayer CropScience GmbH. 140p.

49037902 Kohler, P. (2012) Ethephon 71.3: Effects on the Vegetative Vigour of Six Crop Species of Non-Target

Terrestrial Plants (Tier 2). Project Number: VV12/038, EBETL017, M/443312/01/1. Unpublished study prepared by

Bayer CropScience GmbH. 140p.
77

Appendix A. Selected SWCC Output Files

Summary of Water Modeling of Ethephon and the USEPA 

Standard Pond

Turf

Table 1. Estimated Environmental Concentrations (ppb) for Ethephon.

Peak (1-in-10 yr) 17.7

4-day Avg (1-in-10 yr) 9.00

21-day Avg (1-in-10 yr) 3.97

60-day Avg (1-in-10 yr) 2.89

365-day Avg (1-in-10 yr) 0.489

Entire Simulation Mean 0.434

Table 2. Summary of Model Inputs for Ethephon.

Scenario FLturfSTD

Cropped Area Fraction 1

Kd (ml/g) 30

Water Half-Life (days) @ 25 °C 2.6

Benthic Half-Life (days) @ 25 °C 16

Photolysis Half-Life (days) @ 40 

°Lat

139

Hydrolysis Half-Life (days) 2.4

Soil Half-Life (days) @ 22 °C 13

Foliar Half-Life (days) 35

Molecular Wt 144.5

Vapor Pressure (torr) 1E-7

Solubility (mg/l) 1.2E6
78

Table 3. Application Schedule for Ethephon.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

03/1 Ground 4.48 0.99 0.062

03/15 Ground 4.48 0.99 0.062

03/29 Ground 4.48 0.99 0.062

04/12 Ground 4.48 0.99 0.062

04/26 Ground 4.48 0.99 0.062
79

Appendix B. Toxicity Categories and Levels of Concern

 

 Table B1. Categories of Toxicity for Aquatic Organisms

LC50 (ppm) Toxicity Category

< 0.1 Very highly toxic

> 0.1 - 1 Highly toxic

> 1 - 10 Moderately toxic

> 10 - 100 Slightly toxic

> 100 Practically nontoxic

Table B2. Categories of Toxicity for Terrestrial Organisms

Oral dose LD50 (mg/kg-bw) Toxicity Category

< 10 Very highly toxic

10 - 50 Highly toxic

51 - 500 Moderately toxic

501 - 2000 Slightly toxic

> 2000 Practically nontoxic

Dietary LC50 (ppm) Toxicity Category

< 50 Very highly toxic

50 - 500 Highly toxic

501 - 1000 Moderately toxic

1001 - 5000 Slightly toxic

> 5000 Practically nontoxic

Table B3. Categories of Toxicity for Honey Bee

Bee Acute Contact LD50 (μg/bee) Toxicity Category

<2 Highly toxic

2 – 10.99 Moderately toxic

> 11 Practically nontoxic

Table B4. Levels of Concern for Terrestrial and Aquatic Organisms

Taxa Acute LOC Chronic LOC

Avian

1

(terrestrial phase amphibians) 0.1 1

Mammalian

2

0.1 1

Terrestrial plants31

Aquatic Animals4(aquatic phase

amphibians)

0.05 1

Insects 50.05 1

Used in RQ calculations:

1 LD50 and estimated NOEL

2 LD50 and NOEC

3 EC25

4 LC/EC50 and estimated and reproductive NOEC

5 LD50 per EFED’s CRLF Steering Committee
80

Appendix C. Example T-REX (v. 1.5.2) Input and Output for Ethephon

Table D.1. T-REX Model Inputs: Chemical Application Scenarios and Body Mass for Assessed

Species.

Table D.2. Avian and Mammalian Toxicity Endpoints for RQ Calculation.

TREX MODEL INPUTS You must enable macros for this spreadsheet to work correctly

These values will be used in the calculation of exposure estimates for foliar, granular, liquid and/or 

seed applications of pesticides.

Application No.

Chemical Name: Application Rate (lb ai/acre) 1

Seed Treatment? (Check if yes) FALSE Seeding Rate (lbs/acre) 2

 Use: 3

Product name and form: 4

% A.I. (leading zero must be entered for 

formulations <1% a.i.): 5

Application Rate (lb ai/acre) 4 6

Half-life (days): 35 7

Application Interval (days): 14 8

Number of Applications: 5 9

Are you assessing applications with 

variable rates or intervals? no 1 0

You MUST specify application day in Columns F and G - you may enter up to 30 applications 1 1

1 2

What body weight range is assessed 

(grams)? Birds Mammals 1 3

Small 20 15 1 4

Medium 100 35 1 5

Large

1000 1000

1 6

100.00%

Assessed Species Inputs (optional, use defaults for RQs for national level 

assessments)

You MUST specify application day in Columns F and G - you may enter up to 30 applications

Chemical Identity and Application Information
81
82

Appendix D. STIR Results

Welcome to the EFED 

Screening Tool for Inhalation Risk

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

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

Input

Application and Chemical Information

Enter Chemical Name Ethephon

Enter Chemical Use turf

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

If Spray What Type (enter ground or air) ground

Enter Chemical Molecular Weight (g/mole) 144.5

Enter Chemical Vapor Pressure (mmHg) 1.00E-07

Enter Application Rate (lb a.i./acre) 4

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 596

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 1205

Enter Lowest Rat Inhalation LC50 (mg/L) 2.13

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 7.78E-04

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 9.78E-05

Adjusted Inhalation LD50 5.87E+00

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.66E-05 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 4.23E-01

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 7.20E-02 Exposure not Likely Significant

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 7.78E-04

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.23E-04

Adjusted Inhalation LD50 1.27E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 9.69E-07 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 5.31E-01

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 4.19E-03 Exposure not Likely Significant

**NOTE**: When entering values, press the "Enter" key 

in order to update linked cells.
83

Appendix E. Screening Imbibition Program (SIP) Version 1.0 Inputs and Results

Parameter Value

Chemical name Ethephon

Solubility (in water at 25oC; mg/L) 1240000

Mammalian LD50 (mg/kg-bw) 1205

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 300

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 596

Avian test species northern bobwhite quail

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 106

Bobwhite quail NOAEC (mg/kg-diet) 983

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

Body weight (g) of other avian species

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

Body weight (g) of 2nd other avian species

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 213280.0000 213280.0000

Adjusted toxicity value (mg/kg-bw) 926.8385 230.7482

Ratio of exposure to toxicity 230.1156 924.2977

Conclusion*

Exposure through drinking 

water alone is a potential 

concern for mammals

Exposure through drinking 

water alone is a potential 

concern for mammals

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 1004400.0000 1004400.0000

Adjusted toxicity value (mg/kg-bw) 429.3760 5.2589

Ratio of exposure to acute toxicity 2339.2086 190989.3618

Conclusion*

Exposure through drinking 

water alone is a potential 

concern for birds

Exposure through drinking 

water alone is a potential 

concern for birds

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

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

may contribute to a total exposure that has potential for effects to non-target animals.
84

Appendix F. Accepted ECOTOX Data Table (2008 to 2015 Refresh Report)

The code list for ECOTOX can be found at: http://cfpub.epa.gov/ecotox/blackbox/help/codelist.pdf

Genus Species

Common 

Name

Effect 

Group Effect Meas Endpt1 Endpt2

Dur 

Preferred 

Mean

Dur Unit 

Preferred

Conc Units 

Preferred

% 

Purity Ref #

Rhododendron sp. Azaleas GRO GRO GGRO NOAEL 56 d % 100 81589

Rhododendron sp. Azaleas GRO MPH LGTH NOAEL 21 d % 100 81589

Rhododendron sp. Azaleas GRO MPH LGTH NOAEL 21 d % 100 81589

Rhododendron sp. Azaleas GRO GRO GGRO NOAEL 56 d % 100 81589

Rhododendron sp. Azaleas GRO DVP GDVP NOAEL 42 d % 100 81589

Rhododendron sp. Azaleas GRO DVP GDVP NOAEL 42 d % 100 81589

Abutilon theophrasti Butter print GRO GRO LGTH LOAEL 4 d ppm >=95 106960

Abutilon theophrasti Butter print REP REP VIAB LOAEL 4 d ppm >=95 106960

Fusarium oxysporum Fungi POP POP ABND NOAEL 4 d ppm >=95 106960

Abutilon theophrasti Butter print GRO DVP EMRG NOAEL 28 d ppm >=95 106960

Abutilon theophrasti Butter print REP REP VIAB NOAEL 28 d ppm >=95 106960

Abutilon theophrasti Butter print GRO GRO WGHT LOAEL 28 d ppm >=95 106960

NR Fungi Fungi Kingdom POP POP ABND NOAEL 28 d ppm >=95 106960

Fusarium oxysporum Fungi POP POP ABND NOAEL 28 d ppm >=95 106960

Oryza sativa Rice BCM HRM ABSA NOEC fs M 100 98600

Oryza sativa Rice BCM BCM ETHL LOEC fs M 100 98600

Oryza sativa Rice CEL CEL CDRT NOEC fs M 100 98600

Oryza sativa Rice GRO DVP DVLP NOEC fs M 100 98600

Oryza sativa Rice GRO GRO WGHT NOEC ma M 100 98600

Prays oleae Olive Moth POP POP INDX LOAEL 365 d % 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 365 d % 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 365 d % 100 116440

Prays oleae Olive Moth POP POP PRPE NOAEL 365 d % 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 730 d % 100 116440

Prays oleae Olive Moth POP POP INDX NOAEL 730 d % 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 730 d % 100 116440

Prays oleae Olive Moth POP POP PRPE NOAEL 730 d % 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 1095 d % 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 1095 d % 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 1095 d % 100 116440

Prays oleae Olive Moth POP POP PRPE NOAEL 1095 d % 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 365 d % 100 116440
85

Prays oleae Olive Moth POP POP INDX LOAEL 365d% 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 365d% 100 116440

Prays oleae Olive Moth POP POP PRPE LOAEL 365d% 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 730d% 100 116440

Prays oleae Olive Moth POP POP INDX NOAEL 730d% 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 730d% 100 116440

Prays oleae Olive Moth POP POP PRPE NOAEL 730d% 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 365d% 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 365d% 100 116440

Prays oleae Olive Moth POP POP INDX LOAEL 365d% 100 116440

Prays oleae Olive Moth POP POP PRPE NOAEL 365d% 100 116440

Phloeotribus scarabaeoides

Olive Bark 

Beetle POP POP ABND NOAEL 19d% 48 116051

Phloeotribus scarabaeoides

Olive Bark 

Beetle POP POP ABND NOAEL 26d% 48 116051

Phloeotribus scarabaeoides

Olive Bark 

Beetle POP POP ABND NOAEL 33d% 48 116051

Phloeotribus scarabaeoides

Olive Bark 

Beetle POP POP ABND NOAEL 40d% 48 116051

Triglochin maritima Arrowgrass REP REP GERM LOAEL 20d mM 100 115844

Neoseiulus fallacis Predatory mite MOR MOR MORT LC502d gal/100 gal 100 71217

Tetranychus urticae

Two-spotted 

spider mite MOR MOR MORT LC502d gal/100 gal 100 71217

Anabaena flosaquae

Blue-green 

algae POP POP BMAS EC504d mg/L 85 95681

Microcystis aeruginosa

Blue-green 

algae POP POP BMAS EC504d mg/L 85 95681

Microcystis flosaquae

Blue-green 

algae POP POP BMAS EC504d mg/L 85 95681

Chlorella pyrenoidosa Green algae POP POP BMAS EC504d mg/L 85 95681

Anthonomus grandis Boll Weevil POP POP ABND LOAEL3d AI kg/ha 100 115843

Anthonomus grandis Boll Weevil POP POP ABND LOAEL 10d AI kg/ha 100 115843

Anthonomus grandis Boll Weevil POP POP ABND NOAEL 44d AI kg/ha 100 115843

Anthonomus grandis Boll Weevil POP POP ABND NOAEL 36d AI kg/ha 100 115843

Anthonomus grandis Boll Weevil POP POP ABND NOAEL 30d AI kg/ha 100 115843

Phymatotrichum omnivora Fungus POP POP DMTR LOAELd ppm 100 115652

Oryza sativa Rice BCM BCM ETHL LOAEL2dM 100 108051

Oryza sativa Rice BCM BCM ETHL LOAEL2dM 100 108051

Oryza sativa Rice GRO GRO WGHT LOAEL maM 100 108051
86

Oryza sativa Rice REP REP STRL LOAEL maM 100 108051

Oryza sativa Rice GRO GRO WGHT LOAEL maM 100 108051

Oryza sativa Rice REP REP STRL LOAEL maM 100 108051

Septoria apiicola Fungus REP REP GERM NOAEL LOAEL 3.666666667d ppm 100 116149

Prays oleae Olive Moth POP POP ABND LOAELd AI g/ha 100 116150

Olea europaea Olive POP POP BMAS NOAEL hv lb/acre 100 116150

Oryza sativa Rice BCM BCM MLDH LOAEL9d mM 100 116151

Oryza sativa Rice BCM BCM MLDH LOAEL9d mM 100 116151

Oryza sativa Rice BCM ENZ GENZ LOAEL9d mM 100 116151

Oryza sativa Rice BCM ENZ GENZ LOAEL9d mM 100 116151

Oryza sativa Rice GRO MPH WGHT LOAEL hv mM 100 116151

Oryza sativa Rice GRO MPH WGHT LOAEL hv mM 100 116151

Aphis gossypii Cotton aphid POP POP ABND NOAEL4d AI lb/acre 100 116381

Aphis gossypii Cotton aphid POP POP ABND NOAEL4d AI lb/acre 100 116381

Aphis gossypii Cotton aphid POP POP ABND NOAEL4d AI lb/acre 100 116381

Aphis gossypii Cotton aphid POP POP ABND NOAEL 27d AI lb/acre 100 116381

Aphis gossypii Cotton aphid POP POP ABND NOAEL 27d AI lb/acre 100 116381

Aphis gossypii Cotton aphid POP POP ABND NOAEL 27d AI lb/acre 100 116381

Gossypium hirsutum Cotton POP POP BMAS NOAEL hv AI lb/acre 100 116381

Gossypium hirsutum Cotton POP POP BMAS NOAEL hv AI lb/acre 100 116381

Gossypium hirsutum Cotton POP POP BMAS NOAEL hv AI lb/acre 100 116381

Gossypium hirsutum Cotton POP POP BMAS NOAEL hv AI lb/acre 100 116381

Gossypium hirsutum Cotton POP POP BMAS NOAEL hv AI lb/acre 100 116381

Gossypium hirsutum Cotton POP POP BMAS NOAEL hv AI lb/acre 100 116381

Anabaena flosaquae

Blue-green 

algae POP POP BMAS NOEC LOEC4d mg/L 85 95681

Microcystis aeruginosa

Blue-green 

algae POP POP BMAS NOEC LOEC4d mg/L 85 95681

Microcystis flosaquae

Blue-green 

algae POP POP BMAS NOEC LOEC4d mg/L 85 95681

Chlorella pyrenoidosa Green algae POP POP BMAS NOEC LOEC4d mg/L 85 95681

Anabaena flosaquae

Blue-green 

algae POP POP BMAS MATC4d L/mg 85 95681

Microcystis aeruginosa

Blue-green 

algae POP POP BMAS MATC4d L/mg 85 95681

Microcystis flosaquae

Blue-green 

algae POP POP BMAS MATC4d L/mg 85 95681

Chlorella pyrenoidosa Green algae POP POP BMAS MATC4d L/mg 85 95681

Claviceps fusiformis Fungus REP REP GERM NOAEL1d ppm 100 116052
87

Pennisetum glaucum Pearl millet REP REP SSET NOAEL 20d ppm 100 116052

Pennisetum glaucum Pearl millet REP REP SSET NOAEL 20d ppm 100 116052

Pennisetum glaucum Pearl millet REP REP SSET NOAEL 20d ppm 100 116052

Gossypium hirsutum Cotton POP POP ABND NOAEL LOAEL 55d lb/acre 100 115843

Gossypium hirsutum Cotton POP POPABND NOAEL 48d lb/acre 100 115843

Gossypium hirsutum Cotton POP POP ABND NOAEL 37d lb/acre 100 115843

Gossypium hirsutum Cotton POP POP ABND NOAEL 29d lb/acre 100 115843

Gossypium hirsutum Cotton POP POP ABND NOAEL 23d lb/acre 100 115843

Pennisetum glaucum Pearl millet GRO MPH HGHT LOAEL 20d ppm 100 116052

Pennisetum glaucum Pearl millet GRO MPH HGHT LOAEL 20d ppm 100 116052

Anthonomus grandis Boll Weevil BEH AVO CHEM NOAEL 90d ppm 100 115845

Anthonomus grandis Boll Weevil BEH AVO CHEM NOAEL 90d ppm 100 115845

Sclerotinia sclerotiorum Fungus POP POP PGRT NOAEL4d ppm 100 115842

Sclerotinia sclerotiorum Fungus POP POP PGRT NOAEL4d ppm 100 115842

Sclerotinia sclerotiorum Fungus POP POP PGRT NOAEL4d ppm 100 115842

Echinochloa oryzicola

Rice 

Barnyardgrass REP REP GERM NOAEL LOAEL9d mg/L 100 31310

Oryza sativa Rice REP REP GERM NOAEL9d mg/L 100 31310

Echinochloa oryzicola

Rice 

Barnyardgrass GRO MPH LGTH NOAEL LOAEL 18d mg/L 100 31310

Oryza sativa Rice GRO MPH LGTH LOAEL 18d mg/L 100 31310

NR Chrysopidae

Lacewing 

family POP POP PRPE NOAEL hv AI g/ha 100 116150

Malus domestica Apple PHY PHY PSYN NOAEL 35d ppm 100 42817

Malus domestica Apple GRO GRO LGTH LOAEL 14d ppm 100 42817

Malus domestica Apple PHY INJ DAMG NOAEL 35d ppm 100 42817

Epiphyas postvittana

Lightbrown 

Apple Moth POP POP ABND NOAEL 35d ml/L 100 117205

Oryza sativa Rice BCM BCM PNYL LOAEL fi mg/L 100 108344

Oryza sativa Rice BCM BCM PNYL LOAEL fi mg/L 100 108344

Oryza sativa Rice BCM BCM PNYL LOAEL fi mg/L 100 108344

Oryza sativa Rice REP REP STRL LOAEL fi mg/L 100 108344

Oryza sativa Rice REP REP STRL LOAEL fi mg/L 100 108344

Oryza sativa Rice REP REP STRL LOAEL fi mg/L 100 108344