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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

 PC Code: 006314

DP Barcode: D426678

September 8, 2015

MEMORANDUM

SUBJECT: Registration Review: Combined Problem Formulation for Preliminary 

Environmental Fate and Ecological Risk Assessment for Antimycin A

TO: Christina Scheltema, Chemical Review Manager

Avivah Jakob, Team Leader

Risk Management and Implementation Branch III

Pesticide Re-Evaluation Division (7508P)

Will Donovan, Residue Chemist

Alexandra LaMay, Risk Assessor & ORE 

Health Effects Division (7509P)

FROM: Cheryl Sutton, Ph.D., Environmental Scientist

Thomas Steeger, Ph.D., Senior Science Advisor

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

REVIEWED

BY: Catherine Aubee, Senior Scientist

James Carleton, Ph.D., Senior Fate Scientist

Katrina White, Ph.D., Risk Assessment Project Leader

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

THROUGH: Jean Holmes, D.V.M., M.P.H., Branch Chief

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has completed a combined problem 

formulation and preliminary environmental fate and ecological risk assessment in support of the 

Registration Review of the nitrosalicylanilide piscicide antimycin A (also referred as Fintrol® 

Concentrate; PC Code 006314; CAS No: 1397-94-0). Antimycin A is classified as a “Restricted 

Use” pesticide.
-Page 2 of 44-

EFED examined the most recent environmental fate and ecological risk assessment written in 

support of the May, 2007 Reregistration Eligibility Decision (RED) for antimycin A in 

association with updated toxicity, exposure, and usage information to determine if additional 

data are needed to support the Registration Review of antimycin A. In addition, EFED 

considered the latest Agency science policies and risk assessment methodologies. Because the 

database was determined to be sufficient to assess the ecological risk for use of antimycin A, the 

preliminary risk assessment has been combined with the problem formulation for registration 

review. Since the underlying fate and effects data have not changed since the earlier assessment 

in 2007 and no additional data are required at this time, this preliminary risk assessment does not 

differ substantially from the previous and the reader is referred to the earlier document for a 

more detailed discussion of the available data. The previous assessment provides much greater 

detail on the use of antimycin A to restore native fish populations and information on the toxicity 

of potassium permanganate, which is used to deactive the Fintrol®and prevent its movement 

outside of targeted treatment areas. Subsequent to the 2007 ecological risk assessment, the US 

National Park Service finalized their standard operating procedure (SOP) for the use of 

antimycin A to restore fish populations, and this SOP is now referenced on the Fintrol®product 

label. The SOP provides detailed instructions on the use of and deactication of antimycin A with 

potassium permanganate. These procedures help to further ensure that antimycin A will not 

move outside of the targeted treatment area. 

Risk Conclusions

Antimycin A is registered for use as a piscicide for use in fish management and aquaculture 

programs. The single registered end-use product is Fintrol® Concentrate. Antimycin A appears to 

sorb to sediment (potentially at a high level) and to degrade primarily by hydrolysis. It appears 

not to volatilize, does not readily dissolve in water, nor does it bioaccumulate. However, 

antimycin A is rapidly degraded by the deactivation process required in the SOP linked to the 

Fintrol® Concentrate label. 

On an acute exposure basis, antimycin A is moderately toxic to mammals, highly to very highly 

toxic to birds, and very highly toxic to aquatic animals. There are no data to evaluate the chronic 

toxicity of antimycin to animals, and there are no data to evaluate the toxicity of antimycin to 

either terrestrial or aquatic plants.

Like many of the chemicals used for killing fish (i.e., piscicides), for fishery management 

purposes, antimycin A has very detailed standard operating procedures (SOPs) developed by the 

US National Park Service in collaboration with the New Mexico Department of Game and Fish. 

These SOPs are considered part of the federal label and ensure that relatively rigorous methods 

are routinely used to greatly reduce the likelihood of exposure and adverse effects to non-target 

organisms outside of the desired treatment area. Although these SOPs do not apply to Fintrol®

use in catfish production ponds, the chemical’s use in aquaculture is accompanied by long 

holding periods (>1 yr) during which time the compound is expected to degrade to negligible 

levels.

The results of this screening-level risk assessment are similar to those identified in the 

environmental fate and ecological risk assessment written in support of the RED for Antimycin 
-Page 3 of 44-

A in 2007. Exposure to the compound resulting from the maximum treatment concentration is 

expected to kill all fish and aquatic invertebrates in the immediate treatment area. However, in 

lotic (flowing water) environments, after a specified treatment period, the compound is

deactivated (detoxified) through the use of a strong oxidizing agent (potassium permanganate; 

KMnO4) into degradates that are no longer toxic. The oxidizing agent is applied at a deactivation 

station at the perimeter of the Fintrol®treatment area to ensure that it does not move outside of 

the intended treatment area. 

Detoxification is typically verified using caged fish (bioassays) located downstream of the 

permanganate release sites. While there is uncertainty as to the extent to which active compound 

may be able to move outside of the treatment area, available data based on downstream bioassays

indicate that antimycin residues are no longer at a concentratations sufficient to kill fish. The 

effect of potassium permangante on non-target organism has been reviewed in previous 

assessments (USEPA, 2006a) and the extent of its effects depend on the amount of organic 

material in the water treated; however, as a strong oxidizing agent, the compound can be highly 

toxic to aquatic organims. Riparian habitat on the margins of treated water typically contributes

sufficient organic matter to rapidly deplete permanganate close to the detoxification stations.

Within the targeted treatment area and based on the most sensitive species and at the maximum 

treatment concentration, risk quotient (RQ) values for antimycin A exceed acute risk levels of 

concern (LOCs) by several orders of magnitude for direct adverse effects to Federally listed 

threatened and endangered (hereafter referred to as “listed”) and non-listed fish and 

invertebrates. Because the SOP, which is part of the Federal label, requires that antimycin A be 

deactivated to prevent its movement outside of the treatment area, and given that treatment 

concentrations/durations are intended to result in 100% kill of the target species when antimycin 

A is used to restore fish populations, the likelihood of chronic exposure and/or effects is 

considered low. While both birds (and by extension reptiles and terrestrial-phase amphibians) 

may be exposed through consumption of prey impaired by antimycin A, the likelihood of 

adverse effects to these taxa from secondary exposure is considered low.

Although antimycin A is used in catfish production ponds, its use is limited to clearing fingerling 

production ponds of scaled fish, which can compete with catfish and carry disease. For use in 

aquaculture, antimycin is not typically deactivated as it is when used in lotic environmental. 

However, catfish production ponds are not typically drained (if at all) until after catfish have 

been harvested, at least one year after treatment. Based on available data, antimycin A would 

likely degrade during the holding period and is clearly not toxic to the catfish for which it was 

initially used to protect from competition with other species.

Uncertainties

There is a high degree of uncertainty surrounding the quantitative estimation of the 

environmental properties of antimycin A. Only two environmental fate studies (hydrolysis and 

aerobic aquatic metabolism) were submitted for the compound, and results of the two are 

partially contradictory. Additionally, no quantitative information regarding the relative 

concentrations of the transformation products is available. However, uncertainty associated with 

the lack of environmental fate data is somewhat mitigated by the fact that the compound is 
-Page 4 of 44-

deactivated with a strong oxidizing agent following its use in flowing water, and that relatively 

detailed standard operating procedures are in place as part of the label. Bioassays (caged fish) 

are used concurrently with treatments to confirm that antimycin A does not move outside of the 

desired treatment area.

No data are available on the chronic toxicity of antimycin A to terrestrial or aquatic animals; 

however, the likelihood of chronic exposure is considered low for aquatic organisms in the 

treatment area since treatment concentration of up to 25 μg/L are expected to result in 100% 

mortality of both fish (and by extension aquatic-phase amphibians) and aquatic invertebrates. 

No data are available on the toxicity of antimycin A to benthic invertebrates. Although 

antimycin may partition to benthic sediments, the treatment concentrations used in fishery 

management are considered sufficient to result in complete mortality of both fish and 

invertebrates in the water column. If residues move into sediment, a similar situation is 

considered likely, i.e., complete mortality. Available data indicate though that long-term effects 

to macroinvertebrate populations in treated streams were minimal and that recovery occurred 

within several months of treatment.

No data are available for either aquatic or terrestrial plants; the use of the compound by resource 

management agencies such as the National Park Service and state fishery management agencies 

have not reported any incidents involving plants. Also, for fishery management purposes, the 

compound is added directly to water and while backpack sprayers may be used to treat shallow 

waters along shorelines, the spray is not applied to terrestrial plants but rather to the water. 

Similarly, the use of antimycin A in catfish production ponds is a direct application to water and 

production ponds do not typically contain terrestrial and/or emergent aquatic plants since they 

would interfere with catfish harvest and serve as possible habitat for snails which vector 

diseases.

Provided that use of Fintrol®and/or the current formulation of antimycin as currently specified 

on the label does not change, no additional data are recommended at this time. 
Environmental Fate and Ecological Problem Formulation and 

Preliminary Risk Assessment

for the Registration Review of Antimycin A

 

CAS 1397-94-0 PC Code 006314

September 8, 2015

Prepared by

Cheryl Sutton, Ph.D., Environmental Scientist

Thomas Steeger, Ph.D., Senior Science Advisor

U.S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

(EFED)

Environmental Risk Branch IV

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by

Catherine Aubee, Senior Scientist

James Carleton, Ph.D., Senior Fate Scientist

Katrina White, Ph.D., RAPL

Jean Holmes, D.V.M., M.P.H., Branch Chief

O

O

NH O

HO

NH

O

H3C

O

O

H3C

O

O

H3C

CH3
-Page 6 of 44-

Table of Contents

1. Executive Summary .............................................................................................................. 8

2. Problem Formulation ....................................................................................................... 10

2.1. Conclusions from Previous Risk Assessments.............................................................. 10

2.1.1. Ecological Risk Assessment.................................................................................... 10

2.1.2. Drinking Water Exposure Assessments................................................................ 11

2.1.3 Clean Water Act Programs........................................................................................ 11

2.2. Nature of Regulatory Action...................................................................................... 12

2.3. Stressor Source and Distribution .............................................................................. 12

2.3.1. Nature of the Chemical Stressor............................................................................. 12

2.3.2. Overview of Pesticide Usage ................................................................................ 14

2.4. Receptors ................................................................................................................... 15

2.4.1. Aquatic and Terrestrial Effects........................................................................... 15

2.4.2. Ecosystems Potentially at Risk ......................................................................... 16

2.5. Assessment Endpoints ................................................................................................ 16

2.6. Risk Hypotheses......................................................................................................... 16

2.6.2. Potential Exposure Pathways and Effects .......................................................... 17

2.7. Analysis Plan .............................................................................................................. 18

2.7.1. Measures of Exposure........................................................................................ 18

2.7.1.1 Measures of Aquatic Exposure ................................................................................................18

2.7.1.2. Measures of Terrestrial Exposure ............................................................................................18

2.7.2. Measures of Effect.............................................................................................. 19

2.7.3. Integration of Exposure and Effects ................................................................ 20

2.8. Preliminary Identification of Data Gaps ............................................................ 21

3. Analysis.............................................................................................................................. 21

3.1. Use Characterization .................................................................................................. 21

3.2. Exposure Characterization ........................................................................................ 22

3.2.1. Environmental Fate and Transport Characterization ...................................... 22

3.2.1.1. Transport and Mobility ............................................................................................................24

3.2.1.3. Field Studies ............................................................................................................................25

3.2.1.4. Bioaccumulation ......................................................................................................................25

3.2.1.5. Transformation Products..........................................................................................................25

3.2.2. Measures of Aquatic Exposure ............................................................................ 26

3.2.2.1. Estimated Environmental Concentrations in Surface...............................................................26

3.2.2.2. Monitoring Data.......................................................................................................................26

3.2.3. Measures of Terrestrial Exposure....................................................................... 26

3.3. Ecological Effects Characterization .......................................................................... 27

3.3.3. Review of Incident Data ....................................................................................... 31

4. Risk Characterization......................................................................................................... 32

4.1. Screening-Level Risk Quotient (RQ) Values............................................................ 32

4.1.1. RQ Values for Aquatic Organisms...................................................................... 32

4.1.2. RQ Values for Terrestrial Organisms................................................................. 33

4.2. Risk Description.......................................................................................................... 33

4.2.1. Risks to Aquatic Organisms................................................................................. 34

4.2.1.1. Freshwater Fish, Amphibians, and Invertebrates.....................................................................34

4.2.2. Risks to Terrestrial Organisms............................................................................ 36

4.2.2.1. Birds, Reptiles, and Terrestrial-phase Amphibians..................................................................36
-Page 7 of 44-

4.2.2.2. Mammals .................................................................................................................................38

4.2.2.3. Terrestrial Invertebrates...........................................................................................................39

4.2.2.4. Terrestrial Plants......................................................................................................................39

5. Endocrine Disruptor Screening Program (EDSP)........................................................... 39

6. Federally Threatened and Endangered (Listed) Species of Concern ............................ 39

7. Conclusions.......................................................................................................................... 40

8. References............................................................................................................................ 41

9. Appendix A. SIP Results .................................................................................................... 44

List of Tables

TABLE 1. CHEMICAL PROFILE OF ANTIMYCIN A. ......................................................................................13

TABLE 2. AGENCY RISK QUOTIENT (RQ) METRICS AND LEVELS OF CONCERN (LOC) PER RISK CLASS..20

TABLE 3. CHEMICAL PROPERTIES AND ENVIRONMENTAL FATE PARAMETERS OF ANTIMYCIN A............22

TABLE 4. HYDROLYSIS RATES FOR ANTIMYCIN A FROM SUBMITTED DATA AND PUBLISHED 

LITERATURE. ......................................................................................................................................25

TABLE 5. AQUATIC ANIMAL ACUTE AND CHRONIC TOXICITY ESTIMATES FOR ANTIMYCIN A.................28

TABLE 6. TERRESTRIAL ANIMAL ACUTE TOXICITY ESTIMATES FOR ANTIMYCIN A. ................................30

TABLE 7. ACUTE RISK QUOTIENTS FOR FRESHWATER FISH AND INVERTEBRATES BASED ON A TARGETED 

ANTIMYCIN A TREATMENT RATE OF 25 μG/L. ....................................................................................32

TABLE 8. ACUTE RISK QUOTIENTS FOR ESTUARINE/MARINE FISH AND INVERTEBRATES BASED ON A

TARGETED ANTIMYCIN A TREATMENT RATE OF 25 μG/L. ..................................................................33

TABLE 9. ACUTE DOSE-BASED RISK QUOTIENTS FOR PISCIVOROUS BIRDS BASED ON POTENTIAL RESIDUES 

IN DEAD OR DYING FISH......................................................................................................................37

TABLE 10. ACUTE DOSE-BASED RISK QUOTIENTS FOR PISCIVOROUS MAMMALS BASED ON POTENTIAL 

RESIDUES IN DEAD OR DYING FISH. ....................................................................................................39
-Page 8 of 44-

1. Executive Summary

Antimycin A (CAS 1397-94-0, under the tradename Fintrol®), is a restricted use 

nitrosalicylanilide pesticide derived as a fermentation product from Streptomyces mold and is 

registered for use as a means to kill fish, i.e., a piscicide. The chemical is primarily used to 

renovate recreational fish populations by removing unwanted fish species from streams, 

impoundments and small lakes (<50 ha) for subsequent reestablishment of native aquatic 

communities; and to remove scaled fish from catfish fingerling fish production ponds. The 

chemical acts by uncoupling oxidative phosphorylation by blocking the electron transport 

pathway to Complex III within mitochondria.

The residues of concern for this assessment were determined to be antimycin A parent only. 

Antimycin A is applied directly to water via means (e.g., drip stations), thereby avoiding spray 

drift, and is maintained at a targeted treatment concentration for specified periods of time prior to 

deactivation of the compound with a strong oxidizing agent (potassium permanganate) in treated 

streams. Although environmental fate data are limited, the primary route of degradation appears 

to be base hydrolysis, because under alkaline conditions the compound can degrade with a halflife of approximately 30 minutes. However, in a submitted aquatic metabolism study (pH 6.5), 

the compound persisted in an aquatic environment with a half-life of from 23 to 47 days, 

although these results were uncertain since the half-life in that study exceeded the expected halflife from hydrolysis alone at the study pH. Adsorption to sediment in that study may have limited

the availability of the compound to degrade via hydrolysis. Field studies on downstream 

movement also show that the compound, when introduced to flowing waters, can persist and 

remain toxic to aquatic animals for distances of 1.75 km or more beyond the intended treatment 

zone when no effort is made to deactivate (chemically degrade) the compound. There are no 

direct measurements of antimycin sorption to soils or sediments; however, indirect evidence 

suggests that antimycin will partition significantly to soil and sediments, which may reduce 

potential exposures outside of the immediate treatment area.

On an acute exposure basis antimycin is moderately toxic to mammals, highly to very highly 

toxic to birds and very highly toxic to aquatic animals resulting in mortality. There are no data to 

evaluate the chronic toxicity of antimycin to animals and there are no data to evaluate the 

toxicity of antimycin to either terrestrial or aquatic plants. However, given that all aquatic 

animals are likely to be killed by acute exposure to the compound and that other than for use in 

aquaculture the compound is deactivated to prevent movement of the compound outside of the 

desired treatment area, the potential for chronic exposure is considered low. With respect to 

plants, the compound is applied directly to water, and, based on multiple years of use by the 

National Park Service and state fishery management agencies, there are no reports of adverse 

effects to either terrestrial or aquatic plants in the treatment area. Aquatic plants in aquaculture 

operations are minimized as they would interfere with catfish harvest and serve as habitat for 

snails which can vector parasites/diseases of catfish.

Based on the most sensitive species and the maximum treatment concentrations of 25 μg/L, acute 

risk levels of concern are exceeded for aquatic animals by factors of roughly 6,000X. Even for 

the least sensitive fish and aquatic invertebrates tested, treatment concentrations of 25 μg/L 
-Page 9 of 44-

would exceed acute risk levels of concern. These risk conclusions extend to amphibians using 

aquatic habitat treated with antimycin A. Although antimycin is moderately to very highly toxic 

to terrestrial animals on an acute oral exposure basis, the target concentration in water of 25 μg/L 

or less is expected to present a low risk of acute mortality for birds, reptiles, and mammals 

through ingestion of antimycin-treated water or ingestion of dead/dying fish, based on an 

analysis of residues in fish. 

Because there are no chronic toxicity data, it is not possible to estimate potential chronic risk to 

aquatic or terrestrial animals. However, in situations where antimycin is applied to flowing 

water, the chemical is deactivated (detoxified) with a strong oxidizing agent (e.g., potassium 

permanganate) at deactivation stations at the perimeter of the treatment area, as described in the 

US Park Service SOP (USDOI, 2012), which are part of the technical label. Additionally, in 

flowing water, antimycin A would eventually be flushed through the system and would also be 

diluted by inflow from untreated tributaries. Bioassays are required below the treatment area to 

ensure that the antimycin A is no longer active; the extent to which this deactivation process is 

effective is uncertain. However, bioassays downstream of the detoxification stations indicate 

that the compound is no longer at levels which affect the fish used in the bioassay. Also, in both 

lentic and lotic environments, because of the relatively extensive logistics involved in preparing 

for and conducting antimycin treatments, antimycin is typically only applied once per year. Thus, 

the likelihood of chronic exposure in a lotic environment is low; however, in the absence of data, 

risk to nontarget organisms cannot be precluded. In situations where antimycin is not deactivated 

with potassium permanganate and there is not rapid dilution by untreated water, such as in many 

lentic (static water) environments, the chronic risk to non-target aquatic organisms is uncertain. 

However according to the SOP, the use of antimycin in restoring fish populations is for a 

complete kill; therefore, the likelihood that any aquatic animals would survive is considered low.

Where antimycin is used to remove scaled fish from catfish fingerling production ponds, 

treatment concentrations are considerably lower than 25 μg/L in order to not impair the 

health/survival of catfish. Furthermore, the likelihood of either acute or chronic effects in nontarget animals from the use of antimycin in aquaculture is low since the treated water is typically 

retained within the aquaculture facility for a year or longer until the catfish are of marketable 

size. To the extent that treated water is not retained but rather released into surrounding 

streams/rivers, the risk to non-target aquatic animals is uncertain. 

Based on laboratory data, aquatic invertebrates appear to be as sensitive to antimycin as fish; 

however, field studies of antimycin in high-gradient mountain streams, where the compound was 

deactivated with potassium permanganate after the desired treatment time, suggests that aquatic 

invertebrates are not affected or are at worst temporarily affected as they repopulated these areas 

through immigration. Sampling conducted several months to up to a year after treatment indicate 

that aquatic invertebrate abundance and diversity were similar to pretreatment levels. Even in 

first-order streams where antimycin was not deactivated with permanganate, invertebrate drift 

and survival did not appear to be significantly affected during or immediately after 8-hr 

treatments at 10 μg/L. Whether these studies are indicative of aquatic invertebrate communities 

in all antimycin use areas is uncertain.
-Page 10 of 44-

Effects on listed species may be an important consideration for site-specific applications. 

However, antimycin A is an important chemical control measure used by federal and state 

fishery management agencies to restore fish habitat by eliminating invasive species. 

 

2. Problem Formulation

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

ecological risk assessment being conducted for the labeled uses of 3-methylbutanoic acid 3[[3-

(formylamino)-2-hydroxylbenzoyl]amino]-8-hexyl-2,6-dimethyl-4,9-dioxo-1,5-dioxonan-7-yl 

ester (antimycin A, also referred to as Fintrol® Concentrate; PC Code 006314; CAS No: 1397-

94-0). The problem formulation sets the objectives for the risk assessment and provides a plan 

for analyzing the data and characterizing the risk (USEPA 1998a). 

As part of the Registration Review process, a Problem Formulation (PF) for this risk assessment 

has been developed simultaneously with the conduct of the Registration Review Preliminary 

Risk Assessment (PRA) itself, as it was determined that available data are sufficient to conduct 

the risk assessment at this time. A separate Problem Formulation document will not be issued for 

antimycin A. 

2.1. Conclusions from Previous Risk Assessments

The ecological risk assessment written in support of the 2007 Reregistration Eligbility Decision 

(RED; USEPA 20071) document for antimycin A was issued in September 2006 (USEPA 

2006a

2

) and finalized in March 2007 following the comment period. Based on the previous 

analysis of the environmental fate, ecotoxicity, and registered uses of antimycin A, exposure to 

the compound resulting from the maximum treatment concentration is expected to kill fish and 

aquatic invertebrates in the immediate treatment area. However, in lotic environments, the 

compound is deactivated to ensure that it does not move outside of the intended treatment area. 

Bioassays are conducted downstream of the treatment area to ensure that antimycin is no longer 

toxic. Based on the most sensitive species and at the maximum treatment concentration, risk 

quotient (RQ) values exceed acute risk levels of concern (LOCs) by several orders of magnitude. 

2.1.1. Ecological Risk Assessment

The major environmental fate and ecological risk conclusions presented in the RED were as 

follows:

 Antimycin is applied directly to water and is maintained at a targeted treatment 

concentration for specified periods of time. Although environmental fate data are limited, 

 

1USEPA. 2007. Reregistration Eligibility Decision for Antiycin A. List D. Case No. 4121. Available on line at: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2006-1002-0029

2

USEPA. 2006. Revised Environmental Fate and Ecological Risk Assessment Chapter (DP Barcode D310730) in Support of Phase III of the 

Reregistration Eligibility Decision on Antimycin A (PC Code 006314). Available on line at: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2006-1002-0004
-Page 11 of 44-

the primary route of degradation is base hydrolysis, by which, under alkaline conditions

(pH 8-9), the compound can degrade with a half-life of approximately 3 hours. Half-lives 

at environmentally relevant pH values (pH 5 to 8) ranged from less than 1 hour to 10 

hours. A more complete discussion of hydrolysis was included in Appendix G of the 

ecological risk assessment written in support of the 2007 RED2.

 Based on the most sensitive species and typical treatment concentrations of 25 μg/L, acute 

risk levels of concern are exceeded for aquatic animals by several orders of magnitude. 

Even for the least sensitive fish and aquatic invertebrates tested, treatment concentrations 

of 25 μg/L would exceed acute risk levels of concern. Although antimycin is moderately 

to very highly toxic to terrestrial animals on an acute oral exposure basis, treatment rates 

to water of 25 μg/L or less are expected to present a low risk of acute mortality for birds 

and mammals through ingestion of dead/dying fish or direct ingestion of antimycin-treated 

water.

Since the underlying environmental fate and ecological effects (toxicity) data have not changed 

since the earlier assessment in 20073, this preliminary risk assessment does not differ 

substantially from the previous one, and the reader should refer to the earlier document for a 

more detailed discussion of the available data. The previous assessment also provides much 

greater detail on the use of antimycin to restore native fishes and on the toxicity of potassium 

permanganate, which is used to deactive the compound and prevent its movement outside of 

targeted treatment areas.

2.1.2. Drinking Water Exposure Assessments

EFED conducted a drinking water assessment (DWA) of antimycin A4in 2006 to evaluate 

potential risks to humans. The highest environmental concentration was considered the 

maximum treatment concentration of 25 μg/L. Chronic exposure values were estimated using a 

range of hydrolysis degradation rates and the most conservative degradation rate (using the 

longest reported hydrolysis half-life) which yielded a 1-yr average chronic concentration of 4.6 

μg/L. Details may be found in the 2006 assessment. At the time of the previously-conducted 

DWA, deactivation of the compound was not required for streams, as it now is in the current 

SOP for antimycin A use, precluding the need for a DWA.

2.1.3 Clean Water Act Programs 

Antimycin A is not identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act. No Total Maximum Daily Loads (TMDLs) or 

water quality criteria have been developed for antimycin A.

5

 

3

Ibid USEPA 2007.

4

USEPA. 2007a. Antimycin A Drinking Water Characterization. DP Barcode D310732. Dated June 21, 2006. Available on line at: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2006-1002-0011

5 USEPA. 2015. Watershed Assessment, Tracking and Environmental Results. Specific State Causes of Impairment that Make Up the National 

Pesticides Cause of Impairment Group.

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885 \
-Page 12 of 44-

2.2. Nature of Regulatory Action

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

process for pesticide active ingredients. In 1996, FIFRA was amended by the Food Quality 

Protection Act (FQPA), and the Agency was mandated to implement a new program for the 

periodic review of pesticides, i.e., Registration Review6. The Registration Review program is 

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

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

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

use practices will occur over time. Through the new Registration Review program, the Agency 

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

marketplace can be used safely.

2.3. Stressor Source and Distribution

2.3.1. Nature of the Chemical Stressor

Antimycin A (3-methylbutanoic acid 3[[3-(formylamino)-2-hydroxylbenzoyl]amino]-8-hexyl2,6-dimethyl-4,9-dioxo-1,5-dioxonan-7-yl ester) is a Restricted Use nitrosalicylanilide pesticide 

derived as a fermentation product from Streptomyces mold and is registered for use to kill fish, 

i.e., a piscicide. Antimycin A consists of four major components which in turn consist of a pair 

of compounds, for a total of eight significant homologues—four “major” and four “minor”—that 

are distinguished by their chemical substituents (USDOI, 2012). Antimycin A uncouples 

oxidative phosphorylation by blocking the electron transport pathway to Complex III within the 

mitochondria.7

Based on preliminary analyses using liquid chromatography/mass spectroscopy of an antimycin 

sample from the OPP Biological and Economic Assessment Division repository, antimycin is 

composed of eight components that group into two major categories: ones that have a butyl 

chain and the others that have a hexyl chain. Within each of these groups, four different 

structures exist based upon differences in the acyloxy side chain (butyl and propyl structural 

isomers) as depicted in Figure 1. 

 

6

http://www.epa.gov/oppsrrd1/registration_review/

7

Bittermann, A.D., J.M. Lazorchak and J.C. Dorofi. 1996. Profile of toxic response to sediments using whole-animal and in vitro 

submitochondrial particle (SMP) assays. Journal of Environmental Toxicology and Chemistry 15(3): 319 – 324.
-Page 13 of 44-

The chemical profile of antimycin A is provided in Table 1. As described in Section 3.2.1.4, this 

screening-level ecological risk assessment focuses on antimycin A parent only.

Table 1. Chemical Profile of Antimycin A.

Common name Antimycin A

Registered Product Name Fintrol® Concentrate (EPA Registration No. 39096-2)

Chemical name 3-methylbutanoic acid 3[[3-(formylamino)-2-hydroxylbenzoyl]amino]-8-

hexyl-2,6-dimethyl-4,9-dioxo-1,5-dioxonan-7-yl ester

Structure (A3 form of the 

molecule, the most toxic of 

the 8 homologues)

HN

H

O

OH

N

H

O

O

O

O

H3C O

O

H3C

O

1a HN

H

O

OH

N

H

O

O

O

O

H3C O

O

H3C

O

1b

HN

H

O

OH

N

H

O

O

O

O

H3C O

O

H3C

O

2a

HN

H

O

OH

N

H

O

O

O

O

H3C O

O

H3C

O

2b

HN

H

O

OH

N

H

O

O

O

O

H3C O

O

H3C

O

3a

HN

H

O

OH

N

H

O

O

O

O

H3C O

O

H3C

O

HN

H

O

OH

N

H

O

O

O

O

H3C O

O

H3C

O

HN

H

O

OH

N

H

O

O

O

O

H3C O

O

H3C

O

3b

4a 4b

Figure 1. Chemical constituents of antimycin A.
-Page 14 of 44-

SMILES Notation O1C(=O)C(NC(=O)Cc2c(O)c(NC(=O))ccc2)C(C)OC(=O)C(CCCCCC)

C(OC(=O)CC(C)C)C1

Pesticide type Restricted Use piscicide

Chemical class Nitrosalicylanilide

CAS number 1397-94-0

Empirical formula C28H40N2O9 

Molecular mass 548.6 g mol-1

2.3.2. Overview of Pesticide Usage

Antimycin is a relatively minor-use piscicide used primarily for direct applications to mountain 

streams, lakes, ponds and fishery operations. As part of a fish management program, antimycin 

A is used primarily by Federal and state agencies to eliminate invasive or non-native species in 

an area where threatened or indigenous species are intended later to be reestabilished (USDOI 

2012)8. Based on the single registered end-use product (Fintrol® Concentrate), antimycin A is 

applied directly to water (streams, lakes, and ponds) to achieve a maximum single treatment 

concentration of 25 μg active ingredient (a.i.) per liter of water (25 μg a.i./L; maintained for a

maximum 8-hr treatment. period). Actual treatment levels are species and goal specific. For use 

in aquaculture, the label recommends between 7 and 10 μg a.i./L and specifies that for “selective 

kill” use in aquaculture, not to apply the product in a way that will result in a treatment 

concentration greater than 10.0 μg a.i./L. For “complete kill” use, the label specifies not to apply 

the product in a way that will result in treatment concentrations greater than 25.0 μg a.i./L. The

maximum annual number of treatments in an area is 3 (with a minimum retreatment interval of 1 

day), and the maximum annual cummulative treatment concentration is 50.0 μg a.i./L (USDOI, 

20129).

Based on the SOP for the use of Fintrol®for fish habitat restoration (USDOI, 201210), it may be 

used in streams, ponds, and small lakes or impoundments (<50 ha) to remove certain fish species 

for subsequent reestablishment of native aquatic communities by fishery/natural resource 

 

8 USDOI. 2012. National Park Service Standard Operating Practices for the Use of Fintrol (Antimycin A) for Restoration of Native Fish 

Populations. U.S. Department of Interior, National Park Service Natural Resource Repoft NPS/NRSS/WRD/NRR—2012/594.

9

Ibid USDOI. 2012.

10 Ibid USDOI. 2012.

O

O

NH O

HO

NH

O

H3C

O

O

H3C

O

O

H3C

CH3
-Page 15 of 44-

managers. The compound is applied to water by a drip-feed device which is part of a drip 

station, or by backpack sprayer, boat bailer, or other hand-held sprayer. None of these methods 

are expected to result in spray drift. According to the SOP, the compound is applied at levels 

intended to result in a lethal concentration for 100%, i.e., LC100, for the non-native fish targeted 

by the treatment. Deeper water bodies may require the use of a pump mechanism (to ensure 

adequate mixing throughout the water column) using a perforated hose or delivery through the 

boat’s propeller wash. Spray drift from anitmycin A applications is not considered likely even 

when applied by backpack sprayers since hand-held wands are used to dispense the spray 

relatively close to the surface of the water. Prior to application, the active ingredient is mixed 

with a diluent (which contains a surfactant) to increase solubility. Together, these materials (i.e., 

the active ingredient and the diluent) comprise the product Fintrol®.

Similar to other piscicides, antimycin A is a Restricted Use product (RUP) and the chemical has 

relatively detailed SOPs developed by the National Park Service associated with its use to 

renovate fish populations (USDOI, 201211). Since the SOPs are linked to the Federal label, they 

are considered part of the label and must be followed by the end user. Current SOPs require 

deactivation of the compound with potassium permanganate following its use in all streams. The 

Fintrol®label provides instructions for deactivating antimycin A with potassium permanganate 

(KMnO4) at a treatment concentration of 1 mg/L (part per million). Potassium permanganate 

(CAS No. 7722-64-7) is a strong oxidizing agent commonly used to purify drinking water and 

kill pond algae. According to the product label, antimycin may be considered deactivated when 

fingerling rainbow trout (Oncorhynchus mykiss) or juvenile bluegill sunfish (Lepomis 

macrochirus) survive for at least 48 hours in holding tanks (live-cars) placed 91 meters (100 

yards) downstream from the site of potassium permanganate application. Depending on 

environmental conditions (e.g. total organic carbon) higher KMnO4 treatment rates (e.g. 3 – 4 

mg/L) may be required to deactivate antimycin A12.

2.4. Receptors

2.4.1. Aquatic and Terrestrial Effects

A receptor is a biological entity that is exposed to a stressor (USEPA 1998

13)

. Consistent with the 

process described in the Overview of the Ecological Risk Assessment Process in the Office of 

Pesticide Programs (USEPA 200414), this risk assessment uses a surrogate species approach in its 

evaluation of antimycin A. 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 data 

from the available open literature are used to evaluate potential direct effects of antimycin A to 

 

11 Ibid USDOI. 2012.

12 Ibid USDOI. 2012.

13 USEPA. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Published in 63 FR 26846; May 14, 1998. U.S. 

Environmental Protection Agency, Washington, DC. April, 1998.

14 USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, U.S. Environmental Protection 

Agency. Endangered and Threatened Species Effects Determinations. Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide 

Programs, Washington, D.C. Available online at http://www.epa.gov/oppfead1/endanger/consultation/ecorisk-overview.pdf.
-Page 16 of 44-

aquatic and terrestrial receptors. The open literature studies are located through EPA’s database 

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

toxicity data for aquatic life, terrestrial plants, and wildlife. 

2.4.2. Ecosystems Potentially at Risk

Ecosystems at potential risk are often extensive in scope; therefore, it is not possible to identify 

such ecosystems in other than general terms in a screening-level assessment. In general terms, 

terrestrial ecosystems potentially at risk are areas immediately adjacent to treated surface water, 

e.g., riparian habitats.

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

treated areas and may include natural or impounded lentic systems, i.e., ponds, lakes, and 

reservoirs, and lotic (flowing) waterways, i.e., streams and rivers. Within water bodies, the water 

column, sediment, and pore water are all compartments of potential concern. 

2.5. Assessment Endpoints

Assessment endpoints represent the actual environmental values that are to be protected, defined 

by ecological entitities (species, community, etc.) and their attributes or characteristics (USEPA

1998). For antimycin A, the ecological entities assessed include the following: birds, amphibians, 

reptiles, mammals, freshwater fish, terrestrial and aquatic invertebrates, and terrestrial and 

aquatic plants. The assessed attributes for any of these entities may include growth, survival, 

and/or reproduction. (See Table 2 in Section 2.7.3, the Analysis Plan, for further discussion).

The assessment endpoints are intended to reflect population sustainability and community 

structure within ecosystems, and hence relate to ecosystem risk. If risks are identified for given 

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

translate to higher levels of biological organization.

2.6. Risk Hypotheses

For antimycin A, the following risk hypothesis is employed for the ecological risk assessment:

The use of antimycin A in accordance with the label results in adverse effects on survival 

and/or fecundity to non-target aquatic plants and animals. To the extent that terrestrial 

animals may feed on dead or dying fish in the treatment area and/or ingest antimycintreated water, terrestrial animals may experience adverse effects as well.

 
-Page 17 of 44-

2.6.2. Potential Exposure Pathways and Effects

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 include a source, a release mechanism, an environmental transport medium, a point of 

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

pathways and effects of the registered uses of antimycin A are mediated by the fact that the 

compound is deactivated following use. Consequently, most of the normally assessed routes of 

exposure are not considered likely for antimycin A. The sole application type is direct 

application to water as a piscicide via methods not expected to result in spray drift. Organisms

that may be exposed to antimycin A for short periods following application (prior to 

deactivation) include aquatic receptors (e.g., freshwater and estuarine/marine fish and 

invertebrates, aquatic-phase amphibians, and plants). Exposures to terrestrial and semi-aquatic 

wildlife (i.e., mammals, birds, terrestrial-phase amphibians, terrestrial invertebrates, and reptiles) 

and plants could occur, but are expected to be limited both temporally and spatially. Ingestion of 

treated moribund fish by avian and mammalian scavengers is potential route of evaluation which 

is evaluated in the risk characterization section of this document.

When used as a piscicide, antimycin A is deposited directly into a receiving water, which may be 

a stream, pond, lake or reservoir. Once in the water column, non-target aquatic organisms may 

be exposed to antimycin A via three main exposure pathways and two minor pathways.

1. Antimycin A will initially be distributed in the water column of the receiving water, and

organisms in the water column (aquatic invertebrates, fish, amphibians and plants) may

be directly exposed through contact. Antimycin A is applied in conjunction with a diluent 

that increases its solubility. Organisms can take up soluble antimycin A through the gills 

or integument. If sufficient concentrations exist, then individual toxic effects in aquatic 

invertebrates, fish, aquatic-phase amphibians and/or plants can result. This may result in 

reductions in population sizes of species within these taxa. This is expected to be the 

main route of exposure for antimycin A.

2. Antimycin A released into water will likely sorb to sediment and suspended solids. 

Receptors such as aquatic invertebrates, fish, and aquatic-phase amphibians may be 

exposed to sorbed antimycin A through incidental ingestion of sediment and/or 

suspended solids. This can result in changes in populations based on reduced survival, 

growth and reproduction.

3. Antimycin A may also sorb to plant surfaces. Ingestion of plant materials with sorbed 

antimycin A can result in a similar exposure pathway as described for sediment and 

suspended solids. Nonvascular or vascular plants may also be exposed to antimycin A 

through direct contact or root uptake. This could result in changes in plant populations 

due to direct toxicity. However, since no plant toxicity data are available for antimycin A, 

risks to aquatic plants cannot be evaluated. 
-Page 18 of 44-

4. Antimycin A residues may accumulate in target and non-target organisms, although this 

is not considered likely given the low estimated bioconcentration factor. Other organisms 

that live in or around the treatment area may be exposed to antimycin A by consuming 

treated organisms.

5. Direct exposure of terrestrial animals/plants to antimycin is not likely since the chemical 

is only applied to water bodies. Indirect exposure to both mammals and birds is possible 

through the consumption of dead and dying fish and larger invertebrates and through 

ingestion of antimycin-treated water. Exposure via residues on foliage adjacent to the 

water body is not expected because the application methods will not result in spray drift.

Environmental fate data suggest (but have not clearly demonstrated) that antimycin A has a low 

potential to volatilize. Additionally, the compound is applied directly to water. Therefore, the 

likelihood of inhalation exposure in wildlife is considered low.

2.7. Analysis Plan 

2.7.1. Measures of Exposure

2.7.1.1 Measures of Aquatic Exposure

For antimycin A, the registered uses of the compound as a piscicide require the direct application 

of the compound to water to maintain specific water treatment concentrations for defined 

durations of time. Therefore, aquatic exposure values are specific to meet the management 

objective of the treatment, i.e., to result in 100% mortality of the target species. As such, 

exposure modeling per se is not needed for antimycin A within the treatment site, as actual label 

maximum treatment levels will be used. Because the compound is deactivated with a strong 

oxidizing agent (e.g., potassium permanganate) and deactivation is verified using fish bioassays 

downstream of the deactivation stations following use in streams, only acute EECs for the target 

site will be used in risk estimation. 

2.7.1.2. Measures of Terrestrial Exposure

Antimycin A is applied directly to water via methods that will not result in spray drift, and 

exposure to terrestrial environments is expected to be low; therefore, exposure estimates will not 

be calculated for determining residues on terrestrial animal forage items. 

Since antimycin A is applied directly to water, exposure of terrestrial plants to the compound is 

expect to be low; therefore, exposure estimates for terrestrial plants will not be calculated.

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

upper-bound estimate of exposure using the maximum treatment concentration for antimycin 

(i.e., 25 μg/L), that was in turn compared to the most sensitive acute avian and mammalian 

toxicity endpoints (see Table 6). Although antimcyin A is classified as very highly toxic to birds 

(LD50=2.9 mg/kg body weight) and the compound is moderately toxic to mammals (LD50=286 

mg/kg body weight) on an acute oral exposure basis, model output indicates that drinking water 
-Page 19 of 44-

alone is not a potential concern for either birds or mammals. For a sample of the output 

generated by SIP v.1.0, please see Appendix B. Since no data are available to assess the 

potential chronic risks of antimycin A to birds and mammasls, SIP indicates that the risk is 

uncertain. However, as discussed in this assessment, the likelihood of chronic exposure to 

antimycin is considered low. 

Although EPA typically evaluates potential exposure to non-target organisms via exposure using 

the Screening Tool for Inhalation Risk (STIR), for fishery management purposes, antimycin A is 

applied directly to water using metering metering devices (drip stations). Although shorelines 

may be spot treated using a back-pack sprayer, there is a low likelihood that either mammals or 

birds would be in close proximity to the applicators during such applications as applicators walk 

along the shorelines with the hand-held wands typically maintained within a short distance (< 2 

feet) of the water to ensure the delivery of the material to the targeted area. Therefore, the 

Agency did not evaluate potential exposure to non-target organisms using the STIR model.

While the potential for bioaccumulation of antimycin A is considered low based on measured 

residues in bioconcentration studies, given that treatment concentrations used in fish restorataion 

efforts are intended to result in 100% mortality, the KABAM model [Kow (based) Aquatic 

BioAccumulation Model, Version 1.0] is typically used as a screen to estimate potential 

bioaccumulation of hydrophobic organic pesticides in freshwater aquatic food webs and 

subsequent risks to mammals and birds via consumption of aquatic prey contaminated with 

antimycin. The bioaccumulation portion of KABAM relies on a pesticide’s octanol-water 

partition coefficient (Kow) to estimate uptake and elimination constants through respiration and 

diet of aquatic organisms in different trophic levels. Pesticide tissue concentrations in aquatic 

organisms are calculated for different trophic levels of a food web through diet and respiration 

and are used to estimate dose- and dietary-based exposures and associated risk quotients for 

mammals and birds consuming aquatic organisms. While the log Kow for antimycin is estimated 

to be 4.21, other model input values, e.g., organic carbon partition coefficient (Koc), are not 

available for antimycin A; therefore, the model was not run. However, the risk description 

section of the document discusses potential risks to birds and mammals which may forage of fish 

killed by antimycin A treatments. This analysis indicates that the risk to birds and mammals that 

consume aquatic prey contaminated by antimycin is low.

2.7.2. Measures of Effect

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

conducted with a limited number of surrogate test species. The test species are not intended to be 

representative of the most sensitive species but rather were selected based on their ability to 

thrive under laboratory conditions. Toxicity testing reported in this risk assessment utilizes 

surrogate species to represent all freshwater fish (2000+) and bird (680+) species in the U.S. The 

ECOTOXicology database (ECOTOX), was searched in June 2015 to determine whether 

additional, more sensitive ecological effects data were available for antimycin A; however, no 

such data were identified.

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). 
-Page 20 of 44-

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 Effect Concentration) and the NOAEL (No Observed Adverse Effect Level). Toxicity 

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

invertebrates, birds and mammals. 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 were considered to be scientifically valid). 

2.7.3. Integration of Exposure and Effects

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

ecological effects on nontarget species. For the risk assessment of antimycin A, the risk quotient 

(RQ) method is used to compare estimated exposure with measured toxicity endpoints. The RQ 

method involves dividing EECs by the most sensitive acute and chronic toxicity endpoints

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

(USEPA 2004) (Table 2). Any LOC exceedences are used to indicate uses of antimycin A that

have the potential to cause adverse effects to non-target organisms.

Table 2. 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)

1

21-day EEC/NOAEC 

(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

EEC/ EC05

1 LC50 or EC50.

2 EEC based on upper bound Kenaga nomogram values for foliar exposure.
-Page 21 of 44-

2.8. Preliminary Identification of Data Gaps

The database on the environmental fate and transport properties of antimycin is incomplete. 

Since the compound is used exclusively as a piscicide, the terrestrial fate properties are relatively 

undocumented. 

The database on the ecological effects of antimycin is incomplete. There are no chronic toxicity 

data for either terrestrial or aquatic animals; however, the likelihood of chronic exposure to 

antimycin following application to flowing water is likely low due to a combination of 

degradation, advective removal (assuming that exposed animals stay relatively fixed in space and 

do not move with the concentration pulse), deactivation, and dilution. While the chemical is 

expected to partition to sediments and will likely do so in lentic environments (e.g., ponds and 

lakes), the intent of the treatments is to achieve 100% mortality of the target species. Given that 

invertebrates exhibit roughly similar sensitivity as fish to antimycin, the effects to benthic 

invertebrates is expected to be similar. Additionally, there are no data for terrestrial or aquatic 

plants; however, the use of this product in National Parks to restore native fish has not resulted in 

any incident reports for adverse effects to either terrestrial or aquatic plants. The likelihood of 

exposure to terrestrial plants is considered low; however, aquatic plants will be exposed and the 

potential risk to these plants is uncertain.

No toxicity data are available to assess the effects of antimycin A on terrestrial invertebrates 

such as honey bees (Apis mellifera); however, given that the compound is used to treat water 

directly and that these treatments typically occur in high altitude lakes and high gradient streams

(USDOI 2012), the likelihood of exposure for terrestrial invertebrates is considered low.

3. Analysis

3.1. Use Characterization

Antimycin A is a piscicide used for selective (e.g., scaled fish removal from aquaculture 

facilities) or complete fish kills (e.g., fish restoration efforts). Based on the single registered enduse product (Fintrol® Concentrate), antimycin A is applied directly to water (e.g., streams, lakes, 

ponds), using methods described previously, to achieve a maximum single treatment 

concentration of 25 μg active ingredient (a.i.) per liter of water (25 μg a.i./L) and maintained at 

this concentration for a maximum 8-hr treatment period). The maximum annual number of 

treatments in an area is 3 (with a minimum retreatment interval of 1 day), and the maximum 

annual treatment concentration is 50 μg a.i./L (USDOI, 2012). For fish restoration efforts, target 

treatment concentrations vary with the type of fish targeted and treatment goals, as described in 

the SOP (USDOI, 2012). 

Based on the standard operating procedures (SOP) for the use of Fintrol®, it may be used in 

streams, ponds, and small lakes or impoundments (<50 ha) to remove non-native fish species for 

subsequent reestablishment of native aquatic communities (USDOI 2012). The compound must

be deactivated using potassium permanganate following its use in all streams to prevent its 

movement out of the targeted treatment area. 
-Page 22 of 44-

3.2. Exposure Characterization

3.2.1. Environmental Fate and Transport Characterization

Antimycin A (3-methylbutanoic acid 3[[3-(formylamino)-2-hydroxylbenzoyl]amino]-8-hexyl2,6-dimethyl-4,9-dioxo-1,5-dioxonan-7-yl ester) consists of four major components which in 

turn consist of a pair of compounds, for a total of eight significant homologues (i.e., structural 

isomers)—four “major” and four “minor”—that are distinguished by their chemical substituents.

The environmental fate data set submitted for antimycin A is limited, consisting of only an 

hydrolysis and an aerobic aquatic metabolism study. Preliminary estimates of the physical and 

chemical properties that determine the fate and transport of antimycin A are detailed in Table 3. 

These values were estimated using a quantitative structure activity-based calculator, open 

literature, and registrant-submitted studies. There is a high degree of uncertainty surrounding the 

quantitative estimation of the environmental properties of antimycin, as well as the submitted 

data. However, antimycin A can partition to sediment and appeaers to degrade primarily by 

hydrolysis. It appears not to volatilize, does not readily dissolve in water, nor does it

bioaccumulate. Additionally, the environmental fate of antimycin A will be significantly affected 

by the deactivation process required in the SOP linked to the Fintrol® Concentrate label.

Other than the parent compound, no additional residues of concern have been identified. 

Table 3. Chemical Properties and Environmental Fate Parameters of Antimycin A.

Chemical/Fate Parameter Value Description/Comments Source (MRID)

Selected Physical/Chemical Parameters

Chemical name

3-methylbutanoic acid 3[[3-

(formylamino)-2-

hydroxylbenzoyl]amino]-8-

hexyl-2,6-dimethyl-4,9-dioxo1,5-dioxonan-7-yl ester

˗ ˗

Molecular mass 548.6 g mol-1˗ ˗

Vapor pressure (25C) 3.08 x 10-22 Torr Estimated value. Not 

volatile. EPISuiteTM v4.11 

Water solubility (25C) 0.089 mg/L Limited solubility in water. EPISuiteTM v4.11

Octanol-water partition 

coefficient (Log KOW)

4.21 Estimated value. EPISuiteTM v4.11

Henry’s Law Constant 

(25°C) 1.82 x 10

-21

 atm-m

3

/mole Estimated value. Not volatile 

from water or moist soil. EPISuiteTM v4.11

Persistence
-Page 23 of 44-

Chemical/Fate Parameter Value Description/Comments Source (MRID)

Hydrolysis half-life (d)

pH 5, 25C

pH 7, 25C

pH 9, 25C

Submitted Data

pH 5: 15 days

pH 7: 3 days

pH 9: 3 hrs

Scientific Literature

Minutes (higher pHs) to hours

(below pH 9).

Uncertain. Non-guideline,

literature data indicate faster 

base-catalyzed hydrolysis at 

>pH 8. Likely the main 

degradation route at >pH 8.

46023101;

USEPA 2006a

Aqueous photolysis half-life 

(25C) No data. Data were waived in 2001 

(DP Barcode D276036). ˗

Soil photolysis half-life 

(25C) No data. These data are not required 

for an aquatic use.

˗

Aerobic soil metabolism 

half-life (25°C) No data. ˗ ˗

Anaerobic soil metabolism 

half-life (25°C) No data. These data are not required for an aquatic use. ˗

Aerobic aquatic metabolism 

half-life (25°C)

23-47 days (water pH 6.5)

Highly uncertain value since 

it is longer than hydrolytic 

half-life at that pH. 

Adsorption to sediment may 

have limited hydrolysis.

45895901

Anaerobic aquatic 

metabolism half-life (25°C)

No data. Data were waived in 2001 

(DP Barcode D276036). ˗

Mobility

Freundlich soil-water 

partition coefficients (KF); No data. ˗ ˗

Organic carbon-normalized 

soil partition coefficients 

(KFOC)

Adsorption

1030 - 1.658E+004 L/kg

Desorption

No data.

Estimated values. No data 

available. Indicates 

compound will be slightly 

mobile to hardly mobile in 

sediment. Pesticide is 

applied with diluent that 

may alter mobility by 

increasing solubility.

EPISuiteTM v4.11

Field Dissipation

Aquatic field dissipation 

half-life No data Data were waived (1993). ˗

Fish Bioconcentration

Fish bioconcentration factors 

(steady-state); depuration 

rate

277-350X No data available. 

Estimated values.

EPISuiteTM v4.11; 

PBT Profiler.
-Page 24 of 44-

3.2.1.1. Transport and Mobility

Although the registrant did not provide sorption studies for antimycin A, aerobic aquatic 

metabolism study data indicate that antimycin A partitioned to the sediment phase (MRID 

45895901). Rough estimates of sorption were made from the aerobic aquatic study by 

considering the relative distribution of antimycin in the water and the sediment as measured in 

that study. If equilibrium between the water and the sediment were assumed throughout the 

aerobic aquatic study, then Kd values would range from about 1 to 88 ml/g or Koc in the range of 

84 to 10,000 ml/g (USEPA 2006a). While this is a wide range with respect to mobility in 

sediment, it is unclear how it would relate to actual adsorption in the environment, given that the 

compound is applied in conjuction with a diluent to greatly increase its solubility in water.

Estimates of adsorption using a quantitative structural analysis approach yielded an estimated 

Koc range of 1030 - 1.66 x 104L/kg, indicating that the compound would be be slightly mobile to 

hardly mobile in sediment.

3.2.1.2. Degradation 

Antimycin A is degraded abiotically through hydrolysis, with much more rapid degration 

observed at higher pH levels in multiple studies (Hussain, 1969; Walker et al., 1964; Lee et al. 

1971). Submitted data indicate that antimycin hydrolyzes with a half-life of 15 days at a pH of 5, 

3 days at pH 7, and 3 hours at pH 9 (MRID 46023101). However, a more recent study by 

Kenneke (2006), which suggests that hydrolysis is an important mechanism of degradation, does 

not clearly show a correlation between degradation rate and pH. That study estimated half lives 

of approximately 4-10 hours in unmixed systems, and half lives of 1-10 hours in mixed systems. 

Hydrolysis rates from the literature are summarized in Table 4. In all cases hydrolysis half lives 

are on the order of minutes to hours. A more complete discussion of available hydrolysis data for 

antimycin A was presented in the ecological risk assessment (USEPA 2006a) conducted in 

support of the 2007 RED. Antimycin A is also expected to degrade via photolysis (Ott), 

although guideline data have not been submitted.

Transformation products were not identified in the registrant-submitted study15, Lee et al.

16 or 

Kenneke17. In an anecdotal report, Walker et al.

18 claimed that antimycin degrades by base 

hydrolysis and produced a diagram showing the mechanism of degradation along with assumed 

breakdown products. Hussain19 made similar claims as to the degradation products. These 

products are blastmycic acid, antimycin lactone, and antimycic acid. Further degradation via 

hydrolysis yields antimycic acid, formic acid, aminosalicylic acid, and an amino acid (Hubert & 

 

15 Heim D. 2003. Hydrolysis Determination for Antimycin A Complex. Project Number 47132. Unpublished study prepared by Analytical BioChemistry Labs, Inc. 63 p. (MRID 460231-01).

16 Lee T.H., Derse, P.H., and Morton, S. 1971. Effects of Physical and Chemical Conditions on the Detoxification of Antimycin. Transactions of 

the American Fisheries Society 1971; 100: 13–17

17Kenneke, J. 2006 Memo from John Kenneke to Thomas Steeger and “Summary of Antimycin Hydrolysis Research by John F. Kenneke” 

Appendix G of USEPA 2006.

18 Walker C.R., R.E. Lennon, and B.L. Berger. 1964. Preliminary observations on the toxicity of antimycin A to fish and other aquatic animals. 

U.S. Bureau of Sport Fisheries and Wildlife, Investigations in Fish Control No. 2 (Circular No. 186). 18 pp.

19 Hussain, A. 1969. 1969. Kinetics and mechanisms of hydrolysis of antimycin A in solution. Journal of Pharmaceutical Sciences 58: 316-320.
-Page 25 of 44-

Schmidt, 2001). No quantitative information regarding the relative concentrations of the 

transformation products is available. 

The only other registrant submitted environmental fate study is an aerobic aquatic transformation 

study which indicated that antimycin A degrades with a half-life of 23-47 days in pH 6.5 water

(MRID 45895901). This half-life is substantially longer than the expected half-life due to 

hydrolysis alone at this pH, which adds some uncertainty to the half-lives reported in this study 

as well as the hydrolysis studies. However, since the aerobic aquatic study was conducted with 

sediment present, it is possible that the longer half-life could be due to sorption of antimycin A to 

sediment in the still system, which may shield the compound from hydrolytic degradation.

Table 4. Hydrolysis Rates for Antimycin A from Submitted Data and Published Literature.

Property Value Source

Hydrolysis pH 3 9 hours Kenneke (2006)

Hydrolysis pH 4 8.3 hours Kenneke (2006)

Hydrolysis pH 5 10.5 hours Kenneke (2006)

Hydrolysis pH 6 11 hours Kenneke (2006)

Hydrolysis pH 7 7.1 hours Kenneke (2006)

Hydrolysis pH 8 10 hours Kenneke (2006)

Hydrolysis pH 9 3.4 hours Kenneke (2006)

Hydrolysis pH 5 15 days MRID 46023101

Hydrolysis pH 7 3 days MRID 46023101

Hydrolysis pH 9 3 hours MRID 46023101

Hydrolysis pH 4.5 – 5.5 >7 hours Lee et al. (1971)

Hydrolysis pH 7 – 8 5.5 hours Lee et al. (1971)

Hydrolysis pH 8.5 40 minutes Lee et al. (1971)

Hydrolysis pH 9.5 20 minutes Lee et al. (1971)

Hydrolysis pH 10 6 minutes Lee et al. (1971)

Hydrolysis pH 7.55(A1 only) 46 hours Hussain (1969)

Hydrolysis pH 9 (A1 only) 2.2 hours Hussain (1969)

Hydrolysis pH 10.1 (A1 only) 1 minute Hussain (1969)

3.2.1.3. Field Studies

Aquatic field dissipation data have not been submitted for antimycin A. 

3.2.1.4. Bioaccumulation

Bioconcentration in fish data have not been submitted. Based on BCF estimates using EPI Suite, 

the chemical has a relatively low potential for bioconcentrating in aquatic organisms (estimated 

BCF = 270-350X). However, as antimycin A is used as a pisicide, such data would be of limited 

use.

3.2.1.5. Transformation Products

Submitted studies did not characterize transformation products, although published literature has 

tentatively identified hydrolysis products. These products are blastmycic acid, antimycin lactone, 

and antimycic acid (Hussain, 1969; Walker et al., 1964; Lee et al. 1971). Blastmycic acid further 
-Page 26 of 44-

hydrolyses to antimycic acid and formic acid; the antimycic acid may further hydrolize to 

aminosalicylic acid, a relative of aspirin, and an amino acid (Hubert & Schmidt, 2001). No 

quantitative information regarding the relative concentrations of the transformation products is 

available. However, antimycin A must be deactivated following use with a high oxidizing 

compound (potassium permanganate). The byproducts of permanganate treatment are highly 

insoluble manganese oxides (Ott ). The exact nature and extent of these deactivation products is 

uncertain; however, fish bioassays downstream of permanganate deactivation stations indicate 

that remaining antimycin A residues are not at levels sufficient to result in adverse effects to the 

fish used in the assays. 

3.2.2. Measures of Aquatic Exposure

3.2.2.1. Estimated Environmental Concentrations in Surface 

Water

Standard exposure modeling was not conducted for antimycin A. The registered uses of 

antimycin A as a piscicide require the direct application of the compound to water to maintain 

specific water concentrations for defined durations of time. Therefore, aquatic exposure values 

are specific to meet the management objective of the treatment. 

When antimycin is applied to a water body, the most conservative acute concentration that could 

be used for ecological aquatic exposure assessment is the treatment concentration. Thus, 

screening-level acute EECs of antimycin A (parent only) in surface water are the maximum 

labeled use or target rate of 25 μg/L (parts per billion; ppb) as stated on the label and in the 

document (incorporated by reference) “Standard Operating Procedures for the Use of Fintrol®

(Antimycin A) for Restoration of Native Fish Populations” (USDOI, 2012). 

3.2.2.2. Monitoring Data

No monitoring data are available for antimycin A. EFED conducted a search (April 2015) of the 

United States Geological Services (USGS) National Water Quality Assessment (NAWQA) 

Program database (http://cida.usgs.gov/nawqa_queries_public/) and the California Department 

of Pesticide Regulation (CDPR) surface water and sediment database 

(http://cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm). 

For use in fishery restoration efforts, monitoring for antimycin A within the treatment area is 

typically conducted via bioassay, i.e., caged live fish, typically using the species targeted by the 

treatment.

3.2.3. Measures of Terrestrial Exposure

Exposure of terrestrial plants and wildlife to antimycin A is not estimated in this assessment 

because the chemical is applied directly to aquatic systems and is not expected to move to 

terrestrial environments. Although not considered a major exposure pathway, potential 

exposure of terrestrial animals to antimycin by ingestiong of prey (fish) containing residues of 

the compound is considered in the risk description section of the document
-Page 27 of 44-

3.3. Ecological Effects Characterization

The ecological effects characterization for antimycin A is primarily based upon federal 

laboratory data for the TGAI and for specified formulations. The large majority of available 

toxicity data for antimycin A are for aquatic animals (i.e., fish and aquatic invertebrates). 

Additional data were submitted by the registrant and represented a compendium of unpublished 

studies20; however, information on the toxicity of antimycin A contained in many of these 

additional submissions was not of sufficient quality to use quantitatively in this ecological risk 

assessment.

Acute toxicity data are available for 16 species of fish (Table 5), including 15 freshwater species 

and one estuarine/marine species. All of the studies are classified as supplemental since they 

were not conducted according to current standards; however, these data are considered of 

sufficient quality for use in risk assessment. Studies were conducted with either technical grade 

(>95% antimycin A) or with formulations containing either 1% or 10% active ingredient (a.i.). 

The freshwater paddlefish (Polyodon spathula) is the most sensitive (LC50=0.001 μg/L) species 

tested. Although the paddlefish is the most sensitive species, the raw data used to support this

endpoint could not be evaluated; therefore, this value cannot be used to quantitatively assess risk.

The most sensitive species for which raw data could be reviewed is coho salmon (Oncorhynchus 

kisutch); therefore, the freshwater fish acute toxicity endpoint (96-hr LC50) is 0.009 μg/L. Based 

on the sensitivity of freshwater fish to antimycin, the chemical is classified as very highly toxic 

to fish on an acute exposure basis.

Based on the available data, fish in the family Ictaluridae (catfish), like black bullhead (Ictalurus 

melas) and channel catfish (Ictalurus punctatus), are the least sensitive species tested, which 

accounts for how antimycin A can be used to selectively remove scaled fish from catfish

aquaculture ponds. Although paddlefish (sometimes referred to as a spoonbill catfish) do not 

have a pronounced number of scales and yet are the most sensitive species to antimycin, this 

phylogenically primitive fish species is not related to the catfish but is instead distantly related to 

sturgeon and similar to the sturgeon has a limited amount of scales.

Toxicity testing of formulated product (1 to 10% active ingredient) indicates that formulated 

products of antimycin A are less toxic than the technical grade active ingredient; the 96-hr LC50, 

for bluegill sunfish (Lepomis macrochirus) is 1.18 μg/L for the formulated product (Table 5);

whereas the technical grade active ingredient has a 96-hr LC50 of 0.034 μg/L. Similarly, rainbow 

trout (Oncorhynchus mykiss) has LC50 values ranging from 0.063 to 0.185 μg/L for formulated 

product while technical grade antimycin has an LC50 averaging 0.011 μg/L.

No chronic toxicity data are available on antimycin A for freshwater fish. A search of the open 

literature did not identify any additional data on the chronic toxicity of antimycin A to fish.

Although an acute toxicity test measuring effects of technical grade antimycin A to waterfleas 

(D. magna) was submitted (MRID 400980-01), the study failed to establish a definitive EC50

 

20 Ayerst Laboratories. 1964. Efficacy of Antimycin. (Compilation: unpublished study received in 1994 under 8991-5l CDL: 005666-A 

(Accession No. l 00135924))
-Page 28 of 44-

value (Table 5) since greater than 50% mortality was observed in all of the treatment groups. 

However, a 96-hr EC50 value is available for the scud, Gammarus fasciatus (EC50=0.008 μg/L). 

Based on the sensitivity of Gammarus to antimycin A, the compound is classified as very highly 

toxic to freshwater invertebrates on an acute exposure basis. 

A search of the open literature did not identify other studies that would provide additional 

information concerning the acute toxicity of freshwater invertebrates exposed to antimycin A.

No chronic toxicity data on antimycin A are available for freshwater invertebrates. A search of 

the open literature did not identify other studies that would provide additional information 

concerning the chronic toxicity of antimycin A to freshwater invertebrates.

A single estuarine/marine fish acute toxicity study of technical grade antimycin A with the spot 

(Leiostomus xanthurus) resulted in a 48-hr LC50 of 0.23 μg/L; therefore, antimycin A is 

classified as very highly toxic to estuarine/marine fish on an acute exposure basis. 

No chronic estuarine/marine fish toxicity data were submitted and no useable data were located 

in the open literature for antimycin A; therefore, chronic risks associated with estuarine/marine 

fish exposure to antimycin A are unknown.

Antimycin A is very highly toxic to estuarine/marine invertebrates on an acute exposure basis 

with a 96-hr LC50=24 μg/L for pink shrimp (Panaeus duorarum; Table 5). Acute toxicity data 

were also available on the Eastern oyster, Crassostrea virginica, showing that antimycin is very 

highly toxic (LC50=62 μg/L) to mollusks as well.

No chronic estuarine/marine invertebrate toxicity data were submitted and no useable data were 

located in the open literature for antimycin A; therefore, chronic toxicity associated with 

estuarine/marine invertebrate exposure to antimycin A is uncertain.

No data are available to assess the toxicity of antimycin A to vascular or nonvascular aquatic 

plants or to sediment-dwelling (benthic) invertebrates.

Table 5. Aquatic Animal Acute and Chronic Toxicity Estimates for Antimycin A.

Taxonomic 

Group

Surrogate 

Species

Type of 

Risk

Type of 

Endpoint

(% ai)

Endpoint MRID Acute Toxicity 

Classification

Aquatic

Freshwater 

Fish

Bluegill Sunfish

Lepomis 

macrochirus

Acute

96-hr LC50

(95.5%) 0.034 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

96-hr LC50

(10%) 1.18 μg a.i./L TN901006314

Very Highly Toxic

(Supplemental)

48-hr LC50

(1%) 29.5 μg a.i./L TN1533 Highly Toxic(Supplemental)

48-hr LC50

(1%) 29.5 μg a.i./L TN153 Very Highly Toxic(Supplemental)

Green Sunfish

Lepomis 

cyanellus

Acute 96-hr LC50

(95.5%) 0.22 μg a.i./L 40098001 Highly Toxic(Supplemental)
-Page 29 of 44

-

Taxonomic 

Group

Surrogate 

Species

Type of 

Risk

Type of 

Endpoint

(% ai)

Endpoint MRID Acute Toxicity 

Classification

Rainbow Trout (Oncorhynchus 

mykiss)

Acute 96

-hr LC50

(95.5%) 0.012 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Acute 96

-hr LC50

(95.5%) 0.010 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Acute 96

-hr LC50

(10%) 0.185 μg a.i./L TN944006314

Very Highly Toxic

(Supplemental)

Acute 48

-hr LC50

(1%) 0.063 μg a.i./L TN35 Very Highly Toxic(Supplemental)

Cutthroat Trout

Oncorhynchus 

clarki

Acute 96

-hr LC50

(95.5%) 0.057 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Coho Salmon

Oncorhynchus 

kisutch

Acute 96

-hr LC50

(95.5%) 0.009 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Lake Trout

Salvelinus 

namaycush\h

Acute 96

-hr LC50

(95.5%) 0.053 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Goldfish

(Carassius 

auratus)

Acute 96

-hr LC50

(95.5%) 0.180 μg a.i./L 40098001 Highly Toxic(Supplemental)

Fathead 

Minnow

(Pimephales 

promelas)

Acute 96

-hr LC50

(95.5%) 0.025 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Black Bullhead

Ictalurus melas Acute 96

-hr LC50

(95.5%) 4.8 μg a.i./L 40098001 Highly Toxic(Supplemental)

Channel Catfish

Ictalurus 

punctatus

Acute 96

-hr LC50

(95.5%) 1.36 μg a.i./L 40098001 Highly Toxic(Supplemental)

Mosquitofish

Gambusia 

affinis

Acute 96

-hr LC50

(95.5%) 0.19 μg a.i./L 40098001 Highly Toxic(Supplemental)

Largemouth 

Bass

Micropterus 

salmoides

Acute 96

-hr LC50

(95.5%) 0.24 μg a.i./L 40098001 Highly Toxic(Supplemental)

Yellow Perch

Perca 

Flavescens

Acute 96

-hr LC50

(95.5%) 0.04 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

White Crappie

Pomoxis 

annularis

Acute 96

-hr LC50

(95.5%) 0.34 μg a.i./L 40098001 Highly Toxic(Supplemental)

Paddlefish

Polyodon 

spathula

Acute 96

-hr LC50

(95.5%) 0.001 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Estuarine/

Marine Fish

Spot

Leistomus 

xanthurus

Acute 48

-hr LC50

(95.5%) 0.23 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Freshwater 

Invertebrates

Water Flea

Daphnia magna Acute 48

-hr EC50

(95.5%) <10 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Scud

Gammarus Acute 96

-hr EC50

(95.5%) 0.008 μg a.i./L 40098001 Very Highly Toxic(Supplemental)
-Page 30 of 44-

Taxonomic 

Group

Surrogate 

Species

Type of 

Risk

Type of 

Endpoint

(% ai)

Endpoint MRID Acute Toxicity 

Classification

fasciatus

Isopod

Asellus 

brevicaudus

Acute EC50

(95.5%) >1.0 μg a.i./L 40098001 Very Highly Toxic(Supplemental)

Estuarine/

Marine 

Invertebrates

Pink Shrimp

Panaeus 

duorarum

Acute 96-hr EC50

(95.5%) 24 μg a.i./L 40228401 Very Highly Toxic(Supplemental)

Blue Crab

Callinectes 

sapidus

Acute 48-hr LC50

(95.5%) >100 μg a.i./L 40228401 Very Highly Toxic(Supplemental)

Eastern Oyster

Crassostrea 

virginica

Acute LC50

(95.5%) 62 μg a.i./L 40228401 Very Highly Toxic(Supplemental)

No avian toxicity data are available for technical grade antimycin. However, based on acute oral 

(14-day) toxicity studies using formulated product of unspecified strength (MRID 135924), 

antimycin is classified as very highly toxic to water fowl (mallard duck LD50=2.9 mg/kg bw) and 

highly toxic to upland game birds (bobwhite quail LD50=39 mg/kg bw; Table 6). No data are 

available to evaluate the subacute dietary toxicity of antimycin A to birds nor are data available 

to evaluate the chronic toxicity of antimycin A to birds.

No acute oral rat toxicity data are available on technical grade antimcyin A; however, the acute 

oral LD50 for Fintrol® Concentrate (20% solution) is 286 mg/kg for male and 361 mg/kg for 

female rats21 (MRID 455279-01). Based on these data, the formulated endproduct is classified as 

moderately toxic to mammals on an acute oral exposure basis. No chronic toxicity data are 

available for mammals.

No data are available to assess the toxicity of antimycin A to terrestrial invertebrates. EPA has 

identified a process for evaluating the risk of pesticides to bees (Apis mellifera) that relies on a 

suite of laboratory-based studies examining the acute and chronic toxicity of pesticides to 

individual adult and larval bees. Depending on the outcome of the laboratory-based studies and 

risk estimates, higher-tier studies of bee colonies may be required. This risk assessment process 

and the need for effects data on bees are dependent on whether exposure to bees from the use of 

the compound is considered likely. Given that antimycin is applied directly to water and is 

typically used in high altitude lakes and high gradient streams, the likelihood of exposure for 

bees is considered low.

Table 6. Terrestrial Animal Acute Toxicity Estimates for Antimycin A.

Taxonomic 

Group

Surrogate 

Species

Type of 

Risk

Type of 

Endpoint

(% a.i.)

Endpoint MRID Acute Toxicity 

Classification

Terrestrial

 

21 Kuhn, J.O. 2001. Fintrol® Concentrate (Antimycin) Final Report Acute Oral Toxicity in Rats. Stillmeadow, Inc. Report No. 6025-00. 

Submitted to Aquabiotics Corporation, Bainbridge Island, WA. (MRID 455279-01).
-Page 31 of 44-

Taxonomic 

Group

Surrogate 

Species

Type of 

Risk

Type of 

Endpoint

(% a.i.)

Endpoint MRID Acute Toxicity 

Classification

Birds

Mallard duck

Anas 

platyrhynchos

Acute

Oral

14-day LD50

(Not 

Reported)

2.9 mg/kg 135924 Very Highly Toxic

(Supplemental)

Bobwhite quail

Colinus 

virginianus

Acute

Oral

14-day LD50

(Not 

Reported)

39 mg/kg 135924 Highly Toxic

(Supplemental)

Mammals Rat Acute

Oral

LD50

(20%)1

286 mg/kg 

(male)

361 mg/kg 

(female)

45527901 Highly Toxic

(Supplemental)

3.3.3. Review of Incident Data 

The Ecological Incident Information System (EIIS) is an internal OPP database that houses 

ecological incidents that have been reported to the Agency. When available, EIIS includes date 

and location of an incident, type and magnitude of effects observed in various species, use(s) of 

pesticides known or suspected of contributing to the incident, and results of any chemical residue 

analysis or other analyses conducted during incident investigation. EIIS incidents are categorized 

according to the certainty that the incident resulted from pesticide exposure. A search of the EIIS 

for ecological incidents run on February 10, 2015, identified no incident reports for antimycin A. 

However, incidents may have occurred due to antimycin A exposures but may not have been 

reported due to various factors, including lack of reporting or a lack of observation of effects. 

Although the lack of incident reports does not necessarily indicate the absence of incidents, the 

restricted use of the compound coupled with its detailed SOPs is expected to limit the extent of 

unintended exposure. 

No plant or wildlife incidents have been reported through OPP’s aggregate incident report 

database and no avian incidents have been captured in the Avian Incident Monitoring System 

(AIMS; American Bird Conservancy 2013)

22 as of February 10, 2015. The AIMS database 

contains publicly available reports on pesticide-related avian incidents through 2005.

 

22 Available at: http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims/index.cfm
-Page 32 of 44-

4. Risk Characterization

4.1. Screening-Level Risk Quotient (RQ) Values

This screening-level assessment of the labeled uses of antimycin A 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 are compared to the Agency’s Levels of Concern (LOCs), as shown in Table 3. EPA uses 

LOCs to indicate when the use of a pesticide, as directed by the label, has the potential to cause 

adverse effects to nontarget organisms. In this approach, RQs that exceed non-listed species 

LOCs necessarily also exceed the corresponding listed species LOCs. A discussion of the RQ 

values for antimycin A 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.

 

4.1.1. RQ Values for Aquatic Organisms

At the maximum treatment concentration of 25 μg/L, the acute estimated environmental 

concentration (EEC) of antimycin is expected to be equivalent to the treatment rate. At this 

exposure concentration, RQ values (RQ=EEC/LC50) for freshwater fish and invertebrates are 

2,778 and 3,125, respectively. The acute risk to non-listed species levels of concern (RQ≥0.5) for 

fish and invertebrates are exceeded by factors of 5,556 and 6,250X for fish and invertebrates, 

respectively (Table 7). Even if RQ values were based on the least sensitive fish, i.e., black 

bullhead 96-hr LC50=4.8 μg/L, the RQ (5.6) would exceed the acute high risk LOC by a factor of 

11X. Additionally, at the lower treatment concentration (5 μg/L)23 recommended to remove 

scaled fish from aquaculture ponds, the RQ is 1.04 and exceeds the acute risk to non-listed 

species LOC.

Table 7. Acute risk quotients for freshwater fish and invertebrates based on a targeted antimycin A treatment 

rate of 25 μg/L.

Species

Estimated 

Exposure 

Concentration 

(μg/L)

Toxicity

LC50

(μg/L)

Acute RQ Value

Coho Salmon

(Oncorhynchus kisutch)

25 0.009 2,778a

Scud

(Gammarus fasciatus)

25 0.008 3,125a

a Exceeds acute risk (RQ≥0.5), restricted use (RQ≥0.1), and endangered species (RQ≥0.05) levels of concern.

No acceptable toxicity data are available with which to evaluate the chronic risk to aquatic 

animals associated with the use of antimycin; however, given that the treatment concentrations at 

intended to result in 100% morgality of the target fish species and exceed acute median lethal 

concentrations by several orders of magnitude of both fish and invertebrates, it is reasonable to 

believe that most fish and aquatic invertebrates will be killed at the maximum treatment 

 

23 Avery, J.L. 2006. Use of Fintrol

®

to remove scaled fish in catfish ponds. The Catfish Journal. April 2006
-Page 33 of 44-

concentrations and durations of antimycin A. In situations where antimycin is applied to flowing 

water, it is deactivated with a strong oxidizing agent, potassium permanganate. The combination 

of advective removal, dilution with untreated water and deactivation with potassium 

permanganate makes chronic exposure to antimycin at toxic levels unlikely. While the efficacy 

of deactivation is an uncertainty, fish bioassays positioned downstream of the KMnO4 release 

stations indicate that antimycin is no longer at levels that result in acute toxicity to the fish used 

in the bioassay. Additionally, the acute toxicity of antimycin makes it likely that few biological 

receptors will be present to exhibit effects of chronic exposure. However, if/when treated water 

is not deactivated using permanganate nor substantially diluted by untreated water (e.g., in lentic 

environments such as high alpine lakes), the potential for chronic risks is uncertain.

At the maximum application rate, the acute RQ values for estuarine/marine fish and invertebrates 

are 109 and 1.0, respectively (Table 8). Both fish and invertebrate RQ values exceed the acute 

risk to nonlisted species LOC by factors of 218X and 2X, respectively. Although the toxicity 

value for estuarine/marine mollusks (62 μg/L) is higher (less sensitive) than that of pink shrimp, 

the RQ value for mollusks (RQ=0.40) exceeds the acute risk to listed species LOC (RQ≥0.05).

Table 8. Acute risk quotients for estuarine/marine fish and invertebrates based on a targeted antimycin A 

treatment rate of 25 μg/L.

Species

Estimated 

Exposure 

Concentration 

(μg/L)

Toxicity

LC50

(μg/L)

Acute RQ Value

Spot

(Leiostomus xanthurus)

25 0.23 109a

Pink Shrimp

(Panaeus duorarum) 25 24 1.0a

a

 Exceeds acute risk to non-listed species LOC (RQ≥0.5) and acute risk to listed species LOC (RQ≥0.05).

4.1.2. RQ Values for Terrestrial Organisms

The use of antimycin A to achieve fishery management objectives, i.e, wherein the compound is 

applied directly to water, is not likely to represent a route of exposure to birds via consumption 

of antimycin A residues on terrestrial forage items since the compound is applied directly to 

water. Therefore, RQ values are not calculated for terrestrial organisms; however, the risk 

discussion section provides a brief analysis of potential secondary risks to birds and mammals 

from the consumption of prey items containing antimycin A.

4.2. Risk Description

Antimycin A (Fintrol®) is applied directly to water and is maintained at a targeted treatment 

concentration for periods of time specified in the SOP to achieve 100% mortality for the targeted 

species. Based on available data, the primary route of degradation appears to be base hydrolysis,

where under alkaline conditions, the compound can degrade with half-lives of roughly 30 

minutes. While there are no direct measurements of antimycin A sorption, indirect evidence 

suggests that antimycin A will sorb to sediments and may reduce potential exposure outside of 
-Page 34 of 44-

the immediate treatment area. The extent to which non-target organisms will be exposed is also 

mitigated by the fact that where the compound is applied to flowing water, antimycin A is 

intentionally detoxified through the use of a strong oxidizing agent, potassium permanganate. 

Where the compound is used to remove scaled fish from aquaculture facilities, such facilities 

hold water for many months because of the expense of replacing water and the potential to lose 

fish in the process. Therefore, the compound is likely to degrade during the protracted holding 

periods and, based on the fact that fingerling catfish are stocked in the ponds after antimycin 

treatment, there is no indication that antimycin A residues are at levels which adversely affect the 

catfish. 

4.2.1. Risks to Aquatic Organisms

4.2.1.1. Freshwater Fish, Amphibians, and Invertebrates

Antimycin A is applied directly to water and as a piscicide, it is intended to kill fish. Antimycin’s 

high toxicity to fish accounts for the low treatment concentrations (typically 25 μg/L or less) 

needed to kill fish. With fish LC50 values as low as 1 nanogram (n) per liter (part per trillion 

(pptr)) and treatment rates 25 hundred times higher than this LC50 value, the direct application of 

antimycin to flowing and static water to eliminate undesirable fish species is likely to kill many 

of the fish species present. Since fish serve as surrogates for aquatic phase amphibians, risk is 

presumed for aquatic-phase amphibians as well.

Antimycin’s use in aquaculture to remove scaled fish from catfish production ponds does not 

typically involve subsequent deactivation with potassium permanganate; rather, the antimycin is 

allowed to degrade naturally in the production pond water. Fingerling catfish would not be 

harvested as food fish for roughly 1 – 1.5 years post-treatment. Since the intent of these 

treatments is to remove scaled fish and since fingerlings are introduced after treatment, there 

have been no adverse effects reported on the fingerling catfish as a result of this treatment. 

The available laboratory data indicate that freshwater invertebrates have roughly similar 

sensitivities as fish to antimycin A on an acute exposure basis, and many of these species may 

die at treatment concentrations of 25 μg/L. Although there are anecdotal reports24 suggesting that 

plants and invertebrates are relatively unaffected by antimycin treatments, no laboratory data 

have been reviewed by EPA that can substantiate these claims. To the extent that application 

rates are less than 25 μg/L and less sensitive animals are in the treatment areas, aquatic 

invertebrate mortality could be substantially reduced. Although invertebrates are less 

conspicuous members of the aquatic community, they are a major component of aquatic 

ecosystems and food webs. Any significant effects on invertebrates would most likely influence 

other components of the ecosystem. Effects may not be limited to merely a change in total 

biomass as a result of widespread mortality but any changes associated with differential 

sensitivity could bring about significant changes in the community structure, which could alter 

system function.

 

24 Wisconsin Alumni Research Foundation. 1965. Antimycin as a Fish Toxicant: a resume of information and data pertaining to the use of 

antimycin in fish management procedures in ponds and lakes. (Accession No. 00135924)
-Page 35 of 44-

Estuarine/marine invertebrate data on Eastern oysters indicate that they are less sensitive to 

antimycin than other invertebrates, although risk quotients based on mollusk toxicity data exceed 

the acute risk to listed species levels of concern.

In addition to acute risks, there is a potential for chronic effects to freshwater invertebrates when 

antimycin is applied directly to water. The limited data on freshwater invertebrates suggest that 

they are as sensitive to antimycin as fish, and it is possible that many invertebrates will not 

survive antimycin treatment concentrations in the targeted area at the typical application rate; 

therefore, chronic effects will be limited by a lack of receptors. Additionally, at the maximum 

recommended treatment rate, a single application of antimycin directly to water is intended to 

kill all fish in the treated area; therefore, it is unlikely that repeated applications of antimycin will 

occur within the same year. Also, hydrolysis data indicate that antimycin degrades rapidly in the 

environment, particularly at warmer temperatures in alkaline waters and can be deactivated with 

potassium permanganate to prevent its movement to non-target areas, thus further reducing the 

likelihood of chronic exposure.

Based on the available information it is reasonable to believe that one component of the initial 

risk hypothesis discussed in the problem formulation cannot be rejected, i.e., the use of 

antimycin A in accordance with the label will likely result in adverse effects, such as acute 

mortality, to aquatic animals when the chemical is used at maximum target concentration of 25 

μg/L. The extent of mortality to nontarget organisms is uncertain; field studies suggest that while 

aquatic invertebrate populations are immediately affected in terms of decreased numbers,

invertebrate communities can recover to pretreatment levels in terms of both abundance and 

diversity within several months25. Monitoring conducted by the National Park Service in the 

Great Smoky Mountains National Park during efforts to remove non-native rainbow trout and to 

restore a viable population of native brook trout (Salvelinus fontinalis) indicated that negative 

effects to the macroinvertebrate community in streams ranging between 1 – 4

th order treated with 

Fintrol®at 8 μg/L for 8 consecutive hrs were short-lived and the invertebrate community 

recovered within two months post-treatment.

26 The monitoring data indicated that there was 

greater abundance and species richness after treatment among the major stream-dwelling benthic 

marcroinvvertebrate orders. The rapid recolonization of treatment areas by invertebrates (via 

upstream drift/immigration) from untreated areas was attributed to the the initial absence of fish 

(i.e., reduced predation on invertebrates) which in turn facilitated the restocking of insectivorous 

native brook trout shortly thereafter.27 While the initial risk hypothesis included potential risk to 

terrestrial animals feeding on dead or dying fish or through the ingestion of antimycin-treated 

water, the likelihood of adverse effects on these taxa is considered low based on available data; 

further analysis of this is provided in the risk description.

 

25 Moore, S.E., M.A. Kulp, J. Hammonds, and B. Rosenlund. 2005. Restoration of Sams Creek and an Assessment of Brook Trout Restoration 

Methods, Great Smoky Mountain National Park. National Park Service, U. S. Department of the Interior. Technical Report 

NPS/NRWRD/NRTR-2005.

26 Gibbs, W. K. 2013. Effects of Fintrol (Antimycin A) Application on Benthic macroinvertebrate communities in the Lynn Camp Prong 

Watershed, Great Smokey Mountains National Park. Dissertatiaon Presented to the Faculty of the Graduate School Tennessee Technological 

University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Environmental Science. May 2013.

27 Ibid Gibbs, W. K. 2013.
-Page 36 of 44-

4.2.2. Risks to Terrestrial Organisms 

4.2.2.1. Birds, Reptiles, and Terrestrial-phase Amphibians

No RQ values were calculated for birds since antimycin is applied directly to water and the 

likelihood of residues on terrestrial animal forage items on land is considered low; however, on 

the chance that birds forage on dead or dying fish, it is possible to estimate the potential amount 

of antimycin A in their diet. For example, the weight of food ingested (FI) by a great blue heron 

Ardea herodias (body weight=2.576 kg) is given by taking the antilog of the value estimate 

using formula (EQ1) recommended by the Wildlife Exposure Factors Handbook28.

Log10 (FI) = 0.966 log10 (body weight in grams) – 0.640 (EQ 1)

Based on this relationship, a blue heron will consume 452 g of fish per day. Piscivorous birds are 

likely to consume small to medium-sized fish and therefore rainbow trout are used as a surrogate. 

Fish tissue residue data for fish killed with antimycin indicate that rainbow trout contained as 

much as 172 μg antimycin/kg

29

. Therefore, a heron eating 0.45 kg would consume 77 μg (0.45

kg/day x 172 μg/kg) of antimycin. 

Extrapolations from one bird to another need to consider differences in the scaling of toxicity for 

differences in body weight. The LD50 can be adjusted for body weight based on the formula (EQ 

2) recommended by Mineau et. Al

30

:

Adjusted LD50 = LD50 (AW/TW)(a-1) (EQ 2)

Where adjusted LD50 is the median 50% lethal dose for the species being assessed, LD50 is the 

median lethal dose in the test organism, AW is the body weight of the assessed organism, TW is 

the body weight for the test organism, and a is the slope of the regression line for estimating the 

assessed species LD50 from the test species LD50 (EFED default value of 1.15). In the case of 

assessing a blue heron, 2576 g is a suitable value (adult bird) for AW. The test organism is a 

mallard duck, which weighs about 1230 g. With a test LD50 of 2.9 mg kg-1, the adjusted LD50 is 

3.2 mg kg-1. The actual dose is then the LD50 times the weight of the heron (2.576 kg) which 

equals 8.246 mg. Therefore, the amount of antimycin potentially consumed by herons is several 

orders of magnitude less than the acute median lethal dose; the dose-based RQ value is less than 

0.01 and is below acute risk levels of concern for non-listed and listed species (Table 9). 

Based on the Wildlife Exposure Factors Handbook31 the mean food ingestion rate for a bald 

eagle (Haliaeetus leucocephalus) is 0.12 kg/kg bw day. A bald eagle weighing 5.089 kg32 would 

 

28 ORD 1993. Wildlife Exposure Factors Handbook. Office of Health and Environmental Assessment, Office of Research and Development. 

EPA/600/R-93/187. http://www.epa.gov/ncea/pdfs/birds.pdf

29Ritter, P.O. and F.M. Strong. 1966. Residues in tissues of fish killed by antimycin. Journal of Agricultural Food Chemistry 14(4): 403 – 407 

(MRID 461534-01)

30 Mineau, P., B.T. Collins, and A. Baril. 1996. On the use of scaling factors to improve interspecies extrapolation of acute toxicity in birds. 

Regulatory Toxicology and Pharmacology. 24: 24-29.

31 Ibid ORD 1993.

32 According to the USFWS, male and female bald eagles can weigh as much as 14 (6.4 kg) and 10 lbs (4.5 kg), respectively.
-Page 37 of 44-

consume 610 g of fish per day representing a potential antimycin exposure of 105 μg (0.610 

kg/day x 172 μg/kg). The adjusted LD50 for bald eagles is 3.6 mg kg-1and the equivalent dose for 

a 5.089-kg bird is 18.32 mg; therefore, the dose-based RQ value is less than acute risk LOCs 

(Table 9).

Similarly, the mean for food ingestion rate for a belted kingfisher (Ceryle alcyon) is 0.11 g/gday33

. Based on this rate, an adult kingfisher weighing 148 g would consume 16 g of fish per day 

representing a potential antimycin exposure of 2.8 μg (0.016 kg/day x 172 μg/kg). The adjusted 

LD50 for kingfishers is 2.1 mg kg-1and once again, the estimated exposure is well below the 

effects threshold.

Table 9. Acute dose-based risk quotients for piscivorous birds based on potential residues in dead or dying 

fish.

Species Estimated Daily 

Dose (μg)

Adjusted LD50

(μg) Acute RQ Value

Blue Heron

(Ardea Herodias) 77 8246 <0.01

Bald Eagle

(Haliaeetus leucocephalus) 105 18,320 <0.01

Belted Kingfisher

(Ceryle alcyon)

2.8 311 <0.01

Only acute oral toxicity data are available for birds and these indicate that antimcyin is highly to 

very highly toxic to birds on an acute exposure basis. Risk quotients calculated using the dosebased acute toxicity values resulted in values below acute risk LOCs. The dose-based approach 

considers the uptake and absorption kinetics of a gavage toxicity study to approximate exposure 

associated with uptake from a dietary matrix. Toxic response is a function of duration and 

intensity of exposure. For many compounds, a gavage dose represents a very short-term, high 

intensity exposure. Although the dose-based estimates may not reflect reality in that animals do 

not receive a bolus dose while feeding, it is possible that a short-duration, high-intensity 

exposure could occur associated with feeding alongside treated surface waters since many birds 

may gorge themselves when food items are available; this would be particular true as birds 

opportunistically feed on dead and dying fish. 

No chronic avian toxicity data were submitted or located in the open literature for antimycin; 

therefore, chronic risks associated with avian exposure to antimycin are unknown. However, the 

likelihood of chronic exposure is considered low since dead fish would soon sink to the bottom 

of treated water. While exposure is possible through ingestion of antimycin A residues in 

drinking water during treatments when water is maintained at a specific concentration for 

specified duration, the likelihood of acute risk is considered low given the results of the initial 

screen using the Screening Imbibition Program tool. 

 

http://www.fws.gov/midwest/eagle/recovery/biologue.html 

33 Ibid ORD 1993
-Page 38 of 44-

4.2.2.2. Mammals

Similarly, the use of antimycin A as a piscicide is not likely to represent a means of exposure to 

wild mammals via consumption of antimycin residues on terrestrial forage items (plants, seeds, 

insects) since the compound is applied directly to water. Based on the chance that differentlysized mammals forage on dead or dying fish, it is possible to estimate the potential amount of 

antimycin in their diet. Using daily food intake as estimated by Nagy34 (EQ3), a 350 g mammal 

will consume about 68 g of food based on the allometric equation:

F=0.621*BW0.564/(1-W) (EQ3)

where F is the daily food intake in grams of fresh weight, BW is the body mass of the organism 

in grams, and W is the mass fraction of water in the food. For this assessment W is assumed to 

be 0.7535. Piscivorous mammals are not confined to eating small fish and may feed 

opportunistically on any sized fish that may succumb to antimycin; therefore, common carp 

(Cyprinus carpio) are used as surrogates. Based on the data on antimycin tissue residues in 

common carp with a body weight of 99 grams, a small mammal would only consume 68% 

(68/99) of the total carp body mass. According to the data for common carp, maximum total 

body residues of antimycin in carp tissue amounted to 261 μg/kg36. A 350-g mammal consuming 

68 grams represents an equivalent dose of 18 mg of antimycin; this value is below the median 

lethal dose of antimycin (286 mg/kg*0.350 kg=100 mg) for similarly sized mammals.

Similar to birds, extrapolations from one size of mammal to another must consider differences in 

the scaling of toxicity for difference in body weight. The LD50 can be adjusted for body weight 

based on the formula recommended by Mineau et al.37 (EQ4):

Adjusted LD50 = LD50(TW/AW)(0.25) (EQ4)

where adjusted LD50 is the median 50% lethal dose for the species being assessed, LD50 is the 

median lethal dose in the test organism, AW is the body weight of the assessed organism and 

TW is the body weight for the test organism. Since we are assessing a large mammal, 1000 g is a 

suitable value for AW. The test organism is a rat weighing about 350 g. With a test LD50 of 286 

mg/kg, the adjusted LD50 is 220 mg/kg. Using the daily intake equation, a 1000-g mammal will 

consume about 122 g of food. If the animal fed exclusively on carp killed by antimycin, the 

equivalent dose would be 0.122 kg *261 μg/kg or 32 μg of antimycin. Once again, this value is 

well below the estimated median lethal equivalent dose adjusted for body weight (220 mg/kg * 1 

kg=220 mg) and the RQ value is less than 0.01 (Table 10). Therefore, even if fish are available 

for consumption by mammals scavenging along the shoreline for dead or dying fish, it is not 

likely that the mammals would consume sufficient quantities of antimycin to result in acute 

toxicity.

 

34 Nagy, K.A. 1987. Field metabolic rate and food requirement scaling in mammals and birds. Ecological Monographs 57: 111-128.

35 Ibid Nagy 1987.

36 Ibid Ritter and Strong. 1966.

37 Ibid Mineau et al. 1996.
-Page 39 of 44-

Table 10. Acute dose-based risk quotients for piscivorous mammals based on potential residues in dead or 

dying fish.

Species Estimated Daily 

Dose (μg)

Adjusted LD50

(μg) Acute RQ Value

Large Mammal (1000 g) 8.9 220,000 <0.01

4.2.2.3. Terrestrial Invertebrates

RQs for terrestrial invertebrates were not calculated as no toxicity data are available. Given that 

antimycin A is applied directly to water and is typically used in high altitude lakes and high 

gradient streams, the likelihood of exposure to terrestrial invertebrates such as pollinator insects 

is considered low.

4.2.2.4. Terrestrial Plants

No toxicity data are availale for terrestrial plants; however, given that antimycin A is applied 

directly to water, the likelihood of exposure to terrestrial plants is considered low.

5. Endocrine Disruptor Screening Program (EDSP)

Antimycin A was not included in the first group of chemicals for which orders to conduct Tier 1 

EDSP testing were issued. For additional information the EDSP program, visit 

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

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

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the 

National Marine Fisheries Service (NMFS) (collectively, the Services), and the U.S. Department 

of Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks 

to listed species from pesticides. The Interim Approaches were developed jointly by the agencies 

in response to the National Academy of Sciences’ (NAS) recommendations and reflect a 

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

differences between the EPA and the Services. The NAS report outlines recommendations on 

specific scientific and technical issues related to the development of pesticide risk assessments 

that EPA and the Services must conduct in connection with their obligations under the

Endangered Species Act (ESA) and FIFRA. 

The joint Interim Approaches were released prior to a stakeholder workshop held on November 

15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013 

Pesticide Program Dialogue Committee (PPDC) and State-FIFRA Issues Research and 

Evaluation Group (SFIREG) meetings, and held 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 
-Page 40 of 44-

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 antimycin does not contain a 

complete ESA analysis that includes effects determinations for specific listed species or 

designated critical habitat. Although EPA has not yet completed effects determinations for 

specific species or habitats, for this preliminary assessment EPA conducted a screening-level 

assessment for all taxa of non-target wildlife and plants that assumes for the sake of the 

assessment that listed species and designated critical habitats may be present in the vicinity of 

the application of antimycin. This screening level assessment will allow EPA to focus its future 

evaluations on the types of species where the potential for effects exists once the scientific 

methods being developed by the agencies have been fully vetted. This screening-level risk 

assessment for antimycin indicates potential risks of direct effects to listed freshwater and 

estuarine/marine fish and invertebrates. 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 antimycin as part of completing this registration review. 

7. Conclusions

The results of this screening-level risk assessment are similar to those identified in the 

environmental fate and ecological risk assessment written in support of the Reregistration 

Eligibility Decision for antimycin A in 2007. Exposure to the compound resulting from the 

maximum treatment concentration is expected to kill fish and aquatic invertebrates in the 

immediate treatment area; acute risk LOCs are exceeded and the compound is intended to kill 

fish. However, in lotic environments, antimycin A is degraded (deactivated) through the use of a 

strong oxidizing agent (e.g., potassium permanganate) into fragments that are no longer toxic, to 

ensure that it does not move outside of the intended treatment area. While the extent to which the 

deactivation process is effective is uncertain, fish bioassays downstream of the deactivation 

stations are used to demonstrate whether residues are at levels acutely toxic to the test species. 

Given the expense and logistical constraints of treating large lakes with antimycin, the extent of 

this use is expected to be low; however, no data are available with which to evaluate the extent 

of use in lentic environments where the compound would not be deactivated. Based on the most 

sensitive species and at the maximum treatment concentration, risk quotient (RQ) values exceed 

acute risk LOCs by several orders of magnitude for direct adverse effects to listed and non-listed 

fish and invertebrates; however, whether listed species are actually at risk requires a more 

detailed assessment than what is contained in this preliminary risk assessment. The risk 

hypothesis presented in the problem formulation states that the use of antimycin A in accordance 

with the label results in adverse effects on survival and/or fecundity to non-target aquatic plants 

and animals. Based on the current assessment, there is a likelihood of direct effects (i.e., acute 

mortality) on fish and invertebrates from the use of antimycin A as a piscicide. Although no data 
-Page 41 of 44-

are available to assess the potential for adverse effects to aquatic plants, there are no reported 

incidents of such effects by either the National Park Service or state fishery management 

agencies which have employed antimycin A. Monitoring of macroinvertebrate communities in 

treated streams indicate that adverse effects are short-lived; invertebrate communities recovered 

within several months and species richness and abundance especially for benthic 

macroinvertrates increased relative to pretreatment conditions. While the potential risk to 

terrestrial animals was hypothesized, the current analysis does not support that component of the 

risk hypothesis. There are no data with which to evaluate the potential effects of antimycin on 

terrestrial plants and terrestrial invertebrates; however, given the direct application of the 

material to water, the likelihood of exposure to these taxa is considered low. 

8. References

Abidi, S.L. and B.R. Adams. 1987. 1H and 13C resonance designation of antimycin A1 by twodimensional NMR spectroscopy. Magn. Reson. Chem. 25: 1078-1080. 

Abidi, S.L. 1988. High-performance liquid chromatographic separation of subcomponents of 

antimycin A. J. Chromatogr. 447: 65-79.

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the 

EPA food-chain (Kenaga) nomogram, and instrument for estimating pesticide residues on 

plants. Environmental Toxicology and Chemistry 13 (9):1383-1391.

Hoerger, F., and E.E. Kenaga. 1972. Pesticide residues on plants: Correlation of representative 

data as a basis for estimation of their magnitude in the environment. In F. Coulston and F. 

Korte, eds., Environmental Quality and Safety: Chemistry, Toxicology, and Technology, 

Georg Thieme Publ, Stuttgart, West Germany, pp. 9-28.

Hubert, T.D. and L. J. Schmidt, “Antimycin A Use in Fisheries: Issues Concerning EPA

Registration”, USGS, Upper Midwest Environmental Sciences Center, La Crosse, WI, 

2001.

Hussain, A. 1969. Kinetics and mechanisms of hydrolysis of antimycin A in solution. Journal of 

Pharmaceutical Sciences 58: 316-320.

Kenneke, J.F. Summary of Antimycin Hydrolysis Research, US EPA, unpublished report. (See 

USEPA 2006b.)

Lee, T.H., Derse, P.H., and Morton, S. 1971. Effects of Physical and Chemical Conditions on the 

Detoxification of Antimycin. Transactions of the American Fisheries Society 1971; 100: 

13–17.

Ott, Kevin C. Antimycin. A Brief Review of Its Chemistry, Environmental Fate, and 

Toxicology.

http://www.newmexicotu.org/Antimycin%20Summary.pdf
-Page 42 of 44-

U.S. Department of the Interior (USDOI). 2012. Standard Operating Procedures for the Use of 

Fintrol®(Antimycin A) for Restoration of Native Fish Populations. U.S. Dept. of the 

Interior, National Park Service, Natural Resource Stewardship and Science, Ft. Collins 

CO. Nov. 2012.

U.S. Environmental Protection Agency (USEPA). 2015. Ecological Incident Information 

System, v. 2.1. Accessed on February 10, 2015. Description online at:

http://www.epa.gov/pesticides/science/models_db.htm.

USEPA. 2014. Estimation Program Interface (EPI) SuiteTM. 

http://www.epa.gov/opptintr/exposure/pubs/episuite.htm

USEPA. 2009a. Water models. Available online at http://www.epa.gov/oppefed1/models/water/.

USEPA. 2009b. ECOTOXicology Database, v. 4.0. Accessed on 12 April 2012. Available online 

at http://cfpub.epa.gov/ecotox/.

USEPA. 2009c. Guidance for Selecting Input Parameters in Modeling the Environmental Fate 

and Transport of Pesticides, Version 2.1. U.S. Environmental Protection Agency, Office 

of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, 

Environmental Fate and Effects Division, October 22, 2009. Online at: 

http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

USEPA. 2007. Reregistration Eligibility Decision for Antiycin A. List D. Case No. 4121. 

Available on line at: http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP2006-1002-0029

USEPA. 2006a. Revised Environmental Fate and Ecological Risk Assessment Chapter (DP 

Barcode D310730) in Support of Phase III of the Reregistration Eligibility Decision on 

Antimycin A (PC Code 006314). Available on line at: 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2006-1002-0004

USEPA. 2006b. Antimycin A Drinking Water Characterization (Revision 1) (DP Barcode 

D333893). U.S. Environmental Protection Agency, Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effects 

Division. November 29, 2006.

USEPA. 2006c, TerrPlant v. 1.2.2 User’s Guide. Office of Pesticide Programs, Environmental 

Fate and Effects Division, Washington, D.C. December 26, 2006.

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs, U.S. Environmental Protection Agency. Endangered and Threatened Species 

Effects Determinations. Office of Prevention, Pesticides and Toxic Substances, Office of 

Pesticide Programs, Washington, D.C. Available online at 

http://www.epa.gov/oppfead1/endanger/consultation/ecorisk-overview.pdf.
-Page 43 of 44-

USEPA. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Published in 63 

FR 26846; May 14, 1998. U.S. Environmental Protection Agency, Washington, DC. 

April, 1998.

USEPA. 1993b. Wildlife Exposure Factors Handbook. EPA/600/R-13/187a. Office of Research 

and Development, Washington, D.C.

USEPA. 1992. Pesticides in Ground Water Database: A Compilation of Monitoring Studies: 

1971-1991: National Summary. U.S. Environmental Protection Agency, Washington, 

DC.

Walker, C.R., R.E. Lennon, and B.L. Berger. 1964. Preliminary observations on the toxicity of 

antimycin A to fish and other aquatic animals. U.S. Bureau of Sport Fisheries and 

Wildlife, Investigations in Fish Control No. 2 (Circular No. 186). 18 pp.

Willis, G.H. and L.L. McDowell. 1987. Pesticide persistence on foliage. Reviews of 

Environmental Contamination and Toxicology 100: 23-73.
-Page 44 of 44-

9. Appendix A. Screening Imbibition Program (SIP) Results

Table 1. Inputs

Parameter Value

Chemical name Antimycin A

Solubility (in water at 25oC; mg/L) 0.089

Mammalian LD50 (mg/kg-bw) 286

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 0

Mammalian test species

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 2.9

Avian test species mallard duck

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 0

Bobwhite quail NOAEC (mg/kg-diet) 0

NOAEC (mg/kg-diet) for other bird species 0

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) 0.0153 0.0153

Adjusted toxicity value (mg/kg-bw) 219.9799 0.0000

Ratio of exposure to toxicity 0.0001 0.0000

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Due to insufficient data, 

risk cannot be precluded

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 0.0721 0.0721

Adjusted toxicity value (mg/kg-bw) 1.5058 0.0000

Ratio of exposure to acute toxicity 0.0479 0.0000

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for birds

Due to insufficient data, 

risk cannot be precluded

*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.