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Preliminary Ecological Risk Assessment and 

Endangered Species Effects Determination

in Support of the Registration Review 

of Polybutene

PC Code 011402

CAS Number 9003-29-6

Prepared by:

Nicholas Mastrota, Ph.D.

Wildlife Biologist

Environmental Risk Branch 3

Environmental Fate and Effects Division

Reviewed by:

Dana Spatz, Branch Chief

Rosanna Louie-Juzwiak, Risk Assessment Process Leader

February 28, 2013
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Table of Contents

1. Problem Formulation .................................................................................................. 5

1.1. Stressor Description ............................................................................................. 5

1.2. Environmental Fate Summary.............................................................................. 5

1.3. Mode of Action .................................................................................................... 6

1.4. Use Characterization ............................................................................................ 6

1.5. Assessment Endpoints.......................................................................................... 7

1.6. Ecosystems Potentially at Risk ............................................................................ 8

1.7. Risk Hypothesis.................................................................................................... 8

1.8. Results of Previous Assessments ......................................................................... 9

2. Analysis Plan .............................................................................................................. 9

3. Exposure Assessment................................................................................................ 10

3.1. Label Application Rates..................................................................................... 10

3.2. Aquatic Exposure ............................................................................................... 10

3.3. Exposure to Terrestrial Animals ........................................................................ 11

3.4. Terrestrial Plant Exposure.................................................................................. 12

4. Effects Assessment ................................................................................................... 12

4.1. Ecotoxicity Data................................................................................................. 12

4.1.1. Terrestrial Organisms.................................................................................. 12

4.1.2. Aquatic Organisms...................................................................................... 13

4.2. ECOTOX Data ................................................................................................... 14

4.3. Ecological Incident Reports............................................................................... 14

5. Risk Description........................................................................................................ 15

5.1. Aquatic Risk....................................................................................................... 15

5.2. Terrestrial Risk................................................................................................... 16

5.2.1. Birds, Mammals, Reptiles, and Terrestrial-Phase Amphibians.................. 16

5.2.2. Terrestrial Invertebrates.............................................................................. 18

5.2.3. Terrestrial Plants......................................................................................... 18

6. Risk to Threatened and Endangered Species............................................................ 18

References......................................................................................................................... 20
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1. Problem Formulation

The problem formulation provides a strategic framework for the risk assessment. By 

identifying the important components of the problem, it focuses the assessment on the 

most relevant chemical properties, exposure routes, and endpoints.

1.1. Stressor Description

Polybutene is a homopolymer composed of repeating units of the monomer n-butene or 

iso-butene. It is a non-drying, sticky polymer, registered for use primarily as a nuisance 

bird (such as pigeons and starlings) repellent, but is also registered to repel beavers that 

may gnaw on tree trunks. It acts as a tactile repellent. When birds land on treated objects 

or surfaces, they are deterred by the sticky tactile sensation and usually do not return. 

Polybutene's tacky quality is the source of the repellent action of pesticide products 

containing this active ingredient. The product therefore differs from typical pesticides in 

that it is not intended to be ingested by the pest species.

1.2. Environmental Fate Summary

Physical and chemical properties of polybutene are given in Table 1. Polybutene is a 

highly stable and extremely insoluble inorganic material. Water solubility is very low

(<0.1%). An important physical property in the pesticidal activity of polybutene is its 

viscosity, which makes it sticky to touch. EPA has not imposed any environmental fate 

data requirements for the registration of polybutene because its properties and use pattern 

will result in very limited exposure to the environment beyond the point of application.

Polybutene is considered to be persistent to abiotic hydrolysis, direct photolysis in water, 

and microbial degradation. Its use in sealants is a testament of its high stability in the 

environment. Any aging of polybutene may occur from exposure to the environment for 

a prolonged period of time, in which photooxidation of the double bond between carbon 

atoms (–C=C–) may gradually generate epoxides, aldehydes, and carboxylic acids. These 

reactions are known to form other polyalkenes (Minerath et al., 2009), but there are no 

known degradation studies specific for polybutene oligomers. The estimated Koc of 2.5 x 

109L/kg indicates that it absorbs strongly to soil and other surfaces. Therefore, 

polybutene is not expected to be mobile in the terrestrial environment. Furthermore, 

because of its extremely low solubility, and application methods that would produce

little-to-no spray drift, polybutene is not expected to be transported to aquatic 

environments in significant amounts. Any leaching to ground water is also expected to 

be negligible. Therefore, no aquatic exposure or drinking water exposure assessment was 

conducted when evaluating the pesticidal uses of this chemical.
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Table 1. Physical and Chemical Properties of Polybutene and Its Monomer Butene

Common name Polybutene

Chemical name Polybutene oligomer

Pesticide type Pest repellent. Pests include birds and beavers

Chemical class Alkene polymer

CAS number 9003-29-6 (polybutene)

US. EPA Chemical Code 011402

Monomer n-butene and iso-butene

Type of polymer Homopolymer; Oligomer

Empirical formula of the monomer and of the 

polymer

n-butene CH3CH2CH=CH2

Isobutene H2C=C(CH3)

CH2-C(CH3)2 ; C4H8 (monomer)

-[-CH2-C(CH3)2-]n ; (C4H8)n (homopolymer)

SMILES Notation C(C=C)C.C(=C\C)\C

Molecular mass (g/mol) of monomer 56.1063

Molecular mass range (g/mol) of the oligomer 320-420

Range of monomer units in the oligomer ~5-8 monomer units

Vapor pressure 0.13 torr (mmHg), at 25 ̊ C

Henry’s Law Constant (atm-m

3

/mol) 4.88 x 105(estimated; EPISuite); No experimental data

Solubility in water (mg/L) < 0.1 %, negligible 

5.07 x 10-7 mg/L (estimated; EPISuite); No experimental 

data)

Log Kow 17.14 (estimated; EPISuite); No experimental data)

pKa/pKb Not applicable

EPISuite (Estimation Program Interface); EPIWeb 4.0

1.3. Mode of Action

Polybutene acts as a tactile repellent for birds and mammals. The viscosity and sticky 

property of the substance deter animals from perching, roosting, or walking on treated 

surfaces.

1.4. Use Characterization

Polybutene is used as a repellent to birds from perching on buildings and structures, and 

to repel beavers from gnawing on trees. Polybutene products may be used on areas of 

buildings or adjacent structures or plants where birds land or roost (for example, on

ledges, window sills, beams, gutters, trees, shrubs, and vines), and on the lower trunk 

area of trees. (USEPA, 1995).

Current polybutene registrations are described in Table 2. Tanglefoot Bird Repellent, 

Hot Foot Bird Repellent, and 4 the Birds Repellent are ready-to-use gels which come in 

tubes for use in caulk guns, and are applied in beads on horizontal surfaces to repel birds 
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from perching. 4 the Birds Transparent Bird Repellent is a liquid that may be painted on

or sprayed onto surfaces with a hand or pressure sprayer. This is the only polybutenecontaining product registered to repel beavers from gnawing on trees. For this use, the 

product may be applied to the lower trunk of trees up to the height of 2 feet.

Table 2. Current Polybutene Registrations

Product Name

(Registrant)

EPA Registration 

Number

(latest label date)

Active 

Ingredients

(% w/w)

Use Sites

Tanglefoot Bird 

Repellent 1621-17 93.5 Bird roosting and nesting areas on buildings and structures

Hot Foot Bird Repellent 55943-1 93.5 Bird roosting and nesting areas on 

buildings and structures

4 the Birds Repellent 8254-5 93 Bird roosting and nesting areas on 

buildings and structures

4 the Birds Transparent 

Bird Repellent Liquid 8254-3 49

Bird roosting and nesting areas on 

buildings, structures, and woody 

plants, and lower trunks of trees 

for repelling beavers.

1.5. Assessment Endpoints

This assessment evaluates the potential for adverse effects as a result of polybutene use 

per label specifications. As described in the Agency’s Overview Document (U.S. 

USEPA, 2004), the most sensitive endpoint for each taxon is evaluated. Assessment 

endpoints are selected based on ecosystems typically at risk from pesticide use and

include direct toxic effects on the survival, reproduction, and growth of terrestrial and 

aquatic life.

For this assessment, exposure to aquatic organisms, terrestrial invertebrates, and 

terrestrial plants is assumed to be negligible. Therefore, for these taxa, the EPA has not 

asked for toxicity data and a quantitative risk assessment was not conducted. The 

ecological risk assessment is limited to evaluating terrestrial vertebrates. For these taxa, 

available toxicity data for birds (2 studies) and mammals (3 studies) are used as 

assessment endpoints, as described in Table 3. 
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Table 3. Summary of Assessment Endpoints and Measures of Ecological Effect for the Assessment of 

Risk of Polybutene to Terrestrial Wildlife

Assessment Endpoint Measures of Ecological Effect

Terrestrial Environments

Abundance (i.e. survival, reproduction, and 

growth) of individuals and populations of birds1

Avian acute oral toxicity: 

Northern Bobwhite (Colinus virginianus)

LD50 > 2150 mg a.i./kg-bw

Avian dietary toxicity: 

Northern Bobwhite (Colinus virginianus)

LC50 > 5000 mg a.i./kg-diet

Abundance (i.e. survival, reproduction, and 

growth) of individuals and populations of birds 

and mammals)

Acute oral toxicity:

Laboratory Rat LD50 > 5000 mg a.i./kg-bw

Acute Dermal toxicity:

Rabbit LD50 > 980 mg a.i./kg-bw

1 Birds represent surrogates for reptiles and terrestrial-phase amphibians

1.6. Ecosystems Potentially at Risk

Based upon the labeled uses of polybutene and its properties, the only ecosystems 

potentially at risk are the terrestrial ecosystems where the product is applied. As the 

treated product is not expected to migrate from the point of use in any significant amount, 

risk in these ecosystems will be limited to organisms that come into contact with the 

product at the place it is applied. Since the product is used primarily on man-made 

structures, animals inhabiting urban and residential areas are most likely to be exposed. 

Considering that the water solubility of polybutene is negligible, runoff from the 

treatment site is not expected to result in any appreciable movement of residues to aquatic 

habitats. Also, since spraying of this viscous substance is not expected to result in 

appreciable spray drift, aquatic habitats would not be contaminated by spray drift. 

Therefore, aquatic ecosystems are not believed to be at risk from the labeled use of 

polybutene.

1.7. Risk Hypothesis

For polybutene, the following ecological risk hypothesis is being employed for this risk 

assessment:

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

on the survival of nontarget terrestrial animals because of possible direct 

ingestion of the product or because of inadvertent entrapment by the products. 

Given the properties and use pattern of polybutene, exposure to aquatic animals, 

aquatic plants, and terrestrial plants is believed to be insignificant.
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1.8. Results of Previous Assessments

Previous ecological reviews and risk assessments conducted for polybutene include: 

Reregistration Phase IV Review (Memorandum from Fred Betz to Jay Ellenberger, 

February 1993)

Reregistration Eligibility Decision (RED, USEPA December 1994)

Registration Review: Problem Formulation for Polybutene. May 19, 2010 

(D371745)

The registered uses of polybutene have remained the same throughout the period of these 

assessments. In all of these assessments, no risk exceeding the EPA’s level of concern 

(LOC) was identified with the exception of possible entrapment of small birds. For 

aquatic risks, these assessments concluded negligible risks to aquatic organisms because 

of the tacky composition and insolubility of the end-use product. For terrestrial risks, 

these assessments concluded that ingestion of the product by animals was unlikely. 

Considering the lack of exposure, together with the lack of toxicity observed in avian 

acute oral and subacute dietary tests, risk from oral ingestion of polybutene was 

concluded to be below the EPA’s level of concern. However, all of the assessments 

stated that use of the product may pose a risk to small birds, and possibly other small 

terrestrial animals, because they could become entrapped if they come in contact with the 

tacky product. This risk was considered greatest for the liquid product because it may be 

sprayed onto trees, shrubs, bushes, and vines where birds frequently perch. Previous risk 

assessments did not assess risk to nontarget plants or terrestrial insects.

The 2010 Problem Formulation cites an incident reported in 2008 in which some cedar 

waxwings (a passerine bird species) were incapacitated or killed after entrapment by the 

product. An assessment completed in 1993 discusses an earlier bird kill incident in 1990 

which involved the entrapment and deaths of 15 birds following a misuse (overapplication) of the product. As a result of the earlier incident reports, the 1994 RED 

required that polybutene products carry the following warning statement on the label:

“Small birds may become fatally entrapped by this tacky repellent. To reduce 

hazards to legally protected species, and to avoid noncompliance with the Federal 

Migratory bird Treaty Act, follow all instructions in the Direction for Use.”

2. Analysis Plan

Typically, direct and indirect ecological effects are evaluated based on ratios (risk 

quotients) of the estimated exposure to a designated toxicity endpoint. Terrestrial 

exposure is typically based on estimated maximum residues on contaminated food items 

consumed by wildlife, and for terrestrial plant, exposure from runoff and spray drift. 

Aquatic exposure is typically based on estimated maximum concentrations in a modeled 

body of water contaminated by pesticide runoff and/or spray drift. However, due to the 

use pattern and physical properties of polybutene, use of polybutene as a pest repellent is 
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expected to result in negligible contamination of wildlife food items, and negligible 

exposure to nontarget plants and aquatic habitats from runoff and spray drift. Therefore, 

no quantitative risk assessment based on the traditional risk quotient method was

conducted. Instead, exposure and potential risk of polybutene to nontarget organisms 

was assessed qualitatively based on evidence of exposure and toxicity (or lack thereof) 

and a qualitative assessment of the likelihood of nontarget organisms ingesting or coming 

into contact with the product. The risk of nontarget organisms becoming physically 

entangled with the product was also qualitatively assessed.

3. Exposure Assessment

3.1. Label Application Rates

In order to estimate potential exposure from a pesticide application, a pesticide product 

label typically states application rates in terms of amount of product per unit area (e.g., 

pounds of product per acre). Unlike typical pesticide labels, the polybutene product labels

do not specify an application rate, per se. In an effort to quantify the potential amount of 

active ingredient (a.i.) for a given area, the Biological and Economical Analysis Division 

(BEAD) estimated the potential amount of a.i. that may be applied, based on product 

labeling directions. For products applied with a caulk gun (Tanglefoot Bird Repellent, 

Hot Foot Bird Repellent, and 4 the Birds Repellent), the application rate was estimated to 

be approximately 0.05-0.06 lb a.i./linear foot. For use of “4 the Birds Transparent Bird 

Repellent” on tree trunks to repel beavers, BEAD estimates the application rate to be 0.80 

lb ai/ft trunk diameter or 0.124 lb ai/in trunk diameter. For use of “4 the Birds 

Transparent Bird Repellent” on structures and woody plants to repel birds, no application 

rate is given; the label only instructs the user to apply to the point of runoff.

3.2. Aquatic Exposure

Polybutene is highly insoluble in water. Water solubility was estimated by EPISuite to 

be 5.07 x 10-7 mg/L. Therefore, movement of residues from the treatment site to aquatic 

habitats in runoff is expected to be negligible. Negligible exposure is also expected from 

spray drift. Only one product (“4 the Birds Transparent Bird Repellent”) may be applied 

as a spray and thus could conceivably produce spray drift. Although the label instructs 

the user to coat treated surfaces to the point of runoff, given the application methods and 

limited areas that would be treated, little-to-no spray drift exposure is expected far from 

the site of use. Thus, we conclude that use of this product results in negligible 

contamination of aquatic habitats by runoff or spray drift.

While the very low solubility of polybutene precludes significant dissolved 

concentrations in water, acute aquatic toxicity tests show that when significant quantities 

of polybutene are applied to water, a slick can form on the water’s surface. While not a 

mechanism of direct toxicity, this surface slick can possibly result in depletion of 
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dissolved oxygen in the water, thereby causing suffocation. However, polybutene is very 

viscous and tacky, and thus material applied to buildings, structures, and woody plants to 

repel birds is expected to remain in place and not wash off into aquatic habitats in 

appreciable amounts. Given the limited and localized use of polybutene products, this 

scenario is not considered likely. Therefore, any aquatic exposure is expected to be 

negligible. 

3.3. Exposure to Terrestrial Animals

Terrestrial animal dietary exposure to polybutene is expected to be negligible. Being an 

inorganic polymer with known repellent properties, animals are not expected to 

intentionally ingest polybutene at the site of application. Application of the 4 the Birds 

Transparent Bird Repellent product to surfaces on buildings and structures where birds 

may perch is not expected to result in any appreciable contamination of wildlife food 

items. Application of this product to woody plants to repel birds or beavers may result in 

a small amount of material contaminating potential wildlife food items, such as by 

inadvertently being applied to leaves or buds, or dripping onto vegetation beneath the 

treatment site. However, the extent of this contamination is expected to be very small. 

Additionally, the treatment areas are expected to be very limited, such as applications 

made to a small number of woody plants that are located adjacent to homes or buildings, 

where roosting birds would be considered a nuisance. Contamination of wildlife food 

items would be limited to these plants and to areas lying beneath these plants. 

Furthermore, being a repellent, animals are not expected to find these contaminated areas 

attractive for foraging. Therefore, inadvertent ingestion of the product by animals, 

including listed species, is unlikely. Furthermore, considering the low toxicity of 

polybutene, it would not be expected to approach toxic levels should exposure occur. 

The primary route of exposure to terrestrial animals is physical contact with polybutene. 

While the tackiness of the material would generally deter animals, in some cases contact 

may result in small animals becoming entangled in the material. Wildlife and insects 

could come into contact with the products by perching or walking on treated surfaces of 

structures or woody plants. As previously noted, because treatment areas are very small, 

and the geographic locations of applications are generally remote from listed species 

locations, exposures to threatened or endangered animals are unlikely to occur. 

However, given that the target pest includes nuisance birds, risks from such physical 

contact are assessed qualitatively in this risk assessment.

The label of “4 the Birds Transparent Bird Repellent” (the only product that may be 

applied to woody plants), carries the following statement:

Do not apply this product directly to trees, bushes or vines that are in bloom or 

bearing fruit except as indicated on this label for use as a paint on the lower areas 

of tree trunks to discourage damage (debarking and cutting) by beavers.
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This restriction would reduce the risk of inadvertent contamination of fruit, thereby 

reducing the risk of dietary exposure to frugivores. The statement would also mitigate 

the risk of physical contact and possible entanglement of wildlife and insects that feed on 

fruit, as well as hummingbirds, honey bees, and other insect pollinators that feed on 

nectar and/or pollen.

3.4. Terrestrial Plant Exposure

Based upon the nature of the use and the properties of the compound, minimal exposure 

of terrestrial plants is expected. No significant movement or transport of polybutene off 

the site of treatment is expected. Exposure to terrestrial plants is expected to be limited 

to the plants that are directly treated with the product, or that lie immediately beneath 

treated plants, and the chance of occurrence of listed plants at the immediate treatment 

site is extremely small. Therefore, exposure of plants is expected to be low and is not 

expected to result in adverse effect to listed plants.

4. Effects Assessment

4.1. Ecotoxicity Data

4.1.1. Terrestrial Organisms

Table 4 summarizes the available data on the toxicity of polybutene to nontarget 

organisms. Only acute and subacute toxicity studies with birds and mammals have been 

submitted. Based on both acute oral and subacute dietary tests with the northern 

bobwhite, polybutene is classified as practically nontoxic to birds. No mortality or signs 

of toxicity were observed in an acute oral test with birds, although one bird died in a 

subacute dietary test when given a dietary concentration of 5000 mg/kg diet (0.5%). 

Acute oral testing with the rat also classifies polybutene as practically nontoxic to 

mammals. Administration of a dose of 5000 mg/kg-bw resulted in no mortality. The 

only sign of toxicity observed was a dry rale in one rat which lasted for two days. EFED 

does not consider this a frank toxic effect. 

Acute inhalation testing with a mammal was waived in the Polybutene Reregistration 

Eligibility Decision (RED) because the viscosity of polybutene was believed to limit

production of respirable particles during spraying. A dermal toxicity test was conducted 

with the rabbit using the formulated product “4 the Birds Transparent bird Repellent 

Liquid” (Reg. No. 8254-3, 49% AI). In this study, the acute dermal LD50 was determined 

to be > 2000 mg/kg, which is equivalent to > 980 mg ai/kg. Since the test was conducted 

with a product containing 49% AI, the inert ingredients in the formulated product may 

have contributed to the observed toxicity in this study.

No data have been submitted to the EPA on the chronic toxicity of polybutene to birds or 

mammals. Also, no data are available on the toxicity of polybutene to terrestrial plants.
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Table 4. Acute Toxicity of Polybutene to Terrestrial Species.

Taxonomic 

Group,

Study Type

Surrogate Species Toxicity 

(expressed as AI) MRID StudyClassification

Birds1

Birds, Acute 

Oral

Northern Bobwhite

(Colinus virginianus)

LD50 > 2150 mg/kg bw

No mortality or sublethal 

effects observed

42873827 Acceptable

Birds, 

Subacute

Dietary

Northern Bobwhite

(Colinus virginianus)

LC50 > 5000 mg/kg diet

One death at 5000 mg/kg 41832002 Acceptable

Mammals

Mammals, 

Acute Oral

Laboratory rat

(Rattus norvegicus)

LD50 > 5000 mg/kg bw (males

and females)

No mortality. No signs of 

toxicity except for a dry rale in 

one rat 0-2 days after dosing 

with 5000 mg/kg bw.

41772401 Acceptable

Mammals, 

Acute Dermal

Rabbit

LD50 > 2000 mg/kg2

LD50 > 980 mg ai/kg

One mortality at 2000 mg/kg. 

The rabbit that died exhibited 

diarrhea and blanched areas of 

the liver 

40222701 Acceptable

Mammal, 

Acute 

Inhalation

--

--

-- Waived3

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

2. Results for a test of “4 the Birds Transparent bird Repellent Liquid” (Reg. No. 8254-3, 49% AI)

3. Requirement for an inhalation toxicity study was waived because the viscosity of polybutene was 

believed to limit production of respirable particles during spraying. 

4.1.2. Aquatic Organisms

The extremely low solubility of polybutene thwarted successful testing of acute toxicity 

with freshwater fish and invertebrates. In the limit test with the rainbow trout

(Oncorhynchus mykiss) (MRID 43382701), the insoluble test material formed a surface 

slick in the test vessels throughout the trial. At the nominal test concentration of 10,000 

mg/L, dissolved oxygen fell below 60% saturation at 72 hours, apparently because the 

test material formed a seal between the water surface and the air. Five of the ten fish 

exposed at this test level died. After aeration of the test vessels was initiated, all of the 

remaining fish survived and showed no signs of toxicity, indicating that the mortality was 

caused by lack of oxygen rather than by toxicity of polybutene. In an acute toxicity test 

with the water flea (Daphnia magna) (MRID 43382701), mortality ranged from 20% at a 

nominal concentration of 100 mg/L to 100% at a nominal concentration of 10,000 mg/L. 

However, all of the deaths appeared to have occurred from the physical entrapment of 

organisms to globules of undissolved test material floating on the surface and adhered to 

the sides of the test vessels. In a separate test of the water soluble fraction, in which 

undissolved test material was removed, no mortality was observed at any test 

concentration. These tests indicate that the presence of significant amounts polybutene in 
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water may be harmful to aquatic organisms, not because of toxicity, but because of 

adverse physical effects (i.e., oxygen depletion). 

Additional testing found that the solubility could not be enhanced by use of solvents. The 

EPA concluded that appropriate means of increasing the solubility of polybutene had

been exhausted and that further testing would not be productive. Therefore, requirements 

for acute toxicity data with fish and aquatic invertebrates were waived for polybutene 

(USEPA, 1994).

No data have been submitted on the toxicity of polybutene to aquatic plants. As with fish 

and aquatic invertebrates, the extremely low solubility of polybutene is believed to make 

testing of aquatic plant toxicity impractical.

4.2. ECOTOX Data

A search of the aquatic and terrestrial data in the public ECOTOX database 

(http://cfpub.epa.gov/ecotox/quick_query.htm) was conducted in February 2012. This 

search did not yield any ecotoxicological data on polybutene other than the studies that

had been submitted to the EPA and are summarized in Table 4.

4.3. Ecological Incident Reports

EPA’s Ecological Incident Information System (EIIS) contains a record of two reported 

ecological incidents that are associated with use of polybutene as a repellent in 

accordance with the label.

1. Incident I004169-042:

The Virginia Department of Game and Inland Fisheries reported on the mortality 

of two house sparrows attributed to the use of 4-the-Birds Bird Repellent at a 

shopping center in Martinsville, Virginia in March, 1991. Beads of product had 

been applied to an awning at the mall to deter nuisance birds, in accordance to 

label directions. One house sparrow was found dead and coated with the sticky 

product. A second house sparrow was found alive but incapacitated by the 

coating of product on its feathers. The bird was euthanized by a veterinarian.

2. Incident I019575-001:

The Tanglefoot Company reported that use of the product Tanglefoot Bird 

Repellent (97% polybutene, EPA Reg. No. 1621-17) resulted in the death of 

numerous cedar waxwings in early March of 2008 in Richmond, Virginia. The 

product had been applied to a commercial building to deter roosting of pigeons. 

There was no evidence that the product was misused. The incident occurred when 

a flock of cedar waxwings roosted on a treated ledge. The report states that the 
15

“sticky adhesive came in contact with wings [of the birds], limiting their ability to 

fly.” “Approximately 30-80” birds were affected, although this count reportedly 

includes some birds that collided with windows, and also some birds that were 

rehabilitated and released. The exact number of birds that died from direct 

contact with the bird repellent product is therefore unknown. 

One incident was attributed to a misuse of polybutene. The organization Bat 

Conservation International (www.batcon.org) reported on the deaths of a large number of 

bats at the campus of the University of Arizona in Tucson in the fall of 1990. The 

University was attempting to remove bats, mostly Brazilian free-tailed bats (Tadarida 

brasiliensis), that were roosting in expansion joists in the university’s football stadium. 

An unidentified polybutene bird repellent had been applied. University personnel had 

also used a fire extinguisher to spray the bats with carbon dioxide to drive them away. 

Some bats were allegedly killed by the carbon dioxide, while others were allegedly killed 

when the polybutene repellent caused the wings of the bats to become permanently stuck 

to their bodies. Bats are not a registered target pest species for the use of any repellent 

containing polybutene, and therefore this use was not a legal use of polybutene. 

A search of the American Bird Conservancy’s Avian Incident Management System 

(AIMS) and the Office of Pesticide Program’s Aggregate Summary database was 

conducted in February 2012. Neither database contained a record of any ecological 

incident associated with the use of polybutene.

5. Risk Description

5.1. Aquatic Risk

As discussed in Section 2.2, use of polybutene is generally expected to result in 

negligible contamination of aquatic habitats. The insolubility of the compound would 

prevent more than small traces to be dissolved in water. Considering the low toxicity 

observed in birds and mammals, and the lack of any known toxic mode of action to 

aquatic species, dissolved residues of polybutene are expected to remain far below levels 

that might be toxic to aquatic organisms. This conclusion is supported by the findings of 

acute toxicity testing with the water flea, Daphnia magna (MRID 43382701). When 

polybutene was mixed with water and then the water soluble fraction was separated from 

the undissolved test material, no mortality of water fleas occurred when exposed to 

nominal concentrations as high as 10,000 mg/L.

Although the very small traces of soluble polybutene are not expected to result in any 

toxicity, acute toxicity tests indicate that the presence of polybutene in water may cause 

physical hazards to aquatic organisms. In an acute toxicity test with the rainbow trout 

(MRID 43382702), the insoluble test material formed a surface slick in the test vessels 

that remained throughout the trials. The surface slick formed a seal between the test 

solution and the air, causing depletion of dissolved oxygen, and resulting in mortality of 

50% of the fish. Introduction of significant quantities of polybutene into a small body of 

water, such as a small pond, could result in a surface slick and have similar detrimental 
16

effects. In a test with water flea using test solutions containing undissolved test material, 

mortality occurred when the water fleas became physically entrapped by globules of 

polybutene. Globules of polybutene in natural aquatic habitats may likewise pose a

physical hazard to aquatic invertebrates and possibly small vertebrates, yet this is 

considered very unlikely.

Because the product is not mobile, use of polybutene as a bird repellent on buildings, 

structures, and branches of woody plants is not expected to result in significant amounts 

of material reaching water. Use as a repellent for beavers, however, could potentially 

result in unintentional introduction of polybutene into aquatic habitats. The beaver 

repellent use involves painting or spraying the product to the lower section of tree trunks, 

from ground level to 2 feet high. As beavers are aquatic mammals, these applications 

would be made to trees that are near the banks of ponds, streams, and rivers. A rise in the 

water level to a level that submerges the treated section of the tree trunks could cause the 

applied product to come into direct contact with the water, possibly resulting in a surface 

slick. Such water rises may occur from flooding due to heavy rain, or flooding resulting 

from dam building by the beavers. While this risk is uncertain, given the limited and 

localized use of polybutene products, this scenario is considered unlikely and any aquatic 

exposure is expected to be negligible.

5.2. Terrestrial Risk

5.2.1. Birds, Mammals, Reptiles, and Terrestrial-Phase Amphibians

Use of polybutene in registered repellent products is not expected to result in toxic effects 

to terrestrial wildlife. Acute toxicity tests show that polybutene has very low toxicity to 

birds and mammals. As described in Section 2.3, registered use is not expected to result 

in contamination of wildlife food items, and animals are not expected to intentionally 

ingest the tacky inorganic product. Therefore, exposure and risk from ingestion is 

believed to be negligible. Exposure to wildlife will likely be limited mainly to dermal 

exposure from contact with treated surfaces. A dermal toxicity test with “4 the Birds 

Transparent bird Repellent Liquid” (Reg. No. 8254-3, 49% AI) found low toxicity, with 

an LD50 of greater than 2000 mg product/kg bodyweight. As there was one mortality at 

the 2000 mg/kg dose, however, some dermal toxicity with heavy exposure is possible. 

Of greater concern than toxicity is potential risk of physical impairment of wildlife that 

may result from contact with this very tacky substance. Larger animals will not likely be 

significantly impacted, but ecological incidents have shown that small birds may be 

killed or incapacitated if they come into contact with the product. Small birds that get 

significant amounts of the products on their wings may be unable to fly. While 

entrapment as a result of labeled use has only been observed in small birds, entrapment 

could occur with other small vertebrates that may climb on woody vegetation or 

buildings, such as small lizards, newts, and toads. Based on the physical properties of 

polybutene, and the application areas, entrapment of insects and other terrestrial 

arthropods is also possible. The risk of entrapment or entanglement of small mammals is 

uncertain.
17

Polybutene product labels contain warnings that serve to mitigate entanglement and 

entrapment of nontarget bird species. All products contain the following statement in the 

Environmental Hazards section of the label:

Small birds may be fatally trapped by this tacky repellent. To reduce hazards to 

legally protected species, and to avoid noncompliance with Federal Migratory 

Bird Treaty Act, follow all instructions on the Directions For Use.

Some products contain additional label statements to protect birds. These are listed in 

Table 5.

Table 5. Label Statement on Polybutene Product Labels for Protection of Nontarget Birds

Product Name EPA Registration 

Number Warning Statements

Tanglefoot Bird 

Repellent 1621-17

Do not apply where repellent may entangle 

desirable bird species, on feeders or on 

vegetation/structures supporting feeders.

Hot Foot Bird Repellent 55943-1

Do not apply on location where desirable birds 

might become entangled in the repellent.

4-the-Birds Repellent 8254-5

Do not apply on locations where desirable birds 

may become entangled by the repellent.

4-the-Birds Transparent 

Bird Repellent Liquid 8254-3

Do not apply at locations where birds protected by 

the Federal Migratory Bird Treaty Act might 

become entangled in the repellent.

Or

NOTE: Do not apply at locations where the user 

has concern that desirable birds may become 

entangled in the repellent.

Do not apply this product directly to trees, bushes 

or vines that are in bloom or bearing fruit except as 

indicated on the label for use as a point on the 

lower areas of tree trunks to discourage damage 

(debarking and cutting) by beavers.

These label statements are beneficial in informing users of the risk of entanglement of 

small birds. The statement on 4-the-Birds Transparent Bird Repellent Liquid to not apply 

to blooming or fruit bearing woody plants would mitigate risk to birds by avoiding use on 

woody plants that would be attractive to fruit-eating wildlife and to nectar-feeding birds 

(e.g., hummingbirds).

In conclusion, use of polybutene is not expected to result in any significant risk to 

terrestrial wildlife through any toxic mode of action, but may pose some limited risk to 

small wildlife species that may become entangled or entrapped in the product. The fact 

that only two incidents of wildlife mortality from labeled use of polybutene have been 

reported over the several decades these products have been registered suggests that 

mortality events are rare occurrences. Of the two incidents that were associated with 

registered use, one (I004169-042) involved the mortality of a couple of house sparrows, a 

very abundant and invasive species. Only one incident has been reported that was not 

associated with a misuse and involved mortality of birds protected by the Migratory Bird 
18

Treaty Act. This incident (I019575-001) occurred when a large flock of cedar waxwings 

happened to reside on a commercial building treated with polybutene, and an unknown 

number of birds died from entanglement with the product. Such events are considered 

rare. In addition, it should be noted that use of this nontoxic repellent likely poses much 

less risk to nontarget species than use of chemical poisons for excluding pest birds, and 

thus may be safer than alternative products.

5.2.2. Terrestrial Invertebrates

Because of the risk of entrapment or entanglement, use of polybutene products may pose 

a hazard to terrestrial invertebrates, including honey bees and insect pollinators, if they 

were to land on a treated surface. However, since invertebrates are not expected to be 

attracted to typical use sites, such as ledges of buildings, few individuals are expected to 

be impacted. Only one product, 4-the-Birds Transparent Bird Repellent Liquid, may be 

used on woody plants. The label statement on this product that prohibits use on woody 

plants while they are in bloom is expected to effectively mitigate risk of this use to

terrestrial invertebrates which feed on nectar and pollen. 

5.2.3. Terrestrial Plants

As described in Section 2.4, exposure to terrestrial plants is expected to be limited to the 

woody plants that are treated directly. No evidence exists that this treatment does any 

harm to the plants that are treated. To date, no such incidents have been reported. 

Therefore, use of polybutene is not believed to pose any significant risk to terrestrial 

plants.

6. Risk to Threatened and Endangered Species

Considering the low toxicity, non-toxic mode of action, use pattern and the extremely 

low water solubility of polybutene, and that aquatic exposure from use of polybutene is 

expected to be negligible, EFED concludes that the currently registered uses of 

polybutene as bird and beaver repellents are not reasonably expected to cause effects to 

federally listed threatened and endangered species. Adverse effects to listed plants are

not reasonably expected to occur because exposure to plants is expected be limited to the 

immediate treatment site, and the chance of occurrence of listed plants at the immediate 

treatment site is extremely small. Furthermore, exposure of plants to a small amount of 

synthetic polymer is not expected to result in any adverse effect. For terrestrial animals,

exposure from dermal absorption or inadvertent ingestion of the product by listed species 

is expected to be unlikely, and considering the low toxicity of polybutene, it would not be 

expected to approach levels that would cause toxicity even if it did occur. Concerning 

physical entanglement with the product, numerous factors make this very unlikely to 

occur to threatened or endangered animal species. These factors are enumerated below.
19

1. Treated area is very small relative to the range of species

Polybutene repellent products are designed for treatment of small areas. The package 

containers contain only enough product for treating a relatively small area. For 

example, one tube of Tanglefoot®, applied onto a 6-ft ledge according to directions, 

would treat only an area of 2.5 ft2. Typical use would involve application only to 

horizontal ledges of buildings and other elevated perching sites immediately adjacent 

to buildings. Expense and labor of application would likely prohibit persons from 

treating large areas with this product.

These small use sites of polybutene repellent would be widely dispersed across the 

landscape. They would comprise only a tiny proportion of the home range of a 

species. Therefore, the likelihood of any particular threatened or endangered animal 

encountering a treated surface would be very small.

2. Most use is expected to occur outside of areas inhabited by listed species

Polybutene repellents are registered for repelling nuisance commensal bird (pigeons, 

house sparrows, and starlings). These species occur mainly in highly developed 

urban and suburban areas with high human populations. In contrast, listed species 

generally occur in areas with little human disturbance. Furthermore, except for the 

“4-the-birds Transparent Liquid,” labels of products allow use only on buildings and 

man-made structures. Most listed species generally do not routinely alight or climb 

on man-made structures. For example, endangered butterfly species are not likely to 

use ledges of buildings. Only “4-the-birds Transparent Liquid” may be applied to 

woody plants for repelling birds and for controlling beaver damage, and the extent of 

sales of that particular product is very small. 

3. Polybutene is an effective physical repellent 

Polybutene is an effective tactile animal repellent. Therefore, in cases when animals 

do encounter a surface treated with the product, they would likely be immediately 

repelled and move away from the site. There generally would not be food resources 

associated with treated sites, such as building ledges, to motivate it to use the site. 

Therefore, listed species that do encounter treated surfaces would be expected to 

leave the site and avoid the area, thereby preventing further contact.

Because of these mitigating factors, the EPA concludes that there is no reasonable 

expectation for any registered use of polybutene repellents to cause direct or indirect 

adverse effects to threatened and endangered species. A “no effect” determination is 

made for all federally listed species. 
20

References

Minerath, E.C., M.P. Schultz, and M.J. Elrod. 2009. Kinetics of the reactions of 

isoprene-derived epoxides in model tropospheric aerosol solutions. Environ. Sci. 

Technol. 43(21):8311-81393.

USEPA. 1995. Reregistration Eligibility Decision: Polybutene. U.S. Environmental 

Protection Agency. EPA- 738-R-95-007. Washington, DC. Available at: 

http://www.epa.gov/oppsrrd1/REDs/4076.pdf

USEPA. 1995. R.E.D. Facts: Polybutene. U.S. Environmental Protection Agency. EPA738-F-95-080. Washington, DC. Available at: 

http://www.epa.gov/oppsrrd1/REDs/factsheets/4076fact.pdf

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of 

Pesticide Programs. United States Environmental Protection Agency (USEPA). 

Environmental Fate and Effects Division. Office of Pesticide Programs. 

Available at http://www.epa.gov/espp/consultation/ecorisk-overview.pdf