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REGISTRATION REVIEW

PROBLEM FORMULATION FOR: 

POLYBUTENE

PREPARED BY: 

Jim Goodyear, Ph.D., Biologist 

Silvia Termes, Ph.D., Chemist 

APPROVED BY: 

Dana Spatz, Branch Chief 

Environmental Risk Branch 3 

Environmental Fate and Effects Division 

Office of Pesticide Programs 
3

Stressor Source and Distribution 

Polybutene is a synthetic, nondrying liquid or gel that remains a sticky coating after being 

applied. The polymer is registered for use as a bird and small mammal repellent. 

Polybutene does not kill targeted animals through a toxic mode of action, but instead it is 

used to repel birds and mammals because of its sticky nature. Apparently, these animals 

do not like to walk on a sticky surface and that keeps them away from coming back to the 

treated surfaces. Polybutene’s sticky quality therefore is the source of the repellent action 

of pesticide products containing this active ingredient. 

Polybutene is a homopolymer (same repeating unit) of the monomer butene, both normaland isobutene. Polybutene is better defined as an oligomer because the number of units is 

low, typically 5 or 6 units. The chemical substance (polybutene) being assessed should 

not be confused with polybutene-1 or polybutene resins. Polybutene-1 is a saturated 

polymer (polyolefin) of butene-1. Polybutene-1 polymers, unlike polybutene, have high 

molecular weights. They combine the characteristics of polyolefins with certain 

properties of technical polymers. Polybutene resins are also high molecular polymers that 

are rigid and exhibit plastic properties. 

Polybutene is listed in the Food, Drug, and Cosmetics Act as an indirect food additive 

(adhesive) and as an ingredient in lipstick1

.

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) 

Butene 106-98-9 (monomer) 

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 CC(CC)C(C)C(C)CC(CC)C(C(C)CC(CC)C(C)C(C)CC(CC)C(C)C(C)CCCC)C 

 

1 No Authors Cited. 2008 Final report of the cosmetic ingredient review expert panel on the safety 

assessment of Polyisobutene and Hydrogenated Polyisobutene as used in cosmetics, Int. J. Toxicol., 27 

(Supplement) 4: 83-106. 
4

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-m3

/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 

An important physical property in the pesticidal activity of polybutene is its viscosity 

because the adhesive (repellent) properties depend on viscosity. Viscosity increases with 

increasing molecular weight of the polymer. For polybutene oligomers of the same 

number of monomer units (i.e., molecular weight), viscosity will decrease with increasing 

temperature. 

Polybutene products (42.8 to 97% a.i.) may be used outdoors or indoors, on buildings or 

adjacent structures (for example, on beams, girders, ledges, windowsills, gutters, trees, 

shrubs, and vines) where birds land or roost. It is applied inside of buildings to 

discourage birds from perching (frequently in connection with eating the grain that is 

stored in the building). It is also applied to tree trunks up to two feet from the ground to 

deter beavers from gnawing. 

Formulations include a gel, which is applied as a bead strip to surfaces with a ready-touse tube or caulking gun, and a liquid concentrate which is applied with a paint brush or 

sprayed on using a hand or pressure sprayer.

Conclusions from Previous Risk Assessments 

Polybutene has been registered in the United States since 1960 for use as an insect 

control agent. It was registered in 1963 as a bird repellent and in 1967 as a tree squirrel 

repellent. The insect repellents were later deregulated because their mode of action is 

more to trap than repel. In 2007, it was registered as a beaver repellent. A previous tree 

squirrel repellent use no longer appears on any of the four remaining product labels. 

In December 1994, the Agency issued a Reregistration Eligibility Decision (RED) for 

polybutene. It was concluded that based on the nature of the test material, toxic exposure 

was not likely. However, small birds contacting the sticky material may be temporarily 

trapped and their feathers coated with gel, rendering them unable to fly. Such incidents 

can be fatal for small birds, but generally involve only one or several individuals. In the 

RED, the Agency did not anticipate risks to mammals and aquatic organisms. No 

endangered species assessment was performed at that time. 
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The 1994 RED was issued prior to the 1996 enactment of the Food Quality Protection 

Act (FQPA). Therefore, no drinking water assessment was performed at that time. 

Polybutene’s repelling action is not chemical in nature, but physical. Incidental trapping 

of non-target birds on the sticky surface has been documented. Polybutene applied to a 

surface according to the recommendations on the labels, is not likely to move off-site. 

Thus, polybutene exposure in aquatic systems is unlikely. The product is not to be stored 

or disposed of in food or feed sites. 

It was concluded that adverse effects to non-target animals would be incidental and nonspecific. 

Exposure Characteristics 

The Agency imposed no environmental fate data requirements for reregistration of 

polybutene because of its physical properties and use patterns. The hydrolysis data 

requirement was waived based on the limited environmental exposure that results from its 

use. 

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

(short-term study) and microbial degradation. However, any aging of exposed polybutene 

in an open environment for a prolonged period of time may be associated with 

photooxidation of the –C=C- bond to generate epoxides, aldehydes and carboxylic acids 

of low molecular weight. These reactions are known for other polyalkenes2

, but there are 

no specific studies for the polybutene oligomers. Break down of the polymer from 

oxidation of the double bond may be a plausible reason why aged (weathered) polybutene 

is less viscous and effective as a repellent. The estimated Koc of 2.5 x 109

 L/kg indicates 

that it can adsorb strongly to soil or other surfaces. Therefore, polybutene is not a mobile 

chemical. 

Because of the use sites and the sticky composition and insolubility of the end-use 

materials, contamination of water bodies is not expected to occur. When used according 

to the labels, polybutene is not expected to move off-site (i.e., from the treated surface) 

and reach surface water by runoff. It is not expected to leach into ground water. 

Therefore, no aquatic exposure or drinking water exposure assessments are necessary. 

Overview of Pesticide Usage

Polybutene does not have food/feed uses. Its use includes terrestrial non-food, outdoor 

residential, indoor non-food, and indoor residential. 

 

2 Minerath, E.C., Schultz, M.P., Elrod, M.J. 2009. Kinetics of the reactions of isoprene-derived epoxides in 

model tropospheric aerosol solutions. Environ. Sci. Technology, 43(21). Pp.8133-9 
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There are four polybutene end-use products. They are primarily bird repellents, but one 

of the products is intended to repel beavers. 

Use Characterization

Table 2 summarizes the use information for each of the polybutene end-use products. 

All labels emphasize the importance of a clean surface before applying the product. The 

surfaces are to be cleaned of dust and debris and made non-porous prior to application. 

The label(s) recommend that the product(s) be re-applied when the surface becomes dirty 

from dust or debris. Geographical or seasonal limitations are not stated in the labels. 

Therefore, it is assumed that the products may be used throughout the U.S. at any time. 

Table 2 Polybutene End-Use Products 

Product Polybutene 

Content 

EPA Reg. No. Uses Application 

Method(s) 

4 the Birds Bird 

Repellent 

Transparent Liquid 

49% 8254-3 To discourage 

starlings from 

roosting or 

perching on inside 

supports of 

buildings and 

structures and on 

the branches of 

adjacent vegetation 

To discourage 

beavers from 

damaging trees 

Spray 

Paint brush for 

surfaces difficult to 

cover by spraying 

4 the Birds 

Bird Repellent 

93% 8254-5 To discourage 

pigeons and 

starlings from 

buildings and 

structures 

Using the product 

cartridge inside a 

caulking gun 

and/or putty knife 

Hot Foot Bird

Repellent 

93.5% 55943-1 To prevent pigeons 

from perching or 

roosting where 

applied 

Using the product 

cartridge inside a 

caulking gun 

and/or putty knife 

Tanglefoot 

Bird Repellent 

87% 1621-17 To repel pigeons, 

starlings, and 

house sparrows 

from buildings and 

adjacent structures 

Using the product 

cartridge inside a 

caulking gun 

and/or putty knife 
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Ecological Effects

Because of its properties and use patterns, honey bees, small mammals, aquatic 

organisms, and other wildlife are not likely to ingest or otherwise be exposed to 

significant amounts of polybutene. Many of the studies usually required for 

reregistration were therefore waived. 

Table 3 provides a summary of the taxonomic groups and the surrogate species tested to 

help understand potential acute ecological effects of polybutene to these non-target 

taxonomic groups. In addition, the table provides a preliminary overview of the potential 

acute toxicity of polybutene by providing the acute toxicity classifications. 

Table 3. Species Evaluated for Ecological Effects of Polybutene 

Taxonomic Group Species Acute Toxicity 

Classification 

Birds1 Mallard (Anas platyrhynchos) 

Bobwhite (Colinus virginianus) Practically non-toxic 

Mammals Laboratory rat (Rattus norvegicus) Practically non-toxic 

Aquatic Species No aquatic studies were required No data required 

Terrestrial plants No plant studies were required No data required 1

 Birds represent surrogates for terrestrial-phase amphibians and reptiles. 

Attempts to conduct acute toxicity studies with the rainbow trout and Daphnia magna 

were unsuccessful, as the test material is insoluble and formed a surface slick in the test 

vessel, resulting in unacceptably low levels of dissolved oxygen. After all appropriate 

means of increasing the solubility of polybutene were exhausted, EPA waived the 

requirements for freshwater fish and aquatic invertebrate toxicity studies. 

Birds

Based on the nature of the test material, toxic exposure is not likely. Polybutene is 

practically non-toxic to birds on an acute oral and a sub-acute dietary basis. However, 

small birds contacting the sticky material may become temporarily entrapped and their 

feathers coated with gel, rendering them unable to fly. When such incidents occur, they 

can be fatal, but generally involve only one or several individuals. Risk to non-target 

birds also is probably alleviated by the fact that the use sites for these products are 

principally highly localized in urban commercial and industrial buildings where small 

legally protected bird species are unlikely to be exposed. 

At the time of the RED, the Agency was concerned that the liquid formulation of 

polybutene could pose some risks to small bird species. This was because the liquid 

product can be sprayed to the point of runoff on trees, shrubs, bushes, vines, etc., where 

small bird species could be present. 
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Mammals

Polybutene is practically non-toxic to rats on an acute oral (LD50 >5000 mg/kg) basis. 

Moreover, mammals would not be likely to consume polybutene because of the nature 

and consistency of the products. Small, scansorial animals such as tree squirrels and 

chipmunks might be exposed via their feet if they walk across a treated site. However, 

the material is a repellent and is most likely to simply deter them from the site than to be 

lethal. The LD50 was greater than 2000 mg/kg, a limit dose, for acute dermal toxicity 

with rabbits, which is toxicity category III. 

Table 4 provides a summary of toxicity data available for birds and mammals. 

Table 4. Ecological Effects Data Summary for Polybutene

Measures of 

Effect Species Toxicity Value 

Toxicity 

Classification MRID 

14-day Avian 

acute oral 

toxicity LD50 

>2,150 

mg/kg bw 

Practically 

nontoxic 43076601 

9-day Avian 

dietary toxicity 

LC50 

Bobwhite 

Quail 

(Colinus 

virginianus) >5,000 

mg/kg bw 

Practically 

nontoxic 43133001 

Acute Oral 

toxicity LD50

Laboratory 

Rat 

(Rattus 

norvegicus) 

>5,000 

mg/kg 

Tox Category 

IV 41772401 

Dermal LD50 rabbit >2,000 

mg/Kg 

Tox Category 

III 41772402 

Incident Reports

EFED’s Environmental Incident Information System contains the report of an incident 

(IO 19575-001; 2008) involving 30-80 cedar waxwings (Bommycilla cedrorum). One (at 

least) was incapacitated and one (at least) was killed from the use of a polybutene product 

in a building. 

Conceptual Model

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

biologically significant concentrations. An exposure pathway is the means by which a 

pesticide moves in the environment from a source to an ecological receptor. For an 

ecological pathway to be complete, it must have a source, a release mechanism, an 

environmental transport medium, a point of exposure for ecological receptors, and a 

feasible route of exposure. 

The conceptual model for polybutene is simple because the sticky polybutene products 

are applied to clean, non-porous surfaces of buildings or tree trunks to repel undesirable 

birds or beavers. The product stays on the surface. It does not contact soil or water in any 
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significant amounts and does not have the potential for runoff or leaching to ground 

water. However, the sticky nature of the product may affect non-target birds and other 

vertebrate and invertebrate animals that come in contact with it. 

Analysis Plan 

Polybutene is used as a bird and beaver repellent. It does not have a toxic mode of 

action, but instead is used to repel birds and small mammals by its sticky nature. 

Apparently, these animals do not like to walk on a sticky surface and that keeps them 

from coming back to the treated surfaces. The products are used in discrete locations 

with a spatial extent limited to building size areas or tree trunks with negligible potential 

for offsite transport. It does not contact soil or water in appreciable amounts and does not 

have the potential for runoff or leaching to ground water. The application method does 

not allow for drift to terrestrial areas or to water bodies. The product is likely to impact 

terrestrial non-target organisms only at the point of treatment, but beyond this, direct or 

indirect exposure to ecological receptors is not expected. If used as directed on the 

product label, then the likelihood of exposure to non-target wildlife is minimal. 

The Agency anticipates that no quantitative ecological risk assessment will be needed. 

However, a qualitative endangered species assessment will be conducted for the 

polybutene uses. The minimal toxicity testing requirements have been satisfied and 

additional data or further testing will not be needed for the current use patterns.