2 

### 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 Programs3 Stressor Source and Distribution

Polybutene is a synthetic, nondryi ng 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 thr ough 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 containi ng 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 polybut ene resins. Polybuten e-1 is a saturated polymer (polyolefin) of buten e-1. Polybutene-1 polymers, unlike polybutene, have high molecular weights. They combine the char acteristics of polyolefins with certain properties of technical polymers. Polybutene re sins are also high molecular polymers that are rigid and exhibit plastic properties.

Polybutene is listed in the Food, Drug, and Cosm etics Act as an indirect food additive (adhesive) and as an ingredient in lipstick 1

.

Table 1. Physical and Chemical Propert ies 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 CH 3 CH 2 CH=CH 2 Isobutene H 2 C=C(CH 3 )

CH 2 -C(CH 3 ) 2 ; C 4 H 8 (monomer)

-[-CH 2 -C(CH 3 ) 2 -]

n ; (C 4 H 8 )

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 Hydrogenat ed 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-m 3 /mol) 4.88 x 10 5 (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 K

ow 17.14 (estimated; EPISuite); No experimental data) pK

a /pK b Not applicable EPISuite (Estimation Program Interface); EPIWeb 4.0

An important physical property in the pestic idal activity of polybutene is its viscosity because the adhesive (repellent) properties depend on viscosity. Viscosity increases with increasing molecular weight of the polym er. For polybutene oligomers of the same number of monomer units (i.e., molecular weig ht), 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 insi de 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 register ed 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 regist ered as a beaver repell ent. A previous tree squirrel repellent use no longer appears on any of the four remaining product labels.

In December 1994, the Agency issued a Rere gistration Eligibility Decision (RED) for polybutene. It was concluded that based on the na ture of the test material, toxic exposure was not likely. However, small birds contacti ng 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 i nvolve only one or severa l individuals. In the RED, the Agency did not anticipate risk s to mammals and aquatic organisms. No endangered species assessment was performed at that time.5 The 1994 RED was issued prior to the 1996 en actment of the Food Quality Protection Act (FQPA). Therefore, no drinking water as sessment 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 w ould be incidental and nonspecific.

Exposure Characteristics

The Agency imposed no environmental fate data requirements fo r 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, dire ct 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, alde hydes and carboxylic acids of low molecular weight. These reac tions are known for other polyalkenes 2 , but there are no specific studies for the polybutene oligom ers. Break down of the polymer from oxidation of the double bond may be a plausibl e reason why aged (w eathered) polybutene is less viscous and effective as a repellent. The estimated K
oc of 2.5 x 10 9 L/kg indicates that it can adsorb strongly to soil or other surfaces. Therefore, pol ybutene is not a mobile
chemical.

Because of the use sites and the sticky co mposition and insolubility of the end-use materials, contamination of water bodies is no t 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 drinki ng water exposure assessments are necessary.

Overview of Pesticide Usage

Polybutene does not have food/feed uses. Its use includes terr estrial non-food, outdoor residential, indoor non-food, and indoor residential.

2 Minerath, E.C., Schultz, M.P., Elrod, M.J. 2009. Kinetic s of the reactions of isoprene-derived epoxides in model tropospheric aerosol solutions. Environ. Sci. Technology , 43(21). Pp.8133-96 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 fo r each of the polybutene end-use products.

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

surfaces are to be cleaned of dust and debr is and made non-porous prior to application. The label(s) recommend that th e product(s) be re-applied when the surface becomes dirty from dust or debris. Geographical or seasona l limitations are not stated in the labels. Therefore, it is assumed that the products ma y 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 knife7 Ecological Effects

Because of its properties and use patte rns, 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 e ffects of polybutene to these non-target taxonomic groups. In addition, the table provid es 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

Birds 1 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 studie s 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 in soluble and formed a su rface 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 a quatic 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 dietar y basis. However, small birds contacting the sticky material ma y become temporarily entrapped and their feathers coated with gel, re ndering 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 indus trial buildings where small legally protected bird specie s 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 bi rd species. This was because the liquid product can be sprayed to the poi nt of runoff on trees, shrubs , bushes, vines, etc., where small bird species could be present.8 Mammals

Polybutene is practically non-toxic to rats on an acute oral (LD 50 >5000 mg/kg) basis. Moreover, mammals would not be likely to consume polybutene becau se of the nature and consistency of the products . Small, scansorial animal s such as tree squirrels and chipmunks might be exposed via their feet if they walk acro ss 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 LD 50 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 LD 50 >2,150 mg/kg bw Practically

nontoxic 43076601

9-day Avian dietary toxicity

LC 50 Bobwhite Quail ( Colinus virginianus ) >5,000 mg/kg bw Practically
nontoxic 43133001

Acute Oral toxicity LD 50 Laboratory

Rat (Rattus norvegicus) >5,000 mg/kg Tox Category

IV 41772401

Dermal LD 50 rabbit >2,000 mg/Kg Tox Category

III 41772402

Incident Reports

EFED’s Environmental Incident Information Sy stem contains the report of an incident (IO 19575-001; 2008) involving 30-80 cedar waxwi ngs (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 concen trations. 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 si mple 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 surfa ce. It does not contac t soil or water in any9 significant amounts and does not have the pot ential for runoff or leaching to ground water. However, the sticky nature of the product may affect non-ta rget birds and other
vertebrate and invertebrate animal s that come in contact with it.

Analysis Plan

Polybutene is used as a bird and beaver repe llent. It does not ha ve a toxic mode of action, but instead is used to repel bird s and small mammals by its sticky nature. Apparently, these animals do not like to wa lk 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 ar eas or tree trunks with negligible potential for offsite transport. It does not contact so il 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 te rrestrial 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 exposur e to non-target wildlife is minimal.

The Agency anticipates that no quantitative ec ological risk assessment will be needed. However, a qualitative endangered species assessment will be conducted for the polybutene uses. The minimal toxicity tes ting requirements have been satisfied and additional data or further testing will not be needed for the current use patterns.