ADMINISTRATIVE ORDER 

Exemption of Polybutene from the Requirements of Endocrine Disruptor Screening Program 

Pursuant to the requirements of Section 408(p) of the Federal Food, Drug, and Cosmetic Act 

(FFDCA), EPA has developed an Endocrine Disrupter Screening Program (EDSP) to be used to 

determine whether certain chemicals, such as pesticide active and inert ingredients, may have 

an effect in humans or wildlife similar to an effect produced by a "naturally occurring estrogen, 

or other such endocrine effects as the Administrator may designate." Section 408(p)(4) of the 

FFDCA authorizes EPA, by order, to exempt from the requirements of the endocrine screening 

program required by Section 408(p)(l) "a biologic substance or other substance ifthe 

Adm inistrator determines the substance is anticipated not to produce any effect in humans 

similar to an effect produced by a naturally occurring estrogen." 

Pursuant to the requirements of FFDCA Section 408(p), EPA has evaluated polybutene, the 

active ingredient involved in Registration Review Case 4076 [(EPA-HQ-OPP-2009-0649) available 

at www.regulations.gov. Based on the analysis and rationale that follow, EPA has determined 

that the polymer polybutene has a chemical structure that has no biological activity due to its 

physical and chemical characteristics. Therefore, is not anticipated to produce in humans or 

any other organism an effect similar to that produced by a naturally occurring estrogen, 

androgen, or thyroid hormone. Pursuant to FFDCA Section 408(p), EPA hereby exempts 

polybutene from the requirements of the EDSP. 

Description of pesticide products 

Polybutene is considered the pesticide active ingredient in certain registered pesticide products 

used primarily as nuisance bird (such as pigeons and starlings) repellent and a repellent to 

mammals (such as beavers). The product is a very sticky, non-drying gel that acts as a tactile 

repellent. When birds land on treated objects or surfaces, they are deterred by the sticky tactile 

sensation, tending not to return; beavers prefer gnawing on tree trunks that are not sticky. The 

physically tacky nature of this product provides the repellent action, which unlike many 

pesticide products is not intended to be ingested by the pest species to be effective. 

Physical and chemical characteristics of polybutene 

Polybutene, a copolymer of isobutene and n-butene, is the active ingredient serving as the 

tacti le component of the repellent product. It is a light-colored viscous liquid that is non-drying, 

with adhesive or tacky characteristics. The viscosity is proportional to its polymeric molecular 

weight (increasing as the polymeric chain lengthens). It is stable to light and is not reactive. 

Although it may soften in heat, once the product is set, it does not liquefy and run at 

temperatures likely to be encountered in the outdoor or indoor environment. Polybutene is 

insoluble in water and has a specific gravity of 0.89 g/ml at 3rc. The boiling point is 160°C an·d .· 
the vapor pressure is 0.13 mm Hg at 25oC. The active ingredient in the pesticide product is 

highly viscous polybutene with a molecular weight greater than 1000 Daltons. 

Pesticidal Mode of Action of Polybutene 

The pesticidal mode of action is mechanical in nature, producing an adhesive/sticky surface 

which upon contact discourages animals from roosting, perching, walking, or gnawing on 

treated surfaces. The contact is both brief and involves an extremely low surface area. No 

ingestion is required. There is no chemica l reaction or interaction involved (or expected) in the 

use of polybutene as an active ingredient for current registered pesticide uses. 

Rationale for Exemption of Polybutene 

Section 408(p)(4) ofthe FFDCA authorizes EPA, by order, to exempt from the requirements of 

the screening program required by Section 408(p)(1) "a biologic substance or other substance if 

the Administrator determines that the substance is anticipated not to produce any effect in 

humans similar to an effect produced by a naturally occurring estrogen." 

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) 

held an open meeting on January 29-31, 2013 to discuss issues associated with prioritizing the 

universe of chem icals considered under the EDSP using computational toxicology tools which 

included the exemption of certain chemicals from EDSP screening on the basis of their physical 

and chemical properties. Specifically, the SAP made several recommendations concerning 

polymers that pertain to polybutene. 

"The Panel stated that there are several general reasons why certain compounds with 

inherent physico-chemical properties that are outside particular ranges will not be 

active as endocrine disrupters or be suitable for in vitro testing. These reasons include: 

1) Some compounds are not biologically available to cause effects in whole organisms, 

e.g., not susceptible to passive transport or absorption due to physico-chemical 

properties. Compounds that are not transported across a concentration gradient or · 

otherwise not absorbed due to physico-chemical properties will not be bioavailable. 

These include molecular size (compounds that are too large are unable to migrate 

through membranes) or bulky, i.e., the molecular dimensions in terms of breadth and 

width are too great). Compounds lacking in appropriate aqueous or lipid solubility will 

be unable to be absorbed" ... 

Further, "Polymers with an average molecular weight >1,000 Daltons based on its lack of 

ability to interact and bind to the ER, initiate the ER pathway and initiate systemic 

effects are excluded; and," ... 
"Exclusion of polymers. The Panel agreed that the exclusion of polymers from EDSP 

testing is justified for the most part. Such compounds are typically high molecular 

weight and subsequently, are likely to have limited bioavailability. The assumption that 

they will not trigger the ER-alpha molecular initiating event (MIE) is reasonable. 

However, the Panel also noted that proteins and peptides, which are polymers, are able 

to influence estrogenic actions. Thus, the recommendation was made to more 

rigorously define the term "polymer" for the purposes of categorization. The exclusion 

of polymers should be reconsidered when prioritizing for other (MIEs)." 

The pesticide active ingredient, polybutene, is an insoluble organic polymer with a molecular 

weight >1000 Daltons that is highly stable. It is composed of only hydrogen and carbon, unlike 

biological polymeric macromolecules (e.g. proteins and nucleic acids). Polybutene for repellent 

uses is a viscous and tacky high molecular weight polymer such that systemic absorption _is 

extremely improbable. Based on the physical and chem ical characteristics alone, polybutene 

Registration Review case 4076 is not anticipated to produce in humans or any other organism 

an effect similar to that produced by a naturally occurring estrogen, androgen, or thyroid 

hormone. 

Conclusion 

Based on the structure and physical nature of the isomer, polybutene is not anticipated to 

produce in humans or any other organism an effect similar to that produced by a naturally 

occurring estrogen, androgen, or thyroid hormone. 

Date: I 

James J. 1Vones 

Assistan ~ Administrator 

Office of Chemical Safety and Pollution Prevention 
References: 

US EPA, Scientific Advisory Panel Meeting January 29-21, 2013: Prioritization of the Endocrine 

Disruptor Screening Program Universe of Chemicals for an Estrogen Receptor Adverse Outcome 

Pathway Using Computational Toxicology Tools, SAP Minutes No. 2013-01, May 1, 3013, 98 

pages. http://www.epa.gov/scipoly/sap/meetings/2013/january/012913minutes.pdf 

US EPA, Preliminary Environmental Fate and Ecological Risk Assessment in Support of 

Registration Review of Polybutene. Memorandum from F. Mastrota to J. Wolf. February 28, 

2013. Supporting Materials. [EPA-HQ-OPP-2009-0649] U.S Environmental Protection Agency, 

Washington DC. Accessed online at http://www.regulations.gov. 

US EPA. Polybutene. Human Health Risk Assessment to Support Final Registration Review 

Decision. Memorandum from L. Hansen to J. Wolf. June 13, 2012. Supporting Materials. [EPAHQ-OPP-2009-0649] U.S Environmental Protection Agency, Washington DC. 2013. Accessed 

online at http://www.regulations.gov. 

US EPA. Administrative Order. Exemption of Agrobacterium radiobacter strains K84 and K1026 

from the Requirements of the Endocrine Disruptor Screening Program. [EPA-HQ-OPP-2009-

0878] U.S Environmental Protection Agency, Washington, DC. Accessed online at 

http://www.regulations.gov. 

US EPA. End Use Product Chemistry Review. Memorandum from I. Gairola to J. Gains dated 

May, 21, 2013. U.S Environmental Protection Agency, Washington, DC. 

US EPA. De Minimis Subgroup Opinion on Polybutene Resins. Memorandum from Science Policy 

Panel/Risk Management Forum De Minimis Subgroup to J. Wolf dated January 4, 2013. [EPAHQ-OPP-2009-0878] U.S Environmental Protection Agency, Washington, DC. Accessed online at 

http://www.regulations.gov.