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Table of Contents 

I. Introduction ............................................................................................................................... 3

A. General Background ........................................................................................................... 4 

II. Scientific Assessments ............................................................................................................. 4

B. Environmental Assessment ................................................................................................. 4

Threatened and Endangered Species ...................................................................................... 5 

C. Human Health Assessment ................................................................................................. 5 

D. Endocrine Disruptor Screening Program ............................................................................ 6 

III. Registration Review Decision ................................................................................................ 6
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I. Introduction 

 This document is the Environmental Protection Agency’s (EPA or the Agency) 

Registration Review Decision for undecylenic acid (UDA) which is being issued pursuant to 40 

CFR Sections 155.57 and 155.58. UDA is co-formulated with dioctyl sodium sulfosuccinate 

(DSS) for which a separate registration review decision has been issued, located in the DSS 

Registration Review docket, EPA-HQ-OPP-2010-1006. A registration review decision is the 

Agency’s determination that a pesticide meets, or does not meet, the standard for registration in 

the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). 

FIFRA, as amended by the Food Quality Protection Act (FQPA) of 1996, mandated the 

continuous review of existing pesticides. All pesticides distributed or sold in the United States 

must generally be registered by EPA, based on scientific data showing that they will not cause 

unreasonable risks to human health or the environment when used as directed on product 

labeling. The registration review program is intended to make sure that, as the ability to assess 

and reduce 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 or the 

environment. Changes in science, public policy, and pesticide use practices will occur over time. 

Through the registration review program, the Agency periodically reevaluates pesticides to make 

sure that as change occurs, products in the marketplace can be used safely. Information on this 

program is provided at: http://www.epa.gov/oppsrrd1/registration_review/. 

 In 2006, the Agency implemented the Registration Review program pursuant to FIFRA 

section 3(g) and will review each registered pesticide every 15 years to determine whether it 

continues to meet the FIFRA standard for registration. Pursuant to 40 CFR § 155.50, the 

Agency formally initiated registration review for UDA (Case 4095). The following timeline 

highlights significant events that have occurred during the registration review of UDA: 

 December 21, 2011– Publication of the UDA Summary Document that included the 

Preliminary Work Plan (PWP), and was accompanied by the ecological Problem 

Formulation and the human health Scoping Document in the docket (EPA-HQ-OPP2011-0910) for a 60-day public comment period. 

 

 April 18, 2012–Final Work Plan (FWP) for UDA is signed. No public comments were 

received during the 60-day comment period on the UDA Summary Document. In the 

PWP, EPA specifically solicited comments on environmental justice, water quality 

concerns, and trade irritants. The FWP notes that no additional ecological or human 

health data were expected to be needed for UDA registration review because sufficient 

information was available to conduct qualitative risk assessments to support a proposed 

registration review decision, pursuant to 40 CFR Section 155.53(b). 

 March 7, 2013 – Publication of Undecylenic Acid Summary of Human Health Risk 

Assessment in Support of Registration Review1 and Preliminary Environmental Fate and 

Ecological Risk Assessment for the Registration of Dioctyl Sodium Sulfosuccinate (Case 

 

1 http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2011-0910-0004
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#4029) and Undecylenic Acid (Case #4095)2 for a 60-day public comment period; no 

public comments were received. 

 June 4, 2014 –The Undecylenic Acid (UDA) Proposed Registration Review Decision3

published in the Federal Register (79 FR 32284) (FRL-9911-16) for a 60 day comment 

period. One comment was received during the comment period, from the Center for 

Biological Diversity, concurring with the Agency’s “no effect” determination under the 

Endangered Species Act (ESA) for all listed species and designated critical habitat for 

such species. Endangered species are discussed further below. 

 The documents cited above and additional information on UDA can be found in EPA’s 

public docket (EPA-HQ-OPP-2011-0910) at www.regulations.gov. 

A. General Background 

UDA is an insecticide and miticide in shampoos and spray products registered for indoor 

use on pets including dogs, cats, puppies, kittens, and reptiles to kill mites and fleas on contact. 

The first pesticide product containing UDA was registered in 1986. These products may be 

applied to the pet’s coat or to bedding and terrarium surfaces. UDA is co-formulated with the 

active ingredient dioctyl sodium sulfosuccinate (DSS). UDA is an organic unsaturated fatty acid 

that has structural similarities to those found in the human diet. 

In addition to its pesticidal uses registered by EPA, UDA has other uses in unrelated 

products; exposure to UDA is dominated by these non-pesticidal uses. UDA has antifungal 

properties and is approved by the U.S. Food and Drug Administration (FDA) as an over-thecounter drug to treat various skin conditions in humans. It is also used as a fragrance, as a 

flavoring ingredient, is present in human sweat, and is classified as “Generally Recognized as 

Safe” (GRAS) by the Food and Drug Administration. 

II. Scientific Assessments 

B. Environmental Assessment 

A summary of the Agency’s environmental risk assessment is presented below. For a 

detailed discussion, see the Preliminary Ecological Risk Assessment for the Registration of 

Dioctyl Sodium Sulfosuccinate (Case #4029) and Undecylenic Acid (Case #4095) noted above. 

The Agency’s risk assessment evaluated the active ingredients from two different registration 

review cases, DSS and UDA, which are registered for use as co-formulated pet shampoo 

products. The findings of the assessment are applicable to both Registration Review cases. 

UDA is not expected to persist in the environment; it is a naturally occurring unsaturated 

fatty acid that is expected to readily biodegrade into shorter chain fatty acids and carbon dioxide. 

Terrestrial exposure is not expected to result from indoor usage and was not assessed. UDA has 

 

2 http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2011-0910-0009 3

 Available at 
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the potential to enter waterways through wastewater treatment plants (WWTPs) after use as a pet 

shampoo. Risks to aquatic taxa were assessed. 

The EPA Office of Pollution Prevention and Toxics (OPPT) Down the Drain module EFast4

 was used to estimate DSS/UDA concentrations in receiving waters based on confidential 

production data and assumptions of 24% WWTP removal and no dilution. Toxicity endpoints 

were estimated using Quantitative Structure Activity Relationship (QSAR) predictive modeling. 

The estimated environmental concentration of UDA is orders of magnitude below the QSAR 

estimated concentration expected to cause adverse effects in aquatic organisms. Therefore, risk 

to aquatic taxa is not expected. 

Threatened and Endangered Species 

There is no exposure to non-target terrestrial organisms, and the Agency has determined 

that there is minimal risk of adverse effects to non-target aquatic organisms. Therefore, EPA has 

made a “no effect” determination under the Endangered Species Act (ESA) for all listed species 

and designated critical habitat for such species, and has therefore concluded that consultation 

with the Fish and Wildlife Service and the National Marine Fisheries Service under ESA section 

7(a)(2) is not required. 

C. Human Health Assessment 

 The Agency considered the most recent human health risk assessment, the HED scoping 

document, and the most updated Agency science policies and risk assessment methodologies to 

prepare a qualitative risk assessment in support of the registration review of UDA. The most 

recent human health risk assessment was conducted in 1995. Because of the limited uses, 

minimal potential for exposure, low toxicity, and its use as a pharmaceutical drug, the Agency 

determined that a quantitative human health risk assessment was not required under registration 

review. For a detailed discussion, see the Undecylenic Acid Summary of Human Health Risk 

Assessment in Support of Registration Review noted above. A summary of the Agency’s human 

health risk assessment is presented below. 

There are no dietary, residential, occupational, or aggregate risks of concern for UDA. 

All toxicity data requirements were waived when UDA was registered, except for acute toxicity 

studies; therefore endpoints have not been selected for UDA. UDA has no registered food uses as 

a pesticide and no residue chemistry data were required or submitted. There are no tolerances 

established for UDA and no Canadian or Codex MRLs. Based on registered uses, drinking water 

is not a concern. Since no quantitative risk assessment was required under registration review 

due to the low toxicity of UDA, quantitative residential handler, occupational, post-application 

exposure and aggregate assessments were not required. It has not been determined that UDA 

shares a common mechanism of toxicity with other chemicals; therefore a cumulative risk 

assessment was also not required. 

 

4 http://www.epa.gov/oppt/exposure/index.htm
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D. Endocrine Disruptor Screening Program 

Pursuant to FFDCA Section 408(p)(4), EPA has exempted UDA from the requirements 

of the EDSP in an Administrative Order entitled Exemption of Dioctyl Sodium Sulfosuccinate 

(DSS) and Undecylenic Acid (UDA) from the Requirements of the Endocrine Disruptor 

Screening Program, dated April 11, 2014. The Order is available in the docket for this 

registration review at EPA-HQ-OPP-2011-0910. The Administrative Order describes the 

analysis and rationale that the Agency used to evaluate UDA in order to determine that it 

qualifies for the exemption. 

III. Registration Review Decision 

In accordance with 40 CFR Sections 155.57 and 155.58, the Agency is issuing this 

Registration Review Decision document, thus concluding the registration review for UDA. In 

addition, EPA does not expect UDA to have direct or indirect adverse effects to non-listed and 

listed species or to adversely modify any designated critical habitat for such species. EPA has 

made a “no effect” determination under the ESA for all listed species and designated critical 

habitat for such species. Further, the Agency has also determined that based on its structure, 

chemical nature, and history of uses for human consumption and pharmaceutical applications, 

UDA is exempt from the EDSP requirement. EPA’s Registration Review Decision 

determination for UDA is that the pesticide meets the standard for registration under FIFRA.