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Morpel® Repellent 326 – Table of Contents

I. Introduction 3

II. Statutory and Regulatory Authority 3

III. Morpel® Repellent 326 Chemical Facts 4

IV. Use and Usage Information 4

V. Recent Actions 5

VI. Scientific Assessments 5

VII. Combined Work Plan, Summary Document, and Proposed Interim Registration

Review Decision 9

VIII. Next Steps and Timeline 9

Appendix A – Additional Areas Considered in the Morpel® Repellent 326 Registration Review 11

References:

This document summarizes the Environmental Protection Agency’s current position based on the 

following documents:

1. Registration Review – Preliminary Ecological Risk Assessment and Endangered Species Effects 

Determination for Dipropyl isocinchomeronate (aka Morpel® Repellent 326, formerly MGK® Repellent 

326). Melanie Biscoe, Katherine Stebbins, Melissa Panger. October 20, 2014.

2. Dipropyl-isocinchomeronate (Di-N-propyl isocinchomeronate): Scoping and Preliminary Risk Assessment for 

Registration Review. Thurston G. Morton, Kelly O’Rourke, Abdallah Khasawinah. May 19, 2015.

3. BEAD Chemical Profile for Registration Review: Dipropyl isocinchomeronate (PC Code 047201). David 

Brassard, Sepehr Haddad, Michelle Ranville. April 28, 2014.

4. Dipropyl Isocinchomeronate (MGK-326): Tier I Review of Human Incidents. Shanna Recore. April 9, 

2014.

These and other supporting documents for the Morpel® Repellent 326 registration review case may 

be found in the docket EPA-HQ-OPP-2014-0578 at http://www.regulations.gov.
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I. INTRODUCTION

The docket for dipropyl isocinchomeronate (referred to within as Morpel® Repellent 326

and Morpel®; formerly MGK 326) is now open (EPA-HQ-OPP-2014-0578), initiating the first 

public comment period for this registration review. This document is the Environmental Protection 

Agency’s (EPA or the Agency herein) combined Work Plan, Summary Document, and Proposed Interim 

Registration Review Decision for Morpel® Repellent 326. It is being issued pursuant to 40 CFR Sections 

155.50, 155.56, and 155.58. This document explains what EPA’s Office of Pesticide Programs 

knows about Morpel® Repellent 326, highlighting anticipated data and assessment needs and 

providing an anticipated timeline for completing the Morpel® Repellent 326 Registration Review. It 

also includes the Agency’s Proposed Interim Registration Review Decision for Morpel® Repellent 

326. In addition to general areas on which the public may wish to comment, the Appendix 

highlights topics of special interest to the Agency where additional information could be of 

particular use.

A registration review decision is the Agency’s determination whether a pesticide meets, or 

does not meet, the standard for registration under the Federal Insecticide, Fungicide, and 

Rodenticide Act (FIFRA). The Agency may issue, when it determines it to be appropriate, a 

proposed interim registration review decision before completing registration review. Among other 

things, the proposed interim registration review decision may require new risk mitigation measures, 

impose interim risk mitigation measures, identify data or information required to complete the 

review, and include schedules for submitting the required data, conducting the new risk assessment 

and completing registration review.

Morpel® Repellent 326 is an insect repellent registered for use as a human and companion 

animal (dog, cat, and horse) insect repellent. Morpel® is never the sole active ingredient; it is always 

coformulated with other insecticides/repellents, such as DEET, piperonyl buxtoxide, and pyrethrins, to 

broaden their spectrum of repellency. Morpel® 326 is registered for use to repel flies, gnats, and other 

flying and biting insects. Morpel® 326 is only registered for indoor non-food and residential use.

The Reregistration Eligibility Decision document (RED) for dipropyl isocinchomeronate was 

completed on March 11, 2005. For further information about Morpel® Repellent 326, additional 

documents can be found in EPA’s public docket (EPA-HQ-OPP-2014-0578) at www.regulations.gov.

II. STATUTORY AND REGULATORY AUTHORITY

The Food Quality Protection Act (FQPA) of 1996 mandated a registration review program. 

All pesticides distributed or sold in the U.S. generally must 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 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 www.epa.gov/oppsrrd1/registration_review/.
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The Agency is implementing the registration review program pursuant to Section 3(g) of 

FIFRA, and will review each registered pesticide every 15 years to determine whether it continues to 

meet the FIFRA standard for registration. The regulations governing registration review begin at 40 

CFR 155.40. The Agency will consider benefits information and data as required by FIFRA. The 

public phase of registration review begins when the initial docket is opened for each case. The 

docket is the Agency’s opportunity to state what it knows about the pesticide and what additional 

risk analyses and data or information it believes are needed to make a registration review decision.

III. MORPEL® REPELLENT 326 CHEMICAL FACTS

PC code 047201

Case Number 2215

CAS Number 136-45-8, 3737-22-2

Year first registered 1957

Pesticide Type Conventional Chemical

Chemical class Insecticide

Reregistration Eligibility 

Decision (RED)

March 2005

Tolerance Reassessment 

Eligibility Decision 

(TRED)

Not applicable

Cumulative Group Not applicable; The Agency has not determined that dipropyl 

isocinchomeronate shares a common mechanism of toxicity with 

other chemical substances.

40 CFR Citation Not applicable; There are no food/feed tolerances established for 

dipropyl isocinchomeronate in 40 CFR.

Dual-use Not applicable

Non-pesticidal uses Not applicable

Pesticide Re-evaluation 

Division, Chemical Review 

Manager

Marianne Mannix, mannix.marianne@epa.gov, 703-347-0275

Registration Division, 

Product Manager

Jennifer Urbanski, urbanski.jennifer@epa.gov, 703-347-0156

IV. USE AND USAGE INFORMATION

Morpel® Repellent 326 is an ingredient contained in insect repellent products registered for 

application to humans (personal use) and pets (health care products). Morpel® Repellent 326 is 

never used as the sole active ingredient; it is used to expand the repellency of other insecticides. 

Below is a summary of the use/usage of Morpel® Repellent 326. For more details please see BEAD 

Chemical Profile for Registration Review: Dipropyl isocinchomeronate (PC Code 047201) (April 28, 2014).

Summary of Use Morpel® Repellent 326 is formulated with a number of other 

insecticide active ingredients to extend the spectrum and period of 

repellency.

Use Sites Indoor non-food and residential use
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Summary of Usage Annual average of 6,800 pounds/year; 4,800 for insect repellent use 

on humans, 2,000 for animal-only insect repellent uses

Formulation Type(s) Aerosol, impregnated material (towelette), pet dip

Technical Registrant(s) Vertellus Specialties, Inc.

No. of Registrations 39

Restricted Use No

V. RECENT ACTIONS

While use of Morpel® 326 on dairy cattle is mentioned in supporting documents, there are 

no active registrations which include this use site on any technical or end use label.

VI. SCIENTIFIC ASSESSMENTS

A. Human Health Assessment

The human health exposure and toxicological database is adequate for registration review of

Morpel® 326. The Agency does not need additional studies in order to characterize the human 

health exposure, hazard and risk from Morpel® 326. Because no additional human health or toxicity 

data are needed for the registration review of Morpel® 326, the Agency has determined that it is 

appropriate to conduct a preliminary human health risk assessment for Morpel® 326. A summary of 

the Agency's preliminary human health risk assessment is presented below. For detailed information

see: Dipropyl-isocinchomeronate (Di-N-propyl isocinchomeronate): Scoping and Preliminary Risk Assessment for 

Registration Review dated May 19, 2015 dated in the public docket (EPA-HQ-OPP-2014-0578) which 

can be accessed at www.regulations.gov.

A summary of the Agency’s human health and environmental fate and ecological risk 

assessments, and Registration Review – Preliminary Ecological Risk Assessment and Endangered Species Effects 

Determination for Dipropyl isocinchomeronate (aka Morpel® Repellent 326, formerly MGK® Repellent 326) 

(October 20, 2015) is presented below. For the detailed risk assessments, see the Morpel® Repellent 

326 public docket (EPA-HQ-OPP-2014-0578) at www.regulations.gov.

1. Risk Conclusions 

 

Hazard Characterization 

The toxicological database is considered adequate for characterizing hazard and assessing 

risk from Morpel® Repellent 326. The Agency does not anticipate requiring any additional studies 

for registration review.

Dietary Assessment

There are no registered food uses for Morpel® Repellent 326 and it is not likely to occur in 

drinking water; therefore there is no concern for dietary risk. 

Residential Assessment

Residential exposure is expected based on the registered residential uses of Morpel® 326. 

However, based on a conservative quantitative assessment, no risks of concern were identified.
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Occupational Assessment

Based on a screening-level assessment, it was determined that there are no risks of concern 

associated with exposure during occupational treatment of companion animals. Occupational post 

application exposure is expected to be minimal because it is assumed that treated animals would be 

returned to their residential settings after treatment.

Aggregate Assessment

Since there is no concern for dietary risk, an aggregate risk assessment for Morpel® 326 was 

not completed.

2. Human Health Incidents

The Office of Pesticide Programs (OPP) Incident Data System (IDS) was used to retrieve 

pesticide incident data on Morpel® 326. The IDS records incidents in one of two modules: Main 

IDS and Aggregate IDS. Main IDS contains incidents resulting in higher severity outcomes and 

provides more detail with regard to case specifics. Aggregate IDS contains incidents resulting in less 

severe human incidents (minor, unknown, or no effects outcomes). In the Main IDS, from January 

1, 2009 to March 5, 2014, there were no incidents involving the single chemical; Morpel® 326 

reported in the database. There were 26 incidents reported involving more than one chemical. 

Twenty five of these incidents were classified as moderate severity, not life threatening and the 

person returned to his/her pre-exposure state of health with no additional residual disability. In the 

Aggregate IDS, from January 1, 2009 to March 5, 2014, there were 449 reported incidents involving 

Morpel® 326. One hundred seventy nine incidents were classified as unknown or no effects and 270 

incidents were classified as minor severity. 

The Centers for Disease Control and Prevention/National Institute for Occupational Safety 

and Health (CDC/NIOSH) Sentinel Event Notification System for Occupational Risk-Pesticides 

(SENSOR) databases were also queried. The NIOSH SENSOR-Pesticides 1998-2010 data identified 

73 cases involving Morpel® 326, all involving multiple active ingredients. Of the 73 cases involving 

the single active ingredient, 68 cases were low in severity, three cases were moderate in severity, and 

two cases were high severity.

Reports of adverse health effects allegedly due to a specific pesticide exposure (i.e., an 

"incident") are largely self-reported and therefore, generally speaking, neither exposure to a pesticide 

or reported symptom (or the connection between the two) is validated or otherwise confirmed. 

Typically, causation cannot be determined based on incident data. For detailed information, see 

Dipropyl Isocinchomeronate (MGK-326): Tier I Review of Human Incidents dated April 9, 2014 in the public 

docket (EPA-HQ-OPP-2014-0578) at www.regulations.gov.

3. Food Tolerances

There are no existing food tolerances for Morpel® Repellent 326 because it is not 

established for any food or feed uses.

B. Ecological Assessment

Based on the low use pattern, diffusion over a large treatment area, and the low probability 

of non-target organism exposure to Morpel® Repellent 326, the Agency has determined that it is 
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appropriate to conduct an abbreviated preliminary ecological risk assessment for Morpel® 326. A 

summary of the Agency's preliminary ecological risk assessment is presented below. For detailed 

discussions see Registration Review – Preliminary Ecological Risk Assessment and Endangered Species Effects 

Determination for Dipropyl isocinchomeronate (aka Morpel® Repellent 326, formerly MGK® Repellent 326), 

dated October 20, 2014, in the public docket (EPA-HQ-OPP-2014-0578) which can be accessed at 

www.regulations.gov.

The Agency has completed a screening-level endangered and threatened (listed) species 

assessment for Morpel® 326. The Agency is currently working with its federal counterparts and 

other stakeholders to implement an interim approach for assessing potential risk to listed species 

and their designated critical habitats. Once the scientific methods necessary to complete risk 

assessments for listed species and their designated critical habitats are finalized, the Agency will 

complete its endangered species assessment for Morpel® 326. Based on its registered use pattern, 

the Agency does not anticipate listed terrestrial species to come into contact with Morpel® 326. 

Also, based on a conservative analysis, estimated risk quotients for aquatic species are below levels 

of concern (LOCs). Therefore, the Agency anticipates making a "no effects" determination under 

the Endangered Species Act (ESA) for all listed species, and no adverse modification of designated 

critical habitat for such species is expected, unless information provided to the Agency leads to a 

change in this anticipated determination.

1. Environmental Fate and Exposure 

Morpel® 326 remains stable under acidic conditions, and hydrolyzes in neutral and alkaline 

environments. Morpel® 326 is not expected to volatize under field conditions. Based on the use 

pattern, significant environmental exposure (terrestrial or aquatic) is not expected. 

2. Risk Conclusions

Aquatic Organisms

The Agency estimated potential exposure and acute risk to aquatic organisms. The Agency

completed conservative exposure estimates, and resulting acute risk quotients (RQs) are far below

the Agency's level of concern. While chronic RQs were not estimated, given the large margin of

safety observed for acute effects, the Agency believes it unlikely that chronic risks would approach

concern levels. Similarly, risk to aquatic plants is presumed to be below the level of concern based

on Morpel® 326’s low toxicity and low potential to enter aquatic environments.

Terrestrial Organisms

Based on the registered use patterns of Morpel® 326, exposure to terrestrial organisms is 

not expected. Even if a non-target organism were to inadvertently come into contact with Morpel® 

326 the exposure levels would be expected to be low. Given Morpel® 326’s low toxicity profile, 

effects to non-target organisms would not be expected to exceed the Agency’s levels of concern 

(LOCs) even if exposure to terrestrial organisms occurred. 

3. Ecological Incidents

There are no reported ecological incidents involving Morpel® 326. A review of all available 

information in the following databases was completed in April 2014: Ecological Incident 

Information System 8 (EllS), OPP Aggregate Incident Reports database, Avian Monitoring 
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Information System (AIMS). For additional discussion of the reported ecological incidents, see 

Registration Review – Preliminary Ecological Risk Assessment and Endangered Species Effects Determination for 

Dipropyl isocinchomeronate (aka Morpel® Repellent 326, formerly MGK® Repellent 326).

C. Endangered Species Assessment

Because of Morpel® 326’s low use diffused over a large treatment area and the low 

probability of non-target organism exposure to Morpel® 326, the Agency concludes that effects on 

the environment are not reasonably expected to occur from the registered use of Morpel® 326. 

Therefore, the EPA anticipates making a "no effects" determination under the Endangered Species 

Act (ESA) for all listed species and that no adverse modification of designated critical habitat for 

such species is expected from the registered use of Morpel® 326, unless information provided to the 

Agency leads the Agency to change its anticipated determination.

D. Endocrine Disruptor Screening Program

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential 

adverse outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic 

and chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, organ 

weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, and sex ratios 

in offspring. For ecological hazard assessments, EPA evaluates acute tests and chronic studies that 

assess growth, developmental and reproductive effects in different taxonomic groups. As part of its 

most recent registration decision for Morpel® Repellent 326, EPA reviewed these data and selected 

the most sensitive endpoints for relevant risk assessment scenarios from the existing hazard 

database. However, as required by FFDCA section 408(p), Morpel® Repellent 326 is subject to the 

endocrine screening part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other 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.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to interact 

with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA will 

determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 testing is 

designed to identify any adverse endocrine-related effects caused by the substance, and establish a 

dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list of 

chemicals identified for EDSP screening was published on June 14, 20131 and includes some 

 1 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals.
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pesticides scheduled for Registration Review and chemicals found in water. For further information 

on the status of the EDSP, the policies and procedures, the lists of chemicals, future lists, the test 

guidelines and the Tier 1 screening battery, please visit our website.2 

In this Proposed Interim Registration Review Decision, EPA is making no human health or 

environmental safety findings associated with the EDSP screening of Morpel® Repellent 326. 

Before completing this Registration Review, the Agency will make an EDSP FFDCA section 408(p) 

determination.

VII. COMBINED WORK PLAN, SUMMARY DOCUMENT, AND PROPOSED 

INTERIM REGISTRATION REVIEW DECISION

Tolerance Amendments

There are no U.S. tolerances established for Morpel® 326, and so the Agency will not 

pursue any tolerance actions with Morpel® 326.

Risk Mitigation and Rationale

The Agency has identified no human health or ecological risks associated with registered

uses of Morpel® 326. Therefore, the Agency did not identify the need to modify the current 

registered use of Morpel® 326.

Interim Registration Review Decision

In accordance with 40 CFR Sections 155.50, 155.56, and 155.58, the Agency is issuing this 

combined Work Plan, Summary Document, and Proposed Interim Registration Review Decision.

Except for the EDSP component of the Morpel® Repellent 326 registration review case, the 

Agency has made the following proposed interim decision: (1) no additional data are required at this 

time; and (2) no changes to the affected registrations or their labeling are needed at this time. EPA 

has not identified any risks of concern to human health. Currently registered uses of Morpel®

Repellent 326 are not expected to result in adverse effects to listed or non-listed species or critical 

habitats. As such, EPA anticipates making a “no effect” determination under the ESA for all listed 

species and no adverse modification of designated critical habitat for such species is expected for all

currently registered uses of Morpel® Repellent 326.

VIII. NEXT STEPS AND TIMELINE

A Federal Register Notice will announce the availability of this combined Work Plan, 

Summary Document, and Proposed Interim Registration Review Decision for Morpel® Repellent 

326 and allow a 60-day comment period. If there are no significant comments or additional 

information submitted to the docket during the comment period that leads the Agency to change its 

proposed decision, EPA may issue an Interim Registration Review Decision for Morpel® Repellent 

326 (case 2215), in accordance with 40 CFR Sections 155.56 and 155.58. A final decision on the 

Morpel® Repellent 326 registration review case will also occur after an EDSP FFDCA section 

408(p) determination has been made.

EPA has created the following estimated timeline for the completion of Morpel® Repellent 

326 registration review:

 2 http://www.epa.gov/endo/
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Registration Review for Morpel® Repellent 326 – Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket and Combined Work Plan, Summary Document, and Proposed Interim 

Registration Review Decision

Open Public Docket and Public Comment Period for Combined Work 

Plan, Summary Document, and Proposed Interim Registration Review 

Decision 

June 2015

Close Public Comment Period August 2015

Interim Registration Review Decision and Begin Post-Decision Followup3December 2015

Total (years) 0.5

 3 A final decision on the dipropyl isocinchomeronate registration review case, in accordance with 40 CFR 

Section155.158, will occur after an EDSP FFDCA section 408(p) determination has been made.
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Appendix – Additional Areas Considered in the Morpel® Repellent 326 Registration Review

PUBLIC COMMENTS AND FEEDBACK:

Guidance for Commenters: The areas below highlight topics of special interest to the Agency 

where your comments, data submissions, or reference to sources of additional information could be 

of particular use.

Trade Irritants:

Through the registration review process, the Agency intends to solicit information on trade irritants 

and, to the extent feasible, take steps toward facilitating irritant resolution. The Agency will work to 

harmonize tolerances and international maximum residue limits (MRLs) and may modify tolerance 

levels to do so, when possible. Growers and other stakeholders are asked to comment on any 

trade irritant issues resulting from lack of MRLs or disparities between U.S. tolerances and MRLs in 

key export markets, providing as much specificity as possible regarding the nature of the concern. 

Because there are no food/feed tolerances for Morpel® 326, the Agency does not expect any trade 

irritant concerns. 

Water Quality:

Morpel® Repellent 326 is not identified as a cause of impairment for any water bodies listed as 

impaired under section 303(d) of the Clean Water Act.4

 In addition, no Total Maximum Daily 

Loads (TMDL) have been developed for Morpel® Repellent 326.

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 More information on impaired 

water bodies and TMDLs can be found at the Agency’s website.6 The Agency invites submission 

of water quality data for this pesticide. To the extent possible, data should conform to the 

quality standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired Water 

Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and Management Process7 in 

order to ensure they can be used quantitatively or qualitatively in pesticide risk assessments.

Environmental Justice:

EPA seeks to achieve environmental justice, the fair treatment and meaningful involvement of all 

people, regardless of race, color, national origin, or income, in the development, implementation, 

and enforcement of environmental laws, regulations, and policies. To help address potential 

environmental justice issues, the Agency seeks information on any groups or segments of the 

population who, as a result of their location, cultural practices, or other factors, may have atypical, 

unusually high exposure to Morpel® Repellent 326 compared to the general population. Please 

comment if you are aware of any sub-populations that may have atypical, unusually high 

exposure compared to the general population.

 4 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

5http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_g

roup_name=PESTICIDES 6 http://www.epa.gov/owow/tmdl/

7 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm