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Morpel® Repellent 326 – Table of Contents

I. Introduction 3

II. Use and Usage Information 4

III. Scientific Assessments 5

IV. Interim Registration Review Decision 9

V. Next Steps 9

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

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

Review Decision for dipropyl isocinchomeronate (referred to within as Morpel® Repellent 326 and 

Morpel®; formerly MGK 326), pursuant to 40 CFR § 155.56 and § 155.58. 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). The Agency may 

issue, when it deems appropriate, an interim Registration Review decision before completing a 

Registration Review. Among other things, the interim Registration Review decision may (1) require 

new risk mitigation measures; (2) impose interim risk mitigation measures; (3) identify data or

information required to complete the review; and (4) include schedules for submitting the required 

data, conducting the new risk assessment, and completing the Registration Review. 

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 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 and reduce risk evolves and as 

policies and practices change, all registered pesticides continue to meet the statutory standard of no 

unreasonable adverse effect to human health or the environment. Through the Registration Review

program, the Agency periodically reevaluates pesticides to make sure that as these changes occur, 

products in the marketplace can be safely used. Information on this program is provided at: 

http://www2.epa.gov/pesticide-reevaluation/registration-review-process. 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. 

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

cat, and horse) insect repellent. While use of Morpel® 326 on dairy cattle is mentioned in supporting 

documents, there are no registrations which include this use site on any technical or end use label. 

Morpel® is never the sole active ingredient; it is always coformulated with other insecticides/repellents,

such as DEET, piperonyl butoxide, 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 Agency completed its Reregistration Eligibility 

Decision document (RED) for dipropyl isocinchomeronate on March 11, 2005.

Pursuant to 40 CFR section 155.50, EPA formally initiated Registration Review for Morpel® 326 (case 

2215). The following highlights significant events that have occurred during the Registration Review of 

Morpel® 326.

• August 2015 – Issuance of Dipropyl isocinchomeronate (Morpel® Repellent 326) Combined Work 

Plan, Summary Document, and Proposed Interim Registration Review Decision for a 60-day public 

comment period. 

• August 2015 – Publication of Dipropyl-isocinchomeronate (Di-N-propyl isocinchomeronate): 

Scoping and Preliminary Risk Assessment for Registration Review and Registration Review –

Preliminary Ecological Risk Assessment and Endangered Species Effects Determination for Dipropyl 

isocinchomeronate (aka Morpel® Repellent 326, formerly MGK® Repellent 326).
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• October 9, 2015 – The Agency received one public comment submitted on behalf of the 

technical registrant, Vertellus Performance Materials, Inc. (Vertellus), which is discussed 

below. EPA also solicited comments on the specific topics of environmental justice, 

water quality concerns, and trade irritants, but no comments or information were 

received concerning those issues.

• December 2015 – The Agency is now publishing the Morpel® 326 Interim Registration 

Review Decision.

Comment received on behalf of the technical registrant, Vertellus 

Comment: The comment submitted by Technology Services Group Inc., on behalf of the Morpel®

326 technical registrant, Vertellus requested that the Agency lift restrictions placed on the 

registration of Morpel® 326 in the 2005 RED, including (1) a maximum concentration (2.5%) of 

active ingredient in end-use products intended for use on humans and (2) a production and 

distribution cap of 20,000 pounds of active ingredient per year. Vertellus’ justification for its request 

to lift current restrictions is based on the Agency’s re-classification of Morpel® 326 as “not likely to 

be carcinogenic to humans”.

EPA Response: The Agency agrees that based on the re-classification of Morpel® 326 as “not likely 

to be carcinogenic to humans”, as documented in Dipropyl-isocinchomeronate (Di-N-propyl 

isocinchomeronate): Scoping and Preliminary Risk Assessment for Registration Review, the aforementioned 

restrictions are no longer relevant. The maximum annual production and distribution cap is no 

longer necessary. In order to initiate this change, an affected registrant would need to amend the 

terms and conditions of registration for the technical product. Additionally, there is no need to 

restrict the maximum concentration of active ingredient in products intended for use on humans to 

2.5% given that dipropyl-isocinchomeronate is not expected to be carcinogenic. However, the 

Agency notes that any proposed formulation changes to Morpel® Repellent 326 end-use products

(e.g., higher concentrations of active ingredient) would be subject to the Pesticide Registration 

Improvement Extension Act (PRIA) application process which includes a quantitative human health 

assessment. Hence, in order to initiate changes to the restrictions set forth in the 2005 RED, an 

affected registrant would need to make formal requests to the Agency.

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. 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) dated (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

III. SCIENTIFIC ASSESSMENTS

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

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

Registration Review dated May 19, 2015 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 Registration Review docket (EPA-HQ-OPP-2014-0578) at 

www.regulations.gov.

A. Human Health Risk 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 determined that it was

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 in the public docket (EPA-HQ-OPP-2014-0578) which can be 

accessed 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 need 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 are no dietary risk concerns, an aggregate risk assessment for Morpel® 326 was not 

neccesary.

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 no product containing 

this active ingredient is registered for any food or feed uses.
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B. Ecological Risk Assessment

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

non-target organism exposure to Morpel® Repellent 326, the Agency determined that it was

appropriate to conduct a 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.

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

conservatively estimated exposure, 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 even if 

exposure to terrestrial organisms occurred. 

Pollinator studies have not been required for Morpel® 326. However, with the June 2014 Guidance 

for Assessing Pesticide Risks to Bees now in place, EPA has begun to require these data where applicable. 

Consistent with existing guidance 40 CFR, Part 158, Subpart G § 158.630, pollinator data are 

required for pesticide active ingredients with terrestrial, forestry and residential outdoor uses. Based 

upon the typical use pattern for Morpel® 326 (personal repellent spray or towelettes) and the lack of 

a complete terrestrial exposure pathway, EPA is not requiring pollinator data at this time.

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, covering the time period from 

1994 to 2014: Ecological Incident Information System 8 (EllS), OPP Aggregate Incident Reports 
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database, and Avian Monitoring 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 is making a "no effects" determination under the Endangered Species Act 

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

for such species is expected from the registered use of Morpel® 326. 

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 pesticides 

 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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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 

IV. INTERIM REGISTRATION REVIEW DECISION

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

Registration Review Decision. Except for the EDSP component of the Morpel® Repellent 326

Registration Review case, the Agency has made the following interim decision: (1) no additional 

data, including pollinator 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 their critical habitats. As such, EPA is 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. In this 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.

Additionally, with the issuance of this Interim Registration Review Decision, the EPA finds that the 

maximum annual production and distribution quantity and the maximum concentration of 2.5% 

active ingredient set forth in the 2005 RED are no longer necessary. In order to effectuate any 

change to Morpel 326 registrations, the registrant is required to submit a formal request to the 

Agency.

V. NEXT STEPS

In accordance with 40 CFR Sections 155.57 and 155.58, EPA will make a final Registration Review 

decision for Morpel® 326 after an EDSP FFDCA section 408(p) determination has been made.

 2 http://www2.epa.gov/endocrine-disruption/endocrine-disruptor-screening-program-edsp-21st-century