Contents

I. INTRODUCTION...................................................................................................................... 2

II. SCIENTIFIC ASSESSMENTS................................................................................................... 3

A. Human Health Assessment............................................................................................................3

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

1. Environmental Risk Characterization........................................................................................4

2. Endangered Species Assessment ...............................................................................................4

C. Endocrine Disruptor Screening Program .........................................................................................4

III. INTERIM REGISTRATION REVIEW DECISION............................................................... 5

IV. NEXT STEPS ........................................................................................................................... 5
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I. INTRODUCTION

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

Review Decision for the allethrins, 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://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. 

The allethrins are part of the pyrethroid class of pesticides and are registered for use to control flying 

and crawling insects. The allethrins are comprised of four stereoisomers: bioallethrin, s-bioallethrin, 

esbiothrin, and d-allethrin. There are no occupational, food or feed uses of allethrins. After the 

issuance of the Registration Review Data Call-In, all allethrins products with the exception of three 

end use products were voluntarily cancelled with effective cancellation dates of September 30, 2015 

for technical products and December 31, 2016 for end use products. Only d-allethrin remains 

registered for pesticidal use. The remaining registered uses of allethrins are ambient air repellents for 

control of flying pests, such as mosquitoes, in non-occupational settings. These products are 

formulated and sold as impregnated mats that volatize the active ingredient into the air when heated 

by a candle or butane cartridge, repelling pests in the immediate area. The Agency completed a 

Reregistration Eligibility Decision (RED) for allethrins in June of 2007 and amended it in May 2009 to 

incorporate an evaluation of allethrin use in commercial animal housing misting systems.

Pursuant to 40 CFR § 155.50, the Agency formally initiated registration review for allethrins (case 

0437) in March 2010. The following timeline highlights significant events that have occurred during 

the registration review of allethrins:

 March 2010 - Publication of the Allethrins Summary Document, including the Preliminary 

Work Plan (PWP), for a 60-day comment period. The Summary Document was 

accompanied by the scoping document and the problem formulation. 
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 August 2010 - Publication of the Final Work Plan (FWP) and EPA’s response to the single 

public comment received. The FWP did not modify the anticipated risk assessment, data 

needs, or registration review timeline described in the PWP.

 October 2011 – The allethrins Registration Review Generic Data Call-In (GDCI) was issued.

 2014 – Through a number of Federal Register Notices, all allethrins products with the 

exception of three end use products were voluntarily cancelled. The effective cancellation 

dates are September 30, 2015 for technical products and December 31, 2016 for end use 

products.

 September 2014 - EPA published qualitative human health and environmental fate and 

effects risk assessments for allethrins in the allethrins registration review docket for a 60-day 

comment period. No comments were received on the documents: Allethrins. Registration 

Review Preliminary Risk Assessment and EFED Registration Review: Draft Ecological Risk Assessment 

and Endangered Species Effects Determination for d-allethrin.

 September 2014 - EPA published the Proposed Interim Registration Review Decision for 

allethrins in the Federal Register (79 FR 57084; FRL–9916–39). No comments were received. 

For further information on the registration review of allethrins, see EPA’s public docket (EPA-HQOPP-2010-0022) at www.regulations.gov. 

II. SCIENTIFIC ASSESSMENTS

A summary of the Agency’s human health and environmental risk assessments, is presented below. 

These risk assessments only assess the impregnated mat use of d-allethrin because all other uses of 

allethrins have been cancelled effective December 2016. The risk assessments are located in the 

registration review docket, EPA-HQ-OPP-2010-0022. 

A. Human Health Assessment 

The only supported use of allethrins is limited to small-scale, outdoor residential use. The remaining 

use pattern is a heating apparatus that emits d-allethrin from an infused mat for up to four hours 

across a 15-foot diameter radius. This use is not intended for enclosed areas. There are no 

occupational or food uses registered for d-allethrins and the sole remaining use pattern is not 

expected to contaminate surface or ground water; thus, dietary, aggregate, and occupational risk 

assessments were not conducted. EPA evaluated residential exposure only.

Residential handler exposure, both dermal and inhalation, is expected to be negligible as the 

application activity (e.g., lighting a candle) does not involve typical exposure as would spraying a 

liquid pesticide or spreading granules. Therefore, EPA conducted a post-application inhalation 

exposure assessment only and concludes that the inhalation risk estimates for the remaining allethrin 

products are not of concern for adults or children. 

For details, see the Allethrins. Registration Review Preliminary Risk Assessment published on 9/24/2014.
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B. Environmental Assessment 

1. Environmental Risk Characterization

EPA conducted an environmental fate and effects assessment for d-allethrin, the active ingredient in

the remaining registered products. EPA considered potential d-allethrin exposure to non-target 

organisms, available information on the toxicity of d-allethrin, and the registered use of d-allethrin in 

the assessment. 

Based on the available toxicity data and the low exposure potential from the remaining registered 

use of d-allethrin, none of the acute or chronic levels of concern (LOCs) are exceeded for fish, 

aquatic invertebrates, birds, or mammals. In addition, the likelihood of adversely affecting non-target 

insects is expected to be low given the relatively limited “repellency affect area” around the 

dispensing device (~15 feet in diameter), the likely setting of use (e.g., residential backyards), and the 

short half-life of d-allethrin in air. While the Agency does not currently have terrestrial plant toxicity 

data for allethrins, effects to aquatic and terrestrial plants are not reasonably expected to occur due 

to the low exposure potential. Therefore, given the types and extent of the registered uses of 

allethrins, the low potential for exposure, and the diffuse nature of use, the Agency believes that 

registered uses of allethrins should not adversely affect non-target organisms.

For details of the environmental risk assessment, see the EFED Registration Review: Draft Ecological

Risk Assessment and Endangered Species Effects determination for d-allethrin, published on 9/24/2014.

2. Endangered Species Assessment

There is no reasonable expectation for the currently registered use of allethrins to cause direct or 

indirect adverse effects to threatened and endangered species. No adverse modification of critical 

habitat is expected to occur from use of allethrins. EPA has made a “no effect” determination 

under the Endangered Species Act (ESA) for all listed species. EPA also has determined that no 

habitat modification is likely for designated critical habitat for such species. Therefore, EPA has 

concluded that consultation with the U.S. Fish and Wildlife Service and the National Marine 

Fisheries Service under ESA section 7(a)(2) is not required. For details, see the September 5, 2014 

Draft Ecological Risk Assessment cited above. 

C. Endocrine Disruptor Screening Program 

EPA has developed the Endocrine Disruptor Screening Program (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.” Under FFDCA section 408(p), the Agency must screen 

all pesticide chemicals. Between October 2009 and November 2010, EPA issued test orders/data 

call-ins for the first group of 67 chemicals and published a second list of chemicals proposed for 

order issuance in the future. Allethrins was not among the group of 58 pesticide active ingredients 

on the initial list nor is it proposed on the second list of chemicals to be screened under the 

EDSP. Accordingly, as part of registration review, EPA will issue future EDSP orders/data call-ins 

for registration review chemicals, including allethrins. For further information on the status of the 

EDSP, the policies and procedures, the list of 67 chemicals, future chemical lists proposed for 
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screening, the test guidelines and the Tier 1 screening battery, please visit our 

website: http://www.epa.gov/endo/. In the interim, EPA is making no human health or 

environmental safety findings associated with the EDSP screening of allethrins. Before completing 

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

III. 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 allethrins registration review 

case, the Agency has determined the following: (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. In addition, 

EPA does not expect allethrins to have direct or indirect adverse effects to non-listed and listed 

species or to designated critical habitat. As such, EPA has made a “no effect” determination under 

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

species.

IV. NEXT STEPS 

EPA will make a final registration review decision for allethrins after an EDSP FFDCA section 

408(p) determination has been made.