Page 1 of 3

OFFICE OF

CHEMICAL SAFETY AND 

POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

 

PC Code: 004005

DP Barcode: D420151

Date: September 5, 2014

MEMORANDUM

SUBJECT: Registration Review: Draft Ecological Risk Assessment and Endangered Species 

Effects Determination for d-Allethrin

TO: Marianne Mannix, Chemical Review Manager

Avivah Jakob, Team Leader

 Patricia Parrott, Branch Chief

 Risk Management and Implementation Branch 3

Pesticide Re-evaluation Division (7508P)

FROM: Sarah Winfield, Acting Branch Chief 

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

REVIEWED 

BY: Cheryl Sutton, Ph.D., Environmental Scientist

Edward Scollon, Ph.D., Toxicologist

Thomas Steeger, Ph.D., Senior Advisor

Environmental Risk Branch IV (ERB4)

Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has completed the draft ecological risk 

assessment and endangered species effects determination for the pyrethroid insecticide dallethrin (PC code 004005). d-Allethrin is one of the active ingredients (a.i.) considered in the 

broader Registration Review of allethrins that includes multiple active ingredients1. However, dallethrin is the only a.i. contained within allethrin products that is not currently pending 

cancellation. 

 

1 The Allethrins Registration Review case includes multiple active ingredients (bioallethrin, PC Code 004003; 

esbiothrin, PC Code 004007; esbiol, PC Code 004004; and d-allethrin) that contain varying amounts of two to four 

isomers. d-Allethrin is an enrichment containing 4 of the possible 8 allethrin isomers.
Page 2 of 3

The use pattern for allethrins has changed through the Registration Review process. After the

General Data Call-In (GDCI) was published in October 2011 to address uncertainties identified 

in the final work plan for the Registration Review of allethrins, the technical and end-use 

registrants indicated that they would no longer support any of the registrations as of December 

2016. The only exceptions were the end-use registrants for three products: EPA Registration 

Numbers 71910-2, -3, and -4. In July 2013, the registrants for these products submitted to the 

Registration Division (RD) a Pesticide Registration Improvement Act (PRIA) action to amend

their Confidential Statement of Formulas (CSFs) so that their products could be sold after 2016. 

The Registration Review GDCI for the allethrins issued in 2011 required a number of ecological 

and human health data requirements. These studies were identified as data gaps based on the precancellation use pattern. At the time of the EFED problem formulation2

, the allethrins were used 

in residential indoor and outdoor space and surface sprays, total release foggers, and as a foliar 

spray for plants. The registrants for the three remaining products submitted waiver requests or 

data to address all of the Registration Review data requirements applicable to their products; the 

waiver requests have been reviewed3and granted by EPA and the submitted studies have been

reviewed and found to be acceptable by EPA; therefore, all Registration Review data 

requirements for these three products have been addressed.

For the currently registered uses (i.e., repellant candle lanterns intended for small outdoor 

settings), d-allethrin is released into the air via vaporization of the compound by a heat source

(dispersal appliance), allowing the chemical to rise in to the air in the immediate vicinity of the 

dispersal appliance. For this use, the a.i. is volatilized by the heat source and is expected to 

dissipate rapidly via degradation and by dilution in the large volume of air into which it is 

released. Based on the available data, the use pattern, and conservative assumptions regarding 

exposure, none of the acute or chronic risk Levels of Concern (LOCs) are exceeded for fish (and 

by extension to aquatic-phase amphibians for which fish serve as surrogates), aquatic 

invertebrates, birds (and by extension to terrestrial-phase amphibians and reptiles for which birds 

serve as surrogates), or mammals. 

Because d-allethrin is used as an insect repellant and has potential insecticidal properties, it is 

assumed that any terrestrial invertebrate (e.g., flying terrestrial invertebrate species) that is 

exposed to sufficient quantities of d-allethrin (i.e., flying through the d-allethrin released by the 

repellent candle lantern) has the potential to be affected. However, given the relatively limited 

“repellency affect area” around the d-allethrin dispensing device (the label indicates the 

repellency affect area is a 15-foot diameter, that lasts for up to 4 hours), the likely setting of use 

(i.e., in residential areas such as backyards, camp sites or hunting sites), and the short half-life of 

d-allethrin in air (<1 hour), the likelihood of adversely affecting Federally listed 

threatened/endangered (hereafter referred to as “listed”) terrestrial invertebrates is considered to 

 

2 USEPA 2010. Registration Review: Preliminary Problem Formulation for Environmental Fate, Ecological Risk, 

and Endangered Species Assessments for the Allethrin. March 9, 2010, D371344. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2010-0022-0002

3 USEPA 2010b. EFED Review of the Data Waiver Request for Allethrins and Terrestrial Plant and Honey Bee 

Toxicity Data Requirements for Registration Review. June 29, 2010, D379419. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2010-0022-0015
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be low. For the same reasons, the likelihood of exposure and subsequent adverse effects to 

honey bees (Apis mellifera) or other pollinating insect species is considered low. Furthermore, 

the likelihood of bees being drawn to humans within the repellent’s effective area is considered 

low. 

There are currently no data available to assess the potential risk to terrestrial or aquatic plants 

from the remaining registered use of d-allethrin. However, the likelihood of adverse effects to

plants is considered low because of the low exposure potential. 

Therefore, due to a combination of low exposure and relative insensitivity to the active 

ingredient (for many taxa), the likelihood of adverse effects on species other than target 

organisms is expected to be low. Because direct adverse effects are not expected for birds, 

reptiles, amphibians, mammals, fish, or aquatic invertebrates, and there is no reasonable 

expectation of adverse effects to plants or terrestrial invertebrates from exposure to d-allethrin 

from its remaining use, the EPA makes a No Effect (NE) determination for all listed species. 

EPA also has determined that no Habitat Modification is likely for designated critical habitats of 

listed species from the use of d-allethrin.
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REGISTRATION REVIEW

Draft Ecological Risk Assessment and Endangered Species Effects Determination for:

d-Allethrin

(CAS No. 584-79-2; USEPA PC # 004005)

 Cyclopropanecarboxylic acid, 2,2-dimethyl-3-(2-methyl-1-propen-1-yl)-, 2-methyl-4-oxo-3-(2-

propen-1-yl)-2-cyclopenten-1-yl ester

Prepared by:

Sarah Winfield, Acting Branch Chief

EPA/OCSPP/OPP/EFED/ERB4

Reviewed by:

Cheryl Sutton, Ph.D., Environmental Scientist

Edward Scollon, Ph.D., Toxicologist

Thomas Steeger, Ph.D., Senior Advisor

EPA/OCSPP/OPP/EFED/ERB4

U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch IV

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

September 5, 2014
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TABLE OF CONTENTS

1. PROBLEM FORMULATION..........................................................................................................................3

NATURE OF REGULATORY ACTION............................................................................................................................3

PREVIOUS ASSESSMENTS...........................................................................................................................................4

Ecological Risk Assessments................................................................................................................................4

Drinking Water Exposure Assessments................................................................................................................5

STRESSOR SOURCE AND DISTRIBUTION .....................................................................................................................5

PESTICIDAL MECHANISM OF ACTION ........................................................................................................................6

OVERVIEW OF PESTICIDE USE AND USAGE................................................................................................................7

ENVIRONMENTAL FATE AND TRANSPORT..................................................................................................................9

Mobility ..............................................................................................................................................................10

Degradation .......................................................................................................................................................11

Bioaccumulation ................................................................................................................................................12

Monitoring .........................................................................................................................................................12

ECOLOGICAL EFFECTS.............................................................................................................................................13

Effects to Aquatic Organisms.............................................................................................................................13

Effects to Terrestrial Organisms........................................................................................................................14

Terrestrial Plants...............................................................................................................................................15

ECOLOGICAL INCIDENTS..........................................................................................................................................16

2. RISK CHARACTERIZATION......................................................................................................................16

RISK ESTIMATION....................................................................................................................................................16

Aquatic Animals.................................................................................................................................................16

Terrestrial Animals............................................................................................................................................17

Plants.................................................................................................................................................................18

RISK DESCRIPTION ..................................................................................................................................................18

Uncertainties and Assumptions..........................................................................................................................19

ENDANGERED SPECIES ASSESSMENT.......................................................................................................................19

ENDOCRINE DISRUPTOR SCREENING PROGRAM ......................................................................................................20

APPENDIX A: EPISUITE OUTPUT FOR ALLETHRINS (CAS NO. 548-79-2)...............................................21

APPENDIX B: INCIDENT DATA SYSTEM (IDS) FOR ALLETHRINS ..........................................................25

APPENDIX C: T-REX OUTPUT FOR ALLETHRINS........................................................................................26
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1. Problem Formulation

Nature of Regulatory Action

As part of the implementation of the Registration Review program pursuant to Section 3(g) of 

FIFRA, the Agency is evaluating all current and active registrations for allethrins to determine 

whether it continues to meet the FIFRA standard for registration. The structure of this risk 

assessment is based on guidance contained in U.S. EPA’s Guidance for Ecological Risk 

Assessment.

1

At the outset of Registration Review for allethrins, the allethrins, consisting of multiple active 

ingredients (a.i), were used in residential indoor and outdoor space and surface sprays, total 

release foggers, and as a foliar application to plants. However, after the General Data Call-In 

(GDCI2) was published in October 2011 to address uncertainties identified in the final work plan 

for the Registration Review of allethrins, the technical and end-use registrants indicated that they 

would no longer support any of the technical product registrations effective in September 2015 

and the end-use products in December 2016.

3

 The only exceptions were the end-use registrants 

for three products: EPA Registration Numbers 71910-2, -3, and -4. The registrants for these 

products submitted to the Registration Division (RD) a Pesticide Registration Improvement Act 

(PRIA) action to amend their Confidential Statement of Formulas (CSFs) so that their products 

could be sold after 2016. Additionally, the registrant for the three remaining products submitted 

waiver requests for the Registration Review ecological effects data requirements applicable to 

the mat products, which have been granted4.

Additionally, although the Registration Review case for allethrins involved multiple closely 

related active ingredients, the only active ingredient contained in the remaining supported uses is

d-allethrin. Consequently, although data involving all allethrin active ingredients are relied on to 

support this assessment, the focus of this assessment is on d-allethrin. 

 

1 USEPA 1998. Guidelines for Ecological Risk Assessment. U.S. Environmental Protection Agency, Risk 

Assessment Forum, Washington, DC, EPA/630/R095/002F, 1998.

http://www.epa.gov/raf/publications/pdfs/ECOTXTBX.PDF

2 USEPA 2013. d-Allethrin Generic Data Call In (GDCI-004005-1020). 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2010-0022-0017

3 https://www.federalregister.gov/articles/2014/05/20/2014-11685/notice-of-receipt-of-requests-to-voluntarilycancel-certain-pesticide-registrations

4 USEPA 2010b. EFED Review of the Data Waiver Request for Allethrins and Terrestrial Plant and Honey Bee 

Toxicity Data Requirements for Registration Review. June 29, 2010, D379419.

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2010-0022-0015
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Previous Assessments

For a more detailed review of previous assessments, please refer to the Registration Review: 

Preliminary Problem Formulation for Environmental Fate, Ecological Risk, and Endangered 

Species Assessments for the Allethrins5. 

Ecological Risk Assessments

The first synthetic pyrethroid, collectively referred to as “allethrins” was first registered in 1949. 

Because the allethrin compounds are nearly identical except in the ratios and amounts of the 

isomers, the ecological and environmental fate data for the allethrins have been bridged (i.e., 

allowing data on one compound to represent another compound) in previous Agency risk 

assessments. The most recent national-level ecological risk assessment was completed to 

support the Reregistration Eligibility Decision (RED) for the allethrins in 20076. 

The RED indicated that, although there were uncertainties regarding the extent of use in 

residential settings, the combined exposure from the supported outdoor uses (i.e., spot 

treatments) was not likely to be substantial. Therefore, based on the analysis in the assessment 

done for the RED, the supported outdoor allethrins uses were expected to result in exposure 

levels below Agency acute risk Levels of Concern (LOCs) for non-target organisms in both 

aquatic and terrestrial environments. Therefore, the likelihood of adverse effects from acute 

exposure was considered to be low. The likelihood of adverse effects from chronic exposure to 

mammals was also considered low; however, the potential risk to all other taxa from chronic 

exposure to allethrins could not be assessed due to a lack of data. The RED concluded that 

potential risk to aquatic organisms from acute exposure in surface water resulting from indoor 

uses of allethrins (e.g., pet shampoos being washed down the drain) could not be discounted; 

however, the pet shampoo use was cancelled as of April 2009.

Regarding Federally-listed threatened/endangered species (hereafter referred to as listed species), 

the relationship of risk quotients (RQs) to acute and chronic risk LOCs could not be evaluated 

for the supported uses of allethrins because RQs were not calculated in the assessment 

conducted for the RED; however, acute risks to listed species from outdoor uses of allethrins

(with the possible exception of the fogger use) were not expected due to low application rates 

and the types of uses being assessed. The potential for chronic risks could not be dismissed 

because of a lack of available data.

 

5 USEPA 2010. Registration Review: Preliminary Problem Formulation for Environmental Fate, Ecological Risk, 

and Endangered Species Assessments for the Allethrins. March 9, 2010, D371344. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2010-0022-0002

6 USEPA, 2007. Reregistration Eligibility Decision for Allethrins. June 29, 2007.

http://www.epa.gov/pesticides/reregistration/REDs/allethrin_red.pdf
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Drinking Water Exposure Assessments

The Agency has not previously conducted a drinking water assessment for the allethrins because 

the chemical was considered to have mainly indoor non-food uses and was labelled for only 

limited outdoor uses (e.g., spot treatments, foggers). The likelihood of the single remaining use 

pattern of d-allethrin, i.e., as a repellant candle lantern, contaminating human drinking water 

sources is considered low; therefore a drinking water assessment has not been conducted to 

support a human dietary risk assessment for d-allethrin. 

Stressor Source and Distribution

Although the current assessment focuses on d-allethrin, data from all of the allethrin mixtures are 

utilized for bridging to d-allethrin. The allethrin compounds from which data were bridged for 

d-allethrin are composed of mixtures of eight stereoisomers (see Table 1). Following the 

approach used in the bioallethrin registration standard and the allethrins RED7, it is assumed that

the allethrin mixtures are nearly identical except in the ratios and amounts of the isomers, which 

are assumed to be equipotent. Additionally, to more fully characterize the environmental fate 

and transport of the allethrins in spite of numerous data gaps, data for the structurally similar but 

naturally occurring compound, pyrethrin 1 (PC Code 069008; CAS No. 121-21-1) are utilized in 

the assessment in addition to the submitted data for the allethrins. 

 

7

Ibid USEPA 2007.
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TABLE 1: Composition of the Allethrins1

ISOMER

Allethrin [PC Code(s)]

Esbiol 

[004004]

Esbiothrin 

[004007] 

[formerly 

004003/004004]

Bioallethrin 

[004003]

d-Allethrin2

[004005]

Allethrin 

[004001]

d-trans chrysanthemic acid of 

d-allethrolone3

>90% 72% ≥46.5% 36.5% 18%

d-trans chrysanthemic acid of 

l-allethrolone

5% 21% ≥46.5% 36.5% 18%

d-cis chrysanthemic acid of dallethrolone-

4

- - 9% 4.5%

d-cis chrysanthemic acid of lallethrolone- - - 9% 4.5%

l-trans chrysanthemic acid of 

d-allethrolone

- - - - 18%

l-trans chrysanthemic acid of 

l-allethrolone

- - - - 18%

l-cis chrysanthemic acid of dallethrolone- - - - 4.5%

l-cis chrysanthemic acid of lallethrolone- - - - 4.5%

1 Adapted from USEPA 1997 (D222638)8

2 Trade Name is Pynamin Forte®

, and has been used in past EFED assessments to refer to this a.i.

3 Most insecticidally active isomer

4

Indicates <2%

Pesticidal Mechanism of Action

d-Allethrin is a pyrethroid insecticide that acts on target pests by delaying the closing of the 

voltage-gated sodium channel, prolonging the return of the neuron membrane potential to its 

resting state9. This delay in return to the resting state leads to hyperactivity of the nervous 

system which, in turn, can result in paralysis and/or death. Pyrethroids, such as d-allethrin, are 

characterized by their ability to quickly immobilize insect pests, referred to as ‘knockdown’ 

capacity10. 

 

8 USEPA 1997. Allethrin Stereoisomers: AgrEvo Environmental Health (AEH) Rebuttal of Agency requirements 

Concerning the Test Substance for Plant Metabolism Studies. From William O. Smith (HED) to Paula Deschamp 

(HED) D222638.

9 Soderlund. 2002. Toxicology 171:3-59.

10 Ibid Soderlund 2002.
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Overview of Pesticide Use and Usage

The main use of d-allethrin is as a knockdown agent (defined here as an agent that causes rapid 

paralysis that may be reversible and that may or may not lead to death) against a variety of flying 

and crawling insects, mites and spiders; however, they can also result in outright insect mortality 

(i.e., function as insecticides) when used at higher rates. Outdoor uses of d-allethrin will be

limited to localized space “lanterns” that emit the compound from an infused mat for up to 4 

hours across a 15-foot diameter space; whereas all other uses will be cancelled by December 

2016. 

d-Allethrin differs from most other pyrethroids previously assessed by the Agency’s Office of 

Pesticide Programs (OPP) because the outdoor use of the compound is limited strictly to smallscale residential use (i.e., there are no large-scale d-allethrin uses such as agricultural or public 

health/mosquito abatement uses). Standard use rates typically reported for agricultural chemicals 

(i.e., lb/acre [lb/A]) are not appropriate for end-use products of d-allethrin, due to the types of 

uses for which they are registered; however, to help characterize the use pattern, a conservative

application rate of 0.0088 lb a.i./A has been calculated (see Table 2).
Page 8 of 27

Table 2: Registered d-Allethrin End-use Products and Associated Use Patterns

Product Name 

(EPA Reg. 

No.)

Active 

Ingredient

Type of Product and 

Use Sites

Label Language Relevant to 

Environmental Exposure

Application 

Rate**

ThermaCELL®

Mosquito 

Repellant 

(71910-2)

d-allethrin

(21.97%)

Repellant Candle 

Lantern

(pesticide infused mat, 

that is heated by 

butane-filled cartridge 

to dispense repellant)

Use sites are an 

average size deck, or 

patio, or outdoor 

campsite.

Pesticide Disposal and Container 

Handling:

- Non-refillable container; do not 

refill or reuse this container.

- If cartridge is empty or for used 

mats: Do not reuse empty 

packaging, envelopes [wrappers] or 

cartridges. Do not puncture or 

incinerate empty cartridges. Place 

in trash or offer for recycling if 

available.

- If cartridge is partly filled or for 

unused mats: Call your local solid 

waste agency for disposal 

instructions. 

- Never place unused mats down any 

indoor or outdoor drain.

- For unwanted appliance 

[lantern]: Place in trash or offer for 

recycling if available.

- Do not expose appliance/lantern or 

mats to rain

Environmental Hazards:

- This product is toxic to fish 

and aquatic invertebrates.

- Do not apply directly to 

water. Do not contaminate 

water when cleaning equipment or 

disposing of equipment wash 

water or rinsate.

- Drift may be hazardous to aquatic 

organisms in water adjacent to 

treated areas.

Pesticide infused 

mats last a 

maximum of 4 

hours

One 

appliance/lantern 

for each 225 ft2

Provides 15-ft 

diameter 

repellency 

Mat weight* is 

0.08 oz each

(0.017576 oz a.i.

in each mat; or 

0.498 g/mat)

ThermaCELL®

Mosquito 

Repellent with 

Earth Scent 

(71910-3)

d-allethrin 

(21.97%)

Replacement mat

Use site intended for 

where hunters may 

wait for game.

ThermaCELL®

Mosquito 

Repellent 

Candle Lantern 

(71910-4)

d-allethrin 

(21.97%)

Repellant Candle 

Lantern

(pesticide infused mat, 

that is heated by 

butane-filled cartridge 

to dispense repellant)

Use sites are 

backyards, yards, 

decks, patios, 

gardening, social 

events, spectator 

sports, sporting events 

and outdoor campsites.

*Mat weight only specified on 71910-4, and assumed the same for other products.

**For modeling purposes to assess exposure, an application rate of 0.14 oz a.i./A or 0.0088 lb a.i./A was estimated for the candle use by 

assuming there are houses on quarter acre lots throughout a watershed; and that each house had two candles in the yard (consistent with the 

Registration Review Ecological Risk Assessment for metofluthrin, which has a similar use pattern)

11. Additionally, it was assumed that the entire 

amount of a.i. from each candle is released into the environment at the same time, which leads to a very conservative estimate of potential 

exposure. 

 

11 USEPA 2013b. Registration Review: Preliminary Ecological Risk Assessment and Endangered Species Effects 

Determination for Metofluthrin. April 16, 2013, D403437.
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Environmental Fate and Transport

While the environmental fate database for d-allethrin is sparse, there are sufficient data available 

to assess the environmental fate of the compound for the labeled use. The physical/chemical and 

the environmental fate properties for the allethrins as a whole are presented in Table 3. The 

majority of the data reported are for the isomer, d-trans chrysanthemic acid of d-allethrolone (dtrans allethrin; which is 36.5% of d-allethrin, see Table 1). Based on these data, the allethrins 

are low to moderately volatile compounds that are non-persistent to slightly persistent in aerobic 

soil and are expected to have low mobility in most soils. The main transformation products of 

the allethrins are carbon dioxide (CO2, maximum of 71% in an aerobic soil metabolism study), 

allethrolone (maximum of 18.9% in the hydrolysis study), and dihydroxyallethrolone (maximum 

of 34.9% in the photolysis study). There were also unextracted residues in some studies and 

there is uncertainty as to the extent to which the unextracted residues consist of parent 

compound12. 

In order to more fully characterize the environmental fate and transport of the d-allethrin, EFED 

utilized data for the structurally similar but naturally occurring compound pyrethrin 1 (PC Code 

069008; CAS No. 121-21-1). Additionally, because pyrethroids are known to readily photolyze 

in air, but no atmospheric photolyisis data were submitted, the rate of photolysis was estimated 

using Quantitative Structure/Activity Relationship (QSAR) Estimation Program Interface (EPI)

Suite13 software.

TABLE 3. General Physical/Chemical Properties and Environmental Fate Parameters of 

Allethrins.

Property Value Source and/or Comments

Chemical Name [(4'RS)-3-allyl-2-methyl-4-

oxocyclopent-2-enyl (1R)-transchrysanthemate;

CAS name: [1R-[α(S*),3ρ]]-2,2-

dimethyl-3-2(2-methyl-1-

propenyl)cyclopropanecarboxylic 

acid 2-methyl-4-oxo-3-(2-propenyl)-

2-cylcopenten-1-yl ester

d-trans allethrin1is the most 

insecticidally active isomer and is 

present at 72% in esbiothrin, 

>46.5% in bioallethrin, >90% in 

esbiol, and 36% in d-allethrin

Molecular Weight 302.4 Product Chemistry Data Reviews 

Solubility in Water (20°C) 4.6 mg/L

 5.0 mg/L

Bioallethrin, Esbiothrin, Esbiol 

Product Chemistry Data Reviews 

(d-trans allethrin); 

42193303(Esbiol)

41115302; Pynamin Forte Product 

Chemistry Data Review

Vapor Pressure (25°C) 3.3 X 10-4 Torr Bioallethrin, Esbiothrin, Esbiol 

Product Chemistry Data Reviews 

(d-trans allethrin); 

42193303(Esbiol)

 

12 Ibid USEPA 2010

13 USEPA 2014. Estimation Program Interface (EPI) Suite. http://www.epa.gov/opptintr/exposure/pubs/episuite.htm 
Page 10 of 27

Property Value Source and/or Comments

1.24 X 10-6 Torr 41115307; Pynamin Forte Product 

Chemistry Data Review 

Photodegradation in Air (halflife)

<1 hour Estimated value (EPISuite)2

Henry’s Law Constant 1.43 X 10-5

atm-m3/mole Estimated value (EPISuite)

Hydrolysis Half-life (half-life; 

25°C)

stable @ pH 5, 7;

4.3 days at pH 9

MRID 41504401; study on d-trans

allethrin

Aqueous Photolysis Half-life (pH 

5)

No data2 MRID 41504402; study on d-trans

allethrin; half-life could not be 

calculated and the study was 

classified unacceptable for multiple 

reasons. However, study did show 

fairly rapid photolysis in water.

Soil Photolysis Half-life No data3

--

Aerobic Soil Metabolism Half-life 

(25 °C)

Half-lives of 16.9-22.0 days (acidlabeled moiety) and 40.1-42.5 days 

(alcohol-labeled moiety)

MRIDs 42336501, 42336502; 

study on d-trans allethrin

Anaerobic Soil Metabolism Halflife (days)

No data3--

Aerobic Aquatic Metabolism 

Half-life (days) 

No data3--

Anaerobic Aquatic Metabolism 

Half-life (days)

No data3--

Organic Carbon-Normalized Soil 

Partition Coefficient (Koc)

1409, 1358, 1134, 1718 MRID 41900401; study on d-trans

allethrin; compound is slightly 

mobile in soil based on the FAO 

Soil Mobility Classification

Scheme

Soil Adsorption Coefficient (Kd; 

mL/g)

4.1, 6.2, 15.8, 25.9 MRID 41900401; study on d-trans

allethrin

Octanol/Water Partition 

Coefficient Log Kow (pH 7)

>5

4.95

Bioallethrin, Esbiothrin Product 

Chemistry Data Reviews (d-trans

allethrin)

41115302; Pynamin Forte Product 

Chemistry Data Review

Terrestrial Field Dissipation No data3

Bioconcentration Factor in Fish 

(BCF)

2033 Estimated BCF Arnot-Gobas 

method (upper trophic; EPISuite).

1 d-trans allethrin is a synonym for d-trans chrysanthemic acid of d-allethrolone

2The EPISuite output file is presented in APPENDIX A.

3These data are not required under 40 CFR 158.1300 (Environmental Fate Data Requirements) for outdoor residential uses. 

Mobility

In an acceptable batch equilibrium study, organic carbon partition coefficients (Koc) values 

ranged from 1134 to 1718 (mean of 1405 from four soils; MRID 41900401). Based on the Food 

and Agriculture Organization (FAO) Soil Mobility Classification Scheme, these Koc values 

indicate that d-trans allethrin can be expected to be slightly mobile in soil, with greater mobility 

in soils with lower organic matter content. 
Page 11 of 27

While there is some potential for the d-allethrin to reach surface water through drift, it is likely to 

be minimal based on the single supported use (i.e., a repellent candle lantern) which should result 

in very low total application rate for a given time and place of use. For groundwater, the 

potential for contamination is considered even less likely, based on the supported use, the rate of 

aerobic soil degradation, and the low mobility in soils. 

Degradation

The allethrins are stable to hydrolysis at pH 5 and 7, but undergoes fairly rapid hydrolysis (halflife of 4.3 days) at pH 9, with degradation to major degradates including two unidentified 

compounds. This is more rapid than, but somewhat similar to, the hydrolysis rates observed for 

pyrethrin 1.

Although aqueous photolysis data are not required for outdoor residential uses, based on 

available information, aqueous photolysis is potentially a significant degradation pathway for the 

allethrins, as for other synthetic pyrethroids, if the compounds reach surface water and are 

present in an unsorbed state in clear and shallow surface water. Under such conditions, the 

allethrins are expected to photodegrade fairly quickly in water based on the known photolability 

of synthetic pyrethroids. However, the submitted aqueous photolysis study (MRID 41504402) 

was classified “not acceptable,” and an accurate aqueous photodegradation half-life cannot be 

calculated from the data provided. The assumption of rapid aqueous photodegradation would be

consistent with the rapid degradation observed for pyrethrin 1 (PC Code 069008; CAS No. 121-

21-1), which underwent photo-initiated isomerization (to the (E)-isomer) with an observed halflife of approximately 1 hour in sterile aqueous 0.01 M buffer solutions (pH 7) (MRIDs

43096601, 43567601). 

Allethrins are expected to photodegrade rapidly in air, based on an estimated photo-oxidation 

half-life of <1 hour (Table 3). Photodegradation in air is expected to be a significant dissipation 

pathway in the environment.

It is not known whether the allethrins will photodegrade on surface soil; data have not been 

submitted and are not required for outdoor residential uses. In aerobic soil, the allethrins 

biodegraded with half-lives of 16.9-22.0 days (acid-labeled moiety; MRID 42336501) and 40.1-

42.5 days (alcohol-labeled moiety; MRID 42336502). Although the two studies have 

discrepancies between the reported half-lives, the data indicate that aerobic metabolism will be a 

significant degradation process for these compounds in soils. Based on a published classification 

scheme of persistence in soil14, the allethrins are expected to be non-persistent to slightly 

persistent in aerobic soil. In the acid-labeled moiety study, 39% of the applied d-trans allethrin 

had mineralized to CO2 by 6 months, and unextractable, unidentified residues accounted for 

greater than 40% of the applied by that time. In the alcohol-labeled moiety study, CO2 was 71% 

 

14 Goring et. al. 1975. Goring, C.A.I., D.A. Laskowki, J.H. Harnaker, and R.W. Meikle. Principles of pesticide 

degradation in soil. In Environmental Dynamics of Pesticides, R. Haque and V.H. Freed, eds. Plenum Press; New 

York. Pp. 13 5-1 72.
Page 12 of 27

of the applied by 6 months and unextractable, unidentified residues accounted for a maximum of 

19% of the applied by 4 months. The conclusion that aerobic metabolism will occur readily and 

will be a significant degradation pathway for the allethrins is relatively consistent with what has 

been reported for pyrethrin 1, which was metabolized in aerobic soil with a half-life of 10 days, 

yielding similar levels of CO2 and unextractable residues as those seen in the acid-labeled dtrans allethrin study. It is also consistent with the increased persistence expected of the allethrins 

relative to pyrethrin 1 due to the presence of a more stable side chain in the former.

15

Information on metabolism in anaerobic soil or in either aerobic aquatic or anaerobic aquatic 

environments is not available, as data have not been submitted and are not required for outdoor 

residential uses. 

Bioaccumulation

The potential for bioaccumulation of the allethrins in fish is not known; data have not been 

submitted and are not required for outdoor residential uses. High log octanol-water partition 

coefficient (Kow) values of >5 and 4.95, reported in submitted studies (Table 3) suggest that 

there may be a potential for bioaccumulation. However, an estimated BCF of 203 as well as data 

submitted for pyrethrin 1 indicate that the potential for bioaccumulation is low because of 

relatively rapid depuration and/or metabolism. Pyrethrin 1 residues accumulated in bluegill 

sunfish (Lepomis macrochirus) continuously exposed to the compound for 28 days under 

laboratory flow-through conditions with mean bioconcentration factors of 127x for the edible 

tissue, 873x for the non-edible tissue, and 471x for the whole fish (pyrethrin 1 MRIDs 43302301, 

43884102). However, in that study, 77% of the accumulated [14C] residues were eliminated 

from the edible tissues, 66% from the non-edible tissues, and 68% from the whole fish by Day 1

and by Day 14, residues in edible tissues were below the detection limit (1 ppb) and were close 

to the detection limit (average = 1.29 ppb) in viscera. Based on the current labeled uses, the 

limited potential for exposure to the allethrins (and expected depuration/metabolism if exposed), 

bioaccumulation is not expected to be a concern for fish; however, there is uncertainty whether 

the compound might accumulate in other aquatic organisms such as invertebrates given the 

relatively high log Kow.

Monitoring

d-Allethrin was not consistently identified in available environmental monitoring studies, 

consistent with the low concern of environmental exposure based on the limited use pattern

(which is further limited now). The following databases were evaluated for the potential dallethrin detections:

 USGS National Water Quality Assessment (NAWQA) Program database 

(http://cida.usgs.gov/nawqa_queries_public/) – 165 samples returned for “allethrin”, no detects 

above limit of detection

 

15 Worthing 1979. Worthing, C. R. (ed). Pesticide Manual. 6th ed. British Crop Protection Council, l979; 

Worcestershire, England. Pp.7.
Page 13 of 27

 USGS Community Water System (CWS) data (http://pubs.usgs.gov/ds/544/) – no records of 

allethrins

 CDPR surface water and sediment database (http://cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm)

– 18 samples returned for “allethrin,” one above the limit of detection (0.0242 ppb, 2/22/10, St. 

Johns River, Tulare County)

 USEPA/USGS/NWQMC (National Water Quality Monitoring Council) Water Quality Portal 

database (http://www.waterqualitydata.us/) – 1,123 sample results from 297 sites returned for 

“allethrin,” all of which are “not detected” or “*non-detect.”

Ecological Effects

Consistent with the process described in the Overview Document16, the risk assessment for the dallethrin relies on a surrogate species approach. Toxicological data generated from surrogate test 

species, which are intended to be representative of broad taxonomic groups, are used to 

extrapolate the potential effects on a variety of species (receptors) included under these 

taxonomic groupings. 

Effects to Aquatic Organisms

The allethrins as a whole are considered very highly toxic to freshwater fish (esbiol LC50 = 7.8

μg a.i./L, MRID 40098001) and freshwater invertebrates (LC50 = 2.1 μg a.i./L; allethrin; MRID 

40098001) on an acute exposure basis (Table 4). No chronic toxicity data for freshwater 

vertebrates or invertebrates are available for the allethrins and no acute or chronic toxicity data 

are available for estuarine/marine fish or invertebrates. Toxicity data are also lacking for 

vascular and non-vascular aquatic plants.

 

16 USEPA 2004.Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, U.S. 

Environmental Protection Agency. Endangered and Threatened Species Determinations. Office of Chemical Safety 

and Pollution Prevention formerly the Office of Prevention, Pesticides and Toxic Substances. January 23, 2004. 

http://www.epa.gov/espp/consultation/ecorisk-overview.pdf 
Page 14 of 27

TABLE 4: Summary of Toxicity Studies for Aquatic Organisms Exposed to Allethrins

SPECIES CHEM./

(PC CODE)

ENDPOINT

DURATION 

(hrs)

CONC. 

MEAN 

(ppb)

EXPOSURE 

TYPE1

CATEGORY MRID #

Freshwater Fish

Perca flavescens

Yellow Perch Esbiol/ 004004 LC50 96

7.8

(6.5 –

9.4)

S Supplemental 400980012

Oncorhynchus 

kisutch

Coho Salmon

Bioallethrin/

004003 LC50 96

9.4

(7.91 –

11.2)

F Supplemental 00122546

Oncorhynchus 

mykiss

Rainbow Trout

Bioallethrin/

004003 LC50 96

9.7

(8.0 –

11.6)

F Supplemental 40098001

Ictalurus 

punctatus

Channel Catfish

Esbiol/

004004 LC50 96

14.6

(10.1 –

21.0)

F Supplemental 40098001

Salvelinus 

namaycush

Lake Trout

Bioallethrin/

004003 LC50 96

17.3

(14.9 –

20.0)

S Supplemental 40098001

Lepomis 

macrochirus

Bluegill Sunfish

Bioallethrin/

004003 LC50 96

22.5

(20.5 –

24.7)

F Supplemental 40098001

Pimephales 

promelas

Fathead Minnow

Bioallethrin/

004003 LC50 96

48.0

(34.9 –

66.0)

F Supplemental 40098001

Freshwater Invertebrates

Pteronarcys 

californica

Stonefly

Allethrin/

004001 LC50 96

2.1

(1.5 –

2.9)

S Supplemental 400980012

Gammarus 

fasciatus

Scud

Allethrin/

004001 LC50 96

8

(5.0 –

12.0)

S Supplemental 40098001

Daphnia magna 

Water Flea

Esbiothrin/

004007 EC50 48

8.9

(7.5 –

11)

S Acceptable 43235801

Simocephalus 

serrulatus

Water Flea

Allethrin/

004001 EC50 48

56

(40.0 -

78.0)

S Supplemental 40098001

1 Exposure type refers to the conditions under which the study was conducted; ‘S’ refers to static conditions, and ‘F’ refers to flow-through 

conditions.

2 Following EFED guidance on MRID 40098001 [Mayer, F.L. and M.R. Ellersieck (1986). Manual of Acute Toxicity: Interpretation and Data 

Base for 410 Chemicals and 66 Species of Freshwater Animals. United States Department of the Interior, U.S. Fish and Wildlife Service, 

Resource Publication 160], the raw data from this study are considered supplemental.

Bolded endpoints represent the most sensitive endpoint for each taxon.

Effects to Terrestrial Organisms

On an acute oral exposure basis, the allethrins are categorized as practically non-toxic to birds

based on a Bobwhite quail (Colinus virginianus)study of bioallethrin (LD50 = 2030 mg/kg-bw; 

MRID 00123339). On a subacute dietary exposure basis, the allethrins are also categorized as 

practically non-toxic to birds based on a mallard duck (Anas platyrhynchos) dietary toxicity 

study with d-allethrin (LC50 >5,620 mg/kg-diet, MRID 00027548) (Table 5). No avian chronic 

toxicity data are available for the allethrins.

The allethrins are categorized as moderately toxic to mammals on an acute oral exposure basis, 

based on a laboratory rat study with esbiothrin (LD50 = 378 mg/kg-bw, MRID 00151449) (Table

5). 
Page 15 of 27

In a rat 2-generation reproduction study (MRID 41246801) with d-allethrin (PC Code: 004005) 

there was no effect upon reproductive indices. The parental NOAEL is 200 mg/kg diet (13 

mg/kg-bw/day in males and 15 mg/kg-bw/day in females) and the parental LOAEL is 2,000 

mg/kg diet (130 mg/kg-bw/day in males and 145 mg/kg-bw in females) and were based on 

reductions in growth (i.e., decreased body weights and body weight gains) and effects on the 

liver (i.e., increases in absolute and relative liver weights, and hepatocellular hypertrophy). The 

offspring NOAEL is 200 mg/kg diet (15 mg/kg-bw/day) and the LOAEL for offspring toxicity is 

2,000 mg/kg diet (145 mg/kg-bw/day) based on reductions in pup body weights of the F2

generation.

The allethrins are considered moderately toxic to adult honey bees (Apis mellifera) on an acute 

contact exposure basis using an LD50 of 3.4 μg/bee for allethrins (MRID 00162751) (Table 5)

and on an acute oral exposure basis using an LD50 of 9.1 μg/bee for allethrins (MRID

00162751).

TABLE 5: Summary of Submitted Toxicity Studies for Terrestrial Animals Exposed to 

Allethrins

SPECIES CHEM./

(PC CODE)

ENDPOINT

DURATION 

(Days)

CONC. 

MEAN 

EXPOSURE 

TYPE

CATEGORY MRID #

Birds

Colinus 

virginianus

Bobwhite Quail

Bioallethrin/

004003 LD50 14

2030

mg/kg-bw

(1504 –

2738)

N/A Acceptable 00123339

Anas 

platyrhynchos

Mallard Duck

d-Allethrin/

004005 LC50 8

>5,620 

mg/kg-diet N/A Acceptable 00027548

Mammals

Rattus norvegicus

Laboratory Rat

Esbiothrin/ 

004007 LD50 14 378 mg/kg-bw N/A Acceptable 00151449

Rattus norvegicus

Laboratory Rat

d-Allethrin/

004005 NOAEL 2 generation

13 mg/kgbw N/A Acceptable 41246801

Terrestrial Invertebrates

Apis mellifera

Honey Bee

Allethrin/

004001 LD50 1 3.4 μg/bee Contact Supplemental 00162751

Terrestrial Plants

No guideline toxicity data were submitted with which to evaluate the effects of allethrins

exposure to non-target terrestrial plants. Although in previous assessments risk to plants from 

allethrins use was not expected because of the allethrins’ neural toxic mode of action and the 

results of efficacy studies provided by the registrant, there are 13 ‘minor’ incidents involving 

terrestrial plants identified in EFED’s Registration Review Problem Formulation for allethrins17. 

These 13 incidents (APPENDIX B) involved the use of pressurized liquid spray or ready-to-use 

solution formulations containing additional active ingredients and/or inerts. As of August 12,

2014, no additional plant incidents have been recorded. 

 

17 Ibid USEPA 2010
Page 16 of 27

Although no terrestrial plant data are available f or d-allethrin, the chemical’s limited use and 

low likelihood of exposure for plants renders the need for such data as low.

 

Ecological Incidents 

Reviews of the Ecological Incident Information System (EIIS, version 2.1), the Avian Incident 

Monitoring System (AIMS)18, and the Incident Data System (IDS) were conducted on August 

12, 2014. As of August 12, 2014, in addition to the plant incidents discussed in the preceding 

section, two additional minor wildlife incidents were reported in the IDS (APPENDIX B). 

These incidents involved the use of an impregnated material (i.e., mosquito coil) or pressurized 

liquid formulation and are reported in the aggregated IDS; therefore details are not available on 

the specific species affected. None of the incidents involved the lantern use (which is the use 

pattern assessed in this document). No incidents were reported in the AIMS or EIIS databases.

2. Risk Characterization

Risk Estimation

Aquatic Animals

To assess the potential for effects of a pesticide use to aquatic organisms, an estimated 

environmental concentration (EEC) is typically determined by modeling the transport of an 

applied pesticide into the farm pond, which is a water body of defined proportions and volume 

(i.e., 20 x 106 L) used routinely in EFED in ecological risk assessment.

19

 Given that the single 

remaining use of d-allethrin (i.e., repellent candle) does not involve direct application to land or 

water and can be used by any number of people in any locations for any length of time, the use 

does not lend itself to the modeling tools typically used by EFED to develop aquatic exposure

estimates. However, for an LOC not to be exceeded, the RQ calculated from the EEC and the 

toxicity endpoint must be lower than the LOC. This calculation can be reversed to determine the 

lowest EEC that would be expected to lead to an LOC exceedance:

RQ(below LOC) < LOC and

RQ(below LOC) = EEC(below LOC) ÷ toxicity value; therefore

EEC(below LOC) < LOC * toxicity value.

All values and equations used in this calculation are summarized in Table 8. From the available 

data on the effects of allethrins to aquatic animals (both vertebrates and invertebrates), the most 

sensitive endpoint is for the stonefly (Pternoarcys californica) with an LC50 of 2.1 μg a.i./L. The 

highest aquatic risk category is for acute risk to listed species with an LOC of 0.05. Inserting 

these values into the above equation leads to the result that for an aquatic LOC not to be 

exceeded, the EEC must be less than 0.105 μg a.i./L (0.05 * 2.1 μg a.i./L). Based on the quantity 

 

18http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims/login.cfm?CFID=113048231&CFTOKEN=9243482

19 http://www.epa.gov/oppefed1/models/water/
Page 17 of 27

of active ingredient in each device, the entire mass of a.i. from over 4 candles would need to 

enter the farm pond (and be solubilized) to exceed the LOC for aquatic animals. Due to dilution 

in air, low deposition rates due to dissipation in air, low mobility in soil due to the sorbtive 

properties of d-allethrin, and subsequent degradation in air, soil, and water via photolysis, the 

mass of d-allethrin that may reach a water body from a single candle is likely to be far lower than 

the total amount of a.i. contained in each device. The actual number of devices needed to result 

in sufficient exposure to trigger to an LOC exceedance, then, can reasonably be expected to be 

far greater than the number calculated here.

Table 8: Amount of Allethrins in an Aquatic Environment that would exceed the Most 

Sensitive Level of Concern

Parameter Inputs and Results

Most sensitive endpoints LOC = 0.05 (listed species)

Toxicity = 2.1 μg a.i./L (Stonefly LC50)

EEC in farm pond leading to LOC 

exceedance1 0.105 μg a.i./L

Amount of a.i. in farm pond leading to LOC 

exceedance2 2.1 g

Amount of a.i. per device3 Candle

0.498 g a.i./device

No. of devices from which entire contents 

must end up in pond leading to LOC 

exceedance4

~4.2 devices

1 RQ(below LOC) < LOC and RQ(below LOC) = EEC(below LOC) ÷ toxicity value therefore EEC(below LOC) < LOC * toxicity value

2 Volume of pond = 20,000 m3 or 20,000,000 L. Dissolved compound = EEC * volume.

3 See Table 2

4

(Amount of a.i. in pond) ÷ (Amount of a.i. per device) = No. of devices to exceed the LOC

Terrestrial Animals

The allethrins are considered practically non-toxic to birds (and by extension to terrestrial-phase 

amphibians and reptiles) on an acute oral and subacute dietary exposure basis and are moderately 

toxic to mammals on an acute oral exposure basis. All of the exposure values, conservatively 

estimated with T-REX using a rate equivalent to 0.0088 lbs a.i./A, were well below the highest 

concentrations tested in the available acute toxicity studies for terrestrial animals (see 

APPENDIX C for details). Exposures were estimated assuming that all of the d-allethrin in 8 

candles (see the ‘Overview of Pesticide Use and Usage’ section above) was released at the same 

time and deposited as residues on terrestrial animal food items. Based on these conservative 

assumptions, all of the acute avian and mammalian RQs are <0.01 and are well below the acute

risk LOCs (see APPENDIX C for details).
Page 18 of 27

As described earlier, d-allethrin is considered moderately toxic to adult honey bees (Apis 

mellifera). Because the d-allethrin is used as an insect repellent and has potential insecticidal 

properties, it is assumed that terrestrial invertebrates (e.g., honey bee or listed flying terrestrial 

invertebrate species) that is exposed by flying through the d-allethrin released by the candle has 

the potential to be repelled, and perhaps killed. It is possible that a mosquito that flew into a 

cloud of allethrins vapor would be repelled and move away unharmed or move away with effects

that would reduce its ability to grow, reproduce or survive. The same could be true for honey 

bees and listed terrestrial invertebrates that enter the treated area. 

Mosquitoes actively track humans in order to obtain a blood meal and it is this behavior that the 

d-allethrin is intended to target. Most bees and listed terrestrial invertebrate species would not be 

expected to be attracted to humans. Also, periods when mosquitos are most active, e.g., dusk do 

not tend to overlap when honey bees and other insects are typically active. Therefore, a nontarget terrestrial invertebrate would be exposed to the d-allethrin only by chance, or because it 

(e.g., a moth) was flying toward a light (such as with a burning candle). Although the acute 

toxicity value for bees would trigger a bee advisory statement on the label of products, the fact 

that this compound is not applied to plants and the likelihood of bees coming into contact with 

sufficient residues of the compound via ingestion of pollen/nectar or through contact with 

residues on plants, such language is not warranted for the use of d-allethrin as a repellent. 

Furthermore, given the relatively limited area of effects around the d-allethrin dispensing 

devices, the likely setting of use (i.e., in backyards and other residential areas and where people 

hunt and otherwise participate in outdoor activities), the sporadic and dispersed use, and dilution 

by the large volume of air into which it is released, the probability of impacting listed terrestrial 

invertebrates is considered low and there is no reasonable expectation of effects (this is also why 

a standard screening-level assessment for terrestrial invertebrates was not conducted). 

Plants

There are currently no data available to assess the potential risk to terrestrial or aquatic plants 

from d-allethrin. However, there is no reasonable expectation of effects to plants due to the low 

exposure potential and no reported incidents for the use pattern being assessed here.

Risk Description

The risk hypothesis articulated in the preliminary Problem Formulation written in support of the 

Registration Review of allethrins in general stated that “based on mode of action and the 

sensitivity of non-target aquatic and terrestrial species, the outdoor, residential use of allethrins 

(i.e., mosquito repellant candle lantern) has the potential to reduce survival, reproduction, 

and/or growth in terrestrial and aquatic non-target animals through drift and/or runoff. These 

non-target organisms include Federally-listed threatened and endangered species as well as 

non-listed species.” However, based on the available data and the single remaining registered 

use of d-allethrin (i.e., candles), none of the LOCs evaluated in this assessment is exceeded for dallethrin. Where RQs could not be calculated due to the lack of toxicity data, potential for 
Page 19 of 27

exposure is considered low. Therefore, the risk hypothesis is rejected (see below for the 

discussion on listed species). 

The d-allethrin released from the repellant candle lantern is expected to dissipate rapidly. 

Additionally, any d-allethrin released from the candle during daylight hours is expected to have a 

short half-life in air given its susceptibility to photolysis. Furthermore, based on conservative 

estimates of exposure for the candle use, none of the RQs resulted in LOC exceedances for fish

(aquatic-phase amphibians), aquatic invertebrates, birds (terrestrial-phase amphibians, reptiles), 

or mammals. The likelihood of adverse effects to bees and other pollinating insects is also 

considered low given the relatively limited area in which exposure is expected to occur and 

given that the compound is likely to readily dissipate. Therefore, the likelihood of adverse effects 

to non-target species from the use of d-allethrin is considered low based on the results of this

quantitative and qualitative assessment.

Uncertainties and Assumptions

For the currently registered use of d-allethrin, the fate of the a.i. in the environment is primarily 

dependent on its transformation and dissipation in air. Although there were limited data to fully 

describe the environmental fate of d-allethrin in air, soil, and water, this assessment’s 

consideration of allethrins as a whole in air is largely based on estimates of photodegradation in 

air determined through QSAR as used in the estimation software EPI-Suite, and bridging of 

data/information for other pyrethroids. Also, the registered use of d-allethrin consists of small

devices that do not deposit the a.i. directly on land, plant, animal, or water surfaces and only 

affect relatively confined areas. EFED conducted terrestrial exposure modeling based on a set of 

very conservative assumptions, which likely led to overestimates of potential exposure; however, 

even with these conservative estimates, RQ values were below LOCs. The amount of 

overestimation is uncertain, and so this modeling is intended to establish upper bounds on 

potential environmental exposure rather than to accurately predict ambient exposure levels. 

Although the available data were adequate for assessing the exposure and potential effects

associated with the candle use, additional data may be needed in the future if the use pattern 

(and, thus, the exposure potential) for d-allethrin changes.

Endangered Species Assessment

Because direct adverse effects are not expected for birds, reptiles, amphibians, mammals, fish, 

and aquatic invertebrates, and there is no reasonable expectation of effects to plants or terrestrial 

invertebrates, the EPA makes a No Effects (NE) determination for all listed species and a No 

Habitat Modification determination for all designated critical habitats of listed species for the 

currently registered use of d-allethrin.
Page 20 of 27

Endocrine Disruptor Screening Program 

As required by FIFRA and the Federal Food Drug and Cosmetic Act (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 allethrins, 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), allethrins are 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, 201320 and includes some 

pesticides scheduled for Registration Review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors.

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.21

 

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

chemicals.

21 http://www.epa.gov/endo/
Page 21 of 27

APPENDIX A: EPISUITE OUTPUT FOR ALLETHRINS (CAS No. 548-79-2)

CAS Number: 000584-79-2

SMILES : O=C(OC(C(=C(C1(=O))CC=C)C)C1)C(C2(C)C)C2C=C(C)C

CHEM : Allethrin

MOL FOR: C19 H26 O3 

MOL WT : 302.42

------------------------------ EPI SUMMARY (v4.10) --------------------------

Physical Property Inputs:

 Log Kow (octanol-water): ------

 Boiling Point (deg C) : ------

 Melting Point (deg C) : ------

 Vapor Pressure (mm Hg) : ------

 Water Solubility (mg/L): ------

 Henry LC (atm-m3/mole) : ------

Log Octanol-Water Partition Coef (SRC):

 Log Kow (KOWWIN v1.68 estimate) = 5.52

 Log Kow (Exper. database match) = 4.78

 Exper. Ref: HANSCH,C ET AL. (1995)

Boiling Pt, Melting Pt, Vapor Pressure Estimations (MPBPVP v1.43):

 Boiling Pt (deg C): 374.02 (Adapted Stein & Brown method)

 Melting Pt (deg C): 126.18 (Mean or Weighted MP)

 VP(mm Hg,25 deg C): 3.53E-005 (Modified Grain method)

 VP (Pa, 25 deg C) : 0.0047 (Modified Grain method)

 MP (exp database): -40 deg C

 BP (exp database): 163-170 @ 0.15 mm Hg deg C

 VP (exp database): 3.30E+05 mm Hg (4.40E+007 Pa) at 25 deg C

Water Solubility Estimate from Log Kow (WSKOW v1.42):

 Water Solubility at 25 deg C (mg/L): 0.9838

 log Kow used: 4.78 (expkow database)

 no-melting pt equation used

 Water Sol (Exper. database match) = 4.6 mg/L (25 deg C)

 Exper. Ref: TOMLIN,C (1997)

Water Sol Estimate from Fragments:

 Wat Sol (v1.01 est) = 0.29985 mg/L

ECOSAR Class Program (ECOSAR v1.00):

 Class(es) found:
Page 22 of 27

 Esters

 Vinyl/Allyl Ketones

 Vinyl/Allyl Esters

 Pyrethroids 

Henrys Law Constant (25 deg C) [HENRYWIN v3.20]:

 Bond Method : 6.12E-007 atm-m3/mole (6.20E-002 Pa-m3/mole)

 Group Method: Incomplete

 Exper Database: 1.04E-07 atm-m3/mole (1.05E-002 Pa-m3/mole)

For Henry LC Comparison Purposes:

 User-Entered Henry LC: not entered

 Henrys LC [via VP/WSol estimate using User-Entered or Estimated values]:

 HLC: 1.428E-005 atm-m3/mole (1.447E+000 Pa-m3/mole)

 VP: 3.53E-005 mm Hg (source: MPBPVP)

 WS: 0.984 mg/L (source: WSKOWWIN)

Log Octanol-Air Partition Coefficient (25 deg C) [KOAWIN v1.10]:

 Log Kow used: 4.78 (exp database)

 Log Kaw used: -5.371 (exp database)

 Log Koa (KOAWIN v1.10 estimate): 10.151

 Log Koa (experimental database): None

Probability of Rapid Biodegradation (BIOWIN v4.10):

 Biowin1 (Linear Model) : 0.6007

 Biowin2 (Non-Linear Model) : 0.6497

Expert Survey Biodegradation Results:

 Biowin3 (Ultimate Survey Model): 2.4365 (weeks-months)

 Biowin4 (Primary Survey Model) : 3.4647 (days-weeks )

MITI Biodegradation Probability:

 Biowin5 (MITI Linear Model) : 0.4748

 Biowin6 (MITI Non-Linear Model): 0.1153

Anaerobic Biodegradation Probability:

 Biowin7 (Anaerobic Linear Model): -0.3858

Ready Biodegradability Prediction: NO

Hydrocarbon Biodegradation (BioHCwin v1.01):

 Structure incompatible with current estimation method!

Sorption to aerosols (25 Dec C)[AEROWIN v1.00]:

 Vapor pressure (liquid/subcooled): 4.4E+007 Pa (3.3E+005 mm Hg)

 Log Koa (Koawin est ): 10.151

 Kp (particle/gas partition coef. (m3/ug)):
Page 23 of 27

 Mackay model : 6.82E-014 

 Octanol/air (Koa) model: 0.00348 

 Fraction sorbed to airborne particulates (phi):

 Junge-Pankow model : 2.46E-012 

 Mackay model : 5.45E-012 

 Octanol/air (Koa) model: 0.218 

Atmospheric Oxidation (25 deg C) [AopWin v1.92]:

 Hydroxyl Radicals Reaction:

 OVERALL OH Rate Constant = 222.2525 E-12 cm3/molecule-sec

 Half-Life = 0.048 Days (12-hr day; 1.5E6 OH/cm3)

 Half-Life = 0.578 Hrs

 Ozone Reaction:

 OVERALL Ozone Rate Constant = 92.259369 E-17 cm3/molecule-sec

 Half-Life = 0.012 Days (at 7E11 mol/cm3)

 Half-Life = 17.887 Min

 Reaction With Nitrate Radicals May Be Important!

 Fraction sorbed to airborne particulates (phi):

 3.96E-012 (Junge-Pankow, Mackay avg)

 0.218 (Koa method)

 Note: the sorbed fraction may be resistant to atmospheric oxidation

Soil Adsorption Coefficient (KOCWIN v2.00):

 Koc : 3082 L/kg (MCI method)

 Log Koc: 3.489 (MCI method)

 Koc : 5001 L/kg (Kow method)

 Log Koc: 3.699 (Kow method)

Aqueous Base/Acid-Catalyzed Hydrolysis (25 deg C) [HYDROWIN v2.00]:

 Total Kb for pH > 8 at 25 deg C : 9.024E-003 L/mol-sec

 Kb Half-Life at pH 8: 2.434 years 

 Kb Half-Life at pH 7: 24.338 years 

 (Total Kb applies only to esters, carbmates, alkyl halides)

Bioaccumulation Estimates (BCFBAF v3.01):

 Log BCF from regression-based method = 1.562 (BCF = 36.45 L/kg wet-wt)

 Log Biotransformation Half-life (HL) = -0.3033 days (HL = 0.4974 days)

 Log BCF Arnot-Gobas method (upper trophic) = 2.307 (BCF = 202.7)

 Log BAF Arnot-Gobas method (upper trophic) = 2.307 (BAF = 202.9)

 log Kow used: 4.78 (expkow database)

Volatilization from Water:
Page 24 of 27

 Henry LC: 1.04E-007 atm-m3/mole (Henry experimental database)

 Half-Life from Model River: 9792 hours (408 days)

 Half-Life from Model Lake : 1.07E+005 hours (4457 days)

Removal In Wastewater Treatment:

 Total removal: 69.53 percent

 Total biodegradation: 0.62 percent

 Total sludge adsorption: 68.91 percent

 Total to Air: 0.00 percent

 (using 10000 hr Bio P,A,S)

Level III Fugacity Model:

 Mass Amount Half-Life Emissions

 (percent) (hr) (kg/hr)

 Air 0.0104 0.237 1000 

 Water 17.3 900 1000 

 Soil 79.6 1.8e+003 1000 

 Sediment 3.05 8.1e+003 0 

 Persistence Time: 1.08e+003 hr
Page 25 of 27

APPENDIX B: Incident Data System (IDS) for Allethrins 

Report created on 12 August 2014.
Page 26 of 27

APPENDIX C: T-REX Output for Allethrins

Input

Chemical Name: Application Rate (lb ai/acre)

Seed Treatment? (Check if yes) FALSE Seeding Rate (lbs/acre)

 Use:

Product name and form:

% A.I. (leading zero must be entered for 

formulations <1% a.i.):

Application Rate (lb ai/acre) 0.0088

Half-life (days): 35

Application Interval (days):

Number of Applications: 1

Are you assessing applications with 

variable rates or intervals? no

You MUST specify application day in Columns F and G - you may enter up to 30 applications

What body weight range is assessed 

(grams)? Birds Mammals

Small 20 15

Medium 100 35

Large

1000 1000

Chemical Identity and Application Information

Allethrins

residential

ThermaCELL Mosquito Repellant Candle Lantern

100.00%

Assessed Species Inputs (optional, use defaults for RQs for national level 

assessments)

You MUST specify application day in Columns F and G - you may enter up to 30 applications

Avian

Endpoint Toxicity value

Indicate test species 

below

LD50 (mg/kg-bw) 2030.00 1

LC50 (mg/kg-diet) 1

NOAEL (mg/kg-bw) 1

NOAEC (mg/kg-diet) 1

1.15

Mammalian

Acute Study Chronic Study

350 350

Endpoint Toxicity value Reference (MRID)

LD50 (mg/kg-bw) 378.00

LC50 (mg/kg-diet)

Reported Chronic 

Endpoint 1

Is dietary concentration 

(mg/kg-diet) reported from the 

available chronic mammal 

study? (yes or no)

no

Enter dietary concentration (mg/kg-diet)

Estimated Chronic Diet 

Concentration Equivalent to 

Reported Chronic Daily Dose

0 mg/kg-diet based on 

standard FDA lab rat 

conversion

Enter the Mineau et al. Scaling Factor

Size (g) of mammal used in toxicity study

Default rat body weight is 350 grams
Page 27 of 27

Output

20 100 1000

Short Grass 0.00 0.00 0.00

Tall Grass 0.00 0.00 0.00

Broadleaf plants 0.00 0.00 0.00

Fruits/pods 0.00 0.00 0.00

Arthropods 0.00 0.00 0.00

Seeds 0.00 0.00 0.00

Dose-based RQs 

(Dose-based EEC/adjusted LD50)

Avian Acute RQs

Size Class (grams) 15 grams 35 grams 1000 grams

Acute Chronic Acute Chronic Acute Chronic

Short Grass 0.00 #DIV/0! 0.00 #DIV/0! 0.00 #DIV/0!

Tall Grass 0.00 #DIV/0! 0.00 #DIV/0! 0.00 #DIV/0!

Broadleaf plants 0.00 #DIV/0! 0.00 #DIV/0! 0.00 #DIV/0!

Fruits/pods 0.00 #DIV/0! 0.00 #DIV/0! 0.00 #DIV/0!

Arthropods 0.00 #DIV/0! 0.00 #DIV/0! 0.00 #DIV/0!

Seeds 0.00 #DIV/0! 0.00 #DIV/0! 0.00 #DIV/0!

Medium mammal Large mammal Dose-based RQs 

(Dose-based EEC/LD50 or NOAEL)

Small mammal