UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

PC Code: 109709 

DP Barcodes: D403437 

April16, 2013 

Subject: 

To: 

From: 

Reviewed By: 

Through: 

Registration Review: Preliminary Ecological Risk Assessment and 

Endangered Species Effects Determination for Metofluthrin 

Veronica Dutch, Chemical Review Manager 

Risk Management and Implementation Branch V 

Pesticide Re-evaluation Division (7508P) 

Melissa Panger, Ph.D., Senior Scientist ~ '( /I~/IJ James Wolf, Ph.D., Environmental Scientist <L~-,. f<lJ.1 

Environmental Risk Branch III t?..,.,..-.......,. 

Environmental Fate and Effects Division (7507P~ 

Rosanna Louie-Juzwiak, RAPL {))_- ~ Environmental Risk Branch Ill v~ Environmental Fate and Effects Division (7507P) 

Dana Spatz, Branch Chief 

Environmental Risk BrancfN:H:::S..,.l "-.7""--.,..._00:::::N~ 

Environmental Fate and Effects Division (7507P) 

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

risk assessment and endangered species effects determination for the pyrethroid insecticide 

metofluthrin (first registered in 2006). For the currently registered uses (i.e., deck strips, 

personal fans, and candles), metofluthrin is released into the air as a vapor through passive 

dissipation, heat-driven or fan-driven evaporation. For these uses, the active ingredient is 

initially present in the atmosphere in a volatile form but is expected to dissipate rapidly through a 

combination of degradation and dilution by the large volume of air into which it is released. 

Based on the available data, the currently registered use patterns for metofluthrin, and 

conservative assumptions regarding exposure, none ofthe EPA's Levels of Concern are 

exceeded for fish (and, thus, aquatic-phase amphibians), aquatic invertebrates, birds (and, thus, 

reptiles and terrestrial-phase amphibians), or mammals. Furthermore, there are no known 

ecological incidents reported for metofluthrin. 

Because metofluthrin is used as an insect repellent and has potential insecticidal properties, it is 

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

exposed to metofluthrin via ambient exposure (i.e., flying through the metofluthrin released by 

the deck strip, fan or candle) has the potential to be affected. Given the relatively limited area of 

effect around the metofluthrin dispensing devices (up to 5 m), the likely setting ofuse (i.e., in 

1 
2

backyards and other areas around people), the short half-life of metofluthrin in air (ranging from 

1.7 to 1.9 hours), the fact that non-target invertebrates would be exposed to the metofluthrin only 

by chance [unlike the target species (i.e., mosquitoes, that track humans)], the probability of 

impacting endangered invertebrates is low. There are currently no data available to assess the 

potential risk to terrestrial or aquatic plants from the registered metofluthrin uses. Risks to 

plants, however, are not expected due to the low exposure potential. Therefore, there is no 

reasonable expectation of effects to federally listed threatened or endangered terrestrial 

invertebrate, aquatic plant, or terrestrial plant species from use of currently registered 

metofluthrin products. 

Due to a combination of low exposure and relative insensitivity to the active ingredient (for 

many taxa), risks to non-target organisms are not expected. Because direct adverse effects are 

not expected for birds, reptiles, amphibians, mammals, fish, or 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 Federally-listed threatened/endangered species and the 

currently registered uses of metofluthrin. This determination was supported by the the Office of 

Pesticide Program’s Science Policy Council/Risk Management Forum De Minimis Subgroup 

(USEPA, 2013). EPA also has determined that for the currently registered uses of metofluthrin 

no Habitat Modification is likely for designated critical habitats. 
3

REGISTRATION REVIEW 

Preliminary Ecological Risk Assessment and Endangered Species Effects Determination for: 

Metofluthrin 

(CAS Reg. No. 240494-70-6; USEPA PC # 109709) 

2,3,5,6-tetrafluoro-4-(methoxymethyl)benzyl(E,Z)-(1R,3R)-2,2-dimethyl-3-

(prop-1-enyl)cyclopropanecarboxylate

Prepared by:

Melissa Panger, Ph.D., Senior Scientist

James Wolf, Ph.D., Environmental Scientist

Reviewed by:

Rosanna Louie-Juzwiak, RAPL

Dana Spatz, Branch Chief

U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch 3

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

April 16, 2013 
4

TABLE OF CONTENTS 

1. Problem Formulation ....................................................................................... 5

Nature of Regulatory Action ....................................................................................................... 5

Previous Assessments ................................................................................................................. 5

Ecological Risk Assessments ...................................................................................... 5

Drinking Water Exposure Assessment ....................................................................... 6

Stressor Source and Distribution ................................................................................................ 6

Pesticidal Mechanism of Action ................................................................................. 6

Overview of Pesticide Use and Usage ........................................................................ 7

Environmental Fate and Transport ............................................................................................. 7

Environmental Fate Properties .................................................................................. 10

Ecological Effects ..................................................................................................................... 11

Ecological Incidents .................................................................................................. 12

Characteristics of Ecosystems Potentially at Risk .................................................... 12

Assessment Endpoints .............................................................................................. 12

Conceptual Model ..................................................................................................... 13

Analysis Plan ............................................................................................................................ 16

Measures of Exposure ............................................................................................... 16

Measures of Effect .................................................................................................... 18

Integration of Exposure and Effects.......................................................................... 18

Endangered Species Assessments ............................................................................. 19

2. RISK CHARACTERIZATION..................................................................... 19

RISK ESTIMATION ................................................................................................................ 19

RISK DESCRIPTION .............................................................................................................. 22

ENDANGERED SPECIES ASSESSMENT ............................................................................ 23

References ................................................................................................................................. 23
5

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 metofluthrin (2,3,5,6-

tetrafluoro-4-(methoxymethyl)benzyl(E,Z)-(1R,3R)-2,2-dimethyl-3-(prop-1-

enyl)cyclopropanecarboxylate) 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 (USEPA, 1998a).

Previous Assessments 

Ecological Risk Assessments 

Metofluthrin was first registered in 2006 (the current registrants are S.C. Johnson & Sons, Inc., 

and Sumitomo Chemical Company, LTD). As part of the initial registration, the potential 

ecological exposures and risks associated with both the deck strip and fan uses were assessed 

[USEPA, 2006a] (no additional assessment was conducted for the candle use because the risks 

were assumed to be similar to the deck strip use). In the deck strip and fan assessment, no EPA 

levels of concern (LOCs) were exceeded, and it was concluded that risks were not expected for 

aquatic or terrestrial vertebrates or aquatic invertebrates because of low potential exposure. 

However, it was concluded that due to the insecticidal properties of metofluthrin, the uses could 

pose a direct risk to non-target insects including Federally-listed threatened/endangered species 

(hereafter referred to as “listed”) and non-listed species. Therefore, the potential for indirect 

effects to other listed taxa could not be precluded at that time. 

Subsequent to the 2006 assessment, a refined listed species assessment was conducted for the 

deck strip and fan uses [USEPA, 2006b]. In this assessment, EFED determined that no listed 

species would be affected through direct or indirect effects from the use of metofluthrin. This 

was based on the following: 

“While it is possible that non-target invertebrates might inadvertently be exposed to the 

cloud of metofluthrin given off by the devices, further analysis can be done to estimate 

the general distance (radius) within which such effects might be possible. It is estimated 

that effects would be unlikely beyond 5 meters; the distance at which no mortality 

occurred. In addition, metofluthrin was assumed to have a very short half-life in air, with 

estimates ranging from 1.7 to 1.9 hours [see New Chemical Chapter (USEPA, 2006a 

(July)]. Therefore, clouds of the active ingredient are not expected to persist and move 

long distances through numerous habitat types. Given the relatively limited area around 

the metofluthrin dispensing device, the likely setting of use i.e., in backyards and other 

residential areas and where people hike and otherwise participate in outdoor activities, 

and the short half-life, the probability of impacting endangered invertebrates is so low as 

to amount to no effect. Based on this further analysis, no direct effects to endangered 

invertebrates are expected.” (USEPA, 2006b, p. 2) 
6

Drinking Water Exposure Assessment 

Metofluthrin has a relatively high vapor pressure, thus, it would be expected to dissipate into the 

air. If used during daylight hours, metofluthrin can also undergo photodegradation in the air 

(half-life < 2 hours). Metofluthrin that is deposited on land surfaces is expected to have low 

persistence and low mobility, based on the results of laboratory studies (aerobic soil half-lives < 

4 days; Koc > 3700 mL/goc). Metofluthrin that reaches water is stable to hydrolysis in acidic and 

neutral conditions but may hydrolyze in alkaline conditions (pH 9, t1⁄2 = 33 days) and can degrade 

through photolysis (t1⁄2 = 6 days). These properties, along with the low deposition rates, indicate 

that the potential for metofluthrin to reach a water body is very low. 

Based upon the uses and the environmental fate properties of metofluthrin, EFED did not 

conduct a drinking water exposure assessment to quantify the potential concentration of 

metofluthrin residues in drinking water. 

Stressor Source and Distribution 

Metofluthrin is a synthetic pyrethroid insect repellent and insecticide. There are currently three 

end-use outdoor products (all containing metofluthrin as the sole active ingredient) registered for 

metofluthrin, all used to repel adult mosquitoes. One is a folded paper strip that is impregnated 

with metofluthrin and is hung in outdoor areas such as decks, porches, barns, stables and kennels 

[DeckMateTM Mosquito Repellent; EPA Reg. No.: 10308-31; 1.82% active ingredient (a.i.)] 

(deck strip). Another is an impregnated insert that is used with a battery-operated portable, 

personal fan that blows air to create a vapor of chemical [Master Name: NORM1 (alternate 

names: OFF! Clip-On, OFF! Repellent Fan); EPA Reg. No.: 4822-542; 31.2% a.i.] (fan). This 

product is for use outdoors (e.g., when camping, fishing, hunting, boating, on the patio or deck, 

or at the beach). The third registered product is an impregnated fiberglass ring that is heatreleased over a candle meant to be used on patios, decks, and campsites [Charger (alternate 

name: OFF! Patio Protector); EPA Reg. No.: 4822-583; 31.68% a.i.] (candle). There is one enduse indoor product that contains metofluthrin, piperonyl butoxide, and clothianidin as the active 

ingredients [VBC3 Insecticide (alternate name: Crossfire); EPA Reg. No.: 73049-482; 0.1% 

metofluthrin] (soluble concentrate applied as a spray), and is targeted to kill bed bugs. This 

product is registered for indoor commercial and residential uses as a direct surface spray on nonfood areas, mattresses, and for crack and crevice and perimeter applications. For the purpose of 

evaluating potential ecological exposures and effects from uses of metofluthrin, this assessment 

will focus only on the products registered for outdoor uses. 

Pesticidal Mechanism of Action 

Metofluthrin is a synthetic pyrethroid that, when employed as a vapor, repels mosquitoes. 

Repellency is the result of a reaction at the threshold of neural activation and knockdown which 

causes the exposed insect to lose its ability to find its host (see Kawada, et al., 2004b). Although 

it is being reviewed for Registration Review as a repellent, it also has been shown to kill 

mosquitoes (e.g., Kawada et al., 2004a and 2004b) and other insects (MRIDs 47048301, 

47414001). 
7

Overview of Pesticide Use and Usage 

The pesticide is dispersed from impregnated material and is meant to be used outdoors (e.g., 

patios, decks, campsites, beaches, parks, sporting events). Three end-use products are currently 

registered for use (see Table 1). The labels for EPA Registration Numbers (NORM1) 4822-542 

and (Charger) 4822-583 specify percent active ingredient but do not specify an amount (mass of 

product or active ingredient). For EPA Registration No. 10308-31 (DeckMate), the label 

specifies that one strip contains 200 mg of metofluthrin. Where not specified on the label, the 

amount of active ingredient was estimated from product packaging (APPENDIX A). Product 

information for each registration is summarized in Table 1.

TABLE 1. Registered Metofluthrin End-Use Products. 

Product Name

(EPA Reg. No.)

% A.I. [Amount of 

a.i. Per Product]

Type of Product Use Sites Application Rates

DeckMateTM 

Mosquito Repellent 

(10308-31)

1.82% [200 mg per 

strip]

Folded paper strip 

that is impregnated 

with metofluthrin

Hung in outdoor 

areas such as decks, 

porches, barns, 

stables and kennels

Two deck strips per 

100 ft2(can be reused for up to 36 

hrs)

Master Name: 

NORM1 (4822-542)

31.2% [15 mg per 

refill disk]

1

Impregnated insert 

that is used with a 

battery operated 

portable, personal 

fan

Used when outdoors 

(e.g., when camping, 

fishing, hunting, 

boating, on the patio 

or deck, or at the 

beach)

Assumed 1 fan per 

person

Charger (alternate 

name: OFF! Patio 

Protector) (4822-

583)

31.68% [Estimated 

215 mg per ring]

1

Impregnated 

fiberglass ring (the 

ring is heated by a 

candle)

Used outdoors in 

areas such as patios, 

decks, and campsites

Use one candle in an 

area up to 10 ft by 

10 ft; use two or 

more in larger areas

1

 Determined from product packaging (See APPENDIX A). 

For modeling purposes to assess exposure, an application rate of 0.00388 lb a.i./acre (1,720 mg 

a.i./acre) was estimated for the candle use by assuming there are houses on quarter acre lots 

throughout a watershed. It was assumed that each house had two candles in the yard as 

recommended on the label (8 candles/acre). Additionally, it was assumed that the entire amount 

of active ingredient from each candle is released into the environment at the same time, which 

leads to a very conservative estimate of potential exposure. Exposure from the deck strips would 

be essentially the same as for the candles. The exposure from the personal fan is expected to be 

lower than the potential exposure from the deck strip or candle uses (due to a lower amount of 

a.i./device). Therefore, although only the candle use was quantitatively assessed, the deck strip 

and candle estimated application rates are expected to be similar, and are representative of peak, 

conservative exposure values for metofluthrin. 

Environmental Fate and Transport 

A summary of the physical/chemical properties and the environmental fate properties of 

metofluthrin submitted in support of the registration is provided in Table 2. Due to the uses of 

metofluthrin and expected limited exposure, several of the environmental fate studies were not 

required. Metofluthrin is a mixture of two isomers, the E- and the Z-isomer, which differ in the 

position of the final carbon on the prop-1-enyl chain. The active ingredient is made up of 

approximately 92% Z-isomer and 8% E-isomer. Environmental fate studies show that the two 
8

isomers behave in similar ways in the environment. A detailed review of the environmental fate 

studies can be found in the New Chemical Chapter [USEPA, 2006a (July)]. 

Metofluthrin has a relatively high vapor pressure and will readily volatilize and, if exposed to 

sunlight, is also expected to photo-degrade in air with an estimated half-life of less than 2 hours. 

Along with the low quantity of active ingredient in contained in each device, this leads to a low 

likelihood of significant deposition given that the chemical will likely dissipate through a 

combination of degradation and dilution through its release into large volumes of air. Laboratory 

studies suggest that any metofluthrin that is deposited on land surfaces will have low persistence 

and low mobility. Metofluthrin that reaches water is stable to hydrolysis in neutral and acidic 

conditions but degrades in alkaline conditions and through photolysis. Due to its high soil 

partition coefficient, metofluthrin would tend to bind to soil particles rather than remain in the 

water column. 

TABLE 2. Physical/Chemical Properties and Environmental Fate Properties of 

Metofluthrin. 

Parameter Value(s) Source (Classification)

Molecular Structure

Chemical Name 2,3,5,6-tetrafluoro-4-(methoxymethyl)benzyl(E,Z)-(1R,3R)-2,2-dimethyl-3-

(prop-1-enyl)cyclopropanecarboxylate

Chemical Class Pyrethroid ester insecticide

Molecular Formula C18H20F4O3 –

Molecular Weight 360.35 g/mol MRID 46406754

Solubility

in water (20 oC)

0.50 mg/L (Z-isomer)

0.67 mg/L (E-isomer)

MRID 46406708

(Acceptable)

Vapor Pressure (20 oC) 1.47 x 10-5 mmHg (torr) MRID 46402005

Henry’s Law Constant

(20 oC)

1.5 x 10-5atm m3/mol (Z-isomer)

1.1 x 10-5atm m3/mol (E-isomer)

Estimated from vapor 

pressure & solubilitya

Hydrolysis Half-life 

(25 oC)

pH 4 & 7: Stable

pH 9: 33 days

MRID 46406750

(Acceptable)
9

Parameter Value(s) Source (Classification)

Aqueous Photolysis 

Half-life (pH 4)

6 days

MRID 46406754

(Supplemental)

[Based on 12-hour light/

12-hour dark cycle with Xe lamp]

Photodegradation in Air

Metofluthrin 

1.7 to 1.9 hours 46454103

(Supplementalb)

Soil Photolysis - Not required

Aerobic Soil Metabolism 

Half-life

MS sandy loam: T1⁄2 = 2.4 - 3.5 daysc

DT50 = 3-8 days

CA sandy loam: T1⁄2 = 2.3 - 2.9 daysc

DT50 = 1-3 days 

MRID 46406751

(Supplemental)

Aerobic Aquatic 

Metabolism Half-life

- Not required

Soil Partition Coefficient 

(Kd)

57.5, 75.8, 85.3, 163

mL/g

MRID 46406753

(Supplemental)

[EFED calculated, 

based on submitted data]

Organic Carbon Partition

Coefficient (Koc)

3704, 4489, 5414, 7187

mL/goc

MRID 46406753

(Supplemental)

[EFED calculated,

based on calculated Kd]

Octanol/water partition 

coefficient Log Kow (25◦C) 

5.03 (S-RTE, E-isomer)

4.97 (S-RTZ, Z-isomer)

MRID 46406711

(Acceptable)

Terrestrial Field 

Dissipation

- MRID 46406755

(waived)

a Estimated as Hg = vapor pressure (atm) ÷ solubility (mol/L) 

b Estimated photodegradation rates using the Atmospheric Oxidation Program (AOPWIN, Version 1.90, 2000), a 

component of the EPA’s EpiSuite software

c

 Using results of 0 to 14 days for calculation of first-order regression (linear) 
10

Environmental Fate Properties 

The environmental fate of metofluthrin that is deposited in terrestrial and aquatic environments 

can be characterized based on results from guideline environmental fate studies, summarized 

below (see Table 2). Structures of the identified degradates are given in APPENDIX B. In soil, 

metofluthrin has a short half-life (T1⁄2 < 3.5 days) and low mobility (organic carbon partition 

coefficient Koc >3704 mL/goc). DT90s were less than 14 days for both soils. Along with the low 

deposition rates expected for the registered uses, these properties suggest that metofluthrin has a 

low potential for transport to surface water or ground water. Additionally, in water the high Koc

suggests that metofluthrin would preferentially bind with soil particles rather than remain in the 

water column. 

Metofluthrin is stable to abiotic hydrolysis for at least 30 days at 25oC in acidic and neutral 

conditions (pH 4 and 7), but in alkaline conditions (pH 9), it degrades with a half-life of 33 days 

(MRID 46406750). This base-catalyzed degradation proceeded via ester cleavage to form the 

corresponding carboxylic acid MMCA and the alcohol MFOA as major degradates. At study 

termination, each of the degradates remaining were at maximum levels of approximately 50% of 

the applied. Metofluthrin can also degrade through aquatic photolysis with a half-life of 6 days 

(MRID 46406754). A half-life of 6 days was measured for this process, although there is some 

uncertainty in this value, because the concentration of co-solvent was present at 10%. 

Photodegradation leads to the major degradate Diol-1264 (max. 17%), formed through oxidation 

of the prop-1-enyl moiety, as well as the ester cleavage products MMCA (max. 5%) and MFOA 

(max. 24%). Aquatic metabolism studies were not required for assessing these residential 

outdoor uses, and so no aquatic metabolism data were available. The degradation product 

acronyms, structures, and studies where they were formed are summarized in APPENDIX B.

In soil, metofluthrin undergoes rapid microbial metabolism under aerobic conditions. An aerobic 

soil metabolism study measured transformation rates in sandy loam soils from California and 

Mississippi (MRID 46406751). In both soils, calculated half-lives were less than 3.5 days, 

empirical DT50s were less than 8 days, and DT90s were less than 14 days in all cases. The ester 

cleavage product MFOA was immediately oxidized to MFOA-D, which reached a maximum of 

76% of the applied. Further oxidation led to TFPA at up to 57% of the applied. The 

corresponding ester cleavage product, MMCA, was present at up to 22% of the applied. 

Oxidation of MMCA led to t-COOH-CA, present at up to 19% of the applied. By study 

termination, in most cases these degradates were declining or not detectable while bound 

residues and carbon dioxide were increasing, accounting for 5.5 to 14.3% and 48 to 89% of the 

applied compound, respectively. EFED is not aware of any toxicity data that indicate that any of 

the degradates is more toxic than the parent. Because of this, the low exposure potential for 

metofluthrin (and, thus, its degradates), and the conservative exposure assumptions made; the 

risk assessment for the parent only is expected to be protective of exposure to metofluthrin and 

its degradates. Therefore, exposures to parent alone are assessed here. 

Metofluthrin sorbs strongly to soil. Batch equilibrium tests conducted in four soils found Kd

values ranging from 60 to 182 mL/g (MRID 46406753). Strong correlation between soil organic 

carbon and Kd values for different soils (R2

= 0.99) indicates that metofluthrin sorption is 

dependent on soil organic carbon, with Koc values ranging from 3704 to 7187 mL/goc. Based on 

these values, metofluthrin is categorized as slightly mobile according to the FAO mobility 
11

classification scheme (FAO, 2000). Column leaching studies were not conducted, and the 

terrestrial field dissipation requirement was waived. 

Ecological Effects 

Metofluthrin is classified as practically non-toxic to birds and mammals, very highly toxic to 

freshwater animals (vertebrates and invertebrates), and highly toxic to young adult bees on an 

acute exposure basis. No toxicity data are available for plants (aquatic or terrestrial), and the 

only available chronic toxicity data for metofluthrin are for rats. A summary of the toxicity data 

and the resulting measures of ecological effect selected for each taxonomic group are included in 

Table 3.

TABLE 3. Summary of Measures of Effects of Metofluthrin. 

Study

REGISTRANT SUBMITTED STUDIES

MRID Status Measures of Effects

Avian Acute Oral 

[Northern Bobwhite Quail 

(Colinus virginianus)]

464067-57 Acceptable

LD50 >2250 mg/kg-bw 

Ruffled appearance, reduced reaction to stimuli, loss of 

coordination, lower limb weakness, loss of righting 

reflex, minor muscle fasciculation, tremors, and gaping 

during the first day. There was no mortality.

Avian Sub-acute Dietary

[Northern Bobwhite Quail 

(Colinus virginianus)]

464067-58 Acceptable

LC50 >5760 mg/kg-diet

No adverse effects were noted in the study.

Avian Sub-acute Dietary

[Mallard Duck (Anas 

platyrhynchos)]

464067-59 Acceptable

LC50 >5760 mg/kg-diet

Trembling and weight gain reduction were observed. 

There was no mortality.

Rat Acute Oral 46406719 Acceptable LD50 >2,000 mg/kg-bw

Rat Reproductive 

Development 464541-12 Acceptable

NOAEL = 20 mg/kg-bw/day (equivalent to 400 mg 

a.i./kg-diet)

(based on maternal mortality during the 57 days of 

dosing) 

There were no reproductive effects observed during the 

study. However, mortality to parents would reduce 

reproduction in natural populations.

Honey Bee Acute

(Apis mellifera)

474140-01 Acceptable

LD50 = 0.015 μg a.i./bee

NOAEL = 0.00625 μg a.i./bee (based on mortality)

Freshwater Fish Acute 

Toxicity 

[Rainbow Trout

(Onchorynchus mykiss)]

464067-61 Acceptable

LC50 = 1.2 μg a.i./L. 

NOAEC = 0.71 μg a.i./L 

(based on mortality and clinical signs of toxicity)

Loss of equilibrium, lethargy, and mortality were 

observed. 
12

Study

REGISTRANT SUBMITTED STUDIES

MRID Status Measures of Effects

Freshwater Invertebrate 

Acute Toxicity 

[Daphnid (Daphnia magna)]

464067-62 Acceptable

EC50 = 4.7 μg a.i./L 

Effects were immobilization, lethargy and death.

Aquatic and Terrestrial 

Plants No data available

1. Open Literature 

In addition to submitted data, data available from the open literature are considered for this 

assessment. Kawada, et al. (2004a and 2004b) tested the deck strip in both laboratory and field. 

Mosquitoes were placed in cages at varying distances from suspended deck strips. The study 

authors found that all of the mosquitoes in cages directly under the test strip were knocked down 

within three hours and were dead within 24 hours of initial exposure. In the cages that were 

placed 1.5 meters from the metofluthrin strip, 50% of the mosquitoes were dead six hours after 

treatment. The registrant’s submitted material states that one strip will treat about 50 ft2, or 

about 4.5 m2. Kawada, et al. (2004b) determined that no mosquitoes were knocked down 

(killed) at a distance of 5 m from the strip and estimated that a single strip was effective in an 

area of about 5 m

2

. The fan device and candle contain less metofluthrin than the deck strip and 

have a lower rate of emission and so are expected to have a smaller area of impact. 

Ecological Incidents 

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

Monitoring System (AIMS)1, and the Incident Data System (IDS) were conducted on June 6, 

2012. There were no reported ecological incidents associated with metofluthrin. 

Characteristics of Ecosystems Potentially at Risk 

The ecosystems potentially at risk are often extensive in scope; therefore, it may not be possible 

to identify specific ecosystems during the development of a nation-wide ecological risk 

assessment. However, in general terms, terrestrial ecosystems potentially at risk from 

conventional pesticide uses could include the areas immediately adjacent to the application site. 

Aquatic ecosystems potentially at risk include water bodies adjacent to, or downstream from, the 

application site. 

Assessment Endpoints 

A summary of the terrestrial and aquatic toxicological endpoints for metofluthrin can be found in 

Table 3 in the Ecological Effects section. 

 

1

http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims/login.cfm?CFID=113048231&CFTOKEN=9243482 
13

Conceptual Model 

The conceptual models for aquatic and terrestrial exposures are shown in Figures 1 and 2, 

respectively. For the currently registered uses, metofluthrin is released into the air as a vapor 

through passive dissipation or heat- or fan-driven evaporation. For these uses, the active 

ingredient is initially present in the atmosphere in a volatile form but is expected to dissipate 

rapidly through a combination of degradation and dilution by the large volume of air into which 

it is released. Aquatic and terrestrial exposure occurs only after metofluthrin has been deposited 

on land or water surfaces. In the conceptual models, dashed lines denote exposure routes not 

assessed due to the likelihood of low potential exposure. Because the exposure (from all of the 

potential routes) of non-target organisms to metofluthrin from the currently registered uses is 

expected to be low, all of the lines on the conceptual models are dashed. 
14

Figure 1. Conceptual Model for Effects of Metofluthrin on Aquatic Systems 
15

Figure 2. Conceptual Model for Effects of Metofluthrin on Terrestrial Systems 
16

Risk Hypothesis 

The following ecological risk hypothesis is being employed for this national-level ecological risk 

assessment: 

Metofluthrin, when used in accordance with current labels, can result in off-site 

movement of the compound leading to exposure of non-target plants and animals. 

Exposures in these environmental compartments are expected to be below levels 

where adverse effects upon the survival, growth, and reproduction of non-target 

terrestrial and aquatic organisms (including listed species) would occur. 

Analysis Plan 

In order to address the risk hypothesis, the potential for adverse effects to non-target organisms is 

estimated. The use, environmental fate, and ecological effects of metofluthrin are characterized 

and integrated to assess risk by using a risk quotient (ratio of exposure concentration to effects 

concentration) approach when possible. When a risk quotient approach is not possible, risks are 

assessed qualitatively. 

Measures of Exposure 

The candle use is the only use quantitatively assessed via standard exposure models because the 

candle use is expected to result in peak exposure estimates (estimated application rates for the 

candle are expected to be higher than the fan use, and similar to, but slightly higher, than the 

deck strip use). Therefore, potential aquatic exposure to metofluthrin is not quantified directly 

for the fan or deck strip uses. Instead, EFED estimates the amount of active ingredient that 

would have to reach a water body to result in risk to non-target organisms and qualitatively 

discusses the likelihood that this might happen. For the candle use, estimated environmental 

concentrations (EEC) are calculated using Tier I exposure models: Terrestrial Residue Exposure 

(T-REX; version 1.5) for terrestrial environments and the GENeric Estimated Exposure 

Concentration 2 (GENEEC2; version 2.0) for aquatic environments (see Table 4). 

T-REX runs [using the following assumptions: 1 application at 0.00388 lb a.i./acre (candle); 

default foliar dissipation half-life of 35 days] resulted in a peak dietary-based EEC of 0.94 ppm 

(short grass). The EECs for the other dietary categories were 0.43 ppm (tall grass), 0.53 ppm 

(broadleaf plants), 0.06 (fruits/pods/seeds), and 0.37 ppm (arthropods) (see APPENDIX C for 

details). 

An application rate of 0.00388 lb a.i./acre from candles was estimated using a series of 

conservative assumptions about the extent of use and the potential for deposition (see above). 

GENEEC2 runs resulted in a peak EEC of 0.03 μg a.i./L (candle). These models are not 

specifically designed to handle uses such as those for metofluthrin, but by making several 

conservative assumptions in describing the use, these models are sufficient to establish a 

conservative upper bound on potential exposure for the purposes of quantitatively assessing 

ecological risk. 
17

TABLE 4. GENEEC Input Parameters for Metofluthrin (Deck Strips and Candle)a

.

Parameter Input Source

Application Rate 0.00388 lb a.i./A

Estimated:

4 houses/A * 2 strips/house * 

215.6 mg a.i./ring * 1 lb/453590 mg

Number of Applications 1

Wetted in? No

Application Method Ground; 

Low boom, coarse droplets

Sets amount of a.i. reaching water 

body through drift at 0.8%b.

Solubility in Water 0.67 mg/L

MRID 46406750

(Highest reported value; for E -

isomer)

Organic Carbon Partitioning 

Coefficient 

(Koc)

3704 mL/g MRID 46406753

(lowest valuec)

Hydrolysis Half-life at pH 7 Stable MRID 46406750

Aerobic Soil Metabolism 

Half-life Stable Not anticipated to be exposed to soil, thus, assumed no degradation.

Aerobic Aquatic Metabolism 

Half-life Stable No data

Aquatic Photolysis Half-life 6 days MRID 46406754

(assuming 12 hr sunlight/day)

a

 Rate for candle (0.00388 lb a.i./A) is used to also represent the deck strip use (0.00353 lb a.i./A) 

b

 This value is thought to be conservative as drift is related to water droplet size where metofluthrin is in the vapor 

phase. 

c

 http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm. EFED guidance recommends using 

the mean Koc , using the lowest Koc would result in highest EECs. 

The Screening Imbibition Program (SIP v.1.0, Released June 15, 2010) was used to calculate an 

upper bound estimate of exposure to wildlife via drinking water using metofluthrin’s aquatic 

solubility limit [0.67 mg/L (E-isomer)], the most sensitive acute avian toxicity endpoint 

(bobwhite quail LD50 >2,250 mg/kg-bw; no chronic avian data are available), and the most 

sensitive acute and chronic mammalian toxicity endpoints for metofluthrin (rat LD50 >2,000 

mg/kg-bw, and NOAEL = 20 mg a.i./kg-bw, respectively). Drinking water exposure alone was 

determined not to be a potential pathway of concern for avian or mammalian species on an acute 

basis or mammalian species on chronic basis. Although not assessed due to a lack of data, 

drinking water is not expected to be an exposure route of concern for birds from chronic 

exposure to metofluthrin. For a sample of the output generated by SIP v.1.0, please see 
18

APPENDIX D. Detailed information about the SIP v.1.0, as well as the tool, can be found on the 

EPA’s website at http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial.

The Screening Tool for Inhalation Risk (STIR v.1.0, November 19, 2010) was used to calculate 

an upper-bound estimate of vapor-phase exposure using metofluthrin’s vapor pressure (1.47 x 

10-5 mm Hg) and molecular weight (360.35 g/mol). STIR incorporates results from several 

toxicity studies including acute oral and inhalation rat toxicity endpoints obtained from the “sixpack” of core studies, which are a series of six guideline studies that are submitted to the 

Registration Division of the Office of Pesticide Programs for technical and formulated products 

of a pesticide [rat acute oral LD50 >2,000 mg a.i./kg-bw and acute inhalation LC50 = 1.08 mg/L 

(MRID 46406723), respectively], as well as the most sensitive acute oral avian toxicity endpoint 

(bobwhite quail LD50 > 2,250 mg a.i./kg-bw). The conservative estimated application rate of 

0.00388 lb a.i./acre (candle) was used. Based on the results of the STIR model, inhalation 

exposure alone was determined not to be a potential pathway of concern for avian and 

mammalian species on an acute inhalation exposure basis (see APPENDIX E for details). 

Measures of Effect 

Where available, sublethal effects observed in both registrant-submitted and open literature 

studies is evaluated qualitatively. In the available metofluthrin toxicity studies, such effects 

include reduced reaction to stimuli, tremors, loss of coordination, and lethargy. Quantitative 

assessments of risks, though, are limited to those endpoints that can be directly linked to the 

Agency’s assessment endpoints of impaired survival, growth and reproduction. 

The assessment of risk for direct effects to non-target organisms makes the assumption that 

toxicity of metofluthrin to birds is similar to terrestrial-phase amphibians and reptiles. The same 

assumption is made for fish and aquatic-phase amphibians. The acute measures of effect used 

for animals in this screening-level assessment are the acute LD50, LC50, and EC50. Endpoints for 

chronic measures of exposure for listed and non-listed animals are the NOAEL and/or NOAEC. 

Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects characterization to 

determine the potential ecological risk from the use of metofluthrin via deck strips, personal fans, 

and candles, and the likelihood of direct and/or indirect effects to non-target organisms in aquatic 

and terrestrial habitats. The exposure and toxicity data are integrated in order to evaluate the 

risks of adverse ecological effects to non-target species. For the assessment of metofluthrin 

exposure and potential risks associated with the candle use, the risk quotient (RQ) method is 

used to compare exposure and measured toxicity values. EECs are divided by the acute and 

chronic toxicity values (if available). The resulting RQ values are then compared to the 

Agency’s LOC values (USEPA, 2004) (see Table 5). These criteria are used, in addition to 

other available data (e.g., incident data), to indicate when metofluthrin’s uses, as directed on the 

label, have the potential to cause adverse direct or indirect effects to non-target organisms. The 

risks associated with the personal fan and deck strip uses will be qualitatively discussed based on 

the available data. 
19

TABLE 5. Agency Levels of Concern (LOC). 

Risk Description RQ Taxa

Acute

Potential for acute risk to non-target organisms 

which may warrant regulatory action in addition 

to restricted use classification

acute RQ > 0.5 aquatic animals, 

mammals, birds

Acute Restricted 

Use

Potential for acute risk to non-target organisms, 

but may be mitigated through restricted use 

classification

acute RQ > 0.1 aquatic animals

acute RQ > 0.2 mammals and 

birds

Acute Listed 

Species

Listed species may be potentially affected by 

use

acute RQ > 0.05 aquatic animals

acute RQ > 0.1 mammals and 

birds

Chronic

Potential for chronic risk may warrant 

regulatory action, listed species may potentially 

be affected through chronic exposure

chronic RQ > 1 all animals

Non-Listed and 

Listed Plant 

Potential for effects in non-listed and listed 

plants RQ > 1 all plants

Endangered Species Assessments 

Consistent with the EPA’s responsibility under the Endangered Species Act (ESA), EPA 

evaluated risks to listed species from registered uses of metofluthrin. 

2. RISK CHARACTERIZATION 

RISK ESTIMATION 

Aquatic Animals 

To assess the potential for effects of a pesticide use to aquatic organisms, an EEC is typically 

determined by modeling the transport of an applied pesticide into the farm pond, a water body of 

defined proportions and volume (i.e., 20,000,000 L). The devices available for metofluthrin use 

(i.e., personal fan, candle and deck strip) can be used by any number of people in any locations 

for any length of time, so it is difficult to specifically describe the use for the sake of modeling 

aquatic exposure. 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. 
20

All values and equations used in this calculation are summarized in Table 6. From the available 

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

most sensitive endpoint is for rainbow trout with an LC50 of 1.2 μg a.i./L. The highest aquatic 

risk category is for acute risk to endangered 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 0.06 μg a.i./L (0.05 * 1.2 μg a.i./L).

Table 6. Amount of Metofluthrin 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 = 1.2 μg a.i./L (Rainbow Trout LC50)

EEC in farm pond leading to LOC 

exceedance1 0.06 μg a.i./L

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

exceedance2 1.2 g

Amount of a.i. per device3 Personal Fan

15 mg a.i./device

Candle

215.6 mg 

a.i./device

Deck Strip

200 mg a.i./device

No. of devices from which entire contents 

must end up in pond leading to LOC 

exceedance4

80 devices ~6 devices 6 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. Dissolved compound = EEC * volume. 

3 MRID 46406752 

4

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

The entire contents of at least 80 personal fan devices and 6 deck strips/candles would need to 

end up in the farm pond to exceed levels of concern for aquatic animals. Due to low deposition 

rates and subsequent dilution in air combined with rapid degradation in air, soil, and water via 

photolysis, the amount of metofluthrin that may reach a water body from a single device, deck 

strip or candle is, in reality, far lower than the total amount of active ingredient contained in each 

device. The actual number of devices needed to lead to an LOC exceedance, then, is even 

greater than the conservative estimates made here. 

The candle and deck strip have a higher amount of metofluthrin in each unit than the fan. For the 

candle and deck strip, the active ingredient from only 6 devices would need to reach the water 

body to lead to an LOC exceedance. Although unlikely to occur, this situation is within the 

realm of possibility, so a more detailed analysis using the Tier I aquatic model GENEEC2 was 

conducted to assess the potential for risk from metofluthrin released using the candle application 

rate (which was used to represent peak exposures). The peak EEC calculated from GENEEC2 

was 0.03 μg a.i./L (candle) (see Table 4). When this EEC is compared to the available acute 
21

toxicity endpoints for freshwater fish and freshwater invertebrates, none of the RQs for the 

candle use exceed an Agency LOC (see Table 7). 

TABLE 7. RQs for the Candle Use and Freshwater Animals. 

Species

Toxicity 

Endpoint (μg

a.i./L)

Peak EEC (μg

a.i./L) Acute RQ Level of Concern Exceeded

Rainbow Trout LC50 = 1.2 0.03 0.025 None

Daphnid EC50 = 4.7 0.03 0.006 None

Terrestrial Animals 

All of the available acute toxicity data for birds and mammals resulted in non-definitive 

endpoints (i.e., “greater than” values) and indicate that metofluthrin is practically non-toxic to 

these organisms (and by extension to reptiles and terrestrial-phase amphibians for which birds 

serve as surrogates) on an acute exposure basis. Therefore, RQs cannot be calculated for birds 

and mammals from acute exposure to metofluthrin. However, all of the exposure values, 

conservatively estimated using T-REX, were well below the highest concentrations tested in the 

available acute toxicity studies for terrestrial animals (see APPENDIX C for details). For 

evaluating potential risk from chronic exposure, exposures were calculated assuming the 

maximum estimated label application rate for the candle use (which is expected to be higher than 

the application rate for the personal fan and similar to the deck strip). Exposures were estimated 

assuming that all of the metofluthrin in 8 candles/acre (see the ‘Overview of Pesticide Use and 

Usage’ section above) was released at the same time and deposited as residues on food items. 

This is assumed to result in conservative, peak EECs. Assessments for birds and mammals are 

based on dietary exposure to pesticides through the ingestion of contaminated plant or animal 

material that is consumed as food. Based on the EECs from T-REX using an estimated 

application rate of 0.00388 lb a.i./acre for the candle use, none of the RQs for mammals 

(different size and dietary categories) exceed the chronic risk LOC (i.e., all of the chronic 

mammalian RQs are ≤0.39) (see APPENDIX C for details). 

There is one acceptable honey bee contact study available for metofluthrin using the European 

honey bee (Apis mellifera) with an LD50 of 0.015 μg a.i./bee (MRID 47414001). There is also an 

acute contact study available using the Asian bee Apis cerana indica with an LD50 of 0.0089 μg 

a.i./bee (MRID 47048301). This latter study was classified as supplemental because it was not 

conducted with A. mellifera, no raw data were submitted (therefore, the statistics could not be 

verified), and the age of the bees and lighting conditions during the study were not reported. 

However, regardless of whether data from A. mellifera or A. cerana are used, metofluthrin is

classified as highly toxic to bees, and therefore terrestrial invertebrates, on an acute exposure 

basis. 

Because metofluthrin is used as an insect repellent and has potential insecticidal properties, it is 

assumed that any terrestrial invertebrate (e.g., honey bee or listed flying terrestrial invertebrate 

species) that is exposed to metofluthrin via ambient exposure (i.e., flying through the 

metofluthrin released by the deck strip, fan or candle) has the potential to be repelled, and 

perhaps killed. From the Kawada, et al., studies (2004a and 2004b), it is not known how many of 
22

the caged mosquitoes that died would have been repelled and flown away if they had not been in 

a cage. It is possible that a mosquito that flew into a cloud of metofluthrin vapor would be 

repelled and fly away unharmed or fly away with neural damage that would lead to its death or 

reduce its reproductive ability. The same could be true for honey bees and listed terrestrial 

invertebrates that enter the treated area. 

Kawada, et al., (2004b) determined that no mosquitoes were knocked down (killed) at a distance 

of 5 m from the deck strip. The candle has a similar ‘efficacy’ rate as the deck strip based on the 

labels; the labels state that the deck strip and the candle can both treat up to a 10-ft x 10-ft area. 

The fan device contains less metofluthrin than the deck strip or candle and has a lower rate of 

emission and so is expected to have a smaller area of impact. Mosquitoes actively track humans 

in order to obtain a blood meal. Bees and listed terrestrial invertebrate species would not be 

expected to be attracted to humans. Therefore, a non-target terrestrial invertebrate would be 

exposed to the metofluthrin only by chance, or because it (e.g., a moth) was flying toward a light 

(such as with a burning candle). 

Screening-level risk assessments do not typically evaluate risks to terrestrial invertebrates; 

however, toxicity information for beneficial insects is used to develop precautionary label 

language where necessary. Based on the available toxicity data alone, precautionary label 

language for bees would normally be recommended. However, because of the limited exposure 

potential to bees from the registered metofluthrin uses, the precautionary label language is not 

considered necessary for the current uses as a deck strip, fan, or candle. 

Additionally, given the relatively limited area around the metofluthrin dispensing devices, the 

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

otherwise participate in outdoor activities), the short half-life of metofluthrin in air (1.7 to 1.9 

hours), 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. 

Plants 

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

from the registered metofluthrin uses. There is no reasonable expectation of effects to plants due 

to the low exposure potential. 

RISK DESCRIPTION 

Based on the available data and the currently registered use patterns for metofluthrin (i.e., 

deck strips, personal fans, and candles), none of the EPA’s LOCs are exceeded for 

metofluthrin. Where RQs could not be calculated due to the lack of toxicity data, 

potential exposure is considered low. Furthermore, there are no known ecological 

incidents reported for metofluthrin. Therefore, the risk hypothesis articulated in the 

Problem Formulation is supported, i.e., metofluthrin, when used in accordance with 

current labels, can result in off-site movement of the compound leading to exposure of 

non-target plants and animals. Exposures in these environmental compartments are 

expected to be below levels where adverse effects upon the survival, growth, and 
23

reproduction of non-target terrestrial and aquatic organisms (including federally-listed 

threatened and endangered species) would occur (see below for the discussion on listed 

species). 

Consistent with the assumptions described in the Health Effects Division’s Standard 

Operating Procedure on assessing risks to humans from residential uses (USEPA, 2012), 

particles released from the deck strip, fan, and candle uses are expected to remain 

airborne rather than be deposited on surfaces and would likely dissipate rapidly. This is 

due to the size fraction of particles released. Additionally, any metofluthrin released 

from the deck strip, fan, or candle during daylight hours is expected to have a short halflife (< 2 hours) in air. Furthermore, based on conservative estimates of exposure for the 

candle use, none of the RQs resulted in LOC exceedances for fish, aquatic invertebrates, 

birds, or mammals. Therefore, risks to non-target species from the use of metofluthrin 

are not expected based on the results of the quantitative and qualitative assessment. 

Uncertainties and Assumptions 

For the currently registered uses of metofluthrin, the fate of the active ingredient is primarily 

dependent on its behavior in air. Although there were limited data to fully describe the 

environmental fate of metofluthrin in air, soil, and water, this assessment’s consideration of 

metofluthrin in air is largely qualitative. The registered uses of metofluthrin consist of personal 

use devices that do not deposit the active ingredient directly on land or water surfaces and only 

affect small areas. EFED conducted modeling based on a set of very conservative assumptions, 

which very likely lead to overestimates of potential exposure. The amount of overestimation is 

uncertain, and so this modeling is only useful to establish upper bounds on potential 

environmental exposure rather than to predict actual concentrations. Although the available data 

were adequate for assessing the exposure and potential risks associated with the fan, deck strip, 

and candle uses, additional data may be needed in the future if the use pattern (and, thus, the 

exposure potential) for metofluthrin 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 Federally-listed species 

and a No Habitat Modification determination for all designated critical habitats for the currently 

registered uses of metofluthrin. 

References 

FAO. 2000. Appendix 2. Parameters of pesticides that influence processes in the soil. In FAO 

Information Division Editorial Group (Ed.), Pesticide Disposal Series 8. Assessing Soil 

Contamination. A Reference Manual. Rome: Food & Agriculture Organization of the 

United Nations (FAO). (Accessed July 10, 2009). 
24

Kawada, H. 2004a. Laboratory and Field Evaluation of Spatial Repellency with MetofluthrinImpregnated Paper Strip Against Mosquitoes in Lombok Island, Indonesia, 2004. J. 

Amer. Mosquito Control Assn. 20:292-298.

Kawada, H., et al., 2004 b. Trial of Spatial Repellency of Metofluthrin-Impregnated Paper Strip 

Against Anopheles and Culex in Shelters without Walls in Lombok, Indonesia. J. Amer. 

Mosquito Control Assn. 20:434-437.

USEPA. 1998a. Guidance for Ecological Risk Assessment. Risk Assessment Forum. 

EPA/630/R-95/002F, April 1998. 

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs. Office of Prevention, Pesticides, and Toxic Substances. Office of Pesticide 

Programs. Washington, D.C. January 23, 2004. 

USEPA. 2006a. Section 3 Metofluthrin in the “DeckMate” Strip and the “Norm I” Personal Fan 

Device as Mosquito Repellent. Office of Pesticide Programs. Washington, D.C. July 

28, 2006. (DP Barcode: D313232). 

USEPA. 2006b. Refined Analysis of Potential Effects to Endangered Species for Metofluthrin 

Use as a Mosquito Repellant, Relates to July 28, 2006 Review Entitled: Section 3 

Metofluthrin in the “DeckMate” Strip and the “Norm l” Personal Fan Device as Mosquito 

Repellent. Office of Pesticide Programs. Washington, D.C. August 17, 2006. (DP 

Barcode: D313232). 

USEPA. 2013. De Minimis Subgroup Opinion on Metofluthrin. Office of Pesticide Programs, 

United States Environmental Protection Agency. Washington, D.C. April 16, 2013. 

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. 

Endangered Species Consultation Handbook: Procedures for Conducting Consultation 

and Conference Activities Under Section 7 of the Endangered Species Act. Final Draft. 

March 1998. 
25

Environmental Fate Studies Cited 

MRID Study (Guideline No.) Study Author and Title

46406754 Aqueous Photolysis

(161-2)

Ponte, M. (2004) Aqueous Photolysis of (Carbon 14)S-1264 in 

pH 4 Buffer by Artificial Light. Project Number: QAM/0019, 

1238W. Unpublished study prepared by PTRL West, Inc. 251 p.

46406708 Solubility in Water

(830.7840)

Walsh, K.; Lentz, N. (2003) Determination of Water Solubility -

S-1264. Project Number: 015634/1, QAP/0019, 015634. 

Unpublished study prepared by Ricerca Biosciences, LLC. 112 p

46406751 Aerobic Soil 

Metabolism

(162-1)

Kodaka, R.; Sugano, T.; Yoshimura, J.; et. al. (2003) Aerobic 

Soil Metabolism Study of [Carbon-14]S-1264. Project Number: 

SOI2002B, EF/2003/003, QAM/0014. Unpublished study 

prepared by Sumitomo Chemical Co. 67 p.

46454101

46402005

Vapor Pressure

(830.7950)

-

DiFrancesco, D.; Lentz, N. (2004) Determination of Vapor 

Pressure - S-1264. Project Number: 015632/1, QAP/0028. 

Unpublished study prepared by Ricerca Biosciences, LLC. 82 p.

Driver, J.; Ross, J. (2004) Metofluthrin: Non-Dietary 

(Residential) Risk Assessment. Project Number: SCJ/009/04. 

Unpublished study prepared by Infoscientific.Com, Inc. 34 p.

46406753 Soil Partition 

Coefficients

Ponte, M. (2004) Soil Adsorption/Desorption of [Carbon-14]S1264 by the Batch Equilibrium Method. Project Number: 

1191W, 1191W/1, QAM/0018. Unpublished study prepared by 

PTRL West, Inc. 291 p.

46406750 Hydrolysis

(835.2110)

Ponte, M. (2004) Hydrolysis of [Carbon-14]S-1264 at pH 4, 7 

and 9. Project Number: 1192W, 1192W/001. Unpublished study 

prepared by PTRL West, Inc. 187 p.

46406711 Partition Coefficient

(n-octanol/water)

(830.7550)

Walsh, K.; Lentz, N. (2003) Determination of n-Octanol/Water 

Partition Coefficient - S-1264. Project Number: 015633/1, 

QAP/0023, 015633/0/1. Unpublished study prepared by Ricerca 

Biosciences, LLC. 86 p.

46406755 Terrestrial Field 

Dissipation 

(164-1)

Curry, K.; Brookman, D. (2004) Request for a Waiver of the 

Requirement for Data on Metofluthrin Terrestrial Field 

Dissipation. Unpublished study prepared by Technology 

Sciences Group, Inc. 19 p.

46454103 Photodegradation in 

Air

Nishyama, M.; Katagi, Takimoto, Y. (2004) Stability in Air of S1264. Project Number: STA2004A, EF/2004/032, QAP/0032. 

Unpublished study prepared by Sumitomo Chemical Co. 9 p
26

Ecotoxicity Studies Cited 

MRID Study (Guideline No.) Study Author and Title

46406757 Avian Acute Oral 

(850.2100)

Gallagher, S.; Grimes, J.; Beavers, J. (2003) An Acute Oral 

Toxicity Study with the Northern Bobwhite. Project Number: 

QAW/0005, 166/172. Unpublished study prepared by Wildlife 

International, Ltd. 50 p.

46406758 Avian Sub-acute 

Dietary (850.2200)

Gallagher, S.; Grimes, J.; Martin, K.; et. al. (2003) A Dietary LC 

50 Study With the Northern Bobwhite. Project Number: 

QAW/0003, 166/170. Unpublished study prepared by Wildlife 

International, Ltd. 63 p.

46406759 Avian Sub-acute 

Dietary (850.2200)

Gallagher, S.; Grimes, J.; Martin, K.; et al. (2003) S-1264: A 

Dietary LC50 Study With the Mallard. Project Number: 

QAW/0004, 166/171. Unpublished study prepared by Wildlife 

International, Ltd. 64 p.

46406719 Rat Acute Oral 

(870.1100)

Kunimatsu, T. (2002) Acute Oral Toxicity STudy of S-1264 in 

Rats: Final Report. Project Number: QAT/0004, 3670. 

Unpublished study prepared by Sumitomo Chemical Co. Ltd., 

Envr. Health. 30 p.

46454112 Rat 2-Generation 

(870.3800)

Hara, H.; Suyami, S.; Ushimaru, T.; et. al. (2002) Study of 

Fertility and Early Embryonic Development to Implantation of S1264 Administered Orally to Rats. Project Number: QAT/0011, 

ST01083. Unpublished study prepared by Ina Research Inc. 173 

p.

47414001 Honey Bee Acute 

(contact) (850.3020)

Warmers, C. (2008) Acute Contact Toxicity Test of S-1264 TG 

to the Honey Bee, Apis mellifera L.: Final Report. Project 

Number: S/1264/TG, 20071335/02/BLEU, QAW/0012. 

Unpublished study prepared by Eurofins - GAB GmbH. 23 p.

47046301 Honey Bee Acute 

(contact) (850.3020)

Jeyalakshmi, T. (2004) Toxicity of S-1264 to Honey Bee, Apis 

cerana indica. Project Number: 07/067/2004, 14675, 

PK/020301G. Unpublished study prepared by International 

Institute of Biotechnology and Toxicology . 20 p.

46406761 Acute Freshwater Fish

(850.1075)

Lima, W. (2004) S-1264 - Acute Toxicity to Rainbow Trout 

(Oncorhynchus mykiss) Under Flow-Through Conditions. 

Project Number: 13048/6398, QAW/0007. Unpublished study 

prepared by Springborn Smithers Laboratories. 51 p.

46406762 Acute Freshwater Fish

(850.1075)

Sayers, L. (2008) S-1264 Technical Grade- Acute Toxicity to 

Bluegill Sunfish (Lepomis macrochirus): Under Flow-Through 

Conditions. Project Number: 13048/6537, QAW/0014. 

Unpublished study prepared by Springborn Smithers 

Laboratories. 74 p.
27

Appendix A: Estimates of Metofluthrin Mass for Exposure 

Metofluthrin is dispersed from impregnated material and is meant to be used outdoors (e.g., 

patios, decks, campsites, beaches, parks, sporting events). Three end-use products are currently 

registered for outdoor use (see Table A-1). The labels for EPA Registration Numbers (NORM1) 

4822-542 and (Charger) 4822-583 specify % active ingredient (a.i.) but do not specify an amount 

(mass of product or active ingredient) contained in the impregnated material. For EPA 

Registration No. 10308-31 (DeckMate) the label specifies that one strip contains 200 mg of 

metofluthrin. When not specified on the label, the amount of active ingredient was estimated 

from product packaging downloaded from the internet. The amounts are summarized in Table 

A-1.

Appendix A-1. Products containing Metofluthrin with Registration Numbers, Net Weights, Percent Active 

Ingredient (a.i.), and Weight in AI.

Product EPA Reg No. Net wt 

(oz)

Net wt 

(mg) % ai mg ai g ai lb ai/unit Unit

Charger 4822-583 0.0241680.40 31.68 215.55 0.2156 0.000485 Ring

DeckMate 10308-31 - - 1.82 20020.200 0.000441 Pad

Norm1

4822-542

0.0016346 31.2 14.3540.0144 0.0000326 Refill disk

Repellent fan 0.0952552.46 31.2 796.4 0.796 0.00176 Refill disk+

1

 Unit Net weight in oz per ring (from packaging) 

2

 Unit Net weight in mg per strip (Label EPA Reg No. 10308-31) 

3

 Unit Net weight in oz per refill disk (Clip-On from packaging) 

4

 15 mg per refill disk used in previous risk assessment (D312123) 

5

 Unit Net weight in oz per refill disk (from packaging) (pack contains two refills). This also appears to include more than just the 

refill disk. 

Conversion Constants 

oz x 28.35 = mg 

mg x 1000 = g 

mg x 0.000002046 = lb (1 lb = 453.592 g) 
28

APPENDIX B: Parent and Degradate Acronyms, Chemical Name, MRID No., Study 

Type Where Degradate Occurred, and Chemical Structure. 

Appendix E-1. Parent and degradate abbreviation, chemical name, MRID No., Study where 

degradate occurred, and structure

ID Number Chemical 

Name MRID Study Type Structure

S-1264

RTZ

[Z-isomer]

Metofluthrina- -

S-1264

RTE

[E-isomer]

Metofluthrin - -

Diol-1264 Not Reported 464541-03 aqueous 

photolysis

(E)-MMCA Not Reported 46406753

46454103

aerobic soil 

metabolism,

aqueous 

photolysis

(Z)-MMCA Not Reported 46406753

46454103

aerobic soil 

metabolism,

aqueous 

photolysis

O

O

O

F F

F F

O

O

O

F F

F F

HO OH

O

O O

F F

F F

O

HO

O

HO
29

Appendix E-1. Parent and degradate abbreviation, chemical name, MRID No., Study where 

degradate occurred, and structure

ID Number Chemical 

Name MRID Study Type Structure

MFOA Not Reported

46406753

46406750

46454103

aerobic soil 

metabolism,

hydrolysis,

aqueous 

photolysis

MFOA-D Not Reported 46406753

46406750

aerobic soil 

metabolism,

hydrolysis

MFFO Not Reported 46406750

46454103

hydrolysis,

aqueous 

photolysis

TFPA Not Reported 46406753 aerobic soil 

metabolism

t-COOHCA Not Reported 46406753 aerobic soil 

metabolism

F F

F F

O OH

F F

F F

O

O

OH O

O

O

O

F F

F F

F F

F F

OH

O O

HO O

HO

COOH
30

APPENDIX C: T-REX INPUTS AND OUTPUTS 

Inputs: 

Chemical Name: Metofluthrin

Application Rate 0.0039 lbs a.i./acre

Half-life 35 days 

Application Interval 0 days

Maximum # Apps./Year 1

Length of Simulation 1 year

Summary of Risk Quotient Calculations Based on Upper Bound Kenaga EECs

Table 1. Upper Bound Kenaga, Acute Avian Dose-Based Risk Quotients

Size 

Class

(grams)

Adjusted

LD50

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

20 1620.97 1.07 0.00 0.49 0.00 0.60 0.00 0.07 0.00 0.42 0.00 0.01 0.00

100 2063.57 0.61 0.00 0.28 0.00 0.34 0.00 0.04 0.00 0.24 0.00 0.01 0.00

1000 2914.87 0.27 0.00 0.12 0.00 0.15 0.00 0.02 0.00 0.11 0.00 0.00 0.00

Table 2. Upper Bound Kenaga, Acute Mammalian Dose-Based Risk Quotients 

Size 

Class

(grams)

Adjusted

LD50

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

15 4395.66 0.89 0.00 0.41 0.00 0.50 0.00 0.06 0.00 0.35 8E-05 0.0 3E-06

35 3556.56 0.62 0.00 0.28 0.00 0.35 0.00 0.04 0.00 0.24 7E-05 0.01 2E-06

1000 1538.32 0.14 0.00 0.07 0.00 0.08 0.00 0.01 0.00 0.06 4E-05 0.00 1E-06

Table 3. Upper Bound Kenaga, Chronic Mammalian Dietary Based Risk Quotients

NOAEC 

(ppm)

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants

Fruits/Pods/Seeds/Large 

Insects Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

400 0.94 0.00 0.43 0.00 0.53 0.00 0.06 0.00 0.37 0.00

Size class not used for dietary risk quotients 

Table X. Upper Bound Kenaga, Chronic Mammalian Dose-Based Risk Quotients

Size 

Class

(grams)

Adjusted 

NOAEL

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

15 43.96 0.89 0.02 0.41 0.01 0.50 0.01 0.06 0.00 0.35 0.01 0.01 0.00

35 35.57 0.62 0.02 0.28 0.01 0.35 0.01 0.04 0.00 0.24 0.01 0.01 0.00

1000 15.38 0.14 0.01 0.07 0.00 0.08 0.01 0.01 0.00 0.06 0.00 0.00 0.00
31

APPENDIX D: SIP Inputs and Outputs

Table B-1. Inputs

Parameter Value

Chemical name Metofluthrin

Solubility (in water at 25oC; mg/L) 0.67

Mammalian LD50 (mg/kg-bw) 2000

Mammalian test species laboratory rat

Mammalian NOAEL (mg/kg-bw) 20

Mammalian test species laboratory rat

Avian LD50 (mg/kg-bw) 2250

Avian test species northern bobwhite quail

Mineau scaling factor 1.15

Table B-2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 0.1152 0.1152

Adjusted toxicity value (mg/kg-bw) 1538.3211 15.3832

Ratio of exposure to toxicity 0.0001 0.0075

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Table B-3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 0.5427 0.5427

Adjusted toxicity value (mg/kg-bw) 1620.9664 0.0000

Ratio of exposure to acute toxicity 0.0003 0.0000

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for birds

Due to insufficient data, risk 

cannot be precluded

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, when 

aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through drinking water may 

contribute to a total exposure that has potential for effects to non-target animals.
32

APPENDIX E: STIR Inputs and Outputs 

Input

Application and Chemical Information

Enter Chemical Name Metofluthrin

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) ground

Enter Chemical Molecular Weight (g/mole) 360.35

Enter Chemical Vapor Pressure (mmHg) 1.47E-05

Enter Application Rate (lb a.i./acre) 0.0035

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 2250

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 2000

Enter Lowest Rat Inhalation LC50 (mg/L) 1.08

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 2.85E-01

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 3.58E-02

Adjusted Inhalation LD50 6.77E+00

Ratio of Vapor Dose to Adjusted Inhalation LD50 5.29E-03 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 3.70E-04

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 5.46E-05 Exposure not Likely Significant

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 2.85E-01

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 4.50E-02

Adjusted Inhalation LD50 6.43E+01

Ratio of Vapor Dose to Adjusted Inhalation LD50 7.01E-04 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 4.65E-04

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 7.23E-06 Exposure not Likely Significant