Docket Number EPA-HQ-OPP-2012-0105 

www .regulations.gov 

METOFLUTHRIN 

Interim Registration Review Decision 

Case Number 7445 

September 2014 

Approved by:· ~ P >'J) 

Richard P. Keigwin, Jr. 

Director 

Pesticide Re-evaluation Division 
Table of Contents 

I. Introduction .............................................................................................................................. 3 

A. Background ............................................................................................ 5 

II. Scientific Assessments ............................................................................................................. 5 

A. Human Health Assessment .................................................................................................. 5 

Hazard Characterization and Risk ....................................................................................... 5 

Dietary Exposure Assessment ............................................................................................. 5 

Food Tolerances ................................................................................................................... 5 

Residential and Occupational Exposure .............................................................................. 5 

Human Incidents .................................................................................................................. 6 

B. Environmental Assessment ................................................................................................. 6 

Environmental Fate and Exposure ................................................... ........ .......................... .. 7 

Ecological Risk Characterization ......................................................................................... 7 

Ecological Incidents ............................. ....... ·-............................................ 8 

Endangered Species Assessment ........................................................... ........... 8 

Endocrine Disruptor Screening Program ............................................................................. 8 

III. Interim Registration Review Decision .................................................................................. 9 

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I. Introduction 

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

Registration Review Decision for metofluthrin and is being issued pursuant to 40 CFR sections 

155.56 and 155.58. A registration review decision is the Agency's determination whether a 

pesticide meets, or does not meet, the standard for registration in the Federal Insecticide, 

Fungicide, and Rodenticide Act (FIFRA). Further information on metofluthrin can be found in 

EPA's public docket (EPA-HQ-OPP-2012-0105) at www.regulations.gov. 

FIFRA, as amended by the Food Quality Protection Act (FQPA) of 1996, mandated the 

continuous review of existing pesticides. All pesticides distributed or sold in the United States 

generally must be registered by the EPA based on scientific data showing that they will not cause 

umeasonable risks to human health or to the environment when used as directed on product 

labeling. The registration review program is intended to make sure that, as the ability to assess 

and reduce risk evolves and as policies and practices change, all registered pesticides continue to 

meet the statutory standard of no umeasonable adverse effects. Changes in science, public 

policy, and pesticide use practices will occur over time. Through the registration review 

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

occur, products in the marketplace can continue to be used safely. Information on this program is 

provided as www.epa.gov/oppsrrdl/registration review/. 

In 2006, the Agency implemented the registration review program pursuant to FIFRA 

section 3(g) and will review each registered pesticide every 15 years to determine whether it 

continues to meet the FIFRA standard for registration. Pursuant to 40 CFR section 155.50, EPA 

formally initiated registration review for metofluthrin (case 7445). The following highlights 

significant events that have occurred during the registration review of metofluthrin: 

• June 2013- Publication of Metofluthrin Preliminary Work Plan (PWP) for a 60-day 

public comment period. The PWP w~s accompanied by Registration Review: 

Preliminary Ecological Risk Assessment and Endangered Species 

Effects Determination for Metofluthrin; Metofluthrin. Human Health Risk Assessment for 

the New Use to Control Bed Bugs and to Support Registration Review; Metofluthrin: 

Review of Human Incidents; and the De Minimis Subgroup Opinion on Metofluthrin. 

• December 2013- Final Work Plan (FWP) for metofluthrin was issued. Four public 

comments were received during the 60-day comment period for the metofluthrin PWP. 

These comments did not result in changes to the work plan or schedule; thus, the FWP 

did not modify the PWP. 

o The FWP noted that no additional data were anticipated to be needed for the 

metofluthrin registration review because sufficient information was available to 

conduct a risk assessment to support a proposed registration review decision, 

pursuant to 40 CFR section 155.53(b). 

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o The FWP noted that the Agency intended to revisit the human incident data base 

for incidents associated with the use of metofluthrin. 

o A Summary of Public Comments Received on the Preliminary Ecological Risk 

Assessment and Endangered Species Effects Determination Conducted for the 

Registration Review of Metofluthrin was posted to the docket along with the 

FWP. 

• June 2014- The metofluthrin Proposed Interim Registration Review Decision published 

in the Federal Register (79FR 32284) (FRL-9911-16) for a 60 day comment period. 

Three comments were received during the comment period. The Agency has also posted 

for public comment the two documents that finalize the ecological and human health risk 

assessments for metofluthrin: Response to Public Comments Received on the 

Preliminary Ecological Risk Assessment and Endangered Species Effects Determination 

Conducted for the Registration Review of Metofluthrin and Metofluthrin: Review of 

Human Incidents for Preliminary Risk Assessment. 

Comments received from the San Francisco Bay Regional Water Quality Control 

Board and the California Stormwater Quality Association (CASQA) were similar. The 

commenters expressed their belief that a full ecological environmental assessment was 

needed, particularly for metofluthrin in urban waters. Of particular concern to these 

organizations were the metofluthrin tabletop mister and bedbug uses. 

The Agency believes that the low usage, the limited amount of metofluthrin that will 

transfer from the skin or mattresses into washwater, and environmental fate 

characteristics of metofluthrin, particularly the short half-life of metofluthrin due to 

photolysis, result in very low potential for environmental exposures for all registered uses 

of metofluthrin. Given the low exposure potential, the Agency has concluded that 

additional toxicity data or a quantitative ecological assessment are not needed to make 

the ecological risk conclusions at this time. If the use pattern for metofluthrin is 

expanded or changes over time in a way that could result in higher exposure potential, the 

need for additional toxicity data will be revisited. 

A third comment from the Center for Biological Diversity indicated agreement with 

EPA's ESA approach and conclusions and required no substantive response. 

• September 2014- The three comments received during the Proposed Interim Registration 

Decision did not change the data requirements or timeline for registration review, 

therefore, the Agency is now publishing and placing in the public docket its Interim 

Registration Review Decision for metofluthrin. Also being posted to the docket is the 

Agency's Response to Public Comments on the Preliminary Ecological Risk Assessment 

for Metofluthrin. 

The documents cited above and additional information on metofluthrin can be found in 

EPA's public docket, EPA~HQ-OPP 2012-0105, accessed at www.regulations.gov. 

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A. General Background 

Metofluthrin is a Type 1 synthetic pyrethroid insect repellent and insecticide. The first 

pesticide product containing metofluthrin was registered in 2006 for use in residential and 

commercial areas, including barns, stables, kennels, patios, porches and campsites. 

Metofluthrin is formulated as an impregnated material, pressurized liquid and soluble 

concentrate. Metofluthrin is not registered for food uses. There are a number of products 

containing metofluthrin as the sole active ingredient that are registered for use as 

repellents for adult mosquitoes. The products registered for outdoor use include an 

impregnated paper strip, a battery-operated personal outdoor insect repellent fan, an 

impregnated fiberglass ring heated by a candle, and a battery-operated automated mister. 

The registered indoor use is a soluble concentrate used as a spray to kill bedbugs. 

II. Scientific Assessments 

A. Human Health Assessment 

A summary of the Agency's human health risk assessment is presented below. The 

Agency used the most updated Agency science policies and risk assessment methodologies to 

prepare a quantitative risk assessment in support of the registration review of metofluthrin. The 

most recent human health risk assessment was conducted in September 18, 2012. For a detailed 

discussion, see the Metofluthrin. Human Health Risk Assessment for the New Use to Control Bed 

Bugs and to Support Registration Review published on June 26, 2013 in the public docket EPAHQ-OPP-2012-0105, which can be accessed on http://www.regulations.gov/. 

Hazard Characterization and Risk 

The Agency conducted a quantitative human health risk assessment for metofluthrin and 

found that there are no risks of concern associated with its use. A review of human incidents 

associated with the use of metofluthrin was conducted, and the number and overall severity of 

the reported incidents were found to be low. 

Dietary Risk Assessment 

There are no proposed or currently registered food uses for metofluthrin. Further, 

drinking water exposure is not expected based on the indoor use and limited outdoor uses of 

metofluthrin; a dietary assessment is not needed. 

Food Tolerances 

There are no established or proposed tolerances for metofluthrin on or on any food or 

feed crops. 

Residential and Occupational Risk Assessment 

The Agency has determined that there are no residential or occupational risks of concern 

for metofluthrin. 

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Aggregate Risk Assessment 

Since there are no food uses for metofluthrin, an aggregate risk assessment is not needed. 

Further, no exposure through drinking water is expected; the only relevant scenarios assessed 

related to residential and occupational exposure and risk, which were not concern. 

Cumulative Risk Assessment 

Although metofluthrin has been identified as belonging to the pyrethroid cumulative 

group, the Agency has determined that metofluthrin will not contribute significantly to exposure 

from the pyrethroids or change the overall findings from the cumulative risk assessment for the 

pyrethroids. For information regarding EPA's efforts to evaluate the risk of exposure to 

pyrethroids, refer to http://www .epa. gov /oppsrrd 1/reevaluation/pyrethroids-pyrethrins .html. 

Human Incidents 

Metofluthrin incidents were reviewed in 2012, and it was concluded that "overall the 

incident cases reported for metofluthrin were generally [of] low frequency and low severity ... " 

The Agency has continued to monitor metofluthrin incidents. 

Based on a more recent search conducted and reported in 2013, there have been 14 

additional moderate incidents and one major incident reported to IDS since the previous review. 

In addition, four low severity cases reported to SENSOR-Pesticides were reviewed. The 

conclusion from the updated incident review is consistent with the previous conclusion that 

incidents do not support a weight of evidence for human health risk. The Agency will continue 

to monitor the incident information and if a concern is triggered, additional analysis will be 

conducted. 

B. Environmental Assessment 

A summary of the Agency's environmental risk assessment for metofluthrin is presented 

below. For detailed discussions of all aspects of the environmental risk assessment, see the 

Registration Review: Preliminary Ecological Risk Assessment and Endangered Species Effects 

Determination for Metofluthrin, published on June 26, 2013, in the public docket EPA-HQ-OPP2012-0105, which can be accessed on http://www.regulations.gov/. 

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Environmental Fate and Exposure 

Metofluthrin is released into the air from insect repellent products as an aerosol or as 

vapor through passive dissipation or heat-or fan-driven evaporation. The active ingredient is 

expected to dissipate rapidly through a combination of degradation and dilution by the large 

volume of air into which it is released. Metofluthrin will photo-degrade in air with an estimated 

half-life of less than 2 hours. The combined effects of the small quantity of metofluthrin 

contained in each repellent devise, rapid degradation, and dilution in large volumes of air result 

in a low likelihood of significant deposition. Metofluthrin that is deposited on land surfaces will 

have low persistence and low mobility. 

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

assumed that non-target insects that are exposed to metofluthrin via ambient exposure (i.e., 

flying through the metofluthrin released by an impregnated strip, fan, candle, or tabletop mister) 

have the potential to be repelled, and perhaps killed. However, the labels for the metofluthrin 

repellent products indicate that they are effective over small areas only. Mosquitoes actively 

track humans in order to obtain a blood meal so only metofluthrin products used in close 

proximity to humans are effective. Bees and other beneficial insects would not be expected to be 

attracted to humans. Therefore, they would be exposed to the metofluthrin minimally, and 

primarily by chance. 

The amount of metofluthrin present on skin and in the washwater of bed linens in contact 

with mattresses treated for bedbugs is not expected to result in environmentally significant 

concentrations in surface water. 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/water partition coefficient, metofluthrin would tend to bind to soil particles rather than 

remain in the water column. 

In summary, the potential exposure of non-target organisms to metofluthrin from the 

currently registered uses is expected to be low. Although the available data were adequate for 

assessing the exposure associated with the current uses, additional data may be needed in the 

future if the use pattern (and, thus, the exposure potential) for metofluthrin changes. 

Ecological Risk Characterization 

Aquatic Animals 

Because of the limited opportunities for exposure, as explained above, there are no risks 

of concern for aquatic animals associated with the current uses of metofluthrin. 

Birds and Mammals 

All of the available acute toxicity data for birds and mammals yielded 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). Additionally, all of the exposure values, conservatively estimated using TREX, were well below the highest concentrations tested in the available acute toxicity studies for 

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terrestrial animals. There are no risks of concern for birds and mammals associated with the 

current uses of metofluthrin. 

Bees and other terrestrial insects 

Given the likely setting of use, the behavior of insects around humans, and the fate of 

metofluthrin in the environment, the probability of impacting bees and other non-target terrestrial 

insects is considered to be low. There is no reasonable expectation of effects. 

Toxicity information for beneficial insects is used to develop precautionary label 

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

bees would normally be recommended for the outdoor uses of metofluthrin. However, because 

of the limited exposure potential to bees from the registered metofluthrin uses, the precautionary 

label language is not considered necessary. 

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. 

Ecological Incidents 

To date, there are no reported ecological incidents associated with metofluthrin based on 

a search of the data base conducted on June 6, 2012. 

Endangered Species Assessment 

There is no reasonable expectation for any registered use of metofluthrin to cause direct 

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

critical habitat is expected to occur from use of metofluthrin. This is because of the types and 

extent of use, the low toxicity shown by existing studies, the highly diffuse nature of the use site, 

and the extremely low annual usage. EPA has made a "no effect" determination under the 

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

species and has therefore concluded that consultation with the Fish and Wildlife Service and the 

National Marine Fisheries Service under ESA section 7(a)(2) is not required. 

Endocrine Disruptor Screening Program 

EPA has developed the Endocrine Disrupter Screening Program (EDSP) to determine whether 

certain substances (including pesticide active and other ingredients) may have an effect in 

humans or wildlife similar to an effect produced by a "naturally occurring estrogen, or other such 

endocrine effects as the Administrator may designate." Under FFDCA Section 408(p), the 

Agency must screen all pesticide chemicals. Between October 2009 and November 2010, EPA 

issued test orders/data call-ins for the first group of 67 chemicals and published a second list of 

chemicals proposed for order issuance in the future. Metofluthrin was not among the group of 

58 pesticide active ingredients on the initial list nor is it proposed on the second list of chemicals 

to be screened under EDSP. According! y, as part of registration review, EPA will issue future 

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EDSP orders/data call-ins for registration review chemicals, including metofluthrin. For further 

information on the status of the EDSP, the policies and procedures, the list of 67 chemicals, 

future chemical list proposed for screening, the test guidelines and the Tier 1 screening battery, 

please visit our website: http://www.epa.gov/endo/. In the interim, EPA is making no human 

health or environmental safety findings associated with EDSP screening of metofluthrin. Before 

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

determination. 

III. Interim Registration Review Decision 

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

Interim Registration Review Decision. Except for the EDSP component of the case, the Agency 

has made the following decision relative to registrations of metofluthrin: (l) no additional data 

are required at this time and (2) no changes to the affected registrations or their labeling are 

needed at this time. In addition, EPA does not expect metofluthrin to have direct or indirect 

adverse effects to non-listed and listed species. EPA has made a "no effect" determination under 

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

species. The Agency's final registration review decision for metofluthrin will occur after an 

EDSP FFDCA Section 408(p) determination. 

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