Docket Number: EPA-HQ-OPP-2011-0039

www.regulations.gov

Permethrin Summary Document

Registration Review: Initial Docket

June 2011

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TABLE OF CONTENTS

 Page 

I. Preliminary Work Plan (PWP) 4

II. Fact Sheet 13

III. Summary of Data Gaps 22

________________________________________

Please Note

This Preliminary Work Plan and Fact Sheet summarize the Environmental Protection 

Agency's current position based on the following documents:

1. Registration Review– Preliminary Problem Formulation for the Environmental Fate, 

Ecological Risk, and Endangered Species and Drinking Water Assessments for 

Permethrin, June 20, 2011.

2. Permethrin: Registration Review Scoping Document for Human Health Assessments.

June 15, 2011.

3. Permethrin: Review of Human Incidents. March 1, 2011.

4. Permethrin Screening Level Usage Analysis (SLUA), August 24, 2010.

5. BEAD Chemical Profile for Registration Review: Permethrin. May 11, 2011.

6. Appendix A: Food/Feed & Non-Food/Non-Feed Uses Considered in Registration Review 

Work Planning, September 29, 2010.

Additional supporting documents for permethrin may be found in the registration review docket

EPA-HQ-OPP-2011-0039 located on the internet at www.regulations.gov.
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I. PRELIMINARY WORK PLAN – Permethrin

Introduction:

The Food Quality Protection Act (FQPA) of 1996 mandated a registration review program. All 

pesticides sold or distributed in the United States generally must be registered by the 

Environmental Protection Agency (EPA or “the Agency”), based on scientific data showing that 

they will not cause unreasonable risks to human health or the environment when used as directed 

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

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

meet the statutory standard of no unreasonable adverse effects to human health or the 

environment. 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 change occurs, products in the marketplace can be used safely. Information on this 

program is provided at: http://www.epa.gov/oppsrrd1/registration_review/.

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. The Agency will consider benefits information and data as required by FIFRA. The 

public phase of registration review begins when the initial docket is opened for each case. The 

docket is the Agency’s opportunity to state what it knows about the pesticide and what additional 

risk analyses and data or information it believes are needed to make a registration review 

decision. After reviewing and responding to comments and data received in the docket during 

this initial comment period, the Agency will develop and commit to a final work plan and 

schedule for the registration review of permethrin.

Permethrin is a broad spectrum, non-systemic, synthetic pyrethroid insecticide that targets adults 

and larvae of many diverse species of biting, chewing, scaling, soil, and flying invertebrates. 

Permethrin is registered for use on numerous food/feed crops, livestock and livestock housing, 

modes of transportation, structures, buildings, Public Health Mosquito abatement programs, 

numerous indoor and outdoor residential spaces, pets, and clothing. It is also regulated by the 

Food and Drug Administration (FDA) as a pediculicide for the treatment of head lice and 

scabies. Permethrin was first registered on February 25, 1979 and, therefore, was subject to the 

reregistration requirements of FIFRA. A Reregistration Eligibility Decision (RED) was 

completed in April 2006. As a result of the Agency’s review of public comments, the 2006 RED 

was amended in December 2007 to reflect changes to certain mitigation measures. The Agency 

conducted a new occupational and residential (ORE) exposure assessment in April 2009. 

Subsequently the permethrin RED was revised again in May 2009 to incorporate changes to the 

residential and occupational mitigation measures, resulting from the revised ORE assessment. 

Documents related to the reregistration of permethrin can be found in docket EPA-OPP-HQ2004-0385 at www.regulations.gov.
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Anticipated Risk Assessment and Data Needs:

The Agency anticipates requiring data to conduct a comprehensive ecological risk assessment, 

including an endangered species risk assessment, for all uses of permethrin. The Agency also 

anticipates requiring additional toxicity data to reevaluate the toxicological endpoints and safety/ 

uncertainty factors. Revised human health exposure and risk assessments may be needed if new 

data are identified which impact exposure estimates, toxicological endpoints change, new points 

of departure are selected, the FQPA safety factor is revised, or other parameters are modified 

(e.g., changes to standard operating procedures or default exposure assessment assumptions).

Below is a summary of the issues relevant to the registration review of permethrin.

Ecological Risk:

• The most recent comprehensive national-level ecological risk assessment for permethrin 

was completed in support of the permethrin RED in April 2006.

• The Agency completed endangered species assessments evaluating the potential effects

of permethrin on the Valley Elderberry Longhorn Beetle (Desmocerus californicus 

dimorphus) (VELB) consistent with the following court orders and settlements: Center 

for Biological Diversity v. EPA, No. 07-2794 (N.D. Cal., May 20, 2007) [addressing 11 

federally threatened or endangered species in the greater San Francisco Bay area], and 

Center for Biological Diversity v. Johnson, et al., No. 02-1580 (N.D. Cal., October 20, 

2006) [addressing the California red-legged frog (CRLF)]. The Agency will consider any 

prudent measures or risk assessment considerations that may be included in the U.S. Fish 

and Wildlife Service’s future responses to the Agency’s requests for consultation on the 

CRLF.

• The Agency has not conducted a risk assessment that supports a complete endangered 

species determination for permethrin. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether permethrin’s use has “no 

effect” or “may affect” federally listed threatened or endangered species (listed species) 

or their designated critical habitats. When an assessment concludes that a pesticide’s use 

“may affect” a listed species or its designated critical habitat, the Agency will consult 

with the U.S. Fish and Wildlife Service and/or National Marine Fisheries Service (the 

Services), as appropriate.

• On January 19, 2011, the Center for Biological Diversity and the Pesticide Action 

Network North America filed a lawsuit in the United States District Court for the 

Northern District of California, against the Environmental Protection Agency (EPA) for 

allegedly failing to undergo consultation with the Services regarding the effects of over 

350 pesticides, including permethrin, on over 200 endangered and threatened species 

throughout the United States (Center for Biological Diversity, et al. v. EPA, et al., No. C 

11-00293 (N.D.Cal.).

• The Agency anticipates requiring the following data for permethrin in order to conduct a 

complete ecological risk assessment, including an endangered species assessment:
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• GDLN 835.1230 – Adsorption/Desorption

• GDLN 835.2240 – Photodegradation in Water

• GDLN 835.4100 – Aerobic Soil Metabolism (three additional soils)

• GDLN 835.4200 – Anaerobic Soil Metabolism (three additional soils)

• GDLN 835.4300 – Aerobic Aquatic Metabolism (two additional soil systems)

• GDLN 835.4400 – Anaerobic Aquatic Metabolism (two additional soil 

systems)

• GDLN 835.6100 – Environmental Chemistry Analytical Methods (ECM) and 

Independent Laboratory Validation (ILV) for Soil

• GDLN 835.6200 – Environmental Chemistry Analytical Methods (ECM) and 

ILV for Water

• GDLN 850.1010 – Acute Toxicity Freshwater Invertebrates (TEP)

• GDLN 850.1020 – Acute Toxicity Freshwater Invertebrates [TEPs using coformulated products with the highest ratio of the synergist piperonyl butoxide 

(PBO) to permethrin and the highest ratio of the synergist MGK-264 to 

permethrin (Hyalella azteca)]

• GDLN 850.1025 – Acute Toxicity Estuarine/Marine Organisms (oyster shell 

deposition)

• GDLN 850.1075 – Acute Freshwater Fish Toxicity (TEPs using coformulated products with the highest ratio of the synergist PBO to permethrin 

and the highest ratio of the synergist MGK-264 to permethrin)

• GDLN 850.1350 – Aquatic Invertebrate Life-Cycle Toxicity Test (saltwater) 

• GDLN 850.2100 – Avian Oral Toxicity Test (passerine species)

• GDLN 850.4100 – Seedling Emergence, Tier II

• GDLN 850.4150 – Vegetative Vigor, Tier II

• GDLN 850.4400 – Aquatic Plant Growth, (vascular plants) (Tier II)

• GDLN 850.5400 – Aquatic Plant Growth (algal plants) (Tier II)

• NON-GDLN – (Special Study) Leachability from Treated Wood

• NON-GDLN – (Special Study) Publically Owned Treatment Works (POTW)

Treatability Study

o The Agency is anticipating requiring a bench scale study of waste 

water treatment, to assess the percentage removed in the biosolids by 

the treatment, the amount that would degrade, and the amount that 

would remain in the waste water. These data would be used to inform 

removal percentages by waste water treatment, which is an input to the 

Exposure and Fate Assessment Screening Tool (E-FAST) down-thedrain model.

• NON-GDLN – (Special Study) Test Method 100.4: Hyalella azteca 42-d Test 

for Measuring the Effects of Sediment-associated Contaminants on Survival, 

Growth, and Reproduction in USEPA 2000 Methods for Measuring the 

Toxicity and Bioaccumulation of Sediment-associated Contaminants with 

Freshwater Invertebrates EPA 600/R-99/064 

• NON-GDLN – (Special Study) Test Method 100.5: Life-cycle Test for 

Measuring the Effects of Sediment-associated Contaminants on Chironomus 
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dilutus (formerly known as C. tentans) in USEPA 2000 Methods for 

Measuring the Toxicity and Bioaccumulation of Sediment-associated 

Contaminants with Freshwater Invertebrates EPA 6001R-99/064

• NON-GDLN – (Special Study) Leptocheirus plumulosus in USEPA 2001 

Method for Assessing the Chronic Toxicity of Marine and Estuarine 

Sediment-associated Contaminants with the Amphipod Leptocheirus 

plumulosus EPA 600/R-01/020

• Please refer to Environmental Fate and Ecological Risk Assessment Preliminary Problem 

Formulation in Support of Registration Review of Permethrin, June 20, 2011, located in 

the docket, for a detailed discussion of the anticipated risk assessment and data needs.

Human Health Risk:

• The most recent comprehensive human health risk assessment for permethrin was 

completed in February 2006 in support of the reregistration of permethrin. The 

occupational and residential risk assessment for permethrin was updated in April 2009 in 

support of the 2009 Revised Permethrin RED.

• Permethrin is a member of the pyrethroid class of insecticides. This class also includes 

cypermethrin, cyfluthrin, tau-fluvalinate, bifenthrin, fenpropathrin, and lambdacyhalothrin, among others. EPA developed a draft science policy document on the 

proposed common mechanism of toxicity for naturally-occurring pyrethrins and synthetic 

pyrethroids (Proposed common mechanism grouping for the pyrethrins and pyrethroids, 

draft, May 19, 2009; 

http://www.regulations.gov/search/Regs/home.html#documentDetail?R=09000064809a6

2df ). This document was supported by the FIFRA Scientific Advisory Panel (SAP) and 

is available in the docket 

(http://www.regulations.gov/search/Regs/home.html#documentDetail?R=0900006480a1f

8d7). EPA will finalize the policy document on the pyrethroid common mechanism of 

toxicity taking into account the SAP comments. Pesticides with a common mechanism of 

toxicity are subject to cumulative risk assessment under the FQPA. Research is on-going 

by EPA’s Office of Research and Development (ORD) to make improvements to the 

Stochastic Human Exposure and Dose Simulation (SHEDS) probabilistic exposure 

model, which are important for the cumulative risk assessment. EPA ORD is also 

developing physiologically-based pharmacokinetic models for several pyrethroids. The 

status of both of these research modeling efforts was reviewed by the FIFRA SAP in 

July, 2010 and meeting materials are available in the docket 

(http://www.regulations.gov/search/Regs/home.html#docketDetail?R=EPA-HQ-OPP2010-0378

http://www.epa.gov/oppsrrd1/reevaluation/pyrethroids-pyrethrins.html.

). For information regarding EPA’s efforts to evaluate the risk to pyrethroids, 

see 

• The Agency anticipates requiring the following data for permethrin in order to reevaluate toxicological endpoints and update the human health toxicity profile:

• GDLN 870.7800 – Immunotoxicity
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• After the immunotoxicity study that is expected to be required is submitted and reviewed, 

EPA will re-evaluate endpoints and safety/uncertainty factors for permethrin. 

• The uncertainty factor is currently 100X (1 X FQPA safety factor, 10X for inter-species 

variation, 10X for intra-species variation). However, the FQPA safety factor will be reevaluated for permethrin following a final determination of the potential for increased 

susceptibility of infants and children to pyrethroid pesticides based on the review of all 

available data.

• During registration review, the Agency may revise the dietary risk assessment if drinking 

water concentrations, food residues, points of departure, or uncertainty factors are 

revised. Should review of the USDA Pesticide Data Program (PDP) and percent crop 

treated information show that exposure may be increasing, revised anticipated residues 

may need to be generated and incorporated into acute and chronic dietary risk 

assessments.

• The residential and occupational exposure databases are adequate; and therefore, the 

Agency does not anticipate at this time that further residential and occupational exposure 

data will be needed in support of registration review. 

• There are various indoor and outdoor uses of permethrin that could result in residential 

handler and post-application (adults and children) exposure. An updated residential 

exposure risk assessment may be required under registration review based upon revisions 

to the Agency’s Residential Standard Operating Procedures (SOPs), and if new data are 

identified which impact exposure estimates, new points of departure are selected, the 

FQPA safety factor is revised, or revisions to exposure policies and procedures are made. 

Furthermore, based upon the final determination for permethrin uncertainty factors, the

residential assessment of permethrin will be reviewed to ensure that exposure/risk 

estimates do not exceed levels of concern. 

• During registration review, the Agency anticipates updating the aggregate assessment if 

dietary or residential exposure estimates are updated, and if new data are identified which 

impact the permethrin points of departure, the FQPA safety factor, or if revisions are 

made to any exposure and/or risk assessment policies and procedures. 

• EPA expects to reevaluate all occupational dermal and inhalation exposure assessments 

using standards and policies that are in place at the time of registration review. Revised 

occupational handler and postapplication assessments may be needed if toxicological 

endpoints change, other new data are received, or other parameters are modified, such as 

changes to default exposure assessment assumptions.

• The permethrin tolerance expression in 40 CFR §180.378 will be reviewed during

registration review to ensure that it appropriately covers the metabolites and degradates 

of permethrin and that it specifies the residues to be measured for each commodity. The 

Agency anticipates updating the current tolerance expression to reflect current EPA 
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policies. Any permethrin tolerances reassessed during the registration review process 

will be considered for possible harmonization with international maximum residue limits 

(MRLs) should they be established. 

• Permethrin is among several agricultural chemicals included in the Agricultural Health 

Study (AHS). The AHS began in 1993 and is a collaboration of the National Institute of 

Environmental Health Sciences (NIEHS), the National Cancer Institute (NCI), the EPA, 

and the National Institute for Occupational Safety and Health (NIOSH). Designed as a 

large long-term epidemiological study, the AHS collects and analyzes data on the health 

and work practices of nearly 90,000 farmers and their families in Iowa and North 

Carolina who enrolled in the study before any disease developed. The study focuses 

particularly on farmers' exposure to 50 chemicals including many of the most widely 

used pesticides. As data are collected over a period of years, scientists can compare 

overall health outcomes for people who differ in whether they have had exposure to 

various chemicals. While these comparisons cannot conclusively demonstrate how 

exposure affects health, they can show some statistical associations. More information 

on the AHS can be found at: http://aghealth.nci.nih.gov. EPA is monitoring the results of 

the AHS and will consider this study in the registration review of permethrin as 

appropriate.

• Please refer to Permethrin: Registration Review Scoping Document for Human Health, 

June 15, 2011, located in the docket, for a detailed discussion of the anticipated risk 

assessment and data needs.

Endocrine Disruptor Screening Program

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of its reregistration decision, 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), permethrin is subject to the 

endocrine screening part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 
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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. Permethrin

was included on that list and has been issued an order to conduct the Tier 1 testing. Once all 

required Tier 1 and Tier 2 data have been received and reviewed, the endpoints and safety factors 

used for risk assessment purposes will be examined and a new risk assessment performed if 

necessary. For further information on the status of the EDSP, the policies and procedures, the 

list of 67 chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit 

our website: http://www.epa.gov/endo/. 

Timeline:

EPA has created the following estimated timeline for the completion of the permethrin

registration review.

Registration Review for Permethrin – Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and Public Comment Period 2011 – June

Close Public Comment 2011 – August

Case Development

Final Work Plan 2011 – November

Issue DCI 2012 – July – Sept.

Data Submission 2014 – July – Sept.

Open Public Comment Period for Draft Risk Assessments 2016 – Jan. – March

Close Public Comment Period 2016 – April – June

Registration Review Decision

Open Public Comment Period for Proposed Registration Review 

Decision

2016 – July – Sept.

Close Public Comment Period 2016 – Oct. – Dec.

Registration Review Decision and Begin Post-Decision Follow-up 2017

Total (years)

1 6 1 An assessment of the potential cumulative risk from the pyrethroid class of insecticides may impact this time 

estimate.

Guidance for Commenters:

The public is invited to comment on EPA’s preliminary work plan and rationale. The Agency 

will carefully consider all comments, as well as any additional information or data provided in a 

timely manner, prior to issuing a Final Work Plan for permethrin.
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Trade Irritants:

Through the registration review process, the Agency intends to solicit information on trade

irritants and, to the extent feasible, take steps toward facilitating irritant resolution. Growers and 

other stakeholders are asked to comment on any trade irritant issues resulting from lack of MRLs 

or disparities between U.S. tolerances and MRLs in key export markets, providing as much 

specificity as possible regarding the nature of the concern.

Water Quality:

Permethrin is not individually identified as a cause of impairment for any water bodies listed as 

impaired under section 303(d) of the Clean Water Act1. However, the pyrethroids as a group 

have been identified as a cause for impairment for three water bodies in Central Valley, 

California: Del Puerto Creek, Ingram Creek Site (from confluence with Hospital Creek to 

Highway 33 crossing) and second Ingram Creek Site (from confluence with San Joaquin River to 

confluence with Hospital Creek). At the present time, additional bodies of water are being 

evaluated to be included into the list of impaired bodies of water; however, they have not been 

finalized.2 No Total Maximum Daily Loads (TMDL) have been developed specifically for 

permethrin3

. More information on impaired water bodies and TMDLs can be found at the 

Agency’s website4. The Agency invites submission of water quality data for this pesticide. To 

the extent possible, data should conform to the quality standards in Appendix A of the OPP 

Standard Operating Procedure: Inclusion of Impaired Water Body and Other Water Quality 

Data in OPP’s Registration Review Risk Assessment and Management Process5

 

in order to 

ensure they can be used quantitatively or qualitatively in pesticide risk assessments.

Environmental Justice:

EPA seeks to achieve environmental justice, the fair treatment and meaningful involvement of all 

people, regardless of race, color, national origin, or income, in the development, implementation, 

and enforcement of environmental laws, regulations, and policies. To help address potential 

environmental justice issues, the Agency seeks information on any groups or segments of the 

population who, as a result of their location, cultural practices, or other factors, may have 

atypical, unusually high exposure to permethrin, compared to the general population. Please 

comment if you are aware of any sub-populations that may have atypical, unusually high 

exposure compared to the general population.

 1 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

2 http://www.waterboards.ca.gov/water_issues/programs/tmdl/integrated2010.shtml,, 

 http://www.swrcb.ca.gov/rwqcb5/water_issues/tmdl/impaired_waters_list/303d_list.shtml 3 http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_group_name=PESTICIDES 4 http://www.epa.gov/owow/tmdl/

5 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
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Additional Information:

Stakeholders are also specifically asked to provide information and data that will assist the 

Agency in refining its risk assessments, including any species-specific ecological effects 

determinations. The Agency is interested in receiving the following information:

1. confirmation on the following label information

a. sites of application

b. formulations

c. application methods and equipment

d. maximum application rates in units related to mass per unit area of treatment 

zone

e. frequency of application, application intervals and maximum number of 

applications per season

f. geographic limitations on use

2. use or potential use distribution (e.g., acreage and geographical distribution of 

relevant crops)

3. use history

4. median and 90th

5. application timing (date of first application and application intervals) by crop –

national, state and county

percentile reported use rates (lbs. a.i./acre) from usage data –

national, state, and county

6. sub-county crop location data

7. directly acquired county-level usage data (not derived from state level data)

a. maximum reported use rate (lbs. a.i./acre) from usage data – county

b. percent crop treated – county

c. median and 90th

d. total pounds per year – county

percentile number of applications – county

e. the year the pesticide was last used in the county/sub-county area

f. the years in which the pesticide was applied in the county/sub-county area

8. typical interval (days)

9. state or local use restrictions

10. ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian 

and mammalian mortalities) not already reported to the Agency

11. monitoring data, including existing or ongoing Publically Owned Treatment Works

(POTWs) effluent monitoring data for the pyrethroids be submitted to the Agency

12. updated usage information on the use of permethrin in non-agricultural areas

13. information on the exposure and effects to pollinators from permethrin use

Next Steps:

After the 60-day comment period closes, the Agency will review and respond to any comments 

received in a timely manner, and expects to issue a Final Work Plan for permethrin.
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II. FACT SHEET

Background Information:

• Permethrin registration review case number: 2510.

• Permethrin PC code: 109701.

• The first permethrin-containing pesticide was registered in the U.S. in 1979.

• A Reregistration Eligibility Decision (RED) for permethrin was completed in April 2006, 

an Amended RED was completed in December 2007, and a Revised RED was completed

in May 2009. 

• There are approximately 650 FIFRA Section 3 registrations for permethrin, including 21 

technical registrations. There are 19 Section 24(c) Special Local Need registrations. 

• Technical registrants for permethrin include: FMC Corp. Agricultural Products Group;

Bayer Environmental Science; Amvac Chemical Corporation; Clarke Mosquito Control 

Products, Inc.; Gharda Chemicals, Ltd.; United Phosphorus, Inc.; Meghani Organics 

Limited; LG Life Sciences, Ltd.; and Valent Biosciences Corporation.

• Tolerances for residues of permethrin, including its metabolites and degradates, in/on a 

variety of food and feed crops exist under 40 CFR §180.378.

• Pesticide Re-evaluation Division (PRD) Chemical Review Manager (CRM): Kaitlin 

Keller, keller.kaitlin@epa.gov 

• Registration Division (RD) Product Manager (PM): Richard Gebken, 

gebken.richard@epa.gov

Use & Usage Information: For additional details, please refer to Appendix A: Food/Feed & 

Non-Food/Non-Feed Uses Considered in Registration Review Work Planning, September 29, 

2010; Permethrin Screening Level Usage Analysis (SLUA), August 24, 2010; and BEAD 

Chemical Profile for Registration Review: Permethrin (PC Code: 109701), May 11, 2011.

• Permethrin is part of the pyrethroid class of pesticides. It is a broad spectrum, nonsystemic, Type I synthetic pyrethroid. It is a neurotoxic insecticide with contact and 

stomach action, having a slight repellent effect. Permethrin is registered for use on 

numerous food/feed crops, livestock and livestock housing, modes of transportation, 

structures, buildings, Public Health Mosquito abatement programs, numerous indoor and 

outdoor residential spaces, pets, and clothing. It is also regulated by the Food and Drug 

Administration (FDA) as a pediculicide for the treatment of head lice and scabies. The 

majority of use is on non-agricultural outdoor sites, including mosquito abatement 

control. Permethrin is the most widely used mosquito adulticide in the United States. 

The majority of agricultural use is on corn, lettuce, and pistachios.

• Permethrin is the only pesticide registered to pre-treat clothing and fabrics to repel 

mosquitoes, ticks, and other public health pests. It is also the only pesticide registered for 

use in conjunction with “4 Poster” deer treatment bait stations for control of ticks which 

vector Lyme disease. 
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• Permethrin is formulated as emulsifiable concentrate, liquid, wettable powder, liquidready to use, granules, dust, pressurized gas, pressurized liquid, and water dispersable 

granule (dry flowable).

 

• Application methods include direct spray, surface treatment, soil broadcast, spot 

treatment, chemigation, soil injection, and Ultra Low Volume (ULV) applications for 

mosquito control.

• According to the most recent usage data, approximately 400,000 pounds of permethrin 

active ingredient (A.I.) is used per year for agricultural purposes applied to 3 million 

acres. Pistachios, lettuce, corn, and potatoes account for the highest agricultural usage (in 

pounds) of permethrin. Approximately half of all agricultural usage of permethrin occurs 

in California. The majority of non-agricultural usage is by consumers for outdoor use. 

Consumers use approximately 1.75 million pounds A.I. for outdoor use. Pest control 

operators use approximately 450,000 pounds A.I. Additionally, approximately 100,000 

pounds A.I. is used for mosquito abatement and 12,000 pounds A.I. is used in 

nurseries/greenhouses annually.

Recent Actions:

• A revised occupational and residential (ORE) risk assessment was completed in April 

2009 using a decreased dermal absorption factor and a new draft approach for refining 

indoor cancer assessments developed by the Agency. Subsequently, a Revised RED was 

completed in May 2009 to incorporate changes to the ORE mitigation measures, as a 

result of the updated ORE assessment. Documents related to the reregistration of 

permethrin can be found in the docket EPA-OPP-HQ-2004-0385 at:

www.regulations.gov.

• Permethrin product labels are currently being revised as part of product reregistration to 

incorporate mitigation measures specified in the 2009 Revised Permethrin RED (e.g., 

mandatory label language for canine spot-on products and pre-construction termiticide 

application, and revised spray drift language for agricultural products). 

Ecological Risk Assessment Status:

The following are key findings of the most recent ecological risk assessments for permethrin.

For a detailed discussion of the ecological risk assessment status please refer to the

Environmental Fate and Ecological Risk Assessment Preliminary Problem Formulation in 

Support of Registration Review of Permethrin, June 20, 2011, located in the registration review 

docket EPA-HQ-OPP-2011-0039.

• The most recent comprehensive national-level ecological risk assessment for permethrin 

was completed in support of the permethrin RED in April 2006. Acute and chronic risks 

were identified for listed and non-listed aquatic organisms (fish and watercolumn/sediment-dwelling invertebrates) that exceeded the Agency’s Level of Concern 

(LOC). Chronic risks exceeding the Agency’s LOC were identified for mammalian 
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species. Acute risk to mammalian species and acute and chronic risk to avian species did 

not exceed the Agency’s LOC. Risks were not quantified for terrestrial invertebrates. 

The 2006 Permethrin RED specified several risk reduction measures for products labeled 

for wide area mosquito abatement to reduce potential freshwater and estuarine 

invertebrate risks of concern. Mitigation measures included reductions in single and 

seasonal applications rates and buffer zones for agricultural uses of permethrin.

• In the 2006 risk assessment, potential risk was not quantified for terrestrial invertebrates. 

However, the Agency noted that a number of studies demonstrated that applications of 

formulations of permethrin were likely to reduce the numbers and possibly eliminate 

populations of beneficial insects. It was also concluded that toxicity data were not 

available for terrestrial plants and the potential for risk to plants remains an uncertainty.

• The 2006 risk assessment also indicated that there is potential for permethrin runoff from 

residential areas, and that applications, such as perimeter treatments in and around 

buildings, could potentially result in residues being transported to adjacent aquatic areas. 

Additionally, residues of permethrin have been found in aquatic areas that receive runoff 

from suburban developments.

• In October 2008, the Agency conducted a listed species-specific risk assessment to assess 

the potential risk of permethrin to the federally-listed California red-legged frog (CRLF), 

California clapper rail, Salt marsh harvest mouse, San Francisco garter snake, and Bay 

checkerspot butterfly. The Agency made a “May Affect” and “Likely to Adversely 

Affect” determination for all of the abovementioned species from the labeled uses of 

permethrin. This was based on the potential for direct and indirect effects due to 

potential decreases in aquatic and terrestrial prey items. The Agency also determined that 

there is potential for modification of designated critical habitat of the CRLF from the 

labeled uses of permethrin. In October 2008, the Agency transmitted the assessment to 

the U.S. Fish and Wildlife Service and initiated formal consultation under section 7(a)(2) 

of the Endangered Species Act.

• The most recent ecological risk assessment for permethrin was completed in September 

2010 to evaluate potential direct and indirect effects of permethrin use on the threatened 

Valley Elderberry Longhorn Beetle (VELB). The assessment resulted in a “May Affect” 

and “Likely to Adversely Affect” determination for the VELB from the labeled uses of 

permethrin. Additionally, the Agency determined that there is potential for modification 

of designated critical habitat of the VELB from the labeled uses of permethrin. In 

September 2010, the Agency transmitted the assessment to the U.S. Fish and Wildlife 

Service and initiated formal consultation under section 7(a)(2) of the Endangered Species 

Act.

Human Health Risk Assessment Status:

The following are key findings of the most recent human health risk assessments for permethrin. 

For a detailed discussion of the human health risk assessment status, please refer to the
16

Permethrin: Registration Review Scoping Document for Human Health Assessments, June 15, 

2011, located in the registration review docket EPA-HQ-OPP-2009-0039.

• The most recent comprehensive human health risk assessment for permethrin was 

completed in February 2006 in support of the reregistration of permethrin. The 

occupational and residential risk assessment for permethrin was updated in April 2009 in 

support of the Revised Permethrin RED.

Hazard Characterization:

• Permethrin is a Type I synthetic pyrethroid. As with the other pyrethroids, permethrin

causes neurotoxicity in insects and mammals by the modulation of nerve axon sodium 

channels. Pyrethroids interfere with the ability of the nervous system to relay nerve 

transmissions, potentially resulting in tremors, convulsions, salivation, and other clinical 

effects. 

• Permethrin has a low acute toxicity via the oral (Category III), dermal (Category III), and 

inhalation (Category IV) routes of exposure. Permethrin is not an eye or skin irritant and 

not a skin sensitizer.

• The Agency reduced the 10x FQPA safety factor to 1x because the toxicity database was 

adequate to characterize the potential for pre- and postnatal risk for infants and children, 

no reproductive or developmental effects were observed in rats, and there was a lack of 

evidence of increased susceptibility.

• Permethrin is classified as “Likely to be Carcinogenic to Humans” by the oral route based 

on evidence of two reproducible benign tumor types (lung and liver) in the mouse, 

equivocal evidence of carcinogenicity in Long-Evans rats, and supportive structural 

activity relationships (SAR) information. Mutagenicity studies did not demonstrate any 

evidence of mutagenic potential for permethrin.

Dietary:

• Acute, chronic non-cancer, and cancer dietary (food and water) risk assessments were 

conducted for the general U.S. population and various population subgroups, with the 

major emphasis placed on the exposure estimates for infants and children. For all 

supported registered commodities, the acute and chronic dietary exposure to permethrin

did not exceed the Agency’s Level of Concern (LOC) for the general U.S. population and 

vulnerable population subgroups. 

Residential:

• In the 2009 risk assessment, non-cancer (dermal and inhalation) residential handler risk 

estimates for all residential handler exposure scenarios were below the Agency’s target 

LOC. For residential handler cancer risks, several exposure scenarios for use on outdoor 

trees, stored lumber, and wood piles resulted in risk estimates above the Agency’s LOC. 
17

However, the Agency does not believe that these exposure scenarios are feasible or likely 

to occur based on the frequency of application, amount of product handled, and the 

application method paired with the use patterns assessed. Therefore, these scenarios were 

considered not to be of concern to the Agency.

• For residential non-cancer post-application exposure scenarios, all risk estimates were 

below the Agency’s LOC. The Agency also conducted an adult residential postapplication cancer risk assessment as part of the 2009 assessment. Three indoor

scenarios resulted in 5 days or less of allowable post-application exposure. To mitigate 

the identified risk of concern, all permethrin directed broadcast spray and spot treatment 

sprays on all residential indoor surfaces were voluntarily cancelled and the concentration 

of all indoor sprays was limited to 0.5% permethrin.

Aggregate:

• Acute, short- and intermediate-term, chronic non-cancer, and cancer aggregate risk 

assessments were conducted as part of the 2009 Revised RED risk assessment. 

Aggregate risk estimates were below the Agency’s LOC with the exception of some 

scenarios in the non-cancer short- and intermediate-term aggregate assessment. The 

combined residues of permethrin from food, drinking water, and other potential 

residential exposures were assessed which resulted in risk estimates above the LOC for 

the combined turf/indoor carpet broadcast spray exposure to toddlers. To mitigate the 

identified risk of concern, all permethrin directed broadcast spray and spot treatment 

sprays on residential indoor surfaces were voluntarily cancelled and the concentration of 

all indoor sprays was limited to 0.5% permethrin

Occupational:

• Due to the scope of the various permethrin occupational uses (there are hundreds of 

registered permethrin products); the 2009 risk assessment evaluated 39 occupational 

handler scenarios to represent the major permethrin occupational handler scenarios based 

on application equipment and formulation types.

• The non-cancer handler risk estimates presented in the 2009 risk assessment indicated

that all of the occupational handler scenarios resulted in risks that did not exceed the 

Agency’s LOC with some level of personal protective equipment (PPE) was included. 

The level of protective equipment varied based on the occupational handler scenario, 

from baseline exposure (i.e., long-sleeve shirt, long pants, shoes and socks) followed by 

increasing the levels of personal protective equipment (e.g., gloves, double-layer body 

protection, and respirators), and then by engineering controls (e.g., enclosed cabs and 

closed mixing/loading systems).

• For all non-cancer postapplication exposure scenarios assessed, risks did not exceed the 

Agency’s LOC. 
18

• Occupational handler and postapplication cancer risk assessments were also conducted as 

part of the 2009 risk assessment. The same scenarios, assumptions, and exposure data 

were used as in the non-cancer assessment. Cancer risk estimates for workers handling 

dusts resulted in exposures above the Agency’s LOC for multiple scenarios. However, 

the Agency used conservative assumptions that likely overestimate daily usage. Further, 

additional PPE beyond that already in place could cause additional heat related stress to 

the worker. Therefore, the Agency concluded that baseline PPE, chemical resistant 

gloves, and a respirator were protective of cancer risks for all scenarios. For most 

postapplication scenarios, cancer risk estimates did not exceed the Agency’s LOC for 

cancer risks at baseline exposure. While several scenarios resulted in cancer risk 

estimates above the Agency’s LOC, the Agency concluded that it is unlikely that workers 

would be annually exposed to permethrin residues for 30 days. According to Agency 

data, permethrin is primarily used during the post-harvest and dormant seasons, used in 

lower application rates than those assessed, or on crops with production practices that 

make chronic exposure unlikely. Additionally, registrants agreed to reduce maximum 

application rates and number of applications per year or season to help reduce potential 

post-application risks to workers. 

Human Studies:

• Past permethrin risk assessments rely in part on data from studies in which adult

human subjects were intentionally exposed to a pesticide to determine their dermal and

inhalation exposure. Many such studies, involving exposure to many different pesticides,

comprise generic pesticide exposure databases such as the Pesticide Handlers Exposure

Database (PHED) and the Agricultural Reentry Task Force (ARTF) Database. EPA has

reviewed all the studies supporting these multi-pesticide generic exposure databases, and

has found no clear and convincing evidence that the conduct of any of them was either

fundamentally unethical or significantly deficient relative to the ethical standards

prevailing at the time the research was conducted. All applicable requirements of EPA’s 

Rule for the Protection of Human Subjects of Research (40 CPR Part 26) have been 

satisfied, and there is no regulatory barrier to continued reliance on these studies.

Cumulative:

• Permethrin is a member of the pyrethroid class of insecticides. This class also includes 

cypermethrin, cyfluthrin, tau-fluvalinate, bifenthrin, fenpropathrin, and lambdacyhalothrin, among others. EPA developed a draft science policy document on the 

proposed common mechanism of toxicity for naturally-occurring pyrethrins and synthetic 

pyrethroids (Proposed common mechanism grouping for the pyrethrins and pyrethroids, 

draft, May 19, 2009; 

http://www.regulations.gov/search/Regs/home.html#documentDetail?R=09000064809a6

2df ). This document was supported by the FIFRA Scientific Advisory Panel (SAP) and 

is available in the docket 

(http://www.regulations.gov/search/Regs/home.html#documentDetail?R=0900006480a1f

8d7). EPA will finalize the policy document on the pyrethroid common mechanism of 

toxicity taking into account the SAP comments. Pesticides with a common mechanism of 
19

toxicity are subject to cumulative risk assessment under the FQPA. Research is on-going 

by EPA’s Office of Research and Development (ORD) to make improvements to the 

Stochastic Human Exposure and Dose Simulation (SHEDS) probabilistic exposure 

model, which are important for the cumulative risk assessment. EPA ORD is also 

developing physiologically-based pharmacokinetic models for several pyrethroids. The 

status of both of these research modeling efforts was reviewed by the FIFRA SAP in 

July, 2010 and meeting materials are available in the docket 

(http://www.regulations.gov/search/Regs/home.html#docketDetail?R=EPA-HQ-OPP2010-0378

http://www.epa.gov/oppsrrd1/reevaluation/pyrethroids-pyrethrins.html.

). For information regarding EPA’s efforts to evaluate the risk to pyrethroids, 

see 

Incidents:

• The Office of Pesticide Programs (OPP) Incident Data System (IDS) was consulted for 

reports of permethrin incidents. From January 1, 2002 to February 2011, 9,992 cases

were reported for permethrin. There is no unique report that provides details about the 

incidents and single chemical incidents are not distinguished from multiple chemical 

incidents; however, a high frequency of incidents indicates there is a high potential for 

exposure and vice versa. For the Main IDS, from January 1, 2002, to February 1, 2011, 

2,478 cases were reported that involve the active ingredient permethrin. Of these 2,478 

cases, there are 432 cases reported for single chemical permethrin only in the database 

and of these there were 5 deaths and 15 human major incidents. Most of the deaths were 

due to misuse or unintentional exposure to permethrin. Most of the human major 

incidents were exposed to the product while using it without protective clothing and were 

unaware of the adverse effects of permethrin. Based on the number of incidents reported

for permethrin and the effects noted in the incidents, permethrin warrants further incident 

analysis during registration review. This further analysis will include reviewing 

permethrin incident data from other sources as well as case studies and a medical 

literature search on human health effects of permethrin.

• A preliminary review was made on January 4, 2011 of the Ecological Incident 

Information System (EIIS), which is maintained by OPP; and the Avian Monitoring 

Information System (AIMS), which is maintained by the American Bird Conservancy. 

No incidents involving permethrin were found in AIMS. EIIS indicates a total of 41

reported ecological incidents associated with the use of permethrin from 1994 to January 

2011. The report includes 26 aquatic animal incidents, 8 terrestrial animal incidents and 

8 plant incidents (one terrestrial incident involved both plants and animals). The majority 

of ecological incidents involving permethrin occurred in aquatic environments. Of these 

incidents, nine are listed as highly probable, ten as probable, and seven as possible. 

Twenty-three incidents affected fish species, and the other three reports involved 

crayfish. Approximately half (thirteen) of the incidents resulted from registered use of 

permethrin. Many of these incidents originated with permethrin application to residences 

or other buildings, followed by permethrin runoff into nearby water bodies. All

ecological incidents considered “minor” only need to be aggregately reported as quarterly 

counts of incidents by the registrant(s). For permethrin, registrants have reported 14 
20

minor fish and wildlife incidents, 149 minor plant incidents, and 4 other non-target 

incidents.

Tolerances and International Harmonization: 

• Tolerances are established under 40 CFR §180.378(a) for residues of the insecticide 

permethrin, including its metabolites and degradates, in or on a variety of food and feed 

crops. Compliance with the tolerance levels specified is to be determined by measuring 

only permethrin [(3-phenoxyphenyl)methyl 3-(2,2-dichloroethenyl)-2,2-

dimethylcyclopropane carboxylate], as the sum of its cis- and trans- isomers in or on the 

commodity. 

• Both Codex and Canada have established Maximum Residue Levels (MRLs) for 

permethrin. In most cases, the Codex and Canadian MRLs differ from each other as well 

as from the U.S. tolerance. Where possible, the Agency will work to harmonize 

tolerances/MRLs during registration review.

Data Call-In Status:

In May 2009, a generic data call-in (GDCI-109701-26467) for permethrin was issued in support 

of reregistration. Product specific data call-ins (PDCIs) were also issued in May 2009. The 

following is a summary of the status of data not yet received for GDCI-109701-26467:

• GDLN 875.1200, Dermal Exposure Outdoors (ULV Cold Fogger) & GDLN 875.1400,

Inhalation Exposure Indoors (ULV Cold Fogger): The registrant submitted waiver 

requests for these data requirements and the Agency is in the process of reviewing these 

requests. 

• Special Studies: Chronic Freshwater Sediment Testing & Special Study: Chronic 

Estuarine/Marine Sediment Testing: These studies are past due; final Agency review of 

the protocols was not completed until January 2011. The registrants have recently 

provided dates of May 30, 2012 and June 30, 2012, respectively, for the anticipated 

submission of these studies.

• The Agency has yet to receive data to fulfill the following GDLN studies required by the 

2009 GDCI. These studies are past due as of May 28, 2011. The registrants have 

recently provided the following new anticipated dates for the submission of these studies:

o GDLN 860.1380, Storage Stability – September 2011

o GDLN 860.1500, Magnitude of the Residue in Crop Plants (cabbage, grass 

forage, leaf lettuce, tomato) – September 2011

o GDLN 860.1500, Magnitude of the Residue in Crop Plants (collards) – January 

2012
21

Labels:

• Permethrin Section 3 product labels can be obtained from the Pesticide Product Label 

System (PPLS) website: http://oaspub.epa.gov/pestlabl/ppls.hom
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III. SUMMARY OF DATA GAPS – Permethrin

The table below summarizes all anticipated data needs for permethrin in Section I, of this 

document (Preliminary Work Plan), the Registration Review– Preliminary Problem Formulation 

for the Environmental Fate, Ecological Risk, and Endangered Species and Drinking Water 

Assessments for Permethrin, dated June 20, 2011 and the Permethrin: Registration Review 

Scoping Document for Human Health Assessments, dated June 15, 2011.

Table 1. Anticipated Data Needs for Permethrin Registration Review

Guideline Number Anticipated Data Requirement Test 

Material

Study 

Duration

835.1230 Adsorption/Desorption TGAI 12

835.2240 Photodegradation in Water TGAI 24

835.4100 Aerobic Soil Metabolism TGAI 24

835.4200 Anaerobic Soil Metabolism TGAI 24

835.4300 Aerobic Aquatic Metabolism TGAI 24

835.4400 Anaerobic Aquatic Metabolism TGAI 24

835.6100 Environmental Chemistry Methods (ECM) and Independent 

Laboratory Validation (ILV) for Soil6 TGAI 12

835.6200 Environmental Chemistry Methods (ECM) and Independent 

Laboratory Validation (ILV) for Water 6 TGAI 12

850.1010 Acute Toxicity Freshwater Invertebrates TEP 24

850.1020 Acute Toxicity Freshwater Invertebrates (Hyalella azteca)

7,8 TEP 24

850.1025 Acute Toxicity Estuarine/Marine Organisms (oyster) TEP 12

850.1075 Acute Freshwater Fish Toxicity7 TEP 12

850.1350 Aquatic Invertebrate Life Cycle (saltwater) TGAI 12

850.2100 Avian Oral Toxicity (passerine species)8 TGAI 12

850.4100 Nontarget Area Phytotoxicity Tier II, Seedling Emergence 9 TEP 12

850.4150 Nontarget Area Phytotoxicity Tier II, Vegetative Vigor9 TEP 12

850.4400 Nontarget Area Phytotoxicity Tier II, Aquatic Plant Growth 

(Vascular Plants)9 TEP 12

850.5400 Nontarget Area Phytotoxicity Tier II, Aquatic Plant Growth 

(Algal Plants)9 TGAI 12

870.7800 Immunotoxicity TGAI 12

 6 See footnote 7 of 40 CFR 158.1300. EPA anticipates requiring only the environmental chemistry analytical 

method portion of GDLNs 835.6100 – Terrestrial field dissipation and 835.6200 – Aquatic field dissipation. 7

The anticipated DCI will provide that TEP studies on freshwater invertebrates and freshwater fish are required on 

co-formulated products containing the highest ratio of the synergist piperonyl butoxide (PBO) to permethrin and the 

highest ratio of the synergist MGK-264 to permethrin. 8 The anticipated DCI will require a study protocol to be submitted for review and approval by the Agency prior to 

this study being initiated. 

9 A Tier II study is expected to be required. The DCI expected to be issued will provide that a Tier I plant study 

may be conducted in lieu of a Tier II study with the understanding that any adverse effects observed by the Tier I 

study would necessitate conduct and submission of a Tier II study as well. 
23

Guideline Number Anticipated Data Requirement Test 

Material

Study 

Duration

NON-GDLN Special Study on Leachability from Treated Wood TEP 12

NON-GDLN Publically Owned Treatment Works (POTW) Treatability Study TGAI 12

NON-GDLN Test for Measuring the Effects of Sediment Associated 

Contaminants on Survival, Growth, and Reproduction on

Hyalella azteca in USEPA 2000 Methods for Measuring the 

Toxicity and Bioaccumulation of Sediment-associated 

Contaminants with Freshwater Invertebrates. EPA 600/R-99/064

TGAI

8

24

NON-GDLN Life-cycle Test for Measuring the Effects of Sediment-associated 

Contaminants on Chironomus dilutus or C. tentans in USEPA 

2000 Methods for Measuring the Toxicity and Bioaccumulation 

of Sediment-associated Contaminants with Freshwater 

Invertebrates. EPA 600/R-99/064

TGAI

8

24

NON-GDLN Leptocheirus plumulosus in USEPA 2001 Method for Assessing 

the Chronic Toxicity of Marine and Estuarine Sedimentassociated Contaminants with the Amphipod Leptocheirus 

plumulosus. EPA 600/R-01/020

TGAI

8

24