Docket Number: EPA-HQ-OPP-2009-0301 

www.regulations.gov

Esfenvalerate Final Work Plan 

Registration Review 

June 2010 
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 ESFENVALERATE FINAL WORK PLAN 

Introduction: 

This is the Environmental Protection Agency’s (EPA’s) Final Work Plan for the 

registration review of esfenvalerate. This work plan includes the expected registration 

review timeline. The work plan also addresses public comments received concerning the 

Preliminary Work Plan in the Summary Document, which was posted in the 

esfenvalerate registration review docket (EPA-HQ-OPP-2009-0301), and any other 

comments concerning the initial docket postings. The Summary Document provided 

information on what EPA knows about the pesticide and what additional risk analyses 

and data or information the Agency believes are needed to make a registration review 

decision. 

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. Changes in science, public policy, and pesticide use practices 

will occur over time. 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. The public phase of registration 

review begins when the initial docket is opened for each case. Information on this 

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

Esfenvalerate (Case 7406) is a broad spectrum pyrethroid insecticide registered for use on 

a variety of agricultural crops and on residential and industrial use sites (both indoor and 

outdoor). Since esfenvalerate was registered after 1984, it was not subject to the 

reregistration requirements of FIFRA. Esfenvalerate is the S, S-isomer of fenvalerate, 

and for the human health risk assessment, esfenvalerate and fenvalerate are considered 

toxicologically equivalent. All fenvalerate registrations were voluntarily cancelled by the 

registrants in 2008 (73 FR 132). 

Comments Received on Preliminary Work Plan: 

Multiple comments were received during the 60-day public comment period on the 

Preliminary Work Plan. These comments are summarized in this document and changes 

to the work plan set out in the Preliminary Work Plan are explained. In the Preliminary 

Work Plan, EPA also solicited comments on three specific topics: environmental justice, 

water body impairment, and trade irritants. No comments or information were received 

during the comment period concerning these issues. 

Anticipated Risk Assessment and Data Needs:

The Agency will conduct a comprehensive ecological risk assessment for esfenvalerate, 

including an endangered species risk assessment, and update and revise the human health 

risk assessment. Below is a summary of the issues relevant to the registration review of 
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esfenvalerate. 

Ecological Risk: 

• The most recent ecological assessment for esfenvalerate was an endangered 

species assessment evaluating the potential effects of esfenvalerate on the 

Federally-listed threatened California red-legged frog (Rana aurora draytonii) 

consistent with court orders and settlements, Center for Biological Diversity v. 

Johnson, et al.,No. 02-1580 (N.D. Cal., October 20, 2006). The Agency 

concluded in February 2008 that esfenvalerate is Likely to Adversely Affect the 

California red-legged frog and initiated formal consultation with the US Fish and 

Wildlife Service under section 7 of the Endangered Species Act. 

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

endangered species determination. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether esfenvalerate’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 Services (the Services), as appropriate. 

• The Agency will require the following additional data in order to conduct a 

complete ecological risk assessment, including an endangered species assessment, 

for all uses: 

Environmental Fate 

o Guideline number (GLN) 835.4300 - Aerobic Aquatic Metabolism 

(TGAI) 

o GLN 835.4400 - Anaerobic Aquatic Metabolism (TGAI) 

Terrestrial Organisms 

o GLN 850.2100 - Avian acute oral toxicity for a passerine species 

[conducted with technical grade active ingredient (TGAI)] 

o GLN 850.2300 - Avian reproduction for an upland game bird and 

waterfowl (TGAI) 

o GLN 850.4100 - Terrestrial plants seedling emergence, Tier II [conducted 

with a typical end-use product (TEP)] 1

o GLN 850.4150 - Vegetative vigor, Tier II (TEP)

 

1 Registrants may opt to conduct Tier I terrestrial plant studies, with the understanding that any 

adverse effects (even if <25%) may necessitate Tier II studies. Tier II studies will enable the 

Agency to conduct an endangered species assessment for nontarget plants. 
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Aquatic Organisms 

o GLN 850.1075 - Acute toxicity to freshwater fish for one cold water and 

one warm water species (TGAI) 

o GLN 850.1075 - Acute toxicity to estuarine/marine fish for one species 

(TGAI and TEP) 

o GLN 850.1010 - Acute toxicity to freshwater invertebrate (TEP) 

o GLN 850.1025 - Acute toxicity to estuarine/marine invertebrate for the 

mollusk and another invertebrate species (TGAI and TEP) 

o GLN 850.1350- Estuarine/marine invertebrate lifecycle for one species 

(TGAI) 

o GLN 850.1500 - Estuarine/marine fish full life cycle for one species 

(TGAI) 

o GLN 850.1400 - Estuarine/marine early life cycle for one species; data 

from the full lifecycle study may be used to fulfill this guideline (TGAI) 

o Non-GLN - Whole sediment survival, growth, and reproduction tests with 

Chironomus tentans, Leptocheirus plumulosus, and Hyalella azteca 

(TGAI) 

o GLN 850.4400 – Aquatic plant growth studies for algae, Tier II (TGAI)2

o GLN 850.5400 - Aquatic plant growth studies for vascular plants, Tier II 

(TGAI)

Exposure 

o Non-GLN – Publically owned treatment works (POTW) treatability study 

(bench scale wastewater treatment study) (TGAI) 

 The Agency will require a bench scale study of wastewater treatment, 

to assess the percentage of esfenvalerate removed in the biosolids by 

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

would remain in the wastewater. These data would be used to inform 

removal percentages by wastewater treatment, which is an input to the 

Exposure and Fate Assessment Screening Tool (E-FAST) used by the 

Agency to assess “down-the-drain” exposure.

• Please refer to the Revised Registration Review: Revised Preliminary Problem 

Formulation for Ecological Risk, Environmental Fate, Endangered Species, and 

Drinking Water Assessment for Esfenvalerate, completed June 21, 2010, located 

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

Human Health Risk: 

• The most recent comprehensive human health assessment was completed on July 

 

2

 Registrants may opt to conduct Tier I aquatic studies, with the understanding that any adverse 

effects (even if <25%) may necessitate Tier II studies. Tier II studies will enable the Agency to 

conduct an endangered species assessment for nontarget plants. 
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2, 2004 for the new uses of esfenvalerate in/on Brussels sprouts; pistachios; postharvest uses in/on almonds, cocoa beans, peanut kernels and walnuts; canola; 

head lettuce; cardoon; Chinese cabbage (bok choy); and sweet potato.

• The esfenvalerate risk assessment in 2004 determined that the residue chemistry 

database was complete except for crop field trial data for the following raw 

agricultural commodities (RACs): corn, soybean, and sorghum aspirated grain 

fractions, cotton gin byproducts, pea (field) vines and hay. These data have not 

been submitted; therefore, the Agency will include them in the registration review 

Data Call-In (DCI). 

• During registration review, the Agency will reassess the esfenvalerate dietary 

burden to livestock in light of a 2008 update to livestock feedstuff. The Agency 

updated the livestock feedstuff tables to be more consistent with the modern diet 

fed to livestock, and in an effort to harmonize the Agency’s approach for 

assessing dietary burden to livestock with that of other regulatory partners. The 

2008 update resulted in a significant reduction in the percent of several feedstuffs 

in cattle diet, thus likely resulting in a lower dietary burden to ruminants. The 

anticipated reassessment may also indicate a need to lower livestock commodity 

tolerances for esfenvalerate. 

• The tolerance expression in 40 CFR 180.379 will be reviewed during registration 

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

esfenvalerate and that it specifies the residues to be measured for each 

commodity. 

• The Agency expects that a new drinking water exposure assessment (DWA) will 

be needed in order to incorporate the latest modeling methods for surface water 

sources of drinking water. Because esfenvalerate is not likely to leach through the 

soil to reach ground water sources due to its high sorption potential, ground water 

exposure will not be included in the DWA. 

• During registration review, the Agency will update the refined, probabilistic acute 

and chronic dietary (food and drinking water) exposure assessment for 

esfenvalerate to include updated drinking water estimated environmental 

concentrations (EECs), any changes to toxicological endpoints and safety factors, 

and updates to the percent crop treated values and anticipated residue levels. 

• To address potential indoor residential post-application risks of concern, 

esfenvalerate registrants recently submitted an exposure study for floor residues 

following crack-and-crevice or broadcast applications (MRID 47690501). This 

study was reviewed by the Agency and found to be adequate. These floor 

deposition data will be considered in advance of the complete human health risk 

assessment planned for registration review, along with a recently submitted 

residential probabilistic risk assessment: Esfenvalerate Non-Dietary (Residential) 

Risk Assessment - Development of a Random Walk Approach to Estimate 
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Potential Child Incidental Ingestion (Hand-to-Mouth Contact) Exposures 

Following Indoor Crack & Crevice Treatment (MRID 47772701). The more 

refined probabilistic assessment may result in lower residential risks than the 

screening-level deterministic methodology employed in the 2004 human health 

risk assessment. 

 

• During registration review, the Agency will conduct a full reassessment of 

occupational, residential, and aggregate risk, taking into account any relevant 

changes to toxicological endpoints, safety factors, exposure values, and applicable 

occupational and residential standard operating procedures (SOPs). 

• The Agency will require the following data in order to conduct a complete human 

health assessment: 

o GLN 870.7800 - Immunotoxicity 

o GLN 870.3465 - 90-Day Inhalation Toxicity 

o GLN 870.6300 - Developmental Neurotoxicity (DNT) 

o GLN 860.1500 - Crop Field Trials (corn, soybean, and sorghum aspirated 

grain fractions, cotton gin byproducts, pea (field) vines and hay) 

• While the inhalation guideline calls for a 90-day study, a 28-day study will satisfy 

the Agency’s intermediate-term inhalation exposure data needs for this chemical 

based on current use patterns. This modification will be noted in the registration 

review DCI for esfenvalerate. 

• Based on the Agency’s review of existing pyrethroid data, EPA has come to the 

conclusion that the DNT is not a particularly sensitive study for comparing the 

sensitivity of young and adult animals to pyrethroids. EPA has recently 

determined that, as an alternative to the generation and submission of a new DNT 

study, pyrethroid registrants may instead choose to cite to the six previously 

submitted DNT studies for pyrethroid pesticides. The Agency is also 

investigating the need for additional experimentation, specific to the mode of 

action and pharmacokinetic characteristics of pyrethroids, to evaluate the potential 

for increased susceptibility of young organisms. A meeting of the FIFRA 

Scientific Advisory Panel (SAP) is planned for July 2010. For more information 

on the pyrethroid developmental neurotoxicity (DNT) requirement, see 

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

• The Agency will make a decision regarding the need for an FQPA or other 

database uncertainty/safety factors following receipt of the remaining required 

toxicity data, and following a final determination of the potential for increased 

susceptibility of infants and children to pyrethroid pesticides based on the results 

of all available data. 

• Esfenvalerate is a member of the pyrethroid class of insecticides. EPA has

developed a draft science policy document on the proposed common mechanism 
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of toxicity for naturally-occurring pyrethrins and synthetic pyrethroids, which was 

supported by the FIFRA SAP. Upon finalization of this science policy, the 

pyrethroids will be subject to a cumulative risk assessment under the FQPA. 

• Please refer to the Human Health Scoping Document in Support of Registration 

Review for Esfenvalerate, completed December 1, 2009, located in the docket, for 

a detailed discussion of the anticipated risk assessment needs for human health. 

Other Data Needs: 

• GLDN 830.7050 - UV/Visible Light Absorption. This study is a new data 

requirement under 40 CFR part 158 (Product Chemistry Data Requirements) for 

registration of a pesticide (food and non-food uses). The Agency anticipates 

requiring this study to obtain basic information about the compound’s 

identity/composition and the wavelengths at which the compound may be 

susceptible to photochemical degradation. 

Endocrine Disruptor Screening Program

As required under FFDCA section 408(p), EPA has developed the Endocrine Disruptor 

Screening Program (EDSP) to determine whether certain substances (including pesticide 

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

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

Administrator may designate.” 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, and 

or thyroid (E, A, or T) hormonal systems. Chemicals that go through Tier 1 screening 

and are found to have the potential to interact with E, A, or T hormonal systems will 

proceed to the next stage of the EDSP where EPA will determine which, if any, of the 

Tier 2 tests are necessary based on the available data. Tier 2 testing is designed to 

identify any adverse endocrine related effects caused by the substance, and establish a 

quantitative relationship between the dose and the E, A, or T effect. 

 

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. This list of chemicals was selected based on the potential for human 

exposure through pathways such as food and water, residential activity, and certain postapplication agricultural scenarios. This list should not be construed as a list of known or 

likely endocrine disruptors. 

Esfenvalerate is among the group of 58 pesticide active ingredients on the initial list to be 

screened under the EDSP. For information on the status of the orders issued under the 

EDSP for each chemical, please visit our website at http://www.epa.gov/endo/ and click 

on the "Status of EDSP Orders/DCIs" in the Highlights Box. Additional information on 

the EDSP, including the policies and procedures, the list of 67 chemicals, the test 

guidelines and the Tier 1 screening battery, can also be found at this website. 
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Timeline: 

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

review for esfenvalerate. 

Registration Review for Esfenvalerate – Projected Registration Review Timeline 

Activities Estimated Date 

Opening the Docket 

Open Docket and Public Comment Period December 2009 

Close Public Comment February 2010 

Case Development 

Issue Final Work Plan (FWP) June 2010 

Issue Data Call-in (DCI) January – March 2011

Data Submission1 January – March 2015 

Open Public Comment Period for Preliminary Risk 

Assessments July – September 2016 

Close Public Comment Period October - December 2016 

Registration Review Decision 

Open Public Comment Period for Proposed Registration 

Review Decision January – March 2017 

Close Public Comment Period April - June 2017 

Final Registration Review Decision & Begin PostDecision Follow-up 2017 

Total (years) 2 8 

1. If the registrants choose to cite the six previously submitted DNT studies for pyrethroid pesticides, 

as explained above, rather than conduct a DNT study with esfenvalerate, this time estimate will 

likely be shortened by approximately two years. 

2. An assessment of the potential cumulative risk from the pyrethroid class of insecticides may 

impact this time estimate. 

Summary of Comments and Agency Responses: 

The esfenvalerate registration review docket was open for a 60-day comment period 

beginning on December 16, 2009. During the comment period, multiple comments were 

received, which are summarized below. Comments that prompted a change in the work 

plan, or are not addressed by other response documents included in the esfenvalerate 

docket, have responses included below. While some comments did facilitate changes to 

the work plan, they did not affect the timeline set out in the Preliminary Work Plan. 

After consideration of comments received on the Registration Review: Preliminary 

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

Drinking Water Assessment for Esfenvalerate, the Agency revised this document and the 

updated version is available in the esfenvalerate registration review docket (Docket 

Number: EPA-HQ-OPP-2009-0301) at www.regulations.gov. The substantive 

comments received on the ecological Problem Formulation and the human health 
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Scoping Document, the Agency’s response, and the revisions to the ecological Problem 

Formulation are described below. This document makes final the work plan for the 

esfenvalerate registration review process. 

Comments from DuPont Crop Protection 

Ecological Risk Assessment 

Comment: Esfenvalerate is registered for use on more than 50 crops. Given the number 

of crops and the absence of adverse effects on plants found during extensive residue and 

performance testing, the potential for esfenvalerate to reduce survival, reproduction, 

and/or growth of plants is negligible based on usage history and an absence of incidents. 

Response: The absence of reported incidents does not rule out the potential for 

esfenvalerate to reduce survival, reproduction, and/or growth of plants. No terrestrial 

plant toxicity data have been submitted for esfenvalerate. Tier I plant tests are required 

according to CFR 40 Part 158 for all outdoor uses. The registrant should be aware that if 

greater than a 25% effect rate is seen at the maximum annual application rate, a Tier II 

test may be required. The registrant may choose to perform only the Tier II. Whether a 

Tier I or Tier II study is submitted, it is only after this data has been received and 

evaluated by the Agency that any new determination can be made relating to the potential 

for esfenvalerate to reduce survival, reproduction, and/or growth of plants. 

Comment: The fish full life cycle study should not be required to assess the potential for 

chronic effects on fish. The fish early life stage study should be acceptable. The 

rationale for the fish full life cycle study given in Table7-3 neglects a consideration of the 

differences between fish and daphnia and the significance of the reproductive effects 

observed in the daphnia chronic study. The acute endpoints for fish are much higher than 

those for daphnia, and fish would not be expected to respond similarly to daphnia during 

chronic exposures. The reproductive effects observed in the daphnia chronic test were 

observed only at concentrations where there were also effects on survival. For the 

purposes of ecological risk assessments, the endpoints for survival will be sufficiently 

protective. Chronic exposure of fish in the water column is also unlikely. The sorption 

of esfenvalerate to sediment reduces the concentration in the water phase to extremely 

low levels so that long term exposures at significant concentrations is unlikely. 

Response: The request for a fish full life cycle study is not based upon the water flea 

chronic study alone but upon the weight of evidence that reproductive impacts are 

potentially being missed in the fish early life stage test. This includes not only the 

reproductive effects seen in the water flea chronic test, but also the fact that the estimated 

environmental concentration (EEC) is greater than 10 percent of the no-observed adverse 

effect level (NOAEC) in the fish early life stage test (40 CFR part 158), which has been 

identified as characteristic for reproductive concerns. Reproduction physiology was 

affected in the water flea which suggests that reproduction physiology may be affected in 

fish. Though reproductive effects were only observed at concentrations where effects on 

survival were seen, similar effects may not necessarily be seen relative to survival 

between the water flea and fish. Additionally, thinner egg shells are noted in the avian 
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reproduction study which could infer problems with embryogenesis. A fish early life 

stage test does not capture fecundity endpoints that are captured by a fish full life cycle 

test. The outcomes of full life cycle tests on freshwater and estuarine/marine fish, after 

being evaluated by the Agency, will address these uncertainties. 

Human Health Risk Assessment 

Comment: The fenvalerate tolerances in 40 CFR 180.379 have been converted to 

esfenvalerate tolerances in 40 CFR 180.533 (74 FR Notice 46689-46699, September 11, 

2009). During this process, the fenvalerate tolerance for cabbage (10.0 ppm) was 

converted to an esfenvalerate tolerance for “cabbage, except Chinese cabbage (3.0 ppm).” 

The current Section 3 label for the esfenvalerate end-use product, DuPont Asana XL 

Insecticide, has a registered use for “Chinese cabbage (tight headed varieties only, e.g. 

Napa cabbage)”. Therefore, DuPont requests that a correction be made to list an 

esfenvalerate tolerance of 3.0 ppm for “cabbage, Chinese, napa”. 

Response: According to 40 CFR 180.1(g), tolerances established for pesticides on 

cabbage also applies to Chinese cabbage (tight-headed varieties only). Because napa 

cabbage is considered a tight-headed variety, the cabbage tolerance should cover this 

commodity. The Agency agrees that the existing esfenvalerate tolerance for “cabbage, 

except Chinese cabbage” should be changed to “cabbage”, since napa cabbage is part of 

the cabbage commodity definition. The Agency anticipates making this change in 2010 

and it will not affect the Work Plan. 

Comments by California Regional Water Quality Control Board/San Francisco Bay 

Region, County Sanitation Districts of Los Angeles County and Tri-TAC/East Bay 

Municipal Utility District. 

The following individuals submitted comments for the organizations listed above. 

Writing on behalf of the California Regional Water Quality Control Board/San Francisco 

Bay Region was Janet B. O’Hara, Water Resource Control Engineer/Manager, Pesticide 

TMDSs. Writing on behalf of the County Sanitation Districts of Los Angeles County 

was Paul Martyn, Head, Industrial Waste. Writing on behalf of Tri-TAC/East Bay 

Municipal Utility District was Ben Horenstein, Tri-TAC chair. 

The submitters showed strong support for the planned use of the Agency-wide ECOTOX 

database and other sources of available, reliable data, rather than limiting the data used in 

the assessment to registrant-submitted data. Additionally, the submitters indicated their 

support of the requests for environmental fate and aquatic toxicity data as listed in the 

Preliminary Work Plan.

Comment: Inclusion of Impacts on Urban Water Quality from Urban Runoff and Sewer 

DischargeThe submitters would like for the Work Plan to reflect impacts on urban water quality 

from urban runoff and sewer discharge. Specifically mentioned was the planned inclusion 
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of these exposure pathways in a problem formulation for cyphenothrin, another 

pyrethroid. 

Response: The above mentioned exposure pathways will be included in a revised 

problem formulation for esfenvalerate. Relevant public comments received regarding 

other pyrethroid problem formulations and consideration of these exposure pathways will 

be taken into account. 

Comment: Identification and Inclusion of Indoor Uses as a Potential Route of Aquatic 

Exposure from Pesticide Discharge into Sewers and Subsequent Discharge into the 

Environment in Biosolids and Effluent from Publicly Owned Treatment Works (POTW)- 

The submitters stated that the Work Plan does not identify indoor uses as a possible route 

of aquatic exposure. Use of esfenvalerate indoors (e.g., in households, storage areas, or 

processing plants) can result in indoor discharges into sewer systems when treated 

surfaces are washed with water which is disposed of down the drain. Contaminated 

disposal water may be from treated surfaces washed with water; carpet cleaning water; or 

rinse water from mops, rags or brushes used to clean treated surfaces. Pesticides 

discharged in water via this route (as well as from uses on animals) may enter POTWs, 

and subsequently be discharged into the environment in effluent and/or biosolids from the 

POTWs. Submitters stated that EPA should evaluate potential impacts from 

esfenvalerate in both POTW effluents and biosolids (applied to land) as part of the downthe-drain assessment. Submitters cited a study which found that pyrethroids are not 

degraded during wastewater treatment and are present in final POTW effluent. 

Response: The Agency agrees that indoor uses can result in discharges of esfenvalerate 

residues into sewer systems and should be included in the assessment as a possible route 

of exposure to the environment. Assumptions will be used to quantify the potential 

loading to drainage systems. Discharge of esfenvalerate into the environment via POTW 

effluent will be considered to the best degree possible in the assessment. However, EPA 

does not anticipate assessing potential ecological exposure resulting from application of 

biosolids to land in registration review, as the Agency does not have a methodology to 

assess this potential route of exposure. The EPA Office of Pesticide Programs (OPP) is 

currently working with other EPA Offices to explore methodology to make quantitative 

estimates. EPA recognizes the potential exposure from down-the-drain sources of 

pyrethroids, and will continue to investigate ways of more accurately quantifying these 

sources in fate and ecological exposure assessments. With regard to assessing exposure 

due to POTW effluent discharge, see the response to the next comment. 

Comment: Development of Revised Methodology for Down-the-Drain AssessmentThe submitters indicated general support for the use of a down-the-drain model approach 

to estimate ecological exposure resulting from esfenvalerate uses which may travel down 

the drain and enter POTWs. However, while some submitters support the use of the 

Exposure and Fate Assessment Screening Tool (E-FAST) in a down-the-drain 

assessment, they indicated that methodology refinements are needed for down-the-drain 
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assessments to be used in registration review. Reference was made to previously 

submitted general comments stating submitters’ concerns with E-FAST Version 2.0. The 

submitters expressed an interest in working with EPA [both and the Office of 

Wastewater Management (OWM)] to refine the methodology for the down-the-drain 

assessments, particularly with respect to the use of stream dilution factors in a national 

assessment and modifications to the methodology for determining chronic and acute 

estimated environmental concentrations. The submitters requested that the Agency 

collect information on the esfenvalerate use patterns that may result in down-the-drain 

exposure, the amount of esfenvalerate being discharged into sewers, as well as the 

environmental fate and aquatic toxicity data necessary to assess indoor uses and uses on 

animals. 

Response: EPA agrees that the methodology for a down-the-drain wastewater 

assessment, potentially using E-FAST, an Office of Chemical Safety and Pollution 

Prevention (OCSPP) model, would benefit from refinements and inputs from various 

entities including not only the submitters, but other EPA Offices and, potentially, other 

stakeholders. The Agency seeks to compare existing and forthcoming monitoring data 

with the current model (E-FAST) and future, more refined down-the-drain models. To 

this end, OPP is working with individuals in the Office of Water (OW) regarding 

pyrethroids and available data specifically, as well as broader issues such as the use of a 

down-the-drain model for other pesticides with indoor uses. The Agency plans to use EFAST, including potential refinements, at the time of the registration review risk 

assessment. Available data and/or conservative assumptions would be used to 

parameterize the model. 

The Agency recognizes the potential exposure from down-the-drain sources of 

pyrethroids, and will continue to investigate ways of more accurately evaluating these 

sources in fate and ecological exposure assessments. The inclusion of a down-the-drain 

assessment will be reflected in a revised problem formulation for esfenvalerate. 

Additionally, other sources, such as those identified by the Pyrethroid Working Group 

(PWG) in their 1/27/10 report “Problem Formulation: Ecological Evaluation of 

Pyrethroids in the Urban Environment” will be considered. 

Comment: Assessment of Cumulative Risks with Other PyrethroidsThe submitters stated that urban monitoring data indicate that mixtures of pyrethroids are 

contributing to pyrethroid-related toxicity in both the water column and sediments. They 

stated that there is substantial evidence in the scientific literature to demonstrate the 

additive nature of pyrethroid toxicity to aquatic organisms, and urge EPA to evaluate the 

cumulative risks of esfenvalerate with other pyrethroids. 

Response: The Agency has evaluated the cumulative risks of other types of pesticides 

with common modes of action in its human health risk assessments. These assessments 

have been challenging, even given that a single species (humans) is being assessed. EPA 

does not currently have the methodology to conduct similar cumulative risk assessments 

for all of the non-human biological entities under the Agency’s purview. Although EPA 
14

agrees that an assessment of cumulative risk is a desirable goal, the Agency does not 

believe the current state of the science can address this issue quantitatively. However, 

EPA will consider open literature, modeling and other lines of evidence to qualitatively 

address the potential for cumulative effects in the ecological effects risk assessment. 

Comment: Develop and Implement a Methodology Evaluating the Ecological Effects of 

Product SynergistsThe submitters stated that a methodology should be developed to evaluate the ecological 

effects of product synergists for the assessment of esfenvalerate, and for other chemicals 

as well, as a standard part of registration review process. Submitters also stated that enduse products may be more toxic to aquatic organisms (than the pesticide active ingredient 

alone) because the products are formulated with synergists. 

Response: EPA agrees that the presence of synergists may make an end-use product 

more toxic than the active ingredient alone. Available literature also suggests the 

potential for synergism in the environment (e.g., Amweg et al. 2006, Weston et al. 2006, 

Amweg & Weston 2007, and Brander et al. 2009). The Agency routinely assesses 

synergistic formulations for potential exposure from spray drift and direct applications to 

water. Acute toxicity data on the formulation is compared to potential exposure to spray 

drift. Esfenvalerate does have multiple active ingredient formulations that include 

piperonyl butoxide, MGK, and other pesticides; however, the formulations are used to 

treat ant mounds, as surface sprays around homes, as crack-and-crevice treatments, and 

as wasp and hornet sprays. The spray drift associated with these uses will be minimal 

and, therefore, a quantitative assessment of this potential aquatic exposure to 

formulations containing other specified active ingredients is not necessary. 

Evaluating the effects of product synergists in aquatic environments, aside from direct 

applications to water, is not routinely done. It is important to recognize that the active 

ingredient and the synergist have differing fate properties and, therefore, would be 

expected to occur in the environment at different times and at different concentrations 

than present in the end-use product. Consequently, it is necessary to have toxicology data 

which allows the assessment of the level of synergy as the ratio of the pesticide and 

synergist vary in the environment. Datasets which allow the calculation of the ‘pesticidesynergist interaction’ are not often available. EPA recognizes the limitations inherent in 

this approach and is looking into the acquisition of data that would allow the evaluation 

of the effect of both synergist and active ingredient when present in the ecosystem. 

Evaluating the potential toxic effects of the synergist include evaluating ecological 

effects data generated using end-use products and the active ingredient in the presence of 

synergists, in addition to data for the active ingredient alone. At this time, EPA typically 

has data for individual active ingredients, as well as for the synergists alone, but few data 

are available from which to draw conclusions regarding the potential effect of the 

combination. As stated above, the Agency is evaluating its options for obtaining data 

appropriate for this type of evaluation. However, EPA will not be requesting synergist 

data for esfenvalerate, since agricultural-use products with esfenvalerate are not 

formulated with synergists. For esfenvalerate, the environmental exposure for these co-
15

formulated products only occurs through use of residential products via down-the-drain 

exposure. 

Comment: Request Additional Data as Needed for the Down-the-Drain Model and 

Ecological Risk AssessmentComments were also received recommending that additional data be requested to inform 

the risk assessment, including acute and chronic whole sediment toxicity data for both 

freshwater and estuarine/marine species and “all data to conduct the down-the-drain 

assessment.” 

Response: EPA agrees that sediment toxicity data are necessary for the ecological effects 

assessment of pyrethroids such as esfenvalerate. However, because the estimated 

environmental concentration (EEC) is greater than 10 percent of the median lethal 

concentration (LC50) and the half-life is greater than 10 days, only chronic whole 

sediment data is being requested for freshwater and estuarine/marine invertebrates. EPA 

will request a 96-hour Hyallela azteca water column test to better characterize this route 

of exposure for the most sensitive aquatic invertebrate species. Appropriate adjustments 

will be made to the data needs section in a revised problem formulation. 

EPA will use the E-FAST down-the-drain model or a more refined version of the model 

for assessment of wastewater effluent exposure. EPA will use all available data to 

determine the potential for esfenvalerate to reach ecological receptors through wastewater 

effluent. It is requested that any available esfenvalerate monitoring data, or any 

information related to the fate of esfenvalerate in POTWs, be submitted at this time or at 

anytime that it is available during the registration review process. 

Comments from FIFRA Endangered Species Task Force (FESTF)

Comment: In response to the Summary Document, specifically to the need for additional 

information to complete an assessment on federally-listed threatened and endangered 

species that may be exposed to esfenvalerate, FESTF stated that its data on endangered 

species proximity contained in the FESTF Information Management System (FESTF 

IMS) submissions (2004, 05, 07) to the Agency “fulfill the data requirements... and 

provide the best available data necessary for the proximity analysis of esfenvalerate use 

and listed species locations.” FESTF stated that E. I. Dupont De Nemours and Co. is a 

current member of FESTF, and as such, is entitled to the FESTF data on federally-listed 

threatened and endangered species. However, LG Life Sciences Ltd. and Sumitomo 

Chemical Company Ltd. are not members and, therefore, must offer to pay FESTF to rely 

on FESTF-submitted data or develop substantial similar data on their own. 

Response: The Agency thanks FESTF for its comment and will consider this information 

as it conducts the registration review and makes its registration review decisions. 
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Availability of Additional Agency Responses to Public Comments: 

Comments relevant to human health have been addressed by the Health Effects 

Division’s document, Esfenvalerate: Response to Comments Received on the HED 

Scoping Document Prepared in Support of Registration Review, dated April 21, 2010. 

Comments regarding the ecological fate or effects of esfenvalerate have been addressed 

by the Environmental Fate and Effects Division’s document, Response to Comments on 

the Registration Review- Preliminary Problem Formulation for Ecological Risk, 

Environmental Fate, Endangered Species, and Drinking Water Assessment for 

Esfenvalerate, dated June 21, 2010. These documents are available in the esfenvalerate 

docket (EPA-HQ-OPP-2009-0301).

Next Steps: 

o The Agency plans to issue a DCI in early 2011, requiring the esfenvalerate studies 

needed to complete both the ecological and human health risk assessments.

o The Agency will conduct an ecological risk assessment, including an endangered 

species assessment, and a human health risk assessment for esfenvalerate.