UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            WASHINGTON D.C., 20460
                                   OFFICE OF
                              CHEMICAL SAFETY AND
                             POLLUTION PREVENTION

	PC Code:  128722
	DP Barcode: D396740
MEMORANDUM	April 17, 2012

SUBJECT:	Registration Review: Preliminary Problem Formulation for Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments for Prallethrin

TO:		Wilhelmena Livingston, Chemical Review Manager
		Eric Olson, Risk Manager
      Risk Management and Implementation Branch IV
      Pesticide Re-evaluation Division (7508P)

FROM:	Robin Sternberg, Ph.D., Wildlife Biologist
		He Zhong, Ph.D., Biologist
		Environmental Risk Branch I
      Environmental Fate and Effects Division (7507P)

REVIEWED
BY:		Stephen Wente, Ph.D., Biologist
      Edward Odenkirchen, Ph.D., Senior Eco Scientist
      Environmental Risk Branch I
      Environmental Fate and Effects Division (7507P)

APPROVED
BY:		Nancy Andrews, Ph.D., Branch Chief
		Sujatha Sankula, Ph.D., Lead Biologist
		Environmental Risk Branch I
		Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has completed the preliminary problem formulation (attached) for the environmental fate, ecological risk, endangered species, and drinking water exposure assessments to be conducted as part of the Registration Review of the synthetic pyrethroid prallethrin ((S)-2-methyl-4-oxo-3-(2-propynyl) cyclopent -2-enyl (1RS)-cis, trans-2,2 -dimethyl -3-(2-methylprop-1-enyl) cyclopropanecarboxylate; CAS no. 23031-36-9; PC Code 128722).  Functioning as the first stage of the risk assessment process for Registration Review, this problem formulation provides an overview of what is currently known about the environmental fate and ecological effects associated with prallethrin and its degradates.  It also describes the preliminary ecological risk hypothesis and analysis plan for evaluating and characterizing risk to non-target species in support of the registration review of prallethrin.  This document also recommends studies that should be included in a generic data call-in (DCI) to address uncertainties surrounding the environmental fate and potential ecological effects of prallethrin.

Problem Formulation for the Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments in Support of the Registration Review of Prallethrin

(S)-2-methyl-4-oxo-3-(2-propynyl) cyclopent -2-enyl (1RS)-cis, trans-2,2 -dimethyl -3-(2-methylprop-1-enyl) cyclopropanecarboxylate
                        CAS Registry Number: 23031-36-9
                                PC Code: 128722

Prepared by:
Robin Sternberg, Ph.D., Wildlife Biologist
He Zhong, Ph.D., Biologist
U.S. Environmental Protection Agency
Office of Pesticide Programs
Environmental Fate and Effects Division
Environmental Risk Branch I
1200 Pennsylvania Ave., NW
Mail Code 7507P
Washington, DC 20460
Reviewed by:
Stephen Wente, Ph.D., Biologist
Edward Odenkirchen, Ph.D., Senior Eco Scientist
William Eckel, Ph.D., Senior Science Advisor
Amanda Solliday, Biologist

                                April 17, 2012
                               Table of Contents

1.  Purpose	6
2.  Nature of Regulatory Action	6
3.  Conclusions from Previous Assessments	7
3.1  Ecological Risk Assessments	7
3.2  Drinking Water Exposure Assessments	8
4.  Stressor Source and Distribution	9
4.1  Mechanism of Action	9
4.2  Overview of Pesticide Use and Usage	9
4.2.1 Labeled Uses	9
4.2.2 Prallethrin Use with Synergists	10
4.2.3 Environmental Mixtures	11
4.2.4 Usage	11
4.3  Environmental Fate and Transport	12
4.3.1 Photodegradation	12
4.3.2 Aerobic Degradation	12
4.3.3 Anaerobic Degradation	13
4.3.4 Adsorption/Desorption and Leaching	13
4.3.5 Terrestrial and Aquatic Field Dissipation	13
4.3.6 Bioconcentration in Fish	14
4.4  Degradates of Concern	17
4.5  Water Quality	17
5.  Receptors	18
5.1  Effects to Aquatic Organisms	19
5.2  Effects to Terrestrial Organisms	22
5.3  Incident Databases Review	25
5.4  Ecosystems Potentially at Risk	25
6.  Assessment Endpoints	26
7.  Conceptual Model	27
7.1  Risk Hypothesis	27
7.2  Conceptual Diagrams	27
7.2.1 Drinking Water Exposure	29
7.2.2 Inhalation Exposure	29
8.  Analysis Plan	30
8.1  Stressors of Concern	30
8.2  Measures of Exposure	31
8.2.1 Spray Drift	31
8.2.2 Aquatic Exposure	31
8.2.3 Terrestrial Exposure	33
8.3  Measures of Effect	34
8.4  Integration of Exposure and Effects	35
8.5  Deterministic and Probabilistic Assessment Methods	35
8.6  Endangered Species Assessments	35
8.7  Drinking Water Assessment	36
8.8  Endocrine Disruptor Screening	36
9.  Preliminary Identification of Data Gaps	37
9.1  Environmental Fate Data	37
9.2  Ecological Effects Data	39
10.  References	45
Appendix A	52
Appendix B	54
Appendix C	63
Appendix D	71
Appendix E	74
Appendix F	76
1.  Purpose

The purpose of this problem formulation is to provide an understanding of the environmental fate and ecological effects of prallethrin for registered uses.  Prallethrin ((S)-2-methyl-4-oxo-3-(2-propynyl) cyclopent -2-enyl (1RS)-cis, trans-2,2 -dimethyl -3-(2-methylprop-1-enyl) cyclopropanecarboxylate; CAS no. 23031-36-9; PC Code 128722) is a synthetic pyrethroid that modulates voltage-sensitive sodium channels causing disruption of nerve impulses in target insects.  It is a broad spectrum, non-systemic insecticide used to control adult nuisance insects (e.g., mosquitoes, midges, gnats, black flies, etc.).  Formulations of prallethrin often contain additional active ingredients including one or two synergists.  Mosquito control applications include aerial and ground ultra low volume (ULV) applications in residential, commercial, and recreational areas. Other applications include space and crack-and-crevice treatment for structure protection in a variety of commercial, industrial, residential, and institutional sites; foliar and fogger treatment on non-food plants; and direct application to cats, dogs, and horses.  There are no registered crop uses of prallethrin, and this may potentially reduce the environmental loading.  This document provides a plan for analyzing data relevant to prallethrin and for conducting environmental fate, ecological risk, endangered species, and drinking water exposure assessments for its registered uses.  Additionally, this problem formulation identifies data gaps, uncertainties, and assumptions that will be used to address those uncertainties relative to characterizing the potential ecological risk associated with the registered uses of prallethrin.
2.  Nature of Regulatory Action

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides distributed or sold in the United States generally must be registered by the Environmental Protection Agency (Agency).  In determining whether a pesticide can be registered in the U.S., the Agency evaluates its safety to non-target species based on a wide range of environmental and health effects studies.  In 1996, FIFRA was amended by the Food Quality Protection Act, and the Agency was mandated to implement a new program for the periodic review of pesticides, i.e., Registration Review (http://www.epa.gov/oppsrrd1/registration_review/).  The Registration Review program is intended to ensure 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 and 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.
As part of the implementation of the Registration Review program pursuant to Section 3(g) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is beginning its evaluation of prallethrin to determine whether it continues to meet the FIFRA standard for registration.  This problem formulation for the environmental fate, ecological risk, endangered species, and drinking water assessment chapter in support of the registration review of prallethrin will be posted in the initial docket which will initiate the public phase of the review process.
3.  Conclusions from Previous Assessments
      3.1  Ecological Risk Assessments

Prallethrin was first registered in the United States in 1994 for indoor use to control adult nuisance insects.  Since then, EFED has conducted several ecological risk assessments for prallethrin (see Appendix A).  A 1997 assessment to evaluate prallethrin use at 0.00025 to 0.002 lb a.i./A to control adult nuisance insects in domestic outdoor and forestry sites concluded that the uses posed minimal risk to terrestrial organisms from acute and chronic exposure and minimal risk to aquatic organisms from acute exposure; the lack of fish early-life stage  and aquatic invertebrate life cycle tests created uncertainty regarding risk to aquatic organisms from chronic exposure (D219740, D217877).  In 1999, a Section 3 assessment for the use of prallethrin in food-handling establishments for all commodities concluded that the use posed little or no risks to listed and non-listed terrestrial and aquatic organisms (D259553, D239124).

The most recent prallethrin assessments were conducted from 2003 to 2005 and evaluated a prallethrin typical end-use product (TEP), MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795), for use in outdoor residential and recreational areas to control adult nuisance insects (D257595, D291569, D239293, D301123, D312733).  Collectively, these assessments made the following final risk conclusions regarding MULTICIDE Fogging Concentrate 2798 as applied 26 times (with 7-day intervals) at a rate of 0.0008 lb a.i./A:
   * Use is not likely to pose risk to birds or mammals (including listed species) from acute or chronic exposure.
   * Given the high toxicity of prallethrin to honey bees and prallethrin's proposed use to control adult insects, there is a potential for adverse effects to listed species of flying insects (e.g., butterflies).
   * Risk to non-target aquatic and terrestrial plants as a result of use could not be evaluated due to lack of submitted studies.
   * Given its aquatic half-life, prallethrin is likely to occur in the water column and sediment.
   * Use is not likely to pose risk to freshwater or estuarine/marine organisms (including sediment-dwelling organisms) from acute exposure regardless of depth of water body.
Risk to terrestrial and aquatic ecosystems will be reevaluated based on the availability of new data and refined models.

The following outstanding data requirements were identified in the 2003-2005 assessments:
   * 850.1035/72-3(c): Acute Estuarine/Marine Shrimp Toxicity with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795);
   * 850.1735: Whole Sediment: Acute Freshwater Invertebrates with technical grade active ingredient with technical grade active ingredient (TGAI);
   * 850.3030/141-2: Honeybee Toxicity of Residues on Foliage with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795);
   * 850.4100/122-1(a): Seedling Emergence, Tier I with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795)
   * 850.4150/122-1(b): Vegetative Vigor, Tier I with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795); and
   * 122-2: Aquatic Plant Growth, Tier I with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795).
These studies have since been submitted by the registrant, evaluated by EFED, and classified as acceptable (MRIDs 47431601, 47762401, 48055901, 47431602, 47431603, and 48055902, respectively).

The 2003-2005 assessments identified the following studies as data uncertainties but did not request them at that time:
   * 850.1010/72-2(b): Acute Toxicity Freshwater Invertebrate with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795);
   * 850.1075/72-1(b): (Acute) Freshwater Fish Toxicity (Bluegill) with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795);
   * 850.1075/72-1(c) or: Acute Freshwater Fish Toxicity (Rainbow Trout) with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795);
   * 850.1075/72-3(a): Acute Estuarine/Marine Fish Toxicity with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795); and
   * 850.1075/72-3(b): Acute Estuarine/Marine Mollusk Toxicity with TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795).

The 2003-2005 assessments identified the following studies as data uncertainties that should be required if new uses are added for prallethrin:
   * 850.1350/72-4(b): Estuarine/Marine Invertebrate Life Cycle with TGAI;
   * 850.1500/72-5: Fish Life Cycle (Freshwater & Saltwater) with TGAI; and
   * 850.1740: Whole Sediment: Acute Marine Invertebrates with TGAI pending test results using the amphipod Hyallella azteca.

Finally, the 2003-2005 assessments waived all testing with the major degradates of prallethrin, ketolone, PGLS, and keto-PGLS.  EFED determined that these degradates are the outcome of cleavage of the ester linkage of the parent.  This breaking of the basic pyrethroid frame or backbone may result in lost activity and thus decreased toxicity when compared with the parent.
      3.2  Drinking Water Exposure Assessments

The drinking water assessment (DWA) for MULTICIDE(R) Fogging Concentrate 2798 (Reg No. 1021-1795) was completed in June 2003 (DP 274758) to estimate prallethrin environmental concentrations.  Tier I FIRST 1.0 and SCIGROW 2.2 models were used to estimate prallethrin concentrations in surface water and groundwater, respectively (USEPA, 2003).  The results of this DWA are summarized in Table 3-1.

Table 3-1. Estimation of Prallethrin Concentrations in Surface Water and Groundwater Using FIRST 1.0 and SCIGROW 2.2, Respectively, for a June 2003 DWA
Product
                         Application Rate (lb a.i./A)
                Acute (peak) Surface Water Concentration (ppt)
               Annual Average Surface Water Concentration (ppt)
                       Ground Water Concentration (ppt)

MULTICIDE[(R)]

                                    0.0008

                                      236

                                     15.0

                                     0.41

RESPONDÉ[(R)]

                                     0.002

                                      591

                                     37.5

                                     1.04
ppt = parts per trillion

These values generally represent upperbound estimates of the concentrations that might be found in surface water and groundwater as a result of prallethrin outdoor usage at the maximum application rate.  Both models provide estimates suitable for screening purposes.  The drinking water exposure may be reassessed if it is deemed necessary.
4.  Stressor Source and Distribution
      4.1  Mechanism of Action

Prallethrin is a member of a class of pesticides known as synthetic pyrethroids.  Pyrethroids are synthetic chemicals that were originally developed as modifications of the natural pyrethrum structure to produce compounds that had an increased photo-stability while retaining insecticidal activity and low acute mammalian toxicity.  Prallethrin has been assigned to the Mode of Action Group 3 (subgroup 3A) by the Insecticide Resistance Action Committee (IRAC) (http://www.irac-online.org/teams/mode-of-action/) which is comprised of technical personnel from various large agrochemical and public health companies (USEPA, 2011).  Insecticides in this group modulate sodium channels and thus cause disruption of nerve impulses in the target insects.  All pyrethroids "initially stimulate the nerve to produce repetitive discharges and subsequently cause paralysis" (Narahashi, 1976).  Like other compounds derived from the chemical structure of pyrethrum, pyrethroids are most toxic to the target pest on contact and have a quick "knockdown" effect that is characterized by quick intoxication and initial paralysis resulting from nerve stimulation (Doull, 1976).

      4.2  Overview of Pesticide Use and Usage
            4.2.1 Labeled Uses

Prallethrin is used to control adult nuisance insects (e.g., mosquitoes, midges, gnats, black flies, etc.) and is not registered for crop uses according to a recent report by the Biological and Economic Analysis Division (BEAD) of the Office of Pesticide Programs (OPP) (USEPA, 2011).  Non-crop use sites include farm buildings, factories, food handling, storage areas, grain elevators, tobacco warehouses and canneries, domestic dwellings, commercial/institutional/ industrial areas, hospitals, manufacturing plants, office buildings, etc. (USEPA, 2011).  In 2005, prallethrin was registered for use in mosquito adulticide programs involving outdoor residential and recreation areas, and in vegetation surrounding parks, woodlands, swamps, marshes, overgrown areas and golf courses.

Seventy-six (76) labels are currently registered for use in the United States: fourteen (14) technical or formulation intermediate products and sixty-two (62) formulated end-use products (see Appendix B).  Prallethrin is often available in a mixture containing other pyrethroids (e.g., cyfluthrin, cypermethrin, cyphenothrin, d-phenothrin, esfenvalerate, lambda-cyhalothrin, permethrin, phenothrin, pyrethrins) and with or without a synergist including piperonyl butoxide (PBO) and/or MGK 264.  Prallethrin may be formulated as a liquid (may be pressurized), emulsifiable concentrate, ready-to-use solution, soluble concentrate, and pressurized gas.  Methods of application include aerosol can (with or without injection tube); fumigation; cloth, glove, or sponge; sprayer (hand-held, mechanical, pressure, trigger); space and/or surface treatment/spray; crack and crevice and/or spot treatment; injection treatment (including trees and mounds); package applicator; and ultra low volume (ULV) aerosol or fog generator (non-thermal, cold fog) that may be aircraft- (fixed-wing or helicopter) or truck-mounted.  For example, Duet(R) and MULTICIDE[(R)] Fogging Concentrate 2798 are formulated products for aerial and ground ULV application over the residential and recreation areas.

The maximum labeled application rates by use site and formulation are provided in Appendix C.  Additional label information including specific maximum application rate per application and per year, maximum number of applications per year, and defined application intervals would reduce uncertainties in the risk assessment.

            4.2.2 Prallethrin Use with Synergists

PBO and MGK 264 are synergists commonly used in formulations with prallethrin.  PBO acts as a potentiator in both mammals and insects because the pyrethroid is not metabolized and excreted as quickly in its presence (Barile, 2004; Hodgson & Smart, 2001).  Amweg & Weston (2007) and Weston & Lydy (2010) showed increasing toxicity when exposing aquatic invertebrates to mixtures of pyrethroids and PBO.  Amweg et al. (2006) and Weston et al. (2006) also reported the potential for synergism in the environment.  In general, active ingredients and synergists 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.  MGK-264, another potentiator/synergist used with pyrethroids, has similar effects as those observed for piperonyl butoxide (Hodgson & Smart, 2001).  Prallethrin may be co-formulated with either or both PBO and MGK-264 in numerous products (see Appendix B).

Currently, data on the degree to which the toxicity of pyrethroid active ingredients is enhanced by varying concentrations of PBO and MGK-264 are needed to address the ecological risk of pyrethroid products when co-applied with PBO or MGK-264.  The data need is discussed in the EFED Registration Review Problem Formulation for Piperonyl Butoxide, dated December 13, 2010 (USEPA, 2010, D378420).  The PBO Problem Formulation is available in the PBO registration review docket at www.regulations.gov (EPA-HQ-OPP-2010-0498).  Based on data for the acute toxicity of pyrethrin and PBO to target insect species, the degree of toxicity enhancement increases at higher PBO:pyrethrin ratios (or absolute concentrations), and this toxicity enhancement is greater than simple additive toxicity (Stewart, 1998).  The Agency is currently evaluating a proposed study protocol that will quantify the enhancement of acute toxicity of active ingredients used with PBO to the freshwater amphipod, Hyalella azteca, by simultaneous exposure to PBO at varying PBO:active ingredient ratios.  This comprehensive testing strategy, when augmented with similar acute toxicity data for freshwater fish and other selected pesticide active ingredients, should facilitate bridging of the synergist toxicity enhancement to other co-formulated or co-applied pesticide/synergist active ingredients that are not tested at varying synergist:active ingredient ratios.  With respect to evaluating ecological risks from co-applied prallethrin and synergists, the Agency is requesting acute toxicity studies of prallethrin TEPs that are co-formulated with PBO and MGK-264 at the highest synergist:active ingredient ratio.  These TEPs should correspond to those formulated products that are labeled for outdoor uses and would be conducted with a freshwater fish and a freshwater invertebrate.  Additional discussion of the need for combined prallethrin:synergist toxicity data is provided in Section 7.9 (Preliminary Data Gaps).
            4.2.3 Environmental Mixtures

Toxicity data on environmental mixtures of prallethrin and other pesticides may be presented, if available, as part of the ecological risk assessment. The toxic effect of prallethrin, in combination with other pesticides used in the environment, is likely to be a function of many factors including but not necessarily limited to:
   * the exposed species,
   * co-contaminants in the mixture,
   * the ratio of prallethrin and co-contaminant concentrations,
   * differences in the pattern and duration of exposure among contaminants, and
   * the differential effects of other physical/chemical characteristics of the receiving waters (e.g., organic matter present in sediment and suspended water).

Quantitatively predicting the combined/cumulative effects of all these variables on mixture toxicity to any given taxa with confidence is beyond the capabilities of the available data and methodologies.  However, the implications of the data gap for pesticide mixture effects on the confidence of risk assessment conclusions will be addressed in the uncertainty analysis.
EFED will consider open literature, current models, and other lines-of-evidence (e.g., monitoring data), as available, to address the potential for cumulative effects of prallethrin in the risk description of the ecological assessment.
            4.2.4 Usage

There is limited information available for prallethrin usage.  BEAD reported that Kline & Co. prepared a special study in 2006 for EPA which estimated non-agricultural usage of prallethrin for households to be approximately 28,000 lbs and suggested the study probably underestimates non-agricultural usage since it did not include any non-household sites such as food handling establishments and warehouses (USEPA, 2011).  There is no prallethrin usage information for mosquito and other public health pest control.  Previous risk assessments were based on the labeled uses at the time the assessments were conducted.  Obtaining additional information will improve future EFED risk assessment for these uncertainties.  We concur with BEAD's analysis that the following data deficiencies should be considered as part of the registration review of prallethrin:

   * Usage data (pounds a.i. applied, application methods frequently used, and area treated) for indoor /outdoor consumer use, use in food handling establishments/food processing establishment, and use in and around commercial and institutional facilities.
   * Usage data (pounds a.i. applied, application methods frequently used, and area treated) for structural treatment at agricultural and commodity-processing facilities.
   * GIS-mapping data (e.g., frequency of application, pounds a.i. applied) on use of prallethrin as a mosquito adulticide.

	4.3  Environmental Fate and Transport

The structure of prallethrin has a phenyl ring and a cyclopropyl ring.  Prallethrin (also known as ETOC) consists mainly of [1R,trans; S] and [1R,cis; S] isomers in a ratio of approximately 4:1 (http://www.who.int/whopes/quality/en/prallethrin_spec_eval_Nov_2004.pdf).  Prallethrin dissipation appears to be dependent on photodegradation in aqueous environments, hydrolysis, microbially mediated degradation, and soil binding.  Data show that ETOC has low solubility and appears to be stable at pH's 5 and 7.  However, at an elevated pH of 9, it hydrolyzes with a calculated half-life of 4.9 days with two isomeric bicyclic ketones (1A+2A, totaling 82.2  -  93.7%) and PGLS (totaling 4.3 - 14%) as the major degradates (MRID 42838602).  A diagram of prallethrin degradation or metabolic pathway is provided in Appendix G.  In aqueous environments, the compound breaks at the ester bond to yield d-t-CRA (MRIDs 44861001, 44366601) and PGLS (MRIDs 44861002, 44366602).  PGLS can undergo hydration and subsequent keto-enol tautomerism, resulting in ketolone (MRID 43797601).  It can also undergo double bond rearrangement, resulting in PGL-allene, or hydroxylation at C-1, resulting in PGL-OH (MRIDs 44366601, 44366602).  Finally, PGLS can undergo oxidation of the alcohol group to yield keto-PGLS, then keto-ketolone, and ultimately these degradates yield CO2 (MRID 43797601).
            4.3.1 Photodegradation

Photodegradation is the primary route of prallethrin transformation with a pseudo first-order half-life of 0.57 days (13.6 hrs) in the aqueous environment (MRID 43797601).  The major degradates are ketolone, 37.3% ,and PGLS, 26.0%, in 8 days and keto-PGLS, 16.5%, in 1 day of irradiation.  In a sandy loam soil environment, the half-lives of prallethrin photodegradation were 24.8 and 26.9 days respectively with CO2, chrysanthemic acid, and PGLS as the major degradates, but the percentages of formation were unclear from the studies (MRIDs 43797602, 43797603).
            4.3.2 Aerobic Degradation

The observed half-life of prallethrin in aerobic soil was approximately 3 days with CO2 as a major degradate, totaling 42.8  -  44.4% at 112 days post-treatment (MRID 42838601).  The aerobic aquatic metabolism studies (MRIDs 44860101, 44861002) were considered supplemental.  The systems may be partly aerobic and partly anaerobic because they were flooded prior to application of the test material, which may have caused anaerobic conditions.  The registrant showed that dissolved oxygen was measured in the water phase (resulting in 40-73% relative dissolved oxygen, providing an indirect measure of the aerobicity of the water phase; however, the aerobicity of the sediment is uncertain).  For studies conducted in darkness at 25°C for up to 91 days, prallethrin degraded with calculated half-lives of 16 and 17 days for the [14]C radiolabeled at cyclopropyl and cyclopentenyl positions, respectively.  In the cyclopropyl label study, two major degradates, d-t-CRA and t-COOH-CA, reached a maximum of 42.3% at 14 days and 31.1% at 60 days post-treatment, respectively.  In the cyclopentenyl label study, the major degradate PGLS reached a maximum of 24.2% at 7 days post-treatment.  Nonextractable [14]C residues reached a maximum of 52.3% at 60 days, and 46.5% at 91 days post-treatment.  CO2 production reached a maximum 23.3% at 91 days post-treatment (MRIDs 44861001, 44861002).
           4.3.3 Anaerobic Degradation

No study was found for anaerobic soil metabolism.  Two anaerobic aquatic metabolism studies (MRIDs 44366601, 44366602) were considered as supplemental.  They partially satisfy the data requirement although a large portion of the radioactivity was not extracted or identified, which may create uncertainties for the risk assessment.  However, EFED has determined that the deficiency will not affect the prallethrin half-life in anaerobic aquatic conditions.  The studies were conducted in a water-sediment system (water pH 7.0, sediment texture: loam, pH 4.6, organic matter 6.02%, temperature 25 ºC) for up to 181 days.  The first order half-lives of prallethrin in the entire system were 33 and 35 days in two separate studies using [acid [14]C]-d-trans-ETOC and [alc- [14]C]-d-trans-ETOC.  The only major degradate in the first study was d-t-CRA which reached a maximum of 55.2% at 57 days, and the total unidentified radioactivity reached a maximum of13.3 %.  In the second study, four transformation products were identified with a maximum of 14.6% PGL-OH and ketolone at 59 days, 20.7% PGLS at 59 days, 10% PGL-allene at 181 days and 4.7% Keto-PGLS at 181 days (MRIDs 44366601, 44366602).
            4.3.4 Adsorption/Desorption and Leaching

The submitted adsorption/desorption and leaching study (MRID 42810801) was unacceptable because the test soils were autoclaved before use, thus possibly altering the physical and chemical properties of the soils.  The data cited in Table 4-1 are for reference only.  The registrant must demonstrate that autoclaving the soil did not influence the results of this study, and that the observed results are an accurate representation of prallethrin adsorption / desorption from soil or submit a new study.  The Agency has a limited knowledge of how prallethrin behaves in the environment once applied by aerial ULV spray for mosquito control.  Depending on the mobility of the compound and soil characteristics in the environment, prallethrin may or may not be transported to surface water and/or ground water bodies used by organisms in the environment and/or by humans for drinking water.
            4.3.5 Terrestrial and Aquatic Field Dissipation

No terrestrial and aquatic field dissipation studies are available for prallethrin.  Since prallethrin is not registered for agricultural use, data on terrestrial and aquatic field dissipation will be waived at this time.
            4.3.6 Bioconcentration in Fish

Fish bioaccumulation was studied by exposing bluegill sunfish to 0.937 ppb water concentration of [Alc-[14]C]-d-trans-ETOC (parent prallethrin) (MRIDs 42810802, 43758001).  The half-lives of radioactivity in the fish were 1.3-2.5 days. The [14]C concentrations in whole fish ranged from 708 to 1070 ppb, and the bioconcentration factors (BCFs) ranged from 787 to 1160 whereas the maximum BCFs in non-edible tissue were at 2210-3130.  The major metabolites in non-edible tissues were ETOC-Alc (96.3 ppb) and its glucuronide conjugate (1,070 ppb) as well as a taurine conjugate of ETOC-Acid (787 ppb) at day 28 of exposure.

Registrant-submitted data defining the physical, chemical, fate and transport characteristics associated with prallethrin are summarized in Table 4-1.

Table 4-1. Physical, Chemical, and Environmental Fate Properties of Prallethrin and Its Major Degradates.
Parameter
                                     Value
                                   Reference
Comments
Prallethrin
Chemical
                              Prallethrin / ETOC
                                 MRID 41321801
Product Chemistry
Chemical Family
                             Synthetic pyrethroid
                                 MRID 41321800
Product Chemistry
Empirical Formula
                                   C19H24O3
                                 MRID 41321801
Product Chemistry
SMILES
                 O=C2C(=C(C)C(OC(=O)C1C(C=C(C)C)C1(C)C)C2)CC#C
                                   EPI V4.10

IUPAC
(S)-2-methyl-4-oxo-3-(2-propynyl) cyclopent -2-enyl (1RS)-cis, trans-2,2 -dimethyl -3-(2-methylprop-1-enyl) cyclopropanecarboxylate
                                 MRID 41321801
Product Chemistry
CAS Number
                                  23031-36-9
                                 MRID 41321801
Product Chemistry
Structure
--------------------------------------------------------------------------------

                                 MRID 41321801
Product Chemistry
Selected Physical/Chemical Parameters
Molecular mass
                                     300.4
                                 MRID 41321801
Product Chemistry
Boiling point
                                   313.5 ºC
                                 MRID 41321803
Product Chemistry
Solubility  (25°C)
                                   8.03 ppm
                                 MRID 41321803
Product Chemistry
Vapor pressure (23.1°C)
                             <1.0x10[-7] mm Hg
                                 MRID 41321803
Product Chemistry
Henry's law constant (20°C, pH 7)
                           4.92x10[-9] atm·m[3]/mol
                                  Calculated
(VP/760)/(SOL/MWT) (per EFED Guidance ver 2.1, Oct 22, 2009)
Octanol-water partition coefficient (KOW) (25°C)
                                     4.49
                                 MRID 41321803
Product Chemistry
Organic carbon partition coefficient (median Koc)
                                     2004*
                                 MRID 42810801

*The study was unacceptable because the test soils were autoclaved before use.
(Data gap)
Bioconcentration factor (BCF)
                                     1160
                                 MRID 43758001
Based on total [14]C bioconcentration in whole fish at 7 days
Persistence
Hydrolysis                                        pH 5
                                                                           pH 7
                                               	                           pH 9
                   stable
                                    stable
                                   4.9 days
                                 MRID 42838602

Aqueous Photolysis (t (1/2) )
                                   0.57 days
                                 MRID 43797601

Soil Photolysis (t (1/2) )
                                    29 days
                                 MRID 43797602
                                 MRID 43797603
Upperbound value calculated based on 24.8 and 26.9 days (n=2), as per EFED guidance
Aerobic Soil Metabolism (t (1/2) )
                                    9 days
                                 MRID 42838601
 Upperbound value, calculated based on 3x 3 days (n=1), as per EFED guidance
Anaerobic Soil Metabolism
                                      N/A
                                      N/A
(Data gap)
Anaerobic Aquatic Metabolism (t (1/2) )
                                   37 days
                          MRID 44366601 MRID 44366602
Upperbound value, calculated based on 33 and 35 days (n=2), as per EFED guidance
Aerobic Aquatic Metabolism
                                    18 days
                                 MRID 44861001
                                 MRID 44861002
Upperbound value, calculated based on 16 and 17 days (n=2), as per EFED guidance
Bioaccumulation in Fish (Depuration half-life)
                               1.3  -  2.5 days
                                 MRID 42810802
                                 MRID 43758001

Mobility
Soil/Water partition coefficient (The lowest on non-sand Kd)
                                    51.51*
                                 MRID 42810801

*The study was unacceptable because the test soils were autoclaved before use.
(Data gap)
Field Dissipation
Terrestrial Field Dissipation (t (1/2) )
                                      N/A
                                      N/A
(Data gap)
PGLS (Major degradate)
Chemical
                                     PGLS
                                 MRID 42838602
                                 MRID 43797601
                                 MRID 44366602
                                 MRID 44861002

Empirical Formula
                                    C9H10O2
                                   EPI V4.10

SMILES
C1(=C(C(C[C@@H]1O)=O)CC#C)C.
                                   EPI V4.10

Structure
--------------------------------------------------------------------------------

                                 MRID 42838602
                                 MRID 43797601
                                 MRID 44366602
                                 MRID 44861002

Selected Physical/Chemical Parameters
Molecular mass
                                    150.18
                                   EPI V4.10

Boiling point
                                  275.57 ºC
                                   EPI V4.10

Solubility  (25°C)
                                 9.63e+004 ppm
                                   EPI V4.10

Vapor pressure (30°C)
                               2.51x10[-4] mm Hg
                                   EPI V4.10

Henry's law constant (20°C, pH 7)
                          5.15x10[-10] atm·m[3]/mol
                                   EPI V4.10

Octanol-water partition coefficient (KOW) (25°C)
                                     0.48
                                   EPI V4.10

Organic carbon partition coefficient (median Koc)
                                  9.435 ml/g
                                   EPI V4.10

BCF
                                  3.162 L/Kg
                                   EPI V4.10
BCFBAF v3.01
Water Half-Life
                                    15 days
                                   EPI V4.10
Level III Fugacity Model
Soil Half-Life
                                    30 days
                                   EPI V4.10
Level III Fugacity Model
d-t-CRA (Major degradate)
Chemical
                                    d-t-CRA
                          MRID 44366601 MRID 44861001

Empirical Formula
                                   C10H16O2
                                   EPI V4.10

SMILES
O=C(O)C1C(C)(C)C1C=C(C)C
                                   EPI V4.10

Structure
--------------------------------------------------------------------------------

                                 MRID 44366601
                                 MRID 44861001

Selected Physical/Chemical Parameters
Molecular mass
                                    164.24
                                   EPI V4.10

Boiling point
                                    264 ºC
                                   EPI V4.10

Solubility  (25°C)
                                    164 ppm
                                   EPI V4.10

Vapor pressure (30°C)
                              5.87 x10[-3] mm Hg
                                   EPI V4.10

Henry's law constant (20°C, pH 7)
                           2.42x10[-6] atm·m[3]/mol
                                   EPI V4.10

Octanol-water partition coefficient (KOW) (25°C)
                                     3.49
                                   EPI V4.10

Organic carbon partition coefficient (median Koc)
                                  59.47 ml/g
                                   EPI V4.10

BCF
                                  3.162 L/Kg
                                   EPI V4.10
BCFBAF v3.01
Water Half-Life
                                    15 days
                                   EPI V4.10
Level III Fugacity Model
Soil Half-Life
                                    30 days
                                   EPI V4.10
Level III Fugacity Model

      4.4  Degradates of Concern

Two prallethrin degradates, PGLS and d-t-CRA, are formed as the result of cleavage of the ester linkage of the prallethrin structure through hydrolysis.  The d-t-CRA will yield CO2 and polar products.  The PGLS (14-26%) is predicted to have higher water solubility (9.63e+004 ppm), higher mobility (Koc: 9.435 ml/g), and a longer half-life than its parent based on structure estimation (EPI Suite v.4.10; Appendix D).  In addition, PGLS is a precursor for other metabolites and conjugates (Appendix G).  However, PGLS is expected to lose its activity as a sodium channel inhibitor and is probably less toxic than the parent.  Therefore, no additional data on PGLS will be requested at this time.  Should the registrant wish to add new uses of this chemical, the data requirement may be reassessed.

      4.5  Water Quality

Prallethrin is not identified as a cause of impairment for any water bodies under section 303(d) of the Clean Water Act.  In addition, no Total Maximum Daily Load (TMDL) has been developed for prallethrin, and there are no aquatic life criteria for prallethrin.  More information on impaired water bodies and TMDL can be found at http://www.epa.gov/owow/tmdl/.

No monitoring data are available for prallethrin. Neither the USGS's National Water Quality Assessment (NAWQA) program nor the California Department of Pesticide Regulation's monitoring programs included prallethrin as an analyte.

During the risk assessment process, the following databases and sources will be searched for current monitoring information on prallethrin:

   * The United States Environmental Protection Agency (USEPA) STORET Database (http://www.epa.gov/storet/dbtop.html)
   * The United States Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program Data Warehouse (http://infotrek.er.usgs.gov/traverse/f?p=NAWQA:HOME:1405517206944567)
   * The USGS National Stream Quality Accounting Network (NASQAN) program (http://water.usgs.gov/nasqan/)
   * Sampling for Pesticides Residues in California Well Water Cumulative Report; EEH03-08; December 2003 (http://www.cdpr.ca.gov/docs/emon/pubs/ehapreps/eh0308.pdf)
   * California Department of Pesticide Regulation (DPR) Surface Water Database (http://www.cdpr.ca.gov/docs/emon/surfwtr/surfdata.htm)

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 Process (see: http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-sop.pdf) to ensure they can be used quantitatively or qualitatively in pesticide risk assessments.
5.  Receptors

The receptor is the biological entity that is exposed to the stressor (EPA, 1998). Due to the outdoor uses of prallethrin, the types of receptors that may be exposed include both aquatic and terrestrial receptors, such as birds, reptiles, mammals, amphibians, freshwater and estuarine/marine fish, non-target terrestrial and aquatic invertebrates, and terrestrial and aquatic plants, etc.  Spray drift and runoff exposures are expected for both ground and aerial applications of prallethrin. Consistent with the process described in the Overview Document (USEPA, 2004), the risk assessment for prallethrin relies on a surrogate species approach.  Toxicological data generated from surrogate test species, which are intended to be representative of broad taxonomic groups, are used to extrapolate the potential effects on a variety of species (receptors) included under these taxonomic groupings.

Acute and chronic toxicity data from studies submitted by pesticide registrants along with the available open literature are used to evaluate the potential direct and indirect effects of prallethrin to aquatic and terrestrial receptors.  This includes toxicity on the technical grade active ingredient, degradates, and when available, formulated products (e.g., "Six-Pack" studies).  The open literature studies are identified through EPA's ECOTOXicology (ECOTOX) database which employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife (USEPA, 2007b).  The evaluation of both sources of data will provide insight into the direct and indirect effects of prallethrin on biotic communities from loss of species that are sensitive to the chemical and from changes in structure and functional characteristics of the affected communities.  Data from an ECOTOX database for prallethrin will be evaluated for possible quantitative and/or qualitative inclusion in the risk assessment in support of Registration Review.  At that time, endpoints more sensitive than those available from guideline studies will be reviewed from the open literature studies.

A brief summary of the aquatic and terrestrial toxicity data available for prallethrin is provided in Sections 5.1 and 5.2, respectively.  In addition, ecological incidents associated with prallethrin use and a description of ecosystems potentially at risk are summarized in Sections 5.3 and 5.4, respectively.

Acute toxicity to aquatic animals (i.e., fish and aquatic invertebrates), terrestrial vertebrates (i.e., birds and mammals), and terrestrial invertebrates (i.e., honeybees) is categorized using the system shown in Table 5-1 (USEPA, 2004).  Toxicity categories for plants have not been defined.

Table 5-1. Categories of Acute Toxicity for Aquatic and Terrestrial Animals
                                   Aquatic
                        Vertebrates & Invertebrates
                                 Terrestrial
                                  Vertebrates
                           Terrestrial Invertebrates
                               Toxicity Category
                                     LC50
                                     (ppm)
                                  Oral LD50
                                    (mg/kg)
                                 Dietary LC50
                                     (ppm)
                                     LD50
                                (ug a.i./bee)

                                   < 0.1
                                    < 10
                                    < 50

                               Very highly toxic
                                 > 0.1 - 1
                                     10-50
                                    50-500
                                    < 2
                                 Highly toxic
                                  > 1 - 10
                                    51-500
                                   501-1000
                                    2-10.99
                               Moderately toxic
                                 > 10 - 100
                                   501-2000
                                   1001-5000

                                Slightly toxic
                                   > 100
                                   > 2000
                                   > 5000
                                    >= 11
                             Practically non-toxic
      5.1  Effects to Aquatic Organisms

A summary of aquatic toxicity data for prallethrin from registrant-submitted studies is provided in Table 5-2 (animals) and Table 5-3 (plants).  There are no toxicity data for the two major degradates of prallethrin, PGLS and d-t-CRA.

Two acute studies with freshwater fish have been submitted: one with bluegill sunfish (MRID 41321808) and one with rainbow trout (MRID 41321809).  Both studies indicate that prallethrin is very highly toxic to freshwater fish.  A single fish toxicity study with an estuarine/marine species has been submitted (MRID 44729602); this acute toxicity study indicates that prallethrin is also very highly toxic to sheepshead minnow.  The only submitted chronic toxicity study with a fish species, an early-life stage study with rainbow trout (MRID 44729604), yielded a NOEC of 3.0 ug a.i./L which was the highest treatment level in the study; a LOEC could not be determined using the selected treatment concentrations.

For aquatic invertebrates, five acute toxicity studies have been submitted: one with daphnids (MRID 41321810), one with Eastern oyster (MRID 44729601), two with mysid shrimp (MRIDs 44729603 and 48055901), and one with an amphipod in sediment (MRID 47762401).  The latter sediment toxicity study with Hyalella azteca has been classified as supplemental due to uncertainty regarding the accuracy of the LC50 values given potential interference from the solvent.  Collectively, the four former studies indicate that prallethrin is highly toxic to very highly toxic to aquatic invertebrates.  It should be noted that one of the studies with mysid shrimp was conducted with TGAI (MRID 44729603) whereas the other (MRID 48055901) was conducted with the TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795) which also contains two other active ingredients, the synthetic pyrethroid d-phenothrin (PC Code 069005) and the synergist PBO (PC Code 067501).   Results of the study with the TEP indicate that MULTICIDE Fogging Concentrate 2798 is three orders of magnitude more toxic than prallethrin TGAI (96-hr LC50 = 3.9 ug a.i./L with TGAI; LC50 = 0.0079 ug a.i./L with TEP).  The only submitted chronic toxicity study with an aquatic invertebrate species, a life cycle test with daphnids (MRID 44729605), yielded a 21-day NOEC of  0.65 ug a.i./L based on number of offspring per female.

A single aquatic plant toxicity study (MRID 48055902) has been submitted: a Tier II test with an aquatic vascular plant using the TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795).  This study yielded no effects on duckweed up to 1.324 ug a.i./L prallethrin.  No data are available for non-vascular aquatic plants.

Table 5-2. Summary of the Endpoints from Submitted Aquatic Animal Toxicity Studies for Prallethrin
Study Type &
TGAI (%)/TEP
Species
Toxicity Value &
Toxicity Classification
MRID & Classification
Freshwater Fish
Acute
TGAI 92.9%
Bluegill sunfish (Lepomis macrochirus)
Mean-measured concentrations
96-hr LC50 = 22 ug a.i./L
96-hr NOEC = 8.6 ug a.i./L
(based on mortality)
Very highly toxic
41321808
Acceptable
Acute
TGAI 92.6%
Rainbow trout (Oncorhynchus mykiss)
Mean-measured concentrations
96-hr LC50 = 12 ug a.i./L
96-hr NOEC = 4.3 ug a.i./L
(based on mortality)
Very highly toxic
41321809
Acceptable
Early-life stage
TGAI 94.2%
Rainbow trout (Oncorhynchus mykiss)
Mean-measured concentrations
90-day NOEC = 3.0 ug a.i./L
90-day LOEC > 3.0 ug a.i./L
(no effects)
44729604
Acceptable
Estuarine/Marine Fish
Acute
TGAI 94.2%
Sheepshead minnow (Cyprinodon variegates)
Mean-measured concentrations
96-hr LC50 = 26 ug a.i./L
95% C.I.: 23-31 ug a.i./L
96-hr NOEC = 11 ug a.i./L
96-hr LOEC = 16 ug a.i./L
(based on lethargy and erratic swimming behavior)
Very highly toxic
44729602
Acceptable
Freshwater Invertebrates
Acute
TGAI 92.9%
Water flea
(Daphnia magna)
Mean-measured conentrations
48-hr EC50 = 6.2 ug a.i./L
48-hr NOEC = 4.6 ug a.i./L
(based on mortality)
Very highly toxic
41321810
Acceptable
Life cycle
TGAI 94.2%
Water flea
(Daphnia magna)
21-day NOEC = 0.65 ug a.i./L
21-day LOEC = 1.3 ug a.i./L
21-day MATC = 0.93 ug a.i./L
(based on number of offspring per female)
44729605
Acceptable
Acute: whole sediment
TGAI
97.4% radio-chemical purity
93.4% non-radioactive purity

Amphipod
(Hyalella azteca)
Mean-measured bulk sediment concentrations
10-day LC50 = 14.9 mg TRR/kg-dw
10-day NOEC = 5.9 mg TRR/kg-dw
10-day LOAEC = 12 mg TRR/kg-dw
(based on mortality)
Organic carbon-normalized mean-measured sediment concentrations
10-day LC50 = 339 mg TRR/kg-dw
10-day NOEC = 134.09 mg TRR/kg-dw
10-day LOAEC = 272.7 mg TRR/kg-dw
(based on mortality)
Mean-measured pore water concentrations
10-day LC50 = 0.55 mg TRR/L
10-day NOEC = 0.25 mg TRR/L
10-day LOAEC = 0.44 mg TRR/L
(based on mortality)
Mean-measured overlying water concentrations
10-day LC50 = 0.018 mg TRR/L
10-day NOEC = 0.0082 mg TRR/L
10-day LOAEC = 0.014 mg TRR/L
(based on mortality)
47762401
Supplemental
Estuarine/Marine Invertebrates
Acute
TGAI 94.2%
Eastern oyster (Crassostrea virginica)
Mean-measured concentrations
96-hr EC50 = 0.64 mg a.i./L
95% C.I.: 0.58-0.69 mg a.i./L
Probit slope: 10.5+-1.39
96-hr NOEC = 0.41 mg a.i./L
96-hr LOEC = 0.57 mg a.i./L
(based on shell deposition)
Highly toxic
44729601
Acceptable

Acute
TGAI 94.2%
Mysid shrimp (Mysidopsis bahia)
Mean-measured concentrations
96-hr LC50 = 3.9 ug a.i./L
95% C.I.: 3.4-4.3 ug a.i./L
96-hr NOEC = 2.1 ug a.i./L
(based on mortality)
96-hr LOEC = 3.1 ug a.i./L
(based on lethargy and erratic swimming)
Very highly toxic
44729603
Acceptable

Acute
TEP*
Mysid shrimp (Americamysis bahia)
Mean-measured concentrations
96-hr LC50 = 0.0079 ug a.i./L
95% C.I.: 0.0017-0.14 ug a.i./L
96-hr NOEC = 0.002 ug a.i./L
Probit Slope: N/A
48055901
Acceptable
TGAI = technical grade active ingredient; TEP = typical end-use product; TRR = total radioactive residue; N/A = not applicable; dw = dry weight
*conducted with MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795), a typical end-use product containing 0.995% prallethrin, 4.98% d-phenothrin (PC Code 069005), and 4.97% piperonyl butoxide (PC Code 067501)

Table 5-3. Summary of the Endpoints from Submitted Aquatic Plant Toxicity Studies for Prallethrin
Study Type &
TGAI (%)/TEP
Species
Toxicity Value*
MRID & Classification
Tier II, Aquatic plant growth
TEP*
Duckweed
(Lemna gibba)
Measured (TWA) Concentrations
7-day EC50  > 1.324 ug a.i./L
7-day EC05  > 1.324 ug a.i./L
7-day NOEC >= 1.324 ug a.i./L
48055902
Acceptable
TGAI = technical grade active ingredient; TEP = typical end-use product; TWA = time-weighted average
*conducted with MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795), a typical end-use product containing 0.995% prallethrin, 4.98% d-phenothrin (PC Code 069005), and 4.97% piperonyl butoxide (PC Code 067501)
      5.2  Effects to Terrestrial Organisms

Tables 5-4 and 5-5 summarize the terrestrial toxicity data for animals and plants, respectively, for prallethrin based on an evaluation of submitted studies.  There are no toxicity data for the two major degradates of prallethrin, PGLS and d-t-CRA.

No data are available for a passerine species.  Single oral dose, dietary, and reproductive toxicity studies have been submitted for bobwhite quail (MRIDs 41321805, 41321806, 43773403) and mallard ducks (MRIDs 41321804, 41321807, 43797604).  The single oral dose study with mallard ducks (MRID 41321804) has been classified as supplemental because three birds in the highest dosage group regurgitated their doses.  The results of the acute and subacute tests indicate that prallethrin is slightly toxic and practically non-toxic to birds via acute oral and dietary exposures, respectively.  The avian reproductive toxicity studies yielded NOECs of 360 and 120 mg a.i./kg-diet for bobwhite quail and mallard ducks, respectively.

An acute oral toxicity study with rats (MRID 42030903) yielded a toxicity classification of moderately toxic.  A two-generation reproductive study yielded a NOEL of 600 mg a.i./kg-diet and a LOEL of 3000 mg a.i./kg-diet (MRID 42077006).

An acute contact toxicity study with honeybees yielded a toxicity classification of highly toxic (MRID 41321823).  In addition, two alfalfa foliage residue studies with honeybees have been submitted: one with TGAI (MRID 41321823) and one with the TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795).  Both studies showed no effects at the tested concentration (i.e., 0.005 lb a.i./A TGAI and 0.0008 lb a.i./A TEP).

Two Tier I terrestrial plant toxicity studies (i.e., seedling emergence and vegetative vigor) with the TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795) have been submitted for four monocots and six dicots (MRIDs 47431602, 47431603).  Both studies tested the maximum rate for a single application for MULTICIDE Fogging Concentrate 2798.  In the tier I vegetative vigor study (MRID 47431603), there were no significant effects.  Therefore, the most sensitive species of monocots and dicots could not be determined.  In the Tier I seedling emergence study (MRID 47437602), an inhibition of greater than 25% was observed for sugarbeet emergence (32.4%).  In the same study, the mean of the treated group was significantly less than that of the control group for the following species and endpoints: tomato emergence; wheat dry weight; and soybean dry weight.  Therefore, a definitive NOEC could not be determined for these species.

Table 5-4. Summary of the Endpoints from Submitted Terrestrial Animal Toxicity Studies for Prallethrin
Study Type &
TGAI (%)/TEP
Species
Toxicity Value &
Toxicity Classification
MRID &
Classification
Birds
Single dose oral
TGAI 92.6%
Bobwhite quail
(Colinus virginianus)
Nominal concentrations
14-day LD50 = 1171 mg a.i./kg-bw
95% C.I.: 835-1835 mg a.i./kg-bw
Probit slope = 3.7
 (based on mortality)
14-day NOEC = 125 mg a.i./kg-bw
(based on signs of toxicity including lethargy, reduced reaction to sound and movement, ruffled appearance, wing droop, depression, loss of coordination, lower limb weakness, fasciculation, tremors, convulsions, panting, loss of righting reflex, and prostrate posture)
Slightly toxic
41321805
Acceptable
Single dose oral
TGAI 92.9%
Mallard duck
(Anas platyrhynchos)
Nominal concentrations
14-day LD50 > 1000 mg a.i./kg-bw
14-day NOEC = 250 mg a.i./kg-bw
(based on signs of toxicity including lethargy, reduced reaction to sound and movement, loss of coordination, lower limb weakness, fasciculation, tremors, convulsions, panting, loss of righting reflex, prostrate posture, and dorsal head curl)
Slightly toxic
41321804
Supplemental
Dietary
TGAI 92.9%
Bobwhite quail
(Colinus virginianus)
Nominal concentrations
8-day LC50 > 5620 mg a.i./kg-diet
8-day NOEC = 3160 mg a.i./kg-diet
(based on reductions in feed consumption and body weight gain)
Practically non-toxic
41321806
Acceptable
Dietary
TGAI 92.9%
Mallard duck
(Anas platyrhynchos)
Nominal concentrations
8-day LC50 > 5620 mg a.i./kg-diet
8-day NOEC = 1780 mg a.i./kg-diet
(based on reductions in body weight and feed consumption)
Practically non-toxic
41321807
Acceptable
Reproduction
TGAI 92.9%

Bobwhite quail
(Colinus virginianus)
Nominal concentrations
10 week NOEL = 360 mg a.i./kg-diet
10-week LOEL = 600 mg a.i./kg-diet
(based on reduction in percentage of live 3-week  embryos)
43773403
Acceptable
Reproduction
TGAI 92.9%
Mallard duck
(Anas platyrhynchos)
Nominal concentrations
21-week NOEC = 120 mg a.i./kg-diet
21-week LOEC = 360 mg a.i./kg-diet
(based on eggs laid, eggs set, viable embryos, live 3-week embryos, 14-day survivor weight)
43797604
Acceptable
Mammals
Acute oral
TGAI 92.0%
Rat
(Rattus norvegicus)
Nominal concentrations
14-day LD50 (M) = 640 mg a.i./kg
14-day LD50 (F) = 460 mg a.i./kg
Moderately toxic
42030903
Guideline
Two generation reproduction
TGAI 92.9-93.6%
Rat
(Rattus norvegicus)
Nominal concentrations
Parental NOEL = 600 mg a.i./kg-diet
Parental LOEL = 3000 mg a.i./kg-diet
(based on decreased body weight)
Reproductive NOEL = 600 mg a.i./kg-diet
Reproductive LOEL = 3000 mg a.i./kg-diet
(based on decreased pup weight)
42077006
Minimum
Invertebrates
Acute contact
TGAI 92.9%
Honeybee
(Apis mellifera)
Nominal concentrations
48-hr LD50 = 0.028 ug a.i./bee
95% C.I.: 0.025-0.033
Probit slope = 4.8 (95% C.I.: 3.7-5.9)
48-hr NOED = 0.0125 ug  a.i./bee
(based on mortality)
Highly toxic
41321823
Acceptable
Foliage residue
(alfalfa)
Formulation 2.45%
Honeybee
(Apis mellifera)
Nominal concentrations
24-hr NOEC = 0.005 lb a.i./A
(no effects)
43749301
Acceptable
Foliage residue (alfalfa)
TEP*
Honeybee
(Apis mellifera L.)
Nominal concentrations
24-hr NOEC >= 0.0008 lb a.i./A
(no effects)
47431601
Acceptable
TGAI = technical grade active ingredient; TEP = typical end-use product
*conducted with MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795), a typical end-use product containing 1% prallethrin, 5% d-phenothrin (PC Code 069005), and 5% piperonyl butoxide (PC Code 067501)

Table 5-5. Summary of the Endpoints from Submitted Terrestrial Plant Toxicity Studies for Prallethrin
Study Type &
TGAI (%)/TEP
Species
Toxicity Value (Nominal)
MRID & Classification
Seedling emergence Tier 1
TEP*
Monocots
Onion (Allium cepa)
Ryegrass (Lolium perenne)
Wheat (Triticum aestivum)
Corn (Zea mays)

Dicots
Sugarbeet (Beta vulgaris)
Cabbage (Brassica oleracea)
Soybean (Glycine max)
Lettuce (Lactuca sativa)
Tomato (Lycopersicon esculentum)
Radish (Raphanus sativus)
Monocots
Most sensitive monocot:  Wheat
Most sensitive parameter: Dry weight
21-day EC25/IC25  > 0.0008 lb a.i./A
21-day EC05/IC05  < 0.0008 lb a.i./A
21-day NOEC < 0.0008 lb a.i./A

Dicots
Most sensitive dicots:  Sugarbeet, tomato, soybean
Most sensitive parameters: Emergence and dry weight
21-day EC25/IC25  < 0.0008 lb a.i./A
21-day EC05/IC05  < 0.0008 lb a.i./A
21-day NOEC < 0.0008 lb a.i./A
47431602
Acceptable

Vegetative vigor
Tier 1
TEP*
Monocots
Onion (Allium cepa)
Ryegrass (Lolium perenne)
Wheat (Triticum aestivum)
Corn (Zea mays)

Dicots
Sugarbeet (Beta vulgaris)
Cabbage (Brassica oleracea)
Soybean (Glycine max)
Lettuce (Lactuca sativa)
Tomato (Lycopersicon esculentum)
Radish (Raphanus sativus)
 Monocots
Most sensitive monocot: Could not be determined at tested concentration
Most sensitive parameter: Could not be determined at tested concentration
21-day EC25/IC25 > 0.0008 lb a.i./A
21-day EC05/IC05 < 0.0008 lb a.i./A
21-day NOEC >= 0.0008 lb a.i./A

Dicots
Most sensitive dicot: Could not be determined at tested concentration
Most sensitive parameter: Could not be determined at tested concentration
21-day EC25/IC25 > 0.0008 lb a.i./A
21-day EC05/IC05 < 0.0008 lb a.i./A
21-day NOEC >= 0.0008 lb a.i./A
47431603
Acceptable

TGAI = technical grade active ingredient; TEP = typical end-use product
*conducted with MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795), a typical end-use product containing 1% prallethrin, 5% d-phenothrin (PC Code 069005), and 5% piperonyl butoxide (PC Code 067501)
      5.3  Incident Databases Review

Preliminary reviews of the Ecological Information System (EIIS, version 2.1.1), which is maintained by the Agency's Office of Pesticide Programs, and the Avian Monitoring Information System (AIMS), which is maintained by the American Bird Conservatory, on January 5, 2012 did not yield any reported ecological incidents associated with the use of prallethrin.

In addition to the incidents recorded in EIIS and AIMS, additional incidents are reported to the Agency in aggregated form.  Pesticide registrants report certain types of incidents to the Agency as aggregate counts of incidents occurring per product per quarter.  Ecological incidents reported in aggregate reports include those categorized as `minor fish and wildlife' (W-B), `minor plant' (P-B), and `other non-target' (ONT) incidents.  `Other non-target' incidents include reports of adverse effects to insects and other terrestrial invertebrates.  For prallethrin, registrants have reported one minor plant incident (P-B) as of January 5, 2012.

The total number of actual incidents associated with the use of prallethrin may be higher than what is reported to the Agency.  Incidents may go unreported since effects may not be immediately apparent and/or readily attributed to the use of a chemical.  As such, the absence of incident reports cannot be construed as the absence of incidents.
      5.4  Ecosystems Potentially at Risk

Prallethrin may be applied to a variety of terrestrial environments for adult mosquito control.  In addition, it may be used on numerous non-agricultural, residential, and commercial sites. Therefore, the ecosystems at risk are often extensive in scope, and it may not be possible to identify specific ecosystems during the development of a nation-wide ecological risk assessment.  However, in general terms, terrestrial ecosystems potentially at risk from prallethrin exposure could include the treated area and adjacent areas that may receive drift or runoff from outdoor spray, especially during aerial ULV applications for mosquito control.  Areas adjacent to the treated area could include cultivated fields, fencerows and hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats, ecological preserves, and national wildlife refuges. Prallethrin residues may deposit into various water bodies resulting in possible exposure to aquatic species.  Aquatic ecosystems potentially at risk include water bodies adjacent to or downstream from the treated area and could include impounded bodies such as marshes, wetlands, ponds, lakes, and reservoirs, or flowing waterways such as streams or rivers.  For uses in coastal areas, aquatic habitats could also consist of marine ecosystems, including estuaries.
6.  Assessment Endpoints

Assessment endpoints are defined as "explicit expressions of the actual environmental value that is to be protected."  Defining an assessment endpoint involves two steps: 1) identifying the valued attributes of the environment that are considered to be at risk; and 2) operationally defining the assessment endpoint in terms of an ecological entity (i.e., a community of fish and aquatic invertebrates) and its attributes (i.e., survival and reproduction).  Therefore, selection of the assessment endpoints is based on valued entities (i.e., ecological receptors), the ecosystems potentially at risk, the migration pathways of pesticides, and the routes by which ecological receptors are exposed to pesticide-related contamination.  The selection of clearly defined assessment endpoints is important because they provide direction and boundaries in the risk assessment for addressing risk management issues of concern.  Changes to assessment endpoints are typically estimated from the available toxicity studies which are used as the measures of effects to characterize potential ecological risks associated with exposure to pesticides, such as prallethrin.

To estimate exposure concentrations, the ecological risk assessment considers applications at the maximum application rate.  The most sensitive toxicity endpoints are used from surrogate test species to estimate treatment-related direct effects on acute mortality and chronic reproductive, growth, and survival assessment endpoints.  Toxicity tests are intended to determine effects of pesticide exposure on birds, mammals, fish, terrestrial and aquatic invertebrates, and plants.  These tests include short-term acute, sub-acute, and reproduction studies and are typically arranged in a hierarchical or tiered system that progresses from basic laboratory tests to applied field studies.  The toxicity studies are used to evaluate the potential of a pesticide to cause adverse effects, to determine whether further testing is required, and to determine the need for precautionary label statements to minimize the potential adverse effects to non-target animals and plants.

An open literature search will be conducted to determine any relevant endpoints.  The search will focus on survival, growth and reproductive effects for aquatic and terrestrial effects of prallethrin.  More sensitive endpoints from acceptable open literature studies will be included in the ecological risk assessment.
7.  Conceptual Model

The conceptual model for prallethrin provides a written description and visual representation of the predicted relationships between prallethrin, potential routes of exposure, and the predicted effects for the assessment endpoint.  A conceptual model consists of two major components: risk hypothesis and a conceptual diagram (USEPA, 1998).
      7.1  Risk Hypothesis

A risk hypothesis describes the predicted relationship among the stressor, exposure, and assessment endpoint response along with the rationale for their selection.  For prallethrin, the following ecological risk hypothesis is being employed for this ecological risk assessment:

      Based on the application methods, the assumed fate and transport, and the assumed sensitivity of non-target aquatic and terrestrial species, prallethrin has the potential to reduce survival, reproduction, and/or growth in non-target terrestrial and aquatic organisms when used in accordance with the current labels.  These non-target organisms include Federally-listed threatened and endangered species as well as non-listed species.
      7.2  Conceptual Diagrams

The conceptual site model is a generic graphic depiction of the risk hypothesis.  It assumes that the non-agricultural uses of prallethrin are capable of affecting aquatic and terrestrial animals provided environmental concentrations are sufficiently elevated as a result of proposed label uses.  The environmental fate properties of prallethrin indicate that runoff, spray drift and direct spray represent potential transport mechanisms to aquatic and terrestrial habitats where non-target organisms may be either directly or indirectly exposed.  These transport mechanisms (i.e., sources) are depicted in the conceptual diagrams below (Figure 7-1 and Figure 7-2) along with a broad range of biological receptors of concern and the potential attribute changes (i.e., effects such as reduced survival, growth and reproduction) in the receptors due to exposure to prallethrin.

For prallethrin to pose an ecological risk, it must reach ecological receptors in biologically significant concentrations.  An exposure pathway is the means by which prallethrin moves in the environment from a source to an ecological receptor.  For an ecological exposure pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptors, and a feasible route of exposure. In addition, the potential mechanisms of degradation/ transformation (i.e., which degradation/ transformation products may form in the environment, in which media, and how much) must be understood, especially if the metabolites/transformation products are of greater toxicological concern than the parent compound.  Therefore, the assessment of ecological exposure pathways includes an examination of the source and potential migration pathways for constituents and the determination of potential exposure routes.

Figure 7-1.  Conceptual Model for Effects of Prallethrin on Aquatic Organisms. Dotted Lines indicate Exposure Pathways that Have a Low Likelihood of Contributing to Ecological Risk

Figure 7-2.  Conceptual Model for Effects Prallethrin on Terrestrial Organisms. Dotted Lines indicate Exposure Pathways that Have a Low Likelihood of Contributing to Ecological Risk
            7.2.1 Drinking Water Exposure

The Screening Imbibition Program (SIP v.1.0, released June 15, 2010) is used to calculate an upper bound estimate of drinking water exposure alone using the solubility of prallethrin (8.03 mg/L at 25°C; MRID 41321803), the most sensitive acute (LD50 = 1171 mg a.i./kg-bw; MRID 41321805) and chronic (NOEL = 360 mg a.i./kg-diet; MRIDs 43773403, 43797604) avian toxicity endpoints and the most sensitive acute (LD50 = 460 mg a.i./kg; MRID 42030903) and chronic (NOEL = 600 mg a.i./kg; MRID 42077006) mammalian toxicity endpoints.  Appendix E provides a description of the model and assumptions in deriving an upper bound exposure estimate.  Drinking water exposure alone was determined not to be a potential concern for birds and mammals on both acute and chronic bases (see Appendix E for model results). Detailed information about the SIP v.1.0, as well as the tool, can be found on the EPA's website at http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial.
            7.2.2 Inhalation Exposure

STIR v.1.0, Screening Tool for Inhalation Risk, is used to provide an upper bound estimate of exposure of birds and mammals to pesticides through inhalation of spray drift or vapor.  The upper bound exposure estimate requires a number of input parameters including the vapor pressure and molecular weight for the vapor-phase pesticide; additionally it requires the application rate and method of application (i.e., ground or aerial) for spray drift.  The toxicity aspect of the tool requires an avian acute oral LD50 value (LD50 LD50 = 1171 mg a.i./kg-bw; MRID 41321805), the chemical specific avian allometric scaling factor to adjust toxicity based on body weight for the chemical (default = 1.15), the weight of the tested bird (default = 0.178 kg for bobwhite quail), a rat acute oral LD50 value (LD50 = 460 mg a.i./kg; MRID 42030903), a rat acute inhalation LC50 value (LC50 = 0.288 mg/L; MRID 42030904), the duration of the rat inhalation study (assumed to be 4 hours), and the weight of the tested rat (default = 0.35 kg).  This tool was designed for use in the Problem Formulation phase of the ecological risk assessment process to quantitatively evaluate the need for further analysis of inhalation as a potential pathway of concern for birds and mammals.  If further analysis of the inhalation exposure pathway is recommended, additional data will be requested to address uncertainty related to this route of exposure.  Results from the model indicate that exposure of birds and mammals to prallethrin through inhalation of spray drift or vapor is not likely significant regardless of use application method (ground or air spray) (see Appendix F for model results).  Detailed information about the STIR v.1.0, as well as the tool, can be found on the EPA's website (http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial).

8.  Analysis Plan
To address the risk hypothesis, the potential for adverse effects on the environment will be estimated.  Usage, environmental fate, and ecological effects of prallethrin will be characterized and integrated to assess the risks.  Risk quotients (RQ) will be derived for prallethrin by dividing EECs by the most sensitive endpoint from the relevant, available toxicity data for prallethrin. As outlined in the Overview Document (USEPA, 2004), the likelihood of effects to individual organisms from particular uses of a chemical is estimated using the probit dose-response slope and either the level of concern (discussed below) or the actual calculated risk quotient value.

This analysis plan will be revisited and may be revised depending upon a full review of the data available in the open literature and the information submitted by the public in response to the opening of the Registration Review docket.
      8.1  Stressors of Concern

The focus of this assessment is on the parent material, prallethrin.  However, the Agency will review open literature to identify degradate(s) of potential toxicological concern and use of prallethrin with synergists and other pesticides.  Data sources that will be used in the future assessment include: 1) registrant submissions in support of registration review; 2) publicly available literature on ecological effects; 3) monitoring data for freshwater streams, lakes, reservoirs, and estuarine areas; and 4) incident reports of adverse effects on aquatic and terrestrial organisms associated with the use of prallethrin.

Prallethrin may be applied in formulated mixtures with other pesticides and synergists approved for registered uses (see Appendix B).  Toxicity data for TEPs, if available, may be presented as part of the ecological risk assessment, and the data may be used qualitatively or quantitatively in accordance with the Agency's Overview Document and the Services' Evaluation Memorandum (USEPA, 2004; USFWS/NMFS/NOAA, 2004).  Synergistic data for PBO and MGK 264, if available, may also be incorporated into the future assessment.  The options for doing so include, but are not limited to:
   * applying a toxicity enhancement factor (TEF) to the prallethrin toxicity endpoint;
   * applying a TEF that is specific to the ratio of PBO/MGK 264 and prallethrin that corresponds to the EEC for prallethrin;
   * applying a ratio-specific TEF for each daily prallethrin concentration; and
   * modeling the enhanced toxicity by the synergist(s) and co-formulate active ingredient(s).

A discussion of the implications of the available pesticide mixture effects data on the confidence of risk assessment conclusions will be addressed in the risk description of the final ecological assessment.
      8.2  Measures of Exposure

In order to estimate risks of prallethrin exposures in aquatic and terrestrial environments, all exposure modeling and resulting risk conclusions will be made based on maximum application rate, number of applications, and minimum application intervals for the currently registered use as discussed in Section 3.2.  Measures of exposure are based on aquatic and terrestrial models that estimate environmental concentrations of prallethrin using the maximum labeled application rate and application methods that have the greatest potential for off-site transport of the chemical.
            8.2.1 Spray Drift

The AgDRIFT spray drift model (v2.01; May, 2001) or AgDISP model will be used to assess exposures of organisms to prallethrin residue deposited on aquatic and terrestrial habitats by spray drift.  Both models also function as tools for evaluating the potential buffer zones to protect sensitive aquatic and terrestrial habitats from undesired spray drift exposures.  For aerial and ground ULV application of formulated prallethrin to control adult mosquitoes, a list of parameters such as, droplet size, spray volume, vortex decay rate, wind speed and directions will be input into the model for the spray drift and deposit predication.  Descriptions of the above model can be obtained from http://www.epa.gov/pesticides/science/models_pg.htm#atmospheric.

            8.2.2 Aquatic Exposure

For the aquatic assessment, estimated environmental concentrations (EECs) of prallethrin will be modeled by the Pesticide Root Zone Model (PRZM, v3.12.2, May 2005 ) coupled with the EXposure Analysis Model System (EXAMS, v<IP_ADDRESS>, April 2005).  Both are Tier 2 screening simulation models coupled with the input shell PE5.pl (August, 2007) to generate daily exposures and 1-in-10-year EECs of prallethrin (and residues of concern) that may occur in surface water bodies adjacent to application sites receiving prallethrin through runoff and spray drift.  PRZM simulates pesticide application, movement and transformation on an agricultural field and the resultant pesticide loadings to a receiving water body via runoff, erosion, and spray drift.  EXAMS simulates the fate of the pesticide and resulting concentrations in the water body.  The standard watershed geometry used for ecological pesticide assessments assumes application to a 10-hectare agricultural field that drains into an adjacent 1-hectare water body that is 2 meters deep (20,000 m[3] volume) with no outlet.  The PE5 model can also be used for the pesticide concentration estimation at different water depth (e.g., 1 m, 0.3 m and 0.1 m) as the Agency deems it is necessary. The composite model PRZM/EXAMS is used to estimate screening-level exposure of aquatic organisms to prallethrin.  The measure of exposure for aquatic species is the 1-in-10-year peak or rolling mean concentration.  The 1-in-10-year peak is used for estimating acute exposures of direct effects to aquatic organisms.  The 1-in-10-year 60-day mean is used for assessing the effects to fish and aquatic-phase amphibians from chronic exposure.  The 1-in-10-year 21-day mean is used for assessing the effects on aquatic invertebrates from chronic exposure.

At the present time, the use of the impervious scenario (a PRZM modeling scenario) will be considered as the most suitable available modeling approach for impervious runoff.  The PRZM impervious scenario may be used in the Tier 2-coupled aquatic models PRZM/EXAMS along with residential or other suitable scenarios such as rights-of-way (ROW) to obtain EECs.  The conceptual model for the residential scenario integrates simultaneous modeling of the individual use scenario with an impervious scenario.  This approach assumes that no watershed is completely covered by either the (1/4) acre lot (the basis for the residential scenario) or undeveloped land (the basis for the ROW scenario) for residential and ROW use patterns; therefore, differential amounts of runoff will occur within the watershed.  The impervious scenario was developed to represent the paved areas within a watershed not including roads, parking lots, sidewalks, and buildings outside the (1/4) acre lot (the (1/4) acre lot scenario accounts for impervious surfaces such as buildings within the represented area).  By modeling a separate scenario for impervious surfaces, it is also possible to estimate that amount of exposure that could occur when the pesticide is oversprayed onto this surface.  Using two scenarios in tandem requires post-processing of the modeled output to derive a weighted EEC that represents the contribution of both the pervious (i.e., residential and ROW scenarios) and the impervious surfaces.  A Microsoft Excel spreadsheet has been developed that allows for the weighting and aggregation of exposure from both scenarios. The daily time series from each model run should be copied from the times series file (NAME_TS.out) generated from the PRZM graphical user interface (PE5.pl) into the spreadsheet provided.  The time series data are then weighted based on percentage of impervious surface, the percentage of the pervious surface treated, and an adjusted time series is created.  Rolling averages for the relevant durations of exposure (e.g., 21- day and 60-day averages) are calculated, and the relevant one-in-ten year return EEC is generated from these distributions.

For the purposes of risk assessment, it will be assumed that 1% of the application rate could reach the impervious surfaces surrounding each residential lot.  This amount of overspray is not based on empirical data (no published studies on this occurrence have been found in the open literature).  However, the assumption is consistent with the standard assumption of 1% spray drift with ground applications in ecological risk assessments.  In general, incorporation of impervious surfaces into the exposure assessment results in increasing runoff volume in the watershed, which tends to reduce overall pesticide exposure assuming 1% overspray to the impervious surface.  Alternative assumptions for percent impervious surfaces, percentage of use site treated, and percentage of overspray may be considered in order to characterize the assumptions of the ecological risks assessment in the context of the individual exposure assessment and risk conclusions.  For example, previously tested assumptions used in the endangered species assessments may be considered for characterization (i.e., 10% and 30% impervious surfaces,10% lot treated, and 0% and 10% overspray) unless other relevant values can be determined (i.e., modeling may be completed for the impervious surface with 0% and 10% overspray to provide lower and upper bound values). The results of these alternate modeling exercises may be discussed in the assessment.

Given the aquatic toxicity of prallethrin and its likelihood to occur in sediment, the Agency may also evaluate the potential toxicological exposures resulting from benthic/sediment concentrations (EECs).  Pore water concentrations are commonly used to predict toxicity of non-ionic substances in sediments and characterize exposure to organisms that spend time in or near sediments (Di Toro et al., 1991; USEPA, 2002).  PRZM/ EXAMS estimates 1-in-10-year peak and 21-day mean EECs for pore water.

To estimate exposure related to releases of prallethrin from domestic wastewater treatment plants, the Agency will rely on the Office of Pollution Prevention and Toxics (OPPT) model, Exposure and Fate Assessment Screening Tool (EFAST, version 2.0, or EFAST2, 2007).  From this model, the Agency will use the "Down-the-Drain" module, which is designed for releases to domestic wastewater treatment.  It is suitable for all the sources of prallethrin that could potentially occur through a "down-the-drain" scenario.  The model provides screening-level estimate concentrations of chemicals in surface water that may result from household uses and the disposal of consumer products into wastewater using a few simple input parameters (production volume and fraction of the chemical removed during wastewater treatment).
            8.2.3 Terrestrial Exposure

The model used to produce terrestrial EECs on food items is T-REX.  Exposure estimates for terrestrial animals assumed to be in the target area or in an area exposed to spray drift are derived using the T-REX model (version 1.5, 3/22/2012).  This model incorporates the Kenaga nomograph, as modified by Fletcher et al. (1994), which is based on a large set of actual field residue data.  The upper limit values from the nomograph represent the 95[th] percentile of residue values from actual field measurements (Hoerger and Kenaga, 1972).  The Fletcher et al. (1994) modifications to the Kenaga nomograph are based on measured field residues from 249 published research papers, including information on 118 species of plants, 121 pesticides, and 17 chemical classes.  For input into T-REX, the default foliar dissipation half-life of 35 days will be used if there is insufficient foliar dissipation rate data on prallethrin.

EECs for terrestrial plants inhabiting dry and wetland areas will be are derived using TerrPlant (version 1.2.2, 12/26/2006) using relevant reviewed registrant-submitted environmental fate data.  This model uses estimates of pesticides in runoff and in spray drift to calculate EECs.  EECs are based upon solubility, application rate, and minimum incorporation depth.

Prallethrin appears to have the potential to bioconcentrate in aquatic organisms.  The maximum bioconcentration factor was 1160x for whole fish in 7 days and 3130x for non-edible tissue in 14 days.  A depuration study showed half-lives of 1.3-2.5 days (MRIDs 42810812, 43758001).  The potential for bioaccumulation may be assessed using the results from bioaccumulation in fish studies as well as the KABAM model (KOW -based) Aquatic BioAccumulation Model, version 1.0, 2009), adjusting for biotransformation rates.  KABAM is used to estimate potential bioaccumulation of hydrophobic organic pesticides in freshwater aquatic ecosystems and risks to mammals and birds consuming aquatic organisms that have bioaccumulated these pesticides. Monitoring data and biotransformation rates in terrestrial species may also be evaluated to assess the potential for bioaccumulation in terrestrial food webs.
       8.3  Measures of Effect

Ecological effects data are used as measures of direct and indirect effects to biological receptors.  As discussed previously, data are obtained from registrant-submitted studies or from literature studies identified by ECOTOX.  The ECOTOX database provides more ecological effects data in an attempt to bridge existing data gaps.  ECOTOX is a source for locating single chemical toxicity data and potential chemical mixture toxicity data for aquatic life, terrestrial plants, and wildlife.  ECOTOX was created and is maintained by the USEPA, Office of Research and Development, and the National Health and Environmental Effects Research Laboratory's Mid-Continent Ecology Division.

Information on the potential effects of prallethrin on non-target animals is also collected from the Ecological Incident Information System (EIIS; USEPA, 2007a).  The EIIS is a database containing adverse effect (typically mortality) reports on non-target organisms where such effects have been associated with the use of pesticides.  Incidents reported in the aggregate incident reports and the Avian Incident Monitoring System (AIMS) will also be searched.  AIMS is a database administered by the American Bird Conservancy with partial funding from EPA.  It contains publicly available data on reported avian incidents involving pesticides (http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm).

Where available, sub-lethal effects observed in both registrant-submitted and open literature studies will be evaluated qualitatively.  Such effects may include behavioral changes (e.g., lethargy and changes in coloration).  Quantitative assessments of risks, though, are limited to those endpoints that can be directly linked to the Agency's assessment endpoints of impaired survival, growth and reproduction.

The assessment of risk for direct effects to non-target organisms makes the assumption that toxicity of prallethrin to birds is similar to terrestrial-phase amphibians and reptiles.  The same assumption is made for fish and aquatic-phase amphibians.  The acute measures of effect used for animals in this assessment are lethal dose (LD), lethal concentration (LC) or effective concentration (EC), such as: LD50, LC50, and EC50.  The LD50 is the amount of a material, given all at once, that is estimated to cause the death of 50% of the test organisms.  The LC50 is the concentration of a chemical that is estimated to kill 50% of the test organisms.  The EC50 is the concentration of a chemical that is estimated to produce a specific effect in 50% of the test organisms.  Endpoints for chronic measures of exposure for listed and non-listed animals are the NOAEL and NOEC.  NOAEL stands for "No Observed-Adverse-Effect-Level" and refers to the highest tested dose of a substance that has been reported to have no harmful (adverse) effects on test organisms.  The NOEC is the No-Observed-Effects-Concentration.  For non-listed plants, only acute exposures are assessed (i.e., EC25 for terrestrial plants and EC50 for aquatic plants); for listed plants either the NOEC or EC05 is used.
      8.4  Integration of Exposure and Effects

Risk characterization is the integration of exposure and ecological effect characterizations to determine the potential ecological risk from the use of prallethrin and the likelihood of direct and indirect effects to non-target organisms in aquatic and terrestrial habitats.  The exposure and effects data are integrated in order to evaluate potential adverse ecological effects on non-target species. For the prallethrin risk assessment, the risk quotient (RQ) method will be used to compare estimated exposure and measured toxicity values.  Acute and chronic EECs will be divided by acute and chronic toxicity values.  The resulting RQs will then be compared to the Agency's Levels of Concern (LOC) (USEPA, 2004).  These criteria are used to indicate when prallethrin's use, as directed on the labels, has the potential to cause adverse direct or indirect effects to non-target organisms.  In addition, incident data from EIIS, aggregate incident reports, and AIMS will be considered as part of the risk characterization.
      8.5  Deterministic and Probabilistic Assessment Methods

The quantitative assessment of risk will primarily depend on the deterministic point estimate-based approach described in the risk assessment.  Depending on the risk manager's need for additional information regarding risk, an effort will be made to further qualitatively describe risk using probabilistic tools that the Agency has developed.  These tools have been reviewed by FIFRA Scientific Advisory Panels (http://www.epa.gov/scipoly/sap/index.htm) and have been deemed as appropriate means of refining assessments where deterministic approaches have identified risks.
      8.6  Endangered Species Assessments

Consistent with the Agency's responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to Federally-listed threatened and/or endangered (listed) species from registered uses of prallethrin.  This assessment will be conducted in accordance with the Overview Document (USEPA, 2004), provisions of the ESA, and the Services' Endangered Species Consultation Handbook (USFWS/NMFS, 1998).

The assessment of effects associated with the registration of prallethrin is based on an action area.  The action area is considered to be the area directly or indirectly affected by the federal action, as indicated by the exceedance of Agency Levels of Concern (LOCs) used to evaluate direct or indirect effects.  The Agency's approach to defining the action area under the provisions of the Overview Document (USEPA, 2004) considers the results of the risk assessment process to establish boundaries for that action area with the understanding that exposures below the Agency's defined LOCs constitute a no-effect threshold.  For the purposes of this assessment, attention will be focused on the footprint of the action (i.e., the area where prallethrin application occurs), plus all areas where offsite transport (i.e., spray drift, runoff, etc.) may result in potential exposure that exceeds the Agency's LOCs.  Specific measures of ecological effect that define the action area for listed species include any direct and indirect effects and/or potential modification of its critical habitat, including reduction in survival, growth, and reproduction as well as the full suite of sub-lethal effects available in the effects literature.  Therefore, the action area extends to a point where environmental exposures are below any measured lethal or sub-lethal effect threshold for any biological entity at the whole organism, organ, tissue, and cellular level of organization.  In situations where it is not possible to determine the threshold for an observed effect, the action area will be assumed to encompass the entire United States.
      8.7  Drinking Water Assessment

A drinking water exposure assessment (DWA) may be conducted using up-to-date models and data during the risk assessment phase.  The drinking water assessment will incorporate model estimates of prallethrin in surface and ground waters.  Prallethrin concentrations in surface waters will be estimated using Tier II PRZM/EXAMS (see description in Section 7.2).  There is no national default PCA for mosquito control applications.

Ground water estimates of prallethrin concentrations will be established using SCI-GROW (v.2.3, July 2003, http://www.epa.gov/oppefed1/models/water/) (or PRZM-GW if it is available by the time the risk assessment is carried out).  This is a regression model by fitting a linear model to ground water concentration with the Relative Index of Leaching Potential (RILP) as the independent variable.  The model is used as a screening tool for ground water.  The RILP is function of aerobic soil metabolism and the soil-water partition coefficient.  The output of SCIGROW represents the concentrations that might be expected in shallow unconfined aquifers under sandy soils. The DWA will also include available surface and ground water monitoring data, with consideration of changes in use patterns since mitigations have been imposed.  Ground water concentrations will be taken from 90-day average high concentrations from perspective ground water studies.  States and mosquito control communities are encouraged to submit the monitoring data for the water quality risk assessment.
     8.8  Endocrine Disruptor Screening
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 the most recent registration 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), prallethrin 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 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.  Prallethrin is not among the group of 58 pesticide active ingredients on the initial list to be screened under the EDSP.  Accordingly, as part of registration review, EPA will issue future EDSP orders/data call-ins, requiring the submission of EDSP screening assays for prallethrin.  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/.
9.  Preliminary Identification of Data Gaps

The following two sections, 9.1 and 9.2 identify the remaining fate and effect studies needed to complete an environmental fate and ecological risk assessment in support of the registration review of the labeled uses of prallethrin.  Draft Data Call-In (DCI) tables for requested data are provided in Appendix G.  In addition to providing the guideline number and study title, the DCI tables provide a rationale for requiring the data, an explanation of how the data will be used, and a brief description of the how the data could impact the Agency's future decision-making.
      9.1  Environmental Fate Data

Table 9-1 identifies environmental fate studies for prallethrin by MRID that offer data for each guideline requirement, as well as study classifications and data deficiencies (i.e., whether there is a data gap).  Since prallethrin is not registered for agricultural use, no additional data on terrestrial and aquatic field dissipation will be requested at this time.  Data will be waived for the major degradates because they are the result of the cleavage of the ester linkage of the parent.  This breaking of the basic pyrethroid frame or backbone may result in lost activity and thus decreased toxicity when compared with the parent.  Should the registrant wish to add new uses of this chemical or other new evidence of toxicological issues is raised for the degradates, the data requirements may be reassessed.

The following data are needed to correct data deficiencies for the ecological exposure assessment:
         *       Guideline 835.4200  -  Anaerobic Soil Metabolism: No study for anaerobic soil metabolism has been found for prallethrin. The registrant is required to perform an anaerobic soil metabolism study in three different soils to fulfill current OPPTS guidelines 835.4200 and to address the data deficiency for anaerobic soil metabolism. The studies will provide half-lives in different soil systems, resulting in more knowledge and certainty related to the behavior and persistence of prallethrin in anaerobic soils.

         *       Guideline Number 835.1230  -  Adsorption/Desorption (Batch Equilibrium):  One available study was performed in the test soils that were autoclaved before use, thus possibly altering the physical and chemical properties of the soils, the registrant must demonstrate that autoclaving the soil did not influence the results of this study, and that the observed results are an accurate representation of prallethrin adsorption/desorption from soil or submit a new study. The registrant is required to perform an adsorption/desorption study according to current OPPTS guidelines 835.1230. The studies will obtain a sorption value which can be used to predict partitioning under a variety of environmental conditions. The data at concentrations resulting from labeled application rates will facilitate a better understanding of prallethrin mobility in the environment.

Table 9-1.  Environmental Fate Data Requirement Table for Prallethrin.
                                   Guideline
Description
                                     MRID/
                                   Accession
                                Classification
                                   Data Gap?
Comments
                                   835.2120
Hydrolysis
                                   42838602
                                  Acceptable
                                      No

                                   835.2240
Aqueous photolysis
                                   43797601
                                  Acceptable
                                      No

                                   835.2410
Soil photolysis
                                 43797602 and
                                   43797603
                                  Acceptable
                                      No

                                   835.4100
Aerobic soil metabolism
                                    42838601
                                  Acceptable
                                      No

                                   835.4200
Anaerobic soil metabolism
                                       -
                                       -
                                     Yes
Data are needed for sediment-water systems, one each at a neutral and an acidic pH.
                                   835.4300
Aerobic aquatic metabolism
                                   44861001
                                      and
                                   44861002
                                 Supplemental
                                      and
                                 Supplemental
                                      No

                                   835.4400
Anaerobic aquatic metabolism
                                   44366601
                                      and
                                   44366602
                                 Supplemental
                                      and
                                 Supplemental
                                      No

                                   835.1230
Adsorption/ desorption and leaching
                                   42810801
                                 Unacceptable
                                      Yes
Because the test soils were autoclaved before use, thus possibly altering the physical and chemical properties of the soils, the registrant must demonstrate that autoclaving the soil did not influence the results of this study, and that the observed results are an accurate representation of prallethrin adsorption/desorption from soil.
                                   835.6100
Terrestrial field dissipation
                                      --
                                      --
                                      --
 Data are not required at this time.

Freezer storage stability

Analytical method  -  soil

Analytical method  -  water

Analytical method - sediment

                                   850.1730
Fish bioconcentration
                                    42810802
                                      and
                                    43758001
                                  Acceptable
                                      No

      9.2  Ecological Effects Data

Tables 9-2, 9-3, and 9-4 identify ecological effects studies by MRID for aquatic animals, terrestrial animals, and plants (terrestrial and aquatic), respectively, that offer data for each guideline requirement, as well as study classifications and whether or not further data are needed in order to support risk assessment (i.e., whether there is a data gap).  Data on the major degradates of prallethrin will be waived at this time because the Agency considers the degradates to be the outcome of cleavage of the ester linkage of the parent.  This breaking of the basic pyrethroid frame or backbone may result in lost activity and thus decreased toxicity when compared with the parent.  Should the registrant wish to add new uses of this chemical, the data requirement may be reassessed.

Submission of data to eliminate data gaps would reduce uncertainties in the ecological effects assessment.  Data gaps were assigned either a low or high potential to add value to an ecological effects assessment.  While still considered data gaps according to 40 CFR Part 158, low potential studies are unlikely to change risk determinations because alternate methods and weight of evidence may possibly be used in the absence of data.  High potential studies would enable the Agency to better characterize potential risks by eliminating uncertainties for both non-listed and listed species that cannot be accounted for using alternate methods or weights of evidence.

Data from the following guideline studies are considered to have high potential to add value to the ecological risk assessment for prallethrin:

   * Guideline 850.4225  -  Seedling emergence, Tier II (TEP): In the Tier I seedling emergence study with MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795), an inhibition of greater than 25% was observed for sugarbeet emergence (32.4%).  Therefore, a Tier II seedling emergence test with sugarbeets is requested.  In the same study, the mean of the treated group was significantly less than the mean of the control group for the following species and endpoints: tomato emergence; wheat dry weight; and soybean dry weight.  Therefore, a NOEC could be determined for these species, and Tier II seedling emergence tests are recommended for tomato, wheat, and soybean to reduce uncertainty in determining risk to endangered plants.

   * Guideline Number: 850.1020  -  Gammarid Acute Toxicity (TEP): Acute toxicity data of prallethrin TEPs with the synergists PBO and MGK-264 are requested for freshwater invertebrates because there are registered outdoor uses of prallethrin that may result in significant exposure to water bodies.  Products with these synergists are likely to cause increased toxicity to non-target aquatic species.  This is supported by an acute toxicity study with the most sensitive aquatic species, the mysid shrimp, and the TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795) which contains d-phenothrin and PBO.  Results indicate that the MULTICIDE Fogging Concentrate 2798 is three orders of magnitude more toxic than TGAI prallethrin (96-hr LC50 = 22 ug a.i./L with TGAI; LC50 = 0.0079 ug a.i./L with TEP; see Section 4.1).  Since available information indicates that greater toxicity enhancement can occur at higher synergist-to-active ingredient ratios, selection of the TEPs for testing should include those TEPs with the highest synergist-to-active ingredient ratio and are registered for outdoor uses.

The recommended freshwater invertebrate test species is the amphipod, Hyalella azteca.  H. azteca is recommended over other standard test species (e.g., Daphnia magna) due to its much greater sensitivity to pyrethroids compared to D. magna.  Hyalella is also a recommended test species for sediment toxicity testing which enables toxicity extrapolations to be made among water column and benthic exposures within the same species.  The 850.1020 test guideline for Gammarid amphipods is recommended with appropriate modifications to address specific testing needs of H. azteca.  The registrant should submit a test protocol prior to conducting these TEP studies that documents the rationale for the TEP selection and details of the testing procedure for H. azteca.

The Agency notes that the ratios of synergist (PBO or MGK-264) to prallethrin expected in the aquatic environment may be much greater than those used in the formulated products, due in part to the different fate properties of the synergists and prallethrin.  As available data suggest greater toxicity enhancement can occur at higher synergist-to-active ingredient ratios, it is possible that greater toxicity enhancement may occur in the natural environment compared to that measured for formulated products.  To address this concern, the Agency will attempt to bridge results from ongoing "comprehensive" synergist testing at varying synergist-to-active ingredient ratios to address varying ratios of PBO/MGK-264 to prallethrin that are expected to occur in aquatic ecosystems.  However, should the available data be insufficient to enable scientifically defensible bridging to be conducted at the time of the forthcoming prallethrin ecological risk assessment, the Agency may apply a "conservative" toxicity enhancement factor to address the uncertainty regarding differences in synergist-to-prallethrin ratios in the aquatic environment versus those tested using formulated products.  The registrant may wish to submit additional data on prallethrin/synergist toxicity at varying ratios that would be expected to occur in the aquatic environment to address this potential uncertainty.

   * Guideline Number: 850.1075  -  Acute Freshwater Fish Toxicity (TEP): Acute toxicity data of prallethrin TEPs with the synergists PBO and MGK-264 are requested for freshwater invertebrates because there are registered outdoor uses of prallethrin that may result in significant exposure to water bodies.  Products with these synergists are likely to cause increased toxicity to non-target aquatic species as demonstrated by the mysid acute toxicity study with the TEP MULTICIDE Fogging Concentrate 2798 (Reg No. 1021-1795).  Since available information indicates that greater toxicity enhancement can occur at higher synergist-to-active ingredient ratios, selection of the TEPs for testing should include those with the highest synergist-to-active ingredient ratio and are registered for outdoor uses.  The registrant should submit a test protocol prior to conducting these TEP studies that documents the rationale for the TEP selection.  The Agency notes that the ratios of synergist (PBO or MGK-264) to prallethrin in the aquatic environment that may be much greater than those used in the formulated products, due in part to the different fate properties of the synergists and prallethrin.  As available data suggest greater toxicity enhancement can occur at higher synergist-to-active ingredient ratios, it is possible that greater toxicity enhancement may occur in the natural environment compared to that measured for formulated products.  To address this concern, the Agency will attempt to bridge results from ongoing "comprehensive" synergist testing at varying synergist-to-active ingredient ratios to address varying ratios of PBO/MGK-264 to prallethrin that are expected to occur in aquatic ecosystems.  However, should the available data be insufficient to enable scientifically defensible bridging to be conducted at the time of the forthcoming prallethrin ecological risk assessment, the Agency may apply a "conservative" toxicity enhancement factor to address the uncertainty regarding differences in synergist-to-prallethrin ratios in the aquatic environment vs. those tested using formulated products.  The registrant may wish to submit additional data on prallethrin/synergist toxicity at varying ratios that would be expected in the aquatic environment to address this potential uncertainty.

   * Guideline 850.1350  -  Aquatic invertebrate life cycle (saltwater): Aquatic invertebrate life cycle toxicity data have not been submitted for an estuarine/marine species creating uncertainty for estimating risk to these organisms from chronic exposure to prallethrin.  In addition, acute toxicity data show that the mysid shrimp is the most sensitive aquatic animal.  In the absence of this data, approaches that may be used to estimate toxicity to estuarine/marine invertebrates from chronic exposure to prallethrin include using estuarine/marine invertebrate toxicity data for other pyrethroids to extrapolate from existing acute toxicity data for estuarine/marine invertebrates and/or applying an acute to chronic ratio (ACR) for freshwater invertebrates to existing acute toxicity data for estuarine/marine invertebrates.

   * Guideline 850.5400  -  Aquatic plant growth (algal): Algal toxicity data have not been submitted creating uncertainty for estimating risk to algal species from exposure to prallethrin.  In the absence of this data, algal and aquatic vascular plant toxicity data for other pyrethroids may be used to extrapolate from the available toxicity data for aquatic vascular plants to aquatic non-vascular species.

Data from the following guideline studies are considered to have low potential to add value to the ecological risk assessment for prallethrin:

   * Guideline 850.2100  -  Avian oral toxicity (passerine species): Acute avian oral toxicity data are required for either one waterfowl or one upland game species and one passerine species under the 40 CFR Part 158 (CFR 40 2008) data requirements for conventional pesticides.  Data have not been submitted for a passerine species.  The most recent Agency ecological risk assessment to address the risk of prallethrin use to birds found that no acute or chronic LOCs for birds were exceeded (D23929, D291569, D257565).  Estimating EECs in T-REX using conservative estimates for number of applications (i.e., 142) and application interval (i.e., 1 day) for a typical outdoor individual application rate of prallethrin (i.e., 0.0014 lb a.i./A; 142*0.0014 lb a.i./A = ~0.2 lb a.i./A [maximum application rate/year]) indicates that passerines would have to be at least 5 times more sensitive to prallethrin to alter risk conclusions, and this would only be for acute exposures of small birds consuming short grass exclusively.  For all other feeding guilds, passerines would have to be 10 to 100 times more sensitive to alter risk conclusions.  In the absence of this data, acute passerine oral toxicity data from other pyrethroids may be used to extrapolate the toxicity of prallethrin to passerine species.

   * Guideline 850.1400  -  Fish early-life stage (saltwater): Fish early-life stage toxicity data have not been submitted for an estuarine/marine species.  In the absence of this data, an acute to chronic ratio (ACR) for freshwater fish may be applied to existing acute data for estuarine/marine fish to estimate toxicity to estuarine/marine fish from chronic exposure to prallethrin.

   * Guideline 850.1500  -  Fish life cycle (freshwater and saltwater): Fish life cycle toxicity data have not been submitted for a freshwater species or estuarine/marine species.  In the absence of this data, data from the acceptable fish early-life stage toxicity study (MRID 44729604) may be used to characterize risk to fish from chronic exposure to prallethrin.

Table 9-2.  Available Ecological Effects Data for Aquatic Animals Exposed to Prallethrin and Remaining Data Gaps.
Guideline
Description
MRID/ Accession
Classification
                                   Data Gap?
Comments
850.1010
Acute toxicity
freshwater invertebrates
41321810 (TGAI)
      --         (TEP)
Acceptable
--
                                      No
                                      Yes
Data are requested for a TEP with prallethrin and synergist, using Hyalella azteca as the test species.

850.1025
850.1055
Acute toxicity
estuarine/marine mollusk
44729601 (TGAI)
Acceptable
                                      No

850.1035
850.1045
Acute toxicity
estuarine/marine invertebrate
44729603 (TGAI)
48055901 (TEP)
Acceptable
Acceptable
                                      No

850.1075
Acute freshwater fish toxicity
(cold water species)
41321809 (TGAI)
      --         (TEP)
Acceptable
--
                                      No
                                      Yes
Data are requested for a TEP with prallethrin and synergist.

Acute freshwater fish toxicity
(warm water species)
41321808 (TGAI)
      --         (TEP)
Acceptable
--
                                      No
                                      Yes

850.1075
Acute toxicity
estuarine/marine fish
44729602 (TGAI)
Acceptable
                                      No

850.1300
Aquatic invertebrate
 life cycle
(freshwater)
44729605 (TGAI)
Acceptable
                                      No

850.1350
Aquatic invertebrate
 life cycle
(saltwater)
--
--
                                      Yes
Aquatic invertebrate life cycle toxicity data for an estuarine/marine species are required under 40 CFR Part 158 if the product is expected to enter the environment in significant concentrations because of its expected use or mobility patterns.  Therefore, this is identified as a data gap.
850.1400
Fish early-life stage
(freshwater)
44729604 (TGAI)
Acceptable
                                      No

850.1400
Fish early-life stage
(saltwater)
--
--
                                      Yes
Fish life cycle toxicity data for an estuarine/marine species are required under 40 CFR Part 158 if the product is expected to enter the environment in significant concentrations because of its expected use or mobility patterns.  Therefore, this is identified as a data gap.
850.1500
Fish life cycle
(freshwater)
--
--
                                      Yes
Fish life cycle toxicity data for a freshwater species are required under 40 CFR Part 158 if the product is expected to be transported to water from the intended use site.  Therefore, this is identified as a data gap.

Fish life cycle
(saltwater)
--
--
                                      Yes
Fish life cycle toxicity data for an estuarine/marine species are required under 40 CFR Part 158 if the product is expected to enter the environment in significant concentrations because of its expected use or mobility patterns.  Therefore, this is identified as a data gap.
850.1735
850.1740
Whole sediment:
 acute invertebrates
(freshwater and marine)
47762401 (TGAI)
Supplemental
                                      No
For MRID 47762401, there is uncertainty regarding the accuracy of the LC50 values given potential interference from the solvent.  Repeating this study has a low potential to add value to the ecological risk assessment.

Table 9-3.  Available Ecological Effects Data for Terrestrial Animals Exposed to Prallethrin and Remaining Data Gaps.
Guideline
Description
MRID/
Accession
Classification
                                   Data Gap?
Comments
850.2100
Avian oral toxicity  (upland game or waterfowl species)
41321804 (TGAI)
41321805 (TGAI)
Supplemental
Acceptable
                                      No

Avian oral toxicity
(passerine species)
--
--
                                      Yes
Avian acute oral toxicity data are not available for passerines.  These data are required under the new 40 CFR Part 158.  Therefore, this is identified as a data gap.
850.2200
Avian dietary toxicity
(upland game species)
41321806  (TGAI)
Acceptable
                                      No

Avian dietary toxicity
(waterfowl species)
41321807 (TGAI)
Acceptable
                                      No

850.2300
Avian reproduction (upland game species)
43773403 (TGAI)
Acceptable
                                      No

Avian reproduction (waterfowl species)
43797604 (TGAI)
Acceptable
                                      No

850.3020
Honeybee acute contact toxicity
41321823 (TGAI)
Acceptable
                                      No

850.3030
Honeybee toxicity of residues on foliage
43749301 (Form)
47431601 (TEP)
Acceptable
Acceptable
                                      No

Form = formulation

Table 9-4.  Available Ecological Effects Data for Plants Exposed to Prallethrin and Remaining Data Gaps.
Guideline
Description
                                     MRID
                                Classification
                                   Data Gap?
Comments
850.4100
Tier I
Seedling emergence
(terrestrial plants)
                                47431602 (TEP)
                                  Acceptable
                                      No
In the Tier I seedling emergence study, an inhibition of greater than 25% was observed for sugarbeet emergence (32.4%).  Therefore, a Tier II seedling emergence test with sugarbeets is necessary.  In the same study, the mean of the treated group was significantly less than the mean of the control group for the following species and endpoints: tomato emergence; wheat dry weight; and soybean dry weight.  Therefore, a NOEC could be determined for these species, and Tier II seedling emergence tests are recommended for tomato, wheat, and soybean to reduce uncertainty in determining risk to endangered plants.
850.4225
Tier II
Seedling emergence
(terrestrial plants)
                                      --
                                      --
                                      Yes

850.4150
Tier I
Vegetative vigor (terrestrial plants)
                                47431603 (TEP)
                                  Acceptable
                                      No

850.4400
Tier II
Aquatic plant growth (aquatic vascular plant toxicity)
                                48055902 (TEP)
                                  Acceptable
                                      No

850.5400
Tier I
Aquatic plant growth
(algal toxicity)
                                      --
                                      --
                                      Yes
Toxicity data for algal species are required under 40 CFR Part 158.  Therefore, this is identified as a data gap.

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