Page 2 of 41 This document is intended to provide an ov erview of what is currently known and the uncertainties regarding the environmental fate and ecological effects associated with tetramethrin and its transformation products. It describes the preliminary eco logical risk hypot hesis and the processes that will be used dur ing the completion of drinking wa ter exposure and ecological risk assessments in support of registra tion review. This document also identifies data gaps and the importance of obtaining additiona l studies to address data ga ps to the risk assessment.Page 3 of 41 

# Problem Formulation for the Ecological Risk Assessment in Support of the Registration Review of
Tetramethrin

1,3,4,5,6,7-hexahydro-1,3-dioxo-2 H -isoindol-2-yl)methyl 2,2- dimethyl-3-(2-methyl-1- propenyl)cyclopropanecarboxylate

CAS#: 7696-12-0

P

repared b y : Elyssa Gelmann, Biologist Wm. J. Shaughnessy, PhD, Environmental Scientist U. S. Environmental Protection Agency Office of Pesticide Programs

E nvironmental Fate and E ff ects Division

E nvironmental Risk Branch I I 1200 Pennsylvania Ave., NW

M ail Code 7507P Washington, DC 20460 R eviewed b y : Brian Anderson, Branch Chief Reuben Baris, Environmental Scientist Greg Orrick, Environmental Scientist Keith Sappington, Senior Biologist Christina Wendel, BiologistPage 4 of 41 Table of Contents 1. Purpose ................................................................................................................... .................... 6 2. Nature of Regulatory Action ............................................................................................... ....... 6
3. Conclusions from Previous Risk Assessments .......................................................................... 6
4. Stressor Source and Distribution .......................................................................................... ..... 8
4.1. Mechanism of Action ..................................................................................................... ..... 8 4.2. Overview of Pesticide Usage ............................................................................................. . 9 4.3. Environmental Fate and Transport .................................................................................... 12 5. Receptors.................................................................................................................. ................ 16 5.1. Effects to Aquatic Organisms ........................................................................................... 17 5.2. Effects to Terrestrial Organisms ....................................................................................... 18 5.3. Degradate toxicity ...................................................................................................... ....... 19 5.4. Ecological Incidents .................................................................................................... ...... 19 6. Ecosystems Potentially at Risk ............................................................................................ .... 19 7. Assessment Endpoints ...................................................................................................... ....... 20 8. Conceptual Model ........................................................................................................... .......... 20 8.1. Risk Hypothesis ......................................................................................................... ....... 20 8.2. Conceptual Diagram ...................................................................................................... ... 21 9. Analysis Plan ............................................................................................................. .............. 22
9.1. Stressors of Concern .................................................................................................... ..... 22 9.2. Measures of Exposure .................................................................................................... ... 23
9.3. Measures of Effect ...................................................................................................... ...... 26 9.4. Integration of Exposure and Effects ................................................................................. 28

9.4.1. Deterministic and Probab ilistic Assessment Methods ............................................... 28 9.5. Endangered Species Assessments ..................................................................................... 28 9.6. Drinking Water Assessment ............................................................................................. 2 9 9.7. Clean Water Act Programs ............................................................................................... 29 9.7.1 Aquatic Life Criteria and Aquatic Life Benchmarks .................................................... 29 9.7.2 Impaired Water Bodies ................................................................................................ 29 10. Endocrine Disruptor Screening Program ............................................................................... 30 11. Preliminary Identifica tion of Data Gaps ................................................................................ 3 1

11.1. Fate ................................................................................................................... ............... 31
11.2. Effects ................................................................................................................ ............. 32
12. References ............................................................................................................... ............... 38Page 5 of 41 List of Tables

Table 1. Outdoor uses of tetramethrin ......................................................................................... . 10
Table 2. Non-food and non-feed use patterns subject to the re-regis tration and registration review
of tetramethrin ............................................................................................................... ................ 11
Table 3. Chemical structures of tetr amethrin and transformation products ................................. 13
Table 4. Nature of the chemical stressor: Physical and chemical properties ............................... 15 Table 5. Summary of the most sensitive endpoints from submitted toxicity studies for
tetramethrin .................................................................................................................. ................. 16
Table 6. Available environmental fate data fo r tetramethrin and remaining data gaps ............... 31 Table 7. Available ecological effects data for terrestrial animals exposed to technical tetramethrin and remaining data gaps .......................................................................................... . 32 Table 8. Available ecological effects data for aq uatic animals exposed to technical tetramethrin and remaining data gaps........................................................................................................ ........ 33 Table 9. Available ecological eff ects data for plants exposed to tetramethrin and remaining data

gaps .......................................................................................................................... ..................... 36

List of Figures

Figure 1. Conceptual diagram depicting sources of exposure, potential receptors and adverse effects from the supported uses of tetramethrin. Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological risk............................................................... 21Page 6 of 41 

## 1. Purpose

The purpose of this problem formulation is to pr ovide an understanding of the environmental fate and ecological effects of the registered uses of tetramethrin. Tetramet hrin is part of the pyrethroid class of pesticides and was first registered in 19 68. It is a broad spectrum, nonsystemic, synthetic pyrethroid used to cont rol flying and crawling in sects in a number of commercial, horticultural and residential applica tions. Commercial appl ications include space and crack-and-crevice treatment in a variety of commercial, industri al, residential, and
institutional sites. Horticultu ral applications include foliar and f ogger treatment on non-food plants. Residential uses include pest contro l in homes and outdoor domestic structures, on gardens and direct application to cats, dogs and horses. There are no agricultural (food) uses of
tetramethrin.

This document will provide a plan for analyzing data relevant to tetram ethrin and for conducting environmental fate and ecological risk, and enda ngered species assessments for its registered uses. Additionally, this problem formulation is intended to identif y data gaps, uncertainties, and potential assumptions used to address those uncertainties, relative to characterizing the ecological risk associated with the registered us es of tetramethrin.



## 2. Nature of Regulatory Action

The Food Quality Protection Act of 1996 mandated the United St ates Environmental Protection Agency (EPA) to implement a new program for assessing the risks of pesticides, i.e ., registration review ( http://www.epa.gov/oppsrrd1/ registration_review/ ). All pesticides distributed or sold in the United States generally must be registered by EPA. The decision to register a pesticide is
based on the consideration of scie ntific data and othe r factors showing that it will not cause unreasonable risks to human health, workers, or the environment when used as directed on product labeling. The registration review program is intended to ensure that, as the ability to assess risk evolves and as polic ies and practices change, all regi stered pesticides continue to meet the statutory standard of no unreasonable adverse effects to human health and the environment. Changes in science, public policy, and pe sticide use practices will occur over time. Through the new registration review program, the Ag ency periodically reevaluates pesticides to ensure that as change occurs, products in the marketplace can be used safely.

As part of the implementation of the new Regist ration Review program pur suant to Section 3(g) of the Federal Insecticide, Fungi cide and Rodenticide Act (FIFRA ), the Agency is beginning its
evaluation to determine whether tetramethrin continues to meet the FIFRA standard for registration. This problem formulation for the e nvironmental fate and ecological risk assessment chapter in support of the registra tion review is intended for the initial docket opening the public phase of the review process.



## 3. Conclusions from Previous Risk Assessments

The Agency has conducted a comprehensive ecologi cal risk assessment on tetramethrin that serves as a basis for this problem formulation. This risk assessment is briefly summarizedPage 7 of 41 below. Note that this assessment (the RED) di d not quantitatively assess environmental risks of tetramethrin due to assumptions of low exposur e and rapid degradation. In light of updated environmental risk assessment practices and re quirements for a comprehensive, national scale risk assessment to endangered species, the re gistration review proce ss will incorporate a quantitative evaluation. This update d approach is described in th e Analysis Plan below (Section 9).

The Reregistration Eligibility Decision (RED) document for Tetramethrin (USEPA, 2008) was signed on June 23, 2008, and is available on the Fe deral Docket Management System (FDMS), available at http://www.regulations.gov ( document #EPA-HQ-OPP-2008-0014-0019). The
Environmental Fate and Effects Di vision (EFED) chapter of the RED was finalized on February 5, 2008 and is available on the FDMS (doc ument #EPA-HQ-OPP-2008-0014-0009). The major conclusions presented in the RED were as follows:

 Exposures were not quantified because curr ent exposure models are geared toward widespread uses such as agriculture or public health uses and tetram ethrin use patterns do not approach these scales. The localized use pattern of tetramethrin, combined with low total pounds used on a national basis, and rapid degradation due to photolysis and hydrolysis, make it highly unlikely that non-targ et organisms will be exposed at harmful
levels.

 Based on the available ecotoxicity data, th e most acutely sensitive organisms totetramethrin are fish, aquatic invertebrates, and insects. Tetramethrin is practically nontoxic to birds and mammals on an acute basi s. The only chronic (reproductive) data
submitted was for the rat. Th e no-adverse-effect-concentrat ion (NOAEC) was relatively low (25 mg/kg/day); however, quick degradatio n of tetramethrin was expected to reduce the amount of time that exposure po tential would reach this level.

 The only taxa considered at risk were terrest rial invertebrates present at the time and place of localized spraying.

 No toxicity data were available for the tr ansformation products. Only one product (acidNPY) retained the complete ester structure of the parent, so it may be expected to retain some of the parent compound’s efficacy. Ho wever, since it too is subject to rapid hydrolysis, exposure to acid-NPY is unlikely.

The RED identified ecological effect s data gaps for tetramethrin. There were no toxicity data available for estuarine/marine animals, no chr onic toxicity data for any taxa except mammals ( i.e. , birds, reptiles, amphibians, fish, aquatic inve rtebrates, or terrestrial invertebrates), and no guideline plant studies. The RE D did not request any additional data submissions due to the limited exposure potential and rapi d degradation to non-toxic degrad ates, but noted that the need
for additional studies would be r eevaluated during registra tion review. No new fate or ecological effects data has been submitted for tetramethrin since the completion of the RED.

The RED was updated in April 2010 (USEPA, 2010) in response to comments from registrants, and the updated version is available on the FDMS (document #EPA 738-R-08-012). ThePage 8 of 41 updates included revision to human health risk as a result of a higher applic ation rate for aerosol space sprays, additional human health studies submitted, and additional cautionary label language. No changes to ecological risk conclusions or data needs were made in the 2010
amended RED.

As stated in the RED, tetramethrin ma y be co-formulated with synergists ( e.g. , piperonyl butoxide (PBO) and MGK-264), other active ingredients such as other pyrethrins and pyrethroids ( e.g. , permethrin, S-methoprene, D-allethrin, D-phe nothrin, resmethrin, and cypermethrin), and growth inhibitors ( e.g. , fenoxycarb). These other active ingredients are more persistent than tetramethrin, and provide resi dual activity against insects not exposed initially. The RED addresses effects from use of tetramethrin only. The EFED Registration Review Problem Formulation for Piperonyl Butoxide , dated December 13, 2010, discus ses the need for synergist
data. The PBO Problem Formulation is availa ble in the PBO registra tion review docket at www.regulations.gov (EPA-HQ-OPP-2010-0498).



## 4. Stressor Source and Distribution

4.1. Mechanism of Action

Tetramethrin is a member of the pyrethroid class of pesticides and was first registered in 1968. It is a broad spectrum, non-systemic , synthetic pyrethroid used to control flying and crawling insects in a number of commercial, horticultural and residential applicat ions. It is a rapid knockdown agent against flying and cr awling insects; however, it is generally combined with a synergist (PBO or MGK-264) and/or another pyrethroid for greater e ffectiveness. This is largely due to the longer residual activity of the synergists and other mo re persistent co-formulations.

Tetramethrin is a nerve cell membrane sodium channel modulator, which interferes with
entrance of sodium ions into th e channel, leading to hyperactivity of the nervous system which can result in paralysis and/or death. Pyre throids, including tetr amethrin, bind to the α subunit of
the sodium channel and slow the activation (opening), as well as th e rate of inactivation (closing) of the sodium channel, leading to a stable hyper-excitable state. Sodium channels then open at more hyperpolarized potentials, an d are held open longer, allowi ng more sodium ions to cross and depolarize the neuronal membrane. Type I pyr ethroids such as tetr amethrin prolong channel opening only long enough to cause repetitive firi ng of action potential (repetitive discharge), while type II pyrethroids hold the channels open for longer periods, causing the membrane potential to become depolarized to the point at which generation of action potential is not possible (Shafer et al. , 2005).Page 9 of 41 Upon absorption, pyrethroids are rapidly meta bolized through two major biotransformation pathways: hydrolysis of the es ter linkage and oxidation of th e alcohol moiety by cytochromes P450. PBO inhibits cytochromes P450 and there by 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). Exposure to pyrethro ids along with PBO in creases the toxicity of the pyrethroids to aqua tic invertebrates (Amweg & Weston, 2007; Weston & Lydy, 2010). MGK-264, another potentiator/synerg ist used with pyrethroids, ha s similar effects as those observed for PBO (Hodgson & Smart, 2001). Tetramet hrin may be co-formulated with either or both synergists, PBO and MGK-264, in numerous products.



### 4.2. Overview of Pesticide Usage

Commercial applications of tetramethrin incl ude space sprays, surface tr eatments, and crack and crevice treatments in a variety of industrial and institutional sites including: indoor non-food areas; animal premises (not used for human consumption); and outdoors as localized space and contact sprays on ornamental plants and perimete r treatments (sidewalks, entranceways, outside surfaces of buildings, etc.). Ho rticultural applications include foliar and fogger treatment on non-food plants. Residential uses include pest control in homes and outdoor domestic structures, on gardens, houseplants, clothing and bedding, pet premises, and dir ect application to cats, dogs
and horses. Outdoor residential uses are the same as outdoor commercial uses listed above.

Tetramethrin is formulated as pressurized liq uid, ready-to-use (RTU) liquids, emulsifiable concentrates, and liquid concentrat es, and is applied by aerosol can, aerosol can with injection tube, handheld sprayers, foggers, and mechanical sprayers. According to the labels, no agricultural, aerial or ground-spraying equipment ( e.g. , tractor-mounted) are permitted. The formulation of registered products and the total numbers of each breaks down as follows:

 3 - Technical

 24 - Formulation intermediates

 245 - Pressurized liquids

 2 - Pressurized gases

 5 - EC (Emulsifier concentration)

 19 - RTU (Ready to use)

 3 - SC (Suspended concentration)

Based on data provided to the Agency by the tetram ethrin registrants, it appears that tetramethrin usage has increased over the past few years. This is likely due to the fact that pyrethroids are
alternatives to severa l organophosphate pesticides, which are no longer registered for indoor residential areas. In the RED, the Agency estima ted annual usage of tetram ethrin to be between 15,000 and 30,000 pounds of active ingredient (lbs a.i) (USEPA, 2010). The most recent Agency estimate of annual usage is 310,000 lbs a.i. for indoor residential treatments alone (USEPA, 2011). This estimate is based on 2005 da ta, the most recent available. Tetramethrin use data is extremely limited and difficult to interpret because tetramethrin products may be stored for periods of time and pr oduced only as inventory is exhaus ted. In additi on, based on its localized use pattern and “use as needed” directions, sales or production data do not accurately reflect usage.Page 10 of 41 Based on use information provided to the Agen cy prior to the RED by the tetramethrin registrants, the majority of tetramethrin use is in residential outdoor spaces . It appears residential
indoor use sites and institutional and industrial site s make up a small percentage of tetramethrin use. Further, tetramethrin is primarily used by residential consumers as opposed to pest control operators (PCOs). Sources suggest that less th an 1,000 lbs a.i. are used annually by professional applicators (USEPA, 2010).

Outdoor uses may result in exposure of non-targ et organisms; however, because there are no widespread agricultural or public health ( e.g. , mosquitocide) uses, exposure of non-target organisms is limited to spot tr eatments in localized areas.

Outdoor uses considered in this assessment are list ed in Table 1. These uses are consistent with those specified in the 2010 Revised RED. No new uses have been approved since 2010.

Table 1. Outdoor uses of tetramethrin Use Group Crop/Site Terrestrial Non-Food Crop • Barns/Barnyards/Auction Barns • Commercial Storages/Warehouses/Premises
• Commercial/Institutional/Industrial

Premises/Equipments(Outdoor) • Compost/Compost Piles • Food Processing Plant Premises (Nonfood

Contact) • Nonagricultural Outdoor Buildings/Structures
• Ornamental and/or Shade Trees
• Ornamental Herbaceous Plants • Ornamental Non-flowering Plants • Ornamental Woody Shrubs and Vines
• Paths/Patios
• Recreational Areas • Refuse/Solid Waste Sites (Outdoor) Terrestrial Food+Feed Crop • Compost/Compost Piles Outdoor Residential • Household/Domestic Dwellings Outdoor
Premises
• Ornamental and/or Shade Trees
• Ornamental Herbaceous Plants • Ornamental Non-flowering Plants • Ornamental Woody Shrubs and Vines
• Paths/Patios • Refuse/Solid Waste Containers (Garbage Cans)
• Wood Protection Treatment to

Buildings/Products Outdoor

Some of the products listed are for indoor use (total release indoor fogger), while others may be used as outdoor perimeter treatments, outdoor ge neral surface sprays, directed spray, crack and crevice or spot treatment, or spray.Page 11 of 41 Application rates vary dependi ng on the use patter n, indoor or outdoor use, consumer, professional or commercial operator use. Typical concentrations of active ingredient (a.i.) in residential use products, including RTU ( e.g. , ant and roach sprays, wasp and hornet sprays) and indoor and outdoor aerosols or aq ueous sprays for crawling and flying insects, range between
0.1% and 0.35%. Indoor to tal release foggers are typically around 0.54% a.i. Sprays designed for use on pets are typically 0.063% a.i. Emulsifiable concentrate formulations are approximately 2.5% a.i. Application rates are given in pounds per square foot, or per thousand square feet. This indicat es that widespread use ( i.e. , multiple acres) is not intended. The maximum single application rate to an outdoor site is 0.000035 lb a.i./ft 2 , this equa tes to 1.52
lb/acre.

Application rates for existing non -food use profiles are presented in Table 2. These rates reflect the current product labels as presented in the 20 10 Revised RED. Further, these rates may be subject to revision as product labels are curr ently undergoing change as part of the ongoing product re-registration process. Labels that are current when the registration review risk
assessment is conducted will be us ed for the risk assessment.

Table 2. Non-food and non-feed us e patterns subject to the re-regist ration and registration review of
tetramethrin Use Profile Maximum Application Rate (Application Method) % Active Ingredient

(% a.i.) Volume-based Area-based Space-based

General Indoor 1 and Outdoor Spray 2 (Trigger Pump Sprays, Low Pressure Hand Wand, Back Pack Sprayer) 0.20 0.02 lb a.i./gal
solution 0.00002 lb a.i./ft 2 (0.87 lb a.i./acre) 0.000002 lb a.i./ft 3

Aerosol Cans (Indoor & Outdoor Spray) 0.35 0.035 lb a.i./gal
solution 0.000035 lb a.i./ft 2 (1.52 lb a.i./acre) 0.0000035 lb a.i./ft 3

Indoor Total Release Fogger 1 0.54 n/a n/a 6 oz can / 4,600 ft 3

Animal Treatment (Aerosol Can) 0.063 n/a n/a n/a

Outdoor Jet Sprays (intended for wasp and hornet use only) 0.20 1-2 sec burst n/a n/a

Outdoor Fogging Devices 2, 3

0.10 n/a 0.0000001 lb
a.i./ft 2 (0.004 lb a.i./acre) 1.25E-08 lb a.i./ft 3

Source: Revised tetramethrin RED (USEPA, 2010).

1 Use sites include but are not limited to: commercial, indust rial, institutional, and residential locations; agricultural structures and equipment; eating esta blishments; animal kennels and sleeping quarters; empty greenhouses; hospitals.

2 Use sites include but are not limited to: commercial, industrial, institutiona l, and residential locations; compost piles; ornamental plants; patios; paths.

3 Excludes RTU fogging devices.

The synergists PBO and MGK-264 are commonly co -formulated with tetramethrin to increase efficacy, thereby increasing toxicity to target insects. Available literature data also support the potential for synergism in the environment (Amweg et al. , 2006; Weston et al. , 2006). It is important to recognize that in general, active ingred ients and synergists have differing fate properties and therefore would be expected to occur in the envir onment at different times and atPage 12 of 41 different concentrations than present in the end use product.

Currently data on the degree to which the toxicity of pyrethroid active ingred ients is enhanced by varying ratios of PBO and MGK-26 4 are needed to address the ecological risk of products when co-applied with PBO or MGK-264. Based on data on the acute toxicity of pyrethroids and PBO to target insect specie s, it is known that the degree of toxici ty enhancement increases at higher PBO:pyrethroid ratios (or absolute concentrations) and that this toxicity enhancement is greater than simple additive toxicity (Stewart, 1998). The Agency is currently evaluating a proposed study protocol that will quantify the enhancemen t of acute toxicity of pyrethroids to the freshwater amphipod, Hyalella azteca , by simultaneous exposur e to PBO at varying PBO:pyrethroid ratios. It is expected that th is comprehensive testing strategy, when augmented with similar acute toxicity data with freshwater fish and ot her selected pesticide active ingredients, will facilitate bridging of the synerg ist 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 tetramethrin and synergists (PBO and MGK-264), the Agency is requesting acute toxi city studies of tetramethrin typical end-use products (TEPs) that are co-f ormulated with PBO and MGK-264 at the highest synergist:active ingredie nt ratio. These TEPs should correspond to those formulated products
that are labeled for outdoor uses with the greatest potential fo r aquatic exposures and would be
conducted with a freshwater fish and a freshwat er invertebrate. Addi tional discussion of the need for combined tetramethrin:synergist toxici ty data is provided in Section 11.2 (Preliminary Identification of Data Gaps for Effects).



### 4.3. Environmental Fate and Transport

In general, tetramethrin is not very persiste nt in the environment. The major routes of dissipation for tetramethrin include hydrolysis a nd photolysis in shallow, non-turbid water. Tetramethrin is more susceptible to hydrolysis at pH 7 and 9 than pH 5. In an acceptable hydrolysis study (MRID: 41995006), tetramethrin hydrol yzed with half-lives of 16-20 days at pH 5, approximately 1 day at pH 7, and < 21 minutes at pH 9 in sterile buffered aqueous
solutions that were incubated at 25 C for 30 da ys. At pH 5 the main degradates were (1RS)- trans-chrysanthemic acid (trans-CRA) whose amounts increased to 70.6% at day 30, and 3,4,5,6- tetrahydrophthalic acid (THPA) whose maximum was 66.6% at day 30. The other degradates amounted to less than 10% of the applied. At pH 7 trans-CRA and THPA were again the main degradates, amounting to a maximum of 100% a nd 97.3% at day 30, respectively. At pH 9 the primary degradates were trans-CRA, TH PA, and 3,4,5,6-tetrahydrophthalamic acid (THAM) amounting to a maximum of 100% , 68.8%, and 32.7%, respectively.

In an aerobic soil metabolism study tetramethr in degraded in sandy loam soil under aerobic conditions with half-lives ranging from 32.7-33 .3 days (MRID 42563301). In this study seven degradates were identified incl uding one (acid-NPY) that retains the entire ester structure and possibly the mode of action of th e parent tetramethrin. However, it too is subject to rapid hydrolysis, and therefore, exposure to acid-NPY at ecologically relevant levels is unlikely. The seven degradates identified included:Page 13 of 41  3,4,5,6-Tetrahydrophthalimidomethyl (1 RS )- trans -2,2-dimethyl-3-(2-3,4,5,6- Tetrahydrophthalimide (THPI);

 N-Hydroxymethyl-3,4,5,6-tetrahyd rophthalimide (MTI);

 3,4,5,6-tetrahydrophthalic acid (THPA);

 1-hydroxy-1,2-cyclohexanedicar boxylic acid (1-OH-HPA);

 (1 R ,3 R )-2,2-Dimethyl-3-(2-methylpr op-1-enyl)cyclopropanecarboxylic (d-t -CRA); and

 carboxyprop-1-enyl)cyclopropaneca rboxylate (acid-NPY ); and

 (1 R ,3 R )-2,2-Dimethyl-3-carboxycyclopropa necarboxylic acid (COOH-CA)

The major degradates identified in the aer obic soil metabolism study (MRID 42563301) were 1- OH-HPA, COOH-CA, and carbon dioxide. The chemical structures of parent tetramethrin and its transformation products are presented in Table 3.

Table 3. Chemical structures of te tramethrin and transformation products

Structure Name Formation
Mechanism % of Applied Radioactivity Degradate
Class

Parent 1,3,4,5,6,7-hexahydro-1,3-
dioxo-2 H -isoindol-2-yl)methyl 2,2-dimethyl-3-(2-methyl-1- propenyl)cyclopropanecarboxyl

ate N/A N/A N/A

1-OH-HPA 1-hydroxy-1,2- cyclohexanedicarboxylic acid Aerobic soil
metabolism 44.3% at day 58 Major

Acid-NPY carboxyprop-1- enyl)cyclopropanecarboxylate Aerobic soil
metabolism Minor

THPI 3,4,5,6- Tetrahydrophthalimidomethyl (1 RS )- trans -2,2-dimethyl-3-(2- 3,4,5,6-Tetrahydrophthalimide Aerobic soil
metabolism <5.2% Minor H 3 C

C H 3

C H

3 H 3 C O

O

N

O O

O H

O O H O

O H

O

O H H 3 C

C H

3 H 3 C O

O

N

O O

N H

O OPage 14 of 41 THPA 3,4,5,6-tetrahydrophthalic acid Aerobic soil
metabolism

Hydrolysis 6.8% at day 30 Minor

MTI N-Hydroxymethyl-3,4,5,6- tetrahydrophthalimide Aerobic soil
metabolism <5.2% Minor

COOH-CA (1 R ,3 R )-2,2-Dimethyl-3- carboxycyclopropanecarboxylic
acid Aerobic soil
metabolism 24.3% at day 58 Major

chrysanthemic acid (1 R ,3 R )-2,2-Dimethyl-3-(2- methylprop-1- enyl)cyclopropanecarboxylic Aerobic soil
metabolism Hydrolysis Minor

In two acceptable field dissipation studies, tetramethrin dissipated from the upper 15 cm of soil
with a DT50 of 3 hours in a California st udy (MRID 42622401), and less than one hour in a Florida study (MRID 42622402).

Tetramethrin is very susceptible to degradati on by sunlight. Under most ecologically relevant conditions, tetramethrin can be expected to breakdown to le ss than half of the applied concentration within one day. In two studies tetramethrin phot odegraded upon exposure to sun lamp irradiation within 4 hours (MRIDs 164634 and 43773401).

Tetramethrin is slightly mob ile (United Nations Food and Agri culture Organization (FAO) soil mobility classification) in soil with Koc values ranging from 1,249-2,939 (MRID 41995007). Tetramethrin is not very soluble in water (1.83 mg/L) and adheres moderately to soil containing organic material. The mobility and degradatio n profiles suggest that surface and ground water supplies used for drinking water are at a reduced risk of being contaminated. However, because adsorption of tetramethrin is correlated with orga nic carbon content, it is likely to be somewhat more mobile in soils with lower organic matter content, such as coarse sand soils. O H

O O

O H

O H

N

O O

O

O H

O H O

H 3 C C H 3

O

O H

C H 3 H

3 C H

3 C H

3 CPage 15 of 41 At least 9 degradates were detected in a soil column leachate study (MRID 42212901), none of which exceeded 3.2% of the applied radioactivit y. The principal metabolites were THPA and
COOH-CA. Tetramethrin was not detected in the leachate.

Tetramethrin has a high vapor pressure (7.1x10 -6 mm Hg) and is considered volatile. It has an estimated Henry’s law constant of 1.7x10 -6 atm-m 3 /mol (USEPA, 2010).

Tetramethrin has a strong affinity to bind to orga nic solvent than it does to water indicating that when consumed, there is a potential for it to bind to fish or animal tissues. Also, estimated bioconcentration values (BCF=20) found for tetr amethrin indicate that bioaccumulation is not likely to be an exposure pa thway of concern (Hansch et al. , 1995).

Registrant-submitted data defining the physical and chemical properties of tetramethrin are
summarized in Table 4.

Table 4. Nature of the chemical stressor: Physical and chemical properties
Common name Tetramethrin Chemical name (1,3,4,5,6,7-hexahydro-1,3-dioxo-2 H

isoindol-2-yl)methyl 2,2-dimethyl-3-(2- methyl-1- propenyl)cyclopropanecarboxylate Pesticide type, such as herbic ide or insecticide Insecticide Chemical class Pyrethroid

CAS number 7696-12-0 Empirical formula C 19 H 25 NO 4 Molecular mass (g/mol) 331.41 Vapor pressure (mm Hg at 30 o C) 7.1E-06 Henry’s Law Constant at 25 o C (atm m 3 mol -1 ) 1.7E-06 Solubility in water (mg/L at 25 o C) 1.83 Octanol-water partition coefficient (Log K

ow ) at pH 7, 20 o C 4.6 Koc (mL/g) 1423 Hydrolysis ( t 1/2 , days) pH 5 16-20 pH 7 1 pH 9 <1 Photolysis ( t 1/2 , days) <1 Aerobic soil metabolism (DT 50 ) 32.7-33.3

BCF 20

With a log Kow value of 4.6, a BCF study would typi cally be required. However, tetramethrin is unlikely to reach a steady state in fish due to its rapid hydrolysis rate. Using the U.S. EPA’s Kow (based) Aquatic BioAccumulation Model ( KABAM version 1.0, 04/07/2009) the time to steady state is 13 days. The hyd rolysis half-life of tetramethrin exceeds this only in acidic waters. Therefore, a bioaccumulation assessment is not deemed necessary.Page 16 of 41 

## 5. Receptors

Consistent with the process described in th e Overview Document (USEPA, 2004), the risk assessment for tetramethrin will rely on a surrogate species approach. Toxicological data generated from surrogate test species, which are intended to be re presentative of broad taxonomic groups, are used to extrapolate to pote ntial effects on a variet y of species (receptors)
included under these ta xonomic 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 a nd indirect effects of tetramethrin on aquatic and terrest rial receptors. These include toxicity data on the technical grade active ingredient, degradates, and when available, formulated products. The open
literature studies are identif ied using EPA’s ECOTOXicology database (ECOTOX) (USEPA, 2007b), which employs a literature s earch engine for locating chemi cal toxicity data for aquatic life, terrestrial plants, and wildlife. The evalua tion of both sources of data can also provide insight into the direct and indirect effects of tetramethrin on biotic communities from loss of species that are sensitive to the chemical and from changes in st ructure and functional
characteristics of the a ffected communities.

Table 5 provides a summary of the taxonomic groups and most sensitive surrogate species tested to characterize the potentia l acute and chronic ecological effects of tetramethrin. In addition, the table provides a preliminary overview of the potentia l acute toxicity of te tramethrin by providing the acute toxicity classifications.

Table 5. Summary of the most sensitive endpoints from submitted toxicity studies for tetramethrin

Taxonomic

Group Surrogate Species Acute Toxicity (LC 50 or

LD 50 ) Acute Study MRID
and Classification Acute Toxicity
Classification Chronic
NOAEC Chronic Study

MRID

Birds 1 Bobwhite quail ( Colinus virginianus ) Oral

LD 50 >2250 mg a.i./kg 41609604 Acceptable Practically
nontoxic

No data No data Mallard duck ( Anas platyrhynchos )
and Bobwhite quail ( Colinus virginianus ) Dietary

LC 50 >5620 mg a.i./kg
diet 41609605/41609606 Acceptable/ Acceptable Practically
nontoxic

Mammals Laboratory rat ( Rattus norvegicus ) Oral

LD 50 >5000 mg/kg bw 42146405 Acceptable Practically
nontoxic Reproduction 25 mg/kg/day 00161842

Insects Honey bee ( Apis mellifera

L. ) Contact

LD 50 =0.155

μg/bee 41609613 Acceptable Highly toxic No data No dataPage 17 of 41 Taxonomic

Group Surrogate Species Acute Toxicity (LC 50 or

LD 50 ) Acute Study MRID
and Classification Acute Toxicity
Classification Chronic
NOAEC Chronic Study

MRID

Foliage
Residue
<3 hrs 41940801 Acceptable NA

Freshwater fish 2 Bluegill (Lepomis macrochirus) LC 50 =15.9 μg/L 41609607 Acceptable Very highly
toxic

No data No data Rainbow Trout ( Oncorhynchus mykiss ) LC 50 =3.7 μg/L 41609608 Acceptable Very highly
toxic

Freshwater
invertebrates Water flea ( Daphnia

magna ) Unreliable 41609609 Supplemental 3 Very highly
toxic No data No data

Estuarine/marine
fish -- No data No data NA No data No data

Estuarine/marine

invertebrates -- No data No data NA No data No data

Terrestrial plants

-- No data No data NA No data No data

Aquatic plants

and algae -- No data No data NA No data No data

1 Birds represent surrogates for terrest rial-phase amphibians and reptiles.

2 Freshwater fish may be surroga tes for aquatic-phase amphibians.

3 This study cannot be used quantitatively in a risk assessm ent and therefore does not fulfill the 850.1010 guideline requiremen t for an acute freshwater invertebrate toxicity test.



### 5.1. Effects to Aquatic Organisms

The acute toxicity of te chnical grade tetramethrin has been te sted in two species of freshwater fish, rainbow trout ( Oncorhychus mykiss ) and bluegill sunfish ( Lepomis macrochirus ). The 96-
hr LC 50 test results for freshwater fish ranged from 3.7 μg/L for rainbow trout (MRID 41609608) to 21 μg/L for bluegill sunfish (MRID 00121269) . Based on these studies, technical grade tetramethrin is classified as very highly toxic to freshwater fish and aquatic-phase amphibians.

The acute toxicity of technical grade tetramethrin has been tested in one freshwater invertebrate, Daphnia magna . The acute toxicity test for Daphnia magna resulted in a 48-hr EC 50 of 45 μg/L (MRID 41609609). This study is classified suppl emental and does not fulfill the guideline requirement for an acute freshwater inverteb rate study. Though the study used a flow-through method, there was significant decrease in the measured concentrations of the test substance over the course of the test. At test initiation, mean measured concentr ations were 53±8.3% of
nominal and at test termination mean measured concentrations were 13±2.3% of nominal. This equates to a 69-80% drop in measured test c oncentrations from 0 to 48 hrs. Measured concentrations were only provided for these two tim e points. This substan tial deviation from the guideline requirement of ≤ 20% change results in insufficie nt confidence in the exposure concentrations to use the study results quantitativel y in an ecological risk assessment. The 48-hr

EC 50 of 45 μg/L calculated using this study is ba sed on the mean measured concentrations. Using this data, technical grade tetramethrin is classified as very highly toxic to aquatic invertebrates on an acute exposure basis.Page 18 of 41 No chronic toxicity data are avai lable for freshwater fish or invertebrates. Additionally, no acute or chronic toxicity data are available for estuarine/ marine fish or invertebra tes. Toxicity data are also lacking for vascular and non-vascular aquatic pl ants. No toxicity da ta for any aquatic taxa are available for TEPs; thus no toxicity data are available on tetramethrin formulated with synergists. These studies were not requested in the 2008 RED. The studies were held “in
reserve” at that time.



### 5.2. Effects to Terrestrial Organisms

Acute oral and dietary t oxicity for tetramethrin have been tested in an upland game bird, bobwhite quail ( Colinus virginianus ) and acute dietary toxicity has also been tested in a waterfowl, mallard ( Anas platyrhynchos ). Acute oral and chroni c reproductive studies for laboratory rats were study submitted to the Hea lth Effects Division (HED) and used to assess effects to mammalian wildlife. Toxicity to te rrestrial invertebrates was tested by an acute contact study and a foliar residue study using the honey bee ( Apis mellifera ).

Tetramethrin is practically non-tox ic to birds on the basis of acute oral and dietary studies. The bobwhite quail oral toxicity study (MRID 41609604) resulted in an LD 50 >2250 mg/kg body weight (bw). Four avian dietary toxicity stud ies, two with bobwhite qua il and two with mallard, (MRIDs 00121262, 00121268, 41609605, 41609604) resulted in an LC 50 >5620 mg/kg diet. No passerine studies have been submitted to U.S. EPA or identified in the open literature.

Tetramethrin is practically non-toxic to mammals on an acute oral basis. An acute oral toxicity rat study (MRID 42146405) resulted in an LD 50 >5000 mg/kg bw. In a 2-generation reproduction study (MRID 00161842), tetr amethrin was administered to laboratory rats at various dietary concentrations. There was an effect on pup weight in the F 2 generation, which is considered a reproductive effect. The parent al NOAEL = 25 mg/kg-day in both sexes and the parental LOAEL = 150 mg/ kg-day for both sexes of F 0 and F 1 based on reductions in body weights and food consumption. The offspri ng NOAEL is 25 mg/kg/day and the LOAEL is 150 mg/kg-day based on reductions in pup body weights of the F 2 generation during lactation.

Tetramethrin is considered highly toxic to adul t honeybees on an acute contact exposure basis, there is uncertainty regarding the effects of the compound on honeybee larvae (brood). The acute contact honey bee study s ubmitted resulted in an LD 50 = 0.155 μg/bee (MRID 41609613). The toxicity of residues on foliage was tested using 0.3% tetramethrin aerosol on alfalfa (MRID 41940801). Honey bees exposed to sprayed foliage showed no treatment rela ted mortality at 3, 8, and 24 hours post treatment; residues decreased to a negligible level 3 hours post treatment.

No toxicity data are available for terrestrial plants. No toxicity data for birds or insects are available for TEPs; thus no toxicity data are available on tetramethr in formulated with synergists
for these taxa. While all of this data is ordina rily required for outdoor residential uses, these studies were not requested in th e 2008 RED due to low exposure assumptions. The studies were
held “in reserve” at that time.Page 19 of 41 

### 5.3. Degradate toxicity

The degradates of tetramethrin are identified in Section 4.3. The only degradate that retains the entire ester structure of the pare nt (and which therefore might retain the mode of action) is acidNPY.

No toxicity data are available for tetramethrin degradates. HED reviewed the metabolism of tetramethrin (MRIDs 42448901 and 42448902), and conc luded that for risk assessment, the parent compound, tetramethrin, is the only residue of t oxicological concern. EFED concurs with
this conclusion.



### 5.4. Ecological Incidents

A review of the Ecological Incident Informa tion System (EIIS, version 2.1.1), the ‘Aggregate Incident Reports’ (v. 1.0) data base, and the Avian Monitoring Information System (AIMS) for ecological incidents involving tetramet hrin was completed on 11 July 2011.

The searches of EIIS and AIMS identified no ec ological incidents involv ing tetramethrin. The
number of documented incidents in EIIS is believed to be a very small fraction of total mortality caused by pesticides for a variety of reasons. In cident reports for non-targ et organisms typically provide information only on mortality events and pl ant damage. Sub-lethal effects in organisms such as abnormal behavior, reduced growth an d/or impaired reproduction are rarely reported, except for phytotoxic effects in terrestrial plants . An absence of reports does not necessarily equate to an absence of incidents give n the nature of the incident reporting.

Incidents have been reported to the Agency in a ggregated incident reports . 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 a dverse effects to insects and other terrestrial invertebrates. For tetramethrin, registrants ha ve reported 1 minor fish and wildlife incident, 9 minor plant incidents, and no other non-targ et incidents between 1998 and 2009. Unless additional information on these aggregated incident s becomes available, they will be assumed to be representative of registered uses of tetramethrin in the risk assessment.



## 6. Ecosystems Potentially at Risk

Based on the use patterns of tetram ethrin, exposure of ecosystems is likely to be limited. There are no widespread uses of tetramethrin, such as application to agricultur al fields or mosquito spraying by public health agencies . Pet, clothing, and bedding applications could result in washoff and down-the-drain exposures through pet ba thing and laundering of clothing or bedding. However, these products account for only a small numb er of the registered uses so this exposure pathway is not expected to be significant.Page 20 of 41 Based on the available ecotoxicity information, the organisms facing th e greatest hazard are insects, fish and aquatic invertebrates. Thus, localized terrestrial and aquatic ecosystems in the immediate area of tetramethrin outdoor spraying ar e most likely to be affected. Terrestrial ecosystems potentially at risk could include area s immediately adjacent to treated structures and areas that may receive drift or runoff of residue s sorbed to suspended sediment. Areas adjacent to the aerosol spray treated areas could includ e lawns, ornamental plantings, and stream and pond edges. Aquatic ecosystems potentially at risk include water bodies adjacent to, or downstream from, the spray treated areas and might include impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as streams or rivers. In coastal areas, aquatic habitat also includes marine ecosystems, including estuaries.



## 7. Assessment Endpoints

Assessment endpoints represent the ac tual environmental value that is to be protected, defined by an ecological entity (species, community, or other entity) and its attribute or characteristics (EPA 1998). For tetramethrin, the ecological entities incl ude the following: birds, reptiles, terrestrialphase amphibians, mammals, freshwater fis h, freshwater aquatic-phase amphibians and invertebrates, estuarine/marine fish and invertebrates, terrestrial plants, insects, aquatic plants, and algae. The attributes for each of these ent ities include growth, repr oduction, and survival.



## 8. Conceptual Model

For a pesticide to pose an ecological risk, it must reach ecological r eceptors in biologically significant concentrations. An exposure pathway is the means by which a pesticide moves in the environment from a source to an ecological recepto r. For an ecological pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptors, an d a feasible route of exposure.

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



### 8.1. Risk Hypothesis

A risk hypothesis describes the predicted re lationship among the stressor, exposure, and assessment endpoint response along w ith the rationale for their sele ction. For tetramethrin, the following ecological risk hypothesi s is being employed for this national-level ecological risk

assessment:

Tetramethrin, when used in accordance with curre nt labels, can result in off-site movement of the compound via direct spray and spray drift leading to exposure of non-target plants and animals. Direct applications to and atmospheri c deposition to foliar surfaces may serve as a major source of tetramethrin exposure to w ildlife. Exposure in these environmental compartments will result in adverse effects upon the survival, growth, and reproduction of non-Page 21 of 41 target terrestrial and, to a lesser degree, aquatic organisms. These non-target organisms include federally-listed threatened and endangered species.



### 8.2. Conceptual Diagram

The environmental fate properties of tetramethrin indicate that direct spray, spray drift, and atmospheric deposition, and to a lesser degree runoff, represent potential transport mechanisms
of tetramethrin. These transport mechanisms ( e.g ., sources) are depicted in the conceptual model below (Figure 1) and result in the movement of tetr amethrin into terrestrial (soil and foliage), and to a lesser degree aquatic (water and sediment) ha bitats. The movement away from the site of application in turn represents exposure pathwa ys for a broad range of biological receptors of concern (non-target animals) and the potential attribute changes ( i.e. , effects such as reduced survival, growth and reproduction, in the receptors due to tetram ethrin exposure). EFED does
not believe that tetramethrin is a threat to contaminate groundwa ter because of its limited use and rapid hydrolysis.

Figure 1. Conceptual diagram depicting sources of exposure, pote ntial receptors and adv erse effects from the supported uses of tetramethrin. Dotted lines indica te exposure pathways that have a low likelihood of contributing to ecological risk.

As indicated in Figure 1, the po ssible exposure mechanisms considered are runoff, spray drift, and direct spray. While tetramethrin’s low pers istence suggests that transport may be limited under some conditions, and that the pesticide’s lo w use volume may limit concern for spray drift, the aerobic soil metabolism study shows that residues may be longer-lived in some
environments. Stressor Tetramethrin Outdoor Spraying

Source/ Transport Pathways Direct Deposition Runoff/
Erosion Spray
drift

Source/ Exposure
Media Terrestrial Food Residues (foliage,

fruit, insects Surface Water body

Exposure
Route ingestion gill/integument uptake and contact

Receptors

Attribute Changes Terrestrial Vertebrates Birds, Mammals, Reptiles, Terrestrial Phase Amphibians

Individual Animals
Reduced survival Reduced growth Reduced reproduction Aquatic
Vertebrates and

Invertebrates

Individual vertebrates
and invertebrates
Reduced survival Reduced growth Reduced reproduction Upland and
Wetland Soils

contact/root uptake

Upland and
Wetland Plants

Individual plants Reduced seedling emergence and vegetative vigor contact/root uptake

Aquatic
Plants

Reduced
Biomass Aquatic
Food Chain
bioaccumlation ingestion contact

Beneficial

Insects

Individual insects
Reduced survivalPage 22 of 41 

## 9. Analysis Plan

Most of the standard methods used by the Agency for assessing environmental risk are established for large-scale uses su ch as applications to agricultura l fields or public health uses. Conversely, tetramethrin us es considered here are lim ited to spot treatments ( e.g ., spraying a wasp hive), space treatments ( e.g ., aerosol can contents release in a storage room or other enclosed space), and ornamental applicati ons against crawling and flying insects ( e.g ., spraying hedges with an aerosol can). Thus, in this assessment, standard expected environmental concentrations (EECs) cannot be directly calculated (without ma jor assumptions) using the tools on which OPP typically relies. Th e difficulty in calculating standa rd EECs is due to a number of factors including non-standard use rates ( e.g ., “1-2 second burst,” “lbs a.i./ft 3” ) and estimations of the magnitude of use in a given area ( e.g ., a neighborhood or campsite) at a given time. The approach used in this risk assessment will be to use available tools and information to help quantitatively characterize the potential for risk instead of the more typical approach of comparing risk quotients (RQs) derived from Agency models to levels of concern (LOCs) (see the examples below).

Information regarding exposure includes the fo llowing factors: (1) small amounts are used outdoors at one time, (2) most outdoor uses are limited to spot treatments, and (3) methods of application ( i.e ., spray cans, coils, foggers) are not feasible for treating large spatial areas. Additionally, based on submitted data, there is a tendency for tetramethrin to sorb to surface soils, particularly in soils that are not low in organic matter. Furthermore, tetramethrin tends to photodegrade fairly quickly, and, as an early-generation pyreth roid, tetramethrin is one of the least persistent pyrethroids.

Although there are uncertainties rega rding the extent of use in resi dential settings , the cumulative exposure from multiple spot treatments across a partic ular setting is not likel y to be substantial.

This analysis plan will be revisited and may be revised depending upon a fu ll 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. At a minimum, EFED will undertake analyses as described in Section 9.2, to provide a prelim inary screening level estimates of potential exposures to surface water systems. As additi onal data become availa ble EFED will conduct further analyses, as appropriate, to refine these preliminary estimates. In formation that would be of particular interest includes am ount of tetramethrin and the asso ciated size of treated areas for
the various labeled uses.

Available monitoring data will be used to quali tatively characterize exposure. The Agency is aware of monitoring conducted by Federal and st ate agencies and this information will be
considered in the assessment to the extent that data on tetramethrin are available.



### 9.1. Stressors of Concern

The stressors of ecologic concern are the pare nt tetramethrin and th e synergists PBO and MGK264. One identified degrad ate of tetramethrin, carboxyprop-1-Page 23 of 41 enyl)cyclopropanecarboxylate (acid-NPY), retains th e ester linkage that is known to be needed for synthetic pyrethroid activity; ho wever, because hydrolysis of the ester moiety is very rapid in non-acid environments, consid eration of exposure to ac id-NPY is not necessary.

Tetramethrin is frequently co-formulated with synergists ( e.g. , PBO and MGK-264). These synergists increase the toxicity of tetramethri n, and may provide residual activity against insects not exposed initially. The EFED Registration Review Problem Formulation for Piperonyl

Butoxide , dated December 13, 2010, discusses the need for synergist data (available in the PBO registration review docket at www.regulations.gov (EPA-HQ-OPP-2010-0498)). The effect of synergists in combination with tetramethrin w ill be evaluated through toxicity studies using
TEPs formulated with PBO and TEPs formulated with MGK-264.

Evaluation of pesticide mixtures is beyond the sc ope of this assessment because of the myriad factors that cannot be quantified based on the ava ilable data. Those factor s include identification of other possible co-contaminants and their c oncentrations, 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). Evaluation of factors that could influence additivity/synergism is beyond the scope of this assessment and the capabilities of the available data to allow for an evaluation. However, it is acknowledged that not consid ering mixtures could over- or under-estimate risks depending on the type of interaction and factors discussed ab ove. The assessment will, however, analyze the toxicity of formulated products (including fo rmulations involving more than one active ingredient) and will determine whether formulated products are more toxic than the technical grade active ingredient data used for asse ssing both direct an d indirect risks.



### 9.2. Measures of Exposure

9.2.1. Aquatic Exposures

Indoor Uses

To estimate aquatic exposure related to releases of tetramethrin from indoor uses, EFED relied
on the Office of Pollution Prevention and Toxics (OPPT) model, Exposure and Fate Assessment Screening Tool (EFAST, version 2.0, or EFAST 2, 2007). From this model, EFED used the “Down-the-Drain” module, which is designed for releases from indoor uses to domestic
wastewater treatment. The “Down-the-Drain” module of E-FAST v.2.0 is specifically designed
to address all sources of one chemical that could potentially be disposed to domestic wastewater from a “down-the-drain” application. This mode l provides screening-level estimates of chemical residues in surface water that may result from household uses ( e.g. , treatment of clothing, bedding, and pets with tetramethrin products) and the disposal of these consumer products into wastewater using a few simple input parameters ( e.g. , yearly production volume for indoor use
and fraction of the chemical rem oved during wastewater treatment).

Conceptually, the model assumes that in a gi ven year the entire produc tion volume for indoor uses ( i.e. , 310,000 lbs for tetramethrin) is parceled out on a daily basis to the U.S. population and converted to a mass release per cap ita and daily per capita release of a chemic al to a wastewaterPage 24 of 41 treatment facility ( i.e. , g/person/day). This mass is then diluted into the average daily volume of wastewater released per person to arrive at an estimated concentration of the chemical in wastewater prior to entering a tr eatment facility. The chemical ’s concentration in untreated wastewater is then reduced by the fraction re moved during wastewater treatment processes before release into a river or stream where it undergoes dilution.

Based on this analysis, it was determined that in door uses are of low concern for environmental effects. E-FAST generated EECs were approxima tely 1.12 μg/L for surface water. Using this value to calculate RQs resulted in exceedance s of acute LOCs for listed species (0.05) and restricted uses (0.1) for freshwat er fish (RQ=0.3). However, due to (1) the small percentage of
the overall indoor use volume that would be expected to enter wastewater systems ( e.g. , clothing, bedding, and pet treatments) and (2 ) the rapid degradation of tetr amethrin in non-acid systems,
the actual amount of chemical that would enter and pass through a domestic wastewater treatment system is expected to be negligible. The U.S. EPA water quality standard for pH of wastewater treatment plant discharge is 6.5-9.0. At this neutral to basic pH range, rapid degradation of tetramethrin is observed, which is not accounted for in the EFAST model. Therefore, indoor uses will not be further considered.

Outdoor Uses

Tetramethrin is used in reside ntial and industrial/commercial ar eas in relatively small quantities through aerosols, foggers, and space sprays. On a nationwide basis, tetramethrin use is relatively limited. It is not used on a wide scale, such as agriculture or in mosquito abatement by public authorities. The use pattern is, therefore, in in dividual, isolated areas, and again, in relatively
small amounts. These characteristics limit the u tility of standard models used to derive EECs ( e.g. , PRZM/EXAMS). Further, non-target organism exposure is most likely to result from outdoor uses, such as spraying wasp or hornet nests under the eaves of houses, and backyard foggers for flying insects. Orga nisms present in a treated area at the time of spraying are most likely to be exposed and are at risk of acute effects.

Deriving aquatic EECs for tetramethrin is difficult due to the use patterns of this chemical. Water bodies may be contaminated if use occurs in close proximity to them. Spray drift is expected to be limited by the use patterns, and runoff is generally expected to be limited by the rapid degradation of tetramethrin. However, tetramethrin is more persistent under certain
conditions such as acidic or shaded environments. Given that (1) median lethal concentrations (LC 50 s) for tetramethrin are currently approximately 3 μg/L with associated concern levels at approximately 0.1 μg/L, (2) LC 50 s may decrease upon submitted data, and (3) toxicity occurs very rapidly in aquatic animals, the potential for aquatic contamina tion, although limited, may still be sufficient to cause localized mortality in aquatic systems. A concentration of 1 μg/L can be thought of as approximately 1 drop of water in a swimming pool. Current concern levels are exceeded at approximately 1/10 th of this concentration.

Therefore, risk potential will be estimated by dete rmining the feasibility that exposure levels may approach levels of concern. An initial risk feas ibility analysis suggests that potential risks to aquatic organisms could exceed concern levels unde r some conditions. However, risk is likely limited to organisms that are in close proximity to a larger scale application sites such asPage 25 of 41 nurseries or large residential area s. Risk is also likely limited to application methods that may result in greater volume of material being appl ied such as backpack sprayers and hand wands. Use of small spray cans is unlikely to result in exposures that exceed concern levels. Additional information on the amount of material that may be applied for various uses would allow for better characterization of expos ure and potential risks.

EFED’s initial analysis suggest s that approximately 1⁄2 gallon of spray solution (based on 0.02 lbs a.i./gallon for general outdoor sprays (Table 2) entering a 20,000,000 liter pond would result in
risks of concern based on the conc entration of active i ngredient in the produc ts. The feasibility of this volume of spray solu tion entering a water body depends on the amount of spray solution applied to a nearby area. For small scale spray applications it is unlikel y that this amount of solution will enter water bodies. However, for larg er scale operations, it appears reasonable that this amount of spray material can enter a receiving water body. Further, this calculation does not account for the likely increased toxici ty of tetramethrin products form ulated with synergists. If a product co-formulated with a synergist such as PBO or MGK-264 were to enter a water body via spray drift or if tetramethrin we re to enter a water body previously contaminated with synergists, the quantity required to result in risks of concern is expected to be substantially lower than 1⁄2 gallon. A review of studies on other pyrethroids co-formulated with PBO revealed increases in toxicity to non-target aquatic or ganisms of up to 16 times that of the active ingredient alone. Assuming a 16-fold toxicity enhancement factor, a spray volume of 1/32 of a gallon (1⁄2 of a cup) entering a water body would result in risks of concern. Toxi city data for freshwater and estuarine/marine aquatic organism s are needed to quantify the expe cted increase in toxicity for tetramethrin products co-formulate d with synergists. Degradation in estuarine/marine systems is expected to be rapid, as seawater pH is sli ghtly basic, ranging fr om 7.4 to 9.6 (Marion et al.

, 2011), and hydrolysis of tetramethrin in this pH ra nge is <1 day. However, acute toxicity effects occur rapidly (within the first measurement, which occurred at 24 hour s after dosing) in a freshwater fish study (MRID 41609608) and are assumed to occu r immediately upon exposure for risk assessment purposes. Therefore, risks to both freshwater and estuarine/marine organisms
will be considered.

9.2.2. Terrestrial Exposures

There is a potential for terrestrial exposure to non-target terrestrial organisms through direct application or spray drift. Organisms present at the time of spraying are most likely to be exposed and are at risk of acute e ffects. The use patterns of tetr amethrin described in detail in
Section 4.2 and reiterated above preclude the traditional use of terrestrial exposure models ( e.g. , T-REX and TerrPlant) used by EFED to estim ate environmental concentrations based on widespread applications such as use on field cr ops or turf. EEC values used for terrestrial exposure are typically derived from the Kena ga nomograph (Hoerger and Kenaga, 1972), as modified by Fletcher et al. (1994), using the T-REX model (version 1.4.1, 10/09/2008). EFED does not currently have standard models for sma ll-scale outdoor urban uses. Furthermore, the potential for tetramethrin to re ach non-target terrestrial animals at levels approaching effect
concentrations is considered minimal based on the supported uses (inc lusive of use type, formulations, and application type and rates). Therefore, terres trial exposure modeling will not be used to directly ca lculate standard risk quot ients for tetramethrin; in stead, T-REX calculations will be used to help characterize expected exposure to terrestrial animals. Like for aquaticPage 26 of 41 exposures, risk potential will be estimated by dete rmining the feasibility that exposure levels may approach levels of concern.

EFED has conducted an initial analysis to estim ate risk potential and determine the potential utility of additional data and analysis. The highes t calculated use rate for an aerosol spray can is equivalent to a rate of 1.52 lbs a.i./acr e (15.8 mg/ft 2 ). Aerosol sprays are the most prevalent application method for tetramethrin products a nd are used for many registered outdoor use products. However, this applicati on rate would be limited to the ar ea treated as part of the spot treatment and would not apply to an actual acre. Using the 1.52 lb a.i./acre rate (0.000035 lbs a.i./sq. ft) and available toxicity data (Table 5), a small bird (20 g) needs to consume the mass in approximately 2 square feet treated with tetramethrin to exceed the LD 50 of >2250 mg/kg-bw and approximately 1/5 of a square foot to exceed the listed species LOC (0.1).

Mg per square foot: 0.000035 lbs a.i./sq ft *453592 mg/lb = 15.8 mg a.i./sq ft
Scaled LD 50 for a 20 g bird 1 : 2250 mg a.i./kg bw * (20 g/178 g) (1.15-1) = 1621 mg/kg-bw
Mass associated with LD 50 : 1621 mg/kg-bw * 0.02 kg = 32 mg

This is a reasonable area for treatment with a spray can. This analysis is based on an LD 50 that exceeds the limit dose for acute oral toxicity data ; therefore, true risks may be lower than concern levels. However, if passerine species are more sensitive than species tested to date, then RQs may be higher than suggested by the above analysis.

Tetramethrin breaks down rapi dly via photolysis and hydrolysis in non-acidic environments; however, it may persist for longer durations in dr yer climates when attenuated from light. The aerobic soil metabolism half-life was approximately 1 month. Therefore, there is potential for acute exposures. The use patterns of tetramethr in include use on woody and herbaceous plants, which may be habitat for passerine species.

Terrestrial plant exposures ar e most likely to result from plants sprayed directly with tetramethrin products, some of which are labeled for use on ornamentals. Terrestrial plant toxicity data will provide a basis on which to estimate risk potential to sprayed terrestrial plants.



### 9.3. Measures of Effect

Ecological effect data are used as measures of direct and indirect effects to biological receptors. Data were obtained from registrant-submitted studies or from literature studies identified by
ECOTOX. The ECOTOX database was searched in or der to provide more ecological effects data to bridge existing data gaps. ECOTOX is a sour ce for locating single chemical toxicity data and potential chemical mixture toxicity data for a quatic life, terrestrial plants, and wildlife.
ECOTOX was created and is mainta ined by the US EPA, Office of Research and Development,

1 This calculation uses the allometric equation from the T-REX model: Adj LD LD AW

TW x

. ( )

50 50 1

       

TW = the body weight of the tested animal (178 g bobwhite quail), AW = body weight of the assessed animal (20 g bird), and x = the default Mineau scaling factor for birds (1.15)Page 27 of 41 and the National Health and Environmental E ffects Research Laboratory's Mid-Continent Ecology Division (USEPA, 2007b).

Information on the potential effects of tetramethrin on non-target animals is also collected from the Ecological Incident Information System (E IIS; USEPA, 2007a). The EIIS is a database containing adverse effect (typically mortality) reports on non-target organisms where such
effects have been associated w ith the use of pesticides.

Where available, sub-lethal effects observed in both registrant-submitted and open literature studies will be evaluated qualitatively. Such effects have included behavioral changes ( e.g. , lethargy, changes in coloration and effects olfaction). Quantitativ e 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 ma kes the assumption that toxicity of tetramethrin to birds is similar to terrestrial-phase amphibians and reptiles. The same assumption is made for fish a nd aquatic-phase amphibians.

The acute measures of effect used for animal s in this screening-level assessment are the LD 50 , LC 50 and EC 50 . LD stands for "Lethal Dose", and LD 50 is the amount of a material, given all at once, that is estimated to cause the death of 50% of the test organisms. LC stands for “Lethal
Concentration” and LC 50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. EC stands for “Effective Concentration” and the EC 50 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 liste d and non-listed animals are the NOAEL/NOAEC and
NOEC. NOAEL stands for “No Observed-Adverse-Eff ect-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 NOAEC ( i.e. , “No-Observed-Adverse-Effect-Concen tration”) is the highest test
concentration at which none of the observed effect s were statistically different from the control.
The NOEC is the No-Observed-Effects-Concen tration. For non-listed plants, only acute exposures are assessed ( i.e. , EC 25 for terrestrial plants and EC 50 for aquatic plants); for listed plants, either the NOAEC or EC 05 is used.Page 28 of 41 

### 9.4. Integration of Exposure and Effects

Risk characterization is the in tegration of exposure and ecologi cal effects characterization to determine the potential ecological risk from th e uses of tetramethrin listed in Table 2 and the
likelihood of direct and indirect e ffects to non-target organisms in a quatic and terrestrial habitats. The exposure and toxicity effects data are integrat ed in order to evaluate the risks of adverse ecological effects on non-target species. For the assessment of tetramethrin risks, the risk quotient (RQ) method is used to compare exposur e and measured toxicity values. EECs are divided by acute and chronic t oxicity values. The resulting RQs are then compared to the Agency’s LOCs (USEPA, 2004). Thes e criteria are used to indicate when uses of tetramethrin, as directed on the label, have th e potential to cause adverse direct or indirect effects to non-target organisms. As noted previously, where data are l acking on the toxi city of tetramethrin, risk will be presumed.

9.4.1. Deterministic and Probab ilistic Assessment Methods

The quantitative assessment of risk will primar ily depend on the deterministic point-estimate based approach described in the risk assessment. If necessary, an effort will be made to further qualitatively describe risk using probabilistic tools that the Agency has developed, provided
sufficient data are available. These tools have been reviewed by FIFRA Scientific Advisory Panels and have been deemed as appropriate means of refining assessments where deterministic approaches have identified risks.



### 9.5. Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Sp ecies Act (ESA), the Agency will evaluate risks to Federally-listed th reatened and/or endangere d (listed) species from registered uses of tetramethrin. This asse ssment will be conducted in accordance with the Overview Document (USEPA, 2004), provis ions of the ESA, and the Services’ Endangered Species Consultation Handbook (USFWS/NMFS 1998).

The assessment of effects associated with the re gistration of tetramethrin is based on an action
area. The action area is considered to be the ar ea directly or indirectly affected by the federal action, as indicated by the exceedance of Agency LO Cs 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) consider s the results of the risk asse ssment 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 tetramethrin application occurs), plus all areas where offsite transport 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 repr oduction 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 le thal or sub-lethal e ffect threshold for any biological entity at the whole organism, organ, tissu e, and/or cellular leve l of organization. InPage 29 of 41 situations where it is not possible to determin e the threshold for an observed effect, the action area is not spatially limited and is assumed to be the entire United States.



### 9.6. Drinking Water Assessment

The Agency has not previously conducted a dri nking water assessment for the tetramethrin
because the chemical's use was considered limite d to indoor non-food uses, and was labelled for only limited outdoor uses ( e.g., spot treatments, foggers). Ther efore, because of the relatively limited use of the compound as an aerosol/fogger spot treatment in residential settings, and the fate properties that limit mobility, there is a low likelihood of the compound contaminating human drinking water sources, so a drinking wate r assessment will not be conducted to support a human dietary risk assess ment for tetramethrin.



### 9.7. Clean Water Act Programs

9.7.1 Aquatic Life Criteria and Aquatic Life Benchmarks

The Clean Water Act requires the Agency to publis h water quality criteria that accurately reflect the latest scientific knowledge on the kind and ex tent of all identifiable effects on health and welfare which might be expected from the pres ence of pollutants in any body of water, including ground water. While these recommended criter ia do not, in themselves, impose any requirements, states and authorized tribes can us e them to develop water quality standards. An Aquatic Life Ambient Water Quality Criteria docu ment has not been published for tetramethrin (refer to url: http://water.epa.gov/scitech /swguidance/standard s/criteria/index.cfm ).

Based on toxicity values revised by the EPA, the OPP publishes aquatic life benchmarks for freshwater species, based on the most sensitive sp ecies from the most recent risk assessments. For tetramethrin, no aquatic life benc hmarks have been published (see url: http://www.epa.gov/oppefed1/ecorisk_ders/a quatic_life_benchmark.htm#benchmarks ).

9.7.2 Impaired Water Bodies

Tetramethrin is not identified as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act, based on information provided at http://iaspub.epa.gov/tmdl_waters10/attains_ nation_cy.cause_detail_303d?p_cause_group_id=88

5 . However, the pyrethroids as a group have been identified as a cause for impairment for three water bodies in Central Valley, CA: Del Puerto Creek, Ingram Creek Site (confluence with Hospital Creek to Hwy 33 crossing) and second Ingram Creek Site (confluence with San Joaquin River to confluence with Hospital Creek).

Nonetheless, no Total Maximum Daily Load (T MDL) criteria have been developed for tetramethrin, based on in formation provided at http://iaspub.epa.gov/tmdl_waters10/attains_ nation.tmdl_pollutant_de tail?p_pollutant_group_id =885&p_pollutant_group_name=PESTICIDES . More information on impaired water bodies and TMDLs can be found at http://water.epa.gov/ lawsregs/lawsguidance/cwa/tmdl/index.cfm . The Agency invites submission of water quality data for this pesticide. To the extent possible, dataPage 30 of 41 should conform to the quality standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Im paired Water Body and Other Water Quality Data in OPP’s Registration Review Risk Asse ssment and Management Process (see: http://www.epa.gov/oppsrrd1/regist ration_review/water_quality_sop.htm ), in order to ensure they can be used quantitatively or qual itatively in pesticide risk assessments.



## 10. Endocrine Disruptor Screening Program

As required by FIFRA and FFDCA, EPA reviews nu merous studies to a ssess potential adverse outcomes from exposure to chemicals. Collectiv ely, these studies include acute, subchronic and chronic toxicity, including assessments of carcinogenicity, neurotox icity, developmental, reproductive, and general or systemic toxicit y. These studies include endpoints which may be susceptible to endocrine influe nce, including effects on endocr ine target organ histopathology, organ weights, estrus cyclicity, sexual maturati on, fertility, pregnancy rates, reproductive loss, and sex ratios in offspring. For ecological ha zard assessments, EPA evaluates acute tests and chronic studies that assess growth, developm ental and reproductive effects in different taxonomic groups. As part of its reregistration decision, EPA reviewed these data and selected the most sensitive endpoints for relevant risk assessment scenarios from the existing hazard database. However, as requir ed by FFDCA section 408(p), tetr amethrin is subject to the endocrine screening part of the Endocrine Disruptor Screenin g Program (EDSP).

EPA has developed the EDSP to determine whet her 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 ot her such endocrine effects as the Administrator may designate.” The EDSP employs a two-tiered approach to making th e 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 estrog en, androgen, or thyroid (E, A, or T) hormonal systems. Chemicals that go through Tier 1 scr eening and are found to have the potential to interact with E, A, or T hormonal systems will pr oceed 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 a ny 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-i ns for the first group of 67 chemicals, which contains 58 pesticide active ingr edients and 9 inert ingredients. Tetramethrin is not among the group of 58 pesticide active ingred ients on the initial list to be screened under the EDSP. Accordingly, as part of registrati on review, EPA will issue future EDSP orders/data call-ins, requiring the submission of EDSP scr eening assays for tetram ethrin. For further information on the status of the EDSP, the polic ies 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/

.Page 31 of 41 

## 11. Preliminary Identification of Data Gaps

11.1. Fate

The environmental fate data currently availabl e are sufficient to conduct a risk assessment, although environmental chemistry methods are need ed for soil and water, as described after
Table 6.

One identified degradate (acid-NPY) retains the ester linkage that is known to be needed for synthetic pyrethroid activity; however, because hydr olysis of the ester moiety is very rapid, exposure to acid-NPY will not be considered.

Table 6. Available environ mental fate data for tetramethrin and remaining data gaps

158
Guideline (OPPTS) Description MRID Classification Would
additional data
be useful to risk

assessment?

835.1230 (163-1) Leaching MRID 42212901 Acceptable No

835.1240 (163-1) Adsorption/Desorption MRID 41995007

MRID 42212901 Acceptable Acceptable No

835.1410 (163-2) Laboratory Volatility No data No

835.2120 (161-1) Hydrolysis MRID 41995006 Acceptable No

835.2240 (161-2) Photodegradation in water MRID 164634

MRID 43773401 Supplemental No

835.2370 (161-4) Photodegradation in air No data No

835.2410 (161-3) Photodegradation on soil No data No

835.4100 (162-1) Aerobic soil metabolism MRID 42563301 Acceptable No

835.4200 (162-2) Anaerobic soil metabolism No data No

835.4300 (162-4) Aerobic aquatic metabolism No data No

835.4400 (162-3) Anaerobic Aquatic Metabolism No data No

835.6100 (164-1) Terrestrial Field Dissipation MRID 42622401

MRID 42622402 Acceptable Acceptable No

835.6200 (164-2) Aquatic Field Dissipation No data No

835.6100 (164-1) Environmental Chemistry Methods No data Yes

For registration review, the following study would be useful to fulfill the identified data gap for environmental chemistry methods for soil and water:Page 32 of 41 Guideline Number: 850.6100 (164-1) Study Title: Environmental Chemistry Methods Environmental chemistry methods for soil and water are used to determine th e fate of pesticides in the environment. The methods identify a nd quantify the pesticide residues of interest, determining the total concentra tion of pesticides, including the extractable parent compound and significant metabolites and degradates.



### 11.2. Effects

Although many submissions have been made to provi de data on the effects of tetramethrin to aquatic and terrestrial organisms, da ta gaps still exist (See Table 7
, Table 8
, and Table 9). Rationale for the additional data requ ested is presented below the tables.

Table 7. Available ecological eff ects data for terrestrial animals expo sed to technical tetramethrin and remaining data gaps

158
Guideline (OPPTS) Description Does EPA Have Data to Satisfy this

Guideline? (Yes, No, or Partially) MRID Classification Would additional
data be useful to
risk assessment?

850.2100

(71-1) Avian oral toxicity Partially 121237 BQ 1
41609604 BQ Acceptable Acceptable Yes 2

850.2200

(71-2) Avian dietary toxicity Yes 121262 MD 3
121268 BQ 41609605 BQ

41609606 MD Acceptable Acceptable Acceptable Acceptable No

850.2300

(71-4) Avian reproduction No No data No 4

850.3020

(141-1) Honey bee acute contact toxicity Yes 41609613 Acceptable No

850.3030 (141-2) Honey bee residue on foliage Yes 41940801 Acceptable No

1 Northern bobwhite quail

2 According to the 40 CFR 158 (2010), acute oral toxicity data are required for a passerine sp ecies. Because no acute oral toxicity data have been submitted for a passe rine species exposed to tetram ethrin, this is a data gap. No acute oral toxicity data involving tetramethrin or its degradates have been identified in the sc ientific literature us ing ECOTOX (USEPA, 2007b).

3 Mallard Duck

4 According to the 40 CFR 158 (2010), an avian reproduction study is required for all outdoor use chemicals. However, due to the rapid degradation of tetramethrin in the environment, no chronic data is being requested for the registration review.

For registration review, the following study would be useful to fulfill the identified data gap for terrestrial animals. However, submission of additional data that clarifies the use pattern of tetramethrin may reduce or eliminate the ut ility of additional data submissions.

Guideline Number: 850.2100 Study Title: Avian acute oral t oxicity test (passerine species) Acute avian oral toxicity data are required for either one waterf owl or one upland game speciesPage 33 of 41 and one passerine species under the 40 CFR Part 158 (2010) data requirements for conventional pesticides with outdoor uses. Submitted acute or al avian effects data show no treatment-related mortality to bobwhite quail ( Colinus virginianus ) at levels >2,250 and >2,510 mg a.i./kg-body weight (MRIDs 121237, 41609604). Because passerine species have higher metabolic rates due
to their smaller sizes than eith er waterfowl or upland game bird species and because they may utilize different metabolic pathways, they may be more or less sensitive to tetramethrin. In addition, an open literature study has documented the increased sensitivity of canaries ( Serinus

sp. ) to another pyrethroid, beta -cyfluthrin (Addy-Orduna et al. , 2011). In this study, canaries
were 13 times more sensitive to beta -cyfluthrin than shiny cowbirds ( Molothrus bonariensis ) and eared doves ( Zenaida auriculata ) based on LD 50 calculations. These data suggest that there may be substantial differences in the sensitivities of various avian species to some pyrethroids. There is sufficient mass in approximately 1/5 of a squa re foot applied to result concerns for listed species based on the currently av ailable data. Tetramethrin br eaks down rapidly via photolysis and hydrolysis; however, it may persist for longer durations in dryer climates when attenuated from light. Therefore, there is potential for acu te exposures. The use pa tterns of tetramethrin include use on woody and herbaceous plants, which may be habitat for passerine species. A passerine study protocol should be submitted for revi ew by the Agency prior to initiation of the study.

Table 8. Available ecological eff ects data for aquatic animals expose d to technical tetramethrin and remaining data gaps

Guideline Description Does EPA Have Data to Satisfy this Guideline? (Yes, No, or Partially) MRID Classification Would additional
data be useful to risk
assessment?

850.1010

(72-2) Freshwater invertebrate acute toxicity No 41609609 Supplemental,
does not fulfill

guideline No 1

850.1020 Aquatic invertebrate acute toxicity ( Hyalella azteca ) No No data Yes 1

850.1025

850.1035

850.1045

850.1055

(72-3) Saltwater invertebrate acute toxicity No No data Yes 2

850.1075

(72-1) Saltwater fish acute toxicity No No data Yes 2

850.1075

(72-1) Freshwater fish acute toxicity Partially 121296

41609607

41609608 Supplemental Acceptable Acceptable Yes 1

850.1300

(72-4) Freshwater invertebrate life cycle test No No data No 3

850.1400

(72-4) Freshwater fish early life stage

test No No data No 3

850.1735 Freshwater invertebrate whole sediment acute toxicity No No data No 4Page 34 of 41 Guideline Description Does EPA Have Data to Satisfy this Guideline? (Yes, No, or Partially) MRID Classification Would additional
data be useful to risk
assessment?

850.1740 Saltwater invertebrate whole sediment acute toxicity No No data No 4

1 TEP studies on freshwater invertebrates and fish are required on a product containing tetramethrin and the synergist piperonyl butoxide in addition to a product containing tetramethrin and the synergist MGK-264. Tetramethrin may be co-formulated with either or both synergists, PBO and MGK-264, in numerous produc ts. Because available inform ation indicates that greater toxicity enhancement can occur at higher sy nergist-to-a.i. ratios, sele ction of the TEPs for testin g should include those with the highest synergist-to-a.i. ratio and are registered for outdoor uses . The registrant should submit a test protocol prior to con ducting
these TEP studies that documents the rationale for the TEP selection.

2 TGAI studies are required on one estuarine/marine mollusk, one estuarine/marine invertebrate, and one estuarine/marine fish species.

3 According to the 40 CFR 158 (2010), a freshwater invertebrate lif e cycle test and a freshwater fi sh early life stage test are required for all outdoor use chemicals. However, due to the rapi d degradation of tetramethrin in the environment, no chronic data is being requested for the registration review.

4 In 1999 a Science Advisory Pane l (SAP) called for sediment toxicity testing for pyrethroids (USEPA, 1999). However, these studies are not requested for tetramethrin because of the low ex pected environmental concentration (EEC) of tetramethrin in sediment. Using the US EPA EFAST2 mode l’s down-the-drain module (see Section 9.2 for a detailed description of the model), the expected EEC of tetramethrin in surface water from all indoor use production (310,000 lbs/yr) and under the most conservative assumptions is 1.12 μg/L. While the listed species LOC (0.05) is exceeded for freshwater fish at this level, only a small fraction of the indoor use production value is expected to enter domestic wastewater treatme nt systems, which would then undergo rapid degradation via hydrolysis in th e pH-controlled discharge into waterways.

For registration review, the following studies woul d be useful for risk assessment and have not been submitted. However, additional information on the amount of material applied to a given location may mitigate the need for these studies.

Guideline Number: 850.1020 Study Title: Gammarid Acute Toxicity Test ( Hyalella azteca ) (TGAI) No acceptable aquatic invertebrate study for te tramethrin TGAI has been submitted to the Agency. One study submitted using test species Daphnia magna under guideline number 850.1010 is classified supplemental and cannot be used quantitatively in an Agency risk assessment due to significant guideline deviations in the test procedures (MRID 41609609). Acute toxicity data for freshwater invertebrate s are required under 40 CF R Part 158 (2010) data requirements for pesticides with outdoor uses. These data are n ecessary to determine if acute exposure to tetramethrin may adversely affect the survival of a quatic invertebrates.

Acute water column tests with Hyallela azteca have been requested in other pyrethroid problem formulations based on the increased sensitivity of this species to pyrethroid insecticides. An acute water column test examining the toxicity of tetramethrin to Hyalella azteca would be useful. The 850.1020 test guideline for Gammarid amphipods is recommended with appropriate
modifications to address specific testing needs of Hyalella azteca . The registrant should submit a protocol prior to test initiatio n or submit any open literature studi es that may fulfill this data

gap.

Guideline Number: 850.1020 Study Title: Gammarid Acut e Toxicity Test (TEP) Data regarding the acute toxicity of tetramethr in TEPs to aquatic invertebrates have not been submitted to the Agency. Acute toxicity data fo r freshwater invertebrates are required under 40 CFR Part 158 (2010) data requirements for pesticid es with outdoor uses. TEP testing is required when an ingredient in the end-use formulation is expected to enhance th e toxicity of the activePage 35 of 41 ingredient of a product. These data are necessary to determine if acute exposure to tetramethrin TEP may adversely affect the surv ival of aquatic invertebrates.

Because there are registered outdoor uses of tetramethrin that may result in exposure to water bodies, acute toxicity data of tetramethrin TEP s with the synergist PBO and MGK-264 would be
useful for freshwater invertebrates. 2 Products with these synergists are likely to cause increased toxicity to non-target aquatic species. Currentl y, no data is available to quantify the difference in toxicity for fish or invertebra tes that may be concu rrently exposed to te tramethrin and these synergists compared to the active ingredients al one. Therefore, the Agency is requesting acute toxicity studies of tetramethrin TEPs that ar e co-formulated with PBO and with MGK-264. Because available information indicates that great er toxicity enhancement can occur at higher synergist-to-a.i. ratios, selec tion of the TEPs for te sting should include t hose TEPs with the highest synergist-to-a.i. ratio and are registered for outdoor uses. Hyalella azteca is recommended due to its much greater se nsitivity to pyrethroids compared to Daphnia magna

. Hyalella azteca 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 Ga mmarid amphipods is recommended with appropriate modifications to a ddress specific testing needs of Hyalella azteca . The registrant should submit a test protocol pr ior to conducting these TEP studies that documents the rationale
for the TEP selection and detail s of the testing procedure for Hyalella azteca

.

Guideline Number: 850.1025 Study Title: Oyster Acute Toxicity Test (Shell Deposition) (TGAI) Data regarding the acute toxicity of tetramethr in TGAI to marine/estuarine mollusks have not been submitted to the Agency. Acute toxicity data for mollusks are required under 40 CFR Part 158 (2010) data requirements for pesticides with outdoor uses. These data are necessary to determine if acute exposure to tetramethrin TGAI may adversely affect the survival of mollusks. Registered outdoor uses of tetramethrin may resu lt in exposure to marine/estuarine water bodies
when used near coastal areas.

Guideline Number: 850.1035 Study Title: Mysid Acute Toxicity Test (TGAI) Data regarding the acute toxicity of tetramethrin TGAI to marine/estuarine invertebrates have not been submitted to the Agency. Acute toxicity data for marine/estua rine invertebrates are required under 40 CFR Part 158 (2010) data require ments for pesticides with outdoor uses.

2 The Agency notes that the ratios of synergist (PBO or MGK-264) to tetramethrin 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 tetramethrin. As availabl e data suggest greater toxicity enhancement can occur at higher synergist-to-a.i. ratios, it is possible that greater toxicity enhancement may occur in the natural environment compared to that measured for formulated products. Theref ore, to address this concern, the Agency will attempt to bridge results from ongoing “comprehensive” synergist tes ting at varying synergist-to-a.i. ratios to address varying
ratios of PBO/MGK-264 to tetramethrin 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 tetramethrin ecological risk assessment, th e Agency may apply a “conservative” toxicity enhancement factor to address the uncertainty regarding differences in synergist-to-tetramethrin ratios in the aquatic environment vs. those tested using formulated products. The registrant may wish to submit additional data on tetramethrin/synergist toxicity at varying ratios that would be expected to occur in the aquatic environment to address this potential uncertainty.Page 36 of 41 These data are necessary to de termine if acute exposure to te tramethrin TGAI may adversely
affect the survival of marine/est uarine invertebrates. Registered outdoor uses of tetramethrin may result in exposure to marine/estuarine wa ter bodies when used near coastal areas.

Guideline Number: 850.1075 Study Title: Fish Acute T oxicity Test, Marine (TGAI) Data regarding the acute toxicity of tetramethrin TGAI to estuarine/marine fish have not been submitted to the Agency. Acute toxicity data for estuarine/marine fish are required under 40 CFR Part 158 (2010) data requirements for pest icides with outdoor uses. These data are necessary to determine if acute exposure to tetr amethrin TGAI may adversely affect the survival of estuarine/marine fish. Registered outdoor us es of tetramethrin may result in exposure to
marine/estuarine water bodies wh en used near coastal areas.

Guideline Number: 850.1075 Study Title: Fish Acute T oxicity Test, Freshwater (TEP) Because there are registered outdoor uses that may result in exposure to water bodies, acute toxicity data of tetramethrin TEPs with the synerg ist PBO and MGK-264 would be useful for freshwater fish. Products with these synergists are likely to cause increased toxicity to nontarget aquatic species. Acute to xicity data for freshwater fish are required under 40 CFR Part 158 (2010) data requirements for pes ticides with outdoor uses. TEP testing is required when an ingredient in the end-use formulation is expected to enhance the toxicity of the active ingredient of a product. These data are necessary to dete rmine if acute exposure to tetramethrin TEP may adversely affect the survival of freshwater fish.

Currently, no data is available to quantify the difference in toxicity for fish or invertebrates that may be concurrently exposed to tetramethrin and these synerg ists compared to the active ingredients alone. Therefore, the Agency is re questing acute toxicity studies of tetramethrin
TEPs that are co-formulated with PBO and w ith MGK-264. Because available information indicates that greater toxicity enhancement can o ccur at higher synergist-to-a.i. ratios, selection of the TEPs for testing should in clude those with the highest s ynergist-to-a.i. ratio and are registered for outdoor uses. The registrant sh ould submit a test protocol prior to conducting
these TEP studies that documents the rationa le for the TEP selection. (See Footnote 1.)

Table 9. Available ecological eff ects data for plants exposed to te tramethrin and remaining data gaps

Guideline Description Does EPA Have Data to Satisfy this Guideline? (Yes, No, or Partially) MRID Classification Would Additional
Data be Useful for
Risk Assessment?

850.4100

(122-1) Terrestrial Plant toxicity: Tier II seedling emergence No No data Yes 1

850.4150

(122-1) Terrestrial Plant toxicity: Tier II vegetative vigor No No data Yes 1

850.4400

(123-2) Aquatic Plant Growth: Tier II vascular plants No No data No 2

850.5400

(123-2) Aquatic Plant Growth: Tier II algae No No data No 2

1 If a Tier I study exhibits a <25% effect, a Tier II study is not required.

2 Exposure to aquatic plants is expected to be negligible.Page 37 of 41 For registration review, the following studies would be useful to fu lfill identified data gaps for plants:

Guideline Number: 850.4100 Study Title: Terrestrial Plan t Toxicity (Seedling Emergence) Data regarding the toxicity of tetramethrin TEPs to terrestrial plants have not been submitted to the Agency. These data are required under the 40 CFR Part 158 (2010) data requirements for pesticides with outdoor uses. These data are necessary to dete rmine whether the outdoor use of tetramethrin could adversely affect seedling emergence of non-target plant species in the
terrestrial environment. Nine minor plant incidents resulting fr om tetramethrin use have been reported. If a Tier I study exhibits a ≥ 25% effect, or if a NOAEC cannot be established when conducted as a limit test, a Ti er II study is required.

Guideline Number: 850.4150 Study Title: Terrestrial Plan t Toxicity (Vegetative Vigor) Data regarding the toxicity of tetramethrin TEPs to terrestrial plants have not been submitted to the Agency. These data are required under the 40 CFR Part 158 (2010) data requirements for pesticides with outdoor uses. These data are necessary to dete rmine whether the outdoor use of tetramethrin could adversely affect vegetative vigor of non-target plant species in the terrestrial environment. Nine minor plant incidents resulti ng from tetramethrin use have been reported. If a Tier I study exhibits a ≥ 25% effect, or if a NOAEC cannot be established when conducted as a limit test, a Tier II study is required.Page 38 of 41 

## 12. References

MRID Citation

Fate

00164634 Chen, Y.; Casida, J. (1970) Photodecomposition of pyrethrin I, allethrin, phthalthrin, and dimethrin modifications in the acid moiety. Pyrethum Post 10(3):7-16

41995006 Katagi, T.; Mikami, N.; Matsuo, M.; et al. (1991) Hydrolysis of Trans-Neo-Pynamin in Buffered Aqueous Solutions: Lab Project Number: HYD90001: HYD91001. Unpublished study prepared by Sumi- tomo Chemical Co., Ltd, Environmental Health Science Lab. 127 p.

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