Page 2 of 41 

This document is intended to provide an overview 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 ecological risk hypothesis and the 

processes that will be used during the completion of drinking water exposure and ecological risk 

assessments in support of registration review. This document also identifies data gaps and the 

importance of obtaining additional studies to address data gaps 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-2H-isoindol-2-yl)methyl 2,2-dimethyl-3-(2-methyl-1-

propenyl)cyclopropanecarboxylate 

CAS#: 7696-12-0

Prepared by:

Elyssa Gelmann, Biologist 

Wm. J. Shaughnessy, PhD, Environmental Scientist 

U. S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division

Environmental Risk Branch II 

1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington, DC 20460

Reviewed by: 

Brian Anderson, Branch Chief 

Reuben Baris, Environmental Scientist 

Greg Orrick, Environmental Scientist 

Keith Sappington, Senior Biologist 

Christina Wendel, Biologist 
Page 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 Probabilistic Assessment Methods ............................................... 28

9.5. Endangered Species Assessments ..................................................................................... 28

9.6. Drinking Water Assessment ............................................................................................. 29

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 Identification of Data Gaps ................................................................................ 31

11.1. Fate .................................................................................................................................. 31

11.2. Effects ............................................................................................................................. 32

12. References .............................................................................................................................. 38

 

 
Page 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-registration and registration review 

of tetramethrin ............................................................................................................................... 11

Table 3. Chemical structures of tetramethrin 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 for 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 aquatic animals exposed to technical tetramethrin 

and remaining data gaps................................................................................................................ 33

Table 9. Available ecological effects 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............................................................... 21
Page 6 of 41 

1. Purpose 

The purpose of this problem formulation is to provide an understanding of the environmental fate 

and ecological effects of the registered uses of tetramethrin. Tetramethrin is part of the 

pyrethroid class of pesticides and was first registered in 1968. It is a broad spectrum, nonsystemic, synthetic pyrethroid used to control flying and crawling insects in a number of 

commercial, horticultural and residential applications. Commercial applications include space 

and crack-and-crevice treatment in a variety of commercial, industrial, residential, and 

institutional sites. Horticultural applications include foliar and fogger treatment on non-food 

plants. Residential uses include pest control 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 tetramethrin and for conducting 

environmental fate and ecological risk, and endangered species assessments for its registered 

uses. Additionally, this problem formulation is intended to identify data gaps, uncertainties, and 

potential assumptions used to address those uncertainties, relative to characterizing the 

ecological risk associated with the registered uses of tetramethrin. 

2. Nature of Regulatory Action 

The Food Quality Protection Act of 1996 mandated the United States 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 scientific data and other 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 policies and practices change, all registered pesticides continue to 

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

environment. Changes in science, public policy, and pesticide use practices will occur over time. 

Through the new registration review program, the Agency 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 Registration Review program pursuant to Section 3(g) 

of the Federal Insecticide, Fungicide 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 environmental fate and ecological risk assessment 

chapter in support of the registration 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 ecological risk assessment on tetramethrin that 

serves as a basis for this problem formulation. This risk assessment is briefly summarized 
Page 7 of 41 

below. Note that this assessment (the RED) did not quantitatively assess environmental risks of 

tetramethrin due to assumptions of low exposure and rapid degradation. In light of updated 

environmental risk assessment practices and requirements for a comprehensive, national scale 

risk assessment to endangered species, the registration review process will incorporate a 

quantitative evaluation. This updated approach is described in the 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 Federal Docket Management System (FDMS), 

available at http://www.regulations.gov (document #EPA-HQ-OPP-2008-0014-0019). The 

Environmental Fate and Effects Division (EFED) chapter of the RED was finalized on February 

5, 2008 and is available on the FDMS (document #EPA-HQ-OPP-2008-0014-0009). The major 

conclusions presented in the RED were as follows: 

 Exposures were not quantified because current exposure models are geared toward 

widespread uses such as agriculture or public health uses and tetramethrin 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-target organisms will be exposed at harmful 

levels. 

 Based on the available ecotoxicity data, the most acutely sensitive organisms to 

tetramethrin are fish, aquatic invertebrates, and insects. Tetramethrin is practically nontoxic to birds and mammals on an acute basis. The only chronic (reproductive) data 

submitted was for the rat. The no-adverse-effect-concentration (NOAEC) was relatively 

low (25 mg/kg/day); however, quick degradation of tetramethrin was expected to reduce 

the amount of time that exposure potential would reach this level. 

 The only taxa considered at risk were terrestrial invertebrates present at the time and 

place of localized spraying. 

 No toxicity data were available for the transformation 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. However, since it too is subject to rapid 

hydrolysis, exposure to acid-NPY is unlikely. 

The RED identified ecological effects data gaps for tetramethrin. There were no toxicity data 

available for estuarine/marine animals, no chronic toxicity data for any taxa except mammals 

(i.e., birds, reptiles, amphibians, fish, aquatic invertebrates, or terrestrial invertebrates), and no 

guideline plant studies. The RED did not request any additional data submissions due to the 

limited exposure potential and rapid degradation to non-toxic degradates, but noted that the need 

for additional studies would be reevaluated during registration 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). The 
Page 8 of 41 

updates included revision to human health risk as a result of a higher application 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 may 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-phenothrin, resmethrin, and cypermethrin), and 

growth inhibitors (e.g., fenoxycarb). These other active ingredients are more persistent than 

tetramethrin, and provide residual 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, discusses the need for synergist 

data. The PBO Problem Formulation is available in the PBO registration 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 applications. It is a rapid 

knockdown agent against flying and crawling insects; however, it is generally combined with a 

synergist (PBO or MGK-264) and/or another pyrethroid for greater effectiveness. This is largely 

due to the longer residual activity of the synergists and other more persistent co-formulations. 

Tetramethrin is a nerve cell membrane sodium channel modulator, which interferes with 

entrance of sodium ions into the channel, leading to hyperactivity of the nervous system which 

can result in paralysis and/or death. Pyrethroids, including tetramethrin, bind to the α subunit of 

the sodium channel and slow the activation (opening), as well as the rate of inactivation (closing) 

of the sodium channel, leading to a stable hyper-excitable state. Sodium channels then open at 

more hyperpolarized potentials, and are held open longer, allowing more sodium ions to cross 

and depolarize the neuronal membrane. Type I pyrethroids such as tetramethrin prolong channel 

opening only long enough to cause repetitive firing 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 metabolized through two major biotransformation 

pathways: hydrolysis of the ester linkage and oxidation of the alcohol moiety by cytochromes 

P450. PBO inhibits cytochromes P450 and thereby 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 pyrethroids along with PBO increases the toxicity 

of the pyrethroids to aquatic invertebrates (Amweg & Weston, 2007; Weston & Lydy, 2010). 

MGK-264, another potentiator/synergist used with pyrethroids, has similar effects as those 

observed for PBO (Hodgson & Smart, 2001). Tetramethrin 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 include space sprays, surface treatments, 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 perimeter treatments (sidewalks, entranceways, outside 

surfaces of buildings, etc.). Horticultural 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 direct application to cats, dogs 

and horses. Outdoor residential uses are the same as outdoor commercial uses listed above. 

Tetramethrin is formulated as pressurized liquid, ready-to-use (RTU) liquids, emulsifiable 

concentrates, and liquid concentrates, 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 tetramethrin 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 several organophosphate pesticides, which are no longer registered for indoor 

residential areas. In the RED, the Agency estimated annual usage of tetramethrin 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 data, 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 produced only as inventory is exhausted. In addition, 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 Agency 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 sites 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 than 1,000 lbs a.i. are used annually by professional 

applicators (USEPA, 2010). 

Outdoor uses may result in exposure of non-target organisms; however, because there are no 

widespread agricultural or public health (e.g., mosquitocide) uses, exposure of non-target 

organisms is limited to spot treatments in localized areas. 

Outdoor uses considered in this assessment are listed 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 general surface sprays, directed spray, crack and 

crevice or spot treatment, or spray. 
Page 11 of 41 

Application rates vary depending on the use pattern, 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 aqueous sprays for crawling and flying insects, range between 

0.1% and 0.35%. Indoor total 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 indicates 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./ft2

, this equates 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 2010 Revised RED. Further, these rates may be 

subject to revision as product labels are currently 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 used for the risk assessment. 

Table 2. Non-food and non-feed use patterns subject to the re-registration and registration review of 

tetramethrin 

Use Profile Maximum Application Rate 

(Application Method) % Active 

Ingredient 

(% a.i.) 

Volume-based Area-based Space-based 

General Indoor1 and Outdoor 

Spray2

 (Trigger Pump Sprays, Low 

Pressure Hand Wand, Back Pack 

Sprayer) 

0.20 0.02 lb a.i./gal 

solution 

0.00002 lb a.i./ft2 

(0.87 lb a.i./acre) 

0.000002 lb a.i./ft3 

Aerosol Cans (Indoor & Outdoor 

Spray) 

0.35 0.035 lb a.i./gal 

solution 

0.000035 lb a.i./ft2

 (1.52 lb a.i./acre) 

0.0000035 lb a.i./ft3

Indoor Total Release Fogger1 0.54 n/a n/a 6 oz can / 4,600 ft3

 

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 Devices2, 3

0.10 n/a 

0.0000001 lb 

a.i./ft2 

(0.004 lb a.i./acre) 

1.25E-08 lb a.i./ft3

 

Source: Revised tetramethrin RED (USEPA, 2010). 

1 Use sites include but are not limited to: commercial, industrial, institutional, and residential locations; agricultural 

structures and equipment; eating establishments; animal kennels and sleeping quarters; empty greenhouses; 

hospitals. 

2 Use sites include but are not limited to: commercial, industrial, institutional, 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 ingredients and synergists have differing fate 

properties and therefore would be expected to occur in the environment at different times and at 
Page 12 of 41 

different concentrations than present in the end use product. 

Currently data on the degree to which the toxicity of pyrethroid active ingredients is enhanced by 

varying ratios of PBO and MGK-264 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 species, it is known that the degree of toxicity 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 enhancement of acute toxicity of pyrethroids to the 

freshwater amphipod, Hyalella azteca, by simultaneous exposure to PBO at varying 

PBO:pyrethroid ratios. It is expected that this comprehensive testing strategy, when augmented 

with similar acute toxicity data with freshwater fish and other selected pesticide active 

ingredients, will facilitate bridging of the synergist toxicity enhancement to other co-formulated 

or co-applied pesticide/synergist active ingredients that are not tested at varying synergist:active 

ingredient ratios. With respect to evaluating ecological risks from co-applied tetramethrin and 

synergists (PBO and MGK-264), the Agency is requesting acute toxicity studies of tetramethrin 

typical end-use products (TEPs) that are co-formulated with PBO and MGK-264 at the highest 

synergist:active ingredient ratio. These TEPs should correspond to those formulated products 

that are labeled for outdoor uses with the greatest potential for aquatic exposures and would be 

conducted with a freshwater fish and a freshwater invertebrate. Additional discussion of the 

need for combined tetramethrin:synergist toxicity 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 persistent in the environment. The major routes of 

dissipation for tetramethrin include hydrolysis and 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 hydrolyzed 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 days. 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% and 97.3% at day 30, respectively. At pH 9 the 

primary degradates were trans-CRA, THPA, 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 tetramethrin 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 including one (acid-NPY) that retains the entire ester structure and 

possibly the mode of action of the 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 (1RS)-trans-2,2-dimethyl-3-(2-3,4,5,6-

Tetrahydrophthalimide (THPI); 

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

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

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

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

 carboxyprop-1-enyl)cyclopropanecarboxylate (acid-NPY ); and 

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

The major degradates identified in the aerobic 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 tetramethrin and transformation products

Structure Name Formation 

Mechanism 

% of Applied 

Radioactivity 

Degradate 

Class 

Parent 

1,3,4,5,6,7-hexahydro-1,3-

dioxo-2H-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 

(1RS)-trans-2,2-dimethyl-3-(2-

3,4,5,6-Tetrahydrophthalimide 

Aerobic soil 

metabolism 

<5.2% Minor 

H3C

CH3

CH3

H3C

O

O

N

O

O

OH

O

OH

O

OH

O

OH

H3C

CH3

H3C

O

O

N

O

O

NH

O

O
Page 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 

(1R,3R)-2,2-Dimethyl-3-

carboxycyclopropanecarboxylic 

acid 

Aerobic soil 

metabolism 

24.3% at day 58 Major 

chrysanthemic acid 

(1R,3R)-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 study (MRID 42622401), and less than one hour in a 

Florida study (MRID 42622402). 

Tetramethrin is very susceptible to degradation by sunlight. Under most ecologically relevant 

conditions, tetramethrin can be expected to breakdown to less than half of the applied 

concentration within one day. In two studies tetramethrin photodegraded upon exposure to sun 

lamp irradiation within 4 hours (MRIDs 164634 and 43773401). 

Tetramethrin is slightly mobile (United Nations Food and Agriculture 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 degradation 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 organic carbon content, it is likely to be somewhat 

more mobile in soils with lower organic matter content, such as coarse sand soils. 

OH

O

O

OH

OH

N

O

O

O

OH

O

HO

H3C

CH3

O

OH

CH3

H3C

H3C

H3C
Page 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 radioactivity. 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-m3

/mol (USEPA, 2010). 

Tetramethrin has a strong affinity to bind to organic 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 tetramethrin indicate that bioaccumulation is not 

likely to be an exposure pathway 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-2Hisoindol-2-yl)methyl 2,2-dimethyl-3-(2-

methyl-1-

propenyl)cyclopropanecarboxylate 

Pesticide type, such as herbicide or insecticide Insecticide

Chemical class Pyrethroid 

CAS number 7696-12-0

Empirical formula C19H25NO4

Molecular mass (g/mol) 331.41

Vapor pressure (mm Hg at 30oC) 7.1E-06 

Henry’s Law Constant at 25oC (atm m3 mol-1) 1.7E-06

Solubility in water (mg/L at 25oC) 1.83 

Octanol-water partition coefficient (Log Kow) at pH 7, 20oC 4.6 

Koc (mL/g) 1423 

Hydrolysis (t1/2, days) pH 5 16-20 

pH 7 1 

pH 9 <1 

Photolysis (t1/2, days) <1 

Aerobic soil metabolism (DT50) 32.7-33.3

BCF 20 

With a log Kow value of 4.6, a BCF study would typically 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 hydrolysis 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 the 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 representative of broad 

taxonomic groups, are used to extrapolate to potential effects on a variety of species (receptors) 

included under these taxonomic groupings. 

Acute and chronic toxicity data from studies submitted by pesticide registrants along with the 

available open literature are used to evaluate the potential direct and indirect effects of 

tetramethrin on aquatic and terrestrial receptors. These include toxicity data on the technical 

grade active ingredient, degradates, and when available, formulated products. The open 

literature studies are identified using EPA’s ECOTOXicology database (ECOTOX) (USEPA, 

2007b), which employs a literature search engine for locating chemical toxicity data for aquatic 

life, terrestrial plants, and wildlife. The evaluation 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 structure and functional 

characteristics of the affected communities. 

Table 5 provides a summary of the taxonomic groups and most sensitive surrogate species tested 

to characterize the potential acute and chronic ecological effects of tetramethrin. In addition, the 

table provides a preliminary overview of the potential acute toxicity of tetramethrin 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 

(LC50 or 

LD50) 

Acute Study MRID 

and Classification 

Acute 

Toxicity 

Classification 

Chronic 

NOAEC 

Chronic 

Study 

MRID 

Birds1

Bobwhite quail 

(Colinus 

virginianus) 

Oral 

LD50>2250 

mg a.i./kg 

41609604 

Acceptable 

Practically 

nontoxic 

Mallard duck No data No data 

(Anas 

platyrhynchos) 

and 

Bobwhite quail 

(Colinus 

virginianus) 

Dietary 

LC50>5620 

mg a.i./kg 

diet 

41609605/41609606 

Acceptable/ Acceptable 

Practically 

nontoxic 

Mammals 

Laboratory rat 

(Rattus 

norvegicus) 

Oral 

LD50>5000 

mg/kg bw 

42146405 

Acceptable 

Practically 

nontoxic 

Reproduction

25 mg/kg/day 00161842 

Insects 

Honey bee 

(Apis mellifera 

L.) 

Contact 

LD50=0.155 

μg/bee 

41609613 

Acceptable Highly toxic No data No data 
Page 17 of 41 

Taxonomic 

Group 

Surrogate 

Species 

Acute 

Toxicity 

(LC50 or 

LD50) 

Acute Study MRID 

and Classification 

Acute 

Toxicity 

Classification 

Chronic 

NOAEC 

Chronic 

Study 

MRID 

Foliage 

Residue 

<3 hrs

41940801 

Acceptable NA 

Freshwater fish2

Bluegill 

(Lepomis 

macrochirus)

LC50=15.9 

μg/L 

41609607 

Acceptable 

Very highly 

toxic 

No data No data Rainbow Trout 

(Oncorhynchus 

mykiss) 

LC50=3.7 

μg/L 

41609608 

Acceptable 

Very highly 

toxic 

Freshwater 

invertebrates 

Water flea 

(Daphnia 

magna)

Unreliable 41609609 

Supplemental3

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 terrestrial-phase amphibians and reptiles. 2

 Freshwater fish may be surrogates for aquatic-phase amphibians. 3

 This study cannot be used quantitatively in a risk assessment and therefore does not fulfill the 850.1010 guideline requirement 

for an acute freshwater invertebrate toxicity test. 

5.1. Effects to Aquatic Organisms 

The acute toxicity of technical grade tetramethrin has been tested in two species of freshwater 

fish, rainbow trout (Oncorhychus mykiss) and bluegill sunfish (Lepomis macrochirus). The 96-

hr LC50 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 EC50 of 45 μg/L 

(MRID 41609609). This study is classified supplemental and does not fulfill the guideline 

requirement for an acute freshwater invertebrate 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 concentrations 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 concentrations from 0 to 48 hrs. Measured 

concentrations were only provided for these two time points. This substantial deviation from the 

guideline requirement of ≤20% change results in insufficient confidence in the exposure 

concentrations to use the study results quantitatively in an ecological risk assessment. The 48-hr 

EC50 of 45 μg/L calculated using this study is based 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 available for freshwater fish or invertebrates. Additionally, no acute 

or chronic toxicity data are available for estuarine/marine fish or invertebrates. Toxicity data are 

also lacking for vascular and non-vascular aquatic plants. No toxicity data 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 toxicity 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 chronic reproductive studies for 

laboratory rats were study submitted to the Health Effects Division (HED) and used to assess 

effects to mammalian wildlife. Toxicity to terrestrial invertebrates was tested by an acute 

contact study and a foliar residue study using the honey bee (Apis mellifera). 

Tetramethrin is practically non-toxic to birds on the basis of acute oral and dietary studies. The 

bobwhite quail oral toxicity study (MRID 41609604) resulted in an LD50 >2250 mg/kg body 

weight (bw). Four avian dietary toxicity studies, two with bobwhite quail and two with mallard, 

(MRIDs 00121262, 00121268, 41609605, 41609604) resulted in an LC50 >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 LD50 >5000 mg/kg bw. In a 2-generation 

reproduction study (MRID 00161842), tetramethrin was administered to laboratory rats at 

various dietary concentrations. There was an effect on pup weight in the F2 generation, which is 

considered a reproductive effect. The parental NOAEL = 25 mg/kg-day in both sexes and the 

parental LOAEL = 150 mg/kg-day for both sexes of F0 and F1 based on reductions in body 

weights and food consumption. The offspring NOAEL is 25 mg/kg/day and the LOAEL is 150 

mg/kg-day based on reductions in pup body weights of the F2 generation during lactation. 

Tetramethrin is considered highly toxic to adult 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 submitted resulted in an LD50 = 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 related 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 tetramethrin formulated with synergists 

for these taxa. While all of this data is ordinarily required for outdoor residential uses, these 

studies were not requested in the 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 parent (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 concluded that for risk assessment, the 

parent compound, tetramethrin, is the only residue of toxicological concern. EFED concurs with 

this conclusion. 

5.4. Ecological Incidents 

A review of the Ecological Incident Information System (EIIS, version 2.1.1), the ‘Aggregate 

Incident Reports’ (v. 1.0) database, and the Avian Monitoring Information System (AIMS) for 

ecological incidents involving tetramethrin was completed on 11 July 2011. 

The searches of EIIS and AIMS identified no ecological incidents involving 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. Incident reports for non-target organisms typically 

provide information only on mortality events and plant damage. Sub-lethal effects in organisms 

such as abnormal behavior, reduced growth and/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 given the nature of the incident reporting. 

Incidents have been reported to the Agency in aggregated 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 adverse effects to insects and other terrestrial 

invertebrates. For tetramethrin, registrants have reported 1 minor fish and wildlife incident, 9 

minor plant incidents, and no other non-target incidents between 1998 and 2009. Unless 

additional information on these aggregated incidents 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 tetramethrin, exposure of ecosystems is likely to be limited. There 

are no widespread uses of tetramethrin, such as application to agricultural fields or mosquito 

spraying by public health agencies. Pet, clothing, and bedding applications could result in washoff and down-the-drain exposures through pet bathing and laundering of clothing or bedding. 

However, these products account for only a small number 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 the greatest hazard are 

insects, fish and aquatic invertebrates. Thus, localized terrestrial and aquatic ecosystems in the 

immediate area of tetramethrin outdoor spraying are most likely to be affected. Terrestrial 

ecosystems potentially at risk could include areas immediately adjacent to treated structures and 

areas that may receive drift or runoff of residues sorbed to suspended sediment. Areas adjacent 

to the aerosol spray treated areas could include 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 actual 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 include the following: birds, reptiles, terrestrialphase amphibians, mammals, freshwater fish, freshwater aquatic-phase amphibians and 

invertebrates, estuarine/marine fish and invertebrates, terrestrial plants, insects, aquatic plants, 

and algae. The attributes for each of these entities include growth, reproduction, and survival. 

8. Conceptual Model 

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically 

significant concentrations. An exposure pathway is the means by which a pesticide moves in the 

environment from a source to an ecological receptor. 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, and 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 exposure, and the predicted 

effects for the assessment endpoint. A conceptual model consists of two major components: risk 

hypothesis and a conceptual diagram (USEPA, 1998). 

8.1. Risk Hypothesis 

A risk hypothesis describes the predicted relationship among the stressor, exposure, and 

assessment endpoint response along with the rationale for their selection. For tetramethrin, the 

following ecological risk hypothesis is being employed for this national-level ecological risk 

assessment: 

Tetramethrin, when used in accordance with current 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 atmospheric deposition to foliar surfaces may serve as a 

major source of tetramethrin exposure to wildlife. 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 tetramethrin into terrestrial (soil and foliage), and 

to a lesser degree aquatic (water and sediment) habitats. The movement away from the site of 

application in turn represents exposure pathways 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 tetramethrin exposure). EFED does 

not believe that tetramethrin is a threat to contaminate groundwater because of its limited use and 

rapid hydrolysis. 

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. 

As indicated in Figure 1, the possible exposure mechanisms considered are runoff, spray drift, 

and direct spray. While tetramethrin’s low persistence suggests that transport may be limited 

under some conditions, and that the pesticide’s low 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 survival
Page 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 such as applications to agricultural fields or public health uses. 

Conversely, tetramethrin uses considered here are limited 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 applications 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 major assumptions) using the tools 

on which OPP typically relies. The difficulty in calculating standard EECs is due to a number of 

factors including non-standard use rates (e.g., “1-2 second burst,” “lbs a.i./ft3”) 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 following 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 pyrethroid, tetramethrin is one of the 

least persistent pyrethroids. 

Although there are uncertainties regarding the extent of use in residential settings, the cumulative 

exposure from multiple spot treatments across a particular setting is not likely to be substantial. 

This analysis plan will be revisited and may be revised depending upon a full review of the data 

available in the open literature and the information submitted by the public in response to the 

opening of the Registration Review docket. At a minimum, EFED will undertake analyses as 

described in Section 9.2, to provide a preliminary screening level estimates of potential 

exposures to surface water systems. As additional data become available EFED will conduct 

further analyses, as appropriate, to refine these preliminary estimates. Information that would be 

of particular interest includes amount of tetramethrin and the associated size of treated areas for 

the various labeled uses. 

Available monitoring data will be used to qualitatively characterize exposure. The Agency is 

aware of monitoring conducted by Federal and state 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 parent tetramethrin and the synergists PBO and 

MGK264. One identified degradate of tetramethrin, carboxyprop-1-
Page 23 of 41 

enyl)cyclopropanecarboxylate (acid-NPY), retains the ester linkage that is known to be needed 

for synthetic pyrethroid activity; however, because hydrolysis of the ester moiety is very rapid in 

non-acid environments, consideration of exposure to acid-NPY is not necessary. 

Tetramethrin is frequently co-formulated with synergists (e.g., PBO and MGK-264). These 

synergists increase the toxicity of tetramethrin, 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 will be evaluated through toxicity studies using 

TEPs formulated with PBO and TEPs formulated with MGK-264. 

Evaluation of pesticide mixtures is beyond the scope of this assessment because of the myriad 

factors that cannot be quantified based on the available data. Those factors include identification 

of other possible co-contaminants and their concentrations, differences in the pattern and 

duration of exposure among contaminants, and the differential effects of other physical/chemical 

characteristics of the receiving waters (e.g. organic matter present in sediment and suspended 

water). 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 considering mixtures could over- or under-estimate risks depending on 

the type of interaction and factors discussed above. The assessment will, however, analyze the 

toxicity of formulated products (including formulations involving more than one active 

ingredient) and will determine whether formulated products are more toxic than the technical 

grade active ingredient data used for assessing both direct and 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 EFAST2, 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 model 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 removed during wastewater treatment). 

Conceptually, the model assumes that in a given year the entire production 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 capita and daily per capita release of a chemical to a wastewater 
Page 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 treatment facility. The chemical’s concentration in untreated 

wastewater is then reduced by the fraction removed during wastewater treatment processes 

before release into a river or stream where it undergoes dilution. 

Based on this analysis, it was determined that indoor uses are of low concern for environmental 

effects. E-FAST generated EECs were approximately 1.12 μg/L for surface water. Using this 

value to calculate RQs resulted in exceedances of acute LOCs for listed species (0.05) and 

restricted uses (0.1) for freshwater 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 tetramethrin 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 residential and industrial/commercial areas 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 individual, isolated areas, and again, in relatively 

small amounts. These characteristics limit the utility 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. Organisms 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 

(LC50s) for tetramethrin are currently approximately 3 μg/L with associated concern levels at 

approximately 0.1 μg/L, (2) LC50s may decrease upon submitted data, and (3) toxicity occurs 

very rapidly in aquatic animals, the potential for aquatic contamination, 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 1/10th of this concentration. 

Therefore, risk potential will be estimated by determining the feasibility that exposure levels may 

approach levels of concern. An initial risk feasibility analysis suggests that potential risks to 

aquatic organisms could exceed concern levels under some conditions. However, risk is likely 

limited to organisms that are in close proximity to a larger scale application sites such as 
Page 25 of 41 

nurseries or large residential areas. Risk is also likely limited to application methods that may 

result in greater volume of material being applied 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 exposure and potential risks. 

EFED’s initial analysis suggests 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 concentration of active ingredient in the products. The feasibility 

of this volume of spray solution entering a water body depends on the amount of spray solution 

applied to a nearby area. For small scale spray applications it is unlikely that this amount of 

solution will enter water bodies. However, for larger 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 toxicity of tetramethrin products formulated 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 were 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 organisms 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. Toxicity data for freshwater and 

estuarine/marine aquatic organisms are needed to quantify the expected increase in toxicity for 

tetramethrin products co-formulated with synergists. Degradation in estuarine/marine systems is 

expected to be rapid, as seawater pH is slightly basic, ranging from 7.4 to 9.6 (Marion et al., 

2011), and hydrolysis of tetramethrin in this pH range is <1 day. However, acute toxicity effects 

occur rapidly (within the first measurement, which occurred at 24 hours after dosing) in a 

freshwater fish study (MRID 41609608) and are assumed to occur 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 effects. The use patterns of tetramethrin 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 estimate environmental concentrations based on 

widespread applications such as use on field crops or turf. EEC values used for terrestrial 

exposure are typically derived from the Kenaga 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 small-scale outdoor urban uses. Furthermore, the 

potential for tetramethrin to reach non-target terrestrial animals at levels approaching effect 

concentrations is considered minimal based on the supported uses (inclusive of use type, 

formulations, and application type and rates). Therefore, terrestrial exposure modeling will not 

be used to directly calculate standard risk quotients for tetramethrin; instead, T-REX calculations 

will be used to help characterize expected exposure to terrestrial animals. Like for aquatic 
Page 26 of 41 

exposures, risk potential will be estimated by determining the feasibility that exposure levels 

may approach levels of concern. 

EFED has conducted an initial analysis to estimate risk potential and determine the potential 

utility of additional data and analysis. The highest calculated use rate for an aerosol spray can is 

equivalent to a rate of 1.52 lbs a.i./acre (15.8 mg/ft2). Aerosol sprays are the most prevalent 

application method for tetramethrin products and are used for many registered outdoor use 

products. However, this application rate would be limited to the area 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 LD50 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 LD50 for a 20 g bird1: 2250 mg a.i./kg bw * (20 g/178 g)(1.15-1) = 1621 mg/kg-bw

Mass associated with LD50: 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 LD50 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 rapidly via photolysis and hydrolysis in non-acidic environments; 

however, it may persist for longer durations in dryer 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 tetramethrin include use on woody and herbaceous plants, 

which may be habitat for passerine species. 

Terrestrial plant exposures are 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 order to provide more ecological effects data 

to bridge existing data gaps. ECOTOX is a source for locating single chemical toxicity data and 

potential chemical mixture toxicity data for aquatic life, terrestrial plants, and wildlife. 

ECOTOX was created and is maintained by the 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 Effects 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 (EIIS; USEPA, 2007a). The EIIS is a database 

containing adverse effect (typically mortality) reports on non-target organisms where such 

effects have been associated with the use of pesticides. 

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). Quantitative assessments of risks, though, 

are limited to those endpoints that can be directly linked to the Agency’s assessment endpoints of 

impaired survival, growth and reproduction. 

The assessment of risk for direct effects to non-target organisms makes the assumption that 

toxicity of tetramethrin to birds is similar to terrestrial-phase amphibians and reptiles. The same 

assumption is made for fish and aquatic-phase amphibians. 

The acute measures of effect used for animals in this screening-level assessment are the LD50, 

LC50 and EC50. LD stands for "Lethal Dose", and LD50 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 LC50 is the concentration of a chemical that is estimated to kill 50% of the 

test organisms. EC stands for “Effective Concentration” and the EC50 is the concentration of a 

chemical that is estimated to produce a specific effect in 50% of the test organisms. Endpoints 

for chronic measures of exposure for listed and non-listed animals are the NOAEL/NOAEC and 

NOEC. NOAEL stands for “No Observed-Adverse-Effect-Level” and refers to the highest tested 

dose of a substance that has been reported to have no harmful (adverse) effects on test 

organisms. The NOAEC (i.e., “No-Observed-Adverse-Effect-Concentration”) is the highest test 

concentration at which none of the observed effects were statistically different from the control. 

The NOEC is the No-Observed-Effects-Concentration. For non-listed plants, only acute 

exposures are assessed (i.e., EC25 for terrestrial plants and EC50 for aquatic plants); for listed 

plants, either the NOAEC or EC05 is used. 
Page 28 of 41 

9.4. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects characterization to 

determine the potential ecological risk from the uses of tetramethrin listed in Table 2 and the 

likelihood of direct and indirect effects to non-target organisms in aquatic and terrestrial habitats. 

The exposure and toxicity effects data are integrated 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 exposure and measured toxicity values. EECs are 

divided by acute and chronic toxicity values. The resulting RQs are then compared to the 

Agency’s LOCs (USEPA, 2004). These criteria are used to indicate when uses of tetramethrin, 

as directed on the label, have the potential to cause adverse direct or indirect effects to non-target 

organisms. As noted previously, where data are lacking on the toxicity of tetramethrin, risk will 

be presumed. 

 

9.4.1. Deterministic and Probabilistic Assessment Methods 

The quantitative assessment of risk will primarily depend on the deterministic point-estimate 

based approach described in the risk assessment. 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 Species Act (ESA), the 

Agency will evaluate risks to Federally-listed threatened and/or endangered (listed) species from 

registered uses of tetramethrin. This assessment will be conducted in accordance with the 

Overview Document (USEPA, 2004), provisions of the ESA, and the Services’ Endangered 

Species Consultation Handbook (USFWS/NMFS 1998). 

The assessment of effects associated with the registration of tetramethrin is based on an action 

area. The action area is considered to be the area directly or indirectly affected by the federal 

action, as indicated by the exceedance of Agency LOCs used to evaluate direct or indirect 

effects. The Agency’s approach to defining the action area under the provisions of the Overview 

Document (USEPA, 2004) considers the results of the risk assessment process to establish 

boundaries for that action area with the understanding that exposures below the Agency’s 

defined LOCs constitute a no-effect threshold. For the purposes of this assessment, attention will 

be focused on the footprint of the action (i.e., the area where 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 reproduction as well as the full suite of sub-lethal 

effects available in the effects literature. Therefore, the action area extends to a point where 

environmental exposures are below any measured lethal or sub-lethal effect threshold for any 

biological entity at the whole organism, organ, tissue, and/or cellular level of organization. In 
Page 29 of 41 

situations where it is not possible to determine 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 drinking water assessment for the tetramethrin 

because the chemical's use was considered limited to indoor non-food uses, and was labelled for 

only limited outdoor uses (e.g., spot treatments, foggers). Therefore, 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 water assessment will not be conducted to support a 

human dietary risk assessment 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 publish water quality criteria that accurately reflect 

the latest scientific knowledge on the kind and extent of all identifiable effects on health and 

welfare which might be expected from the presence of pollutants in any body of water, including 

ground water. While these recommended criteria do not, in themselves, impose any 

requirements, states and authorized tribes can use them to develop water quality standards. An 

Aquatic Life Ambient Water Quality Criteria document has not been published for tetramethrin 

(refer to url: http://water.epa.gov/scitech/swguidance/standards/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 species from the most recent risk assessments. 

For tetramethrin, no aquatic life benchmarks have been published (see url: 

http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_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 (TMDL) criteria have been developed for 

tetramethrin, based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?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, data 
Page 30 of 41 

should conform to the quality standards in Appendix A of the OPP Standard Operating 

Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s 

Registration Review Risk Assessment and Management Process (see: 

http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm), in order to ensure 

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

10. Endocrine Disruptor Screening Program 

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

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

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

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

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

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

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

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

taxonomic groups. As part of its reregistration decision, EPA reviewed these data and selected 

the most sensitive endpoints for relevant risk assessment scenarios from the existing hazard 

database. However, as required by FFDCA section 408(p), tetramethrin is subject to the 

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

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

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

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

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

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

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

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

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. Tetramethrin 

is not among the group of 58 pesticide active ingredients on the initial list to be screened under 

the EDSP. Accordingly, as part of registration review, EPA will issue future EDSP orders/data 

call-ins, requiring the submission of EDSP screening assays for tetramethrin. For further 

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

future lists, the test guidelines and the Tier 1 screening battery, please visit our website: 

http://www.epa.gov/endo/. 
Page 31 of 41 

11. Preliminary Identification of Data Gaps 

11.1. Fate

The environmental fate data currently available are sufficient to conduct a risk assessment, 

although environmental chemistry methods are needed 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 hydrolysis of the ester moiety is very rapid, 

exposure to acid-NPY will not be considered. 

Table 6. Available environmental 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 the fate of pesticides 

in the environment. The methods identify and quantify the pesticide residues of interest, 

determining the total concentration of pesticides, including the extractable parent compound and 

significant metabolites and degradates. 

11.2. Effects 

Although many submissions have been made to provide data on the effects of tetramethrin to 

aquatic and terrestrial organisms, data gaps still exist (See Table 7, Table 8, and Table 9). 

Rationale for the additional data requested is presented below the tables. 

Table 7. Available ecological effects data for terrestrial animals exposed 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 BQ141609604 BQ 

Acceptable 

Acceptable Yes2

 850.2200 

(71-2) Avian dietary toxicity Yes 

121262 MD3

121268 BQ 

41609605 BQ 

41609606 MD 

Acceptable 

Acceptable 

Acceptable 

Acceptable 

No 

 850.2300 

(71-4) Avian reproduction No No data No4

 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 species. Because no acute oral 

toxicity data have been submitted for a passerine species exposed to tetramethrin, this is a data gap. No acute oral toxicity data 

involving tetramethrin or its degradates have been identified in the scientific literature using 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 utility of additional data submissions. 

Guideline Number: 850.2100 

Study Title: Avian acute oral toxicity test (passerine species) 

Acute avian oral toxicity data are required for either one waterfowl or one upland game species 
Page 33 of 41 

and one passerine species under the 40 CFR Part 158 (2010) data requirements for conventional 

pesticides with outdoor uses. Submitted acute oral 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 either 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 LD50 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 square foot applied to result concerns for listed 

species based on the currently available data. Tetramethrin breaks 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 acute exposures. The use patterns of tetramethrin 

include use on woody and herbaceous plants, which may be habitat for passerine species. A 

passerine study protocol should be submitted for review by the Agency prior to initiation of the 

study. 

Table 8. Available ecological effects data for aquatic animals exposed 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 

No1

850.1020 

Aquatic invertebrate acute 

toxicity 

(Hyalella azteca) 

No No data Yes1

850.1025 

850.1035 

850.1045 

850.1055 

(72-3) 

Saltwater invertebrate acute 

toxicity No No data Yes2

 850.1075 

(72-1) Saltwater fish acute toxicity No No data Yes2

 850.1075 

(72-1) Freshwater fish acute toxicity Partially 

121296 

41609607 

41609608 

Supplemental 

Acceptable 

Acceptable 

Yes1

 850.1300 

(72-4) 

Freshwater invertebrate life 

cycle test No No data No3

 850.1400 

(72-4) 

Freshwater fish early life stage 

test No No data No3

850.1735 Freshwater invertebrate whole 

sediment acute toxicity No No data No4
Page 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 No4

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 products. Because available information indicates that greater 

toxicity enhancement can occur at higher synergist-to-a.i. ratios, selection of the TEPs for testing 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 conducting 

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 life cycle test and a freshwater fish early life stage test are 

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. 

4

 In 1999 a Science Advisory Panel (SAP) called for sediment toxicity testing for pyrethroids (USEPA, 1999). However, these 

studies are not requested for tetramethrin because of the low expected environmental concentration (EEC) of tetramethrin in 

sediment. Using the US EPA EFAST2 model’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 treatment systems, which would then 

undergo rapid degradation via hydrolysis in the pH-controlled discharge into waterways. 

For registration review, the following studies would 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 tetramethrin 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 invertebrates 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 may adversely affect the survival of aquatic 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 initiation or submit any open literature studies that may fulfill this data 

gap. 

Guideline Number: 850.1020 

Study Title: Gammarid Acute Toxicity Test (TEP) 

Data regarding the acute toxicity of tetramethrin TEPs to aquatic invertebrates have not been 

submitted to the Agency. Acute toxicity data for freshwater invertebrates are required under 40 

CFR Part 158 (2010) data requirements for pesticides with outdoor uses. TEP testing is required 

when an ingredient in the end-use formulation is expected to enhance the toxicity of the active 
Page 35 of 41 

ingredient of a product. These data are necessary to determine if acute exposure to tetramethrin 

TEP may adversely affect the survival of aquatic invertebrates. 

Because there are registered outdoor uses of tetramethrin that may result in exposure to water 

bodies, acute toxicity data of tetramethrin TEPs 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. Currently, no data is available to quantify the difference in 

toxicity for fish or invertebrates that may be concurrently exposed to tetramethrin and these 

synergists compared to the active ingredients alone. Therefore, the Agency is requesting acute 

toxicity studies of tetramethrin TEPs that are co-formulated with PBO and with MGK-264. 

Because available information indicates that greater toxicity enhancement can occur at higher 

synergist-to-a.i. ratios, selection of the TEPs for testing should include those TEPs with the 

highest synergist-to-a.i. ratio and are registered for outdoor uses. Hyalella azteca is 

recommended due to its much greater sensitivity 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 Gammarid amphipods is recommended with 

appropriate modifications to address specific testing needs of Hyalella azteca. The registrant 

should submit a test protocol prior to conducting these TEP studies that documents the rationale 

for the TEP selection and details of the testing procedure for Hyalella azteca. 

Guideline Number: 850.1025 

Study Title: Oyster Acute Toxicity Test (Shell Deposition) (TGAI) 

Data regarding the acute toxicity of tetramethrin 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 result 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/estuarine invertebrates are 

required under 40 CFR Part 158 (2010) data requirements 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 available 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. Therefore, to address this concern, the Agency will attempt to 

bridge results from ongoing “comprehensive” synergist testing 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, the 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 determine if acute exposure to tetramethrin TGAI may adversely 

affect the survival of marine/estuarine invertebrates. Registered outdoor uses of tetramethrin 

may result in exposure to marine/estuarine water bodies when used near coastal areas. 

Guideline Number: 850.1075 

Study Title: Fish Acute Toxicity 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 pesticides with outdoor uses. These data are 

necessary to determine if acute exposure to tetramethrin TGAI may adversely affect the survival 

of estuarine/marine fish. Registered outdoor uses of tetramethrin may result in exposure to 

marine/estuarine water bodies when used near coastal areas. 

Guideline Number: 850.1075 

Study Title: Fish Acute Toxicity 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 synergist 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 toxicity data for freshwater fish are required under 40 CFR Part 

158 (2010) data requirements for pesticides 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 determine 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 synergists compared to the active 

ingredients alone. Therefore, the Agency is requesting acute toxicity studies of tetramethrin 

TEPs that are co-formulated with PBO and with MGK-264. Because available information 

indicates that greater toxicity enhancement can occur at higher synergist-to-a.i. ratios, selection 

of the TEPs for testing 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 conducting 

these TEP studies that documents the rationale for the TEP selection. (See Footnote 1.) 

Table 9. Available ecological effects data for plants exposed to 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 for 

Risk Assessment? 

 850.4100 

(122-1) 

Terrestrial Plant toxicity: 

Tier II seedling emergence No No data Yes1

 850.4150 

(122-1) 

Terrestrial Plant toxicity: 

Tier II vegetative vigor No No data Yes1

 850.4400 

(123-2) 

Aquatic Plant Growth: 

Tier II vascular plants No No data No2

 850.5400 

(123-2) 

Aquatic Plant Growth: 

Tier II algae No No data No2

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 fulfill identified data gaps for 

plants: 

Guideline Number: 850.4100 

Study Title: Terrestrial Plant 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 determine 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 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. 

Guideline Number: 850.4150 

Study Title: Terrestrial Plant 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 determine whether the outdoor use of 

tetramethrin could adversely affect vegetative vigor of non-target plant species in the terrestrial 

environment. Nine minor plant incidents resulting 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.

41995007 Yoshimura, J.; Mikami, N.; Matsuo, M.; et al. (1991) Adsorption and Desorption of 

Tetramethrin in Water-Soil Suspension Systems: Lab Project Number: ADS91001. 

Unpublished study prepared by Sumitomo Chemical Co., Ltd, Environ. Health 

Science Lab. 60 p.

42212901 Yoshimura, J.; Mikami, N.; Matsuo, M.; et al. (1992) Aged Column Leaching Study 

of carbon 14-Tetramethrin in Soil: Lab Project Number: LEA91001. Unpublished 

study prepared by Sumitomo Chemical Co., Ltd. 81 p.

42563301 Yoshimura, J.; Mikami, N.; Matsuo, M. (1992) Aerobic Soil Metabolism Study of 

(Carbon 14)-(1RS)-trans-Tetramethrin: Lab Project Number: SOI90001. Unpublished 

study prepared by Sumitomo Chemical Co., Ltd. 209 p.

42622401 Ver Hey, M. (1992) A Terrestrial Field Dissipation Study with Tetramethrin (NeoPynamin) Applied for Control of Insects in Plants (California Field Study): Lab 

Project Number: SUMITOMO-1150. Unpublished study prepared by Colorado 

Analytical Research & Development Corp. 397 p.

42622402 Ver Hey, M. (1992) A Terrestrial Field Dissipation Study with Tetramethrin (NeoPynamin) Applied for Control of Insects in Plants (Florida Field Study): Lab Project 

Number: SUMITOMO-1150. Unpublished study prepared by Colorado Analytical 

Research & Development Corp. 450 p.

43773401 Chen, Y.; Casida, J. (1969) Photodegradation of pyrethrin I, allethrin, phthalthrin, and 

dimethrin: Modifications in the acid moiety. J. Agr. Food Chem. 17(2):208-215.

Effects 

00121262 Fink, R.; Beavers, J.; Brown, R. (1978) Eight-day Dietary LC50-- Mallard Duck: 

Neo-pynamin: Project No. 163-103. Final rept. (Unpublished study received Jun 

19, 1978 under 1021-1384; prepared by Wildlife International Ltd. and 

Washington College, submitted by McLaughlin Gormley King Co., Minneapolis, 

MN; CDL:234384-A) 

00121268 Fink, R.; Beavers, J.; Brown, R. (1978) Eight-day Dietary LC50-- Bobwhite 

Quail: Neo-pynamin: Project No. 163-101. Final rept. (Unpublished study 

received Aug 17, 1978 under 1021-1384; prepared by Wildlife International Ltd. 

and Washington College, submitted by McLaughlin Gormley King Co., 

Minneapolis, MN; CDL:235959-A) 

00121269 Ralston Purina Co. (1978) Fish Pesticide: Acute Toxicity on Bluegill Sunfish, 

Fish Pesticide Acute Toxicity on Rainbow Trout: RT. No. 80402331. 

(Unpublished study received Sep 1, 1978 under 1021-1384; submitted by 

McLaughlin Gormley King Co., Minneapolis, MN; CDL:235960-A) 

00121273 Fink, R.; Beavers, J.; Grimes, J.; et al. (1978) Acute Oral LD50- Bobwhite Quail-
Page 39 of 41 

-Neo-pynamin: Project No. 166-101. Final rept. (Unpublished study received Feb 

21, 1979 under 1021-1384; prepared by Wildlife International Ltd. and 

Washington College, submitted by McLaughlin Gormley King Co., Minneapolis, 

MN; CDL:238214-A) 

00121279 Thompson, G. (1979) Aquatic Invertebrate (Daphnia) Toxicity Study: Neopynamin T.G.: RT No. 718940. (Unpublished study received May 2, 1979 under 

1021-1386; prepared by Raltech Scientific Services, Inc., submitted by 

McLaughlin Gormley King Co., Minneapolis, MN; CDL:238275-F) 

00161842 Pence, D.H.; Wolfe, G.W.; Kulwich, B.A.; Hepner, K.E. (1986) Two-Generation 

Reproduction Study in Rats Neopynamin Forte. Unpublished Study Prepared by 

Sumitomo Chemical Co. Ltd. 422 p. 

41609604 Culotta, J. et al. (1990) Neo-Pynamin: An Acute Oral Toxicity Study with the 

Bobwhite: (IW-01-0008): Final Report: Lab Project Number: IW/01/0008. 

Unpublished study prepared by Sumitomo Chemical Company. 17 p. 

41906905 Long, R.; Hoxter, K.; Smith, G. (1990) Neo-Pynamin: A Dietary LC50 Study 

with the Northern Bobwhite: Lab Project Number: 166/133. Unpublished study 

prepared by Sumitomo Chemical Company. 54 p. 

41906906 Long, R.; Hoxter, K.; Smith, G. (1990) Neo-Pynamin: A Dietary LC50 Study 

with the Mallard: Lab Project Number: 166/134. Unpublished study prepared by 

Sumitomo Chemical Company. 54 p. 

41609607 Bowman, J. (1990) Acute Flow-through Toxicity of Neo-Pynamin to Bluegill: 

(Lepomis-macrochirus): Lab Project Number: IW/01/0010. Unpublished study 

prepared by Analytical Bio-Chemistry Labora- tories, Inc. 188 p. 

41609608 Bowman, J.; Gormley, M. (1990) Acute Flow-Through Toxicity of Neo- Pynamin 

to Rainbow Trout (Oncorhynchus mykiss): Lab Project Number: IW/01/0011. 

Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc., 189 

p. 

41609609 Burgess, D. (1990) Acute Flow-through Toxicity of Neo-Pynamin to Daphnia 

magna: Lab Project Number: IW/01/0009. Unpublished Study Prepared by 

Analytical Bio-Chemistry Laboratories, Inc., 176 p. 

41609613 Hoxter, K.; Smith, G.; Jaber, M. (1990) Neo-Pynamin: An Acute Contact 

Toxicity Study with the Honey Bee: Lab Project Number: 1W/01/0012. 

Unpublished study prepared by Sumitomo Chemical Co. Ltd. 13 p. 

41940801 Hoxter, K.; Lynn, S. (1991) Neo-Pynamin: A Foliage Residue Toxicity Study 

With the Honey Bee: Lab Project Number: 166-151C. Unpublished study 

prepared by Wildlife International Ltd. 23 p. 

42146405 Kohda, H; Misaki, Y.; Suzuki, T. (1981) Acute Oral, Subcutaneous, 

Intraperitoneal, and Dermal LD50 of Neopynamin-Forte in Rats and Mice. 

Unpublished study prepared by Sumitomo Chemical Co. Ltd. 40 p. 

Addy-Orduna, L.M., M-E. Zaccagnini, S.B. Canavelli, and P. Mineau. 2001. Formulated betacyfluthrin shows wide divergence in toxicity among bird species. Journal of Toxicology 2011, 

Article ID 803451: 10 pages.
Page 40 of 41 

Amweg, E.L. and D.P. Weston. 2007. Whole-sediment toxicity identification evaluation tools for 

pyrethroid insecticides: I. Piperonyl Butoxide addition. Environ Toxicol & Chem 26(11):2389-

2396. 

Anderson, B.S., B.M. Phillips, J.W. Hunt, V. Connor, N. Richard, and R.S. Tjeerdema. 2006. 

Identifying primary stressors impacting macroinvertebrates in the Salinas River (California, 

USA): Relative effects of pesticides and suspended particles. Environ Pollution 141:402-408. 

Barile, F.A. 2004. Clinical Toxicology: Principles and Mechanisms. Boca Raton, FL: CRC 

Press. 

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the 

EPA food-chain (Kenaga) nomogram, an instrument for estimating pesticide residues on plants. 

Environ Tox Chem 13:1383-1391. 

Hansch, C. et al. 1995. Exploring QSAR. Hydrophobic, Electronic, and Steric Constants. ACS 

Prof Ref Book. Heller SR, consult. ed., Washington, DC: Amer Chem Soc p. 164. 

Hodgson, E. and Smart, R. C. (Eds.). 2001. Introduction to Biochemical Toxicology (Third ed.). 

New York: Wiley-Interscience. 

Hoerger, F. and E. E. Kenaga. 1972. Pesticide Residues on Plants: Correlation of Representative 

Data as a Basis for Estimation of their Magnitude in the Environment. In F. Coulston and F. 

Korte, eds., Environmental Quality and Safety: Chemistry, Toxicology, and Technology, Georg 

Thieme Publ., Stuttgart, West Germany, pp. 9-28. 

Kohda, H. 1985. Acute toxicity of S-1844 in rates. IH178505. Sumitomo Chemical 

Co. Ltd. Takarazuka Research Center, Hyogo, Japan. Unpublished report (LLT-50-0002). 

Marion, G.M., F.J. Millero, M.F. Camoes, P. Spitzer, R. Feistel, and C.-T.A. Chen. 2011. pH of 

seawater. Marine Chemistry 126(1-4):89-96. 

Maund, S.J., M.J. Hamer, M.C.G. Lane, E. Farrelly, J.H. Rapley, U.M. Goggin, and W.E. 

Gentle. 2002. Partitioning, Bioavailability, and Toxicity of the Pyrethroid Insecticide 

Cypermethrin in Sediments. Environmental Toxicology and Chemistry 21(1):9-15. 

Shafer, T.J., D.A. Meyer, and K.M. Crofton. 2005. Developmental neurotoxicity of pyrethroid 

insecticides: Critical review and future research needs. Environ Health Perspect 113:123-136. 

Stewart, D. 1998. The Evaluation of Synergistic Action in the Laboratory and Field. P. 173-198 

In: Piperonyl Butoxide: the Insecticide Synergist. Academic Press. 

U.S. Environmental Protection Agency. 1998. Guidelines for Ecological Risk Assessment. Risk 

Assessment Forum, Office of Research and Development, Washington, D.C. EPA/630/R951002F. April 1998. 
Page 41 of 41 

U.S. Environmental Protection Agency. 1999. FIFRA Scientific Advisory Panel Meeting, 

February 23, 1999 held at the Holiday Inn Hotel, Arlington, Virginia. S.R.N. 99-03A. March 

25. 1999. Office of Pesticide Programs. Available at 

http://www.epa.gov/scipoly/sap/meetings/1999/022399_mtg.htm#materials. 

U.S. Environmental Protection Agency. 2004. Overview of the Ecological Risk Assessment 

Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency. Endangered 

and Threatened Species Effects Determinations. Office of Prevention, Pesticides and Toxic 

Substances, Office of Pesticide Programs, Washington, D.C. January 23, 2004. 

U.S. Environmental Protection Agency. 2007a. Ecological Incident Information System. 

http://www.epa.gov/espp/consultation/ecorisk-overview.pdf 

U.S. Environmental Protection Agency 2007b. ECOTOXicology Database. Office of Research 

and Development National Health and Environmental Effects Research Laboratory’s 

(NHEERL’s) Mid-Continent Ecology Division (MED). http://cfpub.epa.gov/ecotox/ 

U.S. Environmental Protection Agency. 2008. Reregistration Eligibility Decision (RED) 

Document for Tetramethrin, EPA-HQ-OPP-2008-0014-0019, June 2008. 

U.S. Environmental Protection Agency. 2010. Reregistration Eligibility Decision (RED) 

Document for Tetramethrin, EPA 738-R-08-012, Revised April 2010. 

U.S. Environmental Protection Agency. 2011. BEAD Chemical Profile for Registration Review: 

Tetramethrin (PC Code: 069003). 

Weston, D.P. and M.J. Lydy. 2010. Urban and agricultural sources of pyrethroid insecticides to 

the Sacramento-San Joaquin delta of California. Environ Sci Techno. 44:1833-1840.