Environmental Fate and Ecological Risk Assessment 

for Section 3 and IR-4 Registration of 

New Uses of Zeta-cypermethrin 

ci 

CH, 

Date: May 8,2007 

PC Code: 129064 

DP Barcode: D335628, D335629, D335630 and D33563 1 

Prepared by: United States Environmental Protection Agency 

N.E.Federoff, Wildlife Biologist Office of Pesticide Programs 

JosC L. Meltndez, Chemist Environmental Fate and Effects Division 

Reviewed by: Environmental Risk Branch V 

Mah T. Sharnim, Branch Chief Ariel Rios Building 

Environmental Risk Branch V 1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington, DC 20460 

TEXT SEARCHABLE DOCUMENT
MEMORANDUM 

SUBJECT: Section 3 and IR-4 Registration of Zeta-cypermethrin (FURY and 

MUSTANG) for use on Wild rice, Safflower, Citrus and Okra. 

TO: Daniel Rosenblatt, Chief 

Richard Gebken, Chief 

George Larocca, Chief 

Sidney Jackson, Risk Manager Reviewer 

Linda DeLuise, Risk Manager Reviewer 

Registration Division (791 3P, 72 19P and 7237P) 

-9 

FROM: N.E. Federoff, Wildlife Biologist ep 

Josk Luis Melendez, Chemist -//6 d~ -aM 

Environmental Risk Branch V 

Environmental Fate and Effects Division (7507P) 

THROUGH: Mah T. Shamim, Ph.D., Chief 

Environmental Risk Branch V 

Environmental Fate and Effects Division (7507P) 

EFED has completed the assessment for wild rice for zeta-cypermethnn. EFED will rely on previous 

assessments for use of zeta-cypermethrin on Safflower, Okra and Citrus. 

Water Column Exposure for Wild Rice - Acute and Chronic Risk 

The Rice Model ("Policy for Estimating Aqueous Concentrations from Pesticides Labeled for 

Use on Rice," 10129102 Memorandum, From Steven Bradbury, To EFED), was utilized to obtain 

column water EECs for Wild Rice. Acute and chronic RQs for aquatic animals in the water 

column are summarized in the tables below. Based on the toxicity data for all cypermethrin 

products (alpha-, beta-, theta-, and zeta-cypermethrin), there is potential for acute risk to nontarget listed and non-listed freshwater and estuarinelmarine fish and invertebrates resulting from 

spray applications of zeta-cypermethrin to wild rice. Based on a comparison of acute LCs0 values, 

invertebrates appear to be the most sensitive aquatic animals. Acute RQs for invertebrates 

(854.73 - 1127.77) are much higher than those derived for fish (4.27 - 10.41). As anticipated, 

based on a comparison of the chronic NOAEC values, chronic RQs derived for aquatic 

invertebrates (2038 - 2695) are much higher than those derived for fish (1.8 - 4.3). 
Previous and current assessment 

The following attached assessment (DP Barcodes: D290875, D292524, D3 121 36, D3 12 138, 

D3 12470, D3 12474, D3 12476, D3 15421, D3 18775, D322954 and D322955) may be used in place of 

a new terrestrial and aquatic assessment for the currently proposed new uses of zeta-cypermethrin 

(DP Barcodes: D335628, D33 5629, D335630 and D33563 1). The previous assessment for cilantro, 

leafy vegetables, headlstem brassica, poine and stone hit can be used in place of a new assessment 

for okra. Grass, forage, hay group, rapeseed and canola can be used in place of citrus and wild rice. 

Non-grass forage, feed and fodder can be used in place of safflower. The rates are the same (0.2 lbs 

ailA1season for 4 applications for citrus and wild rice, 0.3 1bs ailA1season for 6 applications for okra 

and 0.15 lbs ai/A/season for 3 applications for safflower) for the crops groupings mentioned above. 

In addition, previous assessments, other than the one presently attached, also had similar rates for 

other crops (ie., corn, alfalfa, cotton, etc). A listing of endangered species is not attached because the 

listing would be extremely large in volume. 

Acute RQs for freshwater and estuarinelmarine fish and invertebrates exposed to zeta-cypermethrin ." 

Terrestrial EECs and resulting RQs can be used from the attached assessment since use rates were 

the same. A table of previous and current aquatic EECs are provided below for comparison purposes. 

EstuarinelMarine 

Invertebrate 

Acute RQ 

854.73 ' " 

Estuarinemarine 

Fish 

Acute RQ 

4.27 h' * 

Crop Use 

Wlld R~ce 

a RQs = EEC /LC v,, whe~e EFCs ate the peak concentlatlons In sutface water gene~ated from PRZMIEXAMS for the varlous clop scenarios 

consldered. and acute toxlclty tefe~ence values ale as follows fieshwatel fish, lambow t~out 96-h~ LC5,, = 0 39 pg a I IL, freshwater lnvertebrates 

amphlpod 96-h~ LC,,, = 0 0036 kig a I /L . estuar~~ielmar~ne fish, sheepshead mlnnow 96-hou~ LC,(, = 0 95 pg a I IL. and est~~arlnel~nar~ne 

~nvel-tehlates, lnys~d sh~nnp 96-hou~ LC,,, = 0 00475 pg a I /L 

" RQs meet 01 exceed I OC for acute iisk (LOC 0 5) 

RQs meet or exceed LOC fo~ acute test1 lcted use ( LOC 0 I ) 

"QS meet 01 exceed LOC fo~ acute endangered speclea (LOC 0 05) 

Chronic RQs for freshwater and estuarinetmarine fish and invertebrates exposed to zeta-cypermethrin .' 

Freshwater 

Fish 

Acute RQ 

10.41 "" 

Rice Model 

Acute Scenario 

EECs @pb) 

4 06 

Freshwater 

Invertebrate 

Acute RQ 

11 27.77 " ' 

Estuarinemarine 

Invertebrate 

Chronic RQ 

2038.5 

Crop Use 

Wlld Rlcc 

RQs = EEC NOAEC, whele the ch~on~c EECs foi ~nberteb~ates and fish ale the 21day and the 60-day avelage concentlatlons In su~face water 

genelated from PRZMIEXAMS fo~ the vallous clop scenario?, ~espectlvely, and chlonlc toxlclty refe~ence values are as follows freshwater fish, 

tathead Ininnom 30-day NOAFC = 0 14 pg a I IL. tieshmater lnvertebrates, estnnated chron~c NOAEC = 0 00059 pg a I IL. estuarlnel~narlne fish, 

estnnated cliron~c NOAFC = 0 34 pg a I IL. and estuar~~ielmar~nevertebrates. mqsid ~hr~mp 28-day NOAEC = 0 000781 pg a I IL Detalls for 

all estl~nated chlon~c toxlc~ty talues ale plov~ded ~n the Ecolog~cal Effects Chatacte~lzatlon sectron 

" RQs exceed LOCs fo~ chton~c I lsk (LOC I ) 

Rice Model 

Chronic Scenario 

EECs (ppb) 

21 day-1 59 

60 daq-0 62 

Freshwater 

Fish 

Chronic RQ 

4.43 

Freshwater 

Invertebrate 

Chronic RQ 

2695 

Estuarinernarine 

Fish 

Chronic RQ 

1.8 " 
Previous Estimated Environmental Concentrations (EECs) of Zeta-cypermethrin (ppb) in the water 

column, benthic pore water, and in benthic sediment. 

Current Estimated Environmental Concentrations (EECs) of zeta-cypermethrin (ppb) in the water 

60-day 

0 0106 

0 00104 

5 89 

0 01 19 

0 00161 

9 15 

0 0641 

0 0142 

71 9 

0 00215 

0 000343 

1 94 

column, benthic 

Crop Scenario 

FL cucu~nbe~ gound" 

FL cucu~nbe~ 

(I'A cltrus gound " 

C A clllus ae~~al ' 

Wild R~ce 

" A chosen leptesentatlve scenalto fo~ splay appllcat~ons of zeta-cypenneth~~n to agtlcultu~al clops 

h chosen leplesentatl\e scenat~o Sol g~anula~ appllcatlons of zeta-cype~ineth~~n to ~es~dentlal lawns, home pelllnetelq, galdens, and 

lndustt ldl non-agllcultul a] areas. 

Crop Scenario 

CA Gtapes* 

GA Peaches " 

PA Apples" 

F I SUI~ 

Peak 

0 0841 

0 00159 

9 04 

0 201 

0 00255 

14 4 

1 46 

0 0197 

112 

0 0405 

0 000624 

3 53 

Media 

Wdte~ Colu~nn 

Benth~c Pole Water 

Benth~c Sed~rnent 

Watet Column 

Bcnth~c Pole Wate~ 

Benth~c Scd~~nent 

Water Colu~nn 

Benth~c Pole Wate~ 

Benth~c Sednnent 

Wate~ Column 

Benth~c Pore Wate~ 

Benthic Sednnent 

" chosen ~eplesentat~ve scenallo foi splay appl~cat~ons of zeta-cypenneth~~n to agt~cultu~al clops 

21-day 

0 0150 

000137 

7 79 

0 0195 

0 00225 

12 8 

0 122 

0 0173 

80 3 

0 00403 

0 000466 

2 64 

60-day 

0 00487 

0 000966 

5 47 

0 0132 

0 00170 

9 63 

0 00206 

0 000285 

1 62 

0 00803 

0 001 10 

6 28 

0 62 

pore water, and benthic sediment. 

21-day 

0 00832 

0 00129 

7 31 

00191 

0 00227 

12 87 

0 00289 

0 000384 

2 18 

0 01 12 

0 00149 

8 47 

1 59 

Media 

Wate~ Colu~nn 

Benth~c Pole Wate~ 

Benth~c Sed~tnent 

Water Column 

ae~lalVenth~c Pole Watet 

Benth~c Sedttnent 

Water Column 

Benth~c Pole Watet 

Benth~c Sednnent 

Wate~ C olu~nn 

Benth~c Pole Wate~ 

Benth~c Sednnent 

Water Colu~nn 

Peak 

0 0883 

0 00147 

8 35 

0 0932 

0 00256 

14 51 

0 0215 

0 000414 

2 35 

0 0838 

0 00161 

9 14 

4 06 
TABLE OF CONTENTS 

I . Executive Summary ........................................................................................................................ 8 

A . Nature of Chemical Stressor ...................................................................................................... 8 

B . Potential Risks to Nan-Target Organisms ........................................................................... 8 

C . Conclusions - Exposure Characterization .............................................................................. 11 

D . Conclusions - Effects Characterization ................................................................................... 13 

E . Uncertainties and Data Gaps .................................................................................................. 14 

1 . Environmental Fate ................................................................................................................. 14 

2 . Ecological Effects ..................................................................................................................... 15 

................................................................................................................... I1 . Problem Formulation 15 

A . Stressor Source and Distribution ................................................................................................ 15 

1 . Source and Intensity ............................................................................................................ 15 

2 . PhysicaYChemicaVFate and Transport Properties ........................................................... 16 

3 . Pesticide Type, Class, and Mode of Action ........................................................................ 17 

4 . Overview of Pesticide Usage ................................................................................................. 17 

B . Receptors .................................................................................................................................. 18 

1 . Aquatic Effects ..................................................................................................................... 19 

2 . Terrestrial Effects ................................................................................................................ 19 

3 . Ecosystems at Risk ............................................................................................................... 20 

C . Assessment Endpoints ................................................................................................................. 20 

D . Conceptual Model ..................................................................................................................... 21 

1 . Risk Hypotheses ................................................................................................................... 21 

2 . Diagram .................................................................................................................................... 22 

E . Analysis Plan ............................................................................................................................. 26 

1 . Preliminary Identification of Data Gaps and Methods .................................................. 26 

2 . Measures to Evaluate Risk Hypotheses and Conceptual Model ...................................... 27 

a Measures . of Exposure ..................................................................................................... 27 

b . Measures of Effect ........................................................................................................... 29 

c . Measures of Ecosystem and Receptor Characteristics .................................................. 30 

I11 . Analysis ......................................................................................................................................... 30 

A . Use Characterization ................................................................................................................... 30 

B . Exposure Characterization ......................................................................................................... 33 

1 . Environmental Fate and Transport Characterization ......................................................... 33 

a . Summary .............................................................................................................................. 33 

b . Hydrolysis ............................................................................................................................ 33 

c . Photolysis ............................................................................................................................. 34 

d . Metabolism .......................................................................................................................... 34 

e . SedimentIWater Systems .................................................................................................... 35 

f . Mobility ................................................................................................................................ 35 

g . Field Dissipation .................................................................................................................. 36 

h . Bioaccumulation .................................................................................................................. 37 

i . Nomenclature and Degradation Products of Cypermethrin .......................................... 37 

2 . Measures of Aquatic Exposure ............................................................................................... 37 

a . Aquatic Exposure Modeling ............................................................................................... 37 

b . Aquatic Exposure Monitoring (Field Data) ...................................................................... 41 

3 . Terrestrial Exposure Assessment ........................................................................................... 41 

a . Terrestrial Animal Exposure Modeling- Spray Applications ......................................... 42 
b . Terrestrial Animal Exposure Modeling-Granular Applications ..................................... 44 

C . Ecological Effects Characterization .......................................................................................... 47 

1 . Aquatic Effects Characterization .......................................................................................... 48 

a . Aquatic Animals ............................................................................................................... 51 

i . Acute Effects ................................................................................................................... 51 

ii . Chronic Effects ............................................................................................................... 53 

iii . Sub-lethal Effects ........................................................................................................ 55 

iv . Field Studies .................................................................................................................... 56 

b . Plants Inhabiting Aquatic Areas ........................................................................................ 56 

2 . Terrestrial Effects Characterization ...................................................................................... 56 

a . Terrestrial Animals ............................................................................................................. 57 

i . Acute Effects ................................................................................................................... 57 

ii . Chronic Effects ............................................................................................................... 58 

iii . Sub-lethal Effects ........................................................................................................ 59 

iv . Field Studies .................................................................................................................... 59 

b . Terrestrial Plants ................................................................................................................ 60 

IV . Risk Characterization .................................................................................................................. 60 

A . Risk Estimation - Integration of Exposure and Effects Data ................................................. 60 

1 . Non-Target Aquatic Animals and Plants .............................................................................. 60 

a . Water Column Exposure - Acute and Chronic Risk ..................................................... 61 

b . Sediment Exposure - Acute and Chronic Risk .............................................................. 62 

c . Aquatic Plants ..................................................................................................................... 63 

2 . Non-Target Terrestrial Animals ............................................................................................ 63 

a . Spray Applications: Acute Risk to Birds and Mammals ................................................ 64 

b . Spray Applications: Chronic Risk to Birds and Mammals ............................................. 68 

c . Granular Applications: Acute and Chronic Risk to Birds and ....................................... 69 

Mammals ...................................................................................................................................... 69 

3 . Non-target Plants Inhabiting Terrestrial and Semi-Aquatic Areas .................................... 70 

B . Risk Description ........................................................................................................................... 70 

1 . Risks to Aquatic Organisms .................................................................................................. 71 

a . Aquatic Animals: Water Column Exposure ..................................................................... 72 

b . Aquatic Animals: Sediment Exposure ............................................................................... 73 

c . Aquatic Plants .................................................................................................................... 74 

d . Summary of Risk to Aquatic Systems ............................................................................... 74 

2 . Risks to Terrestrial Organisms .............................................................................................. 76 

a . Spray Applications: Acute and Chronic Risk to Birds and Mammals ........................... 76 

b . Granular Applications: Acute and Chronic Risk to Birds and Mammals ..................... 78 

c . Non-Target Terrestrial Invertebrates ............................................................................... 79 

d . Terrestrial Plants ................................................................................................................ 79 

3 . Review of Incident Data .......................................................................................................... 79 

a . Incidents Involving Aquatic Organisms ............................................................................ 80 

b . Incidents Involving Terrestrial Organisms ....................................................................... 80 

4 . Endocrine Effects .................................................................................................................. 81 

5 . Threatened and Endangered Species Concerns .................................................................... 81 

a . Action Area .......................................................................................................................... 81 

b . Taxonomic Groups Potentially at Risk .......................................................................... 83 

i . Discussion of Risk Quotients .......................................................................................... 84 

ii . Probit Dose Response Relationship ............................................................................... 85 
c . Indirect Effects Analysis ..................................................................................................... 87 

d . Critical Habitat ................................................................................................................... 88 

e . Co-occurrence Analysis ...................................................................................................... 88 

C . Description of Assumptions. Limitations. Uncertainties. Strengths and Data Gaps ............. 89 

1 . Exposure For All Taxa ............................................................................................................ 89 

2 . Exposure For Aquatic Species ................................................................................................ 90 

3 . Exposure For Terrestrial Species ........................................................................................... 91 

a . Location of Wildlife Species ............................................................................................... 91 

b . Routes of Exposure ............................................................................................................. 91 

i . Incidental Soil Ingestion Exposure ................................................................................ 91 

ii . Inhalation Exposure ....................................................................................................... 92 

iii . Dermal Exposure ........................................................................................................ 92 

iv . Drinking Water Exposure .............................................................................................. 93 

c . Incidental Pesticide Releases Associated with Use .......................................................... 93 

d . Residue Levels Selection ..................................................................................................... 93 

e . Dietary Intake - The Differences Between Lab & Field Conditions ............................... 93 

4 . Effects Assessment ................................................................................................................... 94 

a . Age Class and Sensitivity of Effects Thresholds ............................................................... 95 

b . Lack of Effects Data for Amphibians and Reptiles ......................................................... 95 

c . Use of the Most Sensitive Species Tested ........................................................................... 96 

5 . Acute and Chronic LOCs ....................................................................................................... 96 

V . Literature Cited ............................................................................................................................... 96 

VI . Appendices 

A . Environmental Fate and Transport Data 

B . Information About PRZMIEXAMS Run 

C . T-REX Model (Version 1.2.3, August. 2005) 

D . Fugacity Model: Terrestrial Chronic Exposure Estimates for Granular Applications of 

Zeta- cypermethrin 

E . Ecological Effects Data 

F . The Risk Quotient Method and Levels of Concern 

G . Equilibrium Partitioning and Concentration in the Sediment 

H . Summary of EndangeredIThreatened Species 

I . Data Requirement Tables - Environmental Fate and Effects and Ecological Effects 

J . Incident Reports 

K . Environmental Fate and Monitoring Bibliography And Ecotoxicology Bibliography 
I. Executive Summary 

A. Nature of Chemical Stressor 

Zeta-cypermethrin (CAS number 97955-44-7) is a pyrethroid pesticide prepared from the esterification of 

3-phenoxybenzaldehyde and 3-(2.2-dichloroviny1)-2,2-dimethylcyclopropane carboxylic acid. It consists 

of a mixture of four diastereoisomers, each of which is present as a pair of enantiomers, resulting in eight 

geometrical and optical isomers. Zeta-cypermethrin is an enriched mixture of the (S) alcohol isomers. 

Different ratios of the eight isomers have resulted in four different cypermethrin products (alpha-, beta-, 

theta-, and zeta-cypermethrin) all of which have similar environmental fate and toxicological properties. 

Therefore, for the purposes of this risk assessment, the Agency has allowed use of the cypermethrin TGAI 

database to fulfill many registration requirements for zeta-cypermethrin and exposure and toxicity data for 

all cypermethrin products (alpha-, beta-, theta-, and zeta-cypermethrin) have been bridged. 

Cleavage at the ester moiety of zeta-cypermethrin results in two primary degradation products, 3-(2,2- 

dichloroetheny1)-2,2-dimethylcyclopropane carboxylic acid (DCVA) and 3-phenoxybenzaldehyde, which 

degrades further to 3-phenoxybenzoic acid (3-PBA). Based on the assumption that cleavage of the ester 

bond in the parent compound results in biologically inactive degradates, these compounds should not 

present a significant risk to non-target organisms and only the parent compound was considered of concern 

for both aquatic and terrestrial ecosystems. In fact, this assumption is supported by the results of acute 

toxicity studies in freshwater fish and invertebrates which indicate that the zeta-cypermethrin degradate 3- 

phenoxy benzoic acid is much less toxic than the parent compound. 

Like all pyrethroids, zeta-cyper~nethrin is a neural toxin that binds to voltage-gated sodium channels, 

prolongs the sodium ion penneability during the excitatory phase of the action potential, results in 

spontaneous depolarizations, augmented neurotransmitter secretion rate, and neuromuscular block, and 

eventually leads to muscle spasms, paralysis, and/or death. Forlnulations for zeta-cypermethrin include an 

emulsifiable concentrate and a granular. Zeta-cypermethrin is already used to control many pests, including 

those of cotton, alfalfa, bulb vegetables corn, fruiting vegetables (except cucurbits), legume vegetables, 

succulent edible-podded peas and beans, rice, sorghum (grain) and millet, soybeans, sugar beets, wheat and 

triticale crops. The registrant is also requesting tolerances or new agricultural uses for the emulsifiable 

concentrate to include cilantro, head and stem brassica vegetables, leafy vegetables (except brassica), 

sunflowers, grass forage, fodder, hay group, canola rapeseed, barley, grapes, tree nut group (almond, 

pecan), berries, peanuts, root and tuber vegetables, cucurbit vegetable group, non-grass feeds (forage, 

fodder, straw and hay), pome fruits, and stone fruits. Furthermore, a granular zeta-cypermethrin 

formulation is proposed for use on turf on residential lawns, home perimeters, gardens, and other industrial 

non-agricultural areas, while a zeta-cyperinethrin emulsion is proposed for use as a termiticide. Zetacypermethrin emulsifiable concentrate formulations are to be applied as a groundlaerial broadcast 

foliagelfruit spray while the granular fonnulations are to be applied by ground broadcast equipment to 

infested areas. 

B. Potential Risks to Non-Target Organisms 

This is the Environmental Fate and Effects Division's (EFED) national screening-level ecological risk 

assessment for the proposed uses of zeta-cypermethrin. Table 1 and Table 2 summarize the major 

conclusions and uncertainties of this assessment for aquatic and terrestrial receptors, respectively. 

Functionally, the estimated risks may translate to reduced survival and reproduction of impacted species 

with subsequent effects at higher levels of biological organization. Based on the toxicity data for all 

cypermethrin products (alpha-, beta-, theta-, and zeta-cypemethrin), this national screening-level risk 

8 
assessment suggests the potential for acute risk to non-target federally endangered and threatened species 

(listed) and non-listed freshwater and estuarinetmarine fish (and aquatic-phase amphibians) and 

invertebrates resulting from both granular and spray applications of zeta-cypermethrin. Overall, risks to 

aquatic organisms resulting from exposure to granular applications of zeta-cypennethrin are lower than 

risks resulting from exposure to spray applications. Based on a comparison of acute LCs" values, 

invertebrates appear to be the most sensitive aquatic animals, and RQs for invertebrates are much higher 

than those derived for fish. The results also suggest the potential for chronic risk to all aquatic 

invertebrates (estuarinetmarine and freshwater) and benthic organisms based on modeled national spray 

and granular applications of zeta-cyperinethrin. 

For terrestrial organisms, there appears to be both acute and chronic risk to mammals, but no risk avian 

species. Specifically, there is the potential for acute risk to listed and non-listed mammals resulting from 

zeta-cypermethrin granular applications, while zeta-cypermethrin spray applications result in acute and 

chronic dose-based RQs for mammals exceeding the acute endangered species LOC and the chronic LOC, 

respectively. 

Although the Agency does not quantitatively evaluate risks to terrestrial invertebrates, a qualitative 

assessment of toxicity tests on beneficial insects and terrestrial invertebrates indicates that zeta-cypermethrin 

can be classified as highly toxic to non-target beneficial insects and earthworms. Therefore, risks to these 

taxonornic groups resulting from zeta-cypennethrin granular and spray applications cannot be precluded at 

this time. 

Risks to aquatic and terrestrial plants were not assessed because toxicity data are not available; however, 

based on zeta-cypermethrin's neural toxic mode of action, the Agency does not expect zeta-cypennethrin 

to have phytotoxic effects. In addition, based on the lack of studies demonstrating adverse effects of zetacypermethrin or any other pyrethroid to plants, and the fact that no incident reports have reliably linked 

zeta-cyper~nethrin or any synthetic pyrethroid to phytotoxic effects despite being applied on or near 

agricultural plants, it appears unlikely that zeta-cypermethrin poses a phytotoxic concern. 

7 

Table 1. Summary of environmental risk conclusions for aquatic organisms and plants exposed to nongranular andlor granular zeta-cypermethrin. 

Assessment 

Endpoint 

Acute Risks to 

Fish and Aquatic 

lnvertehrates 

(Freshwater & 

Estuarine'Marine) 

Granular 

or NonGranular? 

Non-Granular 

Granular 

Summarized Risk Characterization and Major Uncertainties 

The LOC for acute restricted use (L,OC 0.1 ) is exceeded for all aquatic animals and modeled spray 

application crop scenarios, except for estuarinelmarine fish under the CA grapes scenario (RQ = 0.09). The 

highest acute RQs are obsec-ved for freshwater inve~tebrates, ranging from 23.33 (CA grapes) to 404.44 

(PA apples), greatly exceeding all acute L,OCs. Acute RQ values derived for estuarinelma~ine invertebrates 

also greatly exceed acute LOCs for spray applications, with RQ values ranging from 17.68 (CA grapes) to 

306.53 (PA apples). Because acute toxicity values for frcshwater and estuarine!marine tish are similar in 

magnitude. the ranges of acute RQs for these taxonornic goups are also similar (0.22 to 3.73 for freshwater 

fish and 0.09 to 1.53 for estuarine:marine fish). 

Overall, RQs to aquatic organisms resulting tiwn exposure to granular applications of zeta-cypennethrin 

are lower than RQs resulting from exposure to spray applications. For granular applications of zetacypennethrin, the LOC for acute restricted use (LOC 0. I) is exceeded for all aquatic animals, except for 

estuarinel~narine fish under the FL. turf scenario (RQ = 0.04). The acute RQs for freshwater fish, 

freshwater invertebrates, and estuarine!marine invetteb~ates are 0.10, 1 1.25, and 8.53, respectively. 
Table 1. Summary of environmental risk conclusions for aquatic organisms and plants exposed to nongranular and/or 

Assessment 

Endpoint 

Chronic Risks to 

Fish and Aquatic 

Invertebrates 

(1:reshwater & 

EstuarinelMarine) 

Acute and 

Chronic Risks to 

Benthic 

Organisms 

Risks to Aquatic 

Vascular and 

Non-Vascular 

Plants 

Table 2. Summary of environmental risk conclusions for terrestrial organisms and plants exposed to nongranular andlor granular zeta-cypermethrin. 

Assessment 

Endpoint 

Acute and 

Ch~on~c Risk 

to Rnds 

granuiar 

Granular 

or NonGranular? 

Non-Granular 

& 

Granular 

Non-Granular 

Granular 

Non-Granular 

& Granular 

zeta-cypermethrin. 

Summarized Risk Characterization and Major Uncertainties 

('hronic RQs derived for aquatic invertebrates are much higher than those deiived for tish, and exceed the 

chronic L OC' (I) in all instances for both spray and granular applications. For splay and granular 

applications, chronic RQs exceed the chronic LOC (LOC I ) by factors ranging from 5 to 156 and fiom 7 to 

207 for estuarinel~narine and freshwater invertebrates, respectively. The chronic RQs for tish do not exceed 

the chronic LOC for any of thc crop scenarios considered in this assessment; RQs range from 0.02 to 0.46 

and fi-om <0.0\ to 0.19 for fieshwater and estuarine!inarine fish, respectively. For all aquatic animal 

species, the highest chronic RQs are observed for the PA apples spray application scenario, and the lowest 

chronic RQs are observed for the FL turf granular application scenario. 

IIue to chronic toxicity data gaps for fieshwater invertebrates and estuarinel~narine fish, there is uncertainty 

regarding the magnitude of chronic risk esti~nates for these taxonomic groups because RQs are based on 

estimated chronic toxicity values (detailed description provided in the Ecological Effects Characterization 

section of the chapter). 

All acute (RQ ranges = 2.51 to 3 1.08 and 0.78 to 7.78 for sediment and pore water. respectively) and 

chronic (RQ ranges = 13.20 to 165.90 and 2.38 to 40.48 for sediment and pore water, respectively) RQs for 

benthic organisms exceed the LO('s for acute risk (LOC 0.5), acute restricted use (LOC 0.1 ), acute 

endangered species (I.OC 0.05) and chronic risk (LOC I) for all spray application scenarios. 

For granular applications, all sediment RQs for benthic organisms exceed the LOCs for acute risk (LOC 

0.5). acute restricted use (LOC 0. I), acute endangered species (LOC 0.05) and chronic risk (LOC 1) (Acute 

and chronic RQs = 0.98 and 4.47, respectively); however, pore water RQs for benthic organisms only 

exceed the LOCs for acute restricted use (LOC 0. I), acute endangered species (LOC 0.05), and chronic risk 

(LOC I) (Acute and chronic RQs = 0.24 and 1.1 1, respectively!, _ - _ _ - - - - _ - _ _ _ _ _ _ _ _ - _ - - - - _ _ - - - _ _ _ - - - -----------------~~~~------~~~~~.~.....---~~

There is uncertainty regarding acute and chronic risk estimates for benthic organisms for the following 

reasons that are discussed in greater detail in the Ecological Effects and Risk Characterization sections of 

the assessment: I ) Acute RQs for pore water were derived using a toxicity value estimated with the 

Equilibrium I'artitioning Theory and the definition of the k,v; 2) The acute sediment toxicity value (in tenns 

of whole sediment) used to esti~nate risk and to generate acute pore water and chronic pore water and 

sediment toxicity values was obtained from a study using a water-sediment system that was not at 

equilibrium and may underestimate sediment toxicity; and 3) Due to chronic toxicity data gaps for benthic 

organisms, there is uncertainty regarding the magnitude of chronic risk estimates for this taxonomic group 

because RQs are based on estimated chronic toxicity values. 

Toxicity data are not available to evaluate the risk of zeta-cypennethrin exposure to non-target plants 

inhabiting aquatic environments; however, EFEII is not concerned about the level of phytotoxicity of zetacypennethrin products because its neural toxic mode of action is not expected to be a phytotoxic concern, 

there are no studies demonstrating adverse effects of zeta-cypamethrin or any other pyrethroid to plants, 

and no incident reports have reliably linked zeta-cypennethrin or any other compound in the synthetic 

pyrethroid class of chemicals to phytotoxic effects in algae or aquatic macrophytes. 

Granular 

or NonGranular? 

Non-Gtanulat 

GI anula~ 

Summari~ed Risk Characterization and Major Uncertainties 

All dose-based (RQs 5 0 02 for all crop us scenar~os) and d~etarq-based (RQs 5 0 01 for all crop use 

scenarios) avlan acute RQs ate below all acute LOCs fo~ spray apphcat~ons ot zeta-cype~meth~ln In add~t~on, 

all chton~c RQs fo~ bnds are below the LOC fo~ chron~c r~sk (LOC 1) (RQ range= 0 03 to 0 63) 

All acute RQs (~~~,,lft' value<) fo~ ganula~ appl~cat~ons ofzeta-cype~~netht~n, are below all acute LO( s (RQs 

i 0 08) tor avlan spscles In add~t~on the chronlc avlan RQ IS below the LOC for chron~c r~sk (RQ =0 1 ) to1 

granula~ apphcat~onz 
C. Conclusions - Exposure Characterization 

Table 2. 

granular 

Assessment 

Endpoint 

Acute Risk to 

Ma~n~nals 

Chronic Risk 

to Mammals 

Non-target 

Beneficial 

Insectsrre~~est 

rial 

lnve~teb~ates 

Terrestrial 

Plants 

It appears that zeta-cypermethrin degradation is mainly the product of metabolic activity. Aerobic and 

anaerobic soil metabolism were found to be about 60 and 52-63 days, respectively. In contrast, the rates 

for aerobic and anaerobic aquatic metabolisrn were 9-10 and 14-17 days, respectively. All abiotic 

processes appeared to represent relatively insignificant dissipation mechanisms for zeta-cypermethrin. 

11 

Summary of 

and/or granular 

Granular 

or NonGranular? 

Non-Granular 

Granular 

Non-Granular 

Granular 

Non-Granular 

& Granular 

Non-Granular 

& Granular 

environmental risk conclusions for terrestrial organisms and plants exposed to nonzeta-cypermethrin. 

Summarized Risk Characterization and Major Uncertainties 

For spray applications of zeta-cypennetrhin, no acute dose-based RQs for any size of ma~nmals under any crop 

scenario exceed the LOC for acute risk (LOC 0.5) or acute restricted use (LOC 0.2). However, for 15g and 

35g ~nannnals that consume short grass exposed to zeta-cypennethrin via splay applications (RQs range from 

0.05 to 0.16 for all sizes of inammals feeding on short pass under all crop use scenarios), dose-based acute 

RQs exceed the LOCs for acute endangered species (LOC 0.1). None of the RQs for l000g ~nannnals feeding 

on any dietary item excced any of the acute I.OCs. and all RQs for matn~nals feeding strictly on broadleaf 

plantsis~nall insects, tall grass, fi.uitslpods~large insects, 01. seeds are below the acute LOCs. 

The acute RQ (LD,~/A~ values) for 15g ~nannnals (RQ=0.83) exceeds all acute LOCs, while the RQ for 35g 

~nannnals (RQ=0.44) exceeds the LOC's for acute restricted use (LOC 0.2) and acute endangered species 

(LOC 0.1). For larger ~nannnals (1000 g), the acute RQ (RQ=0.04) is below all acute LOCs. 

Dieta~y-based chronic RQs for ~namrnals range from 0.02 (mammals feeding on fiuitslpodsllarge insects for 

zeta-cypennethrin use on barley) to 0.39 (mammals feeding on short grass for zeta-cype~methrin use on stone 

fruits), with no RQs exceeding the chronic LOC (1 ). Dose-based chronic RQs exceed the LOC for chronic 

risk (LOC I ) for all modeled crop uses for exposure via short grass; RQs range fiom 0.8 1 ( 1000g ~nannnals 

for zeta-cypenneth~in use on barley) to 2.73 ( 15 g ~narnmals for zeta-cypennethrin use stone fruits). For 

mammals feeding on tall grass, dose-based chronic RQs range from 0.37 ( 1000 gram rnam~nals for zetacypennethrin use on barley) to 1.25 ( 15 gram ~na~n~nals for zeta-cypennethrin use on stone fiuits); chronic 

RQs exceed the chronic LOC for the stone fruits (RQ range = 0.57 to 1.25) and canola (RQ range = 0.5 1 to 

I. I I ) scenarios, but not for the non-grass animal feeds (RQ range = 0.45 to 0.98) or barley scenarios (RQ 

range = 0.37 to 0.81). For ~nannnals feeding on broadleaf plants~insects. dose-based chronic RQs range from 

0.45 ( 1000 gram tna~n~nals for zeta-cypc~~nethrin use on barley) to 1.53 (1 5 gram ~nannnals for zetacypennethrin use on stone fiuits); chronic RQs exceed the chronic LOC for the stone fixits (RQ range = 0.70 

to 1.53), canola (RQ range = 0.63 to 1.37). and non-grass aniinal feeds (RQ range = 0.55 to 1.21) scenarios, 

but not for the barley scenario (RQ range = 0.45 to 0.99). All RQs for ma~ntnals feeding on fiuits!pods/large 

insects and seeds are below the chronic LOC. 

The chronic RQ for rnam~nals exposed to granular zeta-cypenneth~in is less than the chronic risk LOC 

(RQ=0.05). In addition, based on a co~nparison of estimated chronic doses for insectivorous ~namnlals and 

adjusted NOAEIs for three size classes, chronic risk resulting from exposure to granular zeta-cypennethrin 

appears unlikely (RQ range=0. 19 to 0.4 1 ). -- --------- -------- ............................................

For chronic risk to ~nam~nals, it is unclear whether other routes of granular zeta-cypermethrin exposure or 

combined routes of exposure (i.e., direct consumption of granules, ingestion of granules that adhere to soil 

inve~tebrates. partitioning of dissolved zeta-cypa~nethrin to on-site sources of wildlife drinking water, and 

dermal exposure of granules released to sutx-ounding soil and on-site puddles) would result in chronic risk 

concelns for terrestrial receptors. 

Although EFEII does not quantitatively estimate risk to non-target terrestrial invertebrates, this hazard 

assesslnent shows that zeta-cypennethrin exposure can he expected to result in acute toxicity to honey bees 

and is considered to be highly toxic on both a contact (LDS0 = 0.023 ug a.i./bee) and an oral basis (LD5,, = 

0.172 ug a.i.ihee). In addition. results of an acute study with eatthwonns yielded a 48-hour contact 12C'5,~ value 

of 26.09 ug a.i.lctn2 for cypennethrin applied to filter paper, categorizing zeta-cype~methrin as vely toxic to 

earthwo~lns. Based on the data available at this time, acute and chronic toxic effects to non-target insects and 

terrestrial inve~tebrates resulting htn the proposed zeta-cypel-inethrin uses cannot be precluded and risk is 

presumed. 

Toxicity data are not available to evaluate the risk of zeta-cypennethrin exposure to non-target te~vestrial 

plants; however, EFED is not concerned about the level ofphytotoxicity of zeta-cypennethrin products 

because its neural toxic mode of action is not expected to be a phytotoxic conceln, there are no studies 

demonstrating adverse effects of zeta-cypennethrin or any other pyethmid to plants, and no incident repo~ts 

have reliably linked zeta-cypermethrin or any other co~npound in the synthetic pyrethroid class of chernicals to 

phytotoxic effects non-target te~vestrial plants. 
Zeta-cypermethrin appears to be stable to hydrolysis (except in alkaline media at pH 9, tlh-2 days) and in 

the presence of light. Photolysis in water was 36 days and on soil, 128-215 days (dark control corrected). 

The basic mechanism of degradation of zeta-cypermethrin is cleavage at the ester moiety, which results in 

two primary degradation products, 3-(2,2-dichloroetheny1)-2,2-dimethylcyclopropane carboxylic acid 

(trans-DCVA, maximum. 79% in pH 9 solution, and 34% in anaerobic aquatic ~netabolism study) and 3- 

phenoxybenzaldehyde, which is further oxidized to 3-phenoxybenzoic acid (3-PBA, maximum 35% in 

aqueous photolysis study). Another degradation product was cyperamide. This product keeps a similar 

structure to that of the parent; however, it was observed only in one laboratory study, the soil photolysis 

study, at a maximum of 13.3%, which approaches the limit that EFED generally considers of concern 

(10% of the applied). Zeta-cypermethrin is not likely to leach to ground water, as shown by an 

adsorptionldesorption batch equilibrium study (Koc = 20,800 - 328,500 LIKg) and an aged leaching study. 

Zeta-cypermethrin shows a relatively low potential for volatilization from moist soils and water (vapor 

pressure 2.5x10-hm~~ and Henry's Law constant 3.4~10.' ~tm-m3/mol; relatively low solubility in 

water 0.0040 tngIL, and high soillwater partitioning). 

When zeta-cypennethrin is applied to the field, due to the relatively low mobility of the chemical, it is 

expected to reach adjacent bodies of water via spray drift or through runoff events accompanied by 

erosion. Once there, zeta-cypermethrin may be expected to remain adsorbed to suspended solids or 

organic matter in the water colu~nn, or partition with the sediment phase, where it could persist (the aerobic 

and anaerobic aquatic tnetabolism studies for zeta-cypennethrin indicate that the chemical is not persistent; 

however, field studies conducted on rice, with zeta-cypennethrin, show high persistence in aquatic 

environments). If zeta-cypermethrin is applied repeatedly, it is possible that the chemical may accumulate 

in the sediment in ever larger amounts, with slow biodegradation. Generally zeta-cypermethrin is not 

expected to leach substantially into groundwaters. 

Zeta-cypennethrin shows a moderate potential to bioaccumulate in fish, with maximum BCF of 468 for 

whole fish in a 28 day study. Depuration appeared to be moderate, with near 10-15% of the initial residues 

remaining after 2 1 days. 

The uncertainties related to the fate database are related to the difference observed between the laboratory 

aquatic metabolism studies, which predict short half-lives, while the supplemental aquatic field dissipation 

studies showed longer term half-lives. 

Estimated environmental concentrations (EECs) for zeta-cypermethrin calculated using the Tier 2 

PRZMIEXAMS aquatic models and employing tnaxi~num application rates, indicate that zetacypermethrin preferentially partitions to the sediment compartment in model water bodies. Four crop 

usage scenarios, which represent worst case scenarios, were considered: apples, peaches, turf, and grapes. 

Ecological exposure can occur through several pathways. Terrestrial and avian species may inadvertently 

be exposed to cypennethrin as a result of its direct application to crops (both dermal and inhalation 

pathways are possible). Ingestion of food and drinking water contaminated with zeta-cypermethrin are also 

possible exposure pathways. Spray drift from the target area as well as runoff and erosion of zetacypermethrin to soils can result in exposure to aquatic organisms. 

To estimate exposure of terrestrial animals, terrestrial EECs were generated using the Tier 1 model T-REX 

(T-REX, Version 1.2.3, dated August 8, 2005) for spray applications based on maximum application rates 

and use patterns. For foliar spray applications, EECs and acute and chronic RQs were estimated for 

residues on various forage categories (short grass, tall grass, broadleaf plants/small insects, 

fruitslpods/large insects, and seeds) for four representative crop uses: stone fruits, canola, non-grass animal 

feeds, and barley. 
For granular applications, acute exposure and risks were estimated with the conceptual approach using the 

~~~"lft' method given in the Tier 1 model T-REX. Terrestrial EECs were calculated based on an 

estimation of loadings of pesticide per unit area (expressed in terms of mg a.i./ft2), assuming that 100% of 

the application was present on the surface of the soil. 

Estimates for chronic exposure of terrestrial wildlife to granular zeta-cypermethrin in this risk assessment 

were based only on direct ingestion of soil invertebrates that have bio-concentrated zeta-cyperinethrin 

residues of granules in soil. This estimation of earthworm concentration was calculated using a hgacitybased (equilibrium partitioning) approach based on the work of Trapp and McFarlane (1 995) and Mackay 

and Paterson (1 98 1). 

D. Conclusions - Effects Characterization 

Based on the results of acute toxicity studies with all cypennethrin products (alpha-, beta-, theta-, and zetacypennethrin), zeta-cypennethrin can be classified as very highly toxic on an acute basis to freshwater fish, 

freshwater invertebrates (e.g. daphnids, midge, amphipods, and gastropods), estuarinelmarine fish, and 

estuarinelmarine invertebrates (e.g. shrimp and crustaceans). In addition, zeta-cypermethrin can be 

categorized as highly toxic to oysters. Acute toxicity studies on the cypermethrin degradate 3- 

phenoxybenzoic acid in freshwater fish and invertebrates show that the degradate is much less toxic than 

cypermethrin TGAI. 

The lowest acute LCSo values reported for freshwater fish and estuarinelrnarine fish range from 0.39 pg 

a.i.1L in rainbow trout to 0.95 pg a.i.lL in sheepshead minnow, whereas the lowest acute LC50 values for 

freshwater and estuarinelmarine invertebrates are approximately two orders of magnitude less and range 

from 0.0036 pg a.i./L in amphipods to 0.00475 pg a.i./L in mysids; thus, invertebrates are expected to be 

at a greatest risk for acute effects (lethality). The LCSo values for benthic organisms based on exposure to 

cyperinethrin in bulk sediment and pore water were 3.6 pg a.i.1kg sediment and 0.00257 pg a.i./L, 

respectively. 

In addition to lethality data, several acute toxicity studies provide information regarding sub-lethal effects 

of cypermethrin. For fish, sub-lethal effects include rapid and erratic swimming, partiallcomplete loss of 

equilibrium, jaw spasms, gulping respiration, lethargy, and darkened pigmentation. In aquatic 

invertebrates, sub-lethal effects include lethargy, erratic swimming behavior, loss of equilibrium, surfacing, 

immobilization, and decreased movement in response to stimulation. In most studies, the acute NOAEC 

values for sub-lethal effects are approxiinately 2- to 3-fold lower than the corresponding LC50 values, 

indicating that sub-lethal effects can occur at exposure levels below the concentrations that cause lethality. 

Chronic toxicity studies with cyperinethrin are available for freshwater fish and estuarinelmarine 

invertebrates. Results of these studies suggest that zeta-cypermethrin can be expected to adversely affect 

neonate survival of freshwater fish (NOAEC = 0.14 pg a.i.lL) and reproduction and growth of 

estuarinelmarine invertebrates (NOAEC= 0.781 ng ai1L). Currently, there are no data available on the 

chronic effects of zeta-cypennethrin or any other cypermethrin product on benthic organisms, 

estuarinelmarine fish, or freshwater invertebrates. However, estimates of chronic toxicity to benthic 

organisms (NOAECs = 0.59 ug ailkg sediment and 0.0042 pg a.i./L pore water), estuarinelrnarine fish 

(NOAEC = 0.34 pg a.i./L), and freshwater invertebrates (NOAEC = 0.00059 pg a.i.1L) were derived to 

estimate risk using the methodology described in the Ecological Effects Characterization section of the 

assessment. 
Results of acute toxicity studies on birds suggest that zeta-cypermethrin can be classified as practically 

non-toxic to slightly toxic to avian species (LDSo >2,000 mg a.i./kg body weight LCj0 > 2,634 ing a.i.1kg 

diet), moderately toxic to mammalian species (LDSo = 86 mglkg body weight ), highly toxic to honey bees 

on both an acute contact (LDSo = 0.023 pg a.i./bee) and acute oral basis (LD50 = 0.172 pg a.i./bee), and 

very toxic to earthworms (LCSO = 26.09 pg/cm2) on an acute contact basis. 

Avian reproduction studies showed no adverse effects at 50 ing a.i./kg diet (the highest concentration 

tested), while the NOAEC value of 100 mg a.i./kg diet (5 mg a.i./kg/day) was established for mammals 

based on decreased body weight and body weight gain in adults and offspring in the available 2- and 3- 

generation reproduction studies with rats. 

Currently, there are no data available regarding the effects of zeta-cypermethrin degradates to any 

terrestrial organism or the effects of zeta-cypermethrin to terrestrial or aquatic vascular and non-vascular 

plants. 

E. Uncertainties and Data Gaps 

1. Environmental Fate 

The environmental fate database for zeta-cypermethrin is considered to be complete. However, monitoring 

data specific for zeta-cvpermethrin in U.S. groundwater, drinking water, surface water, and sediment were 

not identified in searches of the National Drinking Water Contaminant Occurrence Database (NCOD), 

National Water Quality Assessment Program (NAWQA), or the Storage and Retrieval (STORET) 

database. 

Estimations regarding the spray drift fraction in the PRZMIEXAMS model runs were based upon the Tier I 

mode of AgDRIFTB program. The primary assumption is that the wind speeds at each site are generally 

below 10 tnph. This is consistent with the label language that indicates "Make aerial or ground 

applications when the wind velocity favors on target product deposition (approximately 3 to 10 mph). Do 

not apply when wind velocity exceeds 15 mph." However, there may be uncertainty with respect to 

unconcerned applicators that would apply the chemical at wind speeds above 10 mph. 

There is uncertainty with respect to the level of mitigation that a buffer zone of 150 ft plus a vegetative 

strip of 10 ft can provide. The estimation of spray drift was obtained from AgDRIFTB; however, there is 

no way to know how well the buffer zone will protect the bodies of water from runoff. In certain cases, the 

level of runoff is the most important factor, rather than the level of spray drift. This is an assumption made 

in the Tier I calculation of AgDRIFTO. 

Cypermethrin is an enhanced mixture of four diastereoisomers, each of which is present as a pair of 

enantiomers, resulting in eight isomers. Different ratios of the eight isomers have resulted in four different 

cypermethrin products (alpha-, beta-, theta-, and zeta-cypermethrin) all of which have similar 

environmental fate properties. The cis:trans ratio of zeta-cypermethrin isomers was found to vary in 

different toxicity tests (e.g., 48.8:42.7, 55:45, 53.6:46.4, 54:46). However the cis:trans ratio is close to a 

5050 ratio suggesting that toxicity profiles should be accurate. The label for Fury and Mustang 

Insecticide specify cisltrans ratio: maximum 55% (k) cis and minimum 45% (i) trans. An enhanced zetacypermethrin [(S) alcohol enriched] has an equivalent toxicity profile to the cypermethrin enantioineric 

mixture but is more efficacious (half the application rate of the enantiomeric mixture). 

The maximuin rate of application for the emulsifiable concentrate to crops is 0.05 lb a.i.1A with a 

maximum of 6 applicationslseason and a minimum interval of 7 days between applications (a total 

14 
maximuin seasonal application rate of 0.3 lbs a.i./A). However, for this risk assessment EFED assumed 

that zeta-cyperinethrin was applied at a inaxiinuln of 6 times per year. If there are conditions under which 

there is more than one growing season for a crop within a single year, exposure estimates and risk to 

aquatic and terrestrial organisms could be significantly underestimated. Examples of crops that have 

multiple seasons where this may be a concern include leafy, brassica, and fruiting vegetables in CA, AZ, 

FL, GA, LA, NC, TX, andlor SC. 

It is assumed for pesticides which have residential outdoor uses (applications to home lawns, gardens, 

parks, etc.) that runoff water from rain and/or lawn watering may remove pesticide to storm sewers and 

then directly to surface water. However, in general, outdoor residential uses are comprised of multiple, 

relatively small, temporally and spatially variable applications that are not simulated in agricultural models. 

Therefore, there is some uncertainty in the aquatic exposure assessment because a model specifically aimed 

at simulating pesticide fate and transport in a complex urban landscape has not yet been developed to 

generate exposure estimates strictly for urban areas. 

Furthermore, the Agency does not have a method to obtain EECs for termiticide uses in urban areas as 

well. However, EFED believes that the exposure due to this particular use (subterranean) would be 

ininimal and that both surface and ground waters are not at a high risk. Zeta-cypermethrin is likely to bind 

strongly to soils, and although it is unlikely that the use will result in substantial exposure, there is 

uncertainty. In addition, the likelihood of significant exposure from the use of zeta-cypermethrin as a 

barrier treatment is also uncertain. 

2. Ecological Effects 

The screening level risk assessment for zeta-cypennethrin has been conducted despite unfulfilled 

guideline requirements and existing data gaps. Table 1-2 (Appendix I) lists the status of the ecological 

effects data requirements for zeta-cypermethrin. The following is a brief synopsis of the major ecological 

effects data gaps and uncertainties. 

There is uncertainty surrounding estimates of chronic toxicity to freshwater invertebrates, 

estuarinelmarine fish, and benthic organisms, because no data are currently available. To 

assess risk to these taxonomic groups, RQs were based on chronic NOAEC values derived 

using acute-to-chronic ratios. 

The available acute toxicity study for benthic organisms was not conducted with the 

exposure system at equilibrium. Since the chronic RQ for sediment and acute and chronic 

RQs for pore water were derived from the sediment toxicity value, uncertainty is 

introduced to all categories of the risk assessment for benthic organisms. Acute and 

chronic sediment studies have been recently submitted by the pyrethroid working group 

(PWG) but were not reviewed in time for inclusion in this assessment. 

11. Problem Formulation 

A. Stressor Source and Distribution 

1. Source and Intensity 

This assessment considers only the current proposed uses of zeta-cypermethrin; for use on agricultural 

crops and turf on residential lawns, home perimeters, gardens, and other industrial non-agricultural areas 

for the control of certain insect pests and termites. The various formulations can be applied via 
groundlaerial broadcast foliagelfruit spray or by ground broadcast treatment of infested areas using 

granular formulations. 

The major degradation products of zeta-cypermethrin in the environment are cis- and trans-DCVA, 3-PBA, 

and 3-phenoxybenzaldehyde. However the available toxicity data suggest that degradates should not be 

considered as major stressor sources because of efficacious inactivity of the parent compound after the 

ester bond has been cleaved. For the purposes of this risk assessment, only the parent compound is 

considered an important stressor. 

Terrestrial exposure to the parent compound is based on direct spray application on food items including 

short grass, tall grass, seeds, and broadleaf plants and insects resulting from applications of zetacypermethrin at the maxiinurn label rates. Exposure to aquatic organisms is the result of runofflerosion 

and spray drift from labeled applications and is functionally the amount of compound in the water that 

would directly contact organisms. The maximum rate of spray application to crops is 0.05 lb a.i.1A with a 

maximum of 6 applications/season and a minimum interval of 7 days between applications. The maximum 

use scenario of granular zeta-cypermethrin is a single application at the inaximuln rate of 0.225 lb 

a.i.lAlyear. The magnitude of exposure estimates are largely dependent on the biology of the receptor (e.g., 

food consumption rate), the use patterns and environmental fate and transport, which are further explored 

later in this document. 

2. PhysicaWChemicaVFate and Transport Properties 

Cypermethrin ((RS)-a-cyano-3-phenoxybenzyl (I RS,3RS; 1 RS,3SR)-3-(2,2-dichloroviny1)-2,2- 

dimethylcyclopropanecarboxylate) is a mixture of four diastereoisomers, each of which is present as a pair 

of enantiomers, resulting in eight isomers. It is prepared by the esterification of 3-phenoxybenzaldehyde 

and 3-(2,2-dichloroviny1)-2,2-dimethylcyclopropane carboxylic acid. Different ratios of the eight isomers 

have resulted in four different cypermethrin products (alpha-, beta-, theta-, and zeta-cypermethrin) all of 

which have similar environmental fate properties. Zeta-cypermethrin is an enhanced mixture of (S) 

alcohol isomers. 

For the purposes of this risk assessment, the Agency has allowed use of the cypermethrin TGAI database 

to fulfill many registration requirements for zeta-cypermethrin and exposure data for all cypennethrin 

products (alpha-, beta-, theta-, and zeta-cypermethrin) have been bridged. The two isomeric mixtures are 

expected to behave similarly in the environment. Zeta-cypermethrin is expected to have little mobility in 

soil surfaces (Koc>20,800 LIKg) and leaching into groundwater is not expected to be an important 

transport process. Volatilization is not expected to be an important transport process neither, since zetacypermethrin has a relatively low vapor pressure and Henry's Law constant (refer to Table 3). Zetacypermethrin is moderately persistent in the environment and degrades through a combination of biotic and 

abiotic mechanisms. Zeta-cypermethrin is relatively stable to hydrolysis at acidic and neutral pH levels, 

but degrades in a few days under alkaline conditions (pH 9, t :/, - 2 days). Zeta-cypennethrin is relatively 

light stable, but still undergoes photolysis in water, with half-lives of about a month or more in distilled 

water. The rate of photolysis appears to be enhanced in natural waters (which contain photosensitizing 

agents like hu~nic and fulvic acids), where the accelerated degradation results in half-lives of a few days. 

Zeta-cypennethrin photodegrades on soil with a dark control corrected half-lives of 1128 days. Under both 

aerobic and anaerobic soil conditions, zeta-cypermethrin biodegrades relatively slowly in soils, with halflives on the order of about 2 months. In contrast, under aerobic and anaerobic aquatic metabolism 

conditions, the degradation rate is enhanced, with half-lives of around 9 to 17 days. If released to water, 

zeta-cypermethrin partitions to sediment and may degrade slowly. Degradates observed in laboratory 

studies result from cleavage at the ester moiety of zeta-cypermethrin, which formed 3-(2,2-dichloro- 
etheny1)-2,2-dimethylcyclopropane carboxylic acid (cis- and trans-DCVA, maximum 79% in pH 9 

solution, and 34% in anaerobic aquatic metabolism study) and 3-phenoxybenzaldehyde (maximum 65% in 

pH 9 solution). The latter one is further oxidized to 3-phenoxybenzoic acid (3-PBA, maximum 35% in 

aqueous photolysis study). Another product observed in the soil photolysis study only, was cyperamide 

(maximum 13.3%). The main chemical and physical properties of zeta-cypermethrin are summarized in 

Table 3. 

3. Pesticide Type, Class, and Mode of Action 

Table 3. Physical and chemical properties of zeta-cypermethrin . 

The pyrethroids (including zeta-cwennethrin) share similar modes of action, and are considered axonic 

poisons that affect both the peripheral and central nervous system. It is now well established that severe 

neurological symptoms of poisoning with pyrethroids in mammals and insects are the result of modification of 

Na' channel activity (cellular pores through which sodium ions are permitted to enter the axon to cause 

excitation) (Matsumura,l985). Advanced electrophysiological experiments using a voltage clamp and a patch 

clamp, together with ligand-binding and ionic flux experiments, have unveiled unique actions of pyrethroids of 

keeping the Na' channel in the open state for an extremely long period, sometimes as long as several seconds. 

This modification of ~a' channel properties leads to hyperactivity of the nervous system. This action leads to 

spontaneous depolarizations, augmented neurotransmitter secretion rate and neuro~nuscular block, which 

ultimately results in paralysis of the insect. Pyrethroids have also been shown to suppress GABA and 

glutamate receptor-channel complexes and voltage-activated Ca " channels, but the toxicological significance 

of these actions is uncertain. 

Relative to physiological responses, researchers have designated two types of pyrethroids, Type I (e.g., 

pyrethrins, S-bioallethrin, resmethrin, permethrin) and Type I1 (e.g., cypennethrin, deltamethrin, fenvalerate). 

Zeta-cypermethrin is classified as a type 11 synthetic pyrethroid, with a cyano group at the a-carbon 

position of the alcohol moiety, and is considered a third generation pyrethroid, that is, more light- stable 

and persistent in the environment than early pyrethroids like allethrin, phenothrin (also commonly known 

as sumithrin) and resinethrin. Zeta-cypermethrin has three optically active centers and is composed of 8 

isomers, and like all pyrethroids, is a contact poison that can quickly penetrate the nervous system and 

have an effective "knockdown" action (induction of temporary paralysis) for most flying insects. 

Reference 

Laskowsk~ (2002) 

Property 

Molecula~ we~ght 

4. Overview of Pesticide Usage 

Value 

416 3 

SM ll FS notallon 

C AS numbel 

Wate~ solub~l~ty 

Meltlng polnt 

Bolllng polnt 

Vapor pl essure 

log K,,, 

Henty's Law constant 

CIC(CI)=C'C I C(C)(C )C IC'(=O)OC(C#N)c2cccc(Oc3ccccc3)c2 

97955-44-7 (52315-07-8 fol zeta-cype~inethnn) 

4 0x10' mg/~ 

78-81 "C 

200 "C at 9 3 Pa (0 070 mm lig) 

2 SXIO'I~I~H~ 

6 54 

3 4x 10 ' ~tm-~n'l~nol 

11111) \\\\\\ Lh~~~~~r~clt~\~~\ < <*111 LII~*IIII&J 

0 1<)5') 11~1111 

Laskowsk~ (2002) 

To~nl~n 1994 

roml~n 1994 

Iaskowsk~ (2002) 

Laskowsk~ (2002) 

Laskowsk~ (2002) 
Zeta-cypermethrin is an insecticide already registered for use on a number of agricultural crops (including 

cotton and rice); however, this assessment focuses on the registrant's proposed uses and requested 

tolerances for cilantro, head and stem brassica vegetables, leafy vegetables (except brassica), sunflowers, 

grass forage, fodder, hay group, canola rapeseed, barley, grapes, tree nut group (almond, pecan), berries, 

peanuts, root and tuber vegetables, cucurbit vegetable group, non-grass feeds (forage, fodder, straw and 

hay), pome fruits, stone fruits. Zeta-cypermethrin is also proposed for use on turf and as a termiticide (see 

Use Characterization section of the assessment for additional detail). Zeta-cypermethrin formulations 

proposed for use include emulsifiable concentrates (for agricultural spray applications), granular 

formulations (for use on turf on residential lawns, home perimeters, gardens, and other industrial nonagricultural areas), and emulsion fonnulations (for use as a termiticide). 

B. Receptors 

Each assessment endpoint requires one or more measures of ecological effect, which are defined as 

changes in the attributes of an assessment endpoint itself or changes in a surrogate entity or attribute in 

response to exposure to a pesticide. Ecological measures of effect for this screening level risk assessment 

are based on a suite of registrant-submitted toxicity studies performed on a limited number of organisms in 

broad groupings. Table 4 gives examples of taxonomic groups and test species evaluated for ecological 

effects in this screening level risk assessment. Within each of these very broad taxonomic groups, an acute 

andlor chronic endpoint is selected from the available test data. A complete discussion of all toxicity data 

available for this risk assessment and the resulting measures of effect selected for each taxonomic group 

are included in Appendix E. It should be noted that zeta-cypermethrin is a modified form of 

cypermethrin, and a comparison of their respective databases (although it is limited for zeta-cypennethrin) 

indicates that they have similar toxicity to non-target organisms. Therefore, the Agency assumes 

equivalent toxicity and has allowed use of the cyperinethrin TGAI database to fulfill many registration 

requirements for zeta-cypermethrin; toxicity data for all cyperlnethrin products (alpha-, beta-, theta-, and 

zeta-cypennethrin) are being bridged for risk assessment purposes. 

Table 4. Taxonomic groups and test species evaluated for ecological effects in this screening-level risk 

assessment for zeta-cypermethrin. 

Taxonomic group 

Birds " 

Mammals 

Benficial Insects / Terrestrial 1nvertebl.ates 

Freshwater Fish 

Example(s) of representative species 

Mallard duck (Antrs pItr@~h.vnchos) 

Bobwhitc quail (Colin~rs lmirginiatltr~) 

Laborato~y rat (Rattw norvegiclis) 

Honey bee (.?pis ntellifiro) 

Earthwo~rn (Ei.~etiia.fetida) 

Bluegill sunfish (L.e~?on~i.~ nzcrcrochir~u) 

Rainbow trout (Oncorh.vncA~rs n~-vkiss) 

Fathead minnow (Pintephnles promelns) 
1. Aquatic Effects 

Table 4. Taxonomic groups and test species evaluated for ecological effects in this screening-level risk 

assessment for zeta-cypermethrin. 

For aquatic effects, registrant-submitted studies on cypermethrin technical grade active ingredient (TGAI) 

are available for acute and chronic exposure of freshwater fish, acute exposure of freshwater invertebrates, 

acute exposure of estuarineharine fish, and acute and chronic exposure of estuarinelmarine invertebrates. 

Additional ecological effects data are available from registrant-submitted studies of acute cypermethrin 

exposure to benthic organisms. No scientifically valid studies on zeta-cypermethrin TGAI were submitted 

by the registrant for chronic exposure of freshwater invertebrates or estuarinelmarine fish. No toxicity 

studies on zeta-cypermethrin were submitted for algae or aquatic macrophytes. 

Taxonomic group 

FI-eshwater Invertebrates ' 

Benthic Organisms ' 

Estuarinelmarine Fish 

I:stuarine!~narine Invertebrates 

" Birds represent sunogates for reptiles and te~rest~ial phase amphibians. 

In addition to studies on the parent compound, ecological effects data for the zeta-cyperinethrin degradate 

3-phenoxybenzoic acid are available for freshwater fish and invertebrates 

Example(s) of representative species 

Water flea (Dcrphrtin ntagno) 

Crayfish (Oronecte.~ sp.) 

Maytly larvae (Enelis rltodarli) 

Maytly la~-vae(Cloeon dipteruni) 

Whirligig (Gvrinw natritor ) 

Backswi~nrner (Notonectn sp.) 

Waterboatman (Corixa ptlttctota) 

Water mite (Piona ccfutca ) 

Amphipod (Ganinicrr11.~ pulc,.~) 

Midge (C'ltir-o~~omtr.~ thlrninli) 

lsopod (A.~cllrrs .spp) 

Gastropod (L.vnittea peregrtr) 

Midge (Cltaoborirs sp. ) 

Midge (C'hirortontirs riparil~s) 

Midge (Cltironornt~s trntarts) 

Amphipod (/<i,alella azteca) 

Sheepshead tninnow (C:vprinodort ~~crriegatrts) 

Atlantic salmon (Scrlnro scrlar) 

Eastern oyster (Gassostrca rirgi~~ica) 

Mysid shrimp (Mlsidopsis Bohia) 

Pink shrimp (Penaetls iflrorarlrm) 

Shrimp (C.septem.~pirtosn) 

Lobster (tjomartu nrnerircrn~ls) 

I'acific oyster (Crassosrreo gigos) 

Fiddler crab (Uca plcgilrrtor) 

2. Terrestrial Effects 

" Freshwater ti sh may be surrogates for aquatic phase amphibians. 

"Only studies that exposed benthic organisms via water-sediment systems were used to evaluate potential risk to benthic organisms; all other 

studies that exposed benthic organisms via water-only systems werc used to evaluate risk to water colu~nn dwelling organisms. 

For terrestrial effects, registrant-submitted studies on cyperinethrin TGAI are available for acute, subacute, and chronic exposure to birds, and acute and chronic exposure to mammals. Additional ecological 

effects data for cyperinethrin are available for honey bees (Apis mellife~*u) and earthworms (Eisenia,fetida); 

results of these studies have been incorporated into the risk characterization as an additional line of 

evidence. No toxicity studies on zeta-cypermethrin were submitted for plants inhabiting terrestrial areas. 
Toxicity data of terrestrial organisms to zeta-cypennethrin degradates were not submitted. 

3. Ecosystems at Risk 

The ecosystems that could be potentially at risk from drift and runoff of zeta-cypennethrin include 

freshwater, estuarineharine, and terrestrial ecosystems. Zeta-cyperlnethrin can be applied directly to 

terrestrial habitats as a spray or as granules. The spray application is limited to agricultural settings; 

however, the granular forlnulations and the emulsion formulations for termiticide use can be used in 

residential and other non-crop areas. Given the number and nature of uses of zeta-cypermethrin (proposed 

and already registered), the area of the United States that could be potentially exposed to the chemical is 

expansive (virtually everywhere). Due to zeta-cypermethrin's potential use across the United States as an 

insecticide and the nature of its application in both agricultural (spray) and residential settings (granular), it 

may be introduced to a more diverse array of ecosystems than are typically exposed to other pesticides that 

are applied primarily around agricultural areas. From these terrestrial ecosystems the chemical is expected 

to be transported to aquatic ecosystems via spray drift and/or runoff/erosion. 

Given zeta-cypermethrin's low solubility and affinity for binding to organic carbon and particulate matter, 

the bio-availability of the chemical in the water colu~nn may be limited after 24 to 48 hours. Therefore, 

while there is potential for acute risk to organisms living in this media within an aquatic ecosystem, 

chances of chronic exposure and risk to organisms strictly residing there is much lower. However, because 

zeta-cypermethrin is expected to quickly precipitate out of the water column, settle on the benthos, bind to 

the sediment, and persist for extended periods of time, the anticipated nature of the exposure in the benthos 

may result in significant potential for acute and chronic risk to organisms living in this compartment of the 

aquatic ecosystem. 

Ecosystems potentially at risk reflect a potential concern by the Agency and can be expressed in terms of 

the selected assessment endpoints. The typical assessment endpoints for screening-level pesticide 

ecological risk assessments are reduced survival, and reproductive and growth impairment for both aquatic 

and terrestrial animal species. Potential effects on a set of surrogate species are used to extrapolate risk to 

all species. For both aquatic and terrestrial animal species, direct acute and direct chronic effects are 

considered. Although these endpoints are measured at the individual level, they provide insight about risks 

at higher levels of biological organization (e.g. populations and communities). For example, pesticide 

effects on individual survivorship have important i~nplications for both population rates of increase and 

habitat carrying capacity. Indirect effects and effects on critical habitat are only considered in the risk 

characterization for potential effects on endangered species. 

C. Assessment Endpoints 

This risk assessment considers the maximum application rates of zeta-cypermethrin on vulnerable soils as 

reported on the label, the maximum numbers of applications, and the minimum application intervals as 

reported by the registrant to estimate exposure concentrations as a result of the proposed uses of zetacypennethrin. This assessment is not intended to represent a site or time-specific analysis. Instead, this 

assessment is intended to represent high-end exPosures at a national level. Likewise, the most sensitive 

toxicity endpoints are used from surrogate test species to estimate treatment-related direct effects on acute 

mortality and chronic reproductive, growth and survival assessment endpoints. The ecological relevance 

of selecting the above-mentioned assessment endpoints is as follows: 1) complete exposure pathways exist 

for these receptors; 2) the receptors may be potentially sensitive to pesticides in affected media and in 

residues on plants, seeds, and insects; and 3) the receptors could potentially inhabit areas where pesticides 

are applied, or areas where runoff and/or spray drift may impact the sites because suitable habitat is 
available. These endpoints are meant to reflect population sustainability and ecosystem biodiversity, and 

are standard assessment endpoints that are considered for the majority of pesticides with agricultural uses. 

Specifically, this assessinent addresses assessment endpoints for birds, mammals, reptiles, amphibians, 

beneficial insectslterrestrial invertebrates, fish, aquatic invertebrates, and benthic organisms. Although 

data on direct toxicity to reptiles and amphibians are not required as part of the standard dataset submitted 

to the Agency for pesticide registration and are not currently available for zeta-cypennethrin, toxicity and 

risks to reptiles are based on surrogate data from studies with avian species. For amphibians, freshwater 

fish are considered a suitable surrogate for the aquatic life-stage and birds a suitable surrogate for the 

terrestrial life-stage. 

The toxicity studies are used to evaluate the potential of zeta-cypermethrin to cause adverse effects, to 

detennine whether further testing is required, and to determine the need for precautionary label statements 

to minimize the potential adverse effects to non-target animals and plants (40 CFR 3 158.202,2002). A 

summary of the assessment endpoints and measures of effects selected to characterize potential ecological 

risks associated with exposure to zeta-cypennethrin is provided in Table 5. 

Table 5. Summary of assessment and measures of effect for zeta-cypermethrin. 

Assessment Endpoint Measure of Effect 

la. Bobwhite quail and mallard duck acute 01x1 LD~II. 

I. Abundance (i.e., survival, reproduction, and growth) of I b. Bobwhite quail and mallard duck subacute dietary LCsII. 

individuals and populations of birds. Ic. Bobwhite quail and mallard duck chronic reproduction > NOAEC. 

2a, laboratoty rat acute oral LD5(,. 

2. Abundance (i.e., survival, reproduction, and growth) of 2b. laboratoty rat 2- and 3-generation reproduction chronic NOAEC 

individuals and populations of maintnals. and LOAEC'. 

3a. Rainbow trout and bluegill suntish acute LC;O (guidelinerecommended species). Acute LCrll in several other species of 

freshwater tish 

3b. Fathead minnow chronic (early-life) NOAEC and LOAEC. 

3c. Water flea acute LCsll and ECill (guideline-recommended species). 3. Survival and reproduction of individuals and cotnmunities of Acute LC5,, and EC5,, in several other species of freshwater 

freshwater fish and invertebrates. invertebrates. 

4a. Sheepshead minnow acute LCIO. 

4b. Eastern oyster and mysid shrimp acute I.Cill and EGO (guidelinerecommended species). Acute LCil, and ECiO in several other species 

4. Sut-vival and reproduction of individuals and communities of of estuarineimarine invertebrates. ctustaceans. and molluscs. 

estuarinelmarine fish and invertebrates. 4c. Mysid shrimp chronic NOAEC and LOAEC. 

5. Survival of individuals and communities of freshwater benthic 5a. Midge and amphipod acute LCqII. 

organisms. 

6. Survival of terrestrial invertebrate populations (beneficial insects 6a. I-Ioneybee acute contact l.D51,. 

and ea~thwonns). 6b. Ea~thwonn acute contact LCill 

I.Ui,, = Lethal dose to 50% of the test population. 

LC'~I~(ECiIl) = Lethal (effective) concentration to 50% of the test population. 

NOAEC = No-observed-adverse-effect concentration. 

IDAEC = 1-owest-observed-adverse-effect concenhation. 

D. Conceptual Model 

1. Risk Hypotheses 

Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in assessment 
endpoints) and may be based on theory and logic, empirical data, mathematical models, or probability 

models (US EPA 2004). For this assessment, the risk is stressor-initiated, where the stressor is the release 

of zeta-cypermethrin to the environment. The following risk hypothesis is presumed for this screening 

level assessment: 

Based on ir?for.mation on persistence, mode qf action, direct toxicity, and potential indirect effects 

to trophic,food webs, tlie use qfzeta-cypermetltrin in accordance wit11 tlzepi*oposed labels will 

result in crdver-se effects or1 survival, ,fecundity, and/or growtli of non-target terrestrial and/or 

lrq~~atic animals. 

Ecological receptors that may potentially be exposed to zeta-cyperinethrin include terrestrial and semiaquatic wildlife (i.e., mammals, birds, and reptiles), terrestrial plants and terrestrial plants in semi-aquatic 

areas, and soil invertebrates. In addition to terrestrial ecological receptors, aquatic receptors (e.g., 

freshwater and estuarinelmarine fish and invertebrates, and amphibians) may also be exposed to zetacypermethrin by its migration from the site of application to various watersheds and other aquatic 

environments via runoff accompanied by erosion and spray drift. Data from toxicity studies formed the 

basis for identifying potential endpoints, stressors, and ecological effects associated with uses of zetacypennethrin. Despite that exposure of aquatic and terrestrial plants to zeta-cypermethrin is likely, EFED is 

not concerned about the level of phytotoxicity of zeta-cypermethrin products because its neural toxic mode 

of action is not expected to be a phytotoxic concern, there are no studies demonstrating adverse effects of 

zeta-cypennethrin or any other pyrethroid to plants, and no incident reports have reliably linked zetacypermethrin or any other compound in the synthetic pyrethroid class of chemicals to phytotoxic effects 

non-target terrestrial plants. In addition, although zeta-cypermethrin degradate exposure to aquatic and 

terrestrial organisms is also possible, based on the assumption that cleavage of the ester bond moiety in the 

parent structure results in biologically inactive degradates, these compounds are not expected to present a 

significant risk to non-target organisms. 

2. Diagram 

In order for a chemical 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 exposure pathway to be complete, 

it must have a source, a release mechanism, an environmental transport medium, a point of exposure for 

ecological receptors, and a feasible route of exposure. In addition, the potential mechanisms of 

transformation (i.e., which transformation products may fonn in the environment, in which media, and 

how much) must be understood, especially for a chemical whose metabolitesltransformation products are 

of greater toxicological concern than the parent compound. The assessment of ecological exposure 

pathways, therefore, includes an examination of the source and potential migration pathways for 

constituents, and the determination of potential exposure routes (e.g., ingestion, inhalation, dermal 

absorption). 

The conceptual model used to depict the potential ecological risk associated with zeta-cypermethrin is 

fairly generic and assumes that as a pesticide, zeta-cypermethrin is capable of affecting terrestrial and 

aquatic organisms provided that environmental concentrations are sufficiently elevated as a result of 

proposed label uses. However, through a preliminary iterative process of examining fate and effects data, 

the conceptual model, i.e., the risk hypothesis, has been refined to reflect the exposure pathways and the 

organisms that are most at risk (Figures 1 and 2). 

In the specific case of zeta-cypermethrin, the source and mechanism of release may include ground or 

aerial spray applications to agricultural crops. For turf applications it is a granular application directly over 
the turf. For termiticide uses it is to be applied directly to subterranean environments, or to building or 

structure surfaces, perimeters, and foundations. Surface runoff from the areas of application is assumed to 

depend on factors such as topography, irrigation, and rainfall events. Additional transport mechanisms 

include spray drift and wind erosion, which may potentially transport contaminants to the surrounding 

sites. In addition, direct deposition may result in contamination of food items that may be consumed by 

terrestrial organisms. 

The major point of exposure for aquatic organisms is direct effects from the water column, as well as 

sediment and pore water (gill/ integument uptake). However, indirect effects to aquatic organisms 

(especially fish) can also occur through impact to various food chains. Zeta-cypermethrin exposure to 

terrestrial animals is expected through ingestion of food items such as grass, foliage, and small insects. 
Stressor 

Sourcel 

Transport 

Pathways 

Sourcel 

Exposure 

Media 

Exposure 

Point 

Receptors 

Attribute 

Changes 

Zeta-cypermethrin applied as an emulsifiable concentrate to agricultural crops 

via groundlaerial broadcast foliagelfruit spray. 

I 

6 t t t t 

; Volatilization ; 

; /Wind ; Deposition 

1 Suspension ! m Drift Erosion 

r----------------- 

I I 

I Leaching I I Infiltration/Percolation 

------------------ 

I I 

Terrestrial Food 

Residues (foliage, 

fruit, insects) 

1 Gill1 Integument 

Ingestion & Dermal Uptake and 

Uptake I I I lngegtion 

Birds, Mammals, Invertebrates 

Reptiles, Terrestrial and Vertebrates 

Invertebrates Amphibians 

I r------------- I 

Individual Animals 

Reduced survival 

Reduced growth 

Reduced reuroduction 

r_----------------- 

; Individual Plants ; 

! Seedling emergence ! 

Vegetative vigor I------------------- 

; Plant ~ouulation ;

; Reduced 

population ; 

! growth ! 

Individual Animals 

Reduced survival 

Reduced growth 

Reduced 

reproduction 

** The dotted lines represent unlikely routes of exposure/effects 

Figure 1. Ecological conceptual model for spray applications of zeta-cypermethrin. 

24 
Stressor Granular zeta-cypermethrin applied to turf via broadcast ground application. 

Source1 

Transport 

Pathways 

Source1 

Exposure 

Media 

Exposure 

Point 

t 

Deposition 

1 

items that have 

bioconcentrated 

1 Ingestion 

1 

Receptors 

I Reduced reproduction I 

Terrestrial Oraanisms: 

Birds, Mammals, 

Reptiles, Terrestrial 

lnvertebrates 

Attribute 

Changes 

r----------------- 

Leaching I 

Erosion ; InfiltrationIPercolation 

------------------ 

Individual Animals 

Reduced survival 

Reduced growth 

Plants Plants 

Gill1 Integument 

Uptake and 

lnge tion I 

Aquatic 

lnvertebrates 

and Vertebrates r-l Amphibians 

I Plant population Individual Plants ; I Reduced 

; Seedling emergence I I I population Reduced survival Vegetative vigor '------------------I 1 , arowth ! Reduced growth - -------------- Reduced I reproduction 

** The dotted lines represent unlikely routes of exposure/effects 

Figure 2. Ecological conceptual model for granular applications of zeta-cypermethrin. 
E. Analysis Plan 

1. Preliminary Identification of Data Gaps and Methods 

The primary method used to assess risk in this screening-level assessment is the risk quotient (RQ) and 

follows closely methods outlined in the EPA Overview Document (EPA, 2004). The RQ is the primary 

risk value for the screening-level assessment and is the result of comparing measures of exposure to 

measures of effect. A commonly used measure of exposure is the estimated exposure concentration (EEC) 

and comlnonly used measures of effect include toxicity values such as the LDso or NOAEC. Assessment 

endpoints and their respective measures of effect are listed in Table 5. The resulting RQ is then compared 

to a specified level of concern (LOC), which represents a point of departure for concern; if the RQ exceeds 

the LOC, then risks are triggered. Although not necessarily a true estimate of risk since there is no 

estimated probability of effect, in general, the higher the RQ, the more certain the potential risks. Risk 

presumptions, along with the corresponding RQs, equations, and LOCs are summarized in Appendix F. 

Levels of concern (LOC) are the policy tool for interpreting risks from direct pesticide effects and have a 

magnitude, duration, frequency, and spatial extent. The magnitude is set by the risk presumption for each 

endpoint. The frequency of potential risk is once every ten years for aquatic endpoints and one in every ten 

foliage samples for terrestrial risk. The spatial extent is defined by the use area, and the areas downstream 

and areas potentially affected by spray drift. 

Generation of robust RQs are dependent on the quality of data from both fate and toxicological studies. 

The adequacy of the submitted data was evaluated relative to Agency guidelines. The following identified 

data gaps for ecological fate and toxicity endpoints result in a degree of uncertainty in evaluating the 

ecological risk of zeta-cypermethrin. 

There is uncertainty regarding chronic toxicity to freshwater invertebrates and 

estuarinelmarine fish because no data are currently available. To assess risk to these 

taxonomic groups, RQs were based on chronic NOAEC values derived using acute-tochronic ratios. 

Risks to terrestrial plants and terrestrial plants in semi-aquatic areas were not evaluated 

because toxicity data on these receptors are not available; however, EFED is not 

concerned about the level of phytotoxicity of zeta-cypermethrin products because its 

neural toxic mode of action is not expected to be a phytotoxic concern, there are no studies 

demonstrating adverse effects of zeta-cypennethrin or any other pyrethroid to plants, and 

no incident reports have reliably linked zeta-cypermethrin or any other compound in the 

synthetic pyrethroid class of chemicals to phytotoxic effects to non-target terrestrial plants. 

Results of acute toxicity studies in freshwater fish and invertebrates indicate that the zetacypermethrin degradate 3-phenoxy benzoic acid is much less toxic than the parent 

compound. No information is available on the toxicity of other zeta-cypermethrin 

degradates or on the toxicity of any degradate to terrestrial organisms; therefore, risk 

resulting from exposure to zeta-cypermethrin degradates could not be evaluated in this 

assessment. However, based on the assumption that cleavage of the ester bond moiety in 

the parent structure results in biologically inactive degradates, these compounds should 

not present a significant risk to non-target organisms. 
There were no chronic data available to estimate chronic risk of zeta-cypermethrin 

exposure to benthic organisms, there were no acute toxicity data for benthic organisms 

based on pore water concentrations, and estimates of acute toxicity to benthic organisms 

based on sediment concentrations may underestimate toxicity because the water-sediment 

systems were not at equilibrium. Therefore, acute to chronic ratios were used to derive 

chronic NOAEC values for the purposes of this risk assessment, the equilibrium 

partitioning (EqP) theory and definition of the koc were used to estimate toxicity values in 

terms of pore water concentrations, and additional sediment toxicity studies have recently 

been submitted to the Agency by the Pyrethroid Working Group (PWG) to address these 

uncertainties. 

2. Measures to Evaluate Risk Hypotheses and Conceptual Model 

a. Measures of Exposure 

The maximum rate of application for the emulsifiable concentrate to crops is 0.05 Ib a.i.1A 

with a maximum of 6 applicationslseason and a minimum interval of 7 days between 

applications (a total maximum seasonal application rate of 0.3 lbs a.i./A). However, for 

this risk assessment EFED assumed that zeta-cypermethrin was applied at a maximum of 6 

times per year. If there are conditions under which there is more than one growing season 

for a crop within a single year, exposure estimates and risk to aquatic and terrestrial 

organisms could be significantly underestimated. Examples of crops that have multiple 

seasons where this may be a concern include leafy, brassica, and fruiting vegetables in 

CA, AZ, FL, GA, LA, NC, TX, andlor SC. 

It is assumed for pesticides which have residential outdoor uses (applications to home 

lawns, gardens, parks, etc.) that runoff water from rain andlor lawn watering may remove 

pesticide to storm sewers and then directly to surface water. However, in general, outdoor 

residential uses are comprised of multiple, relatively small, temporally and spatially 

variable applications that are not simulated in agricultural models. Therefore, there is 

some uncertainty in the aquatic exposure assessment because a model specifically aimed at 

simulating pesticide fate and transport in a complex urban landscape has not yet been 

developed to generate exposure estimates strictly for urban areas. 

There is also uncertainty with respect to the exposure due to the use of zeta-cypermethrin 

as a termiticide in residential or industrial areas because the Agency does not have a model 

to calculate the EECs for this use. However, the EFED believes that the exposure due to 

the termiticide subterranean uses are likely to be minimal due to the nature of the 

application method, and the fate properties of zeta-cypermethrin (strongly adsorbed by 

soils). However, the perimeter treatments are more uncertain because the chemical may be 

exposed to the elements. 

Zeta-cypermethrin seems to be degraded mainly by metabolism. In soils, the metabolism 

appears to be somewhat slower than in aquatic media. The rates for aerobic and anaerobic 

- soil metabolism were about 60 and 52-63 days, respectively. In contrast, the rates for 

aerobic and anaerobic aquatic metabolism were 9-10 and 14-1 7 days, respectively. All 

abiotic processes appeared to be insignificant dissipation mechanisms for zetacypermethrin. The chemical appears to be stable to hydrolysis, except on alkaline media 
(at pH 9 tlp2 days). In the presence of light, zeta-cypermethrin photolyses relatively 

slowly, both in water and on soil. The potential impact to water quality from the use of 

zeta-cypermethrin is mostly due to the parent. The laboratory studies indicate that zetacypermethrin is moderately to highly persistent under most environmental conditions. 

This makes the chemical available for lengthy periods of time for runoff. The impact of 

zeta-cypennethrin would also be affected by its mobility. The available studies indicated 

that zeta-cypermethrin has very low mobility in the various soils tested. Therefore, the 

means to runoff for zeta-cypermethrin from crop sites to adjacent bodies of water can be 

runoff accompanied by erosion. Another means to reach adjacent waters is via spray 

drift. 

For agricultural uses, exposure concentrations for aquatic ecosystems assessments were 

estimated based on EFED's Tier 2 aquatic model PRZMIEXAMS. A graphical user 

interface (pe4), developed by the EPA <Ilttv. \I \\ n .cna.rrot oppclkd 1 ~nodels 'M ntcr>, was 

used to facilitate inputting chemical and use specific parameters into the appropriate 

PRZM input files (inp) and EXAMS chemical files. This approach employs PRZM, 

which simulates the processes in the agricultural field, such as runoff and erosion, on a 

daily time step. The runoff and erosion flux output data from PRZM are used as chemical 

loadings to EXAMS, which simulates surface water in order to predict the EECs. Five 

PRZM field (crop) scenarios were modeled: CA grapes, GA peaches, ID potatoes, PA 

apples, and FL trrrf: An effort was made to cover all areas of the continental United States 

and to select crops with the highest application rates. EECs for ecological risk assessment 

were determined using a pond modeling scenario which describes a generic scenario for 

the EXAMS component of the modeling exercise. It was found that the EECs for CA 

grapes and ID potatoes were very similar. Therefore, since they would yield similar RQs, 

only the CA grapes scenario was kept in the assessment. The results from 

PRZMIEXAMS for the ID potatoes scenario appear in the Appendix B. 

Since zeta-cypermethrin, like other pyrethroids, binds to organic carbon (mean Koc = 

141,700 mg1L) and eventually accumulates in aquatic sediment, toxic exposure to 

organisms living in this media is a concern. EFED has estimated zeta-cypermethrin 

sediment exposure to benthic organisms by calculating sediment and pore water exposure 

values using the PRZMIEXAMS model. Screening level RQs for sediment dwelling 

organisms were estimated with an extrapolation method recommended by the Office of 

Water (USEPA). This was based on the Agency Equilibrium Partitioning Sediment 

Guidelines (ESG) under the Clean Water Act [CWA Section 304(a)(2)]. After consultation 

with the OW, EFED adopted the equilibrium partitioning (EqP) sediment method to be used 

when sediment toxicity and exposure data are not available (Appendix G). This 

extrapolation method is useful for estimating potential sediment exposure values, as well as 

sediment toxicity values that can be used in a screening level risk assessment. The EqP 

theory holds that a nonionic compound in the sediment partitions between sediment 

organic carbon, interstitial (pore) water and benthic organisms (Di Toro et al., 1991, U.S. 

Environmental Protection Agency, 2000~). At equilibrium, if the concentration in any 

phase is known, then the concentration in the other phases can be predicted through the 

organic1 carbon soil partition coefficient. The EECs are calculated from the pore water 

concentration (an output from PRZMI EXAMS) through the Gc. 

The measurement of the level of drift was performed with the model AgDRIFTB, which 

is capable to determine the level of drift to the EXAMS standard pond from a 
predetermined buffer zone. The ground portion of the model was validated with actual 

field data. 

For exposure of terrestrial organisms to spray applications of zeta-cypermethrin, residues 

in potential dietary sources (e.g., vegetation and insects) for marmnals and birds were 

estimated using the conceptual approach given in the Tier 1 model T-REX (T-REX, 

Version 1.2.3, dated, August 8, 2005). This model provides estimates of concentrations 

(maximum, or upper bound, and average) of chemical residues on the surfaces of different 

forage that may be sources of dietary exposure for avian, mammalian, reptilian, or 

terrestrial-phase amphibian receptors. The surface residue concentration (ppm) is 

estimated by multiplying the application rate (pounds active ingredient per acre) by a 

value specific to each food item. The T-REX model was run for four crop use scenarios: 

stone fruits, canola, non-grass animal feeds, and barley. These scenarios were selected to 

represent a variety of crops and use scenarios in the continental US. 

For acute exposure of terrestrial organisms to granular applications of zeta-cypermethrin, 

exposure and risks were estimated with the conceptual approach using the ~~~~lft' method 

given in the Tier 1 model T-REX. Terrestrial EEC values were calculated based on an 

estimation of loadings of pesticide per unit area. The T-REX model was run the maximum 

use scenario of granular zeta-cypermethrin on turf. 

For chronic exposure of terrestrial organisms to granular zeta-cypermethrin, only direct 

ingestion of soil invertebrates that have bio-concentrated zeta-cypermethrin residues of 

granules in soil was considered. This estimation of earthworm concentration was 

calculated using a fugacity-based (equilibrium partitioning) approach based on the work of 

Trapp and McFarlane (1 995) and Mackay and Paterson (1 98 1 ). 

b. Measures of Effect 

Measures of ecological effects are obtained from a suite of registrant-submitted guideline studies 

conducted with a limited number of surrogate species. The test species are not intended to be 

representative of the most sensitive species but rather were selected based on their ability to thrive under 

laboratory conditions. Measures of effect are based on deleterious changes in a receptor as a result of 

chemical exposure. Functionally, measures of effect typically used in risk assessments include changes in 

survival, reproduction, or growth as determined from standard laboratory toxicity tests. The focus on these 

effects for quantitative risk assessment is due to their clear relationship to higher-order ecological systems 

such as populations, communities, and ecosystems. Although monitoring data may also be used to provide 

supporting lines of evidence for the risk characterization, monitoring data is lacking for this new chemical. 

In addition, effects other than survival, reproduction, and growth may be considered, rarely are they used 

quantitatively to estimate risks since, in many cases, the relationship between these effects and higherorder processes is tenuous at best. Commonly used laboratory-derived toxicity values include estimates of 

acute mortality (c.g., LD50, LC50, or EC50) and estimates of effects due to longer term, chronic exposures 

(e.g., NOAEC, NOAEL). The latter can reflect changes seen in mortality, reproduction, or growth. 

Registrant-submitted data are available for all cypermethrin products (alpha-, beta-, theta-, and zetacypermethrin); the Agency assumes equivalent toxicity is bridging the TGAI data for risk assessment 

purposes. Limited toxicity data on the zeta-cypernethrin degradate 3-phenoxybenzoic acid has also been 

identified and incorporated into this risk assessment. A complete summary of the measures of effect based 

on toxicity studies for different ecological receptors and measures of effect (acutelchronic) for 

cypermethrin (TGAI) is given in Table 5, with study details provided in Appendix E. 
c. Measures of Ecosystem and Receptor Characteristics 

The changes in ecosystems and free-ranging receptors in response to proposed uses of zeta-cypermethrin 

are not explicitly quantified in this assessment. It would be nearly impossible to address the myriad of 

uses, ecosystems and receptors that may interact as a result of zeta-cypermethrin use. Instead, the measures 

of exposure and measures of effect are used to generate estimates of risk that can be applied to a wide 

variety of receptorlecosystem combinations that are represented by the specified assessment endpoints. 

The assessment endpoints specified in Table 5 can be summarized as survival, growth, and reproduction 

of terrestrial and aquatic receptors to include birds, mammals, reptiles, amphibian, fish, and invertebrates. 

The response of these receptors to zeta-cypennethrin exposure is represented by a small number of toxicity 

studies on representative or surrogate species. Hence, there is uncertainty regarding the response of a freeranging receptor since data for all species potentially exposed are not available. The lowest available 

measure of effect for a given assessment endpoint is used to calculate RQs to accommodate for some of 

this inherent uncertainty. However, the extent to which this is sufficient is unknown. 

For the assessments using the Tier I1 aquatic model PRZMIEXAMS and the Tier I terrestrial model TREX, the ecosystems that are modeled are intended to be generally representative of any aquatic or 

terrestrial ecosystem associated with areas where zeta-cypermethrin is used. The receptors addressed by 

the aquatic and terrestrial risk assessments for zeta-cypermethrin are summarized in Table 4. For aquatic 

assessments, fish and aquatic invertebrates in both freshwater and estuarine/marine environments are 

represented. For terrestrial assessments, three different size classes of small mammals are represented, 

along with five potential foraging categories (short grass, tall grass, broadleaf plantslsmall insects, 

fruitslpods/large insects, and seeds). For birds, three different size classes are represented, along with four 

potential foraging categories are considered (short grass, tall grass, broadleaf plantslsmall insects, and 

fruits/pods/seeds/large insects). 

111. Analysis 

A. Use Characterization 

Zeta-cypermethrin is an insecticide that is formulated as an emulsion, an emulsifiable concentrate, and a 

granular. Zeta-cypermethrin is already used to control many pests, including those of cotton, alfalfa, bulb 

vegetables corn, fruiting vegetables (except cucurbits), legume vegetables, succulent edible-podded peas 

and beans, rice, sorghum (grain) and millet, soybeans, sugar beets, wheat and triticale crops. The registrant 

is also requesting tolerances or new agricultural uses for the emulsifiable concentrate to include cilantro, 

head and stem brassica vegetables, leafy vegetables (except brassica), sunflowers, grass forage, fodder, hay 

group, canola rapeseed, barley, grapes, tree nut group (almond, pecan), berries, peanuts, root and tuber 

vegetables, cucurbit vegetable group, non-grass feeds (forage, fodder, straw and hay), pome fmits, and 

stone fruits. Furthermore, a granular zeta-cypermethrin formulation is proposed for use on turf on 

residential lawns, home perimeters, gardens, and other industrial non-agricultural areas, while a zetacypennethrin emulsion is proposed for use as a tenniticide. Zeta-cypermethrin emulsifiable concentrate 

formulations are to be applied as a groundlaerial broadcast foliagelfruit spray while the granular 

formulations are to be applied by ground broadcast equipment to infested areas. 

The maximum rate of application for the emulsifiable concentrate to crops is 0.05 lb a.i.1A with a 

maximum of 6 applications/season and a minimum interval of 7 days between applications (a total 

Pecans 

RIL~ 

Sot ghum 

Soybean$ 

5uga1cdne 

Wheat 

0 05 

0 05 

0 05 

0 05 

0 05 

0 05 

Crops propoved in 

C~lantro 

Head aud Stem 

Bra~sica 

Vegetables 

L.eafy Vegetables 

(except Brassica) 

Sunflowers 

Grass forage, 

fodder, hay 

grou P 

Canola, 

Rapeseed 

Ual lej 

Grapes 

rree nut group 

(almood, pecan) 

Berrie? 

Peanuts 

Hoot aud ruber 

Vegetables 

6 

4 

5 

6 

4 

5 

th~s Section 3: 

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

0 3 

0 2 

0 25 

0 3 

0 2 

0 25 

6 

6 

6 

5 

4 

4 

5 

6 

5 

6 

6 

6 

NS 

7 

10 

7 

2 1 

14 

0.3 

0.3 

0.3 

0.25 

0.2 

0.2 

0.25 

0.3 

0.25 

0.3 

0.3 

0.3 

G 

6. A 

G A 

G, A 

G A 

6. A 

0 

0 

0 

0 

0 

0 

7 

7 

7 

NS 

7 

7 

14 

7 

7 

7 

NS 

NS 

G, A 

G, A 

G, A 

G, A 

G, A 

C, A 

G, A 

G, A 

G, A 

G 

G, A 

G, A 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 
B. Exposure Characterization 

J 

1. Environmental Fate and Transport Characterization 

Termiticide 

a. Summary 

May be applied as subterranean treatment to critical areas, by removing the soil and applyi~~g the material as a 

liquid, as a preconstruction subterranean treatment, postconstruction soil treatment (drill holes in the 

foundation to allow for the application), or foam applications for spot tratments, and perimeter treatment. 

The registrant has submitted an extensive and complete body of data. Based on mostly valid and some 

supplemental studies, the behavior of zeta-cypennethrin in the environment can be predicted with 

reasonable certainty. Studies were performed with cypermethrin or with zeta-cypermethrin. The field 

study appears to corroborate what is predicted by the laboratory studies. It appears that zeta-cypermethrin 

degradation is mainly the product of metabolic activity. Aerobic and anaerobic soil metabolism were found 

to be about 60 and 52-63 days, respectively. In contrast, the rates in aquatic media appear to be more 

rapid, with aerobic and anaerobic aquatic metabolism of 9-10 and 14-17 days, respectively. All abiotic 

processes appeared to represent relatively insignificant dissipation mechanisms for zeta-cypermethrin. 

Zeta-cypermethrin appears to be stable to hydrolysis (except in alkaline media at pH 9 t:p2 days) and in 

the presence of light (photolysis in water was 20 - 36 days and on soil, 57 - 100 days). In the field, the 

half-lives were 12.2 and 3.2 days in CA and LA, respectively. In aquatic field dissipation studies, the halflives indicated persistence, with 18 1 and 126 days in CA and LA, respectively. Cypermethrin shows a 

inoderate potential for bioaccumulation in fish, with lnaxilnum BCF of 468 for whole fish in a 28 day 

study. Depuration appeared to be moderate, with near 10-1 5% of the initial residues remaining after 2 1 

days. The major transformation products for zeta cypermethrin are cis- and trans-DCVA, 3-PBA and 3- 

phenoxybenzoic acid. They are the product of the cleavage of the ester bond. 

G=ground; A=aerial; IJLV=ultra low volu~ne application; NS=Not specified. 

' For use on residential lawns, home perimeter, ornamental and flower gardens. 

b. Hydrolysis 
Cypermethrin was approximately stable to abiotic hydrolysis in pH 5 and 7 solutions, while in pH 9 

solutions, the half-lives were 1.8-2.5 days (cyclopropyl and the benzyl [I4c]-labeled materials). Two major 

degradates were detected in the pH 9 solutions. A mixture of cis- and trans-DCVA steadily increased to 

78.7% at hour 120. And 3-phenoxybenzaldehyde, which increased to 64.9% at hour 120. 

c. Photolysis 

Cypermethrin photolysed in aqueous solutions exposed to sunlight, with half-lives of 20 and 36.2 days, 

compared to an essentially stable dark control. One major individual cyclopropyl-labeled degradate 

(maximum 21.2% of the applied on day 30) was not identified). Another major degradate was 3- 

phenoxybenzoic acid which steadily increased to 34.6% (day 35) in the sunlight irradiated solution. 

On a thin layer of sandy loam soil, cypermethrin, exposed to sunlight, degraded with half-lives of 56.2 and 

56.5 days, compared to dark controls of 75.9 and I00 days. The EFED's calculated half-lives for 

photodegradation only (substracting the contribution presented by the dark control). The results were 21 5 

and 128 days. The major degradate was cypermethrin amide which steadily increased on both the 

irradiated soil and on the dark control (observed in both labels at up to 13.3%). All values for the phenyl 

and the cyclopropyl labels, respectively. 

Cypermethrin has a relatively low solubility and vapor pressure (reported solubility from 0.2 to as low as 

4.0x10-bg/~, and vapor pressure between 2.5~10.~ torr and 6.7x10-~ torr or 8.8 x 10.'~ atm). The 

corresponding Henry's Law Constant varies from 1.6x10-' at~narn~l~nol and 3.4x10-' atmarn~z/mol. 

Cypermethrin is not expected to have any significant potential for volatilization from water or soil, and 

therefore, air photolysis would be a very little component in the environmental fate of the chemical. 

d. Metabolism 

In an aerobic soil inetabolisin study, conducted on a sandy loam, cypermethrin degraded with calculated 

half-lives of 60.7, and 59.8 days, for the cyclopropyl, and phenyl labeled material, respectively. In the 

cyclopropyl labeled study, the major degradates were C02 (a maximum of 35.8% of applied at day 128), 

and a mixture of cis- and trans-DCVA (which increased to a maximum of 24.2% of applied on day 62 and 

then decreased to 4.4% by day 150). In the phenyl labeled study, there was one major degradate: COr 

which steadily increased to a maximum of 46.1% of applied on day 150. The minor degradate 3- 

phenoxybenzoic acid was 28.4% of the applied throughout the study. 

Some supplemental studies show shorter degradation half-lives for cypermthrin. In three foreign soils, the 

half-lives were 2.7, 7.3, and 6.9 days in British clay loam, loamy sand soil, and peat soil. In all three cases, 

the major degradate was I4co2, which reached between about 60 and 70% of the applied by 25 days. The 

studies were conducted only with the benzyl labeled material. The only non-volatile degradate detected at 

>lo% was 3-phenoxybenzoic acid, which was up to 12.3% (day 1) in the peat soil. 

In an anaerobic soil metabolism study, cypermethrin was incubated aerobically for 32 days in the same 

sandy loam soil used in the aerobic study. After this period, the soil was flooded to establish anaerobic 

conditions. At the time the anaerobic conditions were established, cypermethrin accounted for about 66- 

67% of the applied. Based upon cypermethrin declines during 60 days of flooded conditions, the anaerobic 

soil metabolism half-lives were 5 1.5 and 62.9 days for the cyclopropyl and the phenyl labeled 

cypermethrin, respectively. The major cyclopropyl labeled degradate was a mixture of cis- and transDCVA (inax. of 33.3% of the applied 30 days after flooding). The major phenyl labeled degradate was 3- 
phenoxybenzoic acid (max. at the end of the study, 60 days, with 25.9% of the applied). C02 increased 

from 13.2% of applied on day 0 of the flooded period to 20.9% (day 60). 

e. SedimenttWater Systems 

The sedimentlwater studies were conducted with zeta-cypermethrin. 

In one aerobic aquatic metabolism study, total [14~]-zeta-cypermethrin (sedimentlwater system), at a 

nominal application rate of 0.15 ppin, degraded with calculated half-lives of 8.9 and 10.1 days for the 

phenyl and cyclopropyl radiolabel materials, respectively, in flooded clay loam sediment that was 

incubated aerobically in the dark at 25f 1 OC for up to 30 days. The approximate DT50 obtained by 

inspection of the data appeared to be about 3 days. Close inspection of the data reveals that the dissipation 

of the cypermethrin becomes slow (perhaps biphasic) with time, which explains the long calculated halflives and short observed DT50's. 

In the phenyl label study the major degradate was 3-phenoxybenzoic acid, which increased to a maximum 

of 48.4% at 21 days posttreatment Evolved I4co2 reached 7.1% of the nominal application 30 days 

posttreatment. Nonextractable [I4c] residues were a maximum of 16.8% of the applied at 30 days 

posttreatment.. In the cyclopropyl label study, the major degradate was trans-DCVA, which was a 

rnaximum of 48.8% of the nominal application by 30 days posttreatment. In addition, cis-DCVA was a 

maximum of 19.4% of the applied at 30 days. 

In an anaerobic aquatic metabolism study, ['4~]-zeta-cypermethrin, at a nominal application rate of 0.15 

ppm, degraded with half-lives of 13.8 days and 16.5 days, in flooded clay loam sediment, incubated 

anaerobically in the dark, at 25*1 OC for up to 90 days (benzyl label) or 183 days (cyclopropyl label). In 

studies conducted with both radiolabels, the majority of the radioactivity of the parent was associated with 

the sediinent. 

In the benzyl label study the major degradate was 3-phenoxybenzoic acid. In the sediment, it reached a 

lnaximuln in the sediment at 30 days posttreatment, with 42.5% of the applied. Evolved I4c02 was 69.8 of 

the applied after 90 days posttreatment. Nonextractable radioactivity was a maximum of 14.7% of the 

applied at 14 days posttreatment. In the cyclopropyl label study, the major degradate was trans-DCVA, 

which increased in the aqueous phase to a maximum of 34.1 % of the applied by 30 days and decreased to 

10.8% by 18 1-1 83 days. In the sediment, the same degradate, was present at a maximum of 3 1.3% of the 

applied by 71 days posttreatment. By 183 days it was only 21% of the applied. Nonextractable [I4c] 

residues were a maximum of 14.0% of the applied at 183 days posttreatment. 

f. Mobility 

Data on the adsorption and desorption of cypermethrin were provided for four soils with a variety of 

properties, like %OC ranging from 0.2 to 2.3. The reported adsorption and desorption constants for 

cyperlnethrin binding to the 4 test soils indicated low mobility for cypennethrin in all four soils. The Kqads) 

ranged from 4 16 to 1900, while the value corrected for organic carbon, Koc. ads, ranged from 20,800 and 

328,500. lln values were between 1.16 and 1.47. There are several aspects of the above data that are 

unusual and are as yet unexplained, the major one being lower desorption than adsorption values for 3 of 

the soils. Binding isotherms and Freuendlich parameters were not provided for any of the cypennethrin 

degradates. 
14 In an aged leaching study, C-cyclopropyl labeled and I4c-benzyl labeled cypermethrin were applied to 

the tops of 30 cm soil columns containing a sandy loam soil (1 1 % clay, 1.8%OM, pH 6.9), aged for 30 

days and then leached with 20 inches of water. Of the total '4~-cyclopropyl labeled residues added to the 

top of replicate soil columns, 1 1.3-1 3.6% was recovered froin the leachate. Of that amount, 89-97% was 

identified as a mixture of cis- and trans DCVA. Of the total I4c-benzyl labeled residues added to the top 

of replicate soil columns, < 1% was recovered from the leachate. 

The results of this aged soil column leaching study indicated that the degradate DCVA was substantially 

more mobile than cypermethrin and benzyl labeled degradates such as 3-phenoxybenzoic acid. 

Conclusions with respect to the mobility of benzyl labeled degradates should be limited by the relatively 

low levels of such degradates formed within the relatively short aging period of 30 days. 

g. Field Dissipation 

In a terrestrial field dissipation study, conducted at Madera, CA, cypermethrin in the EC fonn was applied 

three times at 0.2 Ib a.i.lAiapplication to a bare silt loam soil. Based upon dissipation in the top 0-3" soil 

cores, half-life of 12.2 days was estimated over the 28 days required for the chemical to dissipate to a level 

below the detection limit. 

Cypennethrin was detected in 3-6" cores collected immediately after each application (max. 33 ugikg), and 

days 2, and 4 after the 3rd application (20 and 29 uglkg, respectively). Cypennethrin was detected at 10 

uglkg only in one 6-12" core collected 2 days after the last application, but it was not detected above a 

detection limit of 7 uglkg in any soil cores collected below 6 inches. 

The degradate 3-phenoxybenzoic acid was detected in 0-3" cores collected immediately after the 2nd and 3rd 

applications (8 and 17 uglkg, respectively), and the following days after the 3rd application (max. 32 

uglKg on day 4). It was not detected above a detection limit of 7 uglkg in any soil cores collected below 3 

inches. 

Potential degradates cis- and trans-DCVA were not detected above a detection limit of 7 uglkg in any of 

the soil cores. No other degradates were monitored in the study. Total rainfall and irrigation combined 

during the study was 16.5 inches. 

In another terrestrial field dissipation, conducted at Cheneyville, LA, cypermethrin in the EC form was 

applied three times at 0.2 lb a.i./A/application to a bare loamy sand soil. Based upon dissipation in the top 

0-3" soil cores, the dissipation half-life for cypermethrin was 3.2 days over the 28 days required for the 

chemical to dissipate to a level below the detection limit. Cypermethrin was not detected above a detection 

limit of 7 ugikg in any cores collected below 3 inches. 

The degradate trans-DCVA was detected in 0-3" cores collected on a few days after the 3rd application: 

days 2 and 7 (16 and 8 uglkg, respectively). The degradate 3-phenoxybenzoic acid was detected in 0-3" 

cores collected immediately after the 2"d and 3rd application (10 and 20 ugfkg, respectively), and 2 days 

after the 3rd application (44 uglkg). The degradate cis-DCVA was not detected above a detection limit of 

7 uglkg in any of the soil cores. 

None of the analytes were detected above a detection limit of 7 uglkg in any of the soil cores collected 

below 3 inches. Total rainfall and irrigation during the study was 53.7 inches. 
Two aquatic field dissipation studies were performed with zeta-cypermethrin on rice plots in California 

and Louisiana; these studies provide limited supplemental infonnation. The reported half-lives of 181 and 

126 days in CA and LA, respectively, do not agree with the values of the aerobic aquatic or the anaerobic 

aquatic metabolism studies (tI,<'s ranged between 9 and 17 days). The reported aquatic field dissipation 

half-lives included the sediments only, not the flood water. 

h. Bioaccumulation 

Bluegill sunfish were exposed in separate tests to nominal 0.20 ug/L cyclopropyl and benzyl labeled 

cypermethrin in flow-through tanks for a 28 day uptake phase. After 28 days of exposure the bluegill 

sunfish were placed in cypennethrin free water for a 2 1 day depuration phase. 

Maximum total cyclopropyl residue BCFs were observed on day 28: 161 for edible tissue, 833 for viscera, 

and 444 for whole fish. BCFs gradually increased with increasing exposure time, and steady state may not 

have been obtained by the last day of exposure. After 2 1 days depuration, total cyclopropyl residues 

. declined from 29 uglkg to 3.2 uglkg in edible tissues, from 150 uglkg to 13 ugkg in viscera, and from 80 

uglkg to 1 1 uglkg in whole fish. 

Maximum total benzyl residue BCFs were observed on day 28 for edible tissue, and day 21 for viscera and 

whole fish. Max. BCF's were: 11 1 for edible tissue, 579 for viscera, and 468. BCFs rapidly increased 

with increasing exposure time and appeared to reach approximate steady state by only 1 day of exposure 

for viscera and whole fish. For edible tissue, BCFs gradually increased with increasing exposure time, and 

steady state may not have been obtained by the last day of exposure. After 21 days depuration, total benzyl 

residues declined from 2 1 uglkg to 2.9 uglkg in edible tissues, from 93 uglkg to 12 ugkg in viscera, and 

from 57 uglkg to 10 ugikg in whole fish. 

i. Nomenclature and Degradation Products of Cypermethrin 

trans-DCVA = (*)trans-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane carboxylic acid 

cis-DCVA = ~cis-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane carboxylic acid 

MPB-acid = 3-PB-acid = 3-phenoxybenzoic acid 

3-PBA = 3-phenoxybenzaldehyde 

2. Measures of Aquatic Exposure 

a. Aquatic Exposure Modeling 

For agricultural uses, exposure concentrations for aquatic ecosystems assessments were estimated based on 

EFED's Tier I1 aquatic model PRZMIEXAMS. A graphical user interface (pe4), developed by the EPA 

<11111): it n L{ .cl-t,l.~cn ov~clcd 1 m~)dcla ivaies>, was used to facilitate inputting chemical and use specific 

parameters into the appropriate PRZM input files (inp) and EXAMS chemical files. The Pesticide Root 

Zone Model (PRZM) field or orchard crop scenario is the basic file which describes the local or regional 

cliinatological information, soil hydrology, soil characteristics, crop characteristics, and the pesticide 

properties necessary to determine pesticide loadings to ground or surface water. This basic file constitutes 

the first part of the "exposure scenario." It simulates the processes in the agricultural field, such as runoff 

and erosion, on a daily time step. The runoff and erosion flux output data from PRZM are used as 

chemical loadings to EXAMS (Exposure Analysis Modeling System), which simulates surface water in 
order to predict the EECs. The PRZM scenario selected for modeling were California grapes, Georgia 

peaches, Idaho potatoes, Pennsylvania apples and Florida turf. EECs for ecological risk assessment were 

determined using a pond inodeling scenario which describes a standard scenario for the EXAMS 

component of the lnodeling exercise (EXAMS Mississippi pond). 

To determine the level of spray drift with the buffer zones imposed in the label for this chemical, the model 

AgDRIFTB was utilized. Following is a table of input parameters for zeta-cypermethrin. It was found 

that the EECs for CA grapes and ID potatoes were very similar. Therefore, since they would yield the 

same RQs, only the CA grapes scenario was reported in the assessment. The results from PRZMIEXAMS 

for the ID potatoes scenario appear in the Appendix B. 

Table 7. Input Parameters 

Parameter (units) 

Output File Name 

Chemical Name 

Crop Narne 

Application Rate (Kg a.i./ha) 

Day of Application (day-month) 

Number of Applications Allowed 

Interval between Applications 

(days) 

Koc 

Aerobic Soil Metabolis~n (days) 

Incorporation Depth 

Method of Application 

Buffer Zone (ft.) 

Application Efficiency (fraction) 

Spray Drifi (fiaction) 

Solubility in Water (ppm) 

Aerobic Aquatic Metabolistn 

(days) 

Utilized in PRZMIEXAMS 

Value(s) 

zcyper 

Zeta-cypamcthrin 

C'A gapes 

GA peaches 

ID potatoes 

PA apple 

FL turf 

0.056 

0.252 for turf 

C'A grapes 01 -07 

GA peachcs 0 1-07 

ID potatoes 2 1-08 

PA apples 15-08 

FL turf 0 1-06 

6 

I for FL turf 

7 days for grapes, potatoes, 

peaches and apples, 3 days 

for cotton. 

141,700 

61 

0.0 in 

Ground or Aerial 

25 ground, 150 aerial 

1 .OO for turf 

0.99 for peaches and apples 

0.95 for other crops 

0.0 for turf 

0.028 for peaches and apples 

0.039 for othet. crops 

0.040 

10.7 

for Zeta-cypermethrin: 

Sources 

--- 

Label 

label 

ILabel 

--- 

Label 

Label 

MRID: 42129003 

MRID: 42 156601 

Label 

Label 

Label 

--- 

AgDRIFT 

Laskowski. 2002 

MRlD 45920801 

Comments 

--- 

Proposed label Mustang Max and 

Fuly lnsecticides 

Mustang Max and Futy Insecticides 

Mustang Max (0.050 Ib aiIA; 0.225 

Ib a.i./A for turf) 

Estimated from ~netadata tile. 

Mustang Max and Fury 

Mustang Max and Fury 

Represents the average bc value 

among four values ranging from 

20,800 to 328,000 mVg; the KQ~ 

model was utilized as per 

recommendation of the SAP. 

Represents the 90"' percentile of the 

upper confidence bound on the 

mean of two half-life values: 60.7. 

59.8 days; mean = 60.25 days; std. 

dev. = 0.45 days 

Mustang Max and Fury 

Mustang Max and Fu~y 

Mustang Max and Fury 

EFED guidance on input parameters 

for PR%M/EXAMS dated 2128102 

rurf is a granular application, 

peaches and apples are airblast 

applications, and the other crops are 

aerial applications. 

10X the actual solubility as per 

EFED guidance on input parameters 

for PRZMIEXAMS. At 20°C. 

Laskowski, 2002 Rev. Environ. 

Contam. Toxicol. 1 74:49- 170 

Represents the 90"' percentile of the 

upper contidence bound on the 
Table 7. Input Parameters 

Parameter (units) 

Anaerobic Aquatic Metabolism 

(days) 

tlydrolysis at pti 7 

Aqueous Photolysis @ pH 7 (days) 

Molecular Weight (glmole) 

Vapor Pressure (ton or mmHg) 

Henry's Law Constant 

(atrn-rn';mol) 

Environment 

Field Size 

Runoff 

PRZM Scenario 

Metfile Scenario 

CAM (C'hernical Application 

Method) 

FEXTRC, Foliar extraction 

PI.DKRT, Decay rate on foliage 

PI-VKRT. Volatilization rate from 

Ibllage 

IIPI'KF, llptake factor 

Table 8. Estimated environmental concentrations of zeta-cypermethrin (ppb) in the water column, 

benthic pore water, and benthic sediment. 

Utilized in PRZMIEXAMS 

Value(s) 

18.1 

Stable 

36.2 

416.3 

2.5 x 10.' 

3.4 10.' 

pond298.exv 

Pond 

overall 

CAgtapesOC.txt 

CiApeaches.txt 

IDNpotato-Ni~uigC,txt 

PAappleC. txt 

FLtu~ff .txt 

Gape - w93 193.dvf 

Peach - w038 13.dvf 

Potato - w24156.dvf 

Apple - w 14737.dvf 

Turf w 12834.dvf 

2 

0.5 

0 

0 

0 

Crop Scenario 

CA Grapes" 

GA Peaches' 

PA Apples " 

W~ite Benthic Pore Water 

C'oncenh-ations? 

Write Benthic Sediment File'? 

for Zeta-cypermethrin: 

Sources 

MRlD 42156602 

MRlD 42620501 

MRlD 42395701 

Laskowsky 2002 

Laskowsky 2002 

Laskowsky 2002 

--- 

--- 

--- 

-.. 

--- 

..- 

Media 

Water Column 

Benthrc Pore Wate~ 

Benthrc Sednnent 

Water Column 

Benth~c Pole Water 

Benth~c Sed~ment 

Wata Column 

Benthrc Pole Wate~ 

Benth~c Sed~ment 

Comments 

mean of two half-life values: 8.9 

and 9.8 days; rnean = 9.35 days; 

std. dev. = 0.45 days 

Represents the 90"' percentile of the 

upper confidence bound on the 

mean of two half-life values: 13.8 

and 16.5 days; mean = 15.15 days; 

std. dev. = 1.35 days 

--- 

--- 

Laskowski, 2002 Rev. Environ. 

Contarn. Toxicol. 174:49-170 

Laskowski, 2002 Rev. Environ. 

Contam. Toxicol. 174:49- 170 

Laskowski, 2002 Rev. Environ. 

Contam. Toxicol. 174:49- 1 70 

Default for pond scenario. as 

opposed to index reservoir. 

--- 

Selected to be representative of 

crops existent and new crops, taking 

into consideration geographical 

areas. 

As indicated by the shell (pe4). 

Linear foliar based on crop canopy 

EFED guidance on input parameters 

for PRZMIEXAMS dated 2/28/02 

EFED guidance on input parameters 

for PRZMIEXAMS dated 2/28/02 

EFED guidance on input parameters 

for PRZMIEXAMS dated 2/28/02 

EFED guidance on input parameters 

Yes 

Yes 

Peak 

0 0841 

0 00159 

9 04 

0 201 

0 00255 

14 4 

1 46 

0 0197 

112 

--- 

for PRZMIEXAMS dated 2/28/02 

Necessa~y to calculate the benthic 

risk quotients. 

21-day 

00150 

0 00137 

7 79 

0 0195 

0 00225 

12 8 

0 122 

0 0173 

80 3 

60-day 

0 0106 

0 00104 

5 89 

0 01 19 

0 00161 

9 15 

0 0641 

0 0142 

71 9 
At first glance at Table 8, it is noted that all three types of peak EECs followed the same trend. Apples 

had the highest peak EECs while turf had the lowest. The turf scenario had the lowest peak EEC despite 

the fact that it had the highest application rate, and only one application. It is possible that this scenario 

had a small runoff component and the level of drift, being 0, did not contribute towards the EEC, which 

remained small. 

Table 8. Estimated environmental concentrations of zeta-cypermethrin (ppb) in the water column, 

benthic pore water, and benthic sediment. 

Equilibrium Partitioning and Concentration in the SediinentlPore water 

As mentioned previously, zeta-cypermethrin, like other pyrethroids, is a lipophilic compound that can 

adsorb readily to particulate and sediment, thus possibly limiting its exposure to aquatic life in the water 

column but increasing toxic exposure in the benthos. Sediment can act as a reservoir for lipophilic 

persistent compounds. The sediinent and particulate likely adsorb a high percentage of zeta-cypermethrin 

TGAI, as indicated by its relatively high Koc. Therefore, coupled with zeta-cypermethrin's persistence in 

anaerobic environments, sediment bound zeta-cypermethrin TGAI could present a toxicity risk for benthic 

aquatic life and aquatic ecosystems in general. 

Crop Scenario 

FL Turf 

Therefore, in order to assess this potential for pesticide risk to aquatic benthic systems, the Environmental 

Fate and Effects Division (EFED) of the Office of Pesticides Program (OPP) has adopted the method used 

by the Office of Water that relies on equilibrium partitioning (EqP) of chemicals. The EqP theory is based 

on the hydrophobicity and concentrations of the chemical normalized to organic carbon (OC) in sediment 

(De Toro et nl. 1991) and holds that a nonionic chemical in sediment partitions between sediment organic 

carbon, interstitial (pore) water and benthic organisms. At equilibrium, if the concentration in any phase is 

known, then the concentration in the other phases can be predicted. A key component to this theory is the 

chemicals organic carbon coefficient (Koc), which is constant for every chemical and represents the ratio 

of the chemical concentration in water to the concentration in organic carbon. The document, " Technical 

Basis for the Derivation of Equilibrium Partitioning Sediment Guidelines (ESGs) for the Protection of 

Benthic Organisms: Nonionic Organics" (USEPA, 2000a), demonstrates that biological responses of 

benthic organisms to nonionic organic chemicals in sediments are different when the sediment 

concentrations are expressed on a dry weight basis, but similar when expressed on a ug chemicallg organic 

carbon basis (uglg,,). Similar responses were also observed across sediments when interstitial water 

concentrations were used to normalize biological availability. The Technical Basis Document hrther 

demonstrates that if the toxic effect concentration in water is known (e.g., LC5& the effect concentration in 

sediment on a uglg,, basis can be predicted by lnultiplying the effect concentration in water by the 

chemical KO,. 

Since, EFED uses a deterministic method for its screening level risk assessment, the calculation of risk 

quotient values (RQ) is important for assessing possible risk. The RQ values are calculated by taking the 

A chosen tepresentatlve scenalro fo~ splay appllcatrons of zeta-cypennethr~n to agt~cultural crops 

" A chosen ~epesenta~~ve scenalro fol g~anuldr appl~catrons of zeta-cypertneth~rn to restdenttal lawns. home per Itnetets, gardens, and 

~ndust~ lal non-agncultutal at eas. 

Media 

Watet Colu~nn 

Benth~c Pore Wate~ 

Benthrc 5edunent 

60-day 

000215 

0 000343 

1 94 

Peak 

0 0405 

0 000624 

3 53 

21-day 

0 00403 

0 000466 

2 64 
ratio of the estimated exposure concentrations (EEC) to the toxicity effect value (e.g., LC50, NOAEC). The 

EEC values are model generated (e.g., PRZMI EXAMS) and reflect peer evaluated and approved scenarios 

for assessing pesticide exposure to an aquatic environment. However, the PRZMI EXAMS output 

produces water column EEC values, as well as sediment and pore water EEC values. Therefore, to assess 

possible toxic pesticide exposure to aquatic organisms from sediments, EFED is using the PRZMI 

EXAMS to generate EECs for sediment and pore water model based on the principles of the equilibrium 

partitioning theory. By relying on sediment andlor pore water output values, EFED has two ways for 

calculating RQ values for sediments by using pore water exposure values and bulk sediment values. 

The calculations that rely on pore water can be calculated by dividing the PRZM/ EXAMS output value for 

pore water concentrations by the dissolved concentrations in the water column that caused toxicity in 

bioassays using zeta-cypermethrin TGAI (e.g., LC5o). 

EEC pore water ugL / LC50 ugL 

If sediment effects data are available (LC50 uglkg,,), RQ can be produced by using the PRZMI EXAMS 

sediment output value for sediment. 

EEC sediment uglugoc I LC50 ugikg,, 

In the case of zeta-cypennethrin, toxicity data were available in terms of bulk sediment, but not in terms of 

pore water concentrations. Subsequently, the equivalent concentrations in pore water were calculated 

based on the equilibrium partitioning theory and the definition of the Kc: 

K,, (Wkg OC) = Sediment Conc in OC (mg/kg OC) + Conc in pore water (mg/L). 

Additional details on the equilibrium partitioning theory can be found in Appendix G. 

b. Aquatic Exposure Monitoring (Field Data) 

Deposits of cvperinethrin on the surface of three streams adjacent to vineyards in France that were sprayed 

(via mistblowers) with cypermethrin insecticide were in the range of 0.04-0.45 mg/sq m(1); cypermethrin 

concns in subsurface water of the streams were in the range of 0.4-1.7 ugll soon after spraying, and 

decreasing to c0.1 ugll within a period of about 5 hours(1). [(I) Crossland NO et al; Aquatic Toxicol 2: 

253-70 (1 982)-as cited in HSDB] 

A search was conducted using the USGS National Water Quality Assessment (NAWQA) database of the 

Pesticides National Synthesis Project. It appears that zeta-cypermethrin was not targeted pesticides in this 

survey. However, a survey of cypermethrin performed in Alabama showed no detections in 13 ground 

water samples from five site, and 26 surface water samples from five sites (at the pglL level). In addition 

the Pesticides in Ground Water Database (1 971 -1 99 1) was searched, it reports 3 1 1 wells sampled for 

cyper~nethrin only from 1986 to 1988 in AR, MO, and TX. No detections were reported in any case. Due 

to the nature of the database, it is not known the limit of detection or the methodology used. 

3. Terrestrial Exposure Assessment 

Terrestrial wildlife exposure estimates are typically calculated for bird and mammals, emphasizing a 

dietary exposure route for uptake of pesticide active ingredients. These exposures are considered as 
surrogates for terrestrial-phase amphibians as well as reptiles. For exposure to terrestrial organisms, such 

as birds and small mammals, pesticide residues on food items are estimated, based on the assumption that 

organisms are exposed to a single pesticide residue in a given exposure scenario. Application methods of 

zeta-cypermethrin include ground or aerial spray application for agricultural uses, granular application for 

residential lawn, home perimeter, garden, and industrial non-agricultural uses, and subterranean, barrier, 

and perimeter treatments for termiticide uses. For this terrestrial exposure assessment, both spray 

applications and granular applications are considered, as described below. 

a. Terrestrial Animal Exposure Modeling- Spray Applications 

A primary concern with zeta-cypermethrin is that birds and mammals may be exposed shortly after 

application through oral or dietary exposure to vegetative plant material or insects when foraging in the 

treated fields for nesting material or food. Therefore, for zeta-cyperrnethrin spray applications, estimation 

of pesticide concentrations in wildlife food items focuses on quantifying possible dietary ingestion of 

residues on vegetative matter and insects. The EFED terrestrial exposure model T-REX (T-REX, Version 

1.2.3, dated August 8,2005) is used to estimate exposure and risks in conservative scenarios to avian 

species for four forage food types and to mammalian species for five forage food types for spray 

applications of zeta-cypennethrin. Input values for avian and mammalian toxicity as well as chemical 

application and foliar dissipation half-life data are required to run the model. The model provides 

estimates of exposure concentrations and risk quotients (RQs). Specifically, the model provides estiinates 

of concentrations (upper-bound and mean) of chemical residues on the surface of different types of foliage 

and insects that may be dietary sources of exposure to avian, mammalian, reptilian, or terrestrial-phase 

amphibian receptors. The surface residue concentration (ppm) is estimated by multiplying the application 

rate (pounds active ingredient per acre) by a value specific to each food item. These values (termed the 

Hoerger-Kenaga estimates) along with a more detailed discussion of the methodology implemented by TREX, are presented in Appendix C. 

For multiple applications, the EEC is detennined by adding the mass on the surface iinrnediately following 

the application to the mass of the chemical still present on the surfaces on the day of application 

(determined based on first order kinetics using the foliar half-life as the rate constant). For this risk 

assessment, terrestrial EECs as a result of spray applications of zeta-cypennethrin were estimated using the 

inaxiinuin proposed application rates, the maximum number of applications, and the minimum application 

interval for four representative crop uses: stone fruits, canola, non-grass animal feeds, and barley. These 

usage scenarios (application rate, application interval, and number of applications) were evaluated because 

they are expected to be representative of the exposure to wildlife resulting from the broad range of 

proposed uses of zeta-cypennethrin. Input values used for estimating avian and mammalian exposure risks 

to zeta-cypermethrin are summarized in Table 9. The inaximuin number of applications per year, the 

minilnuin application intervals, and the maximuin application rates for each crop scenario were derived 

from the product labels, whereas the foliar half-life of 1 1.1 days was based on data for cypermethrin in 

Willis and McDowe11 (1 987). 

The foliar half-life of 11.1 days represents the 90% upper confidence limit of the mean half-life for all 

crops that had half-life estimates based on total residues (internal plus dislodgeable residues). Data on all 

available crops (i.e., cotton and beans) were considered because T-REX is used to calculate terrestrial 

exposure concentration estimates on all plant surfaces following pesticide application, and not just 

concentration estiinates on a particular crop. However, half-lives based on dislodgeable residues alone 

were not considered for zeta-cypermethrin because the compound (based on cypermethrin's log 16, ) has a 

high log lq,, (6.54) and is expected to bind strongly to plants. Therefore, half-lives based on total residues 
(i.e., half-lives of 7.9 and 4.8 for cotton and beans, respectively) will likely provide more realistic 

estimates, whereas half-lives based on dislodgeable residues alone will likely underestimate exposure 

concentrations. 

By comparing estimated concentrations to acute and chronic toxicity reference values, acute and chronic 

RQs are calculated. The EECs on food items may be compared directly with dietary toxicity data or 

converted to an oral dose. The residue concentration can be converted to a daily oral dose based on the 

fraction of body weight consumed daily as estimated through allometric relationships; for both birds and 

mammals, three weight categories (or sizes) were considered. The screening-level risk assessment for zetacypern~ethrin uses upper-bound predicted residues as the measure of exposure. Summaries of the 

predicted residues of zeta-cypermethrin that may be expected to occur on selected avian or mammalian 

food items immediately following application for representative maximum use scenarios are presented in 

Table 10. 

Exposure and risks could be overestimated if the actual application rate, frequency of application, or 

number of applications are lower than the input parameters used for the conservative exposure scenarios 

that were modeled. On the other hand, terrestrial EECs could be an underestimation of actual exposure 

concentrations in the environment. Although the label stated that zeta-cypermethrin can be applied via 

foliar spray application up to a maximum of 6 times per season, for this risk assessment, EFED assumed 

that zeta-cypermethrin was applied at a maximum of 6 times per year. If there are conditions under which 

there is more than one growing season for a crop within a single year, exposure estimates and risk to 

terrestrial organisms could be significantly underestimated. Examples of crops that have multiple seasons 

where this may be a concern include leafy, brassica, and fruiting vegetables in CA, AZ, FL, GA, LA, NC, 

TX, and/or SC. 

Stone Fruits 

C'anola 

Non-grass Animal Feeds 

Barley 

"This half-life represents the 90% upper confidence limit of the mean half-life for all crops that had half-life estimates based on total residues 

(internal plus dislodgeable residues) in Willis and McDowe11 ( 1987). 

0.05 

0.05 

0.05 

11.1 

11.1 

11.1 

7 

7 

14 

4 

3 

5 
b. Terrestrial Animal Exposure Modeling-Granular Applications 

Stone Fruits 

Canola 

Non-grass Animal Feeds 

Barley 

There is potential for exposure of birds and mammals to granular zeta-cypermethrin used on residential 

lawns, home perimeters, gardens, and industrial non-agricultural areas by direct ingestion of granules. 

They also may be exposed by other routes, such as incidental ingestion of contaminated soil, dermal 

contact with treated granular surfaces and soil during activities in the treated areas, preening activities, and 

ingestion of drinking water contaminated with pesticide. It should be noted, however, that the primary 

route of exposure to zeta-cypermethrin granules will be via the oral route because it is not volatile and it is 

not expected to appreciably absorb through the skin. Therefore, ingestion of granules and consumption of 

terrestrial invertebrates that have bio-concentrated pesticide residues were considered as routes of exposure 

in this assessment. 

Although a bird's or mammal's habitat is not limited to a square foot, there is presumably a direct 

correlation between the concentration of a pesticide in the environment (mg/ft2) and the chance that an 

animal will be exposed to a concentration that could adversely affect its survival. Typically for ground 

application of granular formulations, acute exposure and risks are estimated with the conceptual approach 

using the ~~~~/ft' method given in the Tier 1 model T-REX (T-REX, Version 1.2.3, dated August 8, 

" EEC equivalent dose = tipper-bound Kenega value * (%UW consumed!100). %UW consumed = 1 14%, 65%, and 29% for small, medium, 

and large birds, rcspectively. 

Short grass 

Tall grass 

Broadleaflforage plants & s~nall insects 

F~uits/pods/seedsllatge insects 

Shott pass 

Tall grass 

Broadleaflforage plants & s~nall insects 

Fmitsipodslseedsilarge insects 

Sho~t grass 

Tall grass 

Broadleaflforage plants & sinall insects 

Fruitslpodslseedsilarge insects 

Shoit grass 

Tall grass 

Broadleaflforage plants 61 s~nall insects 

Ruitsipodslseeds!lat.ge insects 

3 1 

14 

18 

2 

28 

13 

16 

2 

25 

I I 

14 

2 

20 

9 

I I 

1 

I I 

5 

6 

I 

10 

4 

5 

1 

9 

4 

5 

1 

7 

3 

4 

I 
2005). Terrestrial EECs are calculated based on an estimation of loadings of pesticide per unit area 

(expressed in terms of mg a.i./ft2), assuming that 100% of the application was present on the surface of the 

soil. This approach compares the available mass of pesticide per square foot to the acute oral dose for 

toxicity (LD50 values adjusted for body weight and percent body weight consumed) to derive risk quotients 

(Further description of the mg/ft2 index is provided in Appendix C, U.S. EPA, 2004, and U.S. EPA, 

1992). Exposure and risk resulting from granular applications to turf were evaluated using this method and 

the input values provided in Table 11. The EECs generated by T-REX represent the application rate (lb 

a.i./A) expressed in terms of ing a.i./ft2. The EEC for the maximum zeta-cypermethrin granular application 

scenario was 2.34 mg a.i./ft2. 

- - - - - - -- -- - - - -- - - -- - - .- -- - -- - -- - - 

11. Input parameters used in T-REX (v1.2.3) to determine terrestrial acute EECs for the 

application of granular zeta-cypermethrin to turf. 

Maxiinuin 

application rate I 

Input Variable Parameter Value 

Maximuin number of 

applications per year 

Minimum application 

interval 

I Soil 1 Fo~~nulation type: granular 1 

Source 

Inputs for the 

LD$,J~~~ Method for 

Granular Applications to 

EFED has no standard methodology for assessing chronic risk to terrestrial organisms from granular 

applications. The chronic exposure estimation and risk characterization for terrestrial wildlife in this risk 

assessment considers granular routes of exposure including direct ingestion of soil invertebrates that have 

bioconcentrated zeta-cypermethrin residues of granules in soil. This estimation of earthworm concentration 

was calculated using a fugacity-based (equilibrium partitioning) approach based on the work of Trapp and 

McFarlane (1 995) and Mackay and Paterson (1981). Earthworms dwelling within the soil are exposed to 

contaminants in both soil pore water and via the ingestion of soil (Belfroid et al. 1994). Soil 

concentrations of zeta-cypennethrin were calculated based on a depth of 7.6 cm (three inches; a chemical 

concentration averaged over a 7.6-cm soil depth was used to reflect a concentration across the earthworm 

occupied area of soil), the use characterization for the application of granular zeta-cypermethrin to turf (a 

maximum one-time application of 0.225 lb a.i./A), and a I-acre terrestrial environment. The concentrations 

of zeta-cypennethrin in earthworms were calculated as a combination of uptake from soil pore water and 

gastrointestinal absorption from ingested soil: 

1 

NIA 

Application method: broadcast 

where: 

Product Label 

CSoils the concentration of chemical in bulk soil (note: a chemical concentration 

averaged over a 7.6 cm soil depth was used to reflect a concentration 

across the earthworm occupied area of soil) 

Z,,r,~l,,onl, isthe fugacity capacity of chemical in earthworms = 

(lipid)(&w)(~eart11won11)lH 

ZSoil is the fugacity capacity of chemical in soil = (Kd)(psoil)/H 

Zwater isthe fugacity capacity of chemical in water = 1/H 
CSOil is the concentration of chemical in soil water = Csoil/Kbw 

Kbw is the bulk soil-to-water partitioning coefficient = 

(~soil)(Kd)+0 +(~-0)(Kaw) 

K,, is the air-to-water partitioning coefficient = HIRT 

H = Henry's Constant specific to zeta-cypennethrin = 3.4E-07 

R = universal gas constant, 8.3 1 ~oules-dlmol-OK 

T = temperature OK, assumed to be 298 OK 

Kd = soil partitioning coefficient = 2834= 

(chemical K,,, )(0.02 assumed fraction of soil organic carbon) 

psOil = bulk density of soil, assumed to be 1.3 g/cm3 

0 = volumetric fraction of the soil, assumed to be 0.30 

E = volumetric total porosity of the soil, assumed to be 0.50 

lipid = fraction of lipid in organism = 0.01 (Cobb et al. 1995) 

k, = zeta-cypermethrin (based on cypermethrin's) octanol to water partitioning 

coefficient = 3467368.5 

Pean,lwonn = the density of the organism g/cm3, assumed to be 1 g/cin" 

Assuming the maximum application rate of zeta-cypermethrin of 0.225 lb a.i./acre to a bare, very low 

density soil (I .3 g/cm7) incorporated to 7.6-cm depth, the following soil concentrations can be calculated 

for a depth of 7.6 an: 

. = applicrrtior~ r-ute - 

- 

AR x CF, x CF, 

soil depth x soil density z x CF, x px0,, 

where, 

Coil = concentration in soil immediately following a single application (mglkg) 

AR = application rate (lb a.i./acre) 

z = soil depth (cm) 

pi = soil bulk density (g/cm7) 

CFI = conversion factor, 453582.4 mg = 1 lb 

CF2 = conversion factor, 1 acre = 40468730 cm' 

CF3 = conversion factor, 0.001 kg = 1 g 

Based on this soil concentration calculation of 0.26 mglkg, the concentration of zeta-cypermethrin in an 

earthworm based on the above earthworm fugacity model equation (using the maximum application rate) 

would be 4.8 mg a.i./kg (for detailed calculations, see Appendix D). 

Table 12 summarizes the model inputs and exposure estimates (i.e., earthworm concentrations in ppm) for 

insectivorous birds and mammals, based on a granular zeta-cypermethrin application rate of 0.225 lb 

a.i./A. 

Table 12. Model Input Parameters and Dietary Exposure Estimates for 

Avian and Mammalian Receptors 

Parameter I .I 

I C,,I,,,., (mg/kg @ 7 6 cm depth) 

Farthworln Concentratlun (~ng'kg) (C,,,, ,,,,,,,,) 

0 26 

4 8 
Chronic risks for birds and inammals that consume terrestrial invertebrates as the majority of their diet 

were estimated based on comparison of the concentration of zeta-cypermethrin in earthworm tissue 

(Cearthwonn) with chronic toxicity values for birds and mammals. In addition to dietary estimates, residue 

concentrations in terrestrial invertebrates were converted to daily oral doses for mammals based on the 

fraction of body weight consumed as estimated through mammalian allometric relationships, and were then 

compared with chronic oral toxicity values for mammals. A detailed description of the fugacity model and 

methodology used to estimate chronic exposure and risk for granular applications of zeta-cypermethrin are 

presented in greater detail in Appendix D. 

C. Ecological Effects Characterization 

In screening-level ecological risk assessments, the effects characterization describes the types of effects a 

pesticide can have on aquatic or terrestrial organisms. This characterization is based on registrantsubmitted studies that describe information regarding acute and chronic effects toxicity for various aquatic 

and terrestrial animals. Appendix E summarizes the results of the registrant-submitted toxicity studies 

used to characterize effects for this risk assessment. It should be noted that ecological toxicity data specific 

to zeta-cypermethrin is sparse. However, zeta-cypermethrin is a modified form of cypermethrin, and a 

comparison of their respective databases (although it is limited for zeta-cypennethrin) indicates that they 

have similar toxicity to non-target organisms. Therefore, the Agency has allowed use of the cypermethrin 

TGAI database to fulfill many registration requirements for zeta-cypermethrin and toxicity data for all 

cypennethrin products (alpha-, beta-, theta-, and zeta-cypermethrin) are being bridged for risk assessment 

purposes. 

Toxicity testing reported in this section does not represent all species of birds, mammals, or aquatic 

organisms. Only a few surrogate species for both freshwater fish and birds are used to represent all 

freshwater fish (2000+) and bird (680+) species in the United States. For mammals, acute studies are 

usually limited to the Norway rat or the house mouse. Estuarinelmarine testing is usually limited to a 

crustacean, a mollusk, and a fish. Also, testing for reptiles and amphibians are not required. The risk 

assessment assumes that avian and reptilian toxicities are similar. The same assumption is used for fish 
and amphibians. 

In general, categories of acute toxicity ranging from "practically nontoxic" to "very highly toxic" have 

been established for aquatic organisms (based on LC50 values), terrestrial mammals (based on LD50 

values), avian species (based on LCs0 values), and non-target insects (based on LDso values for honey bees) 

(U.S. EPA 2001). These categories are presented in Appendix E. 

1. Aquatic Effects Characterization 

The most sensitive acute and chronic toxicity reference values associated with zeta-cypermethrin (based on 

data for any of cypermethrin's four different products; alpha-, beta-, theta-, and zeta-cypermethrin) 

exposure to freshwater and estuarinelmarine species are sumlnarized in Table 13. All toxicity reference 

values used to assess the potential risks of zeta-cypermethrin exposure are obtained from studies using the 

technical grade ingredient, rather than from studies using metabolites or formulated products. A more 

detailed summary of the aquatic toxicity data available to characterize risks associated with zetacypermethrin applications is given in Appendix E. 

Results of acute toxicity studies indicate that zeta-cypermethrin can be classified as very highly toxic on an 

acute basis to freshwater fish, freshwater invertebrates, estuarinelmarine fish, estaurinelmarine 

invertebrates (shrimp and crustaceans), and benthic organisms. In addition, zeta-cypennethrin can be 

categorized as highly toxic to oysters. Acute toxicity studies on the cypermethrin degradate 3- 

phenoxybenzoic acid in freshwater fish and invertebrates show that the degradate is much less toxic than 

cypermethrin TGAI. 

The lowest acute LCSo values reported for freshwater fish and estuarinelrnarine fish range from 0.39 pg 

a.i./L in rainbow trout to 0.95 pg a.i./L in sheepshead minnow. These results suggest that freshwater and 

estuarinelmarine fish should have a similar susceptibility to zeta-cypermethrin toxicity. For freshwater and 

estuarinelmarine invertebrates, the lowest acute LCjo values range from 0.0036 pg a.i./L in amphipods to 

0.00475 pg a.i.1L in mysids, approximately 100 times lower than the LCjo values reported for aquatic fish, 

indicating that aquatic invertebrates are likely to be more sensitive to zeta-cypermethrin toxicity than 

aquatic vertebrates. Thus, invertebrates are expected to be at a greatest risk for acute effects (lethality). 

In addition to lethality data, several acute toxicity studies provide information regarding sub-lethal effects 

of cypermethrin. For fish, sub-lethal effects include rapid and erratic swimming, partiallcomnplete loss of 

equilibrium, jaw spasms, gulping respiration, lethargy, and darkened pigmentation. In aquatic 

invertebrates, sub-lethal effects include lethargy, erratic swimming behavior, loss of equilibrium, surfacing, 

immobilization, and decreased movement in response to stimulation. In most studies, the acute NOAEC 

values for sub-lethal effects are approximately 2- to 3-fold lower than the corresponding LCso values, 

indicating that sub-lethal effects can occur at exposure levels below the concentrations that cause lethality. 

Calculations for sediment and pore water exposure to benthic organisms followed the equilibrium 

partitioning model as noted previously and in Appendix G. The LCjo values for benthic organisms based 

on exposure to cypermethrin in bulk sediment and pore water were 3.6 pg a.i./kg sediment and 0.00257 pg 

a.i./L, respectively. 

Chronic toxicity studies with cypermethrin are available for freshwater fish and estuarinelrnarine 

invertebrates. Results of these studies suggest that zeta-cypermethrin can be expected to adversely affect 

neonate survival of freshwater fish and reproduction and growth of estuarinelrnarine invertebrates. No data 
are currently available on the chronic effects of zeta-cypermethrin or any other cypermethrin product to 

benthic organisms, estuarinelmarine fish, or freshwater invertebrates. However, estimates of chronic 

toxicity to benthic organisins (NOAECs = 0.59 ug ailkg sediment and 0.0042 pg a.i./L pore water), 

estuarinelinarine fish (NOAEC = 0.34 pg a.i./L), and freshwater invertebrates (NOAEC = 0.00059 pg 

a.i./L) were derived to estimate risk using the inethodology described below. There are no data available on 

the effects of zeta-cypermethrin to aquatic vascular or non-vascular plants. 
Table 13. Zeta-cyperrnethrin toxicity reference values (TRVs) for aquatic organisms. 

Toxicity Reference Effects Reference 

Value (pg a.i.L) 

Freshwater Fish 

Exposure 

Duration 

Exposure 

Scenario Species 

MRlD 44546027 

MRlD 89039 

Mol b~d~ty 

G~owth and ~no~b~dity 

LCqI,=O 39yga11L 

NOAEC=O 1411gallL 

LOAFC = 0 33 pg ad1 

Acute 

C h~on~c 

Freshwater 111,ertebrates 

Ra~nbow t~out 

(OIILOI II~IIC~IIS 

n1oX1rs) 

I-athcad lnlnnow 

(Plme/~/lole~ 

promeln Y) 

MRlD 44423501 

96 houls 

30 days 

LC5,,=00036pga~IL Motb~d~ty 

Ch~on~c 

Acute 

No adequate data suhmltted, to assess chion~c r~sk to freshwater lnverteblates, a sunogate NOAEC value of 0 00059 pg 

a I 'L was da wed based on the acute-to-ch~on~c ratlo method uslng acute and chron~c data for estua~ ~nelmar~ne 

~nve~tebrates " 

Atnph~pod 

(Hvalella arteca) 

96 hou~ s 

Bentl~ic Organisn~s 

Acute Mo~b~d~ty and Glowth MRlD 44074406 

C ht on~c No chron~c data subm~tted. to assess ch~on~c r~sk to benth~c organisms. suliogate chronlc NOAEC tox~clty values fol 

sedument of 0 59 pg a I /kg sed~ment' and to1 pole watel of 0 00042 pg a I /Ld wwne de~~ved based on the acute-toch~on~c latlo method uslng acute and ch~on~c data fo~ estua~~neltnar~ne ~vertebtates 

Amph~pod 

(Hvolellir crztetcr) 

10 dd)s 

Estuarine/Marioe Fish 

Exneinnentdl sed~ment value 

LC 511 = 3 6 11g a I /kg sednnent 

I1e1red note water value1' 

LC%(, = 0 00257 pg a I iL 

Acute 

C htonlc 

Shecp<head 

lnlnnow 

(Cvp1 lrlldoll 

I ur rester) 

EstuarineIMarine Invertebrates 

No datd subm~tted, to assess ch~on~c 11sk to estua~~ne~ina~tne fish. a suliogate NOAEC value of 0 34 pg a I /L fol 

sheepshead rnlnnow was de~~ved based on the acute-to-chtonlc latlo method uslng acute and chion~c data fo~ fieshwate~ 

fish ' 

96 houls 

Acute 

Ch~on~c 

LC ,,, = 0 95 pg a I IL 

Mys~d sh~~mp 

(Mi srdop~rs 

Bahra) 

Mysid shninp 

(MI rrdoprrs 

Rolrra) 

Morb~d~ty 

96 bouts 

28 daysf 

MRlD 90075 

LC;(, = 0 00475 pg a I IL 

NOAEC = 0 00078 1 pg a I IL 

I OAR = 0 00197 pg a I 11 

NOAEC = 0 00 IS pg a I IL 

LOAEC = 0 0028 11g a I IL 

Molhld~ty 

We~ght of females 

 educed 

Numbel of offsp~ing 

Ace No 070562 

MRlD 42725301 
The acute toxicity of technical grade cypermethrin to freshwater fish was evaluated in several species, with 

96-hour LCs0 values ranging from 0.39 pg a.i./L in rainbow trout (MRID 44546027) to 4.5 pg a.i./L in 

bluegill sunfish (MRID 44546030). Details of these studies are provided in Appendix E. Based on 

these results, zeta-cypermethrin can be categorized as very highly toxic to freshwater fish on an acute basis. 

Taking the most conservative approach, the lowest 96-hour LCso of 0.39 pg a.i./L in rainbow trout is used 

to evaluate acute toxic exposure of freshwater fish to zeta-cypermethrin. 

Acute toxicity studies in freshwater fish were also submitted for the cypermethrin degradate 3- 

phenoxybenzoic acid in rainbow trout (MRID 89037) and bluegill sunfish (MRID 89038). Results yield 

96-hour LCSo values of 13.3 and 36.3 mg degradatelL in rainbow trout and bluegill sunfish, respectively 

(details provided in Appendix E). Based on these 96-hour LC50 values, 3-phenoxy benzoic acid is 

categorized as slightly toxic to freshwater fish on an acute basis and is much less toxic than cypermethrin 

TGAI to freshwater fish. 

No acute toxicity studies with zeta-cypermethrin formulations and freshwater fish were submitted. 

Freshwater Invertebrates 

Acute toxicity studies of technical grade cypermethrin to freshwater invertebrates yield toxicity values 

ranging from a 96-hour LC50 value of 0.0036 pg a.i./L in Hynlella (MRID 44423501) to a 24-hour LCjo 

value of >5.0 pg a.i./L in Notonectn, Cl~ironomus tl~ummi, and Lymneaperegrn (Acc. No. 070562). Study 
details are provided in Appendix E. Based on these results, zeta-cypermethrin can be categorized as very 

highly toxic on an acute basis. Taking the most conservative approach, the lowest LCso value reported (96- 

hour LC5o value of 0.0036 yg a.i./L) is used to evaluate acute toxic exposure of freshwater invertebrates to 

zeta-cyperinethrin. 

Acute toxicity tests in freshwater invertebrates using the cyperinethrin degradate 3-phenoxybenzoic acid to 

daphnids were also submitted. Results yield 48-hour EC50 values of 89.0 mg degradatell (MRID 152739) 

and 1 1 1 mg degradatell (Acc. No. 070562). Based on these acute toxicity values, 3-phenoxy benzoic acid 

is categorized as practically non-toxic to slightly toxic to freshwater invertebrates on an acute basis. Thus, 

the 3-phenoxy benzoic acid degradate is much less toxic than cyperinethrin TGAI to freshwater 

invertebrates. 

No acute toxicity studies with zeta-cypermethrin formulations and freshwater invertebrates were submitted. 

EstuarineIMarine Fish 

The acute toxicity of technical grade cypermethrin to estuarinelmarine fish was evaluated in sheepshead 

minnow and Atlantic salmon, with 96-hour values of 0.95 pg a.i./L (MRID 90075) and 3.42 pg a.i./L 

(MRID 41 96821 2) respectively, indicating that zeta-cypermethrin can be classified as very highly toxic to 

estuarinelmarine fish on an acute basis. Study details are provided in Appendix E. Taking the most 

conservative approach, the lowest 96-hour LCso value of 0.95 pg a.i.1L for sheepshead minnow is used to 

evaluate acute toxic exposure of estuarinelrnarine fish to zeta-cypermethrin. No acute toxicity studies with 

zeta-cypermethrin formulations or degradates and estuarinelmarine fish were submitted. 

EstuarineIMarine Invertebrates 

Acute toxicity tests with estuarinelrnarine invertebrates using the cypermethrin TGAI were conducted with 

shrimp, inollusks, and crustaceans. Study details are provided in Appendix E. Toxicity values (ECSo and 

LCS0) reported for shrimp range from the 96-hour LCso value of 0.00475 yg a.i.1L (Acc. No. 070562) to 

the 96-hour LCso value of 0.01 pg a.i./L (MRID 41068003). Similar results were observed in lobster (96- 

hour LC50 = 0.04 pg a.i./L; MRID 41068003) and fiddler crab (96-hour LCso = 0.197 pg a.i./L; MRID 

89045). Based on these results, zeta-cypermethrin can be categorized as very highly toxic to 

estuarinelrnarine shrimp and crustaceans. Results of acute toxicity tests with cypermethrin TGAI and 

mollusks demonstrate that zeta-cypermethrin can be classified as moderately to highly toxic to oysters, 

with a 96-hour ECso value of 0.37 mg a.i.iL in Eastern oyster (MRID 89049) and a 48-hour LCSo value of 

>2.27 mg a.i./L in Pacific oyster (Acc. No. 070562). Results of these studies indicate that it can be 

expected that mollusks are less susceptible than shrimp and crustaceans to zeta-cypermethrin toxicity on an 

acute basis. Taking the most conservative approach, the 96-hour LC50 value of 0.00475 pg a.i./L for lnysid 

shrimp will be used to estimate acute risk to estuarinelmarine invertebrates exposed to zeta-cypermethrin. 

No acute toxicity studies with zeta-cypermethrin fornlulations or degradates and estuarinelmarine 

invertebrates were submitted. 

Benthic Organisms 

Several studies on the toxicity of cypennethrin TGAI to benthic organisms have been submitted; details are 

summarized in Appendix E. However, studies were conducted using two types of experimental protocols, 

exposure in a water-only system and exposure in a water-sediment system. In the water system studies, 

organisms were exposed to cypermethrin in overlying (surface) water; no sediment was present in the test 

chamber. Because the exposure scenario under which the endpoints were derived in the water-only studies 

were not considered appropriatelrepresentative of that group of organisms, only those studies that exposed 

sediment dwellers to cypermethrin in a water-sediment svstern were considered for determining risk to 
benthic organisms. 

The only two studies that met these criteria were MRID 44074402 and MRID 44074406; MRID 44074402 

was conducted with midge while MRID 44074406 was conducted with amphipods. Both studies were 

conducted using the same protocol and sediments from three sources (Florissant, Mississippi, and Duluth). 

All toxicity values for these studies are expressed in terms of the concentration of cypermethrin in 

sediment (pg a.i./kg) on Day 0. Results yield 10-day LC5() values ranging from 3.6 pg a.i./kg sediment 

(Florrisant sediment) in amphipods to 67 pg a.i./kg sediment in midge (Mississippi sediment). In general, 

toxicity decreased (as reflected by higher LCj0 values), with increasing organic carbon content of the 

sediment. Taking the most conservative approach, the lowest 10-day LCso value of 3.6 pg a.i./kg sediment 

in amphipods will be used to estimate the acute risk of exposure of benthic organisms to zetacypermethrin. 

Although compounds bound to the sediment present potential toxicity concerns, those residues that have 

reached equilibrium in the pore water are considered a greater source of toxic risk to benthic invertebrates 

(Di Toro et nl., 1991). In order to assess the risk associated with acute exposure of benthic organisms to 

zeta-cypermethrin in pore water, the equivalent toxicity value in pore water is derived using the lowest 10- 

day LCso value of 3.6 pg a.i./kg sediment in amphipods as follows. The LCs0 value in whole sediment [3.6 

pg a.i./kg sediment] is divided by the proportion of organic carbon (OC) in the sediment [0.0099 kg OC/kg 

whole sediinent]. Thus, the LCs0 value in units of OC is 364 pg a.i./kg OC [3.6 pg a.i./kg sediment + 

0.0099 kg OC/kg sediment]. The equivalent concentration in pore water is based on the equilibrium 

partitioning theory and the definition of the kc: 

KO, (Llkg OC) = Sediment Conc in OC (mglkg OC) -+ Conc in pore water (mg/L). 

For cypermethrin, the Kc is taken as 141,700 [Llkg OC] (MRID 42129003). Thus, the calculated 

concentration in pore water corresponding to the LCSo value of 364 pg a.i./kg OC is 0.00257 pg a.i./L [364 

1-18 a.i./kg OC + 141,700 L/kg OC]. To assess the risk associated with acute exposure of benthic organisms 

to zeta-cypermethrin in pore water, the derived LCso value of 0.00257 pg a.i./L is used. 

It should be noted that for the above two sediment toxicity studies, cypermethrin was applied to watersediinent systems and allowed to settle for only 2 days, after which organisms were introduced to the 

water-sediment systems, and toxicity was assessed after a 10-day exposure period. Therefore, these studies 

present a degree of uncertainty because of the lack of equilibration of spiked sediments with the pore 

water; measurement of cypennethrin in sediment and surface water on Days 0 and 10 of exposure indicates 

that the water-sediment system was not at equilibrium. Since residues that have reached equilibrium in the 

pore water are considered a greater source of toxic risk to benthic invertebrates (Di Toro et nl., 1991), the 

studies presented in this assessment may underestimate sediment toxicity and equilibration should have 

occurred for at least one month prior to testing. Although the registrant has conducted new sediment 

studies in order to address this uncertainty, the studies are currently in review and have not been included 

in this risk assessment. 

No tests on the toxicity of zeta-cypermethrin degradates to freshwater benthic organisms were submitted. 

ii. Chronic Effects 

Freshwater Fish 

An early life-stage study in fathead minnow was submitted by the registrant to establish the chronic 
toxicity of cypennethrin to freshwater fish (MRID 89039); data are summarized in Appendix E. Results 

of this 30-day exposure study show that survival was significantly reduced compared to controls at 0.33 pg 

a.i./L, yielding a 30-day NOAEC value for survival of 0.14 pg a.i./L. No treatment-related effects were 

observed for hatchability or growth. The NOAEC value for survival of 0.14 pg a.i./L will be used to assess 

the risk of chronic exposure of freshwater fish to zeta-cypermethrin. No chronic toxicity studies with zetacypermethrin degradates and freshwater fish were submitted. 

Freshwater Invertebrates 

No valid chronic toxicity studies with zeta-cypermethrin and freshwater invertebrates were submitted. 

However, a chronic NOAEC was estimated for freshwater invertebrates based on the acute-to-chronic ratio 

method, determined by the following mathelllatical relationship: 

Estuarinelmarine invertebrate LC5() (0.00475 pg a.i.1L) I Estuarinelmarine invertebrate 

NOAEC (0.000781 pg a.i.1L) = Freshwater invertebrate LCso (0.0036 pg a.i./L)/ X 

(estimated value for Freshwater invertebrate NOAEC), where X = 0.00059 pg a.i./L. 

To assess the risk to freshwater invertebrates as a result of chronic exposure to zeta-cypermethrin, the 

estimated NOAEC for freshwater invertebrates of 0.00059 pg a.i./L is used. No chronic toxicity studies 

with zeta-cypermethrin degradates and freshwater invertebrates were submitted. 

EstuarineIMarine Fish 

No valid chronic toxicity studies with zeta-cypennethrin and estuarinelmarine fish were submitted. 

However, a chronic NOAEC was estimated for estuarinelmarine fish based on the acute-to-chronic ratio 

method, determined by the following mathematical relationship: 

Freshwater fish LC5,] (0.39 pg a.i./L) I Freshwater fish NOAEC (0.14 pg a.i./L) = 

EstuarinelMarine fish LCso (0.95 pg a.i.1L)l X (estimated value for EstuarineIMarine fish 

NOAEC), where X = 0.34 pg a.i./L. 

To assess the risk to estuarinelmarine fish as a result of chronic exposure to zeta-cypermethrin, the 

estimated NOAEC for estuarinelmarine invertebrates of 0.34 pg a.i.iL is used. No chronic toxicity studies 

with zeta-cypermethrin degradates and estuarinelmarine fish were submitted. 

Estuarinehlarine Invertebrates 

Three studies involving life-cycle tests in mysid shrimp were submitted by the registrant to establish the 

chronic toxicity of cypermethrin to estuarinelmarine invertebrates; data are summarized in Appendix E. 

The NOAEC values reported in these studies range from 0.78 1 ng a.i./L for effects on first generation 

mortality, male length and weight and female weight (MRID 42725301), to 1.5 ng a.i./L for number of 

offspring (Acc. No. 070562) and survival and reproduction (MRID 44546035). Taking the most 

conservative approach, the lowest NOAEC value of 0.781 ng a.i.1L will be used to assess the risk of 

chronic exposure of estuarinelmarine fish to zeta-cypennethrin. No chronic toxicity studies with zetacypermethrin degradates and estuarinelmarine invertebrates were submitted. 

Benthic Orrranisms 

Although the registrant has conducted chronic sediment studies with cypermethrin, the studies are 

currently in review and have not been included in this risk assessment. However, chronic NOAECs based 

on sediment and pore water concentrations were estimated for benthic organisms based on the acute-tochronic ratio method. The chronic NOAEC estimated for benthic organisms in terms of pg a.i./kg 
sediment was determined by the following mathematical relationship: 

Estuarinelmarine invertebrate LCs0 (0.00475 pg a.i.1L) I Estuarinelmarine invertebrate 

NOAEC (0.000781 pg a.i./L) = Benthic LC5o in sediment 3.6 yg a.i.1kg sediment 1 X 

(estimated benthic NOAEC value in sediment), where X = 0.59 pg a.i./kg sediment. 

The chronic NOAEC estimated for benthic organisms in units of yg a.i./kg pore water is based on the 

acute-to-chronic ratio method, determined by the following mathematical relationship: 

Estuarinelmarine invertebrate LCso (0.00475 pg a.i.1L) 1 Estuarinelmarine invertebrate 

NOAEC (0.000781 pg a.i.1L) = Benthic LCso in pore water (0.00257 pg a.i./L 1 X 

(estimated benthic NOAEC value in pore water ), where X = 0.00042 yg a.i.1L. 

To assess the risk to benthic organisms as a result of chronic exposure to zeta-cypermethrin, the estimated 

NOAEC values of 0.59 yg a.i.1kg sediment and 0.00042 yg a.i.1L pore water are used. No chronic toxicity 

studies with zeta-cypermethrin degradates and benthic organisms were submitted. 

iii. Sub-lethal Effects 

Freshwater Fish 

In addition to lethality endpoints, sub-lethal effects of acute cypermethrin (TGAI) exposure were assessed 

in studies in rainbow trout and bluegill sunfish. Study details are provided in Appendix E. The sub-lethal 

signs of toxicity include rapid and erratic swimming, partiallcomplete loss of equilibrium, jaw spasms, 

gulping respiration, lethargy, and darkened pigmentation. The acute NOAEC values for sub-lethal effects 

ranged from 0.1 1 pg a.i./L in rainbow trout (MRID 44546027) to 2.1 pg a.i./L in bluegill sunfish (MRID 

44546030). 

Results of a chronic toxicity study in fathead minnow report that no significant treatment-related effects on 

hatchability or growth were observed during a 30-day exposure to technical grade cypermethrin (MRID 

89039). Thus, no sub-lethal effects were observed at concentrations up to 0.33 yg a.i./L, the highest dose 

tested. 

Freshwater Invertebrates 

The sub-lethal effects of acute cypermethrin (TGAI) exposure were assessed in studies in waterflea. Study 

details are provided in Appendix E. The sub-lethal signs of toxicity include immobilization and decreased 

movement in response to stimulation. Acute NOAEC values for sub-lethal effects range from 0.085 yg 

a.i./L (MRID 44546032) to 0.14 yg a.i.1L (MRID 44546031). 

EstuarineIMarine Fish 

Sub-lethal effects of acute cypermethrin exposure in estuarinelmarine fish (loss of equilibrium and 

lethargy) were reported in two studies of sheepshead minnow (Appendix E). Acute NOAEC values for 

sub-lethal effects ranged from 0.84 yg a.i.1L (MRID 44546034) to 1.4 pg a.i./L (MRID 44546033) and are 

approximately 2- to 3-fold lower than the corresponding LCSo values of 2.7 and 2.4 pg a.i./L, respectively. 

EstuarineIMarine Invertebrates 

Sub-lethal effects (lethargy, erratic swimming behavior, loss of equilibrium, and surfacing) of 

cypermethrin TGAI in estuarinelmarine invertebrates were reported in two studies of mysid shrimp 

(Appendix E). Acute NOAEC values for sub-lethal effects range from 1.7 ng a.i.1L (MRID 4456 12 10) to 
2.3 ng a.i./L (MRID 44561209) and are approximately 2- to 3-fold lower than the corresponding LC50 

values of 5.5 and 5.9 ng a.i./L, respectively. 

Results of chronic toxicity studies in mysid shrimp show that exposure to technical grade cypermethrin had 

adverse effects on reproductive and growth parameters; study details are provided in Appendix E. For 

decreased number of young, a chronic NOAEC value of 1.5 ng a.i./L was reported in two studies (Acc. No. 

070562, MRID 44546035). For decreased growth and length, the chronic NOAEC value reported is 0.781 

ng a.i./L (MRID 42725301). 

Benthic Organisms 

Acute toxicity tests using the water-sediment system (Appendix E) report decreased growth (length and 

dry weight) in both ainphipod (MRID 44074406) and midge (MRID 44074402). Acute NOAEC values 

range from <1.8 yg a.i./kg sediment in amphipod (Florrisant sediment) and 25 pg a.i./kg sediment in 

midge (Mississippi sediment). Acute toxicity studies in benthic organisms using the water-only system did 

not specifically report sub-lethal effects resulting from cypennethrin exposure. 

iv . Field Studies 

No field studies on the effects of zeta-cypermethrin on aquatic organisms were submitted. 

b. Plants Inhabiting Aquatic Areas 

No data were available to evaluate the risk of zeta-cypermethrin exposure to aquatic plants; however, 

EFED is not concerned because zeta-cypemethrin's neural toxic mode of action is not expected to induce 

phytotoxic effects. In addition, based on the lack of studies demonstrating adverse effects of zetacypennethrin or any other pyrethroid to plants, and the fact that no incident reports have reliably linked 

zeta-cypermethrin or any other compound in the synthetic pyrethroid class of chemicals to phytotoxic 

effects despite being applied on or near agricultural plants, it appears unlikely that zeta-cypermethrin poses 

a phytotoxic concern. Therefore, Tier I aquatic plant growth studies with algae (Guideline 122-2) and 

duckweed (Guideline 123-2) are in reserve and are not being requested at this time. 

2. Terrestrial Effects Characterization 

The most sensitive acute and chronic toxicity reference values associated with zeta-cypermethrin (based on 

data for any of cypermethrin's four different products; alpha-, beta-, theta-, and zeta-cypermethrin) 

exposure to mammals and birds are summarized in Table 14. All toxicity reference values used to assess 

the potential risks of zeta-cypermethrin exposure are obtained from studies using the technical grade 

ingredient, rather than from studies using metabolites or formulated products. A more detailed sulnmary of 

the terrestrial toxicity data available to characterize risks associated with zeta-cypermethrin applications is 

given in Appendix E. Based on the results of acute oral and acute dietary avian toxicity studies with 

cypennethrin, zeta-cypermethrin can be categorized as practically non-toxic and slightly toxic, 

respectively. In mammals, results of acute exposure studies indicate that zeta-cypermethrin is moderately 

toxic. Results of available toxicity studies with cypennethrin indicate that zeta-cypermethrin can be 

classified as highly toxic to honey bees and very toxic to earthworms on an acute contact basis. Thus, 

honey bees and non-target insects are expected to be the species at risk for acute effects (lethality). 

Although there is a concern for chronic risk to mammals based on parental toxicity and toxicity to 

offspring (decreased body weight and body weight gain) in the available rat reproduction studies, 
cypermethrin exposure does not appear to induce adverse chronic effects in birds and zeta-cypermethrin is 

not expected to pose a risk to this taxonomic group. 

Currently, there are no data available regarding the effects of zeta-cypennethrin degradates to any 

terrestrial organism or the effects of zeta-cypermethrin to terrestrial plants. 

a. Terrestrial Animals 

reproduction study offspring) = 100 ppm ( 5 mg/kg/day) 

I,OAEC = (toxicity to parents and 

offspring) = 500 ppm (25 ing/kg/day) 

Birds 

1. Acute Effects 

Birds 

Acute toxicity studies on technical grade cypennethrin have been conducted with bobwhite quail and 

MRID 9007 1 

MRlD 44546024 

MRlD 90073 and MRlD 

90074 a 

LCsl, >2,634 lng a.i.ikg diet 

LDc1, >2,000 mg a.i./kg body wt 

NOAEC = 50 ppm 

LOAEC > 50 ppln 

5-day dieta~y 

Single oral dose 

Reproduction study 

Acute 

Acute 

Chronic 

Non-Target Terrestrial Invertebrates 

Mallard duck 

(Atlas 

plo~r.l~v~tchos) 

Bobwhite quail 

(Co1i11r1.s 

virginionus) 

Mallard duck and 

Bobwhite 

quail(Anos 

pla~~~rl~vnclios 

and Colin~ts 

~,ii.ginion~rs) 

Acc. No. 260647 

Acc. No. 260647 

Roberts and Dorough 1984 

LD5,, = 0.023 pg a.i./bee 

LDq, = 0.172 pg a.i./bee 

L('sI, = 26.09~1glcni~ 

48-Hour acute contact 

toxicity test 

48-Hour acute oral 

toxicity test 

48-Hour acute contact 

toxicity test 

Acute 

Acute 

Acute 

Honey bee 

, yo 

Honey bee 

(Apis n~ellifir.cr) 

Earthwor~n 

(Eisenio ,foetido) 
mallard ducks; results are summarized in Appendix E. Results of the acute oral toxicity studies in mallard 

ducks (Acc. No. 241598) and bobwhite quail (MRID 44546024) yield LDSo values for cypermethrin of 

>9,520 and >2,000 mg a.i./kg body weight, respectively, indicating that zeta cypermethrin can be classified 

as practically non-toxic to birds on an acute oral basis. Results of acute dietary toxicity studies in mallard 

ducks and bobwhite quail yield LCSo values for cypermethrin ranging from>2,634 mg a.i./kg diet in 

mallard ducks (MRID 9007 1) to >5,290 mg a.i./kg diet in mallard ducks (MRID 44546025) and bobwhite 

quail (MRID 44546026), indicating that zeta-cypermethrin can be categorized as practically non-toxic to 

slightly toxic on an acute dietary basis. To assess acute risk of zeta-cypennethrin to birds, the lowest acute 

oral LD50 value of >2,000 mg a.i./kg body weight and the lowest acute dietary LCso value of >2,634 mg 

a.i./kg diet are used. 

No acute toxicity studies with zeta-cypermethrin formulations or degradates and avian species were 

submitted. 

Mammals 

Results of an acute oral toxicity study in rats yield LDSO values for cypermethrin TGAI of 247 mg a.i./kg 

body wt in lnales and 309 mg a.i./kg body weight in females (MRID 00056800). Results of an acute oral 

toxicity study in rats yield LDso values for zeta-cypermethrin TGAI of 134 mg a.i./kg body wt in males and 

86 mg a.i./kg body weight in females (MRID 417761 15). Study details are provided in Appendix E. 

Based on these results, zeta-cypennethrin TGAI is classified as moderately toxic to mammals. The lowest 

oral LDSo of 86 mg a.i./kg body weight is used to assess acute risk in mammals. 

No acute toxicity studies with zeta-cypermethrin formulations or degradates and mammalian species were 

submitted. 

Non-Target Terrestrial Invertebrates 

Although EFED does not assess risks to non-target terrestrial invertebrates, results of an acute contact 

study in honey bees using technical grade cypermethrin yield a 48-hour LDSO value of 0.023 ug a.i./bee, 

categorizing cypermethrin and zeta-cypennethrin as highly toxic to honey bees (Acc. No. 260647). 

Results are summarized in Appendix E. In an oral exposure study in honey bees, a LDS0 value of 0.172 

ug a.i./bee was reported (Acc. No. 260647). 

An acute contact study in earthworms was identified from an open literature study (Roberts and Dorough 

1984; Appendix E). Results of this study yield a 48-hour contact LCSo value of 26.09 ug a.i./cm2 for 

cypermethrin applied to filter paper, categorizing cypennethrin and zeta-cypermethrin as very toxic to 

earthworms. 

No acute toxicity studies with zeta-cypermethrin degradates and terrestrial invertebrates were submitted. 

ii. Chronic Effects 

Birds 

One-generation reproductive studies were submitted for mallard ducks (MRID 90073) and bobwhite quail 

(MRID 90074). Results of both studies show no treatment-related effects on adults, reproductive 

parameters, or offspring, as a result of cypermethrin exposure at dietary concentrations up to 50 mg a.i./kg 

diet (the highest concentration tested). To assess chronic risk to avian species, the lowest NOAEC value of 

50 mg a.i./kg diet is used. Details are summarized in Appendix E. 
No chronic toxicity studies with zeta-cypermethrin formulations or degradates and avian species were 

submitted. 

Mammals 

Results of 2- and 3-generation reproduction studies in rats show that exposure to technical grade 

cypermethrin (MRIDs 001 12912,42068504,9202704, and 00090040) and zeta-cypermethrin (MRID 

41968204) results in decreased body weight and decreased body weight gain in both adults and offspring, 

with NOAECs ranging from 100 mg a.i.1kg diet (equivalent to 5 mg a.i./kg body weight/day) (MRID 

00090040) to 150 mg a.i./kg diet (equivalent to 7.5 mg a.i./kg body weightlday) (MRIDs 001 12912, 

42068504, 9202704). No other significant treatment-related effects on reproductive parameters were 

reported in these studies. To assess chronic risk to mammalian species, the lowest NOAEC value of 100 

mg a.i.1kg diet (equivalent to 5 mg a.i./kg body weightlday) is used. Details are summarized in Appendix 

E. 

No chronic toxicity studies with zeta-cypermethrin formulations or degradates and mammalian species 

were submitted. 

Non-Target Terrestrial Invertebrates 

No chronic toxicity studies with the TGAI, formulation, or degradates of any cypermethrin product (alpha-, 

beta-, theta-, and zeta-cypermethrin) and non-target terrestrial invertebrates were available for this 

assessment. 

iii. Sub-lethal Effects 

Birds 

Acute toxicity studies in birds report aversion to feed containing cypermethrin at concentrations greater 

than approximately 2,000 mg a.i./kg diet (MRIDs 44546025,44546026, 90072, and 90071). In addition, 

reductions in body weight, which may have been caused by aversion to feed, were reported, with NOAEC 

values ranging from 1290 to 2550 mg a.i.1kg diet (MRDs 44546025 and 44546026). No other gross 

pathological findings, clinical signs of toxicity, or adverse effects on reproductive parameters or offspring 

were reported in the submitted acute and chronic toxicity studies in avian species. 

Mammals 

Exposure of rats to a single dose of cypennethrin produced clinical signs of neurotoxicity and abnormal 

gait. Results of chronic toxicity studies show that exposure to technical grade cypermethrin and zetacyperinethrin results in decreased body weight and decreased body weight gain in both adults and 

offspring, with NOAELs ranging from 100 mg a.i./kg diet (equivalent to 5 mg a.i./kg body weightiday) 

(MRID 00090040) to 150 mg a.i./kg diet (equivalent to 7.5 mg a.i./kg body weightlday) (MRIDs 

001 12912, 42068504, 9202704). Other sub-lethal effects include signs of emaciation, ataxia, increased 

sensitivity to sound, increased relative brain weight, chromodacryorrhea, chromorhinorrhea, softlliquid 

stools, decreased food consumption, and high stepping gait (MRIDs 001 12912,42068504, 9202704, and 

41 968204). No other significant treatment-related effects on reproductive parameters were reported in 

these studies. 

Terrestrial Invertebrates 

No information on sub-lethal effects of zeta-cypermethrin on terrestrial invertebrates was reported in the 

available studies in honey bees and earthworms. 

iv. Field Studies 
No field studies on the effects of zeta-cypermethrin on terrestrial organisms were submitted. 

b. Terrestrial Plants 

No data were available to evaluate the risk of zeta-cypermethrin exposure to non-target terrestrial plants; 

however, EFED is not concerned because zeta-cypermethrin's neural toxic mode of action is not expected 

to induce phytotoxic effects. In addition, based on the lack of studies demonstrating adverse effects of zetacypermethrin or any other pyrethroid to plants, and the fact that no incident reports have reliably linked 

zeta-cypermethrin or any other compound in the synthetic pyrethroid class of chemicals to phytotoxic 

effects despite being applied on or near agricultural plants, it appears unlikely that zeta-cypermethrin poses 

a phytotoxic concern. Therefore, Tier I plant studies [Guideline 122-1 (a) Seedling Emergence and 

Guideline 122-1 (b) Vegetative Vigor] are in reserve and are not being requested at this time. 

IV. Risk Characterization 

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

risk from the use of zeta-cyperinethrin and the likelihood of effects on aquatic life and wildlife based on 

varying pesticide-use scenarios. The risk characterization provides an estimation and a description of the 

risk; articulates risk assessment assumptions, limitations, and uncertainties; synthesizes an overall 

conclusion; and provides the risk managers with information to make regulatory decisions. 

A. Risk Estimation - Integration of Exposure and Effects Data 

Results of the exposure and toxicity effects data are used to evaluate the likelihood of adverse ecological 

effects on non-target species. For the assessment of zeta-cypennethrin risks, the risk quotient (RQ) method 

is used to compare exposure and measured toxicity values (Appendix F). Estimated environmental 

concentrations (EECs) are divided by acute and chronic toxicity values. The resulting RQs are then 

compared to the Agency's levels of concern (LOCs). These LOCs, summarized in Appendix F, are the 

Agency's interpretive policy used to analyze potential risk to non-target organisms and the need to consider 

regulatory action. These criteria are used to indicate when a pesticide's use as directed on the label has the 

potential to cause adverse effects on non-target organisms. For non-target aquatic animals (i.e., fish and 

invertebrates), surface water, pore water, and sediment EECs were obtained from the Tier 2 model 

PRZMIEXAMS. For non-target terrestrial animals (i.e., birds and mammals), EECs and RQs were 

obtained from T-REX (Appendix C). Toxicity reference values for aquatic and terrestrial organisms 

exposed to zeta-cypermethrin are summarized in Table 13 and Table 14, respectively. 

1. Non-Target Aquatic Animals and Plants 

To assess risks of zeta-cypermethrin to non-target aquatic animals (i.e., fish and invertebrates), surface 

water, pore water, and sediment EECs were obtained from the Tier I1 model PRZMIEXAMS (Table 8). 

The PRZMIEXAMS model was run using the following four representative scenarios: California grapes, 

Georgia peaches, Pennsylvania apples, and Florida turf. All of the scenarios except the Florida turf 

scenario represent proposed spray applications of zeta-cypermethrin; the Florida turf scenario was used to 

estimate EECs for granular applications of zeta-cyperinethrin to residential lawns, home perimeters, 

gardens, and other industrial non-agricultural areas. EFED uses the peak concentration to derive RQs for 

acute exposure. The 2 1 -day average concentration and the 60-day average concentrations to derive chronic 

RQs for invertebrates (including benthic organisms) and fish, respectively. To evaluate the potential for 
toxic risk from zeta-cypermethrin exposure in the water column, EFED divided the water column EEC by 

an effects endpoint (LC5o, ECso, or NOAEC) from water column toxicity studies to generate acute and 

chronic RQ values. The evaluation of toxic risk to benthic organisms was approached by assuming 

equilibrium partitioning of a high &, coinpound like zeta-cypermethrin between the sediment and the pore 

water (i.e., the water found between particulates in the sediment). Risk to the benthos was assessed using 

two approaches: (1) EECs for sediment were model-generated (PRZMIEXAMS) and compared to the 

toxicity value as reported for sediment exposure (LCSO) from the available toxicity studies with watersediment systems; and (2) EECs for pore water were model-generated (PRZMIEXAMS) and compared to 

a derived toxicity value for pore water (based on the sediment exposure toxicity value). 

Since results of acute toxicity studies in freshwater fish and invertebrates (See Appendix E) indicate that 

the major cypermethrin degradate (3-phenoxy benzoic acid) is much less toxic than the parent compound, 

EECs and RQs were derived only for the parent compound, not for total residue (parent plus degradates). 

The major biodegradation transformation products: 3-PBA, cis- and trans-DCVA and 3- 

phenoxybenzaldehyde, are the result of the cleavage of the ester moiety of the parent compound. 

a. Water Column Exposure - Acute and Chronic Risk 

Acute RQs for aquatic animals are suminarized in Table 15. Based on the toxicity data for all 

cypennethrin products (alpha-, beta-, theta-, and zeta-cypermethrin), there is potential for acute risk to nontarget listed and non-listed freshwater and estuarinelmarine fish and invertebrates resulting from both 

granular and spray applications of zeta-cyperinethrin. The LOC for acute restricted use (LOC 0.1) is 

exceeded for all aquatic animals and modeled crop scenarios, except for estuarinelmarine fish under the 

CA grapes and FL turf scenarios (RQs = 0.09 and 0.04, respectively). As discussed previously (Ecological 

Effects Characterization section), based on a comparison of acute LC5() values, invertebrates appear to be 

the most sensitive aquatic animals, and RQs for invertebrates are much higher than those derived for fish. 

The highest acute RQs are observed for freshwater invertebrates, ranging from 1 1.25 (FL turf) to 404.44 

(PA apples), greatly exceeding all acute LOCs. Acute RQ values derived for estuarineimarine 

invertebrates also greatly exceed acute LOCs, with RQ values ranging from 8.53 (FL turf) to 306.53 (PA 

apples). Because acute toxicity values for freshwater and estuarinelmarine fish are similar in magnitude, 

the ranges of acute RQs for these taxonomic groups are also similar (0.10 to 3.73 for freshwater fish and 

0.04 to 1.53 for estuarinelmarine fish). For all aquatic animal species, the highest acute RQs are observed 

for the PA apples scenario, and the lowest acute RQs are observed for the FL turf scenario. This trend 

reflects the same trend of the values of the EECs (Table S), which are used in the calculation of the RQs. 

Chronic RQs for aquatic animals are summarized in Table 16. As anticipated based on a comparison of 

the chronic NOAEC values, chronic RQs derived for aquatic invertebrates are much higher than those 

derived for fish, and exceed the chronic LOC (1) in all instances. Chronic RQs exceed the chronic LOC 

(LOC I) by factors ranging from 5 to 156 and from 7 to 207 for estuarinelmarine and freshwater 

invertebrates, respectively. The chronic RQs for fish do not exceed the chronic LOC for any of the crop 

scenarios considered in this assessment; RQs range from 0.02 to 0.46 and from <0.01 to 0.19 for 

freshwater and estuarinelmarine fish, respectively. Due to chronic toxicity data gaps for freshwater 

invertebrates and estuarinelmarine fish, there is uncertainty regarding the magnitude of chronic risk 

estimates for these taxonomic groups because RQs are based on estimated chronic toxicity values (detailed 

description provided in Ecological Effects Characterization section). For all aquatic animal species, the 

highest chronic RQs are observed for the PA apples scenario, and the lowest chronic RQs are observed for 

the FL turf scenario. 
Table 15. Acute RQs for freshwater and estuarinelmarine fish and invertebrates exposed to zetacypermethrin .' 

b. Sediment Exposure - Acute and Chronic Risk 

Table 16. Chronic RQs for freshwater and estuarinelmarine fish and invertebrates exposed to zetacypermethrin . ' 

Acute and chronic RQs have been derived for exposure of benthic organisms via sediment and pore water 

(Table 17). All acute (RQ ranges = 2.51 to 3 1.08 and 0.78 to 7.78 for sediment and pore water, 

respectively) and chronic (RQ ranges = 13.20 to 165.90 and 2.38 to 40.48 for sediment and pore water, 

respectively) RQs for benthic organisms exceed the LOCs for acute risk (LOC 0.5), acute restricted use 

(LOC 0.1), acute endangered species (LOC 0.05) and chronic risk (LOC 1) for all spray application 

scenarios. For granular applications (FL turf), all sediment RQs for benthic organisms exceed the LOCs 

for acute risk (LOC 0.5), acute restricted use (LOC 0. l), acute endangered species (LOC 0.05) and chronic 

risk (LOC 1) (Acute and chronic RQs = 0.98 and 4.47, respectively); however, pore water RQs for benthic 

organisms only exceed the LOCs for acute restricted use (LOC 0. I), acute endangered species (LOC 0.05), 

and chronic risk (LOC 1) (Acute and chronic RQs = 0.24 and 1.1 1, respectively). Higher RQs were 

EstuarineIMarine 

Invertebrate 

Acute RQ 

17.68 " ' " 

42.32 "' " 

306.53 "' * 

8.53 h'" 

a RQs = EEC /LC 50, whe~e EEC s ate the peak concenhattons In su~face wate~ generated from PRZMiEXAMS for the vartous crop scenattos 

constdeled, and acute tox~c~ty refe~ence values ate as follows freshwatet fish, ta~nbow ttout 96-hr LC<,] = 0 39 pg a I IL. freshwater ~nvertebrates. 

amph~pod 96-h~ LC',,] = 0 0036 pg a I /I . estoartneln~ar~ne f~cli. sheepshead mlnnou 96-hout I C<,, = 0 95 pg a I IL. and estuarlneimar~ne 

~nvet-teblates, mystd sh~~tnp 96-hout LCqo = 0 00475 pg a I /L 

I' RQc meet 01 exceed LOC fot acute 11sk (LO< 0 5) 

' RQs meet 01 exceed LO(' fo~ acute ~estllcted use ( LOC 0 I ) 

" RQs meet 01 exceed 1 OC fot acute endange~ed specles (LOC' 0 05) 

EstuarinetMarine 

Fish 

Acute RQ 

0.09 

0.21 ' " 

1.53~'" 

0 04 

EstuarineIMarine 

Invertebrate 

Chronic RQ 

19.21 " 

24.97' 

156.21 

5.16' 

Crop Use 

GI apes 

Peaches 

Apples 

Turf 

" RQs = FFC 'NOAFC, where the ch~on~c EECs fo~ tnvetteb~ates and fish ate the 21day and the 60-day average concenhatlons In surface water 

genetated from I'RZMIEXAMF fo~ the vanous clop scenallos, respect~vely, and chronlc toxtc~ty reference values are as follows freshwater fish, 

fathead mlnnow 30-da) NOAEC = 0 14 pg a I IL, fresli\cater Invertebrates, estnnated chron~c NOAEC = 0 00059 pg a I /L, estuarttie/mar~ne fish. 

estnnated chron~c NOAEC = 0 34 pg a I /L, and estuar~nel~nartne tnvettebtates, mystd shrnnp 28-day NOAEC = 0 000781 pg a I /L Detatls for 

all estnnated ch~on~c toxtc~ty values ate prov~ded In the Fcologtcal Effects Chatacta~zat~on sectlon 

h~Qs exceed LOCs fot chton~c nsk (I 0C' 1 ) 

Crop Use 

gt apes 

pcaches 

apples 

tut t 

Freshwater 

Fish 

Acute RQ 

0.22 ' " 

0.52 ' 

3.73 " ' 

0.10 ' " 

PRZMJEXAMS 

Scenario 

CA gtapes 

(;A peaches 

I'A apples 

FL turf 

Freshwater 

Invertebrate 

Chronic RQ 

25.42" 

33.05" 

206.78" 

6.83 

Freshwater 

Invertebrate 

Acute RQ 

23.33 " ' 

55.83 "' 

404.44 ' " 

11.25 "" 

EstuarineAMarine 

Fish 

Chronic RQ 

0 03 

0 04 

0 19 

<0 01 

PRZMIEXAMS 

Scenario 

CA grapes 

G A peaches 

PA apples 

FL tu~f 

Freshwater 

Fish 

Chronic RQ 

0 08 

0 09 

0 46 

0 02 
observed in the acute and chronic values derived from the sediment EECs than from the pore water EECs 

in all scenarios. 

c. Aquatic Plants 

Table 17. Acute and chronic RQs for benthic organisms exposed to zeta-cypermethrin. 

Toxicity data on the effects of zeta-cyper~nethrin on non-target aquatic plants are currently unavailable; 

thus RQs cannot be derived. 

Crop Use 

grapes 

peaches 

apples 

tul f 

2. Non-Target Terrestrial Animals 

The EFED terrestrial exposure model T-REX (v 1.2.3) was used to estimate exposure and risks in 

conservative scenarios to avian species for four forage food types and to mammalian species for five forage 

food types for spray applications of zeta-cypermethrin as described in the Exposure Characterization. For 

this risk assessment, terrestrial EECs as a result of spray applications of zeta-cypermethrin were estimated 

using the maxilnuln proposed application rates, the maximum number of applications, and the minimum 

application interval for four representative crop uses: stone fruits, canola, non-grass animal feeds, and 

barley. Risk quotients were calculated using upper-bound EECs. For birds, acute RQs were derived using 

dietary-based and dose-based acute toxicity values, and chronic RQs were derived using a dietary-based 

chronic toxicity value. For mammals, acute RQs were derived using a dose-based acute toxicity value, and 

chronic RQs were derived using a dietary-based chronic toxicity value and a calculated dose-based chronic 

toxicity value (as determined using the standard FDA lab rat conversion in T-REX). Dietary-based RQs 

were calculated using EECs expressed in terms of residue concentration for the various forage categories, 

and toxicity values (LCs0 or NOAEC) are expressed in units of dietary concentration. Dose-based RQs 

' Sedltnent acute RQs = EECi LCV,. whe~e EFCs ale the peak concentratlon In sed~ment generated fiom PRZMiFXAMS for the vallouc clop 

scenatlos, and acute toxlc~ty ~efe~ence value IS the alnphlpod 10-day LC ,,, = 3 6 pg a I kg sedlment 

"pore watel acute RQs = EECi LCII,, where CEC s ale the peak concentlat~on In pole watel t~oln PRZMIEXAMS fo~ the varlous clop scenarios, 

and estllnated acute LC$(, = 0 00257 pg a I /L. pore water (detalls for estimated toxlclty value ale plov~ded m the tcological Effects 

Cha~acte~lrat~on section) 

' Sedllnent ch~onlc RQs = EECINOAEC , whe~e EEC s are the 21-day avaage concentratlon In sedltnent fioln PRZM'EXAMS for the vallous crop 

scenarios, and estlniated chron~c NOAEC = 0 59 pg a I 'kg sed~ment (deta~ls for estllnated toxlclty value ale p~ov~ded the Ecolog~cal Effects 

C halactn lratlon sect~on) 

" Pole watel ch~onlc RQs = EECINOAEC, whe~e EFCs ate the 21-day avetdge concentratlon In pole water fiom PRZMIEXAMS fo~ the vallous 

crop scenallos, and estnnated chronlc NOAI-C = 0 00042 pg a I IL pore water (detalls for estllnated toxiclty value ale prov~ded In the Ecological 

Eftec& Cha~actalzatlon section) 

All RQs exceed LOC s 101 acute 11sk (1 OC 0 5). acute lest~~cted use (LO( 0 1 ). acute endangeled specles (LOC 0 05), and chronlc tlsk (LOC 1 ) 

' RQs meet 01 exceed LOC for acute 11sk (LOC 0 5) 

"Qs meet 01 exceed LO( to1 acute lest1 lcted use (LO( 0 1 ) 

RQs meet ol exceed LOC tor acute endange~ed species (LOC 0 05) 

'RQs exceed IBCs to1 chron~c 11sk (LOC 1 ) 

PRZMIEXAMS 

Scenario 

CA glapes 

GA peaches 

PA apples 

FL tul f 

Sediment 

Acute RQ " 

2.51"~ 

4.00'" 

31.08"~ 

0.98" 

Pore Water 

Acute RQ 

0.78" 

0.99 

7.78'" 

0.24 ' 

Sediment 

chronic RQ ' 

13.20' 

21.69' 

165.90 ' 

4.47' 

Pore Water 

Chronic RQ 

2.38' 

5.36' 

40.48 ' 

1.11' 
were calculated using a body weight-adjusted LD50 and consumption-weighted equivalent dose sorted by 

food source and body size. For both birds and mammals, three weight categories (or sizes) were 

considered. 

For granular applications of zeta-cypermethrin, acute exposure and risks were estimated with the 

conceptual approach using the ~~~~/ft~ method given in the Tier 1 model T-REX (T-REX, Version 1.2.3). 

Terrestrial EEC values were calculated based on an estimation of loadings of pesticide per unit area. By 

comparing the available mass of pesticide per square foot to the acute oral dose for toxicity (LD5o), an 

acute oral RQ was calculated that could be compared to the Agency's LOCs. 

Terrestrial chronic exposure estimates and risks for granular applications of zeta-cypennethrin were 

derived using a fugacity-based (equilibrium partitioning) approach that focuses on direct ingestion of soil 

invertebrates that have bioaccumulated zeta-cypermethrin residues of granules in soil. This methodology is 

discussed in greater detail in the Exposure Characterization and Appendix D. 

a. Spray Applications: Acute Risk to Birds and Mammals 

Dietary-based and dose-based acute RQs for birds are summarized in Table 18 and Table 19, respectively. 

All dose-based (RQs 5 0.02 for all crop use scenarios) and dietary-based (RQs 5 0.01 for all crop use 

scenarios) avian acute RQs are below the LOCs for acute risk (LOC 0.5), acute restricted use (LOC 0.2), 

and acute endangered species (LOC 0.1). In addition, acute RQs are less than the reported value for birds, 

since the available acute toxicity studies did not establish definitive acute LCs0 or LDS0 values (toxicity 

values are reported as "greater than" the highest doselconcentration tested). However, since all avian acute 

RQs are well below LOCs for acute risks, this uncertainty does not affect the acute avian risk 

characterization. 

Dose-based acute RQs for mammals are summarized in Table 20. No acute dose-based RQs for any size 

of mammals under any crop scenario exceed the LOC for acute risk (LOC 0.5) or acute restricted use 

(LOC 0.2). However, for 15g and 35g mammals that consume short grass exposed to zeta-cypennethrin 

TGAI via spray applications (RQs range from 0.05 to 0.16 for all sizes of mammals feeding on short grass 

under all crop use scenarios), dose-based acute RQs exceed the LOCs for acute endangered species (LOC 

O.l)(Table 20). None of the RQs for 1 OOOg mammals feeding on any dietary item exceed any of the acute 

LOCs, and all RQs for mammals feeding strictly on tall grass, broadleaf plantslsmall insects, 

fruitslpodsllarge insects, or seeds are below the acute LOCs. 

Table 18. Avian dietary-based acute" and chronic" RQvaIuesfor proposed uses of zeta-cypermethrin 

based on uwer-bound Kenaga residues on short grass, tall grass, broadleaf plants/small insects, and 

fruits/pods/seeds/large insects as calculated by T-REX (v1.2.3). 

Crop Use 

Stone Ftu~ts 

Maximum 

Application 

Rate in Ibs. 

a.i./A 

(no. of 

applications, 

interval in days) 

0 05 

Food Items 

Short grass 

Acute RQ 

0 01 

Chronic RQ ' 

0 63 
Table 19. Avian dose-based acute RQ valuesa for proposed uses of zeta-cypermethrin based on uDaerbound Kenaga residues on short grass, tall grass, broadleaf plants/small insects, and fruits/pods/seedsAarge 

insects as calculated by T-REX (v1.2.3). 

I I I 

Table 18. Avian dietary-based acute' and chronicbv value sf or proposed uses of zeta-cypermethrin 

based on u~~er-bound Kenaga residues on short grass, tall grass, broadleaf plantslsmall insects, and 

Chronic RQ' 

0 29 

0 35 

0 04 

0 56 

0 26 

0 31 

0 03 

0 50 

0 23 

0 28 

0 03 

0 41 

0 19 

0 23 

0 03 

(mg a I kg dlet) 

fruits/pods/seedsilarge 

Crop Use 

Canola 

Non-@ass Anlmal 

Feeds 

Barley 

" Acute dletaly-based 

Crop Use 

genelated from T-RFX and the toxlclty value IS the acute dletaly-based LC'sl, >2,634 tng a I /kg dlet In lnalla~d duck 

"C hronlc dletaty-based RQ = tFC/NOAFC, where FEC values ate uppel-bound resldues explessed as dletaly concentlatlons (mg a I kg dlet) 

genelated tiom 1 -RFX and the toxrclty value 1s the chronlc dletaly NOAFC value of 50 Ing a I /kg dlet In bobwhlte qua11 and mallald ducks 

' All RQs ale below the I OC fol acute rlsk (LO( 0 5). acute lestllcted use (1 0C 0 2), and acute endangered specles (1.OC 0 I ) 

" All acutc RQs ale < the lepolted value because the non-defin~tlve LC,(, value of >2,634 mg a I /kg dlet was used to estlmate tisk 

All RQs ale below the LOC fol chlonlc IISL (LOC 1) 

insects as 

Maximum 

Application 

Rate in Ibs. 

a.i./A 

(no. of 

applications, 

interval in days) 

(6 17) 

0 05 

(4 17) 

0 05 

(3 17) 

0 05 

(51 14) 

RQ = EECILCS~,, whele 

Maximum 

Application Rate in 

Ibs. a.i./A 

(no. of applications, 

interval in days) 

calculated by T-REX (v1.2.3). 

Food Items 

Tall glass 

B~oadleaf plantsls~nallnsects 

Fmlts, pods, seeds, and lalge Insects 

Sholt glass 

rail glass 

Bloddleaf plants/stna~~ lnsects 

Fruits, pods, seeds, and large Insects 

Sholt glass 

7 all grass 

B~oadleaf plantstslnall insects 

Frults, pods, seeds, and lalge Insects 

Short grass 

Tall glass 

B~oadleaf plantsls~nallnsects 

Fruits, pods, seeds, and lalge Insects 

EEC values are upper-bound resldues expressed 

~~d~ 

Weight 

(g) 

Acute RQ c~d 

0 01 

0 01 

<O 01 

0 01 

10 01 

0 01 

<O 01 

0 01 

<O 01 

0 01 

<O 01 

0 01 

<O 01 

<O 01 

<O 01 

as d~etary concentrations 

Avian Acute Risk ~uotients"" 

Short Grass Tall Grass 

Broadleaf 

Plants/Small 

Insects 

FruitslPods/ 

Seeds/ 

Large 

Insects 
Table 18. Avian dietary-based acutea and chronicb RQvaluesfor proposed uses of zeta-cypermethrin 

based on uwwer-bound Kenaga residues on short grass, tall grass, broadleaf plantslsmall insects, and 

fruitslpodslseedsllarge insects as calculated by T-REX (v1.2.3). 

Crop Use 

Maximum 

Application 

Rate in Ibs. 

a.i./A 

(no. of 

applications, 

interval in days) 

Food Items 

Stone F~ults 

Canola 

Non-gass 

Annnal Feeds 

Barley 

0 05 

(6 7) 

0 05 

(4 17) 

0 05 

(3 17) 

0 05 

(5 1 14) 

20 

loo 

1000 

20 

100 

1000 

20 

100 

1000 

20 

100 

1000 

Acute RQGd 

a Acute dose-based RQ = EECILD~II, where EEC 

generated fioln T-REX and the tox~c~ty value IS the acute dose-based LD5(, >2,000 mg a I /kg body we~ght In bobwhite qua11 

I' All RQs are below the LOC for acute r~sk (I OC 0 S), acute restricted use (LOC 0 2), and acute endangered specles (LOC 0 I) 

All acute RQF ale < the leported value because the non-definlt~ve LCro value of >2,000 tng a i /kg body we~ght was used to estnnate 11sk 

Table 20. Mammalian dose-based acute RQ valuesa for proposed uses of zeta-cypermethrin based on 

uwwer-bound Kenaga residues on short grass, tall grass, broadleaf plantslsmall insects, and 

fruits/podslseedsllarge insects as calculated by T-REX (v1.2.3). 

Chronic RQ' 

values are uppel-bound lesldues explessed as equ~valent dose (mg a I kg body we~ght) 

0 02 

0 01 

<o Ol 

0 02 

0 01 

<o Ol 

0 02 

0 01 

<o 01 

0 02 

0 01 

<o 01 

Crop Use 

Stone Fru~ts 

-. 

c anola 

0 01 

0 01 

<o 01 

0 01 

<o 01 

<o 01 

0 01 

<O 01 

<o 01 

0 01 

<O 01 

<o 01 

Maximum 

Application 

Rate in Ibs. 

a.i./A 

(no. of 

applications, 

interval in 

days) 

0 05 

(6 17) 

0 05 

0 01 

0 01 

<o 01 

0 01 

0 01 

<o 01 

001 

<O 01 

<o Ol 

0 01 

<O Ol 

<o 01 

Body 

Weight 

(g) 

15 

35 

1000 

15 

<o 01 

<o 01 

<O 01 

<o 01 

<o 01 

<o 01 

10 01 

<O 01 

<o 01 

<o 01 

<O 01 

<o 01 

Mammalian Acute Risk Quotients 

Grass 

0.16~ 

0.14h 

0 07 

0.14O 

Tall Grass 

0 07 

0 06 

0 03 

0 06 

Small 

Insects 

0 09 

0 08 

0 04 

0 08 

FruitstPods 

/ Large 

Insects 

0 01 

0.01 

<O 01 

0 01 

Seeds 

<O 01 

<0.01 

<O 01 

<O 01 
Table 18. Avian dietary-based acutea and chronicb RQvaluesfor proposed uses of zeta-cypermethrin 

based on upper-bound Kenaga residues on short grass, tau grass, broadleaf plants/smaU insects, and 

fruitslpodslseedsllarge insects as calculated by T-REX (v1.2.3). 

Crop Use 

I interval in days) I 

(4 : 7) 

Non-grass 

Animal 1 005 

(3 17) Feeds 

Maximum 

Application 

Rate in Ibs. 

a.i.1A 

(no. of 

applications, 

Barley 

35 

15 

3 5 

Table 21. Mammalian dose-based chronic RQ valuesa for proposed uses of zeta-cypermethrin based on 

upper-bound Kenaga residues on short grass, tall grass, broadleaf plantslsmall insects, and 

Food Items 

"cute dose-based KQ = EE(I':LDi(,, where EEC values are upper-bound residues expressed as equivalent dose (mg a.i./kg body weight) 

generated l?om T-REX and the toxicity value is the acute dose-based LDco = 86 mg a.i./kg body weight in female rats. 

" RQs meet 01. exceed the LOC for acute endangered species (LOC 0.1). 

0.05 

(5 114) 

fruits/pods/seeds/large 

Crop Use 

\tone Ftults 

Canola 

Non-grass 

Animal 

I I I I 

0.12" 

O.lZh 

0.1 I 

Acute RQGd 

1000 

I5 

35 

1000 

insects 

Maximum 

Application 

Rate in Ibs. 

a.i.1A 

(no. of 

applications, 

interval in 

days) 

0 05 

(6 17) 

0 05 

(4 17) 

0 05 

(3 ' 7) 

Chronic RQ ' 

0 06 

0.06 

0.05 

0.06 

0.10" 

0.09 

0.05 

as calculated 

Body 

Weight 

(g) 

15 

3 5 

1000 

15 

3 5 

1000 

15 

3 5 

0 07 

0.07 

0.06 

0.03 

0.05 

0.04 

0.02 

by T-REX (v1.2.3). 

0 01 

0.01 

0.0 1 

Short 

Grass 

2.73 " 

2.33 " 

1.25 I' 

2.43 I' 

2.07 I' 

1.1 I I' 

2.15" 

1.83 I' 

<O 01 

40.01 

<0.01 

0.03 

0.06 

0.05 

0.03 

Mammalian 

Tall 

Grass 

1.25 I' 

1.07 I' 

0 57 

1.11~' 

0 95 

0 51 

0 98 

0 84 

<0.01 

0.01 

0.01 

<0.01 

10.0 1 

<0.01 

<0.01 

<0.01 

Chronic 

Broad1eaf 

Plants1 

Small 

Insects 

1.53 I' 

1.31" 

0 70 

1.37 " 

1.17" 

0 63 

1.21 

1.03 " 

Risk Quotients 

FruitsIPods 

1 Large 

Insects 

0 17 

0 15 

0 08 

0 15 

0 13 

0 07 

0.13 

0 11 

Seeds 

0 04 

0 03 

0 02 

0 03 

0 03 

0 02 

0 03 

0 03 
Table 18. Avian dietary-based acutea and chronicb valuesf sf or proposed uses of zeta-cypermethrin 

based on u~~er-bound Kenaga residues on short grass, tall grass, broadleaf plants/small insects, and 

fruits/pods/seeds/large insects as calculated by T-REX (v1.2.3). 

I I I I 

Table 22. Mammalian dietary-based chronic RQ values a for proposed uses of zeta-cypermethrin based on 

u~~er-bound Kenaga residues on short grass, tall grass, broadleaf plants/small insects, and 

. fruits/pods/seeds/large insects as calculated by T-REX (v1.2.3). 

I I 

Crop Use 

Non-grass Animal 0.05 

Feeds I (317) I 0.25 1 0.1 1 1 0.14 1 0.02 1 

Maximum 

Application 

Rate in Ibs. 

a.i./A 

(no. of 

applications, 

interval in days) 

Crop Use 

Stone Frutts 

C anola 

I I I I I 

I>iet:ir).-h;csed KO?; .- Ll:( U( )At (', w hz1.c I.l.('?; \sluts arc upper hound residues exprezsed as d~eta~v concentrations (~np a i ,kg d1e0 

reeds 

Bal ley 

- - generated fi-om T-REX and the toxicity value is the chronic diet& NOAEC value of 100 mg a.i./kg diet in rats. 

" All KQs are below the LOC' for chronic risk (L.OC I ). 

Food Items 

Maximum 

Application 

Rate in lbs. 

a.i./A 

(no. of 

applications, 

interval in 

days) 

0 05 

(6 ' 7) 

0 05 

14 i 7) 

b. Spray Applications: Chronic Risk to Birds and Mammals 

a C hlonlc dose-based RQ = EFC'INOAEL, whe~e EtC values are uppel-bound tesldues expressed as equivalent dose (mg a I /kg body welght) 

generated fiom T-REX and the chron~c toxlclty \slue IS the chronlc NOAFL = 5 mg a I /kg body welght In rats. converted from the NOAEC of 

100 mg a I )kg diet In the lat uslng the standard FDA lab rat conversion by T-REX 

I' RQs meet or exceed the LOC for chtonlc I ~sh (LOC I) 

Acute RQG" 

0 01 

0 02 

0 02 

0 01 

0 05 

(5 14) 

Mammalian Chronic Risk Quotients 

Chronic RQ ' 

Short Grass 

0 31 

0 28 

1000 

15 

3 5 

Tall Grass 

0 14 

0 13 

0 98 

1.76" 

1.51 I' 

1000 I 0 81 

P1antslSmal' 

Insects 

0 18 

0 16 

0 45 

0 81 

0 69 

Fruits/Pods/Seeds/ 

Large Insects 

0 02 

0 02 

0 37 

0 55 

0 99 

0 85 

0 06 

0 I1 

0 09 

0 45 0 05 
All chronic RQs for birds are below the LOC for chronic risk (LOC l)(Table 18). Chronic RQs for birds 

range from 0.03 (birds feeding on fruitslpodsllarge insects for application of zeta-cypermethrin to barley) 

to 0.63 (birds feeding on short grass for application of zeta-cypermethrin to stone fruits). 

Dietary-based chronic RQs for mammals range from 0.01 (mammals feeding on fruits/pods/large insects 

for zeta-cypermethrin use on barley) to 0.3 1 (mammals feeding on short grass for zeta-cypermethrin use on 

stone fruits), with no RQs exceeding the chronic LOC (Table 22). 

Dose-based chronic RQs for mammals are summarized in Table 21. Dose-based chronic RQs exceed the 

LOC for chronic risk (LOC 1) for all modeled crop uses for exposure via short grass; RQs range from 0.81 

(1 000g mammals for zeta-cypermethrin use on barley) to 2.73 (1 5 g mammals for zeta-cypermethrin use 

stone fruits). For mammals feeding on tall grass, dose-based chronic RQs range from 0.37 (1000 gram 

mammals for zeta-cyperinethrin use on barley) to 1.25 (15 gram mammals for zeta-cypermethrin use on 

stone fruits); chronic RQs exceed the chronic LOC for the stone fruits (RQ range = 0.57 to 1.25) and 

canola (RQ range = 0.5 1 to 1.1 1) scenarios, but not for the non-grass animal feeds (RQ range = 0.45 to 

0.98) or barley scenarios (RQ range = 0.37 to 0.8 1). For mammals feeding on broadleaf plantslinsects, 

dose-based chronic RQs range from 0.45 (1000 gram mammals for zeta-cypennethrin use on barley) to 

1.53 (1 5 gram mammals for zeta-cypermethrin use on stone fruits); chronic RQs exceed the chronic LOC 

for the stone fruits (RQ range = 0.70 to 1.53), canola (RQ range = 0.63 to 1.37), and non-grass animal 

feeds (RQ range = 0.55 to 1.21) scenarios, but not for the barley scenario (RQ range = 0.45 to 0.99). All 

RQs for mammals feeding on fruits/pods/large insects and seeds are below the chronic LOC. 

c. Granular Applications: Acute and Chronic Risk to Birds and 

Mammals 

Acute RQs (~~~~lft' values) for birds and mammals exposed to zeta-cypermethrin as a granular application 

are summarized in Table 23. Although none of the acute LOCs are exceeded for avian species of any size, 

acute RQs suggest that granular applications of zeta-cyperinethrin may pose an acute risk to 15g and 35g 

mammals; the RQ for 15g mammals (RQ=0.83) exceeds the LOCs for acute risk (LOC 0.5), acute 

restricted use (LOC 0.2), and acute endangered species (LOC 0. I), while the RQ for 35g mammals 

(RQ=0.44) exceeds the LOCs for acute restricted use (LOC 0.2) and acute endangered species (LOC 0.1). 

For larger mammals (1000 g), the acute RQ (RQ=0.04) is below all acute LOCs. 

Terrestrial chronic exposure estimates and risks for granular applications of zeta-cypennethrin were 

derived according to the methodology presented in Appendix D. Chronic risks to birds and malnlnals 

associated with ingestion of earthworms that have bioaccumulated zeta-cypermethrin granules are not 

expected based on a comparison of the estimated earthworm residue (4.8 mg a.i.ikg diet) with the avian 

and mammalian chronic dietary endpoints (50 and 100 mg a.i./kg diet, respectively); RQs are less than the 

chronic risk LOC (1). In addition, based on a comparison of estimated chronic doses for insectivorous 

mammals and adjusted NOAELs for three size classes, chronic risk resulting from exposure to granular 

zeta-cypermethrin appears unlikely; chronic RQ values ranged from 0.19 for 1000g mammals to 0.41 for 

15g mammals (Table 24). 

Table 23. Acute RQ values (~~~dft') for birds and mammals for the proposed granular uses of zetacypermethrin as calculated by T-REX (v1.2.3). 

I I Crop Use / Maximum I Birds I Mammals I 
3. Non-target Plants Inhabiting Terrestrial and Semi-Aquatic Areas 

No toxicity data on the effects of zeta-cypennethrin on non-target terrestrial plants and terrestrial plants in 

semi-aquatic areas plants are available; thus RQs cannot be derived. 

Mammalian 

Acute RQ" 

(IJD,dftf) 

0.83 ' * 

0.44 ' " 

0 04 

B. Risk Description 

- 

Mammalian 

Weight 

fg) 

15 

3 5 

1000 

Although the label stated that zeta-cypermethrin emulsifiable concentrate formulations can be applied up to 

a nlaximum of 0.3 lb a.i./A per season, for this risk assessment, EFED assumed that zeta-cypermethrin was 

applied at a maximum of 0.3 lb a.i./A per year for spray applications. If there are conditions under which 

there is more than one growing season for a crop within a single year, exposure estimates and risk to 

aquatic and terrestrial organisms could be significantly underestimated. However, despite this possibility, 

the Agency has still identified acute risk concerns to fish, aquatic invertebrates (benthic and water columndwelling), terrestrial invertebrates, and mammals, and chronic risk to aquatic invertebrates (benthic and 

water column-dwelling) based on the proposed use patterns and the fate and toxicity databases for all 

cypermethrin products (alpha-, beta-, theta-, and zeta-cypennethrin). This concern includes risk to listed 

and non-listed fish, aquatic crustaceans, snails, clams, amphibians, mammals, and terrestrial invertebrates. 

Turf 

' RQ = ulb a I /A) x (I aclel43.560 sauare feet) x (453.590 nlellbU 

[(LDSO 1ng1kg) x (we~ght of anunal (kg))] 

" RQs meet 01 exceed the L OC fol acute r~sk (RQ 30 5) 

" RQs meet 01 exceed the LOC for restr~cted use (LOC 0.2) 

" RQs meet 01 exceed thc LOC fol acute endangered specles (l OC 0 1 ) 

Table 24. Dose-based chronic RQs for insectivorous mammals for the proposed granular uses of 

zeta-cypermethrin. 

For spray applications of zeta-cypermethrin, there is acute risk to all aquatic invertebrates and fish, and 

chronic risk to all aquatic invertebrates. For granular applications, there is acute risk to freshwater fish and 

all aquatic invertebrates, and chronic risk to aquatic invertebrates. 

0 225 

(IINA) 

Avian 

Body Weight 

(g) 

20 

100 

1000 

- - 

Avian 

Acute RQ'Body 

(LD,,Jft2) 

0 08 

0 01 

<0 01 

Body Weight (g) 

15 

3 5 

1000 

" Dose-adjusted EFCw = Dletaly FEC, (ppm) * (%BW consu1ned/100) 

" Adjusted NOAI-L = NOAEL (TWIAW)"~' 

' Chlon~c RQ = Dose-adjusted EEC, / Adjusted NOAEL 

" All RQs ale below the LOC for chronlc rlsk (LOC I ) 

Adjusted NOAEL 

(mglkg-BW~day)~ 

10 99 

8.89 

3 85 

Dose-adjusted EEC,, 

(mglkg-BWIday)" 

4.56 

3 17 

0 72 

Chronic RQcd 

0 41 

0 36 

0 19 
Although this compound binds readily to particulate and organic carbon in the water column (average I&, 

= 14 1,700 LIKE), possibly limiting bioavailability in this media after 24 to 48 hours, the bound residues 

settle onto the benthos, increasing zeta-cypermethrin concentrations in the sediment. Zeta-cypermethrin is 

expected to be relatively stable to breakdown from sunlight (aqueous photolysis half-life of approximately 

36 days and a dark control corrected soil photolysis half-life of over 100 days) and biodegrade slowly with 

a half-life of about 2 months in aerobic and anaerobic soils. Therefore the sediment compartment can serve 

as a repository of pesticide residues that can result in a direct toxic risk concern for benthic and epibenthic 

aquatic organisms (e.g. early life stage of many invertebrates and fish, as well as crabs and shrimp). The 

cypennethrin data pertaining to sediment toxicity shows that zeta-cypermethrin can be expected to be 

potentially very highly toxic and biologically available. Therefore, coupled with its persistence and toxicity 

profile, sediment bound zeta-cypennethrin from both granular and spray applications presents a potential 

for direct acute and chronic toxic risk to aquatic life in the benthos and a potential indirect sub-lethal risk 

to fish through food chain alterations that can affect freshwater and estuarine fish year classes. 

Relative to the proposed use patterns identified in this assessment, acute and chronic risk to avian species 

is not expected for spray or granular applications of zeta-cypermethrin. However, exposure of mammals to 

zeta-cypermethrin spray applications is expected to result in acute risk to listed species, and chronic risk to 

listed and non-listed species, while exposure of mammals to zeta-cypermethrin granular applications is 

expected to result in acute risk to both listed and non-listed species. Chronic risks to birds and mammals 

associated with ingestion of earthworms that have bioaccu~nulated zeta-cyperrnethrin granules are not 

expected. Although EFED does not quantitatively estimate risk to non-target terrestrial invertebrates, a 

qualitative analysis of the available information leads to concern for the potential for risk to listed and nonlisted terrestrial invertebrates, such as honey bees and earthworms. 

Results of acute toxicity studies in freshwater fish and invertebrates indicate that the zeta-cypermethrin 

degradate 3-phenoxy benzoic acid is much less toxic than the parent compound. No information is 

available on the toxicity of other zeta-cypermethrin degradates or on the toxicity of any degradate to 

terrestrial organisms; therefore, risk resulting from exposure to zeta-cypermethrin degradates could not be 

evaluated in this assessment. However, based on the assumption that cleavage of the ester bond moiety in 

the parent structure results in biologically inactive degradates, these compounds should not present a 

significant risk to non-target organisms. 

It is assumed for pesticides, such as zeta-cypermethrin, which may have residential outdoor uses 

(applications to home lawns, gardens, parks or tenniticide uses applied subterranean or for perimeter 

treatment, etc), that runoff water from rain and/or lawn watering may remove pesticide to storm sewers and 

then directly to surface water. However, in general, outdoor residential uses are comprised of multiple, 

relatively small, temporally and spatially variable applications that are not simulated in agricultural models. 

Therefore, there is some uncertainty in the aquatic exposure assessment because a model specifically aimed 

at simulating pesticide fate and transport in a complex urban landscape has not yet been developed to 

generate exposure estimates strictly for urban areas. 

1. Risks to Aquatic Organisms 

This risk assessment of zeta-cypennethrin shows that aquatic systems are potentially at risk from acute and 

chronic toxic exposure to this chemical. Evaluation of this risk to aquatic organisms was approached by 

dividing the aquatic system into two general compartments, the water column and the benthos. 

The first compartment, the water column, which is defined as the aquatic area between surface and the 

benthos (approximately 6 inches above the bottom) represents an area where organisms are free-swimming 
and can feed and breed at the surface, mid water andlor on the benthos (sediment). Direct pesticidal 

contact (e.g., gill lamella, ingestion, and integument) to these organisms is assumed to be from the surface 

water via drift andlor runoff. The toxicity assessment points are the acute LCs0/ EC50 and chronic NOAEC 

that are generated through standard water column toxicity tests. 

The second aquatic compartment to be considered is the benthos, which is composed of sediments and an 

area 6 inches above the sediment (epibenthos). The benthos is composed of a diversity of aquatic 

invertebrates (e.g., insect larvae, crustaceans, mollusks) and species of fish (e.g., catfish, loachs), as well as 

certain critical life stages of organisms that reside in the water column; the benthos is also the initial 

breeding strata and nursery area for several species of fish, especially commercial species such as 

salmonids. The benthos can also be a source of food items for several species of fish that are actively 

feeding on the organisms in the sediment andlor capturing organisms that are emerging from this area. 

a. Aquatic Animals: Water Column Exposure 

Since zeta-cypermethrin can be classified as very highly toxic on an acute basis to freshwater (lowest LCj" 

= 0.39 pg a.i./L) and estuarinelmarine fish (lowest LC50 = 0.95 pg a.i./L) and freshwater (lowest LC5" = 

0.0036 pg a.i./L) and estuarinelmarine (lowest LCjo = 0.00475 pg a.i./L) invertebrates (Table 13), the 

potential for risk to aquatic systems was anticipated. Results of this assessment show that PRZMIEXAMS 

modeled surface water concentrations resulting from drift and runoff from agricultural areas pose acute risk 

to listed and non-listed fish and invertebrates (freshwater and estuarinelrnarine), and chronic risk to 

freshwater and estuarinelrnarine invertebrates. As shown in Table 15, all acute RQs (for all spray and 

granular scenarios considered) exceed the acute risk, acute restricted use, and acute endangered species 

LOCs for all aquatic invertebrates, and the risk appears to be several orders of magnitude greater than the 

potential risk to fish. This was an expected outcome of this risk analysis, based on comparison of toxicity 

values for aquatic animals. However, there is still potential for acute risk to fish, as acute RQs exceed the 

acute risk, acute restricted use, and acute endangered species LOCs for the most conservative spray 

application crop scenario considered (PA apples). For granular applications (FL turf scenario), the acute 

RQ exceeds the acute restricted use and acute endangered species LOCs for freshwater fish, but there are 

no exceedances of acute LOCs for estuarinelmarine fish. Based on the available toxicity data (the lowest 

LCS~IEC~~ for all aquatic water column dwelling organisms; 0.0036 pg a.i./L), it is expected that a peak 

surface water EEC less than 0.00018 pg a.i.1L would be sufficiently low to achieve acute RQ values for all 

aquatic water colurnn-dwelling organisms that are less than the endangered species LOC (0.05). This 

means that the highest peak water coluinn EEC of 1.456 pg a.i.lL would have to be reduced by -100%. 

Results of this risk analysis identify the potential for acute risks to aquatic animals based on measures of 

acute lethality, and indicate that zeta-cypermethrin exposure has the potential to reduce survival of aquatic 

animal populations. However, in addition to acute lethality, results of acute toxicity studies in fish and 

invertebrates show that sub-lethal effects can occur at zeta-cypermethrin concentrations 2-3 times lower 

than corresponding acute LCjo values. Development of these sub-lethal effects, which include erratic 

swimming, partiallcomplete loss of equilibrium, immobility, lethargy, and darkened pigmentation, is likely 

to leave fish and invertebrates more vulnerable to predation pressure, resulting in indirect effects on 

survival of aquatic populations (Hill et al., 1973; Sousa, 1998). Sub-lethal effects and subsequent indirect 

effects on population survival are anticipated to occur at concentrations lower than those triggering acute 

risks to aquatic animals. 

Results of an early-life stage study in freshwater fish show that long-term exposure to zeta-cypermethrin at 

a level half of the magnitude of the most sensitive acute toxicity endpoints for the taxonomic group can 
significantly reduce larval survival. In addition, results of mysid life-cycle studies show that long-term 

exposure to zeta-cypermethrin at a concentration about one-third of the magnitude of the acute toxicity 

endpoints for the taxonomic group can significantly reduce growth and offspring survival. However, as 

shown in Table 16, results of this assessment show that the chronic LOC is exceeded for all aquatic 

invertebrates under every scenario considered, whereas there are no exceedances for freshwater or 

estuarinelmarine fish under any scenario. Based on the available toxicity data (the lowest NOAEC for 

aquatic water column dwelling organisms; 0.00059 pg a.i./L), it is expected that a 21 -day surface water 

EEC less than 0.00059 pg a.i./L would be sufficiently low to achieve chronic RQ values for all aquatic 

water column dwelling organisms that are less than the chronic LOC (1). This means that the highest 2 1 - 

day surface water EEC of 0.122 pg a.i./L would have to be reduced by -99.5%. 

One important point regarding the estimated chronic risk to freshwater invertebrates and estuarine!marine 

fish is that despite the absence of data on the chronic effects of zeta-cypermethrin on these taxonomic 

groups, EFED assumed that there are physiological similarities (e.g., developmental, reproduction, etc.) 

between freshwater invertebrates and estuarinelmarine invertebrates, and between freshwater fish and 

estuarinelmarine fish. In addition, as noted by scientists in EFED, the ratio between acute and chronic 

toxicity values can be expected to vary depending upon the pesticide, but typically within a median ratio 

range of 5 - 25 (Brian Montegue, personal comnzt~nicntion). Based on assumed physiological similarities 

and correlations between acute and chronic toxicity values, EFED extrapolated NOAEC values for 

freshwater invertebrates and estuarinelmarine fish by using the acute-to-chronic ratio method described in 

the Ecological Effects Characterization section of the assessment. This extrapolation method consists of 

applylng the lowest observed similar species' acute and chronic effects values as a ratio (e.g., 

LCS0/NOAEC) to a similar relationship in another aquatic group (e.g., freshwater fish vs. estuarinelmarine 

fish and fieshwater invertebrates vs. estuarinelmarine invertebrates). Therefore, there is uncertainty 

regarding estimates of chronic risk for freshwater invertebrates and estuarinelmarine fish dwelling in the 

water columnn. 

b. Aquatic Animals: Sediment Exposure 

Risk estimates for benthic organisms show that zeta-cypennethrin poses acute and chronic risks to benthic 

organisms, based on acute and chronic RQs calculated using both sediment and pore water EECs (Table 

17). However, it should be noted that there are uncertainties regarding acute and chronic risk estimates for 

benthic organisms. First, the acute LC,,, value for pore water and the chronic NOAECs for sediment and 

pore water that were used to generate RQs were not determined in controlled laboratory studies. Rather, 

acute RQs for pore water were derived using a toxicity value estimated with the Equilibrium Partitioning 

Theory and the definition of the Km, and the chronic RQs for sediment and pore water were generated 

based on NOAECs calculated using the acute-to-chronic ratio method (details provided in the Ecological 

Effects Characterization section and the previous section entitled, Aquatic Animals: Water Column 

Exposure). 

Second, the acute sediment toxicity value (in terms of whole sediment) used to estimate risk and to 

generate acute pore water and chronic pore water and sediment toxicity values was obtained from a study 

using a water-sediment system that was not at equilibrium; sediment concentrations decreased throughout 

the exposure period. Since residues that have reached equilibrium in the pore water are considered a 

greater source of toxic risk to benthic invertebrates (Di Toro et nl., 1991), the studies presented in this 

assessment may underestimate sediment toxicity and equilibration should have occurred for at least one 

month prior to testing. If the exposure system had been at equilibrium, it is likely that the acute and 

chronic toxicity reference values for sediment and pore water would be lower, resulting in RQs that are 
higher than those derived in this assessment. However, even with these uncertainties, there are acute and 

chronic risks to benthic organisms for all modeled crop uses. 

EFED also realizes that there is uncertainty regarding the amount of sorbed pesticide that may contribute 

to the toxicity of organisms, that the model-generated pore water values may be an overestimation or 

underestimation of actual exposure values noted in the laboratory or field, and that inherent variations in 

biological uptake as result of differences in feeding pathways (Landrum, et. al., 1994; McGroddy et al., 

1996; Bott and Standley 2000), organism life stage (Leppanen and Kukkonen 1998), and population-level 

effects versus individual responses (Hallam et al., 1990) could affect the toxicity of sorbed pesticide to 

benthic organisms. Although the registrant has conducted acute and chronic sediment studies with 

cypermethrin to address some of the current uncertainties associated with risk to benthic organisms 

exposed to zeta-cypermethrin, the studies are currently in review and have not been included in this risk 

assessment. 

Based on the available toxicity data (the lowest LCSo for benthic organisms; 0.00257 pg a.i./L pore water 

and 3.6 pg a.i./kg sediment), it is expected that a peak pore water EEC less than 0.000129 pg a.i./L pore 

water and a peak sediment EEC less than 0.18 pg a.i./kg sediment would be sufficiently low to achieve 

acute RQ values for all benthic organisms that are less than the endangered species LOC (0.05). This 

means that the highest peak pore water and sediment EECs of 0.02 pg a.i./L pore water and 11 1.9 pg 

a.i./kg sediment, respectively, would have to be reduced by -99.4% and 99.8%, respectively. 

Based on the available toxicity data (the lowest NOAEC for benthic organisms of 0.00042 pg a.i./L pore 

water and 0.59 pg a.i./kg sediment), it is expected that a 21 -day pore water EEC of approximately 0.00041 

ppb and a 21-day sediment EEC of 0.58 pg a.i./kg sediment would be sufficiently low to achieve chronic 

RQ values for all benthic organisms that are less than the chronic LOC (1). This means that the highest 21 - 

day pore water and sediment EECs of 0.017 pg a.i./L pore water and 80.3 pg a.i./kg sediment, 

respectively, would have to be reduced by -97.6% and 99.3%, respectively. 

c. Aquatic Plants 

Toxicity data are not available to evaluate the risk of zeta-cypermethrin exposure to non-target plants 

inhabiting aquatic environments; however, EFED is not concerned about the level of phytotoxicity of zetacypermethrin products because zeta-cypermethrin's neural toxic mode of action is not expected to be a 

phytotoxic concern. In addition, based on the lack of studies demonstrating adverse effects of zetacypermethrin or any other pyrethroid to plants, and the fact that no incident reports have reliably linked 

zeta-cypermethrin or any other compound in the synthetic pyrethroid class of chemicals to phytotoxic 

effects in algae or aquatic macrophytes, it appears unlikely that zeta-cypermethrin poses a phytotoxic 

concern. 

d. Summary of Risk to Aquatic Systems 

The complexities of natural aquatic systeins forgoes the use of a single factor approach in evaluating even 

a screening-level assessment of risk to fish and aquatic invertebrates from toxic exposure to zetacypermethrin. Thus, EFED approached the zeta-cypermethrin evaluation by assessing the potential toxic 

impact to the aquatic system from exposure in the water column and in sediment and pore water. As noted 

earlier, EFED modeled the possible exposure of zeta-cypermethrin use from the proposed use areas for 

application to grapes, peaches, apples, and turf. These crops were chosen because their use patterns are 
representative of all of the proposed uses for zeta-cypennethrin. One of the crops is representative of 

granular applications (turf), while the rest are representative of spray applications. 

Exposure estimates for aquatic environments could not be generated strictly for urban areas because a 

model specifically aimed at simulating pesticide fate and transport in a complex urban landscape has not 

yet been developed. In general, outdoor residential uses are comprised of multiple, relatively small, 

teinporally and spatially variable applications that are not simulated in agricultural models. However, for 

aquatic ecological exposure assessments for pesticides which have residential outdoor uses (applications to 

residential lawns, home perimeters, gardens, and other industrial non-agricultural areas), it is assumed that 

runoff water from rain andior lawn watering may remove pesticide to storm sewers and then directly to 

surface water. Therefore, the Agency is concerned with the potential for zeta-cypennethrin runoff and/or 

erosion from residential areas. Even though pyrethroids generally have a strong affmity to bind to soils and 

surfaces, residue monitoring in non-agricultural areas (e.g., California) have shown that residues of 

pyrethroids toxic to aquatic organisms are occurring in aquatic areas that receive runoff from suburban 

developments. Weston et al. (2005) found residues of pyrethroids from these residential areas and 

suggested that these areas are unlikely to be unique with similar residue profiles occurring in other 

suburban areas, particularly in dry regions where landscape irrigation can dominate seasonal flow in some 

water bodies. 

Despite the limitations in modeling capabilities for outdoor residential uses, this screening-level 

assessment of zeta-cypemethrin shows that the use of this pyrethroid on crops can result in the potential 

for significant toxic exposure and risk to aquatic systems. This concern includes organisms that frequent 

the surface and water column, as well as those that live inion the benthos. As zeta-cypermethrin is 

introduced to surface water via drift or runoff from a crop area, it can disperse down through the water 

column causing acute toxicity (sub-lethal and lethal effects) to sensitive species. In addition to acute risk, 

chronic effects are a potential concern for aquatic organisms that are exposed to zeta-cypermethrin in the 

water colulnn during critical life stages. Possible chronic effects to aquatic life inay also be a concern 

where an initial zeta-cypennethrin exposure may cause embryological effects (possible neonate mortality 

and growth effects inay reflect toxin exposure at an early embryological stage) or possible reproductive 

effects 2 1 days to 60 days following initial exposure. Because zeta-cypermethrin has a high affinity to 

bind to particulate and organic carbon, sediment can act as a sink where zeta-cypennethrin can accumulate. 

Toxic exposure of zeta-cypermethrin in the sediment can present a more far-reaching impact on a 

multitude of organisms than exposure in the water column (e.g., zeta-cypermethrin residues can be 

expected to rapidly decline in the water column). A wide variety of aquatic organisms depend upon the 

benthos for food (e.g., fish feeding on invertebrates), reproduction (e.g., salmonid and other species using 

the benthic substrate for breeding), and shelter (e.g., bottom dwelling fish, mollusks, aquatic invertebrates, 

etc.); the benthos is a dynamic system that interacts directly or indirectly with most, if not all aquatic 

species at some point in their development or life stages. Because of their influence on various functional 

parameters in streams, such as primary productivity, detritus processing, and energy flow, changes in 

abundances and distributions of benthic macroinvertebrates have the potential to reflect changes in stream 

ecosystems. In addition, because benthic macroinvertebrates are the major prey of many species of fish 

(freshwater and estuarineimarine), they also have societal relevance in terms of recreation and ecological 

biodiversity. As food resources decline or widely fluctuate, fish communities often display increased 

disease, parasitism, and deformities as a result of less than adequate diet. 

EFED has a concern for the potential chronic risk that may occur to aquatic organisms from zetacypennethrin load in sediments. Chronic toxicant loads in sediments may drive populations toward a 
limited set of tolerant genotypes over time. Such reductions in genetic diversity could reduce a population's 

plasticity to adapt to the new stresses that can arise as anthropogenic stress on aquatic ecosystems increases 

(especially in agricultural areas). This impact cumulatively results in structural and functional responses of 

the aquatic ecosystems and biota. The time required for invertebrate assemblages to return to their natural 

state, following disturbances such as those of pesticide drift andlor runoff, can be on the order of many 

years for streams, and decades for lakes. 

2. Risks to Terrestrial Organisms 

a. Spray Applications: Acute and Chronic Risk to Birds and Mammals 

Pesticide exposure can vary substantially in space, mostly because of use patterns. However, terrestrial 

exposure tends to localize near the application site, extended somewhat by spray drift down wind. In some 

cases, long range aerial transport can extend this range for a volatile compound. However, in the case of 

zeta-cypennethrin, volatility is not an issue of concern. Therefore, to assess risks to terrestrial organisms 

(e.g., birds and mammals) from spray applications of zeta-cypennethrin, this assessment focuses on the 

potential for toxic exposure to zeta-cypermethrin residues on food items. 

Given the low order of toxicity observed in acute toxicity studies in birds (LCs0 >2,634 mg a.i./kg diet and 

LDsO >2,634 lng a.i./kg body weight) and the fact that no effects were observed in the available avian 

reproduction studies (LOAEC > 50 mg a.i./kg diet, the highest concentration tested), acute and chronic 

risks to avian species resulting from exposure to spray applications of zeta-cypermethrin were not 

expected. In fact, results of this assessment show that all acute RQs for birds are below acute risk, acute 

restricted use, and acute endangered species LOCs (Tables 18 and 19), and all chronic RQs are below the 

chronic risk LOC (Table 18). Therefore, acute and chronic risks resulting in adverse effects on growth, 

reproduction, and survival of avian species are not expected for the maximum application scenarios 

considered in this assessment. 

Relative to the use patterns identified in this assessment, exposure of terrestrial organisms to zetacypermethrin spray applications is expected to result in acute dose-based risk to listed mammals (Table 

20), and chronic dose-based risk to listed and non-listed mammals (Table 21), but not chronic dietarybased risk to listed or non-listed species (Table 22). Acute dietary-based risk to mammals is not typically 

evaluated, and was not estimated in this risk assessment. 

Given the moderate toxicity of zeta-cypermethrin in mammals (LDS0 = 86 mg a.i./kg body weight) and the 

adverse effects of zeta-cypennethrin on body weight and body weight gain in parents and offspring in the 

available 2- and 3-generation reproduction studies in rats (NOAEC = 100 mg a.i./kg diet or 5 mg a.i./kg 

body weightlday), acute and chronic risks to malnmalian species resulting from exposure to spray 

applications of zeta-cypermethrin were expected. Acute risks (listed species only) to 15g and 35g 

mammals feeding on short grass under all scenarios except the barley scenario are anticipated. Risk 

appears to be highest for mammals exposed under the stone fruits scenario, and lowest for those exposed 

under the barley scenario. Based on the highest acute dose-based RQ value of 0.16, a zeta-cypermethrin 

application rate about one-half of the proposed rate (<0.03 Ib a.i.1A) would be required to ensure that all 

acute RQ values for spray applications of zeta-cypenllethrin are less than the acute LOCs for all terrestrial 

organisms. 

Although no dietary-based chronic RQs for mammals exceed the chronic LOC, the potential for chronic 

dose-based risk was identified for mammals feeding on short grass, tall grass, and broadleaf plantslsmall 
insects (Table 21). Dose-based chronic RQs exceed the LOC for chronic risk (LOC 1) for all modeled 

crop uses for exposure via short grass. For mammals feeding on tall grass, dose-based chronic RQs exceed 

the chronic LOC for the stone fruits and canola scenarios, but not for the non-grass animal feeds or barley 

scenarios. For mammals feeding on broadleaf plantslinsects, dose-based chronic exceed the chronic LOC 

for the stone fruits, canola, and non-grass animal feeds scenarios, but not for the barley scenario. All RQs 

for mammals feeding on fruitslpodsllarge insects and seeds are below the chronic LOC. 

Based on these analyses, zeta-cypermethrin exposure resulting from the proposed uses has the potential for 

chronic effects to mammals, including decreased body weight and decreased body weight gain in adults 

and offspring. The estimated upper-bound dose-based EEC (-3 1 mglkg bwlday) on short grass for small 

mammals under the most conservative application scenario considered in this risk assessment (stone fruits 

scenario; application rate of 0.05 lb a.i./A, 6 applications, and a 7-day interval) is about three times higher 

than the adjusted NOAEL for small mammals (-1 1 mgikg bwlday). Based on the highest chronic RQ value 

of 2.73, a zeta-cypennethrin application rate of <0.018 lb a.i.1A would be required to ensure that chronic 

RQ values are less than the chronic LOCs for all mammals. 

One source of uncertainty for this risk assessment is that the dietary-based chronic RQs suggest a lower 

risk to inammals than do the dose-based chronic RQs. In general, dose-based estimates of toxicity are the 

basis of risk conclusions since they are body-weight specific and typically present a more conservative 

estimate of risk (higher RQs), although the dietary-based estimates do provide further insight into potential 

risks of some compounds. The dose-based approach considers the uptake and absorption kinetics of a 

gavage toxicity study to approximate exposure associated with uptake from a dietary matrix. Toxic 

response is a function of duration and intensity of exposure. For many compounds a gavage dose 

represents a very short-term high intensity exposure. Although the dose-based estimates may not reflect 

reality in that animals do not receive a gavage while feeding, it is possible that a short-duration, highintensity exposure could occur associated with feeding on an agricultural field since many animals may 

gorge themselves when food items are available. While the dietary-based estimates may suggest greater 

"realism", they too suffer from some uncertainties. Primarily, the dietary-based approach assumes that 

animals in the field are consuming food at a rate similar to that of confined laboratory animals despite the 

fact that energy content in food items differs between the field and the laboratory as does the energy 

requirements of wild and captive animals. 

To bound the estimates of risk to mammals resulting from acute and chronic exposure to zetacypermethrin, RQs using mean Kenaga residue values rather than upper-bound values were calculated. 

Using the non-conservative mean residue values, implying that higher predicted residue values are 

expected half the time, the acute LOC is not exceeded for mammals based on the acute dose-based risk 

quotients (RQ range = <0.01 to 0.07) when mean Kenaga residue values are used. In addition, the chronic 

LOC is not exceeded for mammals based on the dose-based risk quotients (RQ range = <0.01 to 0.96) or 

the dietary-based RQs (RQ range = 0.01 to 0.1 1) when mean residues are used. However, relying on the 

mean Kenaga residue values for calculating RQs would not protect birds and mammals that consume food 

items that have residues on the higher end of the residue distribution. An analysis of the residue 

distribution for the different food items using input values from Fletcher et al. (1 994) and assuming a lognormal distribution of residues on food items shows that the inean Kenaga values range from about the 62- 

87 percentile indicating that up to 38% of the higher-end food item residue estimates are not captured by 

using the inean Kenaga values. In contrast, for the upper-end Kenaga residue estimates, about 3-13% of 

the upper-end residue estimates were not captured. This highlights the fact that the upper-end Kenaga 

values are not a maximum exposure level. 
b. Granular Applications: Acute and Chronic Risk to Birds and 

Mammals 

Birds and mammals in the field may be exposed to granules treated with pesticides by ingesting material 

directly with the diet. They also may be exposed by other routes, such as incidental ingestion of 

contaminated soil, dermal contact with treated granular surfaces and soil during activities in the treated 

areas, preening activities, and ingestion of drinking water contaminated with pesticide. To estimate risk 

resulting from granular applications of zeta-cypermethrin to turf in this risk assessment, ingestion of 

granules and consumption of terrestrial invertebrates that have bioconcentrated pesticide residues were 

considered as routes of exposure. 

Although none of the acute LOCs are exceeded for avian species of any size, exposure of terrestrial 

organisms to granular zeta-cypermethrin applied to turf is expected to result in acute risk to both listed and 

non-listed lna~nlnals (Table 23). Specifically, based on the ~~~~lft' method given in the T-REX model, 

acute RQs (~~~~lft') suggest that granular applications of zeta-cypermethrin may pose an acute risk to 15g 

and 35g mammals, but not to 1000g mammals; the RQ for 15g mammals exceeds the LOCs for acute risk, 

acute restricted use, and acute endangered species, while the RQ for 35g mammals exceeds the LOCs for 

acute restricted use and acute endangered species. Based on the highest RQ value of 0.83, a zetacypermethrin application rate of about 0.025 lb a.i.1A would be required to ensure that all acute RQ values 

for granular applications of zeta-cypermethrin are less than the acute LOCs for all terrestrial organisms. 

Terrestrial chronic exposure estimates and risks for granular applications of zeta-cypermethrin derived 

according to a fugacity-based (equilibrium partitioning) approach (Appendix D) demonstrate that chronic 

risks to birds and lnainmals associated with ingestion of terrestrial invertebrates that have bioaccumulated 

zeta-cyperrnethrin granules are not expected based on a comparison of the estimated earthwonn residue 

(4.8 mg a.i./kg diet) with the avian and mammalian chronic dietary endpoints (50 and 100 mg a.i./kg diet, 

respectively); RQs are less than the chronic risk LOC (1). In addition, based on a comparison of estimated 

chronic doses for insectivorous malnmals and adjusted NOAELs, it does not appear likely that chronic risk 

will result from exposure to granular zeta-cypemethrin for all three size classes of mammals (Table 24). 

There are a number of uncertainties associated with the estimations of zeta-cypermethrin concentrations in 

earthworm tissue and subsequent risks to insectivorous terrestrial wildlife that need to be discussed. First, 

a zeta-cypermethrin concentration averaged over a 7.6-cm soil (3-inch) depth was used to reflect a 

concentration across the earthwonn occupied area of soil. However, in some instances it is possible that 

earthworms may be restricted to shallower depths; therefore, exposure and risk estimates based on a 7.6 cm 

averaging depth assumption could potentially underestimate exposure and risk depending on the actual 

depth of earthworm occupied soil. For instance, if concentrations were averaged over a 1-cm soil depth, 

the estimated earthworm residue would be 36.5 ppm, and there would be potential for chronic risk 

resulting from exposure to granular zeta-cypermethrin; chronic RQ values would range from 1.42 for 

1000g mammals to 3.16 for 15g mammals. In fact, it has been estimated that if soil concentrations were 

averaged over depths of 53.2 cm, there would be chronic risks to mammals associated with ingestion of 

terrestrial invertebrates that have bioaccumulated zeta-cypennethrin granules. 

Second, the fugacity-based model assumes equilibrium partitioning between bulk soil and soil pore water. In 

addition, the model assumes a fixed value for soil density, earthworm density, temperature, pore space, organic 

carbon, and the lipid content of the earthworm. Resulting concentrations of zeta-cypermethrin in earthwonn 

tissue may be either under- or over-estimated depending on the soil type, temperature, and sizellipid content of 

the earthworm, at the time of exposure. 
And lastly, this assessment considers only one route of chronic exposure (i.e., ingestion of terrestrial 

invertebrates that have bioaccumulated zeta-cypermethrin from granules in the soil) for insectivorous birds and 

mammals. In addition, it is assumed that 100% of the diet is comprised of terrestrial soil invertebrates. Given 

species-specific feeding habits and dietary requirements, this assumption may overestimate risks associated 

with ingestion of soil invertebrates that have accumulated zeta-cypermethrin. Other potential routes of 

exposure including direct ingestion of granules, ingestion of granules that adhere to soil invertebrates, 

partitioning of dissolved zeta-cypermethrin to sources of wildlife drinking water, and dermal exposure of 

granules released to surrounding soil and puddles or combined routes of exposure were not considered. 

Although this model shows that risk to birds and mammals strictly exposed to only bioaccumulated zetacypermethrin in terrestrial invertebrates is low, it is unknown whether other routes of exposure or aggregate 

routes of exposure would result in unacceptable risk for avian or mammalian receptors. 

c. Non-Target Terrestrial Invertebrates 

Although EFED does not quantitatively estimate risk to non-target terrestrial invertebrates, risks can be 

assessed qualitatively. This hazard assessment shows that zeta-cypermethrin exposure can be expected to 

result in acute toxicity to honey bees and is considered to be highly toxic on both a contact (LDSo = 0.023 

ug a.i./bee) and an oral basis (LDSo = 0.172 ug a.i.ibee). In addition, results of an acute study with 

earthworms yielded a 48-hour contact LCs0 value of 26.09 ug a.i./cm2 for cypermethrin applied to filter 

paper, categorizing cypermethrin and zeta-cypemethrin as very toxic to earthworms. This rate is 

equivalent to 2.32 lb a.i./A, a rate about ten times the single maximum application rate of granular zetacypermethrin (0.225 Ib a.i./A), and almost 8 times the maximum annual application rate for spray 

applications of zeta-cypermethrin (0.3 lb a.i./A). Based on the data available at this time, acute and 

chronic toxic effects to non-target insects and terrestrial invertebrates resulting from the proposed zetacypermethrin uses cannot be precluded and risk is presumed. 

d. Terrestrial Plants 

No data were available to evaluate the risk of zeta-cypermethrin exposure to non-target terrestrial plants; 

however, EFED is not concerned about the level of phytotoxicity of zeta-cypermethrin products because 

zeta-cypermethrin's neural toxic mode of action is not expected to be a phytotoxic concern. In addition, 

based on the lack of studies demonstrating adverse effects of zeta-cypermethrin or any other pyrethroid to 

terrestrial plants, and the fact that no incident reports have reliably linked any other compound in the 

synthetic pyrethroid class of chemicals to phytotoxic effects despite being applied on or near agricultural 

plants, it appears unlikely that zeta-cypermethrin poses a phytotoxic concern. 

Review of Incident Data 

Incident reports submitted to EPA since approximately 1994 have been tracked by assignment of "incident 

numbers" in an Incident Data System (IDS), microfiched, and then entered to a second database, the 

Ecological Incident Information System (EIIS). An effort has also been made to enter information to EIIS 

on incident reports received prior to establishment of current databases. Incidents entered into EIIS are 

categorized into one of several certainty levels: highly probable, probable, possible, unlikely, or unrelated. 

In brief, "highly probable" incidents usually require carcass residues, substantial ChE inhibition in avian 

and/or mammalian species, andlor clear circumstances regarding the exposure. "Probable" incidents 

include those where residues were not available and/or circumstances were less clear than for "highly 

probable." "Possible" incidents include those where multiple chemicals may have been involved and it is 

not clear what the contribution was of a given chemical. The "unlikely" category is used, for example, 

where a given chemical is practically nontoxic to the category of organism killed and/or the chemical was 
tested for but not detected in samples. "Unrelated incidents are those that have been confirmed to be not 

pesticide-related. 

Incidents entered into the EIIS are also categorized as to use/misuse. Unless specifically confirmed by a 

state or federal agency to be misuse, or there was very clear misuse such as intentional baiting to kill 

wildlife, incidents would not typically be considered misuse. Data entry personnel often do not have a 

copy of the specific label used in a given application, and would not usually be able to detect a variety of 

label-specific violations, for example. 

The number of documented kills in EIIS are believed to be a very small fraction of total mortality caused 

by pesticides. Mortality incidents must be seen, reported, investigated, and have investigation reports 

submitted to EPA to have the potential for entry into the database. Incidents often are not seen, due to 

scavenger removal of carcasses, decay in the field, or simply because carcasses may be hard to see on many 

sites andlor few people are systematically looking. Poisoned birds may also move off-site to less 

conspicuous areas before dying. Incidents seen may not get reported to appropriate authorities capable of 

investigating the incident because the tinder may not know of the importance of reporting incidents, may 

not know who to call, may not feel they have the time or desire to call, may hesitate to call because of their 

own involvement in the kill, or the call may be long-distance and discourage callers, for example. 

Incidents reported may not get investigated if resources are limited or may not get investigated thoroughly, 

with residue analyses, for example. Also, if kills are not reported and investigated promptly, there will be 

little chance of documenting the cause, since tissues and residues may deteriorate quickly. Reports of 

investigated incidents often do not get submitted to EPA, since reporting by states is voluntary and some 

investigators may believe that they don't have the resources to submit incident reports to EPA. An effort 

has also been made to enter information to EIIS on incident reports received prior to establishment of 

current databases. Although many of these have been added, the system is not yet a complete listing of all 

incident reports received by EPA. 

In addition, there are a number of uncertainties associated with the data that are reported. Incident reports 

are not received in a consistent format (e.g., states and various laboratories usually have their own 

formats), may involve multiple incidents involving multiple chemicals in one report, and may report on 

only part of a given incident investigation (e.g., residues). While some progress has been made in recent 

years, both in getting incident reports submitted and entered, there has never been the level of resources 

assigned to incidents that there has been to the tracking and review of laboratory toxicity studies, for 

example. This adds to the reasons cited above for why EPA believes the documented kills are but a 

fraction of total mortality caused by pesticides. Incident reports associated with zeta-cypermethrin are 

summarized below and in Appendix J. 

a. Incidents Involving Aquatic Organisms 

No incidents involving aquatic organisms have been identified for zeta-cypermethrin. 

b. Incidents Involving Terrestrial Organisms 

A total of 2 incidents involving terrestrial exposure have been reported to EPA and tracked by EIIS 

(Appendix J, Table J-1). Incident reports show there is one "possible" allegation, and one "unlikely" 

allegation, that zeta-cypermethrin containing products applied to alfalfa caused mortality to honey bees. 

The "possible" incident was based on a report from a bee keeper on 8/8/2002 that 6 of a pre-existing 32 

hives disappeared, and 8 of the remaining hives were queenless and failing. In addition, an erratic or 

spotty brood pattern was common. An alfalfa field 2.75 miles from the bee keeper's yard was treated 23 

days prior to the observations with the zeta-cypermethrin containing product, Fur*. No traces of zeta- 
cypermethrin were detected when pollen samples were taken and analyzed, although the insecticide 

coumaphos was identified. 

The second and "unlikely" incident was based on a report from a bee keeper on 9/4/2002 that dead bees 

were detected in his yard, despite that 7 days prior all hives were fine. A nearby alfalfa field had been 

treated 50 days prior to the observed symptoms with zeta-cyperinethrin containing product, Fur*. No 

traces of zeta-cypermethrin were detected when pollen and bee tissue samples were taken and analyzed, 

although the insecticide coumaphos was identified at unspecified levels. 

No information regarding application rate, residue analysis, or time of event relative to application was 

provided for either of these incidents. In addition, other pesticides were identified as being present while 

zeta-cyperinethrin was not. Therefore, the strength of these incidents involving exposure of terrestrial 

organisms as an additional line of evidence for this assessment is highly uncertain. 

4. Endocrine Effects 

Results of the available toxicity studies show that zeta-cypermethrin does not appear to affect reproductive 

parameters in birds or mammals (effects on rats reflected a decrease in pup body weight and body weight 

gain), but does adversely affect the reproduction of aquatic species (decreased number of offspring in 

estuarinelinarine invertebrates). 

Under the Federal Food, Drug and Cosmetic Act (FFDCA), as amended by the Food Quality Protection 

Act (FQPA), EPA is required to develop a screening program to determine whether certain substances 

(including all pesticide active and other ingredients) "may have an effect in humans that is similar to an 

effect produced by a naturally-occurring estrogen, or other such endocrine effects as the Administrator may 

designate." Following the recommendations of its Endocrine Disruptor Screening and Testing Advisory 

Committee (EDSTAC), EPA determined that there was scientific basis for including, as part of the 

program, the androgen- and thyroid hormone systems, in addition to the estrogen hormone system. EPA 

also adopted EDSTAC's recorninendation that the Program include evaluations of potential effects in 

wildlife. For pesticide chemicals, EPA will use FIFRA and, to the extent that effects in wildlife may help 

determine whether a substance may have an effect in humans, FFDCA authority to require the wildlife 

evaluations. As the science develops and resources allow, screening of additional hormone systems may 

be added to the Endocrine Disruptor Screening Program (EDSP). When the appropriate screening and or 

testing protocols being considered under the Agency's Endocrine Dismptor Screening Program have been 

developed, zeta-cyperinethrin may be subjected to additional screening and or testing to better characterize 

effects related to endocrine disruption. 

5. Threatened and Endangered Species Concerns 

a. Action Area 

For listed species assessment purposes, the action area is considered to be the area affected directly or 

indirectly by the Federal action and not merely the immediate area involved in the action. At the initial 

screening-level, the risk assessment considers broadly described taxonomic groups and so conservatively 

assumes that listed species within those broad groups are collocated with the pesticide treatment area. This 

means that terrestrial plants and wildlife are assumed to be located on or adjacent to the treated site and 

aquatic organisms are assumed to be located in a surface water body adjacent to the treated site. The 

assessment also assumes that the listed species are located within an assumed area which has the relatively 

highest potential exposure to the pesticide, and that exposures are likely to decrease with distance from the 

treatment area. Section III(A) of this risk assessment presents the pesticide use sites that are used to 

establish initial collocation of species with treatment areas. 
If the assumptions associated with the screening-level action area result in RQs that are below the listed 

species LOCs, a "no effect" determination conclusion is made with respect to listed species in that taxa, 

and no further refinement of the action area is necessary. Furthermore, RQs below the listed species LOCs 

for a given taxonomic group indicate no concern for indirect effects upon listed species that depend upon 

the taxonomic group covered by the RQ as a resource. However, in situations where the screening 

assu~nptions lead to RQs in excess of the listed species LOCs for a given taxonomic group, a potential for a 

"may affect" conclusion exists and may be associated with direct effects on listed species belonging to that 

taxono~nic group or may extend to indirect effects upon listed species that depend upon that taxonoinic 

group as a resource. In such cases, additional information on the biology of listed species, the locations of 

these species, and the locations of use sites could be considered to determine the extent to which screening 

assumptions regarding an action area apply to a particular listed organism. These subsequent refinement 

steps could consider how this information would impact the action area for a particular listed organisin and 

may potentially include areas of exposure that are downwind and downstream of the pesticide use site. 

Table 25 summarizes the potential concerns for direct and indirect adverse effects to federally-listed 

threatened or endangered plants and animals (listed species) due to the proposed uses of zeta-cypermethrin. 

Table 25. Listed species risks associated with direct or indirect effects due to applications of zetacypermethrin. 

Listed Taxon 

Te~~estrial and 

Semi-Aquatic 

Plants - lnonocots 

and dicots 

Beneficial 

Insects~e~restrial 

Invettebrates 

Birds, Reptiles, 

and Terrestrialphase amphibians1 

Mammals 

Aquatic Vascular 

Plants 

Direct 

Effects 

No 

Yes 

No 

No 

Basis for Direct Effects 

Conclusion 

Although toxicity data are not available to 

evaluate the risk of zeta-cypemethrin 

exposure to non-target te~restrial and scmiaquatic plants, EFED is not concerned 

about the level of phytotoxicity of zetacypennethrin products because zetacypennethrin's neural toxic mode of action 

is not expected to be a phytotoxic concetm. 

In addition, based on the lack of studies 

demonstrating adverse effects of zetacypennethrin or any other pyl-ethroid to 

plants, and the fact that no incident reports 

have reliably linked zeta-cypennethrin or 

any other compound in the synthetic 

pyrethroid class of chemicals to phytotoxic 

effects in tctrestrial or semi-aquatic plants, 

it appears unlikely that zeta-cype~methrin 

poses a phytotoxic concem. 

Zeta-cypennethrin is registered as an 

insecticide and is highly toxic to non-target 

insects; therefore, potential risk to nontarget insects is anticipated. 

l'he acute endangered species LOC and 

chronic risk I.OC were not exceeded. 

The acute endangered species L.OC and 

chronic risk LOC were exceeded. 

Although toxicity data are not available to 

evaluate the tisk of zeta-cypennethrin 

exposure to non-target vascular plants, 

EFED is not concerned about the level of 

phytotoxicity of zeta-cype~methrin 

products because zeta-cype~methrin's 

neural toxic mode of action is not expected 

Indirect 

Effects 

Yes 

Yes 

Yes 

Yes 

Yes 

Basis for Indirect Effects 

Conclusion 

Potential for indirect effects to plants 

based on potential effects to mammals or 

insectslinvertebrates as pollinators or 

seed dispetsers 

lndirect effects to beneficial insects may 

occur ham potential direct effects to 

insectivorous mammals. 

Indirect effects to birds may occur from 

potential direct effects to te~~est~ial 

insects/invertebrates or mammals. 

lndirect effects to mammals may occur 

from direct effects to tet~estrial 

insectslinve~tebrates. 

Potential indirect effects to aquatic plants 

may occur froin direct effects to 

pollinators, dispersers, and/or 

consumers. 
b. Taxonomic Groups Potentially at Risk 

Freshwater and 

Estuarine1 Marine 

Fish and Aquaticphase 

~rn~hibians' 

Freshwater and 

EstuarineIMarine 

Invertebrates 

Aquatic 

Nonvascular 

Plants - algae and 

diatotns 

I Birds are used as 

The Level I screening assessment process for listed species uses the generic taxonomic group-based 

process to make inferences on direct effect concerns for listed species. The first iteration of reporting the 

results of the Level I screening is a listing of pesticide use sites and taxonomic groups for which RQ 

calculations reveal values that meet or exceed the listed species LOCs. In the majority of cases, screeninglevel risk assessments report RQ calculations for the following broad taxonomic groupings: 

Birds (also used as surrogate for terrestrial-phase amphibians and reptiles) 

Mammals 

Freshwater fish (also used as a surrogate for aquatic phase amphibians) 

Freshwater invertebrates 

Estuarinelmarine fish 

Estuarinelmarine invertebrates 

Terrestrial plants 

Algae and aquatic plants 

reptilian, and amphibian species are considered equivalent. ' Fish are used as a su~~ogate for aquatic phase amphibians; therefore, potential direct and indirect efl'ects to endangered fish and amphibian species are 

considered equivalent. 

Yes 

Yes 

No 

sumgate species 

to be a phytotoxic concem. In addition, 

based on the lack of studies detnonst~ating 

adverse effects of zeta-cypeiinethrin or any 

other pyrethroid to plants. and the fact that 

no incident reports have reliably linked 

zeta-cype~inethrin or any other compound 

in the synthetic pyrethroid class of 

chemicals to phytotoxic effects in aquatic 

vascular plants, it appears unlikely that 

zeta-cypennethrin poses a phytotoxic 

concetn. 

The acute risk LO(', but not the chronic 

risk LOC, was exceeded. 

The acute risk LOC and chronic risk LOC 

were exceeded. 

Although toxicity data are not available to 

evaluate the risk of zeta-cypermethlin 

exposure to non-target aquatic nonvascular 

plants, EFED is not concerned about the 

level of phytotoxicity of zeta-cype~inethrin 

products because zeta-cypeimethrin's 

neural toxic inode of action is not expected 

to be a phytotoxic concetn. In addition, 

based on the lack of studies demonstrating 

adverse effects of zeta-cype~methrin or any 

other pyethroid to plants. and the fact that 

no incident reports have reliably linked 

zeta-cype~inethrin or any other compound 

in the synthetic pyrethroid class of 

chemicals to phytotoxic effects in aquatic 

nonvascular plants. it appears unlikely that 

zeta-cypermethrin poses a phytotoxic 

concem. 

for terrestrial-phase amphibians and reptiles; 

Yes 

Yes 

Yes 

therefore, potential direct 

Potential indirect effects to fish and 

amphibians may occur from direct 

effects to aquatic invertebrates or 

mam~nals. 

Potential indirect effects to aquatic 

invertebrates tnay occur from direct 

effects to fish. 

Indirect effects to aquatic nonvascular 

plants are possible; however, there are no 

listed aquatic nonvascular plants in the 

endangered species database. 

and indirect effects to endangered avian. 
I. Discussion of Risk Quotients 

Should estimated exposure levels occur in proximity to listed resources, the available screening level 

infonnation suggests a potential concern for direct effects to listed fish (freshwater and estuarinelmarine), 

aquatic-phase amphibian, invertebrate (freshwater and estuarinelmarine), beneficial insect/terrestrial 

invertebrate, and mammalian species associated with areas where zeta-cypermethrin is employed for the 

proposed uses in this assessment (Table 6). More specifically, the available screening level information 

indicates the following: 

Based on the toxicity data for all cypermethrin products (alpha-, beta-, theta-, and zetacypermethrin), zeta-cypermethrin granular applications result in acute RQs exceeding acute 

restricted use and acute endangered species LOCs for freshwater fish. 

Based on the toxicity data for all cypermethrin products (alpha-, beta-, theta-, and zetacypermethrin), zeta-cypermethrin spray applications result in acute RQs exceeding acute risk, 

acute restricted use, and acute endangered species LOCs for fish (freshwater and 

estuarinelmarine). 

Based on the toxicity data for all cypermethrin products (alpha-, beta-, theta-, and zetacypermethrin), zeta-cypermethrin granular and spray applications result in acute RQs exceeding 

acute risk, acute restricted use, and acute endangered species LOCs for invertebrates 

(estuarinelmarine and freshwater invertebrates). 

Based on the toxicity data for all cypermethrin products (alpha-, beta-, theta-, and zetacypermethrin), zeta-cypennethrin granular and spray applications result in RQs exceeding the 

chronic risk LOC for all invertebrates (estuarinelmarine and freshwater invertebrates). 

Based on the toxicity data for all cypermethrin products (alpha-, beta-, theta-, and zetacypennethrin), zeta-cypennethrin granular and spray applications result in acute and chronic RQs 

exceeding all LOCs for benthic organisms. 

Based on the toxicity data for all cypermethrin products (alpha-, beta-, theta-, and zetacypermethrin), risk to terrestrial invertebrates (including non-target beneficial insects and 

earthworms) resulting from zeta-cypemethrin granular and spray applications cannot be precluded 

at this time. 

Based on the toxicity data for all cypermethrin products (alpha-, beta-, theta-, and zetacypermethrin), zeta-cypermethrin granular applications result in acute RQs exceeding acute risk, 

acute restricted use, and acute endangered species LOCs for mammals. 

Based on the toxicity data for all cypennethrin products (alpha-, beta-, theta-, and zetacypermethrin), zeta-cypermethrin spray applications result in acute dose-based RQs exceeding the 

acute endangered species LOC for mammals. 

Based on the toxicity data for all cypermethrin products (alpha-, beta-, theta-, and zetacypermethrin), zeta-cypermethrin spray applications result in chronic dose-based RQs exceeding 

the chronic LOC for mammals. 
ii. Probit Dose Response Relationship 

The Agency uses the probit dose response relationship as a tool for providing additional information on the 

listed animal species acute levels of concern. Acute listed species LOCs of 0.1 and 0.05 are used for 

terrestrial and aquatic animals, respectively. As part of the risk characterization, an interpretation of acute 

LOCs for listed species is discussed. This interpretation is presented in terms of the chance of an 

individual event (i.e., mortality or immobilization) should exposure at the estimated environmental 

concentration actually occur for a species with sensitivity to zeta-cypermethrin on par with the acute 

toxicity endpoint selected for RQ calculation. To accomplish this interpretation, the Agency uses the slope 

of the dose response relationship available from the toxicity study used to establish the acute toxicity 

measures of effect for each taxonomic group. The individual effects probability associated with the LOCs 

is based on the mean estimate of the slope and an assumption of a probit dose response relationship. In 

addition to a single effects probability estimate based on the mean, upper and lower estimates of the effects 

probability are also provided to account for variance in the slope. The upper and lower bounds of the 

effects probability are based on available information on the 95% confidence interval of the slope. A 

statement regarding the confidence in the estimated event probabilities is also included. Studies with good 

probit lit characteristics (i.e., statistically appropriate for the data set) are associated with a high degree of 

confidence. Conversely, a low degree of confidence is associated with data from studies that do not 

statistically support a probit dose response relationship. In addition, confidence in the data set may be 

reduced by high variance in the slope (i.e., large 95% confidence intervals), despite good probit fit 

characteristics. 

Lndividual effect probabilities are calculated based on an Excel spreadsheet tool IECV1.l (Individual 

Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental Fate and Effects 

Division (June 22, 2004). The model allows for such calculations by entering the mean slope estimate 

(and the 95% confidence bounds of that estimate) as the slope parameter for the spreadsheet. In addition, 

the LOC (0.1 for terrestrial animals and 0.05 for aquatic animals) is entered as the desired threshold. The 

chance of an individual event corresponding to the listed species acute LOCs is calculated based on the 

formula logLCk = logLCSO+(z/b), where z is the standard normal deviate and b equals the slope. It is 

important to note that the IEC model output can estimate an event probability as low as 1 in 1 x 1 016. This 

cut-off is a limit in the Excel spreadsheet environment and is not to be interpreted as an agreed upon lower 

bound threshold for concern for individual effects in any given listed species. 

If an LDjo or LCso has been established for a particular taxonomic group, but information is unavailable to 

estimate a slope from a study, a default slope assumption of 4.5 is used as per original Agency assumptions 

of typical slope cited in Urban and Cook (1 986). In instances where an LC5() or LDjO has not been 

established for a particular taxonomic group, an individual effects probability is not estimated. 

Freshwater Fish (MRID 44546027) 

Based on an assumption of a probit dose response relationship with a mean estiinated slope of 38.9, the 

corresponding estimated chance of individual mortality associated with the listed species LOC of 0.05 the 

acute toxic endpoint for freshwater fish is -1 in 1.0 x 10': It is recognized that extrapolation of very low 

probability events is associated with uncertainty in the resulting estimates. To explore possible bounds to 

such estimates, the upper and lower values for the mean slope estimate (-363560 to 363637) were used to 

calculate upper and lower estimates of the effects probability associated with the listed species LOC. 

These values are -1 in 1 and -1 in 1.0 x 1016, respectively. 

Although the Agency has assumed a probit dose response relationship in establishing the listed species 
LOCs, the available data for the toxicity study generating RQs for this taxonomic group do not statistically 

support a probit dose response relationship (Pearson Chi-Square; p < 0.001) and so the confidence in 

estimated event probabilities based on this dose response relationship and the listed species LOC is low. 

Freshwater Invertebrates (MRID 44423501) 

Based on an assumption of a probit dose response relationship (Pearson Chi-Square; p = 0.99) with a 

mean estimated slope of 4.5, the corresponding estimated chance of individual mortality associated with 

the listed species LOC of 0.05 the acute toxic endpoint for freshwater invertebrates is -1 in 4.18 x lo8. 

It is recognized that extrapolation of very low probability events is associated with uncertainty in the 

resulting estimates. To explore possible bounds to such estimates, the upper and lower values for the mean 

slope estimate (2.3 to 6.7) were used to calculate upper and lower estimates of the effects probability 

associated with the listed species LOC. These values are -1 in 722 and -1 in 6.99 x 1017, respectively. 

EstuarineIRIarine Invertebrates (Acc. No. 070562) 

Based on an assumption of a probit dose response relationship with a mean estimated slope of 3.74, the 

corresponding estimated chance of individual mortality associated with the listed species LOC of 0.05 the 

acute toxic endpoint for estuarinelmarine invertebrates is -1 in 1.75 x lo6. It is recognized that 

extrapolation of very low probability events is associated with uncertainty in the resulting estimates. To 

explore possible bounds to such estimates, the upper and lower values for the mean slope estimate (1.2 to 

6.3) were used to calculate upper and lower estimates of the effects probability associated with the listed 

species LOC. These values are -1 in 16.9 and -1 in 8.08~ 10'" respectively. 

Although the Agency has assumed a probit dose response relationship in establishing the listed species 

LOCs, the available data for the toxicity study generating RQs for this taxonomic group do not statistically 

support a probit dose response relationship (Pearson Chi-Square; p = 0.003) and so the confidence in 

estimated event probabilities based on this dose response relationship and the listed species LOC is low. 

EstuarineIMarine Fish (MRID 90075) 

Based on an assumption of a probit dose response relationship with a mean estimated slope of 54.6, the 

corresponding estimated chance of individual mortality associated with the listed species LOC of 0.05 the 

acute toxic endpoint for estuarinelmarine fish is -1 in 1 x 1016. It is recognized that extrapolation of very 

low probability events is associated with uncertainty in the resulting estimates. To explore possible bounds 

to such estimates, the upper and lower values for the mean slope estimate (-557139 to 557248) were used 

to calculate upper and lower estimates of the effects probability associated with the listed species LOC. 

These values are -1 in 1 and -1 in 1.0 x 1016, respectively. 

Although the Agency has assumed a probit dose response relationship in establishing the listed species 

LOCs, the available data for the toxicity study generating RQs for this taxonomic group do not statistically 

support a probit dose response relationship (Pearson Chi-Square; p < 0.001) and so the confidence in 

estimated event probabilities based on this dose response relationship and the listed species LOC is low. 

Benthic Invertebrates (MRID 44074406) 

Based on an assumption of a probit dose response relationship (Pearson Chi-Square; p = 0.86) with a 

mean estimated slope of 4.2, the corresponding estimated chance of individual mortality associated with 

the listed species LOC of 0.05 the acute toxic endpoint for freshwater benthic invertebrates is -1 in 4.30 

x lo7. It is recognized that extrapolation of very low probability events is associated with uncertainty in 

the resulting estimates. To explore possible bounds to such estimates, the upper and lower values for the 
mean slope estimate (3.1 to 5.3) were used to calculate upper and lower estimates of the effects probability 

associated with the listed species LOC. These values are -1 in 3.63 x lo4 and -1 in 3.73 x loL', 

respectively. 

Mammals (MRID 00056800) 

Based on an assumption of a probit dose response relationship (Pearson Chi-Square; p = 0.31) with a 

mean estimated slope of 4.1, the corresponding estimated chance of individual mortality associated with 

the listed species LOC of 0.1 the acute toxic endpoint for mammals is -1 in 4.84 x lo4. It is recognized 

that extrapolation of very low probability events is associated with uncertainty in the resulting estimates. 

To explore possible bounds to such estimates, the upper and lower values for the mean slope estimate (2.0 

to 6.2) were used to calculate upper and lower estimates of the effects probability associated with the listed 

species LOC. These values are -1 in 44 and -1 in 3.54 x lo9, respectively. 

Birds (MRID 90071 and 44546024) 

The available acute toxicity studies (both dietary and dose-based) on avian species were unable to establish 

toxicity values (LCso or LDSo). It was demonstrated that the LCs0 is greater than 2634 ppm and the LDSO is 

greater than 2000 mg a.i./kg-bw with no treatment-related mortality occurring up to these test levels. 

Therefore, this risk assessment is unable to fit a probit dose response relationship to the available data to 

estimate an individual effects probability for avian species based on LCso or LDsO values. 

c. Indirect Effects Analysis 

The Agency acknowledges that pesticides have the potential to exert indirect effects upon the listed 

organisms by, for example, perturbing forage or prey availability, altering the extent of nesting habitat, and 

creating gaps in the food chain. In conducting a screen for indirect effects, direct effect LOCs for each 

taxonomic group are used to make inferences concerning the potential for indirect effects upon listed 

species that rely upon non-endangered organisms in these taxonomic groups as resources critical to their 

life cycle. Species specific concerns for zeta-cypennethrin indirect effects to listed organisms will require 

a determination of the coincidence of zeta-cypennethrin use with locations of listed species and the 

biologically based resources upon which they depend. 

The Agency uses the dose response relationship from the toxicity study used for calculating the RQ to 

estimate the probability of acute effects associated with an exposure equivalent to the EEC (see Probit 

Dose response Relationship above). In instances where infonnation on the dose response is available, it 

serves as a guide to establish the need for and extent of additional analysis that may be performed using 

Services-provided "species profiles" as well as evaluations of the geographical and temporal nature of the 

exposure to ascertain if a "not likely to adversely affect" determination can be made. The degree to which 

additional analyses are performed is commensurate with the predicted probability of adverse effects from 

the comparison of the dose response information with the EECs. The greater the probability that exposures 

will produce effects on a taxa, the greater the concern for potential indirect effects for listed species 

dependant upon that taxa, and therefore, the more intensive the analysis on the potential listed species of 

concern, their locations relative to the use site, and information regarding the use scenario (e.g., timing, 

frequency, and geographical extent of pesticide application). 

Relative to zeta-cypennethrin proposed usage, EFED's screening level analysis shows that there is a 

concern for indirect effects to listed species that may depend upon other taxonomic group for their survival 

(e.g., invertebrates as a food source for listed fish, etc.). This assessment identified the potential for direct 

effects (risks) to beneficial insectslterrestrial invertebrates, mammals, and freshwater and estuarinelmarine 
fish and invertebrates as result of the proposed uses of zeta-cyperrnethrin. Therefore, the nature of the 

toxicological endpoint, Services-provided "species profiles", and further evaluation of the geographical 

and temporal nature of the exposure will need to be considered to determine if a rationale for a "not likely 

to adversely effect" determination is possible. Indirect effects analyses for organisms that depend on 

insects, mammals, fish, and aquatic invertebrates as a critical component of their resource needs are 

described in Table 25. 

d. Critical Habitat 

In the evaluation of pesticide effects on designated critical habitat, consideration is given to the physical 

and biological features (constituent elements) of a critical habitat identified by the U.S Fish and Wildlife 

and National Marine Fisheries Services as essential to the conservation of a listed species and which may 

require special management considerations or protection. The evaluation of impacts for a screening level 

pesticide risk assessment focuses on the biological features that are constituent elements and is 

accoinplished using the screening-level taxonomic analysis (risk quotients, RQs) and listed species levels 

of concern (LOCs) that are used to evaluate direct and indirect effects to listed organisms. 

The screening-level risk assessment has identified potential concerns for indirect effects on listed species 

for those organisms dependant upon freshwater and estuarinelmarine fish and invertebrates, beneficial 

insectslterrestrial invertebrates, and mammals. In light of the potential for indirect effects, the next step for 

EPA and the Service(s) is to identify which listed species and critical habitat are potentially implicated. 

Analytically, the identification of such species and critical habitat can occur in either of two ways. First, 

the agencies could determine whether the action area overlaps critical habitat or the occupied range of any 

listed species. If so, EPA would examine whether the pesticide's potential impacts on non-endangered 

species would affect the listed species indirectly, or directly affect a constituent element of the critical 

habitat. Alternatively, the agencies could determine which listed species depend on biological resources, 

or have constituent elements that fall into the taxa that may be directly or indirectly impacted by the 

pesticide. Then EPA would determine whether use of the pesticide overlaps the critical habitat or the 

occupied range of those listed species. At present, the information reviewed by EPA does not permit use 

of either analytical approach to make a definitive identification of species that are potentially impacted 

indirectly or critical habitats that is potentially impacted directly by the use of the pesticide. EPA and the 

Service(s) are working together to conduct the necessary analysis. 

This screening-level risk assessment for critical habitat provides a listing of potential biological features 

that, if they are constituent elements of one or more critical habitats, would be of potential concern. These 

correspond to the taxa identified above as being of potential concern for indirect effects and include the 

following: freshwater and estuarinelmarine fish and invertebrates, beneficial insects/terrestrial 

invertebrates, and mammals. This list should serve as an initial step in problem formulation for further 

assessment of critical habitat impacts outlined above, should additional work be necessary. 

e. Co-occurrence Analysis 

The goal of the analysis for co-location is to determine whether sites of pesticide use are geographically 

associated with known locations of listed species. At the screening level, this analysis is accomplished using 

the LOCATES database. The database uses location information for listed species at the county level and 

compares it to agricultural census data for crop production at the same county level of resolution. The product 

is a listing of federally listed species that are located within counties known to produce the crop upon which 

the pesticide will be used. Because the Level I screening assessment considers both direct and indirect 

effects across generic taxonomic groupings, it is not possible to exclude any taxonomic group from a 
MRID 65812 

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MRID 89038 

MRID 89039 

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LOCATES database run for a screening level risk assessment. Given the extent of zeta-cypermethrin usage 

across the U.S. for the proposed uses as well as already registered uses (virtually everywhere) and the expected 

large number of listed species that are likely to occur in counties where zeta-cypennethrin is used, a list of 

endangeredlthreatened species and crop acreage at the county level for the taxonomic groups and crops of 

concern is not included in this phase of the risk assessment process. 

Given that the potential extent of zeta-cypermethrin usage for the proposed uses as well as already registered 

uses includes every state, and that all taxonomic groups are included in the initial LOCATES run for a 

screening level risk assessment, Appendix H provides the entire list of endangeredlthreatened species at the 

state level. The registrant must provide information on the proximity of Federally listed birds, fish, mammals, 

amphibians, crustaceans, reptiles, arachnids, insects, plants, snails, and clams to the zeta-cypennethrin use 

sites. This requirement may be satisfied in one of three ways: 1) having membership in the FIFRA Endangered 

Species Task Force (Pesticide Registration [PR] Notice 2000-2); 2) citing FIFRA Endangered Species Task 

Force data; or 3) independently producing these data, provided the information is of sufficient quality to meet 

FIFRA requirements. The information will be used by the OPP Endangered Species Protection Program to 

develop recommendations to avoid adverse effects to listed species. 

C. Description of Assumptions, Limitations, Uncertainties, Strengths and Data Gaps 

1. Exposure For All Taxa 

This screening-level risk assessment relies on best available estimates of environmental fate and 

physicochemical properties, maximum application rate of zeta-cypermethrin, maximum number of 

applications, and the shortest interval between applications. However, several uncertainties and limitations 

are noted and should be considered in interpreting the results of this risk assessment. 

Cypermethrin is an enhanced mixture of four diastereoisomers, each of which is present as 

a pair of enantioiners, resulting in eight isomers. Different ratios of the eight isomers have 

resulted in four different cypennethrin products (alpha-, beta-, theta-, and zetacypermethrin) all of which have similar environmental fate properties. Therefore, the 

Agency has allowed use of the cypermethrin TGAI database to fulfill many registration 

requirements for zeta-cypermethrin and exposure data for all cypermethrin products 

(alpha-, beta-, theta-, and zeta-cypermethrin) have been bridged for risk assessment 

purposes. 

The toxicity assessment for terrestrial and aquatic animals is limited by the number of 

species tested in the available toxicity studies. Use of toxicity data on representative 

species does not provide information on the potential variability in susceptibility acute and 

chronic exposures. 

This screening-level risk assessment relies on labeled statements of the maximum rate of 

cypermethrin application, the maximum number of applications, and the shortest interval 

between applications. These assumptions constitute a maximum use scenario. The 

frequency at which actual uses approach these maximums is dependant on resistance to 

the pesticide, timing of applications, and market forces. 

Although the label stated that zeta-cypennethrin can be applied up to a maximum of 0.3 lb 

a.i./A per season, for this risk assessment, EFED assumed that zeta-cypennethrin was 

applied at a maximum of 0.3 lb a.i./A per year. If there are conditions under which there 

is more than one growing season for a crop within a single year, exposure estimates and 

risk to aquatic organisms could be significantly underestimated. Examples of crops that 
have multiple seasons where this may be a concern include leafy, brassica, and fruiting 

vegetables in CA, AZ, FL, GA, LA, NC, TX, andlor SC. 

2. Exposure For Aquatic Species 

There are a number of uncertainties and model limitations that should be considered in interpreting the 

results of this Tier I1 aquatic exposure assessment, including: 

It is assumed for pesticides, such as zeta-cypermethrin, which may have residential 

outdoor uses (applications to home lawns, gardens, and parks, or termiticide uses applied 

to subterranean environments or for perimeter treatment, etc), that runoff water from rain 

and/or lawn watering may remove pesticide to storm sewers and then directly to surface 

water. However, in general, outdoor residential uses are comprised of multiple, relatively 

small, temporally and spatially variable applications that are not simulated in agricultural 

models. Therefore, there is some uncertainty in the aquatic exposure assessment because a 

model specifically aimed at simulating pesticide fate and transport in a complex urban 

landscape has not yet been developed to generate exposure estimates strictly for urban 

areas. 

For an acute risk assessment, there is no averaging time for exposure. An instantaneous 

peak concentration, with a 1 in 10 year return frequency, is assumed. The use of the 

instantaneous peak assumes that instantaneous exposure is of sufficient duration to elicit 

acute effects comparable to those observed over more protracted exposure periods tested 

in the laboratory, typically 48 to 96 hours. In the absence of data regarding time-to-toxic 

event analyses and latent responses to instantaneous exposure, the degree to which risk is 

overestimated cannot be quantified. 

There are no monitoring studies for zeta-cypermethrin in freshwater or marine; therefore, 

the exposure of aquatic species to zeta-cypennethrin is based entirely on the modeled data. 

It is noted that the fate characteristics of zeta-cypermethrin indicate that it will partition 

with the sediment. Sediment monitoring data are not available either. The output of 

models such as PRZMIEXAMS is dependent upon the quality of the environmental fate 

input parameters. 

For zeta-cypennethrin, the environmental fate database is considered to be complete. 

Estimations regarding the spray drift fraction in the PRZMIEXAMS model runs were 

based upon the assutnption that the wind speeds at each site are generally below 10 mph. 

Meteorological data fiom coastal regions in California where lettuce is grown suggest that 

this assumption may not be accurate for this particular scenario. 

Major uncertainties associated with the standard runoff scenario include the physical 

construct of the watershed and representation of vulnerable aquatic environments for 

different geographic regions. The physicochemical properties (pH, redox conditions, etc.) 

of the standard farm pond are based on a Georgia farm pond. These properties are likely 

to be regionally specific because of local hydrogeological conditions. Any alteration in 

water quality parameters may impact the environmental behavior of a pesticide. The farm 

pond represents a well mixed, static water body. Because the farm pond is a static water 

body (no flow through), it does not account for pesticide removal through flow through or 

water releases. The lack of flow through the farm pond provides an environmental 

condition for accumulation of persistent pesticides. The assumption of uniform mixing 

does not account for stratification due to thermoclines (e.g., seasonal stratification in deep 

water bodies). Additionally, the dimensions of the standard runoff scenario assumes a 
watershed area to water body volume ratio of 10 ha: 20,000m" This ratio is 

recommended to maintain a sustainable constructed pond in the Southeastern United 

States. The use of higher watershed area to water body volume ratios (as recommended 

for sustainable ponds in drier regions of the United States) may lead to higher pesticide 

concentrations when compared to the standard watershed area to water body volume ratio. 

The standard runoff scenario assumes uniform soils and agronomic management practices 

across the standard 10 hectare field. Soils can vary substantially across even small areas; 

this variation is not reflected in the model simulations. Additionally, the impact of unique 

soil characteristics and soil manageinent practices (e.g., tile drainage) are not considered in 

the standard runoff scenario. The assumption of uniform site and manageinent conditions 

is not expected to represent some site-specific conditions. Extrapolating the risk 

conclusions from the standard pond scenario to other aquatic habitats (e.g., marshes, 

streams, creeks, and shallow rivers, intermittent aquatic areas) may either underestimate or 

overestimate the potential risks in those habitats. 

3. Exposure For Terrestrial Species 

The data available to support the terrestrial exposure assessment for zeta-cypermethrin is considered to be 

substantially complete. However, a number of uncertainties and model limitations that should be 

considered in interpreting the results of this terrestrial exposure assessment are discussed below. 

a. Location of Wildlife Species 

For screening terrestrial risk assessments, a generic bird or mammal is assumed to occupy either the treated 

field or adjacent areas receiving the pesticide at a rate commensurate with the treatment rate on the target 

field. This assumption may lead to an overestimation of exposure to species that do not occupy the treated 

field. The actual habitat requirements of any particular terrestrial species are not considered, and it is 

assumed that species occupy, exclusively and permanently, the treated area being modeled. This 

assumption leads to a maximum level of exposure in the risk assessment. 

b. Routes of Exposure 

Screening-level risk assessments for spray applications of pesticides consider dietary exposure alone, and 

assume that 100% of the diet is relegated to single food types foraged only from treated fields. These 

assumptions are likely to be conservative for many species and will tend to overestimate potential risks. 

The assumption of 100% diet from a treated area may be realistic for acute exposures, but long-term 

exposures modeled as single food types composed entirely of material from a treated field is uncertain. It is 

unclear whether other routes of zeta-cyperinethrin exposure or combined routes of exposure would result 

in increased or decreased risk concerns for terrestrial receptors. Other routes of exposure, not considered in 

this assessment, are discussed below. 

I. Incidental Soil Ingestion Exposure 

This risk assessment does not consider incidental soil ingestion. Available data suggests that up to 15% of 

the diet can consist of incidentally ingested soil depending on the species and feeding strategy (Beyer et 

al., 1994). A simple first approximation of soil concentration of pesticide from spray application shows 

the effect of not considering incidental soil ingestion: 

The maximum concentration of the zeta-cypennethrin in the soil can be determined by employing the 

Fugacity Model that was used to assess chronic risk of birds and mammals to granular zeta-cypermethrin 
(Appendix D). Assuming the maximuin exposure scenario (spray application rate of zeta-cypermethrin of 

0.05 lb a.i./A the maximum number of times (6) and with the minimum application interval (7-days) 

applied directly to a bare, very low density soil (1 g/cm3) incorporated tol-cm depth), the maximum 

concentration of zeta-cypermethrin that can be expected to be found in the top 1 -cm of soil is 2.14 mg 

a.i./kg soil. 

Including this concentration into the standard screening-level method and assumptions for food item 

pesticide residues (e.g., 3 1 ppm residue assumption for short grass under the stone fruits scenario) shows 

that ingestion of soil at an incidental rate of up to 15% of the diet would not significantly increase dietary 

exposure. For example, a 20 g bird consumes approximately 22.8 g food daily. The amount of zetacypermethrin ingested from short grass is approximately 0.71 mg (0.0228 kg food consumed x 3 1 ppm in 

food). The amount of zeta-cypermethrin ingested as a result of incidental soil ingestion is approximately 

0.007 mg (0.15 x 0.0228 x 2.14 ppin), which represents about 1% of the total exposure due to eating zetacypermethrin-contaminated food-items. 

ii. Inhalation Exposure 

The screening risk assessment does not consider inhalation exposure. Such exposure may occur through 

three potential sources: (1) spray material in droplet form at the time of application (2) vapor phase 

pesticide volatilizing from treated surfaces, and (3) airborne particulate (soil, vegetative material, and 

pesticide dusts). 

Available data suggest that inhalation exposure at the time of application is not an appreciable route of 

exposure for birds. According to research on mallards and bobwhite quail, respirable particle size in birds 

(particles reaching the lung) is limited to a maximum diameter of 2 to 5 microns. The spray droplet spectra 

covering the majority of pesticide application situations (AgDrift model scenarios for very-fine to coarse 

droplet applications) suggests that less than 1 % of the applied material is within the respirable particle size. 

However, the particles still may be ingested, and the model does not address this. 

Theoretically, inhalation of pesticide active ingredient in the vapor phase may be another source of 

exposure for some pesticides under some exposure situations. However, considering zeta-cypermethrin's 

relatively low vapor pressure value and Henry's Law constant, it is unlikely that zeta-cypermethrin will 

exist in the gaseous phase at levels high enough to cause any adverse effects via inhalation. Therefore, 

volatilization from water and soil surfaces and inhalation is not expected to be an important exposure 

pathway. 

The impact from exposure to dusts contaminated with the pesticide cannot be assessed generically as 

partitioning issues related to application site soils and chemical properties render the exposure potential 

from this route highly situation-specific. 

iii. Dermal Exposure 

The screening assessment does not consider dermal exposure, except as it is indirectly included in 

calculations of RQs based on lethal doses per unit of pesticide treated area. Dermal exposure may occur 

through three potential sources: (1) direct application of spray to terrestrial wildlife in the treated area or 

within the drift footprint, (2) incidental contact with contaminated vegetation, or (3) contact with 

contaminated water or soil. 
The available measured data related to wildlife dermal contact with pesticides are extremely limited. The 

Agency is actively pursuing modeling techniques to account for dermal exposure via direct application of 

spray and by incidental contact with vegetation. 

iv. Drinking Water Exposure 

Drinking water exposure to a pesticide active ingredient may be the result of consumption of surface water 

or consumption of the pesticide in dew or other water on the surfaces of treated vegetation. For pesticide 

active ingredients with a potential to dissolve in runoff, puddles on the treated field may contain the 

chemical. Since zeta-cypennethrin is not highly soluble in water and is expected to adsorb appreciably to 

suspended solids and sediment in the water column, the potential for exposure to zeta-cypermethrin from 

drinking water relative to dietary exposure is likely to be low. 

c. Incidental Pesticide Releases Associated with Use 

This risk assessment is based on the assumption that the entire treatment area is subject to zetacypermethrin application at the rates specified on the label. In reality, there is the potential for uneven 

application of zeta-cypermethrin through such plausible incidents as changes in calibration of application 

equipment, spillage, and localized releases at specific areas of the treated field that are associated with 

specifics of the type of application equipment used (e.g., increased application at turnabouts when using 

older ground application equipment). 

d. Residue Levels Selection 

As discussed earlier in the exposure section of this document, the Agency relies on the work of Kenaga 

and Fletcher et al. (1994) for setting the assumed pesticide residues in wildlife dietary items. The Agency 

believes that these residue assumptions reflect a realistic upper-bound residue estimate, although the 

degree to which this assumption reflects a specific percentile estimate is difficult to quantify. It is 

important to note that the field measurement efforts used to develop the Fletcher estimates of exposure 

involve highly varied sampling techniques. It is entirely possible that much of these data reflect residues 

averaged over entire above ground plants in the case of grass and forage sampling. Depending upon a 

specific wildlife species' foraging habits, whole aboveground plant samples may either underestimate or 

overestimate actual exposure. 

e. Dietary Intake - The Differences Between Lab & Field Conditions 

The acute and chronic characterization of risk rely on comparisons of wildlife dietary residues with LC50 or 

NOAEC values expressed in concentrations of pesticides in laboratory feed. These comparisons assume 

that ingestion of food items in the field occurs at rates commensurate with those in the laboratory. 

Although the screening assessment process adjusts dry-weight estimates of food intake to reflect the 

increased mass in fresh-weight wildlife food intake estimates, it does not allow for gross energy and 

assi~nilative efficiency differences between wildlife food items and laboratory feed. 

On gross energy content alone, direct comparison of a laboratory dietary concentration- based effects 

threshold to a fresh-weight pesticide residue estimate would result in an underestimation of field exposure 

by food consumption by a factor of 1.25 - 2.5 for most food items. Only for seeds would the direct 

comparison of dietary threshold to residue estimate lead to an overestimate of exposure. 
Differences in assimilative efficiency between laboratory and wild diets suggest that current screening 

assessment methods do not account for a potentially important aspect of food requirements. Depending 

upon species and dietary matrix, bird assimilation of wild diet energy ranges from 23 - 80%, and mammal's 

assitnilation ranges from 41 - 85% (U.S. Environmental Protection Agency, 1993). If it is assumed that 

laboratory chow is formulated to maximize assimilative efficiency (e.g., a value of 85%), a potential for 

underestimation of exposure may exist by assuming that consumption of food in the wild is comparable 

with consumption during laboratory testing. In the screening process, exposure may be underestimated 

because metabolic rates are not related to food consumption. 

Finally, the screening procedure does not account for situations where the feeding rate may be above or 

below requirements to meet free living metabolic requirements. Gorging behavior is a possibility under 

some specific wildlife scenarios (e.g., bird migration) where the food intake rate may be greatly increased. 

Kirkwood (1 983) has suggested that an upper-bound limit to this behavior might be the typical intake rate 

multiplied by a factor of 5. 

In contrast, there is the potential for avoidance, operationally defined as animals responding to the presence 

of noxious chemicals in their food by reducing consumption of treated dietary elements. This response is 

seen in nature where herbivores avoid plant secondary compounds. However, reduced food intake, 

particularly over an extended period, could result in reduced survival or reproductive output. 

4. Effects Assessment 

Data gaps, uncertainties, and limitations for the terrestrial and aquatic ecological effects assessment for 

zeta-cypermethrin are summarized as follows: 

As mentioned previously, the Agency has allowed use of the cypermethrin TGAI database 

to fulfill many registration requirements for zeta-cypermethrin, toxicity data for all 

cypennethrin products (alpha-, beta-, theta-, and zeta-cypermethrin) have been bridged for 

risk assessment purposes, and equivalent toxicity has been assumed. 

Results of acute toxicity studies in freshwater fish and invertebrates indicate that the zetacypermethrin degradate 3-phenoxy benzoic acid is much less toxic than the parent 

compound. No information is available on the toxicity of other zeta-cypennethrin 

degradates or on the toxicity of any degradate to terrestrial organisms; therefore, risk 

resulting from exposure to zeta-cypermethrin degradates could not be evaluated in this 

assessment. However, based on the assumption that cleavage of the ester bond moiety in 

the parent structure results in biologically inactive degradates, these compounds should 

not present a significant risk to non-target organisms. 

Although there were no aquatic or terrestrial plant data available to the Agency, EFED is 

not concerned because zeta-cypermethrin's neural toxic mode of action is not expected to 

induce phytotoxic effects. In addition, based on the lack of studies demonstrating adverse 

effects of zeta-cypermethrin or any other pyrethroid to plants, and the fact that no incident 

reports have reliably linked zeta-cypermethrin or any other compound in the synthetic 

pyrethroid class of chemicals to phytotoxic effects despite being applied on or near 

agricultural plants, it appears unlikely that zeta-cypermethrin poses a phytotoxic concern. 

There is uncertainty surrounding estimates of chronic toxicity to freshwater invertebrates, 

estuarinelmarine fish, or benthic organisms, because no data are currently available. To 
assess risk to these taxonomic groups, RQs were based on chronic NOAEC values derived 

using acute-to-chronic ratios as decribed in the Ecological Effects Characterizaion section 

of this chapter. 

• The available acute toxicity study for benthic organisms was not conducted with the 

exposure system at equilibrium, adding uncertainty to the acute RQs derived for exposure 

via the sediment. Furthermore, since the chronic RQ for sediment and acute and chronic 

RQs for pore water were derived from the sediment toxicity value, this uncertainty is 

introduced to all categories of the risk assessment for benthic organisms. These studies 

have been recently submitted by the pyrethroid working group (PWG) but were not 

reviewed in time for inclusion in this assessment. 

a. Age Class and Sensitivity of Effects Thresholds 

It is generally recognized that test organism age may have a significant impact on the observed sensitivity 

to a toxicant. The screening risk assessment acute toxicity data for fish are collected on juvenile fish 

between 0.1 and 5 grams. Aquatic invertebrate acute testing is performed on recommended immature age 

classes (e.g., frlst instar for daphnids, second instar for amphipods, stoneflies and mayflies, and third instar 

for midges). Similarly, acute dietary testing with birds is also performed on juveniles, with mallard being 

5-1 0 days old and quail at 10-14 days of age. 

Testing of juveniles may overestimate the toxicity of direct acting pesticides in adults. As juvenile 

organisms do not have fully developed metabolic systems, they may not possess the ability to transform 

and detoxify xenobiotics equivalent to the olderiadult organism. The screening risk assessment has no 

current provisions for a generally applied method that accounts for this uncertainty. In so far as the 

available toxicity data may provide ranges of sensitivity information with respect to age class, the risk 

assessment uses the most sensitive life-stage information as the conservative screening endpoint. 

b. Lack of Effects Data for Amphibians and Reptiles 

Currently, toxicity studies on amphibians and reptiles are not required for pesticide registration. Since 

these data are lacking, the Agency uses fish as surrogates for aquatic phase amphibians and birds as 

surrogates for terrestrial phase amphibians and reptiles. These surrogates are thought to be reflective of or 

protective (more sensitive) of herpetofauna. Amphibians are characterized by a permeable skin. The most 

important route of exposure for aquatic amphibians would likely be the dermal route. Using freshwater 

fish may be suitable surrogates since exposure would likely be surface area dependent and the gill surface 

of many fish is a fairly large surface area. Also, both fish and amphibians are ectothermic so metabolic 

rates and demands would likely be similar. For terrestrial species, however, the difference between 

amphibians and birds and reptiles and birds is quite large. Terrestrial amphibians and reptiles are both 

ectotherinic while birds are endothermic; birds have a higher basal metabolic rate to required to maintain 

constant body temperature. The higher metabolic demands of birds may be predispose birds to higher 

relative exposures. However, this does not address any potential differences in toxicity. To date, there are 

few controlled studies on reptile species that could be used to compare to similar studies on birds. A 

pviol-i, there is no strong reason to think that one taxa is more or less sensitive than another. Therefore, it 

was assumed that the use of surrogate effects data is sufficiently conservative to apply the broad of species 

within taxonomic groups. If other species are more or less sensitive to zeta-cypermethrin than the 

surrogates, risks may be under- or overestimated, respectively. The Agency is not limited to a base set of 

surrogate toxicity information in establishing risk assessment conclusions. The Agency also considers 

toxicity data on non-standard test species when available. Further research is required to determine 
whether, in general, reptiles and terrestrial-phase amphibians are suitably represented by birds species in 

assessing risks for zeta-cypennethrin. 

c. Use of the Most Sensitive Species Tested 

Although the screening risk assessment relies on a selected toxicity endpoint from the most sensitive 

species tested, it does not necessarily mean that the selected toxicity endpoints reflect sensitivity of the 

most sensitive species existing in a given environment. The relative position of the most sensitive species 

tested in the distribution of all possible species is a hnction of the overall variability among species to a 

particular chemical. The relationship between the sensitivity of the most sensitive tested species versus 

wild species (including listed species) is unknown and a source of significant uncertainty. In addition, in 

the case of listed species, there is uncertainty regarding the relationship of the listed species' sensitivity and 

the most sensitive species tested. 

The use of laboratory species has historically been driven by availability and ease of maintenance. A 

widespread comparison of species is lacking, however, even variation within a species can be quite high. 

5. Acute and Chronic LOCs 

The risk characterization section of the assessment includes an evaluation of the potential for individual 

effects at an exposure level equivalent to the LOC. This evaluation is based on the median lethal dose 

estimate and doselresponse relationship established for the effects study corresponding to each taxonomic 

group for which the LOCs are exceeded. 

V. Literature Cited 

Environmental Fate MRID Studies Submitted to EPA 

MRID 421 2900 1 Estigoy, L.; Ruzo, L.; Shepler, K. (1991) Photodegradation of Carbon 14- 

Acid and Carbon 14-Alcohol Cypermethrin in Soil by Natural Sunlight: 

Lab Project Number: 2491250W: 191E1390El: PC- 0159. Unpublished 

study prepared by PTRL West. 1 15 p. 

MRID 42 129002 

MRID 42 129003 

MRID 42 15660 1 

MRID 42 156602 

Froelich, L. (1 991). Soil Mobility Studies: Adsorption/Desorption 

Studies of Cypermethrin: Lab Project Number: 191 E3290E1. 

Unpublished study prepared by FMC Corp. 65 p. 

Curry, S. (1 99 1) Leaching of Carbon 14-Cypermethrin in Soil Following 

Aerobic Aging: Lab Project Number: 191 E3 190E1. Unpublished study 

prepared by FMC Corp. 97 p. 

Ramsey A. (1991) Environmental Fate Studies: Aerobic Soil Metabolism 

of Cypermethrin in a Sandy Loam Soil: Lab Project Number: 19 1E2 

190EI. Unpublished study prepared by FMC Corp. 99 p. 

Ramsey A. (1 991) Environmental Fate Studies: Anaerobic Soil 

Metabolism of Cypermethrin in a Sandy Loam Soil: Lab Project Number: 

19 1E2 190EI. Unpublished study prepared by FMC Corp. 93 p. 
MRID 42395701 

MRID 42459601 

MRID 42620501 

MRID 42868203 

MRID 44876105 

MRID 45920801 

Estigoy, L.; Ruzo, L.; Shepler, K. (1 992) Photodegradation of I4c 

Cypermethrin in Buffered Aqueous Solution at pH 7 by Natural Sunlight: 

Revised: Lab Project Number: 2471248W: 2471248W-1; 191 El 290E1. 

Unpub- lished study prepared by Pharmacology and Toxicology Research 

Research Lab (PTRL-West) and FMC Corp. 144 p. 

Leppert, B. (1992) Amno 2.5 EC Insecticide--Terrestrial Field 

Dissipation: Lab Project Number: 191 E4191 El : RAN-0239. Unpublished 

study prepared by FMC Corporation. 182 p. 

Clifton 5.(1992) Environmental Fate Studies: Hydrolysis Studies of 

Cypermethrin in Aqueous Buffered Solutions: Lab Project Number: 

191E1192E1: P-2771. Unpublished study prepared by FMC Corp. 77 p. 

Giroir, E.; Sherman, L. (1 993) Cypermethrin (carbon 14) 

Bioconcentration by Bluegill Sunfish (Lepomis macrochirus): Lab Project 

Number: 191 E5491E1: 400 18: PC-01 89. Unpublished study prepared 

by ABC Labs, Inc. 3 11 p. 

Ramsey, A.A. 1998. Anaerobic aquatic metabolism of I4C-zetacypennethrin. Unpublished study performed, sponsored and submitted by 

FMC Corporation, Princeton, NJ. 

Curry, S.J. 2003. Aerobic aquatic metabolism of '4~-zeta-cyperinethrin. 

Unpublished study perfonned, sponsored and submitted by FMC 

Corporation, Princeton, NJ. FMC Study No.: 194E2202El. 

Experimental initiation September 17, 2002 (p. 17), and completion April 

2,2003 (p. 12). Final report issued April 28,2003. 

Open Literature and Government Reports 

EXAMS. 2002. Surface Water Model, Version 2.98.04. Environmental Fate and Effects Division, Office 

of Pesticide Programs, U.S. Environmental Protection Agency, Washington, D.C. 

Georgia Pecan Commission. A Commercial Users Guide for Georgia Pecans. Available at : 

http://www.georgiapecans.org/cominercial.html 

Gorsuch CS. Clemson University Pest Management Handbook. Fruits and Nuts (last updated 3-1 1-2003). 

 hit^): cu1;~n.clcmson.edu ~~incu~tir: mdln htni 

Helsel, D.R. and R.M. Hirsch. 1993. Statistical Methods in Water Resources. Elsevier. Amsterdam. 

Jackson L., Mayberry K., Laemmlen F., Koike S., Schulbach K., Chaney W. Iceberg lettuce production in 

California. Vegetable Research and Information Center Univ of California Div of Agriculture and Natural 

Resources. Publication Number 72 15 (1 996). 

Laskowski D.A.. 2002. Physical and Chemical Properties of Pyrethroids. Rev. Environ. Contam. Toxicol. 

174:49-170 
National Agricultural Statistical Service (NASS). U.S. Dept. Of Agriculture. htl~. ww\\ .usda.(.cn nass 

NCFAP. 2003. National Center for Food and Agricultural Policy, National Pesticide Use Database. 

Information taken on February 28, 2005 from the website: hltp. \\ti14 .~lcf'ap.or~ dataknse del'ault.litm 

PRZM 3.12 beta. 1998. Surface Water Model, Version 3.12 Beta. Environmental Fate and Effects 

Division, Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington, D.C.. 

Information downloaded from the website htt~llwww.epa.e;ov/ceain~ubl/e;water1vrzm3/index.htm. 

Roof ME. Clemson University Pest Management Handbook. Cotton Insect Control (last updated 5-26- 

2004). hftp: cuf;in.clcmso~~.cci~i pn~cu~dc. ma~n.hl~n 

Takahashi N., Mikami I., Matsuda T., Miyamoto J. 1985. Photodegradation of the pyrethroid insecticide 

cypermethrin in water and on soil surface. Nippon Noyaku Gakkaishi 10:629-42. 

Tolnlin C. 1994. Pesticide Manual 10"' edition. British Crop Protection Council. The Royal Society of 

Chemistry, Cambridge U.K. 

U.S. EPA. 2002. U. S. Environmental Protection Agency. Guidance for Selecting Input Parameters in 

Modeling the Environmental Fate and Transport of Pesticides, Version 11. Office of Pesticide Programs, 

Environmental Fate and Effects Division, U.S. Environmental Protection Agency, Washington, D.C. 21 

Pgs. 

Willis and McDowell 1987, as cited in Carsel, R.F., et.al., "PRZM-3, A Model for Predicting Pesticide 

and Nitrogen Fate in the Crop Root and Unsaturated Soil Zones: User's Manual for Release 3.0." National 

Exposure Research Laboratory USEPA, Athens, GA; AQUA TERRA Consultants, Mountain View, CA; 

and Waterborne Environmental, Inc., Leesburg, VA. p. 5-12. 

Ecotoxicology Bibliography 

Ecolo~ical Effects MRID Studies Submitted to EPA 

Acc. No. 070562 Edwards, P.J., Brown, S.M., Swaine, H. (1980). 3-phenoxybenzoic acid : 

Toxicity to first instar Daphnia magna. Unpublished report by the Plant 

Protection Division, submitted 12/28/81 by I C I Americas Inc., 

Wilmington, Delaware. 

Acc. No. 070562 

Acc. No. 070562 

Jaber, M.J. (1 98 1). The acute and chronic toxicity of cypemethrin to 

mysid shrimp (Mysidopsis bahia). Unpublished report by EG&G 

Bionomics, submitted 1212818 1 by ICI Americas Inc., Wilmington, 

Delaware. 

Jaber, M.J. (1981). The acute toxicity of cypermethrin to crayfish, 

(Unpublished report from Union Carbide Environmental Services 

Laboratory, submitted 1212818 1 by I C I Americas, Wilmington,Delaware. 
Acc. No. 070562 

Acc. No. 070562 

Acc. No. 070562 

Acc. No. 241598 

Acc. No. 241 598 

Acc. No. 241598 

Acc. No. 260647 

MRID 00056800 

MRID 62792 

MRID 62793 

Stephenson, R. (1 980) The acute toxicity of WL 43467 to some 

freshwater invertebrates in static water tests. Unpublished report by Shell 

Toxicology Laboratory, Tunstall, submitted 1212818 1 by ICI Americas 

Inc. 

Stephenson, R.R, Kane, D.F. (1980). The acute toxicity of cypermethrin 

(WL 43467) to the freshwater shrimp (Gammerus pulex) and larvae of the 

mayfly (Cleon dipterum), in continuous-& low tests. Unpublished report 

from Shell Research Ltd, submitted 1212818 1 by I C I Americas, 

Wilmington, Delaware. 

Thompson, R.S. (1981) Investigation of the Acute Toxicity of PP 383 to 

Larvae of the Pacific Oyster (Crassostrea gigas). Unpublished report by 

the Brixhain Laboratory of Imperial Chemical Industries, Ltd., submitted 

1212818 1 by ICI Americas, Inc.; Wilmington, Delaware. 

Hill, R.W., Maddock, B.G., Hart, B. (1976). Determination of the acute 

toxicity of PP383 to Rainbow trout (Salmo gairdneri). ICI Brixham 

Laboratory Report No. BLlB117 1 1, March 1976. 

Hill, R. W, Maddock, B.G., Hart, B., Gilbert, J. L. (1977). Determination 

of the acute toxicity of PP383 to bluegill sunfish (Lepomis macrochirus) . 

ICI Brixham Laboratory Report NO. BLlB11775, March 1977. 

Ross, D.B., D.M. Cameron, N.L. Roberts (1 977). The Acute Qral 

Toxicity (LDSO) of PP383 to the Mallard Duck. Huntington Research 

Centre Report No. ICI 128WLl7733, August 1977. 

Bull, J.M., Wilkinson, W. (1 980). Cypermethrin: Laboratory 

determination of the acute oral and contact toxicity to honeybees of 

technical material and an emulsifiable concentrate (GFUO61) . Submitted 

by 1C1, Plant Protection Division . Reg. NO. 10182-65. 

Henderson, C.; Oliver, G.A.; Smith, I.K.; et al. (1980) Cypermethrin 

(PP383): Acute Toxicity and Local Irritation: Report No. CTLR1537. 

(Unpublished study received Dec 29, 1980 under 101 82-EX-1 9; prepared 

by Imperial Chemical Industries, Ltd., United Kingdom, submitted by ICI 

Americas, Inc., Wilmington, Del.; CDL:099855-B). 

ICI (1980) Determination of the acute toxicity of cypermethrin (PP383) to 

Rainbow Trout (Salmo gairdneri). 

Cypermethrin (PP3838): Toxicity of technical and formulated material to 

first instar Daphnia inagna. Submitted by ICI Americas for Phase 4 List B 

review. MRID 92027-0 14 (Summary Report) and MRID 00062793 

(Study Report) . No date given.