2

analysis plan for evaluating and characterizing risk to non-target species in support of the 

registration of lambda-cyhalothrin and gamma-cyhalothrin. 

Many of the environmental fate properties of lambda-cyhalothrin and gamma-cyhalothrin 

are known. Nonetheless, there is uncertainty with respect to the anaerobic soil and 

anaerobic aquatic metabolism of lambda-cyhalothrin and gamma-cyhalothrin and their 

overall persistence in the environment. Lambda-cyhalothrin and gamma-cyhalothrin are 

moderately persistent in aerobic environments, but appear to be more persistent in 

anaerobic environments. The fate of lambda-cyhalothrin and gamma-cyhalothrin in 

publicly-owned treatment works is also an uncertainty. 

In addition, there are ecological data gaps that need to be addressed to reduce 

uncertainties in the preliminary risk picture for lambda-cyhalothrin and gammacyhalothrin. Lambda- and gamma-cyhalothrin are very highly toxic to fish, aquatic 

invertebrates and terrestrial invertebrates. However, there is uncertainty concerning the 

potential for acute and chronic adverse aquatic effects to listed and non-listed species. 

Specifically, uncertainty is particularly high for estimating risks to benthic aquatic 

invertebrates via sediment exposure, aquatic invertebrates via acute and chronic water 

column exposures, fish via chronic exposures and aquatic vascular plants. There is also 

uncertainty concerning the potential for adverse effects for via acute exposures to listed 

and non-listed passerine birds and terrestrial plants. 

The potential risk to pollinators and other beneficial insects from use of lambdacyhalothrin and gamma-cyhalothrin appears to be high. Based on a bioconcentration 

factor of 4,600X in whole fish, lambda-cyhalothrin and gamma-cyhalothrin are highly 

bioaccumulative and depuration occurs at moderately slow rates. 
Environmental Fate and Ecological Risk 

Assessment Problem Formulation in

Support of Registration Review 

of Lambda-cyhalothrin and 

Gamma-cyhalothrin 

Lambda-cyhalothrin Gamma-cyhalothrin 

PC Code 128897 PC Code 128807 

Case No. 7408 Case No. 7437 

November 22, 2010 

Environmental Fate and Effects Division 

Office of Pesticide Programs 

US Environmental Protection Agency 

3
Prepared by: 

Amanda Solliday, Biologist 

José L. Meléndez, Chemist 

Keith Sappington, Senior Scientist 

Secondary Review: 

Mah T. Shamim, Ph.D., Branch Chief 

Environmental Risk Branch 5 

4
5

Table of Contents 

1. Purpose.................................................................................................................................... 6 

2. Problem Formulation .............................................................................................................. 6 

2.1 Nature of Regulatory Action................................................................................................ 6 

2.2. Previous Risk Assessments.................................................................................................. 7 

3. Stressor Source and Distribution .......................................................................................... 12

3.1. Mechanism of Action........................................................................................................ 18 

3.2. Overview of Pesticide Usage............................................................................................ 19 

3.3. Environmental Fate and Transport.................................................................................... 32 

4. Receptors............................................................................................................................... 46 

4.1. Aquatic and Terrestrial Effects ......................................................................................... 46 

4.2. Incident Database Review................................................................................................. 57 

4.3. Ecosystems Potentially at Risk ......................................................................................... 59

5. Assessment Endpoints .......................................................................................................... 46 

6. Conceptual Model.............................................................................................................. 61 

6.1. Risk Hypothesis ............................................................................................................... 61 

6.2. Conceptual Diagram ........................................................................................................ 62 

7. Analysis Plan ..................................................................................................................... 67 

7.1. Stressors of Concern ......................................................................................................... 68 

7.2. Measures of Exposure....................................................................................................... 68 

7.3. Measures of Effect ............................................................................................................ 71 

7.4. Integration of Exposure and Effects ................................................................................. 72 

7.5. Deterministic and Probabilistic Assessment Methods...................................................... 73 

7.6. Endangered Species Assessments..................................................................................... 73 

7.7. Drinking Water Assessment ............................................................................................. 74 

7.8. Preliminary Identification of Data Gaps........................................................................... 75 

7.8.1. Fate............................................................................................................................. 75 

7.8.2 Effects ......................................................................................................................... 79 

8. References................................................................................................................................ 87 

9. Bibliography..................................................................... 

Appendix A. SRRD data request justification tables................................................................ 108 

Appendix B. Aquatic Ecological Effects Data ......................................................................... 126 

Appendix C. Open Literature Information................................................................................ 130 
6

1. Purpose 

The purpose of this problem formulation is to provide the foundation for the ecological risk 

assessment being conducted for the registered uses of lambda-cyhalothrin and gammacyhalothrin. As such, it articulates the purpose and objectives of the risk assessment, evaluates 

the nature of the problem, and provides a plan for analyzing the data and characterizing the risk 

(USEPA, 1998). Additionally, this problem formulation is intended to identify data gaps, 

uncertainties and potential assumptions needed to address those uncertainties in characterizing the 

ecological risk associated with the registered uses of lambda-cyhalothrin and gamma-cyhalothrin. 

Lambda-cyhalothrin is a Type II synthetic pyrethroid insecticide that is registered for numerous 

agricultural, non-agricultural and residential uses. Type II pyrethroids are characterized by the 

cyano moiety in the alpha carbon in their chemical structure (Type I pyrethroids do not contain 

this moiety, see Mechanism of Action for additional distinctions between the two types). 

Lambda-cyhalothrin is a mixture of two of the 16 possible isomers in its structure. Lambdacyhalothrin is a restricted-use, broad-spectrum, insecticide registered in the U.S. for most major 

aphid, caterpillar, and beetle pests on a wide variety of crops and for public health pests such as 

mosquitoes and cockroaches in non-agricultural uses. It is registered on a wide range of crops 

(prominent brand names include Warrior® and Karate®, among others) as well as for the 

treatment of various non-agricultural settings (residential lawns, pet living quarters, ships and 

boats, etc.). There are no postharvest treatment uses. Crops for which it is registered include 

fruits, vegetables, and row and field crops such as alfalfa, rice, soybean, and wheat. The major 

agricultural use sites appear to be alfalfa, cotton, soybeans, winter wheat, and rice. 

Gamma-cyhalothrin is another Type II pyrethroid, consisting of one of the two isomers of 

lambda-cyhalothrin. The environmental fate and ecological effects properties of lambdacyhalothrin and gamma-cyhalothrin are expected to be similar to each other. The database for 

gamma-cyhalothrin was supplemented by available data for lambda-cyhalothrin and vice versa. 

Gamma-cyhalothrin is a restricted-use, broad-spectrum, insecticide registered in the U.S. for most 

major aphid, caterpillar and beetle pests on a wide variety of crops and non-agricultural uses. It is 

registered on a wide range of crops under the brand names Cobalt® and Proaxis®, among others, 

as well as for the treatment of various non-agricultural settings (eating establishments, feed mills, 

animal kennels, etc.). It also has a few labels for use as a postharvest treatment for almonds, 

cherries, nectarines, and peaches. Crops for which it is registered include tree fruit, vegetables, 

and row and field crops such as alfalfa, rice, soybean, and wheat. The major use sites appear to 

be alfalfa, soybean, and winter wheat. 

2. Problem Formulation 

 2.1. Nature of Regulatory Action 

This report summarizes the Environmental Fate and Effects Division’s (EFED) Problem 

Formulation for the Registration Review of lambda-cyhalothrin and gamma-cyhalothrin. 
7

Previous risk assessments were completed for the uses of these chemicals, which serve as the 

basis for this assessment. 

The Food Quality Protection Act (FQPA) of 1996 mandated the EPA to implement a new 

program, i.e., registration review (http://www.epa.gov/oppsrrd1/registration_review/). All 

pesticides distributed or sold in the United States generally must be registered by the EPA. The 

decision to register a pesticide is based on the consideration of scientific data and other factors 

showing that it will not cause unreasonable risks to human health, workers, or the environment 

when used as directed on product labeling. The registration review program is intended to ensure 

that, as the ability to assess risk evolves and as policies and practices change, all registered 

pesticides continue to meet the statutory standard of no unreasonable adverse effects to human 

health and the environment. Changes in science, public policy, and pesticide use practices will 

occur over time. Through the new registration review program, the Agency periodically 

reevaluates pesticides to make sure that as change occurs, products in the marketplace can be used 

safely. 

As part of the implementation of the new Registration Review program pursuant to Section 3(g) 

of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is beginning its 

evaluation to determine whether lambda-cyhalothrin and gamma-cyhalothrin continue to meet the 

FIFRA standard for registration. This problem formulation for the environmental fate and 

ecological risk assessment chapter in support of the registration review is intended for the initial 

docket opening the public phase of the review process. 

2.2. Previous Risk Assessments and Scientific Advisory Panels 

Previous Assessments: Lambda-Cyhalothrin 

Recent risk assessments conducted on lambda-cyhalothrin and gamma-cyhalothrin, indicated risk 

concerns for freshwater and estuarine/marine organisms. In addition, there were risk concerns for 

organisms living in the benthos. 

In November of 2008, the Agency issued an incremental assessment for the use of lambdacyhalothrin on non-bearing citrus orchards (D355940; Meléndez & Solliday 2008). It relied 

extensively on two previous assessments for the chemical (D262918+ and D324224+; Ramasamy 

et al. 2002 and Meléndez & Hoffmann 2006). The proposed maximum seasonal application rate 

of 0.24 lb a.i./A was found to be similar to previously assessed crops. 

Prior to the 2008 review, the Agency issued a risk assessment for the use of the chemical on 

cereal grains, cucurbit vegetables, grass forage, fodder and hay, wild rice, and tuberous and corm 

vegetables (D324224+; Meléndez & Hoffmann 2006). This review, dated December of 2006, 

included both aerial and ground applications and the seasonal application rates ranged from 0.06 

to 0.18 lb a.i./A. The terrestrial risk portion of this assessment was completely based on a 

previously issued review (D262918+; Ramasamy et al. 2002) because the estimated exposure 

concentrations (EECs) derived for the new scenarios using T-REX were very similar to those 
8

 

derived using ELL-FATE1 for the previously assessed crops. However, the aquatic EECs in this 

review were higher (particularly the chronic EECs for the new use on wild rice). Furthermore, in 

the review, risk towards benthic communities was evaluated, utilizing the equilibrium partitioning 

approach (refer to Section 7.2). Multiple levels of concern (LOCs) were exceeded for aquatic 

species, with the highest risks predicted for aquatic invertebrates via water column exposure. For 

freshwater and marine invertebrates, acute risk quotients (RQs) ranged from 3.57 to 82.80 and the 

chronic RQs were 2 to 850. For freshwater and marine fish, acute RQs ranged from 0.03 to 1.97 

and the chronic RQs exceeded the LOC under the NC sweet potato and wild rice scenarios. With 

respect to the benthic communities, acute RQs were 0.09 to 1.58 for freshwater and 

estuarine/marine organisms (including freshwater and estuarine/ marine benthic organisms), and 

the chronic RQs ranged from 0.32 to 38.65. For aquatic plants, the RQs were well below the 

LOC (≥1), with all values ≤0.01. It was stated that risk to terrestrial plants could not be evaluated 

due to lack of toxicity data. 

In June of 2002, a risk assessment for several new uses of lambda-cyhalothrin was issued 

(D262918+; Ramasamy et al. 2002). The new uses included peas and beans (succulent and 

dried), fruiting vegetables, canola, sugarcane, sorghum, wheat, wheat hay and other small grains, 

peanut, pome fruits, stone fruits, tree nuts, tobacco, termite barrier, non-cropland, and conifers 

and deciduous trees (plantations, nurseries, and seed orchards). The seasonal application rates 

ranged from 0.08 to 0.36 lb a.i./A and both ground and aerial applications were possible. The 

proposed uses exceeded LOCs for freshwater and estuarine/ marine fish and invertebrates (see 

also above for a discussion of aquatic organisms). Using ELL-FATE, a wide range of exposure 

scenarios, and the most sensitive species, acute RQs for birds were well below the LOCs; 

however, some of the chronic RQs exceeded the chronic LOC (≥1), with a range from <0.1 to 2.5. 

For mammals, the acute RQs ranged from <0.01 to 1.26 while the chronic RQs were <0.1 to 2.5. 

Lambda-cyhalothrin is considered highly toxic to honeybees, thus, potential risk was presumed 

for pollinators and other beneficial insects. 

Several reviews were issued for lambda-cyhalothrin prior to 2002, which are not discussed here in 

detail. These included uses such as rice, cotton, turf and ornamentals, uses in and around 

buildings, soybeans and sunflowers. 

Previous Assessments: Gamma-Cylahothrin 

There are two reviews for gamma-cyhalothrin. In May of 2009, an incremental risk assessment 

for the use of gamma-cyhalothrin (D357895+; DeCant 2009) on wheat in several states was 

issued, which was based on a previously issued assessment (D288057+; Maher et al. 2004). The 

proposed maximum seasonal rate of 0.0176 lb a.i./A was lower than the previously assessed 

maximum rate. 

The full risk assessment dated March of 2004 is also the new chemical review for gammacyhalothrin. The review was considered supplemental to the assessment for lambda-cyhalothrin 

of June of 2002 discussed above (D262918+; Ramasamy et al. 2002). The available studies for 

1

 ELL-FATE is a model, which is the precursor of T-REX. T-REX is described in the Analysis segment of this 

document (Section 7.2). 
9

gamma-cyhalothrin, despite being mostly supplemental, were considered sufficient for the 

purpose of bridging and supplementing existing lambda-cyhalothrin data. In the review, it was 

indicated that the potential risks from the proposed gamma-cyhalothrin uses are consistent with 

risks estimated for lambda-cyhalothrin and other pyrethroids, which include aquatic organisms 

(fish and invertebrates) and non-target insects. Risks to sediment dwelling organisms were also 

considered possible. The proposed uses included among others alfalfa, cole crops, corn, fruiting 

vegetables, legume vegetables, pome fruits, rice, cotton, soybean, stone fruits, tree nuts, wheat 

and conifers and deciduous trees. The maximum proposed application rate appeared to be 0.25 lb 

a.i./A/season (Appendix A of the review). The conclusions of the review relied extensively on 

the lambda-cyhalothrin review, but a spray drift analysis of the aquatic risks was performed with 

three possible levels of binding (0, 50 and 99%), and two levels of drift exposure (high and low), 

for ground, aerial and airblast applications. 

1999 Scientific Advisory Panel 

A FIFRA Scientific Advisory Panel (SAP) in 1999 examined the sediment toxicity and fate of 

synthetic pyrethroids. In response to a question regarding whether sediment toxicity data on one 

pyrethroid (cypermethrin) could be used to predict sediment toxicity to all pyrethroids, the panel 

generally supported the method of using data from a few pyrethroids to extrapolate information 

on toxicity to other pyrethroids. The panel recommended testing cypermethrin, bifenthrin 

(relatively non-toxic to freshwater aquatic organisms, very insoluble in water, large 

bioconcentration factor) and possibly tefluthrin (highly toxic to freshwater aquatic organisms, 

stable in water, intermediate solubility in water to cypermethrin and bifenthrin) (USEPA 1999). 

Although this agreement was made in 1999, the new CFR Part 158 ecological effects data 

requirements include sediment toxicity tests which are considered particularly important for 

assessing ecological risks of synthetic pyrethroids, including lambda-cyhalothrin and gammacyhalothrin. 

The SAP commented on the use of Kd or KOC to estimate concentrations of synthetic pyrethroids 

in sediments, recommending that the Agency reconsider KOC as a measure of the binding 

potential of synthetic pyrethroids to sediment and soil because the use of Kd alone limits 

extrapolation to experimental conditions while KOC “allows one to estimate partitioning across a 

wide variety of soil/sediment types” (USEPA 1999). The Panel expressed concern that standard 

methods used to measure sorption may not be applicable to highly hydrophobic compounds due 

to high solids to water ratio, consideration of the character of the organic matter, presence of 

dissolved organic carbon, use of non-representative soils and sediments as sorbents, and improper 

methods used to measure organic carbon. 

While the biota-sediment accumulation factor is a widely accepted method of assessment of 

bioaccumulation in sediments, the Panel indicated that the bioconcentration data for Daphnia and 

Hyalella should be sufficient to predict bioconcentration of pyrethroids. Finally, the Panel 

indicated that use of a solid phase microextraction (SPME) method to determine the dissolved 

concentration in water could be used to account for sorption of pyrethroids to organic carbon and 

colloids present in the water column in the measurement of bioconcentration factors. 
10

In 2003 and in response to the comments from the SAP on pyrethroids, EFED requested the 

following studies on the pyrethroids cyfluthrin, cypermethrin, esfenvalerate and bifenthrin 

(Rexrode & Meléndez, memorandum dated 12/22/03): 

850.1735: Acute Sediment (freshwater)

- Test organism: Hyalella azteca and Chironomus dilutus. 

- Duration: 10 days, endpoint is survival. 

EPA/600/R01/020: Chronic Estuarine/Marine Sediment Testing

- 28 day test on Leptocheirus plumulosus. 

- Percentage of neonates that survive as adults. 

- Growth rate. 

- Reproduction (#eggs/ female, etc.). 

- Behavior. 

A chronic 65-day freshwater test was also requested only for cypermethrin. 

EPA/600/R-991064: Chronic Freshwater Sediment Testing 

- 65 day test on Chironomus dilutus. 

- Survival. 

- Growth rate. 

- Reproduction (# eggs/ female, time to oviposition, proportion of females ovipositing, % 

hatch).

2009 Scientific Advisory Panel

OPP presented a “Proposed Common Mechanism Grouping for the Pyrethrins and Synthetic 

Pyrethroids to a FIFRA SAP in June 2009. OPP proposed two subgroups based on Type I or 

Type II effects related to sodium current tails and neurobehavioral impact, with esfenvalerate and 

fenpropathrin showing symptoms of both types. The panel indicated that substances with mixed 

characteristics could be included in both groups (see p. 18 of SAP minutes, USEPA 2009). 

Lambda-cyhalothrin and gamma-cyhalothrin are Type II synthetic pyrethroids; they are cyanosubstituted in the alpha position. This mechanism of action assessment was performed by 

HED/OPP and presented to the SAP to determine if a cumulative assessment is required for the 

synthetic pyrethroids. Information on the SAP is available in the docket (with non-copyright 

material available at http://www.regulations.gov) under EPA-HQ-OPP-2008-0489. 

EFED does not currently conduct cumulative ecological risk assessments. EFED does not 

currently have the methodology to conduct similar cumulative risk assessments for all of the 

(non-human) biological entities for which EFED has responsibility. In addition to addressing the 

toxicological aspects of the cumulative effects of multiple pyrethroids to multiple biological 

entities, a cumulative ecological risk assessment would likely require consideration of exposure at 

a watershed scale in order to incorporate spatial and temporal variability in pyrethroid 

applications into cumulative exposure assessment. EFED does not currently have the modeling 

tools developed for conducting this type of assessment. However, EFED will consider open 

literature, currently available models and other lines-of-evidence (e.g., monitoring data), as 
11

available to address the potential for cumulative effects of pyrethroids in the risk description of 

the ecological assessment for lambda- and gamma-cyhalothrin. 

Open Literature Information 

There are multiple articles in the open literature that indicate concern over lambda-cyhalothrin, 

gamma-cyhalothrin and other pyrethroids’ toxicity towards benthic and other non-target aquatic 

organisms. Also, the articles illustrate cyhalothrin’s prevalence over the environment. Please, 

refer to the Appendix B for further details. 

Lambda-cyhalothrin is among the constituents monitored by the National Water Quality 

Assessment (NAWQA), maintained by the U.S. Geological Survey. One kind of parameter (type 

of samples) is reported: “lambda-Cyhalothrin_ water_ filtered_ recoverable_ micrograms per 

liter,” with a reported percent of samples with this parameter of 7.4 (report units of μg/L). 

Aquatic Life Criteria and Aquatic Life Benchmarks 

The Clean Water Act requires the Agency to publish water quality criteria that accurately reflect 

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

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

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

states and authorized tribes can use them to develop water quality standards. US EPA Aquatic 

Life Ambient Water Quality Criteria document has not been published for lambda-cyhalothrin or 

gamma-cyhalothrin (at http://www.epa.gov/waterscience/criteria/). However, the Agency is aware 

of other efforts to derive aquatic life criteria for lambda-cyhalothrin and gamma-cyhalothrin, and 

will consider this work when characterizing risk in the forthcoming assessment 

(http://www.swrcb.ca.gov/rwqcb5/water_issues/tmdl/central_valley_projects/central_valley_pesti

cides/criteria_method/ and Giddings et al., 2009). 

Based on toxicity values revised by the EPA, the OPP publishes aquatic life benchmarks for 

freshwater species, based on the most sensitive species from the most recent risk assessments. 

For lambda-cyhalothrin and gamma-cyhalothrin, aquatic life benchmarks have been published (at 

http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm#benchmarks). The 

aquatic life benchmarks are as follows: 

Table 2.1. OPP Aquatic Life Benchmarks (Freshwater) for Lambda- and Gamma-cyhalothrin 

All values in μg/L Fish Invertebrates Non-vascular plants 

Chemical Name Acute Chronic Acute Chronic Acute 

Gamma-cyhalothrin 0.0145 - - 0.00024 - - >2,850 

Lambda-cyhalothrin 0.105 0.031 0.0035 0.002 >310 

There were no available acute benchmarks for vascular plants; thus, a column for vascular plants 

does not appear in the table. 
12

Impaired Water Bodies 

Lambda-cyhalothrin and gamma-cyhalothrin are not individually identified as a cause of 

impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act, 

based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885. 

However, the pyrethroids as a group have been identified as a cause for impairment for three 

water bodies in Central Valley, California: Del Puerto Creek, Ingram Creek Site (from confluence 

with Hospital Creek to Highway 33 crossing) and second Ingram Creek Site (from confluence 

with San Joaquin River to confluence with Hospital Creek). At the present time, additional 

bodies of water are being evaluated to be included into the list of impaired bodies of water; 

however, they have not been finalized. 

Nonetheless, no Total Maximum Daily Load (TMDL) criteria have been developed specifically 

for lambda-cyhalothrin and gamma-cyhalothrin, based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=

885&p_pollutant_group_name=PESTICIDES. More information on impaired water bodies and 

TMDLs can be found at http://www.epa.gov/owow/tmdl/. The Agency invites submission of 

water quality data for these pesticides. To the extent possible, data should conform to the quality 

standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired 

Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and 

Management Process (at

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

can be used quantitatively or qualitatively in pesticide risk assessments. 

3. Stressor Source and Distribution

Lambda-cyhalothrin (Table 3.1a) is a synthetic pyrethroid insecticide. Its structure has three 

rings, two phenyl rings attached to each other by an oxygen atom (phenyl and phenoxy), and a 

cyclopropyl ring. It is a Type II synthetic pyrethroid (it is cyano-substituted in the alpha 

position). The chemistry of cyhalothrin may be dictated by its ester moiety. It would be expected 

to hydrolyze as the pH increases; this is confirmed from the hydrolysis study, where lambdacyhalothrin and gamma-cyhalothrin were stable at pH 5, nearly stable at pH 7 and hydrolyzed at 

pH 9. The structure of the molecule has three chiral centers and a double bond which raise the 

number of possible isomers to 24

 = 16. However, lambda-cyhalothrin consists only of two of 

these isomers. Lambda-cyhalothrin has a 2-chloro-3,3,3-trifluoropropenyl group and it is 2,2-

dimethyl substituted in the cyclopropane ring. Chemically, it is the (S)-alcohol (Z)-(1R)-cis acid 

and the (R)-alcohol (Z)-(1S)-cis acid out of 16 isomeric esters. 

Gamma-cyhalothrin (Table 3.1a) is a single isomer out of 16 possibilities of its structure, and one 

of the two isomers in lambda-cyhalothrin. Chemically, it is the (S)-alcohol (Z)-(1R)-cis acid out 

of 16 isomeric esters. 

In addition, cyhalothrin (not lambda- nor gamma-cyhalothrin) consists of four of the 16 possible 

isomers in its structure, of which two of them appear in lambda-cyhalothrin and one appears in 
13

gamma-cyhalothrin (Table 3.1b). Cyhalothrin is not a registered pesticide in the U.S. 

In general, the physicochemical and environmental fate properties of cyhalothrin, lambdacyhalothrin and gamma-cyhalothrin may be expected to be similar to each other. Information 

about the identification of lambda-cyhalothrin and gamma-cyhalothrin is provided in Table 3.1a. 

A summary of physicochemical properties of lambda-cyhalothrin and gamma-cyhalothrin is 

included in Table 3.1b.

Table 3.1a. Identification information for lambda-cyhalothrin and gamma-cyhalothrin 

CHEMICAL LAMBDA-CYHALOTHRIN GAMMA-CYHALOTHRIN 

PARAMETER VALUE(S) (units) SOURCE VALUE(S) (units) SOURCE

CAS Chemical 

Name 

(R)-cyano(3-

phenoxyphenyl)methyl (1S,3S)-

rel-3-[(1Z)-2-chloro-3,3,3-

trifluoro-1-propenyl]-2,2-

dimethylcyclopropanecarboxylate 

Lambda-cyhalothrin data sheet 

(S)-cyano(3-

phenoxyphenyl)methyl (1R,3R)-3-

[(1Z)-2-chloro-3,3,3-trifluoro-1-

propenyl]-2,2-

dimethylcyclopropanecarboxylate 

Gamma-cyhalothrin data sheet 

PC Code 128897 OPP Databases 128807 OPP Databases 

Case Number 7408 OPP Databases 7437 OPP Databases 

IUPAC Chemical 

Name 

reaction product comprising equal 

quantities of: 

(R)-α-cyano-3-phenoxybenzyl 

(1S,3S)-3-[(Z)-2-chloro-3,3,3-

trifluoropropenyl]-2,2-

dimethylcyclopropanecarboxylate 

and (S)-α-cyano-3-phenoxybenzyl 

(1R,3R)-3-[(Z)-2-chloro-3,3,3-

trifluoropropenyl]-2,2-

dimethylcyclopropanecarboxylate 

or of 

(R)-α-cyano-3-phenoxybenzyl 

(1S)-cis-3-[(Z)-2-chloro-3,3,3-

trifluoropropenyl]-2,2-

dimethylcyclopropanecarboxylate 

and (S)-α-cyano-3-phenoxybenzyl 

(1R)-cis-3-[(Z)-2-chloro-3,3,3-

trifluoropropenyl]-2,2-

dimethylcyclopropanecarboxylate 

Lambda-cyhalothrin data sheet 

(S)-α-cyano-3-phenoxybenzyl 

(1R,3R)-3-[(Z)-2-chloro-3,3,3-

trifluoropropenyl]-2,2-

dimethylcyclopropanecarboxylate 

or 

(S)-α-cyano-3-phenoxybenzyl 

(1R)-cis-3-[(Z)-2-chloro-3,3,3-

trifluoropropenyl]-2,2-

dimethylcyclopropanecarboxylate 

Gamma-cyhalothrin data sheet 

CAS Reg. No. 91465-08-6 Lambda-cyhalothrin data sheet 76703-62-3 Gamma-cyhalothrin data sheet 
14

Table 3.1a. Identification information for lambda-cyhalothrin and gamma-cyhalothrin 

CHEMICAL LAMBDA-CYHALOTHRIN GAMMA-CYHALOTHRIN 

PARAMETER VALUE(S) (units) SOURCE VALUE(S) (units) SOURCE

Chemical Structure 

(from chemical’s 

data sheet) 

Lambda-cyhalothrin data sheet accessed 05/24/10: http://www.alanwood.net/pesticides/lambda-cyhalothrin.html . 

Gamma-cyhalothrin data sheet accessed 05/24/10: http://www.alanwood.net/pesticides/gamma-cyhalothrin.html .
15

Table 3.1b. Summary of physicochemical properties of lambda-cyhalothrin and 

gamma-cyhalothrin 

PARAMETER VALUE(s) units (chemical name) SOURCES

CAS Reg. No. 

68085-85-8 (cyhalothrin) 

91465-08-6 (lambda-cyhalothrin) 

76703-62-3 (gamma-cyhalothrin) 

TOXNET/ HSDB2

Lambda- and gammacyhalothrin data sheets 

Composition 

Cyhalothrin Lambda-cyhal Gamma-cyhal 

60:40 A:B 1:1 enantiomers 

of pair B 

Only S-alcohol 

(Z)-(1R)-cis acid 

where, 

(1R,3R,alphaR) and (1S,3S,alphaS) is known as pair A 

(1R,3R,alphaS) and (1S,3S,alphaR) is known as pair B 

Alternative nomenclature for Pair B is also (S)-alcohol (Z)-

(1R)-cis acid and (R)-alcohol (Z)-(1S)-cis acid 

Laskowski, 2002 & 

lambda- and gammacyhalothrin data sheets 

Molecular Formula C23H19ClF3NO3 

(cyhalothrin, lambda-cyhalothrin and gamma-cyhalothrin) 

Lambda-cyhalothrin and 

gamma-cyhalothrin’s data 

sheets 

Molecular Weight 449.86 

(cyhalothrin, lambda-cyhalothrin and gamma-cyhalothrin) TOXNET/ HSDB 

Melting Point Below 10oC (cyhalothrin) 

49.2oC (lambda-cyhalothrin) 

TOXNET/ HSDB & 

EXTOXNET3

NPIC4

Boiling Point 187-190°C @ 0.2 mmHg; 

decomposes at 275°C (cyhalothrin) 

TOXNET/ HSDB 

Solubility in Organic 

Solvents 

In acetone, dichloromethane, methanol, diethyl ether, ethyl 

acetate, hexane, toluene, all >500 g/l at 20°C (cyhalothrin) TOXNET/ HSDB 

Solubility in Water 

5.0 x 10-3 mg/L or 5.0 ppb, temp not spec. (cyhalothrin) 

5 x 10-3 mg/L @ pH 6.5 and 20°C (lambda-cyhalothrin) 

5.00 x 10-3 mg/L or 5.00 ppb @ 20°C (lambdacyhalothrin) 

0.0021 ppm or 2.1 ppb at 20oC (gamma-cyhalothrin) 

‘Not Soluble’ 

TOXNET/ HSDB 

EXTOXNET & 00151580 

Laskowski 2002, 

MRID 45794902 

FAO, 2000 

Vapor Pressure 

7.5 x 10-9 mm Hg at 25°C (cyhalothrin) 

1.56 x 10-9 mmHg at 20°C (lambda-cyhalothrin) 

2.60 x 10-9 mmHg at 25o

C (gamma-cyhalothrin) 

7.73 x 10-10 mmHg at 20o

C (gamma-cyhalothrin) 

‘Non-volatile under field conditions’ (≤9.98 x 10-7 mmHg) 

TOXNET/ HSDB 

Laskowski 2002 

MRID 45794902 

USEPA, 2008 

Henry’s Law Constant 

1.5 x10-6 atm-m3

/mol (cyhalothrin) 

1.9 x 10-7 atm-m3

/mol at 20oC (lambda-cyhalothrin) 

2.18 x 10-7 atm-m3

/mol at 20oC (gamma-cyhalothrin) 

TOXNET/ HSDB 

Laskowski, 2002 

MRID 45794901 

Octanol-Water Partition 

Coefficient 

KOW (log KOW) 

6.3 x 106

 (6.8) (temp. not specified) (cyhalothrin) 

1.00 x 107

 (7.00) (temp. not spec.) (lambda-cyhalothrin) 

90698 (4.96) at 19o

C (gamma-cyhalothrin) 

TOXNET/ HSDB 

Laskowski, 2002 

MRID 45794902 

Octanol-Air Partition 

Coefficient 

KOA (log KOA) 

Constant Law sHenry'

RTK

K

K

K OW

AW

OW

OA ==

1.3 x 1012 (12.1) (lambda-cyhalothrin) 

1.0 x 1010 (10.0) (gamma-cyhalothrin) 

1.282 x 1010 – 1.043 x 1011 (10.108-11.018) (lambdacyhalothrin); EPIWEB estimate 

Calculated Values 

EPIWEB v.4.0 Estimate 

 

2 http://toxnet.nlm.nih.gov/ (data for cyhalothrin, accessed 05/24/10). 3

 EXTension TOXicology NETwork at http://extoxnet.orst.edu/pips/lambdacy.htm (accessed 05/24/10). 4

 National Pesticide Information Center at http://npic.orst.edu/npicfact.htm (accessed 05/24/10). 
16

Table 3.1b. Summary of physicochemical properties of lambda-cyhalothrin and 

gamma-cyhalothrin 

PARAMETER VALUE(s) units (chemical name) SOURCES

KAW (log KAW) 

KAW = Cair/Cwater = HLC/RT 

7.9 x 10-6 (-5.1) (lambda-cyhalothrin) 

9.0 x 10-6 (-5.0) (gamma-cyhalothrin) 

6.05 x 10-5 (-4.22) (lambda-cyhalothrin); EPIWEB v. 4.0 

estimate 

‘Non-volatile’ 

Calculated Values 

EPIWEB v.4.0 

USEPA, 2008 

Cwater/Cair 

⎟

⎠

⎞ ⎜

⎝

⎛

××

××× = 6

air

water

10GMW P

760RT S

C

C = RT/HLC 

130,000 (unitless) (lambda-cyhalothrin) 

110,000 (unitless) (gamma-cyhalothrin) 

‘Non-volatile’ 

Calculated 

USEPA, 2008 

OH Radical Reaction 

Half-life 

0.340 days (lambda-cyhalothrin) 

(Assumptions: 12-hr days; 1.5 x 106

 OH/cm3) EPIWEB v.4.0 Estimate 

Biomagnification 

Potential 

Presumption: If log KOA > 5, log KOW > 2 and the rate of 

chemical transformation is low, the chemical may 

biomagnify in terrestrial food chains**

For lambda-cyhalothrin and gamma-cyhalothrin, log KOA> 

5, log KOW> 2 and rate of transformation is moderate in the 

environment, and it appears to moderate in fish, with very 

high bioconcentration factors (4,600x) and moderate to 

slow depuration (~9 days, based on a bioaccumulation in 

fish study conducted with cyhalothrin); it appears that 

lambda-cyhalothrin and gamma-cyhalothrin may have 

some potential to biomagnify in terrestrial food chains 

under certain circumstances. 

**Gobas et al. 2003 and 

Armitage & Gobas, 2007 

support this presumption 

utilized here only as a broad 

reference to determine the 

potential for 

biomagnification. 

Cyhalothrin, lambda-cyhalothrin and gamma-cyhalothrin have a high molecular weight of 449.9 

g/mol. They also have a small solubility (only 2-5 ppb) and a high octanol/ water partition 

coefficient (log KOW = 5.0 to 7.0). Based on their octanol/ water partition coefficient, it appears 

that lambda- and gamma-cyhalothrin have the potential to bioaccumulate/ bioconcentrate (KOW ≥

1000) in fish and other aquatic organisms. With a vapor pressure of ~10-9 mmHg, they are 

considered “non-volatile under field conditions.” Their calculated Henry’s Law Constant is low 

(~10-7 atm-m3/mol). In addition, their Cwater/Cair is ≥110,000, which classify them as “nonvolatile” (USEPA 2008). Thus, lambda-cyhalothrin and gamma-cyhalothrin do not have a 

potential to volatilize from dry or wet surfaces. The potential to volatilize may be further 

attenuated in the environment by their tendency to bind to organic matter (e.g., soils, sediments, 

or organic matter and particulate in natural water). 

Lambda-cyhalothrin was found to be highly bioaccumulative (4,600x in the whole body), and its 

depuration rate is considered moderately slow (half-depuration time of around 9 days). It is noted 

that its predicted depuration rate based on KOW alone would be much longer (i.e., 30 to > 300 

days), thus suggesting that biotransformation processes may be contributing to its faster 

depuration. Biotransformation in biota is typical for synthetic pyrethroids. For lambdacyhalothrin and gamma-cyhalothrin, the log KOA is in the range of 10-12 (calculated and 

EPIWEB v.4.0 estimates), the log KOW is ~5-7 and the rate of transformation is moderate in the 

environment and in fish, with high bioconcentration factors and a moderately slow rate of 
17

depuration, it appears that lambda-cyhalothrin and gamma-cyhalothrin may have some potential 

to biomagnify in terrestrial food chains under certain circumstances (i.e., if biotransformation 

rates are sufficiently slow), based on the presumption made by Gobas et al. and Armitage & 

Gobas, in 2003 and 2007 articles, respectively, as they relate to poorly metabolized chemicals. 

Even though EFED has not adopted an official reference or guideline to distinguish chemicals 

that biomagnify, Gobas et al. and Armitage & Gobas’ presumption was utilized here as a general 

or broad reference to detect the potential for biomagnification in terrestrial food chains for these 

chemicals. 

Even though various degradates were observed in the laboratory studies (e.g. Compound Ia and 

Compound V), it was found that the majority were the result of the rupture of the ester bond of 

the parent molecule. It has been believed that the resulting molecules are not as toxic as the 

parent because they presumably have lost the neurotoxic mode of action. Table 3.1c shows the 

chemical structures of cyhalothrin’s major degradation products. At this time, it appears that only 

Compound XV may be considered a stressor of concern in the forthcoming environmental fate 

and ecological risk assessment. 
18

Table 3.1c. Major Transformation Products of Lambda-cyhalothrin & Gamma-cyhalothrin 

Common 

Name Chemical Name Structure 

Compounds 

Ia and Ib 

Ia: (1RS)-cis-3-(ZE)-2-chloro3,3,3-trifluoro-1-propenyl)-2,2-

dimethylcyclopropanecarboxylic 

acid and

Ib: (1RS)-trans-3-(ZE)-2-chloro3,3,3-trifluoroprop-1-enyl)-2,2-

dimethylcyclopropanecarboxylic 

acid 

Compound IV 3-Phenoxybenzaldehyde 

O

O

Compound V 3-Phenoxybenzoic acid 

O

O

OH

Compound VI 3-Phenoxybenzenemethanol 

O

OH

Compound XV 

1α(S*),3α(Z)-(±)-cyano-[3-(4'-

hydroxyphenoxy)phenylmethyl]-

3-(2-chloro-3,3,3-trifluoro-1-

propenyl)-2,2-dimethylcyclopropanecarboxylate 

3.1. Mechanism of Action 

Both, lambda-cyhalothrin and gamma-cyhalothrin are neural toxic insecticides acting through 

direct contact and ingestion. The insecticidal effect of pyrethroids is characterized by a rapid 

“knock down,” or paralysis, of insects. All pyrethroids act as axonic poisons, affecting both the 

peripheral and central nervous systems, and share similar modes of action. The primary 
19

biological effects of lambda-cyhalothrin, gamma-cyhalothrin and other pyrethroids on insects and 

vertebrates reflect an inhibition of the correct firing of neurotransmitter delivery signals from one 

cell to another. Specifically, this involves nerve membrane inhibition of the voltage-gated Ca2+

(calcium ion) channels coupled with a stimulatory effect on the voltage-gated Na+

 (sodium ion) 

channels. The pyrethroids (including lambda-cyhalothrin and gamma-cyhalothrin) 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 the Na+ channels activity (cellular pores 

through which Na+

 ions are permitted to enter the axon to cause excitation) (Matsumura, 1985). 

Advanced electrophysiological experiments using voltage clamp and 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 Na+

 channel properties leads to hyperactivity of the nervous 

system. This action leads to spontaneous depolarizations, augmented neurotransmitter secretion 

rate and neuromuscular 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 Ca2+ 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., bifenthrin, resmethrin, permethrin) and Type II (e.g., deltamethrin, 

fenvalerate, cyfluthrin, lambda-cyhalothrin and gamma-cyhalothrin). Type I pyrethroids action is 

mainly associated with compounds that cause nerve excitation symptoms typified by the 

appearance of repetitive firing of axons in the peripheral nervous system and a negatively 

correlated temperature reversible knockdown property (Clark & Matsumura, 1987). In insects, 

the type II pyrethroids predominantly cause ataxia and uncoordinated movement. 

3.2. Overview of Pesticide Usage

The Label Use Information System (LUIS) report & Usage/Label Use Reports for lambdacyhalothrin and gamma-cyhalothrin were based on all labels available for the chemical. The use 

information presented in this problem formulation was obtained from the LUIS report, from the 

Chemical Profiles for lambda-cyhalothrin and gamma-cyhalothrin, supplied by BEAD, and from 

various labels as indicated. Lambda-cyhalothrin and gamma-cyhalothrin have numerous uses. A 

summary of agricultural use patterns for lambda-cyhalothrin and gamma-cyhalothrin, based on 

the indicated labels for lambda-cyhalothrin and gamma-cyhalothrin, are shown Tables 3.2a and 

3.2b. 

Table 3.2a. Summary use information for LAMBDA-cyhalothrin based on Karate® Insecticide with Zeon 

TechnologyTM (EPA Reg. No. 100-1097) and WARRIOR Insecticide with Zeon Technology® Insecticide 

(EPA Reg. No. 100-1112) representative labels. 

Use 

Single App. 

Rate (lb. a.i./A) 

Number 

of Apps. 

Seasonal 

App. Rate 

(lbs. a.i./A) 

Interval 

Between 

Apps. (days) 

App. 

Method 

Incorporation Depth 

(inches) 
20

Table 3.2a. Summary use information for LAMBDA-cyhalothrin based on Karate® Insecticide with Zeon 

TechnologyTM (EPA Reg. No. 100-1097) and WARRIOR Insecticide with Zeon Technology® Insecticide 

(EPA Reg. No. 100-1112) representative labels. 

Use 

Single App. 

Rate (lb. a.i./A) 

Number 

of Apps. 

Seasonal 

App. Rate 

(lbs. a.i./A) 

Interval 

Between 

Apps. (days) 

App. 

Method 

Incorporation Depth 

(inches) 

Barley, Buckwheat, Oat, 

Rye, Triticale, Wheat, 

Wheat hay 

0.03 2 0.06 3 G,A 0 

Cucurbit Vegetables: 

Chayote (fruit), Chinese 

waxgourd, Citron melon, 

Cucumber, Gherkin, 

Ghourd (edible), 

Momordica species, 

Muskmelon (hybrids and/or 

cultivars of Cucumis melo), 

Pumpkin, Summer squash 

(includes various varieties), 

Winter squash (also 

includes various types of 

squash), Watermelon 

(includes hybrids and/or 

varieties) 

0.03 6 0.18 5 G,A 0 

Grass Forage, Fodder and 

Hay: Pasture and rangeland 

grass, Grass grown for hay 

or silage, and Grass grown 

for seeds. 

0.03 1 per 

cutting; 

3 per 

season 

0.03 per 

cutting; 

0.09 per 

season 

30 per 

cutting 

G,A 0 

Tuberous and Corm 

Vegetables: Arracacha, 

Arrowhoot, Artichoke 

(Chinese and Jerusalem 

only), Edible canna, 

Cassava (bitter and sweet), 

Chayote (root), Chufa, 

Dasheen, Ginger, Leren, 

Potato, Sweet potato, 

Tanier, Turmeric, Yam 

(bean and true) 

0.03 4 0.12 7 G,A 0 

Cotton 0.04 5 0.2 3 G,A,ULV 0 

Peanuts 0.03 4 0.12 7 G,A 0 

Rice, Wild rice 0.04 3 0.12 3 first applic. 

& 5-7 for 

subsequent 

applications

G,A 0 

Sorghum 0.03 2-3 0.08 3 G,A 0 

Sugarcane 0.04 4 0.16 7 G,A 0 

Alfalfa and Alfalfa Grown 

for Seed 

0.03 per cutting 4 0.12 Not Specified G,A 0 

Canola 0.03 3 0.09 5 G,A 0 
21

Table 3.2a. Summary use information for LAMBDA-cyhalothrin based on Karate® Insecticide with Zeon 

TechnologyTM (EPA Reg. No. 100-1097) and WARRIOR Insecticide with Zeon Technology® Insecticide 

(EPA Reg. No. 100-1112) representative labels. 

Use 

Single App. 

Rate (lb. a.i./A) 

Number 

of Apps. 

Seasonal 

App. Rate 

(lbs. a.i./A) 

Interval 

Between 

Apps. (days) 

App. 

Method 

Incorporation Depth 

(inches) 

Corn, Field corn, Popcorn, 

Seed corn, Sweet corn 

0.09 at plant, 0.03 

for foliar 

applications 

Field corn, 

popcorn, 

seed corn 

2-4 

Sweet 

corn: 

14-16

Field corn, 

popcorn, seed 

corn: 0.12

from at plant 

and foliar 

applications 

Sweet corn: 

0.48

Field corn, 

popcorn, seed 

corn: 3 

 

Sweet corn: 

Not specified 

G,A, T 

band and 

In-furrow 

0 

Cole Crops: Broccoli, 

Brussels sprouts, Cabbage, 

Cavalo broccolo, 

Cauliflower, Chinese 

broccoli, Chinese cabbage, 

Chinese Mustard, Kohlrabi 

0.03 8 0.24 5 G,A 0 

Fruiting Vegetables: 

Tomato, Tomatillo, Peppers 

(bell and non-bell), 

Eggplant, Ground cherry, 

Pepino 

0.03 12 0.36 5 G,A 0 

Legume Vegetables: (Beans 

and Peas): Edible podded, 

Succulent, Shelled or Dried 

shelled 

0.03 4 0.12 5 G,A 0 

Soybeans 0.03 2 0.06 5 G,A 0 

Lettuce (head and leaf) 0.03 10 0.3 5 G,A 0 

Onion (bulb), Garlic 0.03 8 0.24 5 G,A 0 

Pome Fruits: Apple, 

Crabaple, Loquat, Mayhaw, 

Oriental pear, Pear, Quince 

0.04 5 0.20 5 G,A 0 

Stone Fruits: Apricot, 

Sweet and tart cherry, 

Nectarine, Peach, Plum, 

Chickasaw plum, Damson 

plum, Japanese plum, 

Plumcot, Prune 

0.04 5 0.20 5 G,A 0 

Sunflower 0.03 4 0.12 5 G,A 0 

Tobacco 0.03 3 0.09 7 G,A 0 
22

Table 3.2a. Summary use information for LAMBDA-cyhalothrin based on Karate® Insecticide with Zeon 

TechnologyTM (EPA Reg. No. 100-1097) and WARRIOR Insecticide with Zeon Technology® Insecticide 

(EPA Reg. No. 100-1112) representative labels. 

Use 

Single App. 

Rate (lb. a.i./A) 

Number 

of Apps. 

Seasonal 

App. Rate 

(lbs. a.i./A) 

Interval 

Between 

Apps. (days) 

App. 

Method 

Incorporation Depth 

(inches) 

Tree Nuts: Almonds, Beech 

nut, Brazil nut, Butter nut, 

Cashew, Chestnut, 

Chinquapin, Filbert 

(hazlenut), Hickory nut, 

Macadamia nut, Black 

walnut, English walnut 

(Persian), Pecan 

0.04 4 0.16 5 G,A 0 

Conifers and deciduous 

trees (plantations and 

nurseries) 

0.04 6 0.24 Not specified G,A 0 

Conifers and deciduous 

trees (seed orchards) 

Apply directly to 

the tree, or for 

ground application 

apply at max of 

0.156

For aerial 

applications: max. 

0.117

4@0.125 

5@0.1 

0.5 Not specified G,A 0 

Non-cropland (adjacent to 

crops) (excluding public 

land) 

As per general 

use directions 

As per 

general 

use 

directions 

0.2 As per 

general use 

directions 

G 0 

Non-Bearing Citrus 

Orchards (Calamondin, 

Citron, Citrus hybrids, 

Grapefruit, Kumquat, 

Lemon, Lime, Mandarin, 

Orange (sweet and sour), 

Pummelo, Satsuma 

mandarin, Tangerine, Uniq 

fruit and/or hybrids of 

these) 

0.04 6 0.24 Not specified G,A 0 
23

Table 3.2b. Summary use information for GAMMA-cyhalothrin based on Proaxis® EX Insecticide (EPA 

Reg. No. 62719-522) and Proaxis® Insecticide (EPA Reg. No. 74921-3) labels. 

Use 

Single App. 

Rate (lb. a.i./A) 

Number 

of Apps. 

Seasonal 

App. Rate 

(lbs. a.i./A) 

Interval 

Between 

Apps. (days) 

App. 

Method 

Incorporation Depth 

(inches) 

Wheat, Wheat hay and 

Triticale 

0.015 2 0.03 5 G,A 

Cotton 0.02 5 0.1 3 G,A,ULV 0 

Peanuts 0.015 4 0.06 7 G,A 0 

Rice 0.02 3 0.06 3 first applic. 

& 5-7 for 

subsequent 

applications

G,A 0 

Sorghum 0.015 2-3 0.04 3 G,A 0 

Sugarcane 0.02 4 0.08 7 G,A 0 

Alfalfa and Alfalfa Grown 

for Seed 

0.015 per cutting 4 0.06 Not Specified G,A 0 

Canola 0.015 3 0.045 5 G,A 0 

Corn, Field corn, Popcorn, 

Seed corn, Sweet corn 

0.045 at plant, 

0.015 for foliar 

applications 

Field corn, 

popcorn, 

seed corn 

2-4 

Sweet 

corn: 

14-16

Field corn, 

popcorn, seed 

corn: 0.06

from at plant 

and foliar 

applications 

Sweet corn: 

0.24 from at 

plant and 

foliar applics. 

Field corn, 

popcorn, seed 

corn: 3 

 

Sweet corn: 

Not specified 

G,A, T 

band and 

In-furrow 

0 

Cole crops: Broccoli, 

Brussels sprouts, Cabbage, 

Cavalo broccoli, 

Cauliflower, Chinese 

broccoli, Chinese cabbage, 

Chinese Mustard, Kohlrabi 

0.015 8 0.12 5 G,A 0 

Fruiting Vegetables: 

Tomato, Tomatillo, Peppers 

(bell and non-bell), 

Eggplant, Ground cherry, 

Pepino, Okra 

0.015 12 0.18 5 G,A 0 

Legume Vegetables: (Beans 

and Peas): Edible podded, 

Succulent, Shelled or Dried 

shelled 

0.015 4 0.06 5 G,A 0 

Soybeans 0.015 2 0.03 5 G,A 0 

Lettuce (head and leaf) 0.015 10 0.15 5 G,A 0 

Onion (bulb), Garlic 0.015 8 0.12 5 G,A 0 

Pome Fruits: Apple, 

Crabaple, Loquat, Mayhaw, 

Oriental pear, Pear, Quince 

0.02 5 0.1 5 G,A 0 
24

Table 3.2b. Summary use information for GAMMA-cyhalothrin based on Proaxis® EX Insecticide (EPA 

Reg. No. 62719-522) and Proaxis® Insecticide (EPA Reg. No. 74921-3) labels. 

Use 

Single App. 

Rate (lb. a.i./A) 

Number 

of Apps. 

Seasonal 

App. Rate 

(lbs. a.i./A) 

Interval 

Between 

Apps. (days) 

App. 

Method 

Incorporation Depth 

(inches) 

Stone Fruits: Apricot, 

Sweet and tart cherry, 

Nectarine, Peach, Plum, 

Chickasaw plum, Damson 

plum, Japanese plum, 

Plumcot, Prune 

0.02 5 0.1 5 G,A 0 

Sunflower 0.015 4 0.06 5 G,A 0 

Tobacco (air dried) 0.015 3 0.045 7 G,A 0 

Tree Nuts: Almonds, Beech 

nut, Brazil nut, Butter nut, 

Cashew, Chestnut, 

Chinquapin, Filbert 

(hazlenut), Hickory nut, 

Macadamia nut, Black 

walnut, English walnut 

(Persian), Pecan, Pistachios 

0.02 4 0.08 5 G,A 0 

Conifers and deciduous 

trees (plantations and 

nurseries) 

0.02 6 0.12 Not specified G,A 0 

Conifers and deciduous 

trees (seed orchards) 

Apply directly to 

the tree, or for 

ground applic. 

apply at max of 

0.078

For aerial 

applications: max. 

0.059

4@0.0625 

or 

5@0.05 

0.25 Not specified G,A 0 

Non-cropland (adjacent to 

crops) (excluding public 

land) 

As per general 

use directions 

As per 

general 

use 

directions 

0.1 As per 

general use 

directions 

G 0 

Ornamentals (Commercial 

greenhouses, Shadehouses, 

Nurseries) 

0.027 lb a.i./100 

gal1

Not 

specified 

0.28 Not specified G 0 

Turf (Sod farms and Grass 

seed farms) 

0.1 2-3 0.28 

1

. The actual application rate is not stated, according to the instructions, the plants should be thoroughly covered, including

stems, twigs and foliage. 

In general, for a given crop, the application rate for gamma-cyhalothrin is around half that for 

lambda-cyhalothrin. For agricultural products, application methods include aerial or ground 

spray (foliar) and ULV. In addition, soil applications are possible, particularly for corn, at plant. 

Various differences were noted between the labels. The following groups were only present in 

the labels for lambda-cyhalothrin: cucurbit vegetables; grass forage, fodder and hay; tuberous and 

corm vegetables and non-bearing citrus. In addition, the following individual crops were not 
25

present in the gamma-cyhalothrin labels: wheat, wheat hay and triticale. The following crops 

appear only in the evaluated gamma-cyhalothrin labels: okra and pistachio. Also, ornamentals 

and turf appear in the labels for gamma-cyhalothrin (see also Tables 3.5a and 3.5b). 

The inspected labels for lambda-cyhalothrin and gamma-cyhalothrin have the following 

Environmental Hazards statements: 

 “This pesticide is extremely toxic to fish and aquatic organisms and toxic to wildlife. 

[For terrestrial uses: (in the evaluated labels for lambda-cyhalothrin)] Do not apply 

directly to water or to areas where surface water is present or to intertidal areas below 

the mean high water mark. Do not apply when weather conditions favor drift from treated 

areas. Drift and runoff from treated areas may be hazardous to aquatic organisms in 

neighboring areas. Do not contaminate water when disposing of equipment washwater. 

This product is highly toxic to bees exposed to direct treatment or residues on blooming 

crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds 

if bees are visiting the treatment area.”

Under spray drift precautions, the labels for lambda-cyhalothrin and gamma-cyhalothrin require a 

buffer zone of 10 ft around certain bodies of water, such as lakes, reservoirs, rivers, permanent 

streams, marshes or natural ponds, estuaries and commercial fish farm ponds, so as to allow 

growth of a maintained vegetative filter strip. The agricultural products should not be applied by 

ground equipment within a distance of 25 ft, or by aerial equipment within a distance of 150 ft, or 

by ULV within a distance of 450 ft from freshwater or estuarine/ marine bodies of water (e.g.

lakes, reservoirs, rivers, permanent streams, marshes or natural ponds, estuaries and commercial 

fish farm ponds). 

For lambda-cyhalothrin, formulations include microencapsulated, pelleted/tableted, emulsifiable 

concentrate, wettable powder, granular, ready-to-use, and impregnated material. This chemical is 

applied in a number of ways. Agricultural application methods include sprays made with ground 

and aerial application equipment, chemigation via irrigation equipment, foliar treatment, and soil 

treatments (in-furrow, T-banding, etc.). Non-agricultural application methods for lambdacyhalothrin include soil treatments (e.g., subslab injection and “rodding”), foam application, 

contact and/or surface treatment, premise treatment (including outdoor premise treatment), crack 

and crevice and/or spot treatment, perimeter treatment, indoor general surface treatment, spot 

treatment, ultra low volume, broadcast, mound treatment, mound drench, band treatment, indoor 

premise treatment, barrier treatment, void treatment, prepaving treatment, impregnated covering 

application, wood surface treatment, manual brush treatment, and injection treatment. 

For gamma-cyhalothrin, formulations include microencapsulated, liquid, emulsifiable 

concentrate, ready-to-use, impregnated collar-tag, pressurized liquid, and granular. Gammacyhalothrin products are applied as crack and crevice and/or spot treatment, indoor general 

surface treatment, indoor premise treatment, void treatment, contact and/or surface treatment, 

spray, directed spray, perimeter treatment, broadcast, chemigation, high volume spray (dilute), 
26

low volume spray (concentrate), outdoor treatment, outdoor premise treatment, animal treatment 

(pour-on), animal treatment (ear tag), mound drench, soil treatment (T-banding), soil in-furrow 

treatment, conservation tillage, mound treatment, band treatment, dip treatment, and bark 

treatment. 

Both lambda-cyhalothrin and gamma-cyhalothrin have uses on cattle and calves (beef and nonlactating). They are used “[F]or the control of lice and horn flies on beef cattle, cows and calves” 

(sample language from label 53883-248). In all instances, the products are formulated with 

piperonyl butoxide (PBO). A summary of the use information for the three products for lambdacyhalothrin appears in Table 3.3a. For lambda-cyhalothrin, there are two types of products: ear 

tags and pour on insecticides. 

Table 3.3a. End Use Labels for Lambda-cyhalothrin for the Use on Cattle 

Label 

(EPA Reg. No.) 

lambdacyhalothrin Application 

Method 

Max. App. Rate 

per Treatment 

No. of Apps. 

per Season 

Int. Between 

Applications 

Saber® Extra 

Insecticide Ear Tags 

(773-75) 

10% a.i. 

(plus 13% 

PBO) 

Application to 

beef and nonlactating cattle 

and calves 

9.5 g product per 

tag, 2 tags per head 

(~2.09x10-4 lb a.i./ 

tag or 4.18x10-4 lb 

a.i./ cattle) 

Not specified 

Not specified, 

effective for 4-

5 months 

Ultra Saber Pour 

On Insecticide 

(773-92) 

1.0% a.i. 

(plus 5.0% 

PBO) 

Pour on 

application to 

beef and nonlactating cattle 

and calves 

10-15 mL or 1⁄3-1⁄2 

fl oz/ cattle or up to 

approx. 3.13x10-4

lb a.i./ cattle 

4 per 6 month 

period 14 days 

Lambda Pour On 

Plus or Cyonara 

Plus Pour-On 

Topical Insecticide 

(53883-248) 

1.0% a.i. 

(plus 5.0% 

PBO) 

Pour on 

application to 

beef and nonlactating cattle 

and calves 

10-15 mL or 1⁄3-1⁄2 

fl oz/ cattle or up to 

approx. 3.13x10-4

lb a.i./ cattle 

4 per 6 month 

period 14 days 

Table 3.3b provides equivalent information for gamma-cyhalothrin for the single product 

registered for use on cattle as a pour on insecticide. A comparison of the pour on products with 

lambda-cyhalothrin indicates that the proportion of PBO to active ingredient is higher for the 

product containing gamma-cyhalothrin. 

Table 3.3b. End Use Label for Gamma-cyhalothrin for the Use on Cattle 

Label 

(EPA Reg. No.) 

gammacyhalothrin Application 

Method 

Max. App. Rate 

per Treatment 

No. of Apps. 

per Season 

Int. Between 

Applications 

Gamma Pour On 

Plus or CSI 

GammaCyhalothrin 

Synergized Topical 

Insecticide Pour-On 

(53883-270) 

0.5% a.i 

(plus 5.0% 

PBO) 

Pour on 

application to 

beef and nonlactating cattle 

and calves 

10-15 mL or 1⁄3-1⁄2 

fl oz/ cattle or up to 

approx. 1.56x10-4

lb a.i./ cattle 

4 per 6 month 

period 14 days 
27

Figure 3.1 shows the cattle and calves inventory as of 2002.5

Figure 3.1. Cattle and Calves Inventory as of 2002 

The usage of lambda-cyhalothrin, from the Screening Level Usage Analysis (SLUA) is provided 

in Table 3.4a. The table is arranged in alphabetical order of crops. According to the table, the 

major agricultural uses for lambda-cyhalothrin (crops for which ≥5,000 lb a.i. are applied), are 

alfalfa, corn, cotton, onions, rice, soybeans, sweet corn and wheat. Crops with relatively high 

percent crop treated (≥40%) include apricots, cabbage, lettuce, onions and sweet corn (maximum 

of 40, 45, 40, 55 and 60% crop treated, respectively). Both onion and sweet corn, which are the 

crops with the highest maximum percent crop treated, are among the major crops (with ≥5,000 lb 

a.i., as identified above). For these crops, the average percent crop treated is also high, with 45 

and 40%, respectively. According to the BEAD Chemical Profile for lambda-cyhalothrin, from 

1998-2008, the largest markets in terms of total pounds of active ingredient applied were cotton, 

soybeans, corn, alfalfa, winter wheat and rice. 

 

5

Information obtained from the following website accessed 08/17/10: 

http://www.nass.usda.gov/research/atlas02/Livestock/Cattle/Cattle%20and%20Calves/Cattle%20and%20Calves%20-

%20Inventory.gif 
28

Table 3.4a. Screening-Level Estimates of Agricultural Uses of Lambda-cyhalothrin 

(SLUA, dated 01/25/10). 

Percent Crop Treated 

Crop lb a.i. Avg. Max. 

Alfalfa 20,000 5 10 

Almonds 2,000 10 10 

Apples 2,000 10 15 

Apricots <500 10 40 

Artichokes <500 5 5 

Asparagus <500 <1 <2.5 

Barley <500 10 10 

Beans, Green 1,000 10 25 

Broccoli 1,000 10 20 

Cabbage 2,000 30 45 

Canola/Rapeseed <500 <1 <2.5 

Cantaloupes <500 <2.5 5 

Carrots <500 <1 <2.5 

Cauliflower <500 15 30 

Celery <500 10 20 

Cherries <500 5 15 

Corn 20,000 <2.5 <2.5 

Cotton 50,000 10 15 

Cucumbers <500 5 10 

Dry, Beans/Peas 1,000 <2.5 <2.5 

Eggplant <500 15 15 

Garlic <500 10 30 

Hazelnuts, (Filberts) <500 5 10 

Lettuce 4,000 30 40 

Onions 5,000 45 55 

Peaches 1,000 5 15 

Peanuts 3,000 10 15 

Pears 1,000 20 30 

Peas, Green <500 <2.5 <2.5 

Pecans <500 <2.5 5 

Peppers <500 5 15 

Potatoes <500 <1 <2.5 

Prunes <500 <2.5 5 

Pumpkins <500 5 10 
29

Table 3.4a. Screening-Level Estimates of Agricultural Uses of Lambda-cyhalothrin 

(SLUA, dated 01/25/10). 

Percent Crop Treated 

Crop lb a.i. Avg. Max. 

Rice 10,000 15 25 

Seed Crops (NPUD '02) <500 NC 25 

Sod (NPUD '02) + <500 NC 5 

Sorghum 2,000 <2.5 10 

Soybeans 60,000 5 10 

Spinach + <500 <2.5 5 

Squash <500 <2.5 10 

Strawberries + <500 <1 <2.5 

Sugar Beets + <500 <1 <2.5 

Sugarcane 1,000 5 10 

Sunflowers 7,000 10 20 

Sweet Corn 20,000 40 60 

Tobacco <500 5 5 

Tomatoes 3,000 20 25 

Walnuts 1,000 5 10 

Watermelons <500 <1 <2.5 

Wheat 10,000 <2.5 <2.5 

All numbers are rounded. '<500' indicates less than 500 pounds of active ingredient. '<2.5' indicates less 

than 2.5 percent of crop is treated. '<1' indicates less than 1 percent of crop is treated. ‘+’ Crops not known 

to be listed on active end use product registrations or as Section 18 emergency exemptions when the report 

was run. ‘N/C’ not calculated. The sources of the SLUA include the USDA-NASS, Private Pesticide 

Market Research, National Pesticide Use Database (NPUD 2002) of the CropLife America Foundation and 

California Department of Pesticide Regulation (CDPR) data. The information reflects amalgamated data 

developed by the Agency and are in a releasable format. 

The usage of gamma-cyhalothrin, from the Screening Level Usage Analysis (SLUA) is provided 

in Table 3.4b. The table is also arranged in alphabetical order of crops. It appears that the major 

uses for gamma-cyhalothrin are soybeans and rice, with 3000 and 1000 lb a.i., respectively, but 

the percent crop treated is less than 2.5%. Several other uses show <500 lb a.i. each, which 

include major crops such as alfalfa, corn and cotton. The crop with the highest percent crop 

treated is apples with 5% (average) and 5% (maximum). According to the BEAD Chemical 

Profile for gamma-cyhalothrin, from 2004-2008, the largest markets in terms of total pounds of 

active ingredient applied were soybeans (more than half of the pounds), alfalfa, rice, winter 

wheat, apples, and cotton. 
30

Table 3.4b. Screening-Level Estimates of Agricultural Uses of Gamma-cyhalothrin 

(SLUA, dated 01/25/10). 

Percent Crop Treated 

Crop lb a.i. Avg. Max. 

Alfalfa <500 <1 <2.5 

Almonds <500 <2.5 <2.5 

Apples <500 5 5 

Beans, Green <500 <1 <2.5 

Broccoli <500 <2.5 <2.5 

Cabbage <500 <1 <2.5 

Corn <500 <1 <2.5 

Cotton <500 <1 <2.5 

Cucumbers + <500 <1 <2.5 

Dry Beans/Peas <500 <1 <2.5 

Lettuce <500 <2.5 <2.5 

Onions <500 <2.5 5 

Peaches <500 <1 <2.5 

Peanuts <500 <1 <2.5 

Pears <500 <2.5 <2.5 

Pecans <500 <2.5 <2.5 

Peppers <500 <1 <2.5 

Rice 1,000 <2.5 <2.5 

Tomatoes <500 <2.5 <2/5 

Sorghum <500 <1 <2.5 

Soybeans 3,000 <1 <2.5 

Sunflowers <500 <1 <2.5 

Sweet Corn <500 <1 <2.5 

Wheat <500 <1 <2.5 

All numbers are rounded. '<500' indicates less than 500 pounds of active ingredient. '<2.5' indicates less 

than 2.5 percent of crop is treated. '<1' indicates less than 1 percent of crop is treated. ‘+’ Crops not known 

to be listed on active end use product registrations or as Section 18 emergency exemptions when the report 

was run. The sources of the SLUA include the USDA-NASS, Private Pesticide Market Research, the 

National Pesticide Use Database (NPUD 2002) of the CropLife America Foundation and California 

Department of Pesticide Regulation (CDPR) data. The information reflects amalgamated data developed 

by the Agency and are in a releasable format. 

According to the BEAD Chemical Profile for lambda-cyhalothrin, the states with the most 

agricultural usage in terms of pounds active ingredient applied are Arkansas, Minnesota, North 

Carolina, Illinois, Louisiana, Texas, Mississippi, and California. These states are also the largest 

in terms of total acres treated from 1998-2008. The U.S. Geological Survey (USGS) pesticide 

agricultural use maps (Fig. 3.2) show regional scale patterns in use intensity within the United 
31

States. The USGS pesticide maps are based on State level estimates of pesticide use rates for 

individual crops, which have been compiled by the National Center for Food and Agricultural 

Policy (NCFAP) for 1999 through 2004, and on the 2002 Census of Agriculture for county crop 

acreage crop. According to the map, the major agricultural uses for lambda-cyhalothrin are 

soybeans and cotton with 19.34 and 17.65% of the use, respectively. These crops are followed by 

corn, sweet corn and rice with 10.57-13.32% of the use. Other crops with >1% of the use 

included alfalfa hay, wheat for grain, tomatoes, peanuts and dry onions. As expected, there is a 

general agreement between the SLUA and the data in the USGS map. The map shows a 

generalized use of lambda-cyhalothrin for agricultural purposes throughout the country, with 

higher use towards the East of the country. It also shows potential uses in estuarine/ marine 

regions of the US. Multiple agricultural uses are approved for lambda-cyhalothrin, other than the 

ones in the map, as indicated above in the Table 3.2a. 

Fig. 3.2. Estimated Use of Lambda-cyhalothrin in 2002 

Note of Caution: The pesticide use maps available (http://water.usgs.gov/nawqa/pnsp/usage/maps/compound_listing.php?year=02 ) show the 

average annual pesticide use intensity expressed as average weight (in pounds) of a pesticide applied to each square mile of agricultural land in a 

county. The area of each map is based on state-level estimates of pesticide use rates for individual crops that were compiled by the CropLife 

Foundation, Crop Protection Research Institute during based on information collected during 1999 through 2004 and on 2002 Census of Agriculture 

county crop acreage. The maps do not represent a specific year, but rather show typical use patterns over the five year period 1999 through 2004. Use 

intensity rates are expressed as the pounds applied per square mile of mapped agricultural land in a county. The area of mapped agricultural land for 

each county was obtained from an enhanced version of the 1992 USGS National Land Cover Data (NLCD). The key limitations of the data used to 

produce these maps include the following: (1) state use coefficients represent an average for the entire state and consequently do not reflect the local 

variability of pesticide management practices found within states and counties, (2) pesticide use estimates are not for a specific year, but represent 
32

typical use patterns for the five year period, (3) state pesticide use coefficients may not have been available for all states where a pesticide may have 

been applied to agricultural land, and therefore, are not displayed on the maps, (4) the county crop acreage is based on the 2002 Census of Agriculture 

and may not represent all crop acreage because of Census nondisclosure rules, and (5) agricultural land area used to calculate the pesticide use 

intensity and display the data was derived from 30-meter satellite remote sensing data that may over estimate or underestimate the actual agricultural 

land area. The maps are not intended for making local-scale estimates of pesticide use, such as estimates at the county level. Please refer to Method for 

Estimating Pesticide Use for a detailed discussion of how the pesticide use data were developed. 

At the present time, there is no similar USGS agricultural use map for gamma-cyhalothrin. 

However, according to the BEAD Chemical Profile for gamma-cyhalothrin, the states with the 

most agricultural usage in terms of “pounds ai applied” are Minnesota, South Dakota, Mississippi, 

Iowa, Colorado, and New York. The report also indicates that the use has been steadily 

increasing from 2004 to 2008.

In addition to the classical agricultural use sites, lambda-cyhalothrin and gamma-cyhalothrin have 

multiple other non-agricultural uses. Lambda-cyhalothrin and gamma-cyhalothrin may also be 

used in multiple urban environments. Examples of uses that may be classified as outdoor 

residential include ornamental lawns and turf, recreation area lawns, residential lawns and paths/ 

patios. Tables 3.5a and 3.5b provide a summary of the nonagricultural (terrestrial or outdoor) 

use sites for lambda-cyhalothrin and gamma-cyhalothrin, respectively. Application methods vary 

(see above). Many of these uses could involve substantive exposure to wildlife, specifically, 

aquatic organisms, and they will be assessed accordingly (e.g., conifers - seed orchard, forest 

trees, commercial/ industrial lawns, residential lawn, golf course turf, ornamental lawns and turf, 

recreation area lawn and residential lawns). Note that there are fewer non-food uses for gammacyhalothrin than for lambda-cyhalothrin. For example, lambda-cyhalothrin has uses on nonagricultural rights-of-way/ fencerows/ hedgerows, but gamma-cyhalothrin does not have this use. 

Another use that will be evaluated is wood protection treatment (outdoors). 

Table 3.5a. Terrestrial Non-Food Uses for Lambda-cyhalothrin 

Use 

Max. App. Rate/ 

units

Max. No. 

Applications/ 

Year 

Max. App. 

Rate per 

Year 

Min. App. 

Interval/ 

days 

agricultural rights-of-way/fencerows/hedgerows 0.03 lb/A NS 0.08 lb 5 

agricultural/farm premises .0033 lb 1K sq. ft. NS NS 21 

agricultural/farm structures/buildings and equipment stated in lb/1 gal NS .3594 lb/yr 7 

airports/landing fields stated in lb/1 gal NS .3594 lb/yr 7 

animal kennels/sleeping quarters (commercial) 0.0033 lb 1K sq. ft. NS NS 7, 21 

automobiles, taxis, limousines, recreational vehicles, & tires stated in lb/1 gal NS .3594 lb/yr 7 

commercial storages/warehouses premises stated in lb/1 gal NS .3594 lb/yr 7 

commercial/industrial lawns 

0.0032 lb/mound 

0.0032 lb 1K sq. ft. NS, 6/yr Various NS, 7 

commercial/institutional/industrial premises/equipment 

(outdoor) 0.0033 lb 1K sq. ft. NS 

NS, 0.3594 

lb/yr 7, 21 

conifers (seed orchard) 0.156 lb/A NS .5 lb/yr NS 

eating establishments stated in lb/1 gal NS 

NS, 0.3594 

lb/yr 7, 21 

forest nursery plantings (for transplant purposes) 0.0416 lb/A NS 0.2496 lb/yr NS 

forest plantings (reforestation programs)(tree farms, tree 

plantations, etc.) 0.0416 lb/A NS 0.2496 lb/yr NS 

forest trees (all or unspecified) 0.0416 lb/A NS 0.2496 lb/yr NS 

forest trees (softwoods, conifers) 0.04 lb/A NS 

0.24 lb/cc, 0.24 

lb/yr NS 

golf course turf 0.0032 lb 1K sq. ft NS, 6/yr 0.36 lb/yr 7 

grasses grown for seed 0.0784 lb/A 6/1 yr, NS .36 lb/yr NS, 7 

household/domestic dwellings outdoor premises 

0.0033 lb 1K sq. ft., 

3.281E-04 lb/mound 6/yr, NS 

NS, 0.3594 

lb/yr 

NS, 7, 21, 

56 
33

Table 3.5a. Terrestrial Non-Food Uses for Lambda-cyhalothrin 

Use 

Max. App. Rate/ 

units

Max. No. 

Applications/ 

Year 

Max. App. 

Rate per 

Year 

Min. App. 

Interval/ 

days 

nonagricultural outdoor buildings/structures 0.0019 lb sq. ft. 6/yr, NS NS, 0.36 lb/yr NS, 7 

nonagricultural rights-of-way/fencerows/hedgerows 0.0150 lb linear ft NS 

NS, 0.3594 

lb/yr NS, 7 

nonagricultural uncultivated areas/soils 

0.0033 lb 1K sq. ft., 

0.0076 lb lin. ft/ft 

depth, 0.0038 lb linear 

ft. NS 

NS, 0.3594 

lb/yr 

NS, 7, 21, 

AN 

ornamental and/or shade trees 

1.125E-04 lb/mound, 

0.0018 lb 1K sq. ft. 6/yr, NS NS, 0.36 lb/yr NS, 7 

ornamental grasses 

0.0025 lb/mound, 

0.0032 lb 1K sq. ft. NS 

NS, 0.3594 

lb/yr 7 

ornamental ground cover 

0.0018 lb 1K sq. ft., 

1.125E-04 lb/mound 6/yr, NS NS, 0.36 lb/yr NS, 7 

ornamental herbaceous plants 

0.0018 lb 1K sq. ft., 

1.125E-04 lb/mound 6/yr, NS NS, 0.36 lb/yr NS, 7 

ornamental lawns and turf 

0.0030 lb 1K sq. ft., 

6.563E-04 lb/mound 6/yr, 7/yr, NS NS, 0.41 lb/yr NS, 7 

ornamental nonflowering plants 

0.0018 lb/sq. ft., 

1.125E-04 lb/mound 6/yr, NS NS, 0.36 lb/yr NS, 7 

ornamental sod farm (turf) 

0.0032 lb/sq. ft., 

0.0025 lb/mound 6/yr, NS NS, 0.36 lb/yr NS, 7 

ornamental woody shrubs and vines 

0.0018 lb/sq. ft., 

1.125E-04 lb/mound 6/yr, NS NS, 0.36 lb/yr NS, 7 

paths/patios 0.0033 lb 1K sq. ft. NS NS, 0.36 lb/yr 7, 21 

recreation area lawns 

0.0032 lb 1K sq. ft., 

0.0032 lb/mound 6/yr, NS 

NS, 0.4117 

lb/yr NS, 7 

residential lawns 

0.0032 lb 1K sq. ft., 

0.0032 lb/mound 6/yr, NS 

NS, 0.4117 

lb/yr NS, 7 

seed orchard trees 0.0042 lb/tree NS 0.52 lb/yr NS 

wide area/general outdoor treatment (public health use) 0.0032 lb 1K sq. ft. NS .3594 lb/yr 7 

wood protection treatment to buildings/products outdoor 

0.0075 lb 1K sq. ft., 

0.015 lb lin. ft/ft depth NS NS NS 

NS = Not Specified; AN = As Needed; cc = crop cycle. Data obtained from LUIS Report. 

Table 3.5b. Terrestrial Non-Food Uses for Gamma-cyhalothrin 

Use 

Max. App. Rate/ 

units

Max. No. 

Applications/ 

Year 

Max. App. 

Rate per 

Year 

Min. App. 

Interval/ 

days 

agricultural/farm premises 0.0081 lb 1K sq. ft. NS NS 21, AN, NS 

agricultural/farm structures/buildings and equipment 0.0081 lb 1K sq. ft. NS NS NS, 21 

airports/landing fields 0.0016 lb 1K sq. ft. NS NS NS, AN 

animal kennels/sleeping quarters (commercial) 0.0081 lb 1K sq. ft. NS NS 21, AN, NS 

automobiles, taxis, limousines, recreational vehicles, & tires 0.0026 lb 1K sq. ft. NS NS 21, AN, NS 

christmas tree plantations 0.02 lb/A NS 0.12 lb/yr NS 

commercial storages/warehouses premises 0.0079 lb 1K sq. ft. NS NS 21, AN, NS 

commercial/industrial lawns 

0.0625 lb/A, 

0.0079 lb 1K sq. ft., 

0.0016 lb/mound NS 

0.1641 lb/yr, 

NS NS, 7, 30 

commercial/institutional/industrial premises/equipment 

(outdoor) 0.0016 lb/mound NS NS AN, NS 

conifers (seed orchard) 

0.0781 lb/A 

0.0020 lb/tree NS, 3 cc 0.25 lb/yr, NS NS, 7 

eating establishments 0.0016 lb 1K sq. ft. NS NS 21, AN, NS 

forest trees (all or unspecified) .0200 lb/A NS 0.12 lb/yr NS 

forest trees (softwoods, conifers) .0200 lb/A 3/cc 

0.1203 lb/yr, 

NS 7, NS 
34

Table 3.5b. Terrestrial Non-Food Uses for Gamma-cyhalothrin 

Use 

Max. App. Rate/ 

units

Max. No. 

Applications/ 

Year 

Max. App. 

Rate per 

Year 

Min. App. 

Interval/ 

days 

golf course turf 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS 

NS, 

0.1641 lb/yr 7, AN 

household/domestic dwellings outdoor premises 

0.021 lb 1K sq. ft., 

1.635E-04 lb/mound NS, 6/yr NS NS, 60, AN 

nonagricultural areas (public health use) 0.0126 lb 1K sq. ft. NS NS NS, AN 

nonagricultural outdoor buildings/structures 0.0079 lb 1K sq. ft NS NS NS, AN 

nonagricultural rights-of-way/fencerows/hedgerows 0.0016 lb 1K sq. ft NS NS NS, AN 

nonagricultural uncultivated areas/soils 0.0026 lb 1K sq. ft NS NS NS, AN 

ornamental and/or shade trees 

0.0625 lb/A, 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS 

0.1641 lb/yr, 

NS 

7, 30, NS, 

AN 

ornamental ground cover 

0.0625 lb/A, 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS 

0.1641 lb/yr, 

NS 7, 30, AN 

ornamental herbaceous plants 

0.0625 lb/A, 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS 

0.1641 lb/yr, 

NS 

7, 30, NS, 

AN 

ornamental lawns and turf 

0.0625 lb/A, 

0.0421 lb 1K sq. ft., 

0.0016 lb/mound NS, 7/yr, 14/yr 

0.1641 lb/yr, 

NS 

7, NS, 21, 

30, AN 

ornamental nonflowering plants 

0.0625 lb/A, 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS 

0.1641 lb/yr, 

NS 7, 30, NS 

ornamental sod farm (turf) 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS 0.1641 lb/yr 7, AN 

ornamental woody shrubs and vines 

0.0625 lb/A, 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS 

0.1641 lb/yr, 

NS 

7, 30, NS, 

AN 

paths/patios 0.0016 lb 1K sq. ft. NS NS NS, AN 

pet living/sleeping quarters 0.0079 lb 1K sq. ft. NS NS NS 

recreation area lawns 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS 

0.1641 lb/yr, 

NS 7, AN 

recreational areas 

0.0625 lb/A, 

0.0016 lb/mound NS 0.1641 lb/yr 7, 30 

refuse/solid waste sites (outdoor) 0.0081 lb 1K sq. ft. NS NS 21 

residential lawns 

0.0625 lb/A, 

0.0015 lb 1K sq. ft., 

0.0016 lb/mound NS, 6/yr 

0.1641 lb/yr, 

NS 

7, 30, NS, 

AN 

sewage disposal areas 0.0016 lb 1K sq. ft. NS NS NS, AN 

wood protection treatment to buildings/products outdoor 0.0043 lb 1K sq. ft. NS NS NS 

NS = Not Specified; AN = As Needed; cc = crop cycle. Data obtained from LUIS Report. 

In addition, there are several other indoor non-food or indoor residential use sites for both 

lambda-cyhalothrin and gamma-cyhalothrin, like for example, commercial storage/ warehouse 

premises, commercial/ institutional/ industrial premises/ equipment (indoor), eating 

establishments, food stores/ markets/ supermarkets premises, hospitals/ medical institutions 

premises (human/ veterinarian), household/ domestic dwellings and pet living/ sleeping quarters. 

Lambda-cyhalothrin and gamma-cyhalothrin also have greenhouse uses. 

For the indoor uses, the Division has conducted environmental risk assessments for a few 

chemicals (such as permethrin, resmethrin and pyrethrins) for Re-registration Eligibility 

Decisions. In one study (Weston and Lydy 2010), several synthetic pyrethroids were observed in 

effluents after secondary treatment from POTWs in the Sacramento-San Joaquin Delta. In the 

study, bifenthrin was the most frequently detected pyrethroid. Lambda-cyhalothrin was found in 
35

17% of the municipal wastewater treatment plant effluents (POTWs) tested in the SacramentoSan Joaquin Delta (18 samples tested), at a maximum concentration of 5.5 ng/L, and it exceeded 

the Hyalella azteca EC50 of 2.3 ng/L in 17% of the samples. There is the potential for synthetic 

pyrethroids to reach surface waters via exposure from contaminated drains, and even after 

treatment in plants (POTWs) (for further information about this study, see Appendix B). EFED 

will evaluate the potential for exposure to aquatic organisms from the indoor uses of lambdacyhalothrin and gamma-cyhalothrin in the final ecological risk assessment (see Section 6. 

Conceptual Model, and Section 7, Analysis Plan for further details).

Toxicity data on environmental mixtures of lambda-cyhalothrin and gamma-cyhalothrin with 

other pesticides may be presented, if available, as part of the ecological risk assessment. It is 

expected that the toxic effect of lambda-cyhalothrin and gamma-cyhalothrin, in combination with 

other pesticides used in the environment, is likely to be a function of many factors including but 

not necessarily limited to: (1) the exposed species, (2) the co-contaminants in the mixture, (3) the 

ratio of lambda-cyhalothrin or gamma-cyhalothrin and co-contaminant concentrations, (4) 

differences in the pattern and duration of exposure among contaminants, and (5) the differential 

effects of other physical/ chemical characteristics of the receiving waters (e.g. organic matter 

present in sediment and suspended water). Quantitatively predicting the combined effects of all 

these variables on mixture toxicity to any given taxa with confidence is beyond the capabilities of 

the available data and methodologies. However, a discussion of implications of the available 

pesticide mixture effects data regarding the confidence of risk assessment conclusions will be 

addressed as part of the uncertainty analysis. EFED will consider open literature, currently 

available models and other lines-of-evidence (e.g., monitoring data), as available to address the 

potential for cumulative effects of pyrethroids in the risk description of the ecological assessment 

for lambda- and gamma-cyhalothrin. 

Piperonyl butoxide (PBO) and MGK-264 are commonly used in formulations with pyrethroids. 

PBO acts as a potentiator in both mammals and insects because the pyrethroid is not metabolized 

and excreted as quickly in its presence (Barile 2004; Hodgson & Smart 2001). Exposure to 

pyrethroids along with PBO increases the toxicity of the pyrethroids (Amweg & Weston 2007; 

Weston & Lydy 2010). MGK-264, another potentiator/synergist used with pyrethroids, has 

similar effects as those observed for piperonyl butoxide (Hodgson & Smart 2001). 

A total of 4 active product registrations exist for lambda-cyhalothrin and gamma-cyhalothrin 

formulations with PBO: 

• Lambda-cyhalothrin and PBO: # 773-75, #773-92, #53883-248 

• Gamma-cyhalothrin and PBO: # 53883-270 

The registrations are for cattle ear tags (#773-75) or cattle pour-on treatments (#773-92, #53883-

248 and #53883-270). (See discussion above and Tables 3.3a and b.). 

Lambda-cyhalothrin and gamma-cyhalothrin are not co-formulated with MGK-264 in any 

currently active registrations. 
36

The Agency routinely assesses potential exposure to formulations by examining acute exposure to 

spray drift or direct applications to water. Toxicity data may be also requested if there is any 

indication that a formulated product may be more toxic than the technical grade active ingredient. 

Acute toxicity data on the formulation containing PBO will be compared to estimated exposure of 

runoff resulting from cattle pour-on treatments. 

PBO and/or MGK-264 from other pyrethroid applications (e.g. the application of an adulticide 

containing PBO), could interact with lambda-cyhalothrin and gamma-cyhalothrin in the 

environment. Available literature data also suggest the potential for synergism in the environment 

(Amweg et al. 2006, Weston et al. 2006). Therefore, potential interactions will be discussed in the 

risk assessment. EPA is evaluating options for gathering and designing studies that would 

improve the evaluation of pyrethroid end use products co-formulated with a synergist. 

3.3. Environmental Fate and Transport 

Cyhalothrin (PP563) is a racemic mixture that consists of four isomers (1R,cis,Z-S’; 1S,cis,Z-R’; 

1R,cis,Z-R’; and 1S,cis,Z-S’); while lambda-cyhalothrin (PP321) is a racemic mixture that consist 

of two of the isomers present in cyhalothrin (1R,cis,Z-S’ and 1S,cis,Z-R’). Greater than 98% of 

gamma-cyhalothrin (XDE-225 or XR-225) is the biologically active enantiomer (1R,cis,Z-S’) 

(please, refer to further discussion in Section 3). 

Table 3.6 summarizes the environmental fate/transport properties of lambda-cyhalothrin and 

gamma-cyhalothrin. For information about the physicochemical properties of these compounds, 

refer to Table 3.1b. 
37

Table 3.6. Summary of environmental fate parameters for lambda- and gamma-cyhalothrin

Lambda-cyhalothrin Gamma-cyhalothrin

Parameters Value Source Value Source

Hydrolysis T1/2 pH 5 stable 

pH 7 stable 

pH 9 13 days 

00151604 (S) 

Rate exceeded the 

limit of solubility. 

pH 5 stable 

pH 7 relatively stable 

pH 9 2.5 days* 

Natural river water 26.8 

days* 

45447409 (pH 5, 7, A)

(pH 9, U, upgradable) 

*River water and pH 9 

T1/2 values are of high 

uncertainty. 

Aqueous Photolysis 

(pH 5) T1/2

Reviewer calculated 

linear half-lives: 

29.5 days* (phenyl label)

36.9 days* (cyclopropyl)

44861501 (U) *Halflives are uncertain. 

Test substance did not 

remain in solution 

throughout the study. 

8.2 days (cyclopropyl) 

8.3 days (phenoxy label) 

8.6 days (combined lab) 

13 days (environmental 

phototransformation T1/2) 

46394702 (A) 

Soil Photolysis T1/2 Fairly stable loam, only 

13-16% degraded after 

ca. 35 days. Compound 

II was a minor product. 

40052405 (A) Not Available Not Available 

Aerobic Soil Metabolism 

T1/2

T1/2 46.2 days sandy 

loam 

Reported DT50 31, 55, 26 

days sandy loam 

102 days loamy sand 

*12.2 days loam 

14.5 days silt loam 

(CS formulation Warrior 

T; purity 11.8% a.i.) 

[**For cypermethrin: 

24 days clay loam, 

73 d. loamy coarse sand,

42 days fen peat]

00151607 & 44861504 

(A) [For cyhalothrin: 

DT50 26, 48 days SL 

83 days loamy sand] 

*45447410 (S) 

[**00089995 (A) 

Cypermethrin tested to 

provide info on 

alcohol moiety] 

28.2 days sandy loam 

36.9 days silt loam 

*32.5 days loam 

51.5 days silt loam

(CS formulation GF-231; 

purity 14.8% a.i.) 

45447411 (S) 

[+For cyhalothrin: 

46.8 days sandy loam 

60.5 days - silt loam]

*45447410 (S) 

Anaerobic Soil Metabolism 

T1/2

Aerobic 30 days, then 

flooded, T1/2 = 30 days

sandy loam cyhalothrin; 

flooded DT50 110 days 

for cyhalothrin; 107 days 

for lambda-cyhalothrin 

00151607 & 44861504 

(A) 

Not Available Not Available

Aerobic aquatic 

metabolism T1/2

21.1 days sand 

34.1 days sandy loam 

52.9 days loam 

(123.8 days silty clay – 

T1/2 is of limited value) 

44861506 (A) 

44367402 (S) 

Silty clay sediment: 

40.1 days - total system 

41.0 days - in sediment 

<3 days - water column 

(Extrapolated values) 

45447412 (S) 

Anaerobic aquatic 

metabolism T1/2

142 days silty clay 44367401 (S) Not Available Not Available 

Soil Partition Coefficient 

(Kd in mL/g) 

Mean Kd (lambdacyhalothrin) = 4,350 mL/g 

Mean Kd (gammacyhalothrin) = 622 mL/g 

Sandy Loam 3810 

Loamy Sand 1970 

Silty Clay Loam 5880 

Loamy Sand 2100 

Silty Clay Loam 4490 

Sandy Loam 6890 

Sandy Loam 7610 

Loamy Sand 3470 

Sand 2400 

Sandy Loam 4870

44861503 (A) Loamy Sand 672, 

Sandy Loam 751, 

Silty Loam 826, 

Sandy Loam 239 

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

Loamy Sand 555, 

Sandy Loam 601, 

Silty Loam 630, 

Sandy Loam 355 

45447413 (S) 

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

These values are for 

cyhalothrin, which was 

tested along with 

gamma-cyhalothrin. 
38

Table 3.6. Summary of environmental fate parameters for lambda- and gamma-cyhalothrin

Lambda-cyhalothrin Gamma-cyhalothrin

Parameters Value Source Value Source

Soil Partition Coefficient 

(KOC in mL/gOC) 

Mean KOC (lambdacyhalothrin) = 333,200 

mL/gOC

Mean KOC (gammacyhalothrin) = 59,700 

mL/gOC

Sandy Loam 346,000 

Loamy Sand 200,000 

Silty Clay Loam 298,000

Loamy Sand 724,000 

Silty Clay Loam 209,000 

Sandy Loam 270,000 

Sandy Loam 305,000 

Loamy Sand 352,000 

Sand 518,000 

Sandy Loam 110,000

44861503 (A) Loamy Sand 34133, 

Sandy Loam 92692, 

Silty Loam 69952, 

Sandy Loam 41932 

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

Loamy Sand 28176, 

Sandy Loam 74212, 

Silty Loam 53345, 

Sandy Loam 62242 

45447413 (S) 

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

These values are for 

cyhalothrin, which was 

tested along with 

gamma-cyhalothrin. 

Mean = 54,500 

Aged Adsorption/ 

Desorption 

In aged batch equilibrium 

study (up to 8 weeks of 

incubation in darkness at 4 

and 20°C, sandy loam), 

≥97.6% of the applied 

radioactivity remained 

adsorbed after 24 hr of 

equilibration. However, it 

was >80% for soil incubated 

under ambient light and 

subject to wet/ dry cycles. 

44861509 (S) Not Available Not Available 

Column Leaching The aged (30 days) residues 

of cyhalothrin and lambdacyhalothrin were immobile 

in two soil columns (loamy 

sand and sandy loam). All 

residues were wthin the 

upper 0-5 cm soil depth. 

00151608 (A, partial) Not Available Not Available 

Terrestrial Field 

Dissipation T1/2

IL Clay Loam 33 days 

(~18-21% AR remained 

at 279 days) 

MS Silty Loam 12 days 

In IL & MS most of the 

AR in the 0-5 & 5-10 cm 

depth (1 lb/gal EC 14CPP321, 2 labels). 

40052407 (A) MS Silty Loam 15.6 days 45794902 (A) 

CA Loam 29.5 days 

All residues in the 0-15 

cm soil depth. 

GF-231 CS; 14.8% a.i. 

Aquatic Field Dissipation 

T1/2

MS (rice) 0.4-1.8 days 

CA (rice) 1.0-1.8 days 

(T1/2 from water, no data 

on soil/ sediment) 

44367403 (S) 

44367404 (S) 

Artificial pond 

Not Available Not Available 

Dissipation in Aquatic 

Microcosm T1/2

17 hours water layer, 

34 hours total system 

44861508 (S) 

(water pH 9.83) 

Not Available Not Available 

Bioaccumulation in Fish Cyhalothrin: 4600x whole 

fish (carp); DT50 ~9 days

depuration. 77-79% of the 

radioactivity eliminated 

after 28 days. ~50-70% of 

the residues were 

cyhalothrin and ~10-19% 

was Compound Ia. 

Cypermethrin: Benzyl label: 

111x edible; 468x whole 

fish; 579X non-edible; 83-

87% depurate after 21 days. 

DT50 ~1.2 days for 

depuration. mPBacid was 

~7% in edible tissue.

00152744, 00152745 

(A) 

42868203 (A) 

[Cypermethrin: 

provided information 

about the alcohol 

moiety] 

Not Available Not Available 
39

Lambda-cyhalothrin and gamma-cyhalothrin are Type II synthetic pyrethroids (they are cyano 

substituted in the alpha position). They have a 2-chloro-3,3,3-trifluoropropenyl group and they 

are 2,2-dimethyl substituted in the cyclopropane ring. The environmental fate database for 

lambda-cyhalothrin is substantially complete, but it contains various supplemental studies. The 

database for gamma-cyhalothrin is smaller and it consists mostly of supplemental studies, but it 

was largely supplemented with data from lambda-cyhalothrin. All studies on gamma-cyhalothrin 

were considered supplemental, except for the terrestrial field dissipation study. Both lambdacyhalothrin and gamma-cyhalothrin show very low solubilities (≤5.0 ppb). They are hydrophobic 

compounds and their octanol/ water partition coefficients are high (log KOW ≥ 4.96). Based on 

their octanol/water partition coefficient, they would be predicted to be hightly bioaccumulative 

(which appears to be confirmed by the bioaccumulation in fish study, see further details below). 

Volatilization from moist or dry surfaces is not expected to be an important transport process, 

since both chemicals have relatively low vapor pressures and Henry’s Law constants (see Section 

3 for further details). Furthermore, lambda-cyhalothrin and gamma-cyhalothrin readily bind to 

soils or partition with suspended matter and sediment. Thus, potential volatilization would be 

greatly reduced. 

Based on a combination of data for lambda-cyhalothrin and gamma-cyhalothrin, it is concluded 

that they are moderately persistent in the environment and degrade slowly through a combination 

of biotic and abiotic mechanisms. Lambda-cyhalohrin and gamma-cyhalothrin are stable to 

relatively stable in acidic and neutral water, but hydrolyze in a matter of several days to weeks 

under alkaline conditions (half-life 13 days for lambda-cyhalothrin at pH 9). Lambda-cyhalothrin 

and gamma-cyhalothrin are more stable to light than the first or second generation pyrethroids 

like, for example, allethrin and resmethrin, but still undergo some photolysis in water, with halflives of several weeks in water (half-life 13 environmental days for gamma-cyhalothrin). It 

appears that the alpha-cyano group stabilizes somewhat the molecules and they do not undergo 

photolysis readily. On soil, lambda-cyhalothrin is fairly stable (with very little degradation on the 

order of only ~13% in 35 days). Under both aerobic and anaerobic soil metabolism conditions, 

cyhalothrin, lambda-cyhalothrin and gamma-cyhalothrin biodegrade at moderate rates, with 

comparable half-lives of several weeks. Various aerobic soil studies available with all three test 

substances, which included even additional capsule suspension formulated studies, corroborate 

that the rates of aerobic transformation is similar for these chemicals (range of aerobic soil halflives is 28.2-60.5 days out of five studies). In aquatic metabolism conditions, lambda-cyhalothrin 

and gamma-cyhalothrin may biodegrade at moderate rates under aerobic condition, with half-lives 

on the order of about 21-53 days (aerobic, both chemicals), but more slowly under anaerobic 

condition, with a half-life of 142 days (lambda-cyhalothrin only). Terrestrial field dissipation 

studies confirm the results observed in the laboratory, indicating that a combination of biotic and 

abiotic mechanisms of dissipation take place. Half-lives of 12-33 days were observed in the field 

for both lambda-cyhalothrin and gamma-cyhalothrin, with the majority of the residues remaining 

in the uppermost soil layer. Due to their low mobility observed in laboratory studies and in the 

field, both chemicals are expected to have little mobility on soil surfaces and, therefore, leaching 

into groundwater is not expected to be an important environmental fate process. However, 

despite the protective imposed buffer zone and vegetated buffer strip, they could reach adjacent 

surface waters via spray drift or runoff events accompanied by erosion. In aquatic environments, 
40

 

these chemicals will partition with the sediment and will linger for long periods of time (several 

months). The sediments could serve as repositories of lambda-cyhalothrin and gammacyhalothrin in dynamic equilibrium with the pore water and with the surface water, occurring 

after numerous applications. Lambda-cyhalothrin and gamma-cyhalothrin are highly 

bioaccumulative (~4,600x), based on a study performed with cyhalothrin, and they depurate at 

moderately slow rates (~9 days). There is the potential for bioaccumulation and biomagnification 

to take place. Willis and McDowell (1987) indicate that for synthetic pyrethroids with similar 

structure to that of lambda-cyhalothrin and gamma-cyhalothrin, dissipation from plant foliage 

occurs with half-lives on the order of 5-6 days, but it may be higher for the total residues. A low 

rate of volatilization was observed from leaves (88% of applied remaining on the leaves after 24 

hours).6 The chemical does not translocate in the plant tissue. 

Abiotic Degradation

Both, lambda-cyhalothrin and gamma-cyhalothrin have an ester moiety that is expected to be 

susceptible to hydrolysis (particularly at high pHs). This behavior is confirmed in the hydrolysis 

studies, where both lambda-cyhalothrin and gamma-cyhalothrin are fairly stable in pH 5 and pH 7 

buffered solutions. In pH 9 solution, lambda-cyhalothrin degraded with a half-life of 13 days 

(however, the pH 9 part of the study conducted with gamma-cyhalothrin was considered highly 

uncertain, and the study conducted with lambda-cyhalothrin was conducted at a rate that 

exceeded the solubility limit). (1RS)-cis-3(ZE)-2-chloro-3,3,3-trifluro-1-propenyl)-2,2-

dimethylcylopropane-carboxylate (Compound Ia, maximum 68% AR at 30 days) was the major 

metabolite observed in the lambda-cyhalothrin study. Even though there is a reported half-life for 

gamma-cyhalothrin at pH 9, it was not considered in this assessment; however, in the study, two 

major metabolites were observed. For gamma-cyhalothrin, at pH 9, the major early degradate 

observed was 3-phenoxybenzaldehyde (Compound IV, maximum 55.6% AR at 2 days), followed 

by subsequent oxidation into 3-phenoxybenzoid acid (Compound V or 3-PBA, maximum 54.6% 

AR at 30 days). 

Upon aqueous photolysis (pH 5), gamma-cyhalothrin showed a half-life of 13 environmental 

days. This half-life was considered representative for both chemicals. The half-life of 30-37 days 

observed in the study conducted with lambda-cyhalothrin was not considered accurate because 

there was evidence of precipitation in the study. Aquatic photolysis appears to be a moderate 

route of dissipation for these chemicals when compared to other soil, sediment, and water halflives. In the new chemical review of gamma-cyhalothrin, and considering the registrant’s 

bridging plan, the aqueous photolysis study was not requested, since aqueous photolysis is not 

expected to be enantioselective (although it was submitted and found acceptable). For the 

assessment it was assumed that the gamma-cyhalothrin photodegradation rate is comparable to 

that of lambda-cyhalothrin. It is worth noting that for aqueous photolysis, the relative 

contribution of this route of degradation in surface water modeling and the environment is not 

expected to be significant. Lambda-cyhalothrin and gamma-cyhalothrin’s high soil binding 

affinity and the limited light penetration into most water bodies greatly reduce the potential for 

aqueous photodegradation. Nonetheless, both studies coincided with respect to the identity of the 

metabolites. Compounds Ia and Ib were a maximum of 13.7 and 7.1% AR, respectively in the 

6 European Commission Review Report for the Active Substance Lambda-Cyhalothrin, 7572/VI/97-final; Jan 25, 2001
41

study with lambda-cyhalothrin. Unspecified compounds Ia and Ib were a maximum of 45.0% AR 

in the study with gamma-cyhalothrin. The other metabolite identified was Compound V, which 

was a maximum of 25.0-42.0% AR (both chemicals). 

Upon soil photodegradation, lambda-cyhalothrin appeared to be persistent through the testing 

period. Only 13-16% of the applied lambda-cyhalothrin degraded after ca. 35 days. Compound 

V was a minor product in the study. Gamma-cyhalothrin is expected to show a similar photolytic 

behavior on soils. 

Metabolism

Several aerobic soil metabolism studies were identified for cyhalothrin, lambda-cyhalothrin and 

gamma-cyhalothrin. Among the studies, half-lives were in the relatively narrow range of 28.2-

60.5 days (5 half-lives, observed in three soils and three test substances). Further, the registrant 

conducted aerobic soil metabolism studies with lambda-cyhalothrin and gamma-cyhalothrin in 

capsule suspension (CS) formulation in order to evaluate whether encapsulating would increase 

the persistence of the test substances relative to the technical material. For lambda-cyhalothrin, 

the half-lives were 12.2 and 14.5 days and for gamma-cyhalothrin, the half-lives were 32.5 and 

51.5 days, for a loam and a silt loam, respectively. The CS half-lives will not be considered in 

assessment because they represent other additional processes which are not related to metabolism, 

but they generally also indicate that the aerobic soil half-lives are of the same order of magnitude 

for both chemicals and relatively comparable. Degradation of gamma-cyhalothrin in aerobic soil 

appears to occur in a similar manner to that of cyhalothrin and lambda-cyhalothrin. The studies 

submitted for bridging purposes do not provide an indication of those soil properties that may 

increase or decrease the rate of degradation. However, the degradates observed in the aerobic soil 

metabolism studies for lambda-cyhalothrin and gamma-cyhalothrin (e.g., hydroxylated products) 

suggest that the type and activity of soil microbes could affect the rate of lambda-cyhalothrin and 

gamma-cyhalothrin degradation. Hydroxylation at the para-carbon of the phenoxy ring of 

lambda-cyhalothrin and gamma-cyhalothrin appears to yield 3-(2-chloro-3,3,3-trifluoro-1-

propenyl)-2,2-dimethyl-cyclopropanecarboxylic acid cyano[3-(4-hydroxyphenoxy) 

phenyl]methyl ester (Compound XV, 12.5% at 63 days for lambda-cyhalothrin). Compound XV 

and the parent compound can yield 3-(4-hydroxyphenoxy)-benzaldehyde and Compound V, 

respectively, following ester cleavage, and loss of the cyano group. Further oxidation and 

hydrolysis reactions presumably result in the ultimate formation of carbon dioxide (CO2). In 

aerobic soil metabolism study of technical product gamma-cyhalothrin the major degradation 

product was 3-(4-hydroxyphenoxy)-benzaldehyde (maximum 12.2% AR at 17 days). Other 

metabolites were only minor (<10% AR). 

One anaerobic soil metabolism study conducted on cyhalothrin was identified in this assessment. 

The half dissipation time was roughly 30 days, after which the degradation appeared to proceed 

much slower. Due to the limited number of data points in the study, the DT50 was considered 

highly uncertain. After reaching natural water bodies, lambda-cyhalothrin and gammacyhalothrin will partition to dissolved organic material, suspended solids, and sediment. Four 

aerobic aquatic metabolism studies were identified in this assessment (three for lambdacyhalothrin and one for gamma-cyhalothrin). The half-lives were in the range of 21.1 to 52.9 
42

days for lambda-cyhalothrin and it was 40.1 days for gamma-cyhalothrin, indicating that both test 

substances degrade with similar rates under the test conditions. In the aerobic aquatic metabolism 

study, gamma-cyhalothrin dissipated from the water layer very rapidly and was detected at ≤4.5% 

AR at any sampling interval from time zero through 30 days posttreatment. The first 

measurement of gamma-cyhalothrin in the dissolved phase on day 0 of the study was 3.7% of 

applied material. On day 14 the dissolved level had decreased to 1.8% of the applied material. In 

the sediment gamma-cyhalothrin degraded with an extrapolated half-life of 41 days. The end 

products of the aeroibic aquatic process are consistent with those observed in the aerobic soil 

metabolism study. One of the products appears to be Compound V (16.0% AR at 30 days for 

lambda-cyhalothrin and 26.9% AR at 30 days for one replicate in the gamma-cyhalothrin study) 

and Compound Ia (22.0% AR at 30 days for gamma-cyhalothrin). Compound XV was a minor 

product. Under anaerobic aquatic conditions, lambda-cyhalothrin appears to be more stable than 

under aerobic condition. For a single study, the anaerobic aquatic metabolism half-life was 142 

days. Consistent with the other metabolism studies, the major metabolites were Compound 1a 

and Compound V. 

Mobility

In an acceptable study, for lambda-cyhalothrin, the Kd values ranged from 1970 to 6890 mL/g and 

the KOC values ranged from 110,000 to 518,000 mL/gOC (10 soils were tested, immobile 

according to FAO mobility classification, FAO 2000). It is noted that this study was conducted 

with sterile soils. Gamma-cyhalothrin simple Kd values ranged from 239 to 826 mL/g, while for 

cyhalothrin (tested concurrently) Kd values ranged from 355-601 mL/g. For gamma-cyhalothrin 

the corresponding KOC values ranged from 34,133 to 92,692 mL/gOC (hardly mobile as per FAO 

2000) for all tested soils and for cyhalothrin KOC values were 28,176 -74,212 mL/gOC (hardly 

mobile, FAO 2000). Just as for cyhalothrin and lambda-cyhalothrin there was no linear 

relationship between the soil organic carbon content and the Kd values for different soils for 

gamma-cyhalothrin. Because Kd values were obtained only at one concentration, the Freundlich 

adsorption/desorption coefficients could not be calculated for gamma-cyhalothrin or for 

cyhalothrin. However, the data suggest that gamma-cyhalothrin, similar to cyhalothrin and 

lambda-cyhalothrin, is expected to be largely immobile in soil and water environments with 

settled sediment. The bulk of lambda-cyhalothrin and gamma-cyhalothrin transport would most 

likely occur with movement of soil as erosion in runoff and suspended sediment in lotic (moving) 

water bodies. 

In a soil column study (two soils tested: loamy sand and sandy loam), aged (30 days) lambdacyhalothrin’s residues remained mostly in the uppermost soil layer (0-5 cm). Residues were 

characterized as immobile. In a supplemental study, lambda-cyhalothrin was aged for up to 8 

weeks in darkness at 4 and 20°C in a sandy loam. The soil was then equilibrated in a batch 

equilibrium-type study for 24 hours. It was found that ≥97.6% AR remained adsorbed to the soil. 

In the same study, another sample of sandy loam soil was incubated under ambient light and 

subject to wet/ dry cycles. In this latter instance ≥80% AR remained in the soil after 

equilibration. 

Field Dissipation
43

Lambda-cyhalothrin and gamma-cyhalothrin appear to be immobile and moderately persistent in 

laboratory studies and in the field environment. It is highly unlikely that lambda-cyhalothrin and 

gamma-cyhalothrin will reach ground water resources due to their high soil adsorption affinity. 

For lambda-cyhalothrin, two terrestrial field dissipation studies indicated half-lives of 33 days 

(IL) and 12 days (MS). The test substance remained mostly in the uppermost layers of soil (0-5 

and 5-10 cm). Gamma-cyhalothrin was not detected below the 0-15 cm soil depth, with the 

exception of a single detection below the LOQ (0.010 μg/g) at 4 days post-treatment in the 15-30 

cm soil depth in MS site. Gamma-cyhalothrin dissipation half-lives were similar to those of 

lambda-cyhalothrin with 15.6 days (MS) and 29.5 days (CA). Because the capsule suspension 

formulation might be expected to behave differently in the environment compared to nonencapsulated formulations, a terrestrial field dissipation study using the gamma-cyhalothrin 

capsule suspension (CS) was conducted. In the terrestrial field dissipation study conducted with 

lambda-cyhalothrin, transformation products monitored at the two sites were reported to be at low 

levels (<7%). Field soil samples were not analyzed for transformation products in the gammacyhalothrin study. The study authors stated that gamma-cyhalothrin was the only residue of 

environmental concern because the major degradates are fully and rapidly mineralized in soil and 

water, do not leach, and are formed via the detoxification process of ester cleavage. In two 

supplemental aquatic field dissipation studies conducted on rice plots in MS and CA, lambdacyhalothrin appeared to dissipate rapidly from the water (half-lives were 0.4-1.8 days in the 

water); however the studies did offer suitable information about the dissipation of the chemical 

from the soil/sediment. 

As indicated earlier, lambda-cyhalothrin and gamma-cyhalothrin will likely reach surface waters 

via soil erosion and particulate runoff after rainfall, and via spray drift during or shortly after 

application. A published report measured 73% to 90% of synthetic pyrethroids are bound to 

eroding sediment in runoff (Liu et al., 2004). The major routes of lambda-cyhalothrin and 

gamma-cyhalothrin transport and dissipation are binding to soil particles (KOC values 110,000 to 

518,000 in an acceptable study), degradation through abiotic processes in alkaline environments 

(at pH 9.0 t1/2=13 days), and through biotic processes via aerobic soil metabolism (t1/2=28.2-60.5 

days) and aerobic aquatic metabolism (t1/2=21.1-52.9 days in total system). It appears that in 

acidic or anaerobic environments, lambda-cyhalothrin and gamma-cyhalothrin would be more 

persistent. 

Bioaccumulation in Fish

In a study performed with cyhalothrin, the chemical appears to be highly bioaccumulative (4,600x 

in the whole fish), but it depurates at moderately slow rates (depuration t1/2 about 9 days). It 

appears that situations may occur, where this test substance, as well and lambda-cyhalothrin and 

gamma-cyhalothrin, may persist in fish tissue for extended periods of time. Compound Ia was up 

to 22% in muscle and viscera. In a study performed with cypermethrin, which provided some 

information on the alcohol moiety of lambda-cyhalothrin and gamma-cyhalothrin, around 7% was 

Compound V in the edible tissue. 

Table 3.7a provides a summary of the data on the occurrence of the transformation products of 

lambda-cyhalothrin and gamma-cyhalothrin. 
44

Table 3.7a. Summary of degradate formation for lambda-cyhalothrin & gamma-cyhalothrin 

DEGRADATE and MAXIMUM CONCENTRATION (% of the applied) 

STUDY TYPE 

Compound Ia7 and/ 

or Compound Ib8 Compound IV9 Compound V10 Metabolite XV11

Hydrolysis (1) Lambda-cyhalothrin: 

(at pH 9, Ia 68% at 30 

days) 

Gamma-cyhalothrin: 

 (at pH 9, 55.6%, 2 days) 

Gamma-cyhalothrin: 

 (at pH 9, 54.6%, 30 

days) 

Gamma-cyhalothrin: 

(river water, 21.6%, 30 

days) 

Aqueous Photolysis (1) Lambda-cyhalothrin: 

(Ia 13.7% at 31 days) 

(cyclopropane ring) 

(Ib 7.1% at 31 days) 

(cyclopropane ring) 

Gamma-cyhalothrin: 

(unspecified 45.0% at 

21 days) 

Lambda-cyhalothrin: 

Minor product 

Lambda-cyhalothrin: 

(25.0% at 31 days) 

Gamma-cyhalothrin: 

(42.0% at 15 days) 

Soil Photolysis Lambda-cyhalothrin: 

Minor product 

Aerobic Soil Metabolism (2) Lambda-cyhalothrin: 

Minor product 

Cypermethrin: 

Minor product 

Cypermethrin: 

Minor product 

Gamma-cyhalothrin: 

Minor product 

Lambda-cyhalothrin: 

(12.5% at 63 days) 

Gamma-cyhalothrin: 

Minor product 

Anaerobic Soil Metabolism Lambda-cyhalothrin: 

Ia 10.8% at 30 days 

postflooding. 

Lambda-cyhalothrin: 

11.1% at time of 

flooding (30 days) 

Aerobic Aquatic Metabolism Lambda-cyhalothrin: 

Ia 11.4% in the water 

and 10.6% in the 

sediment of the SL 

sediment system at 30 

days (total 22.0%). 

Lambda-cyhalothrin: 

Minor product 

Gamma-cyhalothrin: 

(14.4% in sediment, 

16.0% in total system at 

30 days, last interval) 

Lambda-cyhalothrin: 

Minor product. 

Anaerobic Aquatic 

Metabolism 

Lambda-cyhalothrin: 

Ia 0.023 ppm at 365 

days water; 0.008 

ppm at 182 days soil 

(information was not 

provided as percent of 

the applied) 

Lambda-cyhalothrin: 

0.010 ppm at 91 days in 

water; 0.039 ppm at 120 

days in soil (information 

was not provided as 

percent of the applied) 

Lambda-cyhalothrin: 

Minor product. 

Degradation in Aquatic 

Microcosm (3) 

Lambda-cyhalothrin: 

Ia 40.6% at 4 days in 

water; it was minor in 

the sediment 

Bioaccumulation in Fish (4) Lambda-cyhalothrin: 

Ia 22% in mucle and 

viscera 

Cypermethrin: 

Detected 

Cypermethrin: 

~7% in edible tissue 

 

7

 (1RS)-cis-3(ZE)-2-chloro-3,3,3-trifluro-1-propenyl)-2,2-dimethylcylopropanecarboxylate. 8

 (1RS)-trans-3-(ZE)-2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethylcyclopropane-carboxylic acid. 9

 3-phenoxybenzaldehyde 

10 3-PBA or 3-phenoxybenzoic acid 

11 (1R) cis α-(S) cis α-(R) α-cyano-3-(4-hydroxyphenoxy) benzyl 3-(Z-2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-

dimethylcyclopropanecarboxylate. 
45

Table 3.7a. Summary of degradate formation for lambda-cyhalothrin & gamma-cyhalothrin 

DEGRADATE and MAXIMUM CONCENTRATION (% of the applied) 

STUDY TYPE 

Compound Ia7 and/ 

or Compound Ib8 Compound IV9 Compound V10 Metabolite XV11

(1). Hydrolysis: Isomerization was rapid in the pH 9 solution and moderate in pH 7 solution. It did not occur in the pH 5 solution. 

Isomerization also occurred in the aqueous photolysis study. 

(2). 3-(4-Hydroxyphenoxy)-benzaldehyde was a major product in the sandy loam (12.2% at 17 days, gamma-cyhalothrin study). 

(3). In the TFD study conducted with lambda-cyhalothrin, transformation products monitored at the two sites were reported to be at 

low levels (<7%). In the study conducted with gamma-cyhalothrin no transformation products were monitored. 

(4). In the cypermethrin study, 3-phenoxybenzyl alcohol (mPBalc) was also detected. 

The Compounds Ia [(1RS)-cis-3-(ZE)-2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-

dimethylcyclopropane-carboxylic acid] (and possibly Ib, the trans-isomer), and Compound IV (3-

phenoxybenzaldehyde) are the expected result of the hydrolysis of the ester linkage of the 

pyrethroid structure, followed by loss of the cyano group. However, in general, the major 

degradates appear to be Compounds Ia and Ib, and Compound V (3-phenoxybenzoic acid, also 

named 3-PBA, m-PBA, 3-PBAc or 3-PBacid), which were observed mostly in the metabolism 

studies. It appears that Compound IV oxidizes quickly to Compound V in metabolic 

environments. The findings in the field corroborate the laboratory predictions. Compound V 

shows relatively high mobility, with KOC values 118-215 mL/gOC and KF values ≤3.11 mL/g 

(moderately mobile according to FAO mobility classification, three soils tested, while for a sand 

soil, the KFOC could not be determined because of the low sorption) (Table 3.7b). 

Ring-hydroxylated lambda-cyhalothrin, (1R) cis α-(S) cis α-(R) α-cyano-3-(4-hydroxyphenoxy) 

benzyl 3-(Z-2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethylcyclopropanecarboxylate 

(Compound XV), formed in aerobic soil microbial degradation (12% of the applied at 63 days 

post-treatment) appears to degrade readily to carbon dioxide in a separate aerobic soil metabolism 

study, and it appears to partition with soils and sediments. Its solubility is only 9 ppb (WSKOW 

SAR modeling), similar to the parent compound, which is not surprising due to their structural 

similarity. It also has low mobility based on the estimated KOC value of 770,900 mL/gOC, from 

structure activity relationship (SAR) modeling. The aerobic soil metabolism linear half-lives 

(t1/2s) for Compound XV ranged from 13.9 to 17.4 days (three soils tested, Table 3.7b). The 

potential for groundwater contamination with the degradate is low. However, it has the potential 

to reach surface water via runoff (in erodible particles), after rainfall events. 

Table 3.7b summarizes the available environmental fate/transport properties of Compounds V 

and XV, which are relevant metabolites of lambda-cyhalothrin and gamma-cyhalothrin. 
46

Table 3.7b. Summary of Environmental Fate Parameters for Compounds V and XV

Parameters Value Source

Soil Partition Coefficient 

Compound V (3-PBA) 

(KF in mL/g)

Not Determined Sand 

3.11 Silt Loam 

0.98 Sandy Loam 1 

2.44 Sandy Loam 2

43424901 (S) 

[Reported Freundlich correlations were 

good (r2 close to unity), but n values 

were around 1.5 (or 1/n of around 0.7).]

Soil Partition Coefficient 

Compound V (3-PBA) 

(KFOC in mL/gOC)

Not Determined Sand 

122 Silt Loam 

118 Sandy Loam 1 

215 Sandy Loam 2

43424901 (S) 

[See note above.] 

Solubility of Compound XV 0.009 ppm or 9 ppb 

- - - - - 

(reported as <0.01 ppm in a study)

Estimated from log KOW 

(SAR; WSKOW v1.40) 

44861505

Aerobic Soil Metabolism for 

Compound XV, T1/2

Sandy clay loam 13.9 days 

Loamy sand 14.7 days 

Sandy Loam 17.4 days 

44861505 (S) 

Reviewer calculated first order log-linear 

half-lives. Three UK soils tested.

Soil Partition Coefficient for 

Compound XV (KOC in mL/gOC)

770,900 SAR Modeling

There are multiple articles in the open literature that document the occurrence and behavior 

(which pertains to Section 3.3) and as well as the ecotoxicity (which pertains to Section 4.1) of 

synthetic pyrethroids such as lambda-cyhalothrin and gamma-cyhalothrin in the environment. 

Particularly, there has been recent concern for the toxicity of pyrethroids to sediments dwelling 

organisms. For a summary of selected literature articles, please, refer to the Appendix B. 

4. Receptors 

4.1. Aquatic and Terrestrial Effects 

The receptor is the biological entity that is exposed to the stressor (EPA, 1998). Due to the 

outdoor uses of lambda-cyhalothrin and gamma-cyhalothrin, the types of receptors that may be 

exposed include both aquatic and terrestrial receptors, such as birds, reptiles, mammals, 

amphibians, freshwater and estuarine/marine fish, non-target terrestrial & aquatic invertebrates 

and terrestrial & aquatic plants. This list may not be comprehensive. Spray drift and runoff 

exposures are expected for both ground and aerial applications of lambda-cyhalothrin and 

gamma-cyhalothrin. Consistent with the process described in the Overview Document (USEPA, 

2004), this risk assessment uses a surrogate species approach in its evaluation of lambdacyhalothrin and gamma-cyhalothrin. Toxicological data generated from surrogate test species, 

which are intended to be representative of broad taxonomic groups, are used to extrapolate to 

potential effects on a variety of species (receptors) included under these taxonomic groupings. 

Tables 4.1, 4.2, 4.3 and 4.4 provide a summary of the taxonomic groups and the surrogate 

species tested to help understand potential acute ecological effects of pesticides to these nontarget taxonomic groups. In addition, the tables provide a preliminary overview of the potential 

acute toxicity of lambda-cyhalothrin and gamma-cyhalothrin, by providing the acute toxicity 
47

classifications. 

Terrestrial Species – Lambda Cyhalothrin 

Birds

The available toxicity data suggests that lambda-cyhalothrin appears to be practically non-toxic to 

slightly toxic on an acute basis to avian species. A mallard duck (Anas platyrynchos) acute oral 

LD50 >3950 mg ai/kg bw (MRID 00151594, acceptable). In this study, no mortalities were 

observed in the controls or at any of the five treatment level tested (739-3950 mg ai/kg bw). In an 

8-day dietary study with mallard duck, the LC50 = 3948 (2868-7602) mg ai/kg diet, and sublethal 

effects included subdued behavior and unsteadiness in the 2030-5040 mg ai/kg diet treatment 

levels (MRID 00151595, acceptable). In an 8-day dietary study with bobwhite quail (Colinus 

virginianus), the LC50 > 5300 mg ai/kg diet because there was only one mortality per 10 birds in 

each of the 577, 1020, 3040 and 5300 mg ai/kg diet treatment levels (no control mortality). No 

sublethal effects were observed at any level during the test (MRID 00151596, acceptable). 

No data have been submitted to evaluate lambda-cyhalothrin acute toxicity to passerine species of 

birds. 

Three tests were submitted to examine the chronic effects of cyhalothrin (not lambda-cyhalothrin 

or gamma-cyhalothrin)12 on avian species. Two chronic studies with mallard ducks have been 

submitted. The most sensitive test resulted in a NOAEL = 5 ppm and LOAEL = 50 ppm based on 

a statistically significant reduction in the number of eggs laid and eggs set when compared to 

control birds. Postmortem examination of test birds showed evidence of aggressive behavior 

(bruising and missing feathers) and underdeveloped ovaries in all treatment levels (5 and 50 ppm) 

(MRID 00153504, supplemental). The study was classified as supplemental because the raw data 

were not included in the study report and the NOAEL may potentially be less than 5 ppm if an 

adequate statistical review could be conducted. In the other chronic mallard duck test, the 

NOAEL= 30 ppm and LOAEL > 30 ppm based on no statistically significant adverse effects on 

hatchling body weight, eggshell thickness, food consumption or body weight. Pathological results 

showed an increase in egg yolk peritonitis in all treatment groups (5-30 ppm) when compared to 

the control birds. A residue analysis of the egg, liver and fat tissue of the test birds showed that 

lambda-cyhalothrin primarily accumulates in the fat tissue, but there was no increase in 

concentrations over the course of the study (MRID 41512101, supplemental). The study was 

designated as supplemental because the test birds were sharing a room with another avian 

reproductive test for hexaconazole, and the study authors shared the control birds for these two 

tests. In a reproductive study with bobwhite quail, the NOAEL was determined to be 50 ppm and 

LOAEL was greater than 50 ppm due to no statitistically significant adverse effects on the 

number of eggs laid, eggs cracked, eggs set, viable embryos, normal hatchlings and 14-day 

survivors at the highest treatment level tested (MRID 00153505, acceptable). Effects noted during 

the postmortem examination of this test include underdeveloped ovaries and testes, blotchy livers, 

no eggs in developed oviduct and egg binding at levels as low as 5 ppm. 

 

12 Note: As indicated previously, cyhalothrin consists of four enantiomers out of the 16 possibilities in its structure; 

lambda-cyhalothrin consists of two of those isomers, while gamma-cyhalothrin consists of a single isomer. 
48

While all three avian reproduction studies are on cyhalothrin, cyhalothrin showed similar chronic 

toxicity to lambda-cyhalothrin and gamma-cyhalothrin in submitted mammalian data – see 

Lambda-Cyhalothrin and Gamma-Cyhalothrin Human Health Assessment Scoping Document in 

Support of Registration Review, D379544). In addition, the different isomeric mixtures present in 

lambda-cyhalothrin and gamma-cyhalothrin have similar acute avian toxicity. In the risk 

assessment, the cyhalothrin avian reproductive endpoints will be used to calculate chronic risk 

quotients for birds. 

Mammals

The mammalian toxicity profiles for the cyhalothrins are similar. Lambda-cyhalothrin is 

categorized as moderately toxic to mammals on an acute oral basis based on studies conducted on 

rats (most sensitive acute LD50 = 56 mg a.i./kg bw, MRID 00259805). In the 90-day rat studies, 

gamma-cyhalothrin, lambda-cyhalothrin, and cyhalothrin technical had similar NOAELs (50 

ppm), however, more severe effects were seen at a lower dose with gamma-cyhalothrin (mortality 

and neuromuscular effects at the LOAEL of 100 ppm) than with cyhalothrin (decreased body 

weight/body weight gain at the LOAEL of 250 ppm) and lambda-cyhalothrin (decreased body 

weight gain, food consumption and food efficiency at the LOAEL of 250 ppm) (LambdaCyhalothrin and Gamma-Cyhalothrin Human Health Assessment Scoping Document in Support 

of Registration Review, D379544). 

For mammalian toxicity, EFED will coordinate with HED to determine the most sensitive 

endpoints for acute and chronic studies. 

Terrestrial Invertebrates

Acute contact and oral studies were conducted with both lambda-cyhalothrin technical and the 

formulated product (Karate, 5.04% active ingredient) (MRID 40052409, acceptable). Both the 

technical grade active ingredient and the formulated product were highly toxic to honey bees. For 

lambda-cyhalothrin technical, the 48-hour contact LD50 = 0.038 μg ai/bee and the 48-hour oral 

LD50 = 0.909 μg ai/bee. For the lambda-cyhalothrin formulated product, the 48-hour contact LD50

= 0.098 μg ai/bee and the 48-hour oral LD50 = 0.483 μg ai/bee. A foliar residue study was also 

conducted with a lambda-cyhalothrin formulated product The LT50 was between 4 and 12 hours 

at the 0.013 lbs a.i./acre application rate and 23 hours at 0.031 lbs ai/acre, also indicating high 

toxicity to nontarget terrestrial invertebrates. The time to no-effect, based on mortality, was 24-48 

hours at the lower application rate, and greater than 96 hours at the higher application rate (MRID 

40436302). In another submitted study (that fulfills no guideline), lambda-cyhalothrin was 

applied at rates of 7.5 g a.i./hectacre and 15 g a.i./hectare to winter wheat with simulated 

honeydew (sprayed sucrose solution). Honeybee foraging was inhibited for up to three days 

compared to control conditions, and there was no significant increase in mortality at these 

treatment levels when compared to controls (MRID 40436303). 
49

Table 4.1 Summary of most sensitive endpoints from submitted terrestrial toxicity studies for 

lambda-cyhalothrin. 

Species 

(common 

name)

Taxa 

Represented

Endpoint Concentration 

Test 

Substance 

(% a.i.) 

MRID 

Acute 

Toxicity 

Classification 

LD50 56 mg/kg bw 92.6-96 00259805 Moderately 

NOAEL 10 mg ai/kg/day 

Rattus 

norvegicus 

(Laboratory 

Rat) 

Mammals 

LOAEL 15 mg ai/kg/day 

89.3 00154800 Not 

Applicable 

LD50

 >3950 mg ai/kg 

bw 96 

00151594 

Acceptable 

 Practically 

non-toxic 

LC50 3948 mg ai/kg diet 96.5 

00151595 

Acceptable 

Slightly toxic 

NOAEC 5 ppm1 

Anas 

platyrynchos 

(Mallard duck) 

Birds, terrestrialphase 

amphibians, and 

reptiles 

LOAEC 50 ppm 

92 

(cyhalothrin) 

00153504 

Supplemental 

Not 

Applicable 

Apis mellifera

(Honey bee) 

Terrestrial 

invertebrates 

Contact 

LD50

0.038 μg/bee 96 

40052409 

Acceptable 

Highly toxic 

1

 Adequate statistical analysis could not be performed because raw data was not included in the study report. 

Therefore, some uncertainty exists for this endpoint but it is currently the most sensitive study available. 

Terrestrial Species – Gamma Cyhalothrin 

Birds

The registrant has submitted two studies evaluating the acute effects of gamma-cyhalothrin on 

birds following oral dosing of the chemical. Both studies were conducted with the bobwhite quail 

(Colinus virginianus). The study conducted on the technical grade active ingredient (100%) 

resulted in an LD50 greater than 2000 mg a.i./kg bw during a 14-day observation period, based on 

mortality (MRID 45447210, acceptable). Decreased body weight and food consumption were 

observed in the treatment birds on days 0-3 compared to the control, but these difference were not 

observed on days 7 and 14. In another study with a formulated product (XR-225, 14.7% a.i.), the 

LD50 was also greater than 2000 mg a.i./kg bw during a 14-day observation period, based on 

mortality (MRID 45447211, acceptable). Food consumption in the 1400 and 2000 mg a.i./kg bw 
50

treatment group was significantly lower on days 0-3 compared to the control. However, these 

differences were not observed on days 7 and 14. No significant effects on bodyweight were 

observed during the study. All dosed groups displayed head twitching behavior indicative of 

intoxication during the first two days of the study.

No data have been submitted to evaluate gamma-cyhalothrin acute toxicity to passerine species of 

birds. 

Two avian 8-day dietary studies have been conducted on gamma-cyhalothrin technical. In the 

dietary study with the mallard duck, after 5 days on treated diets, there were 20 and 40% mortality 

in the 2400 and 4430 mg a.i./kg diet treatment groups, respectively. The controls and other 

treatment groups had no mortalities. There were significant reductions in body weight change for 

all treatment groups during the exposure period. Food consumption decreased as the treatment 

concentrations increased during the test period. The food consumption improved over the 

recovery period. The sublethal effects of ataxia, swollen/weepy right eyes, and/or hyporeactivity 

were observed in the 933, 1430, 2400, and 4430 mg a.i./kg diet treatment groups. The gross 

pathological findings observed in the 2400 and 4430 mg a.i./kg diet treatment groups were 

emaciation, lesion/growth on intestines, and/or discoloration of internal organs. The 8-day acute 

dietary LC50 was >4430 mg a.i./kg diet. The NOAEC was <617 mg a.i./kg diet, based on 

reductions in body weight (MRID 45447213, acceptable). In a dietary study with the bobwhite, 

quail, after 5 days on treated diets, there was 10, 10, 30, and 90% mortality in the 933, 1430, 

2400, and 4430 mg a.i./kg diet treatment groups, respectively. The controls and 617 mg a.i./kg 

diet treatment group had no mortalities. Significant reductions in body weight change for all 

treatment groups occurred during the exposure period and these reductions were not apparent 

during the recovery period. Food consumption decreased as the treatment concentrations 

increased during the test period. The food consumption improved over the recovery period. The 

sublethal effects of ataxia, hyporeactivity, and moribundity were observed in the 1430, 2400, and 

4430 mg a.i./kg diet treatment groups. No significant gross pathological findings were observed. 

The 8-day acute dietary LC50 was 2794 mg a.i./kg diet (MRID 45447212, acceptable). 

Three tests were submitted to examine the chronic effects of cyhalothrin (not lambda-cyhalothrin 

or gamma-cyhalothrin) on avian species. See the discussion of the submitted cyhalothrin avian 

reproduction studies in the bird section for lambda-cyhalothrin above, and summary in Table 4.2. 

Terrestrial Invertebrates

Acute contact and oral studies were conducted with both gamma-cyhalothrin technical and a 

formulated product (GF-231, 14.7% active ingredient). For the acute contact study conducted on 

the technical product, the LD50 value was 0.0061 μg a.i./bee. Sublethal effects (lethargy and live 

animals on their backs) were observed in all treatment groups (0.0013 – 0.080 μg a.i./bee). As a 

result, gamma-cyhalothrin technical is categorized as highly toxic to honeybees on a contact basis 

(MRID 45464802, acceptable). In the acute oral honeybee study submitted for the technical 

product, all concentrations were reported in nominal values. Measurements of actual 

concentrations were not conducted, and stock solutions (prepared in 500 g/L sucrose solutions) 
51

are likely to have exceeded the solubility limit of gamma-cyhalothrin, making estimated exposure 

values questionable and invalidating the study for use in risk assessment (MRID 45447408). 

In another submitted study, the honey bee, Apis mellifera, was exposed to a 14.7% gammacyhalothrin formulation (GF-231) for 48 hours in an acute contact test (MRID 45464803). 

Sublethal effects (lethargy and/or live animals on their backs) were observed in all treatment 

groups (0.0063 – 0.10 μg GF-23l/bee) during the study. The LD50 value was 0.030 μg GF231/bee equal to an LD50 of 4.4 ng a.i./bee for gamma-cyhalothrin. As a result, the gammacyhalothrin formulation (GF-231) is categorized as highly toxic to honeybees on a contact basis. 

This study was categorized as supplemental, as only nominal concentrations were reported. In an 

acute oral study with a gamma-cyhalothrin formulation (GF-231), honeybees were exposed to 

diluted in sucrose water for 48 hours, at nominal concentrations of 0.625 – 10 μg GF-23l/bee 

(actual ingested doses averaged 0.601 – 4.88 μg GF-231/bee). By 48 hours, mortality ranged from 

10 to l00%, and the LD50 value was 1.259 μg GF-231/bee, equal to an LD50 of 0.185 μg a.i./bee 

for gamma-cyhalothrin. As a result, the gamma-cyhalothrin formulation (GF-231) is categorized 

as highly toxic to honeybees on an acute oral basis. This acute oral study is classified as 

supplemental, as it is a non-guideline study. 

A honey bee toxicity study with 14.7% gamma-cyhalothrin formulation (GF-231) residues on 

foliage has also been submitted to the Agency (MRID 45464805). The alfalfa foliage was 

exposed to GF-231 at an application rate of 17 g a.i./ha and weathered for 3, 6, and 24 hours. The 

honeybees were exposed to the weathered foliage for 24 hours. There was 0% bee mortality in the 

control and all treatment groups (exposure to 3, 6, and 24 hour-old residues), and no signs of 

toxicity were observed during the study. Leaves were not chemically analyzed to determine the 

actual residue concentrations, so this foliar residue study is classified as supplemental. 

Table 4.2 Summary of most sensitive endpoints from submitted terrestrial toxicity studies for 

gamma-cyhalothrin. 

Species 

(common 

name)

Taxa 

Represented

Endpoint Concentration 

Test 

Substance 

(% a.i.) 

MRID 

Acute 

Toxicity 

Classification 

LD50

 >2000 mg ai/kg 

bw 100 and 14.7 

45447210, 

45447211 

Acceptable 

 Practically 

non-toxic 

Colinus 

virginianus 

(Bobwhite 

quail) 

LC50 2794 mg ai/kg diet 100 

45447212 

Acceptable 

Slightly toxic 

Anas 

platyrynchos 

Birds, terrestrialphase 

amphibians, and 

reptiles 

NOAEC 5 ppm1 92 00153504 Not 

Applicable 
52

Table 4.2 Summary of most sensitive endpoints from submitted terrestrial toxicity studies for 

gamma-cyhalothrin. 

Species 

(common 

name)

Taxa 

Represented

Endpoint Concentration 

Test 

Substance 

(% a.i.) 

MRID 

Acute 

Toxicity 

Classification 

(Mallard duck)

LOAEC 50 ppm (cyhalothrin) Supplemental 

Apis mellifera

(Honey bee) 

Terrestrial 

invertebrates 

Contact 

LD50

4.4 ng a.i./bee 48 

45464803 

Supplemental 

Highly toxic 

1

 Adequate statistical analysis could not be performed because raw data was not included in the study report. 

Therefore, some uncertainty exists for this endpoint but it is currently the most sensitive study available. 

Aquatic Species 

 

Freshwater Fish

Lambda-cyhalothrin technical is very highly toxic to freshwater fish, with a 96-hour LC50 range 

from 0.078 μg a.i./L to 0.240 μg a.i./L in submitted acute toxicity tests (MRIDs 00151598, 

00151601, 43908812, 00151597, 00151600, 43908813, 00153506; Tables 4.3 and A.1). The 

most sensitive species in the submitted acute toxicity tests is golden orfe (Leuciscus idus). In this 

study, the NOAEC value was 0.055 μg ai/L based on mortality and sublethal effects. Sublethal 

effects (quiescent, sounding, erratic swimming, spiraling, loss of balance, rapid respiration, 

labored respiration, ceased swimming, light discoloration, surfacing, irregular respiration, gulping 

air) were observed in the groups exposed to time-weighted average concentrations as low as 0.11 

μg ai/L of lambda-cyhalothrin (MRID 00153506, supplemental because not a preferred test 

species). In other submitted toxicity tests with lambda-cyhalothrin technical, the most sensitive 

endpoints for standard test species are a 96-hour LC50 = 0.240 μg a.i./L for coldwater rainbow 

trout (Oncorhynchus mykiss) (MRID 00151597, acceptable) and a 96-hour LC50 = 0.210 μg a.i./L 

for warmwater bluegill sunfish (Lepomis macrochirus) (MRID 00151598, acceptable). 

For lambda-cyhalothrin formulated products (either 12.9 or 23.7 % active ingredient), the 96-hour 

LC50 ranged from 1.2 to 3.4 μg ai/L (MRIDs 0015601, 43908812, 00151600 and 43908813, all 

acceptable). 

A chronic full life cycle freshwater fish study for lambda-cyhalothrin technical resulted in a 

NOAEC of 0.031 μg a.i./L and LOAEC of 0.062 μg a.i./L for fathead minnow (Pimephales 

promelas) based on reduced growth in adult (F0) and offspring (F1), as well as offspring survival 

(MRID 41519001, supplemental). This study was determined to be supplemental because of 

numerous factors including low-level contamination in the solvent and negative controls, use of 

lower number of eggs than guideline recommendations, and other guideline deviations. It is 
53

worthy to note that the NOAEC of 0.031 μg a.i./L is only about a factor of two less than the 96-h 

LC50 of 0.078 μg a.i./L for the golden orfe for lambda-cyhalothrin and virtually identical to the 

96-h LC50 of 0.029 μg a.i./L for bluegill with gamma-cyhalothrin (MRID 45447215). 

Fewer toxicity data for fish are available for gamma-cyhalothrin (Tables 4.4 and A.1). 

Specifically, 96-h LC50 values determined with the TGAI are available for two species of fish 

range from 0.029 μg a.i./L (bluegill, MRID 45447215) to 0.19 μg a.i./L for rainbow trout (MRID 

45447217). In the bluegill study, fish were exposed to mean-measured concentrations of <5 

(LOQ, negative and solvent controls), 7.74, 12.4, 20.2, 38.1, 60.3, and 105 ng/L under flow 

through conditions. After 96 hours of exposure, mortality was 10, 10, 20, 60, 90, and 100% in the 

7.74, 12.4, 20.2, 38.1, 60.3, and 105 ng/L treatment groups, respectively. The LC50 (29 ng/L or 

0.029 ug/L) was calculated using the solvent control (0% mortality) since the negative control had 

20% mortality on the last day of the study. This deviation, along with the use of fish with mean 

weight less than the 0.5 to 5g guideline recommendation, resulted in its classification as 

supplemental. The NOAEC for sublethal effects was 0.0077 ug/L based on lethargy and loss of 

equilibrium. 

For gamma-cyhalothrin, a 96-hour LC50 of 1.1 μg ai/L (14.7% a.i.; MRID 45447218) was 

determined for bluegill which approximates the low end of the range of LC50 values described 

earlier for lambda-cyhalothrin (1.2 to 2.2 μg ai/L). 

Regarding the comparative toxicity of lambda- and gamma-cyhalothrin, bluegill appear somewhat 

more sensitive to gamma-cyhalothrin (TGAI) on an acute toxicity basis (i.e., about 4X more 

sensitive based on species mean LC50 values of 0.16 and 0.04 μg ai/L for lambda and gammacyhalothrin, respectively). However, rainbow trout appear similarly sensitve to lambda- and 

gamma-cyhalothrin TGAI (i.e., within a factor of 2X; Table A.1). 

No freshwater fish chronic toxicity data for were submitted for gamma-cyhalothrin. 

Estuarine/Marine Fish

For lambda-cyhalothrin, estuarine/marine fish are represented by the sheepshead minnow 

(Cyprinodon variegatues). Acute toxicity studies indicates that lambda-cyhalothrin technical is 

very highly toxic to estuarine/marine fish, with an LC50 = 0.81 μg a.i./L (MRID 00153506, 

acceptable). A lambda-cyhalothrin early life-stage test was conducted with sheepshead minnow 

(Cyprinodon variegatus). The NOAEC = 0.25 μg a.i./L and the LOAEC = 0.38 μg a.i./L based on 

effects to larval growth (MRID 00152732). This study was initially determined to be 

supplemental because fewer than the recommended number of 80 eggs were used per treatment, 

raw data were not provided for statistical analysis and the measured concentrations of the test 

material were only 20 to 64% of the nominal values. Subsequently, this study was upgraded to 

“core/acceptable” upon submission of further information from the registrant. 

For gamma-cyhalothrin, no acute or chronic toxicity data were submitted for estuarine/marine 

fish. 
54

Freshwater Invertebrates

Acute toxicity values for daphnids suggest that lambda-cyhalothrin technical is very highly toxic 

to freshwater invertebrates. The most sensitive 96-hour EC50 = 0.0067 μg a.i./L with the 

amphipod Gammarus pulex (MRID 00152730, supplemental). This test was classified as 

supplemental because Gammarus pulex is not the guideline test species (typically Daphnia 

magna), the raw data were not included in the study report, and calculation of the EC50 required 

extrapolation for exposure estimates of the three lowest treatment levels because test 

concentrations were below the level of detection (2.3 ng a.i./L). Several Daphnia magna studies 

were submitted for lambda-cyhalothrin technical and formulated products. The daphnid 48-hour 

EC50 for the technical product is 0.24 μg a.i./L (MRID 00151599, acceptable), and the studies 

conducted with formulated products containing 5.5-24 % active ingredient resulted in slightly 

more sensitive EC50s ranging from 0.04 to 0.18 μg a.i./L (MRIDs 00151602, supplemental and 

43908811, acceptable). 

Two daphnid life cycle studies were submitted for lambda-cyhalothrin. In the most sensitive 

daphnid chronic life-cycle test, the NOAEC = 0.0002 μg a.i./L and the LOAEC = 0.0035 μg a.i./L 

based on adverse effects to # of young/female and total young at mean-measured concentrations 

in static renewal conditions (MRID 41217501, supplemental). This study was classified as 

supplemental because only the healthiest organisms in the source population were chosen for the 

test and there were only two replicates at each treatment level. Exposure concentrations also 

varied substantially within a treatment (approximately 3x), such that maximum and minimum 

values overlapped among treatments. Another daphnid life cycle submitted earlier by the 

registrant resulted in a NOAEC = 0.0004 μg a.i./L and the LOAEC = 0.005 μg a.i./L based on 

adverse effects to # of young/female at mean-measured concentrations in flow-through conditions 

(MRID 00152733, supplemental). The study was classified as supplemental because the measured 

concentrations varied greatly throughout the course of the test (from 3x to 10x), so much that the 

treatment levels overlapped in their exposure concentrations. Although this study is considered 

supplemental, EFED is requesting an additional freshwater invertebrate life cycle test due to the 

high uncertainty caused by the overlapping test concentrations on interpretation of the study 

results and the extreme chronic sensitivity of daphnia (and aquatic invetebrates in general) to

lambda-cyhalothrin (i.e., NOAEC values below 1 ng/L). 

Similar to lambda-cyhalothrin, gamma-cyhalothrin is very highly toxic to freshwater invertebrates 

is indicated by an 96-h LC50 value of 0.00048 ug/L for the amphipid, Gammarus 

pseudolimnaeus. However, this study was classified as supplemental due to problems in the study 

with rapidly declining test concentrations occurred over the duration of the study, thus suggesting 

that a more accurate LC50 value would be lower. The high sensitivity of Gammarus to lambdaand gamma-cyhalothrin is consistent with sensitivity trends observed for other pyrethroids for 

which amphipods were found to be among the most sensitive freshwater invertebrates. To address 

uncertainties in the acute toxicity endpoints with freshwater invertebrates for both lambda and 

gamma-cyhalothrin, an additional acute toxicity study with a freshwater amphipod is being 

requested for gamma-cyhalothrin. 
55

No acute or chronic freshwater invertebrate studies were submitted for gamma-cyhalothrin. 

Estuarine/Marine Invertebrates

Estuarine/marine aquatic invertebrates are represented by the mysid shrimp (Mysidopsis bahia) 

and eastern oyster (Crassostrea virginica). Submitted toxicity studies indicate that lambdacyhalothrin is very highly toxic to crustaceans and practically nontoxic to bivalves. In an acute 

study with mysid shrimp, the 96-hour LC50 = 0.0041 μg a.i./L for lambda-cyhalothrin technical 

(MRID 00152728). In a study with the eastern oyster, the 96-hour EC50 >590 μg a.i./L for 

lambda-cyhalothrin technical (MRID 00152728). A chronic estuarine/marine study with 

estuarine/marine invertebrates has also been submitted for lambda-cyhalothrin technical. The 

NOAEC = 0.0002 μg a.i./L and LOAEC = 0.0005 μg a.i./L based on reductions in the number of 

young per reproductive day and number of young per treatment (Accesion #073989, acceptable). 

No acute or chronic estuarine/marine invertebrate studies were submitted for gamma-cyhalothrin. 

Table 4.3. Summary of most sensitive endpoints from submitted aquatic toxicity studies 

for lambda-cyhalothrin. 

Species 

(common name) 

Taxa 

Represented 

Endpoint Duration 

(hours) 

 Mean 

concentration 

(μg a.i./L) 

Citation 

MRID 

Acute 

Toxicity 

Classification 

Leuciscus idus

 (Golden orfe) LC50 96 0.078 

00153506 

Supplemental Highly toxic 

NOAEC Pimephales 0.031 

promelas 

(Fathead Minnow)

Freshwater fish 

and aquaticphase 

amphibians LOAEC 

60 (days) 0.062 

41519001 

Supplemental 

NA 

Gammarus pulex 

(amphipod) EC50 48 0.007 

00152730 

Supplemental 

Very highly 

toxic 

NOAEC 0.0020 Daphnia magna 

(Water Flea)

Freshwater 

Invertebrates 

LOAEC 

 21 (days) 0.0035 

41217501 

Supplemental 

NA 

LC50 96 0.807 

00153506 

Supplemental 

Very highly 

toxic 

NOAEC 0.25 

Cyprinodon 

variegatus

(Sheepshead 

minnow) 

Estuarine/ 

Marine Fish 

LOAEC 

28 (days) 0.38 

00152732 

Supplemental 

NA 

LC50 96 0.0041 00152728 

Acceptable 

Very highly 

toxic 

Mysidopsis bahia 

(Mysid shrimp) 

Estuarine/ 

Marine 

Invertebrates 

NOAEC 28 (days) 0.0002 Acc 073989 

NA
56

Table 4.3. Summary of most sensitive endpoints from submitted aquatic toxicity studies 

for lambda-cyhalothrin. 

Species 

(common name) 

Taxa 

Represented 

Endpoint Duration 

(hours) 

 Mean 

concentration 

(μg a.i./L) 

Citation 

MRID 

Acute 

Toxicity 

Classification 

LOAEC 0.0005 Acceptable 

Table 4.4. Summary of most sensitive endpoints from submitted aquatic animal toxicity 

studies for gamma-cyhalothrin. 

Species 

(common name) 

Taxa 

Represented 

Endpoint Duration 

(hours) 

 Mean 

concentration 

(μg a.i./L) 

Citation 

MRID 

Acute 

Toxicity 

Classification 

Lepomis 

macrochirus 

(Bluegill sunfish) 

Freshwater fish 

and aquaticphase 

amphibians

LC50 96 0.029 

45447215 

supplemental Highly toxic 

Gammarus 

pseudolimnaeus

(Amphipod) 

Freshwater 

Invertebrates EC50 96 0.00048 

46065601 

supplemental 

Very highly 

toxic 

Plants 

No terrestrial plant data or aquatic vascular plants studies are available to the Agency for lambdaor gamma-cyhalothrin. One study conducted using aquatic non-vascular plant (freshwater green 

algae) reported the EC50 as >310 ppb. Two studies conducted using aquatic non-vascular plants 

were conducted with gamma-cyhalothrin, and these studies also show low toxicity to algal species 

(EC50 >2850 μg a.i. /L and EC50 = 15000 μg a.i. /L, MRIDs 45447406 and 45447407). In these 

studies, the algae were exposed to levels much higher than the solubility of either chemical.

Table 4.5. Acute Toxic Effects of Lambda-cyhalothrin and Gamma-cyhalothrin to Aquatic Plants 

Species Study 

Guideline 

% 

A.I. 

Toxicity Endpoint 

μg a.i. /L 

Study 

Classification 

MRID # 

Freshwater Non-vascular Plants 

Green Algae 

Selenastrum 

capricornutum 

(Lambdacyhalothrin)

123-2 

 

96.5 EC50 96 hr :>310 

NOAEC : ≥310 

Supplemental 152731 

Green Algae 123-2 EC50 96 hr :>2850 
57

Table 4.5. Acute Toxic Effects of Lambda-cyhalothrin and Gamma-cyhalothrin to Aquatic Plants 

Selenastrum 

capricornutum 

(Gammacyhalothrin)

 

100 NOAEC : <1340 Supplemental 45447406 

Green Algae

Selenastrum 

capricornutum 

(Gammacyhalothrin)

123-2 

 

14.7 Cell density

EC5072 hr: 15000 

NOAEC: 5480 

Growth rate

EC5072 hr:41300 

NOAEC: 5480 

Area under curve

EC5072 hr:16100 

NOAEC: N.R. 

Supplemental 45447407 

ECOTOX 

Available open literature will be used to evaluate the potential direct effects of lambdacyhalothrin and gamma-cyhalothrin to the terrestrial receptors identified in this section. This 

includes toxicity data on the technical grade active ingredient, and when available, formulated 

products (e.g. “Six-Pack” studies). 

At this time, a full and complete ECOTOX search has not been performed, but will be conducted 

prior to issuance of any Data Call-in. The open literature studies will be identified through EPA’s 

ECOTOX database (http://cfpub.epa.gov/ecotox/), which employs a literature search engine for 

locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. The evaluation of 

data can also provide insight into the direct and indirect effects of lambda-cyhalothrin and 

gamma-cyhalothrin on biotic communities from loss of species that are sensitive to the chemical 

and from changes in structure and functional characteristics of the affected communities. Open 

literature toxicity data for other ‘target’ insect species (not including bees, butterflies, beetles, and 

non-insect invertebrates including soil arthropods and worms), which include efficacy studies, are 

not currently considered in deriving the most sensitive endpoint for terrestrial insects. Efficacy 

studies do not typically provide endpoint values that are useful for risk assessment (e.g., NOAEC, 

EC50, etc.), but rather are intended to identify a dose that maximizes a particular effect (e.g., 

EC100). Therefore, efficacy data and non-efficacy toxicological target insect data will not be 

included in the ECOTOX open literature search. 

4.2. Incident Database Review 

A preliminary review on August 12, 2010 of the Ecological Incident Information System (EIIS, 

version 2.1), which is maintained by the Agency’s Office of Pesticide Programs indicates reported 

ecological incidents associated with the use of lambda-cyhalothrin and gamma-cyhalothrin. A 

search for incidents involving lambda-cyhalothrin or gamma-cyhalothrin was also conducted in 

the American Bird Conservancy’s Avian Incident Monitoring System (AIMS). These incidents 

are summarized in Table 4.5. This total excludes incidents classified as ‘unlikely’ and only 
58

includes those incidents with certainty categories of ‘highly probable’, and ‘probable’ and 

‘possible’ (for EIIS) and ‘certain’, ‘highly likely’, ‘likely’, ‘probable’, and ‘possible’ (for AIMS). 

In the EIIS and AIMS databases, the “unlikely” category is used when a chemical is not likely to 

be responsible for the incident. For example, an ‘unlikely’ classification might be applied in 

situations where a given chemical is practically nontoxic to the category of organism killed and/ 

or there is evidence that another pesticide or stressor likely caused the incident. Incidents 

classified as ‘unlikely’ for lambda-cyhalothrin and gamma-cyhalothrin will not be included in this 

Problem Formulation or the ecological risk assessment conducted for Registration Review (one 

“unlikely” incident was reported in EIIS for lambda-cyhalothrin). 

There were 12 total incidents reported to the Agency for lambda-cyhalothrin. Of these incidents, 

1 was reported as highly probable, 4 were reported as probable and 7 reported as possible for 

association with lambda-cyhalothrin use. Nine of the reported incident involved aquatic species of 

fish and invertebrates, and three of the incidents involved terrestrial plant species. These incidents 

indicate that aquatic organisms and possibly plants may be adversely affected if exposed to 

lambda-cyhalothrin, even if used as registered. See Table 4.5 for summary. 

No incidents were reported in EIIS for gamma-cyhalothrin. The AIMS database contains no avian 

incidents involving lambda-cyhalothrin or gamma-cyhalothrin. 

Table 4.5. Wildlife Incidents Associated with lambda-cyhalothrin 

Incident 

Number 

Taxa 

Involved Magnitude Year 

Location 

(County, 

State) Use 

Legality 

of Use 

Certainty 

Category1

I007462-

001 Fish 16 1998 Jackson, MO 

Broadcast 

near 

building 

M Probable 

I007176-

001 Crayfish 90 to 100 acre area 

1998 LA Spray, corn RU Probable 

I000922-

001 Fish Not reported 1991 Laurens, GA Broadcast, cotton RU Possible 

I000921-

001 

Bass 

Bream 

Catfish 

Hundreds 1991 Lowndes, 

GA 

Broadcast, 

cotton RU Probable 

I003826-

029 Bass 200 1994 Cumberland, NC 

Cotton (no 

details) RU Possible 

I015186-

003 Crayfish Not reported 2004 Wilson, TX Spray, Cotton RU Highly Probable 

I005805-

003 

Not 

reported 

Not 

reported 1997 Scott, IN Unknown UN Possible 
59

Incident 

Number 

Taxa 

Involved Magnitude Year 

Location 

(County, 

State) Use 

Legality 

of Use 

Certainty 

Category1

I009314-

007 

Not 

reported 

Not 

reported 1997 Scott, IN Unknown UN Possible 

I007650-

001 Crayfish Not reported 1998 Acadia, LA 

In field, no 

crop 

specified 

M Probably 

I016036-

006 Basil Not reported 2004 Stanislaus, CA Air blast RU Possible 

I014597-

027 Cotton 78 acres 2003 Hardin, IA Suspension RU Possible 

I014597-

047 Tobacco 200 acres 2003 Breckinridge, KY Spray M Possible 

1

Incidents classified as ‘unlikely’ are excluded; RU = Registered Use; M = Misuse; UN = Unknown

Incident reports for non-target organisms typically provide information only on mortality events 

and plant damage incidents. Except for phytotoxic effects in terrestrial plants, sublethal effects for 

organisms such as reduced growth or impaired reproduction are rarely reported. EPA’s changes in 

the registrant reporting requirements for incidents in 1998 may account for a reduced number of 

reported incidents. Registrants are now only required to submit detailed information on ‘major’ 

fish, wildlife, and plant incidents. Minor fish, wildlife, and plant incidents, as well as all other 

nontarget incidents, are generally reported aggregately and are not included in EIIS. In addition, 

there have been changes in state monitoring efforts due to lack of resources. 

In the forthcoming ecological risk assessment, these incidents will be further evaluated to 

determine if they represent current patterns of use for lambda-cyhalothrin and/ or gammacyhalothrin. Examples of additional considerations are mitigation (e.g., reduced application 

rates), product cancellations, and changes in use patterns that have occurred since the date of the 

reported incidents. 

Lambda-cyhalothrin is among the constituents monitored by the National Water Quality 

Assessment Data Warehouse, (NAWQA) maintained by the U.S. Geological Survey; furthermore, 

multiple articles from the literature document the presence of synthetic pyrethroids like lambdacyhalothrin and/ or gamma-cyhalothrin in both urban and agricultural water and sediments (refer 

to Appendix B). 

4.3. Ecosystems Potentially at Risk 

Lambda-cyhalothrin and gamma-cyhalothrin may be applied on a variety of food/feed crops, 

including (but not limited to), wheat, cotton, peanut, sugarcane, alfalfa, corn, cole crops, fruiting 

vegetables, legume vegetables, lettuce, onion, soybean, pome fruits, stone fruits and tree nuts. In 

addition, they may be used on numerous non-food sites (e.g. conifers, forest trees, ornamentals, 
60

golf courses, and ornamental lawns and turf). Finally, these chemicals may be used on an aquatic 

environment (i.e. use on rice). Thus, the ecosystems at risk may be extensive in scope, and as a 

result it may not be possible to identify specific ecosystems during the development of a baseline 

risk assessment. In general terms, terrestrial ecosystems potentially at risk due to the use of 

lambda-cyhalothrin and gamma-cyhalothrin, could include the treated field and areas immediately 

adjacent to the treated field that may receive drift or runoff. Areas adjacent to the treated field 

could include cultivated fields, fencerows and hedgerows, meadows, fallow fields or grasslands, 

woodlands, riparian habitats and other uncultivated areas. Due to the potential persistence of 

lambda-cyhalothrin and gamma-cyhalothrin, they are expected to drift and/or runoff due to 

application to food crops, resulting in possible exposure to aquatic ecosystems. Aquatic 

ecosystems potentially at risk due to the use of lambda-cyhalothrin and gamma-cyhalothrin 

include water bodies adjacent to, or down stream from, the treated field and might include 

impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as streams or 

rivers. For uses in coastal areas, aquatic habitat also includes marine ecosystems, such as 

estuaries. 

5. Assessment Endpoints 

Assessment endpoints are defined as “explicit expressions of the actual environmental value that 

is to be protected.” Defining an assessment endpoint involves two steps: 1) identifying the valued 

attributes of the environment that are considered to be at risk; and 2) operationally defining the 

assessment endpoint in terms of an ecological entity (i.e., a community of fish and aquatic 

invertebrates) and its attributes (i.e., survival and reproduction). Therefore, selection of the 

assessment endpoints is based on valued entities (i.e., ecological receptors), the ecosystems 

potentially at risk, the migration pathways of pesticides, and the routes by which ecological 

receptors are exposed to pesticide-related contamination. The selection of clearly defined 

assessment endpoints is important because they provide direction and boundaries in the risk 

assessment for addressing risk management issues of concern. Changes to assessment endpoints 

are typically estimated from the available toxicity studies, which are used as the measures of 

effects to characterize potential ecological risks associated with exposure to pesticides, such as 

lambda-cyhalothrin and gamma-cyhalothrin. 

To estimate exposure concentrations, the ecological risk assessment considers applications at the 

maximum application rate to fields that have vulnerable soils. The most sensitive toxicity 

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

mortality and chronic reproductive, growth and survival assessment endpoints. Toxicity tests are 

intended to determine effects of pesticide exposure on birds, mammals, fish, terrestrial and 

aquatic invertebrates, and plants. These tests include short-term acute, sub-acute, and 

reproduction studies and are typically arranged in a hierarchical or tiered system that progresses 

from basic laboratory tests to applied field studies. The toxicity studies are used to evaluate the 

potential of a pesticide to cause adverse effects, to determine whether further testing is required, 

and to determine the need for precautionary label statements to minimize the potential adverse 

effects to non-target animals and plants. 
61

An open literature search will be conducted to determine any relevant endpoints. The search will 

focus on survival, growth and reproductive effects for aquatic and terrestrial effects of lambdacyhalothrin and/ or gamma-cyhalothrin. More sensitive endpoints from acceptable open literature 

studies will be included in this risk assessment. 

 6. Conceptual Model

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

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

environment from a source to an ecological receptor. For an ecological pathway to be complete, 

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

exposure for ecological receptors, and a feasible route of exposure. 

A conceptual model provides a written description and visual representation of the predicted 

relationships between lambda-cyhalothrin or gamma-cyhalothrin, potential routes of exposure, 

and the predicted effects for the assessment endpoint. A conceptual model consists of two major 

components: risk hypothesis and a conceptual diagram (USEPA, 1998). 

6.1. Risk Hypothesis 

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 (USEPA 1998). For this assessment, the risk is stressor-initiated, 

where the stressor is the release of lambda-cyhalothrin or gamma-cyhalothrin into the 

environment. The following risk hypotheses are presumed for this screening-level assessment: 

Lambda-cyhalothrin and gamma-cyhalothrin, when used in accordance with registered 

labels, will likely lead to off-site movement of the compound via runoff, spray drift, and 

eroded soil leading to exposure of nontarget plants and animals Based on information on 

the environmental fate, mode of action, direct toxicity and potential indirect effects, EFED 

assumes that registered uses of lambda-cyhalothrin and gamma-cyhalothrin have the 

potential to cause reduced survival, growth, and reproduction to non-target terrestrial 

and/ or aquatic animals and plants. 

Lambda-cyhalothrin and gamma-cyhalothrin, when used indoors, in accordance with 

current labels, may result in off-site movement of the compound via wash-off into surface 

waters via drains and treatment plants, leading to exposure of nontarget aquatic plants 

and animals. This potential exposure pathway may result in adverse effects upon the 

survival, growth, and/or reproduction of non-target aquatic animals and plants. 

Lambda-cyhalothrin and gamma-cyhalothrin, when used in ear tag and cattle pour on 

products, in accordance with current labels, may result in off-site movement of the 

compound via wash-off of cattle and calves or accidental fall of an ear tag into surface 

waters, leading to exposure of nontarget aquatic plants and animals. This potential 
62

exposure pathway may result in adverse effects upon the survival, growth, and/or 

reproduction of non-target aquatic animals and plants.

 

The conceptual model is a generic graphic depiction of the risk hypothesis. It includes the 

potential pesticide or stressor (lambda-cyhalothrin, gamma-cyhalothrin and possible metabolites, 

as well as synergists), the source of the pesticide and/or transport pathways, exposure media, 

exposure point, biological receptor types, and attribute changes. 

6.2. Conceptual Diagram

The conceptual site model is a generic graphic depiction of the risk hypothesis, and assumes that 

the insecticides lambda-cyhalothrin and gamma-cyhalothrin, which are Type II synthetic 

pyrethroids, having multiple outdoor agricultural and non-agricultural uses, are capable of 

affecting aquatic and terrestrial animals provided that environmental concentrations are 

sufficiently elevated as a result of proposed label uses. Based on an examination of the 

physicochemical properties of lambda-cyhalothrin and gamma-cyhalothrin, the fate and 

disposition in the environment, and mode of application, a conceptual model was developed that 

represents the possible relationships between the stressors, ecological receptors, and the 

assessment endpoints. Through a preliminary iterative process of examining available data, the 

conceptual model (i.e., the representation of the risk hypothesis) may be refined to reflect the 

likely exposure pathways and the organisms that are most relevant and applicable to this 

assessment (Figures 6.1a and 6.1b). They include the potential pesticide or stressor (lambdacyhalothrin and/or gamma-cyhalothrin, but the presence of toxicologically important metabolites 

cannot be ruled out), the sources and/ or transport pathways, exposure media and exposure points, 

biological receptor types and attribute changes. 

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 degradation/ transformation (i.e., which degradation/ 

transformation products may form in the environment, in which media, and how much) must be 

understood, especially if for the chemical, its metabolites/ transformation 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. 

Under the possible uses of lambda-cyhalothrin and gamma-cyhalothrin, the sources and 

mechanisms of release of the compounds are from ground or aerial spray or ULV applications. 

Note that this conceptual model considers agricultural applications as well as certain nonagricultural applications. Surface runoff from the areas of application is assumed to depend on 

factors such as topography, irrigation, and rainfall events. Direct deposition may result in 

contamination of food items that may be consumed by terrestrial organisms. Spray drift results in 
63

contaminated adjacent areas, including bodies of water. Leaching to groundwater is not 

considered an important source because lambda-cyhalothrin and gamma-cyhalothrin show low 

mobility in a variety of soils. Lambda-cyhalothrin and gamma-cyhalothrin appear to have a low 

potential for volatilization, with a low vapor pressure and Henry’s Law Constants. Further, the 

hydroxyl radical reaction half-life for lambda-cyhalothrin is 0.34 days (and the ozone reaction 

half-life is 7.05 days, both are EPI Suite v.4.0 estimates). The short (atmospheric) half-life, the 

low vapor pressure (~10-10 to ~10-9 mmHg) and Henry’s Law constants (~10-7 atm/m3

-mol), and 

their binding capacity, suggest that the potential for atmospheric transport for lambda-cyhalothrin 

and gamma-cyhalothrin is relatively low and that this source of the chemical is of low 

importance, compared to spray drift, runoff and/ or direct contact after application. 

For aquatic receptors, the major point of exposure is through direct contact with the water 

column, sediment, and pore water (gill/ integument) contaminated with spray drift (from spray 

application) and/or runoff from treated areas. Indirect effects to aquatic organisms (both fish and 

aquatic invertebrates) can also occur through impact to various food chains. It was established 

earlier in this document that lambda-cyhalothrin and gamma-cyhalothrin have the potential to 

bioaccumulate/ bioconcentrate. The representative aquatic receptors are certain freshwater and 

estuarine/ marine fish, invertebrates, and, in certain cases, aquatic plants. The major point of 

exposure for terrestrial animals is consumption of food contaminated with residues such as grass, 

foliage, and small insects. For plants, the point of exposure is direct contact or root uptake. The 

representative terrestrial receptors are mammals, birds and terrestrial plants. The attribute 

changes used to assess risk to terrestrial receptors depend on the type of test (e.g., reduced 

survival, growth, or reproduction for animals and seedling emergence and vegetative vigor for 

plants). It should be noted, that these species do not cover all the possible species in the animal 

and plant kingdoms; certain taxa are considered as surrogates for other taxa. For example, fish 

are considered surrogates for aquatic phase amphibians. 

This conceptual model also shows details about biomagnification for a chemical (see piscivorous 

birds and mammals in Fig. 6.1b). Lambda-cyhalothrin and gamma-cyhalothrin have a very high 

KOW and according to its physicochemical and fate properties, there is a potential for 

bioaccumulation/ bioconcentration in aquatic organisms, and biomagnification in terrestrial 

organisms. 

Lambda-cyhalothrin and gamma-cyhalothrin show a very low solubility, a very high KOW and 

also high KOCs. These properties suggest that the chemicals partition with the sediments, and 

with organic matter, suspended in the water bodies. Lambda-cyhalothrin and gamma-cyhalothrin 

are likely to concentrate in the sediments, especially after repeated exposures (applications), 

where they could persist. Such sediments could serve as repositories of the chemical for extended 

periods of time and could potentially be toxic to sediment dwelling organisms, affecting the food 

chain. These issues will also be assessed in the risk assessment for lambda-cyhalothrin and 

gamma-cyhalothrin. 
64

Figure 6.1a. Aquatic conceptual model depicting stressors, exposure pathways, and 

potential effects to aquatic organisms from the use of lambda-cyhalothrin and gammacyhalothrin on agricultural and certain non-agricultural sites 

**Route of exposure includes only ingestion of fish and aquatic inverts. 

Stressor 

Source 

Receptors 

Attribute 

Change 

Bifenthrin applied to agricultural or non-agricultural use site 

Spray drift 

Aquatic animals 

Invertebrates 

Vertebrates 

**Piscivorous mammals 

 and birds 

Individual organisms 

Reduced survival 

Reduced growth

Reduced reproduction 

Food chain 

Reduction in algae and 

 vascular plants 

Reduction in prey 

Modification of PCEs 

 related to prey availability 

Habitat integrity 

Reduction in primary 

 productivity

Reduced cover 

Community change 

Modification of PCEs related to 

 habitat 

Surface water/ 

Sediment 

Runoff

Aquatic Animals

Invertebrates 

Vertebrates 

Exposure 

Media 

Uptake/gills 

or integument 

Ingestion Ingestion 

Atmospheric 

transport 

Wet/dry deposition 

Soil Leaching to 

Groundwater

Uptake/gills 

or integument 

Aquatic Plants 

Non-vascular 

Vascular 

Uptake/cell, 

roots, leaves Riparian plants

terrestrial 

exposure 

pathways; see 

Figure 6.1b 

Impervious 

Surfaces

Flow1

1

 Includes flow across vegetation and vegetated drainage systems (e.g., swales) and flow across impervious surfaces 

and through impervious (piped) storm drains. 

Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological risk. 
65

Figure 6.1b. Terrestrial conceptual model depicting stressors, exposure pathways, and 

potential effects to terrestrial organisms from the use of lambda-cyhalothrin and gammacyhalothrin on agricultural and certain non-agricultural sites 

Stressor 

Source 

Attribute 

Change 

Lambda-cyhalothrin and/ or gamma-cyhalothrin applied to 

agricultural or non-agricultural use sites 

Direct 

application Spray drift 

Terrestrial 

vertebrates 

Terrestrial 

invertebrates 

Individual 

organisms 

Reduced survival 

Reduced growth 

Reduced reproduction 

Food chain 

Reduction in prey and food

Modification of PCEs 

 related to prey availability 

Habitat integrity 

Reduction in primary productivity

Reduced cover 

Community change 

Modification of PCEs related 

Terrestrial plants 

grasses/ forbs, fruit, seeds 

(trees, shrubs) 

Runoff 

Terrestrial 

vertebrates 

Exposure Media 

& Receptors Soil 

Ingestion 

Ingestion

Ingestion

Dermal uptake/Ingestion

Atmospheric 

transport 

Root uptake/contact 

Wet/dry deposition 

Ingestion

Leaching to

Groundwater Irrigation 

water 

 to habitat 

Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological risk. 

The conceptual model for potential risks of lambda-cyhalothrin and/or gamma-cyhalothrin to 

aquatic organisms due to various indoor uses of the chemical that could potentially end up in a 

“drain” is depicted in Fig. 6.2. The stressor is the chemical of concern, lambda-cyhalothrin and 

gamma-cyhalothrin. It is noted that the transport pathway is wastewater flow, the exposure media 

is the treatment facility and the exposure point or route, receptor, and attribute changes for aquatic 

organisms are similar to the conceptual model for agricultural applications.
66

Figure 6.2. Conceptual model for potential risks of lambda-cyhalothrin and gammacyhalothrin to aquatic organisms for various indoor uses of the chemical that could 

potentially end up in the “drain.” 

Stressor 

Source/ 

Transport 

Pathways 

Wastewater flow 

Source/ 

Exposure 

Media 

Treatment facility 

discharges into surface 

waters 

Exposure 

Route 

Gill/ 

 Integument 

Uptake 

Receptors 

Attribute 

Changes 

Aquatic 

Invertebrates, 

Vertebrates

Individual 

Vertebrates and 

Invertebrates

Reduced survival 

or reproduction 

Plant Population

Reduced 

population 

growth

Aquatic 

Plants

Uptake/ 

Adsorption

Lambda-cyhalothrin and gamma-cyhalothrin applications 

that could potentially end up “down-the-drain”

 

The conceptual model for potential risks of lambda-cyhalothrin and/ or gamma-cyhalothrin to 

terrestrial and aquatic organisms as a result of the ear tags or pour on treatment on cattle or calves 

is depicted in Fig. 6.3. The stressor is the chemical of concern, lambda-cyhalothrin and gammacyhalothrin, and potentially interactions caused by applications with the synergist PBO. The 

organisms that could be expected to be affected are terrestrial plants, aquatic plants and aquatic 

animals. It is noted that the potential transport pathway, the exposure media and the exposure 

point or route, receptor, and attribute changes for plant and aquatic organisms are similar to the 

conceptual model for agricultural applications Fig. 6.1a. 

Figure 6.3: Conceptual model for potential risks of lambda-cyhalothrin or gammacyhalothrin to aquatic organisms a result of the ear tags or pour on treatment on cattle or 

calves. 
67

Stressor Lambda-cyhalothrin or Gamma-cyhalothrin Used as Ear Tags or Pour-On Treatment 

(Immersion in Surface Water Body or Washoff Transported Nearby or to Surface Waters) 

Source/ 

Transport 

Pathways 

Surface waters 

Source/ 

Exposure 

Media 

Riparian/ 

Wetland 

Foliage/Soil Receiving Water Body/ 

Sediment 

Exposure 

Route 

Direct Contact/ 

Root Uptake Gill/ 

 Integument 

Uptake 

Receptors 

Attribute 

Changes 

Aquatic 

Invertebrates, 

Vertebrates 

Wetland/ 

Riparian 

Plants 

Individual Plants

Reduced survival, 

growth, or reproduction 

Individual 

Vertebrates and 

Invertebrates

Reduced survival 

or reproduction 

Plant Population

Uptake/ 

Adsorption

Aquatic 

Plants 

Reduced 

population 

growth 

 

7. Analysis Plan 

In order to address the risk hypothesis, the potential for adverse effects on the environment is 

estimated. Usage, environmental fate and transport, and ecological effects of lambda-cyhalothrin 

and gamma-cyhalothrin are characterized and integrated to assess the risks. This is accomplished 

using a risk quotient (ratio of exposure concentration to effects concentration) approach. 

Although risk is often defined as the likelihood and magnitude of adverse ecological effects, the 

risk quotient-based approach does not provide a quantitative estimate of likelihood and/ or 

magnitude of an adverse effect. However, as outlined in the Overview Document (USEPA 2004), 

the likelihood of effects to individual organisms from particular uses of a chemical is estimated 

using the probit dose-response slope and either the level of concern (discussed below) or the 

actual calculated risk quotient value. 

This analysis plan will be revisited and may be revised depending on the data available in the 

open literature and the information submitted by the public or the registrant in response to the 

opening of the Registration Review docket. 
68

7.1. Stressors of Concern 

The focus of this assessment is on the parent materials, lambda-cyhalothrin and gammacyhalothrin. However, the Agency will review open literature to identify degradate(s) of potential 

toxicological concern (e.g., Compound XV, Compounds Ia and Ib, and Compound V). Also, risk 

resulting from use of lambda-cyhalothrin and gamma-cyhalothrin with the synergist PBO will be 

assessed for cattle pour-on treatments. 

Toxicity data for environmental mixtures of lambda-cyhalothrin and gamma-cyhalothrin with 

other pesticides (those mixtures occurring in the environment following application), if available, 

may be presented as part of the ecological risk assessment. Lambda-cyhalothrin and gammacyhalothrin may be applied in tank mixtures with other products approved for use on registered 

crops. It is expected that the toxic effect of lambda-cyhalothrin and gamma-cyhalothrin, in 

combination with other pesticides used in the environment, is likely to be a function of many 

factors including, but not necessarily limited to (1) the exposed species, (2) the co-contaminants 

in the mixture, (3) the ratio of lambda-cyhalothrin and/or gamma-cyhalothrin and co-contaminant 

concentrations, (4) differences in the pattern and duration of exposure among contaminants, and 

(5) the differential effects of other physical/ chemical characteristics of the receiving waters (e.g.

organic matter present in sediment and suspended water). A discussion of implications of the 

available pesticide mixture effects data on the confidence of risk assessment conclusions will be 

addressed in the risk description of the final ecological assessment. 

7.2. Measures of Exposure 

In order to estimate risks of lambda-cyhalothrin and gamma-cyhalothrin exposures in aquatic and 

terrestrial environments, all exposure modeling and resulting risk conclusions will be made based 

on maximum application rates for the current use patterns. Available monitoring data will also be 

considered when describing potential environmental exposure to non-target organisms. 

Measures of exposure are based on aquatic and terrestrial models that predict estimated 

environmental concentrations of lambda-cyhalothrin and gamma-cyhalothrin using maximum 

labeled application rates and methods, as well as any mitigation measures specifically indicated 

on the label. The models used to predict aquatic EECs are the Pesticide Root Zone Model 

coupled with the Exposure Analysis Model System (PRZM/EXAMS). Also, to estimate aquatic 

exposure related to releases of lambda-cyhalothrin and gamma-cyhalothrin from domestic 

wastewater treatment plants, the Exposure and Fate Assessment Screening Tool’s (E-FAST2) 

down-the-drain module will be used. The Tier 1 Rice Model v.1.0 is used to derive aquatic 

exposure estimates related to the uses of these chemicals on rice plots. For the cattle ear tag and 

pour on uses, measures of exposure will be calculations assuming direct applications to water 

considering living habits of cattle livestock. The model used to predict terrestrial exposure is TREX. The model used to derive EECs relevant to terrestrial and wetland plants is TerrPlant. The 

potential for bioaccumulation for the chemical is assessed using the KABAM model, as well the 

results from bioconcentration in fish studies (e.g. the bioconcentration factors). These models are 

parameterized using relevant reviewed registrant-submitted environmental fate and transport data. 
69

PRZM (v.3.12.2, May 2005) and EXAMS (v.2.98.4.6, April 2005) are screening simulation 

models coupled with the input shell PE5.pl (August, 2007) to generate daily exposures and 1-in10 year EECs of lambda-cyhalothrin and gamma-cyhalothrin, that may occur from spray drift and 

runoff to surface water bodies adjacent to application sites. PRZM simulates pesticide 

application, movement and transformation on an agricultural field and the resultant pesticide 

loadings to a receiving water body via runoff, erosion and spray drift. The EXAMS model 

simulates the fate of the pesticide and resulting concentrations in the water body. The standard 

scenario used for ecological pesticide assessments assumes application to a 10-hectare 

agricultural field that drains into an adjacent 1-hectare water body that is 2 meters deep (20,000 

cubic meters volume) with no outlet. PRZM/ EXAMS is used to estimate screening-level 

exposure of aquatic organisms to lambda-cyhalothrin and/ or gamma-cyhalothrin and/ or their 

transformation products, should they be of concern. The measure of exposure for aquatic species 

is the 1-in-10 year return peak or rolling mean concentration. The 1-in-10 year peak is used for 

estimating acute exposures of direct effects to aquatic organisms. The 1-in-10-year 60-day mean 

is used for assessing chronic exposure to fish and aquatic-phase amphibians. The 1-in-10-year 21-

day mean is used for assessing aquatic invertebrate chronic exposure. 

At the present time, EFED considers the use of the impervious scenario (a PRZM modeling 

scenario) as the most suitable available modeling approach for impervious runoff. The PRZM 

impervious scenario may be used in the tier 2 coupled aquatic models PRZM/EXAMS along with 

a residential or other suitable scenario such as rights-of-way (ROW) to obtain EECs. The 

conceptual model for the residential scenario integrates simultaneous modeling of the individual 

use scenario with an impervious scenario. This approach assumes that no watershed is 

completely covered by either the 1⁄4 acre lot (the basis for the residential scenario) or undeveloped 

land (the basis for the ROW scenario) for residential and ROW use patterns; therefore, differential 

amounts of runoff will occur within the watershed. The impervious scenario was developed to 

represent the paved areas within a watershed not including roads, parking lots, sidewalks, and 

buildings outside the 1⁄4 acre lot (the 1⁄4 acre lot scenario accounts for impervious surfaces such as 

buildings within the represented area). By modeling a separate scenario for impervious surfaces, 

it is also possible to estimate that amount of exposure that could occur when the pesticide is 

oversprayed onto this surface. Using two scenarios in tandem requires post-processing of the 

modeled output in order to derive a weighted EEC that represents the contribution of both the 

pervious (i.e., residential and ROW scenarios) and the impervious surfaces. A Microsoft Excel 

spreadsheet has been developed that allows for the weighting and aggregation of exposure from 

both scenarios. The daily time series from each model run should be copied from the times series 

file (NAME_TS.out) generated from the PRZM graphical user interface (PE5.pl) into the 

spreadsheet provided. The time series data are then weighted based on percentage of impervious 

surface, the percentage of the pervious surface treated, and an adjusted time series is created. 

Rolling averages for the relevant durations of exposure (e.g., 21 day and 60 day averages) are 

calculated, and the relevant one-in-ten year return EEC is generated from these distributions. 

Given the aquatic toxicity of lambda-cyhalothrin and gamma-cyhalothrin and their likelihood to 

occur in sediment, the Agency will also consider the potential exposures resulting from benthic/ 
70

 

sediment concentrations (EECs). Pore water concentrations are commonly used to predict 

toxicity of non-ionic substances in sediments and characterize exposure to organisms that spend 

time in or near sediments (Di Toro et al. 1991; US EPA 2002). PRZM/ EXAMS estimates 1-in10-year peak and 21-day mean EECs for pore water. 

To estimate exposure related to releases of lambda-cyhalothrin and gamma-cyhalothrin from 

domestic wastewater treatment plants, the Agency will rely on the Office of Pollution Prevention 

and Toxics (OPPT) model, Exposure and Fate Assessment Screening Tool (EFAST, version 2.0, 

or EFAST2, 2007). From this model, the Agency will use the “Down-the-Drain” module, which 

is designed for releases to domestic wastewater treatment. It is suitable for all the sources of 

lambda-cyhalothrin and gamma-cyhalothrin that could potentially be exposed through a “downthe-drain” scenario. The model provides screening level estimate concentrations of chemicals in 

surface water that may result from household uses and the disposal of consumer products into 

wastewater using a few simple input parameters (production volume and fraction of the chemical 

removed during wastewater treatment). 

Since lambda-cyhalothrin and gamma-cyhalothrin have uses on rice (and wild rice for lambdacyhalothrin), the screening-level Tier 1 Rice Model v.1.0 will be utilized to obtain estimated 

exposure concentrations (EECs) related to that use. The Tier I Rice Model v1.0 relies on an 

equilibrium partitioning concept to provide conservative estimates of environmental 

concentrations resulting from application of pesticides to rice paddies. When a pesticide is 

applied to a rice paddy, the model assumes that it will instantaneously partition between a water 

phase and a sediment phase. Among the assumptions of this model, the degradation of the 

pesticide and the mass transfer from the aqueous phase to the sediment are not considered. Also, 

volatilization and other dissipation processes are not considered. 

There are three possible scenarios whereby lambda-cyhalothrin and gamma-cyhalothrin residues 

can enter the aquatic ecosystem due to treatment to cattle. First, ear tags can fall off cattle into 

water bodies (note that ear tags apply only to lambda-cyhalothrin). Second, multiple cattle that 

are treated with lambda-cyhalothrin and gamma-cyhalothrin can directly enter a water body. 

Third, rainfall can cause washoff of lambda-cyhalothrin and/ or gamma-cyhalothrin residues to be 

transported from treated multiple cattle to water bodies via runoff. For each of these cases, 

surface water concentrations will be calculated using the maximum mass of lambda-cyhalothrin 

and gamma-cyhalothrin per animal, 4.18x10-4 lb a.i./ cattle (0.190 g) for the lambda-cyhalothrin 

ear tag use, 3.13x10-4 lb a.i./ cattle (0.142 g) for the lambda-cyhalothrin pour on products, and 

1.56x10-4 lb a.i./ cattle (0.0708 g) of gamma-cyhalothrin for the single pour on product, spilling 

into a standard farm pond of 1 ha area and 2 m depth or a volume of 2.0 x 107 L. Surface water 

EECs will be calculated utilizing a suitable program which considers the soil-water partition 

coefficient and the depth of the sediment layer such as the KdCalc (v.1.0 10/02/02). Certain 

assumptions are required for these scenarios. For example, for the second scenario, 20 treated 

cattle may be assumed to enter the water and for the third scenario, a 1000 treated cattle feedlot 

may be assumed (USDA NASS data).13 A maximum of 20% is assumed to wash off cow hide for 

13 http://www.nass.usda.gov/Surveys/Guide_to_NASS_Surveys/Cattle_On_Feed/index.asp and 

http://usda.mannlib.cornell.edu/usda/current/CattOnFe/CattOnFe-07-23-2010.pdf (both accessed 08/16/10) “Cattle on 
71

 

the ear tags treatment; however, 100% is assumed for pour on products. 

Exposure estimates for terrestrial animals assumed to be in the target area are derived using the TREX model (version 1.3.1, 12/07/2006). This spreadsheet-based model calculates the residues on 

avian and mammalian food items along with the dissipation rate of a chemical applied to foliar 

surfaces (for single or multiple applications) in order to estimate acute and reproductive risk 

quotients. T-REX calculates EECs and risk quotients based on both the upper bound and mean 

residue concentrations as presented by Hoerger and Kenaga (1972) and modified by Fletcher et 

al. (1994). These concentrations are determined using nomograms that relate application rate of a 

pesticide to residues remaining on dietary items of terrestrial organisms. EECs for terrestrial 

plants inhabiting dry and wetland areas are derived using TerrPlant (version 1.2.2, 12/26/2006). 

This model uses estimates of pesticides in runoff and in spray drift to calculate EECs. EECs are 

based upon solubility, application rate and minimum incorporation depth. 

As indicated in Table 3.1 and its associated text in Section 3, lambda-cyhalothrin and gammacyhalothrin appear to have a potential to bioconcentrate in aquatic organisms and it appears that 

there is also some potential to biomagnify in terrestrial organisms. The potential for 

bioaccumulation of lambda-cyhalothrin and gamma-cyhalothrin will also be examined in the risk 

assessment. Because lambda-cyhalothrin and gamma-cyhalothrin have a fairly high KOW (105 to 

107

) and the chemical may be persistent in water and sediments, there is a potential for 

bioaccumulation. The maximum bioconcentration factor was 4,600x for whole fish and 

depuration rate is moderate (half depuration time of ~9 days, MRID 00152744, 00152745). 

Bioaccumulation will be assessed using the results from bioaccumulation in fish studies, as well 

as the KABAM model (KOW (based) Aquatic BioAccumulation Model, version 1.0, 2009), 

adjusting for biotransformation rates. KABAM is used to estimate potential bioaccumulation of 

hydrophobic organic pesticides in freshwater aquatic ecosystems and risks to mammals and birds 

consuming aquatic organisms which have bioaccumulated these pesticides. Monitoring data and 

biotransformation rates in terrestrial species will also be evaluated, to assess the potential for 

bioaccumulation in terrestrial food webs. 

7.3. Measures of Effect 

Ecological effects data are used as measures of direct and indirect effects to biological receptors. 

Data are typically obtained from registrant-submitted studies or from literature studies identified 

by ECOTOX. The ECOTOX database provides more ecological effects data in an attempt to 

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

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

was created and is maintained by the USEPA, Office of Research and Development, and the 

National Health and Environmental Effects Research Laboratory's Mid-Continent Ecology 

Division. 

feed in feedlots with 1,000 or more head accounted for 84 percent of the total cattle on feed on July 1, 2010, down 

slightly from July 1, 2009.” 
72

The acute measures of effect used for animals in this assessment are the LD50, LC50 and EC50. 

LD stands for "Lethal Dose", and LD50 is the amount of a material, given all at once, that is 

estimated to cause the death of 50% of the test organisms. LC stands for “Lethal Concentration” 

and LC50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. 

EC stands for “Effective Concentration” and the EC50 is the concentration of a chemical that is 

estimated to produce a specific effect in 50% of the test organisms. Endpoints for chronic 

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

NOAEL stands for “No Observed-Adverse-Effect-Level” and refers to the highest tested dose of a 

substance that has been reported to have no harmful (adverse) effects on test organisms. The 

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

which none of the observed effects were statistically different from the control. The NOEC is the 

No-Observed-Effects-Concentration. For non-listed plants, only acute exposures are assessed 

(i.e., EC25 for terrestrial plants and EC50 for aquatic plants); for listed plants either the NOAEC or 

EC05 is used. 

Information on the potential effects of lambda-cyhalothrin and gamma-cyhalothrin on non-target 

animals is also collected from the Ecological Incident Information System (EIIS). The EIIS is a 

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

such effects have been associated with the use of pesticides. Information on incidents involving 

avian species is also provided through the Avian Monitoring Information System (AIMS), which 

is maintained by the American Bird Conservancy. 

Where available, sub-lethal effects observed in both registrant-submitted and open literature 

studies will be evaluated qualitatively. Such effects may include behavioral changes (e.g., 

lethargy and changes in coloration). Quantitative assessments of risks, though, are limited to 

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

survival, growth and reproduction. 

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

toxicity of lambda-cyhalothrin and gamma-cyhalothrin to birds is similar to terrestrial-phase 

amphibians and reptiles. The same assumption is made for fish and aquatic-phase amphibians. 

Past Agency ecological risk assessments of lambda- and gamma-cyhalothrin have bridged aquatic 

toxicity data for the two active ingredients using assumptions of relative compositions of the most 

biologically active isomers (US EPA, 2004a; D289801, 289799, 289797, 289794, 289798, 

288057). Based on the review of the available data, some aquatic organisms show greater 

sensitivity to gamma-cyhalothrin than lambda-cyhalothrin. 

7.4. Integration of Exposure and Effects 

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

potential ecological risk from the use of pesticides and the likelihood of direct and indirect effects 

to non-target organisms in aquatic and terrestrial habitats. The exposure and toxicity effects data 

are integrated in order to evaluate the risks of adverse ecological effects on non-target species. 
73

For the assessment of risks, the risk quotient (RQ) method is used to compare exposure and 

measured toxicity values. EECs are divided by acute and chronic toxicity values. The resulting 

RQs are then compared to the Agency’s Levels of Concern (LOCs) (USEPA 2004). These 

criteria will be used to indicate when lambda-cyhalothrin and/ or gamma-cyhalothrin’s uses, as 

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

organisms. In addition, incident data from the EIIS will be considered as part of the risk 

characterization. 

7.5. Deterministic and Probabilistic Assessment Methods 

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

based approach described in the risk assessment. An effort may also be made to further 

qualitatively describe risk using probabilistic tools that the Agency has developed. These tools 

have been reviewed by FIFRA Scientific Advisory Panels 

(http://www.epa.gov/scipoly/sap/index.htm) and have been deemed as appropriate means of 

refining assessments where deterministic approaches have identified risks. 

7.6. Endangered Species Assessments 

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the 

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

registered uses of lambda-cyhalothrin and gamma-cyhalothrin. This assessment will be 

conducted in accordance with the Overview Document (USEPA 2004), provisions of the ESA, 

and the Services’ Endangered Species Consultation Handbook (USFWS/NMFS, 1998). 

The assessment of effects associated with the registration of lambda-cyhalothrin and gammacyhalothrin is based on an action area. The action area is considered to be the area directly or 

indirectly affected by the federal action, as indicated by the exceedance of Agency Levels of 

Concern (LOCs) used to evaluate direct or indirect effects. The Agency’s approach to defining 

the action area under the provisions of the Overview Document (USEPA 2004) considers the 

results of the risk assessment process to establish boundaries for that action area with the 

understanding that exposures below the Agency’s defined LOCs constitute a no-effect threshold. 

For the purposes of this assessment, attention will be focused on the footprint of the action (i.e., 

the area where lambda-cyhalothrin and gamma-cyhalothrin application occurs), plus all areas 

where offsite transport may result in potential exposure that exceeds the Agency’s LOCs. 

Specific measures of ecological effect that define the action area for listed species include any 

direct and indirect effects and/ or potential modification of its critical habitat, including reduction 

in survival, growth, and reproduction as well as the full suite of sub-lethal effects available in the 

effects literature. Therefore, the action area extends to a point where environmental exposures are 

below any measured lethal or sub-lethal effect threshold for any biological entity at the whole 

organism, organ, tissue, and/ or cellular level of organization. In situations where it is not 

possible to determine the threshold for an observed effect, the action area is not spatially limited 

and is assumed to be the entire United States. 
74

Currently, EFED does not assess risk to non-target insects. Results of acceptable studies are used 

for recommending appropriate label precautions. Lambda-cyhalothrin and gamma-cyhalothrin 

are both classified as highly toxic on an acute contact basis. This study suggests that the acute 

toxicity to non-target beneficial endangered insects may also be of concern should exposure 

occur. 

Toxicity data are not available for terrestrial plants; thus, risks associated with lambdacyhalothrin and gamma-cyhalothrin exposure to terrestrial plants cannot be assessed. In the past, 

it had been indicated that a review of lambda-cyhalothrin and gamma-cyhalothrin’s mode of 

action (neural toxin) suggested that direct toxicity to plants would not be an issue of concern. 

Nonetheless, data for these chemicals are required in the absence of any information to support 

conclusions regarding lambda-cyhalothrin and gamma-cyhalothrin phytotoxicity. 

7.7. Drinking Water Assessment 

A drinking water assessment will be conducted to support future human health risk assessments 

of lambda-cyhalothrin and gamma-cyhalothrin should it be required, based on all the available 

environmental fate information. The drinking water assessment will incorporate model estimates 

of lambda-cyhalothrin and/ or gamma-cyhalothrin in surface and ground waters. Concentrations 

in surface waters will be estimated using FQPA Index Reservoir Screening Tool (FIRST, v.1.1.1, 

12/18/07) (or subsequently using PRZM/ EXAMS, with the Index Reservoir – for description see 

above – if refinements are required). Ground water estimates of concentrations will be obtained 

using the Screening Concentration In GRound Water (SCI-GROW) model (v.2.3, July 2003). 

The drinking water assessment will also include a summary of available surface and ground water 

monitoring data. 

7.8. Endocrine Disruptor Screening Program 

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

Program (EDSP) to determine whether certain substances (including pesticide active and other 

ingredients) may have an effect in humans or wildlife similar to an effect produced by a 

“naturally occurring estrogen, or other such endocrine effects as the Administrator may 

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

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

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

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

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

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

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

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

 

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

of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. This list 

of chemicals was selected based on the potential for human exposure through pathways such as 
75

food and water, residential activity, and certain post-application agricultural scenarios. This list 

should not be construed as a list of known or likely endocrine disruptors. 

Lambda-cyhalothrin and gamma-cyhalothrin are not among the group of 58 pesticide active 

ingredients on the initial list to be screened under the EDSP. The Agency will review the EDSP 

Tier 1 data and any “other scientifically relevant information” submitted in response to test 

orders. Based on this review the Agency will determine the need for additional testing. For 

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

chemicals, the test guidelines and the Tier 1 screening battery, please refer to the following 

website: http://www.epa.gov/endo/ . 

7.9. Preliminary Identification of Data Gaps 

7.9.1. Fate 

After evaluation of the available data for lambda-cyhalothrin and gamma-cyhalothrin, the 

following data gaps for registration review have been identified. 

835.2120 Hydrolysis – At this time, there is one available study that was deemed acceptable at 

pH 5 and 7, conducted on gamma-cyhalothrin; however, the part conducted at pH 9 was deemed 

unacceptable, but upgradable. The other study was conducted at a rate that exceeded the 

solubility limit of lambda-cyhalothrin. In order to clarify the rate of reaction of the test substance 

in pH 9 buffered solutions, the registrant should submit data to upgrade the pH 9 study, or a new 

study should be conducted at pH 9. 

835.4200 Anaerobic Soil Metabolism – There is one available anaerobic soil metabolism study, 

conducted on lambda-cyhalothrin, conducted with one soil, but it supplies only very limited 

information, with only a few data points. Anaerobic studies with one soil type are generally 

sufficient for the evaluation of transformation pathways. Rates of transformation should be 

determined in at least three additional soils (from Fate, Transport and Transformation Test 

Guidelines – OCSPP Guideline 835.4100 & 835.4200). For metabolism studies, domestic soils 

are preferred. The study should be performed with lambda-cyhalothrin or gamma-cyhalothrin. 

835.4400 Anaerobic Aquatic Metabolism – A study is available in one soil/ sediment system. 

According to the OCSPP Fate, Transport and Transformation Test Guidelines (835.4300 & 

835.4400) “At least two sediments and their associated waters are used for both the aerobic and 

the anaerobic studies respectively... However, there may be cases where more than two aquatic 

sediments should be used, for example, for a chemical that may be present in freshwater and/or 

marine environments. Sediments should be representative of intended use sites.” Since both 

lambda-cyhalothrin and gamma-cyhalothrin have the potential for use near estuarine/ marine 

areas, one of the required sediment systems should be from estuarine/ marine environment. Two 

sediment systems are required for lambda-cyhalothrin, one of which should be of marine origin. 

For the metabolism studies, domestic sediments are preferred. 
76

 

Other studies: 

Leachability from Treated Wood – A study is required for lambda-cyhalothrin and/ or gammacyhalothrin. It should be conducted using TEP and according to the American Wood Preservers 

Association Standard Method of Determining the Leachability of Wood Preservatives (E11, 

edition 06). It is strongly preferred that the registrant provided a protocol to be evaluated by the 

Agency prior to performing the study. 

Environmental Chemistry Methods (ECMs), and Independent Laboratory Validations 

(ILVs), for Soil, Water and Sediment. ECMs associated with the Terrestrial Field Dissipation 

study (Field dissipation §158.1300; OPPTS guidelines 835.6100, 835.6200, and 835.6300), along 

with successful confirmatory method trials (validation) by an independent laboratory (i.e. ILVs), 

are required. If there is risk concern for a given taxon, ECMs should be available for the 

environmental media in which organisms of the taxon reside. These ECMs should have limits of 

quantitation for the residues of concern that are lower than the relevant toxicological levels of 

concern. Previous reviews on lambda-cyhalothrin and gamma-cyhalothrin indicate that there is 

high concern for acute and chronic toxicity to aquatic animals. Certain scenarios may have 

triggered acute and chronic levels of concern for freshwater and/ or estuarine/ marine aquatic 

invertebrates and/ or for fish and/ or organisms living in the benthos. Therefore, ECMs for water 

and sediment are required in addition to the ECM for soil. The ECMs should include parent and 

those residues found in the laboratory studies that exceeded 10% of the applied. Based on the 

available data at this time, the following appear to be the residues of concern for each media, but 

this could change, based upon the results of new environmental fate studies: 

Soil – parent, Compounds XV, Ia, Ib and 3-(4-hydroxyphenoxy) benzaldehyde 

Water and Sediment – parent, Compounds Ia, Ib and V 

The registrant is encouraged to submit state-of-the-art environmental chemistry methods; further, 

multi-residue methods (MRMs) for soil, water and sediment are preferred, if applicable. The 

registrant submitted one method (MRID 40515901, published in the Agency’s ECM website),14

that could quantify lambda-cyhalothrin in water and sediment. EFED located an Environmental 

Chemistry Method Evaluation (ECME) performed by the Analytical Chemistry Branch (ACB) of 

the water portion of this study (BEAD review dated 9/23/93, Environmental Chemistry Method 

Validation Report No. ECM 0004W1). The ACB determined an LOD of 10 ng/L (ppt) while the 

registrant’s value is 1 ppt. This method cannot be used to determine lambda-cyhalothrin’s 

transformation products. Furthermore, there is one ECM and one ILV that quantifies lambdacyhalothrin and other pyrethroids in sediments (MRID 47053001 and 47053002). It is uncertain 

wether this method can distinguish gamma-cyhalothrin from lambda-cyhalothrin. The Agency 

will verify the suitability of these methods and the appropriateness of their levels of 

quantification. At this time, no specific methods have been identified for the analysis of gammacyhalothrin. A full description of the method validation procedures performed by an independent 

laboratory should also be submitted. It should include the following information (Corbin et al.

2006): (a) Recovery level(s) of the test compound(s) from the soil, water and sediment 

(substrates) at various relevant fortification level(s) using the residue analytical methodology; (b) 

a validated method sensitivity level; (c) results of the study and statistical test applied, including a 

14 Available at url: http://www.epa.gov/oppbead1/methods/ecmindex.htm
77

stepwise presentation of the procedure for calculating percent recovery from the raw data; (d) all 

the data/ information necessary to independently verify the results; (e) summary of the results; 

and, (f) discussion and conclusions of the results. 

POTW Effluent Monitoring – EFED requests any existing or ongoing POTW effluent 

monitoring data for the pyrethroids be submitted to the Agency. 

POTW Treatability Study – The Agency has recently requested and provided comments on a 

protocol developed by the Pyrethroid Working Group (PWG) for a bench scale study of waste 

water treatment, to assess the percentage removed in the biosolids by the treatment, the amount 

that would degrade during treatment, and the amount that would remain in the waste water. 

These data would be used to inform removal percentages by waste water treatment, which is an 

input to the Exposure and Fate Assessment Screening Tool’s (E-FAST) down-the-drain module. 

The Office of Pesticide Programs will continue to confer with the Office of Water with the goal of 

refining our down-the-drain assessment for registration review. It is the responsibility of the 

registrant to ensure that lambda-cyhalothrin and gamma-cyhalothrin are included in the study 

completed by the PWG or conduct a similar study on their own (following submission of a 

protocol for review). 

Table 7.1 lists the status of the environmental fate data requirements for lambda-cyhalothrin and 

gamma-cyhalothrin. 

Table 7.1. Summary of Environmental Fate Data Requirements for Lambda-cyhalothrin and Gamma-cyhalothrin

Study Identification 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This Requirement? Bibliographic Citation 

Must Additional 

Data Be Submitted 

Under FIFRA 

3(c)(2)(B)? 

§158.1300 ENVIRONMENTAL FATE

Degradation Studies-Lab:

835.2120 Hydrolysis 1,2 Yes 00151604, 45447409 Yes2

835.2240 Photodegradation in 

Water 

1,2 Yes 44861501, 46394702 No 

835.2410 Photodegradation on 

Soil 

1,2 Yes 40052405 No 

835.2370 Photodegradation in 

Air 

1,2 No Not Available No 

Metabolism Studies-Lab:

835.4100 Aerobic Soil 1,2 Yes 00089995, 00151607, 

44861504, 45447410, 

45447411 

No 

835.4200 Anaerobic Soil 1,2 Yes 00151607, 44861504 Yes3 
78

Table 7.1. Summary of Environmental Fate Data Requirements for Lambda-cyhalothrin and Gamma-cyhalothrin

Study Identification 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This Requirement? Bibliographic Citation 

Must Additional 

Data Be Submitted 

Under FIFRA 

3(c)(2)(B)? 

835.4300 Aerobic Aquatic 1,2 Yes 44367402, 44861506, 

45447412 

No

835.4400 Anaerobic Aquatic 1,2 No 44367401 Yes4 

Mobility Studies:

835.1230 Leaching – 

Adsorption/ Desorption 

1,2 Yes 00151608, 44861503, 

44861509, 45447613 No 

835.1410 Volatility (Lab) 1,2 No Not Available No 

835.8100 Volatility (Field) 1,2 No Not Available No 

Dissipation Studies-Field:

835.6100 Terrestrial Field 

Dissipation 

1,2 Yes 40052407, 45794902 No

835.6200 Aquatic Field 

Dissipation 

1,2 Yes 44367403, 44367404 No 

835.6300 Forestry Dissipation 1,2 No Not Applicable N/A 

Ground Water Monitoring Studies:

835.7100 Ground Water 

Monitoring 

1,2 No Not Available Reserved 

§158.1100 SPRAY DRIFT

201-1 Droplet Size Spectrum 1,2 Yes Not Available No5 

202-1 Drift Field Evaluation 1,2 Yes Not Available No5

Other Studies: 

Environmental Chemistry 

Methods (ECMs) and 

Independent Laboratory 

Validations (ILVs) 

1,2 Yes 40515901, 47053001, 

47053002 

Yes6

Leachability from Treated 

Wood 

1, 2 No Not Available Yes7 

POTW Effluent Monitoring 

and POTW Treatability Study 

Indoor Uses No Not Available Yes8 

1. Use Patterns: 1=Terrestrial/Food; 2=Terrestrial/Feed. 

2. The registrant should submit data to upgrade the pH 9 study conducted with gamma-cyhalothrin or a new study 

conducted at pH 9 is required. 
79

Table 7.1. Summary of Environmental Fate Data Requirements for Lambda-cyhalothrin and Gamma-cyhalothrin

Study Identification 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This Requirement? Bibliographic Citation 

Must Additional 

Data Be Submitted 

Under FIFRA 

3(c)(2)(B)? 

3. Data are required for lambda-cyhalothrin on four soils, as per current guidance. 

4. Additional data are required in one sediment system of freshwater origin and another of estuarine/ marine origin. 

5. Data requirements covered by submission of the Spray Drift Task Force. 

6. The data requirement remains unfulfilled for lambda-cyhalothrin, pending evaluation of three available studies. No data 

have been identified for gamma-cyhalothrin. 

7. It is preferred that the registrant provided a protocol to be evaluated by the Agency prior to performing the study. 

8. It is anticipated that these studies will be required. 

7.9.2 Effects

Based on previously submitted studies, the Environmental Fate & Effects Division believes that 

the ecological effects data can be bridged for lambda- and gamma-cyhalothrin (see discussion in 

Section 4). Therefore, toxicity data may be submitted for either lambda- and gamma-cyhalothrin 

to address data concerns. For registration review, the following studies are being requested to 

fulfill any data gaps: 

Study Title: Endocrine Disruptor Screening Program

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

Program (EDSP) to determine whether certain substances (including pesticide active and other 

ingredients) may have an effect in humans or wildlife similar to an effect produced by a 

“naturally occurring estrogen, or other such endocrine effects as the Administrator may 

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

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

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

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

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

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

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

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

 

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

of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. This list 

of chemicals was selected based on the potential for human exposure through pathways such as 

food and water, residential activity, and certain post-application agricultural scenarios. This list 

should not be construed as a list of known or likely endocrine disruptors. 

Lambda- and gamma-cyhalothrin are not among the group of 58 pesticide active ingredients on 

the initial list to be screened under the EDSP, but data may be required in future screening lists. 

The Agency will review the EDSP Tier 1 data and any “other scientifically relevant information” 

submitted in response to test orders. Based on this review the Agency will determine the need for 
80

additional testing. For further information on the status of the EDSP, the policies and procedures, 

the list of 67 chemicals, the test guidelines and the Tier 1 screening battery, please refer to the 

following website: http://www.epa.gov/endo/ . 

Guideline Number: 850-2100 

Study Title: Passerine Acute Avian Oral 

Although an acute avian oral study was received for both the mallard duck (lambda-cyhalothrin) 

and bobwhite quail (gamma-cyhalothrin), the Agency updated its data requirements in 40 CFR 

Part 158 (October 26, 2007) to include an acute oral toxicity study for both a passerine species 

and either a waterfowl or an upland game species. Prior to starting toxicity testing, a protocol will 

need to be provided for review. Many passerine species utilize agricultural fields, forests, 

residential areas and surrounding areas, and, therefore, have the potential to be exposed to 

pesticides used in agricultural, forest, and residential settings. It is likely that, for most pesticide 

use patterns, passerines are more likely to be exposed to pesticides than upland game species and 

waterfowl. Passerines are smaller in size and generally have faster metabolisms than the 

waterfowl and upland game bird species traditionally used in avian toxicity tests which could 

impact their sensitivity to chemicals. A study is requested with either lambda- or gammacyhalothrin. 

Guideline Numbers: Non-guideline 

Study Title: Aquatic Invertebrate Acute Toxicity (Hyalella azteca)

Based on a review of the registrant-submitted studies, amphipods (Gammarus pseudolimnaeus, 

EC50=0.00048 μg a.i./L) are more sensitive to gamma-cyhalothrin technical than the Daphnia 

magna (EC50=0.045 μg a.i./L) by two orders of magnitude. For lambda-cyhalothrin, the same 

trend is observed (EC50=0.0067 μg a.i./L for Gammarus pulex compared to an EC50=0.24 μg 

a.i./L for Daphnia magna based on studies with the technical product). The previously submitted 

amphipod study is classified as supplemental and believed to be an underestimation of the true 

toxicity of gamma-cyhalothrin technical because of rapidly declining exposure concentration over 

the duration of the study. In addition, available information in the Agency ECOTOX database and 

studies in the open literature (Weston and Lydy, 2010; Solomon et al 2001) indicate that the 

freshwater amphipod, Hyalella azteca, is substantially more sensitive to pyrethroids than Daphnia 

magna, the commonly tested freshwater invertebrate. Information on the acute toxicity of 

lambda- or gamma-cyhalothrin to Hyalella azteca was not identified in this problem formulation. 

Therefore, in order to ensure that risk to sensitive aquatic invertebrates (e.g., amphipods) are 

appropriately quantified, additional acute toxicity testing of the amphipod Hyalella azteca is 

needed (water column exposure, not sediment-spiked). In addition to its high sensitivity, the 

freshwater amphipod, Hyalella azteca, is recommended as the test species because it is also being 

requested for chronic freshwater sediment toxicity testing, thereby enabling acute risk to Hyalella

to be estimated via porewater exposure. A study is requested with gamma-cyhalothrin, based on 

the increased sensitivity of aquatic species to gamma- compared to lambda-cyhalothrin. 

Guideline Numbers: 850.1075 

Study Title: Freshwater Fish Acute Toxicity (fathead minnow) 
81

The only available study on chronic toxicity of lambda-cyhalothrin to freshwater fish was 

conducted with the fathead minnow, Pimephales promelas (MRID 41519001; supplemental). 

The NOAEC from this study (0.031 μg a.i./L) is only about a factor of two less than the 96-h 

LC50 of 0.078 μg a.i./L for the most acutely sensitive freshwater fish species (golden orfe) to 

lambda-cyhalothrin. Furthermore, this NOAEC is virtually identical to the 96-h LC50 of 0.029 μg 

a.i./L determined for bluegill with gamma-cyhalothrin (MRID 45447215). It is therefore apparent 

that the fathead minnow is likely not among the most sensitive freshwater fish species tested to 

lambda- or gamma-cyhalothrin. In order to estimate the chronic toxicity to sensitive freshwater 

fish species (e.g., bluegill, golden orfe), an acute-chronic ratio (ACR) will likely be needed. This 

ACR would be applied to the most acutely sensitive fish species to estimate its corresponding 

chronic sensitivity. ACRs should be determined on the same species (in this case, fathead 

minnow) in order to reduce uncertainty in predicted chronic toxicity values. However, there are 

no submitted acute toxicity studies with fathead minnow from which to derive an ACR. Deriving 

an ACR based on an acutely sensitive species (e.g., bluegill) and a chronically insensitive species 

(fathead minnow) would likely grossly under estimate chronic risk to sensitive fish species. 

Without this study, estimation of chronic risks to sensitive fish species will involve substantial 

uncertainty. Therefore, the Agency is requesting an acute toxicity test of lambda-cyhalothrin to 

the fathead minnow in order to appropriately estimate chronic toxicity to fish based on existing 

chronic data with fathead minnow. Fathead minnow is one of the recommended test species in 

the OPPTS test guidelines. 

Guideline Numbers: 850.1075, 850.1010 and non-guideline 

Study Title: Freshwater Fish Acute Toxicity (TEP) 

Freshwater Aquatic Invertebrate Acute Toxicity (TEP) 

Whole sediment: chronic invertebrates freshwater and marine 

Because there are registered outdoor uses that may result in significant exposure to water bodies, 

acute lambda- and gamma-cyhalothrin TEP data with the synergist PBO is requested for 

freshwater fish and freshwater invertebrates. The registrations are for cattle ear tags (#773-75) or 

cattle pour-on treatments (#773-92, #53883-248 and #53883-270). 

A total of 4 active product registrations exist for lambda-cyhalothrin and gamma-cyhalothrin 

formulations with PBO: 

• Lambda-cyhalothrin and PBO: # 773-75, #773-92, #53883-248 

• Gamma-cyhalothrin and PBO: # 53883-270 

Products with the synergist PBO are likely to cause increased toxicity to nontarget aquatic 

species. Currently, no data is available to quantify the difference in toxicity for fish or 

invertebrates that may be concurrently exposed to lambda- and gamma-cyhalothrin and PBO 

compared to the active ingredients alone. While these studies are requested for the "TEP," the 

registrant must submit a protocol prior to conducting these TEP studies that addresses the 

expected toxicity from differing concentration ratios of PBO and the TGAI that are likely to occur 

in the aquatic environment. Results from the acute freshwater toxicity tests can be used to 

optimize the design of the chronic sediment toxicity test. This approach is being followed by the 

Agency with TEP testing of PBO and pyrethrins. 
82

Guideline Number: 850.1350 

Study Title: Aquatic Invertebrate Life-Cycle (freshwater) 

Previously submitted studies indicate that freshwater invertebrates are among the most 

chronically sensitive species to lambda- and gamma-cyhalothrin, with chronic effects expected 

below 1 ng/L. While two supplemental studies have been submitted on the chronic toxicity of 

lambda-cyhalothrin to Daphnia magna (MRID 41217501, 00152733), the toxicity endpoints 

derived from these studies are considered highly uncertain. Specifically, the exposure 

concentrations used in these studies varied so much (3X to more than 10X) that maximum and 

minimum values overlapped among treatments. This excessive variability in exposure 

concentrations within treatments brings into question the ability to accurately determine a chronic 

toxicity endpoint from these studies (e.g., NOAEC). Other guideline deviations were also noted in 

these two studies (e.g., high light intensities, use of too few replicate chambers per treatment, 

culling of less healthy organisms during the course of the study). Obtaining an accurate chronic 

NOAEC for freshwater invertebrates (e.g., daphnids) is critical to future risk assessment since this 

value will likely be used to estimate chronic toxicity to other more sensitive freshwater 

invertebrates (e.g., amphipods) which will form the basis of the risk assessment conclusions. As 

substantial advances in both analytical and biological test methods have occurred over the past 

two decades (the previously submitted studies were conducted in 1985 and 1989), it is highly 

likely that a repeat of these studies would yield results that are much more scientifically 

defensible. Without this study, estimation of chronic risks to sensitive freshwater invertebrates 

(e.g., daphnia, amphipods) will involve substantial uncertainty. A study is requested with gammacyhalothrin, based on the increased sensitivity of aquatic species to gamma- compared to lambdacyhalothrin. 

Guideline Number: Non-guideline 

Study Title: Whole sediment: chronic invertebrates freshwater and marine 

No chronic sediment toxicity tests for freshwater or marine invertebrates have been submitted to 

satisfy the Agency’s updated data requirements for outdoor uses in 40 CFR Part 158 (October 26, 

2007). For lambda- and gamma-cyhalothrin, available information indicates that benthic 

organisms may be exposed via run-off or spray drift applications used in agricultural, forest, and 

residential settings. Based on calculations in the most recent EFED assessment for lambdacyhalothrin (Section 18 Emergency Exemption for the Use of Lambda-cyhalothrin in Washington 

on Asparagus, D379522, August 2010) (see Appendix D for modeling information), the peak 

sediment porewater EECs predicted for lambda-cyhalothrin (0.00253 μg a.i./L) exceeds 0.1 of the 

most sensitive acute LC/EC50 (0.00048 μg a.i./L for Gammarus pseudolimnaeus), which satisfies 

one of the criteria for requiring chronic whole sediment toxicity testing under 40 CFR Part 158. 

This comparison is based on exposure concentrations predicted for lambda-cyhalothrin and the 

most sensitive toxicity information for gamma-cyhalothrin. However, the exposure would is 

expected to be similar for gamma-cyhalothrin based on similar fate properties. Additionally, the 

rates proposed for asparagus (3 applications of 0.034 kg a.i./ha at 21 day intervals) were not the 

highest currently registered use rates (see Section 3.2). Chronic effects were also seen in all 

aquatic taxa tested at levels as low as 0.0002 μg a.i./L (Accession #073989, mysid shrimp). 
83

The expected half-life of lambda- and gamma-cyhalothrin in sediment (28 – 61 days for aerobic 

soil metabolism and 21 – 53 days for aerobic aquatic metabolism) is substantially greater than 40 

CFR Part 158 criterion of 10 days. The potential for persistent exposure from lambda- and 

gamma-cyhalothrin in sediment is also indicated by open literature studies on pyrethroids 

(Weston et al. 2005, Amweg et al. 2006 and Ding et al. 2009). 

The third set of trigger criteria for requiring chronic testing (Kd > 50, or log KOW >3 or KOC > 

1000) is also met for lambda- and gamma-cyhalothrin (for lambda-cyhalothrin Kd mean value is 

4350, log KOW is 7, and mean KOC value 333,200; for gamma-cyhalothrin Kd mean value is 622, 

log KOW is 5, and KOC mean value is 59,700). The physicochemical property triggers (Kd, KOW

and KOC) reflect the propensity of the chemical to partition onto the particulate or organic matter 

phases of sediments. Exceeding any one of the physicochemical property triggers listed above is 

sufficient for indicating the pesticide has reasonable potential for partitioning to the sediment 

compartment. 

For sediment studies involving pyrethroids, chronic whole sediment tests on Hyalella azteca, 

Chironomus tentans, and Leptocheirus plumulosus are requested. Although both are freshwater 

species, Hyalella and Chironomus differ substantially in their ecological niche (i.e., epibenthic v. 

infaunal species), physiology, and there is some evidence suggesting Hyalella is among the more 

sensitive invertebrates to some pyrethroids based on water column tests (Anderson et al. 2006, 

Maund et al. 2002). Lambda- and gamma-cyhalothrin have the potential to enter estuarine/marine 

water bodies based on current usuage patterns that include coastal areas. Therefore, testing is also 

required for an estuarine/marine sediment-dwelling invertebrate species. 

A study is requested with gamma-cyhalothrin, based on the increased sensitivity of aquatic 

species to gamma- compared to lambda-cyhalothrin. 

Guideline Numbers: 850.4150 and 850.4250 

Study Title: Vegetative vigor and Seedling emergence, Tier I/ Tier II 

No acceptable toxicity data are currently available to assess the risk of lambda- and gammacyhalothrin to non-target terrestrial plants. Since lambda- and gamma-cyhalothrin have residential 

outdoor uses, vegetative vigor and seedling emergence studies are required. These phytotoxicity 

data are needed to assess the impact of pesticides on endangered and threatened non-target 

terrestrial plants. A study is requested with either lambda- or gamma-cyhalothrin. 

Guideline Number: 850.4400 

Study Title: Aquatic Vascular Plant Growth-Lemna spp. Tiers I/II 

No acceptable toxicity data are currently available to assess the risk of lambda- and gammacyhalothrin to non-target aquatic vascular plants. Since lambda- and gamma-cyhalothrin have 

residential outdoor uses, aquatic vascular plant studies are required. These phytotoxicity data are 

needed to assess the impact of pesticides on endangered and threatened aquatic vascular plants. A 

study is requested with either lambda- or gamma-cyhalothrin. 
84

Table 7.2 lists the status of the ecological effects data requirements for lambda- and gammacyhalothrin. 

Table 7.2. Ecological Effects Data Requirements for lambda- and gamma- cyhalothrin. 

Data Requirement 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This 

Requirement? 

(Yes, No, or 

Partially) 

Bibliographic 

Citation 

Must 

Additional 

Data Be 

Submitted 

Under FIFRA 

3(c)(2)(B)? 

§158.490 TERRESTRIAL ORGANISMS

71-1(a) Acute Avian Oral, Quail/Duck 1,2 Partially 00151594, 45447210, 

45447211 

Yes2 

71-2(a) Acute Avian Diet, Quail 1,2 Yes 45447212 No

71-2(b) Acute Avian Diet, Duck 1,2 Yes 00151595, 45447213 No 

71-3 Wild Mammal Toxicity 1,2 N/A 

71-4(a) Avian Reproduction Quail 1,2 Yes 00153505 No 

71-4(b) Avian Reproduction Duck 1,2 Yes 00153504, 41512101 No 

§158.630 AQUATIC ORGANISMS TESTING

72-1(a) Acute Fish Toxicity Bluegill 1,2 Yes 00151597, 45447215 No 

72-1(b) Acute Fish Toxicity (TEP) 1,2 Partially 0015601, 43908812, 

00151600, 43908813 

and 45447218 

Yes3 

72-1(c) Acute Fish Toxicity Rainbow 

Trout 

1,2 Yes 00151598, 45447217 No 

72-2(a) Acute Aquatic Invertebrate 1,2 Yes 00152730, 00151599, 

45447219, 45447220 

No 

72-2(b) Acute Aquatic Invertebrate 

(TEP) 

1,2 Partially 00151602, 43908811, 

00151599, 45447221 

Yes3

72-3(a) Acute Est/Mar Toxicity Fish 1,2 Yes 00153506 No 

72-3(b) Acute Est/Mar Toxicity Mollusk 1,2 Yes 00152728 No 

72-3(c) Acute Est/Mar Toxicity Shrimp 1,2 Yes 00152728 No 

72-3(d) Acute Est/Mar Toxicity Fish (TEP) 1,2 No N/A No 

72-3(e) Acute Est/Mar Toxicity Mollusk 

(TEP) 

1,2 No N/A No 

72-3(f) Acute Est/Mar Toxicity Shrimp 

(TEP) 

1,2 No N/A No 
85

Table 7.2. Ecological Effects Data Requirements for lambda- and gamma- cyhalothrin. 

Data Requirement 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This 

Requirement? 

(Yes, No, or 

Partially) 

Bibliographic 

Citation 

Must 

Additional 

Data Be 

Submitted 

Under FIFRA 

3(c)(2)(B)? 

72-4(a) Early Life Stage Fish 1,2 Yes 00152732 No 

72-4(b) Life Cycle Aquatic Invertebrate 

(freshwater) 

1,2 No 00152733, 41217501 Yes4

850.1350 Life Cycle Aquatic Invertebrate 

(saltwater) 

1,2 Yes Acc #073989 No 

72-5 Life Cycle Freshwater Fish 1,2 Yes 41519001 No 

72-6 Aquatic Organism Accumulation 1,2 N/A 

72-7(1) Simulated Aquatic Field Study 1,2 N/A 

72-7(b) Actual Aquatic Field Study 1,2 N/A 

850.1730 Bioaccumulation in Fish 1,2 Yes 00152744, 00152745 No 

Whole sediment: chronic invertebrates 

freshwater & marine 

1, 2 No N/A Yes5

Non-guideline Aquatic Invertebrate Acute 

Toxicity (Hyalella) 1, 2 No N/A Yes5

850.1075 Freshwater Fish Acute Toxicity 

(fathead minnow) 1, 2 No N/A Yes6

§158.540 PLANT PROTECTION

122-1(a) Seed Germ, Seedling Emergence 1,2 No NA Yes 

122-2 Aquatic Plant Growth 1,2 No NA Yes 

122-1(b) Vegetative Vigor 1,2 No NA Yes 

123-1(a) Seed Germ./Seedling Emerg. 1,2 No NA No7 

123-1(b) Vegetative Vigor 1,2 No NA No7 

123-2 Aquatic Plant Growth 1,2 No NA No8 

§158.490 NONTARGET INSECT TESTING

141-1 Honey Bee Acute Contact 1,2 Yes 40052409 No 

141-2 Honey Bee Residue on Foliage 1,2 Yes 40436302 No 

141-5 Field Test for Pollinators 1,2 NA 
86

1

 Use Patterns: 1=Terrestrial/Food; 2=Terrestrial/Feed. 

2

 Data are required for one passerine species and either on waterfowl or one upland game bird species. At this time, only 

acute oral tests for a game bird species and a waterfowl have been submitted. Data are required for either lambda- or 

gamma-cyhalothrin. Registrant is required to submit a protocol for review. 

3

 Data are required for a TEP acute toxicity study with lambda- or gamma- cyhalothrin and the synergist PBO. 

4 Previously submitted studies are not considered acceptable to meet guideline requirements. Data are required for gammacyhalothrin. 

5 Data requested for gamma-cyhalothrin. 6 Data required for an acute toxicity test of lambda-cyhalothrin to the fathead minnow in order to appropriately estimate 

chronic toxicity to fish based on existing chronic data with fathead minnow. Fathead minnow is one of the recommended 

test species in the test guidelines. 

7 Required if a tested terrestrial species exhibits a 25 percent or greater detrimental effect in the Tier I study. 

8 Required if a tested aquatic species exhibits a 50 percent or greater detrimental effect in a Tier I study. 
87

8. References 

Amweg, E.L., D.P.Weston, and N.M. Ureda. 2005. Use and Toxicity of Pyrethroid Pesticides in 

the Central Valley, California, USA. Environmental Toxicology and Chemistry, Vol. 24, No. 4, 

pp. 966–972 

Amweg, E.L., D.P. Weston, C.S. Johnson, J. You and M.J. Lydy. 2006a. Effect of Piperonyl 

Butoxide on Permethrin Toxicity in the Amphipod Hyalella azteca. Environ. Tox. & Chem. 

25(7), pp. 1817-1825. 

Amweg, E.L. D.P. Weston, J. You and M.J. Lydy. 2006b. Pyrethroid Insecticides and Sediment 

Toxicity in Urban Creeks from California and Tennessee. Environ. Sci. Technol., 2006, 40 (5), 

pp 1700–1706. 

Amweg, E.L. and D.P. Weston. 2007. Whole-Sediment Toxicity Identification Evaluation Tools 

for Pyrethroid Insecticides: I. Piperonyl Butoxide Addition. Environ. Toxicol. & Chem., Vol. 26, 

No. 11, pp. 2389–2396, 2007 

Armitage, J.M., & Gobas, F.A.P.C. 2007. A terrestrial food-chain bioaccumulation model for 

POPs. Environmental Science and Technology, 41, 4019-4025. 

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

CRC Press. 

Bennett E.R., M.T. Moore, C.M. Cooper, and S. Smith, Jr. 2005. Vegetated Agricultural 

Drainage Ditches for the Mitigation of Pyrethroid-Associated Runoff. Environ. Tox. Chem. 24 

(9) pp. 2121–2127. 

Bouldin, J.L., J.L. Farris, M.T. Moore, S. Smith, Jr., W.W. Stephens, and C.M. Cooper. 2005. 

Evaluated Fate and Effects of Atrazine and Lambda-Cyhalothrin in Vegetated and Unvegetated 

Microcosms. Environ Toxicol 20: 487–498. 

Brown, J.S., M. Sutula, C. Stransky, J. Rudolph, and E. Byron, 2010. Sediment Contaminant 

Chemistry and Toxicity of Freshwater Urban Wetlands in Southern California. Journal of the 

American Water Resources Association (JAWRA) 46(2):367-384. 

Budd, R, S. Bondarenko, D. Haver, J. Kabashima, and J. Gan. 2007. Occurrence and 

Bioavailability of Pyrethroids in a Mixed Land Use Watershed. J. Environ. Qual. 36: 1006–1012 

(2007). 

Clark, J.M and F. Matsumura. 1987. The action of two classes of pyrethroids on the inhibition of 

brain Na-Ca and Ca + Mg ATP hydrolyzing activities of the American cockroach, Comp. 

Biochem. Physiol. C. 86 (1987) (1), pp. 135–145. 
88

Cooper, C.M., M.T. Moore, E.R. Bennett, S. Smith, Jr., and J.L. Farris. 2002. Alternative 

environmental benefits of agricultural drainage ditches. Verh. Internat. Verein. Limnol. 28, 1678-

1682. 

Corbin, M, W. Eckel, M. Ruhman, D. Spatz, N. Thurman, R. Gangaraju, T. Kuchnicki, R. 

Mathew, and I. Nicholson. 2006. NAFTA Guidance Document for Conducting Terrestrial Field 

Dissipation Studies. Available at url: 

http://www.epa.gov/oppefed1/ecorisk_ders/terrestrial_field_dissipation.htm (accessed 06/24/10). 

DeCant, J. 2009. Section 3 new use registration for gamma-Cyhalothrin in the product 

COBALTTM on wheat in the following states: Alabama, Arkansas, Georgia, Illinois, Indiana, 

Iowa, Kentucky, Louisiana, Michigan, Missouri, North Carolina, Ohio, South Carolina, 

Tennessee, Virginia, and Wisconsin. Memorandum to V. Eagle and A. Abramovich dated 

05/11/09 (DP Barcodes D357895 and D357900). Environmental Fate and Effects Division, OPP, 

OCSPP, USEPA. 

Di Toro, D.M., C.S. Zarba, D.J. Hansen, W.J. Berry, R.C. Swartz, C.E. Cowan, S.P. Pavlou, H.E. 

Allen, N.A. Thomas and P.R. Paquin. 1991. Technical basis for establishing sediment quality 

criteria for nonionic organic chemicals using equilibrium partitioning. Environ. Toxicol. Chem. 

10:1541-1583. 

Ding, Y., A.D. Harwood, H.M. Foslund, and M.J. Lydy. 2010. Distribution and Toxicity of 

Sediment-Associated Pesticides in Urban and Agricultural Waterways from Illinois, USA. 

Environmental Toxicology and Chemistry, Vol. 29, No. 1, pp. 149–157, 2010. 

Fojut, T.L. and R.S. Tjeerdema. 2010. Water Quality Criteria Report for Lambda-cyhalothrin. 

Prepared for the Central Valley Regional Water Quality Control Board. University of California, 

Davis. 

http://www.swrcb.ca.gov/rwqcb5/water_issues/tmdl/central_valley_projects/central_valley_pestic

ides/criteria_method/lambda_cyhalothrin/final_lambda_cyhalothrin_criteria_rpt.pdf 

Food and Agriculture Organization of the United Nations. FAO PESTICIDE DISPOSAL 

SERIES 8. Assessing Soil Contamination: A Reference Manual. Appendix 2. Parameters of 

pesticides that influence processes in the soil. Editorial Group, FAO Information Division: 

Rome, 2000. http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm 

Gan, J., S.J. Lee, W.P. Liu, D.L. Haver, and J.N. Kabashima. 2005. Distribution and Persistence 

of Pyrethroids in Runoff Sediments. J. Environ. Qual. 34:836–841 (2005). 

Giddings, J.M., I. Barber, and W. Warren-Hicks. 2009. Comparative aquatic toxicity of the 

pyrethroid insecticide lambda-cyhalothrin and its resolved isomer gamma-cyhalothrin. 

Ecotoxicology (2009) 18:239–249. 

Gobas, F.A.P.C., B.C. Kelly and J.A. Arnot. 2003. Quantitative structure activity relationships for 
89

predicting the bioaccumulation of POPs in terrestrial food webs. QSAR Comb. Sci. 22:329-336. 

Gu B.G., H.M. Wang, W.L. Chen, D.J. Cai, Z.J. Shan. 2007. Risk assessment of λ-cyhalothrin 

on aquatic organisms in paddy field in China. Regulatory Toxicology and Pharmacology 48 

(2007) 69–74. 

Hamer M.J., U.M. Goggin, K. Muller and S.J. Maund. 1999. Bioavailability of lambdacyhalothrin to Chironomus riparius in sediment-water and water-only systems. Aquat Ecosys 

Health Manag 2:403–412 (as cited by He et al. 2008). 

Hand, L.H., S.F. Kuet, M.C.G. Lane, S.J. Maund, J.S. Warington, and I.R. Hill. 2001. Influences 

of Aquatic Plants on the Fate of the Pyrethroid Insecticide Lambda-cyhalothrin in Aquatic 

Environments. Environ. Tox. Chem. 20(8), pp. 1740–1745. 

He, L., J. Troiano, A. Wang, and K. Goh. 2008. Environmental Chemistry, Ecotoxicity, and Fate 

of Lambda-Cyhalothrin. Reviews of Environmental Contamination and Toxicology. D.M. 

Whitacre (ed.), Springer 2008. pp 71-91. 

Heckmann, L. and N. Friberg. 2005. Macroinvertebrate Community Response to Pulse Exposure 

with the Insecticide Lambda-cyhalothrin Using In-stream Mesocosm. Environ. Tox. Chem. 

24(3), pp. 582–590. 

Hill B.D. and D.J. Inaba. 1991. Dissipation of lambda-Cyhalothrin on Fallow vs Cropped Soil. 

J. Agric. Food Chem. 1991, 39, 2282-2284. 

Hintzen, E.P., M.J. Lydy, and J.B. Belden. 2009. Occurrence and potential toxicity of pyrethroids 

and other insecticides in bed sediments of urban streams in central Texas. Environ Pollut 

157:110–116. 

Hodgson, E., & Smart, R. C. (Eds.). 2001. Introduction to Biochemical Toxicology

(Third ed.). New York: Wiley-Interscience. 

Holmes, R.W., B.S. Anderson, J.W. Hunt, D.B. Crane, A. Mekebri and V. Connor. 2008. 

“Statewide Investigation of the Role of Pyrethroid Pesticides in Sediment Toxicity in California’s 

Urban Waterways.” Environ. Sci. Technol. 2008, 42, 7003–7009. 

Hunter, W., Y. Yang, F. Reichenberg, P. Mayer, and J. Gan. 2009. Measuring Pyrethroids in 

Sediment Pore Water Using Matrix-Solid Phase Microextraction. Environ. Tox. Chem. 28(1), pp. 

36–43, 2009. 

Jiang, W., K. Lin, D. Haver, S. Qin, G. Ayre, F. Spurlock, and J. Gan. 2010. Wash-off Potential 

of Urban Use Insecticides on Concrete Surfaces. Environ. Tox. Chem. 29(6), pp. 1203–1208, 

2010. 
90

Jorgenson, B., and T. Young. 2010. Formulation Effects and the Off-Target Transport of 

Pyrethroid Insecticides from Urban Hard Surfaces. Environ. Sci. Technol. 2010, 44, 4951–4957. 

Kumar, A., B. Sharma and R.S. Pandey. 2007. Preliminary Evaluation of The Acute Toxicity of 

Cypermethrin and λ-Cyhalothrin to Channa Punctatus. Bull Environ Contam Toxicol (2007) 

79:613–616. 

Laskowski, D.A., 2002. Physical and chemical properties of pyrethroids. Rev. Environ. Contam. 

Toxicol. 2002; 174:49-170. 

Lao, W, D. Tsukada, D.J. Greenstein, S.M. Bay, and K.A. Maruya. 2010. Analysis, Occurrence, 

and Toxic Potential of Pyrethroids, and Fipronil in Sediments from and Urban Estuary. Environ. 

Tox. Chem. 29(4), pp. 843–851, 2010. 

Lauridsen, R.B., and N. Friberg. 2005. Stream Macroinvertebrate Drift Response to Pulsed 

Exposure of the Synthetic Pyrethroid Lambda-Cyhalothrin. Environmental toxicology 20(5) pp. 

513-521. 

LeBlanc, L. & B. Perkins. 2009. Pyrethroid Analysis for Maine Board of Pesticide Control. 

University of Maine Food and Chemical Safety Laboratory, Orono Maine. An e:mail 

communication from G. Fish to R. Gebken, dated 11/02/09 and forwarded to EFED on 11/19/09. 

Original communication from L. LeBlanc to G. Fish and H. Jennings, dated 05/25/09. 

Lee, D. 2009. Pyrethroid Pesticide Contamination of Urban Runoff in Stormwater Detention 

Ponds. Pesticides in Stormwater Runoff. May 11, 2009. 21 pp. 

Leistra, M., A.J. Zweers, J.S. Warinton, S.J.H. Crum, L.H. Hand, W.H.J. Beltman, and S.J. 

Maund. 2003. Fate of the insecticide lambda-cyhalothrin in ditch enclosures differing in 

vegetation density. Pest Manag Sci 60:75–84. 

Liu, W., J.J. Gan, S. Lee, and J.N. Kabashima. 2004. Phase Distribution of Synthetic Pyrethroids 

in Runoff and Stream Water. Environ Tox Chem 23(1) pp. 7–11. 

Maher, I, N. Birchfield, P. Jennings and S. Abel. 2004. Ecological risk assessment and human 

drinking water assessment for gamma-cyhalothrin use on multiple agricultural use sites and noncropped areas. Memorandum to W. Sproat and G. LaRocca dated 03/19/04 (DP Barcodes 

D288057, D289794, D289797, D289799, D289798 and D289801). Environmental Fate and 

Effects Division, OPP, OCSPP, USEPA. 

Matsumura, F. 1985. Toxicology of insects. 2nd ed. Plenum New York. 

Maund, S.J., M.J. Hamer, J.S. Warinton, and T.J. Kedwards. 1998. Aquatic Ecotoxicology of the 

Pyrethroid Insecticide Lambda-cyhalothrin: Considerations for Higher-Tier Aquatic Risk 

Assessment. Pestic. Sci. 1998, 54, 408-417. 
91

Meléndez, J.L. and Hoffmann, M. 2006. Environmental Fate and Ecological Risk Assessment 

for Section 3 Registration of Lambda-cyhalothrin, an Insecticide for New Uses on Cereal Grains, 

Cucurbit Vegetables, Grass Forage, Fodder and Hay, Wild Rice and Tuberous and Corm 

Vegetables. Memorandum to G. LaRocca and D. Rosenblatt dated 12/29/06 (DP Barcode 

D324224 and D313316). Environmental Fate and Effects Division, OPP, OCSPP, USEPA. 

Meléndez, J.L. and A. Solliday. 2008. EFED New Use Registration for Lambda-cyhalothrin on 

Non-bearing Citrus Orchards. Memorandum to O. Odiott, K. Nesci and M. Johnson dated 

11/04/08 (DP Barcode D355940). Environmental Fate and Effects Division, OPP, OCSPP, 

USEPA. 

Moore M.T., E.R. Bennett, C.M. Cooper, S. Smith Jr., F.D. Shields Jr., C.D. Milam, and J.L. 

Farris. 2001. Transport and fate of atrazine and lambda-cyhalothrin in an agricultural drainage 

ditch in the Mississippi Delta, USA. Agriculture, Ecosystems and Environment 87 (2001) 309–

314. 

Moore M.T., R.E. Lizotte Jr. and S. Smith Jr. 2007. Responses of Hyalella azteca to a Pyrethroid 

Mixture in a Constructed Wetland. Bull Environ Contam Toxicol (2007) 78:245–248. 

Moore, M.T., C.M. Cooper, S. Smith, Jr., R.F. Cullum, S.S. Knight, M.A. Locke and E.R. 

Bennett. 2009. Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed 

wetland. Environmental Pollution 157 (2009) 250–256. 

Ramasamy, S., I. Maher, P. Jennings, and S. Abel. 2002. Section 3 request for new uses of 

lambda cyhalothrin (P.C. Code: 128897) on peas and beans, fruiting vegetables, canola, 

sugarcane, sorghum, wheat, wheat hay and other small grains, peanut, hay, pome fruit, stone fruit, 

tree nuts, termite barrier, tobacco, non-cropland and trees (conifer and deciduous trees). 

Memorandum to A. Layne and W. Sproat dated 06/12/02 (DP Barcodes D262918, D262919, 

D279087 and D279088). Environmental Fate and Effects Division, OPP, OCSPP, USEPA. 

Rexrode, M. and J.L. Meléndez. 2003. EFED’s rationale for choosing Cypermethrin, 

Esfenvalerate, Bifenthrin, and Cyfluthrin for sediment testing as discussed with the Pyrethroid 

Working Group (PWG). Memorandum to M. Johnson & G. LaRocca dated 12/22/03. 

Environmental Fate and Effects Division, OPP, OPPTS, USEPA. 

Smith Jr., S., R.E. Lizotte Jr. 2007. Influence of Selected Water Quality Characteristics on the 

Toxicity of λ-Cyhalothrin and γ-Cyhalothrin to Hyalella azteca. Bull Environ Contam Toxicol 

(2007) 79:548–551. 

Solomon, K.R., J.M. Giddings, and S.J. Maund. 2001. Probabilistic Risk Assessment of Cotton 

Pyrethroids: I. Distributional Analyses of Laboratory Aquatic Toxicity Data. Environ. Tox. 

Chem., 20(3), pp. 652–659, 2001. 
92

Stout II, D.M., K Bradham, P.P. Egeghy, P. Jones, C.W. Croghan, P.A. Ashley, E. Pinzer, W. 

Friedman, M.C. Brinkman, M.G. Nishioka and D.C. Cox. 2009. American Healthy Homes 

Survey: A National Study of Residential Pesticides Measured from Floor Wipes. Environ. Sci. 

Technol., 2009, 43, 4294–4300. 

Trimble, A.J, D.P. Weston, J.B. Belden, and M.J. Lydy. 2009. Identification and Evaluation of 

Pyrethroid Insecticide Mixtures in Urban Sediments. Environ Toxicol & Chem 26 (8) pp. 1687–

1695. 

Ureda, N. 2004. Sediment LC50 Analyses of the Pyrethroid Pesticides Cyfluthrin, Deltamethrin, 

and Lambda-Cyhalothrin. [Available at url: 

http://nature.berkeley.edu/classes/es196/projects/2004final/Ureda.pdf accessed 06/25/10]. 

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

Assessment Forum, Office of Research and Development, Washington, D.C. EPA/630/R95/002F. April 1998. 

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

February 23, 1999 held at the Holiday Inn Hotel, Arlington, VA. SAP Report No. 99-03A. March 

25, 1999. Office of Pesticide Programs. Available at url: 

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

15, 2009) 

U.S. Environmental Protection Agency. 2000. Risk Characterization Handbook. Science Policy 

Council, U.S. Environmental Protection Agency, Washington, D.C. 20460. EPA 100-B-00-002. 

December 2000. 

U.S. Environmental Protection Agency. 2002. Technical Basis for the derivation of Equilibrium 

Partitioning Sediment Guidelines (ESGs) for the Protection of Benthic Organisms: Nonionic 

Organics [Draft]. EPA Document No. 822R02041. October 2002. 

U.S. Environmental Protection Agency. 2004a. Ecological risk assessment and human drinking 

water assessment for gamma-cyhalothrin use on multiple agricultural use sites and non-cropped 

areas. DP barcode: 289801, 289799, 289797, 289794, 289798, 288057. March 19, 2004. 

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

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

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

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

U.S. Environmental Protection Agency. 2005. Generic Format and Guidance for the Level I 

Screening Ecological Risk Assessments Conducted in the Environmental Fate and Effects 

Division. Office of Pesticide Programs, Washington, D.C. January 24, 2005. 

U.S. Environmental Protection Agency. 2008. OPPTS 835.6100 Terrestrial Field Dissipation. 
93

EPA 712-C-08-020. October 2008. Office of Prevention, Pesticides, and Toxic Substances. 

United States Environmental Protection Agency. Available at 

http://www.epa.gov/opptsfrs/publications/835_6100.pdf (Accessed March 31, 2010). 

U.S. Environmental Protection Agency. 2009. A Set of Scientific Issues Being Considered by the 

EPA Regarding: Evaluation of the Common Mechanism of Action of Pyrethroid Pesticides. SAP 

Minutes No. 2009-07. FIFRA SAP Meeting held 6/16/09 in Arlington, VA. Meeting Minutes 

dated 9/9/09. 

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. 

Endangered Species Consultation Handbook: Procedures for Conducting Consultation and 

Conference Activities Under Section 7 of the Endangered Species Act. Final Draft. March 1998. 

Van Wijngaarden, R.P.A., T.C.M. Brock, P.J. van den Brink, R. Gylstra, and S.J. Maund. 2006. 

Ecological Effects of Spring and Late Summer Applications of Lambda-Cyhalothrin on 

Freshwater Microcosms. Arch. Environ. Contam. Toxicol. 50, 220–239 (2006). 

Van Wijngaarden, R.P.A. I. Barber, and T.C.M. Brock. 2009. Effects of the pyrethroid 

insecticide gamma-cyhalothrin on aquatic invertebrates in laboratory and outdoor microcosm 

tests. Ecotoxicology (2009) 18:211–224. 

Wang, W., D.J. Cai, Z.J. Shan, W.L. Chen, Nick Poletika, and X.W. Gao. 2007. Comparison of 

the acute toxicity for gamma-cyhalothrin and lambda-cyhalothrin to zebra fish and shrimp. 

Regulatory Toxicology and Pharmacology 47 (2007) 184–188. 

Weston, D.P., J. You, and M.J. Lydy. 2004. Distribution and Toxicity of Sediment-Associated 

Pesticides in Agriculture-Dominated Water Bodies of California’s Central Valley. Environ. Sci. 

Technol. 2004, 38, 2752-2759. 

Weston, D.P., R.W. Holmes, J. You and M.J. Lydy. 2005. Aquatic Toxicity Due to Residential 

Use of Pyrethroid Insecticides. Environ. Sci. Technol., 2005, 39 (24), pp 9778–9784. 

Weston, D. 2007. Impacts of Pyrethroid Pesticides on Water Quality from Urban and 

Agricultural Sectors. Conference Proceedings; California Plant and Soil Conference: 

Opportunities for California Agriculture. California Chapter of the American Society of 

Agronomy, pp. 35-37. 

Weston, D.P., J. You, A.D. Harwood and M.J. Lydy. 2009a. Whole Sediment Toxicity 

Identification Evaluation Tools for Pyrethroid Insecticides: III. Temperature Manipulation. 

Environ. Tox. & Chem., Vol. 28, No. 1, pp. 173–180, 2009 

Weston, D.P., R.W. Holmes, and M.J. Lydy. 2009b. Residential runoff as a source of pyrethroid 

pesticides to urban creeks. Environmental Pollution 157 (2009) 287–294 
94

Weston D.P. and C.J. Jackson. 2009. Use of Engineered Enzymes to Identify Organophosphate 

and Pyrethroid-Related Toxicity in Toxicity Identification Evaluations. Environ. Sci. Technol. 

2009, 43, 5514–5520. 

Weston, D.P. and M.J. Lydy. 2010. Urban and Agricultural Sources of Pyrethroid Insecticides to 

the Sacramento-San Joaquin Delta of California. Environ. Sci. Technol. 2010, 44, 1833–1840. 

Wheelock, C.E., J.L. Miller, M.J. Miller, S.J. Gee, G. Shan, and B.D. Hammock. 2004. 

Development of Toxicity Identification Evaluation Procedures for Pyrethroid Detection Using 

Esterase Activity. Environ. Tox. Chem. 23(11), pp. 2699–2708, 2004. 

Wheelock, C.E., J.L. Miller, M.J. Miller, B.M. Phillips, S.A. Huntley, S.J. Gee, R.S. Tjeerdema, 

and B.D. Hammock. 2006. Use of Carboxylesterase Activity to Remove Pyrethroid-Associated 

Toxicity to Ceriodaphnia Dubia and Hyalella azteca in Toxicity Identification Evaluations. 

Environ. Toxicol. Chem. 25(4): 973–984. 

Willis, G.H. and L.L. McDowell. 1987. Pesticide persistence on foliage. Reviews of 

Environmental Contamination and Toxicology, Vol. 100, page 23 (Springer-Verlag, New York, 

Inc) 

Woudneh, M.B and D.R. Oros. 2006. Pyrethroids, pyrethrins, and piperonyl butoxide in 

sediments by high-resolution gas chromatography/high-resolution mass spectrometry. J. of 

Chromatography A 1135 (2006) 71–77. 

Xu, C., J. Wang, W. Liu, G.D. Sheng, Y. Tu, and Y. Ma. 2008. Separation and Aquatic Toxicity 

of Enantiomers of the Pyrethroid Insecticide Lambda-cyhalothrin. Environ. Tox. Chem. 27(1), 

pp. 174–181, 2008. 

Xu, Y., J. Gan, Z. Wang, and F. Spurlock. 2008. Effect of Aging on Desorption Kinetics of 

Sediment-Associated Pyrethroids. Environ. Tox. Chem. 27(6), pp. 1293–1301, 2008. 

Yang, W., F. Spurlock, W. Liu, and J. Gan. 2006. Inhibition of Aquatic Toxicity of Pyrethroid 

Insecticides by Suspended Sediment. Environ. Tox. Chem. 25(7), pp. 1913–1919, 2006. 

Yang, W.C., W. Hunter, F. Spurlock and J. Gan. 2007. Bioavailability of Permethrin and 

Cyfluthrin in Surface Waters with Low Levels of Dissolved Organic Matter. J. Environ. Qual. 

36:1678–1685 (2007). 

Zhou, J., S. Rowland, and R.F. Mantoura. 1995. Partition of Synthetic Pyrethroid Insecticides 

Between Dissolved and Particulate Phases. Wat. Res. 29(4), pp. 1023-1031, 1995. 
95

9. Fate and Ecotoxicity Bibliography 

Lambda-Cyhalothrin Environmental Fate Bibliography 

161-1 Hydrolysis 

MRID Citation Reference 

151604 Collis, W.; Leahey, J. (1984) PP321: Hydrolysis in Water at pH 5, 7 and 9: Report No. 

RJ 0338B. Unpublished study prepared by Jealotts Hill Research Station, ICI Plant 

Protection Division. 20 p. 

40052404 Wagner, J. (1987) Environmental Fate Data Overview and Summary for Resubmission 

for PP321 on Cotton: [Response to EPA's Comments]. Unpublished study prepared by 

ICI Americas Inc. 36 p. 

161-2 Photodegradation-water 

MRID Citation Reference 

151605 Curl, E.; Leahey, J.; Lloyd, S. (1984) PP321: Aqueous Photolysis at pH 5: Report No. 

RJ 0362B. Unpublished study prepared by Jealotts Hill Research Station, ICI Plant 

Protection Division. 23 p. 

40052404 Wagner, J. (1987) Environmental Fate Data Overview and Summary for Resubmission 

for PP321 on Cotton: [Response to EPA's Comments]. Unpublished study prepared by 

ICI Americas Inc. 36 p. 

44861501 Priestley, D.; Leahy, J. (1988) PP321: Aqueous Photolysis at pH 5: Lab Project 

Number: RJ 0605B. Unpublished study prepared by Zeneca Agrochemicals. 61 p. 

44861508 Hand, L.; Mehta, P. (1999) Lambda-Cyhalothrin: Degradation in an Aquatic Microcosm: 

Lab Project Number: 98JH083: RJ2730B. Unpublished study prepared by Zeneca 

Agrochemicals. 69 p. 

161-3 Photodegradation-soil 

MRID Citation Reference 

151606 Curl, E.; Leahey, J.; Lloyd, S. (1984) PP321: Photodegradation on a Soil Surface: 

Report No. RJ 0358B. Unpublished study prepared by Jealotts Hill Research Station, 

ICI Plant Protection Divi- sion. 36 p. 

40052404 Wagner, J. (1987) Environmental Fate Data Overview and Summary for Resubmission 

for PP321 on Cotton: [Response to EPA's Comments]. Unpublished study prepared by 

ICI Americas Inc. 36 p. 

40052405 Parker, S.; Leahey, J. (1986) PP321: Photodegradation on a Soil Surface: Laboratory 

Project ID: RJ0537B. Unpublished study prepared by ICI Americas Inc., Jealott's Hill 
96

Research Station. 55 p. 

162-1 Aerobic soil metabolism 

MRID Citation Reference 

151607 Bharti, H.; Bewick, D.; White, R. (1985) PP563 and PP321: Degrada- tion in Soil: 

Report No. RJ0382B. Unpublished study prepared by Jealotts Hill Research Station, 

ICI Plant Protection Divi- sion. 66 p. 

44861504 Harvey, B. (1996) PP563 and PP321: Degradation in Soil: Report Addendum Number 

1): Lab Project Number: RJ 0382B-ADD1. Unpublished study prepared by Zeneca 

Agrochemicals. 24 p. 

44861505 Shi, C.; Ericson, J. (1998) (Carbon-14)R211133 (Ref. XV), A Metabolite of LambdaCyhalothrin: Rate of Degradation in Soil under Aerobic Laboratory Conditions: Lab 

Project Number: RR98-019B. Unpublished study prepared by Zeneca Ag Products. 41 

p. 

162-2 Anaerobic soil metabolism 

MRID Citation Reference 

151607 Bharti, H.; Bewick, D.; White, R. (1985) PP563 and PP321: Degrada- tion in Soil: 

Report No. RJ0382B. Unpublished study prepared by Jealotts Hill Research Station, 

ICI Plant Protection Divi- sion. 66 p. 

162-3 Anaerobic aquatic metab. 

MRID Citation Reference 

44075504 Wagner, J. (1996) Karate Insecticide (Containing Lambda-Cyhalothrin): Discussion of 

Environmental Fate Data Requirements to Support Registration on Rice: Lab Project 

Number: ZA0724961. Unpublished study prepared by Zeneca Ag Products. 10 p. 

44367401 Tambling, D.; Goldsby, G.; Labatore, D. et al. (1997) (Carbon 14)-Lambdacyhalothhrin: Anaerobic Aquatic Soil Metabolism: Lab Project Number: PMS 420: 

WINO 15859: RR 96-102B. Unpublished study prepared by Zeneca Ag Products 

(Western Research Center) 69 p. 

162-4 Aerobic aquatic metab. 

MRID Citation Reference 

44075504 Wagner, J. (1996) Karate Insecticide (Containing Lambda-Cyhalothrin): Discussion of 

Environmental Fate Data Requirements to Support Registration on Rice: Lab Project 

Number: ZA0724961. Unpublished study prepared by Zeneca Ag Products. 10 p. 

44367402 Tambling, D.; Goldsby, G.; Labatore, D. et al. (1997) (Carbon 14)-Lambda-
97

cyhalothhrin: Aerobic Aquatic Soil Metabolism: Lab Project Number: PMS 421: WINO 

15858: RR 96-094B. Unpublished study prepared by Zeneca Ag Products (Western 

Research Center) 77 p. 

163-1 Leach/adsorp/desorption 

MRID Citation Reference 

151608 Stevens, J.; Bewick, D. (1985) PP563 and PP321: Leaching of PP563 and PP321 and 

Their Degradation Products in Soil Columns: Re- port No. RJ 0408B. Unpublished 

study prepared by Jealotts Hill Research Station, ICI Plant Protection Division. 17 p. 

152748 Stevens, J.; Poole, N. (1981) Cyhalothrin: Leaching on Soil Thick- layer 

Chromatograms: No. 6/HA/003802: Report No. RJ0206B. Un- published study 

prepared by Imperial Chemical Industries PLC. 29 p. 

40052404 Wagner, J. (1987) Environmental Fate Data Overview and Summary for Resubmission 

for PP321 on Cotton: [Response to EPA's Comments]. Unpublished study prepared by 

ICI Americas Inc. 36 p. 

40052406 Vickers, J.; Bewick, D. (1986) PP321: Adsorption and Desorption in Soil: Laboratory 

Project ID: RJ0535B. Unpublished study pre- pared by ICI Americas Inc., Jealott's Hill 

Research Station. 108 p. 

44861503 Muller, K.; Goggin, U.; Lane, M. (1996) Lambda-Cyhalothrin: Adsorption and 

Desorption Properties in Soil and Sediment: Lab Project Number: 94JH243. 

Unpublished study prepared by Zeneca Agrochemicals. 56 p. 

44861509 Kuet, S.; Lane, M. (1999) Lambda-Cyhalothrin: Aged Desorption in Soil: Lab Project 

Number: 98JH135: RJ2761B. Unpublished study prepared by Zeneca Agrochemicals. 

36 p. 

164-1 Terrestrial field dissipation 

MRID Citation Reference 

40052404 Wagner, J. (1987) Environmental Fate Data Overview and Summary for Resubmission 

for PP321 on Cotton: [Response to EPA's Comments]. Unpublished study prepared by 

ICI Americas Inc. 36 p. 

40052407 Bewick, D.; Bartlett, D.; Hendley, P. (1986) PP321: Fate of Radio- labelled Material in 

Soil under Field Conditions: Laboratory Project ID: RJ0529B. Unpublished study 

prepared by ICI Americas Inc., Jealott's Hill Research Station. 159 p. 

164-2 Aquatic field dissipation 

MRID Citation Reference 

44075504 Wagner, J. (1996) Karate Insecticide (Containing Lambda-Cyhalothrin): Discussion of 

Environmental Fate Data Requirements to Support Registration on Rice: Lab Project 

Number: ZA0724961. Unpublished study prepared by Zeneca Ag Products. 10 p. 
98

44367403 Patterson, S.; Francis, P.; Robbins, J. et al. (1997) Lambda-cyhalothhrin: Aquatic Field 

Dissipation after Application to Rice in Mississippi During 1996: Lab Project Number: 

LCYH-96-SD-01: WINO 23631: RR 97-002B. Unpublished study prepared by Zeneca 

Ag Products (Western Research Center) 143 p. 

44367404 Patterson, S.; Francis, P.; Robbins, J. et al. (1997) Lambda-cyhalothhrin: Aquatic Field 

Dissipation after Application to Rice in California During 1996: Lab Project Number: 

LCYH-96-SD-02: 94-CA-96-592: WINO 15346. Unpublished study prepared by Zeneca 

Ag Products (Western Research Center) 146 p. 

165-4 Bioaccumulation in fish 

MRID Citation Reference 

152740 ICI Americas Inc. (1985) Karate Insecticide (Containing PP321): Environmental Fate. 

Unpublished compilation. 27 p. 

152744 Yamauchi, S.; Yamauchi, F.; Shigeoka, T.; et al. (1984) PP-563 (Cyhalothrin): 

Accumulation in Fish (Carp) in a Flow-through Water System: Report No. 58-367. 

Unpublished study prepared by Mitsubishi-Kasei Institute of Toxicological & 

Environmental Sciences. 53 p. 

152745 Leahey, J.; Parker, S. (1985) Cyhalothrin: Characterisation of Re- sidues Accumulated 

by Carp Continuously Exposed to [Carbon-14]- Cyhalothrin: Report No. RJ0407B. 

Unpublished study prepared by Imperial Chemical Industries PLC. 22 p. 

152746 Hamer, M.; Hill, I. (1985) Cyhalothrin: The Accumulation of Cyhalo- thrin and Its 

Degradation Products by Channel Catfish & Daphnia magna in a Soil/Water System: 

Report No. RJ0427B. Unpublished study prepared by Imperial Chemical Industries PLC. 

40 p. 

40052404 Wagner, J. (1987) Environmental Fate Data Overview and Summary for Resubmission 

for PP321 on Cotton: [Response to EPA's Comments]. Unpublished study prepared by 

ICI Americas Inc. 36 p. 

Gamma-Cyhalothrin Environmental Fate Bibliography

45447409. Smith, J.K. and A.D. Thomas. 2001. Hydrolysis of 14C-XDE-225 in natural water 

and buffered water as a function of pH. Unpublished study performed, sponsored and submitted 

by Global Environmental Chemistry Laboratory-Indianapolis Lab, Dow AgroSciences LLC, 

Indianapolis, Indiana. Laboratory Study ID: 000379. Experimental start November 13, 2000, and 

termination May 10, 2001 (p. 3). Final report issued May 23, 2001. 

45447410. Yoder, R.N. 2001. Aerobic soil degradation of lambda-cyhalothrin and XDE-225 

formulated as a capsule suspension. Unpublished study performed, sponsored and submitted by 

Dow AgroSciences LLC, Indianapolis, IN. Study ID No.: 010008. Experiment initiation 

February 6, 2001, and completion May 16, 2001 (p. 3). Final report issued May 23, 2001. 

45447411. Cook, W.L. 2001. Aerobic soil degradation of XDE-225 and cyhalothrin at 25°C. 

Unpublished study performed, sponsored and submitted by Dow AgroSciences LLC, 
99

Indianapolis, IN. Study ID No.: 990065. Experiment initiation September 6, 2000, and 

completion May 1, 2001 (p. 3). Final report issued June 1, 2001. 

45447412. Yoder, R.N. 2001. Aerobic aquatic degradation of XDE-225. Unpublished study 

performed, sponsored and submitted by Dow AgroSciences LLC, Indianapolis, IN. Study ID 

No.: 010009. Experiment initiation March 26, 2001, and completion May 3, 2001 (p. 3). Final 

report issued May 25, 2001. 

45447413. Cook, W.L. and A.D. Thomas. 2001. Batch equilibrium sorption of XDE-225 and 

cyhalothrin on four soils. Unpublished study performed, sponsored , and submitted by Global 

Environmental Chemistry Laboratory- Indianapolis Lab, Dow AgroSciences LLC, Indianapolis, 

Indiana. Laboratory Study ID: 000307. Experimental initiation April, 2000, and completion July, 

2000 (p. 3). Final report issued May 29, 2001. 

45794902. Roberts, D.W., D.R. Foster and G.E. Schelle. 2002. Terrestrial dissipation of XDE225. Unpublished study performed by Dow AgroSciences LLC, Indianapolis, IN and AGVISE 

Laboratories, Inc., Northwood, ND, and sponsored and submitted by Dow AgroSciences LLC, 

Indianapolis, IN. Laboratory Study ID: 010038.01. Experiment initiation April 30, 2001 and 

completion January 23, 2002 (p. 3). Final report issued August 26, 2002. 

46394702. Yoder, R.N., K.P. Smith, J.L. Balcer, and S. Hilla. 2003. Aqueous photolysis of 

XDE-225 in pH 5 buffer under xenon light. Unpublished study performed, sponsored, and 

submitted by Dow AgroSciences LLC, Indianapolis, IN. Dow AgroSciences Study Number: 

020015. Experimental start date April 10, 2002, and completion date April 18, 2003 (p. 6). Final 

report issued May 6, 2003. 

Lambda-Cyhalothrin Ecotoxicology Bibliography 

71-1 Avian Single Dose Oral Toxicity 

MRID Citation Reference 

151594 Roberts, N.; Fairley, C. (1984) The Acute Oral Toxicity (LD50) of PP321 to 

the Mallard Duck: Report No. ICI 438BT/831011. Unpub- lished study 

prepared by Huntingdon Research Centre. 17 p. 

40052408 Wagner, J. (1987) Fish and Wildlife Data Overview and Summary for 

Resubmission for PP321 on Cotton: [Response to EPA's Comments]. 

Unpublished study prepared by ICI Americas Inc. 50 p. 

42291107 Hakin, B.; Johnson, A.; Anderson, A.; et al. (1991) Fonofos/LambdaCyhalothrin: Acute Oral Toxicity (LD50) to Mallard Duck of a 240/4 g/kg 

GR Formulation: Lab Project Number: ISN 240/9193. Unpublished study 

prepared by Huntingdon Research Centre Ltd. 40 p. 

42291108 Hakin. B.; Johnson, A.; Anderson, A.; et al. (1991) Fonofos/LambdaCyhalothrin: Dietary Toxicity (LC50) to Mallard Duck of a 200/4 g/kg GR 
100

Formulation: Lab Project Number: ISN 242/9158. Unpublished study 

prepared by Huntingdon Research Centre Ltd. 30 p. 

71-2 Avian Dietary Toxicity 

MRID Citation Reference 

151595 Roberts, N.; Fairley, C.; Anderson, A.; et al. (1985) The Subacute Dietary 

Toxicity of PP321 to the Mallard Duck: Report No. ISN 46BT/85171. 

Unpublished study prepared by Huntingdon Research Centre. 34 p. 

151596 Roberts, N.; Fairley, C.; Anderson, A.; et al. (1985) The Subacute Dietary 

Toxicity of PP321 to the Bobwhite Quail: Report No. ISN/45BT/841287. 

Unpublished study prepared by Huntingdon Research Centre. 34 p. 

40052408 Wagner, J. (1987) Fish and Wildlife Data Overview and Summary for 

Resubmission for PP321 on Cotton: [Response to EPA's Comments]. 

Unpublished study prepared by ICI Americas Inc. 50 p. 

42291109 Hakin, B.; Johnson, A.; Anderson, A.; et al. (1991) Fonofos/LambdaCyhalothrin: Dietary Toxicity (LC50) to Bobwhite Quail of a 200/4 g/kg GR 

Formulation: Lab Project Number: ISN 241/901822. Unpublished study 

prepared by Huntingdon Research Centre Ltd. 30 p. 

71-4 Avian Reproduction 

MRID Citation Reference 

153504 Roberts, N.; Fairley, C.; Chanter, D.; et al. (1982) The Effect of the Dietary 

Inclusion of Cyhalothrin on Reproduction in the Mallard Duck: Study No. 

JX0089: Report No. 375/82701. Unpub- lished study prepared by 

Huntingdon Research Centre. 178 p. 

153505 Roberts, N.; Fairley, C.; Chanter, D.; et al. (1982) The Effect of the Dietary 

Inclusion of Cyhalothrin on Reproduction in the Bobwhite Quail: Study No.: 

JX0090: Report No.: 376/82768. Unpublished study prepared by 

Huntingdon Research Centre. 207 p. 

41512101 Beavers, J.; Hoxter, K.; Jaber, M. (1990) PP321: A One-Generation 

Reproduction Study with the Mallard (Anas platyrhynchos): Lab Project 

Number: 123-143. Unpublished study prepared by Wildlife International 

Ltd. 192 p. 

72-1 Acute Toxicity to Freshwater Fish 

MRID Citation Reference 

151597 Hill, R. (1984) PP321: Determination of Acute Toxicity to Rainbow Trout 

(...): Report No. BL/B/2405. Unpublished study prepared by Imperial 
101

Chemical Industries Ltd. 19 p. 

151598 Hill, R. (1984) PP321: Determination of Acute Toxicity to Bluegill Sunfish 

(...): Report No. BL/B/2406. Unpublished study prepared by Imperial 

Chemical Industries Ltd. 19 p. 

151600 Hill, R. (1985) PP321: Determination of Acute Toxicity of a (...) EC 

Formulation to Rainbow Trout (...): Report No. BL/B/2609. Unpublished 

study prepared by Imperial Chemical Industries Ltd. 13 p. 

151601 Hill, R. (1985) PP321: Determination of Acute Toxicity of (...) EC 

Formulation to Bluegill Sunfish: Report No. BL/B/2610. Unpub- lished 

study prepared by Imperial Chemical Industries Ltd. 13 p. 

152738 Hill, R. (1984) PP890: Determination of Acute Toxicity to Rainbow Trout 

(Salmo gairdneri): Study No. M027/B: Report No. BL/B/2457. 

Unpublished study prepared by Imperial Chemical Industries PLC. 17 p. 

42291110 Tapp, J.; Sankey, S.; Caunter, J.; et al. (1990) Fonofos and LambdaCyhalothrin: Acute Toxicity to Rainbow Trout (Salmo gairdneri) of a 

200/4 g/kg GR Formulation: Lab Project Number: T545/A FT86/90: 

BL3951/B. Unpublished study prepared by Imperial Chemical Industries 

PLC. 27 p. 

42291111 Tapp, J.;Sankey, S.;Caunter, J.;et al. (1990) Fonofos and LambdaCyhalothrin: Acute Toxicity to Bluegill Sunfish (Lepomis macrochirus) of 

a 200/4 g/kg GR Formulation: Lab Project Number: T545/B FT87/90: 

BL3984/B. Unpublished study prepared by Imperial Chemical Industries 

PLC. 27 p. 

43908812 Kent, S.; Sankey, S.; Caunter, J.; et al. (1995) Lambda-Cyhalothrin: 

Acute Toxicity to Bluegill Sunfish (Lepomis macrochirus) of a 25 CS 

Formulation: Lab Project Number: AA1091/C: BL5380/B. Unpublished 

study prepared by Brixham Environmental Lab. 24 p. 

43908813 Kent, S.; Sankey, S.; Caunter, J.; et al. (1995) Lambda-Cyhalothrin: 

Acute Toxicity to Rainbow Trout (Oncorhynchus mykiss) of a 25 CS 

Formulation: Lab Project Number: AA1091/B: BL5379/B. Unpublished 

study prepared by Brixham Environmental Lab. 24 p. 

44584001 Kent, S.; Shillabeer, T. (1997) Lambda-Cyhalothrin: Acute Toxicity to 

Golden Orfe (Leuciscus idus): Lab Project Number: BL6142/B. 

Unpublished study prepared by Zeneca Limited. 22 p. 

45447216 Marino, T.; Rick, D. (2001) XR-225 and Lambda-cyhalothrin: An Acute 

Toxicity Comparison Study with the Bluegill Sunfish, Lepomis 

macrochirus Rafinesque: Lab Project Number: 001074(B). Unpublished 

study prepared by The Dow Chemical Company. 67 p. 

850.1075 Fish acute toxicity test, freshwater and marine 

MRID Citation Reference 

45447217 Machado, M. (2001) XDE-225 and Lambda-cyhalothrin: Comparative 

Toxicity to Rainbow Trout (Oncorhynchus mykiss) under Flow-Through 
102

Conditions: Lab Project Number: 12550.6140: 011056. Unpublished study 

prepared by Springborn Laboratories, Inc. 76 p. 

72-2 Acute Toxicity to Freshwater Invertebrates 

MRID Citation Reference 

151599 Farrelly, E.; Hamer, M.; Hill, I. (1984) PP321: Toxicity to First Instar 

Daphnia magna: Report No. RJ 0359B. Unpublished study prepared by 

Jealotts Hill Research Station, ICI Plant Protection Division. 13 p. 

151602 Farrelly, E.; Hamer, M.; Hill, I. (1985) PP321: Toxicity of Formu- lations 

JF9509 and GFU383C to First Instar Daphnia magna: Re- port No. RJ 

0426B. Unpublished study prepared by Jealott's Hill Research Station, ICI 

Plant Protection Division. 19 p. 

152730 Hamer, M.; Farrelly, E.; Hill, I. (1985) PP321: Toxicity to Gam- marus 

pulex: Report No. RJ0414B. Unpublished study prepared by Imperial 

Chemical Industries PLC. 29 p. 

152733 Hamer, M.; Farrelly, E.; Hill, I. (1985) 21 Day Daphnia magna Life-cycle 

Study: Study No. PP321/CN/02: Report No. RJ0541B. Unpublished study 

prepared by Imperial Chemical Industries PLC. 35 p. 

40052408 Wagner, J. (1987) Fish and Wildlife Data Overview and Summary for 

Resubmission for PP321 on Cotton: [Response to EPA's Comments]. 

Unpublished study prepared by ICI Americas Inc. 50 p. 

40515901 Kennedy, J.; Cole, J.; Ekoniak, P.; et al. (1988) PP321: Evalua- tion of the 

Impact of Run-off and Spray-drift on Aquatic Ecosys- tems, using USA 

Experimental Ponds (Mesocosms): Laboratory Pro- ject ID: RJ0614B. 

Unpublished study prepared by ICI Plant Pro- tection Division. 1855 p. 

42275602 Farrelly, E.; Hamer, M. (1991) Fonofos/Lambda-Cyhalothrin: Acute 

Toxicity to First Instar Daphnia magna of a 200/4 g/kg Granular 

Formulation: Lab Project Number: 90JH341. Unpublished study prepared 

by ICI Americas, Inc. 21 p. 

43908811 Kent, S.; Sankey, S.; Banner, A.; et al. (1995) Lambda-Cyhalothrin: Acute 

Toxicity to Daphnia magna of a 25 CS Formulation: Lab Project Number: 

AA0679/C: BL5235/B. Unpublished study prepared by Brixham 

Environmental Lab. 22 p. 

850.1010 Aquatic invertebrate acute toxicity, test, freshwater 

daphnids 

MRID Citation Reference 

45447220 Machado, M. (2001) XDE-225 and Lambda-Cyhalothrin: Comparative 

Toxicity to Daphnids (Daphnia magna) Under Static-Renewal Conditions: 

Lab Project Number: 12550.6139: 011055. Unpublished study prepared by 

Springborn Laboratories, Inc. 76 p. 
103

72-3 Acute Toxicity to Estuarine/Marine Organisms 

MRID Citation Reference 

152728 Thompson, R. (1985) PP321: Determination of the Acute Toxicity to 

Larvae of the Pacific Oyster (Crassostrea gigas): Study No. M258/D: No. 

FT 17/84: No.: BL/B/2643. Unpublished study prepared by Imperial 

Chemical Industries, PLC. 14 p. 

152729 Thompson, R. (1985) PP321: Determination of Acute Toxicity to Mysid 

Shrimps (Mysidopsis bahia): Study No. M258/C: Report No. BL/B/2635. 

Unpublished study prepared by Imperial Chemical Industries PLC. 12 p. 

152732 Hill, R.; Caunter, J.; Cumming, R. (1985) PP321: Determination of the 

Chronic Toxicity to Sheepshead Minnow (Cyprinodon variega- tus) 

Embryos and Larvae: Study No. N090B: Report No. BL/B/2677. 

Unpublished study prepared by Imperial Chemical Industries PLC. 35 p. 

153506 Hill, R. (1985) PP321: Determination of Acute Toxicity to Sheeps- head 

Minnow (Cyprinodon variegatus): Study No. M258/B: Report No. 

BL/B/2615. Unpublished study prepared by Imperial Chemical Industries 

PLC. 17 p. 

72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study 

MRID Citation Reference 

41217501 Farrelly, E.; Hamer, M. (1989) PP321: Daphnia magna Life-Cycle Study 

Using a Flow-through System: Rept. No. RJ0764B. Unpub- lished study 

prepared by ICI Agrochemicals, Jealotts Hill Re- search Station. 29 p. 

41217500 ICI Agricultural Products (1989) Submission of Daphnia Lifecycle Study 

in Compliance with Registration Standard for Karate In- secticide: 

(10182-96). Transmittal of 1 study. 

No MRID on 

DER Thompson, R.S. 1987 Mysid Lifecycle Study with PP321 

72-5 Life cycle fish 

MRID Citation Reference 

41016101 Tapp, J.; Maddock, B.; Harland, B.; et al. (1989) Second Interim Report--

Lambdacyhalothrin (Karate PP321): Determination of Chro- nic Toxicity to 

Fathead Minnow (Pimephales promelas) Full Life- cycle: Report No. 

BL/B/3489. Unpublished study prepared by Imperial Chemical Industries 

PLC. 32 p. 

41519001 Tapp, J.; Maddock, B.; Harland, B. et al. (1989) Lambda-Cyhalothrin in 

(Karate PP321): Determination of Chronic Toxicity to Fathead minnow 

(Pimephales promelas) Full Lifecycle: Lab Project No.: Q600/E (FT35/87). 
104

Unpublished study prepared by Imperial Chemi- cal Industries PLC. 255 

p. 

41745501 Tapp, J. (1990) Summary of Control Data Generated During Full Lifecycle Studies with the Fathead Minnow Pimephales promelas ...: Lab 

Project Number: P171/C: Q600/E: S001/A. Unpublished study prepared 

by ICI Americas. 11 p. 

41739801 Tapp, J.; Smith, C. (1990) ICI Response to the July 26, 1990 EEB Review 

of the PP321 Fish Lifecycle Study: Unpublished Study prepared by ICI 

Group Environmental Laboratory. 14 p. 

72-7 Simulated or Actual Field Testing 

MRID Citation Reference 

40515902 Kennedy, J.; Cole, J.; Ekoniak, P. et al. (1988) USA Experimental Ponds 

(Mesocosms): Biological Development of the Ponds During the 3 Months 

following Construction, II: Laboratory Project ID: RJ0612B. Unpublished 

study prepared by ICI Plant Protection Division. 379 p. 

41253901 Hill, I.; Cole, J.; Hadfield, S.; et al. (1989) ICI Response to EEB's Review 

of April 11, 1989, of the PP321 Mesocosm Study: RJ0612B: RJ0614B. 

Unpublished study prepared by ICI Agrochemi- cals, Jealott's Hill 

Research Station. 293 p. 

42675703 Runnalls, J. (1992) Lambda-Cyhalothrin: Addendum to RJ0614B; 

Evaluation of the Impact of Run-Off and Spray-Drift on Aquatic 

Ecosystems, Using USA Experimental Ponds (Mesocosms); Additional 

Water Residue Data: Lab Project Number: PP321CF01: RJ0614B. 

Unpublished study prepared by ICI Agrochemicals, Jealott's Hill 

Research Station. 27 p. 

141-1 Honey bee acute contact 

MRID Citation Reference 

40052409 Gough, H.; Collins, I.; Everett, C.; et al. (1986) PP321: Acute Contact and 

Oral Toxicity to Honey Bees (Apis mellifera): Labo- ratory Project ID: 

RJ0390B. Unpublished study prepared by ICI Americas Inc., Jealott's Hill 

Research Station. 23 p. 

123-1 or 2 Plant Testing 

152731 Thompson, R. (1985) PP321: Toxicity to the Green Alga Selenastrum 

capricornutum: Study No. M068/B: Report No. BL/B/2584. Unpub- lished 

study prepared by Imperial Chemical Industries PLC. 17 p. 

141-2 Honey bee residue on foliage 

MRID Citation Reference 
105

40436302 Gough, H.; Brown, R. (1987) PP321: Toxicity of Residues on Foliage to 

Honey Bees (Apis mellifera): Laboratory Project ID RJ 0611B. 

Unpublished study prepared by ICI Plant Protection Div. 29 p. 

40436303 Gough, H.; Collins, I.; Wilkinson, W. (1986) PP321: Effects on Honey Bees 

(Apis mellifera) Foraging on Simulated Honeydew on Winter Wheat, 1985: 

Laboratory Project ID RH 0464B. Unpublished study prepared by ICI Plant 

Protection Div. 54 p. 

128807 Gamma Cyhalothrin Eco Effects bibliography 

71-1 Avian Single Dose Oral Toxicity 

MRID Citation Reference 

45447210 Medlicott, B.; Harris, T. (2000) XR-225 Technical: Avian Acute Oral 

Toxicity Test with Northern Bobwhite (Colinus virginianus): Lab Project 

Number: 000030: 00008. Unpublished study prepared by Genesis 

Laboratories, Inc. 43 p. 

45447211 Medlicott, B.; Harris, T. (2000) XR-225 Formulation (GF-231): Avian 

Acute Oral Toxicity Test with Northern Bobwhite (Colinus virginianus): 

Lab Project Number: 000118: 00024. Unpublished study prepared by 

Genesis Laboratories, Inc. 42 p. 

71-2 Avian Dietary Toxicity 

MRID Citation Reference 

45447212 Medlicott, B.; Harris, T. (2000) XR-225 Technical: Avian Acute Dietary 

Toxicity Test with Northern Bobwhite (Colinus virginianus): Lab Project 

Number: 000033: 00009. Unpublished study prepared by Genesis 

Laboratories, Inc. 62 p. 

45447213 Medlicott, B.; Harris, T. (2000) XR-225 Technical: Avian Acute Dietary 

Toxicity Test with the Mallard (Anas platyrhynchos): Lab Project Number: 

000034: 00010. Unpublished study prepared by Genesis Laboratories, 

Inc. 62 p. 

72-1 Acute Toxicity to Freshwater Fish 

MRID Citation Reference 

45447214 Marino, T.; Rick, D. (2000) XR-225: An Acute Toxicity Study with the 

Rainbow Trout, Oncorhynchus mykiss Walbaum: Lab Project Number: 

001073. Unpublished study prepared by The Dow Chemical Company. 
106

50 p. 

45447215 Marino, T.; Rick, D. (2001) XR-225: An Acute Toxicity Study with the 

Bluegill Sunfish, Lepomis macrochirus Rafinesque: Lab Project Number: 

001074(A). Unpublished study prepared by The Dow Chemical 

Company. 48 p. 

45447216 Marino, T.; Rick, D. (2001) XR-225 and Lambda-cyhalothrin: An Acute 

Toxicity Comparison Study with the Bluegill Sunfish, Lepomis 

macrochirus Rafinesque: Lab Project Number: 001074(B). Unpublished 

study prepared by The Dow Chemical Company. 67 p. 

45447218 Marino, T.; Rick, D.; Staley, J.; et. al. (2001) XDE-225 Insecticide: GF231 (150G/L Formulation): An Acute Toxicity Study with the Rainbow 

Trout, Oncorhynchus mykiss Walbaum: Lab Project Number: 001191. 

Unpublished study prepared by The Dow Chemical Company. 46 p. 

45447217 Machado, M. (2001) XDE-225 and Lambda-cyhalothrin: Comparative 

Toxicity to Rainbow Trout (Oncorhynchus mykiss) under Flow-Through 

Conditions: Lab Project Number: 12550.6140: 011056. Unpublished 

study prepared by Springborn Laboratories, Inc. 76 p. 

72-2 or 850-1010 Acute Toxicity to Freshwater Invertebrates 

MRID Citation Reference 

45447219 Marino, T.; Rick, D. (2000) XDE-225: An Acute Toxicity Study with the 

Daphnia, Daphnia magna Straus: Lab Project Number: 001075. 

Unpublished study prepared by The Dow Chemical Company. 44 p. 

45447221 Marino, T.; McClymont, E.; Staley, J. (2001) XDE-225 Insecticide; GF231 (150G/L Formulation): An Acute Toxicity Study with the Daphnia, 

Daphnia magna STRAUS: Lab Project Number: 001192. Unpublished 

study prepared by The Dow Chemical Company. 49 p. 

45447220 Machado, M. (2001) XDE-225 and Lambda-Cyhalothrin: Comparative 

Toxicity to Daphnids (Daphnia magna) Under Static-Renewal Conditions: 

Lab Project Number: 12550.6139: 011055. Unpublished study prepared 

by Springborn Laboratories, Inc. 76 p. 

46065601 Henry, K.; McClymont, E.; Najar, J. (2003) XDE-225: Toxicity Testing 

with Various Life Stages of the Amphipod, Gammarus pseudolimnaeus. 

Project Number: 021119. Unpublished study prepared by The Dow 

Chemical Co. 83 p. 

46394703 Henry, K.; McClymont, E.; Najar, J. (2003) XDE-225: An Acute Toxicity 

Study With The Amphipod, Gammarus pseduolimnaeus. Project 

Number: 021059. Unpublished study prepared by The Dow Chemical 

Co. 39 p. 

72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study 
107

MRID Citation Reference 

45447222 Kirk, H.; McClymont, E.; Staley, J.; et. al. (2001) XDE-225: Evaluation of 

the Chronic Toxicity with the Daphnid, Daphnia magna STRAUS: Lab 

Project Number: 011051. Unpublished study prepared by The Dow 

Chemical Company. 92 p. 

123-2 Aquatic plant growth 

MRID Citation Reference 

45447406 Kirk, H.; Gilles, M.; McClymont, E.; et. al. (2000) XR-225: Growth 

Inhibition Test with the Freshwater Green Alga, Selenastrum 

capricornutum PRINTZ: Lab Project Number: 001093. Unpublished 

study prepared by The Dow Chemical Company. 41 p. 

45447407 Kirk, H.; Gilles, M.; McClymont, E. et al. (2001) Gf-231 Insecticide: 

Growth Inhibition Test with the Freshwater Green Algae, Selenastrum 

capricornutum PRINTZ: Lab Project Number: 001203. Unpublished 

study prepared by The Dow Chemical Company. 45 p. 

141-1 Honey bee acute contact 

MRID Citation Reference 

45447408 Hahne, R. (2000) XR-225 Technical: Acute Oral Toxicity Test with the 

Honeybee (Apis mellifera): Lab Project Number: 46098: 000112. 

Unpublished study prepared by ABC Laboratories, Inc. 21 p. 

45464802 Hahne, R.; Whitaker, J. (2000) XR-225 Technical: Acute Contact Toxicity 

Test with the Honeybee, Apis mellifera: Lab Project Number: 46099: 

000113. Unpublished study prepared by ABC Laboratories, Inc. 18 p. 

45464803 Hahne, R.; Whitaker, J. (2000) XR-225 Formulation (GF-231): Acute 

Contact Toxicity Test with the Honeybee, Apis mellifera: Lab Project 

Number: 46101: 000115. Unpublished study prepared by ABC 

Laboratories, Inc. 17 p. 

45464804 Hahne, R. (2000) XR-225 Formulation(GF-231): Acute Contact Toxicity 

Test with the Honeybee, Apis mellifera: Lab Project Number: 46100: 

000114. Unpublished study prepared by ABC Laboratories, Inc. 21 p. 

141-2 Honey bee residue on foliage 

MRID Citation Reference 

45464805 Hahne, R. (2000) XR-225 Formulation (GF-231): Toxicity of Residues on 

Foliage to the Honeybee (Apis mellifera): Lab Project Number: 46102: 

000116. Unpublished study prepared by ABC Laboratories, Inc. 17 p. 
108

Appendix A. PRD data request justification tables 

The following proposed Data Call-in tables include rationales for requiring the data requested in 

this problem formulation, explanations of the utility of the data, and explanations for how the data 

might impact risk assessment, following the format provided by PRD. 

Guideline Number: 835.2120 

Study Title: Hydrolysis

Rationale for Requiring the Data 

According to 40 CFR Part 158, Subpart N (Environmental Fate) §158.1300 

(Environmental fate data requirements table), these data are required for all terrestrial use 

patterns. 

At this time, there is one available study that was deemed acceptable at pH 5 and 7, 

conducted on gamma-cyhalothrin; however, the part conducted at pH 9 was deemed 

unacceptable, but upgradable. The other study was conducted at a rate that exceeded the 

solubility limit of lambda-cyhalothrin. “Experiments are performed to determine the rate 

of hydrolysis of the test substance as a function of pH and the identity or nature and rates 

of formation and decline of hydrolysis products to which organisms may be exposed.” 

(From Fate, Transport and Transformation Test Guidelines – OCSPP Guideline 

835.2120.) In order to clarify the rate of reaction of the test substance in pH 9 buffered 

solutions, the registrant should submit data to upgrade the pH 9 study, or a new study 

should be conducted at pH 9. 

Practical Utility of the Data 

How will the data be used? 

Lambda-cyhalothrin and gamma-cyhalothrin are synthetic pyrethroids with high toxicity 

towards aquatic organisms, including those living in the benthos. Knowledge of their 

persistence in terrestrial and aquatic environments is important. The results of this study 

will be used in the environmental fate assessment, and later on, in the ecological risk 

characterization. 

How could the data impact the Agency’s future decision-making? 

Without these data, the Agency would have to make certain conservative assumptions 

(e.g. assume that the chemicals are stable under alkaline conditions). These conservative 

assumptions could lead to incorrect conclusions about the environmental fate assessment 

and consequently about the ecological risk characterization. Also, there would be a 

higher degree of uncertainty in the environmental fate assessment. Knowledge of these 

dissipation pathways in detail is essential to perform a better and accurate environmental 

fate assessment and ecological risk assessment. 

The lack of these data will limit the flexibility the Agency and registrants have in coming 

into compliance with the Endangered Species Act and could result in use restrictions for 
109

lambda-cyhalothrin and gamma-cyhalothrin that may be unnecessary. 
110

Guideline Number: 835.4200 

Study Title: Anaerobic Soil Metabolism

Rationale for Requiring the Data 

According to 40 CFR Part 158, Subpart N (Environmental Fate) §158.1300 

(Environmental fate data requirements table), these data are required for all terrestrial use 

patterns. 

The available supplemental anaerobic soil metabolism study, conducted on lambdacyhalothrin, was performed with only one soil, for a period of only two months of 

anaerobic incubation, and sampling was insufficient to determine a suitable half-life. 

Furthermore, the pattern of anaerobic degradation appeared to be biphasic, but this could 

not be corroborated with the limited available data. A new study is required. Anaerobic 

studies with one soil type are generally sufficient for the evaluation of transformation 

pathways, but for lambda-cyhalothrin, cyclopropyl- and phenyl- or phenoxy-labeled 

studies are needed. Rates of transformation should be determined in at least three 

additional soils (from Fate, Transport and Transformation Test Guidelines – OCSPP 

Guideline 835.4100 & 835.4200). 

Practical Utility of the Data 

How will the data be used? 

Lambda-cyhalothrin and gamma-cyhalothrin are synthetic pyrethroids with high toxicity 

towards aquatic organisms, including those living in the benthos. Knowledge of their 

persistence in terrestrial and aquatic environments is important. The results of this study 

will be used in the environmental fate assessment, and later on, in the ecological risk 

characterization. 

How could the data impact the Agency’s future decision-making? 

Without these data, the Agency would have to make certain conservative assumptions 

(e.g. assume that the chemicals are stable under anaerobic soil metabolism conditions). 

These conservative assumptions could lead to incorrect conclusions about the 

environmental fate assessment and consequently about the ecological risk 

characterization. Also, there would be a higher degree of uncertainty in the 

environmental fate assessment. Knowledge of these dissipation pathways in detail is 

essential to perform a better and accurate environmental fate assessment and ecological 

risk assessment. 

The lack of these data will limit the flexibility the Agency and registrants have in coming 

into compliance with the Endangered Species Act and could result in use restrictions for 

lambda-cyhalothrin and gamma-cyhalothrin that may be unnecessary. 
111

Guideline Number: 835.4400 

Study Title: Anaerobic Aquatic Metabolism

Rationale for Requiring the Data 

According to 40 CFR Part 158, Subpart N (Environmental Fate) §158.1300 

(Environmental fate data requirements table), these data are required for all terrestrial use 

patterns. 

There is only one anaerobic aquatic metabolism study (soil/ sediment system) that was 

conducted with [14C-cyclopropyl]- or [14C-phenoxy]-labeled lambda-cyhalothrin. Two 

studies should be conducted utilizing lambda-cyhalothrin on one sediment system of 

freshwater and one of estuarine/ marine origin. According to the OCSPP Fate, Transport 

and Transformation Test Guidelines (835.4300 & 835.4400)...“At least two sediments 

and their associated waters are used for both the aerobic and the anaerobic studies 

respectively...However, there may be cases where more than two aquatic sediments 

should be used, for example, for a chemical that may be present in freshwater and/or 

marine environments. Sediments should be representative of intended use sites.” Since 

both lambda-cyhalothrin and gamma-cyhalothrin have the potential for use near 

estuarine/ marine areas, one of the required sediment systems should be from estuarine/ 

marine environment. 

Practical Utility of the Data 

How will the data be used? 

Lambda-cyhalothrin and gamma-cyhalothrin are synthetic pyrethroids with high toxicity 

towards aquatic organisms, including those living in the benthos. Knowledge of their 

persistence in soil and aquatic environments is important. The results of this study will 

be used in the environmental fate assessment, and later on, in the ecological risk 

characterization. 

In addition, the data will be used to derive the rate of reaction input parameter to be used 

in the aquatic models GENEEC2, PRZM/ EXAMS and FIRST. The results from these 

models are used for ecological risk estimation and in drinking water exposure 

assessments. 

How could the data impact the Agency’s future decision-making? 

Without these data, the Agency would have to make certain conservative assumptions 

(e.g. use three times the single available half-life value as half-life input for the anaerobic 

aquatic metabolism). This conservative assumption could lead to higher predicted 

concentrations (EECs), according to the models, and consequently, higher risk quotients. 

Also, there would be a higher degree of uncertainty in the environmental fate assessment. 

At this time, the anaerobic aquatic metabolism of lambda-cyhalothrin and gammacyhalothrin is uncertain because only one value is available. Knowledge of this 

dissipation pathway in detail is essential to perform a better and accurate environmental 

fate assessment and risk assessment. 
112

The lack of these data will limit the flexibility the Agency and registrants have in coming 

into compliance with the Endangered Species Act and could result in use restrictions for 

lambda-cyhalothrin and gamma-cyhalothrin that may be unnecessary. 
113

 

Guideline Number: None 

Study Title: Environmental Chemistry Methods (ECM) and Independent 

Laboratory Validation (ILV) for Soil, Water and Sediment

Rationale for Requiring the Data 

According to the data requirements in 40 CFR Part 158, ECMs are currently required 

along with successful confirmatory method trials (validation) by an independent 

laboratory (i.e. ILVs). The registrant submitted one method (MRID 40515901, published 

in the Agency’s ECM website),15 that could quantify lambda-cyhalothrin in water and 

sediment. EFED located an Environmental Chemistry Method Evaluation (ECME) 

performed by the Analytical Chemistry Branch (ACB), of the water portion of this study 

(BEAD review dated 9/23/93, Environmental Chemistry Method Validation Report No. 

ECM 0004W1). The ACB determined an LOD of 10 ng/L (ppt) while the registrant’s 

value was 1 ppt. This method cannot be used to determine lambda-cyhalothrin’s 

transformation products. Furthermore, there is one ECM and one ILV that quantifies 

lambda-cyhalothrin and other pyrethroids in sediments (MRID 47053001 and 47053002). 

It is uncertain whether this method can distinguish gamma-cyhalothrin from lambdacyhalothrin. The Agency will verify the suitability of these methods and the 

appropriateness of their levels of quantitation. At this time, no methods have been 

identified for the analysis of gamma-cyhalothrin. In addition to the method for soil, at 

this time, methods are required for water and sediment. The results of previous 

assessments indicate that there is risk for freshwater and estuarine/ marine fish, 

invertebrates and benthic organisms. Therefore, ECMs for water and sediment are 

required in addition to the ECM for soil. The ECMs should include parent and those 

residues found in the laboratory studies that exceed 10% of the applied. Acceptable 

ECMs for the residues of concern (parent and its transformation products, Compounds 

XV, Ia, Ib, V and 3-(4-hydroxyphenoxy)-benzaldehyde) should have levels of 

quantitation that are adequate to address risk concerns or that are at levels below the 

toxicological endpoints for the relevant aquatic organisms. The registrant is encouraged 

to submit state-of-the-art environmental chemistry methods; further, multi-residue 

methods (MRMs) for soil, water and sediment are preferred. 

Practical Utility of the Data 

How will the data be used? 

The data will be used to verify the suitability of the methods. Subsequently the methods 

could be used by states or other enforcement agencies, departments or entities, to monitor 

concentrations of the residues of concern. Validated analytical methods in environmental 

media (a.k.a., ECMs) are useful for conducting and evaluating submitted environmental 

fate and toxicity field and monitoring studies and for addressing potential risks to the 

environment posed by the use and/or accidental release of pesticides. 

How could the data impact the Agency’s future decision-making? 

If monitoring of the chemical is required or performed, the Agency could be able to 

determine if the chemical is present in the environment at concentrations that are 

 

15 Available at url: http://www.epa.gov/oppbead1/methods/ecmindex.htm
114

Guideline Number: None 

Study Title: Environmental Chemistry Methods (ECM) and Independent 

Laboratory Validation (ILV) for Soil, Water and Sediment

threatening to wildlife (or to humans, in the case of drinking waters), according to the 

levels of concern (LOCs or DWLOCs). If that is the case, measures to prevent these 

concentrations to occur could be taken. The data could also be used by enforcement 

entities like the states or government agencies or departments. Without these data, the 

potential for the determination of residues of lambda-cyhalothrin, gamma-cyhalothrin 

and transformation products (e.g., Compounds XV, Ia, Ib, V and 3-(4-hydroxyphenoxy)-

benzaldehyde) in soil, water and sediment is restricted. The lack of these data will limit 

the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act, and could result in use restrictions for lambda-cyhalothrin and 

gamma-cyhalothrin which may otherwise be avoided, or which are unnecessarily severe. 
115

Guideline Number: Non-guideline 

Study Title: Wood Leachability 

Rationale for Requiring the Data 

A study is required. It should be conducted according to the American Wood Preservers 

Association Standard Method of Determining the Leachability of Wood Preservatives 

(E11-06). It is suggested that the registrant provide a protocol to be evaluated by the 

Agency prior to performing the study. 

Practical Utility of the Data 

How will the data be used? 

Lambda-cyhalothrin and gamma-cyhalothrin are synthetic pyrethroids with high toxicity 

towards aquatic organisms, including those living in the benthos. They are used for wood 

protection treatment to buildings/products outdoor. The results of this study will be used 

in the ecological risk characterization, and in particular, for aquatic assessments. At the 

present time, based on the binding capacity of these chemicals to soil organic carbon, and 

their high octanol/ water partition coefficient, the EFED believes that lambda-cyhalothrin 

and gamma-cyhalothrin bind strongly to the wood material, but there are uncertainties as 

to the degree to which this occurs. Knowledge of the leachability from treated wood for 

these chemicals is important. 

In addition, the data will be used to derive the equivalent application rate to be used in the 

aquatic models GENEEC2 and PRZM/ EXAMS. The results from these models are used 

for exposure assessment, ecological risk estimation, and ultimately in risk assessment. 

How could the data impact the Agency’s future decision-making? 

Without these data, the Agency would have to make certain conservative assumptions 

(e.g. assume that 100% of the lambda-cyhalothrin and/ or gamma-cyhalothrin leaches 

instantaneously from the wood, to estimate the application rate in GENEEC and PRZM/ 

EXAMS). These conservative assumptions could lead to higher predicted concentrations 

(EECs), according to the models, and consequently, higher risk quotients. The 

application rate input parameter has a major effect in the determination of the aquatic 

EECs. Also, there would be a higher degree of uncertainty in the overall transport 

assessment for ecological effects. Knowledge of the leachability from treated wood of 

this chemical in detail is essential to perform a better and accurate environmental fate/ 

transport and risk assessment. 

The lack of these data will limit the flexibility the Agency and registrants have in coming 

into compliance with the Endangered Species Act and could result in use restrictions for 

this chemical that may be unnecessary. 
116

Guideline Number: None 

Study Title: POTW Effluent Monitoring and POTW Treatability Study

Rationale for Requiring the Data 

POTW Effluent Monitoring – Request any existing or ongoing POTW effluent 

monitoring data for the pyrethroids be submitted to the Agency. 

POTW Treatability Study – The Agency has recently requested and provided 

comments on a protocol developed by the Pyrethroid Working Group (PWG) for a bench 

scale study of waste water treatment, to assess the percentage removed in the biosolids by 

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

would remain in the waste water. These data would be used to inform removal 

percentages by waste water treatment, which is an input to the Exposure and Fate 

Assessment Screening Tool’s (E-FAST) down-the-drain module. The Office of 

Pesticide Programs will continue to confer with the Office of Water with the goal of 

refining our down-the-drain assessment for registration review. It is the responsibility of 

the registrant to ensure that lambda-cyhalothrin and gamma-cyhalothrin are included in 

the study completed by the PWG or conduct a similar study on their own (following 

submission of a protocol for review). 

Practical Utility of the Data 

How will the data be used? 

These data would be used to inform removal percentages by waste water treatment, 

which is an input to the Exposure and Fate Assessment Screening Tool’s (E-FAST) 

down-the-drain module. 

How could the data impact the Agency’s future decision-making? 

Without these data, the Agency will have to make assumptions regarding the level of 

removal of lambda-cyhalothrin and gamma-cyhalothrin (e.g., results of modeling from 

the EPIWEB v.4.0 may be used). These assumptions are likely to be crude and 

conservative. The lack of these data will limit the flexibility the Agency and registrants 

have in coming into compliance with the Endangered Species Act, and could result in use 

restrictions for lambda-cyhalothrin and gamma-cyhalothrin which may otherwise be 

avoided, or which are unnecessarily severe. 

Guideline Number: 850-2100 

Study Title: Passerine Acute Avian Oral 

Rationale for Requiring the Data 

Although an acute avian oral study was received for both the mallard duck (lambdacyhalothrin) and bobwhite quail (gamma-cyhalothrin), the Agency updated its data 

requirements in 40 CFR Part 158 (October 26, 2007) to include an acute oral toxicity study for 

both a passerine species and either a waterfowl or an upland game species. Prior to starting 
117

toxicity testing, a protocol will need to be provided for review. Many passerine species utilize 

agricultural fields, forests, residential areas and surrounding areas, and, therefore, have the 

potential to be exposed to pesticides used in agricultural, forest, and residential settings. It is 

likely that, for most pesticide use patterns, passerines are more likely to be exposed to 

pesticides than upland game species and waterfowl. Passerines are smaller in size and generally 

have faster metabolisms than the waterfowl and upland game bird species traditionally used in 

avian toxicity tests which could impact their sensitivity to chemicals. Data are required for 

either lambda- or gamma-cyhalothrin. 

Practical Utility of the Data 

How will the data be used? 

Data from passerine toxicity studies will be used to estimate potential risks to birds associated 

with uses of lambda- and gamma-cyhalothrin. The data will reduce uncertainties associated 

with the current risk assessment for passerine species and will improve our understanding of the 

potential effects of lambda- and gamma-cyhalothrin. 

How could the data impact the Agency’s future decision-making? 

Because birds significantly contribute to overall environmental quality, a solid understanding of 

the potential risks to birds, including passerine species, is essential for sound environmental 

management. Without acceptable data for lambda- and gamma-cyhalothrin, the Agency cannot 

determine the levels of these chemicals that result in effects to passerine species. If the data 

indicates that registered usage may pose a risk of adverse effects to non-target birds above the 

Agency Level of Concern, the Agency may explore decision options to mitigate this risk. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act, and could result in use restrictions for lambdaand gamma-cyhalothrin which may otherwise be avoided, or which are unnecessarily severe. 

Guideline Number: Non-guideline 

Study Title: Aquatic Invertebrate Acute Toxicity (Hyalella)

Rationale for Requiring the Data 

Based on a review of the registrant-submitted studies, amphipods (Gammarus pseudolimnaeus, 

EC50=0.00048 μg a.i./L) are more sensitive to gamma-cyhalothrin technical than the Daphnia 

magna (EC50=0.045 μg a.i./L) by two orders of magnitude. For lambda-cyhalothrin, the same 

trend is observed (EC50=0.0067 μg a.i./L for Gammarus pulex compared to an EC50=0.24 μg 

a.i./L for Daphnia magna based on studies with the technical product). The previously submitted 

amphipod study is classified as supplemental and believed to be an underestimation of the true 

toxicity of gamma-cyhalothrin technical because of rapidly declining exposure concentration over 

the duration of the study. In addition, available information in the Agency ECOTOX database and 

studies in the open literature (Weston and Lydy, 2010; Solomon et al 2001) indicate that the 

freshwater amphipod, Hyalella azteca, is substantially more sensitive to pyrethroids than Daphnia 

magna, the commonly tested freshwater invertebrate. Information on the acute toxicity of 

lambda- or gamma-cyhalothrin to Hyalella azteca was not identified in this problem formulation. 
118

Therefore, in order to ensure that risk to sensitive aquatic invertebrates (e.g., amphipods) are 

appropriately quantified, additional acute toxicity testing of the amphipod Hyalella azteca is 

needed (water column exposure, not sediment-spiked). In addition to its high sensitivity, the 

freshwater amphipod, Hyalella azteca, is recommended as the test species because it is also being 

requested for chronic freshwater sediment toxicity testing, thereby enabling acute risk to Hyalella

to be estimated via porewater exposure. 

A study is requested with gamma-cyhalothrin, based on the increased sensitivity of aquatic 

species to gamma- compared to lambda-cyhalothrin. 

Practical Utility of the Data 

How will the data be used? 

The freshwater acute toxicity study with Hyalella would allow the Agency to analyze acutely 

toxic effects to one of the most sensitive species of freshwater aquatic invertebrates. The effects 

data would be used to determine the likelihood that acute risks can potentially impact aquatic 

communities, either by direct effects on invertebrates or by indirect effects by reducing the food 

source for their predators (e.g., fish). By refining the assessment, the Agency would be able to 

determine whether the mitigation imposed as part of the registration review process was 

appropriate due to toxicity concerns with lambda- and gamma-cyhalothrin. 

How could the data impact the Agency’s future decision-making? 

If future risk assessments are performed without these data, the Agency would have to account 

for the potential increased sensitivity of Hyalella to lambda- and gamma-cyhalothrin using other 

means which may include using an extrapolation factor based on sensitivity differences with other 

pyrethroids. Since this extrapolation factor would involve uncertainty, it is likely that a 

conservative factor would be applied. This may impinge on the Agency’s flexibility in coming 

into compliance with the Endangered Species Act and could result in use restrictions for which 

are unnecessarily severe. 

Guideline Number: 850.1075 

Study Title: Fish Acute Toxicity (freshwater) 

Rationale for Requiring the Data 

The only available study on chronic toxicity of lambda-cyhalothrin to freshwater fish was 

conducted with the fathead minnow, Pimephales promelas (MRID 41519001; supplemental). 

The NOAEC from this study (0.031 μg a.i./L) is only about a factor of two less than the 96-h 

LC50 of 0.078 μg a.i./L for the most acutely sensitive freshwater fish species (golden orfe) to 

lambda-cyhalothrin. Furthermore, this NOAEC is virtually identical to the 96-h LC50 of 0.029 μg 

a.i./L determined for bluegill with gamma-cyhalothrin (MRID 45447215). It is therefore apparent 

that the fathead minnow is likely not among the most sensitive freshwater fish species tested to 

lambda- or gamma-cyhalothrin. In order to estimate the chronic toxicity to sensitive freshwater 

fish species (e.g., bluegill, golden orfe), an acute-chronic ratio (ACR) will likely be needed. This 

ACR would be applied to the most acutely sensitive fish species to estimate its corresponding 
119

chronic sensitivity. ACRs should be determined on the same species (in this case, fathead 

minnow) in order to reduce uncertainty in predicted chronic toxicity values. However, there are 

no submitted acute toxicity studies with fathead minnow from which to derive an ACR. Deriving 

an ACR based on an acutely sensitive species (e.g., bluegill) and a chronically insensitive species 

(fathead minnow) would likely grossly under estimate chronic risk to sensitive fish species. 

Without this study, estimation of chronic risks to sensitive fish species will involve substantial 

uncertainty. Therefore, the Agency is requesting an acute toxicity test of lambda-cyhalthrin to 

the fathead minnow in order to appropriately estimate chronic toxicity to fish based on existing 

chronic data with fathead minnow. Fathead minnow is one of the recommended test species in 

the test guidelines. 

Practical Utility of the Data 

How will the data be used? 

The acute toxicity study with fathead minnow would allow the Agency to estimate chronic effects 

and risks to sensitive freshwater (and estuarine/marine) species by facilitating the derivation of an 

ACR. The effects data would be used to determine the likelihood that the chronic risks can 

potentially impact aquatic communities, either by direct effects on invertebrates or by indirect 

effects on fish by reducing their food sources. By refining the assessment, the Agency would be 

able to determine whether the mitigation imposed as part of the registration review process was 

appropriate due to toxicity concerns with lambda- and gamma-cyhalothrin. . 

How could the data impact the Agency’s future decision-making? 

Without this data, future risk assessments (including those for endangered species) would have to 

acknowledge substantial uncertainty in chronic risk estimation for freshwater and 

estuarine/marine fish, such that the Agency’s “effect determinations” for endangered fish, 

aquatic-phase amphibians, and endangered species from other taxa indirectly could be called into 

question. This in turn might affect the determination of risk mitigation measures (e.g., use 

restrictions in areas where endangered species could be exposed). The lack of these data will 

limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act and could result in use restrictions for lambda- and gamma-cyhalothrin 

which are unnecessarily severe. 

Guideline Numbers: 850.1075, 850.1010 and non-guideline 

Study Title: Freshwater Fish Acute Toxicity (TEP) 

Freshwater Aquatic Invertebrate Acute Toxicity (TEP) 

Whole sediment: chronic invertebrates freshwater and marine 

Rationale for Requiring the Data 

Because there are registered outdoor uses that may result in significant exposure to water bodies, 

acute lambda- and gamma-cyhalothrin TEP data with the synergist PBO is requested for 

freshwater fish and freshwater invertebrates. The registrations are for cattle ear tags (#773-75) or 

cattle pour-on treatments (#773-92, #53883-248 and #53883-270). 
120

A total of 4 active product registrations exist for lambda-cyhalothrin and gamma-cyhalothrin 

formulations with PBO: 

• Lambda-cyhalothrin and PBO: # 773-75, #773-92, #53883-248 

• Gamma-cyhalothrin and PBO: # 53883-270 

Products with the synergist PBO are likely to cause increased toxicity to nontarget aquatic 

species. Currently, no data is available to quantify the difference in toxicity for fish or 

invertebrates that may be concurrently exposed to lambda- and gamma-cyhalothrin and PBO 

compared to the active ingredients alone. While these studies are requested for the "TEP," the 

registrant must submit a protocol prior to conducting these TEP studies that addresses the 

expected toxicity from differing concentration ratios of PBO and the TGAI that are likely to occur 

in the aquatic environment. Results from the acute freshwater toxicity tests can be used to 

optimize the design of the chronic sediment toxicity test. This approach is being followed by the 

Agency with TEP testing of PBO and pyrethrins. 

Practical Utility of the Data 

How will the data be used? 

These data are needed for a registration review decision and for an endangered species 

assessment, which will be conducted as part of that decision. The data would allow the Agency 

to determine acute risk to freshwater organisms from exposure to lambda- and gammacyhalothrin in conjunction with the synergist PBO. The effects data would be used to determine 

the likelihood that use of lambda- and gamma-cyhalothrin and PBO can potentially impact 

aquatic communities, either by direct effects or by indirect effects on other organisms by reducing 

their food sources. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency 

would have to assume that lambda- and gamma-cyhalothrin “may affect" endangered 

invertebrates directly (and endangered species from other taxa indirectly), and use might need to 

be restricted in areas where endangered species could be exposed. The lack of these data will 

limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act and could result in use restrictions which are unnecessarily severe. 

Guideline Number: 850.1300 

Study Title: Aquatic Invertebrate Life-Cycle (freshwater) 

Rationale for Requiring the Data 

Previously submitted studies indicate that freshwater invertebrates are among the most 

chronically sensitive species to lambda- and gamma-cyhalothrin, with chronic effects expected 

below 1 ng/L. While two supplemental studies have been submitted on the chronic toxicity of 

lambda-cyhalothrin to Daphnia magna (MRID 41217501, 00152733), the toxicity endpoints 

derived from these studies are considered highly uncertain. Specifically, the exposure 

concentrations used in these studies varied so much (3X to more than 10X ...?) that maximum 
121

and minimum values overlapped among treatments. This excessive variability in exposure 

concentrations within treatments brings into question the ability to accurately determine a chronic 

toxicity endpoint from these studies (e.g., NOAEC). Other guideline deviations were also noted in 

these two studies (e.g., high light intensities, use of too few replicate chambers per treatment, 

culling of less healthy organisms during the course of the study). Obtaining an accurate chronic 

NOAEC for freshwater invertebrates (e.g., daphnids) is critical to future risk assessment since this 

value will likely be used to estimate chronic toxicity to other more sensitive freshwater 

invertebrates (e.g., amphipods) which will form the basis of the risk assessment conclusions. As 

substantial advances in both analytical and biological test methods have occurred over the past 

two decades (the previously submitted studies were conducted in 1985 and 1989), it is highly 

likely that a repeat of these studies would yield results that are much more scientifically 

defensible. Without this study, estimation of chronic risks to sensitive freshwater invertebrates 

(e.g., daphnia, amphipods) will involve substantial uncertainty. 

A study is requested with gamma-cyhalothrin, based on the increased sensitivity of aquatic 

species to gamma- compared to lambda-cyhalothrin. 

Practical Utility of the Data 

How will the data be used? 

The aquatic invertebrate life-cycle study would allow the Agency to analyze chronic effects, 

including effects on reproductive success and growth, to freshwater invertebrates. The effects 

data would be used to determine the likelihood that the chronic risks can potentially impact 

aquatic communities, either by direct effects on invertebrates or by indirect effects on fish by 

reducing their food sources. By refining the assessment, the Agency would be able to determine 

whether the mitigation imposed as part of the reregistration process was appropriate due to 

toxicity concerns with lambda- and gamma-cyhalothrin. 

How could the data impact the Agency’s future decision-making? 

Without this data, future risk assessments (including those for endangered species) would have to 

acknowledge substantial uncertainty in chronic risk estimation for freshwater invertebrates, such 

that the Agency’s “effect determinations” for endangered invertebrates directly (and endangered 

species from other taxa indirectly) could be called into question. This in turn might affect the 

determination of risk mitigation measures (e.g., use restrictions in areas where endangered species 

could be exposed). The lack of these data will limit the flexibility the Agency and registrants 

have in coming into compliance with the Endangered Species Act and could result in use 

restrictions for lambda- and gamma-cyhalothrin which are unnecessarily severe. 

Guideline Numbers: Non-guideline 

Study Title: Chronic whole sediment: Freshwater and marine invertebrates

Rationale for Requiring the Data 

No chronic sediment toxicity tests for freshwater or marine invertebrates have been 

submitted to satisfy the Agency’s updated data requirements for outdoor uses in 40 CFR 

Part 158 (October 26, 2007). For lambda- and gamma-cyhalothrin, available information 

indicates that benthic organisms may be exposed via run-off or spray drift applications 
122

used in agricultural, forest, and residential settings. Based on calculations in the most 

recent EFED assessment for lambda-cyhalothrin (Section 18 Emergency Exemption for 

the Use of Lambda-cyhalothrin in Washington on Asparagus, D379522, August 2010) 

(see Appendix D for modeling information), the peak sediment porewater EECs predicted 

for lambda-cyhalothrin (0.00253 μg a.i./L) exceeds 0.1 of the most sensitive acute 

LC/EC50 (0.00048 μg a.i./L for Gammarus pseudolimnaeus), which satisfies one of the 

criteria for requiring chronic whole sediment toxicity testing under 40 CFR Part 158. This 

comparison is based on exposure concentrations predicted for lambda-cyhalothrin and the 

most sensitive toxicity information for gamma-cyhalothrin. However, the exposure would 

is expected to be similar for gamma-cyhalothrin based on similar fate properties. 

Additionally, the rates proposed for asparagus (3 applications of 0.034 kg a.i./ha at 21 

day intervals) were not the highest currently registered use rates (see Section 3.2). 

Chronic effects were also seen in all aquatic taxa tested at levels as low as 0.0002 μg 

a.i./L (Accession #073989, mysid shrimp). 

The expected half-life of lambda- and gamma-cyhalothrin in sediment (28 – 61 days for 

aerobic soil metabolism and 21 – 53 days for aerobic aquatic metabolism) is substantially 

greater than 40 CFR Part 158 criterion of 10 days. The potential for persistent exposure 

from lambda- and gamma-cyhalothrin in sediment is also indicated by open literature 

studies on pyrethroids (Weston et al. 2005, Amweg et al. 2006 and Ding et al. 2009). 

The third set of trigger criteria for requiring chronic testing (Kd > 50, or log KOW >3 or 

KOC > 1000) is also met for lambda- and gamma-cyhalothrin (for lambda-cyhalothrin Kd

mean value is 4350, log KOW is 7, and mean KOC value 333,200; for gamma-cyhalothrin 

Kd mean value is 622, log KOW is 5, and KOC mean value is 59,700). The 

physicochemical property triggers (Kd, KOW and KOC) reflect the propensity of the 

chemical to partition onto the particulate or organic matter phases of sediments. 

Exceeding any one of the physicochemical property triggers listed above is sufficient for 

indicating the pesticide has reasonable potential for partitioning to the sediment 

compartment. 

For sediment studies involving pyrethroids, chronic whole sediment tests on Hyalella 

azteca, Chironomus tentans, and Leptocheirus plumulosus are requested. Although both 

are freshwater species, Hyalella and Chironomus differ substantially in their ecological 

niche (i.e., epibenthic v. infaunal species), physiology, and there is some evidence 

suggesting Hyalella is among the more sensitive invertebrates to some pyrethroids based 

on water column tests (Anderson et al. 2006, Maund et al. 2002). Lambda- and gammacyhalothrin have the potential to enter estuarine/marine water bodies based on current 

usuage patterns that include coastal areas. Therefore, testing is also required for an 

estuarine/marine sediment-dwelling invertebrate species. 

A study is requested with gamma-cyhalothrin, based on the increased sensitivity of 

aquatic species to gamma- compared to lambda-cyhalothrin. 

Practical Utility of the Data 
123

How will the data be used? 

Data from sediment toxicity studies will be used to estimate potential risks to benthic 

organisms associated with uses of lambda- and gamma-cyhalothrin. The data will reduce 

uncertainties associated with the current risk assessment for benthic species and will 

improve our understanding of the potential effects of lambda- and gamma-cyhalothrin. 

How could the data impact the Agency’s future decision-making? 

Although there was uncertainty in estimating the effect of lambda- and gammacyhalothrin on benthic organisms in previous assessments, there was a potential risk 

associated with adverse effects identified for other aquatic organisms. Acceptable data 

for benthic organisms will reduce the uncertainty from the previous assessment If the 

data indicates that registered lambda- and gamma-cyhalothrin usage may pose a risk of 

adverse effects to non-target benthic organisms above the Agency Level of Concern, the 

Agency may explore decision options to mitigate this risk. The lack of these data will 

limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act, and could result in use restrictions which may otherwise be 

avoided, or which are unnecessarily severe. 

Guideline Numbers: 850.4150 and 850.4250 

Study Title: Vegetative vigor and Seedling emergence, Tier I/ Tier II 

Rationale for Requiring the Data 

No acceptable toxicity data are currently available to assess the risk of lambda- and 

gamma-cyhalothrin to terrestrial plants. 

Since lambda- and gamma-cyhalothrin has outdoor uses, vegetative vigor and seedling 

emergence studies are required. These phytotoxicity data are needed to evaluate the level 

of pesticide exposure to non-target terrestrial and aquatic plants and to assess the impact 

of pesticides on endangered and threatened plants. Data are required for either lambda- or 

gamma-cyhalothrin. 

Practical Utility of the Data 

How will the data be used? 

Data from terrestrial plant toxicity studies will be used to estimate potential risks to plants 

associated with uses of lambda- and gamma-cyhalothrin. The data will reduce 

uncertainties associated with the current risk assessment for terrestrial plants and will 

improve our understanding of the potential effects of lambda- and gamma-cyhalothrin on 

plants. 
124

How could the data impact the Agency’s future decision-making?

Because plants form the basis of most habitats and significantly contribute to overall 

environmental quality, a solid understanding of the potential risks to terrestrial plants is 

essential for sound environmental management. Without acceptable plant growth data, 

the Agency cannot determine the levels of lambda- and gamma-cyhalothrin that result in 

effects to terrestrial plants. If the data indicates that registered usage may pose a risk of 

adverse effects to non-target terrestrial plants plants above the Agency Level of Concern, 

the Agency may explore decision options to mitigate this risk. The lack of these data will 

limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act, and could result in use restrictions for lambda- and gammacyhalothrin which may otherwise be avoided, or which are unnecessarily severe. 

Guideline Number: 850.4400 

Study Title: Aquatic Vascular Plant Growth-Lemna spp. Tiers I/II 

Rationale for Requiring the Data 

No acceptable studies for lambda- or gamma-cyhalothrin have been submitted for vascular 

aquatic plants. The Agency has finalized its update to the data requirements in 40 CFR Part 

158. In these updated data requirements, which were promulgated on October 26, 2007, 

vascular plant testing is required for pesticides with outdoor uses such as lambda- and gammacyhalothrin. Data are required for either lambda- or gamma-cyhalothrin. 

Practical Utility of the Data 
125

How will the data be used? 

Data from aquatic plant toxicity studies will be used to estimate potential risks to plants 

associated with uses of lambda- and gamma-cyhalothrin. The data will reduce uncertainties 

associated with the current risk assessment for aquatic plants and will improve our 

understanding of the potential effects on vascular aquatic plants. 

How could the data change the Agency’s decision, or impact the Agency’s future 

decision-making? 

Because plants form the basis of most habitats and significantly contribute to overall 

environmental quality, a solid understanding of the potential risks to aquatic plants is essential 

for sound environmental management. Without plant growth data for lambda- and gammacyhalothrin, the Agency cannot determine the levels that may result in effects to vascular 

aquatic plants. If the data indicates that registered lambda- and gamma-cyhalothrin usage may 

pose a risk of adverse effects to non-target aquatic vascular plants above the Agency Level of 

Concern, the Agency may explore decision options to mitigate this risk. 

If future endangered species risk assessments are performed without these data, the Agency 

would have to assume that lambda- and gamma-cyhalothrin "may affect" endangered plants 

and use might need to be restricted in areas where endangered species could be exposed. The 

lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in use restrictions that may be 

unnecessarily severe.
126

Appendix B: Aquatic Ecological Effects Data

Fish Toxicity

 

Table B-1. Acute Toxic Effects of Lambda cyhalothrin and Gamma cyhalothrin (shaded) to Freshwater and 

Estuarine Fish 

Species Study 

Guideline 

% 

A.I. 

Toxicity Endpoint 

(95 % Confidence 

Interval) μg a.i. /L 

Toxicity 

Classification 

Study 

Classification 

MRID 

# 

Freshwater Fish

Bluegill Sunfish 

(Lepomis 

macrochirus)

72-1a 98 LC50 96 hr : 0.210 (0.16-

0.31) 

NOAEC : 0.16 (mortality) 

very highly toxic Core 00151598 

Bluegill Sunfish 

(Lepomis 

macrochirus)

72-1b 12.9 LC50 96 hr : 2.2 (1.9-2.7) 

NOAEC : 0.77 

very highly toxic Core 00151601 

Bluegill Sunfish 

(Lepomis 

macrochirus)

72-1b 24 LC50 96 hr : 1.2 (1.0-1.5) 

NOAEC :0.46 

very highly toxic Core 43908812 

Bluegill Sunfish 

(Lepomis 

macrochirus)

72-1b 100 LC50 96 hr: 0.051 (0.039-

0.066) 

NOAEC : <0.013 

(mortality and sublethal) 

very highly toxic Supplemental 45447216 

Bluegill Sunfish 

(Lepomis 

macrochirus)

72-1b 100 LC50 96 hr: 0.029 (0.021-

0.039) 

NOAEC : 0.02 (mortality) 

NOAEC : 0.0077 

(sublethal effects) 

very highly toxic Supplemental 45447215 

Rainbow Trout 

(Oncorhynchus 

mykiss)

72-1c 98 LC50 96 hr : 0.240 (0.20-

0.29) 

NOAEC : 0.11 (mortality) 

very highly toxic Core 00151597 

Rainbow Trout 

(Salmo gairdneri)

72-1d 12.9 LC50 96 hr : 3.4 

NOAEC : N/A 

very highly toxic Core 00151600 

Rainbow Trout 

(Oncorhynchus 

mykiss)

72-1c 24 LC50 96 hr : 2.7 (2.3-3.1) 

NOAEC :1.3 (mortality) 

very highly toxic Core 43908813 

Rainbow Trout 

(Oncorhynchus 

mykiss)

72-1c 100 LC50 96 hr: 0.19 (0.16-

0.22) 

NOAEC : 0.031 (sublethal 

effects) 

very highly toxic Supplemental 45447217 

Rainbow Trout 

(Salmo gairdneri)

72-1d 100 LC50 96 hr: 0.072 (0.057-

0.091) 

NOAEC: <0.0093 

(mortality and sublethal 

effects) 

very highly toxic Supplemental 45447214 
127

Table B-1. Acute Toxic Effects of Lambda cyhalothrin and Gamma cyhalothrin (shaded) to Freshwater and 

Estuarine Fish 

Rainbow Trout 

(Oncorhynchus 

mykiss)

72-1c 14.7 LC50 96 hr: 1.10 (0.86-

1.89) 

NOAEC: 0.28 (mortality 

and sublethal effects) 

very highly toxic Core 45447218 

Golden orfe 

(Leuciscus idus)

72-1d 87.7 

LC50 96 hr : 0.078 (0.055-

0.11) 

NOAEC :0.055 (mortality) 

very highly toxic Supplemental 00153506 

Estuarine/Marine Fish

Sheepshead Minnow 

(Cyprinodon 

variegatus) 

72-3a 96.5 LC50 96 hr : 0.807 (0.672-

0.967) 

NOAEC :≥0.29 (mortality) 

very highly toxic Core 00153506 

 

Table B-2. Chronic Toxicity Effects of Lambda cyhalothrin to Fish 

Species Study 

Guideline 

% 

A.I. 

Toxicity Endpoint 

(95% Confidence Interval) 

μg a.i. /L 

Study 

Classification 

MRID # 

Freshwater Fish

Fathead Minnow 

(Pimephales promelas) 

72-5 96.7 NOAEC: 0.031 

LOAEC: 0.062 

(adult growth; young survival and 

growth) 

Supplemental 41519001 

Estuarine/Marine Fish

Sheepshead Minnow 

(Cyprinodon variegatus) 

72-4a 96.6 NOAEC: 0.25 

LOAEC: 0.38 

(weight of the survival) 

Core 00153506 

Aquatic Invertebrate Toxicity

Table B-3. Acute Toxic Effects of Lambda-cyhalothrin (non-shaded) and Gamma cyhalothrin (shaded) to 

Aquatic Invertebrates 

Species Study 

Guideline 

% 

A.I. 

Toxicity Endpoint 

(95% Confidence 

Interval) μg a.i. /L 

Acute 

Toxicity 

Classification 

Study 

Classification 

MRID # 

Freshwater Invertebrates 

Daphnia magna 72-2a 

 

96.5 EC50 48 hr :0.23 

(0.18-0.29) 

NOAEC : 0.04 

very highly toxic Core 00151599 

Daphnia magna 72-2 

 

5.5 EC50 48 hr : 0.04 

 (0.03-0.06) 

NOAEC: Not established 

very highly toxic Supplemental 00151602 

Daphnia magna 72-2 12.9 EC50 48 hr : 0.065 

 (0.04-0.11) 

very highly toxic Supplemental 00151602 
128

Table B-3. Acute Toxic Effects of Lambda-cyhalothrin (non-shaded) and Gamma cyhalothrin (shaded) to 

Aquatic Invertebrates 

 NOAEC: Not established 

Daphnia magna 72-2 

 

24 EC50 48 hr : 0.18 

 (0.14-0.23) 

NOAEC : 0.03 (immobility) 

very highly toxic Core 43908811 

Daphnia magna 72-2 

 

100 EC50 48 hr : 0.045 

 (0.020-0.079) 

NOAEC: <0.015 

very highly toxic Core 45447220 

Daphnia magna 72-2 

 

100 EC50 48 hr : 0.095 

 (0.078-0.114) 

NOAEC: <0.0263 

very highly toxic Supplemental 45447219 

Daphnia magna 72-2 

 

14.7 EC50 48 hr : 0.154 

 (0.099-0.310) 

NOAEC: <0.011 

very highly toxic Supplemental 45447221 

Gammarus pulex 72-2a 94 EC50 96 hr : 0.007 

 (0.005-0.009) 

NOAEC : 0.0005 

(mortality) 

very highly toxic Supplemental 00152730 

Gammarus 

pseudolimnaeus 72-2a 99.2 

LC50: 

0.00048 (neonate), 0.00385 

(juvenile), 0.00812 (adult) 

very highly toxic Supplemental 46065601 

Estuarine/Marine Invertebrates 

Eastern Oyster 

(Crassostrea 

gigas) 

Mollusk Shell 

Deposition 

72-3b 96.5 LC50 48 hr : >590 

NOAEC : 590 

(immobility) 

highly toxic Core 00152728 

Mysid Shrimp 

(Mysidopsis 

bahia) 

72-3c >97 LC50 96 hr : 0.0041 

(0.004-0.006) 

NOAEC :Not established 

very highly toxic Core 00152729 
129

Table B-4. Chronic Toxic Effects of Lambda-cyhalothrin to Aquatic Invertebrates 

Species Study 

Guideline 

% 

A.I. 

Toxicity Endpoint 

(95% Confidence Interval) 

μg a.i. /L 

Study 

Classification 

MRID # 

Freshwater Invertebrates

Daphnia magna 72-4b 

 

92.8 NOAEC: 0.004 

LOAEC:0.005 

Number of young/female 

Supplemental 00152733 

Daphnia magna 72-4b 

 

96.6 NOAEC: 0.002 

LOAEC: 0.0035 

Number of young/female, Total young 

Supplemental 41217501 

Estuarine/Marine Invertebrates

Mysid 72-4b 

 

98.5 NOAEC: 0.0002 

LOAEC: 0.0005 

Number of young per reproductive day 

and Number of young/treatment 

 Core MRID (not 

available) Accession 

Number 073989 

Aquatic Plant Toxicity

Table B-5. Acute Toxic Effects of Lambda-cyhalothrin (non-shaded) and Gamma cyhalothrin (shaded) to 

Aquatic Plants 

Species Study 

Guideline 

% 

A.I. 

Toxicity Endpoint 

μg a.i. /L 

Study 

Classification 

MRID # 

Freshwater Non-vascular Plants 

Green Algae

Selenastrum 

capricornutum

123-2 

 

96.5 EC50 96 hr :>310 

NOAEC : ≥310 

Supplemental 152731 

Green Algae

Selenastrum 

capricornutum

123-2 

 

100 EC50 96 hr :>2850 

NOAEC : <1340 

Supplemental 45447406 

Green Algae

Selenastrum 

capricornutum

123-2 

 

14.7 Cell density

EC5072 hr: 15000 

NOAEC: 5480 

Growth rate

EC5072 hr:41300 

NOAEC: 5480 

Area under curve

EC5072 hr:16100 

NOAEC: N.R. 

Supplemental 45447407 
Appendix C. Open Literature Information 

The following is a cursory search of the available literature on lambda-cyhalothrin, gammacyhalothrin and synthetic pyrethroids in general, mostly about their prevalence/ occurrence, and 

about their toxicity to aquatic invertebrates and sediment dwelling organisms. It is not intended 

to be exhaustive. In the relatively recent past there has been an increased awareness of the 

prevalence and toxicity of lambda-cyhalothrin, gamma-cyhalothrin, and other synthetic 

pyrethroids, in sediment environments of urban and agricultural sites, particularly in California. 

Ureda 2004 determined the LC50s for deltamethrin, lambda-cyhalothrin and cyfluthrin, in 

sediments, using the test species Hyalella azteca. Also, sediment samples from two locations in 

Central Valley, California were tested. They found that there was a linear relationship between 

the LC50 and the total organic carbon for cyfluthrin. They found that for lambda-cyhalothrin, the 

LC50s ranged from 0.20 to 0.46 μg/gOC. Lambda-cyhalothrin appeared to be the most toxic of the 

three pyrethroids. The LOEC for lambda-cyhalothrin were of around 0.23 μg/gOC. In addition, 

Amweg, et al., 2005 determined the toxicity of six pyrethroids in three Central Valley, CA 

sediments towards Hyalella azteca. They found that of all the synthetic pyrethroids tested, 

bifenthrin exhibited the highest toxicity, while lambda-cyhalothrin was the chemical with the 

next highest toxicity with the average sediment 10-day median LC50 of 0.45 μg/gOC, which is of 

the same order of magnitude to Ureda 2004. 

Two major factors affect the toxicity of the pyrethroids: the presence of a synergist, such as 

piperonyl butoxide (PBO) and the temperature. The dissolved organic matter (DOM) appears to 

have an effect on the bioavailability of certain pyrethroids. Amweg et al. 2006a documented the 

effect of PBO on the pyrethroid permethrin’s toxicity towards Hyalella azteca in sediment 

samples. It was found that PBO could increase the toxicity of permethrin in sediment up to 

seven-fold. Also, Amweg and Weston 2007, documented the effects of the presence of PBO in 

sediments containing the synthetic pyrethroid bifenthrin and other representative chemicals, 

which included cadmium (a metal), chlorpyrifos (an organophosphate), DDT (an 

organochlorine), and flouranthene (a polycyclic aromatic hydrocarbon). The presence of PBO 

was considered as a Toxicity Identification Evaluation (TIE) tool. The bifenthrin 10-day 

Hyalella azteca LC50 was 0.26 μg/gOC, compared to 0.12 μg/gOC in the presence of PBO in the 

overlying water at 25 μg/L (increased toxicity by a factor of 2.2). For the other chemicals, the 

factor was around or less than 1 with no statistical difference in toxicity for all but chlorpyrifos. 

Eight field collected sediments, containing a variety of synthetic pyrethroids, or synthetic 

pyrethroids and chlorpyrifos (except for one sediment that contained only chlorpyrifos), that 

were previously tested and found to be toxic to Hyalella azteca, were examined with and without 

the presence of PBO. All the sediments exhibited higher toxicity in the presence of PBO except 

for the sediment that contained only chlorpyrifos. 

The effect of temperature was documented by Weston et al., 2009a. In an effort to identify 

factors affecting the toxicity identification evaluation (TIE) of the synthetic pyrethroids 

(“manipulating a sample in a manner that alters the toxicity of some toxicants but not others”), 

they performed sediment toxicity tests at various temperatures (13, 18, 23 and 28oC). 10-day 

LC50’s to Hyalella azteca were determined for four pyrethroids (lambda-cyhalothrin, permethrin, 

bifenthrin and esfenvalerate), also for chlorpyrifos, cadmium and DDT (which were 

 130
representative of other classes of chemicals). For the four pyrethroids, the toxicity 

approximately doubled when the temperature was decreased from 23 to 18oC, and approximately 

tripled when the temperature was further decreased to 13oC. The results at 28oC were mixed, but 

for some of the control samples, survival was low, which could indicate that the test species was 

not tolerant of the change to high temperature. For DDT, there was a similar response profile 

with temperature, but not as pronounced as for the synthetic pyrethroids. For chlorpyrifos and 

cadmium, the responses with temperature were nearly independent of temperature, and opposite 

to the one for the pyrethroids, respectively. For lambda-cyhalothrin, at the standard temperature 

of 23oC, the 10-day Hyalella azteca LC50 was found to be 0.42 μg/gOC and it was found to be the 

most toxic of all the pyrethroids analyzed. Various field samples with known amounts of seven 

pyrethroids (some of which included lambda-cyhalothrin) and chlorpyrifos, also showed similar 

responses to those of the tested pyrethroids (as indicated above), with a few exceptions. The 

authors discussed the possible repercussions of the temperature dependence of the synthetic 

pyrethroids during the winter season, when the temperatures of the waters and sediments are 

lower. 

Other TIE tools were explored by Wheelock et al. (2004). They described the uses of a 

pyrethroid selective antibody (an antibody synthetized in their laboratory that selectively binds to 

permethrin and to a lesser degree to cypermethrin), PBO and carboxyl esterase (an enzyme that 

degrades pyrethroids) as TIE for pyrethroids. It was indicated that PBO blocks the toxicity of 

the OPs, while synergizes the synthetic pyrethroids, which could confound results of samples of 

unknown composition, containing both types of compounds. Six pyrethroids, including lambdacyhalothrin were explored in the study and Cerodaphnia dubia was the test organism. It was 

found that the antibody reduced the toxicity of cypermethrin samples towards C. dubia, but that 

the antibody controls presented some toxicity towards the species. PBO at 100 μg/L synergized 

the pyrethroids by factors ranging from 9- to 137-fold. Lambda-cyhalothrin presented a toxicity 

ratio of 40-fold. In the presence of esterase, mortality was removed for all the pyrethroids tested, 

but not for diazinon and chlorpyrifos. The authors indicate that esterase could be a promising 

TIE tool for synthetic pyrethroids. It is noted that the esterase activity (hydrolysis rate) for 

lambda-cyhalothrin could not be measured under the testing conditions. In 2006, Wheelock et 

al. published an article on the use of carboxyl esterase in TIE using both C. dubia and H. azteca

in a variety of water samples (activity was shown also in municipal effluents and seawater), 

showing the usefulness of this enzyme in TIE. The pyrethroids used in this latter study were 

permethrin and bifenthrin. 

Weston and Jackson (2009) also evaluated enzimes as toxicity identification evaluation (TIE) 

tools for pyrethroids and organophosphates in water and sediment. The carboxylesterase from 

Lucilia cuprina (E3) was able to reduce the toxicity of three pyrethroids towards Hyalella azteca

in water 12-70-fold for three representative pyrethroids (not including lambda- or gammacyhalothrin). In sediments, a reduction of only 2-fold was achieved in toxicity of pyrethroids. 

On the other hand, the phosphotriesterase from Agrobacterium radiobacter (OpdA) achieved at 

least a reduction of 35-fold in toxicity towards chlorpyrifos, an organophosphate insecticide. 

The authors indicated that for pyrethroids, which are strongly hydrophobic, exposure towards H. 

azteca through interstitial water may be important, but that the E3 enzime may not diffuse 

effectively into sediments (to reduce the toxicity). 

 131
In 2008, Xu et al. published a report about the desorption kinetics of pyrethroids in sediments. 

They observed that aging sediments may have a marked effect on the desorption rates of 

pyrethroids in sediments. Two spiked sediments and two field samples containing pyrethroids 

were aged for various periods of time through 200 days. For the spiked sediments, four 

representative pyrethroids were used (including lambda-cyhalothrin). Their observation was that 

the fraction of the pyrethroids that desorbs quickly (Frapid) decreases with time rapidly, while the 

fraction that desorbs very slowly increases with time. For all the pyrethroids tested, the halflives for Frapid were two months or less. This was the coupled result of the degradation. The 

Frapid was considered the potentially bioavailable fraction of the pyrethroids. 

Using solid phase microextraction (SPME) technique, Liu et al. (2004) achieved low levels of 

detection for two representative pyrethroids (bifenthrin and permethrin) in runoff and stream 

waters. They found that in stream waters, the freely dissolved pyrethroid concentrations 

contributed to only 0.4 to 1.0% of the overall concentration, while in the runoff waters, it was 10 

to 27%. Partitioning was dominated by the adsorption to suspended solids, followed by 

dissolved organic matter (DOM). Concentration determination following liquid-liquid 

partitioning of the water samples overestimated the concentrations, compared to the SPME 

sampling followed by GC analysis even after filtration of the samples or centrifugation. The 

authors suggested that a better understanding of water quality could be achieved using the SPME 

sampling for pyrethroids. 

The Hunter et al. team (2009) used solid phase microextraction (SPME) to measure pyrethroids 

in sediment pore water. They used disposable polydimethylsiloxane fibers to detect seven 

pyrethroids (not including lambda- or gamma-cyhalothrin). They observed that the fibersediment partition equilibrium was reached in less than 5 days when the samples were agitated at 

low speed, but more than 23 days without agitation. SPME applied to field samples was able to 

detect pore-water concentrations as low as 0.1 ng/L. Three sediments were used in method 

development, and two urban runoff sediments were also tested. The authors pondered on the 

advantages and disadvantages of agitation to measure pyrethroids. They indicated that the 

matrix-SPME method is “simple, inexpensive, and relatively fast...as well as sensitive.” 

In an early study, it was found that lambda-cyhalothrin adsorbed to suspended matter with 

organic coatings with variable sorptive capacities (Zhou et al. 1995). They observed that both 

the quantity and the character of the organic matter are important in describing the distribution of 

lambda-cyhalothrin. Adsorption was low on mineral particles (without organic coatings) and 

followed the order montmorillonite > aluminum oxide > kaolinite. The adsorption to clay 

minerals with variable levels of organic material was greater. The increase was directly related 

to the fraction of organic carbon (ƒoc). The KOCs varied with the composition of the organic 

coating. The highest KOCs were observed for coatings with the highest levels of aromatic 

material. The KOCs decreased with increasing polarity of the organic material. 

In another study, Yang et al. (2006) used SPME to determine the freely dissolved pyrethroid 

concentrations of four pyrethroids (that did not include lambda-cyhalothrin or gammacyhalothrin) in waters containing low levels of suspended solids (SS). As the SS levels 

increased, the acute toxicity of the pyrethroids decreased. The highest level of SS was 200 mg/L 

 132
which was indicated to be similar to what would be observed in storm runoff and irrigation 

runoff. Four types of sediments were used in this study. 

Smith and Lizotte Jr. (2007) used waters from 12 ponds and lakes from Mississippi and assessed 

the influences of dissolved organic carbon, turbidity, suspended solids and phytoplankton 

(measured as chlorophyll a) on the acute toxicity of lambda-cyhalothrin and gamma-cyhalothrin 

towards Hyalella azteca. It was observed that the recoveries of these chemicals were relatively 

low which may have been due to the holding period of 24 hours allowed for stabilization of the 

solutions. The 48-hour immobilization EC50 values varied by around one order of magnitude 

“ranged from 1.4 to 15.7 ng/L and 0.6 to 13.4 ng/L for lambda-cyhalothrin and gammacyhalothrin, respectively”). Gamma-cyhalothrin was found to be around 1.9 times more toxic to 

H. azteca than lambda-cyhalothrin. For both compounds, significant linear relationships were 

observed between the EC50s and suspended solids, turbidity, DOC and chlorophyll a. It was 

indicated that due to regional climate conditions, turbidity and suspended solids were associated 

with phytoplankton density in the study. 

Yang et al. 2007 observed the effect of dissolved organic matter (DOM) on the bioavailability of 

the pyrethroids cyfluthrin and permethrin, and their toxicity towards Daphnia magna and 

Ceriodaphnia dubia. A total of 15 surface water samples from southern California were utilized. 

The dissolved organic content (DOC) ranged from 3.3-20.2% and the pH ranged from 6.67-7.76. 

Various indicators were also characterized in the waters like an indicator of the level of 

aromaticity, the carboxyl group capacity and the phenol group capacity. The authors also 

estimated bioconcentration factors (BCFs) for D. magna. Using polydimethylsiloxane (PDMS) 

activated fiber, a measure of the freely dissolved pesticide concentration was obtained (the 

PDMS fibers were placed in scintillation vials and measured via LSC). Based on their low 

absortivity at 254 nm, it was suggested that the water samples had low DOM aromaticity. The 

E4/E6 (a ratio of absorbance at two specified wavelengths) of <5 suggested humic acid 

dominated composition and lesser fulvic acids. Finally, the molar content of carboxylic acid and 

phenolic acid, normalized for DOC varied widely. The DOM did not affect the freely available 

permethrin, but for cyfluthrin, the freely available cyfluthrin was lower in the natural waters than 

for the control samples in all instances. The KDOCs were less for cyfluthrin than for permethrin 

by about twice, suggesting affinity of cyfluthrin towards the DOM. 

KDOC = (Cw – Cfree) / (DOC x Cfree) 

The cyfluthrin D. magna body residues were lower in natural waters than in the control in 14 of 

the 15 samples (for 9 samples, the difference was significant). There was a significant 

correlation between the cyfluthrin body residue and Cfree, but not for permethrin. In 96-hour 

static exposure tests with C. dubia neonates, the cyfluthrin LC50s were greater than the controls 

in every case (for 7 samples, the difference was significant). These findings suggest high affinity 

of cyfluthrin with organic carbon and organic matter, and lower bioavailability in natural waters 

than in control waters. However, for permethrin, the DOM appeared to have little effect on the 

bioavailability and toxicity. 

In a recent study (Stout II, et al. 2009), conducted by the US Department of Housing and Urban 

Development, in collaboration with the Agency, several chemicals were surveyed on floors of 

occupied homes. The survey included several synthetic pyrethroids like lambda-cyhalothrin. 

The most frequently detected pesticide was permethrin (89% of the samples). Piperonyl 

 133
butoxide was also commonly observed (52% of the samples). Lambda-cyhalothrin was detected 

with a frequency of 21% (n = 467 samples; mean not reported for chemicals with detection 

frequency below 30%; maximum value = 61 ng/cm2

), illustrating that this chemical is commonly 

applied, detected and present in homes. 

Lambda-cyhalothrin is among the constituents monitored by the National Water Quality 

Assessment (NAWQA), maintained by the U.S. Geological Survey. One kind of parameter (type 

of samples) is reported: “lambda-Cyhalothrin_ water_ filtered_ recoverable_ micrograms per 

liter,” with a reported percent of samples with this parameter of 7.4 (report units of μg/L). 

Multiple articles from the literature document the presence of synthetic pyrethroids, like lambdacyhalothrin and gamma-cyhalothrin, in both urban and agricultural sediments. Weston et al.

2005, studied the presence of synthetic pyrethroids in Roseville, CA, selected as a typical 

suburban development. Sediments from creeks that drain subdivisions of single-family homes 

were found to be toxic to Hyalella azteca. The sediments were tested for several pesticides, as 

well as 7 pyrethroids, including lambda-cyhalothrin. Bifenthrin was present in all the sediment 

samples. It was considered to be the primary cause of the toxicity towards the organism, with 

additional significant contributions of the pyrethroids cyfluthrin and cypermethrin. The 

maximum concentration of lambda-cyhalothrin was found to be 13 ng/g dry weight, for the 

tributary 13, Kaseberg Creek sample. It was detected in 16 out of 24 sediment samples. The 

authors indicate that the presence of synthetic pyrethroids was not likely to be due to agricultural 

uses. In Placer County, the use of synthetic pyrethroids for agricultural purposes was reported to 

amount to around 1%. 

Amweg et al. 2006b also studied synthetic pyrethroids in urban areas of California and 

Tennessee. Bifenthrin was found to be the major contributor to the toxicity of sediments 

sampled in California to Hyalella azteca, due to its high reported concentrations and toxicity. 

Cypermethrin, cyfluthrin, deltamethrin and lambda-cyhalothrin may have contributed to the 

toxicity in some of the sites. The concentrations of cypermethrin and cyfluthrin were typically 

higher than for other synthetic pyrethroids (usually 2-30 ng/g), but the bifenthrin and permethrin 

concentrations were the highest. On the other hand, in Tennessee only a few samples contained 

synthetic pyrethroids and none of the samples were toxic to Hyalella azteca. The differences 

between the two sites were attributed to different climate, types of residential development and 

pesticide use practices. 

Holmes et al. 2008 presented the occurrence and toxicity of the synthetic pyrethroids throughout 

the state of California’s urban creek sediment samples. First, 90 samples were screened for 

toxicity to Hyalella azteca, of which around one third caused significant toxicity to the organism. 

Later, 30 sample locations were selected for the final study. Of the 30 samples, 25 were toxic to 

Hyalella azteca at 23oC and all 30 samples were toxic at 15oC (the synthetic pyrethroids often 

show higher toxicity at lower temperatures, as indicated above). Seven of eight pyrethroids were 

detected in the sediment samples. Fenpropathrin was not detected in any of the samples, and 

deltamethrin and esfenvalerate were detected infrequently; but bifenthrin was present in all the 

30 samples (2.19 to 219 ng/g dry weight). Permethrin was the second most detected pyrethroid 

and lambda-cyhalothrin was detected in 10 samples and it was observed in most regions. The 

results suggested an important role of the synthetic pyrethroids in California’s urban creeks 

sediment toxicity. Bifenthrin accounted for around two thirds of the toxicity on an average basis, 

 134
with cyfluthrin and cypermethrin also playing an important role in the pyrethroid toxicity 

statewide. 

Trimble et al. 2009 screened a previously referenced database of 24 pesticides and 94 urban 

sediment samples, with minimal agricultural or industrial contribution, collected from creeks and 

streams throughout central and northern California. The seven synthetic pyrethroids tested and 

chlorpyrifos were the pesticides most commonly occurring in toxicologically significant 

mixtures. Bifenthrin, permethrin and DDT were observed in greater than 90% of the samples. 

After normalizing the chemical concentrations for organic carbon “to provide better estimates of 

the biologically available chemical fractions,” all the seven pyrethroids monitored had levels 

exceeding the established level of interest, LOI (defined as 0.005 toxic units, 0.005 TU) for at 

least one sample. Lambda-cyhalothrin was detected in around 65% of the samples (Fig. 1 of the 

report) and it exceeded the LOI in around 65% of the samples (apparently in all the samples). 

The chemical exceeded 0.5 TU in greater than 5% of the samples (Fig. 1, and p. 1690). 

Bifenthrin, cypermethrin and cyfluthrin exceeded 0.5 TU (100x the initially established LOI) in 

greater than 30% of the samples. It was stated that... “The three pesticides with the highest 

average TU values were bifenthrin (2.4 TU), cypermethrin (1.2 TU), and cyfluthrin (0.5 TU).” 

These are just a few examples that illustrate the high use of synthetic pyrethroids in urban 

settings and potential ecological ramifications. The concentration addition model (CA) was 

found to adequately predict the toxicity of pyrethroid mixtures; however, it was stated that there 

is the potential for mixtures to deviate from additivity. Furthermore, their results indicated that 

there is no substantial synergistic or antagonistic effect to H. azteca from exposures to mixtures 

of pyrethroids. 

Budd et al. 2007 sampled sediments in mixed land (urban and agricultural) in the San Diego 

Creek in Newport Bay Watershed in southern California. Bifenthrin and fenpropathrin were 

among the most frequently detected synthetic pyrethroids, with bifenthrin found in 95-100% of 

the samples. Lambda-cyhalothrin was observed less frequently, at a highest concentration of 

2.51 μg/kg. The highest concentrations were associated with commercial nurseries. The authors 

found in this case that the concentration of synthetic pyrethroids was generally lower in 

residential or commercial areas as opposed to agricultural sites. They observed that the 

sediments from the wet season had “a more diverse profile of detections,” as compared to the dry 

season sediment samples. Also, the frequency of detections of pyrethroids was higher during the 

wet season (e.g., for lambda-cyhalothrin 56% vs. 16%), but the total concentration was not 

statistically different between the wet and dry seasons. In the study, the SPME methodology was 

utilized to determine the free concentration of the pyrethroids in the pore water. With the 

exception of bifenthrin, other pyrethroids were not detected frequently. Based on results of a 

poor correlation of the organic carbon normalized concentration in the sediment against the Cfree, 

for bifenthrin, it was suggested that SPME methods would be a better alternative to monitor for 

pyrethroids in sediments instead of the whole sediment analysis. 

Weston et al. 2004 studied the presence of 26 pesticides, including five pyrethroids, in 70 

sediment samples taken from the agriculture dominated Central Valley in California. Ten-day 

sediment tests were conducted for Hyalella azteca and Chironomus dilutus (formerly known as

Chironomus tentans), for some of the samples. Synthetic pyrethroids were found in 75% of the 

sediment samples; also they were found, based on a toxicity unit basis, to be sufficiently high to 

 135
cause toxicity in 40% of the samples toxic to C. dilutus and around 70% of the samples toxic to 

H. azteca. The most commonly found pyrethroids were permethrin > esfenvalerate > bifenthrin 

> lambda-cyhalothrin. The presence of several synthetic pyrethroids illustrated the possibility of 

high levels of several synthetic pyrethroids in agricultural zones. 

In a study, Gan et al. 2005 monitored the spatial distribution and enrichment (as measured by the 

enrichment ratio, ER, or ratio of the concentration of a substance in eroded sediment to that of 

the source matrix) of the synthetic pyrethroids permethrin and bifenthrin, along a 260 meters 

runoff path. A sedimentation pond was used as the source point for the study (permethrin and 

bifenthrin had been used extensively at the site, for ant control, in a nursery environment). It was 

observed that, in general, the sediment concentration of permethrin and bifenthrin increased with 

distance (downstream from the source). Using the source as the reference value, ERs were 

calculated for these chemicals. The ERs reached 25.7-32.2 for bifenthrin at 145 m and beyond, 

and they were lower for permethrin. Also, the persistence of the test substances was assessed, 

both, in aerobic and anaerobic environments. Despite the fact that this study was not conducted 

with lambda-cyhalothrin or gamma-cyhalothrin, this study illustrated the possibility of 

enrichment through a runoff path for the synthetic pyrethroids. Both chemicals have very high 

KOC values and are very highly hydrophobic. 

Woudneh & Oros 2006 presented a multi-chemical analytical method that included among others 

lambda-cyhalothrin (it appears that the method could separate isomers A from isomers B) and 

piperonyl butoxide (PBO). Analysis of the San Francisco Bay tributary sediment samples (six 

samples from five sites) revealed that lambda-cyhalothrin was detected in four of the sediments, 

at a maximum of 1.71 ng/g and was less than the detection limit in the other two samples. PBO 

was detected in all the samples at 0.010-0.215 ng/g. 

Most of the studies related to the synthetic pyrethroids were conducted in California, but other 

studies document the presence of synthetic pyrethroids elsewhere. 

Hintzen et al. 2009 monitored for 12 insecticides and degradation products, including synthetic 

pyrethroids and fipronyl in Texas stream sediments from urban sites in 2006, as a model to 

evaluate their potential impact in Southern US. Bifenthrin was the pyrethroid found with the 

highest frequency. Lambda-cyhalothrin and permethrin were also frequently detected; the 

detections of lambda-cyhalothrin occurred frequently at concentrations of concern, but the 

concentrations of permethrin were below the LC50 for H. azteca. Bifenthrin was the greater 

contributor to the TUs, followed by lambda-cyhalothrin. Lambda-cyhalothrin’s frequency of 

detection was 56.9% (mean = 0.50 μg/gOC; maximum = 1.7 μg/gOC; compared to the 10-day LC50

to Hyalella azteca of 0.45 μg/gOC). The TUs generally correlated well with the toxicity of the 

samples, although some discrepancies between the TUs and toxicity were noted (even after 

normalization for organic carbon). There were no seasonal variations of the TUs. 

Ding et al. 2010 conducted monitoring for 29 pesticides, including pyrethroids like bifenthrin, 

fenpropathrin and lambda-cyhalothrin, from both urban and agricultural sites in central and 

southern counties in the state of Illinois in 2008. Most of the urban samples were from 

constructed storm drains, while the agricultural samples were from small waterways between 

farmlands in areas where mostly corn and soybeans were grown and the major pesticides used 

 136
were tefluthrin and atrazine. Furthermore, sediment toxicity tests towards Hyalella azteca were 

performed. In the urban samples, the synthetic pyrethroids were detected in 95% of the samples. 

Bifenthrin was detected in 80% of the samples, while permethrin, lambda-cyhalothrin and 

fenpropathrin were also frequently detected. Lambda-cyhalothrin was detected in 8 out of 20 

samples (frequency of detection 40%). In the agricultural samples, bifenthrin, permethrin, 

cypermethrin and tefluthrin were detected (frequency of detection 47%), while cyfluthrin, 

fenpropathrin and lambda-cyhalothrin were not detected (n = 49). Ten of 17 urban sediment 

samples tested were significantly more toxic to H. azteca than the controls. Only one of the 

agricultural sediment samples was significantly more toxic than the controls. The major source 

of TUs were the pyrethroids (in particular, bifenthrin). It was indicated that the detections of 

fenpropathrin in the urban samples was unexpected because it is a pesticide primarily used in 

agriculture. 

LeBlanc & Perkins, 2009, documented the presence of synthetic pyrethroids in Maine sediments. 

Of five synthetic pyrethroids monitored, only bifenthrin was detected, at levels of 1.26 – 16.68 

ng/g (means). The other synthetic pyrethroids monitored were lambda-cyhalothrin, permethrin, 

cyfluthrin and cypermethrin. Four sediments were monitored: Mill Creek Lower Intertidal, Mill 

Creek Upper Intertidal, Back Cove and Payson Park. 

Weston 2007 said that, “Contrary to popular perception, non-agricultural use of pyrethroids far 

exceeds agricultural use, at least in California, one of the few areas where data are available. A 

similar situation is likely elsewhere where there is substantial urban development. Whereas 

agricultural use of pyrethroids in California is about 300,000 lb/yr, non-agricultural commercial 

use (mostly applications done by professional pest control firms) is currently about 700,000 

lb/yr. Retail sales to homeowners are not included in this non-agricultural figure, but are 

probably about another 100,000 lb/yr. Some of the major urban uses of pyrethroids include 

cypermethrin and permethrin for termite control, permethrin to maintain landscaping, and 

bifenthrin and cyfluthrin for a variety of pests around homes.” 

Analysis of pyrethroids has not been limited to sediments. Weston et al.2009b, found that 

bifenthrin was the most frequently detected pyrethroid from runoff waters from Roseville and 

Elk Grove urban sites. Cyfluthrin and permethrin were also detected frequently. Lambdacyhalothrin was detected in two out of eight samples at a maximum concentration of 7 ng/L in 

the wet season, but it was not detected in the four samples of the dry season. It was noted that 

stormwater runoff (which occurs mostly around the winter) was responsible for more transport 

than irrigation runoff (which occurs mostly around the summer), towards surface waters. 

Suspended sediments were found to have higher concentrations of pyrethroids with no apparent 

seasonal patterns. They contained lambda-cyhalothrin at up to 7 times the acutely toxic 

threshold (reported LC50 to H. azteca of 7.2 ng/g dry weight). The highest concentration was 67 

ng/g dry weight. It was suggested that mitigation of the effects of the synthetic pyrethroids 

would need to target both sources of runoff. It was reported that the use of bifenthrin (for retail 

and for professional use) was higher approximately in the months around the summer. 

In an article, Weston & Lydy 2010 studied the possible sources of pyrethroids in California’s 

Sacramento – San Joaquin River Delta, including three types of samples: (a). urban runoff, (b). 

municipal wastewater treatment plants (or Publicly Owned Treatment Works, POTWs), and (c). 

 137
agricultural discharges, in a study that focused on water samples (as opposed to most of the 

studies above that are related to sediments). Samples were taken during the wet and dry seasons. 

First, urban runoff samples were taken from concrete sumps, from which pumps lift waters to 

adjacent rivers over levees. Second, POTW effluents with secondary (and in one case, tertiary) 

treatment were sampled just prior to discharge to surface waters. And finally, third, agricultural 

discharges were collected at pump stations, where the runoff is lifted over the levees. Samples 

were tested for 8 pyrethroids and chlorpyrifos (LOQ around 1 ng/L for most samples). Tests to 

Hyalella azteca were also performed on the water samples. Lambda-cyhalothrin was found in 

45, 17 and 11% of the samples of urban runoff, POTWs and agricultural drains, respectively. 

Also, 24, 17, and 9% of the samples, respectively, exceeded the EC50 = 2.3 ng/L for H. azteca. 

The maximum measured lambda-cyhalothrin concentration was 17.5 ng/L in agricultural drain 

samples. Through TIE, it was found that the toxicity of most samples was increased in the 

presence of PBO. A similar effect was observed when the temperature of the samples was 

decreased. In the presence of the enzyme E3, which is capable to degrade the pyrethroids, the 

effect was a decreased toxicity of the samples towards H. azteca. In the presence of bovine 

serum albumin (BSA), no effect on the toxicity of the samples towards H. azteca, was observed. 

The pyrethroid presence in POTWs was unexpected because the effluents had low suspended 

material and for the possible partitioning with biosolids within the plants. The authors indicated 

that possible sources of pyrethroids are sewer disposal of household insecticides, lice control 

shampoos, pet products and permethrin treated clothing. 

Lee (2009) observed the presence of pyrethroid pesticides at the inlet and outlet of four different 

stormwater detention ponds in Alameda and Marin Counties, in northern California, during two 

rain events occurring during the winter and spring (2008-2009). Of the total 18 samples tested, 

66% were toxic to Hyalella azteca. The most toxic samples were collected from the inlets of 

Heron Bay and Tysons Pond sites. Via toxicity identification evaluation (TIE), pyrethroids were 

considered the cause of mortality in every toxic sample. At all sites, there was significant 

difference in toxicity between the inlet and the outlet waters. The ponds showed reductions of 

pesticide concentrations as high as 90% (for the Tysons Pond, which is the largest detention 

pond). Five of 8 pyrethroids were detected in the Alameda County ponds, while only bifenthrin 

was detected in the Marin County pond. Bifenthrin was the most commonly detected pyrethroid 

in Alameda County ponds, followed by cyfluthrin and lambda-cyhalothrin. Permethrin and 

cypermethrin were also detected, but at small concentrations. Samples with less than 1 toxic unit 

(<1 TU) generally were non-toxic to H. azteca while samples with >2 TUs were toxic. The fall 

samples overall had higher populations of H. azteca (as measured 1 week after the first 

significant rain event (11/08), compared to those sampled 1 week after the last rain event 

(3/2009). The author indicated that the number of amphipods could not correlate solely on 

pesticide concentrations, but that other factors may be present. 

The presence of pyrethroids and fipronil in sediments from an urban estuary was presented 

recently by Lao et al. (2010). They tested sediments from the Ballona Creek (in Los Angeles, 

CA), for eight pyrethroids (including lambda-cyhalothrin), using two gas chromatographic 

methods. The observed, that “permethrin, bifenthrin, and cypermethrin were the most abundant 

compounds.” In the 18 sediment samples tested from the Ballona estuary, seven of the eight 

pyrethroids were detected (except fenpropathrin). The sum of toxic units (TU) of pyrethroids 

(based on the LC50 to Hyalella azteca and the observation that H. azteca is approximately twice 

 138
as sensitive to pyrethroids to Eohastorius estuarius, a toxicologically relevant species) was 

estimated and found to significantly correlate to percent mortality of E. estuarius. The lambdacyhalothrin TU values exceeded 1 (one unit) for 3 out of 18 sediment samples. Concentrations 

and TUs of fipronil and degradates were relatively low. The spatial pattern of pyrethroid 

concentrations correlated with fine grained sediments with higher organic carbon (OC) 

concentrations. The pyrethroids alone did not explain the observed toxicity of three sediments 

with relatively low sum of TU of pyrethroids; the authors indicated that it was possible that other 

toxicants may be present in the sediments. 

Pyrethroids were also documented in urban wetlands in southern California, by Brown et al.

(2010), in another recent article. In this extensive study, the team measured sediment toxicity, 

chemistry and macroinvertebrate (MI) community metrics for 21 southern CA wetlands that 

received urban runoff (plus 2 reference wetlands). Several metals, PAHs, PCBs, organochlorine, 

organophosphate and pyrethroid pesticides were tested (10 pyrethroids and pyrethrins, including 

lambda-cyhalothrin). Lambda-cyhalothrin exceeded the Hyalella azteca LC50 (1 toxic unit, TU) 

in 5 out of 23 sites, but it was detected in 8 sites (it was not detected in the reference sites). 

Bifenthrin exceeded 1 TU in 13 out of the 23 sites. Ten sites were toxic to H. azteca. Via 

chemical analysis and toxicity identification evaluation (TIE), the pyrethroids were identified as 

the most plausible cause for the decreased survival to H. azteca species. It was found that an 

index of the degree of sediment contamination correlated negatively with the MI diversity in the 

wetlands. 

In an effort to understand the fate of various insecticides on hardscapes such as concrete, Jiang et 

al. (2010) measured the wash-off potential of pesticides from impervious (concrete) surfaces, as 

possible source of pesticide runoff following applications around homes. Four model 

pyrethroids were used, including lambda-cyhalothrin, and the insecticide fipronil. They studied 

two formulations of lambda-cyhalothrin (granular and liquid), spiking concrete disks as per label 

recommendations and transferring them to outdoors under sunlight. After various intervals, the 

concrete disks were subjected to washing with water (samples were equilibrated with 0.01 M 

CaCl2 solution). In general, the percent of pesticide transferred to water decreased with time, but 

it followed a biphasic pattern, with rapid decrease approximately during the first 7 days (112 day 

study duration). Data from both phases fitted first order decay with good correlations, with 

certain exceptions. The DT50s for lambda-cyhalothrin were as follows: the initial (0-7 days) 

half-lives were 1.1 and 2 days for the liquid formulation and granule, respectively. Final halflives were 6.2 and 35.7 days for the same formulations, respectively. The solid formulations 

(e.g., the granule for lambda-cyhalothrin) appeared to be more persistent overall, which was 

attributed to the solid carrier materials, which may have shielded the test substance from 

exposure to the elements. For lambda-cyhalothrin, the washoff for the day 0 samples was the 

lowest of all the pyrethroids (4.3% and 7.9% for the liquid and the granule, respectively). It was 

speculated that the insecticides may have been irreversibly retained by concrete. Also, washed 

concrete disks pulled 56 days after treatment were thoroughly extracted to determine how much 

pesticide remained in the concrete. After this period of 56 days, 11.0% of the lambdacyhalothrin was extracted with the first acetone extraction from the washed concrete disks 

treated with granular formulation, and only 1.0% from the ones treated with the liquid 

formulation. In an experiment assessing repeated washes of concrete surfaces, it was observed 

that the granule formulation of lambda-cyhalothrin was among the most persistent treatments. 

 139
The authors suggested that concrete surfaces may serve as reservoirs or repositories of 

pyrethroids for extended periods of time, and were possibly “retained below the surface, likely in 

the micropores, due to physical trapping or chemical sorption.” 

Another effort to study pyrethroids on impervious surfaces was offered by Jorgenson and Young 

(2010). They studied the washoff profiles among different formulations, and were led to also 

study the effects of inert ingredients such as surfactants on the wash-off from concrete surfaces. 

Four pyrethroids (three types of formulations and five products), including lambda-cyhalothrin 

(EC dilutable formulation), were used. Analysis of the formulations tested revealed complex 

mixtures. It was determined analytically that four of the five products contained linear 

alkylbenzene sulfonate surfactant (LAS) at various concentrations; thus, LAS was selected as a 

model surfactant to determine the role of formulation components on pyrethroid wash-off. The 

experiments included: formulated products (including lambda-cyhalothrin), neat pyrethroids 

(only esfenvalerate and bifenthrin), and pyrethroid plus LAS (only bifenthrin). These 

researchers used a rain simulator to model runoff events. For the pyrethroids, during a runoff 

event, an initial rapid dissipation was followed by a steadier rate of wash-off in most instances 

(named Type A profile). In other instances, a relatively constant rate of pyrethroid wash-off 

during the whole runoff-event was noted (named Type B profile). Lambda-cyhalothrin EC had 

the third highest wash-off factor in the order of percentages of the total mass applied. Increasing 

the set time decreased the wash-off for all the products. It appeared that the EC formulation 

tended to yield Type B profiles, as observed for lambda-cyhalothrin and esfenvalerate. When 

bifenthrin and esfenvalerate were applied in hexane (as opposed to formulation), the dissipation 

followed the Type B profile. Testing of bifenthrin with LAS surfactant alone, resulted in a Type 

A profile, and in an increase (7-fold) of the total mass wash-off and of the event mean 

concentrations (EMC). However, the total mass removed was not as high as for the formulation 

2007 Bifenthrin CE (microemulsion RTU). The authors indicate that the complexities and 

differences of a formulated product may be responsible for the behavior (order of magnitude 

differences) of the pyrethroids on concrete surfaces. 

Solomon et al. (2001) evaluated the distribution analysis of laboratory aquatic toxicity data for 

several pyrethroids. For lambda-cyhalothrin, the 10th centile value for all organisms was 10 ng/L 

(n = 9). The most sensitive species was A. bahia. Two species were omitted because their 

effects concentrations were in excess of the chemical’s solubility limit. 

In an in-stream mesocosm study, Heckman and Friberg (2005) studied the impact of lambdacyhalothrin on aquatic biota. The study was designed such that the main route of exposure was 

through the water phase due to unidirectional current (stream), which in turn, allowed for the 

measurement of catastrophic drift as an endpoint. Pronounced catastrophic drift was found for 

several taxa, which was also dose dependent and species specific. For the low doses, the 

macroinvertebrate communities were stabilized fast. The lowest concentrations measured were 

indicated to occur under actual use of lambda-cyhalothrin while the highest concentrations were 

indicated to represent worst case conditions. 

In another in-stream design study (Lauridsen and Friberg 2005), stream macroinvertebrates were 

exposed to 1-hour pulse of lambda-cyhalothrin at concentrations ranging from 0.001 to 1.0 μg/L. 

The setup of the experiment was described as seminatural outdoor experimental (stream 

 140
microcosms). The drift response was concentration dependent. Gammarus was found to be the 

most sensitive species. Two insect and one amphipod species responded with catastrophic drift 

even at the lowest concentration (amphipod Gammarux pulex) and at 0.01 μg/L (insects Beatis 

rhodani and Leuctra fusca/ digitata). 

Van Wijngaarden et al. (2006), and Van Wijngaarden et al. (2009), published microcosm studies 

conducted on lambda-cyhalothrin and gamma-cyhalothrin, respectively. The first study used 

macrophyte dominated experimental ditch systems treated in spring and late summer. No major 

treatment related differences were observed between seasons. Only slight and transient effects 

were observed at the community level in the lowest treatment level (10 ng/L). In the second 

study, a laboratory derived HC5 (based on eight species) was 2.12 ng/L for gamma-cyhalothrin, 

compared to the multi-species ecosystem NOECcommunity of 5 ng/L, which were considered 

comparable. 

Kumar et al. 2007 determined the acute 96-hour LC50 of the freshwater species Channa 

punctatus towards cypermethrin and lambda-cyhalothrin. The latter was around 50x more toxic 

with an LC50 of 7.92 μg/L. An EC formulation was used in this test for both chemicals. Effects 

on behavioral patterns were observed at concentrations as low as 0.8 μg/L. 

In 2008, He et al. (of CalDPR and CalEPA) published a comprehensive summary that included 

physicochemical properties, ecological effects and environmental fate of lambda-cyhalothrin. 

The article provides information from literature as well as approved documents and databases. 

Only one highlight is included here. Citing Hamer et al. (1999) information about the 

bioaccumulation of lambda-cyhalothrin to Chironomus riparius in 10 water/sediment systems, 

exposed for a period of 48 hours, it was found that the BCFs were nearly independent from the 

sediment. BCFs ranged from 1,300 to 3,400 (mean 2,300, coefficient of variation 25%), based 

on aqueous phase concentrations. The results support the equilibrium partitioning theory. 

A study was performed to assess the risk of various formulations of lambda-cyhalothrin to 

aquatic organisms in paddy field in China (Gu et al. 2007). Four tests species were used (zebra 

fish, shrimp, crab and clam species). Shrimp was found to be much more sensitive than zebra 

fish to both formulations of lambda-cyhalothrin, but the 2.5% SC formulation was found to be 

less toxic to both species. Lambda-cyhalothrin concentrations decreased to below the limit of 

detection after 5 days of application in the simulated paddy field. The WP and the EC 

formulations dissipated faster than the SC formulation. In the water, the reported half-lives were 

0.23 to 0.53 days; the half-lives in the soil were 0.96 to 7.35 days. The water in the paddy field 

ws drained to a pond from 1 to 4 days after pesticide application. It was found that all 

formulations were safe to shrimp the fourth day. 

A comparison of the acute toxicity of lambda-cyhalothrin and gamma-cyhalothrin towards two 

species (zebra fish and shrimp) was conducted by Wang et al. (2007). The 96-hour LC50 towards 

zebra fish was found to be similar for both chemicals (1.94 and 1.93 μg/L for lambda- and 

gamma-cyhalothrin, respectively). However, both chemicals were much more toxic to shrimp 

(respective LC50s of 0.04 and 0.28 μg/L). In the same study, they observed the fate and effects 

of these chemicals in simulated rice paddies. Following a holding period of 96 hours, no 

lambda-cyhalothrin or gamma-cyhalothrin was detected in the water; but after diluting 5x the 

 141
water, it was still toxic to shrimp. Following a holding period of 7 days and a 5x dilution of the 

water, neither lambda- nor gamma-cyhalothrin were toxic to zebra fish or shrimp. 

In 2009, Giddings et al. compared the toxicities of lambda-cyhalothrin and gamma-cyhalothrin 

towards aquatic invertebrates and fish. They found using a range of species tested for regulatory 

purposes, and species sensitivity distribution curves, that gamma-cyhalothrin was approximately 

twice as toxic as lambda-cyhalothrin. Since the application rate for lambda-cyhalothrin is twice 

that for gamma-cyhalothrin, they concluded that the aquatic risks of these chemicals were in 

essence the same. 

C. Xu et al. (2008) separated the enantiomers of lambda-cyhalothrin using HPLC with various 

chiral stationary phases. They found that the (-) enantiomer was more toxic to zebra fish than the 

(+) enantiomer using standard acute tests and embryo tests. The (+) or (-) assignment was done 

based on their circular dichroism (CD) detector response, coupled with HPLC. The 96-hour 

LC50 was found to be 0.875 μg/L for the racemate, 0.740 μg/L for the (-) enantiomer and <0.012 

μg/L for the (+) enantiomer. For the embrios, the 96-hour LC50 was 1.30 mg/L for the racemate 

and 0.18 mg/L for the (-) enantiomer. The lowest malformation 96-hour EC50 were 0.03, 0.09 

and 0.03 mg/L for the racemate, the (+) enantiomer, and the (-) enantiomer, respectively. 

Much work has been done with lambda-cyhalothrin and its partitioning with vegetation. Hand et 

al. (2001) investigated the influence of aquatic plants on the fate and behavior of lambdacyhalothrin, the extent of adsorption to the plants, and the metabolism of lambda-cyhalothrin in 

water/ plant systems. The mean adsorption KP (the concentration of the analyte in the plant 

material divided by the concentration in the water) were 1,100 and 1,800 L/Kg for two aquatic 

plant species (see also report MRID 44861507, supplemental). Secondly, the authors assessed 

the metabolism of lambda-cyhalothrin in aquatic plants. In the test system, 40-50% of the 

activity was adsorbed to the plant tissue at 1 day, while >70% of the radioactivity was in the 

water after 14 days. Formation of Compound Ia was mainly responsible for this radioactivity. 

For lambda-cyhalothrin, the DT50 in the aqueous phase and the total system was <1 day. Finally, 

in an indoor aquatic microcosm study, by 1 day <10% of the applied lambda-cyhalothrin was in 

the water column and 4.3% was in the plant tissue and 5% of the applied was in the sediment by 

the second day, when a plateau was reached in the sediment. Compound Ia, which was mainly 

associated with the water, reached 42% of the applied by 4 days. The dissipation DT50 of 

lambda-cyhalothrin in the water column and the total system were found to be <3 hours (in both 

cases). It is noted that in the microcosm, a pH of 9.8 was observed, which may have promoted 

the hydrolysis of lambda-cyhalothrin; however, the study suggests that aquatic plants may affect 

the fate of this chemical in aquatic environments (see also report MRID 44861508, 

supplemental). 

Moore et al. (2001) reported on the effects of agricultural vegetated drainage ditches in the 

Mississipi Delta area on atrazine and lambda-cyhalothrin after simulating a storm runoff event. 

Sampling occurred over a 28 day period. After only 1 hour, mean percentages of lambdacyhalothrin in water, sediment and plants were only 12, 1 and 87%, respectively (indicating that 

the plant tissue adsorbs much of the chemical). After 24 hours, 97 and 3% of the lambdacyhalothrin was associated with the plant material and the sediment, respectively. The observed 

half-lives were 14.3, 15.1 and 4.6 days in the plant material, sediment and water, respectively. It 

 142
was predicted through regression analysis that the concentration of lambda-cyhalothrin would be 

below a no effect concentration of 0.02 μg/L 50 meters down the ditch. 

Copper et al. (2002) also explored the potential of agricultural drainage ditches to mitigate 

pesticides in the Mississippi Delta region. In the first part of this study, atrazine and lambdacyhalothrin were used while in the second part bifenthrin and lambda-cyhalothrin were used. 

Within 3 hours of a simulated rain event, 97% and 96% of the measured lambda-cyhalothrin was 

associated with the ditch vegetation in the first and the second parts of the study, respectively. 

At the end of the study 2 ± 1% and 12 ± 16% of the lambda-cyhalothrin was associated with the 

sediment for the first and second part of the study, respectively. The authors discussed that ditch 

vegetation could play an important role in trapping pesticides associated with runoff, and in 

particular, the pyrethroids used on cotton in MS. 

The fate of lambda-cyhalothrin in experimental ditch enclosures with variable levels of 

vegetation and a silty clay loam sediment layer was studied by Leistra et al. (2003). The 

nominal applied concentration was based on a 5% spray drift event (at 0.25 μg/L). Applications 

were performed in May and in August. They observed that the lambda-cyhalothrin 

concentration in the water decreased rapidly; the concentrations of the chemical were lower in 

the enclosures with phytoplankton than in the ones with macrophytes. In the August experiment, 

the concentration of lambda-cyhalothrin was found to be lower with greater plant mass, a trend 

observed at 1 and 3 days. After 7 days, the concentrations of lambda-cyhalothrin were very low. 

Up to 12% of the dose was found in the sediments. The authors indicated that the most likely 

route of dissipation of lambda-cyhalothrin is alkaline hydrolysis in the water. The mean pH 

values were 9.5-10 (registered at noon) in May and 7.6 in August. Another possible route of 

dissipation identified was aqueous photolysis. 

In 2005, Bouldin et al. evaluated the fate and effects of two pesticides (atrazine and lambdacyhalothrin, separately and in combination), in vegetated and unvegetated microcosm in a 

greenhouse. Study design included atrazine, lambda-cyhalothrin, a combination or control, in 

two vegetated monocultures and in a field and ditch sediment-types (a total of 12 microcosms). 

Samples were collected from 3 hours to 28 days postapplication. At 3 hours, the highest 

concentrations of lambda-cyhalothrin were registered. Based on the results, the authors 

concluded that vegetation provides increased binding sites for both chemicals and that they may 

be important in the remediation of pesticides. They indicate that diverse macrophyte 

communities may be required due to the possible co-occurrence of chemicals with diverse 

chemical properties. 

Bennett et al. (2005) evaluated the retention and partitioning of two pyrethroids (bifenthrin and 

lambda-cyhalothrin) in vegetated agricultural ditches in the area of the Mississippi Delta, the 

possible role of aquatic plants to mitigate such chemicals, and the drainage ditch lengths required 

to mitigate the two pyrethroids. They simulated a runoff event by applying bifenthrin and 

lambda-cyhalothrin into a 650-meter ditch segment with approximately 88% vegetative cover. 

Sampling of water, plant and sediment revealed that concentrations in water decreased rapidly 

with distance. This behavior was consistent during the initial 14 days of the study. The 

maximum lambda-cyhalothrin concentration measured at 3 hours (distance of 0 meters) was 375 

μg/L. During and after 14 days, concentrations were below 0.02 μg/L. The maximum 

 143
concentration in plant tissue and sediment was 8.79 mg/Kg (dry weight) within 50 meters of the 

inlet and 0.0538 mg/Kg within the first 25 meters of the ditch system, respectively. Based on 

regression analysis, of concentrations in water, it was found that the first 120 meters of the ditch 

would reduce the concentrations of bifenthrin and lambda-cyhalothrin to 1% of the initial value, 

and 0.1% within 280 meters. Material balance showed that the majority of these pyrethroids 

were in the plant compartment by 12 hours, showing that this compartment may be important 

and effective in the mitigation of the tested substances. It was indicated that relatively little 

partitioning with the sediment was due to the dense plant community. 

Moore et al. 2007 examined the use of constructed wetlands in Leflore County, MS to mitigate 

exposure and ecological impacts in runoff from agricultural fields. The synthetic pyrethroids 

cyfluthrin and lambda-cyhalothrin were used as model contaminants. Testing with Hyalella 

azteca was performed to determine the efficiency of the system. There was spatial and temporal 

variation of the two pyrethroids’ concentrations in water, sediment and leaf litter in all three 

wetland constructed cells. By 61 days, there were little or no pyrethroids in water or leaf-litter. 

The concentration of the pyrethroids decreased with distance from the application point, but 

there was no decrease in the H. azteca toxicity in water during the 61-day observation period 

even though the pyrethroids’ concentrations decreased significantly. The authors concluded that 

the pyrethroids can move, affecting non-target aquatic organisms for weeks to months after 

entering a constructed wetland. 

In 2009, Moore et al. also used cyfluthrin and lambda-cyhalothrin in constructed wetlands 

(comprised of a sediment retention basin, and two treatment cells) in a study lasting 55 days. A 

high percentage of the measured cyfluthrin was associated with vegetation while for lambdacyhalothrin, it was associated with the sediment. It was determined that wetlands lengths of 210-

217 m were required to mitigate inflow of both chemicals from a 14 ha contributing field. 

In a 3-year field test studying honey bee (Apis mellifera) colony health, Chauzat et al. (2009) 

found no residues of cyfluthrin at levels of 0.7 μg/bee (MRID 47775501) (Note that the acute 

contact LD50 for honeybees is 0.037 μg/bee according to registrant-submitted studies). Although 

no statistical significant relationships were found between colony mortality and the presence of 

pesticides overall, the authors state that “more work is needed to determine the role these 

residues play in affecting colony health”. In another study, Dai et al. (2010) examined the 

sublethal effects of two pyrethroids, deltamethrin and bifenthrin, on bee colony health. The 

authors concluded that both chemicals adversely impacted bees by reducing bee fecundity and 

decreasing the rate of bee development into adulthood. 

 144