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Appendix 3. Weiner Study DER

DATA EVALUATION RECORD

12 PYRETHROIDS

OPPTS 

STUDY TYPE: Acute Neurotoxicity (non-guideline)

MRID 47050505 and 47050504 (range-finding)

Prepared for

Health Effects Division

Office of Pesticide Programs

U.S. Environmental Protection Agency

One Potomac Yard

2777 S. Crystal Drive

Arlington, VA 22202

Prepared by

Toxicology and Hazard Assessment Group

Life Sciences Division

Oak Ridge National Laboratory

Oak Ridge, TN 37831

Task Order No. 206-2009

Primary Reviewer:

Carol S. Wood, Ph.D., D.A.B.T.

Date:

Signature:

Secondary Reviewers:

Sylvia S. Talmage, Ph.D., D.A.B.T.

Date:

Signature:

Robert H. Ross, M.S., Group Leader

Date:

Signature:

Quality Assurance:

Kimberly Slusher, M.S.

Date:

Signature:

Disclaimer

This review may have been altered subsequent to the contractor=s signatures above.

Oak Ridge National Laboratory managed and operated by UT-Battelle, LLC., for the U.S. Department of 

Energy under Contract No. DE-AC05-00OR22725.
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EPA Reviewer: Marquea D. King, Ph.D.

Registration Action Branch IV, Health Effects Division (7509P) Date: 

Signature: 

EPA Work Assignment Manager: Lori Brunsman

Science Information Management Branch, Health Effects Division (7509P)Date:

Signature: 

Template version 02/06

TXR: 0055106

DATA EVALUATION RECORD

STUDY TYPE: Acute Neurotoxicity - Rats (non-guideline)

PC CODE: See Table Below DP BARCODE: 363024

Pyrethroid PC Code CAS No.

Beta-Cyfluthrin 118831 68359-37-5

S-Bioallethrin 004004 28434-00-6

Fenpropathrin 127901 39515-41-8

Lambda-Cyhalothrin 128897 91465-08-6

Cypermethrin 109702 52315-07-8

Permethrin 109701 52645-53-1

Resmethrin 097801 10453-86-8

Deltamethrin 097805 52918-63-5

Pyrethrins 069001 8003-34-7

Tefluthrin 128912 79538-32-2

Esfenvalerate 109303 66230-04-4

Bifenthrin 128825 82657-04-3

TEST MATERIAL (PURITY): β-cyfluthrin; S-bioallethrin; fenpropathrin; λ-cyhalothrin; 

cypermethrin; permethrin; resmethrin; deltamethrin; 

pyrethrins; tefluthrin; esfenvalerate; bifenthrin (purity of each 

responsibility of sponsor). 

SYNONYMS: none given

CITATION: Nemec, M.D. (2006) An Acute Functional Observational Battery Comparison 

Study in Rats. WIL Research Laboratories, LLC, 1407 George Road, Ashland, 

OH 44805-9281. Laboratory report numbers: 02-PWG-001 and WIL-409002, 

April 28, 2006. MRID 47050505. Unpublished.

Nemec, N.D. (2005) A Range-Finding Acute Functional Observational Battery 

Study in Rats. WIL Research Laboratories, LLC, 1407 George Road, Ashland, 

OH. November 3, 2005. MRID 47050504. Unpublished.

SPONSOR: Pyrethroid Working Group, Consortium No. 64977, Beveridge and Diamond, 

1350 I Street, NW, Washington, DC 20005
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EXECUTIVE SUMMARY:

In an acute neurotoxicity study (MRID 47050505), Groups of 10 male Crl:CD®(SD)IGS BR rats 

received one of 12 pyrethroid compounds by oral gavage followed by testing in a modified 

Functional Observational Battery (FOB) at the time of peak effect for each compound. Dose 

levels and times of peak effect were established in a range-finding study (MRID 4750504). 

Testing of the chemicals was staggered with several chemicals tested at a time along with a 

concurrent vehicle control group. The vehicle control was Mazola® corn oil. The dose volume 

was 5 mL/kg. A complete necropsy was performed on all animals found dead or euthanized in 

extremis (via carbon dioxide inhalation); surviving animals were euthanized and discarded 

without examination following the FOB evaluation. Time to peak effect and dosing was as 

follows:

2 hours, β-cyfluthrin (12.5, 25, 45 mg/kg), S-bioallethrin (150, 200, 300 mg/kg), fenpropathrin 

(15, 30 mg/kg); 4 hours, λ-cyhalothrin (10, 20 mg/kg), cypermethrin (65, 100, 150 mg/kg), 

permethrin (200, 250 mg/kg), resmethrin (350, 500, 700 mg/kg), deltamethrin (12.5, 25, 35 

mg/kg), pyrethrins (400, 800 mg/kg);

8 hours, tefluthrin (10, 15 mg/kg), esfenvalerate (15, 25, 50 mg/kg), bifenthrin (40, 55 mg/kg).

β-Cyfluthrin: One high-dose animal was found dead; all remaining rats dosed with this chemical 

survived to scheduled termination. Dose-related weight loss was found in the mid- and highdose groups (-9 and -11 g, respectively versus +2 g for controls). During home cage 

observations, an increased number of animals with abnormal posture and drooping eyelids were 

seen at the mid- and high-dose; four animals of the low-dose group were observed with clonic 

convulsions but only one each in the mid- and high-dose groups. In-hand observations revealed 

an increased number of animals with salivation and wet or stained fur at the mid- and high-dose; 

two high-dose animals also exhibited lacrimation. During open field observations, an increased 

number of animals were seen with abnormal gait at all three dose levels and clonic convulsions, 

low arousal and stereotypic behavior at the mid- and high-dose groups; the number of rears was 

slightly decreased in all treated groups. All three treated groups had an increase in the number of 

animals with a more energetic response to tail pinch and the mid- and high-dose groups had a 

decrease in the air righting reflex (slightly uncoordinated). Hind limb weakness was found in 

two animals in each of the mid- and high-dose groups and corresponded with reduced hind limb

grip strength for these groups.

S-Bioallethrin: Two high-dose animals were found dead; all remaining rats dosed with this 

chemical survived to scheduled termination. No effects on body weight were seen. During 

home cage observations, an increase in the incidences of abnormal posture, clonic convulsions, 

and tremors in all three dose groups was found. An increase in the incidences of resistance to 

removal and resistance to handling in all three groups was noted during in-hand observations. 

During open field observations, an increase in the incidences of abnormal gait, clonic 

convulsions, and tremors in all three dose groups were found. All three treated groups showed a 

more energetic startle response, and the high-dose group had a decreased air righting reflex. 

Reduced hind limb grip strength was found in the high-dose group.

Fenpropathrin: All animals survived to scheduled termination. No effects on body weight were 

seen. During home cage observations, slightly increased incidences of abnormal posture and 
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tremors were seen in both treated groups. While handling, slightly increased incidences of 

resistance to removal and salivation were seen in both treated groups; the low-dose group also 

had three animals with resistance to handling but none in the high-dose group. During open field 

observations, increased incidences of abnormal gait, clonic convulsions, tremors, and stereotypic 

behaviors were seen in both treated groups, but were more pronounced at the high dose; the 

number of rears was slightly decreased in the high-dose group. Both groups showed an increase 

in the number of animals with a more energetic response to tail pinch. Reduced hind limb grip 

strength was found in the high-dose group.

λ-Cyhalothrin: All animals survived to scheduled termination. Dose-related weight loss was 

found in both groups (-7 and -9 g, respectively versus +4 g for controls). During home cage 

observations, a dose-related increased number of animals were found with abnormal posture and 

drooping eyelids in both treated groups and clonic convulsions at the high-dose. In-hand 

observations found a dose-related increased number of animals with resistance to removal and 

handling, salivation, and wet or stained fur in both treated groups. During open field 

observations, a dose-related increased number of animals with abnormal gait and stereotypic 

behavior in both treated groups and low arousal at the high-dose were seen; the number of rears 

was slightly decreased in the treated groups. At the high dose, an increased number of animals 

showed no reaction to startle response, touch response, approach response, olfactory orientation, 

decreased hind limb extension, and greatly reduced air righting reflex. In contrast, the high-dose 

group had an increased number of animals with a more energetic reaction to tail pinch. Four 

animals in the high-dose group showed hind limb weakness and mean fore- and hind limb grip 

strengths, landing footsplay, and rotarod performance time were decreased in the high-dose 

group. Mean body temperature was decreased in the high-dose group.

Cypermethrin: All animals survived to scheduled termination. Dose-related weight loss was

found in the mid- and high-dose groups (-2 and -7 g, respectively versus +4 g for controls). 

During home cage observations, the mid- and high-dose groups had a slight increase in the 

incidences of abnormal posture, clonic convulsions, and drooping eyelids. The mid- and highdose cypermethrin groups had increased incidences of resistance to removal and handling (highdose), salivation, wet or stained fur, and lacrimation during handling. During open field 

observations, all three groups had increased incidences of abnormal gait and low arousal and the 

mid- and high-dose groups had a slight increase in the incidences of stereotypic behaviors; the 

number of rears was slightly decreased in all treated groups. The high-dose group had a more 

energetic reaction to startle response and tail pinch but a decrease in olfactory orientation; both 

mid- and high-dose groups had a decrease in number of animals with hind limb extension and 

normal air righting reflex. Fore- and hind limb grip strengths were decreased in the high-dose 

group. Rotarod performance time was reduced in the mid- and high-dose groups. Mean body 

temperature was decreased in the high-dose group.

Permethrin: All animals survived to scheduled termination. No change in body weight, 

compared to a gain in the controls, was observed in the high-dose group. During home cage 

observations, both treated groups showed an increase in clonic convulsions and tremors. Both 

treated groups showed an increase in resistance to removal from the cage. During open field 

observations, both groups showed an increase in abnormal gait, clonic convulsions, and tremors; 

two high-dose animals also displayed stereotypic behavior; the number of rears was slightly 
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decreased in all treated groups. In the high-dose group, an increased number of animals showed 

more energetic approach and startle responses.

Resmethrin: One high-dose animal was found dead; all remaining rats dosed with this chemical 

survived to scheduled termination. No change in body weight, compared to a gain in the 

controls, was observed in the mid- and high-dose groups. During home cage observations, an 

increased incidence was found of abnormal posture at the mid- and high-dose, and clonic 

convulsions and tremors at all three doses. An increased incidence of red deposits around the 

nose in the mid- and high-dose groups was seen during handling. During open field 

observations, an increased incidence of abnormal gait, clonic convulsions, and tremors at all 

three doses was found; the number of rears was slightly decreased in all treated groups. An 

increase in the number of animals with a more energetic startle response was observed at all 

three doses. Rotarod performance time was reduced in the mid- and high-dose groups.

Deltamethrin: All animals survived to scheduled termination. Dose-related weight loss was 

found in all three treated groups (-3, -16, and -18 g, respectively versus +4 g for controls). 

During home cage observations, increased incidences of abnormal posture and clonic 

convulsions at the mid- and high-doses, and biting and drooping eyelids at the high dose were 

observed. In-hand observations showed that incidences of resistance to removal and handling 

were increased in all three dose groups, and salivation, wet or stained fur, and red deposits 

around the nose in the mid- and high-dose groups were increased. During open field 

observations, incidences of abnormal gait were increased in all three groups and clonic 

convulsions, low arousal, and stereotypic behavior were increased at the mid- and high-doses; 

the number of rears was slightly decreased in all treated groups. The high-dose group showed a 

marked increase in the mean time to first step. The high-dose group had an increased number of 

animals with more energetic touch and startle responses as well as an absence of hind limb

extension and all three groups had an increase tail pinch response; greatly diminished air righting 

reflex was found in the mid- and high-dose groups. Two mid-dose and seven high-dose animals 

showed hind limb weakness and mean fore- and hind limb grip strengths were decreased in both 

groups and landing footsplay was reduced in the high-dose group. Rotarod performance time 

was reduced in all groups. Mean body temperature was decreased in the mid- and high-dose 

groups. An increase in the mean catalepsy time was measured in the high-dose group.

Pyrethrins: All animals survived to scheduled termination. No effects on body weight were seen. 

During home cage observations, all high-dose animals showed clonic convulsions. Both treated 

groups had increased incidences of resistance to removal and handling. During open field 

observations, high-dose animals showed tremors, and both treated groups had a low incidence of 

animals with abnormal gait and clonic convulsions. Both groups had a slight increase in the 

number of animals with a more energetic startle response.

Tefluthrin: All animals survived to scheduled termination. No change in body weight, compared 

to a gain in the controls, was observed in both groups. During home cage observations, slight 

increases in the incidence of abnormal posture, clonic convulsions, and tremors were found in 

the high-dose group. The high-dose group had an increased incidence of resistance to removal 

from the cage. During open field observations, both treated groups had increases in the 

incidences of abnormal gait, clonic convulsions, and tremors and the high-dose group had two 
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animals with stereotypic behavior; the number of rears was slightly decreased in all treated 

groups. 

Esfenvalerate: All animals survived to scheduled termination. No change in body weight, 

compared to a gain in the controls, was observed in the mid- and high-dose groups. During 

home cage observations, slight increases in the incidence of abnormal posture, clonic 

convulsions, and tremors were found in high-dose group. During in-hand observations, increases 

in the incidence of resistance to handling and removal, and salivation were noted in the mid- and 

high-dose groups and wet or stained fur was seen in the high-dose group. During open field 

observations, treatment resulted in abnormal gait at all three doses, and clonic convulsions, 

tremors, and stereotypic behaviors in the mid- and high-dose groups; additionally three highdose animals had low arousal; the number of rears was slightly decreased in the mid- and highdose groups. Forelimb grip strength was reduced in the high-dose group.

Bifenthrin: One high-dose animal was found dead; all remaining rats dosed with this chemical 

survived to scheduled termination. Dose-related weight loss was found in both dose groups (-7

and -13 g, respectively versus +5 g for controls). During home cage observations, both treated 

groups showed marked dose-related increased incidences of abnormal posture, clonic 

convulsions, and tremors. Both treated groups showed dose-related increased incidences of 

resistance to removal and handling, salivation, and wet or stained fur. During open field 

observations, both treated groups showed marked dose-related increased incidences of abnormal 

gait, clonic convulsions, tremors, and stereotypic behavior; two high-dose animals had low 

arousal; the number of rears was slightly decreased in the high-dose group. Both groups had an 

increase in the number of animals with a more energetic startle response and an uncoordinated 

air righting reflex. Forelimb grip strength was reduced in both groups.

A NOAEL/LOAEL could not be established for most compounds as effects were observed at all 

doses tested. However, it was not the intent of the study to establish a NOAEL or to clearly 

define the dose-response for each compound. The results of the study demonstrated that the 

FOB can be used to evaluate the acute neurotoxic effects of pyrethroid compounds.

This neurotoxicity study is classified as Acceptable/Non-guideline and does not satisfy the 

guideline requirement for an acute neurotoxicity study in rats (870.6200; OECD 424). The study 

fulfilled the purpose for which it was intended, evaluation of the acute neurotoxic potential of the 

test articles in a FOB comparison using the same methodology and dosing regimen.

COMPLIANCE: Signed and dated GLP, Quality Assurance, and Data Confidentiality 

statements were provided.
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I. MATERIALS AND METHODS:

A. MATERIALS:

The following test substances which appear in the table below were evaluated in this study. Purity 

and stability verification for the test substances were confirmed by the respective suppliers by 

Certificates of Analysis or GLP analysis. All test substance formulations were stirred continuously 

throughout the preparation sampling and dose administration procedures allowing for uniform 

suspensions or solutions. Dose volumes for each animal were based on the technical grade material 

and were not adjusted for purity.

1. Test material: Pyrethrins

Description: Clear, viscous, yellowish-orange liquid

Lot/batch #: 2000/4.2

Purity: 53.755% a.i.

Test material: S-bioallethrin

Description: Clear, yellow liquid

Lot/batch #: 9N0357B

Purity: 95.9% a.i.

Test material: Permethrin Technical

Description: Clear, light brown liquid

Lot/batch #: PL00-0507

Purity: Not given

Test material: Deltamethrin

Description: Fine, off-white powder

Lot/batch #: ABDL0026

Purity: >99.6% a.i.

CAS # of TGAI: 52918-63-5

Structure:

Test material: Beta-cyfluthrin

Description: Fine, off-white powder

Lot/batch #: AS024

Purity: 96.8% a.i.

CAS # of TGAI: 68359-37-5

Structure:

Test material: Tefluthrin

Description: Very light brown solid

Lot/batch #: Y01059/143/002

Purity: 92.4% a.i.

Test material: Cypermethrin Technical

Description: Clear, brown, viscous liquid
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Lot/batch #: PL00-0508

Purity: Not given

Test material: Lambda-cyhalothrin

Description: Yellow solid

Lot/batch #: Y02637/321/001

Purity: 87.7% a.i.

Test material: Fenpropathrin Technical

Description: Yellow to orange fine powder with dark solids

Lot/batch #: AS 459K

Purity: 90.8% a.i.

Test material: Esfenvalerate Technical

Description: Waxy, light brown solid

Lot/batch #: YB656-84

Purity: 98.58% a.i.

Test material: Bifenthrin Technical

Description: Light yellow solid

Lot/batch #: PL00-0509

Purity: Not given

Test material: Resmethrin

Description: Brown solid containing dark brown solids

Lot/batch #: 99N0803B

Purity: 91.9% a.i.

2. Vehicle and/or positive control:

Mazola® corn oil (Bestfoods, Englewood Cliffs, New Jersey) was used as the vehicle and 

negative control. A positive control was not used in this study.

3. Test animals:

Species: Rat (males only)

Strain: Crl: CD®(SD)IGS BR

Age/weight at dosing: 6 weeks; 167-279 g

Source: Charles River Laboratories, Inc., Raleigh, NC

Housing: Individually in wire-mesh cages suspended above cageboard

Diet: Certified Rodent LabDiet® 5002, PMI Nutrition International, Inc. ad libitum

Water: Reverse-osmosis treated municipal water, ad libitum

Environmental conditions: Temperature:

Humidity:

Air changes:

Photoperiod:

19.6-23.2ΕC

40.7-65.6%

Not given

12 hrs dark/ 12 hrs light

Acclimation period: Minimum of 14 days

B. STUDY DESIGN:

1. In life dates: Start: May 7, 2002; End: September 28, 2002

2. Animal assignment and treatment: Animals were assigned to the test groups noted in 

Table 1 by a computerized random sort program based on body weight such that individual 
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body weight was within ±20% of the mean. Rats were given a single dose by gavage in corn 

oil at a volume of 5 mL/kg followed by FOB testing at the time of peak effect. Dose levels 

and time to peak effect were chosen based on a range-finding study (MRID 47050504; see 

Appendix). Following the FOB, survivors were sacrificed and discarded without necropsy. 

The study was conducted in blocks of one to three test articles; each block had a concurrent 

control group. Each control and treated group consisted of 10 males.

TABLE 1. Study design for male rats treated with a pyrethroid prior to FOB testing

Test article Dose Levels

(mg/kg)

Number of 

males Time of peak effect (hr)

Vehicle 0 10/time 2, 4, 8

β-Cyfluthrin 12.5, 25, 45 10/dose 2

S-bioallethrin 150, 200, 300 10/dose 2

Fenpropathrin 15, 30 10/dose 2

λ-Cyhalothrin 10, 20 10/dose 4

Cypermethrin 65, 100, 150 10/dose 4

Permethrin 200, 250 10/dose 4

Resmethrin 350, 500, 750 10/dose 4

Deltamethrin 12.5, 25, 35 10/dose 4

Pyrethrins 400, 800 10/dose 4

Tefluthrin 10, 15 10/dose 8

Esfenvalerate 15, 25, 50 10/dose 8

Bifenthrin 40, 50 10/dose 8

Data from text table p. 12, MRID 47050505.

3. Test Substance preparation and analysis: Dose formulations were prepared as 

weight/volume mixtures. The appropriate amount of the test article was ground using a 

mortar and pestle, if necessary, and weighed into a storage container. A sufficient amount of 

vehicle was added and the formulation mixed overnight using a magnetic stirrer. All 

formulations were stirred continuously throughout dosing. Dose calculations were not 

adjusted for purity. Samples of each dosing formulation were collected on the day of 

preparation, but were not analyzed for concentration, stability, or homogeneity.

Results

Homogeneity analysis: not performed

:

Stability analysis: not performed

Concentration analysis: not performed

4. Statistics: Data are presented as mean ± SD (standard deviation) and the number of animals 

used to calculate the mean. Standard statistical analyses typically performed on FOB data were 

not conducted. The study notes that due to the complexity of the data produced, the sponsor 

analyzed the data set using Principle Component Analysis and Factor Analysis. Some plots from 

that analysis are extracted here. This analysis is reported separately and was not available for 

the current review, therefore, EPA has not performed a formal review of the PCA data (i.e., 
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repeated the analysis) but believes that the procedures conducted are a reasonable approach to 

evaluating these data. (See Breckenridge, C., and Holden, L., 2007. Evidence for separate 

mechanisms of action for Type I and Type II pyrethroid insecticides, PWG study number PWGTOX—2007-001). 

C. METHODS / OBSERVATIONS:

1. Mortality and clinical observations: Animals were observed twice daily for mortality and 

morbidity. Detailed clinical observations were recorded daily except on the day of the FOB.

2. Body weight: Animals were weighed at randomization and prior to dose administration. 

Body weight was also recorded on the day the FOB was performed and prior to sacrifice. 

3. Food consumption: Food consumption was not measured.

4. Cholinesterase determination: Cholinesterase activity was not determined.

5. Neurobehavioral assessment:

a. Functional Observational Battery (FOB): The special FOB was conducted at the time of 

peak effect for each test article. Testing was performed without the technician’s knowledge 

of dose group assignment and inter-observer reliability was established to verify consistency 

among the technicians by verification of training in the laboratory with standard pyrethroids. 

The FOB was performed in a sound-attenuated room equipped with a white noise generator 

set to operate at 70 ± 10 dB, while home cage observations were performed in the animal 

room. Study technicians were given special training to distinguish classical symptoms of 

pyrethroid intoxication. Duration of the open field observation was two minutes.

Detailed scoring criteria were included for each parameter. The standard FOB parameters appear 

in Table 2. The data from the enhanced FOB were divided into 56 numerical analysis variables 

summarized in Table 3 and the correlations between pairs of the four final factors are shown in 

Figure 1 in the results section. The FOB was modified to include additional details (e.g., the 

coarseness of tremor) to distinguish findings particularly associated with pyrethroid intoxication.

For instance, tremors were graded during home cage observations on a scale of coarseness: 

slight, moderate and marked, and extreme. Duration of the open field observation was two 

minutes. Detailed scoring criteria were included for each parameter. The CHECKED (X) 

parameters were examined.
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X HOME CAGE OBSERVATIONS X HANDLING OBSERVATIONS X OPEN FIELD OBSERVATIONS

X Posture* X Reactivity* X Mobility

X Biting X Lacrimation* / chromodacryorrhea X Rearing+

X Convulsions* X Salivation* X Arousal/ general activity level*

X Tremors* X Piloerection* X Convulsions*

Abnormal Movements* X Fur appearance X Tremors*

X Palpebral closure* X Palpebral closure* X Abnormal movements*

X Feces consistency X Respiratory rate+ X Urination / defecation*

X Red/crusty deposits* X Grooming

SENSORY OBSERVATIONS X Mucous membranes /eye /skin 

color X Gait abnormalities / posture*

X Approach response+ X Eye prominence* X Gait score*

X Touch response+ X Muscle tone* X Bizarre / stereotypic behavior*

X Startle response* X Backing

X Pain response* PHYSIOLOGICAL 

OBSERVATIONS X Time to first step

X Pupil response* X Body weight*

X Eye blink response X Body temperature+ NEUROMUSCULAR 

OBSERVATIONS

X Forelimb extension X Hind limb extensor strength

X Hind limb extension OTHER OBSERVATIONS X Forelimb grip strength*

X Air righting reflex+ X Catalepsy X Hind limb grip strength*

X Olfactory orientation X Landing foot splay*

X Rotarod performance

*Required parameters; +Recommended parameters

b. Locomotor activity: Locomotor activity was not evaluated.

6. Sacrifice and pathology: Animals found dead were subjected to a complete gross necropsy. 

All surviving animals were sacrificed by carbon dioxide inhalation after completion of the 

FOB and discarded without examination.

7. Positive controls: Positive control data were not included. The reported stated that the 

technicians were trained to reliably identify all clinical signs of neurotoxicity typically 

expected for pyrethroids and that inter-observer reliability had been established. Reference 

was made to two validation studies, WIL-409006 and WIL-409007 conducted in 2001. It is 

assumed that these studies as well as other positive control data from the testing facility have 

been submitted to EPA and are considered adequate.

II. RESULTS:

A. OBSERVATIONS:

1. Clinical signs: Treatment-related clinical signs were only observed in a few groups. At 25 

and 35 mg deltamethrin/kg, dried yellow matting on the ventral abdominal area was seen in 4 

and 6 animals, respectively; dried brown material at the base of the tail was seen in 5 and 5 

animals, respectively; and dried red material around the eyes and nose was seen in 2 and 2 

animals, respectively. Tremors were observed in one animal administered 55 mg 

bifenthrin/mg.
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2. Mortality: A total of five rats were found dead during the study, one each in the 45 mg βcyfluthrin/kg, 750 mg resmethrin/kg, and 55 mg bifenthrin/kg groups and two in the 300 mg 

S-bioallethrin group.

B. BODY WEIGHT AND BODY WEIGHT GAIN: 

Selected body weight data are shown in Table 3. Only the groups which either lost weight or 

did not gain weight between dosing (day 0) and sacrifice (day 1) are shown with their 

concurrent control group. Dose-related weight loss was found in the mid- and high-dose βcyfluthrin groups, both λ-cyhalothrin groups, the low-, mid-, and high-dose cypermethrin 

groups, the low-, mid-, and high-dose deltamethrin groups, and both bifenthrin groups. No 

change in body weight, compared with a slight gain in the controls, was seen in the high-dose 

permethrin group, the mid- and high-dose resmethrin groups, both tefluthrin groups, and the 

mid- and high-dose esfenvalerate groups.

TABLE 3. Selected body weight data (g ± SD)

Treatment group Day 0 (prior to dosing) Day 1 (post-FOB)

Vehicle 216±11.6 218±12.6

β-Cyfluthrin, 25 mg/kg 215±15.2 206±20.0

β-Cyfluthrin, 45 mg/kg 216±13.9 205±15.5

Vehicle 219±17.9 223±17.5

λ-Cyhalothrin, 10 mg/kg 217±23.4 210±25.2

λ-Cyhalothrin, 20 mg/kg 219±11.6 200±11.0

Cypermethrin, 100 mg/kg 220±11.8 218±12.5

Cypermethrin, 150 mg/kg 222±16.8 215±16.8

Permethrin, 250 mg/kg 217±18.9 216±20.6

Vehicle 243±14.0 247±14.7

Resmethrin, 500 mg/kg 238±18.2 232±24.8

Resmethrin, 750 mg/kg 241±13.6 240±13.1

Deltamethrin, 25 mg/kg 242±16.3 226±25.9

Deltamethrin, 35 mg/kg 241±18.8 223±14.4

Vehicle 233±12.7 238±11.6

Tefluthrin, 10 mg/kg 230±13.2 229±10.9

Tefluthrin, 15 mg/kg 230±18.5 226±22.9

Esfenvalerate, 25 mg/kg 229±16.0 227±16.9

Esfenvalerate, 50 mg/kg 232±16.1 226±17.4

Bifenthrin, 40 mg/kg 232±14.7 225±14.6

Bifenthrin, 55 mg/kg 231±18.6 218±18.8

Vehicle 197±10.4 201±10.7

Deltamethrin, 12.5 mg/kg 197±11.9 194±9.8

Vehicle 210±14.8 211±15.0

Cypermethrin, 65 mg/kg 209±15.5 207±14.3

Data taken from Table 3, pp. 113-120, MRID 47050505.
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C. FOOD CONSUMPTION: 

Food consumption was not measured.

D. CHOLINESTERASE ACTIVITIES:

Cholinesterase activity was not measured.

E. NEUROBEHAVIORAL RESULTS:

1. FOB findings: 

Home cage observations: Findings during home cage observations are shown in Table 4. βCyfluthrin resulted in an increased number of animals with abnormal posture and drooping 

eyelids at the mid- and high-dose; four animals of the low-dose group were observed with 

clonic convulsions but only one each in the mid- and high-dose groups. Treatment with Sbioallethrin caused an increase in the incidences of abnormal posture, clonic convulsions, and 

tremors in all three dose groups. Slightly increased incidences of abnormal posture and 

tremors were seen in both fenpropathrin treated groups. λ-Cyhalothrin resulted in a doserelated increased number of animals with abnormal posture and drooping eyelids in both 

treated groups and clonic convulsions at the high-dose. The mid- and high-dose 

cypermethrin groups had a slight increase in the incidences of abnormal posture, clonic 

convulsions, and drooping eyelids. Both groups treated with permethrin showed an increase 

in clonic convulsions and tremors. Administration of resmethrin resulted in an increased 

incidence of abnormal posture at the mid- and high-dose, and clonic convulsions and tremors 

at all three doses. With deltamethrin, incidences of abnormal posture and clonic convulsions 

at the mid- and high-doses, and biting and drooping eyelids at the high dose were observed. 

All animals treated with the highest dose of pyrethrins showed clonic convulsions. Slight 

increases in the incidence of abnormal posture, clonic convulsions, and tremors were found 

in both the high-dose tefluthrin and high-dose esfenvalerate groups. Both groups treated with 

bifenthrin showed marked dose-related increased incidences of abnormal posture, clonic 

convulsions, and tremors.
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TABLE 4. Findings during home cage observation (no. animals showing sign/no. animals)

Treatment group

Abnormal 

posture

Clonic 

convulsions a Tremors b Biting

Drooping 

eyelids

Vehicle 0/10 0/10 0/10 0/10 0/10

β-Cyfluthrin, 25 mg/kg 5/10 1/10 1/10 0/10 4/10

β-Cyfluthrin, 45 mg/kg 7/10 1/10 1/10 1/10 2/10

S-Bioallethrin, 200 mg/kg 2/10 6/10 5/10 0/10 0/10

S-Bioallethrin, 300 mg/kg 3/10 6/10 6/10 0/10 0/10

Fenpropathrin, 15 mg/kg 2/10 0/10 2/10 1/10 0/10

Fenpropathrin, 30 mg/kg 1/10 1/10 3/10 0/10 0/10

Vehicle 7/10 0/10 0/10 0/10 6/10

β-Cyfluthrin, 12.5 mg/kg 2/10 4/10 0/10 2/10 0/10

S-Bioallethrin, 150 mg/kg 3/10 2/10 3/10 0/10 2/10

Vehicle 1/10 0/10 0/10 0/10 1/10

λ-Cyhalothrin, 10 mg/kg 3/10 1/10 1/10 0/10 2/10

λ-Cyhalothrin, 20 mg/kg 6/10 3/10 1/10 1/10 4/10

Cypermethrin, 100 mg/kg 2/10 3/10 1/10 1/10 2/10

Cypermethrin, 150 mg/kg 4/10 3/10 1/10 0/10 2/10

Permethrin, 200 mg/kg 1/10 3/10 4/10 0/10 0/10

Permethrin, 250 mg/kg 2/10 6/10 9/10 1/10 0/10

Vehicle 3/10 0/10 0/10 0/10 5/10

Cypermethrin, 65 mg/kg 1/10 0/10 0/10 0/10 1/10

Vehicle 0/10 0/10 0/10 0/10 0/10

Resmethrin, 500 mg/kg 5/10 7/10 7/10 0/10 1/10

Resmethrin, 750 mg/kg 2/10 7/10 9/10 0/10 1/10

Deltamethrin, 25 mg/kg 5/10 2/10 0/10 0/10 0/10

Deltamethrin, 35 mg/kg 9/10 4/10 1/10 3/10 4/10

Pyrethrins, 400 mg/kg 0/10 1/10 1/10 0/10 0/10

Pyrethrins, 800 mg/kg 1/10 1/10 2/10 0/10 0/10

Vehicle 1/10 1/10 0/10 1/10 1/10

Resmethrin, 350 mg/kg 1/10 3/10 4/10 0/10 1/10

Deltamethrin, 12.5 mg/kg 3/10 0/10 0/10 0/10 2/10

Vehicle 0/10 0/10 0/10 0/10 0/10

Tefluthrin, 10 mg/kg 1/10 1/10 2/10 0/10 0/10

Tefluthrin, 15 mg/kg 3/10 2/10 3/10 0/10 1/10

Esfenvalerate, 25 mg/kg 1/10 0/10 0/10 0/10 0/10

Esfenvalerate, 50 mg/kg 2/10 3/10 2/10 1/10 0/10

Bifenthrin, 40 mg/kg 3/10 5/10 6/10 0/10 0/10

Bifenthrin, 55 mg/kg 4/10 9/10 10/10 0/10 1/10

Vehicle 3/10 0/10 0/10 1/10 1/10

Esfenvalerate, 15 mg/kg 0/10 0/10 0/10 0/10 0/10

Data taken from Table 4, pp. 121-134, MRID 47050505. a

Includes lying on side or curled up, alert, sitting with head held low, rearing, and prostration. b

Includes twitches of back, head, or body, jerking movements of limbs, whole-body convulsions, and repetitive 

chewing movements.
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Handling observations: Observations recorded while the animals were being handled are 

shown in Table 5. β-Cyfluthrin resulted in an increased number of animals with salivation 

and wet or stained fur at the mid- and high-dose; two high-dose animals also exhibited 

lacrimation. Treatment with S-bioallethrin caused an increase in the incidences of resistance 

to removal and resistance to handling in all three groups. Slightly increased incidences of 

resistance to removal and salivation were seen in both fenpropathrin treated groups; the lowdose group also had three animals with resistance to handling but none in the high-dose 

group. λ-Cyhalothrin resulted in a dose-related increased number of animals with resistance 

to removal and handling, salivation, and wet or stained fur in both treated groups. The midand high-dose cypermethrin groups had increased incidences of resistance to removal and 

handling (high-dose), salivation, wet or stained fur, and lacrimation. Both groups treated 

with permethrin showed an increase in resistance to removal. The only clear effect from 

administration of resmethrin was an increased incidence of red deposits around the nose in 

the mid- and high-dose groups. With deltamethrin, incidences of resistance to removal and 

handling were increased in all three dose groups, and salivation, wet or stained fur, and red 

deposits around the nose in the mid- and high-dose groups were increased. Both groups 

treated with pyrethrins had increased incidences of resistance to removal and handling. The 

high-dose tefluthrin group had an increased incidence of resistance to removal from the cage. 

Increases in the incidence of resistance to handling and removal, and salivation were noted in 

the mid- and high-dose esfenvalerate groups and wet or stained fur was seen in the high-dose 

group. Both groups treated with bifenthrin showed dose-related increased incidences of 

resistance to removal and handling, salivation, and wet or stained fur.
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TABLE 5. Handling observations (no. animals showing sign/no. animals)

Treatment group

Resistance to 

removal

Resistance to 

handling Salivation

Fur 

wetness/staining

Red deposit 

– nose

Vehicle 1/10 3/10 0/10 0/10 0/10

β-Cyfluthrin, 25 mg/kg 0/10 0/10 4/10 2/10 0/10

β-Cyfluthrin, 45 mg/kg 1/10 1/10 10/10 5/10 0/10

S-Bioallethrin, 200 mg/kg 3/10 2/10 2/10 0/10 0/10

S-Bioallethrin, 300 mg/kg 2/10 4/10 1/10 0/10 0/10

Fenpropathrin, 15 mg/kg 4/10 3/10 2/10 0/10 0/10

Fenpropathrin, 30 mg/kg 2/10 0/10 2/10 0/10 0/10

Vehicle 1/10 2/10 0/10 0/10 0/10

β-Cyfluthrin, 12.5 mg/kg 2/10 3/10 0/10 0/10 0/10

S-Bioallethrin, 150 mg/kg 5/10 3/10 0/10 0/10 1/10

Vehicle 2/10 0/10 1/10 0/10 0/10

λ-Cyhalothrin, 10 mg/kg 6/10 2/10 4/10 4/10 0/10

λ-Cyhalothrin, 20 mg/kg 4/10 5/10 10/10 9/10 0/10

Cypermethrin, 100 mg/kg 5/10 0/10 2/10 6/10 0/10

Cypermethrin, 150 mg/kg 6/10 2/10 4/10 8/10 0/10

Permethrin, 200 mg/kg 3/10 0/10 0/10 1/10 0/10

Permethrin, 250 mg/kg 9/10 0/10 1/10 1/10 0/10

Vehicle 1/10 1/10 0/10 0/10 0/10

Cypermethrin, 65 mg/kg 2/10 2/10 1/10 0/10 0/10

Vehicle 2/10 2/10 0/10 0/10 0/10

Resmethrin, 500 mg/kg 2/10 5/10 1/10 0/10 3/10

Resmethrin, 750 mg/kg 2/10 3/10 0/10 1/10 3/10

Deltamethrin, 25 mg/kg 6/10 2/10 5/10 6/10 2/10

Deltamethrin, 35 mg/kg 6/10 3/10 10/10 10/10 2/10

Pyrethrins, 400 mg/kg 2/10 4/10 0/10 1/10 0/10

Pyrethrins, 800 mg/kg 4/10 4/10 1/10 1/10 2/10

Vehicle 1/10 3/10 0/10 0/10 0/10

Resmethrin, 350 mg/kg 1/10 1/10 0/10 0/10 0/10

Deltamethrin, 12.5 mg/kg 3/10 2/10 1/10 0/10 0/10

Vehicle 1/10 4/10 1/10 0/10 1/10

Tefluthrin, 10 mg/kg 2/10 1/10 0/10 1/10 0/10

Tefluthrin, 15 mg/kg 5/10 2/10 0/10 2/10 0/10

Esfenvalerate, 25 mg/kg 4/10 2/10 4/10 0/10 0/10

Esfenvalerate, 50 mg/kg 4/10 4/10 5/10 5/10 1/10

Bifenthrin, 40 mg/kg 4/10 4/10 4/10 3/10 4/10

Bifenthrin, 55 mg/kg 5/10 4/10 2/10 6/10 1/10

Vehicle 0/10 3/10 0/10 0/10 0/10

Esfenvalerate, 15 mg/kg 0/10 1/10 1/10 0/10 0/10

Data taken from Table 6, pp. 149-172, MRID 47050505.
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Open field observations: Findings during the open field observation are shown in Table 6. βCyfluthrin resulted in an increased number of animals with abnormal gait at all three dose 

levels and clonic convulsions, low arousal and stereotypic behavior at the mid- and high-dose 

groups. Treatment with S-bioallethrin caused an increase in the incidences of abnormal gait, 

clonic convulsions, and tremors in all three dose groups. Increased incidences of abnormal 

gait, clonic convulsions, tremors, and stereotypic behaviors were seen in both fenpropathrin 

treated groups, but were more pronounced at the high dose. λ-Cyhalothrin resulted in a doserelated increased number of animals with abnormal gait and stereotypic behavior in both 

treated groups and low arousal at the high-dose. All three cypermethrin groups had increased 

incidences of abnormal gait and low arousal and the mid- and high-dose groups had a slight 

increase in the incidences of stereotypic behaviors. Both groups treated with permethrin 

showed an increase in abnormal gait, clonic convulsions, and tremors; two high-dose animals 

also displayed stereotypic behavior. Administration of resmethrin resulted in an increased 

incidence of abnormal gait, clonic convulsions, and tremors at all three doses. With 

deltamethrin, incidences of abnormal gait were increased in all three groups and clonic 

convulsions, low arousal, and stereotypic behavior were increased at the mid- and highdoses. Animals treated with the highest dose of pyrethrins showed tremors, and both treated 

groups had a low incidence of animals with abnormal gait and clonic convulsions. Both 

groups treated with tefluthrin had increased in the incidences of abnormal gait, clonic 

convulsions, and tremors and the high-dose group had two animals with stereotypic behavior. 

Treatment with esfenvalerate resulted in abnormal gait at all three doses, and clonic 

convulsions, tremors, and stereotypic behaviors in the mid- and high-dose groups; 

additionally three high-dose animals had low arousal. Both groups treated with bifenthrin 

showed marked dose-related increased incidences of abnormal gait, clonic convulsions, 

tremors, and stereotypic behavior; two high-dose animals had low arousal.
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TABLE 6. Open field observations (no. animals showing sign/no. animals)

Treatment group

Abnormal 

gait

Clonic 

convulsions a Tremors b Low arousal

Bizarre 

behavior 

(stereotypic)

Vehicle 1/10 0/10 0/10 0/10 0/10

β-Cyfluthrin, 25 mg/kg 7/10 5/10 0/10 2/10 4/10

β-Cyfluthrin, 45 mg/kg 8/10 2/10 0/10 5/10 4/10

S-Bioallethrin, 200 mg/kg 5/10 5/10 6/10 1/10 0/10

S-Bioallethrin, 300 mg/kg 6/10 7/10 7/10 0/10 0/10

Fenpropathrin, 15 mg/kg 1/10 2/10 1/10 0/10 2/10

Fenpropathrin, 30 mg/kg 4/10 6/10 4/10 0/10 2/10

Vehicle 1/10 0/10 0/10 0/10 0/10

β-Cyfluthrin, 12.5 mg/kg 4/10 0/10 2/10 0/10 0/10

S-Bioallethrin, 150 mg/kg 4/10 3/10 4/10 0/10 0/10

Vehicle 0/10 0/10 0/10 0/10 0/10

λ-Cyhalothrin, 10 mg/kg 5/10 0/10 0/10 1/10 6/10

λ-Cyhalothrin, 20 mg/kg 10/10 0/10 0/10 8/10 5/10

Cypermethrin, 100 mg/kg 8/10 0/10 1/10 4/10 2/10

Cypermethrin, 150 mg/kg 10/10 1/10 1/10 4/10 2/10

Permethrin, 200 mg/kg 2/10 3/10 4/10 1/10 0/10

Permethrin, 250 mg/kg 6/10 4/10 6/10 0/10 2/10

Vehicle 1/10 1/10 1/10 0/10 0/10

Cypermethrin, 65 mg/kg 6/10 0/10 1/10 2/10 0/10

Vehicle 0/10 0/10 0/10 0/10 0/10

Resmethrin, 500 mg/kg 7/10 9/10 9/10 0/10 0/10

Resmethrin, 750 mg/kg 4/10 5/10 10/10 0/10 0/10

Deltamethrin, 25 mg/kg 9/10 1/10 0/10 4/10 3/10

Deltamethrin, 35 mg/kg 10/10 6/10 0/10 7/10 4/10

Pyrethrins, 400 mg/kg 3/10 2/10 1/10 0/10 0/10

Pyrethrins, 800 mg/kg 5/10 2/10 4/10 1/10 0/10

Vehicle 0/10 0/10 0/10 1/10 0/10

Resmethrin, 350 mg/kg 7/10 3/10 9/10 0/10 0/10

Deltamethrin, 12.5 mg/kg 5/10 0/10 0/10 0/10 1/10

Vehicle 0/10 0/10 0/10 0/10 0/10

Tefluthrin, 10 mg/kg 6/10 4/10 3/10 2/10 0/10

Tefluthrin, 15 mg/kg 5/10 5/10 3/10 4/10 2/10

Esfenvalerate, 25 mg/kg 3/10 6/10 2/10 0/10 2/10

Esfenvalerate, 50 mg/kg 9/10 6/10 2/10 3/10 3/10

Bifenthrin, 40 mg/kg 10/10 10/10 9/10 0/10 7/10

Bifenthrin, 55 mg/kg 8/10 10/10 10/10 2/10 8/10

Vehicle 0/10 0/10 0/10 0/10 0/10

Esfenvalerate, 15 mg/kg 4/10 1/10 0/10 0/10 0/10

Data taken from Table 8, pp. 197-216, MRID 47050505. a

Includes walking on tiptoes, dragging body, hind limbs splayed, hunched body, ataxia, and exaggerated hind limb

flexion.

b

Includes twitches of back, head, or body, jerking movements of limbs, whole-body convulsions, and repetitive 

chewing movements.
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Count data: Count data collected during open field observation are shown in Table 7. The 

main effect was a decrease in the mean number of rears for many treated groups although the 

data were highly variable. The mean number of rears was slightly decreased in animals 

treated with β-cyfluthrin, fenpropathrin (high-dose), λ-cyhalothrin, cypermethrin, permethrin, 

resmethrin, deltamethrin, tefluthrin, esfenvalerate (mid- and high-dose), and bifenthrin (highdose). The high dose of deltamethrin also resulted in a marked increase in the time to first 

step. Grooming data were highly variable such that no dose-related trends could be 

discerned.
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TABLE 7. Count data from open field observations (mean ± S.D.)

Treatment group

Time to first step 

(s) Rearing Backing Grooming

Vehicle 0.4 ± 0.07 4.8 ± 3.43 0.0 1.1 ± 1.60

β-Cyfluthrin, 25 mg/kg 0.5 ± 0.44 2.8 ± 3.29 0.0 0.9 ± 1.20

β-Cyfluthrin, 45 mg/kg 0.4 ± 0.09 1.7 ± 1.42 0.0 0.4 ± 0.97

S-Bioallethrin, 200 

mg/kg

0.4 ± 0.21 3.6 ± 3.95 0.0 1.7 ± 2.98

S-Bioallethrin, 300 

mg/kg

0.4 ± 0.14 4.1 ± 4.25 0.0 0.2 ± 0.42

Fenpropathrin, 15 mg/kg 0.3 ± 0.04 5.7 ± 2.21 0.0 2.7 ± 2.58

Fenpropathrin, 30 mg/kg 0.4 ± 0.15 3.3 ± 3.02 0.0 1.8 ± 1.55

Vehicle 0.4 ± 0.23 7.3 ± 1.64 0.0 0.1 ± 0.32

β-Cyfluthrin, 12.5 mg/kg 0.4 ± 0.09 5.8 ± 2.35 0.0 0.0

S-Bioallethrin, 150 

mg/kg

0.5 ± 0.19 6.9 ± 3.03 0.0 0.3 ± 0.67

Vehicle 0.4 ± 0.15 5.3 ± 2.21 0.0 0.6 ± 0.84

λ-Cyhalothrin, 10 mg/kg 0.4 ± 0.18 3.8 ± 2.97 0.0 0.7 ± 0.95

λ-Cyhalothrin, 20 mg/kg 0.5 ± 0.14 0.2 ± 0.42 0.0 0.0 ± 0.00

Cypermethrin, 100 mg/kg 0.4 ± 0.09 2.6 ± 2.37 0.0 0.5 ± 0.85

Cypermethrin, 150 mg/kg 0.5 ± 0.16 1.0 ± 1.89 0.0 0.0 ± 0.00

Permethrin, 200 mg/kg 0.4 ± 0.11 2.9 ± 2.85 0.0 1.1 ± 1.60

Permethrin, 250 mg/kg 0.4 ± 0.22 3.0 ± 2.98 0.0 1.0 ± 0.94

Vehicle 0.5 ± 0.21 6.8 ± 2.57 0.0 0.3 ± 0.48

Cypermethrin, 65 mg/kg 0.8 ± 1.07 4.0 ± 2.11 0.0 0.8 ± 0.92

Vehicle 0.4 ± 0.05 5.5 ± 4.30 0.0 0.2 ± 0.42

Resmethrin, 500 mg/kg 0.5 ±0.14 3.1 ± 3.25 0.1 ± 0.32 0.5 ± 1.08

Resmethrin, 750 mg/kg 0.7 ± 0.39 3.2 ± 2.78 0.0 0.4 ± 0.70

Deltamethrin, 25 mg/kg 0.5 ± 0.23 2.7 ± 3.33 0.1 ± 0.32 0.4 ± 0.97

Deltamethrin, 35 mg/kg 2.1 ± 3.86 0.2 ± 0.42 0.0 0.1 ± 0.32

Pyrethrins, 400 mg/kg 0.4 ± 0.16 5.3 ± 3.27 0.0 0.5 ± 0.53

Pyrethrins, 800 mg/kg 0.5 ± 0.17 5.9 ± 2.92 0.0 0.3 ± 0.48

Vehicle 0.4 ± 0.05 6.7 ± 2.95 0.0 0.1 ± 0.32

Resmethrin, 350 mg/kg 0.5 ± 0.20 3.6 ± 3.03 0.0 0.5 ± 0.71

Deltamethrin, 12.5 mg/kg 0.4 ± 0.16 4.8 ± 3.65 0.0 0.7 ± 0.95

Vehicle 0.4 ± 0.17 6.6 ± 2.07 0.0 0.9 ± 1.10

Tefluthrin, 10 mg/kg 0.4 ± 0.16 3.7 ± 2.58 0.0 0.5 ± 1.27

Tefluthrin, 15 mg/kg 0.6 ± 0.50 1.3 ± 1.25 0.0 0.8 ± 1.03

Esfenvalerate, 25 mg/kg 0.4 ± 0.09 4.2 ± 2.86 0.0 1.7 ± 2.45

Esfenvalerate, 50 mg/kg 0.5 ± 0.19 2.7 ± 2.95 0.0 0.6 ± 0.84

Bifenthrin, 40 mg/kg 0.6 ± 0.56 6.0 ± 5.23 0.0 1.1 ± 1.10

Bifenthrin, 55 mg/kg 0.9 ± 0.79 3.2 ± 3.33 0.0 1.8 ± 1.55

Vehicle 0.4 ± 0.08 5.6 ± 2.27 0.0 0.0

Esfenvalerate, 15 mg/kg 0.6 ± 0.28 6.2 ± 2.49 0.0 0.6 ± 0.84

Data taken from Table 8, pp. 197-216, MRID 47050505.
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Sensory observations: Several findings in the sensory observations showed either an increase 

or decrease to stimuli. Treatment with β-cyfluthrin resulted in an increase in the number of 

animals with a more energetic response to tail pinch in all three groups and a decrease in the 

air righting reflex (slightly uncoordinated) in the mid- and high-dose groups. S-bioallethrin 

resulted in a more energetic startle response in all three treatment groups, and a decreased air 

righting reflex in the high-dose group. Both fenpropathrin groups showed an increase in the 

number of animals with a more energetic response to tail pinch. At the high dose of λcyhalothrin, an increased number of animals showed no reaction to startle response, touch 

response, approach response, olfactory orientation, decreased hind limb extension, and 

greatly reduced air righting reflex. In contrast, the high dose λ-cyhalothrin group had an 

increased number of animals with a more energetic reaction to tail pinch. The high dose of 

cypermethrin resulted in more energetic reaction to startle response and tail pinch but a 

decrease in olfactory orientation; both mid- and high-dose cypermethrin groups had a 

decrease in number of animals with hind limb extension and normal air righting reflex. At 

the high-dose of permethrin, an increased number of animals showed more energetic 

approach and startle responses.

An increase in the number of animals with a more energetic startle response was the only 

effect observed at all three doses of resmethrin. Treatment with deltamethrin resulted in an 

increased number of animals with more energetic touch and startle responses at the high dose 

and tail pinch response at all three doses as well as no hind limb extension at the high dose 

and greatly diminished air righting reflex at the mid- and high-dose groups. Both groups 

administered pyrethrins had a slight increase in the number of animals with a more energetic 

startle response. Both groups treated with bifenthrin had an increase in the number of 

animals with a more energetic startle response and an uncoordinated air righting reflex.

No consistent dose- or treatment-related changes in sensory observations were seen 

following treatment with tefluthrin or esfenvalerate.

Neuromuscular evaluations: Findings from neuromuscular measurements are shown in Table 

8. Hind limb weakness was found in two animals in each of the mid- and high-dose βcyfluthrin groups and corresponded with reduced mean hind limb grip strength for these 

animals. Four animals in the high-dose λ-cyhalothrin group showed hind limb weakness and 

mean fore- and hind limb grip strengths and landing footsplay were decreased in this group. 

Two animals in the mid-dose and seven in the high-dose deltamethrin groups showed hind 

limb weakness and mean fore- and hind limb grip strengths were decreased in both groups 

and landing footsplay was reduced in the high-dose group. Reduced hind limb grip strength 

was also found in the high-dose S-bioallethrin and fenpropathrin groups. Fore- and hind 

limb grip strengths were decreased in the high-dose cypermethrin group. Forelimb grip 

strength was reduced in the high-dose esfenvalerate and both bifenthrin groups.

Rotarod performance time was reduced for the high-dose λ-cyhalothrin, the mid- and highdose cypermethrin, the mid- and high-dose resmethrin, and all three deltamethrin groups.
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TABLE 8. Neuromuscular observations

Treatment group

Hind limb

weakness

Forelimb grip 

strength (g) a

Hind limb

grip strength 

(g)

Rotarod 

performance (s)

Hind limb

footsplay (mm)

Vehicle 0/10 448.2 ± 71.65 175.1 ± 41.97 50.4 ± 47.76 65.2 ± 12.15

β-Cyfluthrin, 25 mg/kg 2/10 327.5 ± 73.62 146.6 ± 24.92 52.0 ± 49.58 55.1 ± 18.73

β-Cyfluthrin, 45 mg/kg 2/10 335.1 ± 120.73 149.3 ± 33.88 94.1 ± 45.69 60.5 ±21.52

S-Bioallethrin, 200 

mg/kg

0/10 406.6 ± 81.27 162.6 ± 61.81 78.6 ± 36.60 64.4 ±13.53

S-Bioallethrin, 300 

mg/kg

0/10 330.8 ± 70.29 133.4 ± 31.27 48.0 ± 49.50 49.1 ± 20.87

Fenpropathrin, 15 mg/kg 0/10 378.3 ± 109.09 156.6 ± 36.51 86.3 ± 48.77 60.2 ± 16.30

Fenpropathrin, 30 mg/kg 0/10 418.3 ± 86.78 141.8 ± 40.50 93.0 ± 39.71 64.1 ± 19.48

Vehicle 0/10 490.1 ± 86.73 264.1 ± 36.39 87.1 ± 46.69 61.9 ± 10.75

β-Cyfluthrin, 12.5 mg/kg 0/10 478.3 ± 111.93 252.5 ± 30.40 99.9 ± 33.66 75.5 ± 13.53

S-Bioallethrin, 150 

mg/kg

0/10 436.7 ± 88.84 270.8 ± 55.47 48.4 ± 42.46 64.7 ± 9.62

Vehicle 0/10 510.9 ±72.28 235.1 ± 40.56 95.3 ± 43.54 71.1 ± 8.97

λ-Cyhalothrin, 10 mg/kg 0/10 513.3 ± 156.62 195.9 ± 51.85 109.8 ± 29.84 67.4 ± 14.00

λ-Cyhalothrin, 20 mg/kg 4/10 341.8 ± 154.44 153.2 ± 50.70 53.2 ± 45.34 51.0 ± 21.85

Cypermethrin, 100 mg/kg 1/10 463.4 ± 80.29 189.2 ± 46.82 79.9 ± 51.61 78.2 ± 11.68

Cypermethrin, 150 mg/kg 0/10 374.9 ± 107.41 156.6 ± 56.78 38.5 ± 43.81 66.4 ± 18.45

Permethrin, 200 mg/kg 0/10 423.2 ± 136.26 204.3 ± 52.20 94.6 ± 33.84 76.5 ± 13.18

Permethrin, 250 mg/kg 0/10 426.0 ± 86.69 180.7 ± 45.38 108.7 ± 35.73 66.8 ± 12.16

Vehicle 0/10 492.4 ± 91.62 279.1 ± 53.55 86.8 ± 43.93 65.3 ± 13.63

Cypermethrin, 65 mg/kg 0/10 505.8 ± 50.62 285.0 ± 63.34 82.4 ± 39.25 69.0 ± 5.75

Vehicle 0/10 518.4 ± 102.52 240.0 ± 60.47 85.9 ± 42.45 72.6 ± 12.38

Resmethrin, 500 mg/kg 0/10 410.1 ± 113.58 199.1 ± 40.73 55.7 ± 39.06 69.9 ± 12.86

Resmethrin, 750 mg/kg 0/10 517.4 ± 102.30 202.4 ±68.83 63.3 ± 41.04 64.0 ± 15.03

Deltamethrin, 25 mg/kg 2/10 325.1 ± 166.21 148.2 ± 57.40 73.3 ± 52.54 59.2 ± 21.83

Deltamethrin, 35 mg/kg 7/10 175.8 ± 130.48 85.7 ± 34.63 30.3 ± 49.97 45.9 ± 22.68

Pyrethrins, 400 mg/kg 0/10 543.5 ± 103.75 260.0 ± 48.46 93.7 ± 40.90 79.0 ± 12.62

Pyrethrins, 800 mg/kg 0/10 439.1 ± 99.20 177.4 ± 43.80 109.7 ± 25.22 66.0 ± 15.74

Vehicle 0/10 483.4 ± 74.73 265.7 ± 38.61 106.2 ± 30.16 72.0 ± 10.65

Resmethrin, 350 mg/kg 0/10 406.7 ± 74.40 244.2 ± 31.15 82.3 ± 45.49 70.2 ± 14.40

Deltamethrin, 12.5 mg/kg 0/10 430.9 ± 96.20 214.2 ± 55.73 76.7 ± 55.98 57.3 ± 14.19

Vehicle 0/10 536.6 ± 118.13 238.2 ± 47.48 69.8 ± 50.43 66.6 ± 13.91

Tefluthrin, 10 mg/kg 0/10 450.7 ± 136.26 221.6 ± 69.58 109.0 ± 34.88 59.9 ± 17.25

Tefluthrin, 15 mg/kg 0/10 417.4 ± 151.71 188.3 ± 66.19 83.5 ± 50.75 65.1 ± 12.69

Esfenvalerate, 25 mg/kg 1/10 410.9 ± 115.24 214.0 ±82.86 108.5 ± 35.36 53.8 ± 19.93

Esfenvalerate, 50 mg/kg 0/10 379.0 ± 79.71 184.4 ± 34.82 64.0 ± 44.06 54.8 ± 22.65

Bifenthrin, 40 mg/kg 0/10 300.8 ± 102.10 170.1 ± 61.20 77.3 ± 50.29 53.6 ± 11.58

Bifenthrin, 55 mg/kg 1/10 311.6 ± 71.25 177.6 ± 58.86 50.2 ± 52.27 46.9 ± 12.04

Vehicle 0/10 456.6 ± 95.80 264.3 ± 50.40 112.8 ± 15.83 69.3 ± 13.34

Esfenvalerate, 15 mg/kg 0/10 385.1 ± 79.42 236.0 ± 42.15 88.3 ± 38.62 59.8 ± 19.54

Data taken from Table 12, pp. 169-276, MRID 47050505. a

No. animals showing some weakness/No. tested
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Physiological measurements: Mean body temperature was decreased in the mid- and highdose β-cyfluthrin, high-dose λ-cyhalothrin, high-dose cypermethrin, and mid- and high-dose 

deltamethrin groups. An increase in mean catalepsy time was measured in the high-dose 

deltamethrin group. The other test articles did not affect body temperature or catalepsy time.

2. Motor activity: Motor activity measurements were not done.

F. SACRIFICE AND PATHOLOGY:

1. Gross pathology: The high-dose bifenthrin animal that was found dead had dark red areas in 

the glandular portion of the stomach. No gross lesions were seen in the other animals that 

died on study. The surviving animals were sacrificed and discarded without examination.

2. Brain weight: Brain weight was not recorded.

3. Neuropathology: No neuropathology investigations were done.

III. DISCUSSION AND CONCLUSIONS:

PCA INFORMATION: 

Principal Component Analysis (PCA) and Factor Analysis (FA) are techniques which are 

powerful statistical tools suited for the present dataset. The PCA approach is able to 

simultaneously analyze 56 separate neurobehavioral findings across the 38 control and treatment 

groups that comprise this study in an objective manner. PCA also avoids the limitations of visual 

or subjective examination. PCA can demonstrate associations or correlations empirically, based 

on mathematical models. Such associations provide a deeper and more rigorous understanding of 

possible patterns of pyrethroid toxicity syndromes. 

In the PWG analysis, the different behavioral response patterns of pyrethroids were defined by 

four principal components, which demonstrate a dose response relationship with one or more 

pyrethroids. Based on this analysis, individual chemicals were arrayed by a group of highly 

correlated (p>0.5) behaviors, which constituted principle component factors. The non-cyano 

pyrethroids tended to array themselves in a dose-response manner primarily along two of the 

principal components that were described by the following behavioral effects: tremors, 

myoclonus, elevated temperature, exaggerated response to sensory stimuli, difficulty handling, 

head flicking, jerking movements, pulsating eyes (spontaneous nystagmus). The cyano 

pyrethroids arrayed themselves in a dose-related manner, primarily along two different principal 

components described by these behavioral effects: excessive salivation, impaired mobility, lower 

temperature, non-reactivity to sensory stimuli, lacrimation, writhing, neuromuscular weakness, 

abnormal posture.

Table 10 defines the four primary patterns of variation in the FOB data that were attributed to 

pyrethroid effects. For ease of comparison, the principle components that best described the 
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Type I pyrethroids were designated Ta and Tb, while those for Type II pyrethroids were labeled 

CSa and CSb. 

Extracted from p. 107 in PWG Study Number: TOX-2007-01

A. INVESTIGATOR’S CONCLUSIONS:

The study author concluded that the FOB findings in this study were consistent with the 

known effects of pyrethroid compounds including tremors, body dragging, ataxia, profuse 

salivation, clonic convulsions, abnormal hind limb function, and writhing. Findings in the 

pyrethrins and tefluthrin groups were limited to effects on CNS and neuromuscular 

parameters. The remaining compounds also affected autonomic endpoints. The author also 

mentioned that two patterns of clinical signs could be statistically distinguished by the 

principle component analysis and factor analysis of the FOB data. These patterns were 

defined as Type I (or T) syndrome, characterized by the occurrence of tremors, and the Type 

II (or CS) syndrome, associated with choreoathetosis and salivation.

B. REVIEWER COMMENTS:

A modified FOB was used to evaluate the effects of twelve pyrethroid compounds in rats. The 

reviewer agrees with the study author in that the results are consistent with this class of chemical. 

Doses and time to peak effect were appropriately chosen for each compound based on the results 

of the range-finding study. Despite similarity of effects, a wide range of potency was evident in 

the doses used and severity of findings for the individual compounds. Deaths of five animals are 

considered treatment-related as they occurred at the highest dose administered for four of the 

compounds.

A NOAEL/LOAEL could not be established for most compounds as effects were observed at all 

doses tested. However, it was not the intent of the study to establish a NOAEL or to clearly 

define the dose-response for each compound. It is unfortunate that the statistical analyses 

discussed by the study author were not available to the current reviewer.
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The results from the present study are consistent with the early reports of differences in 

behavioral response patterns associated with Type I and Type II pyrethroids, which were 

described by Vershoyle and Aldridge (1980), Casida et al. (1983) and Soderlund et al. (2002). 

The results from this study indicate that some pyrethroids clearly exhibit the historic 

classification symptoms of the T and CS syndromes while others do so less obviously. 

Use of the statistical technique of Principal Component Analysis (PCA) further helped interpret 

the study findings. Based on a review of the FOB data, analyzed by PCA, and other in vivo and 

in vitro published data, two common mechanism groups are proposed by the Agency. Type I 

would include pyrethrins, bifenthrin, resmethrin, permethrin, S-bioallethrin and tefluthrin. Type 

II would include cypermethrin, deltamethrin, β-cyfluthrin and λ-cyhalothrin, while fenpropathrin 

and esfenvalerate exhibited features of both groups.

C. STUDY DEFICIENCIES:

No deficiencies were noted in the conduct of this non-guideline study that would prevent 

interpretation of the results.
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APPENDIX: Range –Finding Study - Functional Observational Battery for Pyrethroids

TEST MATERIAL (PURITY): See Appendix Table below.

CITATION: Nemec, N.D. (2005) A Range-Finding Acute Functional Observational Battery 

Study in Rats. WIL Research Laboratories, LLC, 1407 George Road, Ashland, 

OH. November 3, 2005. MRID 47050504. Unpublished.

SUMMARY: Groups of 5 male Crl: CD®(SD)IGS BR rats received one of 12 pyrethrin 

compounds at each dose by oral gavage in order to determine dose levels and to establish times 

of peak effect of 12 pyrethroid compounds. Testing of the chemicals was staggered with several 

chemicals tested at a time along with a concurrent vehicle control group. The vehicle control 

was Mazola® corn oil. The dose volume was 5 mL/kg. Following completion of the initial 

dosing, additional dosage levels of β-cyfluthrin, deltamethrin, pyrethrins and tefluthrin were 

evaluated to more fully characterize the neurotoxicity or time of peak effect. Rats were treated 

on day 0 and sacrificed on day 1. All animals were observed for clinical signs and mortality 

prior to dosing and on study days 0 and 1. Animals were weighed on study days -3, -1, 0, and 1. 

Neurotoxic effects and time of peak effect were evaluated during a modified functional 

observational battery (FOB). The FOB was conducted at 3-4 specific times (2, 4, 8, or 12 hours, 

depending on the specific compound) on the day of test material administration. A complete 

necropsy was performed on all animals found dead or euthanized in extremis (via carbon dioxide 

inhalation); surviving animals were euthanized and discarded without examination following the 

FOB evaluation. For each chemical, dose level and time of peak effect during the FOB is 

provided in the Appendix Table. Time of peak effect was generally from 2-8 hours post-dose. 

Only the predominant clinical signs are summarized in the Table. Not all animals in a group 

displayed all signs. Small group mean body weight losses were noted at the higher dose levels 

for several chemicals. Losses were also noted in several concurrent control groups. 

Macroscopic examination revealed red discoloration or multiple dark red areas in the lungs of 

one animal in each of the high-dose groups of deltamethrin, λ-cyhalothrin, and bifenthrin. Other 

observations were incidental to treatment.

Compliance: Signed and dated GLP, Data Confidentiality, and Flagging statements were 

provided.
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Appendix Table. Mortality, Time of Peak Effect, and Clinical Signs in Male Rats Administered 1 of 12 Pyrethroid Compounds

(Clinical signs and time of peak effects observed during Functional Observational Battery)

Chemical (purity) Doses tested (mg/kg) Mortality by dose

(no of animals/no of 

animals tested)

Dose/Time of 

Peak Effect

after dosing

Clinical signs

Pyrethrins (53.8%) 150, 250, 350, 375, 400 No mortality 400, 800: 4 hours Impaired mobility, altered gait, 

convulsions, tremors, stereotypic 

behavior, difficulty in removal from cage

Deltamethrin (>99.6%) 20, 30, 35, 40, 50 30: 5/5

40: 5/5

50: 5/5

25, 35: 4 hours Salivation, whole-body convulsions, 

splayed hind limbs, writhing

S-Bioallerethrin (95.9%) 150, 250, 300 No mortality 200, 300: 2 hours Tremors, body dragging, ataxia

β-Cyfluthrin (96.8%) 5, 25, 45, 60, 75 60: 1/5

75: 5/5

25, 45: 2 hours Salivation, whole-body convulsions, 

splayed hind limbs, writhing

Tefluthrin (92.4%) 5, 10, 15, 20 20: 2/5 10, 15: 8 hours Tremors, gait abnormalities, whole-body 

convulsions 

Cypermethrin (not provided) 100, 150, 200 100: 1/5

200: 2/5

100, 150: 4 hours Salivation, whole-body convulsions, 

splayed hind limbs, writhing

Permethrin (not provided) 200, 250, 300 300: 2/5 200, 250: 4 hours Tremors, body dragging, ataxia

λ-Cyhalothrin (87.7%) 10, 20, 35 35: 1/5 10, 20: 4 hours Salivation, whole-body convulsions, 

splayed hind limbs, writhing

Fenpropathrin (90.8%) 10, 20, 30 No mortality 15, 30: 2 hours Difficulty in handling, tremors, clonic 

convulsions, low arousal

Esfenvalerate (98.6%) 5, 25, 50 No mortality 25, 50: 8 hours Difficulty in handling, salivation, slight 

tremors, altered gait/mobility, clonic 

convulsions

Bifenthrin (not provided) 40, 55, 70 70: 1/5 40, 55: 8 hours Vocalization, salivation, alterations in 

gait, impaired mobility, ataxia

Resmethrin (91.1%) 500, 750, 900 500: 1/5

900: 1/5

500, 750: 4 hours Tremors, clonic convulsions, salivation, 

impaired mobility

Dose calculations not adjusted for purity.