### DATA EVALUATION RECORD Tribenuron Methyl PC Code: 128887 TXR#: 00562 13 MRID#: 48737601 Study Ty pe: Subchronic Neurotoxicity Study in Rats; OPPTS 870.6200 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 b y Tetrahedron Incorporated 1414 Key Highway , Suite B Baltimore, MD 21230 Principal Reviewer:

______________________________________ Date: 4/23/2012 Ahmed Elnabawi, Ph.D. Secondary

Reviewer: _____________________________________ Date: 4/24/2012

Katherine Squibb, Ph.D. Quality Assurance: _________________________________________ Date: 4/26/2012

Nasrin Begum, Ph.D. Contract Number: EP
- W
- 10013 Work Assignment No.: WA
- 0
- 01 Task Number: 1
- 1
- 8 7 EPA Reviewer//WAM: Christina Swartz and Alan L evy// Kit Farwell and Lori Brunsman **Disclaimer This review may have been altered by the EPA subsequent to the contractors’ signature**  **above.**Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 2 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### EPA Reviewer: Jaime D’Agostino **Signature** : **Risk Assessment Branch 2**  **, Health Effects Division (7509P) Date:**  **Work Assignment Manager** : Lori B run sman **Signature** : **Science Info. Mgmt. Branch, Health Effects Division (7509P)**  **Date: Template version 09/11**  

### TXR# **:** 005 6 2 1 3 **DATA EVALUATION RECORD STUDY TYPE**  **:** Subchronic Neurotoxicity , (oral, feeding)

– (rat); OPPTS 870.6200b [§82
- 7 ] , **PC CODE :**  128887 **DP BARCODE :**  D397 466; D39 8740; D39 8929 **TEST MATERIAL (PURITY) :**  Tribenuron Methyl (DPX
- L5300) ( 9 8.2 % a.i.). **SYNONYMS :**  Methyl2
- [4
- methoxy
- 6
- methyl
- 1,3,5
- triazin
- 2
- yl (methyl)carbamoyl]benzoate;

Methyl 2
- [ [[[(4
- methoxy
- 6
- methyl
- l,3,5
- triazin
- 2
- yl ) methylamino] carbo n]amino]sulfonyl] benzoate; DPX
- L5300
- 281. **CITATION :**  Carpenter, C. (20 1 2 ). Tribenuron Methyl (DPX
- L5300) Technical: Subchronic

Oral Neurotoxicity

Study in Rats
. E.I . du Pont de Nemours and Company , DuPont Haskell Global Centers for Health and Environmental Sciences, Newark, Delaware, U.S.A . Laboratory project number s : DuPont
- 3 337 1 , January 27 , 20 1 2
. MRID 48 73 7601 . Unpublished
. **SPONSOR :**  E.I . du Pont de Nemours and Company , Wilmington, Delaware 19898, U.S.A. **EXECUTIVE SUMMARY :**  In a subchronic neurotoxicity study (MRID 4 8 73 7601 ) , Tribenuron Methyl (DPX
- L5300) ( 98.2 % a.i., batch # MAY10MA047 ) w as administered in the diet to Crl:CD(SD) rats ( 1 2 /sex/dose ) at concentration levels of 0, 50, 200, or 700 ppm (equivalent to 0/0, 2.8/3.2, 11.3/12.8, and 40.1/46.6 mg/kg/day

in males and females, respectively) for approximately 90 days Neurobehavioral assessment (functional observational battery and motor activity testing) was performed o n all animals prior to test substance administration (baseline ), and during Weeks 4, 8, and 13. At study

termination (D ays 95 and 96), 6 animals/sex in the control and high dose groups were euthanized and perfused in situ for neurop athological examination. The brain and peripheral nervous s ys tem tissues collected from the perfused animals in the control and 700 ppm groups were subjected to histopathological evaluation. There were no treatment - related effects on mortality or clinical signs at any dietary concentration level s in males and females. Treatment
- related effects on body weights and body

weight gains were evident at the dietary concentration level of 700 ppm in males and females, but not at 50 ppm or 200 ppm. Body weights were significantly reduced by ↓6
- 12% (Day 7 through 91) in males and ↓6
- 13% (Day 14 through 91) in females. Mean body weight gains were significantly decreased by ↓20
- 34% onSubchronic Neurotoxicity Study (rats) (201 2 ) /Page 3 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### Day 0
- 7, Day 14
- 21, Day 21
- 28, Day 0
- 28, Day 42
- 4 9 , and Day 28
- 56 in the 700 ppm males
. In the 700 ppm females, mean body weight gains were significantl y decreased by ↓ 23
- 37% on test Day 0
- 7 , Day 0
- 28, Day 28
- 56, and Day 56
- 91. Overall (Day 0
- 91) body weight gains were significantl y decreased by 20% and 2 9% in males and females, respectivel y , in the 700 ppm groups . Treatment
- related decreases on food consumption and food efficiency were also evident in the 700 ppm males and females. Lower (p ≤0.05) overall (Day 0
- 91) mean food consumption was noted at 700 ppm in males ( ↓ 7%) and females ( ↓ 6%). In addition, overall (Day 0
- 91) mean food efficiency

at 700 ppm was significantly decreased b y ↓14% and ↓24% in males and females, respectivel y. No treatment - related effects on FOB (home cage, open field, removal from the home cage and handling) parameters, rearing, hindlimb grip strength, body temperature or motor activity (duration of movements and number of movements) were observed at any dose level in either sex. However, decreased (p ≤0.05) forel imb grip strength was noted in the 700 ppm males ( ↓ 19%) during Week 13 compared to control, but not in the females. In addition, hindlimb splay was significantly

decreased by ↓ 23
- 24% at 50, 200, and 700 ppm in males during Week 13, but there was no effect on females. The decreases in forelimb grip strength and hindlimb splay observed in males were not considered treatment related, however, since the mean values were similar to or within the historical control mean data, and the mean of the control values ex ceeded the historical control mean and range. In addition, there were no effects on forelimb grip strength in any other male exposure groups (50 ppm or 200 ppm) or in any of the exposed females. No treatment - related alterations were observed in gross his topathology observations or microscopic neurohistopathology in the 7 00 ppm male and female groups
. It is concluded that there were no neurotoxic effects observed at any dietary concentration level , based on the lack of altered behavior in the FOB parameters, no significant changes observed on motor activity (duration of movements and number of movements) , and no effects on the macroscopic and microscopic pathology of nervous system tissues. However, systemic toxicity was apparent in the 700 ppm males and females. This was characterized by decreased body weight and body

weight gains , and significant reductions in food consumption, and food efficiency
. **T he**  **L OAEL**  **is 700**  **ppm for males and females**  **(equivalent to 40.1/46.6 m g** **/kg/day, respectively** **), based on**  **decreased body weight and body weight gains, reduced food consumption, and food efficiency,**  **with a NOAEL of**  **200 ppm for males and females (equivalent to 11.3/12.8 m**  **g /kg/day,**  **respectively )**  **. There w**  **ere no treatment -**  **related neurotoxic signs observed in the study.**  This study is classified as **acceptable/guideline** and satisfies the guideline requirement ( OPPTS 870.6200b ; OECD 424 ) for a subchronic neurotoxicity study in rats. **COMPLIANCE :**  Signed and dated GLP, Quality Assurance, Flagging, and Data Confidentiality (no claim of confidentiality under FIFRA, but waiver does not appl y to other regulatory agencies and information is labeled trade secret) were provided.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 4 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200b/ MAFF 12 Nousan 8147/OECD 424 

### I. **MATERIALS AND METHODS: A.**  **MATERIALS :**  **1. Test material**  **:** Tribenuron Methyl(DPX
- L5 300) Technical **Description:** Solid **Lot/Batch #:** MAY10MA047 **Purity:** 98.2 % a.i. **Compound Stability:** The test substance was stable in the diet for up to 15
- days refrigerated
. **CAS # of TGAI:** 101200
- 48
- 0 **Structure:**



### 2. **Vehicle :**  Diet
. **3. Test animals**  **: Species:**  Rat **Strain:** Crl : CD(SD ) **Age/w eight at study initiation:**  50 days of age
. Males: 199.8
- 255.5 g; Females: 160.3
- 193.4 g . **Source:** Charles River Laboratories International, Inc., Kingston, NY
. **Housing:** Housed in pairs in solid bottom caging with bedding mixed with enrichment (Shepherd’s TM Cob + PLUS TM). **Diet:** PMI ® Nutrition International, LLC Certified Rodent LabDiet ® 5002 , ad libitum , except during neurobehavioral testing
. **Water:** Tap water, ad libitum , except during neurobehavioral testing
. **Environmental conditions: Temperature:**  **Hum idity:**  **Air changes: Photoperiod:**  18
- 2 6 °C

30
- 70 % Not stated 12 hrs dark / 12 hrs light **Acclimation period:** 1 2 days 

### B. **STUDY DESIGN :**  **1. In life dates:**  Start: July 8 , 20 1 1 ; End: October 12 , 20 11
. **2. Animal assignment and**  **dose rational :**  Animals were randomly assigned to the test groups noted in Table 1 using a weight stratification
- based computer program. The body weights of all animals were within ±20% of the mean weight for each sex. Following assignment to groups, rats were subdivided into 4 replicates, each of which contained an equal representation of each group and sex. Test substance was administered ora lly in the diet to rats at dietary

concentration levels of 0, 50 , 2 00 and 7 00 ppm for 90 days (96 or 97 days). Dose levels were chosen based on the results of two studies: (1) a subchronic toxicity study in rats, conducted with the test substance at conc entration levels of 100, 1,750 and 5,000 ppm (MRID 00148638) and (2) a 2
- generation reproduction study in rats, conducted with test substance at dietary

concentration levels of 0, 25, 250 and 1,000 ppm (MRID 40245515)
.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 5 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### In the subchronic toxicity study , re duced body

weights and reduced food consumption/efficiency

were observed at a dietary concentration level of 1,750 ppm in males and females. In addition, changes in clinical chemistry parameters and in organ weights were noted in the 1,750 ppm group males and females. Therefore, the no - observed
- adverse
- effect level (NOAE L) for the subchronic toxicity study was 100 ppm. In the 2
- generation rat reproduction study , the NOAELfor parental s ys temic toxicity during the 70
- day

pre - mating phase was 25 ppm, based on reduced mean body weights and body weight gains in males and females at 250 ppm and above. Based on these combined results, the concentration levels selected for the current study were 5 0, 2 00 and 700 ppm (Table 1)
. The hi ghe st dose was expected to result in reduction in body weight and/or nutritional parameters. The 50 ppm and 200 ppm concentration s were expected to demonstrate an absence of or decreased severity of these parameters and to define the NOAEL
. **TABLE 1. Stud y Design** 

**Experimental param eter**  **Concentration in Diet (ppm) 0**  **5 0**  **2 00**  **7 00**  **Achieved dose (mg/kg/day; M/F)** 0/0 2.8/3.2 11.3/12.8 40.1 /46.6 **Total number of anim als/sex/group**  12 12 12 1 2 **Behavioral testing (FOB, Motor activity)** 1 2 /sex 1 2 /sex 1 2 /sex 1 2 /sex **Neuropathology (m** **icroscopic evaluation)** 6 /sex 0 /sex 0 /sex 6 /sex Concentrations of test substance were adjusted for purity
. Data were extracted from page 12 and 14 of the study report. 

### 3. **Test Substance preparation and analysis :**  All diet formulations were prepared weekl y by mixing appropriate amounts of test substance with the diet (PMI ® 

### Nutrition International, LLC Certified Rodent LabDiet® 

### 5002) and stored refrigerated until filling the feeders
. Homogeneity

and concentration anal ys es of test substance were verified in samples (top, middle and bottom) of all dietary concentrations at the start of the study . Stability of test substance in the diet was verified at concentration s of 50, 200 and 700 ppm for approximately

22 days at room temperature storage prior to the start of the study
. Based on the results additional samples were anal yz ed that had been stored up to one week at room temperature, refrigerated for 15 days, and refrigerated for 15 days followed by one week at room temperature . **Results Homogeneity analysis (**  **% RSD):** ≤ 1 %. **Stability analysis:** The test substance was stable in the diet at all concentration levels for up to 15
- days of refrigeration. However, the test substance was stable onl y at 200 and 700 ppm levels for 15
- days of refrigeration followed b y 1
- week of room temperature storage. The test substance was stable at the 200 and 700 ppm levels but not stable at 50 ppm when stored at room temperature for 22 days prior to feeding
. **Concentration analysis (range as % nominal)**  **:** 96. 6
- 10 4 %
. The se analy

tical data indicated that the mixing procedure was adequate and that the variance between nominal and actual dosage to the animals was acceptable.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 6 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### 4. **Statistics** : The data were presented as mean ± standard deviation (SD). Each test substance exposed group was compared to the control group for the parameters listed below. The data were anal yz ed using the following statistical methods and significance was defined at p < 0.05 for all tests
. **Parameters Statistical Methods** 

- Body weight

- Body weight gain

- Food consumption

- Food efficiency Levene’s test for homogeneity and Shaprio
-Wilk test for normality. If preliminary test was not significant, o ne -way analysis of variance followed by Dunnett’s test was used to compare treated groups with control groups . If preliminary test was significant, transforms of the data were used. The rank order of transform was log, square
-root, and rank
- order
.

- Rearing

- Grip strength

- Foot splay

- Body temperature

- Motor activity Levene’s test for homogeneity and Shaprio
-Wilk test for normality. If preliminary test was not significant, repeated measures analysis of variance was followed by linear contra sts . If preliminary test was significant, a normalizing, variance stabilizing transformation followed by repeated measures analysis of variance or sequential application of the Jonckheere
Terpstra trend test was used
. Incidence of FOB, descriptive parameters Cochran
-Armitage test for trend; if the incidence was not significant, but a significant lack of fit occurred, then Fisher’s Exact test with a Bonferroni
Holm correction was used. Data were obtained from page 22 of the study report. 

### The se stati stical analyses were considered to be appropriate
. **C. METHODS / OBSERVATIONS**  **: 1.**  **Mortality and C**  **linical O**  **bservations :**  Animals were observed twice daily for mortality and morbi dity throughout the study
. General clinical observations were recorded once dail y between 6 a.m. and 12 p.m. throughout the study . **2. Body**  **W eight**  **:** Animals were weighed on the days of FOB assessment and weekl y during the exposure period. Body weights were not recorded on the day of sacrifice. **3. Food**  **C onsumption**  **:** Food consumption was recorded weekly throughout the study and reported as g/animal/day . The mean dail y food efficiency and mean dail y intake of test substance were calculated from the food consumption and body weight data. **4 .**  **Cholinesterase determination :**  Cholinesterase activity was not evaluated. **5 .**  **Neurobehavioral A**  **ssessment :**  **a. Functional**  **O bserv**  **ational B**  **attery (FOB) :**  All animals were subjected to a FOB during acclimation (baseline) and during Weeks 4 , 8 and 1 3
. Animals were counterbalanced b y sex and treatment and tested in replicates over multiple days to minimize the influence of uncontrolled f

actors. The FOB was conducted b y an observer who was “blind” to the treatment status of the animal, and the same observer performed all of the evaluations. Animals were acclimated for at least 10 minutes prior to evaluation. The FOB evaluations were conduc ted in a sound
- attenuated room equipped with a white
- noise
- generation system to minimize variations in environmental test conditions. Animals were weighedSubchronic Neurotoxicity Study (rats) (201 2 ) /Page 7 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### on the day

of the FOB assessment. The time in the open
- field was at least 2 minutes. Fore
- and hindlimb grip strength were measured with a Chatillon Digital Force gauge. Rectal body

temperature was measured with a YSI Precision 4000 thermometer and temperature probe. The following CHECKED (X) parameters were examined. **HOME CAGE OBSERVATIONS REMOVAL**  **FROM THE HOME CAGE AND HANDLING**  **OPEN FIELD OBSERVATIONS** X Posture X Ease of removal X Righting reflex X Gait/coordination X Ease of handling X Gait/coordination X Convulsions X Vocalization X Muscle spasms/fasciculation X Tremors X Muscle tone X Convulsions X Palpebral closure X Pi loerection X Tremors X Fur/skin appearance X Ease of respiration X Mucous membrane s X Rate of respiration X Palpebral closure X Posture **NEUROMUSCULAR OBSERVATIONS**  X Exophthalmus X Palpebral closure X Landing foot splay X Lacrimation X Arousal X Forelimb grip strength X Salivation X Vocalization X Hindlimb grip strength X Dehydration X Diarrhea Hindlimb extensor strength X Emaciation X Polyuria **PHYSIOLOGICAL OBSERVATIONS**  X Number of rearing movements X Approach and touch X Body temperature X Tail pinch X Body weight X Sharp auditory stimulus P arameters based on OPPTS Guideline 870. 62 00
. Data were obtained from pages 2 0
- 21 of the study report. 

### b. **Loco m**  **otor A**  **ctivity :**  Lo com otor activity was evaluated after the last animal completed the FOB pre
- exposure and during Weeks 4, 8 , and 1 3
. Animals were counterbalanced b y sex and treatment and tested in replicates over multiple days to minimize the influence of uncontrolled factors. An automated Coulbourn ® 

### Instruments activity monitor was used with infrared beams for motor activity data collection. The infrared monitoring device enabled measurements of two dependent variables: duration of movement and number of movements. A continuous movement, regardless of its duration, was counted as one movement by

the activity measurement s ys tem. The technical characteristics of the measurement s ys tem are such that duration of movement wa s analogous to “counts” in other ty pes of devices that employ int erruption of light beams. Duration of movement and number of movement s were evaluated in 9 consecutive intervals of 10 minutes each as well as for the total 90
- minute session
. **6 .**  **Sacrifice and P**  **athology :**  Animal s selected for neuropathological evaluation ( 6 rats/sex in the control and high dose groups ) were deeply anaesthetized by i.p. injection of a mixture of ketamine/xyl azine and perfused in situ . The perfusion and necrops y procedures were conducted according to Haskell Standard Operating Procedure
-Neurotoxicity Necrops y Procedures. Animals were subjected to gross necropsy . The remaining animals were sacrificed by

isoflurane anesthesia and CO 2 

### asphyxiation and were disposed of without any pathological examinations.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 8 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### The tissues from the control and high
- dose animal s ( 700 ppm) were processed for microscopic evaluation. The brain, spinal cord sections, eyes, optic nerve, and gastrocnemius muscle were embedded in paraffin, sectioned at 5μm, and stained with hematoxyl in
- eosin (H&E). The dorsal root ganglia (including dorsal and ventral root fibers) from the cervical and lumbar swellings, gasserian ganglia, and peripheral nerves were embedded in gl ycolmethacrylate (GMA) , section ed at 3 μm, and stained with hematoxyl in
eosin (H&E)
. Stained histological sections were examined by light microscopy
. Brain weight and measurements were not evaluated in this study
. The following CHECKED (X) tissues from the control and high
- dose animals, as well as all gross le sions were evaluated.

**CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM** 

**BRAIN SCIATIC NERVE**  X Olfactory bulb Mid
- thigh Region X Cerebral cortex X Sciatic N erve X Hippocampus X Basal ganglia X Cerebellum X Thalamus X Pons X Medulla oblongata **OTHER** X Midbrain X T ibial n erve X Hy pothalamus X Sural n erve

**SPINAL CORD** Peroneal Nerve X Cervical swelling X Lumbar dorsal root ganglion X Lumbar swelling X Lumbar dorsal root fibers Thoracic swelling X Lumbar ventral root fibers

**OTHER** X Cervical dorsal root ganglion X Gasserian Ganglion X Cervical dorsal root fibers Trigeminal nerves Cervical ventral root fibers X Optic nerve X Eyes X Gastrocnemius muscle Data were obtained from page 21 of the study report. 

### 7 **. Positive**  **C ontrols**  **:** It was stated in this report that three separate reports ( MRID 44628703, MRID 47053501, and MRID 48710304 , performed in 1997, 2002 and 2011, respectivel y) were previousl y performed by DuPont Haskell to generate positive control data and validate the procedures and the inter
- observer reliability of the performing lab to conduct and assess neurobehavioral and neuropathology tests. The data also document s that the equipment and procedures are capable of detecting effects that may be seen in neurotoxicity

studies. The positive control data is acceptable for use with the current study. **II. RESULTS**  **: A.**  **OBSERVATIONS :** Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 9 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### 1 **. General C**  **linical Observation**  **s :**  There were no significant treatment - related clinical findings in the 50, 200 or 7 00 ppm group males or females. Scabs and hair loss were observed in a small number of both control and treated animals. **2 .**  **Mortality:** There were no treatment - related mortalities. One animal assigned to the low concentration (50 ppm) group was found dead on tes t Day 44. The cause of death was not determined. There were no significant gross findings in this animal. All other animals survived to scheduled termination. **B. BODY WEIGHT AND BODY WEIGHT GAIN**  **:** Summary results of mean body

weights and body weight gains are presented in Table 2 (a and b) and Table 3, respectively
. Treatment
- related effects on body weights were evident at the high dose (700 ppm) in males (Day 7 through 91) and females (Day 14 throu gh 91). At 700 ppm, lower (p ≤0.05) body weights ranged from ↓6
- 12% in males and from ↓6
- 13% in females (Table 2a and b). No significant differences in body weights were noted in either sex at dietary concentration levels of 50 or 200 ppm compared to the co ntrols. On Day 7, body weight was reduced b y ↓ 5% in the 700 ppm females compared to the control, but was not statistically significant. **TABLE 2 a**  **. Mean ( ±SD) Body Weights in**  **Male Rats**  **Exposure Time Concentration on Diet**  **( ppm** **) 0**  **5 0**  **2 00**  **7 00**  **Day 0**  232.2 ± 13.3 235.6 ± 9.5 232.2 ± 15.9 232.2 ± 14.5 **Day 7**  296.0± 16.9 296.7 ± 13.1 288.7 ± 19.2 **279.4±17.3*** **( ↓6%)**  **Day 14**  343.6 ± 21.0 346.5 ± 20.2 332.9 ± 23.8 **321.7±20.5*** **( ↓6%)**  **Day 21**  387.3 ± 26.2 385.4± 26.1 368.8 ± 29.1 **355.7±24.1*** **( ↓8%)**  **Day 28**  416.9 ± 31.1 415.7 ± 30.5 392.9 ± 33.3 **377.3±27.7*** **( ↓10%)**  **Day 35**  446.1 ± 34.1 447.5 ± 35.9 420.2 ± 37.0 **403.9±29.3*** **( ↓10%)**  **Day 42**  471.2 ± 38.5 471.9 ± 39.3 441.8 ± 40.5 **423.9±32.0*** **( ↓10%)**  **Day 49**  495.7 ± 40.6 493.0± 45.7 464.4± 44.4 **440.1±31.4*** **( ↓11%)**  **Day 56**  508.3 ± 43.3 506.2 ± 46.8 475.0± 43.8 **450.2±33.6*** **( ↓11%)**  **Day 63**  527 .1 ± 46.5 522.6 ± 51.2 491.6 ± 44.8 **465.6 ±** **35.0*** **( ↓12%)**  **Day 70**  541.0± 46.7 539.7 ± 53.0 504.4± 47.2 **478.7 ±** **36.0*** **( ↓12%)**  **Day 77**  552.2 ± 44.6 548.3 ± 54.9 514.1 ± 47.3 **489.8 ±** **37.9*** **( ↓11%)**  **Day 84**  560.7 ± 50.9 555.1 ± 51.1 524.8 ± 46.2 **496.7 ±** **38.9*** **( ↓11%)**  **Day 91**  569.5 ± 48.2 558.4± 51.2 533.7 ± 47.8 **502.4 ±** **39.2*** **( ↓12%)**  Values represent mean± SD, n=1 2 , except at 50 ppm n=11 from Day 49 to 91 because one male was found dead
. Percent difference from the control is included in parentheses and was calculated by the Investigator s. * Significantly different from the control group, p ≤0.0 5
. Statistically s ignificant results are shown in bold. Data were obtained from Table 3 on pages 33
- 35 of the study report.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 10 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 **TABLE 2 b**  **. Mean ( ±SD) Body Weights in**  **Female Rats**  **Exposure Time**  **Concentration on Diet (ppm)**  **0 50**  **2 00**  **700 Day**  **0** 177.7 ± 8.6 178.0± 9.9 176.7 ± 10.2 175.6 ± 8.6 **Day 7**  204.8 ± 10.0 204.5 ± 12.9 202.6 ± 13.7 194.6 ± 10.9 **Day 14**  222.9 ± 12.2 222.3 ± 14.6 218.2 ± 14.0 **209.0±10.1*** **( ↓6%)**  **Day 21**  240.5 ± 15.3 424.0± 20.0 237.3 ± 13.1 **221.9±13.3*** **( ↓8%)**  **Day 28**  252.1 ± 14.4 252.5 ± 20.3 246.8 ± 18.9 **232.7±15.6*** **( ↓8%)**  **Day 35**  265.9 ± 15.0 264.6 ± 21.0 259.6 ± 20.2 **240.2±15.8*** **( ↓10%)**  **Day 42**  273.9 ± 17.8 269.4± 21.6 263.6 ± 19.5 **244.8 ±**  **14.4*** **( ↓11%)**  **Day 49**  280.7 ± 17.8 276.7 ± 24.2 271.7 ± 18.8 **250.9 ±**  **16.1*** **( ↓11%)**  **Day 56**  288.3 ± 19.6 283.0± 22.7 279.6 ± 21.4 **256.1 ±**  **18.0*** **( ↓11%)**  **Day 63**  295.0± 16.5 289.2 ± 24.1 283.1 ± 24.0 **260.8 ±**  **18.6*** **( ↓12%)**  **Day 70**  298.5 ± 17.9 292.5 ± 23.4 282.4± 25.0 **262.8 ±** **20.3*** **( ↓12%)**  **Day 77**  304.9 ± 19.1 299.7 ± 25.4 289.7 ± 23.6 **265.6 ±** **21.6*** **( ↓13%)**  **Day 84**  305.7 ± 19.1 303.0± 23.7 292.7 ± 24.0 **267.4 ±** **24.3*** **( ↓13%)**  **Day 91**  310.3 ± 20.2 307.0± 24.1 299.9 ± 25.5 **269.9 ±** **23.3*** **( ↓13%)**  Values represent mean± SD, n=12
. Percent difference from the control is included in parentheses and was calculated by the Investigators. * Significantly different from the control group, p ≤0.05. Statistically s ignificant results are shown in bold. Data were obtained from Table 4 on pages 3 6
- 3 8 of the study report. 

### Treatment
- related effects on body weight gains were also evident at the dietary concentration level of 700 ppm in males and females (Table 3). In males, lower (p ≤0.05) mean body weight gains were observed during test Day 0
- 7 ( ↓ 26 %) , Day 14
- 21 ( ↓ 22 %) , Day 21
- 28 ( ↓ 27 %) , Day 0
- 28 ( ↓ 21 %) , Day 42
- 49 ( ↓ 34 %) , Day 28
- 56 ( ↓ 20 %) , and overall ( Day 0
- 91; ↓ 20 %)
. Additional ly , in the 200 ppm males, mean body weight gains w ere reduced by ↓ 11 % , ↓ 18 % and ↓ 13% during test Day 0
- 7, Day 14
- 21, and Day 0
- 28 compared to the controls (Table 3). However, overall (0
- 91) mean body gain was decreased b y ↓ 11% in the 200 ppm males, but was not statistically

significant. In the 700 ppm females, lower (p ≤0.05) mean body weight gains were observed during test Day 0
- 7 ( ↓ 30 %) , Day

0
- 28 ( ↓ 23 %) , Day 28
- 56 ( ↓ 35 %) , Day 56
- 91 ( ↓ 37 %) , and overall (Day 0
- 91; ↓ 29 %) compared to the controls (Table 3). No significant differences in body weight gains were noted in the 50 and 200 ppm females or in the 50 ppm males compared to the controls. It is concluded that lower body weight gains observed in males and females in the high dose (700 ppm) groups were associated with the reduction in body weights observed over the entire study

period and were treatment - related.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 11 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 **TABLE 3**  **. Selected**  **Mean ( ±SD) Body Weight**  **Gain s**  **in Male**  **and Female Rats**  **Exposure Time Concentration on Diet**  **(ppm) 0**  **50 2**  **00 700**  **Males Day**  **0 -**  **7** 63.8 ± 6.7 61.1 ± 7.9 **56.5±5.6*** **( ↓11%)**  **47.2±5.5***

**( ↓26%)**  **Day 14**  **- 21**  43.7 ± 7.5 38.9 ± 7.3 **35.9±6.9*** **( ↓18%)**  **34.0±5.7***

**( ↓22%)**  **Day 21**  **- 28**  29.6 ± 7.3 30.3 ± 7.3 24.1 ± 5.0 **21.6±5.4*** **( ↓27%)**  **Day 0**  **- 28**  184.7 ± 26.9 180.0± 29.2 **160.7±20.7*** **( ↓13%)**  **145.2±16.9***

**( ↓21%)**  **Day 42**  **- 49**  24.5 ± 5.6 24.8 ± 8.7 22.6 ± 5.1 **16.3±2.5*** **( ↓34%)**  **Day 28**  **- 56**  91.4 ± 15.0 94.6 ±23.0 82.1 ± 12.9 **72.8±8.4*** **( ↓**  **20 %)**  **Overall ( Day**  **0 -**  **91 )**  337.3 ± 44.5 324.6 ± 53.0 301.5 ± 36.1 ( ↓ 11 %) **270.2 ±** **29.8***

**( ↓20%)**  **Fem ales**  **Day 0**  **- 7**  27.1 ± 6.0 26.5 ± 7.0 25.9 ±4.9 **19.0±3.8*** **( ↓**  **30 %)**  **Day 0**  **- 28**  74.4 ± 9.1 74.6 ± 12.4 70.2 ± 11.2 **57.1±8.9*** **( ↓**  **23 %)**  **Day 28**  **- 56**  36.2 ± 7.8 30.5 ± 5.6 32.8 ± 6.4 **23.4±4.9*** **( ↓**  **35 %)**  **Day 56**  **- 91**  22.1 ± 7.6 24.0 ± 8.7 20.3 ± 6.8 **13.9 ±**  **6.7*** **( ↓**  **37 %)**  **Overall ( Day**  **0 -**  **91 )**  132.6 ± 17.0 129.0± 17.1 123.2 ± 18.6 **94.4 ±**  **16.0*** **( ↓**  **2 9**  **%)** Values represent mean± SD, n=12, except at 50 ppm n=11 from Day 49 to 91 because one male was found dead. Percent difference from the control is included in parentheses and was calculated by the Investigators. * Significantly different from the control group, p ≤0.05. Statistically s ignificant results are shown in bold. Data were obtained from Tables 5 (pages 39
- 41 ) and 6 (pages 42
- 44) of the study report. 

### C **. FOOD CONSUMPTION**  **:** Results of mean food consumption (g/animal/day) in males and females are presented in Table 4 . Treatment
- related effects on food consumption were evident at the high dose (700 ppm) in males and females
. Lo wer food consumption at 700 ppm was observed earlier in males (Day 0
- 7, ↓9% , p ≤0.05) compared to females (Day 0
- 28 , ↓9% , p ≤0.05 ). In the 700 ppm group males, lower (p ≤0.05) food consumption ranged between a decrease of ↓ 6
- 9% on D ays 0
- 7 , 21
- 28, 56
- 63, 35
- 63, 63
- 70, 77
- 84, 56
- 91, and overall (0
- 91) (Table 4). No significant differences were noted on food consumption in the 50 and 200 ppm males when compared to the control group. In females, lower (p ≤0.05) mean food consumption w as observed on test Days 0
- 28 ( ↓ 5 %) , 28
- 35 ( ↓ 6 %) , 35
- 42 ( ↓ 10 %) , 42
- 49 ( ↓ 8 %) , 49
- 56 ( ↓ 7 %) , 28
- 56 ( ↓ 8 %) , 56
- 63 ( ↓ 6 %) , 70
- 77 ( ↓ 8 %) , and overall (0
- 91; ↓ 6 %) (Table 4). In addition, lower (p ≤0.05) mean food consumption in females was observed in the low dose (50 ppm) on test Day 56
- 63 ( ↓ 5%) and in the mid dose (200 ppm) on Day 21
- 28 ( ↓ 6%) and Day

56
- 63 ( ↓ 7%). However, overall (0
- 91) mean food consumption was not statistically different from the control groups at the low (50 ppm) or mid dose (200 ppm)
.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 12 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### It is conc luded that the effect on body weight and body

weight gains reflected the effects observed on food consumption in the 700 ppm groups, but the small decreases observed in food consumption at the low and mid doses were not associated with a significant decrea se in body weight
. **TABLE 4**  **. Selected**  **Mean ( ±SD)**  **Food Consumption (g/animal/day)**  **in Male and Female**  **Rats Exposure Time**  **Concentration on Diet (ppm)**  **0 50**  **200 700**  **Males Day**  **0 -**  **7** 23.7 ± 1.5 23.8 ± 1.9 22.8 ± 0.8 **21.6±1.0*** **( ↓9%)**  **Day 21**  **- 28**  25.1 ±2.0 25.0 ±2.5 23.6 ± 1.0 **22.9±2.0*** **( ↓9%)**  **Day 56**  **- 63**  25.5 ± 1.6 24.8 ±2.1 24.2 ± 0.9 **23.6±1.2*** **( ↓7%)**  **Day 35**  **- 63**  25.8 ± 1.9 25.4 ±2.2 24.4 ± 0.8 **23.9±1.4*** **( ↓7%)**  **Day 63**  **- 70**  25.5 ± 1.2 25.0 ±2.3 24.0 ± 0.5 **23.6±1.4*** **( ↓7%)**  **Day 77**  **- 84**  24.7 ± 1.9 23.6 ± 1.8 23.7 ± 0.5 **23.0±1.4*** **( ↓7%)**  **Day 56**  **- 91**  24.9 ± 1.3 24.1 ± 1.9 23.8 ± 0.6 **23.3±1.4*** **( ↓6%)**  **Overall ( Day**  **0 -**  **91 )**  25.1 ± 1.6 24.7 ±2.1 23.9 ± 0.6 **23.4±1.4*** **( ↓7%)**  **Fem ales**  **Day 21**  **- 28**  17.0 ± 0.5 17.0 ± 1.6 **16.0 ±**  **1.0** ***** **( ↓6%)**  16.2 ± 0.9 **Day 0**  **- 28**  16.7 ± 0.6 16.6 ± 0.9 16.2 ± 0.6 **15.9 ±**  **1.0*** **( ↓5%)**  **Day 28**  **- 35**  17.8 ± 0.7 17.2 ± 0.8 17.2 ± 1.0 **16.7 ±** **0.8*** **( ↓6%)**  **Day 35**  **- 42**  18.4 ± 1.3 17.9 ± 1.2 17.2 ± 0.7 **16.5 ±**  **1.5*** **( ↓10%)**  **Day 42**  **- 49**  17.8 ± 1.0 16.6 ± 1.2 17.1 ± 1.0 **16.3±1.5*** **( ↓**  **8 %)**  **Day 49**  **- 56**  17.1 ± 0.9 16.3 ± 0.9 16.8 ± 1.1 **16.0 ±**  **1.3*** **( ↓7%)**  **Day 28**  **- 56**  17.7 ± 0.8 17.0 ± 0.6 17.1 ± 0.9 **16.3 ±**  **1.2*** **( ↓8%)**  **Day 56**  **- 63**  16.9 ± 0.3 **16.2 ±** **0.7** ***** **( ↓**  **5 %)**  **15.7 ±**  **1.1** *****

**( ↓**  **7 %)**  **15.9 ±**  **1.5***

**( ↓6%)**  **Day 70**  **- 77**  17.1 ± 0.6 16.4 ± 1.2 16.5 ± 1.0 **15.7±1.6*** **( ↓8%)**  **Overall ( Day**  **0 -**  **91 )**  16.9 ± 0.4 16.6 ± 0.6 16.4 ± 0.8 **15.9 ±**  **1.2*** **( ↓6%)**  Values represent mean± SD, n=12, except at 50 ppm n=11 from Day 49 to 91 because one male was found dead. Percent difference from the control is included in parentheses and was calculated by the Investigators. * Significantly different from the control group, p ≤0.05. Statistically significant results are shown in bold. Data were obtained from pages Tables 7 (pages 45
- 47) and 8 (pages 48
- 50) of the study report.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 13 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### D. **FOOD EFFICIENCY** A s ummary

of mean daily

food efficiency

(average weight gain/average food consumption) in males and females is presented in Table 5. Treatment
- related effects on food efficiency were noted in the high dose (700 ppm) in males and females, but not at 50 ppm or 200 ppm males and females. Overall (0
- 91) mean food efficiency was significantly (p ≤0.05) reduced by ↓14% in males and ↓24% in females at a dietary concentration level of 700 ppm. On D ay 0
- 7 after treatment, mean food efficiency was significantly

decreased b y ↓ 19% in males and ↓25% in females at 700 ppm. Lo wer (p ≤0.05) food efficiency was also observed on several test days in the 700 ppm males: Days 1 4
- 21 ( ↓17%), Days 21
- 28 ( ↓20%), Days 0
- 28 ( ↓15%), Days 42
- 49 ( ↓28%), and Days 28
- 56 ( ↓14%) . Additionally, in the 700 ppm females, l ower (p ≤0.05) food efficiency

was also observed on Days 0
- 28 ( ↓20%), 28
- 56 ( ↓30%), and 56
- 91( ↓34%). No treatment - related effe cts on food efficiency were noted at 50 or 200 ppm in males or females. The reduction in overall food efficiency was consistent with the reduced food consumption observed in males and females. **TABLE 5**  **. Selected**  **Mean ( ±SD)**  **Daily Food Efficiency (g/g)**  **in Male and Female**  **Rats**

**Exposure Time Concentration on Diet**  **(ppm) 0**  **50 200**  **700**

**Males Day**  **0 -**  **7** 0.385±0.032 0.366±0.32 0.354±0.033 **0.311±0.033*** **( ↓19%**  **) Day**  **14 -** **21** 0.247±0.030 0.223±0. 0 37 **0.211±0.039*** **( ↓15%**  **) 0.206±0.027** *

**( ↓17%**  **) Day**  **21 -** **28** 0.168±0.034 0.173±0.037 0.146±0. 0 28 **0.135±0.029*** **( ↓20%**  **) Day**  **0 -**  **28** 0.268±0.027 0.261±0.032 0.244±0.030 **0.228±0.020*** **( ↓15%**  **) Day**  **42 -** **49** 0.134±0.027 0.137±0.043 0.133±0.031 **0.097±0.015*** **( ↓28%**  **) Day**  **28 -**  **56** 0.126±0.014 0.131±0.028 0.120±0.018 **0.108±0.012*** **( ↓14%**  **) Day**  **0 -**  **91** 0.147±0.013 0.144±0.018 0.139±0.016 **0.127±0.011*** **( ↓14%**  **) Females**  **Day 0**  **- 7**  0.235±0.048 0.231±0.063 0.228±0.040 **0.175±0.033*** **( ↓25%**  **) Day**  **0 -**  **28** 0.159±0.018 0.160±0.024 0.154±0.023 **0.128±0.018*** **( ↓20%**  **) Day**  **28 -**  **56** 0.073±0.014 0.064±0.011 0.068±0.012 **0.051±0.009*** **( ↓30%**  **) Day**  **56 -**  **91** 0.038±0.013 0.042±0.014 0.036±0.011 **0.025±0.012*** **( ↓34%**  **) Day**  **0 -**  **91** 0.086±0.010 0.085±0.010 0.083±0.011 **0.065±0.010*** **( ↓24%**  **)** Food efficiency was reported as average weight gain/average food consumption Values represent mean± SD, n=12, except at 50 ppm, n=11 from Day 49 to 91because one male was found dead. Percent difference from the control is included in parentheses and was calculated by the Investigators. * Significantly different from the control group, p ≤0.05. Significant results are sh own in bold. Data were obtained from pages Tables 9 (pages 51
- 5 3 ) and 10 (pages 5 4
- 5 6 ) of the study report. 

### E. **TEST SUBSTANCE INTAKE** : The mean daily intake (mg/kg/day) of Tribenuron Methyl over the entire study

period is presented in Table 6. **TABLE 6. Intake of Tribenuron Methyl in Males and Females**  **Test Group Concentration in Diet** 

**(ppm) Me**  **an daily intake (m**  **g/kg bw/day)**Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 14 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 **Male Fem**  **ale 1**  50 2.8 ±0. 2 3. 2 ±0. 2 **2** 200 11.3 ± 1.0 12.8 ±0. 7 **3** 700 40.1 ±2.5 46. 6 ± 3.1 Data were obtained fro m Table s 11 (p ages 57
- 58) and 12 (p ages 59
- 60) of the study report. 

### F **. NEUROBEHAVIORAL RESULTS:**  **1. FOB findings**  **:** No treatment - related effects on FOB (home cage, open field, removal from the home cage and handling) parameters were noted at any dietary concentration level for either sex. However, a significantly (p ≤0.05) higher incidence of low arousal was observed in the 50 ppm males (6/12 treated vs. 0/12 control) during Week 13, but not at 200 or 700 ppm. In addition, low arousal was seen in male control animals at baseline, week 4 and week 8 (ranging from 2/12
- 4/12 )
. Thus , the lack of a dose response and the observation in control animals indicates this effect was not treatment - related.

**TABLE 7. Selected FOB Observations in Male and Female Rats Observation**  **Dose level (** **ppm )**  **0 50**  **200 700** 

**Males Arousal**  **(low)** Baseline Week 4 Week 8 Week 1 3 2/12 2/12 4/12 0/12 1/12

1/12 3/12 6/12* 0/12 3/12 2/12 3/12 0/12 1/12 0/12* 1/12 **Females Arousal (low** 

**)** Baseline Week 4 Week 8 Week 1 3 0/12 0/12 0/12 0/12 0/12

0/12 0/12 0/12 0/12 0/12 0/12 0/12 0/12 0/12 0/12 0/12 Data were extracted from Table 15(page 67) and 16 (page 74). Values represent incidence * Significantly different from the control group, p ≤0.05. 

### 2. **Loco m**  **otor activity :**  No treatment - related effects were observed on motor activity (duration of movements and number of movements) in either sex at any dietary concentration level of the test substance. In addition, there were no statistically significant differences between the control and the test substance
- exposed groups at any time point. **TABLE 8**  **. Motor Activity**  **in Male and Female**  **Rats Exposure Time**  **Concentration on Diet (ppm)**  **0 50**  **200 700**  **Males Duration of Movem**  **ents (sec)**  **Baseline** 1094± 256 1129 ± 368 1266± 417 1180± 256 **Week 4** 1821 ± 535 1939 ± 505 1810± 464 1936± 521 **Week 8** 1583 ± 521 1629 ± 558 1946± 483 1616± 471 **Week13** 1599 ± 334 1722 ± 637 1588 ± 608 1790± 384 **Fem ales**  **Duration of Movem ents (sec)** Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 15 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 **TABLE 8**  **. Motor Activity**  **in Male and Female**  **Rats Exposure Time**  **Concentration on Diet (ppm)**  **0 50**  **200 700**  **Baseline** 1526± 607 1653 ± 552 1674± 549 1732 ± 647 **Week 4** 2003 ± 601 1828 ± 685 1910± 507 1991 ± 599 **Week 8** 1724± 610 1750± 573 1644± 465 1837 ± 548 **Week13** 1937 ± 583 2005 ± 489 1838 ± 596 1862 ± 430 **Males Number of Move**  **me nts**  **Baseline** 471 ± 125 520 ±243 595 ±219 518 ± 94 **Week 4** 809 ± 199 899 ±211 848 ±273 881 ±255 **Week 8** 733 ±207 811 ±290 931 ±270 778 ±224 **Week13** 776 ± 175 960 ± 326 878 ± 355 926 ±241 **Fem ales**  **Number of Movem ents**  **Baseline** 702 ±276 766 ± 192 811 ±267 840 ±294 **Week 4** 970 ±280 885 ±288 894 ±236 991 ±258 **Week 8** 868 ±262 911 ± 302 837 ±254 946 ±260 **Week13** 1076± 266 1052 ± 216 954 ±245 1052 ± 238 Values represent mean±SD, n=12, except at 50 ppm n= 11 from Day 49 to 91because one male was found dead. No results from treatment groups are s ignificantly different from the control group. Data were obtained from Tables 17
- 20 on pages 76
- 79 of the study report
. 

### 3. **Rearing:** Mean number of rearing movements was unaffected by the test diet consumption at 50, 200, or 700 ppm in males and females. There were no statisticall y significant differences between the control and the test substance
- exposed groups (b y sex) at the study We ek 4, 8, and 13 evaluations. **4 .**  **Forelimb and Hindlimb Grip Strength :**  Forelimb grip strength was significantly decreased by 19% in the 700 ppm males during Week 13 , but not in females (Table 9 ). This effect was not treatment related since the mean forelimb grip value (1.19±0.34 kg) was within the historical control range ( 0.93

– 1.40 kg) 

### and the concurrent control (1.47 kg) exceeded the historical control range (Table 9 ). There were no treatment - related or statistically significant effects on hindlimb grip strength in either sex at any dose level. **TABLE 9**  **. Mean ( ±SD)**  **Forelimb Grip Strength (kg)**  **fo r**  **Male Rats**  **Exposure Time Concentration in Diet (ppm)**  **0 50**  **200 700**  **Baseline (Pretest)** 0.72 ± 0.10 0.69 ± 0.07 0.68 ± 0.10 0.69 ± 0.09 **Week 4** 1.17 ± 0.24 1.16 ± 0.23 1.10 ± 0.13 1.11 ± 0.13 **Week 8** 1.07 ± 0.09 1.08 ± 0.05 1.05 ± 0.08 1.03 ± 0.10 **Week 13** 1.47 ± 0.27 1.31 ± 0.26 1.27 ± 0.25 **1.19 ±** **0.34*** **( ↓19%)**  **Historical control data for male**  **forelim b grip**  **at Week 13 #**  Mean = 1.19 ± 0. 05 ( 0.93 ± 0.14

– 1.40 ± 0.14 ); n= 1 1
- 12 Values represent mean±SD, n= 11
- 12. Percent difference from the control is included in parentheses and was calculated by the Reviewers. * Significantly different from the control group, p ≤0.05. Statistically significant results are shown in bold. # Data were obtained from Appendix K on page s 292
- 293 of the study report. Data were obtained from Table 1 3 on page 61 of the study report. 

### 5 **. Foot Splay:**  Foot splay was significantly

reduced by ↓23
- 24% at 50, 200, and 700 ppm inSubchronic Neurotoxicity Study (rats) (201 2 ) /Page 16 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### males, but not in females. This effect was not treatment related since the mean hindlimb splay value s w ere within the historical control range , no dose response relationship was evident, and the c oncurrent control group ( 10.1 cm) exceeded the historical control range (Table 10 ). No treatment
- related effects on hindlimb splay occurred at any dietary concentration level in females. **TABLE 10**  **. Mean ( ±SD)**  **Hindlimb Splay ( cm** **) for Male**  **Rats Exposure**  **Time Concentration in Diet (ppm)**  **0 50**  **200 700**  **Baseline (Pretest)** 6.4 ± 1.9 5.2 ± 1.4 6.3 ± 2.3 6.6 ± 1.7 **Week 4** 8.1 ± 2.4 7.2 ± 2.5 7.3 ± 2.6 7.8 ± 2.7 **Week 8** 8.7 ± 2.3 8.1 ± 3.1 6.8 ± 2.4 7.0 ± 2. 0 **Week 13** 10.1 ± 1.6 **7.8 ±** **3.1*** **( ↓23%)**  **7.7 ±** **2.6***

**( ↓24%)**  **7.7 ±** **2.4** *****

**( ↓24%)**  **Historical control data for male hindlimb splay at Week 13**  **#** Mean = 8.0 ± 0.4 (7.5 ± 2.1

– 8.5 ± 1.7); n= 11
- 12 Values represent mean±SD, n=11
- 12. Percent difference from the control is included in parentheses and was calculated by the Reviewers. * Significantly different from the control group, p ≤0.05. Statistically significant results are shown in bold. # Data were obtained from Appendix K on page s 292
- 293 of the study report. Data were obtained from Tables 13 on page 61 of the study report. 

### 6 **. Body Temperature:**  Body temperature was unaffected by the administration of test substance at 50, 200, or 700 ppm in males and females. There were no statistically significant differences between the control and test substance
- treated groups **G .**  **SACRIFICE AND PATHOLOGY**  **: 1.**  **Gross P**  **athology** : No adverse, treatment
- related effects were noted during gross pathology
. **2 .**  **Neuropathology :**  No adverse, treatment
- related histologic al changes were noted in the 700 ppm group males or females.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 17 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### III. **DISCUSSION AND CONCLUSIONS: A.**  **INVESTIGATORS’ CONCLUSIONS :**  The investigator s concluded that under the conditions of this study, the no
- observed
- adverse
effect level (NOAEL) for systemic toxicity in males and females was 200 ppm (or 11.3 and 12.8 mg/kg/day

for males and females, respectively) based on decreased body weight and nutritional parameters at 700 ppm (40.1 and 46.6 mg/kg/day for males and females, respectivel y). The NOAELfor neurotoxicity in males and females was greater than 700 ppm (the high est concentration tested) due to the absence of effects on neurobehavioral and neuropathological endpoints. **B. REVIEWER COMMENTS**  **:** Tribenuron Methyl , at all dietary concentration levels tested, had no effect on mortality or clinical signs in either male or female rats
. No treatment - related effects were observed on FOB (home cage, open field, removal from the home cage and handling) parameters, rearing, forelimb and hindlimb grip strength, hindlimb splay, body

temperature or motor activity (duration of movements and number of movements) at any dietary concentration level in either sex. Decreased (p ≤0.05) forelimb grip strength was noted in the 700 ppm males ( ↓ 19%) during Week 13 compared to control, but n ot in the females. In addition , hindlimb splay was significantl y decreased by 23
- 24% at 50, 200, and 700 ppm in males during Week 13, but not in females. The decreases in forelimb grip strength and hindlimb splay observed in males were not considered treatment related , however, since their mean values were similar to or within the historical control mean data , and the mean of their control values exceeded the historical control mean and range
. In addition, there were no effect s on forelimb grip strength in any other male exposure group s (50 ppm or 200 ppm) or in any of the exposed females. Treatment
- related effects on body weights, body weight gains, food consumption and/or food efficiency were evident at the high dose (700 ppm) in males and females, but n ot in the low dos e (50 ppm) or mid dose (200 ppm). At 700 ppm, lower (p ≤0.05) body weights ranged from ↓6
- 12% in males (Day 7 through 91) and from ↓6
- 13% in females (Day 14 through 91). No significant differences in body weights were noted in either sex at dietary concentration levels of 50 or 200 ppm compared to the controls. In 700 ppm males, lower (p ≤0.05) mean body weight gains were observed on test Day 0
- 7 ( ↓ 26 %) , Day 14
- 21 ( ↓ 22 %) , Day 21
- 28 ( ↓ 27 %) , Day 0
- 28 ( ↓ 21 %) , Day 42
- 49 ( ↓ 34 %) , Day 28
- 56 ( ↓ 20 %) , and overall (Day 0
- 91; ↓ 20 %) . Significant decreases in body weight gains were observed in the 700 ppm females on Day 0
- 7 ( ↓ 30%), Day 0
- 28 ( ↓ 23%), Day 28
- 56 ( ↓ 35%), Day 56
- 91 ( ↓ 37%), and overall (Days 0
- 91; ↓ 29 %). Lower (p ≤0.05) overall (0
- 91) food consumption was noted in males ( ↓ 7%) and females ( ↓ 6%) at the dietary concentration level of 700 ppm. This reduction in food consumption was consistent with the significant decreases in overall (0
- 91) food efficiency observed in males ( ↓ 14%) and females ( ↓ 24%). It is concluded that impairment of body weight gains observed in the 700 ppm males and females were associated with the significant reduction in body weight observed over the entire study period, as well as reduced food c onsumption and food efficiency
.Subchronic Neurotoxicity Study (rats) (201 2 ) /Page 18 of 18

Tribenuron Methyl/ 128887 OPPTS 870.6200 b/ MAFF 12 Nousan 8147/OECD 424 

### No treatment - related alterations were observed in gross histopathology observations or microscopic neurohistopathology in the 7 00 ppm male and female groups. It is concluded that tribenuron m ethyl did not exhibit treatment - related neurotoxic effects on Crl:CD(SD) male and female rats at dietary concentration levels of 50 , 2 00 and 700 ppm , based on the lack of altered behavior in the FOB parameters, no significant effects in motor activity (duration of movements and number of movements) , and no effects on the macroscopic and microscopic pathology of nervous system tissues. However, systemic toxicity of Tribenuron Methyl was apparent in the 700 ppm males and females. This was characterized b y decreased body weight s and body weight gains, significant reductions in food consumption, and/or food efficiency
. **T he**  **L OAEL**  **is 700**  **ppm for males and females (equivalent to**  **40.1 /** **46.6 m**  **g /kg/day**  **, respectively** **), based on**  **decreased body weight and body weight gains, reduced food consumption, and food efficiency**  **, with a NOAEL**  **of 200 ppm for males and females (equivalent to 11.3/12.8**  **m g** **/kg/day ,**  **respectively )**  **. There was no evidence of neurotoxicity in the study.** This study is classified as **acceptable/guideline** and satisfies the guideline requirement ( OPPTS 870.6200b ; OECD 424 ) for a sub chronic neurotoxicity study in rats. **C. STUDY DEFICIENCIES**  **:** Tribenuron methylin the diet was not stable over the feeding periods used for the 50 ppm dose. This deficiency

did not affect the conclusions of the study as no systemic toxicity

was seen at the next highest dose (200 ppm) but was seen at the highest dose (700 ppm), both of which were stable over the course of the experiment.