UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: 08-MA Y -14 

SUBJECT: Sulfentrazone; Review and generation of a Data Evaluation Record 

PC Code: 129081 

Decision No.: 485307 

Petition No.: NA 

Risk Assessment Type: NA 

TXR No.: 0056843 

MRID No.: 49253901, 49253902 

DP Barcode: D416335 

Registration No.: NA 

Regulatory Action: NA 

Case No.: NA 

CAS No.: 122836-35-5 

40 CFR: §180.498 

Ver.Apr. 2010 

FROM: Anwar Y. Dunbar, Ph.D. ~ ~ tJ~ Pharmacologist, Risk Assessment Branch 1 / ' 

Health Effects Division (HED) (7509P) 

THROUGH: Charles W. Smith III, (__) ~...,;2-. Chief, 

Health 

Risk 

Effects 

Assessment 

Division (HED) 

~ 

(7509P) 

TO: Bethany Benbow, Risk Review Manager 

Registration Division (7505P) 

I. CONCLUSIONS 

RAB 1 has reviewed the 26-day inhalation exposure toxicity study and it is acceptable/nonguideline studies. 

II. ACTION REQUESTED 

Please review this 26-day inhalation exposure toxicity study in rodents. 

Page I of 1 
DATA EVALUATION RECORD 

SULFENTRAZONE 

STUDY TYPE: 26-DAY INHALATION TOXICITY STUDY - RAT; 

NON-GUIDELINE

MRID 49253902

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 

Summitec Corporation 

9724 Kingston Pike, Suite 602 

Knoxville, Tennessee 

Task 6-83 

Primary Reviewer: 

H. T. Borges, Ph.D., M.T.(A.S.C.P.), D.A.B.T. Signature: 

Date: 

Secondary Reviewers: 

Thomas C. Marshall, Ph.D., DABT Signature: 

Date: 

Robert H. Ross, M.S., Program Manager Signature: 

Date: 

Quality Assurance: 

Jennifer Goldberg, B.S. Signature: 

Date: 

Disclaimer 

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

Summitec Corp. for the U.S. Environmental Protection Agency under Contract No.EP-W-11-014 
SULFENTRAZONE / 129081 

26-Day Inhalation Toxicity Study (2013) I Page 2 of 15 

Non-guideline 

EPA 

Risk Assessment 

Reviewer: 

Branch 

Anwar 

I, 

Y. 

Health 

Dunbar, 

Effects 

Ph.D. 

Division (7509P) 

Signature

Date: 

: ~ (>(}-110/-J!., ~ I£/' 

EPA Secondary Reviewer: Ayaad Assaad, D.V.M .. Ph.D. Signature: ~;o::;""'T-l~~'='---

Risk Assessment Branch IV, Health Effects Division (7509P) Date: -=.,.......,;.__-&:rl-l:t-7.r*'"tTXR#: 0056843 

DATA EVALUATION RECORD 

STUDY TYPE: Subchronic Inhalation Toxicity-[Rats]; OPPTS 870.3465 [§82-4]; OECD 413. 

PC CODE: 129081 DP BARCODE: D 416335 

TEST MATERIAL (PURITY): Sulfentrazone Technical (91.7% a.i.) 

SYNONYMS: Sulfentrazone technical; N-(2, 4-dich1oro-5-( 4 -( difl uoromethy 1)-4,5 -dihydro-3-

me thy 1-5-oxo-1 H -1 ,2, 4-triazol-1-y I )pheny I )methanesulfonamide 

CITATION: Koester, A. (2013). 28-Day inhalation study ofsulfentrazone in rats with a 28-

day recovery period. Battelle Toxicology West Jefferson, 1425 State Route 142 (Plain CityGeorgesville Road), West Jefferson, OH 43162. Study Number 21621. October 2013. 

MRID 49253902. Unpublished. 

SPONSOR: FMC Corporation, Agricultural Products Group, 701 Princetonsouth Corporate 

Center, Ewing, NJ 08628 

EXECUTIVE SUMMARY: 

In a subchronic inhalation toxicity study (MRID 49253902), sulfentrazone (purity 91.7%, Lot 

No. PL12~0268) was administered to groups of 5 male and 5 female Sprague Dawley rats/group 

by nose only exposure at concentrations ofO, 0.085 (LCT), 0.256 (MCT), or 1.71 (HCT) mg!L, 6 

hours/day for 26 days (calculated dose levels of20, 60, and 400 mg/kg/day). An additiona15 

rats/sex were exposed either to 0 or 1.71 mg!L test material for 26 days followed by a 28-day 

recovery period. At scheduled sacrifice after the 26 day exposure period or the 28-day recovery 

period, the rats were weighed, blood collected, necropsied, and tissues and organs collected for 

microscopic examination. 
 26-Day Inhalation Toxicity Study (2013) / Page 3 of 15 

SULFENTRAZONE / 129081 Non-guideline 

There were no treatment-related effects on moribundity or mortality. 

There were no treatment related effects at 0.085 mg/L. 

At 0.256 mg/L there were decreased the body weights in male and female rats (↓7 – 13%) during 

the treatment phase of the study. Statistically significant decreases were found in female rats 

treated for 26 days on mean corpuscular volume (MCV) and mean corpuscular hemoglobin 

(MCH) (both ↓6%). 

At 1.71 mg/L there were increased incidences of excessive salivation in male and female rats 

from Day 17 through the end of the exposure phase. This observation ceased immediately 

during the recovery portion of the study. An increased incidence of squinting/shut eyes was also 

observed during the exposure phase. There were decreased body weights in both sexes (↓7 – 

13%) during the treatment phase of the study. On day 26 in male rats there were decreases in 

numerous hematological parameters; hemoglobin (↓12%), hematocrit (↓11%), MCH (↓7%), and 

the reticulocytes (↓80%). On Day 26, females had statistically significant decreases in red blood 

cell count (↓15%), hemoglobin (↓23%), hematocrit (↓22%), mean corpuscular volume (↓8%), 

and mean corpuscular hemoglobin (↓10%) relative to controls. Except for mean corpuscular 

hemoglobin, which was statistically decreased on Day 54 but not on Day 26, these effects resolved during the recovery period. Exposure to the test material for 26 days increased the incidence 

of minimal nasal respiratory epithelial hyperplasia in male and female rats, as well as minimal 

laryngeal epithelial attenuation in all test material exposure groups. These effects in the nasal 

passage and larynx were not resolved following the recovery period. 

The systemic LOAEL is HTC or 1.71 mg/L based on significant reduction in Red Blood 

Cell (RBC) parameters, including RBC count, HGB, hematocrit, MCV, MCH, and/or 

reticulocytes in male and female rats following 26 days inhalation exposure to the test 

material. The NOAEL is 0.256 mg/L. 

Port of entry LOAEL is HTC or 1.71 mg/L based on incidence of minimal nasal respiratory 

epithelial hyperplasia in male and female rats. Portal of entry NOAEL is 0.265 mg/L.

This study is classified as acceptable/non-guideline and satisfies the guideline requirement 

(OPPTS 870.3465; OECD 413) for a subchronic inhalation study in the rat. 

COMMENTS: Minor deficiencies were the use of 5 male and 5 female rats for the LCT, MCT, 

or HCT groups 26-day exposure interval. Also, the time to chamber equilibrium was not 

reported. A major deficiency is that findings in the lung, which is the target organ of the study, 

were not reported

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

statements were located in the study report. 
 26-Day Inhalation Toxicity Study (2013) / Page 4 of 15 

SULFENTRAZONE / 129081 Non-guideline 

I. MATERIALS AND METHODS:

A. MATERIALS:

1. Test material: Sulfentrazone 

Description: Technical, white powder 

Lot/batch #: PL12-0268 

Purity: 91.7% a.i. 

Compound stability: Stable until December 18, 2014 

CAS # of TGAI: 122836-35-5

Structure: 

2. Vehicle and/or positive control: None 

3. Test animals: 

Species: Rat 

Strain: Sprague Dawley 

Age/weight at study initiation: 9 -10 weeks / males 247.3 – 302.2 g; females 178.8 – 218.3 g 

Source: Charles River Laboratories, Portage, MI 

Housing: Individually in polycarbonate cages containing hardwood bedding 

Diet: Certified Harlan Teklad Global Diet 2018C-Pellet, ad libitum (except during 

exposure) 

Water: Municipal water, ad libitum

Environmental conditions: Temperature: 

Humidity: 

Air changes: 

Photoperiod: 

20.0 – 26.1°C 

30 - 70% 

≥10/hour 

12 hours light/dark 

Acclimation period: 7 days 

B. STUDY DESIGN:

1. In-life dates: Start: April 1, 2013; End: Primary Phase April 26, 2013; Recovery Phase May 

24, 2013 

2. Animal assignment: The rats were randomly assigned through a computer program to 

ensure similar group mean body weights (±20% of mean weight) to the test groups noted in 

Table 1. 
 26-Day Inhalation Toxicity Study (2013) / Page 5 of 15 

SULFENTRAZONE / 129081 Non-guideline 

Table 1: Study design a

Test group 

(Calculated 

Dose) 

Nominal 

(Target) conc.b

(mg/L) 

Analytical conc. 

(mg/L) 

MMAD 

(μm) GSD No. Rats 

(males) 

No. Rats 

(females) 

Control (0) 0.0 0.0 - - 10 10 

Low 

(20 mg/kg/day) 

0.085 0.094 2.1 2.0 5 5 

Mid 

(60 mg/kg/day) 

0.256 0.251 1.9 2.0 5 5 

High 

(400 mg/kg/day) 

1.71 1.93 2.3 1.9 10 10 

Table was taken from page 21 and 30 of the study report a Rats were exposed 6 hours/day for 26 consecutive days 

b Based on 91.7% Sulfentrazone purity 

Five rats/sex in the control and HCT group, as well as the LCT and MCT rats were sacrificed on Day 26, while the remaining rats

were sacrificed on Day 54 (Recovery period). 

3. Dose selection rationale: In a prior 7-day range-finding inhalation toxicity study (MRID 

49253901), no adverse test material related findings were found in male rats exposed 6 

hours/ day at concentrations of 0, 0.076, 0.229, or 0.764 mg/L. The NOAEL for the study 

was 0.764 mg/L. The Study Sponsor selected target sulfentrazone aerosol concentrations 

0.085, 0.256, and 1.71 mg/L (target inhaled dose concentrations of 20, 60, and 400 mg/kg 

bw/day calculated inhaled Sulfentrazone, respectively) for the 26-day inhalation toxicity 

study. 

4. Generation of the test atmosphere / chamber description: The rats were exposed to high 

efficiency particulate air (HEPA) or the test material using Cannon-style rodent nose-only 

inhalation exposure systems. Four separate exposure chambers were used to deliver either 

HEPA filtered air or Sulfentrazone technical aerosol. One-7 tier (56 ports) chamber was 

used to deliver HEPA filtered air to control group animals. Three separate 7 tier (56 port) 

chambers were used to deliver an aerosol of the test material to the low-, mid- or high dose 

rats. The exposure system flow rates were set to ~28 L/minute for all groups, which provided a test atmosphere flow rate of ~ 0.50 L/minute/exposure port. During exposures, the rats 

were restrained in polycarbonate exposure tubes. To promote better thermo-regulation, each 

tube contained a series of slots on the top portion of the tube above the neck of each animal. 

Because of the "open" system, the exposure units were operated at a positive pressure relative 

to ambient atmosphere to prevent dilution of the test atmosphere with room air. The inhalation exposure chambers were exhausted at the required flow rate using a central vacuum 

pump system. 

Dosage to the animals was controlled by varying the aerosol concentrations of the test 

material within each exposure plenum. Target test substance aerosol concentrations were 

calculated by estimating animal minute volumes using Bide's formula and an animal body 

weight of 0.250 kg (Bide et al, 2000) [0.499 x (group average body weight kg)0.809] and a 360 

minute exposure duration to achieve the intended target dosage. The actual respiratory 

minute volumes were measured during exposures 1 day each week for each dose group and 

used to calculate the actual inhaled dose. 
 26-Day Inhalation Toxicity Study (2013) / Page 6 of 15 

SULFENTRAZONE / 129081 Non-guideline 

The aerosol generation and delivery system was designed to deliver a homogeneous exposure 

atmosphere, with respect to particle size distribution (PSD) and aerosol concentration, to the 

breathing zone of each rat. Aerosols of the test material powders for the low-, mid-, and 

high-dose groups were generated using a Wright Dust Feed mechanism at various operational 

speeds. Test material powders were packed in multiple layers with a hydraulic packing 

press. For the low- and mid-dose, the powders were packed at an applied load of 500 pounds 

while the high-dose was packed at 2000 pounds. Compressed air was supplied to each at 

28.0 L/min. Percent oxygen, temperature, and humidity of the atmosphere were measured a 

minimum of three times during each animal exposure (all were unaffected). 

Time to equilibrium was not located in the study report. 

 

Analytical chemistry: Aerosol concentrations were measured daily by collecting filter 

samples from each group during each exposure and analyzed gravimetrically. Selected 

aerosol concentration filter samples collected at least weekly were used for chemical analysis 

by HPLC with UV detection (further details not located in study report). The estimated 

Sulfentrazone technical aerosol concentration was based on 91.7% test material purity. 

Test atmosphere concentration: Daily sampling for aerosol concentrations was done using 

25 mm glass fiber filters (Pall Corporation, Ann Arbor, MI). Prior to use, the filters were 

dried overnight in a vacuum desiccator before determining filter tare weights. The filters 

were then placed into labeled Petri dishes until use. Before sampling, the filters were placed 

into in-line filter holders and attached via flexible tube to a sampling location in the breathing 

zone of the rats. A metered volume of test atmosphere was drawn across the filter at a rate of 

0.5 L/minute for a specific time interval. The filter holder was removed from the sampling 

location, the filter removed and re-weighed to obtain a post-sampling gross weight. The net 

gain of the dry filter mass was divided by the total volume of atmosphere sampled to 

calculate the total aerosol mass per liter of atmosphere. Results are in Table 2. 

Table 2. Overall total mass aerosol concentration 

Test Group Target (mg/L) Total mass aerosol concentration (mg/L) 

Average ± SD % RSD % Target 

Control 0.0 0.0 - - 

Low (LCT) 0.093 0.102 ± 0.015 15 109 

Mid (MCT) 0.280 0.274 ± 0.029 11 98 

High (HCT) 1.86 2.10 ± 0.473 23 113 

Data from page 29 of MRID 49253902 

Particle size determination (PSD): PSD was measured a minimum of once per week per 

group (except for the air control group) using a nine stage Andersen style cascade impactor 

fitted with a 0.5 L/min isokinetic dilutor. The isokinetic dilutor allowed the impactor to 

operate at its nominal airflow rate while allowing aerosol to be sampled at an airflow rate of 

0.5 L/min. Results are in Table 1 above. 

5. Statistics: Although various summary tables in the study report indicated statistical analyses 

were done, the statistical methods used were not provided. The study protocol stated that 

appropriate quantitative in-life, clinical pathology (hematology, serum chemistry, and 

coagulation), and post-mortem data were analyzed when N ≥ 3. According to the study 

protocol, data were analyzed by analysis of variance when considered homogenous by 
 26-Day Inhalation Toxicity Study (2013) / Page 7 of 15 

SULFENTRAZONE / 129081 Non-guideline 

Bartlett’s test. Tests for group differences were done using Dunnett's test. For nonhomogeneous data, pairwise differences between the control and each of the comparison groups 

using Cochran and Cox's modified two-sample t-test were done. Statistical significance for 

all comparisons was p = 0.05. 

C. METHODS:

1. Observations:

1a. Cageside observations: Cage-side clinical observations for morbidity and mortality 

were done at least three times daily beginning on Day 1 of exposure. Observations 

were done once prior to each inhalation exposure, at least once during the inhalation 

exposure, and 1 to 2 hours following exposure. Observations were done once daily 

(on the weekends) during the 4-week exposure. Observations were also recorded at 

least weekly during the recovery period.

 1b. Clinical examinations: Detailed clinical examinations were not reported. 

 1c. Neurological evaluations: Neurological examinations were not reported. 

2. Body weight: All rats were weighed before treatment for group assignment and on days 5, 8, 

12, 15, 19, 22, and 25. The rats were also weighed at necropsy (Days 26 or 54). During the 

28 days of recovery, animals were weighed on Days 29, 36, 43, 50, and 53. 

3. Food consumption: Individual animal food consumption was measured starting on day 8 of 

the study. Food was placed in the feed container for each animal and re-weighed after 1 

week. Food efficiency was not calculated. 

4. Ophthalmoscopic examination: Ophthalmoscopic examinations were not done. 

5. Hematology and clinical chemistry: Rats necropsied on Day 26 were fasted only during 

exposure (~6 hours) and had blood collected at the end of exposure. Rats necropsied following 28 days of recovery were fasted overnight before sample collection. The animals were 

anesthetized with CO2/O2 and blood was collected from the retro-orbital sinus for hematology and serum chemistry parameters, and via the posterior vena cava for coagulation 

parameters. The tubes for hematology contained EDTA while those for serum chemistry 

determinations did not contain an anticoagulant. Tubes for coagulation parameters contained 

sodium citrate. The CHECKED (X) parameters were examined. Historical control data were 

provided. 

 a. Hematology:

X Hematocrit (HCT)* X Leukocyte differential count* 

X Hemoglobin (HGB)* X Mean corpuscular HGB (MCH)* 

X Leukocyte count (WBC)* X Mean corpusc. HGB conc.(MCHC)* 

X Erythrocyte count (RBC)* X Mean corpusc. volume (MCV)* 

X Platelet count* X Reticulocyte count 

X Platelet volume X Cell morphology 

 Blood clotting measurements* 
 26-Day Inhalation Toxicity Study (2013) / Page 8 of 15 

SULFENTRAZONE / 129081 Non-guideline 

X (Activated partial thromboplastin time) 

X (Fibrinogen) 

X (Prothrombin time) 

* Recommended for subchronic inhalation studies based on Guideline 870.3465

 b. Clinical chemistry:

X ELECTROLYTES X OTHER 

X Calcium X Albumin* 

X Chloride X Creatinine* 

 Magnesium X Urea nitrogen* 

X Phosphorus X Total Cholesterol* 

X Potassium* X Globulins (Calculated) 

X Sodium* X Glucose* 

X ENZYMES (more than 2 hepatic enzymes eg., *) X Total bilirubin 

X Alkaline phosphatase* X Total serum protein (TP)* 

 Cholinesterase (ChE) X Triglycerides 

X Creatine kinase (CK) Serum protein electrophoresis 

X Lactic acid dehydrogenase (LDH) X Albumin/globulin ratio (calculated) 

X Alanine aminotransferase (ALT/also SGPT)* 

X Aspartate aminotransferase (AST/also SGOT)* 

 Sorbitol dehydrogenase* 

 Gamma glutamyl transferase (GGT)* 

 Glutamate dehydrogenase 

* Recommended for subchronic inhalation studies based on Guideline 870.3465

6. Urinalysis: Urinalysis was not done. 

7. Sacrifice and pathology: All rats were sacrificed by CO2 inhalation followed by exsanguination. The necropsy included examination of the external surface of the body and all 

orifices; and the cranial, thoracic, abdominal, and pelvic cavities and contents. The 

CHECKED (X) tissues were collected for histological examination and the (XX) organs, in 

addition, were weighed. Collected tissues were placed in 10% neutral buffered formalin, 

with the exceptions. The testes were preserved in Bouin's fixative, transferred to 70% 

ethanol, and subsequently transferred to 10% neutral buffered formalin. The eyes with optic 

nerve were fixed in Davidson's fixative before transfer to 10% neutral buffered formalin. 

Bone marrow smears were fixed in methanol. The lungs were inflation fixed with 10% 

neutral buffered formalin via the trachea. All tissue preparations were stained with 

hematoxylin and eosin for microscopic examination. Only tissues from the control and highdose group were examined microscopically, with the exception of the laryngeal tissue, which 

was examined in all animals. 
 26-Day Inhalation Toxicity Study (2013) / Page 9 of 15 

SULFENTRAZONE / 129081 Non-guideline 

X DIGESTIVE SYSTEM X CARDIOVASC./HEMAT. X NEUROLOGIC

X Tongue X Aorta, thoracic* XX Brain*+ 

X Salivary glands* XX Heart*+ X Peripheral nerve* 

X Esophagus* X Bone marrow* X Spinal cord (3 levels)* 

X Stomach* X Lymph nodes* XX Pituitary* 

X Duodenum* XX Spleen*+ X Eyes (optic nerve )* 

X Jejunum* XX Thymus*+ X GLANDULAR

X Ileum* XX Adrenal gland*+ 

X Cecum* X UROGENITAL Lacrimal gland 

X Colon* XX Kidneys*+ XX Parathyroid* 

X Rectum* X Urinary bladder* XX Thyroid* 

XX Liver*+ XX Testes*+ X OTHER

 Gall bladder* (not rat) X Epididymides*+ X Bone (sternum and/or femur) 

 Bile duct* (rat) X Prostate* X Skeletal muscle 

X Pancreas* X Seminal vesicles* X Skin 

X RESPIRATORY XX Ovaries*+ X Harderian glands 

X Trachea* XX Uterus*+ X Nasal turbinates 

XX Lung* X Mammary gland* X All gross lesions and masses* 

X Nose* X Vagina 

X Pharynx* 

X Larynx* 

* Recommended for subchronic rodent studies based on Guideline 870.3465 

+ Organ weights required 

II. RESULTS: 

A. OBSERVATIONS:

1. Clinical signs of toxicity: Treatment-related clinical signs of toxicity included excessive 

salivation and squinting/shut eyes for males and females in the high-exposure group. The 

observations of salivation occurred from Days 17 to 26 in 10/10 males and from Days 17 to 

25 in 10/10 females. The squinting/shut eyes occurred from Days 3 to 19 in 7/10 males and 

from Days 3 to 23 in 9/10 females. No other clinical signs of toxicity were observed. 

2. Mortality: All rats survived to scheduled sacrifice. 

3. Neurological evaluations: Neurological examinations were not done. 

B. BODY WEIGHT AND WEIGHT GAIN: 

The body weights of male and female rats exposed to sulfentrazone by inhalation are shown 

in Table 3. Male group mean body weights were statistically decreased in the mid- and highexposure groups on Day 19 through Day 25 (↓11-13%). On Day 25, the last day of exposure, 

the male group mean body weights were decreased 2, 11, and 13 percent, in the low-, mid-, 

and high-exposure groups, respectively, relative to the control group. 

Female group mean body weights were statistically decreased in the mid- and high-exposure 

groups starting on Day 12 through 25 (↓7-13%, excluding Day 15). On Day 25, the female 

group mean body weights were decreased 4, 10, and 7 percent, in the low-, mid-, and highexposure groups, respectively, relative to the control group. Following the 28-day recovery 

period, male and female group mean body weights were not statistically different than their 
 26-Day Inhalation Toxicity Study (2013) / Page 10 of 15 

SULFENTRAZONE / 129081 Non-guideline 

respective control groups. 

TABLE 3. Mean (±SD) body weights during 26 days of treatment with Sulfentrazone and 28 days of recovery via 

inhalation a 

Day(s) Targeted concentration (mg/L) 

0 0.085 0.256 1.71 

Males 

Body Weights 

1 277.7 ± 11.9 273.5 ± 9.5 269.1 ± 15.6 273.3 ± 7.6 

8 308.3 ± 20.8 300.9 ± 17.6 286.4 ± 24.3 288.6 ± 9.2.8 

15 329.0 ± 28.0 322.2 ± 25.9 301.9 ± 27.2 301.8 ± 12.2 

22 353.2 ± 32.5 347.9 ± 29.0 313.7* ± 29.5 (↓11%) 311.9* ± 19.3 (↓12%) 

25 357.7 ± 34.2 351.1 ± 32.1 317.1* ± 29.1 (↓11%) 312.3* ± 15.0 (↓13%) 

29 362.2 ± 33.0 - - 338.7 ± 16.2 

53 443.4 ± 37.9 - - 445.1 ± 42.4 

Females

Body Weights 

1 200.7 ± 6.6 202.8 ± 12.4 196.7 ± 8.5 198.9 ± 9.9 

8 200.8 ± 11.1 218.3 ± 7.6 209.0 ± 7.6 218.5 ± 9.0 

15 238.1 ± 13.8 234.9 ± 12.5 222.0 ± 15.5 225.4 ± 9.1 

22 252.0 ± 12.1 244.0 ± 10.7 232.9* ± 17.4 (↓8%) 238.5* ± 8.1 (↓7%) 

25 254.3 ± 13.7 244.9 ± 12.1 228.7* ± 12.1 (↓11%) 237.1* ± 8.0 (↓7%) 

29 266.9 ± 17.5 - - 234.6 ± 14.2 

53 297.9 ± 20.0 - - 280.5 ± 6.5 

Data from pages 44 – 47 of MRID 49253902 

C. FOOD CONSUMPTION:

1. Food consumption: The food consumption of HCT male and female rats was statistically 

decreased on Day 26 of exposure (16%, and 11%, respectively). No other significant effects 

on food consumption were noted during treatment or recovery. 

2. Food efficiency: Food efficiency was not calculated. 

D. OPHTHALMOSCOPIC EXAMINATION: 

Ophthalmoscopic examinations were not done. 

E. BLOOD ANALYSES: 

1. Hematology: No treatment-related effects were noted on coagulation parameters. As shown 

in Table 4, treatment- and dose-related effects on RBC-related parameters were noted in 

MCT and HCT male and female treatment groups following 26 days of exposure. On Day 

26, females in the HCT group had statistically significant decreases in RBC count (↓15%), 

HGB (↓23%), hematocrit (↓22%), MCV (↓8%), and MCH (↓10%) relative to control 

females. Statistically significant decreases were also found in MCT female rats treated for 

26 days on MCV and MCH (both ↓6%). Except for MCHC, which was statistically 

decreased on Day 54 but not on Day 26, these effects resolved during the recovery period. In 
 26-Day Inhalation Toxicity Study (2013) / Page 11 of 15 

SULFENTRAZONE / 129081 Non-guideline 

male rats, HGB (↓12%), hematocrit (↓11%), MCH (↓7%), and the percent reticulocytes 

(↓80%) were decreased in HCT rats following 26 days of treatment with the test material. 

All effects resolved during the 28-day recovery period in male rats. Other statistically 

significant effects were noted in WBC parameters, but were considered unrelated to 

treatment due to a lack of dose-response. The treatment-related effects were consistent with 

protoporphyrinogen oxidase inhibition, which had been demonstrated in previous studies 

(FMC Report Nos. A90-3354 and A89-2881, data not provided). 

Table 4. Selected group mean (± SD) hematology parameters of male and female rats treated with sulfentrazone 

Parameter / Group Males Females 

Day 26 Day 54 Day 26 Day 54 

RBC (106 cells/μL) 

 Control 

 LCT 

 MCT 

 HCT 

9.08 ± 0.50 

9.38 ± 0.27 

9.18 ± 0.51 

8.58 ± 0.15 

9.48 ± 0.36 

- 

- 

9.15 ± 0.78 

8.17 ± 0.37 

8.51 ± 0.16 

8.47 ± 0.55 

6.95* ± 0.51 

(↓15%) 

8.93 ± 0.24 

- 

- 

9.19 ± 0.33 

HGB (g/dL) 

 Control 

 LCT 

 MCT 

 HCT 

16.6 ± 0.7 

16.7 ± 0.1 

15.8 ± 0.8 

14.6* ± 0.5 (↓12%) 

17.2 ± 0.8 

- 

- 

16.1 ± 1.3 

15.4 ± 0.6 

15.8 ± 0.4 

15.1 ± 0.7 

11.9* ± 0.9 (↓23%) 

16.9 ± 0.6 

- 

- 

16.7 ± 0.3 

HCT (%) 

 Control 

 LCT 

 MCT 

 HCT 

50.7 ± 2.5 

51.8 ± 0.7 

49.3 ± 3.4 

45.0* ± 1.6 (↓11%) 

52.2 ± 2.3 

- 

- 

50.6 ± 3.9 

47.2 ± 2.4 

47.9 ± 1.3 

45.7 ± 2.7 

36.9* ± 2.5 (↓22%) 

50.4 ± 1.9 

- 

- 

52.6 ± 2.2 

MCV (fL) 

 Control 

 LCT 

 MCT 

 HCT 

55.9 ± 2.7 

55.2 ± 1.7 

53.7 ± 1.6 

52.4 ± 2.0 

55.0 ± 1.9 

- 

- 

55.4 ± 1.5 

57.7 ± 1.0 

56.3 ± 0.7 

54.0* ± 1.1 (↓6%) 

53.2* ± 0.8 (↓8%) 

56.5 ± 1.4 

- 

- 

57.2 ± 1.7 

MCH (pg) 

 Control 

 LCT 

 MCT 

 HCT 

18.3 ± 0.9 

17.8 ± 0.5 

17.3* ± 0.2 (↓5%) 

17.1* ± 0.6 (↓7%) 

18.1 ± 0.6 

- 

- 

17.6 ± 0.8 

18.9 ± 0.3 

18.6 ± 0.1 

17.8* ± 0.4 (↓6%) 

17.1* ± 0.5 (↓10%) 

18.9 ± 0.3 

- 

- 

18.2 ± 0.4 

MCHC (g/Dl) 

 Control 

 LCT 

 MCT 

 HCT 

32.7 ± 0.8 

32.2 ± 0.6 

32.2 ± 0.7 

32.5 ± 0.4 

33.0 ± 0.4 

- 

- 

31.8 ± 1.0 

32.8 ± 0.4 

33.1 ± 0.3 

33.0 ± 0.7 

32.1 ± 0.8 

33.5 ± 0.4 

- 

- 

31.7* ± 0.9 

Reticulocytes (%) 

 Control 

 LCT 

 MCT 

 HCT 

2.0 ± 0.3 

1.9 ± 0.3 

2.1 ± 0.4 

0.4* ± 0.2 (↓80%) 

2.4 ± 0.6 

- 

- 

2.4 ± 0.8 

2.2 ± 0.4 

2.1 ± 0.3 

1.8 ± 0.3 

2.3 ± 3.8 

2.2 ± 0.5 

- 

- 

1.6 ± 0.5 

Data from pages 155-162 of MRID 49253902 

*p≤0.05 

2. Clinical chemistry: Although statistically significant effects were noted, all were within 

established normal ranges and none were biologically relevant. 

F. URINALYSIS: 

Urinalysis was not done. 

G. SACRIFICE AND PATHOLOGY: 
 26-Day Inhalation Toxicity Study (2013) / Page 12 of 15 

SULFENTRAZONE / 129081 Non-guideline 

1. Organ weight: Although statistically significant effects were noted on absolute and relative 

to body or brain organ weights, none were biologically or toxicologically relevant and all 

lacked microscopic correlates. 

2. Gross pathology: No treatment-related effects were noted at necropsy. 

3. Microscopic pathology: Microscopic evaluation of the tissues was only done for control and 

HCT animals, with the exception of laryngeal tissues which were examined from all rats. As 

shown in Table 5, microscopic findings in the nose of air control and the HCT group included respiratory epithelial hyperplasia (increased number of cells), respiratory epithelial goblet 

cell hyperplasia (increased number of cells), olfactory epithelial metaplasia (change to 

respiratory epithelium), and respiratory epithelial inflammation (cellular infiltrate). The 

microscopic findings were generally of minimal severity. The hyperplasia was defined as 

increased cell thickness, increased number of cells, disorganized cells, increased cytoplasmic 

basophilia, and/or intraepithelial cyst formation. The incidence of respiratory epithelial 

hyperplasia was increased in 4/5 male and female HCT rats following 26 days of treatment 

and was still increased in males, but not females, following the recovery period. 

TABLE 5. Incidence of selected microscopic lesions in the nose a 

Concentration Group 

Targeted concentration (mg/L) 

Day 26 Males Day 54b Males Day 26 Females Day 54b

Females 

Air Control 

Microscopic 

Change 

Respiratory 

epithelium 

hyperplasia 

2/5 1/5 3/5 1/5 

Respiratory 

epithelium 

goblet cell 

hyperplasia 

0/5 1/5 3/5 1/5 

1.71 mg/L 

Respiratory 

epithelium 

hyperplasia 

4/5 5/5 4/5 2/5 

Respiratory 

epithelium 

goblet cell 

hyperplasia 

2/5 3/5 2/5 2/5 

a. Number with findings per number examined 

b. Recovery period was initiated on Day 27, thus the final day of exposure was Day 26 

From page 249 of MRID 49253902 

As shown in Table 6, microscopic findings in the larynx consisted of submucosal mononuclear cell infiltrate (found in control and HCT rats at Days 26 and 54 recovery necropsy 

time points) and minimal epithelial attenuation (observed only in rats exposed to the test 

substance at all concentrations). The attenuation was observed at the base of the epiglottis 

and consisted of a change from the expected cuboidal-to-transitional epithelium normally 

found to a more flattened morphology. Epithelial attenuation remained evident in several 

HCT rats at the end of the recovery period. 
 26-Day Inhalation Toxicity Study (2013) / Page 13 of 15 

SULFENTRAZONE / 129081 Non-guideline 

TABLE 6. Incidence of selected microscopic lesions in the larynxa 

Concentration Group 

Targeted concentration (mg/L) 

Day 26 Males Day 54b Males Day 26 Females Day 54b

Females 

Air Control 

(mg/L) 

Microscopic 

Change 

Epithelial 

attenuation 0/5 0/5 0/5 0/5 

Cellular 

infiltrate 1/5 1/5 1/5 2/5 

0.085 

Epithelial 

attenuation 1/5 

No Recovery 

Animals 

3/5 

No Recovery 

Cellular Animals 

infiltrate 0/5 0/5 

0.256 

Epithelial 

attenuation 3/5 

No Recovery 

Animals 

4/5 

No Recovery 

Cellular Animals 

infiltrate 0/5 0/5 

1.71 

Epithelial 

attenuation 3/5 3/5 4/5 1/5 

Cellular 

infiltrate 1/5 0/5 3/5 2/5 

a. Number with findings per number examined 

b. Recovery period was initiated on Day 27, thus the final day of exposure was Day 26 

From page 249 of MRID 49253902 

A few additional microscopic findings were sporadically observed in various air control and 

exposed rats and included pancreatic hyperplasia, pituitary gland cyst, pituitary gland hyperplasia, thyroid gland cellular infiltrate, liver cellular infiltrate, liver cytoplasmic vacuolization, Harderian gland cellular infiltrate, lymphoid hyperplasia in the lung, alveolar macrophage focal infiltrates in the lung, and mandibular lymph node edema. These results were of 

low incidence, minimal severity, sporadically observed, and not related to dose. They were, 

therefore, considered unrelated to treatment. 

III. DISCUSSION AND CONCLUSIONS: 

A. INVESTIGATOR’S CONCLUSIONS:

The study author concluded that treatment with sulfentrazone induced salivation and 

squinting of the eyes (HCT group), decreased body weight (MCT and HCT groups), 

decreased food consumption (HCT group), and decreased RBC parameters (MCT and HCT 

groups). Nasal respiratory epithelial hyperplasia at Day 26 in HCT groups was associated 

with administration of sulfentrazone for 28 days with incomplete recovery by Day 54. 

Laryngeal epithelial attenuation was noted in all sulfentrazone treatment groups after 28 

days; possibly due to the potential slightly acidic characteristic of the test material. 

Laryngeal attenuation had decreased incidence and severity among HCT recovery rats which 

may suggest partial resolution. The laryngeal epithelial attenuation was considered an 

adaptive response as a result of repetitive local irritation at the site during inhalation 

exposure. The study author stated the NOAEL for the study was the low-concentration, 
 26-Day Inhalation Toxicity Study (2013) / Page 14 of 15 

SULFENTRAZONE / 129081 Non-guideline 

0.085 mg/L for male and female rats. 

B. REVIEWER COMMENTS: 

The reviewer generally agrees with the study author. Treatment with the test material 

increased the incidence of excessive salivation in HCT male and female rats from Day 17 

through the end of the exposure phase on Day 26. This observation ceased immediately 

during the recovery portion of the study in HCT animals. An increased incidence of 

squinting/shut eyes was also observed from HCT rats during the exposure phase of the study. 

These observations are likely a result of the acidic nature of the test material and not due to 

systemic toxicity. Exposure to the test material also decreased the body weight of MCT and 

HCT male and female rats 7 – 13% during the treatment phase of the study. 

Red Blood Cell (RBC) parameters, including RBC count, HGB, hematocrit, MCV, MCH, 

and/or reticulocytes were significantly reduced in male and female rats following 26 days 

inhalation exposure to the test material. These effects were primarily observed in HCT 

animals, and resolved by the end of the recovery period. However, significant decreases in 

MCH were observed in MCT male and female rats. As speculated by the study author, these 

effects were likely due to protoporphyrinogen oxidase inhibition that had been demonstrated 

in previous studies. No significant treatment-related effects were found on absolute and 

relative-to-body or brain organ weights. Exposure to the test material for 26 days increased 

the incidence of minimal nasal respiratory epithelial hyperplasia in male and female rats in 

the HCT group, as well as minimal laryngeal epithelial attenuation in all test material 

exposure groups. 

The systemic LOAEL is HTC or 1.71 mg/L based on significant reduction in Red Blood 

Cell (RBC) parameters, including RBC count, HGB, hematocrit, MCV, MCH, and/or 

reticulocytes in male and female rats following 26 days inhalation exposure to the test 

material. The NOAEL is 0.256 mg/L. 

Port of entry LOAEL is HTC or 1.71 mg/L based on incidence of minimal nasal 

respiratory epithelial hyperplasia in male and female rats. Portal of entry NOAEL is 

0.265 mg/L.

This study is classified as acceptable/non-guideline and satisfies the guideline requirement 

(OPPTS 870.3465; OECD 413) for a subchronic inhalation study in the rat. 

C. STUDY DEFICIENCIES: 

Minor deficiencies to the study were the use of 5 male and 5 female rats for the LCT, MCT, or 

HCT groups 26-day exposure interval. Subchronic guideline recommendations state that 10 

animals/sex/group be used. Also, the time to chamber equilibrium was not reported. 

D. REFERENCES: 
 26-Day Inhalation Toxicity Study (2013) / Page 15 of 15 

SULFENTRAZONE / 129081 Non-guideline 

Bide, R.W., et al. (2000). Allometric respiration/body mass data for animals to be used for 

estimates of inhalation toxicity to young adult humans. J. Appl. Toxicol. 20:273-290.